SOUTH BAY RESEARCH NOTES & RESOURCES:
1795-1895 Wharf Lines
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1630 Shoreline
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Investigation of Subsoil and Foundation Conditions, Boston Redevelopment Authority, South End Project Mass. R-56, South End Urban Renewal Area (December 27, 1963)
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Bedrock, Formation, & Strata
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A paleomagnetic study of the Late Precambrian Roxbury formation, consisting of extrusives and clastic sediments, has yielded a steeply downward directed and pre-folding characteristic magnetization (D/I = 219°/71°, α95 = 5°, k = 311, paleopole at 13°N, 267°E, N = 4 sites), which indicates a significantly higher paleolatitude (55°) than would be expected if the Boston basin were part of the equatorial North American craton in the latest Precambrian and earliest Paleozoic. This characteristic magnetization reveals dual polarities and is further supported by a positive conglomerate test. A ubiquitous post-folding late Paleozoic overprint is present in nine sites (D/I = 183°/14°, α95 = 8°, k = 42), with a paleopole at 41°S, 285°E. The pre-folding magnetization resides in hematite, which is inferred to have formed during early oxidation of the rocks; the high stability of this hematite may have prevented its magnetization from being reset during the late Paleozoic chemical event responsible for the magnetic overprint. The Boston basin has a marked geological similarity to the Avalon basement terranes in Nova Scotia and Newfoundland, as well as the Armorican Massif in France, and the high paleolatitudes observed for all these terranes suggest a common paleogeographical affinity; a likely paleolocation is near the northwestern margin of Gondwana which was located at the southpole in the latest Precambrian and Early Cambrian.
Eocambrian paleomagnetism of the Boston Basin: Evidence for displaced terrane, December 1986
Eocambrian paleomagnetism of the Boston Basin: Evidence for displaced terrane, December 1986
Boston Basin
After the terrane-making period had passed away, owing to the rising of the land above the sea, there came a second advance of the glaciers, which had clung to the higher hills, and had not passed entirely away from the land. This second advance did not cover the land with ice ; it only caused local glaciers to pour down the valleys.
The Neponset, the Charles, and the Mystic valleys were filled by these river-like streams, which seem never to have attained as far seaward as the peninsula of Boston.
This second advance of the ice seems to have been very temporary in its action, not having endured long enough to bring about any great changes. At about the time of its retreat, the last considerable change of line along these shores seems to have taken place. This movement was a subsidence of the land twenty feet or more below the former high-tide mark.
The mud brought down by these streams, consisting in part of clay and in part of decomposed vegetable matter, derived from land and water plants, coats the sandy bottoms or under-water terraces.
In this mud, even at considerable depths, eel-grass and some sea-weeds take root, and their stems make a dense jungle. In this grass more mud is gathered, and kept from the scouring action of the tide by being bound together by the roots and cemented by the organic matter.
This mass slowly rises until it is bare at low-tide. Then our marsh-grasses creep in, and in their interlaced foliage the waste brought in by the tide is retained, and helps to raise the level of the swamp higher. The streams from the land bring out a certain amount of mud, which at high-tide is spread in a thin
sheet over the surface of the low plain.
Some devious channels are kept open by the strong scouring action of the tide, but the swamp rapidly gains a level but little lower than high-tide. Except when there is some chance deposit of mud or sand from the bluffs along its edges, these swamps are never lifted above high-tide mark, for the forces that build them work only below that level.
Their effect upon the harbor of Boston has been disadvantageous. They have diminished the area of storage for the tide-water above the town, and thereby enfeebled the scouring power of the tidal currents.
Winsor, J., The Memorial History Of Boston (1882).
The Neponset, the Charles, and the Mystic valleys were filled by these river-like streams, which seem never to have attained as far seaward as the peninsula of Boston.
This second advance of the ice seems to have been very temporary in its action, not having endured long enough to bring about any great changes. At about the time of its retreat, the last considerable change of line along these shores seems to have taken place. This movement was a subsidence of the land twenty feet or more below the former high-tide mark.
The mud brought down by these streams, consisting in part of clay and in part of decomposed vegetable matter, derived from land and water plants, coats the sandy bottoms or under-water terraces.
In this mud, even at considerable depths, eel-grass and some sea-weeds take root, and their stems make a dense jungle. In this grass more mud is gathered, and kept from the scouring action of the tide by being bound together by the roots and cemented by the organic matter.
This mass slowly rises until it is bare at low-tide. Then our marsh-grasses creep in, and in their interlaced foliage the waste brought in by the tide is retained, and helps to raise the level of the swamp higher. The streams from the land bring out a certain amount of mud, which at high-tide is spread in a thin
sheet over the surface of the low plain.
Some devious channels are kept open by the strong scouring action of the tide, but the swamp rapidly gains a level but little lower than high-tide. Except when there is some chance deposit of mud or sand from the bluffs along its edges, these swamps are never lifted above high-tide mark, for the forces that build them work only below that level.
Their effect upon the harbor of Boston has been disadvantageous. They have diminished the area of storage for the tide-water above the town, and thereby enfeebled the scouring power of the tidal currents.
Winsor, J., The Memorial History Of Boston (1882).
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Aeromagnetic Map of the Boston South Quadrangle, GP-677, USGS/MA (1969)
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Faults & Folds
USGS, Kaye, 1980
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USGS, Kaye, 1980
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Geology of the Boston Basin (2011/2012)
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Formation
"The ancient North American and African plates - referred to as Laurentia and Gondwana, respectively collided in a zone just west of Boston about 650 to 620 million years ago. The geologic character of this margin and the structure to the east of this belt are not seen elsewhere on the Atlantic coast of the United States. When the much later rifting of about 225 million years ago began to form the present North Atlantic Basin, the split left a piece of northwest Africa clinging to North America. This fragment became the foundation upon which Boston was built. The city and its harbor lie in their own much smaller rift basin formed during a pause in the collision at the very end of the Proterozoic (pre-Cambrian) about 600 million years ago. An array of volcanic debris, gravel, sand and mud gradually filled and overflowed the rift. As the collision ended in the late Ordovician about 440 million years ago, volcanic upheavals formed masses of granite on both sides of the rift to give added character. These and subsequent events produced numerous kinds of structures and rock representing almost all later geologic periods. The region remains active, with earthquake activity and other indications of crustal movement, and is not at all passive."
There were several major geological influences that affected the founding of Boston (Kaye, 1976a). Being a seafaring people, the early settlers looked for a safe harbor. Boston's island studded harbor is formed by a deep indentation in the coastline of Massachusetts. This indentation exists primarily because the underlying rock, mostly argillite, is softer and more easily eroded than the hard highland conglomerate and granitic rock, which surround the Boston Basin (the name of this large topographic and structural depression). Glacial ice further eroded the broad valley and, with subsequent melting of the ice, the sea level rose and flooded the depression, thereby forming the bay and "a safe and pleasant harbor." "This harbor is made by a great company of island, whose high cliffs shoulder out the boisterous seas, yet may easily deceive any unskilfull [sic] pilot; presenting many fair openings and broad sounds, which afford too shallow waters for any ships" (Wood, 1634)."
Barosh & Woodhouse, A City Upon a Hill: Geology of the City of Boston & Surrounding Area, Settlement, Topography & Geologic Studies of Boston, Civil Engineering Practice, Vol. 26-27 (2011/2012).
There were several major geological influences that affected the founding of Boston (Kaye, 1976a). Being a seafaring people, the early settlers looked for a safe harbor. Boston's island studded harbor is formed by a deep indentation in the coastline of Massachusetts. This indentation exists primarily because the underlying rock, mostly argillite, is softer and more easily eroded than the hard highland conglomerate and granitic rock, which surround the Boston Basin (the name of this large topographic and structural depression). Glacial ice further eroded the broad valley and, with subsequent melting of the ice, the sea level rose and flooded the depression, thereby forming the bay and "a safe and pleasant harbor." "This harbor is made by a great company of island, whose high cliffs shoulder out the boisterous seas, yet may easily deceive any unskilfull [sic] pilot; presenting many fair openings and broad sounds, which afford too shallow waters for any ships" (Wood, 1634)."
Barosh & Woodhouse, A City Upon a Hill: Geology of the City of Boston & Surrounding Area, Settlement, Topography & Geologic Studies of Boston, Civil Engineering Practice, Vol. 26-27 (2011/2012).
"Three detrital zircon samples from Ediacaran sandstone of the Roxbury Conglomerate and a quartzite clast in the Squantum diamictite in the Boston Basin (Fig. 1C) show abundant ca. 610–580 Ma and ca. 2.1–1.0 Ga zircon and few ca. 2.8–2.5, ca. 3.0, and ca. 3.2 Ga grains based on isotope dilution–thermal ionization mass spectrometry (ID-TIMS) methods (Thompson and Bowring, 2000; Thompson et al., 2014)."
Kuiper, Yvette D., Daniel P. Murray, Sonia Ellison, and James L. Crowley. "U-Pb detrital zircon analysis of sedimentary rocks of the southeastern New England Avalon terrane in the U.S. Appalachians: Evidence for a separate crustal block." Special Paper of the Geological Society of America 554, (2022). doi: 10.1130/ 2021.2554(05).
The Squantum Member (Roxbury Conglomerate Formation) crops out in the Boston Basin, northeast USA, and was deposited on the Avalonian palaeoplate in the late Neoproterozoic. It is reasonably well-constrained in age by radiometric dates to between 595.8 ± 1.2 Ma (from the underlying Lynn-Mattapan volcanic complex; Thompson et al. 2007) and Ma (from the overlying Cambridge Argillite; Thompson and Bowring 2000). The Boston Basin in the Ediacaran was a back-arc basin setting within the Avalon Terrane, the modern extent of which is strongly demarcated by faults (Carto and Eyles 2012). The Ediacaran stratigraphy in the Boston Basin is organized into the Boston Bay Group, which comprises two formations: the lower Roxbury Conglomerate and upper Cambridge Argillite. The Roxbury Conglomerate is divided into three members. The lower Brookline Member is predominantly composed of conglomerates, the middle Dorchester Member is primarily fine-grained (argillaceous) turbidites with minor conglomerates, and the upper Squantum Member is mostly diamictite facies interbedded with sandstones and siltstones (Carto and Eyles 2012). The Cambridge Argillite comprises approximately 5.5 km of tuff-rich finely laminated to thinly bedded fine-grained (argillaceous) turbidites (Carto and Eyles 2012). Three primary and conformably associated facies are recognized across the Roxbury Conglomerate (Carto and Eyles 2012): (1) conglomerate and sandstone, (2) diamictite, and (3) mudrock.
The diamictite facies (2), typically associated with the upper Squantum Member, comprises massive 1097 or chaotic matrix-supported polymict diamictites with pebble- to boulder-sized, moderately to well 1098 sorted subrounded to angular clasts of predominantly local lithologies (felsic and mafic volcanics, 1099 granodiorite, quartzite, siltstone, and sandstone), similar to the clasts of the conglomerate facies 1100 (Carto and Eyles 2012). The diamictites vary in thickness from approximately 8 m in outcrop to 215 1101 m in the subsurface (Tierney et al. 1968; Carto and Eyles 2012). The diamictite facies is typified by 1102 sharp, erosive basal contacts and transitional upper boundaries as the diamictites grade into 1103 sandstones or conglomerates (Carto and Eyles 2012). The chaotic diamictites can show crude 1104 stratification with large rafts of conglomerate, sandstone, and mudrock poorly mixed through the diamictite (Carto and Eyles 2012). Facetted clasts have not been found, and striated clasts identified by earlier workers (Sayles 1914) were not found by subsequent investigators (Carto and Eyles 2012). Carto and Eyles (2012) note that the distinction between the Roxbury Conglomerate diamictite and 1108 conglomerate facies is the proportion of matrix (10 vol.% to 30 vol.% in the conglomerates and 80 vol.% in the diamictites) with other characteristics, particularly clast composition and form, being remarkably similar – a similarity noted by previous workers who were also dubious of a glaciogenic origin (Dott 1961; Socci and Smith 1990). The diamictite facies is interpreted as the result of the 1112 earlier stages of downslope mixing of conglomeratic and muddy material deriving from primary fan or slope-deposited conglomerates, an interpretation that is supported by the conformable, interbedded, relationship between the diamictite facies with coarse- and fine-grained turbidites (Carto and Eyles 2012).
The argillite facies (3) refers to “rhythmically laminated (0.1 to 1 mm thick) muddy-siltstones that grade subtly into mudstone” (Carto and Eyles 2012, p. 8). The argillite facies is typical of the Cambridge Argillite but is found interbedded with both the conglomerate and diamictite facies throughout the Boston Bay Group on scales of centimetres to hundreds of metres thickness (Carto 1120 and Eyles 2012). Sedimentary structures include parallel to wavy laminations, cross-lamination, and both large- and small-scale slump folds which occur throughout the unit in argillite interbedded with conglomerate and diamictite facies as well as with discrete tuff horizons (Carto and Eyles 2012). The argillite facies has been consistently interpreted as a deep marine (below storm wave base) low-density turbidite (Dott 1961; Thompson and Bowring 2000; Carto and Eyles 2012)
A fourth facies, or perhaps a sub-facies of the argillite facies, is also considered: the pebbly argillite (Carto and Eyles 2012). Stratigraphically and geographically limited to approximately 0.5 m in total directly underlying diamictites at Squantum Head is a laminated argillite with matrix-supported pebbles (approximately 75 vol.% matrix) that is interbedded with non-pebbly laminated and graded argillites (Carto and Eyles 2012). The clasts are all small, typically gravel-size or smaller, rounded to subrounded, and composed of the same local lithologies as the conglomerate and diamictite facies (Carto and Eyles 2012). The pebbly layers form couplets with overlying thin laminae of massive pebble-free argillite (Carto and Eyles 2012). The ‘diamictite-argillite couplets’ have been interpreted as ice-rafted debris or dropstones – and this remains possible – but an interpretation as debrite-turbidite couplets where finer material is sheared off the top of a dilute debris flow as a turbidity current and settles out onto the deposited debrite is more parsimonious with the surrounding facies (Carto and Eyles 2012). Important to this non-glaciogenic origin is the apparent absence of any larger (cobble- or boulder-sized) clasts from the pebbly argillite (Carto and Eyles 2012). The pebbly argillite is interpreted as a slightly more distal equivalent of the diamictite facies, representing part of a debris flow that ran away from or further than the main flow resulting in a more dilute flow (Carto 1140 and Eyles 2012). The most parsimonious interpretation for the depositional context of the Squantum Member diamictite facies may be as part of a continuum of deposits resulting from downslope remobilization of fan or slope sediments including sandstones, mudstones, and conglomerates. The conglomerates may have an originally glaciogenic origin, but that is not certain and could equally, or perhaps more plausibly given the absence of strongly facetted or striated clasts, have a fluvial origin.
Wong Hearing, Thomas & Tindal, Ben & Vandyk, Thomas & Na, Lin & Pohl, Alexandre & Liu, Alexander & Harvey, Thomas & Williams, Mark. (2025). Ediacaran coupling of climate and biosphere dynamics. 10.31223/X5S42P.
The Squantum 'Tillite' (c. 593-570 Ma) consists of thick (up to 215 m) massive and crudely-stratified diamictites conformably interbedded with subaqueously-deposited conglomerates and sandstones within a thick (~7 km) Boston Basin fill which is dominated by argillite turbidites. The Squantum Tillite was first interpreted as being glacigenic in origin in 1914 because of the presence of diamictites; argillites were interpreted as glaciolacustrine 'varves' with rare ice-rafted debris, and conglomerates as glaciofluvial outwash. More recently these have been shown to be the product of deep marine mass flow processes with no glacial influence, yet because of its age equivalence with the deep marine, glacially-influenced Gaskiers Formation, the Squantum Tillite is still seen by some as supporting evidence for a widespread 'Snowball Earth' event at c. 580 Ma. New sedimentological work confirms that conglomerate and sandstone facies are deep marine sediment gravity flows genetically related to massive (homogeneous) and crudely-stratified (heterogeneous) diamictites produced subaqueously by downslope mixing of gravel and cobbles with muddy facies. Rare horizons of 'ice rafted debris' in thin-bedded and laminated turbidite facies interbedded with thick debrites show a weak but positive correlation of lamina thickness with grain size, suggesting these facies are non-glacial co-genetic 'debrite-turbidite' couplets. A significant volcanic influence on sedimentation is identified from reworked lapilli tuff beds and reworked ash in turbidites. The depositional setting of the Squantum 'Tillite' appears to be that of a submarine slope/fan setting in an open marine volcanic arc basin receiving large volumes of poorly-sorted sediment on the mid-latitude active margin of Gondwana. No direct glacial influence is apparent.
Carto, S.L., and Eyles, N., 2012, Sedimentology of the Neoproterozoic (c. 580 Ma) Squantum ‘Tillite’, Boston Basin, USA: Mass flow deposition in a deep-water arc basin lacking direct glacial influence: Sedimentary Geology, v. 269–270, p. 1–14, doi:10.1016/j.sedgeo.2012.03.011.
Kuiper, Yvette D., Daniel P. Murray, Sonia Ellison, and James L. Crowley. "U-Pb detrital zircon analysis of sedimentary rocks of the southeastern New England Avalon terrane in the U.S. Appalachians: Evidence for a separate crustal block." Special Paper of the Geological Society of America 554, (2022). doi: 10.1130/ 2021.2554(05).
The Squantum Member (Roxbury Conglomerate Formation) crops out in the Boston Basin, northeast USA, and was deposited on the Avalonian palaeoplate in the late Neoproterozoic. It is reasonably well-constrained in age by radiometric dates to between 595.8 ± 1.2 Ma (from the underlying Lynn-Mattapan volcanic complex; Thompson et al. 2007) and Ma (from the overlying Cambridge Argillite; Thompson and Bowring 2000). The Boston Basin in the Ediacaran was a back-arc basin setting within the Avalon Terrane, the modern extent of which is strongly demarcated by faults (Carto and Eyles 2012). The Ediacaran stratigraphy in the Boston Basin is organized into the Boston Bay Group, which comprises two formations: the lower Roxbury Conglomerate and upper Cambridge Argillite. The Roxbury Conglomerate is divided into three members. The lower Brookline Member is predominantly composed of conglomerates, the middle Dorchester Member is primarily fine-grained (argillaceous) turbidites with minor conglomerates, and the upper Squantum Member is mostly diamictite facies interbedded with sandstones and siltstones (Carto and Eyles 2012). The Cambridge Argillite comprises approximately 5.5 km of tuff-rich finely laminated to thinly bedded fine-grained (argillaceous) turbidites (Carto and Eyles 2012). Three primary and conformably associated facies are recognized across the Roxbury Conglomerate (Carto and Eyles 2012): (1) conglomerate and sandstone, (2) diamictite, and (3) mudrock.
The diamictite facies (2), typically associated with the upper Squantum Member, comprises massive 1097 or chaotic matrix-supported polymict diamictites with pebble- to boulder-sized, moderately to well 1098 sorted subrounded to angular clasts of predominantly local lithologies (felsic and mafic volcanics, 1099 granodiorite, quartzite, siltstone, and sandstone), similar to the clasts of the conglomerate facies 1100 (Carto and Eyles 2012). The diamictites vary in thickness from approximately 8 m in outcrop to 215 1101 m in the subsurface (Tierney et al. 1968; Carto and Eyles 2012). The diamictite facies is typified by 1102 sharp, erosive basal contacts and transitional upper boundaries as the diamictites grade into 1103 sandstones or conglomerates (Carto and Eyles 2012). The chaotic diamictites can show crude 1104 stratification with large rafts of conglomerate, sandstone, and mudrock poorly mixed through the diamictite (Carto and Eyles 2012). Facetted clasts have not been found, and striated clasts identified by earlier workers (Sayles 1914) were not found by subsequent investigators (Carto and Eyles 2012). Carto and Eyles (2012) note that the distinction between the Roxbury Conglomerate diamictite and 1108 conglomerate facies is the proportion of matrix (10 vol.% to 30 vol.% in the conglomerates and 80 vol.% in the diamictites) with other characteristics, particularly clast composition and form, being remarkably similar – a similarity noted by previous workers who were also dubious of a glaciogenic origin (Dott 1961; Socci and Smith 1990). The diamictite facies is interpreted as the result of the 1112 earlier stages of downslope mixing of conglomeratic and muddy material deriving from primary fan or slope-deposited conglomerates, an interpretation that is supported by the conformable, interbedded, relationship between the diamictite facies with coarse- and fine-grained turbidites (Carto and Eyles 2012).
The argillite facies (3) refers to “rhythmically laminated (0.1 to 1 mm thick) muddy-siltstones that grade subtly into mudstone” (Carto and Eyles 2012, p. 8). The argillite facies is typical of the Cambridge Argillite but is found interbedded with both the conglomerate and diamictite facies throughout the Boston Bay Group on scales of centimetres to hundreds of metres thickness (Carto 1120 and Eyles 2012). Sedimentary structures include parallel to wavy laminations, cross-lamination, and both large- and small-scale slump folds which occur throughout the unit in argillite interbedded with conglomerate and diamictite facies as well as with discrete tuff horizons (Carto and Eyles 2012). The argillite facies has been consistently interpreted as a deep marine (below storm wave base) low-density turbidite (Dott 1961; Thompson and Bowring 2000; Carto and Eyles 2012)
A fourth facies, or perhaps a sub-facies of the argillite facies, is also considered: the pebbly argillite (Carto and Eyles 2012). Stratigraphically and geographically limited to approximately 0.5 m in total directly underlying diamictites at Squantum Head is a laminated argillite with matrix-supported pebbles (approximately 75 vol.% matrix) that is interbedded with non-pebbly laminated and graded argillites (Carto and Eyles 2012). The clasts are all small, typically gravel-size or smaller, rounded to subrounded, and composed of the same local lithologies as the conglomerate and diamictite facies (Carto and Eyles 2012). The pebbly layers form couplets with overlying thin laminae of massive pebble-free argillite (Carto and Eyles 2012). The ‘diamictite-argillite couplets’ have been interpreted as ice-rafted debris or dropstones – and this remains possible – but an interpretation as debrite-turbidite couplets where finer material is sheared off the top of a dilute debris flow as a turbidity current and settles out onto the deposited debrite is more parsimonious with the surrounding facies (Carto and Eyles 2012). Important to this non-glaciogenic origin is the apparent absence of any larger (cobble- or boulder-sized) clasts from the pebbly argillite (Carto and Eyles 2012). The pebbly argillite is interpreted as a slightly more distal equivalent of the diamictite facies, representing part of a debris flow that ran away from or further than the main flow resulting in a more dilute flow (Carto 1140 and Eyles 2012). The most parsimonious interpretation for the depositional context of the Squantum Member diamictite facies may be as part of a continuum of deposits resulting from downslope remobilization of fan or slope sediments including sandstones, mudstones, and conglomerates. The conglomerates may have an originally glaciogenic origin, but that is not certain and could equally, or perhaps more plausibly given the absence of strongly facetted or striated clasts, have a fluvial origin.
Wong Hearing, Thomas & Tindal, Ben & Vandyk, Thomas & Na, Lin & Pohl, Alexandre & Liu, Alexander & Harvey, Thomas & Williams, Mark. (2025). Ediacaran coupling of climate and biosphere dynamics. 10.31223/X5S42P.
The Squantum 'Tillite' (c. 593-570 Ma) consists of thick (up to 215 m) massive and crudely-stratified diamictites conformably interbedded with subaqueously-deposited conglomerates and sandstones within a thick (~7 km) Boston Basin fill which is dominated by argillite turbidites. The Squantum Tillite was first interpreted as being glacigenic in origin in 1914 because of the presence of diamictites; argillites were interpreted as glaciolacustrine 'varves' with rare ice-rafted debris, and conglomerates as glaciofluvial outwash. More recently these have been shown to be the product of deep marine mass flow processes with no glacial influence, yet because of its age equivalence with the deep marine, glacially-influenced Gaskiers Formation, the Squantum Tillite is still seen by some as supporting evidence for a widespread 'Snowball Earth' event at c. 580 Ma. New sedimentological work confirms that conglomerate and sandstone facies are deep marine sediment gravity flows genetically related to massive (homogeneous) and crudely-stratified (heterogeneous) diamictites produced subaqueously by downslope mixing of gravel and cobbles with muddy facies. Rare horizons of 'ice rafted debris' in thin-bedded and laminated turbidite facies interbedded with thick debrites show a weak but positive correlation of lamina thickness with grain size, suggesting these facies are non-glacial co-genetic 'debrite-turbidite' couplets. A significant volcanic influence on sedimentation is identified from reworked lapilli tuff beds and reworked ash in turbidites. The depositional setting of the Squantum 'Tillite' appears to be that of a submarine slope/fan setting in an open marine volcanic arc basin receiving large volumes of poorly-sorted sediment on the mid-latitude active margin of Gondwana. No direct glacial influence is apparent.
Carto, S.L., and Eyles, N., 2012, Sedimentology of the Neoproterozoic (c. 580 Ma) Squantum ‘Tillite’, Boston Basin, USA: Mass flow deposition in a deep-water arc basin lacking direct glacial influence: Sedimentary Geology, v. 269–270, p. 1–14, doi:10.1016/j.sedgeo.2012.03.011.
The softest Boston rocks are argillite (related to slate and shale but harder) and volcanic ash. The argillite was originally deposited as clay in either a lake or marine embayment; the volcanic ash was blown out of the many volcanoes that were active in the area during the time the clay or mud was being deposited. Gravel was interlayered with the clay and cemented into a hard rock called "conglomerate," locally called "puddingstone." This rock crops out widely in Roxbury, Dorchester, and Brookline. Also interlayered with these sediments were volcanic flows, ashes, cinders, and the great variety of deposits formed by volcanoes. These deposits now hard rock are best seen in nearby Mattapan, Hyde Park, Milton, Lynn, and Saugus.
What was the ancient landscape like at the time the Boston rocks were being laid down? In all probability, the region was a broad lowland surrounded by hills or mountains of granite. A large body of water, either a large lake or perhaps an arm of the sea, occupied part of the lowland. Small volcanoes and at least one large cone that rose a mile or more in height dotted the plain and surrounding uplands. The ash from these volcanoes blanketed the plain and was carried by the rivers to the lake or sea where it mixed with silt and clay that was being carried by rivers from the upland. The rivers descending onto the plain from the surrounding highlands also carried gravel, which was deposited in flood plains and -which makes up much of the Roxbury "puddingstone."
Kaye, C. A., The Geology and Early History of the Boston Area of Massachusetts, A Bicentennial Approach, Geological, Survey Bulletin 1476 (1976).
What was the ancient landscape like at the time the Boston rocks were being laid down? In all probability, the region was a broad lowland surrounded by hills or mountains of granite. A large body of water, either a large lake or perhaps an arm of the sea, occupied part of the lowland. Small volcanoes and at least one large cone that rose a mile or more in height dotted the plain and surrounding uplands. The ash from these volcanoes blanketed the plain and was carried by the rivers to the lake or sea where it mixed with silt and clay that was being carried by rivers from the upland. The rivers descending onto the plain from the surrounding highlands also carried gravel, which was deposited in flood plains and -which makes up much of the Roxbury "puddingstone."
Kaye, C. A., The Geology and Early History of the Boston Area of Massachusetts, A Bicentennial Approach, Geological, Survey Bulletin 1476 (1976).
The Boston Basin originated in the Late Precambrian as a failed rift/successor basin, during the opening of the lapetus Ocean. Early sedimentation was characterized by a suite of bimodal volcanics and coarse debris flow deposits in the form of a fan. The geochemistry of the volcanics at the base of the succession suggests that the basin was connected to the open ocean very early in its history.
Subsequent rapid progradation of submarine slope and fan deposits occurred in the Late Precambrian/(?)Cambrian, including ice-derived diamictons and remobilized detritus, which show evidence of transport toward the north-northeast. During periods of more equable climate the slope became the site of sand and mud deposited by gravity and current. The last depositional event was characterized by the development of an overlap sequence in the (?)Late Precambrian/Cambrian. Global climate amelioration is attributed to a tectonically induced eustatic rise in sea level.
This stratigraphic history reflects the evolution of a passive margin during the opening of the lapetus, and eventual closing of the lapetus and comprehensive deformation of the Boston Basin from Ordovician to Carboniferous time. Sediment transport in the basin was largely longitudinal and toward the east-northeast.
Anthony D. Socci, Geoffrey W. Smith, Evolution of the Boston Basin: A Sedimentological Perspective, Sedimentary Basins and Basin-Forming Mechanisms — Memoir 12, 1987, Pages 87-99, Extensional Basins
The Boston basin is one of several late Paleozoic nonmarine sedimentary basins that developed in eastern New England subsequent to the Acadian revolution. Most of the sedimentary rocks in these basins are known to be Pennsylvanian in age; those in the Boston basin are presumably of this age. The principal map units—except for the Blue Hills and Nahant—are the Precambrian basement, the Mattapan and Lynn Volcanic Complexes (Mississippian?), and the Boston Bay Group (Pennsylvanian?). The Boston Bay Group consists of the Cambridge Argillite and the Roxbury Conglomerate. The Roxbury Conglomerate in turn is subdivided, from bottom to top, into the Brookline, Dorchester, and Squantum Members.
During the past 25 years, a series of bedrock tunnels, driven for water supply and drainage purposes, have added greatly to our knowledge. The tunnels, 3 to 3.5 m in diameter, are at a depth of 30 to 90 m below the surface. The total length of these tunnels is 39.57 km; the Dorchester Tunnel, under construction, is another 10.19 km long.
New observations and interpretations are as follows: (1) The maximum thickness of the Boston Bay Group is 5,700 m. (2) The Boston Bay Group thins to the south. (3) The Roxbury Conglomerate, with a maximum thickness of 1,310 m, is a southerly facies of the lower part of the Cambridge Argillite. (4) The Cambridge Argillite reaches a maximum thickness of 5,700 m in the northern part of the basin. (5) The sedimentary rocks were derived from a highland to the south.
The most important new results that bear on structure are that (1) the Northern border fault, where exposed in a tunnel, dips 55°N; (2) the Charles River syncline, exposed in two tunnels 10.5 km apart, plunges 19° in a direction N84°E; and (3) many minor folds and faults complicate the structure.
Although no tunnel crosses the Blue Hills, a new interpretation of the structure is presented. The volcanic complex of that area was erupted onto flat-lying Cambrian sedimentary rocks. The Quincy Granite and Blue Hill Granite Porphyry were injected into the horizontal Cambrian strata and volcanic complex. After a period of uplift and erosion, the Pennsylvanian strata of the Norfolk basin were deposited. All the rocks were then folded into a syncline, the vertical north limb of which is now the Blue Hills. The Blue Hills were then thrust northward over the Boston basin.
Marland P. Billings, Geology of the Boston Basin, January 01, 1976, https://doi.org/10.1130/MEM146-p5
The bathymetry and sidescan-sonar data show natural features and sea floor modification from anthropogenic activities. Dredging and other anthropogenic activities are generally focused in the shipping channels. Evidence of dredging is visible within the imagery as straight-sided channels, unnatural-appearing roughness and/or linear features on the sea floor that are typically oriented parallel to a channel. Disposal of dredged material is clearly displayed within the multibeam echosounder data as rounded mounds; often occurring in a straight line, some have a central high and a surrounding moat thought to be created as the material was deposited on the sea floor. The mounds sometimes are identified in the sidescan-sonar by high backscatter intensity, but are not always resolved. Other anthropogenic features on the sea floor include wrecks of small boats and barges, pipelines, and piles of debris. Almost all of the Inner Harbor from Castle Island to Long Wharf was mapped by multibeam echosounder. In the Outer Harbor and the Harbor Approaches, the 2-m resolution multibeam echosounder data are displayed with the 30-m resolution single-beam echosounder data; interpretation of features and their spatial extent is limited by these mixed observations.
The sea-floor landscape varies from gently sloping sub-tidal flats to areas of rugged elevation exhibiting as much as 7 m of local relief (sheet 1, fig. 3.6). The acoustic backscatter intensity (sheet 3, fig. 3.7) illustrates the general distribution of surficial sediment. The approaches to Boston Harbor and the dredged navigation channels around the Harbor Islands are generally characterized by high backscatter, bedrock, boulder, cobbles, or dense shell beds. The Inner and Outer Harbor are primarily composed of fine-grained sediments, such as fine sand or mud, which displays as low backscatter within the sidescan-sonar imagery (fig. 4.3).
Sea-floor topography and surficial character in the study area vary at scales of several meters and less. For example, high relief bedrock and bouldery glacial deposits (till) are commonly exposed on the sea floor in close proximity to flat-lying deposits of finer sediment (sand, mud). Rocky areas sometimes contain isolated accumulations of shelly sediment that are ponded in small cracks or low-lying areas between rock outcrops.
High-Resolution Geologic Mapping of the Inner Continental Shelf: Boston Harbor and Approaches, Massachusetts
https://pubs.usgs.gov/of/2006/1008/html/discussion.html
Paleocontinental reconstructions (Fig. 1) show that the Iapetus Ocean was initiated by the separation of continental landmasses that had previously collided during the ca. 1.1–0.9 Ga Grenville orogeny during the amalgamation of Rodinia (e.g. Cawood et al., 2001; Rivers, 2009). Geologic, geochronologic and paleomagnetic data from rocks
formed along the Laurentian margin of Iapetus are consistent with a multi-stage rift history in which separation from Baltica occurred between 620 and 570 Ma, and separation from West Gondwana occurred at ca. 570 Ma (Cawood et al., 2001; Cawood and Pisarevsky, 2006). The development of the classic Humber Zone passive margin,
which extends ca. 2000 km along the Laurentian margin, occurred in the interval ca. 540–535 Ma with the separation of peri-Laurentian microcontinents (e.g. Meert et al., 1998; Cawood et al., 2001) known as the Dashwood terrane in the northern Appalachians (Waldron and van Staal, 2001) and the Precordillera in the southern Appalachians
(Thomas and Astini, 1996, 1999). The mechanisms responsible for the origin of Iapetus are unclear, largely because of uncertainties in the paleomagnetic record between
615 and 550 Ma, when high latitude and low latitude positions for Laurentia (and by inference West Gondwana) are permissible (Pisarevsky et al., 2000, 2001, 2008; Murphy et al., 2004; Dalziel, in press). According to Pisarevsky et al. (2008), the location of magmatic provinces and orientations of dyke swarms emplaced during this
interval support the existence of a mantle plume located between Laurentia, Baltica and Amazonia, which then evolved to become a rift– rift–rift triple junction (see also Cawood et al., 2001). In this context, the Dashwood microcontinent would reflect a late-stage branch of the rift system that propagated inboard of the Laurentian margin (Waldron and van Staal, 2001). According to Thomas and Astini (1999), the separation of the Precordillera from Laurentia was accomplished by asymmetric rifting
along a low-angle detachment with the western Precordillera positioned along the lower plate. These relationships indicate that both the Dashwood terrane and the Precordillera formed microcontinental blocks within the Iapetus Ocean during the Cambrian.Comparative evolution of the Iapetus and Rheic Oceans: A North America perspective, Gondwana Research 17 (2010) 482–499
Avalonian terrane makes up a large portion of eastern Massachusetts but is not the only microcontinent terrane found in the northeastern part of North America, because Avalonia was not the only ancient microcontinent that made a journey from the edge of Gondwana to Laurentia (more on that here). Ganderia, which was accreted to Laurentia before Avalonia, formed off the edge of the Amazonian craton rather than in the ocean like Avalonia. Ganderia and Avalonia were geographically in proximity to each other when they were rifted away from Gondwana by the opening of the Rheic Ocean. Ganderia’s accretion to Laurentia happened with the closing of the Iaepetus Ocean and resulted in a significant mountain building event, the Salinian orogen. When Avalonian contacted Ganderian terrane, it was thrust under it; the contact point between Avalonian terrane and Ganderian (Nashoba) terrane is clearly demarcated in Massachusetts by the Bloody Bluff fault (see Figure at left). Like much of New England, the bedrock of Avalonia is extensively igneous or metamorphosed igneous rock.
A bedrock geologic map developed by Thompson et al. 2014 (figure left below) provides more detail on the Avalonian rocks of the Boston basin. The red outline in the map shows the boundaries of Brookline. The rock formations within the Boston basin mark the transition of this part of Avalonia from subduction-island arc magmatism (Act 3) to transform faulting-rifting magmatism and to passive margin sedimentation (Act 4). The Boston basin may originally have formed from shear stress exerted on the Avalonian island arc during subduction, as the angle of subduction was relatively low, exerting significant transverse stress on the arc margin (Figure right below). The combination of this subduction and the shear stress could have initiated pull-apart basins in the arc.
The rocks of the Boston Basin are a repository of a specific period in Avalonia, during the time it made a transition from an active volcanic arc to a passive arc platform. The period of time these rocks cover is about 610 Ma to 540 Ma (Neoproterozoic--Early Cambrian). The figure below shows the time period for deposit of these different rocks. Ages have been established through a variety of isotopic techniques appropriate to rocks of this age. The summary below covers these rocks in chronological order of their formation.
The Avalonian Rocks of the Boston Basin and Their Ancient Depositional Environment, https://www.brooklinerocks.org/avalonian-rocks-of-brookline
A GRAVITY SURVEY OF THE BOSTON BASIN REGION By Merrill S. Ginsburg Submitted to the Department of Geology and Geophysics on October 10, 1959, in partial fulfillment of the requirements for the degree of Master of Science in Geology and Geophysics. ABSTRACT One hundred sixty eight gravity stations were occupied in the Boston Basin area, and Bouguer anomalies were ascertained for the purpose of determining or corroborating facts about the geology and structure of the basin and surrounding region. The relative accuracy of the anomaly determinations is 0.22 milligals. The Bouguer anomaly contour map bears out some of the known phenomena in the region outside of the Boston Basin, but fails to indicate others. Three predominant highs are associated with the occurrence of Salem gabbro-diorite - the rock of greatest density in the region. Hence, it is concluded that the situation and thickness of the Salem throughout the region is the primary cause for the pattern of the gravity contours. Over the main part of the Boston Basin, the gravity contour lines trend east-west. The gradient of over +2 milligals to the north is greater than, and nearly perpendicular to, the regional trend of the area. In the southwest corridor of the basin, a gravity ridge is seen to be in correlation with the stratified formations which are of greater density than the bordering igneous rocks of the area. Hence, the Boston Basin is manifested by the iso-anomaly map. Two profiles, taken in a general north-south direction across the main portion of the Boston Basin, are approximately "U "-shaped, with the low centered over the Quincy granite, which borders the basin on the south. It was found that the profiles could best be interpreted by considering the flanks of each profile "U" separately. The right flanks indicate that the density contrast between the Salem gabbro-diorite and, to the north, the Dedham granodiorite and Quincy granite extends to a maximum depth of over 4400 feet. The left flanks show manifestations of two of the three principal structural units of the basin: the central anticline and southern shingle-block zone. The contour map indicates a gentle plunging of the Boston Basin sediments to the east, corroborating the findings of geologic investigators. But the contours also indicate a sharp upswing of dense basement rocks in Boston Bay. This contradicts the belief of certain investigators. A northern boundary fault is implied by s-shaped offsets of the gravity contour lines. The fault may be continuous from Lynn to Natick, although the s-shaped offset pattern is not apparent between Arlington and Waltham. The northern boundary fault is also manifested slightly on one of the northsouth profiles. No conclusive evidence is found for the presence of a southern boundary fault. Interpretation is hampered by the low density contrast between the major rock formations of the region - only 0. 3 gm/cm3 separates the densities of the rocks of greatest and least density - and is also hampered by a thin layer of low density glacial deposits of undertermined thickness, the total effect of which is not definitely known. Thesis Supervisor: William F. Brace Title: Assistant Professor of Geology
https://dspace.mit.edu/bitstream/handle/1721.1/60436/32553214-MIT.pdf?sequence=2&isAllowed=y
Subsequent rapid progradation of submarine slope and fan deposits occurred in the Late Precambrian/(?)Cambrian, including ice-derived diamictons and remobilized detritus, which show evidence of transport toward the north-northeast. During periods of more equable climate the slope became the site of sand and mud deposited by gravity and current. The last depositional event was characterized by the development of an overlap sequence in the (?)Late Precambrian/Cambrian. Global climate amelioration is attributed to a tectonically induced eustatic rise in sea level.
This stratigraphic history reflects the evolution of a passive margin during the opening of the lapetus, and eventual closing of the lapetus and comprehensive deformation of the Boston Basin from Ordovician to Carboniferous time. Sediment transport in the basin was largely longitudinal and toward the east-northeast.
Anthony D. Socci, Geoffrey W. Smith, Evolution of the Boston Basin: A Sedimentological Perspective, Sedimentary Basins and Basin-Forming Mechanisms — Memoir 12, 1987, Pages 87-99, Extensional Basins
The Boston basin is one of several late Paleozoic nonmarine sedimentary basins that developed in eastern New England subsequent to the Acadian revolution. Most of the sedimentary rocks in these basins are known to be Pennsylvanian in age; those in the Boston basin are presumably of this age. The principal map units—except for the Blue Hills and Nahant—are the Precambrian basement, the Mattapan and Lynn Volcanic Complexes (Mississippian?), and the Boston Bay Group (Pennsylvanian?). The Boston Bay Group consists of the Cambridge Argillite and the Roxbury Conglomerate. The Roxbury Conglomerate in turn is subdivided, from bottom to top, into the Brookline, Dorchester, and Squantum Members.
During the past 25 years, a series of bedrock tunnels, driven for water supply and drainage purposes, have added greatly to our knowledge. The tunnels, 3 to 3.5 m in diameter, are at a depth of 30 to 90 m below the surface. The total length of these tunnels is 39.57 km; the Dorchester Tunnel, under construction, is another 10.19 km long.
New observations and interpretations are as follows: (1) The maximum thickness of the Boston Bay Group is 5,700 m. (2) The Boston Bay Group thins to the south. (3) The Roxbury Conglomerate, with a maximum thickness of 1,310 m, is a southerly facies of the lower part of the Cambridge Argillite. (4) The Cambridge Argillite reaches a maximum thickness of 5,700 m in the northern part of the basin. (5) The sedimentary rocks were derived from a highland to the south.
The most important new results that bear on structure are that (1) the Northern border fault, where exposed in a tunnel, dips 55°N; (2) the Charles River syncline, exposed in two tunnels 10.5 km apart, plunges 19° in a direction N84°E; and (3) many minor folds and faults complicate the structure.
Although no tunnel crosses the Blue Hills, a new interpretation of the structure is presented. The volcanic complex of that area was erupted onto flat-lying Cambrian sedimentary rocks. The Quincy Granite and Blue Hill Granite Porphyry were injected into the horizontal Cambrian strata and volcanic complex. After a period of uplift and erosion, the Pennsylvanian strata of the Norfolk basin were deposited. All the rocks were then folded into a syncline, the vertical north limb of which is now the Blue Hills. The Blue Hills were then thrust northward over the Boston basin.
Marland P. Billings, Geology of the Boston Basin, January 01, 1976, https://doi.org/10.1130/MEM146-p5
The bathymetry and sidescan-sonar data show natural features and sea floor modification from anthropogenic activities. Dredging and other anthropogenic activities are generally focused in the shipping channels. Evidence of dredging is visible within the imagery as straight-sided channels, unnatural-appearing roughness and/or linear features on the sea floor that are typically oriented parallel to a channel. Disposal of dredged material is clearly displayed within the multibeam echosounder data as rounded mounds; often occurring in a straight line, some have a central high and a surrounding moat thought to be created as the material was deposited on the sea floor. The mounds sometimes are identified in the sidescan-sonar by high backscatter intensity, but are not always resolved. Other anthropogenic features on the sea floor include wrecks of small boats and barges, pipelines, and piles of debris. Almost all of the Inner Harbor from Castle Island to Long Wharf was mapped by multibeam echosounder. In the Outer Harbor and the Harbor Approaches, the 2-m resolution multibeam echosounder data are displayed with the 30-m resolution single-beam echosounder data; interpretation of features and their spatial extent is limited by these mixed observations.
The sea-floor landscape varies from gently sloping sub-tidal flats to areas of rugged elevation exhibiting as much as 7 m of local relief (sheet 1, fig. 3.6). The acoustic backscatter intensity (sheet 3, fig. 3.7) illustrates the general distribution of surficial sediment. The approaches to Boston Harbor and the dredged navigation channels around the Harbor Islands are generally characterized by high backscatter, bedrock, boulder, cobbles, or dense shell beds. The Inner and Outer Harbor are primarily composed of fine-grained sediments, such as fine sand or mud, which displays as low backscatter within the sidescan-sonar imagery (fig. 4.3).
Sea-floor topography and surficial character in the study area vary at scales of several meters and less. For example, high relief bedrock and bouldery glacial deposits (till) are commonly exposed on the sea floor in close proximity to flat-lying deposits of finer sediment (sand, mud). Rocky areas sometimes contain isolated accumulations of shelly sediment that are ponded in small cracks or low-lying areas between rock outcrops.
High-Resolution Geologic Mapping of the Inner Continental Shelf: Boston Harbor and Approaches, Massachusetts
https://pubs.usgs.gov/of/2006/1008/html/discussion.html
Paleocontinental reconstructions (Fig. 1) show that the Iapetus Ocean was initiated by the separation of continental landmasses that had previously collided during the ca. 1.1–0.9 Ga Grenville orogeny during the amalgamation of Rodinia (e.g. Cawood et al., 2001; Rivers, 2009). Geologic, geochronologic and paleomagnetic data from rocks
formed along the Laurentian margin of Iapetus are consistent with a multi-stage rift history in which separation from Baltica occurred between 620 and 570 Ma, and separation from West Gondwana occurred at ca. 570 Ma (Cawood et al., 2001; Cawood and Pisarevsky, 2006). The development of the classic Humber Zone passive margin,
which extends ca. 2000 km along the Laurentian margin, occurred in the interval ca. 540–535 Ma with the separation of peri-Laurentian microcontinents (e.g. Meert et al., 1998; Cawood et al., 2001) known as the Dashwood terrane in the northern Appalachians (Waldron and van Staal, 2001) and the Precordillera in the southern Appalachians
(Thomas and Astini, 1996, 1999). The mechanisms responsible for the origin of Iapetus are unclear, largely because of uncertainties in the paleomagnetic record between
615 and 550 Ma, when high latitude and low latitude positions for Laurentia (and by inference West Gondwana) are permissible (Pisarevsky et al., 2000, 2001, 2008; Murphy et al., 2004; Dalziel, in press). According to Pisarevsky et al. (2008), the location of magmatic provinces and orientations of dyke swarms emplaced during this
interval support the existence of a mantle plume located between Laurentia, Baltica and Amazonia, which then evolved to become a rift– rift–rift triple junction (see also Cawood et al., 2001). In this context, the Dashwood microcontinent would reflect a late-stage branch of the rift system that propagated inboard of the Laurentian margin (Waldron and van Staal, 2001). According to Thomas and Astini (1999), the separation of the Precordillera from Laurentia was accomplished by asymmetric rifting
along a low-angle detachment with the western Precordillera positioned along the lower plate. These relationships indicate that both the Dashwood terrane and the Precordillera formed microcontinental blocks within the Iapetus Ocean during the Cambrian.Comparative evolution of the Iapetus and Rheic Oceans: A North America perspective, Gondwana Research 17 (2010) 482–499
Avalonian terrane makes up a large portion of eastern Massachusetts but is not the only microcontinent terrane found in the northeastern part of North America, because Avalonia was not the only ancient microcontinent that made a journey from the edge of Gondwana to Laurentia (more on that here). Ganderia, which was accreted to Laurentia before Avalonia, formed off the edge of the Amazonian craton rather than in the ocean like Avalonia. Ganderia and Avalonia were geographically in proximity to each other when they were rifted away from Gondwana by the opening of the Rheic Ocean. Ganderia’s accretion to Laurentia happened with the closing of the Iaepetus Ocean and resulted in a significant mountain building event, the Salinian orogen. When Avalonian contacted Ganderian terrane, it was thrust under it; the contact point between Avalonian terrane and Ganderian (Nashoba) terrane is clearly demarcated in Massachusetts by the Bloody Bluff fault (see Figure at left). Like much of New England, the bedrock of Avalonia is extensively igneous or metamorphosed igneous rock.
A bedrock geologic map developed by Thompson et al. 2014 (figure left below) provides more detail on the Avalonian rocks of the Boston basin. The red outline in the map shows the boundaries of Brookline. The rock formations within the Boston basin mark the transition of this part of Avalonia from subduction-island arc magmatism (Act 3) to transform faulting-rifting magmatism and to passive margin sedimentation (Act 4). The Boston basin may originally have formed from shear stress exerted on the Avalonian island arc during subduction, as the angle of subduction was relatively low, exerting significant transverse stress on the arc margin (Figure right below). The combination of this subduction and the shear stress could have initiated pull-apart basins in the arc.
The rocks of the Boston Basin are a repository of a specific period in Avalonia, during the time it made a transition from an active volcanic arc to a passive arc platform. The period of time these rocks cover is about 610 Ma to 540 Ma (Neoproterozoic--Early Cambrian). The figure below shows the time period for deposit of these different rocks. Ages have been established through a variety of isotopic techniques appropriate to rocks of this age. The summary below covers these rocks in chronological order of their formation.
The Avalonian Rocks of the Boston Basin and Their Ancient Depositional Environment, https://www.brooklinerocks.org/avalonian-rocks-of-brookline
A GRAVITY SURVEY OF THE BOSTON BASIN REGION By Merrill S. Ginsburg Submitted to the Department of Geology and Geophysics on October 10, 1959, in partial fulfillment of the requirements for the degree of Master of Science in Geology and Geophysics. ABSTRACT One hundred sixty eight gravity stations were occupied in the Boston Basin area, and Bouguer anomalies were ascertained for the purpose of determining or corroborating facts about the geology and structure of the basin and surrounding region. The relative accuracy of the anomaly determinations is 0.22 milligals. The Bouguer anomaly contour map bears out some of the known phenomena in the region outside of the Boston Basin, but fails to indicate others. Three predominant highs are associated with the occurrence of Salem gabbro-diorite - the rock of greatest density in the region. Hence, it is concluded that the situation and thickness of the Salem throughout the region is the primary cause for the pattern of the gravity contours. Over the main part of the Boston Basin, the gravity contour lines trend east-west. The gradient of over +2 milligals to the north is greater than, and nearly perpendicular to, the regional trend of the area. In the southwest corridor of the basin, a gravity ridge is seen to be in correlation with the stratified formations which are of greater density than the bordering igneous rocks of the area. Hence, the Boston Basin is manifested by the iso-anomaly map. Two profiles, taken in a general north-south direction across the main portion of the Boston Basin, are approximately "U "-shaped, with the low centered over the Quincy granite, which borders the basin on the south. It was found that the profiles could best be interpreted by considering the flanks of each profile "U" separately. The right flanks indicate that the density contrast between the Salem gabbro-diorite and, to the north, the Dedham granodiorite and Quincy granite extends to a maximum depth of over 4400 feet. The left flanks show manifestations of two of the three principal structural units of the basin: the central anticline and southern shingle-block zone. The contour map indicates a gentle plunging of the Boston Basin sediments to the east, corroborating the findings of geologic investigators. But the contours also indicate a sharp upswing of dense basement rocks in Boston Bay. This contradicts the belief of certain investigators. A northern boundary fault is implied by s-shaped offsets of the gravity contour lines. The fault may be continuous from Lynn to Natick, although the s-shaped offset pattern is not apparent between Arlington and Waltham. The northern boundary fault is also manifested slightly on one of the northsouth profiles. No conclusive evidence is found for the presence of a southern boundary fault. Interpretation is hampered by the low density contrast between the major rock formations of the region - only 0. 3 gm/cm3 separates the densities of the rocks of greatest and least density - and is also hampered by a thin layer of low density glacial deposits of undertermined thickness, the total effect of which is not definitely known. Thesis Supervisor: William F. Brace Title: Assistant Professor of Geology
https://dspace.mit.edu/bitstream/handle/1721.1/60436/32553214-MIT.pdf?sequence=2&isAllowed=y
Kuiper, Yvette D., et al. "U-Pb, Lu-Hf, and trace element zircon data from plutonic rocks of the New England Avalon terrane, USA." Atlantic Geoscience, volume 61, 2025, p. 281–304. https://doi.org/10.4138/atlgeo.2025.011
Glacial deposits mantle much of the bedrock ana drumlins are prominent features. Recent alluvium and marine deposits also are extensive. The submarine topography suggests that glacial deposits form much of the submarine area along with bedrock outcrops. Glacial ground moraine deposits comprise the major part of the sediments in the area. Ground moraine is characteristically heterogeneous in composition and arrangement, and this condition is fully met in Boston Harbor. Deposits are found to be patchy, and adjacent deposits commonly vary greatly in texture and thickness. In summary, the sediments underlying Boston Harbor are probably mostly glacial in origin. There has been little later sedimentation.
Literature Survey of Oceanographic Information Concerning Boston Harbor, Office of Naval Research, Woods Hole, Massachusetts, Reference No. 51- 84, (October 1951).
Literature Survey of Oceanographic Information Concerning Boston Harbor, Office of Naval Research, Woods Hole, Massachusetts, Reference No. 51- 84, (October 1951).
A very large erratic boulder is incorporated into its base in the Fort Point Channel at the MBTA Silver Line crossing (Leifer, 2006) During dredging for the immersed tube placement, a 6 by 6 by 2.4 meter (20 by 20 by 8 foot) glacial erratic boulder was found at the clay-till contact and had to be broken up in place before dredging could be completed. Leifer, A.L., 2006, tunnel information for new Silver Line, written communication, March, 31, 2006, 1 p.
The integrated thickness of the Cambridge Formation in the northern Boston Basin is 5350 m assuming that CTE and MDT-NMRT sections overlap as shown in figure 8. This total is in unexpectedly good agreement with the 5700 m estimate of
Billings (1975 and 1976) given the revised interpretations outlined above in each of the tunnels.
Thompson, AVALONIAN ARC-TO-PLATFORM TRANSITION IN SOUTHEASTERN NEW ENGLAND
The tectonic significance of the Cambridge Formation which is poorly exposed in the Boston Basin, eastern Massachusetts, but transected by 50 km of tunnels beneath the mainland and Boston Harbor. The youngest detrital zircon in a sample from the northern Braintree Weymouth Tunnel establishes a maximum depositional age of 584.09 1.98 Ma, consistent with sources in sills of that age in underlying Roxbury Conglomerate. A 551.22 0.20 Ma ash bed from the Mystic Quarry in Somerville, Massachusetts lies near the top of an approximately 5350 m thick, dominantly argillaceous section measured in subsurface cross sections. These were constructed from attitudes reported in pre-1960 tunnels and from mapping logs obtained from tunnels completed decades later during the federally ordered clean-up of Boston Harbor. A 488.58 0.16 Ma aplite sill intruding argillite 800 m above the ash bed sets the minimum depositional age on the north side of the Basin. A tighter constraint comes from trilobite-bearing strata of the lower Cambrian Weymouth Formation located south of Boston that overlies the Cambridge Formation without obvious break in the Braintree Weymouth Tunnel. If Cambridge deposition was continuous after 584 Ma, the depositional interval would exceed 40 million years. An estimated 20 Ma depositional hiatus seems more likely because the base of the Cambridge Formation appears to define a regional unconformity above which argillite rests variously on magmatic arc-related units of both the 595 to 584 Ma Roxbury Conglomerate and the 597 to 593 Ma Lynn-Mattapan Volcanic Complex. Cambridge deposition set in once arc activity in more northerly “West” Avalonian terranes extending through Atlantic Canada to the Avalon Peninsula, Newfoundland had given way to wrench faulting and bimodal magmatism. This regime is manifested structurally in Boston-area tunnels by later-reactivated normal faults in which hanging wall blocks of Cambridge argillite were originally downthrown relative to older footwall units. Pyroclastic volcanic textures and thin basaltic flows with soft sediment contacts are present in argillite of the City Tunnel Extension, and whole rock major element and REE compositions reveal mixed terrigenous and volcanic components deposited under marine conditions throughout the Basin. Proposed sources for the latter are voluminous eruptions recorded in the 560 to 550 Ma Coldbrook Group in New Brunswick’s Caledonia terrane.
More accurate and precise crystallization ages now available for Boston-area granites and volcanic rocks (table 1) reinforce cross-terrane correlations with arc-related sequences in more northerly Avalonian terranes (fig. 1). However, a combined chemical abrasion-thermal ionization mass spectrometry [CA-TIMS] and laser ablation-inductively coupled mass spectrometry [LA-ICPMS] approach to dating the Roxbury Conglomerate establishes 595 to 584 Ma U-Pb age constraints that also fall within the interval of arc activity (M. Thompson and others, 2014). Here we present LA-ICPMS and CA-TIMS results indicating that aerially more extensive and much thicker marine deposits of the Cambridge Formation (fig. 2) are significantly younger than the previously reported maximum age of 570 Ma (Thompson and Bowring, 2000). The new dates suggest a considerable Roxbury-Cambridge depositional hiatus and raise many questions about the tectonic scenario preceding platform deposition in SE New England.
Thompson & Crowley; AVALONIAN ARC-TO-PLATFORM TRANSITION IN SOUTHEASTERN NEW ENGLAND: U-Pb GEOCHRONOLOGY AND STRATIGRAPHY OF EDIACARAN CAMBRIDGE “ARGILLITE,” BOSTON BASIN, MASSACHUSETTS, USA; American Journal of Science, Vol. 320, May, 2020, P. 405–449, DOI 10.2475/05.2020.01]
More accurate and precise crystallization ages now available for Boston-area granites and volcanic rocks (table 1) reinforce cross-terrane correlations with arc-related sequences in more northerly Avalonian terranes (fig. 1). However, a combined chemical abrasion-thermal ionization mass spectrometry [CA-TIMS] and laser ablation-inductively coupled mass spectrometry [LA-ICPMS] approach to dating the Roxbury Conglomerate establishes 595 to 584 Ma U-Pb age constraints that also fall within the interval of arc activity (M. Thompson and others, 2014). Here we present LA-ICPMS and CA-TIMS results indicating that aerially more extensive and much thicker marine deposits of the Cambridge Formation (fig. 2) are significantly younger than the previously reported maximum age of 570 Ma (Thompson and Bowring, 2000). The new dates suggest a considerable Roxbury-Cambridge depositional hiatus and raise many questions about the tectonic scenario preceding platform deposition in SE New England.
Thompson & Crowley; AVALONIAN ARC-TO-PLATFORM TRANSITION IN SOUTHEASTERN NEW ENGLAND: U-Pb GEOCHRONOLOGY AND STRATIGRAPHY OF EDIACARAN CAMBRIDGE “ARGILLITE,” BOSTON BASIN, MASSACHUSETTS, USA; American Journal of Science, Vol. 320, May, 2020, P. 405–449, DOI 10.2475/05.2020.01]
"The bottom in the Boston Harbor area is characterized by considerable relief. Isolated hills and depressions closely resemble the land topography. The bedrock surface in the vicinity of Boston appears to be extremely irregular. A few elongated deep areas may represent former stream valleys of Pleistocene or pre-Pleistocene age. Construction of a detailed bedrock contour map of the harbor area is not warranted because of the sparsity of data. Under Boston Harbor, data on the depth of bedrock are practically nonexistent except for determinations for dredging in the main ship channel in the inner harbor.
Known deep points in the bedrock generally lie below low areas in the surface topography. The more important deep areas include... deep areas at the west side of Fort Point Channel both north and south of South Station... Locations of the deep points in the bedrock suggest a valley from the Malden bridge southeast across Little Mystic Channel to the inner harbor where it joins a valley trending northerly from Fort Point Channel through the present inner harbor to the northwestern part of East Boston. Another valley appears to cross the Boston peninsula near the Public Garden in a southeasterly direction toward the Fort Point Channel."
Literature Survey of Oceanographic Information Concerning Boston Harbor, Office of Naval Research, Woods Hole, Massachusetts, Reference No. 51- 84, (October 1951).
Known deep points in the bedrock generally lie below low areas in the surface topography. The more important deep areas include... deep areas at the west side of Fort Point Channel both north and south of South Station... Locations of the deep points in the bedrock suggest a valley from the Malden bridge southeast across Little Mystic Channel to the inner harbor where it joins a valley trending northerly from Fort Point Channel through the present inner harbor to the northwestern part of East Boston. Another valley appears to cross the Boston peninsula near the Public Garden in a southeasterly direction toward the Fort Point Channel."
Literature Survey of Oceanographic Information Concerning Boston Harbor, Office of Naval Research, Woods Hole, Massachusetts, Reference No. 51- 84, (October 1951).
"The future site of Boston then lay at the east side of the lapetus Ocean in a volcano-studded region along the coast of the larger continent now called Gondwana, which is now northwest Africa. The region was undergoing considerable volcanic activity, with sand and more heterogeneous volcanic rock being deposited. Clean sand was laid down near shore between influxes of fine volcanic material and eventually overwhelmed by an irregular mixture of mafic lava flows, including some pillow basalt, basaltic and rhyolitic tuff and some calcareous mud. A deeper marine basin that lay offshore, perhaps around volcanic islands, was filling with a thick sequence of volcaniclastic sediments carried in from the southeast. These sediments were dirty sands with much andesitic debris, interlayered with tuff, tuffaceous silt and mud, aluminous mud, limy mud, thin calcareous material and mafic (dark, low-silica rock such as basalt and andesite) flows. Much of the sediment was carried by turbidity flows and laid down as graded beds that shaped the Nashoba and adjacent formations west of Boston. The Gondwana plate moved relatively westward to squeeze the Iapetus Ocean. The western edge of its plate boundary collided against the deep marine basin offshore of Laurentia and slid under it during the Late Proterozoic.
The initial terrestrial and near-shore rhyolite and andesite flow and ash were spewed from volcanoes that were triggered by the faulting and rose up the fault zone bordering the south side of the basin. The debris intermixed with, and then was succeeded by, boulder fans shed northward from the adjacent highlands. The boulder deposit and sand graded north, downslope into mud and silt, which quietly accumulated in marine waters that invaded from the east as the area began to subside. Earthquakes during deposition caused occasional basinward slumping and sliding of the sediments."
Barosh & Woodhouse, A City Upon a Hill: Geology of the City of Boston & Surrounding Area, Regional Geologic Setting for the
Boston Area, Civil Engineering Practice, Vol. 26-27 (2011/2012).
The initial terrestrial and near-shore rhyolite and andesite flow and ash were spewed from volcanoes that were triggered by the faulting and rose up the fault zone bordering the south side of the basin. The debris intermixed with, and then was succeeded by, boulder fans shed northward from the adjacent highlands. The boulder deposit and sand graded north, downslope into mud and silt, which quietly accumulated in marine waters that invaded from the east as the area began to subside. Earthquakes during deposition caused occasional basinward slumping and sliding of the sediments."
Barosh & Woodhouse, A City Upon a Hill: Geology of the City of Boston & Surrounding Area, Regional Geologic Setting for the
Boston Area, Civil Engineering Practice, Vol. 26-27 (2011/2012).
Geology of the Boston Basin (2011/2012)
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"There is surprisingly little unconsolidated fault breccia or gouge lining the basin faults. However, some faults have silicified cataclastic material, which is difficult to characterize. At present, the average lateral-spacing throughout the area for the larger faults is. indicated to be about 150 meters (490 feet), measured in any direction, although the density of faults varies from place to place and many more small ones exist, as can be seen in all areas of good exposure (Crosby, 1893 & 1894; Bell, 1975a; Wolf, 1976; Ross & Bailey, CML 2001; Ross 2001; Metcalf & Eddy, 1990b) and in tunnels (Clarke, 1888; Kaye, 1980a; Barosh & Woodhouse, 1990; Davidson, 2003). Detailed mapping in the Wellesley Extension Interceptor Tunnel in Dedham, just off the southwest side of the basin, shows closely spaced faults and very complex joint systems (see Figure 3-53). Seven joint trends, chiefly with steep dips, are recognized near the Blue Hills (Chute, 1966) and most, if not all, are throughgoing ones that reflect the fault sets present. The fault pattern varies with the amount of data. That pattern in central Boston appears rather simple (see Figure 3-51), but just to the south between Dorchester and Milton the surface and tunnel exposures show a complexity more representative of the basin (see Figure 3-54). In that area, the general east-northeast structural trends are cut by northeast i.')nd north faults along with a few northwest-trend- .ing ones. The late north-trending faults are prominent across the southern -side of the basin and the late northwest-trending ones more common in the northeast, as is reflected in the bottom topography in Massachusetts Bay and outer islands and trend of the late dikes (see Figure 3-52). Any folds within the longitudinal fault blocks trend parallel to the fault blocks and may pluhge to the east (Crosby, 1880; LaForge, 1932; Kaye, 1980a). Various anticlines and synclines have been interpreted in the Boston Bas.in in the past, but the designations and placements have varied greatly between researchers depending on the data available. However, none of these proposed folds continue along strike into the older metamorphosed strata and granitic rock to the west (Nelson; 1975a & 1975b; Barosh, 1977b) nor are any seen to the north or south of the basin. The older rock to the west does show broad folds, but the fold axes trend northerly (Barosh, 1972 & 2005, Barash & Hermes, 1981) and a nose of a broad northerly plung.ing fold (see Figures 2-17 & 2-18) lies just west of the Boston Bas.in (Nelson, 1975b). These are syntectonic folds, which formed during the intrusion of the . batholithic granite in the Late Proterozoic prior to the formation of the Boston Basin (Barash, 1972 & 2005) and no younger regional folds have been found to cross them. What folds that may be present in the Boston Basin, therefore, cannot be related to any regional folding involving the basement, but are shallow features related to various motions on the longitudinal faults and are therefore drag folds. Many of the earlier interpreted folds are discovered to be tilted fault blocks by the various tunnel exposures. Laforge (1932) in effect labeled each area of older rock in the basin an anticline, although he also showed faults bounding their south sides (see Figure 1-30). Billings (1929, 1976a & 1976b) hypothesized that some of LaForge's faults could be additional folds and later enhanced the size of small folds when he summarized his student's tunnel mapping. He likely interpreted the slump, drag and small-scale folds as indicative of large-scale features (see Figure 1-33). The large-scale map of the City Tunnel Extension shows considerable faulting and apparent drag folds, but the generalized section by Billings and Tierney (1964) does not, in contrast to Kaye's (1980) faulted summary of the geology. Kaye (1984a) considered possible folds between the longitudinal faults, but his map data (1980a) show many of these are fault repetitions. Others, such as Cazier (1987), interpreted different periods of folding in the Norfolk Basin from cleavage where mapping only indicates drag folds. Just a single large fold, the Needham-Savin anticline, appears supported by the dips of the strata at present iri. the basin, but its axis lies to the south of · where LaForge placed it (see Figure 1-30),
Reinterpretations of LaForge's data as folds by Billings have not been supported by additional mapping. Billings (1982a) renamed the faults and folds shown by Laforge (1932) and · -reinterpreted a slice of Roxbury Conglomerate in LaForge's Rock Island Fault on Hough's Neck on the southeast side of the basin as the core of a Hough's Neck Anticline (see Figures 1-30 & 1-33). Borings and mapping of the Braintree-Weymouth Tunnel in Hingham, which crosses this area, shows that not only is the Rock Island Fault present (see Figure 3-55), but many smaller faults are as well (Davidson, 2003). Another example is the Northern or Charles River syncline, which was shown with an axis along the Charles River (see Figure 1-33). The contrasting lithology across the axial zone was interpreted as due to fades change, but the change is so abrupt it demonstrates instead the presence of a fault (see Figure 3-56). The reversal of dips at the river marks a fault zone and the south-dipping strata to the north of it are in a rotated block between this fault and the Northern Boundary Fault. However, some smaller folds are present along the northern edge of the basin. These folds appear to be from drag associated with the reverse faults of the Northern Boundary Fault Zone. Billings (1929) removed faults between three of LaForge' s anticlines to form a single large Central anticline (see Figures 1- 30, 1-32 & 1-33), but recent data show that these faults are present (Kaye, 1982b ). The Needham-Savin Anticline lies along the south side of this "Central Anticline." . The original rift basin was a half-graben, dropping the rock down to form a basin to the north. It had extended much farther to the north, but this portion was later cut off and its original width is unknown. The basin (see Figure 3-10) may have faced a narrow arm of the sea or a gulf to the north and had a similar tectonic and structural setting as the contemporary rift at Saint Johns, New Brunswick (Barosh, 1995), and both basins apparently formed as part of a broader basin-and-range topography (Kaye, 1984a). The position of the Mattapan Volcanic Complex centered in Needham apparently was controlled by the initial faults. The Blue Hills igneous complex, which was a volcanic center in the Late Ordovician, was controlled apparently by the border faults as well. The complex interfingering of the volcanic rock, conglomerate and argillite (along with the slumps, mass movement and graded beds) indicates a rapidly ris"' ing upland to the south consistent with longitudinal normal faults being very active during deposition (Datt, 1961 small faults show a minor left-lateral component as well. Such rotational movement elsewhere in the basin could account for tilted blocks and explain some of the misinterpreted folds. The primary longitudinal faults can --be difficiilftopkkoiifin places because of the later reactivation and offset.
BAROSH & WOODHOUSE, Geology of the Boston Basin, CIVIL ENGINEERING PRACTICE (2011/2012)
Reinterpretations of LaForge's data as folds by Billings have not been supported by additional mapping. Billings (1982a) renamed the faults and folds shown by Laforge (1932) and · -reinterpreted a slice of Roxbury Conglomerate in LaForge's Rock Island Fault on Hough's Neck on the southeast side of the basin as the core of a Hough's Neck Anticline (see Figures 1-30 & 1-33). Borings and mapping of the Braintree-Weymouth Tunnel in Hingham, which crosses this area, shows that not only is the Rock Island Fault present (see Figure 3-55), but many smaller faults are as well (Davidson, 2003). Another example is the Northern or Charles River syncline, which was shown with an axis along the Charles River (see Figure 1-33). The contrasting lithology across the axial zone was interpreted as due to fades change, but the change is so abrupt it demonstrates instead the presence of a fault (see Figure 3-56). The reversal of dips at the river marks a fault zone and the south-dipping strata to the north of it are in a rotated block between this fault and the Northern Boundary Fault. However, some smaller folds are present along the northern edge of the basin. These folds appear to be from drag associated with the reverse faults of the Northern Boundary Fault Zone. Billings (1929) removed faults between three of LaForge' s anticlines to form a single large Central anticline (see Figures 1- 30, 1-32 & 1-33), but recent data show that these faults are present (Kaye, 1982b ). The Needham-Savin Anticline lies along the south side of this "Central Anticline." . The original rift basin was a half-graben, dropping the rock down to form a basin to the north. It had extended much farther to the north, but this portion was later cut off and its original width is unknown. The basin (see Figure 3-10) may have faced a narrow arm of the sea or a gulf to the north and had a similar tectonic and structural setting as the contemporary rift at Saint Johns, New Brunswick (Barosh, 1995), and both basins apparently formed as part of a broader basin-and-range topography (Kaye, 1984a). The position of the Mattapan Volcanic Complex centered in Needham apparently was controlled by the initial faults. The Blue Hills igneous complex, which was a volcanic center in the Late Ordovician, was controlled apparently by the border faults as well. The complex interfingering of the volcanic rock, conglomerate and argillite (along with the slumps, mass movement and graded beds) indicates a rapidly ris"' ing upland to the south consistent with longitudinal normal faults being very active during deposition (Datt, 1961 small faults show a minor left-lateral component as well. Such rotational movement elsewhere in the basin could account for tilted blocks and explain some of the misinterpreted folds. The primary longitudinal faults can --be difficiilftopkkoiifin places because of the later reactivation and offset.
BAROSH & WOODHOUSE, Geology of the Boston Basin, CIVIL ENGINEERING PRACTICE (2011/2012)
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Geology of the Boston Basin (2011/2012)
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Cambridge Agrillite
Cambridge silica contents lie with few exceptions between 60 and 70 weight percent SiO2 (table 2), consistent with reference compostions in figure 6A (data re-calculated volatile-free from Clarke, 1924; El Wakeel and Riley, 1961; Hirst, 1962; Gromet and others, 1984). By contrast, Cambridge compositions are commonly richer than reference muds in Al2O3 and K2O, so that points plot in a broad band that sweeps into the lower left corner of figure 6A. Illite compositions from bentonitic sediments (table 2–16 in Weaver, 1989, calculated volatile-free) likewise fall into that area, in line with the previous suggestion (Thompson and Bowing, 2000) that Cambridge deposits include a component of volcanic ash. Terrigenous detritus is the obvious candidate for the other end member of this mixture.
MASSACHUSETTS HYDROGEOLOGIC INFORMATION MATRIX SIXTH EDITION (2013), 6th Edition Revised and Updated.
The Cambridge slate, named from Cambridge, where it has been encountered in many excavations, consists of perhaps 3,500 feet of slate, shale, argillite, and some interbedded sandstone, and at or near the top about 40 feet of greenish and yellowish quartzite. Beds here and there are composed of reworked tuff. The formation is of rather uniform lithologic character, and appears to have been deposited in a body of fresh water, possibly a lake at the margin of the ice.
GEOLOGY OF MASSACHUSETTS AND RHODE ISLAND, https://pubs.usgs.gov/bul/0597/report.pdf
GEOLOGY OF MASSACHUSETTS AND RHODE ISLAND, https://pubs.usgs.gov/bul/0597/report.pdf
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Argillites within the Cambridge Formation of the Boston Bay Group have been known for quite some time to contain ring-like structures, generally interpreted to be body fossils of the Vendian organism Aspidella (Billings, 1872; Clark, 1923; Bailey & Bland, 2001; McMenamin, 2004). Cross-sections made through these ring structures have thin, dark, seemingly opaque laminations that usually run parallel to bedding, forming broad planar surfaces. Some of these dark layers demarcate the fossil surfaces, but others do not. In either case, the material of the thin dark layers has been interpreted to be a preserved pyritized biomat (Baily & Bland, 2001) which entombed the Aspidella, or was perhaps the organic remains of the fossil itself.
Petrographic analysis reveals the sediment from all three localities to be bimodal in nature. The first sediment type is a siltstone rich in very fine sand to coarse silt-sized quartz (interpreted to be igneous in origin) and plagioclase clasts. Sericite and opaque, or seemingly opaque, minerals are also present. About 50% of the quartz grains have altered to chert, and many of the feldspars have altered to sericite or undetermined clay minerals. EDS analysis indicates that the matrix is a combination of chlorite and iron-rich clay or phengite, of medium silt size or smaller. The second sediment type is a mudstone comprised of clays and chlorite that are medium silt size or smaller. Both the silt and the mud sediment types have a variety of accessory minerals, such as rutile and titanite (sphene), scattered throughout, many of which appear to be weakly reflective.
Cambridge Argillite Float, Nahant Beach, BBNB-A
Figure 1. Slide BB-NB-A1c, a cross section through the Cambridge Argillite float found at Nahant Bay. Note the wavy, at times touching and interbraiding, dark laminae in the bottom half of the thin section. The slide is a standard 22mm x 40mm thin section.
Two thin sections were made of this sample, both of which are argillite dominated by the mudstonetype matrix (Fig. 1). Silty laminations, where present, usually grade into mud at the top of the laminae. Small lenses of silt are also present, as well as lenses of calcite. In one distinct 2-3 mm thick layer, numerous dark laminae of varying thicknesses were observed that interbraid with one another. Numerous crystals of chlorite are present, displaying characteristic anomalous blue birefringence. Reflected light microscopy revealed a pale yellow, reflective mineral comprising segments of some of the dark layers. An estimate of the composition of these reflective segments has not been determined because neither of the slides have been analyzed with SEMEDS yet.
Hewitt’s Cove Argillite, BB-HC-A
Figure 2. Slide BB-HC-A4e, a cross section taken perpendicular to the long axis of an Aspidella from the Hewitt’s Cove Argillite. The Aspidella is visible here as the double lens structure in the center left of the image. The ring-structure lies on top of a coarser silty sequence, and appears to push up overlying fine sequences. Scale is the same as in Figure 1
Figure 3. A dark lamina in BB-HC-A6a from the Hewitt’s Cove Argillite as seen in a back-scattered electron (BSE) image acquired with a VP-SEM. The brightly contrasting minerals in the center of the photograph indicate the location of the dark lamina. EDS analysis of this layer suggests the bright minerals are allanite. This lamina contains a ring structure to the left of the photograph. The scale bar is 100 μm.
A total of 11 thin sections were made from the in situ sample BB-HC-A, including many with Aspidella cross-sections. These cross-sections were cut both parallel and perpendicular to the fossil’s long axis. There are approximately equal amounts of silt and mud in these samples. Some laminae are dominated by silt, some by mud, and others grade upward from silt into mud. Usually, Aspidella are found on silty beds directly overlain by muddy laminae (Fig. 2). The distribution of pale yellow reflective minerals was similar to BB-NB-A, with small segments of some dark laminae exhibiting reflectivity. Chlorite crystals are present, but in smaller numbers than in BB-NB-A, and BB-HC-A contains more sericite. The matrix is composed of chlorite and iron-rich phengite. Calcite lenses are also present, usually in association with a dark lamina. Pyrite framboids were observed under the petrographic microscope at magnifications of 100x or higher. This was a significant finding and will be discussed in more detail in the section “Framboids.” EDS analysis demonstrated no significant difference in composition between the non-reflective portions of the dark laminae and the matrix, although more investigation is needed. Visual inspection of Figure3 shows that the reflective portion of the dark lamina (e.g., bright contrast on center left side of image) is contiguous with the non-reflective, clayrich portion of the same layer. The pale reflective mineral present in the dark layer shown in Figure 3 is a silicate that contains cerium, neodynium, and possibly lanthanum, and thus is likely allanite. Accessory minerals present in the Hewitt’s Cove Argillite, as suggested by EDS, include rutile, ilmenite, zircon, and apatite.
Framboids
Figure 4. A cluster of pyrite framboids in slide BB-HC-A6a from Hewitt’s Cove, as seen in a BSE image acquired with a VP-SEM. Some of the framboids are intact, others appear to have broken apart, scattering the component pyrite grains. The large dark grains are mostly quartz. The scale bar is 100 μm.
Small pyrite framboids were found in most of the eleven thin sections from Hewitt’s Cove (Fig. 4); thus far, framboids have not been found in slides from the other two rocks. The pyrite is bright yellow in reflected light, and EDS analysis confirms the abundance of both sulfur and iron. The framboids range from 20 to 30 micrometers in diameter, with individual pyrite grains no more than a micron or two in width. About a third of the individual pyrite crystals appear to be subhedral cubes, others are almost spherical, or have irregular grain boundaries. These 1-2 μm pyrite grains are found both singly and in groups, comprising spherical framboids, or seemingly split open and scattered.
In one slide, BB-HC-A6a, many of the framboidal crystals have dark centers, as shown in Figure 5. EDS analysis indicates that these framboids are rich in iron, but poor or entirely lacking in sulfur. Energy dispersive spectra also demonstrate that the more distinct the dark center of a framboid crystal, the richer in iron and poorer in sulfur it is. Many of these individual grains have a triangular or rhombohedral shape. The chemical composition indicated by EDS, combined with the shape of the grains, suggest that these framboids are made of hematite. These hematite framboids were located in a group of framboids, and were found toward the left and
right ends of the cluster; the framboids in the center of the cluster, however, were rich in both iron and sulfur. The dark laminae in most slides, including those with Aspidella, were scrutinized and no framboids have been found within the Aspidella structures, or in any of the dark laminae. However, the framboids were most frequently found within silty regions a few millimeters above and/or below dark layers.
Figure 5. A BSE image taken with a VP-SEM of a framboid from BB-HC-A6a of the Hewitt’s Cove Argillite. Individual crystals are dark in their centers. The crystals have a high iron content, but little to no sulfur. The composition and apparent rhombohedral shape of the individual grains suggests the framboid is made of secondary hematite. The scale bar is 50 μm.
Slate Island Float, BB-HC-C
A total of four thin sections were prepared of this slate. The clay grains showed strong foliation and the silt grains elongation parallel to foliation. The mineralogical content of BB-HC-C was similar to the less deformed BB-NB-A and BB-HC-A samples. EDS analysis of isolated accessory minerals that were pale yellow under reflected light microscopy suggests that some are allanite and others are titanite (sphene). Euhedral apatite is also present as an accessory phase. Unlike rocks from the other two localities, almost all the dark laminae were composed of a weakly reflective pale yellow mineral. EDS analysis suggests that these layers, rich in titanium and silica, are sphene. No pyrite framboids were found in BB-HC-C.
Critical for the interpretation of Aspidella as a fossil is the observation that the rocks of the Cambridge Argillite are not so deformed as to preclude the preservation of fossils. The siltstones and slates have clearly undergone considerable recrystallization; the individual phengite and chlorite minerals are rather large in size and are almost certainly recrystallized, and many grains of quartz have been either converted into chert or show extensive dissolution surfaces on their faces. The abundance of chlorite and phengite suggests that although the alteration is likely diagenetic, conditions approached the lower limits of metamorphism. The textures and mineralogy indicate that rocks of the Cambridge Argillite were buried to a depth between approximately 3.5 and 5 km, and were heated to temperatures between approximately 175°C and 250°C.
Nature of the Framboids
While a biogenic origin cannot be confirmed or refuted at present, the framboids seem to be primary to the rock. No sulfur bearing veins or lenses have been discovered anywhere in any of the samples. Any sulfur that is present in the rocks is likely primary. More investigation is needed to determine if there truly is a preferential occurrence of the framboids around the dark layers, and to determine whether or not the framboids are biological in origin. A pseudo-membrane was present around a pair of framboids in slide BB-HC-A7c, similar to a pyritized Sphaerocongregus variabilis reported by Moorman (1974) and needs to be explored further. Iron-rich/sulfur-poor framboids in thin section BBHC- A6a are composed largely of subhedral grains. These grains have a rhombohedral shape consistent with hematite. Subhedral to euhedral crystals in a sedimentary rock are usually indicative of recrystallization, so the hematite “framboids” are probably a replacement of earlier pyrite framboids. Regardless, the framboids in general remain the most significant discovery of this investigation.
Anderson, A PETROGRAPHIC AND SEM-EDS ANALYSIS OF ASPIDELLA BEARING SILTSTONES AND SLATES OF THE CAMBRIDGE ARGILLITE, BOSTON BAY GROUP, MASSACHUSETTS; 21st Annual Keck Symposium: 2008
Petrographic analysis reveals the sediment from all three localities to be bimodal in nature. The first sediment type is a siltstone rich in very fine sand to coarse silt-sized quartz (interpreted to be igneous in origin) and plagioclase clasts. Sericite and opaque, or seemingly opaque, minerals are also present. About 50% of the quartz grains have altered to chert, and many of the feldspars have altered to sericite or undetermined clay minerals. EDS analysis indicates that the matrix is a combination of chlorite and iron-rich clay or phengite, of medium silt size or smaller. The second sediment type is a mudstone comprised of clays and chlorite that are medium silt size or smaller. Both the silt and the mud sediment types have a variety of accessory minerals, such as rutile and titanite (sphene), scattered throughout, many of which appear to be weakly reflective.
Cambridge Argillite Float, Nahant Beach, BBNB-A
Figure 1. Slide BB-NB-A1c, a cross section through the Cambridge Argillite float found at Nahant Bay. Note the wavy, at times touching and interbraiding, dark laminae in the bottom half of the thin section. The slide is a standard 22mm x 40mm thin section.
Two thin sections were made of this sample, both of which are argillite dominated by the mudstonetype matrix (Fig. 1). Silty laminations, where present, usually grade into mud at the top of the laminae. Small lenses of silt are also present, as well as lenses of calcite. In one distinct 2-3 mm thick layer, numerous dark laminae of varying thicknesses were observed that interbraid with one another. Numerous crystals of chlorite are present, displaying characteristic anomalous blue birefringence. Reflected light microscopy revealed a pale yellow, reflective mineral comprising segments of some of the dark layers. An estimate of the composition of these reflective segments has not been determined because neither of the slides have been analyzed with SEMEDS yet.
Hewitt’s Cove Argillite, BB-HC-A
Figure 2. Slide BB-HC-A4e, a cross section taken perpendicular to the long axis of an Aspidella from the Hewitt’s Cove Argillite. The Aspidella is visible here as the double lens structure in the center left of the image. The ring-structure lies on top of a coarser silty sequence, and appears to push up overlying fine sequences. Scale is the same as in Figure 1
Figure 3. A dark lamina in BB-HC-A6a from the Hewitt’s Cove Argillite as seen in a back-scattered electron (BSE) image acquired with a VP-SEM. The brightly contrasting minerals in the center of the photograph indicate the location of the dark lamina. EDS analysis of this layer suggests the bright minerals are allanite. This lamina contains a ring structure to the left of the photograph. The scale bar is 100 μm.
A total of 11 thin sections were made from the in situ sample BB-HC-A, including many with Aspidella cross-sections. These cross-sections were cut both parallel and perpendicular to the fossil’s long axis. There are approximately equal amounts of silt and mud in these samples. Some laminae are dominated by silt, some by mud, and others grade upward from silt into mud. Usually, Aspidella are found on silty beds directly overlain by muddy laminae (Fig. 2). The distribution of pale yellow reflective minerals was similar to BB-NB-A, with small segments of some dark laminae exhibiting reflectivity. Chlorite crystals are present, but in smaller numbers than in BB-NB-A, and BB-HC-A contains more sericite. The matrix is composed of chlorite and iron-rich phengite. Calcite lenses are also present, usually in association with a dark lamina. Pyrite framboids were observed under the petrographic microscope at magnifications of 100x or higher. This was a significant finding and will be discussed in more detail in the section “Framboids.” EDS analysis demonstrated no significant difference in composition between the non-reflective portions of the dark laminae and the matrix, although more investigation is needed. Visual inspection of Figure3 shows that the reflective portion of the dark lamina (e.g., bright contrast on center left side of image) is contiguous with the non-reflective, clayrich portion of the same layer. The pale reflective mineral present in the dark layer shown in Figure 3 is a silicate that contains cerium, neodynium, and possibly lanthanum, and thus is likely allanite. Accessory minerals present in the Hewitt’s Cove Argillite, as suggested by EDS, include rutile, ilmenite, zircon, and apatite.
Framboids
Figure 4. A cluster of pyrite framboids in slide BB-HC-A6a from Hewitt’s Cove, as seen in a BSE image acquired with a VP-SEM. Some of the framboids are intact, others appear to have broken apart, scattering the component pyrite grains. The large dark grains are mostly quartz. The scale bar is 100 μm.
Small pyrite framboids were found in most of the eleven thin sections from Hewitt’s Cove (Fig. 4); thus far, framboids have not been found in slides from the other two rocks. The pyrite is bright yellow in reflected light, and EDS analysis confirms the abundance of both sulfur and iron. The framboids range from 20 to 30 micrometers in diameter, with individual pyrite grains no more than a micron or two in width. About a third of the individual pyrite crystals appear to be subhedral cubes, others are almost spherical, or have irregular grain boundaries. These 1-2 μm pyrite grains are found both singly and in groups, comprising spherical framboids, or seemingly split open and scattered.
In one slide, BB-HC-A6a, many of the framboidal crystals have dark centers, as shown in Figure 5. EDS analysis indicates that these framboids are rich in iron, but poor or entirely lacking in sulfur. Energy dispersive spectra also demonstrate that the more distinct the dark center of a framboid crystal, the richer in iron and poorer in sulfur it is. Many of these individual grains have a triangular or rhombohedral shape. The chemical composition indicated by EDS, combined with the shape of the grains, suggest that these framboids are made of hematite. These hematite framboids were located in a group of framboids, and were found toward the left and
right ends of the cluster; the framboids in the center of the cluster, however, were rich in both iron and sulfur. The dark laminae in most slides, including those with Aspidella, were scrutinized and no framboids have been found within the Aspidella structures, or in any of the dark laminae. However, the framboids were most frequently found within silty regions a few millimeters above and/or below dark layers.
Figure 5. A BSE image taken with a VP-SEM of a framboid from BB-HC-A6a of the Hewitt’s Cove Argillite. Individual crystals are dark in their centers. The crystals have a high iron content, but little to no sulfur. The composition and apparent rhombohedral shape of the individual grains suggests the framboid is made of secondary hematite. The scale bar is 50 μm.
Slate Island Float, BB-HC-C
A total of four thin sections were prepared of this slate. The clay grains showed strong foliation and the silt grains elongation parallel to foliation. The mineralogical content of BB-HC-C was similar to the less deformed BB-NB-A and BB-HC-A samples. EDS analysis of isolated accessory minerals that were pale yellow under reflected light microscopy suggests that some are allanite and others are titanite (sphene). Euhedral apatite is also present as an accessory phase. Unlike rocks from the other two localities, almost all the dark laminae were composed of a weakly reflective pale yellow mineral. EDS analysis suggests that these layers, rich in titanium and silica, are sphene. No pyrite framboids were found in BB-HC-C.
Critical for the interpretation of Aspidella as a fossil is the observation that the rocks of the Cambridge Argillite are not so deformed as to preclude the preservation of fossils. The siltstones and slates have clearly undergone considerable recrystallization; the individual phengite and chlorite minerals are rather large in size and are almost certainly recrystallized, and many grains of quartz have been either converted into chert or show extensive dissolution surfaces on their faces. The abundance of chlorite and phengite suggests that although the alteration is likely diagenetic, conditions approached the lower limits of metamorphism. The textures and mineralogy indicate that rocks of the Cambridge Argillite were buried to a depth between approximately 3.5 and 5 km, and were heated to temperatures between approximately 175°C and 250°C.
Nature of the Framboids
While a biogenic origin cannot be confirmed or refuted at present, the framboids seem to be primary to the rock. No sulfur bearing veins or lenses have been discovered anywhere in any of the samples. Any sulfur that is present in the rocks is likely primary. More investigation is needed to determine if there truly is a preferential occurrence of the framboids around the dark layers, and to determine whether or not the framboids are biological in origin. A pseudo-membrane was present around a pair of framboids in slide BB-HC-A7c, similar to a pyritized Sphaerocongregus variabilis reported by Moorman (1974) and needs to be explored further. Iron-rich/sulfur-poor framboids in thin section BBHC- A6a are composed largely of subhedral grains. These grains have a rhombohedral shape consistent with hematite. Subhedral to euhedral crystals in a sedimentary rock are usually indicative of recrystallization, so the hematite “framboids” are probably a replacement of earlier pyrite framboids. Regardless, the framboids in general remain the most significant discovery of this investigation.
Anderson, A PETROGRAPHIC AND SEM-EDS ANALYSIS OF ASPIDELLA BEARING SILTSTONES AND SLATES OF THE CAMBRIDGE ARGILLITE, BOSTON BAY GROUP, MASSACHUSETTS; 21st Annual Keck Symposium: 2008
The Cambridge Argillite is never well exposed. It consists almost exclusively of gray argillite in which the beds range in thickness from 0 .05 to 3 in~hes. The differences in their gray color is grain size dependent. The larger the size, coarse silt to fine sand, the lighter gray the color. The smaller the size, clay and fine silt, the darker is the gray color. Graded bedding is rare in the argillites. Many of the beds show a rhythmic layering due to the alteration of lighter and darker colors. Within the Cambridge Argillite is a hard, white sericitic quartizte which is 400-500 ft thick. This has been named "Milton Quartzite" by Billings in 1929. The quartzite is visible for about two miles in Quincy. The Boston Bay Group has recently been dated as Proterozoic Z, the late Precambrian, by microfossils from the Cambridge Argillite located north of Harvard Sqaure. (Lenk and others, 1982).
Scattered throughout the Boston Basin are the Mattapan/Brighton Volcanics. These are bard, dense white, pink, and red rhyolites. Also included are "melapbyres" (which are altered basalts and andesites) which are dark to light green and are composed chiefly of secondary minerals albite, hornblende cblorite and epidote. Recently Kaye and Zartman (1980) obtained a Pb-U date of 602 +/- 3 m.y. from analysis of zircon. The Dedham Granite underlies most of the area south of the basin which is separated by the Ponkapoag Fault (see figure 1). This unit is more of a cartographic unit than a lithologic one (La Forge, 1932).
ROCK LITHOLOGY AND GLACIAL TRANSPORT SOUTHEAST OF BOSTON, Boston College, Cl0-1 417, https://scholars.unh.edu/cgi/viewcontent.cgi?article=1363&context=neigc_trips
Scattered throughout the Boston Basin are the Mattapan/Brighton Volcanics. These are bard, dense white, pink, and red rhyolites. Also included are "melapbyres" (which are altered basalts and andesites) which are dark to light green and are composed chiefly of secondary minerals albite, hornblende cblorite and epidote. Recently Kaye and Zartman (1980) obtained a Pb-U date of 602 +/- 3 m.y. from analysis of zircon. The Dedham Granite underlies most of the area south of the basin which is separated by the Ponkapoag Fault (see figure 1). This unit is more of a cartographic unit than a lithologic one (La Forge, 1932).
ROCK LITHOLOGY AND GLACIAL TRANSPORT SOUTHEAST OF BOSTON, Boston College, Cl0-1 417, https://scholars.unh.edu/cgi/viewcontent.cgi?article=1363&context=neigc_trips
"It appears that the fundamental basis for what historically is the most deeply entrenched, stratigraphically derived interpretation of the depositional history and setting of the Boston Basin (ie alluvial fan/braided stream) emerged largely devoid of critical evaluation and discussion."
Boston Bay Group probably originated as a glacially influenced submarine slope/fan/apron deposited at unknown water depths, conceivable within an evolving transtensional basin, possibly a failed rift, associated with or perhaps just pre-dating, the opening of Iapetus and the break-up of a supercontinent.
Cambridge Argillite:
- Thickness: min 7,600 ft and may exceed 18,000 ft
- Lithology: Fine grained, mostly argillaceous (quartz-sericite-chlorite), some silt stone and tuff, typically 90 percent argillite, 10 percent feldspathic sandstone, slightly calcareous
- Bedding: rhythmic banding comprising about half of formation; beds generally .5-3 inches, pinch and swell in beds 0.25 inches thick
- Other: color mostly gray to the north, sixty percent reddish to purplish and fourth percent gray or greenish to the south
The historic stratigraphy of the Boston Basin is ambiguous, untestable, and impractical.
Socci & Smith, Stratigraphic implications of facies within the Boston Basin, Geology of the composite Avalon Terrane of southern New England (1990).
Geology of the Boston Basin (2011/2012)
There can be little doubt that the peninsula of Boston has a foundation of argillaceous slate. This is, indeed, the only rock that has ever been found there in place. And from the occurrence of argillaceous slate in South Boston, and in Charlestown, with a northerly dip in both places, it would be very surprising if anv other rock should be found in Boston ; unless it were an intruding mass of trap rock. But this slate on the peninsula is buried deep by clay, gravel, and sand ; although, from the quantity of diluvium found there above the tertiary beds, 1 have been led to color the peninsula as a diluvial deposite.
"The pre-Cambrian age of the argillite appeared contradicted by the presumed age of the Mattapan Volcanic Complex that is at the base of the sequence. The Mattapan volcanic rock in the basin, rhyolite in the Blue Hills and some rhyolite in the Lynn Volcanic Complex to the north were considered correlative (Kaye, 1984a). The rhyolite ash flows (welded tuffs), breccia and flows in the Blue Hills that were included in the Mattapan by Chute (1966 & 1969) are involved with the Quincy, which intrudes Cambrian strata. However, these volcanic rocks were separated by Kaktins (1976), who found them to be a much younger unit (described below as the Blue Hills Rhyolite). This rhyolite and the Lynn volcanic rock are associated with the Quincy and Cape Ann granites, respectively, which have the same Late Ordovician age (Zartman & Marvin, 1971; Dennen, 1991a), which is about 100 million years younger than the Cambridge Argillite. Radiometric dating has produced mixed results and is not always consistent· with the field relations. The chronological data have become more confused and contradictory as the process of rock dating becomes easier and practitioners multiply. Thompson and Grunow . (2004), Hatch (1991), and Kaye and Zartman (1980) describe the controversy and chronological challenges of the Boston Bay Group and Naylor (1976), who was an expert in the field, emphasized that fossil dating is better in the region. Dating is a difficult task when samples are disturbed by metamorphism or when using detrital zircons. Zircons, and other minerals commonly used for dating, formed with the inclosing igneous rock and the radioactive decay date determines the rock's age. Ratios of various elements are used, such as rubidium/ strontium (Rb /Sr) and lead and argon ratios. However, these ratios can be reset or partially reset by later heating and, therefore, would not give the original age of the rock There have been numerous times of heating in the region that have affected the rock Also the different elements used in dating give somewhat different results. Unlike zircons formed in an igneous rock, detrital zircons are ones carried in with the sediment that later formed sedimentary rock and their age gives a maximum age for the rock A major problem is the sampling of the wrong rock by someone unfamiliar with the geology (usually, an error that tends to favor a younger, fresher looking rock). Invalid interpretations of the laboratory data may thus stem from various problems, including insufficient sample control, misunderstanding the local geologic relations, laboratory error and the general limitations of the methods. Radiometric ages are far from precise in southern New England and experience demonstrates that they are commonly· only suggestions - but are still useful ones within their limits."
BAROSH & WOODHOUSE, Geology of the Boston Basin, CIVIL ENGINEERING PRACTICE (2011/2012)
A vei:y thin deltaic deposit, which is present to the south beneath the Back Bay, is described as 1.2 meters (4 feet) of coarse sand and several centimeters (a few inches) of overlying clay beneath a thin upper till (Judson, 1949). It overlies the Cambridge Argillite, which lies at a depth of between elevation -34 and -43 meters (-112 and -142 feet) MSL below the John Hancock site. The thin blue clay appeared to grade into the till, which is bluish with a high clay content. This deposit appears to be a thinned remnant of the deltaic sand and clay smeared by the overriding till. The relatively limited area of the thick portion of the deposit, plus the recognition of. deltaic foreset and bottomset beds (Kaye, 1976a), indicate that the sand and gravel, clay, and peat were part of a delta complex before being overridden and pushed up into Beacon Hill. The present distribution of the sediment suggests that a large delta was centered in the Charles River Basin and adjacent Cambridge and that this delta was fed from the north by a subglacial river along the ancient Mystic River Valley, which followed the Aberjona-Fresh Pond Buried Valley (west of the present Mystic Valley) and then the Malden Buried Valley (east of the present Mystic River). It may have been similar to the many subsequent well-preserved deltas along coastal Maine that built out into the marine clay equivalent of the "Boston Blue Clay" and the large one on the northeast side of the center of Concord (Koteff, 1964b). Kaye (1961) also felt that the clay beneath the edge of Beacon Hill was marine, but at least some clay seen by Woodhouse appears to be layered bottomset .or lake deposit. Perhaps after the toe of a delta built southeastward onto the Shawmut Peninsula it was overlapped by clay as marine waters flooded the still depressed crust while the ice retreated farther north. The next ice readvance of the Boston Substage tore into the delta and pushed it up to form Tri.mountain, of which Beacon Hill forms a remnant, and the overriding glacier left a capping of till. The deposit is . probably Early Wisconsin, but its exact age is yet to be determined.
BAROSH & WOODHOUSE, Geology of the Boston Basin, CIVIL ENGINEERING PRACTICE (2011/2012)
Argillite - This is perhaps the most common rock type in the basin. It consists of silt-size particles of quartz, feldspar, seritic, chlorite and kaolinite. Darker argillite contains more sericite and chlorite while the lighter argillite contains more kaolinite (Kaye, 1967). The argillite is typically gray, but purple, purplish brown, tan, and green colors also occur. Kaye (1984) describes some mineralogical variations of argillite which include calcareous argillite interbedded with normal argillite, sideritic argillite, gypsiferous and dolomitic argillite, red argillite, and black argillite. The argillite is typically hard and well indurated, more consolidated than shale but not fissile like shale. According to Kaye (1979), fresh rock tends to break across bedding planes. surfaces (Rahm, 19 62) . Bedding is typically laminated, consisting of alternating 0.1- to 0.2-inch-thick light and dark colored layers. Individual beds generally range in thickness from less than 1/16-inch to 4 inches and can be up to 5 feet thick. The individual beds maintain a rather uniform thickness for many feet or tens of feet (Billings and Tierney, 1964) . Grain size can vary locally to sandy or silty. Sedimentary structures such as slump folds, ripple marks and cross beds are common in this unit. Severe alteration of the argillite (known as kaolinization), which results in a soft, whitish rock or even clay, occurs in random areas of the Boston Basin. Thin-section study shows that the normal minerals of the argillite have been replaced by sericite and kaolinite during the alteration process. 16
Kaolinization is probably the result of thermo-alteration of the argillite, with an igneous intrusion acting as the catalyst
(Kaye, 1967)
CONTRACT DOCUMENTS FOR APPENDIX A SUBSURFACE EXPLORATION GEOTECHNICAL INTERPRETIVE REPORT INTER-ISLAND TUNNEL, CONTRACT PACKAGE NO. 151 MASSACHUSETTS WATER RESOURCES AUTHORITY MWRA CONTRACT NO. 5541 EPA NO. C 259713-18
BAROSH & WOODHOUSE, Geology of the Boston Basin, CIVIL ENGINEERING PRACTICE (2011/2012)
A vei:y thin deltaic deposit, which is present to the south beneath the Back Bay, is described as 1.2 meters (4 feet) of coarse sand and several centimeters (a few inches) of overlying clay beneath a thin upper till (Judson, 1949). It overlies the Cambridge Argillite, which lies at a depth of between elevation -34 and -43 meters (-112 and -142 feet) MSL below the John Hancock site. The thin blue clay appeared to grade into the till, which is bluish with a high clay content. This deposit appears to be a thinned remnant of the deltaic sand and clay smeared by the overriding till. The relatively limited area of the thick portion of the deposit, plus the recognition of. deltaic foreset and bottomset beds (Kaye, 1976a), indicate that the sand and gravel, clay, and peat were part of a delta complex before being overridden and pushed up into Beacon Hill. The present distribution of the sediment suggests that a large delta was centered in the Charles River Basin and adjacent Cambridge and that this delta was fed from the north by a subglacial river along the ancient Mystic River Valley, which followed the Aberjona-Fresh Pond Buried Valley (west of the present Mystic Valley) and then the Malden Buried Valley (east of the present Mystic River). It may have been similar to the many subsequent well-preserved deltas along coastal Maine that built out into the marine clay equivalent of the "Boston Blue Clay" and the large one on the northeast side of the center of Concord (Koteff, 1964b). Kaye (1961) also felt that the clay beneath the edge of Beacon Hill was marine, but at least some clay seen by Woodhouse appears to be layered bottomset .or lake deposit. Perhaps after the toe of a delta built southeastward onto the Shawmut Peninsula it was overlapped by clay as marine waters flooded the still depressed crust while the ice retreated farther north. The next ice readvance of the Boston Substage tore into the delta and pushed it up to form Tri.mountain, of which Beacon Hill forms a remnant, and the overriding glacier left a capping of till. The deposit is . probably Early Wisconsin, but its exact age is yet to be determined.
BAROSH & WOODHOUSE, Geology of the Boston Basin, CIVIL ENGINEERING PRACTICE (2011/2012)
Argillite - This is perhaps the most common rock type in the basin. It consists of silt-size particles of quartz, feldspar, seritic, chlorite and kaolinite. Darker argillite contains more sericite and chlorite while the lighter argillite contains more kaolinite (Kaye, 1967). The argillite is typically gray, but purple, purplish brown, tan, and green colors also occur. Kaye (1984) describes some mineralogical variations of argillite which include calcareous argillite interbedded with normal argillite, sideritic argillite, gypsiferous and dolomitic argillite, red argillite, and black argillite. The argillite is typically hard and well indurated, more consolidated than shale but not fissile like shale. According to Kaye (1979), fresh rock tends to break across bedding planes. surfaces (Rahm, 19 62) . Bedding is typically laminated, consisting of alternating 0.1- to 0.2-inch-thick light and dark colored layers. Individual beds generally range in thickness from less than 1/16-inch to 4 inches and can be up to 5 feet thick. The individual beds maintain a rather uniform thickness for many feet or tens of feet (Billings and Tierney, 1964) . Grain size can vary locally to sandy or silty. Sedimentary structures such as slump folds, ripple marks and cross beds are common in this unit. Severe alteration of the argillite (known as kaolinization), which results in a soft, whitish rock or even clay, occurs in random areas of the Boston Basin. Thin-section study shows that the normal minerals of the argillite have been replaced by sericite and kaolinite during the alteration process. 16
Kaolinization is probably the result of thermo-alteration of the argillite, with an igneous intrusion acting as the catalyst
(Kaye, 1967)
CONTRACT DOCUMENTS FOR APPENDIX A SUBSURFACE EXPLORATION GEOTECHNICAL INTERPRETIVE REPORT INTER-ISLAND TUNNEL, CONTRACT PACKAGE NO. 151 MASSACHUSETTS WATER RESOURCES AUTHORITY MWRA CONTRACT NO. 5541 EPA NO. C 259713-18
N o deposits between Carboniferous and Pleistocene in age were found until July, 1905, when a boring made at the Ames Building, on Washington at the head of State street, started at an elevation of 33 feet above mean tide, and was sunk to the unusual depth of 228 feet. A previous test here had reported bed-rock at a depth of 77 feet, directly underearth the drift. Not being satisfied with the
original report, the engineers decided to make a new test, with the result that in the 228-foot boring the following strata were penetrated. According to the system of the Transit Commission, samples were collected from the boring at intervals of every few feet, and are preserved at the office of the Commission, where they were seen by the writer through the courtesy of Mr. Howard A. Carson, chief engineer. Down to 77 feet from the surface the materials are the ordinary sand, gravel, clay and till of the region, shown by their character to he entirely of Pleistocene age. They are mostly rather wet and yield considerable water. The material below 77 feet is dry, and in a previous boring had been called rock and not entered by the drill. All the samples of this bed were seen by the writer and found to consist mostly of a very fine-grained gray to white clay, which became plastic when wet. It varied from very soft and putty-like to nearly as hard as the underlying slate. The material when examined by Dr. W. T. Schaller of the United States Geological Survey was found to consist of Si 0, = 59·18 per cent and (Al,O.,Fe,O.,P,O., Ti02)= 27·11 per cent, thus being a very pure clay. Two masses, one consisting of sandstone, the other of finegrained conglomerate, were found in the clay, and each measured about 1½ feet in thickness. These may be interstratified beds of rock, or, as tl10ir relations and character seem to indicate, they may be bowlders. Difference from Pleistocene clays.-This clay is important for the reason that it is unlike the general type of clay found at Boston. All the Pleistocene clays of the vicinity are of blue-gray to brown or buff colors; this clay is light gray to nearly white. The Pleistocene clays contain numerous bowlders and pebbles composed of all kinds of rock found in New England, but in this clay only two bowlders have been discovered, and these consist of rock only found in the vicinity of Boston, and which forms the bed-rock of the region. The Pleistocene clays are interstratified with glacial deposits; this clay rests on bed-rock and is separated from the overlying Pleistocene clay by a bed of till. This clay is much dryer than the overlying Pleistocene clay. the surface. Some of these fragments are as much as half an inch in diameter. Mr. B. F. Smith, a prominent well driller of Boston, reports a number of wells in the city, in which peculiar soft white deposits were found directly underneath the till. The material is said . to cave badly and sometimes contains much water. To Professor Crosby, who has made extensive investigations regarding the borings of Boston, belongs the credit of being the first to suggest the pre-Pleistocene age of this clay. Professor Crosby writes as follows:* "We may profitably note the fact that some of the borings repol'ting bed-rock in tbe section of Boston south and east of Beacon Hill have clearly not reached any of the hard and thoroughly solid rocks (slate, conglomerate, trap, etc.) such as make up the whole of the bed-rock surface wherever it is exposed in ledges and shallow excavations; but instead the drill has passed from the glacial drift to imperfectly consolidated sands, clays, marls, etc., in part of colors unknown to the drift, and probably rep1·esenting Tertiary strata underlying the drift and filling deep depressions and valleys in the harder formations or true bed-rocks of the region. The artesian well of N. Ward & Co., on Spectacle Island, 560 feet deep, passed through at least 360 feet of unconsolidated material, only part of which could be regarded as glacial drift; and the deep well at the corner of High and Purchase streets in Boston, reported as reaching the bottom of the drift at about 100 feet, is in soft materials comparable with the Tertiary deposits of Martha's Vineyard and Long Island, to a depth of at least 500 feet." Oonclusion8.-Samp1es of .the white clay from the Ames Building boring were compared at the office of the United States Geological Survey with samples of clay collected by Mr. Yeatch from a number of borings on Long Island, New York, and found to ,igree very closely with them in appearance. Mr. Veatch has correlated the Long Island deposits with the Raritan formation of New Jersey. t If this correlation is correct, it is possible that the Boston deposits may be of similar age. This is rendered more probable by the similarity of tlie material in the Boston borings to some of the clays on l\Iartha1s Vineyard, and by the fact that the beds on that island referred to by Professor Crosby as "Tertiary" are said by paleontologists to be in part of Cretaceous age.
original report, the engineers decided to make a new test, with the result that in the 228-foot boring the following strata were penetrated. According to the system of the Transit Commission, samples were collected from the boring at intervals of every few feet, and are preserved at the office of the Commission, where they were seen by the writer through the courtesy of Mr. Howard A. Carson, chief engineer. Down to 77 feet from the surface the materials are the ordinary sand, gravel, clay and till of the region, shown by their character to he entirely of Pleistocene age. They are mostly rather wet and yield considerable water. The material below 77 feet is dry, and in a previous boring had been called rock and not entered by the drill. All the samples of this bed were seen by the writer and found to consist mostly of a very fine-grained gray to white clay, which became plastic when wet. It varied from very soft and putty-like to nearly as hard as the underlying slate. The material when examined by Dr. W. T. Schaller of the United States Geological Survey was found to consist of Si 0, = 59·18 per cent and (Al,O.,Fe,O.,P,O., Ti02)= 27·11 per cent, thus being a very pure clay. Two masses, one consisting of sandstone, the other of finegrained conglomerate, were found in the clay, and each measured about 1½ feet in thickness. These may be interstratified beds of rock, or, as tl10ir relations and character seem to indicate, they may be bowlders. Difference from Pleistocene clays.-This clay is important for the reason that it is unlike the general type of clay found at Boston. All the Pleistocene clays of the vicinity are of blue-gray to brown or buff colors; this clay is light gray to nearly white. The Pleistocene clays contain numerous bowlders and pebbles composed of all kinds of rock found in New England, but in this clay only two bowlders have been discovered, and these consist of rock only found in the vicinity of Boston, and which forms the bed-rock of the region. The Pleistocene clays are interstratified with glacial deposits; this clay rests on bed-rock and is separated from the overlying Pleistocene clay by a bed of till. This clay is much dryer than the overlying Pleistocene clay. the surface. Some of these fragments are as much as half an inch in diameter. Mr. B. F. Smith, a prominent well driller of Boston, reports a number of wells in the city, in which peculiar soft white deposits were found directly underneath the till. The material is said . to cave badly and sometimes contains much water. To Professor Crosby, who has made extensive investigations regarding the borings of Boston, belongs the credit of being the first to suggest the pre-Pleistocene age of this clay. Professor Crosby writes as follows:* "We may profitably note the fact that some of the borings repol'ting bed-rock in tbe section of Boston south and east of Beacon Hill have clearly not reached any of the hard and thoroughly solid rocks (slate, conglomerate, trap, etc.) such as make up the whole of the bed-rock surface wherever it is exposed in ledges and shallow excavations; but instead the drill has passed from the glacial drift to imperfectly consolidated sands, clays, marls, etc., in part of colors unknown to the drift, and probably rep1·esenting Tertiary strata underlying the drift and filling deep depressions and valleys in the harder formations or true bed-rocks of the region. The artesian well of N. Ward & Co., on Spectacle Island, 560 feet deep, passed through at least 360 feet of unconsolidated material, only part of which could be regarded as glacial drift; and the deep well at the corner of High and Purchase streets in Boston, reported as reaching the bottom of the drift at about 100 feet, is in soft materials comparable with the Tertiary deposits of Martha's Vineyard and Long Island, to a depth of at least 500 feet." Oonclusion8.-Samp1es of .the white clay from the Ames Building boring were compared at the office of the United States Geological Survey with samples of clay collected by Mr. Yeatch from a number of borings on Long Island, New York, and found to ,igree very closely with them in appearance. Mr. Veatch has correlated the Long Island deposits with the Raritan formation of New Jersey. t If this correlation is correct, it is possible that the Boston deposits may be of similar age. This is rendered more probable by the similarity of tlie material in the Boston borings to some of the clays on l\Iartha1s Vineyard, and by the fact that the beds on that island referred to by Professor Crosby as "Tertiary" are said by paleontologists to be in part of Cretaceous age.
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Contract #W912DS-12-D-0002, DB01
Marine Geophysical and Geological Investigation,
Boston Harbor, Boston Massachusetts 2015
Reports: Precambrian Age of the Boston Basin: New Evidence from Microfossils
Abstract. A Vendian (Late Proterozoic Z) age has been determined for the Boston Basin by comparison of a microflora from the Cambridge Argillite with other late Precambrian assemblages. The microfossils, which include Bavlinella cf. faveolata, are preserved as petrifactions in pyrite. This age designation for the sedimentary
rocks of the Boston Basin should allow for the reinterpretation of the structure of the basin and its regional correlations.
Lenk, et al., Precambrian Age of the Boston Basin: New Evidence from Microfossils, Science , May 7, 1982, New Series, Vol. 216, No. 4546 (May 7, 1982), pp. 619-620
Abstract. A Vendian (Late Proterozoic Z) age has been determined for the Boston Basin by comparison of a microflora from the Cambridge Argillite with other late Precambrian assemblages. The microfossils, which include Bavlinella cf. faveolata, are preserved as petrifactions in pyrite. This age designation for the sedimentary
rocks of the Boston Basin should allow for the reinterpretation of the structure of the basin and its regional correlations.
Lenk, et al., Precambrian Age of the Boston Basin: New Evidence from Microfossils, Science , May 7, 1982, New Series, Vol. 216, No. 4546 (May 7, 1982), pp. 619-620
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LOWER CAMBRIAN OF EASTERN MASSACHUSETTS: STRATIGRAPHY AND SMALL SHELLY FOSSILS, ED LANDING, J. Paleont., 62(5), 1988, pp. 661-695
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EXPERIMENTAL PRESERVATION OF MUSCLE TISSUE IN QUARTZ SAND AND KAOLINITE, PALAIOS,2019,v.34,437–451
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At the base of the exposure is a clay formation which is usually bluish, but in the lowest parts exposed has a yellowish tinge. Three samples were taken, one about eight feet below the Lower Peat, one about six feet below, and one four feet below. The deposit is homogeneous throughout as regards texture with a median diameter ranging from .001-.003 mm. and with the poor sorting which is characteristic of clays. The fine texture is further emphasized by the high percentages in the clay and colloid groups. The presence of foraminifera indicates that the deposit is marine. There are ten or more species of bottom living forms including: Valvulina conica (Parker and Jones), Bulimina {Desinobulimina) auriculata Bailey, Bulimina aculeata d'Orbigny, Bulimina exilis H. B. Brady, Uvigerina peregrina Cushman var. bradyana Cushman, Elphidium incertum (Williamson), Cassidulina subglobosa H. B. Brady, Cassidulina sp. ?, Cibicides refulgens Montfort and Cibicides pseudoungeriana (Cushman). The first five of these species have not been found off this coast in water shallower than 1 50 meters. There are four pelagic species: Globigerina bulloides d'Orbigny, Globigerina dubia Egger, Globigerina inflaia d'Orbigny and Globorotalia menardii (d'Orbigny). The presence of these together with C. pseudoungeriana and U. peregrina var. bradyana^ which, at the present time, are only found south of Cape Cod, indicates that the water at that time was probably warmer than the present water of Massachusetts Bay.... The foraminifera from the silt show that environmental conditions similar
to those of the present day in Massachusetts Bay may have prevailed. The commonest species are Elphidium incertum (Williamson), Elphidium incertum (Williamson) var. clavatum Cushman and Trochammina subturbinata Cushman. The last species at the present time is recorded on this coast only south of latitude 39 in deep water. The rare occurrence of a few other forms suggest the possibility at least of somewhat warmer water conditions. The presence of oysters from the same formation lends additional support to this supposition.
The environmental conditions under which the clay was deposited were very different from those prevailing today in Massachusetts Bay. As far as the writers are aware, no clay of such fine texture is being deposited in any of the estuaries of the region under present-day marine conditions. Equally fine sediments are, however, found in the deeper parts of the Gulf of Maine and on the continental slope, in some cases covered by silt. In the latter case the foraminifera likewise indicate warmer water conditions.2 A glacial source and a subsequent reworking under marine conditions is suggested The silt, on the other hand, is typical of the deposits now being laid down in the harbors and tidal creeks of Massachusetts Bay. The sediment, brought into suspension by wave action during storms, is carried in by the flooding tide, and a certain amount settles out during each tide.
The Boston area, however, did not have the advantages of nearly complete protection from the sea, but, in so far as the diatomiferous layers are concerned, was always exposed to the influence of salt water. It is this fact that makes difficult any positive statement
as to the nature of the habitat since, although the diatoms may roughly be classified as marine, brackish, and freshwater, there are species that are indifferent to our attempts to classify them in this manner.
Euhalobic to Mesohalobic: Achnanthes brevipes
Mesohalobic: Achnanthes brevipes var. intermedia; Cocconeis scutellum var. parva; Diploneis interrupta; Navicula digito-radiata;
N. peregrina; Nitzschia obtusa; Rhopalodia musculus.
Oligohalobic
(halophile) Eunotia pectinalis
(indifferent) Cocconeis placentula; Cymbella cistula; Epithemia turgida; Gyrosigma acuminatum vars.; Melosira granulata; Nitzschia angustata; Pinnularia major { — P. Dactylus); Rhopalodia gibberula; Surirella ovalis var. ovata
The presence of the two together, even though in relatively small numbers, could be explained if it were possible to postulate that the area, including what is now the Back Bay, had been, at the time, a relatively elevated flat valley land traversed either by tidal brooks or by the Charles River itself; and at this point in the stream the outflowing freshwater mixed with the tidal brackish or salt water. Thus, when floods or exceptionally high tides occurred, the land was inundated, and the diatoms were left behind to become incorporated in the soil or humus layer that was then being formed. Additional evidence for the deposition of this layer above water level is furnished by the matrix, as well as by the fact that roots of a grass or sedge were found in the blue clay below the Amorphous Layer. The matrix is extremely rich in organic material and contains some chitinous parts of insects, fragments of plant tissue that are strongly suggestive of portions of the sheaths or culms of grasses and sedges, and by fragments of fungous hyphae of which some may be recognized as belonging to dematiaceous Fungi Imperfecti, all of which indicate that this layer was laid down above water where it was possible for nearly complete decomposition of the vegetable remains to take place before the process was checked by the action of salt water. Interestingly, Achnanthes intermedia is a species that is rather abundant in the layer, and its presence indicates that other algae also were thriving at the time.
The fluctuations of the grasses and sedges may have been due in part to minor climatic changes, but it is likely that the pronounced maxima, at least, resulted from local ecological changes such as the destruction of forest areas by fire or wind, or the exposure of new areas for colonization by plants along the Charles River estuary. The generic and specific differences in the pollen of grasses and sedges are very small except for their sizes. The dominant sizes of grass grains in the 8|inch and 7 inch levels probably represent sweet vernal grass {Anthoxanthum odoratum, 37 to 46 microns in greatest diameter). 8 The dominant sizes in the four upper levels probably included red fescue {Festuca rubra, 30-32 microns), Kentucky bluegrass {Poa pratensis, 28-32 microns), orchard grass {Dactylis glomerata, 28-36 microns), annual bluegrass {Poa annua, 25-27 microns), and redtop {Agrostis palustris, 25-31 microns). The sedges show less diversity in the sizes of pollen grains, but the graphs exhibit some changes in the dominance of size classes. The pollen profiles of the Lower Peat actually show only three pronounced maxima (in the Gramineae, Cyperaceae, and the Chenopod-Amaranth group); and these may be referred to local ecological changes. The profiles as a whole present a picture of a relatively static vegetation, as the differences between the maxima and the minima of the diagnostic tree genera {Pinus, Picea, Tsuga, Quercus, Fagus, Carya, Ulmus, Nyssa, and Acer) are small. The most prominent change in the vegetation, as shown by
the profiles, occurred between the 5 inch and 3 inch levels, but the coniferous tree-grassland flora shown at the 4 inch level may have resulted from a fire which destroyed the hardwoods. On the other hand, this configuration in the profiles may be due to a destruction of a large share of the pollen of the hardwoods, as it was noted during the counting of the grains from this level that the pollen of the deciduous tree genera was in poor condition.
A NUMBER of bird bones were found in the Amorphous Layer in the L \ trench. These were submitted to Dr. Glover M. Allen1 for identification. He writes, "The bird bones are clearly the trunk bones of a large shorebird, which in the lack of more diagnostic parts, I take to be probably a Greater Yellowlegs.' ,
Dr. William Clapp2 has kindly identified the following mollusks which originated in the building excavation. Unfortunately the provenience of these is unknown. Mulinia lateralis Crepidula plana Vitrinella shimeri Ilyanassa obsoleta Mytilus edulis Mya arenaria Macoma balthica Litorinalla minuta Utriculus caliculata Anomia suriflix Odostomia bisuturalis Gemma gemma Pryamidella nivea Dr. Clapp comments especially upon the presence of Vitrinella shimeri which has a distinctly southern distribution and is an indication of a warm water environment.
Marine borers were found in a majority of the stakes from the Fishweir. All that Dr. William Clapp2 identified were, without question, the remains of Bankia gouldi. It seemed strange that no other borer was discovered. This is the first record of this borer north of Cape Cod. The numbers and large size of the borers indicate that they were probably living under optimum conditions. Bankia gouldi inhabits waters which are considerably warmer than those which are now found in Boston Harbor.
2 Phleger, Fred B., 1939. Foraminifera of Submarine Cores from the Continental Slope. Bull. Geol. Soc. Amer. Vol. 50, pp. 1395-1422.
JOHNSON AND OTHERS'. THE BOYLSTON STREET FISHWEIR; STETSON AND PARKER: THE SEDIMENTS AND FORAMINIFERA
to those of the present day in Massachusetts Bay may have prevailed. The commonest species are Elphidium incertum (Williamson), Elphidium incertum (Williamson) var. clavatum Cushman and Trochammina subturbinata Cushman. The last species at the present time is recorded on this coast only south of latitude 39 in deep water. The rare occurrence of a few other forms suggest the possibility at least of somewhat warmer water conditions. The presence of oysters from the same formation lends additional support to this supposition.
The environmental conditions under which the clay was deposited were very different from those prevailing today in Massachusetts Bay. As far as the writers are aware, no clay of such fine texture is being deposited in any of the estuaries of the region under present-day marine conditions. Equally fine sediments are, however, found in the deeper parts of the Gulf of Maine and on the continental slope, in some cases covered by silt. In the latter case the foraminifera likewise indicate warmer water conditions.2 A glacial source and a subsequent reworking under marine conditions is suggested The silt, on the other hand, is typical of the deposits now being laid down in the harbors and tidal creeks of Massachusetts Bay. The sediment, brought into suspension by wave action during storms, is carried in by the flooding tide, and a certain amount settles out during each tide.
The Boston area, however, did not have the advantages of nearly complete protection from the sea, but, in so far as the diatomiferous layers are concerned, was always exposed to the influence of salt water. It is this fact that makes difficult any positive statement
as to the nature of the habitat since, although the diatoms may roughly be classified as marine, brackish, and freshwater, there are species that are indifferent to our attempts to classify them in this manner.
Euhalobic to Mesohalobic: Achnanthes brevipes
Mesohalobic: Achnanthes brevipes var. intermedia; Cocconeis scutellum var. parva; Diploneis interrupta; Navicula digito-radiata;
N. peregrina; Nitzschia obtusa; Rhopalodia musculus.
Oligohalobic
(halophile) Eunotia pectinalis
(indifferent) Cocconeis placentula; Cymbella cistula; Epithemia turgida; Gyrosigma acuminatum vars.; Melosira granulata; Nitzschia angustata; Pinnularia major { — P. Dactylus); Rhopalodia gibberula; Surirella ovalis var. ovata
The presence of the two together, even though in relatively small numbers, could be explained if it were possible to postulate that the area, including what is now the Back Bay, had been, at the time, a relatively elevated flat valley land traversed either by tidal brooks or by the Charles River itself; and at this point in the stream the outflowing freshwater mixed with the tidal brackish or salt water. Thus, when floods or exceptionally high tides occurred, the land was inundated, and the diatoms were left behind to become incorporated in the soil or humus layer that was then being formed. Additional evidence for the deposition of this layer above water level is furnished by the matrix, as well as by the fact that roots of a grass or sedge were found in the blue clay below the Amorphous Layer. The matrix is extremely rich in organic material and contains some chitinous parts of insects, fragments of plant tissue that are strongly suggestive of portions of the sheaths or culms of grasses and sedges, and by fragments of fungous hyphae of which some may be recognized as belonging to dematiaceous Fungi Imperfecti, all of which indicate that this layer was laid down above water where it was possible for nearly complete decomposition of the vegetable remains to take place before the process was checked by the action of salt water. Interestingly, Achnanthes intermedia is a species that is rather abundant in the layer, and its presence indicates that other algae also were thriving at the time.
The fluctuations of the grasses and sedges may have been due in part to minor climatic changes, but it is likely that the pronounced maxima, at least, resulted from local ecological changes such as the destruction of forest areas by fire or wind, or the exposure of new areas for colonization by plants along the Charles River estuary. The generic and specific differences in the pollen of grasses and sedges are very small except for their sizes. The dominant sizes of grass grains in the 8|inch and 7 inch levels probably represent sweet vernal grass {Anthoxanthum odoratum, 37 to 46 microns in greatest diameter). 8 The dominant sizes in the four upper levels probably included red fescue {Festuca rubra, 30-32 microns), Kentucky bluegrass {Poa pratensis, 28-32 microns), orchard grass {Dactylis glomerata, 28-36 microns), annual bluegrass {Poa annua, 25-27 microns), and redtop {Agrostis palustris, 25-31 microns). The sedges show less diversity in the sizes of pollen grains, but the graphs exhibit some changes in the dominance of size classes. The pollen profiles of the Lower Peat actually show only three pronounced maxima (in the Gramineae, Cyperaceae, and the Chenopod-Amaranth group); and these may be referred to local ecological changes. The profiles as a whole present a picture of a relatively static vegetation, as the differences between the maxima and the minima of the diagnostic tree genera {Pinus, Picea, Tsuga, Quercus, Fagus, Carya, Ulmus, Nyssa, and Acer) are small. The most prominent change in the vegetation, as shown by
the profiles, occurred between the 5 inch and 3 inch levels, but the coniferous tree-grassland flora shown at the 4 inch level may have resulted from a fire which destroyed the hardwoods. On the other hand, this configuration in the profiles may be due to a destruction of a large share of the pollen of the hardwoods, as it was noted during the counting of the grains from this level that the pollen of the deciduous tree genera was in poor condition.
A NUMBER of bird bones were found in the Amorphous Layer in the L \ trench. These were submitted to Dr. Glover M. Allen1 for identification. He writes, "The bird bones are clearly the trunk bones of a large shorebird, which in the lack of more diagnostic parts, I take to be probably a Greater Yellowlegs.' ,
Dr. William Clapp2 has kindly identified the following mollusks which originated in the building excavation. Unfortunately the provenience of these is unknown. Mulinia lateralis Crepidula plana Vitrinella shimeri Ilyanassa obsoleta Mytilus edulis Mya arenaria Macoma balthica Litorinalla minuta Utriculus caliculata Anomia suriflix Odostomia bisuturalis Gemma gemma Pryamidella nivea Dr. Clapp comments especially upon the presence of Vitrinella shimeri which has a distinctly southern distribution and is an indication of a warm water environment.
Marine borers were found in a majority of the stakes from the Fishweir. All that Dr. William Clapp2 identified were, without question, the remains of Bankia gouldi. It seemed strange that no other borer was discovered. This is the first record of this borer north of Cape Cod. The numbers and large size of the borers indicate that they were probably living under optimum conditions. Bankia gouldi inhabits waters which are considerably warmer than those which are now found in Boston Harbor.
2 Phleger, Fred B., 1939. Foraminifera of Submarine Cores from the Continental Slope. Bull. Geol. Soc. Amer. Vol. 50, pp. 1395-1422.
JOHNSON AND OTHERS'. THE BOYLSTON STREET FISHWEIR; STETSON AND PARKER: THE SEDIMENTS AND FORAMINIFERA
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Diabse Dikes
"Dikes of the Boston district. Crosby describes the Triassic diabase dikes of the lower Neponset Valley as follows: * The diabase dikes * * * of the Boston Basin generally, are referable to two distinct series distinct in age, trend, and lithologic character. We may properly emphasize the chronologic distinction as of greatest geologic significance, by designating these two series provisionally the Carboniferous and the Triassic. Evidently the diabase dikes are not related in origin or composition to any of the other igneous rocks of the district, and in size, regularity, and continuity the two systems are essentially similar and normal. * * * The * * * dikes of this series adhere very closely to a north-south trend and vertical attitude, a hade of even a few degrees being very unusual. Their relation to the general geological structure of the region is distinctly transverse, and evidently they date from a period of gravity faulting without folding, such as the Triassic is known to have been. Transverse columnar jointing is commonly well developed. The greenstone alteration is wanting, and the rock yields readily to kaolinization, the tendency to pass by spheroidal weathering to a rusty brown earth being a marked feature of this! diabase."
GEOLOGY OF MASSACHUSETTS AND RHODE ISLAND (1917), https://pubs.usgs.gov/bul/0597/report.pdf
GEOLOGY OF MASSACHUSETTS AND RHODE ISLAND (1917), https://pubs.usgs.gov/bul/0597/report.pdf
"Boston terrane dikes have much higher average TiO2 and K2O contents and lower average SiO2 and MgO contents (for quartz and olive normative dikes, respectively).
Socci & Smith, Mafic dikes of the Avalon Boston terrane, Geology of the composite Avalon Terrane of southern New England (1990).
Socci & Smith, Mafic dikes of the Avalon Boston terrane, Geology of the composite Avalon Terrane of southern New England (1990).
DEPARTMENT OF THE INTERIOR U.S. GEOLOGICAL SURVEY Radiometric Ages on File In the Radiometric Age Data Bank (RADB) of Rocks from Massachusetts by Robert E. Zartman and Richard F. Marvin Open-File Report 87-170
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Dedham-Medford Zone Plutonic Rocks (Granite)
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Organic sediment (silt, Peat, fossils)
It is important to note that assessment/investigation activities conducted by KEY for a real estate transaction discovered soils to be mostly fill overlaying peat at the Property. Therefore, KEY believes the Property was once a wetland that was filled. A short review of other sites in the area of the Property also indicates the same. The fill at the Property consists of mostly urban gray (i.e., urban soil typically found in the Boston areas) with coal ash (i.e., artifact of habitation and is due to the widespread practice of emptying
fireplaces, stoves, boilers, garage, etc. in urban areas over the past several hundred years) and some solid waste such as glass, wood, metal, tires, etc (i.e., also related to artifact of habitation over the past several hundred years). See photographs in Appendix A that show some of the soils at the Property. However, the source of the urban fill is unknown.
Class B-1 Response Action Outcome Statement, Commercial/Industrial Property, 25 Chesterton Street, Roxbury. MA 02119 (Feb. 2005).
fireplaces, stoves, boilers, garage, etc. in urban areas over the past several hundred years) and some solid waste such as glass, wood, metal, tires, etc (i.e., also related to artifact of habitation over the past several hundred years). See photographs in Appendix A that show some of the soils at the Property. However, the source of the urban fill is unknown.
Class B-1 Response Action Outcome Statement, Commercial/Industrial Property, 25 Chesterton Street, Roxbury. MA 02119 (Feb. 2005).
"Organic Sediment. The organic silt and clay, and peat deposits that were laid down throughout much of the lower lying areas surrounding the Shawmut Peninsula following glaciation vary greatly in overall thickness and content, but are generally from 1.5 to 7.5 meters (5 to 25 feet) thick. In those filled-in areas of the Back Ba:» the layer has been compressed considerably due to the weight of the fill. Marsh gas that results from the decomposing organic matter is sometimes encountered in excavations."
Barosh & Woodhouse, A City Upon a Hill: Geology of the City of Boston & Surrounding Area, Geotechnical Factors in Boston, Civil Engineering Practice, Vol. 26-27 (2011/2012).
Barosh & Woodhouse, A City Upon a Hill: Geology of the City of Boston & Surrounding Area, Geotechnical Factors in Boston, Civil Engineering Practice, Vol. 26-27 (2011/2012).
Organic Silt & Peat. "An organic deposit consisting of both fresh water and salt water peat, and organic silt and clay, is found in the present and former tidal flats, estuaries and coastal lowlands that flourished along the margins of what was then the Back Bay and the Mystic River, that were at that time more restricted than today. These marsh and tidal deposits gradually extended onshore and thickened as the sea level rose following the Lexington Substage... The deposit ranges from a feather edge up to a total thickness of 12 meters (40 feet) in the channels. The organic silt usually overlies marine clay, but silt also is found above outwash sand and, in some cases, till. A recent saltwater or brackish estuary peat, usually less than 1.5 meters (5 feet) thick, is found locally on top of the organic silt, as well as the extensive fill placed around the city. The thickness and nature of the organic deposit is determined from the many test borings made for the numerous structures built on, or over, the wetlands and from the many foundation caissons that were augured through it and belled at the top of the underlying marine clay... Dark-gray to black organic estuarine and marine silt with low plasticity and organic clay and fine sand were deposited on top of a basal fresh water peat layer and usually beneath a capping peat... The organic sediment, which smells of hydrogen sulfide (H2S); also contains methane, and is highly fossiliferous with plant fibers and traces of wood as well as remnants of oyster banks predominantly composed of whole or parts of shells belonging to the species Venus mercenarius. Some oyster shells reach 25 centimeters (10 inches) in length and 1 kilogram (2.25 pounds) in weight (Boston Transit Commission, 1913). The stratum rests on the marine clay that generally has a thin, 0 to 1 meter (0 to 3 foot) cover of rusty upper outwash sand that supports tree stumps locally...Dark gray to black generally fibrous peat, which ranges in thick-ness from less than 0.3 to 1.5 meters (1 to 5 feet), is made up of decaying plants and wood formed over the clay and outwash and some times interfingers with dark silt and silty sand of the channels in a complex manner.... The continued flooding of the estuary resulted in the peat being rapidly buried by bay mud that was rich in marine life."
Barosh & Woodhouse, A City Upon a Hill: Geology of the City of Boston & Surrounding Area, Geology of the Boston Basin, Civil Engineering Practice, Vol. 26-27 (2011/2012).
Barosh & Woodhouse, A City Upon a Hill: Geology of the City of Boston & Surrounding Area, Geology of the Boston Basin, Civil Engineering Practice, Vol. 26-27 (2011/2012).
"Marine mollusks, starfish, foraminifera, sponge spicules, echinoid spines and some diatoms occur in the clay at West Lynn at the north edge of the Boston Basin (Sears, 1905; Nichols, 1946; Kaye, 1961). Mollusks, barnacles, foraminifera and ostracodes also are found nearby in clay in Lynn, Revere and Winthrop, and have yielded a mean radiocarbon age of 14,000 years ago (Colgan & Rosen, 2001). Some sparse foraminifera occur in the Back Bay (Stetson & Parker, 1942), along with a few barnacles such as Balanus hameri (Ascanius). The latter yields radiocarbon dates that range from 13,230 (±320) to 14,420 (±300) years ago and average about 14,000 years ~go (Kaye & Barghoom, 1964; Kaye, 1976a). However, locally the clay at Lynn and in other pits bordering Boston, as well as in the Back Bay, is devoid of diatoms and foraminifera (Conger, 1949; Phleger, 1949). Beaver-cut twigs and peat embedded in the upper part of the clay in the Boston Common yield two dates that average 12,200 years ago (Kaye, 1972 & 1976a). The clay also is older than the Lexington outwash sand of circa 12,000 ago that overlies it. The general lack of fossils, especially the microfossils, probably reflects the low salinity, excessive turbidity of the water causing diminishing light, and rapid deposition at the mouth of a major outwash river (Phleger, 1949; Conger, 1949). The clay thus appears to represent a Woodfordian, early Late Wisconsin, marine inundation, which is indicated to have occurred under cold conditions by the mollusks. The most abundant shell found by Sears (1905) was Yoldia arctica (Portlandia Arctica) which now lives in the Arctic at depths of 1 to 60 meters (3 to 197 feet). The spruce pollen that is very abundant in the upper 3 meters (10 feet) of the clay at West Lynn also supports a cold or periglacial depositional environment during its deposition (E.B. Leopold, in Kaye, 1961). The correlation by Sears (1905) with the Leda Clay is a misnomer since the Leda is the quick (sensitive) clay found in certain areas of Canada. The Presumpscot Clay in Maine, however, has a much greater clay particle content than the Boston clay (i.e., less silt), and has been leached of its depositional high salt and is unrelated. The Boston marine clay, however, does correlate northward of the basin with some older clay that has been grouped with the generally younger Presumpscot Formation, also known as the Maine "Blue Clay" that formed after the later Lexington Substage."
Barosh & Woodhouse, A City Upon a Hill: Geology of the City of Boston & Surrounding Area, Geology of the Boston Basin, Civil Engineering Practice, Vol. 26-27 (2011/2012).
Barosh & Woodhouse, A City Upon a Hill: Geology of the City of Boston & Surrounding Area, Geology of the Boston Basin, Civil Engineering Practice, Vol. 26-27 (2011/2012).
"At the present time, the mud line varies from El. to El. -20 at the proposed location of the culvert while the depth of organic silt and fill is between 5 and 30 feet. Underlying the organic silt is a deep stratum overlay varying from stiff yellow clay toward the top surface to soft blue clay at greater depth. Thickness of the clay stratum varies between 40 and 100 ft. Below the clay are thin layers of pervious sands and glacial till, (hardpan) over a blue slaty shale.
The 1950 report by the Port of Boston Authority proposed that fill for the channel be obtained by hydraulic means from the Old Harbor area. Since the size of the area to be filled has been greatly reduced, fill to be placed to Dorchester Avenue only, and since considerable filling has occurred since 1950, it is believed that continued filling by conventional methods is indicated. It is estimated that 700,000 cu. yds. of fill are required to bring the Channel to approximately Elevation 10. Few limitations need to be placed on the type of earth fill used in the Channel once the culvert is constructed.
Foundations for all but the lightest temporary structures which may be constructed in the future will need to be founded on piles where earth fill overlies organic silt. It is considered important to exclude rock, boulders, granite blocks, brick walls, concrete and other hard materials from fill in order to minimize future pile driving and excavation problems. It will be desirable to place a minimum of 2 to 3 ft. of granular soil over the filled area, especially where organic soils are dumped, to provide a sanitary, stable, free draining surface. A careful survey of soil conditions throughout the area prior filling combined with restricted areas for various types of fill may be a promising way of providing a few desirable building sites. For example, if compacted granular fill were placed in areas where little or no organic silt and miscellaneous fill occurs, permanent one and two story structures could probably be built without piling.
Over a period of years the fill placed in the Channel is expected to subside as a result of compression from these sources: 1. Compression of fill material itself. 2. Compression of undisturbed soft organic silt. 3. Compression of deep stratum of "Boston blue clay".
Magnitudes of settlements estimated below are based largely on studies for the Dover Street embankment and from recent settlement observations on Expressway fills near the Fort Point Channel. Compression of earth fill will vary considerably, dependent largely on the type of fill. Where appreciable quantities of organic silt have already been placed, compression could exceed 1 ft. However, where granular fill is used, settlement will be small and will occur primarily during filling. Soft organic silt which has accumulated over a long period of time largely from natural causes will compress from 5 to 10 percent of its thickness under the weight of 20 ft. of fill, (to El. + 10.) Somewhat more than half this compression will occur during filling and within a year thereafter. Settlement of the area from compression in the underlying clay stratum will be small by comparison. Furthermore, the compress will be relatively uniform with gradual transitions as the thickness of clay and depth of fill vary. Maximum compression is not expected to exceed 8 inches over a 20 year period of which half will occur in 3 to 4 years. For purposes of estimating the quantity of fill required to bring the Channel to El. 10.0, an average compression of 1 ft. has been assumed for the area to be filled. Total settlement of the Fort Point Channel area following filling will be relatively non-uniform varying from 6 inches to over 2 ft."
Fort Point Channel and South Bay, Report of the Special Commission Relative to Filling and Improving South Bay and Part of Fort Point Channel in the City of Boston, Senate — No. 498 (1959).
The 1950 report by the Port of Boston Authority proposed that fill for the channel be obtained by hydraulic means from the Old Harbor area. Since the size of the area to be filled has been greatly reduced, fill to be placed to Dorchester Avenue only, and since considerable filling has occurred since 1950, it is believed that continued filling by conventional methods is indicated. It is estimated that 700,000 cu. yds. of fill are required to bring the Channel to approximately Elevation 10. Few limitations need to be placed on the type of earth fill used in the Channel once the culvert is constructed.
Foundations for all but the lightest temporary structures which may be constructed in the future will need to be founded on piles where earth fill overlies organic silt. It is considered important to exclude rock, boulders, granite blocks, brick walls, concrete and other hard materials from fill in order to minimize future pile driving and excavation problems. It will be desirable to place a minimum of 2 to 3 ft. of granular soil over the filled area, especially where organic soils are dumped, to provide a sanitary, stable, free draining surface. A careful survey of soil conditions throughout the area prior filling combined with restricted areas for various types of fill may be a promising way of providing a few desirable building sites. For example, if compacted granular fill were placed in areas where little or no organic silt and miscellaneous fill occurs, permanent one and two story structures could probably be built without piling.
Over a period of years the fill placed in the Channel is expected to subside as a result of compression from these sources: 1. Compression of fill material itself. 2. Compression of undisturbed soft organic silt. 3. Compression of deep stratum of "Boston blue clay".
Magnitudes of settlements estimated below are based largely on studies for the Dover Street embankment and from recent settlement observations on Expressway fills near the Fort Point Channel. Compression of earth fill will vary considerably, dependent largely on the type of fill. Where appreciable quantities of organic silt have already been placed, compression could exceed 1 ft. However, where granular fill is used, settlement will be small and will occur primarily during filling. Soft organic silt which has accumulated over a long period of time largely from natural causes will compress from 5 to 10 percent of its thickness under the weight of 20 ft. of fill, (to El. + 10.) Somewhat more than half this compression will occur during filling and within a year thereafter. Settlement of the area from compression in the underlying clay stratum will be small by comparison. Furthermore, the compress will be relatively uniform with gradual transitions as the thickness of clay and depth of fill vary. Maximum compression is not expected to exceed 8 inches over a 20 year period of which half will occur in 3 to 4 years. For purposes of estimating the quantity of fill required to bring the Channel to El. 10.0, an average compression of 1 ft. has been assumed for the area to be filled. Total settlement of the Fort Point Channel area following filling will be relatively non-uniform varying from 6 inches to over 2 ft."
Fort Point Channel and South Bay, Report of the Special Commission Relative to Filling and Improving South Bay and Part of Fort Point Channel in the City of Boston, Senate — No. 498 (1959).
The factors next in importance to glaciation and the kind of surface rock in forming deposits of peat are wave and stream action and coastal subsidence. Many peat deposits of salt-marsh and freshwater origin are seen in drowned valleys, where the coast has subsided and landlocked lagoons or deltas have been formed, and in flat, imperfectly drained areas farther inland. In some places saltmarsh peat overlies peat of fresh-water origin, indicating coastal subsidence.
One of the chief substances formed by plants during their growth is cellulose (C72H120060 ), which consists of carbon, hydrogen, and oxygen. These constituents are absorbed by the leaves from the atmosphere and by the roots from the soil. Cellulose, because of its complex composition, is an unstable compound and when attacked by fungi and bacteria decomposes rapidly. If at the end of the
growing season the plant debris falls upon drained soil it is vigorously attacked by these microorganisms, and the carbon and hydrogen of the cellulose unite with the atmospheric oxygen and with each other, forming carbon dioxide, water, and marsh gas. In other words, if oxidation is unhampered, the organic matter will disappear in a relatively short time. If, however, the plant matter falls into water or upon soil saturated with moisture, it undergoes a change different from the decay suffered by exposed vegetation. The atmospheric oxygen is largely excluded, and as the activity of fungi and bacteria is controlled by the supply of air, upon which they depend for their existence, decay is slow, the plant debris becomes buried, and a large proportion of the fixed carbon is retained. The salient features in the production of peat (C62H72024 ) from cellulose (C72H120O60 ) are the elimination of hydrogen and oxygen as water (H20) and of carbon and oxygen as carbon dioxide (C02 ) and the generation of methane (CH4 ). This is the process of carbonization.
If the surface conditions are unchanged, carbonization is largely arrested with the formation of peat, and the accumulation of organic matter may exist indefinitely as peat, unless the land is drained and decomposition begins again or unless the peat is deeply buried beneath superposed deposits, generally muds, sands, limestone, and other sedimentary beds, and subjected to pressure, accompanied by heat. Lignite, bituminous coal, anthracite, and graphite are succeeding stages in the process of carbonization of the buried vegetable debris. Most coals were once peats; most coal fields were formerly swamps, and the formation of peat in the bogs and swamps of this country to-day is an example of the first stage in the process of coal formation.
Salt-marsh peat. Salt-marsh peat, though formed in practically the same manner as fresh-water peat, differs from it somewhat in character. Few seed plants tolerate salt water, and the number of plant varieties found in salt marshes is therefore rather small. The most common types are salt-marsh grasses, rushes, and sedges. The entire vegetation of some of the New England salt marshes consists of one dominant and two or three subordinate species. In some of the coastal marshes of New England salt-marsh peat is underlain by peat of fresh-water origin, indicating the subsidence of that part of the Atlantic coast.
Native peat consists of partly decayed vegetable matter, inorganic minerals, and water in varying proportions, the usual ratio being 10 per cent of solid matter to 90 per cent of water. In specific gravity it ranges from 0.1 to 1.06 and in weight from 7 to 65 pounds per cubic foot. Aside from its high water content, peat is extremely variable, and scarcely any two deposits contain material that is exactly similar in physical properties. This diversity is due to many causes, the most notable of which are the variety of plants from which the peat was formed, and differences in climate, in the ages of the deposits, in water level, and in the quantity of sediment deposited during the accumulation of the peat.
Peat ranges in color from light yellow through various shades of brown to jet black, the color representing in a measure the degree of decomposition. Peat that is new or that has been well protected from the air is usually light yellow or brown; well-decomposed humified peat is jet black. Green peat, produced by the decomposition of algae and related aquatic plants, is found at the bottom of some filled-basin deposits.
The affinity of peat for moisture is proverbial. In fact, as previously explained, peat can not form unless the plant debris is saturated or covered with water. The peat in most deposits contains about 90 per cent of moisture, which is held both mechanically and chemically in the plant cells and intercellular spaces. In other words, a short ton of typical raw peat consists of about 200 pounds of solid matter to 1,800 pounds of water.
The affinity of peat for moisture is proverbial. In fact, as previously explained, peat can not form unless the plant debris is saturated or covered with water. A detailed study of the chemical properties of more than 500 samples of peat taken from deposits in different parts of the peat regions of this country leads to the following conclusions: Peat consists of carbon, hydrogen, oxygen, and relatively small quantities of nitrogen.
The ash in native peat, which renders it more or less impure, constitutes from 3 to 30 per cent of its dry weight and is traceable either to the plant cells or to the mineral matter carried in suspension or solution by the water in which the peat formed. The inorganic impurities of peat consist of silica, alumina, iron oxide, magnesia, lime, soda, potash, sulphuric acid, chlorine, and phosphoric acid. If the ash content exceeds 8 per cent, it is due to the mineral matter in the water that covered the peat during formation, and it usually consists of silica in the form of sand or silt or of alumina and silica in the form of clay. Mineral constituents other than silica and alumina in excess of 8 per cent are not common in peat and where found may be traced to the local ground and surface waters. The ash content of the best peats in the United States ranges from about 6 to 12 per cent, though many of the largest deposits in the Great Lakes area contain 15 per cent.
Massachusetts possesses a larger quantity of valuable peat than any other New England State except Maine. Aside from the salt marshes, which were formed by coastal subsidence and wave action, the peat deposits of Massachusetts originated in glacial depressions, Salt marshes near Revere Beach, adjoining the mouth of Saugus and Pines rivers (see fig. 23), are several square miles in area and contain muck about 10 feet in average depth. The surface of these deposits, which were formed from salt-marsh grasses, lies at about high-tide level. The dominant vegetation consists of saltmarsh grasses. The muck is very fibrous and contains a large proportion of clay and silt.
THE OCCURRENCE AND USES OP PEAT IN THE UNITED STATES BY E. K. SOPER AND C. C. OSBON, UNITED STATES GEOLOGICAL SURVEY Bulletin 728 (1922).
Marine Clay / Boston Blue Clay
"The outline of the Shawmut peninsular begins to emerge via the formation of a ridge of this marine clay through processes of both deposition and erosion. The Shawmut Neck was a narrow strip of land that formed the terminus of the Shawmut Peninsula. It was bordered on the west by the Roxbury Tidal Flats and on the east by South Boston Bay and was barely passable at low tide, making Boston essentially an island. The Neck ran along Orange Street (what is now Washington Street)."
Barosh & Woodhouse, A City Upon a Hill: Geology of the City of Boston & Surrounding Area, Geology of the Boston Basin, Civil Engineering Practice, Vol. 26-27 (2011/2012).
Barosh & Woodhouse, A City Upon a Hill: Geology of the City of Boston & Surrounding Area, Geology of the Boston Basin, Civil Engineering Practice, Vol. 26-27 (2011/2012).
Marine Clay. "Fine sediment from an increasingly more distant ice front, coupled with a rising sea level that inundated much of the low-lying areas, produced a thick blanket of marine clay that smoothed out most of the relief across the underlying units. The infilling of topographic lows and channels around islands formed by the higher drumlins is seen in many cross-sections constructed from borehole data and offshore seismic profiles. The marine clay is found in broad channels under much of Massachusetts Bay, Boston Harbor and the rivers and surrounding lowlands that extend inland from the harbor. These areas include the old Mill Pond, Charles and Mystic rivers, the Back Bay and other former estuarine marshlands that are now filled. The marine clay deposit is commonly referred to as the "Boston Blue Clay" and is found throughout the low areas of Boston. The clay extends eastward beyond the harbor. It was mistakenly called the Leda Clay by Sears (1905) who observed it on the north side of the basin and northward, where shells confirmed its marine origin. The clay laps up onto the till of Beacon Hill and the drumlins of Charlestown. The outline of the Shawmut peninsular begins to emerge via the formation of a ridge of this marine clay through processes of both deposition and erosion.
The Shawmut Neck was a narrow strip of land that formed the terminus of the Shawmut Peninsula. It was bordered on the west by the Roxbury Tidal Flats and on the east by South Boston Bay and was barely passable at low tide, making Boston essentially an island. The Neck ran along Orange Street (what is now Washington Street). Yellow clay, possibly gladomarine, on the order of 3 meters (10 feet) thick was encountered during the drilling for the Wang Center on Tremont Street, which would represent the extreme western edge of the neck. Drilling on Washington Street between West Oak Street and Kneeland Street for a housing complex also found clay but only the thinner oxidized yellow crust (the marine day) commonly found around the Boston area. The day is typically light greenish-gray to medium-gray, rather than blue, and usually weathers yellowish in its upper portion. Blue color is seen in the clay under the Boston Company Building and Millennium Place, where deformation of the day was also observed. Throughout most of its thickness the clay is soft and plastic, but less so in the weathered zone and where it contains partings of fine sand, silt or sand lenses. Analyses show that the predominant day mineral is illite.
The clay is only slightly sensitive, with a natural water content of about 30 percent, but it also can be found in a sensitive state in certain areas, such as at Alewife Station. Where redeposited, the clay exhibits anisotropy. The contained lenses and layers of silt and sand increase with depth and in some places the clay grades downward into well stratified sand that becomes coarser with depth and finally grades into gravel (see Figure 3-98). Scattered through the clay are a few pebbles, cobbles and boulders (iceberg drop stones), which may reach several tons in weight. A very large erratic boulder is incorporated into its base in the Fort Point Channel at the MBTA Silver Line crossing (Leifer, 2006). The clay and interbedded silt and sand grade up the valley of the Charles River into littoral sand and, thence, into outwash consisting of sand and gravel deposited by rivers. Because the topographic trough provided by the Boston Basin was a major drainage way for glacial melt water from the west, Boston became the apex of a large, submarine clay delta of outwash origin. Besides the low tidal areas around the Shawmut Peninsula, the clay can also be found in the Squantum area of Quincy to the south; in Charlestown, Cambridge and Somerville to the north and west; the Fenway; Roxbury, South Boston and Dorchester to the south; and East Boston to the east.
The top 1 to 5 meters (3 to 16 feet) of the clay stratum became generally oxidized during a period when it was exposed; much of this area is currently below sea level in Boston Harbor. Borings indicate that where overlain by the Lexington outwash it is oxidized to a depth of I meter (3 feet) and to a maximum depth of 3 meters (10 feet) where exposed on the surface around the Back Bay and Cambridge. A stiff, yellow crust of subaerial origin causing oxidation was formed by the desiccation and resulting over-consolidation that has taken place. Significant over-consolidation is generally limited to the upper 5 meters (16.5 feet), although less over-consolidation can be found to depths of 10 to 12 meters (33 to 39 feet). At depths lower than 18 meters (60 feet), the clay becomes softer, gray and essentially normally consolidated. Where the oxidized clay was overlain by substantial organic matter (such as peat), a chemical reaction involving iron reduction- i.e., ferric iron, Fe+3, is changed to ferrous iron, Fe+2 by bacterial action (Kusel et al., 2008) - has created an upper zone of softened blue clay up to 2 meters (6.5 feet) thick. This zone, representing the top of the clay stratum, may also be silty or sandy and somewhat water bearing. The upper 2 to 5 meters (6.5 to 16 feet) of the clay is structurally disturbed and may be broken, folded and badly contorted in places in the Back Bay and parts of Boston Harbor. The upper clay also is seen in excavations to have prismatic structure or cubical jointing and fissuring, which appears to be evidence of having been frozen, probably at the time of the overlying upper outwash.
The clay may overlie any of the earlier surficial deposits or bedrock because of preceding erosion, and it is normally overlain by the Lexington outwash, Holocene organic deposits or fill. The unit is usually well-bedded with thin horizontal layers. However, both offshore and onshore profiles show it locally conforms to, or is draped over, the surface of the basement on which it was deposited, which imparts a folded appearance to the clay. There are deep funnel-shaped "downfolds" on the order of 100 to 200 meters (330 to 660 feet) across The topographic trough provided by the Boston Basin was a major drainageway for glacial melt water from the west and Boston became the apex of a large, submarine clay 'delta of outwash origin. The marine clay, because it often contains more silt than clay, has lower plastic and liquid limits of its claysized material than would mineral clay. The marine clay represents a high percentage of fine-grained rock flour component of outwash that was carried farther and deposited in coastal marine waters. Miller (2010) considers a significant amount is reworked clay eroded during the Lexington Substage from the older day-rich glaciomarine deposit based on evidence that indicates that the deposit was exposed at places during the time of Lexington day deposition. The occasional glacial gravel to boulder clasts in the clay are apparently iceberg dropstones, perhaps rafted when the ice front was close to Boston. The day is thickest in the lower valley of the Charles River and Boston Harbor, where it wrapped around Beacon Hill, and thins under Massachusetts Bay to the north, east and south. In the Back Bay, as well as along marginal waterfront areas, the clay is typically 15 to 38 meters (50 to 125 feet) thick.
Up the Charles River at the Mount Auburn Cemetery the clay is 25 meters (81 feet) thick near the present river and eroded to zero at
short distances to the north beneath the upper outwash. Even greater thicknesses - up to 60 meters (200 feet) - are found west of Massachusetts Avenue and in Cambridge, where parts of Harvard University and MIT rest on it. Known clay thicknesses, as great as 75 meters (246 feet), occur in the Charles River area. The top of the clay was deeply eroded by the ancestral Charles River and its tributaries during a drop in sea level associated with the Lexington Substage subsequent to 12,600 years ago and the contoured surface (Judson, 1949) shows a well developed stream pattern. The main channel is closely aligned with the present Charles River, a second channel enters from the north between Charlestown and East Boston, and a third exists beneath Fort Point Channel. The surface of the clay is now generally below sea level around the Shawmut Peninsula and is estimated to descend eastward to nearly elevation -60 meters (-200 feet) MSL by Judson (1949). Judson (1949) also reported it rising to about elevation 9 meters (30 feet) MSL on the north and east sides of Beacon Hill. Kaye (1961) only found it reaching to thickness of about 4.6 to 7.6 meters (15 to 2~ feet) over the upper till on the south side, which would be a Boston area local limit since the upper limit of the marine clay varies across New England because the post-glacial rebound has raised the land progressively higher to the north. At the northwest edge of the Boston area, clay has been found as high as elevation 22 meters (72 feet) MSL (Woodworth, 1897; Chute, 1959; Colgan & Rosen, 2001), but these deposits are apparently disturbed or from local ponding. I.B. Crosby (1934) found the highest known marine glacial clay in the environs of Boston (except for small deposits that obviously. formed in glacial lakes) at elevation 7.6 or 10.7 meters (25 or 35 feet) MSL."
Barosh & Woodhouse, A City Upon a Hill: Geology of the City of Boston & Surrounding Area, Geology of the Boston Basin, Civil Engineering Practice, Vol. 26-27 (2011/2012).
The Shawmut Neck was a narrow strip of land that formed the terminus of the Shawmut Peninsula. It was bordered on the west by the Roxbury Tidal Flats and on the east by South Boston Bay and was barely passable at low tide, making Boston essentially an island. The Neck ran along Orange Street (what is now Washington Street). Yellow clay, possibly gladomarine, on the order of 3 meters (10 feet) thick was encountered during the drilling for the Wang Center on Tremont Street, which would represent the extreme western edge of the neck. Drilling on Washington Street between West Oak Street and Kneeland Street for a housing complex also found clay but only the thinner oxidized yellow crust (the marine day) commonly found around the Boston area. The day is typically light greenish-gray to medium-gray, rather than blue, and usually weathers yellowish in its upper portion. Blue color is seen in the clay under the Boston Company Building and Millennium Place, where deformation of the day was also observed. Throughout most of its thickness the clay is soft and plastic, but less so in the weathered zone and where it contains partings of fine sand, silt or sand lenses. Analyses show that the predominant day mineral is illite.
The clay is only slightly sensitive, with a natural water content of about 30 percent, but it also can be found in a sensitive state in certain areas, such as at Alewife Station. Where redeposited, the clay exhibits anisotropy. The contained lenses and layers of silt and sand increase with depth and in some places the clay grades downward into well stratified sand that becomes coarser with depth and finally grades into gravel (see Figure 3-98). Scattered through the clay are a few pebbles, cobbles and boulders (iceberg drop stones), which may reach several tons in weight. A very large erratic boulder is incorporated into its base in the Fort Point Channel at the MBTA Silver Line crossing (Leifer, 2006). The clay and interbedded silt and sand grade up the valley of the Charles River into littoral sand and, thence, into outwash consisting of sand and gravel deposited by rivers. Because the topographic trough provided by the Boston Basin was a major drainage way for glacial melt water from the west, Boston became the apex of a large, submarine clay delta of outwash origin. Besides the low tidal areas around the Shawmut Peninsula, the clay can also be found in the Squantum area of Quincy to the south; in Charlestown, Cambridge and Somerville to the north and west; the Fenway; Roxbury, South Boston and Dorchester to the south; and East Boston to the east.
The top 1 to 5 meters (3 to 16 feet) of the clay stratum became generally oxidized during a period when it was exposed; much of this area is currently below sea level in Boston Harbor. Borings indicate that where overlain by the Lexington outwash it is oxidized to a depth of I meter (3 feet) and to a maximum depth of 3 meters (10 feet) where exposed on the surface around the Back Bay and Cambridge. A stiff, yellow crust of subaerial origin causing oxidation was formed by the desiccation and resulting over-consolidation that has taken place. Significant over-consolidation is generally limited to the upper 5 meters (16.5 feet), although less over-consolidation can be found to depths of 10 to 12 meters (33 to 39 feet). At depths lower than 18 meters (60 feet), the clay becomes softer, gray and essentially normally consolidated. Where the oxidized clay was overlain by substantial organic matter (such as peat), a chemical reaction involving iron reduction- i.e., ferric iron, Fe+3, is changed to ferrous iron, Fe+2 by bacterial action (Kusel et al., 2008) - has created an upper zone of softened blue clay up to 2 meters (6.5 feet) thick. This zone, representing the top of the clay stratum, may also be silty or sandy and somewhat water bearing. The upper 2 to 5 meters (6.5 to 16 feet) of the clay is structurally disturbed and may be broken, folded and badly contorted in places in the Back Bay and parts of Boston Harbor. The upper clay also is seen in excavations to have prismatic structure or cubical jointing and fissuring, which appears to be evidence of having been frozen, probably at the time of the overlying upper outwash.
The clay may overlie any of the earlier surficial deposits or bedrock because of preceding erosion, and it is normally overlain by the Lexington outwash, Holocene organic deposits or fill. The unit is usually well-bedded with thin horizontal layers. However, both offshore and onshore profiles show it locally conforms to, or is draped over, the surface of the basement on which it was deposited, which imparts a folded appearance to the clay. There are deep funnel-shaped "downfolds" on the order of 100 to 200 meters (330 to 660 feet) across The topographic trough provided by the Boston Basin was a major drainageway for glacial melt water from the west and Boston became the apex of a large, submarine clay 'delta of outwash origin. The marine clay, because it often contains more silt than clay, has lower plastic and liquid limits of its claysized material than would mineral clay. The marine clay represents a high percentage of fine-grained rock flour component of outwash that was carried farther and deposited in coastal marine waters. Miller (2010) considers a significant amount is reworked clay eroded during the Lexington Substage from the older day-rich glaciomarine deposit based on evidence that indicates that the deposit was exposed at places during the time of Lexington day deposition. The occasional glacial gravel to boulder clasts in the clay are apparently iceberg dropstones, perhaps rafted when the ice front was close to Boston. The day is thickest in the lower valley of the Charles River and Boston Harbor, where it wrapped around Beacon Hill, and thins under Massachusetts Bay to the north, east and south. In the Back Bay, as well as along marginal waterfront areas, the clay is typically 15 to 38 meters (50 to 125 feet) thick.
Up the Charles River at the Mount Auburn Cemetery the clay is 25 meters (81 feet) thick near the present river and eroded to zero at
short distances to the north beneath the upper outwash. Even greater thicknesses - up to 60 meters (200 feet) - are found west of Massachusetts Avenue and in Cambridge, where parts of Harvard University and MIT rest on it. Known clay thicknesses, as great as 75 meters (246 feet), occur in the Charles River area. The top of the clay was deeply eroded by the ancestral Charles River and its tributaries during a drop in sea level associated with the Lexington Substage subsequent to 12,600 years ago and the contoured surface (Judson, 1949) shows a well developed stream pattern. The main channel is closely aligned with the present Charles River, a second channel enters from the north between Charlestown and East Boston, and a third exists beneath Fort Point Channel. The surface of the clay is now generally below sea level around the Shawmut Peninsula and is estimated to descend eastward to nearly elevation -60 meters (-200 feet) MSL by Judson (1949). Judson (1949) also reported it rising to about elevation 9 meters (30 feet) MSL on the north and east sides of Beacon Hill. Kaye (1961) only found it reaching to thickness of about 4.6 to 7.6 meters (15 to 2~ feet) over the upper till on the south side, which would be a Boston area local limit since the upper limit of the marine clay varies across New England because the post-glacial rebound has raised the land progressively higher to the north. At the northwest edge of the Boston area, clay has been found as high as elevation 22 meters (72 feet) MSL (Woodworth, 1897; Chute, 1959; Colgan & Rosen, 2001), but these deposits are apparently disturbed or from local ponding. I.B. Crosby (1934) found the highest known marine glacial clay in the environs of Boston (except for small deposits that obviously. formed in glacial lakes) at elevation 7.6 or 10.7 meters (25 or 35 feet) MSL."
Barosh & Woodhouse, A City Upon a Hill: Geology of the City of Boston & Surrounding Area, Geology of the Boston Basin, Civil Engineering Practice, Vol. 26-27 (2011/2012).
| Geology of the Boston Basin cep-vol-26-27-05.pdf |
Boston Main Relief Drainage Sewer was built 1950, 3.8 km long, lined diameter of 3.1m, and about 70-80m deep. Built through clay.
Main Drainage Tunnel sewer was built 1954-1959, 11.5 km long, lined diameter of 3.1-3.5m, and about 89-92.5m deep. Built through clay.
Conveyance pipelines and tunnels have been the backbone of sewage collection and treatment in Boston since its initial conception in the late 1840s. Early in its history, Boston managed its sewage by using small pipes to discharge sewage at the nearest shore.
Barosh & Woodhouse, Boston Area Water Supply & Wastewater Tunnels, Civil Engineering Practice (2011/2012)
Main Drainage Tunnel sewer was built 1954-1959, 11.5 km long, lined diameter of 3.1-3.5m, and about 89-92.5m deep. Built through clay.
Conveyance pipelines and tunnels have been the backbone of sewage collection and treatment in Boston since its initial conception in the late 1840s. Early in its history, Boston managed its sewage by using small pipes to discharge sewage at the nearest shore.
Barosh & Woodhouse, Boston Area Water Supply & Wastewater Tunnels, Civil Engineering Practice (2011/2012)
MA DEP directly compared Boston Blue clay to SF and ‘San Francisco Bay Mud.” Also noted deposits exist in Chicago as well. Found in swamps and coastal regions. “Its all over Boston” says James Elliott of the DPW env div. Dep usually 20ft below surface and some up to 200ft thick. Researchers say the clay can make highways sag, buildings settle, and tunnels collapse.”
The Boston Globe Sun, Sep 29, 1974 ·Page 42
MA DEP and Boston want to give out blue clay for everyone to cap all the landfills and put most of it on Spectacle Island. US EPA says no don’t do that.
The Boston Globe, Fri, Dec 15, 1989 ·Page 80
In 1990s learned that Boston Blue Clay is more sensitive to heavy loads then previously thought. MIT.
The Boston Globe, Wed, Feb 17, 1993
The Clays of the Boston Basin, Robert Marshall Browns, Art. XLIII, American Journal of Science, Vol. s4-14, Issue 84, 1902, https://doi.org/10.2475/ajs.s4-14.84.445
This deposit is widely found in eastern MA, the greater Boston region, and southern New Hampshire, is locally known as Boston Blue Clay (BBC), and has a thickness that can vary from a few meters up to 60 meters. BBC has undergone extensive desiccation due to freezing, ground water table fluctuations, possible erosion, and anthropogenic activities. As a result, the deposit often has a stiff overconsolidated crust below which is soft, low overconsolidation BBC. Significant variations in thickness of the crust and the overall deposit are due to the complex depositional environment and subsequent geologic history in the region.
DeGroot, et al, Geology and engineering properties of sensitive Boston Blue Clay at Newbury, Massachusetts, AIMS Geosciences, 5(3): 412–447 (2019).
THE coastline of the Boston Lowland forms the shore of Boston Bay. Boston Harbor is a large estuary nearly cut off from the Bay by the peninsulas reaching out from the north and south shores (Index Map, Fig. i). On both these peninsulas are beaches several miles long. South of Boston proper lay, in colonial times, an expanse of marshland and mud flat, drained by winding creeks, which were part of the estuary of the Charles River. Further to the southeast we still find the hills of Dorchester and the low-lying coast bordering Boston Bay. Inland from this coast, the low areas may be either alluvial plains or swamps, and these are interrupted by rounded hills and slopes of till. The Boston Peninsula enjoyed other advantages than its favorable location between the rivers. Deep water on the harbor side permitted oceangoing
vessels to land their freight and passengers easily. The land upon the slopes of Beacon, Copps, and Fort Hills was suitable for farming and, pasture. There was plenty of fresh-water in the swamps, such as the "Frog Pond" on Boston Common, and wells were easily dug in the gravel.
The Charles and Mystic Rivers were most important to the colonists as a
means of communication with the interior. However these rivers were closed to deep water navigation by oyster banks which were located in their estuaries. These banks must have been large ones in 1634, f°r William Wood writes of the Mystic, "Ships without either Balast or loading, may float downe this River; otherwise the Oyster-banke would hinder them which crosseth the Channell." Concerning the Charles he says, "Ships of small burden may come up to these two Townes (Cambridge and Watertown), but the Oyster-bankes doe barre out the bigger Ships."3 The estuary of the Charles River, forming the western shore of the Boston Peninsula, broadens out into a wide, marshy bay before passing through a relatively narrow mouth into the harbor. This bay together with Fort Point Channel on the eastern shore of Boston proper forms the boundary of the Boston Peninsula (Fig. 1). Descriptions of the estuary and peninsula are many and they begin very early in the seventeenth century. A few years after 1621, when Miles Standish described Boston Harbor and the Mystic River,5 Europeans established permanent settlements in the Boston Lowland. Winsor, noting this description and others, says that Boston was connected with Roxbury by a "long narrow strip of land properly called 'The Neck' which, beginning to narrow just south of Eliot Street, stretched away like a ribbon of varying width to the mainland. Vastly different however, to its present aspect was its condition in those early days when the road which traversed it was well nigh impassable in the spring, when the horses waded knee-deep in water at full tides, when the only timber on the whole peninsula grew upon the Neck, and the marshes on either hand were the favorite hunting-ground of the sportsman." 7
There are several later references from which something of the nature of the Neck may be deduced. In addition to its being flooded by the "full tides," or Spring Tides (?), there were times when storms washed over the Neck, raising havoc with the city even as late as the middle of the nineteenth century. Perley8 has assembled several records of such storms and their accompanying high tides, one of which did considerable damage along Northampton Street. This region, southwest of Massachusetts Avenue, was, during early colonial times, part of an extensive marsh (Fig. 1).
Josselyn in 1663 9 mentions the existence of "marsh" northwest of the Neck (Fig. 1) and says, "Up higher (from Boston) in the Charles-River westward is a broad Bay two miles over, into which runs Stony-River and Muddy-River." The marshes and bay were variously named, until finally the region became known as "The Back Bay," the name which is now applied to the district. The extent of the Back Bay has been indicated on numerous early maps, particularly those of the British Admiralty. In searching for reasons for the location and ranges of the many batteries about the Back Bay one is struck with the idea that, although the Bay was composed of flats and marshes, it may have been possible to move across it in order to approach the Neck and the west side of the peninsula. The conventions on the maps also show that probably there were drainage channels or small creeks which would float small boats at the proper tide.
3 Wood, 1634, pp.41, 42. 4 Josselyn, 1663, p. 127. 6 Winsor, 1880, Vol. 1, p.63, et seq. 6 Wood, 1634, p. 39. 7 Winsor, 1880, Vol. 1, p. 531. 8 Perley, 1891. 9 Josselyn, 1663, P- I27« 10 Bruce, 1940.
The composition of the Neck, which, with the colonial marshes, connected Boston proper with the mainland, is puzzling. According to available borings, 14 the southern end, north of Waltham Street (Fig. i), is made up of "clay and rocks" and "hard clay." Where it widens out to meet the southern slope of Beacon Hill, i.e. south of Eliot Street, "hard, yellow clay" is recorded. The report "clay and rocks," which is only occasionally found in records of the local deposits and "hard clay," is not well differentiated from the records of blue clay which underlies the Neck. From this type of record it is impossible to do more than guess about the characteristics of the Neck… several statements in the literature which say that the Neck was built by tidal action. The most striking feature of the Neck is the narrow tongue projecting to the south of Eliot Street. It may properly belong with the whole extension beginning in the neighborhood of Boston Common. This feature, together with the swamps, i.e. the Frog Pond (Fig. i), and the swamp which once existed between Tremont and Eliot Streets, east of Park Square, are not characteristic of drumlins.
The southern end of the Neck loses itself in a marsh, as is shown on several colonial maps, for example, the Pelham map drawn in 1775. 16 It seems logical to assume that it was this southern section of marshland which was flooded during periods of high water and hampered colonial transportation between Boston and Roxbury. The location of sections of the marsh are recorded in several borings, as well as in Colonial records, and these are responsible for the location of the junction between dry land and the marsh at a point two hundred and fifty feet south of Waltham Street (Fig. 1).
This foundation ranges between eighty feet and 200 feet below tide level. The characteristics of the till, i.e. whether it is weathered or not, are not well known. According to W. O. Crosby this till is distributed on the sides of ancient valleys which have been cut in the bed rock. He believes that the absence of till in the bottoms of these valleys is evidence that glacial ice "continued to move along these lines after it had become stagnant on the uplands."20 Deposits, apparently lenticular in shape, of what seems to be till are found interstratified in the blue clay. These beds range from ten to twenty-five feet in thickness and are found, most frequently, near the bottom of the clay.
The Boston Lowland is dotted with fresh water swamps and, within the range of the tide, salt water marshes line the shores which are protected from the more violent erosive action of the sea. Both fresh water swamps and marine marshes produce peat. Peat varies greatly in thickness and consistency according to the complexity of local conditions. The principle deposit was an irregularly shaped marsh, the eastern margin of which was near Charles Street. The westernmost edge lay in the vicinity of Gloucester Street (Fig. i). Further extension to the west is suggested by a boring on Beacon Street, west of Massachusetts Avenue. The possibility that the bed extended to the east and north is suggested by one or two borings, particularly between Cambridge and Fruit Streets. The principle deposit was an irregularly shaped marsh, the eastern margin of which was near Charles Street. The westernmost edge lay in the vicinity of Gloucester Street (Fig. i). Further extension to the west is suggested by a boring on Beacon Street, west of Massachusetts Avenue. The possibility that the bed extended to the east and north is suggested by one or two borings, particularly between Cambridge and Fruit Streets. Borings in Fort Point Channel and a record from the Commonwealth Flats in South Boston,29 to the east of Boston proper, record the existence of beds which may well be Lower Peat. The possible extent of this bed has been indicated by the stippling in Figure I, but obviously it remains to be corrected by further investigations. A possible record of Lower Peat is found in one boring among several which were made in Mill Cove. The long strip of marsh running along the shore between Tremont and Washington Streets was reported by Colonial surveyors. Borings in this vicinity report areas of blue clay beneath this marsh but there are a few references to underlying silt.
Johnson et al., The Boylston Street Fishweir, Part 1.
The Boston Globe Sun, Sep 29, 1974 ·Page 42
MA DEP and Boston want to give out blue clay for everyone to cap all the landfills and put most of it on Spectacle Island. US EPA says no don’t do that.
The Boston Globe, Fri, Dec 15, 1989 ·Page 80
In 1990s learned that Boston Blue Clay is more sensitive to heavy loads then previously thought. MIT.
The Boston Globe, Wed, Feb 17, 1993
The Clays of the Boston Basin, Robert Marshall Browns, Art. XLIII, American Journal of Science, Vol. s4-14, Issue 84, 1902, https://doi.org/10.2475/ajs.s4-14.84.445
This deposit is widely found in eastern MA, the greater Boston region, and southern New Hampshire, is locally known as Boston Blue Clay (BBC), and has a thickness that can vary from a few meters up to 60 meters. BBC has undergone extensive desiccation due to freezing, ground water table fluctuations, possible erosion, and anthropogenic activities. As a result, the deposit often has a stiff overconsolidated crust below which is soft, low overconsolidation BBC. Significant variations in thickness of the crust and the overall deposit are due to the complex depositional environment and subsequent geologic history in the region.
DeGroot, et al, Geology and engineering properties of sensitive Boston Blue Clay at Newbury, Massachusetts, AIMS Geosciences, 5(3): 412–447 (2019).
THE coastline of the Boston Lowland forms the shore of Boston Bay. Boston Harbor is a large estuary nearly cut off from the Bay by the peninsulas reaching out from the north and south shores (Index Map, Fig. i). On both these peninsulas are beaches several miles long. South of Boston proper lay, in colonial times, an expanse of marshland and mud flat, drained by winding creeks, which were part of the estuary of the Charles River. Further to the southeast we still find the hills of Dorchester and the low-lying coast bordering Boston Bay. Inland from this coast, the low areas may be either alluvial plains or swamps, and these are interrupted by rounded hills and slopes of till. The Boston Peninsula enjoyed other advantages than its favorable location between the rivers. Deep water on the harbor side permitted oceangoing
vessels to land their freight and passengers easily. The land upon the slopes of Beacon, Copps, and Fort Hills was suitable for farming and, pasture. There was plenty of fresh-water in the swamps, such as the "Frog Pond" on Boston Common, and wells were easily dug in the gravel.
The Charles and Mystic Rivers were most important to the colonists as a
means of communication with the interior. However these rivers were closed to deep water navigation by oyster banks which were located in their estuaries. These banks must have been large ones in 1634, f°r William Wood writes of the Mystic, "Ships without either Balast or loading, may float downe this River; otherwise the Oyster-banke would hinder them which crosseth the Channell." Concerning the Charles he says, "Ships of small burden may come up to these two Townes (Cambridge and Watertown), but the Oyster-bankes doe barre out the bigger Ships."3 The estuary of the Charles River, forming the western shore of the Boston Peninsula, broadens out into a wide, marshy bay before passing through a relatively narrow mouth into the harbor. This bay together with Fort Point Channel on the eastern shore of Boston proper forms the boundary of the Boston Peninsula (Fig. 1). Descriptions of the estuary and peninsula are many and they begin very early in the seventeenth century. A few years after 1621, when Miles Standish described Boston Harbor and the Mystic River,5 Europeans established permanent settlements in the Boston Lowland. Winsor, noting this description and others, says that Boston was connected with Roxbury by a "long narrow strip of land properly called 'The Neck' which, beginning to narrow just south of Eliot Street, stretched away like a ribbon of varying width to the mainland. Vastly different however, to its present aspect was its condition in those early days when the road which traversed it was well nigh impassable in the spring, when the horses waded knee-deep in water at full tides, when the only timber on the whole peninsula grew upon the Neck, and the marshes on either hand were the favorite hunting-ground of the sportsman." 7
There are several later references from which something of the nature of the Neck may be deduced. In addition to its being flooded by the "full tides," or Spring Tides (?), there were times when storms washed over the Neck, raising havoc with the city even as late as the middle of the nineteenth century. Perley8 has assembled several records of such storms and their accompanying high tides, one of which did considerable damage along Northampton Street. This region, southwest of Massachusetts Avenue, was, during early colonial times, part of an extensive marsh (Fig. 1).
Josselyn in 1663 9 mentions the existence of "marsh" northwest of the Neck (Fig. 1) and says, "Up higher (from Boston) in the Charles-River westward is a broad Bay two miles over, into which runs Stony-River and Muddy-River." The marshes and bay were variously named, until finally the region became known as "The Back Bay," the name which is now applied to the district. The extent of the Back Bay has been indicated on numerous early maps, particularly those of the British Admiralty. In searching for reasons for the location and ranges of the many batteries about the Back Bay one is struck with the idea that, although the Bay was composed of flats and marshes, it may have been possible to move across it in order to approach the Neck and the west side of the peninsula. The conventions on the maps also show that probably there were drainage channels or small creeks which would float small boats at the proper tide.
3 Wood, 1634, pp.41, 42. 4 Josselyn, 1663, p. 127. 6 Winsor, 1880, Vol. 1, p.63, et seq. 6 Wood, 1634, p. 39. 7 Winsor, 1880, Vol. 1, p. 531. 8 Perley, 1891. 9 Josselyn, 1663, P- I27« 10 Bruce, 1940.
The composition of the Neck, which, with the colonial marshes, connected Boston proper with the mainland, is puzzling. According to available borings, 14 the southern end, north of Waltham Street (Fig. i), is made up of "clay and rocks" and "hard clay." Where it widens out to meet the southern slope of Beacon Hill, i.e. south of Eliot Street, "hard, yellow clay" is recorded. The report "clay and rocks," which is only occasionally found in records of the local deposits and "hard clay," is not well differentiated from the records of blue clay which underlies the Neck. From this type of record it is impossible to do more than guess about the characteristics of the Neck… several statements in the literature which say that the Neck was built by tidal action. The most striking feature of the Neck is the narrow tongue projecting to the south of Eliot Street. It may properly belong with the whole extension beginning in the neighborhood of Boston Common. This feature, together with the swamps, i.e. the Frog Pond (Fig. i), and the swamp which once existed between Tremont and Eliot Streets, east of Park Square, are not characteristic of drumlins.
The southern end of the Neck loses itself in a marsh, as is shown on several colonial maps, for example, the Pelham map drawn in 1775. 16 It seems logical to assume that it was this southern section of marshland which was flooded during periods of high water and hampered colonial transportation between Boston and Roxbury. The location of sections of the marsh are recorded in several borings, as well as in Colonial records, and these are responsible for the location of the junction between dry land and the marsh at a point two hundred and fifty feet south of Waltham Street (Fig. 1).
This foundation ranges between eighty feet and 200 feet below tide level. The characteristics of the till, i.e. whether it is weathered or not, are not well known. According to W. O. Crosby this till is distributed on the sides of ancient valleys which have been cut in the bed rock. He believes that the absence of till in the bottoms of these valleys is evidence that glacial ice "continued to move along these lines after it had become stagnant on the uplands."20 Deposits, apparently lenticular in shape, of what seems to be till are found interstratified in the blue clay. These beds range from ten to twenty-five feet in thickness and are found, most frequently, near the bottom of the clay.
The Boston Lowland is dotted with fresh water swamps and, within the range of the tide, salt water marshes line the shores which are protected from the more violent erosive action of the sea. Both fresh water swamps and marine marshes produce peat. Peat varies greatly in thickness and consistency according to the complexity of local conditions. The principle deposit was an irregularly shaped marsh, the eastern margin of which was near Charles Street. The westernmost edge lay in the vicinity of Gloucester Street (Fig. i). Further extension to the west is suggested by a boring on Beacon Street, west of Massachusetts Avenue. The possibility that the bed extended to the east and north is suggested by one or two borings, particularly between Cambridge and Fruit Streets. The principle deposit was an irregularly shaped marsh, the eastern margin of which was near Charles Street. The westernmost edge lay in the vicinity of Gloucester Street (Fig. i). Further extension to the west is suggested by a boring on Beacon Street, west of Massachusetts Avenue. The possibility that the bed extended to the east and north is suggested by one or two borings, particularly between Cambridge and Fruit Streets. Borings in Fort Point Channel and a record from the Commonwealth Flats in South Boston,29 to the east of Boston proper, record the existence of beds which may well be Lower Peat. The possible extent of this bed has been indicated by the stippling in Figure I, but obviously it remains to be corrected by further investigations. A possible record of Lower Peat is found in one boring among several which were made in Mill Cove. The long strip of marsh running along the shore between Tremont and Washington Streets was reported by Colonial surveyors. Borings in this vicinity report areas of blue clay beneath this marsh but there are a few references to underlying silt.
Johnson et al., The Boylston Street Fishweir, Part 1.
The Cambridge Argillite is a shale, locally and weakly metamorphosed, and occasionally encountered with reworked tuffaceous material. It is generally hard and competent due to its poorly developed bedding planes and general lack of fissility. However, localized zones exist where alteration of the bedrock has produced zones of varying widths of kaolin, a "soil-like" material composed essentially of the clay mineral kaolinite. The abrupt and unpredictable change from the sound Argillite to the kaolinitic weak Argillite occurs in very short distances. To further complicate the situation, preglacial surficial weathering has created a variable
thickness of overlying weathered rock that appears to have characteristics similar to those of the kaolinized zones. Kaye's (1967) study of thin-sections from the altered zone revealed that the commonly present rock minerals, including quartz, have been replaced by sericite and kaolinite at varying levels. This observation led to the possible explanation that the younger igneous intrusions have hydrothermally altered the adjacent weaker rocks and created the zones of highly decomposed kaolinite-rich, clay-like "soil" adjacent and running parallel to the intrusions. The erratic occurrence of the weathered and altered zones, in conjunction with the steeply dipping bedding planes typical of the Argillite, causes difficulty in characterizing the bedrock for engineering purposes. Without test borings at each caisson location, it is difficult to predict the quality of the rock within which a foundation unit will bear (Figure 2 ) .
thickness of overlying weathered rock that appears to have characteristics similar to those of the kaolinized zones. Kaye's (1967) study of thin-sections from the altered zone revealed that the commonly present rock minerals, including quartz, have been replaced by sericite and kaolinite at varying levels. This observation led to the possible explanation that the younger igneous intrusions have hydrothermally altered the adjacent weaker rocks and created the zones of highly decomposed kaolinite-rich, clay-like "soil" adjacent and running parallel to the intrusions. The erratic occurrence of the weathered and altered zones, in conjunction with the steeply dipping bedding planes typical of the Argillite, causes difficulty in characterizing the bedrock for engineering purposes. Without test borings at each caisson location, it is difficult to predict the quality of the rock within which a foundation unit will bear (Figure 2 ) .
Caldera
Ash-flow tuff in the Stony Brook Reservation contains clasts as much as 450 m long. The pyroclastic matrix of this breccia and the large size of its clasts are characteristic of “megabreccias” found in terrains of ash-flow volcanism and caldera collapse. The breccia of the Stony Brook Reservation is intruded by shallow-level (Westwood?) granite, suggesting that both caldera collapse and magmatic resurgence were important processes in the history of this part of the late Precambrian plutonic-volcanic terrain in southeastern New England.
Evidence for a late Precambrian caldera in Boston, Massachusetts, September 01, 1985, Geology (1985) 13 (9): 641–643.
Evidence for a late Precambrian caldera in Boston, Massachusetts, September 01, 1985, Geology (1985) 13 (9): 641–643.
History of Filling & Fill Investigations
"The proposal is to construct a concrete culvert for drainage from Massachusetts Avenue to Dorchester Avenue and to fill entirely the
Roxbury Canal, South Bay, the portion of Dorchester Brook from the end of the existing culvert on railroad property northerly to
South Bay, and that portion of Fort Point Channel down to Dorchester Avenue."
Provisions to collect and dispose of the storm runoff which is tributary to South Bay and the Channel will require construction of a concrete box conduit as shown on Plates No. 2 and 3. The design of the conduit section is based on hydraulic properties which allow for future construction and filling of Fort Point Channel all the way to Northern Avenue. The existing storm and sanitary overflow drains which now discharge into any part of the water-way above Dorchester Avenue will be tied into the main conduit. Until recently, it had been assumed that long point-bearing piles would be required for support of the culvert. However, a section of the culvert already constructed for the Boston Central Artery was built on gravel backfill after excavation of organic silt. Furthermore, studies for the Dover Street embankment indicated long piles were not required for that section of the culvert even though the height of fill will be greater. It is believed, therefore, that long bearing piles driven through the blue clay stratum to refusal are not required for support of any portion of the proposed culvert.
Considerable savings in construction cost will result if the culvert can be constructed in the open without a cofferdam. However, this
ay be possible only where adequate room is available for construction of stable dikes and where the culvert invert is highest. Preliminary details of the conduit design as shown on Plate No. 2 call for three major types of foundation treatment: 1. The upper reach of the conduit will be constructed on a gravel embankment placed after excavation of organic silt, utilizing earth dikes to facilitate dewatering so construction may proceed in the dry. 2. The next section down to the existing expressway culvert will be supported on timber friction piles driven through the organic silt into the clay stratum again utilizing earth dikes. 3. The lower portion of the conduit will be founded on gravel backfill placed after organic silt is excavated down to the blue clay, all construction to take place within a double wall steel sheet pile cofferdam which will remain in place as an integral part of the culvert.
It is probable that the foundation treatment for the culvert will vary considerably over its length due largely to its size and to the proximity of Boston blue clay. A careful survey of soil conditions throughout the area prior to construction may very well indicate the possibility of more extensive use of treatment 1 or 2 and less use of treatment 3 as outlined above resulting in less costly construction. Settlement of the culvert following its construction will be less than the estimated compression of the clay stratum under 20 ft. of fill. A maximum of 3 to 4 inches is expected while differential settlement will be relatively small. Anticipated settlement of the culvert may be compensated for, if necessary, by a slight increase in size or by adjustments in the as-built invert elevation.
To retain the fill and prevent tide water from flowing upstream, a sea wall must be constructed across Fort Point Channel along the easterly side of the Dorchester Avenue Bridge as shown on Plate No. 3. The design as shown calls for adequately braced steel sheet piling to be driven as close as practical to the existing bridge with provisions in the piling for the discharge of the drainage conduit. The scheme offered is tentative only and many variations are feasible and should be investigated based upon more complete subsurface exploration.
Placing of Fill Material. A geologic section showing approximate subsoil conditions underlying the Fort Point Channel area is shown in Plate No. 3. Information from recent John F. Fitzgerald Expressway borings was used to prepare the section between Massachusetts Avenue and Broadway Bridge. In addition, use was made of boring data published by the Boston Society of Civil Engineers and logs of borings for the proposed Dover Street embankment crossing Fort Point Channel. Bottom of the channel corresponding to top of organic silt was obtained from recent soundings taken as part of this investigation. During the past two years, considerable organic silt and other miscellaneous fill from construction of the Expressway have been deposited in the channel, especially from Massachusetts Avenue to Dover Street. As a result, the character of the channel has been altered appreciably. At the present time, the mud line varies from El. 0 to El. -20 at the proposed location of the culvert while the depth of organic silt and fill is between 5 and 30 feet. Underlying the organic silt is a deep stratum of clay varying from stiff yellow clay toward the top surface to soft blue clay at greater depth. Thickness of the clay stratum varies between 40 and 100 ft. Below the clay are thin layers of pervious sands and glacial till (hardpan) over a blue slaty shale.
The 1950 report by the Port of Boston Authority proposed that fill for the channel be obtained by hydraulic means from the Old Harbor area. Since the size of the area to be filled has been greatly reduced, fill to be placed to Dorchester Avenue only, and since considerable filling has occurred since 1950, it is believed that continued filling by conventional methods is indicated. It is estimated that 700,000 cu. yds. of fill are required to bring the Channel to approximately Elevation 10. Proposed construction activity in the Greater Boston area is likely to produce the majority of earth fill required for the Channel. Major projects proposed include the Prudential Center, garage under the Boston Common, the Federal Center near Scollay Square and a second Sumner Tunnel to East Boston. If contracts for these projects specify disposal of earth excavation in the Fort Point Channel area, the cost of filling the Channel is greatly reduced. Furthermore, it is probable that such a convenient disposal area would reduce the construction cost of the specified project itself. Construction of the culvert will require considerable quantities of fill for construction of earth dikes and working platforms for heavy equipment. Thus, the total quantity required from other sources is less than the estimated 700,000 cu. yds.
Few limitations need to be placed on the type of earth fill used in the Channel once the culvert is constructed. Foundations for all but the lightest temporary structures which may be constructed in the future will need to be founded on piles where earth fill overlies organic silt. It is considered important to exclude rock, boulders, granite blocks, brick walls, concrete and other hard materials from fill in order to minimize future pile driving and excavation problems. It will be desirable to place a minimum of 2to 3 ft. of granular soil over the filled area, especially where organic soils are dumped, to provide a sanitary, stable, free draining surface."
1959 Senate Bill 0498. Report of the Special Commission Relative to Filling and Improving South Bay and Part of Fort Point Channel in the City Of Boston: A Comprehensive Report for the Filling and Improving a Portion of Fort Point Channel and South Bay. (1959).
Roxbury Canal, South Bay, the portion of Dorchester Brook from the end of the existing culvert on railroad property northerly to
South Bay, and that portion of Fort Point Channel down to Dorchester Avenue."
Provisions to collect and dispose of the storm runoff which is tributary to South Bay and the Channel will require construction of a concrete box conduit as shown on Plates No. 2 and 3. The design of the conduit section is based on hydraulic properties which allow for future construction and filling of Fort Point Channel all the way to Northern Avenue. The existing storm and sanitary overflow drains which now discharge into any part of the water-way above Dorchester Avenue will be tied into the main conduit. Until recently, it had been assumed that long point-bearing piles would be required for support of the culvert. However, a section of the culvert already constructed for the Boston Central Artery was built on gravel backfill after excavation of organic silt. Furthermore, studies for the Dover Street embankment indicated long piles were not required for that section of the culvert even though the height of fill will be greater. It is believed, therefore, that long bearing piles driven through the blue clay stratum to refusal are not required for support of any portion of the proposed culvert.
Considerable savings in construction cost will result if the culvert can be constructed in the open without a cofferdam. However, this
ay be possible only where adequate room is available for construction of stable dikes and where the culvert invert is highest. Preliminary details of the conduit design as shown on Plate No. 2 call for three major types of foundation treatment: 1. The upper reach of the conduit will be constructed on a gravel embankment placed after excavation of organic silt, utilizing earth dikes to facilitate dewatering so construction may proceed in the dry. 2. The next section down to the existing expressway culvert will be supported on timber friction piles driven through the organic silt into the clay stratum again utilizing earth dikes. 3. The lower portion of the conduit will be founded on gravel backfill placed after organic silt is excavated down to the blue clay, all construction to take place within a double wall steel sheet pile cofferdam which will remain in place as an integral part of the culvert.
It is probable that the foundation treatment for the culvert will vary considerably over its length due largely to its size and to the proximity of Boston blue clay. A careful survey of soil conditions throughout the area prior to construction may very well indicate the possibility of more extensive use of treatment 1 or 2 and less use of treatment 3 as outlined above resulting in less costly construction. Settlement of the culvert following its construction will be less than the estimated compression of the clay stratum under 20 ft. of fill. A maximum of 3 to 4 inches is expected while differential settlement will be relatively small. Anticipated settlement of the culvert may be compensated for, if necessary, by a slight increase in size or by adjustments in the as-built invert elevation.
To retain the fill and prevent tide water from flowing upstream, a sea wall must be constructed across Fort Point Channel along the easterly side of the Dorchester Avenue Bridge as shown on Plate No. 3. The design as shown calls for adequately braced steel sheet piling to be driven as close as practical to the existing bridge with provisions in the piling for the discharge of the drainage conduit. The scheme offered is tentative only and many variations are feasible and should be investigated based upon more complete subsurface exploration.
Placing of Fill Material. A geologic section showing approximate subsoil conditions underlying the Fort Point Channel area is shown in Plate No. 3. Information from recent John F. Fitzgerald Expressway borings was used to prepare the section between Massachusetts Avenue and Broadway Bridge. In addition, use was made of boring data published by the Boston Society of Civil Engineers and logs of borings for the proposed Dover Street embankment crossing Fort Point Channel. Bottom of the channel corresponding to top of organic silt was obtained from recent soundings taken as part of this investigation. During the past two years, considerable organic silt and other miscellaneous fill from construction of the Expressway have been deposited in the channel, especially from Massachusetts Avenue to Dover Street. As a result, the character of the channel has been altered appreciably. At the present time, the mud line varies from El. 0 to El. -20 at the proposed location of the culvert while the depth of organic silt and fill is between 5 and 30 feet. Underlying the organic silt is a deep stratum of clay varying from stiff yellow clay toward the top surface to soft blue clay at greater depth. Thickness of the clay stratum varies between 40 and 100 ft. Below the clay are thin layers of pervious sands and glacial till (hardpan) over a blue slaty shale.
The 1950 report by the Port of Boston Authority proposed that fill for the channel be obtained by hydraulic means from the Old Harbor area. Since the size of the area to be filled has been greatly reduced, fill to be placed to Dorchester Avenue only, and since considerable filling has occurred since 1950, it is believed that continued filling by conventional methods is indicated. It is estimated that 700,000 cu. yds. of fill are required to bring the Channel to approximately Elevation 10. Proposed construction activity in the Greater Boston area is likely to produce the majority of earth fill required for the Channel. Major projects proposed include the Prudential Center, garage under the Boston Common, the Federal Center near Scollay Square and a second Sumner Tunnel to East Boston. If contracts for these projects specify disposal of earth excavation in the Fort Point Channel area, the cost of filling the Channel is greatly reduced. Furthermore, it is probable that such a convenient disposal area would reduce the construction cost of the specified project itself. Construction of the culvert will require considerable quantities of fill for construction of earth dikes and working platforms for heavy equipment. Thus, the total quantity required from other sources is less than the estimated 700,000 cu. yds.
Few limitations need to be placed on the type of earth fill used in the Channel once the culvert is constructed. Foundations for all but the lightest temporary structures which may be constructed in the future will need to be founded on piles where earth fill overlies organic silt. It is considered important to exclude rock, boulders, granite blocks, brick walls, concrete and other hard materials from fill in order to minimize future pile driving and excavation problems. It will be desirable to place a minimum of 2to 3 ft. of granular soil over the filled area, especially where organic soils are dumped, to provide a sanitary, stable, free draining surface."
1959 Senate Bill 0498. Report of the Special Commission Relative to Filling and Improving South Bay and Part of Fort Point Channel in the City Of Boston: A Comprehensive Report for the Filling and Improving a Portion of Fort Point Channel and South Bay. (1959).
Report of the Special Commission Relative to Filling and Improving South Bay and Part of Fort Point Channel in the City of Boston, Senate — No. 498 (1959).
Report of the Special Commission Relative to Filling and Improving South Bay and Part of Fort Point Channel in the City of Boston, Senate — No. 498 (1959).
A Study for the Development of Fort Point Channel, South Bay, and Adjacent Areas, Port of Boston Authority (1950).
Archeology & Tunnels
NPS Map: Siege of Boston fortifications overlaid on South End, South Boston, and Boston (1775)
SOIL & GROUNDWATER FINDINGS BY CANAL/SOUTH BAY AREA
MELNEA CASS BLVD / ISLAND ST / READING ST (AT HAMPSTON ST TO MASS AVE)
"According to the H&A Phase I, prior to the 1850s, the Site was undeveloped land on the north bank of Roxbury Creek. During the 1850s, the Albany Street area was filled behind a granite block seawall. By 1882, the Site was improved with two buildings (which overlapped onto adjacent properties) of the City of Boston Water Department. At that time, the Roxbury Canal conduit abutted the southeastern portion of the Site. Site usage by the Water Department included machine shops, water meter repair and testing, and carpenters shops. Materials likely used/generated by the Water Department included petroleum products, waste oil, metal cutting oil, lubricants and degreasing solvents. Heating of the Site buildings likely used coal, and steam heat from outside sources was used in the 1960s and 1970s. No evidence of underground or aboveground storage tanks was identified by H&A. In the late 1970s, the two building existing at that time were razed, and the Site was subsequently used for Boston City Hospital employee parking. No prior environmental evaluations were conducted on the Site. However, evaluations of an adjacent property identified volatile organic compounds (VOCs), TPH and polychlorinated biphenyls (PCBs) in subsurface soils and groundwater."
"H&A installed four test borings (for environmental and geotechnical purposes) on the Site on July 18 and 19, 1992. The borings, identified as E92-1 through E92-4, were installed within the footprint of the proposed building and rear courtyard, as shown on Figure 2. Soil samples were collected during drilling to determine Site stratigraphy and environmental quality. The Site soils consist of brown to black silty sand and gravel fill, including brick, ash, cinders and concrete, to a depth of 4.5 to 6.5 feet. Brown to dark gray organic silt and peat (some containing marine shell fragments) were present to depths of 11 to 26 feet. These deposits were underlain by soft to stiff olive to gray marine clay. Silver, cadmium, chromium, copper, mercury and lead were detected in the samples above their respective common ranges. A total of 2,544.7 tons of material were transported off-site for disposal at American Reclamation Corporation (Amrec) of Charlton, Massachusetts under Bill of Lading protocol in July and September 1994. During boring installations by H&A, groundwater was encountered at depths from 8 to 11 feet below grade, according to H&A boring logs. H&A installed 2-inch diameter PVC monitoring wells in the four borings, ranging in depth from 24 feet to 39 feet below grade."
"The Site was filled as part of overall expansion of the City of Boston. These fill soils typically contain coal ash and wood ash, and contain concentrations of metals and P AHs similar to those detected in the site soils. In addition, historically, coal was likely used for heating during early Site use. Ash and cinders were identified in soil samples collected from the Site, and are likely associated with the fill material or the use of coal. After initial development, the Site was used by the City of Boston Water Department to, among other supporting activities, test and repair water meters. Materials likely used/generated by the Water Department included petroleum products, waste oil, metal cutting oil, lubricants and degreasing solvents. Some of these materials may have been released to the Site soils during routine Site operations."
"H&A surveyed the tops of the wells and gauged water levels to determine groundwater flow direction. Groundwater levels appeared higher in the center of the Site and lower at the northwest and southeast ends. H&A determined that groundwater flow direction was outward from the center of the Site. H&A further indicated that the groundwater flow regime at the Site was similar to the flow regime on the adjacent parcel northeast of the Site."
"As indicated previously, Site fill soils included ash and cinders, and these were most likely part of the fill material used to fill the Site area. Many of the P AHs and metals detected at the Site fall within background concentrations determined by the DEP. Cadmium is the only compound whose EPC is above the background level. The cadmium EPC is largely driven by a single concentration an order of magnitude higher than other detections at the Site, and is from a sample of soil that was subsequently removed for the property."
RESPONSE ACTION OUTCOME STATEMENT MEDICAL EXAMINER'S BUILDING, 720 ALBANY STREET, BOSTON, MASSACHUSETTS, Prepared for Commonwealth of Massachusetts, RTN 3-4530 (June 22, 2010)
"According to the H&A Phase I, prior to the 1850s, the Site was undeveloped land on the north bank of Roxbury Creek. During the 1850s, the Albany Street area was filled behind a granite block seawall. By 1882, the Site was improved with two buildings (which overlapped onto adjacent properties) of the City of Boston Water Department. At that time, the Roxbury Canal conduit abutted the southeastern portion of the Site. Site usage by the Water Department included machine shops, water meter repair and testing, and carpenters shops. Materials likely used/generated by the Water Department included petroleum products, waste oil, metal cutting oil, lubricants and degreasing solvents. Heating of the Site buildings likely used coal, and steam heat from outside sources was used in the 1960s and 1970s. No evidence of underground or aboveground storage tanks was identified by H&A. In the late 1970s, the two building existing at that time were razed, and the Site was subsequently used for Boston City Hospital employee parking. No prior environmental evaluations were conducted on the Site. However, evaluations of an adjacent property identified volatile organic compounds (VOCs), TPH and polychlorinated biphenyls (PCBs) in subsurface soils and groundwater."
"H&A installed four test borings (for environmental and geotechnical purposes) on the Site on July 18 and 19, 1992. The borings, identified as E92-1 through E92-4, were installed within the footprint of the proposed building and rear courtyard, as shown on Figure 2. Soil samples were collected during drilling to determine Site stratigraphy and environmental quality. The Site soils consist of brown to black silty sand and gravel fill, including brick, ash, cinders and concrete, to a depth of 4.5 to 6.5 feet. Brown to dark gray organic silt and peat (some containing marine shell fragments) were present to depths of 11 to 26 feet. These deposits were underlain by soft to stiff olive to gray marine clay. Silver, cadmium, chromium, copper, mercury and lead were detected in the samples above their respective common ranges. A total of 2,544.7 tons of material were transported off-site for disposal at American Reclamation Corporation (Amrec) of Charlton, Massachusetts under Bill of Lading protocol in July and September 1994. During boring installations by H&A, groundwater was encountered at depths from 8 to 11 feet below grade, according to H&A boring logs. H&A installed 2-inch diameter PVC monitoring wells in the four borings, ranging in depth from 24 feet to 39 feet below grade."
"The Site was filled as part of overall expansion of the City of Boston. These fill soils typically contain coal ash and wood ash, and contain concentrations of metals and P AHs similar to those detected in the site soils. In addition, historically, coal was likely used for heating during early Site use. Ash and cinders were identified in soil samples collected from the Site, and are likely associated with the fill material or the use of coal. After initial development, the Site was used by the City of Boston Water Department to, among other supporting activities, test and repair water meters. Materials likely used/generated by the Water Department included petroleum products, waste oil, metal cutting oil, lubricants and degreasing solvents. Some of these materials may have been released to the Site soils during routine Site operations."
"H&A surveyed the tops of the wells and gauged water levels to determine groundwater flow direction. Groundwater levels appeared higher in the center of the Site and lower at the northwest and southeast ends. H&A determined that groundwater flow direction was outward from the center of the Site. H&A further indicated that the groundwater flow regime at the Site was similar to the flow regime on the adjacent parcel northeast of the Site."
"As indicated previously, Site fill soils included ash and cinders, and these were most likely part of the fill material used to fill the Site area. Many of the P AHs and metals detected at the Site fall within background concentrations determined by the DEP. Cadmium is the only compound whose EPC is above the background level. The cadmium EPC is largely driven by a single concentration an order of magnitude higher than other detections at the Site, and is from a sample of soil that was subsequently removed for the property."
RESPONSE ACTION OUTCOME STATEMENT MEDICAL EXAMINER'S BUILDING, 720 ALBANY STREET, BOSTON, MASSACHUSETTS, Prepared for Commonwealth of Massachusetts, RTN 3-4530 (June 22, 2010)
"Beneath the fill material, the test pits encountered natural deposits of marine sand and clay at Elevations ranging from approximately +6.6 to +11.3 feet. The natural deposit of marine sand was observed to consist of a compact mottled orange brown to yellow-brown silty fine sand. The marine clay was observed to consist of a firm to soft mottled yellow-gray silty clay. The natural deposits of marine sand and marine clay were not penetrated during the subsurface investigations. Based upon borings performed on nearby sites the marine clay extends to depths which exceed 100 feet below ground surface. Underlying the marine clay, a glacial till exists which generally consists of a gray, silty gravelly sand and is known to contain occasional cobbles and boulders.
Groundwater at the site was encountered within observation well OW-1 well at approximately 4.5 feet below ground surface which corresponds to about Elevation +11.8. During our subsurface investigation in June 2010, the surface of groundwater was observed in test pits TP-1 02, TP-104 and TP-105 at depths ranging from approximately 6 to 6.8 feet below the existing ground surface which corresponds to approximate Elevations +9.18 and +9.48, respectively. It is anticipated that the groundwater is seasonally perched on the surface of the relatively impermeable marine deposits. Future groundwater levels across the project site may vary from those reported herein based on such factors such as normal seasonal changes, runoff during or following periods of heavy precipitation, and alterations to existing drainage patterns.
CLASS A-3 RESPONSE ACTION OUTCOME STATEMENT RTN 3-29344, 20 REED STREET ROXBURY MASSACHUSETTS for Department of Environmental Protection, Bureau of Waste Site Cleanup, Project No. 5117 (June 21, 2011).
Groundwater at the site was encountered within observation well OW-1 well at approximately 4.5 feet below ground surface which corresponds to about Elevation +11.8. During our subsurface investigation in June 2010, the surface of groundwater was observed in test pits TP-1 02, TP-104 and TP-105 at depths ranging from approximately 6 to 6.8 feet below the existing ground surface which corresponds to approximate Elevations +9.18 and +9.48, respectively. It is anticipated that the groundwater is seasonally perched on the surface of the relatively impermeable marine deposits. Future groundwater levels across the project site may vary from those reported herein based on such factors such as normal seasonal changes, runoff during or following periods of heavy precipitation, and alterations to existing drainage patterns.
CLASS A-3 RESPONSE ACTION OUTCOME STATEMENT RTN 3-29344, 20 REED STREET ROXBURY MASSACHUSETTS for Department of Environmental Protection, Bureau of Waste Site Cleanup, Project No. 5117 (June 21, 2011).
Borings showing “beds of marsh mud” from 20-86ft deep between Clapp & Magazine St.
Filled to 14ft high
Reports of quicksand
1885 Main Drainage Works.pdf
While laying main drainage excavating occurrence of quicksand esp along water fronts
1899 Report on Boston Main Drainage Works.pdf
Tributary to the Main Drainage System bounded by Charles River and Boston Harbor etc
Lowr portion, not more than 40ft above mean low water , 46 sq miles
Expected to be intercepted by a low level intercepting sewers so always need pumped
1899 Report on Boston Main Drainage Works.pdf
Filled to 14ft high
Reports of quicksand
1885 Main Drainage Works.pdf
While laying main drainage excavating occurrence of quicksand esp along water fronts
1899 Report on Boston Main Drainage Works.pdf
Tributary to the Main Drainage System bounded by Charles River and Boston Harbor etc
Lowr portion, not more than 40ft above mean low water , 46 sq miles
Expected to be intercepted by a low level intercepting sewers so always need pumped
1899 Report on Boston Main Drainage Works.pdf
BRADSTON ST / MASS AVE CONNECTOR (AT MASS AVE TO EAST DEDHAM ST)
Fill Layers were encountered at the surface of all subsurface locations and varied in thickness from 3.0 to 15.0 ft. The fill layers were denoted under the following classifications:
and varied in thickness from 0.5 to 10.0 feet. The organic layers were classified under the following classifications:
Black Brown Sand (SP) was encountered underlying the organic silt in test boring B-1 and was approximately 5.0 feet thick. The sand layer consisted of varying percentages of coarse to fine sand, 0-10% nonplastic fines, and 0-5% organics. The sand layer was dense with a SPT N-Value of 43 blows.
Blue Grey/Light Grey/Dark Brown Sandy Silt (ML) was encountered underlying the sand layer in boring B-1, underlying the miscellaneous fill layer in test boring B-7, and I was approximately 5.0 feet thick. The sandy silt layer consisted of nonplastic to slightly I plastic fines, with 15-25% coarse to fine sand and 0-10% coarse to fine subrounded gravel, 0-5% organics and fibers. The sandy silt layer was loose to very dense with a SPT N-Values varying between 8 to 62 blows.
Grey Brown Clayey Silt (ML) was encountered underlying the organic silt layer in boring B-2, underlying the peat layer in test boring B-4, and varied in thickness from 5 and 15.0 feet. The clayey silt layer consisted of medium plasticity fines, with 0-5% fine
sand. The sandy silt layer was very stiff to hard with SPT N-Values varying between 23 and 35 blows.
Grey/Blue Grey/Green Grey Silty Clay (CL. CH, and CL-CH) was encountered underlying the sandy silt fill layer in boring B-1 and B-7, underlying the clayey silt layer in test boring B-2, underlying the organic silt layer in test boring B-3, and varied in thickness between 67.0 and 105.0 feet. The silty clay layer consisted of low to highly plasticity fines, with 0-5% coarse to fine gravel, 0-30% fine sand, and occasional layers or seams of sandy silt or silt. The silty clay layer was very soft to hard with SPT N-Values varying between 0 (weight of hammer nnn) and 68 blows.
Brown Grey/Grey Glacial Till Layers were encountered underlying the silty clay layer in test boring B-l, B-2, B-3, B-5, B-6, B-7,and varied in thickness from 3 to 7 feet. was approximately 5 feet thick. The glacial till layers consisted of the following types of
materials:
Bedrock - Shale (Cambridge Argillite) was encountered underlying the silty clay till layer in test boring B-4. A split spoon sample of the shale layer was obtained form test boring location B-4 and noted as having the following properties: Light grey green, severely weathered and thinly bedded. Refusal blow counts were recorded in all boring locations.
The groundwater table was encountered approximately 6.0 to 10.4 ft below ground surface in all observation wells. For the purpose of this report, an assumed datum of 100 ft was located on the spindle of the hydrant on South Bay Avenue adjacent to the entrance to the United Trucking Company. Base on the groundwater reading recorded on May 9, 1988 from the observation wells, it was determined that the groundwater flows generally in a southerly direction, with an average hydraulic gradient of 0.0063 ft/ft. MB-8 generally flows in an easterly direction toward Boston Harbor.
20 Bradson, Roxbury MA, Mass. DEP Project Number 75029MA (June 1, 1988).
"Soils at the (Incinerator) site consist of 5 to 50 feet of miscellaneous fill overlying clay."
20 Bradson, Roxbury MA, Mass. DEP Project Number 75029MA (June 1, 1988).
Fill Layers were encountered at the surface of all subsurface locations and varied in thickness from 3.0 to 15.0 ft. The fill layers were denoted under the following classifications:
- Black/Grey/Red Brown/Brown Miscellaneous Fill consisting of a heterogeneous layer of gravel, sand, silt, clay, organics, peat, bricks, metal, rubber, wood, ash, I tires, bottles, wire, granite cobbles, boulders, leaves, roots, brick, concrete blocks, and cinders. It was noted that there was a petroleum odor to the sample collected in boring B-2 at a depth of 5.0-6.5 feet. The miscellaneous fill layer was very loose to very dense with a Standard Penetrations Test (SPT) N-Values varying between 1 and greater than 120 blows
- Black Grey/Dark Grey Clavey Silt (ML) consisting of medium plasticity fines, with 0-5% fine gravel and coarse to fine sand, and 0-10% organics. The sandy silt layer was medium stiff with a SPT N-Values of 5 blows.
- Red Brown Sand (SP-SM) consisting of varying percentages of coarse to fine sand, 10-15% coarse to fine subrounded gravel, and 0-10% nonplastic fines.
- Grey Green Silty Clay (CL-CH) consisting of moderately plasticity fines, with an organic odor. The silty clay fill layer was soft with a SPT N-Value of 2 blows.
and varied in thickness from 0.5 to 10.0 feet. The organic layers were classified under the following classifications:
- Black/Grey Black Organic Silt (OL) consisting of slightly to highly plastic fines, 0-15% organics and peat fibers, 0-5% coarse to fine gravel, 0-30% fine sand, and 0-15% cinders, and pockets of fibers or shells. The organic silt layer was very I soft to medium stiff with a SPT N-Values varying between 0 (weight of hammer run) of 7 blows.
- Black Peat (Pt) consisting of slightly plastic fines, was very loose with a SPT N-Values varying between 1 and 2 blows.
Black Brown Sand (SP) was encountered underlying the organic silt in test boring B-1 and was approximately 5.0 feet thick. The sand layer consisted of varying percentages of coarse to fine sand, 0-10% nonplastic fines, and 0-5% organics. The sand layer was dense with a SPT N-Value of 43 blows.
Blue Grey/Light Grey/Dark Brown Sandy Silt (ML) was encountered underlying the sand layer in boring B-1, underlying the miscellaneous fill layer in test boring B-7, and I was approximately 5.0 feet thick. The sandy silt layer consisted of nonplastic to slightly I plastic fines, with 15-25% coarse to fine sand and 0-10% coarse to fine subrounded gravel, 0-5% organics and fibers. The sandy silt layer was loose to very dense with a SPT N-Values varying between 8 to 62 blows.
Grey Brown Clayey Silt (ML) was encountered underlying the organic silt layer in boring B-2, underlying the peat layer in test boring B-4, and varied in thickness from 5 and 15.0 feet. The clayey silt layer consisted of medium plasticity fines, with 0-5% fine
sand. The sandy silt layer was very stiff to hard with SPT N-Values varying between 23 and 35 blows.
Grey/Blue Grey/Green Grey Silty Clay (CL. CH, and CL-CH) was encountered underlying the sandy silt fill layer in boring B-1 and B-7, underlying the clayey silt layer in test boring B-2, underlying the organic silt layer in test boring B-3, and varied in thickness between 67.0 and 105.0 feet. The silty clay layer consisted of low to highly plasticity fines, with 0-5% coarse to fine gravel, 0-30% fine sand, and occasional layers or seams of sandy silt or silt. The silty clay layer was very soft to hard with SPT N-Values varying between 0 (weight of hammer nnn) and 68 blows.
Brown Grey/Grey Glacial Till Layers were encountered underlying the silty clay layer in test boring B-l, B-2, B-3, B-5, B-6, B-7,and varied in thickness from 3 to 7 feet. was approximately 5 feet thick. The glacial till layers consisted of the following types of
materials:
- Brown Grey Silty Clay (CL) consisting of low plasticity fines, with 0-10% coarse to fine gravel and coarse to fine sand. The silty clay layer was hard with a SPT N-Value of 45 blows.
- Grey Brown Clayey Gravel (GC) consisting of varying percentages of coarse to fine gravel, 5-20% coarse to fine sand, 30-35% slightly plastic fines, with occasional cobbles and boulders. The clayey gravel layer was medium dense to very dense with a SPT N-Values varying between 39 and greater than 120 blows.
- Grey Clavey Sand (SC) consisting of varying percentages of coarse to fine sand, 5-10% fine subangular gravel, 10-20% low plastic fines, and occasional cobbles and boulders. The clayey sand layer was very dense with a SPT N-Value greater than 120 blows.
- Grey Sandy Silt (ML) consisting of nonplastic fines and 20-30% medium to fine sand. The sandy sit layer was very dense with a SPT N-Value greater than 120 blows.
Bedrock - Shale (Cambridge Argillite) was encountered underlying the silty clay till layer in test boring B-4. A split spoon sample of the shale layer was obtained form test boring location B-4 and noted as having the following properties: Light grey green, severely weathered and thinly bedded. Refusal blow counts were recorded in all boring locations.
The groundwater table was encountered approximately 6.0 to 10.4 ft below ground surface in all observation wells. For the purpose of this report, an assumed datum of 100 ft was located on the spindle of the hydrant on South Bay Avenue adjacent to the entrance to the United Trucking Company. Base on the groundwater reading recorded on May 9, 1988 from the observation wells, it was determined that the groundwater flows generally in a southerly direction, with an average hydraulic gradient of 0.0063 ft/ft. MB-8 generally flows in an easterly direction toward Boston Harbor.
20 Bradson, Roxbury MA, Mass. DEP Project Number 75029MA (June 1, 1988).
"Soils at the (Incinerator) site consist of 5 to 50 feet of miscellaneous fill overlying clay."
20 Bradson, Roxbury MA, Mass. DEP Project Number 75029MA (June 1, 1988).
"The Site is located on Bradston Street in Roxbury, Massachusetts and consists of a 0.38-acreparcel of land. The Site is bounded by Bradston Street to the north, parking lots to the east and west, and a commercial building to the south.. The building has been vacant for several years. Boston Consolidated Gas Company constructed the building in 1915 for use as an oil and paint house. It was renovated in 1921 and converted to use as shops. From the 1930's to the 1990's the building was utilized by various manufacturing operations including the manufacture of rubber products.
On Junel4 and 15, 2000 BGS advanced nine test pits at the Site (Figure 2). The test pits were advanced to a depth of approximately 7-feet. Groundwater was encountered at approximately 6-feet. Excavated material generally consisted of layers of sand and gravel fill materials of an urban nature containing wood, wood ash, brick, construction debris, coal and coal ash. Soil samples from the water table were collected at each test pit location. All excavated material was returned to the test pits.
On July 11, 2000 BGS advanced four soil borings/monitoring wells (MW-1, MW-2, MW-3 and MW-4) at the site. Composite soil samples were collected at each well location at a depth of 10 to 12 feet below ground surface (bgs) and submitted for laboratory analysis for EPH. This depth was chosen due to the presence of visual evidence of petroleum smearing due to a fluctuating water table. The soil sample at MW-3 was also analyzed for RCRA 8 metals and PAHs.
On August 9, 2000 three (3) additional soil borings/monitoring wells (MW-5, MW-6 and MW-7) were installed on site. Composite soil samples were collected at each well location at a depth of 4 to 8 feet below ground surface (bgs) and submitted for laboratory analysis for EPH with target compounds and RCRA 8 Metals. On August 16, 2000 groundwater samples were collected from all seven (7) on site monitoring wells to be submitted for laboratory analysis for Dissolved Lead, VPH and EPH.
The results of the subsurface investigation conducted at the Site as part of the RAM indicate the presence of elevated levels of Lead, Arsenic, EPH and several EPH target compounds, and PAHs. Lead above the Method 1 S-2/GW-2 risk based standard was detected in soil samples collected from TP-2 and MW-7. Arsenic above the Method 1 S-2/GW-2 risk based standard was detected in soil samples collected from MW-S and MW-7. EPH above the Method 1 S-2/GW-2 risk based standard was detected in soil samples collected from TP-2, TP-6, TP-7 and MW-5. PAHs above the Method 1 S-2/GW-2 risk based standard was detected in soil sample collected from MW-3.
Groundwater elevation measurements recorded during the July 2000 and August 2000 sampling rounds
indicate that groundwater flow at the Site is generally toward the east-northeast (Figure 3 and Figure 4).
RESPONSE ACTION OUTCOME STATEMENT, 33 Bradston Street Roxbury, MA 02118, RTN 3-19481, Boston GeoScience Corporation for Bradston Associates, L.L.C. 633 Tremont Street, Boston, MA 02118 (September 28, 2001)
On Junel4 and 15, 2000 BGS advanced nine test pits at the Site (Figure 2). The test pits were advanced to a depth of approximately 7-feet. Groundwater was encountered at approximately 6-feet. Excavated material generally consisted of layers of sand and gravel fill materials of an urban nature containing wood, wood ash, brick, construction debris, coal and coal ash. Soil samples from the water table were collected at each test pit location. All excavated material was returned to the test pits.
On July 11, 2000 BGS advanced four soil borings/monitoring wells (MW-1, MW-2, MW-3 and MW-4) at the site. Composite soil samples were collected at each well location at a depth of 10 to 12 feet below ground surface (bgs) and submitted for laboratory analysis for EPH. This depth was chosen due to the presence of visual evidence of petroleum smearing due to a fluctuating water table. The soil sample at MW-3 was also analyzed for RCRA 8 metals and PAHs.
On August 9, 2000 three (3) additional soil borings/monitoring wells (MW-5, MW-6 and MW-7) were installed on site. Composite soil samples were collected at each well location at a depth of 4 to 8 feet below ground surface (bgs) and submitted for laboratory analysis for EPH with target compounds and RCRA 8 Metals. On August 16, 2000 groundwater samples were collected from all seven (7) on site monitoring wells to be submitted for laboratory analysis for Dissolved Lead, VPH and EPH.
The results of the subsurface investigation conducted at the Site as part of the RAM indicate the presence of elevated levels of Lead, Arsenic, EPH and several EPH target compounds, and PAHs. Lead above the Method 1 S-2/GW-2 risk based standard was detected in soil samples collected from TP-2 and MW-7. Arsenic above the Method 1 S-2/GW-2 risk based standard was detected in soil samples collected from MW-S and MW-7. EPH above the Method 1 S-2/GW-2 risk based standard was detected in soil samples collected from TP-2, TP-6, TP-7 and MW-5. PAHs above the Method 1 S-2/GW-2 risk based standard was detected in soil sample collected from MW-3.
Groundwater elevation measurements recorded during the July 2000 and August 2000 sampling rounds
indicate that groundwater flow at the Site is generally toward the east-northeast (Figure 3 and Figure 4).
RESPONSE ACTION OUTCOME STATEMENT, 33 Bradston Street Roxbury, MA 02118, RTN 3-19481, Boston GeoScience Corporation for Bradston Associates, L.L.C. 633 Tremont Street, Boston, MA 02118 (September 28, 2001)
"The Crosstown Center Site is located along Massachusetts Avenue between Albany Street and Melnea Cass Boulevard in Boston (Roxbury), Suffolk County, Massachusetts. The RTN 3-0245 site has an industrial history that dates back to the mid to late 1800s. Former lead manufacturing operations, former gasoline service stations operations, and extensive fill materials, as well as smaller industrial operations (junk storage, auto body repair, welding, etc.) are the known and/or suspected sources of contamination.
RELEASE ABATEMENT MEASURE PLAN CROSSTOWN CENTER REDEVELOPMENT PROJECT, 801 MASSACHUSETTS AVENUE BOSTON, MA, RTN # 3-245 (January 2013)
RELEASE ABATEMENT MEASURE PLAN CROSSTOWN CENTER REDEVELOPMENT PROJECT, 801 MASSACHUSETTS AVENUE BOSTON, MA, RTN # 3-245 (January 2013)
"The approximately 3.5-acre site is located at the intersection of Massachusetts Avenue and Albany Street in a mixed commercial and industrial area of Roxbury. The EDIC Parcel 4 site and adjacent DEC property were occupied by lead product manufacturing facilities and other industries including a lumber company and brewery. A Mobil station occupied the northeast portion of the EDIC Parcel 4 property for approximately 50 years until the 1970's.
The EDIC site is located in the eastern part of the Boston Basin which is a fault-bounded structural depression located within the Milford-Dedham tectonic zone of eastern Massachusetts. The coastal low land is bounded by the waters of Boston Harbor and Boston Bay to the east; the Fells Upland to the north; the Sharon Upland to the south; and, merges with the Needham Upland to the west. The basin is structurally defined by the Northern Border thrust fault and a step-like series of thrust faults to the south. The rocks within the basin are both folded and faulted. Much of the bedrock within the Boston Basin is deeply buried by quaternary glacial deposits. Bedrock was not encountered in test pits or borings excavated at the EDIC Parcel 4 site or adjacent property during the Phase I or II studies.
Regional geology in the Boston Basin was topographically refined by continental glaciation during the Pleistocene. With the exception of coastal areas and valleys lying less than 50 feet above sea level, most of the rocks of the basin are overlain by glacial drift. Based on subsurface explorations conducted during the Phase I and II studies, the site consists of approximately 5 to 15 feet of fill overlying sand and silt or dense silt deposits. The fill generally consists of medium sand and gravel intermixed with construction debris (bricks, concrete, asphalt). Clay was also observed underlying the fill in several locations in the northern and eastern portions of the site. Permeable sand and sand and gravel deposits were observed during the Phase I study at borings excavated in the southwestern portion of the site.
Regionally, groundwater flow direction is northeasterly towards the Fort Point Channel, located approximately one-mile northeast of the site, and continues northeasterly into the Boston Inner Harbor which ultimately discharges approximately two miles east/southeast into Boston Harbor. Localized groundwater flow direction, based on water elevation surveys conducted at the site during the Phase I and II studies, appears to be northeasterly across the site towards Massachusetts Avenue. Depth to groundwater at the site, based on water level measurements during the Phase I and II studies, generally varied from approximately 5 to 10.5 feet below ground surface.
Economic Development and Industrial Corporation of Boston Report on EDIC Crosstown Industrial Park, Parcel 4 PHASE II - COMPREHENSIVE SITE ASSESSMENT October, 1991
The EDIC site is located in the eastern part of the Boston Basin which is a fault-bounded structural depression located within the Milford-Dedham tectonic zone of eastern Massachusetts. The coastal low land is bounded by the waters of Boston Harbor and Boston Bay to the east; the Fells Upland to the north; the Sharon Upland to the south; and, merges with the Needham Upland to the west. The basin is structurally defined by the Northern Border thrust fault and a step-like series of thrust faults to the south. The rocks within the basin are both folded and faulted. Much of the bedrock within the Boston Basin is deeply buried by quaternary glacial deposits. Bedrock was not encountered in test pits or borings excavated at the EDIC Parcel 4 site or adjacent property during the Phase I or II studies.
Regional geology in the Boston Basin was topographically refined by continental glaciation during the Pleistocene. With the exception of coastal areas and valleys lying less than 50 feet above sea level, most of the rocks of the basin are overlain by glacial drift. Based on subsurface explorations conducted during the Phase I and II studies, the site consists of approximately 5 to 15 feet of fill overlying sand and silt or dense silt deposits. The fill generally consists of medium sand and gravel intermixed with construction debris (bricks, concrete, asphalt). Clay was also observed underlying the fill in several locations in the northern and eastern portions of the site. Permeable sand and sand and gravel deposits were observed during the Phase I study at borings excavated in the southwestern portion of the site.
Regionally, groundwater flow direction is northeasterly towards the Fort Point Channel, located approximately one-mile northeast of the site, and continues northeasterly into the Boston Inner Harbor which ultimately discharges approximately two miles east/southeast into Boston Harbor. Localized groundwater flow direction, based on water elevation surveys conducted at the site during the Phase I and II studies, appears to be northeasterly across the site towards Massachusetts Avenue. Depth to groundwater at the site, based on water level measurements during the Phase I and II studies, generally varied from approximately 5 to 10.5 feet below ground surface.
Economic Development and Industrial Corporation of Boston Report on EDIC Crosstown Industrial Park, Parcel 4 PHASE II - COMPREHENSIVE SITE ASSESSMENT October, 1991
BIOSQUARE DRIVE / FRONTAGE RD (AT EAST CONCORD ST TO UNION PARK ST)
NEIDL
"Based on observations made during subsurface investigation activities conducted to date, subsurface conditions at the site include urban fill material with significant quantities of subsurface wood and lumber that were likely the remnants of the former wharfs or piers or other buildings. Large, subsurface void spaces characteristic of urban fill are also present. Starting from the bedrock and extending upward the soil generally consists of a variable thickness of glacial till, stiff to medium gray clay, varying in thickness from 40 feet to over 100 feet, a relatively thin and discontinuous deposit of sand, overlain by peat and organic silt, which in turn is overlain by the granular fill... Groundwater is present on the site at depths 5 to 11 feet below ground surface. Based on local topography, the groundwater at the site is expected to flow generally northeasterly toward the Fort Point Channel which is nearly 1 mile away from the site."
NIH, Final Environmental Impact Statement National Emerging Infectious Diseases Laboratories, BioSquare Research Park in Boston, Massachusetts (Dec. 2005).
NEIDL
"Based on observations made during subsurface investigation activities conducted to date, subsurface conditions at the site include urban fill material with significant quantities of subsurface wood and lumber that were likely the remnants of the former wharfs or piers or other buildings. Large, subsurface void spaces characteristic of urban fill are also present. Starting from the bedrock and extending upward the soil generally consists of a variable thickness of glacial till, stiff to medium gray clay, varying in thickness from 40 feet to over 100 feet, a relatively thin and discontinuous deposit of sand, overlain by peat and organic silt, which in turn is overlain by the granular fill... Groundwater is present on the site at depths 5 to 11 feet below ground surface. Based on local topography, the groundwater at the site is expected to flow generally northeasterly toward the Fort Point Channel which is nearly 1 mile away from the site."
NIH, Final Environmental Impact Statement National Emerging Infectious Diseases Laboratories, BioSquare Research Park in Boston, Massachusetts (Dec. 2005).
601 ALBANY ST, 2001 SOIL TESTS:
601 ALBANY ST, 2002 SOIL TESTS:
Release Abatement Measure, 120 Day Status Report, 601 - 603 Albany Street Roxbury, MA 02116 (March 2002)
- LEAD 1,870 mg/kg 11/21/01; 1,900 mg/kg 12/31/01; 436 mg/kg 12/31/01
- MERCURY 3 mg/kg 11/21/01; 16 mg/kg 01/03/02; 5.98 mg/kg 01/03/02
- CHROMIUM 19.6 mg/kg 11/21/01; 20.5 mg/kg 12/31/01
- BARIUM 435 mg/kg 12/31/01; 199 mg/kg 12/31/01
- SILVER 9.27 mg/kg 12/31/01
601 ALBANY ST, 2002 SOIL TESTS:
- FSL-10 (2002): 1'-3' black fill with asphalt, coal, and slag pieces; 3'-8' gray ash, black fill with ash, coal, asphalt, brick and debris; 7'-8' black organics; 8'-12' blue-green clay; 12'-14' tan clay; 14'-16' blue-green clay.
- FSL-11 (2002): 1'-6' gray ash and gray fill with metal debris; 6'-7' gray ash; 7'-8' black fill with wood debris; 8'-12' void/no recovery; 12'-16' gray clay.
- FSL-12 (2002): 1'-5' blackfill with brick and asphalt; 5'-16' Gray Clay
Release Abatement Measure, 120 Day Status Report, 601 - 603 Albany Street Roxbury, MA 02116 (March 2002)
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"The approximately 32,500 sq. ft. subject site property is located at 650 Albany Street (Parcel C), in downtown Boston. Historically, the Colonial shoreline passed longitudinally (west to east) approximately parallel to Albany Street and the Biosquare II site. The Roxbury Canal was constructed westward from South Bay, south of the site, in the mid 1800's. Following construction of the Roxbury Canal conduit, the canal was filled during the 1960's and early 1970's. The Albany Street area of Boston was filled during the mid-1850's and was occupied by one and two-story brick buildings shortly thereafter.
According to Sanborn Fire Insurance Maps and other historic maps for the site the buildings within the central portion of the Biosquare II site were used as military barracks by the U.S. government until 1868. From approximately 1882-1977, the site was occupied by eight buildings (Buildings 21,22,23,25,26,31,34 and 35) utilized by the City of Boston Water and Sewer Services, the Boston Public Works Department Street Cleaning and Sanitary Services and Highway Division Paving Services.
Buildings 21, 22 and 23 were used mainly for storage and as wagon sheds until they were razed in approximately 1949. Building 23 was briefly occupied by a blacksmith and carpenter shop until it was razed in approximately 1928. Building 25 located at 650 Albany Street, occupied only a portion of the current subject site, with a majority of the building extending onto the adjacent parcels to the south and west. Building 25 utilized a 1,500-gallon underground #2 fuel oil tank which was located along the inside of the southeastern wall of the building. This tank was located immediately to the south of the current subject site. This building was utilized for vehicle storage and repair, carpentry, and forging. Building 26 was erected on the eastern portion of the site in approximately 1874 and was used for storage and office space by the City of Boston Paving Division until it was razed in approximately 1949. Building 34 was constructed on-site in approximately 1939 and Building 31 existed by 1950. Usage of these buildings is unknown. Building 35 was erected at 630 Albany Street in approximately 1949 by the Public Works Department-Street Paving Division. The building occupied a portion of the current subject site (Parcel C) and a portion of the adjacent parcel to the east of the current subject site (Parcel F). The building was used as office space until approximately 1977, when the building and surrounding property was transferred to the Boston Traffic Police Department. The Boston Traffic Police Department operated a tow truck radio dispatch office from this building and operated the Boston Traffic Police Department Tow Lot Number 5, on the eastern half of the site from approximately 1977 to the present. A 275-gallon aboveground storage tank was located along the eastern edge of the building, immediately to the east of the current subject site. By the mid-1970's, all of the buildings were razed and the Biosquare II site was utilized as a parking lot.
Environmental test pits and test borings completed during the 1998 Haley & Aldrich subsurface exploration programs for the subject site indicate the site is underlain by approximately 5 to 20 feet of miscellaneous fill. The fill composition typically consists of intermixed sand, silt, gravel, cinders, bricks, building rubble, cobblestones and ash. The fill is underlain by a layer of organic soils approximately II to 23 feet in thickness. Organic soils are underlain by a 75 to 99 foot layer of marine deposits consisting of gray silty clay with sand and gravel. Underlying this is a thin layer of Glaciomarine soils and Glacial Till. Bedrock was encountered at depths ranging from 106 to 134 ft. below existing ground surface.
Groundwater levels most recently observed in observation wells on-site indicate groundwater levels at depths ranging from 5 to 11.5 ft. below the ground surface. The inferred direction of groundwater flow is to the north/northwest towards Albany Street and ultimately towards the Fort Point Channel. Groundwater levels at the site do not appear to be influenced by tidal action within the Roxbury Canal Conduit.
TIER 1 CLASSIFICATON SUBMITTAL BIOSQUARE II DEVELOPMENT, 650 ALBANY STREET - PARCEL C, BOSTON, MASSACHUSETTS, RTN 3-16655, Haley & Aldrich, Inc. for Massachusetts Department of Environmental Protection, File No. 10666-130 (March 1999).
A National Pollution Discharge Elimination System (NPDES) Permit Exclusion (#98-123) was granted by the EPA on 28 May 1998. The Permit Exclusion authorized discharge of up to 100 gallons per minute of construction dewatering effluent to the municipal storm drain system leading to the Fort Point Channel and Boston Harbor. Discharge to date has typically been intermittent, and has been due to standing water accumulated within the excavation after rain events. The dewatering system was designed in accordance with the permit requirements, installed and operated by J. Derenzo Co. (Earthwork sub-contractor). Monitoring and sampling of the influent and effluent has been conducted by Haley and Aldrich, Inc., and analyzed by a DEP-approved laboratory. Results of discharge water quality analyses indicate levels of contaminants have not been detected above laboratory limits for the discharge water samples.
TIER 1 CLASSIFICATON SUBMITTAL BIOSQUARE II DEVELOPMENT, 650 ALBANY STREET - PARCEL C, BOSTON, MASSACHUSETTS, RTN 3-16655, Haley & Aldrich, Inc. for Massachusetts Department of Environmental Protection, File No. 10666-130 (March 1999).
Groundwater infiltration or discharge of surface water runoff into the Roxbury Canal Conduit provides the primary, currently existing pathway for potential off-site migration of contamination. The Roxbury Canal Conduit discharges into the Fort Point Channel, which is connected to Boston Inner Harbor. The tidal influenced water level in the Roxbury Canal Conduit is anticipated ,to generally range from EI. 10 to EI. 0 (BCB), corresponding to mean high and low water, respectively. Groundwater infiltration into or water exfiltration out of the conduit is possible.
On-site construction dewatering was conducted in accordance with a National Pollution Discharge Elimination System (NPDES) Permit Exclusion (#98-123) granted by the EPA on 28 May1998. Discharge during the period 21 April 1998 to18 August 1998 was intermittent and was due to standing water accumulated within the excavation after rain events. Influent and effluent testing was below the limits specified in the Permit and the applicable Reportable Concentrations (RCGW-2) and there was not a significant difference between the test results of the influent and effluent samples. This resulted in the decision to remove the water treatment portion of the system.
RELEASE ABATEMENT MEASURE (RAM) COMPLETION REPORT IV, BIOSQUARE II, 650 ALBANY STREET, BOSTON, MASSACHUSETTS, RTN 3-16655, Haley & Aldrich, Inc. Boston, Massachusetts, File No. 10666-130, (April 2000).
According to Sanborn Fire Insurance Maps and other historic maps for the site the buildings within the central portion of the Biosquare II site were used as military barracks by the U.S. government until 1868. From approximately 1882-1977, the site was occupied by eight buildings (Buildings 21,22,23,25,26,31,34 and 35) utilized by the City of Boston Water and Sewer Services, the Boston Public Works Department Street Cleaning and Sanitary Services and Highway Division Paving Services.
Buildings 21, 22 and 23 were used mainly for storage and as wagon sheds until they were razed in approximately 1949. Building 23 was briefly occupied by a blacksmith and carpenter shop until it was razed in approximately 1928. Building 25 located at 650 Albany Street, occupied only a portion of the current subject site, with a majority of the building extending onto the adjacent parcels to the south and west. Building 25 utilized a 1,500-gallon underground #2 fuel oil tank which was located along the inside of the southeastern wall of the building. This tank was located immediately to the south of the current subject site. This building was utilized for vehicle storage and repair, carpentry, and forging. Building 26 was erected on the eastern portion of the site in approximately 1874 and was used for storage and office space by the City of Boston Paving Division until it was razed in approximately 1949. Building 34 was constructed on-site in approximately 1939 and Building 31 existed by 1950. Usage of these buildings is unknown. Building 35 was erected at 630 Albany Street in approximately 1949 by the Public Works Department-Street Paving Division. The building occupied a portion of the current subject site (Parcel C) and a portion of the adjacent parcel to the east of the current subject site (Parcel F). The building was used as office space until approximately 1977, when the building and surrounding property was transferred to the Boston Traffic Police Department. The Boston Traffic Police Department operated a tow truck radio dispatch office from this building and operated the Boston Traffic Police Department Tow Lot Number 5, on the eastern half of the site from approximately 1977 to the present. A 275-gallon aboveground storage tank was located along the eastern edge of the building, immediately to the east of the current subject site. By the mid-1970's, all of the buildings were razed and the Biosquare II site was utilized as a parking lot.
Environmental test pits and test borings completed during the 1998 Haley & Aldrich subsurface exploration programs for the subject site indicate the site is underlain by approximately 5 to 20 feet of miscellaneous fill. The fill composition typically consists of intermixed sand, silt, gravel, cinders, bricks, building rubble, cobblestones and ash. The fill is underlain by a layer of organic soils approximately II to 23 feet in thickness. Organic soils are underlain by a 75 to 99 foot layer of marine deposits consisting of gray silty clay with sand and gravel. Underlying this is a thin layer of Glaciomarine soils and Glacial Till. Bedrock was encountered at depths ranging from 106 to 134 ft. below existing ground surface.
Groundwater levels most recently observed in observation wells on-site indicate groundwater levels at depths ranging from 5 to 11.5 ft. below the ground surface. The inferred direction of groundwater flow is to the north/northwest towards Albany Street and ultimately towards the Fort Point Channel. Groundwater levels at the site do not appear to be influenced by tidal action within the Roxbury Canal Conduit.
TIER 1 CLASSIFICATON SUBMITTAL BIOSQUARE II DEVELOPMENT, 650 ALBANY STREET - PARCEL C, BOSTON, MASSACHUSETTS, RTN 3-16655, Haley & Aldrich, Inc. for Massachusetts Department of Environmental Protection, File No. 10666-130 (March 1999).
A National Pollution Discharge Elimination System (NPDES) Permit Exclusion (#98-123) was granted by the EPA on 28 May 1998. The Permit Exclusion authorized discharge of up to 100 gallons per minute of construction dewatering effluent to the municipal storm drain system leading to the Fort Point Channel and Boston Harbor. Discharge to date has typically been intermittent, and has been due to standing water accumulated within the excavation after rain events. The dewatering system was designed in accordance with the permit requirements, installed and operated by J. Derenzo Co. (Earthwork sub-contractor). Monitoring and sampling of the influent and effluent has been conducted by Haley and Aldrich, Inc., and analyzed by a DEP-approved laboratory. Results of discharge water quality analyses indicate levels of contaminants have not been detected above laboratory limits for the discharge water samples.
TIER 1 CLASSIFICATON SUBMITTAL BIOSQUARE II DEVELOPMENT, 650 ALBANY STREET - PARCEL C, BOSTON, MASSACHUSETTS, RTN 3-16655, Haley & Aldrich, Inc. for Massachusetts Department of Environmental Protection, File No. 10666-130 (March 1999).
Groundwater infiltration or discharge of surface water runoff into the Roxbury Canal Conduit provides the primary, currently existing pathway for potential off-site migration of contamination. The Roxbury Canal Conduit discharges into the Fort Point Channel, which is connected to Boston Inner Harbor. The tidal influenced water level in the Roxbury Canal Conduit is anticipated ,to generally range from EI. 10 to EI. 0 (BCB), corresponding to mean high and low water, respectively. Groundwater infiltration into or water exfiltration out of the conduit is possible.
On-site construction dewatering was conducted in accordance with a National Pollution Discharge Elimination System (NPDES) Permit Exclusion (#98-123) granted by the EPA on 28 May1998. Discharge during the period 21 April 1998 to18 August 1998 was intermittent and was due to standing water accumulated within the excavation after rain events. Influent and effluent testing was below the limits specified in the Permit and the applicable Reportable Concentrations (RCGW-2) and there was not a significant difference between the test results of the influent and effluent samples. This resulted in the decision to remove the water treatment portion of the system.
RELEASE ABATEMENT MEASURE (RAM) COMPLETION REPORT IV, BIOSQUARE II, 650 ALBANY STREET, BOSTON, MASSACHUSETTS, RTN 3-16655, Haley & Aldrich, Inc. Boston, Massachusetts, File No. 10666-130, (April 2000).
Prior to the placement of fill, the area including the site was located under the waters of South Bay. The development of the Central Artery transportation corridor in the 1950's brought about the filling of South Bay and the culverting of the Dorchester and Roxbury Canals. The closest surface water is the Fort Point Channel, which is located approximately one-quarter mile to the north. However, the Roxbury Canal culvert and Dorchester Canal culvert, as illustrated on the Site Plan, run in a northerly direction underneath the parcel. These two subsurface drainage channels discharge to surface water, and have been considered surface water bodies in this assessment. The surrounding site receptors are shown on Figure 3, Geographical information Services (GlS) Map. Shallow subsurface soils encountered during soil borings on the property were characterized as mostly urban fill. The urban fill consisted of layers of sand and gravel as well as coal, cinders, brick, ash, glass and other debris.
Phase II - Comprehensive Site Assessment: Release Tracking Number 3-14507, City of Boston, Vehicle Fueling Facility 400 Frontage Road, Boston, Massachusetts (April 5, 2002
Phase II - Comprehensive Site Assessment: Release Tracking Number 3-14507, City of Boston, Vehicle Fueling Facility 400 Frontage Road, Boston, Massachusetts (April 5, 2002
595 Albany st - parcel 1175, 2.7k sqft, 10 ft asl, gw may flow NE "however direction of regional gw flow in the vicinity of the site may vary due to the influence of local topography, underground utilities (e.g. storm drains, utility ducts, water mains, etc.) and heterogeneous subsurface conditions.
brick cellar has direct floors
alley associated with EI Dupont and M&L autobody
previously used by Mac Battery Factory, atuo battery facility
595 Albany St, South Boston, MA, Project No 20129, March 1992
575 Albany dupont no 3-0245, e deadham st,4k gallon underground storage tank (UST) with heatin fuel in alley off east deadham st
unearthed March 1989 and removed shortly after
PHC analysis 6ppm-110ppm (leaking pipe or spill during transfer)
DEQA gave ok to "pave the area where the tank was removed from with the understanding that further work may be requested on the site in the future'
in 1992 fire dept said no record of any USTs within 1/2 mile; no env/heath dept files
Preliminary Environmental Site Assessment Update for the Property Located at 595 Albany St, South Boston, MA, Project No. 20129, (March 6 1992).
MBTA RAIL YARD / WIDETT CIRCLE (AT E DEDHAM ST TO EAST BERKLEY ST)
"Cabot Yard is located immediately south of the intersection of Dorchester Avenue and West Fourth Street The Site includes the eastern half of Cabot Yard encompassing the bus garage and parking areas/access roads located north and south of the garage. The Site also includes abutting portions of properties located at 220, 248, and 250 Dorchester Avenue, all of which are located less than 100 feet east of Cabot Yard. In addition, the Site includes the Pump Station, which is located approximately 150 feet southeast of Cabot Yard along the southern side of the Haul Road and adjacent to West 6"' Street and Dorchester Avenue. The Site is located in an area zoned for mixed use (residential, commercial, and industrial). Cabot Yard is an approximately 28-acre parcel of land occupied by two large multi-story buildings used for offices and repair/maintenance of buses and trains. These buildings occupy approximately 50% of Cabot Yard and the remainder consists of paved parking and access roads or railroad lines. Cabot Yard is bordered to the north by West Fourth Street and commercial businesses, to the east by Dorchester Avenue and commercial businesses, to the south by the Haul Road and a CSX Corporation railroad line, and to the west by the Boston Department of Public Works. The Pump Station is owned and operated by MassPike and pumps collected stormwater for a portion of the Haul Road to the Fort Point Channel located approximately 1/3-mile to the northwest. The Pump Station is an approximately 0.15-acre parcel of land occupied by 1 one-story brick and mortar pump station building. Approximately 75% of the Pump Station is occupied by the building and the remainder consists of concrete walkways and an unpaved hill leading towards the CSX railroad line and the Haul Road. The Pump Station is bordered to the northeast by West Fifth Street and commercial businesses, to the southeast by commercial businesses, West 6"' Street and residences, to the southwest by the Dorchester Avenue overpass, and to the northwest by the CSX railroad line and the Haul Road."
"Cabot Yard (previously known as the South Bay Maintenance Facility) was purchased in 1969 by the Commonwealth of Massachusetts from the Penn Central Transportation Company (Stone & Webster, 1993). The current buildings at Cabot Yard were completed in 1973. Presently Cabot Yard is owned and operated by MBTA. Cabot Yard has been used as a railway facility for over 125 years. In 1875, according to insurance maps of Boston prepared by the Sanborn Company, the Old colony Railway operated a car house, engine house, machine shop, boiler shop, car repair shop, car paint shop, and coal shed on the western half of Cabot Yard. Tenements, a stone yard, and a marble works occupied the eastern half of the property. The Bromely & Co. Atlas of the City of Boston shows that by 1899 rail lines extended to fill the eastern half of the property. The Bromely Atlas of 1919 shows Cabot Yard owned by the Old Colony Railroad Company."
"In general the topography at Cabot Yard slopes gently toward the northeast; however, the northwest corner of Cabot Yard slopes downhill toward the west. Also, Dorchester Avenue slopes downhill to the north and, at Cabot Yard's northern property boundary, it is several feet below Cabot Yard ground surface elevation. The elevation of the South Boston Haul Road near Cabot Yard is approximately 10 to 20 feet below the surrounding topographic elevation and slopes downhill to the northeast. The elevation of the Pump Station, located south of the South Boston Haul Road and northeast of Dorchester Avenue, is approximately 10 feet above the Haul Road and 5 to 10 feet below the topographic elevations to the southwest and southeast. Because Cabot Yard and the surrounding area is predominantly paved, surface water runoff is collected in catch basins and routed to Boston Water & Sewer Commission's sewer in Dorchester Avenue. Surface water runoff on the South Boston Haul Road is collected in a series of catch basins and underdrains and routed to the Pump Station, where the collected water is pumped via two force mains towards the northeast to the Fort Point Channel."
"Groundwater at the Site is categorized as GW-2 and GW-3. GW-2 classification is applicable because contaminated groundwater is located within 30 feet of occupied buildings and the average annual depth to groundwater is approximately 15 feet below grade. Site groundwater is also categorized as GW-3 because groundwater in the area is assumed to eventually discharge to the nearby Fort Point Channel and Boston Harbor. The criteria listed for GW-1 classification specified in 310 CMR 40.0932 (4) are not met at this Site. As shown on the Area Receptors Map in Figure 3 and discussed in Section 1.6, the Site is not in an area designated as a Current or Potential Drinking Water Source Area."
"Seven (7) geologic units were encountered during Weston & Sampson's April 2000 and April 2001 Supplemental Phase II investigation. These units include, in stratigraphic succession from youngest (shallowest) to oldest (deepest):
Clayey silt was noted in the southern portion of the Site in borings WSPS-1, WSPS-2, and SW-1, and in the eastern portion of the Site in boring WSA-4. The encountered clayey silt unit ranged between 3 to 12 feet below grade. Lenses of fine sand and clay were observed in the clayey silt unit. No petroleum odors or staining or non-native materials (e.g., ash, brick, glass, etc.) were noted in soil samples collected from the clayey silt unit. The clay unit was found in the central portion of Cabot Yard, WS-2 and WS-3, and in the eastern area of the Site, WSA-I through WSA3.
The clay unit ranged in thickness of 2 feet in boring WS-3 to 5 feet in boring WS-2. Petroleum odors and staining were observed in WS-2 and WS-3, but no odors or staining were observed in this unit at WSA-1 through WSA-3. No fill material was noted in the soil samples collected from the clay unit. The lower sand unit is generally present in the lower portions of all soil borings except WS-7 and was encountered between 8 feet (WSA-4) and 27 feet (SW-4) below grade. Soil boring WS-7 is located on the northern portion of Cabot Yard. No non-native materials such as brick, glass wood or ash were present in the lower sand unit. Petroleum odors and staining were present in WS-1, WS-3, SW-2, and SW-4.
The sand and silt layer was observed in borings WS-11, SW-1, and SW-4. Tan to gray interlayered fine sand and silt were present in SW-1 at a depth of 15 feet to 21 feet. Tan sand and silt were observed in WS-11 and SW-4 at depths of 19 and 20 feet, respectively. No fill material was observed in the sand and silt layer. No petroleum odors or staining were observed in this unit. A confining layer was not encountered at the Site during the Supplemental Phase II investigation or any other previous investigation. In addition, the depth to bedrock was not determined and no bedrock outcrops were observed at or near the Site. According to the USGS Bedrock Geologic Map of Massachusetts (Zen et al., 1983), the Site is located within the sedimentary rock portion of the Milford-Dedham Tectonic Zone of eastern Massachusetts. The bedrock type underlying the Site is likely a sedimentary (sandstone or conglomerate) rock of the Cambridge Argillite Zone."
"On May 9, 2001, Weston & Sampson collected groundwater depth measurements from all accessible monitoring wells at the Site (Table 6). The depth to groundwater at the Site ranged from 4.29 feet below grade at SW-6 to 22.28 feet at WS-1. Groundwater elevations ranged between 77.00 feet at WS-1 and 89.07 feet at SW-6. Based on the corrected groundwater contours shown in Figure 6, groundwater at the Site flows in two distinct patterns: 1) most groundwater at and east of Cabot Yard flows toward a slight depression located under the Cabot Yard bus garage and 2) groundwater in the southern portion of Cabot Yard flows southeast via a steep gradient toward the South Boston Haul Road and the Pump Station. The hydraulic gradient across the Site was calculated using groundwater elevations collected on May 9, 2001. Horizontal hydraulic gradients were calculated based on groundwater elevations at monitoring wells SW-3 to WSA-1, RIZ-5 to WS-10 and groundwater elevations south of RIZ-4 and north of the Haul Road. The average horizontal hydraulic gradient (IAvG) across the Site was calculated to be 0.060 fl/f. A downward vertical gradient of 0.22 fl/ft was calculated using groundwater and saturated screen elevation data from wells WS-10 and WS-1.
On May 2,2001, Weston & Sampson conducted four (4) slug tests at monitoring wells WS-4, WSA-1, SW-1, and SW-10. Due to the varying locations and screen depth intervals of these wells, each slug test was performed in a separate geologic unit (Figure 5). The WS-4 screen is located in the sand and gravel unit, WSA- 1 is located in the clay (with trace sand) unit, SW- 1 is located in the sand and silt unit, and SW-10 is located in the sand unit. Using the data collected from these slug tests, hydraulic conductivities (K) were calculated for each monitoring well/geologic unit. Hydraulic conductivities at the four wells ranged from 2.36 feet/day to 2.91 feet/day."
"The field screening results and general observations are presented in EST's report in Appendix D. According to their sampling report, EST observed petroleum odors in WS-4 and WSA-2 groundwater wells during sampling. The pH measurements ranged from 4.97 (WSA-5) to 7.22 (WS-4). Specific conductance measurements ranged from 335 micromhos per centimeter (pmhos/cm) in RIZ-6 to 21,899 ptmhos/cm in WS-4. Dissolved oxygen concentrations ranged from 0.11 milligrams per liter (mg/1) in WS-4 to 6.76 mg/I in WSA-4."
"Cabot Yard, Metals/Inorgancis: Dissolved cadmium was not detected in the 3 samples collected. Total iron and manganese were detected at 210,000 pg/1 and 240,000 kg/1 in wells WS- I and WS- 3, respectively. Total manganese was detected at 14,000 jig/1 and 5,200 jlg/1 in wells WS-1 and WS-3, respectively. Dissolved iron was detected at 86,000 jLg/l and 83,000 pg/l in wells WS-1 and WS-3, respectively. Dissolved manganese was detected at 13,000 pg/1 and 3,100 lg/1 in wells WS-1 and WS-3, respectively."
"Cabot Yard, Bacteria Count: Heterotrophic and hexadecane degrading bacteria were detected in well SW-4 at concentrations of 46,000 colony forming units per milliliter (cfu/ml) and 38,000 cfulml, respectively."
"Abutting Properties, Metals/Inorgancis: Total and dissolved iron were detected in well WSA-2 at concentrations of 39,000 ptg/1 and 38,000 pig/l, respectively. Total and dissolved manganese were detected in well WSA-2 at concentrations of 2,800 pg/1 and 2,900 pg/1, respectively."
"Abutting Properties, Alkalinity/Nitrate/Sulfate: Alkalinity (as calcium carbonate) and sulfate were detected in well WSA-2 at concentrations of 520 mg/l and 8.1 mg/1, respectively. Nitrate (as nitrogen was not detected in the WSA-2 sample. Hexadecane bacteria were found at to be lowest in the source area (Cabot Yard) and higher at an abutting property (250 Dorchester Avenue)."
"Abutting Properties, Bacteria Count: Heterotrophic and hexadecane degrading bacteria were detected in well WSA-2 at concentrations of 220,000 cfulml and 230,000 cfu/ml, respectively."
"Product exists at Cabot Yard and within the Pump Station's stormwater collection system. At Cabot Yard, product thicknesses range from less than an inch to almost 6 feet. The product plume is thickest at well WS- 1 and decreases in thickness in every direction from WS-1. Product appears to be migrating in a northerly direction along a large utility corridor in the vicinity of well SW-4. This utility corridor, known as the South Boston Interceptor Trench, contains a 48-inch diameter sewer pipe owned by BWSC. This sewer pipe carries stormwater that is collected over a large portion of South Boston. The pipe is located between approximately 15 to 25 feet below grade and, as such, intersects the groundwater table in the area of product at Cabot Yard. Acting as a preferential pathway, the bedding materials ofthis large sewer line likely contain product and are influencing the shape of the plume as shown on Figure 7. After constructing the South Boston Haul Road and installing numerous utilities and underdrains, a preferential pathway was created south of Cabot Yard that likely acts as a sink. Therefore, as the 48- inch sewer line collects product and carries it via bedding materials towards the north and south, the groundwater sink created by the Haul Road draws the carried product from the sewer line's bedding materials into the Haul Road's stormwater collection system (presumably via underdrains)."
"7.5.1 Enhanced Soil and Groundwater Bioremediation. Enhanced bioremediation involves aerobic biodegradation of petroleum contaminants in soil and groundwater. Aerobic biodegradation involves the use of microorganisms to degrade contaminants to a non-hazardous state, the final end products being carbon dioxide and water. In many cases, bioremediation is naturally occurring in the aquifer. As stated in Section 4.3.3, the results of the bioremediation parameter analyses indicate bioremediation is currently taking place in saturated soils at the Site. Aerobic biodegradation can be enhanced via introduction of oxygen into the aquifer. Injection wells and infiltration galleries are potential methods for distributing oxygen to the areas of contamination."
MBTA, Cabot Yard Facility, 275 Dorchester Ave, Supplemental Phase II - Comprehensive Sit Assessment & Phase III - Identification, Evaluation, and Selection of Remediation Alternatives, Volume 1 of 2 (June 2001).
"Cabot Yard is located immediately south of the intersection of Dorchester Avenue and West Fourth Street The Site includes the eastern half of Cabot Yard encompassing the bus garage and parking areas/access roads located north and south of the garage. The Site also includes abutting portions of properties located at 220, 248, and 250 Dorchester Avenue, all of which are located less than 100 feet east of Cabot Yard. In addition, the Site includes the Pump Station, which is located approximately 150 feet southeast of Cabot Yard along the southern side of the Haul Road and adjacent to West 6"' Street and Dorchester Avenue. The Site is located in an area zoned for mixed use (residential, commercial, and industrial). Cabot Yard is an approximately 28-acre parcel of land occupied by two large multi-story buildings used for offices and repair/maintenance of buses and trains. These buildings occupy approximately 50% of Cabot Yard and the remainder consists of paved parking and access roads or railroad lines. Cabot Yard is bordered to the north by West Fourth Street and commercial businesses, to the east by Dorchester Avenue and commercial businesses, to the south by the Haul Road and a CSX Corporation railroad line, and to the west by the Boston Department of Public Works. The Pump Station is owned and operated by MassPike and pumps collected stormwater for a portion of the Haul Road to the Fort Point Channel located approximately 1/3-mile to the northwest. The Pump Station is an approximately 0.15-acre parcel of land occupied by 1 one-story brick and mortar pump station building. Approximately 75% of the Pump Station is occupied by the building and the remainder consists of concrete walkways and an unpaved hill leading towards the CSX railroad line and the Haul Road. The Pump Station is bordered to the northeast by West Fifth Street and commercial businesses, to the southeast by commercial businesses, West 6"' Street and residences, to the southwest by the Dorchester Avenue overpass, and to the northwest by the CSX railroad line and the Haul Road."
"Cabot Yard (previously known as the South Bay Maintenance Facility) was purchased in 1969 by the Commonwealth of Massachusetts from the Penn Central Transportation Company (Stone & Webster, 1993). The current buildings at Cabot Yard were completed in 1973. Presently Cabot Yard is owned and operated by MBTA. Cabot Yard has been used as a railway facility for over 125 years. In 1875, according to insurance maps of Boston prepared by the Sanborn Company, the Old colony Railway operated a car house, engine house, machine shop, boiler shop, car repair shop, car paint shop, and coal shed on the western half of Cabot Yard. Tenements, a stone yard, and a marble works occupied the eastern half of the property. The Bromely & Co. Atlas of the City of Boston shows that by 1899 rail lines extended to fill the eastern half of the property. The Bromely Atlas of 1919 shows Cabot Yard owned by the Old Colony Railroad Company."
"In general the topography at Cabot Yard slopes gently toward the northeast; however, the northwest corner of Cabot Yard slopes downhill toward the west. Also, Dorchester Avenue slopes downhill to the north and, at Cabot Yard's northern property boundary, it is several feet below Cabot Yard ground surface elevation. The elevation of the South Boston Haul Road near Cabot Yard is approximately 10 to 20 feet below the surrounding topographic elevation and slopes downhill to the northeast. The elevation of the Pump Station, located south of the South Boston Haul Road and northeast of Dorchester Avenue, is approximately 10 feet above the Haul Road and 5 to 10 feet below the topographic elevations to the southwest and southeast. Because Cabot Yard and the surrounding area is predominantly paved, surface water runoff is collected in catch basins and routed to Boston Water & Sewer Commission's sewer in Dorchester Avenue. Surface water runoff on the South Boston Haul Road is collected in a series of catch basins and underdrains and routed to the Pump Station, where the collected water is pumped via two force mains towards the northeast to the Fort Point Channel."
"Groundwater at the Site is categorized as GW-2 and GW-3. GW-2 classification is applicable because contaminated groundwater is located within 30 feet of occupied buildings and the average annual depth to groundwater is approximately 15 feet below grade. Site groundwater is also categorized as GW-3 because groundwater in the area is assumed to eventually discharge to the nearby Fort Point Channel and Boston Harbor. The criteria listed for GW-1 classification specified in 310 CMR 40.0932 (4) are not met at this Site. As shown on the Area Receptors Map in Figure 3 and discussed in Section 1.6, the Site is not in an area designated as a Current or Potential Drinking Water Source Area."
"Seven (7) geologic units were encountered during Weston & Sampson's April 2000 and April 2001 Supplemental Phase II investigation. These units include, in stratigraphic succession from youngest (shallowest) to oldest (deepest):
- Sand (Fill): Brown to black fine to coarse sand, trace gravel and brick.
- Silt: Gray to dark gray silt with little to trace sand.
- Clayey Silt: Yellowish tan to gray clayey silt with trace fine sand.
- Sand & Gavel: Dark gray to black coarse sand and fine gravel.
- Clay: Gray clay with lenses of silt and fine sand.
- Lower Sand: Gray to brown fine to medium sand, trace silt and fine gravel.
- Sand and Silt: Tan to gray fine and medium sand and silt.
Clayey silt was noted in the southern portion of the Site in borings WSPS-1, WSPS-2, and SW-1, and in the eastern portion of the Site in boring WSA-4. The encountered clayey silt unit ranged between 3 to 12 feet below grade. Lenses of fine sand and clay were observed in the clayey silt unit. No petroleum odors or staining or non-native materials (e.g., ash, brick, glass, etc.) were noted in soil samples collected from the clayey silt unit. The clay unit was found in the central portion of Cabot Yard, WS-2 and WS-3, and in the eastern area of the Site, WSA-I through WSA3.
The clay unit ranged in thickness of 2 feet in boring WS-3 to 5 feet in boring WS-2. Petroleum odors and staining were observed in WS-2 and WS-3, but no odors or staining were observed in this unit at WSA-1 through WSA-3. No fill material was noted in the soil samples collected from the clay unit. The lower sand unit is generally present in the lower portions of all soil borings except WS-7 and was encountered between 8 feet (WSA-4) and 27 feet (SW-4) below grade. Soil boring WS-7 is located on the northern portion of Cabot Yard. No non-native materials such as brick, glass wood or ash were present in the lower sand unit. Petroleum odors and staining were present in WS-1, WS-3, SW-2, and SW-4.
The sand and silt layer was observed in borings WS-11, SW-1, and SW-4. Tan to gray interlayered fine sand and silt were present in SW-1 at a depth of 15 feet to 21 feet. Tan sand and silt were observed in WS-11 and SW-4 at depths of 19 and 20 feet, respectively. No fill material was observed in the sand and silt layer. No petroleum odors or staining were observed in this unit. A confining layer was not encountered at the Site during the Supplemental Phase II investigation or any other previous investigation. In addition, the depth to bedrock was not determined and no bedrock outcrops were observed at or near the Site. According to the USGS Bedrock Geologic Map of Massachusetts (Zen et al., 1983), the Site is located within the sedimentary rock portion of the Milford-Dedham Tectonic Zone of eastern Massachusetts. The bedrock type underlying the Site is likely a sedimentary (sandstone or conglomerate) rock of the Cambridge Argillite Zone."
"On May 9, 2001, Weston & Sampson collected groundwater depth measurements from all accessible monitoring wells at the Site (Table 6). The depth to groundwater at the Site ranged from 4.29 feet below grade at SW-6 to 22.28 feet at WS-1. Groundwater elevations ranged between 77.00 feet at WS-1 and 89.07 feet at SW-6. Based on the corrected groundwater contours shown in Figure 6, groundwater at the Site flows in two distinct patterns: 1) most groundwater at and east of Cabot Yard flows toward a slight depression located under the Cabot Yard bus garage and 2) groundwater in the southern portion of Cabot Yard flows southeast via a steep gradient toward the South Boston Haul Road and the Pump Station. The hydraulic gradient across the Site was calculated using groundwater elevations collected on May 9, 2001. Horizontal hydraulic gradients were calculated based on groundwater elevations at monitoring wells SW-3 to WSA-1, RIZ-5 to WS-10 and groundwater elevations south of RIZ-4 and north of the Haul Road. The average horizontal hydraulic gradient (IAvG) across the Site was calculated to be 0.060 fl/f. A downward vertical gradient of 0.22 fl/ft was calculated using groundwater and saturated screen elevation data from wells WS-10 and WS-1.
On May 2,2001, Weston & Sampson conducted four (4) slug tests at monitoring wells WS-4, WSA-1, SW-1, and SW-10. Due to the varying locations and screen depth intervals of these wells, each slug test was performed in a separate geologic unit (Figure 5). The WS-4 screen is located in the sand and gravel unit, WSA- 1 is located in the clay (with trace sand) unit, SW- 1 is located in the sand and silt unit, and SW-10 is located in the sand unit. Using the data collected from these slug tests, hydraulic conductivities (K) were calculated for each monitoring well/geologic unit. Hydraulic conductivities at the four wells ranged from 2.36 feet/day to 2.91 feet/day."
"The field screening results and general observations are presented in EST's report in Appendix D. According to their sampling report, EST observed petroleum odors in WS-4 and WSA-2 groundwater wells during sampling. The pH measurements ranged from 4.97 (WSA-5) to 7.22 (WS-4). Specific conductance measurements ranged from 335 micromhos per centimeter (pmhos/cm) in RIZ-6 to 21,899 ptmhos/cm in WS-4. Dissolved oxygen concentrations ranged from 0.11 milligrams per liter (mg/1) in WS-4 to 6.76 mg/I in WSA-4."
"Cabot Yard, Metals/Inorgancis: Dissolved cadmium was not detected in the 3 samples collected. Total iron and manganese were detected at 210,000 pg/1 and 240,000 kg/1 in wells WS- I and WS- 3, respectively. Total manganese was detected at 14,000 jig/1 and 5,200 jlg/1 in wells WS-1 and WS-3, respectively. Dissolved iron was detected at 86,000 jLg/l and 83,000 pg/l in wells WS-1 and WS-3, respectively. Dissolved manganese was detected at 13,000 pg/1 and 3,100 lg/1 in wells WS-1 and WS-3, respectively."
"Cabot Yard, Bacteria Count: Heterotrophic and hexadecane degrading bacteria were detected in well SW-4 at concentrations of 46,000 colony forming units per milliliter (cfu/ml) and 38,000 cfulml, respectively."
"Abutting Properties, Metals/Inorgancis: Total and dissolved iron were detected in well WSA-2 at concentrations of 39,000 ptg/1 and 38,000 pig/l, respectively. Total and dissolved manganese were detected in well WSA-2 at concentrations of 2,800 pg/1 and 2,900 pg/1, respectively."
"Abutting Properties, Alkalinity/Nitrate/Sulfate: Alkalinity (as calcium carbonate) and sulfate were detected in well WSA-2 at concentrations of 520 mg/l and 8.1 mg/1, respectively. Nitrate (as nitrogen was not detected in the WSA-2 sample. Hexadecane bacteria were found at to be lowest in the source area (Cabot Yard) and higher at an abutting property (250 Dorchester Avenue)."
"Abutting Properties, Bacteria Count: Heterotrophic and hexadecane degrading bacteria were detected in well WSA-2 at concentrations of 220,000 cfulml and 230,000 cfu/ml, respectively."
"Product exists at Cabot Yard and within the Pump Station's stormwater collection system. At Cabot Yard, product thicknesses range from less than an inch to almost 6 feet. The product plume is thickest at well WS- 1 and decreases in thickness in every direction from WS-1. Product appears to be migrating in a northerly direction along a large utility corridor in the vicinity of well SW-4. This utility corridor, known as the South Boston Interceptor Trench, contains a 48-inch diameter sewer pipe owned by BWSC. This sewer pipe carries stormwater that is collected over a large portion of South Boston. The pipe is located between approximately 15 to 25 feet below grade and, as such, intersects the groundwater table in the area of product at Cabot Yard. Acting as a preferential pathway, the bedding materials ofthis large sewer line likely contain product and are influencing the shape of the plume as shown on Figure 7. After constructing the South Boston Haul Road and installing numerous utilities and underdrains, a preferential pathway was created south of Cabot Yard that likely acts as a sink. Therefore, as the 48- inch sewer line collects product and carries it via bedding materials towards the north and south, the groundwater sink created by the Haul Road draws the carried product from the sewer line's bedding materials into the Haul Road's stormwater collection system (presumably via underdrains)."
"7.5.1 Enhanced Soil and Groundwater Bioremediation. Enhanced bioremediation involves aerobic biodegradation of petroleum contaminants in soil and groundwater. Aerobic biodegradation involves the use of microorganisms to degrade contaminants to a non-hazardous state, the final end products being carbon dioxide and water. In many cases, bioremediation is naturally occurring in the aquifer. As stated in Section 4.3.3, the results of the bioremediation parameter analyses indicate bioremediation is currently taking place in saturated soils at the Site. Aerobic biodegradation can be enhanced via introduction of oxygen into the aquifer. Injection wells and infiltration galleries are potential methods for distributing oxygen to the areas of contamination."
MBTA, Cabot Yard Facility, 275 Dorchester Ave, Supplemental Phase II - Comprehensive Sit Assessment & Phase III - Identification, Evaluation, and Selection of Remediation Alternatives, Volume 1 of 2 (June 2001).
"Groundwater flow is dictated by factors including hydraulic conductivity of the aquifer and hydraulic gradient across the Disposal Site. Groundwater in the region is presumed to flow to the north/northeast towards the Boston Harbor/Fort Point Channel; however, groundwater at multiple nearby disposal sites has been calculated to flow in a northerly or westerly direction. The closest surface water body to the Site is the Fort Point Channel located approximately 0.2 miles north of the Site. Certain utilities such as water, sewer and stormwater conduits could intersect the groundwater table and therefore have the potential to serve as preferential pathways. The Dorchester Brook Conduit is known to intersect the groundwater table at the Site; while gas and water connections at the Site are likely to be mostly above the water table.
Therefore, based on the immobile nature of lead in groundwater and the distance of the Charles River relative to the Site, it is unlikely for dissolved lead in groundwater to impact nearby surface water bodies. Although there are no Method 1 GW-3 standards for ammonia in groundwater, the concentrations of ammonia detected in groundwater on-Site are not anticipated to pose a threat to nearby surface water bodies based on their distance to the Site.
The South Bay was once 138 acres of wetlands and surface water that was present at the Site and surrounding properties. By 1931, much of the Site had been filled with the exception of Dorchester Brook, which ran north-to-south through the Site along the western edge of what is now 100 Widett Circle. By 1969, the channel had been culverted underground into what is now referred to as the Dorchester Brook Conduit."
VHB oversaw the advancement of a total of 34 soil borings to depths ranging between 14 and 30 feet below grade. The soil borings were advanced between January and November 2022. Soil boring locations were selected to evaluate whether a reportable release of potential COCs had occurred at the property. Concentrations of metals including antimony, arsenic, cadmium, lead, and zinc were detected in excess of the RCS-2 standards in soil samples collected from across the three properties. Lead was detected in excess of the MCP Method 3 Ceiling Limits at soil borings WC4-2 and WC11-11 at 8,460 and 6,210 mg/kg, respectively. Zinc was also detected in excess of the MCP Method 3 Ceiling Limits at soil borings WC4-5 and WC11-5 at 13,600 mg/kg and 16,400 mg/kg, respectively. Concentrations of lead, cadmium, antimony, arsenic and zinc were detected in several soil samples in excess of the typical Concentrations for Soil Containing Coal Ash or Wood Ash Associated with Fill Material.
All groundwater analytical results were below the applicable RCGW-2 thresholds with the exception of dissolved lead and ammonia. Dissolved lead was detected in groundwater samples in excess of the applicable RCGW-2 thresholds at wells MW-9, MW-18, MW-19, MW-23, MW-26 , MW-27, and MW-28. › Ammonia was detected in excess of the RCGW-2 standards for groundwater samples collected from WC-11 and WC-6 at wells MW-23, MW-24, MW-25, MW-26, MW-28, MW-29, and MW-31. The ammonia is believed to be a result of natural decomposition processes in the fill underlying the Site. Bedrock was not encountered.
Soils at the Site generally consisted of a medium to fine sand with materials typical of urban fill such as brick, coal, coal ash, and wood debris to approximately 14 feet below grade. The sand was generally underlain by a layer of native clay and silt. All soil analytical results were below the applicable RCS-2 standards except for lead detected in excess of the RCS-2 standards in two of the soil samples collected at WC-11 at 16-18 and 22-24 feet below ground surface at concentrations of 5,210 mg/kg and 1,020 mg/kg, respectively. All groundwater analytical results were below the applicable RCGW-2 standards with the exception of ammonia detected in MW-23, MW-25, MW-32, MW-28 and MW-31 at concentrations ranging from 17.2 mg/L to 26.2 mg/L.
Based on the observed depth of fill material and debris observed during soil boring advancement and the heterogenous distribution of contaminants of concern, the elevated concentrations of PAHs and metals in soil as well as dissolved lead in groundwater appear to be attributed to the urban fill material used for the filling of South Bay in the 1930s. Additionally, concentrations of ammonia in groundwater are believed to be attributed to the naturally-occurring decomposition processes occurring in the urban fill or remaining organic material associated with the former South Bay. As an intermediate in the nitrogen cycle, ammonia is naturally present in environmental media. However, since ammonia was also historically utilized at the Site for cold storage purposes, the source of ammonia will continue to be evaluated as part of future assessments on-Site.
Based on groundwater sampling conducted during the Phase II ESA in 2022, dissolved lead was detected equal to or in excess of the applicable reportable concentration (RCGW-2) in groundwater in monitoring wells MW-4, MW-9, MW-18, MW-19, MW-23, MW-26, and MW-27. These wells are located in the northern portion of the Disposal Site, but no apparent source area was identified. Lead was not detected in excess of the applicable RCGW-2 standards in any of the monitoring wells sampled during the May 2024 sampling event. Lead is generally immobile and is not expected to migrate. The detections of lead in groundwater at the Site are likely attributed to the presence of Historic Fill.
Additionally, concentrations of ammonia were detected in excess of the RCGW-2 standards in groundwater samples collected at MW-23 through MW-26 during both the October 2022 and June 2024 groundwater sampling events. These monitoring wells are located in the vicinity of the warehouse spaces at WC-11 and WC-6. The warehouses located on these parcels historically included refrigeration systems which require the storage of large volumes of ammonia and glycol. Documented releases of anhydrous ammonia occurred at WC-11 under RTN 3- 35885; however, the release reportedly dispersed into the atmosphere and no residual contamination was identified. Therefore, the elevated concentrations of ammonia in groundwater are likely attributed to natural processes. However, the source of ammonia will continue to be evaluated as part of future Site investigations."
MBTA Widett Circle Properties, Boston, Massachusetts, PHASE I INITIAL SITE INVESTIGATION, TIER CLASSIFICATION & PHASE II SCOPE OF WORK, Release Tracking Number (RTN) 3-38285 (August 9, 2024).
The former South Bay Incinerator property is listed in the SHWS, RELEASE, and INST CONTROL databases in association with the documented release of OHM assigned to RTNs 3-952 3-17174. As early as 1988, an environmental investigation at the property had revealed the presence of metals and petroleum constituents in soil in excess of the applicable regulatory criteria. At the time of this investigation, groundwater contamination was also identified. It was also known that the area addressed by RTN 3-952 was a closed landfill. RTN 3-952 was assigned to the disposal Site in January 1989. The disposal site achieved initial regulatory closure in June 2002 with the submittal of Class A-3 RAO statement and the filing of an AUL. Residual contamination remained at the disposal site, and a Condition of No Significant Risk is maintained by the implementation of the AUL. RTN 3-17174 was assigned to the disposal site in August 1989 when petroleum products were identified in soil at reportable concentrations. RTN 3-17174 was linked to primary RTN 3-952 in January 1999. All following remedial response actions were completed under the primary RTN.
Based on the subsurface assessment activities conducted on-Site, environmental listings at this property have not impacted environmental conditions on-Site.
MBTA Widett Circle Properties, Boston, Massachusetts, PHASE I INITIAL SITE INVESTIGATION, TIER CLASSIFICATION & PHASE II SCOPE OF WORK, Release Tracking Number (RTN) 3-38285 (August 9, 2024).
It should be noted that most soil samples were collected at depths at or near the groundwater table surface. Soil samples saturated with diesel fuel were not submitted for laboratory analysis. Therefore, it is reasonable to assume that diesel fuel saturated soils are present in the same horizontal and vertical distribution. In addition, as described in the previous section, product is likely migrating into the bedding materials of an on property 48-inch sewer line. As these materials carry product towards the north and south, the surrounding soil (in both the vadose and saturated zones) is likely becoming contaminated.
In addition, product appears to be migrating in a northerly direction along a large utility corridor (South Boston Interceptor Trench) in the vicinity of well SW-4. This utility corridor contains a 48-inch diameter sewer pipe owned by BWSC. This sewer pipe carries stormwater that is collected over a large portion of South Boston. The pipe is located between approximately 15 to 25 feet below grade and, as such, intersects the groundwater table in the area of product at Cabot Yard. Acting as a preferential pathway, the bedding materials of this large sewer line likely contain product and are influencing the shape of the plume.
After constructing the South Boston Haul Road and installing numerous utilities and underdrains, a preferential pathway was created south of Cabot Yard that likely acts as a sink. Therefore, as the 48- inch sewer line collects product and carries it via bedding materials towards the north and south, the groundwater sink created by the Haul Road draws the carried product from the sewer line's bedding materials into the Haul Road's stormwater collection system (presumably via underdrains).
Widett Circle Properties, Boston, MA, Prepared by VHB for MBTA, Phase I Initial Site Investigation, Tier Classification, & Phase II Scope of Work (Aug. 9 2024).
Therefore, based on the immobile nature of lead in groundwater and the distance of the Charles River relative to the Site, it is unlikely for dissolved lead in groundwater to impact nearby surface water bodies. Although there are no Method 1 GW-3 standards for ammonia in groundwater, the concentrations of ammonia detected in groundwater on-Site are not anticipated to pose a threat to nearby surface water bodies based on their distance to the Site.
The South Bay was once 138 acres of wetlands and surface water that was present at the Site and surrounding properties. By 1931, much of the Site had been filled with the exception of Dorchester Brook, which ran north-to-south through the Site along the western edge of what is now 100 Widett Circle. By 1969, the channel had been culverted underground into what is now referred to as the Dorchester Brook Conduit."
VHB oversaw the advancement of a total of 34 soil borings to depths ranging between 14 and 30 feet below grade. The soil borings were advanced between January and November 2022. Soil boring locations were selected to evaluate whether a reportable release of potential COCs had occurred at the property. Concentrations of metals including antimony, arsenic, cadmium, lead, and zinc were detected in excess of the RCS-2 standards in soil samples collected from across the three properties. Lead was detected in excess of the MCP Method 3 Ceiling Limits at soil borings WC4-2 and WC11-11 at 8,460 and 6,210 mg/kg, respectively. Zinc was also detected in excess of the MCP Method 3 Ceiling Limits at soil borings WC4-5 and WC11-5 at 13,600 mg/kg and 16,400 mg/kg, respectively. Concentrations of lead, cadmium, antimony, arsenic and zinc were detected in several soil samples in excess of the typical Concentrations for Soil Containing Coal Ash or Wood Ash Associated with Fill Material.
All groundwater analytical results were below the applicable RCGW-2 thresholds with the exception of dissolved lead and ammonia. Dissolved lead was detected in groundwater samples in excess of the applicable RCGW-2 thresholds at wells MW-9, MW-18, MW-19, MW-23, MW-26 , MW-27, and MW-28. › Ammonia was detected in excess of the RCGW-2 standards for groundwater samples collected from WC-11 and WC-6 at wells MW-23, MW-24, MW-25, MW-26, MW-28, MW-29, and MW-31. The ammonia is believed to be a result of natural decomposition processes in the fill underlying the Site. Bedrock was not encountered.
Soils at the Site generally consisted of a medium to fine sand with materials typical of urban fill such as brick, coal, coal ash, and wood debris to approximately 14 feet below grade. The sand was generally underlain by a layer of native clay and silt. All soil analytical results were below the applicable RCS-2 standards except for lead detected in excess of the RCS-2 standards in two of the soil samples collected at WC-11 at 16-18 and 22-24 feet below ground surface at concentrations of 5,210 mg/kg and 1,020 mg/kg, respectively. All groundwater analytical results were below the applicable RCGW-2 standards with the exception of ammonia detected in MW-23, MW-25, MW-32, MW-28 and MW-31 at concentrations ranging from 17.2 mg/L to 26.2 mg/L.
Based on the observed depth of fill material and debris observed during soil boring advancement and the heterogenous distribution of contaminants of concern, the elevated concentrations of PAHs and metals in soil as well as dissolved lead in groundwater appear to be attributed to the urban fill material used for the filling of South Bay in the 1930s. Additionally, concentrations of ammonia in groundwater are believed to be attributed to the naturally-occurring decomposition processes occurring in the urban fill or remaining organic material associated with the former South Bay. As an intermediate in the nitrogen cycle, ammonia is naturally present in environmental media. However, since ammonia was also historically utilized at the Site for cold storage purposes, the source of ammonia will continue to be evaluated as part of future assessments on-Site.
Based on groundwater sampling conducted during the Phase II ESA in 2022, dissolved lead was detected equal to or in excess of the applicable reportable concentration (RCGW-2) in groundwater in monitoring wells MW-4, MW-9, MW-18, MW-19, MW-23, MW-26, and MW-27. These wells are located in the northern portion of the Disposal Site, but no apparent source area was identified. Lead was not detected in excess of the applicable RCGW-2 standards in any of the monitoring wells sampled during the May 2024 sampling event. Lead is generally immobile and is not expected to migrate. The detections of lead in groundwater at the Site are likely attributed to the presence of Historic Fill.
Additionally, concentrations of ammonia were detected in excess of the RCGW-2 standards in groundwater samples collected at MW-23 through MW-26 during both the October 2022 and June 2024 groundwater sampling events. These monitoring wells are located in the vicinity of the warehouse spaces at WC-11 and WC-6. The warehouses located on these parcels historically included refrigeration systems which require the storage of large volumes of ammonia and glycol. Documented releases of anhydrous ammonia occurred at WC-11 under RTN 3- 35885; however, the release reportedly dispersed into the atmosphere and no residual contamination was identified. Therefore, the elevated concentrations of ammonia in groundwater are likely attributed to natural processes. However, the source of ammonia will continue to be evaluated as part of future Site investigations."
MBTA Widett Circle Properties, Boston, Massachusetts, PHASE I INITIAL SITE INVESTIGATION, TIER CLASSIFICATION & PHASE II SCOPE OF WORK, Release Tracking Number (RTN) 3-38285 (August 9, 2024).
The former South Bay Incinerator property is listed in the SHWS, RELEASE, and INST CONTROL databases in association with the documented release of OHM assigned to RTNs 3-952 3-17174. As early as 1988, an environmental investigation at the property had revealed the presence of metals and petroleum constituents in soil in excess of the applicable regulatory criteria. At the time of this investigation, groundwater contamination was also identified. It was also known that the area addressed by RTN 3-952 was a closed landfill. RTN 3-952 was assigned to the disposal Site in January 1989. The disposal site achieved initial regulatory closure in June 2002 with the submittal of Class A-3 RAO statement and the filing of an AUL. Residual contamination remained at the disposal site, and a Condition of No Significant Risk is maintained by the implementation of the AUL. RTN 3-17174 was assigned to the disposal site in August 1989 when petroleum products were identified in soil at reportable concentrations. RTN 3-17174 was linked to primary RTN 3-952 in January 1999. All following remedial response actions were completed under the primary RTN.
Based on the subsurface assessment activities conducted on-Site, environmental listings at this property have not impacted environmental conditions on-Site.
MBTA Widett Circle Properties, Boston, Massachusetts, PHASE I INITIAL SITE INVESTIGATION, TIER CLASSIFICATION & PHASE II SCOPE OF WORK, Release Tracking Number (RTN) 3-38285 (August 9, 2024).
It should be noted that most soil samples were collected at depths at or near the groundwater table surface. Soil samples saturated with diesel fuel were not submitted for laboratory analysis. Therefore, it is reasonable to assume that diesel fuel saturated soils are present in the same horizontal and vertical distribution. In addition, as described in the previous section, product is likely migrating into the bedding materials of an on property 48-inch sewer line. As these materials carry product towards the north and south, the surrounding soil (in both the vadose and saturated zones) is likely becoming contaminated.
In addition, product appears to be migrating in a northerly direction along a large utility corridor (South Boston Interceptor Trench) in the vicinity of well SW-4. This utility corridor contains a 48-inch diameter sewer pipe owned by BWSC. This sewer pipe carries stormwater that is collected over a large portion of South Boston. The pipe is located between approximately 15 to 25 feet below grade and, as such, intersects the groundwater table in the area of product at Cabot Yard. Acting as a preferential pathway, the bedding materials of this large sewer line likely contain product and are influencing the shape of the plume.
After constructing the South Boston Haul Road and installing numerous utilities and underdrains, a preferential pathway was created south of Cabot Yard that likely acts as a sink. Therefore, as the 48- inch sewer line collects product and carries it via bedding materials towards the north and south, the groundwater sink created by the Haul Road draws the carried product from the sewer line's bedding materials into the Haul Road's stormwater collection system (presumably via underdrains).
Widett Circle Properties, Boston, MA, Prepared by VHB for MBTA, Phase I Initial Site Investigation, Tier Classification, & Phase II Scope of Work (Aug. 9 2024).
"Four test borings ranging in depth from 12 to 17 feet were completed on November 13 and 14, 1985. The fill consisted of a loose to medium dense mixture of fine to coarse sand, fine gravel, and trace silt with varying amounts of cinders, wood and brick. Underlying the granular fill mixture is a layer of dark gray organic silt with trace amounts of wood. At the completion of drilling an observation well consisting of a 2-inch-diameter PVC wellscreen and solid riser pipe was installed in each borehole. A filter of clean silica sand was placed in the annular space around each wellscreen, and a bentonite seal placed 1 to 2 feet below the ground surface. Each well head was equipped with a protective road box to allow for future sampling.% Groundwater levels recorded in each borehole ranged between 5 and 6 feet below the existing ground surface
Soil samples of the fill recovered in each of the borings were screened for volatile organic compounds using an H-N photo ionization detector, Model PI-101. Results of the H-Nu .screening are presented on the boring logs. I general, the results suggest that low concentrations of volatile organic U compounds may be present in fill samples. Based on the H-N screening selected soil samples were also screened for volatile organic compounds using a Century Systems Model OVA-128 portable gas chromatograph with flame ionization detector. Results of the gas chromatograph screening did not indicate the presence of priority pollutant volatile organic compounds., In general, they indicated the presence of methane in fill samples from A-OW-1, A-92-2 and A-OW-4. In addition, samples screened from A-OW-3 and A-OW-4 suggested the presence of low concentrations of weathered oil.
Groundwater samples collected from observation wells A-i-OW, A-2-OW, A-3-OW, 1-4-OW, and G-11-0 were analyzed for pH and specific conductivity was measured using an Orion Research Modell 701A/ digital ionalyzer. An Extech Digital Model 440 I Conductivity Met= was used to analyze specific conductance of the groundwater samples. Test results indicate the pH ranged between 5.72 and 7.44. The specific conductivity of the water samples -ranged between 181 umhos/cm and 2,738 umhcs/cm."
S&I FACILITY SOUTH HAMPTON YARD, BOSTON, MASSACHUSETTS, Evaluation for Chemical Contamination, Prepared for Seelye, Steveason, Value &-Knecht Boston, Massachusetts (Jan. 1986).
Soil samples of the fill recovered in each of the borings were screened for volatile organic compounds using an H-N photo ionization detector, Model PI-101. Results of the H-Nu .screening are presented on the boring logs. I general, the results suggest that low concentrations of volatile organic U compounds may be present in fill samples. Based on the H-N screening selected soil samples were also screened for volatile organic compounds using a Century Systems Model OVA-128 portable gas chromatograph with flame ionization detector. Results of the gas chromatograph screening did not indicate the presence of priority pollutant volatile organic compounds., In general, they indicated the presence of methane in fill samples from A-OW-1, A-92-2 and A-OW-4. In addition, samples screened from A-OW-3 and A-OW-4 suggested the presence of low concentrations of weathered oil.
Groundwater samples collected from observation wells A-i-OW, A-2-OW, A-3-OW, 1-4-OW, and G-11-0 were analyzed for pH and specific conductivity was measured using an Orion Research Modell 701A/ digital ionalyzer. An Extech Digital Model 440 I Conductivity Met= was used to analyze specific conductance of the groundwater samples. Test results indicate the pH ranged between 5.72 and 7.44. The specific conductivity of the water samples -ranged between 181 umhos/cm and 2,738 umhcs/cm."
S&I FACILITY SOUTH HAMPTON YARD, BOSTON, MASSACHUSETTS, Evaluation for Chemical Contamination, Prepared for Seelye, Steveason, Value &-Knecht Boston, Massachusetts (Jan. 1986).
"The Cabot Yard property has been operated by the MBTA as a rapid transit line and bus repair facility since 1973. Typical operations at Cabot Yard include train and bus maintenance and repair, fleet vehicle repair, bus storage and signal repair. Typical operations within the CMF consist mostly of transit car maintenance and repair, painting and cleaning. The CMF also includes a wash alley (Track 9) where assembled sets of transit cars (trains) can be washed automatically as they pass through the bay. The MBTA acquired the Cabot Yard property in 1969 and the CMF, Cabot Bus Garage and Maintenance Facility and select ancillary structures were constructed in 1973. Historically, the Cabot Yard property, or portions thereof, had been used as a rail road facility since at least 1875, primarily as part of the Old Colony Railway (OCR) and later the New York, New Haven and Hartford Railroad. The western portion of the property was historically improved by a carhouse, engine house, machine, shop, boiler shop, car repair shop, car paint shop and a coal shed associated with the OCR. The eastern portion of the property historically included tenements, a stone yard and marble works prior to the property’s conversion to a rail yard circa 1875."
"According to the Jacobs Preliminary Geotechnical Report for the Phase 2 Carhouse Improvements, the Site is located above the Cambridge Argillite of the Milford-Dedham zone of southeastern Massachusetts. The rocks of this area are Proterozoic Z to Paleozoic age and consist mainly of gray argillite with various amounts of sandstone and conglomerate. Bedrock was not encountered during the 2017 borings advanced by Jacobs. Reportedly, historical borings completed in 1972 did core argillite bedrock. Historical site borings indicate bedrock is anticipated at a depth of about 110 feet. The Site and surrounding area are locations of historic filling that created much of the land area of Boston in vicinity of Boston Harbor and its inlets and tributaries. The surrounding area was likely low lying wetlands or mudflats prior to filling. The period of filling of this particular area is not known at this time."
"The subsurface conditions at the Site generally consist of loose urban fill overlying a thick layer of silt and clay, with a till layer at approximately 92 to 100 feet below grade. Approximately 10 to 18 feet of granular fill was encountered in most borings. The fill layer was generally very loose to medium dense and consisted of black/ light brown sand with varying amounts of gravel and silt. Various amounts of foreign material (brick fragments, slag, and coal ash) were also encountered. Visual observations of soil samples revealed sandy fill material comprised of black to dark brown, fine to coarse sands with some fine to coarse gravel and little silt. Varying amounts of brick, coal slag, wood and little coal ash were observed within the soils, typical for urban fill deposits. Up to approximately 72 feet of silt and clay was encountered below the fill. This layer typically consisted of a gray, silty clay. The top 17 to 40 feet of this layer had thin interbedded layers of fine sand. Generally, the top 7 to 25 feet was stiff to very stiff, while up to 60 feet of the bottom portion of the layer was very soft. Glacial till was encountered between about 92 and 100 feet below existing ground surface. The till generally consisted of hard, gray, silty clay and sand with varying amounts of gravel. The thickness of this layer was not determined since the 2017 geotechnical borings did not penetrate through the fill into the underlying bedrock. Groundwater monitoring to date has revealed groundwater ranging from 6.2 to 6.8 feet below ground surface (bgs). Due to the difficult nature of installing groundwater monitoring wells due to underground obstructions, only two monitoring wells have been installed to date at the Site. Empirical determination of groundwater flow direction could not be made. Additional monitoring wells are proposed to be installed in the future and a groundwater elevation survey will be completed at that time"
PHASE I INITIAL SITE INVESTIGATION & TIER CLASSIFICATION SUBMITTAL, Cabot Maintenance Facility 275 Dorchester Avenue South Boston, Massachusetts, DEP Release Tracking Number 3-34777, Prepared For Massachusetts Bay Transpiration Authority, (February 2019)
"According to the Jacobs Preliminary Geotechnical Report for the Phase 2 Carhouse Improvements, the Site is located above the Cambridge Argillite of the Milford-Dedham zone of southeastern Massachusetts. The rocks of this area are Proterozoic Z to Paleozoic age and consist mainly of gray argillite with various amounts of sandstone and conglomerate. Bedrock was not encountered during the 2017 borings advanced by Jacobs. Reportedly, historical borings completed in 1972 did core argillite bedrock. Historical site borings indicate bedrock is anticipated at a depth of about 110 feet. The Site and surrounding area are locations of historic filling that created much of the land area of Boston in vicinity of Boston Harbor and its inlets and tributaries. The surrounding area was likely low lying wetlands or mudflats prior to filling. The period of filling of this particular area is not known at this time."
"The subsurface conditions at the Site generally consist of loose urban fill overlying a thick layer of silt and clay, with a till layer at approximately 92 to 100 feet below grade. Approximately 10 to 18 feet of granular fill was encountered in most borings. The fill layer was generally very loose to medium dense and consisted of black/ light brown sand with varying amounts of gravel and silt. Various amounts of foreign material (brick fragments, slag, and coal ash) were also encountered. Visual observations of soil samples revealed sandy fill material comprised of black to dark brown, fine to coarse sands with some fine to coarse gravel and little silt. Varying amounts of brick, coal slag, wood and little coal ash were observed within the soils, typical for urban fill deposits. Up to approximately 72 feet of silt and clay was encountered below the fill. This layer typically consisted of a gray, silty clay. The top 17 to 40 feet of this layer had thin interbedded layers of fine sand. Generally, the top 7 to 25 feet was stiff to very stiff, while up to 60 feet of the bottom portion of the layer was very soft. Glacial till was encountered between about 92 and 100 feet below existing ground surface. The till generally consisted of hard, gray, silty clay and sand with varying amounts of gravel. The thickness of this layer was not determined since the 2017 geotechnical borings did not penetrate through the fill into the underlying bedrock. Groundwater monitoring to date has revealed groundwater ranging from 6.2 to 6.8 feet below ground surface (bgs). Due to the difficult nature of installing groundwater monitoring wells due to underground obstructions, only two monitoring wells have been installed to date at the Site. Empirical determination of groundwater flow direction could not be made. Additional monitoring wells are proposed to be installed in the future and a groundwater elevation survey will be completed at that time"
PHASE I INITIAL SITE INVESTIGATION & TIER CLASSIFICATION SUBMITTAL, Cabot Maintenance Facility 275 Dorchester Avenue South Boston, Massachusetts, DEP Release Tracking Number 3-34777, Prepared For Massachusetts Bay Transpiration Authority, (February 2019)
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"The MBTA Cabot Bus Yard has operated as a public transportation maintenance facility for over 135 years. The vehicle maintenance/repair facility is open on the first floor with all offices located on the second floor. The Disposal Site is shown on Figure 2 and is entirely covered by building foundations and pavement. Soil at the Site consists of silty fine to medium sand or sandy fill over a lower confining layer of Boston blue clay. The fill is typically about 10 feet thick and the Boston blue clay is approximately 30 feet thick. A layer of silt and clay at approximately 10 to 13 feet below ground surface (bgs) exists over the majority of the Site and, as determined in the Class C-2 Response Action Outcome (RAO) (W&S, 2007), acts as a semiconfining layer with light non-aqueous phase liquid (LNAPL) present below it. Bedrock was not encountered during any investigations performed at the Site.
"The groundwater table at the Site varies between nine and 20 feet bgs. A semi-confining layer is located at 10-13 feet bgs. The majority of groundwater at the Site is present below this confining layer. Historically, in portions of the Site, deep utilities (now abandoned), when after constructed and backfilled with high-permeability sand, have acted as preferential migration and collection pathways for the LNAPL; however, groundwater has been the primary migration mechanism for LNAPL. Groundwater at the Site flows to the east/southeast, towards Pump Station No. 3. There are no drinking water supplies located in the vicinity of the Site."
PERMANENT SOLUTION WITH CONDITIONS STATEMENT, MBTA Cabot Yard, 275 Dorchester Ave., South Boston, Massachusetts, MassDEP Release Tracking Number (RTN) 3-3096 (June 2025).
"The groundwater table at the Site varies between nine and 20 feet bgs. A semi-confining layer is located at 10-13 feet bgs. The majority of groundwater at the Site is present below this confining layer. Historically, in portions of the Site, deep utilities (now abandoned), when after constructed and backfilled with high-permeability sand, have acted as preferential migration and collection pathways for the LNAPL; however, groundwater has been the primary migration mechanism for LNAPL. Groundwater at the Site flows to the east/southeast, towards Pump Station No. 3. There are no drinking water supplies located in the vicinity of the Site."
PERMANENT SOLUTION WITH CONDITIONS STATEMENT, MBTA Cabot Yard, 275 Dorchester Ave., South Boston, Massachusetts, MassDEP Release Tracking Number (RTN) 3-3096 (June 2025).
"The work scheduled in the Cabot Cove area includes the building of a seawall as part of CO9B1 and landscaping and a walkway, which is proposed to be done under C09D2. Due to the depth and location of the excavation and landscaping, the area required additional characterization in order to attain adequate ROWARS coverage. In addition, a Clearance Area previously identified in the C09A7/CO9A8 contracts has been redefined. This addendum report presents the rationale and approach used to define the extent of the Clearance Material. Figure 1 shows the boring locations and the revised Clearance Area. Appendix A contains the boring logs and the survey information for the ROWARS borings discussed in this addendum report. Appendix B contains a summary of the data associated with the ROWARS borings."
Borehole Log & Results:
Central Artery (I-93)/Tunnel (1-90) Project, ROWARS Contract 97159-MO26G, Construction Contracts CO9B/CO9D2, Cabot Cove Characterization/Clearance Report, LO-CAT-02-26G-0372 (November 21, 2002).
Borehole Log & Results:
- UA-SB-93 (1995): 1'-3" Dry, medium dense dark brown. coarse to fine SAND; 7'-9' moist loose brown/grey course to fine SAND and SILT, trace gravel; 12'-14' moist, soft, grey SILT; little course to fine sand, trace wood, trace shells; 15'-17' wet, very soft, grey CLAY, some silt, trace course to fine sand, trace shells.
- UA-SB-94 (1995): 1'-3- Dry, medium dense. Brown, coarse to fine SAND and GRAVEL; 5'-7' Dry, medium dense. Brown-grey, coarse to fine SAND and GRAVEL. little brick, trace silt, trace clay. 10'-12' Moist. loose. Black/grey coarse to fine SAND and SILT, trace clay. trace shells, trace wood. 15'-17" Wet, soft, grey SILT. little coarse fine sand, little peat, trace wood. trace shells, trace clay.
- UA-SB-96 (2002): 1' - 3': Dry, brown, medium-fine SAND, little course-fine gravel, trace silt and red brick; 5' - 7': Moist, dense, brown, medium-fine SAND, little fine gravel, trace glass, wood and red brick; 10' - 12': Moist, dense, grey brown, medium-fine SAND, some silt, trace clay; 15' -17': Wet, grey, SILTY-CLAY
- UA-SB-97 (2002): 1'- 3' - Dry, brown, medium-fine SAND, little course-fine gravel, trace silt and red brick; 5'- 7' - Dense, brown black, medium-fine SAND, little fine gravel, trace silt; 1' - 12': Medium dense, grey-black SILTY CLAY, some fine sand,
trace organics; 15' - 17: Wet, grey CLAY, some silt, trace medium-fine sand.
Central Artery (I-93)/Tunnel (1-90) Project, ROWARS Contract 97159-MO26G, Construction Contracts CO9B/CO9D2, Cabot Cove Characterization/Clearance Report, LO-CAT-02-26G-0372 (November 21, 2002).
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1994 BORING LOG AND WELL CONSTRUCTION
Technical Document in Support of Tier Classification, MBTA Cabot Yard, 275 Dorchester Avenue, South Boston, Massachusetts, DEP RTN 3-3096 (August 2, 1996).
- SW-1 (1994): 4'-8' FILL: Tan to brown fine to coarse Sand, little gravel, trace silt, clay, SR brick, asphalt; 8'-14' FILL; Yellowish-tan clayey Silt. trace sand and gravel. Samples moist; 14'-16' Gray to black clayey organic Silt, some shells and plant matter. Organic odor. Samples moist; 16'-21' Tan to gray interlayered silty fine sand and trace clay. Samples wet; 21'-23' Gray fine to medium Sand, little coarse sand.
- SW-2 (1994): 2'-11' FILL; very dense dark brown to black Sand and Gravel, trace brick and concrete. Light gray to black fine to
coarse Sand, little gravel. some to trace cinder/ash, and trace brick. 10'-12' Dark brown organic Silt (peat) with root/plant matter, little fine sand; 12'-18' Gray interlayered silty fine Sand mottled brown Silt. Samples damp to moist with some petroleum odor. 17'-24' Gray medium Sand, traces of fine and coarse sand. Samples wet with strong petroleum odor. - SW-3 (1994): 1'-12' FILL; Brown to grayish-brown silty Sand and Gravel, little brick. glass, wood and cinders at various depths; 12'-16' Gray silty fine to coarse Sand. some mottled brown silt, trace gravel. Appears to be reworked native material. Samples damp; 16'-23' Gray interlayered silty fine to medium Sand, mottled brown Silt, cohesive clayey silt, and fine to medium sand. Dark gray fine to medium Sand lense with strong diesel odor at about 20 feet; 23'-25' Tan fine to coarse Sand.
- SW-4 (1994): 1'-11' FILL; Brown to grayish-brown silty Sand and Gravel, few cabbies, little brick. glass, wood and cinders at various depths; 11'-15' Gray silty fine to medium Sand. trace clay, some brown mottiing; 15'-17' grey to yellowish-grey interlayered, mottled brown Silt, medium to coarse Sand, silty fine Sand. and silty clayey fine to coarse sand; 17'-24' Tan loose dry medium Sand. Sample dry. Tan fine to coarse Sand. Sample wet. Tan silty fine to medium Sand interlayered with clayey Silt and fine Sand; 24'-28' Gray interlayered silty fine to medium Sand, and mottled brown - Silt with little fine sand. Two 2" lenses of gray silty Clay @ 27 feet.
- SW-6 (1994): 1'-5' FILL; Tan to black fine to coarse Sand with some gravel, trace brick; 5'-8' Gray silty fne to medium Sand.
Damp with some organic odor; 8'-15' Dark gray, mottled black and brown organic clayey Silt. Little plant/ root matter, trace shells. Organic odor. Samples moist; 15'-18' Very slight petroleum odor. Dark gray fine to coarse Sand with little gravel and shells. Gray silty fine to medium Sand. 2" stiff gray mottled brown Silt. Gray silty fine to medium Sand. - SW-7 (1994): 1'-5' FILL Gray to dark gray silty Sand little gravel, trace brick and glass; 5'-10' FILL; Dark brown to olack sandy
angular gravel [old RR ballast/bed], FILL Tan silty Sand and red brick. little clay and gravel in sand. FILL: Dark brown silty Sand, little gravel, wood. glass, cinders; 10'-17' Brownish-gray fine to medium Sand. little silt and gravel. Dark brown fibrous organic silty Sand [peat) grading to grayish-brown sandy Silt with plant fibers. Gray interlayered silty fine to medium Sand, mottled brown organic Silt, trace clay and gravel; 17-25' Tan interlayered fine to coarse Sand. clayey Silt, silty fine Sand, and fine to medium Sand. - SW-8 (1994): 1'-10' FILL; Tan medium to coarse Sand and Gravel. FILL; Tan to black silty fine to coarse Sand, some gravel, little to trace coal cinders/ash, trace brick, and wood; 9'-11' Black to brown rooty fine to medium Sand. some organic silt, little organic odor; 11'-13' Gray clayey mottled brown Slit, little fine to coarse sand, trace rooty matter. Sample damp; 13'-16' Gray to tan medium Sand, little fine and coarse Sand and gravel; 16'-25' Grayish-tan interlayered fine to coarse Sand. mottled brown
clayey Silt, silty fine to medium Sand. Samples wet.
Technical Document in Support of Tier Classification, MBTA Cabot Yard, 275 Dorchester Avenue, South Boston, Massachusetts, DEP RTN 3-3096 (August 2, 1996).
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2001 BORING LOGS:
Massachusetts Bay Transportation Authority, MBTA- Cabot Yard Facility, 275 Dorchester Avenue, South Boston, Massachusetts, RTN 3-3096 and 3·19247, Supplemental Phase II - Comprehensive Site, Assessment and Phase Ill - Identification, Evaluation, and Selection of Remedial Alternatives, Volume 1 of 2, Text, Figures, Tables, Appendices A,B, and C (June 2001).
- WSA-1 (2001): 1'-5' Dark brown, to brown to gray medium SAND, some coarse Gravel, Dry; 5'-7' Brown medium SAND some wood and brick, trace coal and ash, dry; 10'-12' Gray Silty CLAY some fine-medium Sand, trace Clay, Wet; 15'-17' Gray medium SAND, some fine.
- WSA-3 (2001): 1'-5' Dark brown medium-coarse SAND and fine GRAVEL, little medium brown Sand, Dry; 5'-7' Tan medium-coarse SAND, Dry; 10'-12' Gray CLAY with lenses of fine Sand and Silt, trace tan Sand Moist; 15'-17' Black and gray fine SAND, gray SAND, little tan Silt and fine Sand, Wet.
- WS-1 (2001): 1'-4' dry, very dense, brown, medium, SAND some Gravel, trace coarse Gravel; 4'-6' moist, medium dense, dark brown, fine to medium SAND, some Gravel, trace Silt; 9'-11' moist, loose, gray, SILT, some Clay, trace Gravel, trace Ash; 14'-16' wet, medium dense, gray and brown, fine SAND, some Silt, trace Clay; 18'-20' wet, dense, brown, fine SAND, some Silt, trace Clay; 23'-25' wet, dense, fine SAND, some Silt, trace Clay.
- WS-9 (2001): 1'-5' Dark brown medium SAND some fine-coarse Gravel, Dry; 5'-7' Dark brown and black medium coarse SAND, trace Silt, trace fine-coarse Gravel; 10'-12' Black medium-coarse SAND, some fine Gravel, Wet; 15'-17' Dark gray medium-coarse SAND trace fine Sand, Wet
- WS-10 (2001): 1'-3' Brown medium SAND to dark brown medium Sand, trace Brick; 3'-7' Brown medium-coarse SAND some light brown and dark brown medium-coarse Sand, little Brick Dry; 7'-11' Dark brown and gray fine SAND and SILT, some black medium coarse Sand, Moist; 11'-15' Gray fine SAND and SILT little Clay, Wet; 15'-19' Gray CLAY, Wet.
- WS-11 (2001): 1'-3' Brown medium SAND, some black medium-coarse Sand, trace fine Gravel, Dry Black medium-coarse SAND little Brick, Dry; 7'-11' Gray SILTY CLAY grading into tan medium-coarse Sand, some black medium Sand, Dry; 11'-15' Tan medium SAND grading into coarse Sand, Dry; 15'-19' Tan fine-medium SAND some Silt Clay, Wet at 16; 19'-23' Tan fine SANO and SILT little, into Silty Clay, Wet.
- WSPS-1 (2001): 1'-4' light Brown medium SAND some dark brown/black medium-coarse Sand, some fine-coarse Gravel Little Silt, Dry; 4'-8' Gray Silty CLAY, some brown fine -medium Sand, Moist in Tip; 8'-12' Gray SILTY CLAY fine medium Sand little fine Sand and Silt Wet; 12'-15' Gray to Brown fine SAND and SILT, some medium Sand, into Silty Clay, Wet.
- WSPS-2 (2001): 1'-4' Brown fine SAND and SILT, some, brick, little to dark gray Silty, Clay, Dry; 4'-8' Black organic SILT little blue/gray Clay, Dry; 8'-12' Blue/Gray CLAY little brown fine medium Sand, some fine Gravel Wet; 12'-15' Brown medium SAND some reddish brown medium-coarse Sand, Wet.
Massachusetts Bay Transportation Authority, MBTA- Cabot Yard Facility, 275 Dorchester Avenue, South Boston, Massachusetts, RTN 3-3096 and 3·19247, Supplemental Phase II - Comprehensive Site, Assessment and Phase Ill - Identification, Evaluation, and Selection of Remedial Alternatives, Volume 1 of 2, Text, Figures, Tables, Appendices A,B, and C (June 2001).
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Soil Disposal Characterization (10/1/2019 0‐5'; 5/22/2020 5‐7'; 7/20/2020 7'): Conductivity ‐ Soil Matrix 233, 458, 601 umhos/cm; Soil pH at 25C 7.02, 7.48, 8.89; Lead 207, 264, 190 mg/Kg
Dewatering Sediment Disposal Characterization (12/30/2020 CMF‐F T‐SP1): Conductivity ‐ Soil Matrix 1,690 umhos/cm; pH at 25C ‐ Soil 11.2; Arsenic 80.2 mg/Kg; Lead 1,680 mg/kg; TCLP Lead 7.61 mg/L
Subsurface Dewatering Analytical Summary: Total Suspended Solids, 6/1/2020 CMF‐F‐EP 1,400 mg/L
PHASE I – INITIAL SITE INVESTIGATION REPORT AND TIER CLASSIFICATION SUBMITTAL MBTA Contract No. R44CN02, Cabot Yard Rebuild & Maintenance Facility Improvements, South Boston, Massachusetts (Release Tracking Number 3-36307)
Dewatering Sediment Disposal Characterization (12/30/2020 CMF‐F T‐SP1): Conductivity ‐ Soil Matrix 1,690 umhos/cm; pH at 25C ‐ Soil 11.2; Arsenic 80.2 mg/Kg; Lead 1,680 mg/kg; TCLP Lead 7.61 mg/L
Subsurface Dewatering Analytical Summary: Total Suspended Solids, 6/1/2020 CMF‐F‐EP 1,400 mg/L
PHASE I – INITIAL SITE INVESTIGATION REPORT AND TIER CLASSIFICATION SUBMITTAL MBTA Contract No. R44CN02, Cabot Yard Rebuild & Maintenance Facility Improvements, South Boston, Massachusetts (Release Tracking Number 3-36307)
SEX 80ft blue clay and 5ft of sediment, then above bricks, timbers, woods and landfill
The Boston Globe Sun, Dec 15, 1996 ·Page 319
Widett Circle Properties, Boston, MA, Prepared by VHB for MBTA, Phase I Initial Site Investigation, Tier Classification, & Phase II Scope of Work (Aug. 9 2024).
MW-12-13 : 4-14 ft is wet, moist, black, grey, shells (2022)
WC6-8: 4ft-12ft wet, moist, black, grey, shells; 8-14 ft “strong petroleum odor”; clay at 14 ft (2022)
MW-11 8ft-14ft No Recovery (2022)
MBTA, WC4-2, 8-18ft, brown sand pebbles, moist, trace wood, coal, and shells (2022)
MBTA, WC6-5 , 6-8ft, Debris and wood in sleeve (2022)
MBTA MW-17, 2-4 brown/grey sand/clay with “streaks of orange”; 12ft-20ft coal; 12-22 black, wet; 20-22ft black and grey clay
REC #2 – Historical uses of the Site parcels including the former presence of South Bay (and associated fill of unknown origin), railroad tracks, and poor housekeeping.
South Bay that was filled in by the 1930s.
Widett Circle Properties, Boston, MA, Prepared by VHB for MBTA, Phase I Initial Site Investigation, Tier Classification, & Phase II Scope of Work (Aug. 9 2024).
The Boston Globe Sun, Dec 15, 1996 ·Page 319
Widett Circle Properties, Boston, MA, Prepared by VHB for MBTA, Phase I Initial Site Investigation, Tier Classification, & Phase II Scope of Work (Aug. 9 2024).
MW-12-13 : 4-14 ft is wet, moist, black, grey, shells (2022)
WC6-8: 4ft-12ft wet, moist, black, grey, shells; 8-14 ft “strong petroleum odor”; clay at 14 ft (2022)
MW-11 8ft-14ft No Recovery (2022)
MBTA, WC4-2, 8-18ft, brown sand pebbles, moist, trace wood, coal, and shells (2022)
MBTA, WC6-5 , 6-8ft, Debris and wood in sleeve (2022)
MBTA MW-17, 2-4 brown/grey sand/clay with “streaks of orange”; 12ft-20ft coal; 12-22 black, wet; 20-22ft black and grey clay
REC #2 – Historical uses of the Site parcels including the former presence of South Bay (and associated fill of unknown origin), railroad tracks, and poor housekeeping.
South Bay that was filled in by the 1930s.
Widett Circle Properties, Boston, MA, Prepared by VHB for MBTA, Phase I Initial Site Investigation, Tier Classification, & Phase II Scope of Work (Aug. 9 2024).
Bacteria Count: Heterotrophic and hexadecane degrading bacteria were detected in well WSA-2 at concentrations of 220,000 cfulml and 230,000 cfu/ml, respectively. Heterotrophic and hexadecane degrading bacteria were detected in well SW-4 at concentrations of 46,000 colony forming units per milliliter (cfu/ml) and 38,000 cfulml, respectively.
Widett Circle Properties, Boston, MA, Prepared by VHB for MBTA, Phase I Initial Site Investigation, Tier Classification, & Phase II Scope of Work (Aug. 9 2024).
Widett Circle Properties, Boston, MA, Prepared by VHB for MBTA, Phase I Initial Site Investigation, Tier Classification, & Phase II Scope of Work (Aug. 9 2024).
During groundwater Monitoring Well inspections in May 2018 and Feb. 2019, multiple wells were found to be filled with water, well above the later depth to water points. Multiple wells noted "well was filled to the top with water" for both visits but then sunk to a lower elevation by May 2019 (DPE-20, 9.97; DPE-21, 19.16; DPE-26, 15.15). Some wells (DPE-1, DPE-13) noted this on all 2018-2019 visits. Two wells were marked "well was filled to the top with water" in 2018 only but then depth to water lowered by Feb. 2019 (DPE-5 at 16.29, then 17-18' later in 2019).
PERMANENT SOLUTION WITH CONDITIONS STATEMENT, MBTA Cabot Yard 275 Dorchester Ave. South Boston, Massachusetts, MassDEP Release Tracking Number (RTN) 3-3096 (June 2025).
PERMANENT SOLUTION WITH CONDITIONS STATEMENT, MBTA Cabot Yard 275 Dorchester Ave. South Boston, Massachusetts, MassDEP Release Tracking Number (RTN) 3-3096 (June 2025).
MBTA (2001)
1888
FORT POINT CHANNEL
The depth to water in the installed observation well ranged from 7.0 ft to 7.6 ft below the ground surface. In addition Boston Wharf Company has installed several observation wells in the area. These wells indicate that the water levels range from El. 5 to El. 9 (5 ft to 14 ft below ground surface) across the site.
Groundwater levels may fluctuate due to variations in season and precipitation, leakage into or out of existing utilities and utility bedding materials, adjacent construction activities, and other environmental effects. As a results water levels encountered during construction may vary from those recorded in the observation well and borings during the observation period.
Fort Point Channel Combined Sewer Overflow Control Project, BWSC Contract No. 95-206-014 (2006)
The depth to water in the installed observation well ranged from 7.0 ft to 7.6 ft below the ground surface. In addition Boston Wharf Company has installed several observation wells in the area. These wells indicate that the water levels range from El. 5 to El. 9 (5 ft to 14 ft below ground surface) across the site.
Groundwater levels may fluctuate due to variations in season and precipitation, leakage into or out of existing utilities and utility bedding materials, adjacent construction activities, and other environmental effects. As a results water levels encountered during construction may vary from those recorded in the observation well and borings during the observation period.
Fort Point Channel Combined Sewer Overflow Control Project, BWSC Contract No. 95-206-014 (2006)
"According to geotechnical borings performed by the City, the project area is composed of soft clay and mud fill to approximately 25-30 feet below the surface and below that is composed of alternating layers of hard and soft compressible clays, mixed with sporadic sand and shell lenses to approximately 70 feet below existing grade (City of Boston 2020). geotechnical borings performed by the City, the project area is composed of soft clay and mud fill to approximately 25-30 feet below the surface and below that is composed of alternating layers of hard and soft compressible clays, mixed with sporadic sand and shell lenses to approximately 70 feet below existing grade (City of Boston 2020)."
The project area and 100 Acre Master Plan area are primarily characterized by built urban infrastructure with minimal wildlife habitat. The habitat in the project area is limited to landscape vegetation, including street trees, along the Harborwalk and in Binford Street Park.
The proposed project area consists of two wetland resource areas protected by the Massachusetts Wetlands Protection Regulations (310 CMR 10.00), including coastal bank and land subject to coastal storm flowage. Each of these resource areas is described in detail below. Estimated habitats of rare wildlife, essential fish habitat, species protected under the Endangered Species Act, and Chapter 91 Waterways jurisdiction are also discussed below. The coastal bank present at the site is primarily comprised of the wall of Fort Point Channel, running from the parking lot at the southern end of the channel to t he Summer Street Bridge to
the north (Figure C-3). Along approximately the middle of the coastal bank, around the SP+ parking lot, the location of the top of the bank shifts slightly landward. At this location, there is not a steep channel wall, but rather a gentler slopping cobble and riprap shoreline (Figure C-4). Cobble and riprap are bordered by grass and then a concrete sidewalk in the landward direction. An existing outfall and concrete headwall structure is within this portion of the bank. The entire length of the bank within the project area is approximately 2,380 feet. This resource area provides a buffer between the channel and inland areas from storm damage and flooding. The bank does not serve as a sediment source to any nearby coastal beach or dune systems. The top of the coastal bank within the project area was delineated using the most recent aerial imagery from MassGIS (2019) to identify the location of the channel wall.
The project area is located within a special flood hazard area (Zone AE 10) subject to inundation by the one percent annual chance flood, as shown on the FEMA Flood Insurance Rate Map panel 25025C0081J dated March 16, 2016 (Figure C-5). The project area is within the Boston Harbor watershed and the Boston Harbor Coastal Drainage Area (MassDEP 2014). Water drains from the project area into the Fort Point Channel. There are 14 stormwater and combined sewer outfalls into the Fort Point Channel that carry stormwater runoff from the larger neighborhood under the project area into the Fort Point Channel immediately adjacent to the project area. Stormwater that runs off impervious surfaces adjacent to the channel, such as parking lots and buildings, is also conveyed to the channel either through surface runoff or drainage systems. The project area is located within the City of Boston Waterfront Area, which is the portion of the buffer zone that extends twenty-five (25) feet horizontally from the edge of the coastal bank.
According to the NMFS EFH online mapping tool, the Fort Point Channel potentially contains EFH for 25 fish species including, but not limited to, winter flounder, Atlantic wolffish (Anarhichas lupus), Atlantic cod (Gadus morhua), and yellowtail flounder (Limanda ferruginea). No Habitat Areas of Particular Concern (i.e., high-priority areas for EFH conservation) or special aquatic sites (e.g., submerged aquatic vegetation, saltmarsh, coral reefs) are in the project area (NMFS 2020).
According to the National Oceanic and Atmospheric Administration (NOAA) Fisheries Greater Atlantic Region Section 7 Mapper, accessed September 7, 2021, there are two ESA-listed species of fish and four species of sea turtles that occur, or have the potential to occur, in the Fort Point Channel: Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus), shortnose sturgeon (Acipenser brevirostrum), loggerhead turtle (Caretta caretta), leatherback turtle (Dermochelys coriacea), green turtle (Chelonia mydas), and Kemp’s ridley turtle (Lepidochelys kempii). The presence of listed species in the project area is very unlikely because the Fort Point Channel is enclosed and highly developed (R. Mesa, NOAA, personal communication, September 8, 2021).
The project area is characterized by large amounts of buried infrastructure including electrical lines, communication conduits, industrial raw water intakes and outfalls from the Gillette facility, stormwater infrastructure, and the I-90 Massachusetts Turnpike, which is buried approximately 25 feet underground (City of Boston 2020). The construction of the turnpike The project area is characterized by large amounts of buried infrastructure including electrical lines, communication conduits, industrial raw water intakes and outfalls from the Gillette facility, stormwater infrastructure, and the I-90 Massachusetts Turnpike, which is buried approximately 25 feet underground (City of Boston 2020). The construction of the turnpike. The stormwater infrastructure includes 14 outfalls in the project area that flow into Fort Point Channel. Stormwater infrastructure in South Boston is part of a combined sewer overflow system that collects rainwater runoff, domestic sewage, and industrial wastewater in the same pipes (Massachusetts Water Resources Authority 2021). Thus, when stormwater levels are too high, such as when flooding occurs, the combined sewer overflows and can carry human and industrial waste into waterways or get backed up and flood sewers, streets, and buildings."
Environmental Notification Form, Proposed City of Boston Resilient Fort Point Channel Infrastructure Project for Boston Planning & Development Agency, Woods Hole Group, Inc, (December 2021).
The project area and 100 Acre Master Plan area are primarily characterized by built urban infrastructure with minimal wildlife habitat. The habitat in the project area is limited to landscape vegetation, including street trees, along the Harborwalk and in Binford Street Park.
The proposed project area consists of two wetland resource areas protected by the Massachusetts Wetlands Protection Regulations (310 CMR 10.00), including coastal bank and land subject to coastal storm flowage. Each of these resource areas is described in detail below. Estimated habitats of rare wildlife, essential fish habitat, species protected under the Endangered Species Act, and Chapter 91 Waterways jurisdiction are also discussed below. The coastal bank present at the site is primarily comprised of the wall of Fort Point Channel, running from the parking lot at the southern end of the channel to t he Summer Street Bridge to
the north (Figure C-3). Along approximately the middle of the coastal bank, around the SP+ parking lot, the location of the top of the bank shifts slightly landward. At this location, there is not a steep channel wall, but rather a gentler slopping cobble and riprap shoreline (Figure C-4). Cobble and riprap are bordered by grass and then a concrete sidewalk in the landward direction. An existing outfall and concrete headwall structure is within this portion of the bank. The entire length of the bank within the project area is approximately 2,380 feet. This resource area provides a buffer between the channel and inland areas from storm damage and flooding. The bank does not serve as a sediment source to any nearby coastal beach or dune systems. The top of the coastal bank within the project area was delineated using the most recent aerial imagery from MassGIS (2019) to identify the location of the channel wall.
The project area is located within a special flood hazard area (Zone AE 10) subject to inundation by the one percent annual chance flood, as shown on the FEMA Flood Insurance Rate Map panel 25025C0081J dated March 16, 2016 (Figure C-5). The project area is within the Boston Harbor watershed and the Boston Harbor Coastal Drainage Area (MassDEP 2014). Water drains from the project area into the Fort Point Channel. There are 14 stormwater and combined sewer outfalls into the Fort Point Channel that carry stormwater runoff from the larger neighborhood under the project area into the Fort Point Channel immediately adjacent to the project area. Stormwater that runs off impervious surfaces adjacent to the channel, such as parking lots and buildings, is also conveyed to the channel either through surface runoff or drainage systems. The project area is located within the City of Boston Waterfront Area, which is the portion of the buffer zone that extends twenty-five (25) feet horizontally from the edge of the coastal bank.
According to the NMFS EFH online mapping tool, the Fort Point Channel potentially contains EFH for 25 fish species including, but not limited to, winter flounder, Atlantic wolffish (Anarhichas lupus), Atlantic cod (Gadus morhua), and yellowtail flounder (Limanda ferruginea). No Habitat Areas of Particular Concern (i.e., high-priority areas for EFH conservation) or special aquatic sites (e.g., submerged aquatic vegetation, saltmarsh, coral reefs) are in the project area (NMFS 2020).
According to the National Oceanic and Atmospheric Administration (NOAA) Fisheries Greater Atlantic Region Section 7 Mapper, accessed September 7, 2021, there are two ESA-listed species of fish and four species of sea turtles that occur, or have the potential to occur, in the Fort Point Channel: Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus), shortnose sturgeon (Acipenser brevirostrum), loggerhead turtle (Caretta caretta), leatherback turtle (Dermochelys coriacea), green turtle (Chelonia mydas), and Kemp’s ridley turtle (Lepidochelys kempii). The presence of listed species in the project area is very unlikely because the Fort Point Channel is enclosed and highly developed (R. Mesa, NOAA, personal communication, September 8, 2021).
The project area is characterized by large amounts of buried infrastructure including electrical lines, communication conduits, industrial raw water intakes and outfalls from the Gillette facility, stormwater infrastructure, and the I-90 Massachusetts Turnpike, which is buried approximately 25 feet underground (City of Boston 2020). The construction of the turnpike The project area is characterized by large amounts of buried infrastructure including electrical lines, communication conduits, industrial raw water intakes and outfalls from the Gillette facility, stormwater infrastructure, and the I-90 Massachusetts Turnpike, which is buried approximately 25 feet underground (City of Boston 2020). The construction of the turnpike. The stormwater infrastructure includes 14 outfalls in the project area that flow into Fort Point Channel. Stormwater infrastructure in South Boston is part of a combined sewer overflow system that collects rainwater runoff, domestic sewage, and industrial wastewater in the same pipes (Massachusetts Water Resources Authority 2021). Thus, when stormwater levels are too high, such as when flooding occurs, the combined sewer overflows and can carry human and industrial waste into waterways or get backed up and flood sewers, streets, and buildings."
Environmental Notification Form, Proposed City of Boston Resilient Fort Point Channel Infrastructure Project for Boston Planning & Development Agency, Woods Hole Group, Inc, (December 2021).
"In 1872, the Great Boston Fire consumed approximately 800 buildings over sixty acres in downtown Boston. Ash and debris from the cleanup was used to fill tidelands along Fort Point Channel. In-1877, this filled land was developed by the Roxbury Gas Light Company for use as a plant to manufacture natural gas from coal for use in the City of Boston. The manufactured gas was stored in a circular building that housed a gas holder. This building was constructed through the ash-containing fill and deep into the impermeable Boston blue clay beneath. This gas holder and the approximate 0.4 acres of filled tideland on which it is located.
Three contaminant regimes were identified at levels exceeding Reportable Concentrations: 1. diesel fuel on the southern portion of the Property; 2. mineral spirits along the northern boundary of the Roundhouse Property; and, 3. fill containing ashrelated
contaminants, such as polycyclic aromatic hydrocarbons (PAHs), lead, and aromatic fractions of hydrocarbons. The diesel fuel and mineral spirits originated on the adjoining properties. The ash-related contaminants are related to filling that occurred over a century ago."
Phase I Initial Site Investigation Report & Method 3 Risk Characterization, 8 Gerard Street, Boston (Roxbury), MA, DEP RTNs: 3-18967, 3-3774, 3-18421, ENSOL (1999).
An effort was made to identify groundwater flow paths by performing a textural analysis of
the clay/silt fill, the sand lenses located at and below the water table, and from the
underlying native soil above the Boston blue clay
The laboratory analysis is presented in Appendix E and summarized in Table 7. The
particle size analysis indicates that a narrow region of soil at a depth of approximately 10
feet below grade is quite permeable. It is evident from the boring logs that this unit is not
homogeneous, and that the permeable samples were collected from narrower lenses over a
depth interval of approximately 1.5 feet spanning the water table. This sand-lens
containing unit is overlain and underlain by essentially impermeable soil.
The risk estimates derived in the foregoing analysis as a consequence of hypothetical or
actual exposure to PAHs and metals in fill on the Roundhouse Property should be viewed
in light of the observation that the levels are consistent with fill found in the area.
Soil texture is an important soil property because it controls, in part, the rate at which water
and other fluids flow through the soil, as well as the amount of fluid retained by the soil.
The organization of an aquifer into layers with recognized textural variation is important
because this level of organization has a profound effect on the fate of chemicals released to
the subsurface
8 Gerard Street, Roxbury, MA ENSOL, Inc. I September 1999, page 22
The vicinity of the Roundhouse Property was formerly the South Bay tidal area, which was filled in the 1800s. Some of this fill might have included debris from burnt buildings.7 In this part of the City of Boston, the soil lithology consists of fill overlying shallow marine sediments or salt marsh sediment, which is underlain by the Boston blue clay.
The central portion of the Site is improved with a circular building, known as the Roundhouse, that is approximately 105 feet in diameter and 55 feet in height. The building extends approximately 24 feet below grade into Boston blue clay, and has been filled to approximately 12 feet below grade, where the current basement floor is located. The building is currently undergoing a gut renovation for use as a hotel. A small loading dock I addition to the southwest of the Roundhouse has been recently demolished. Narrow bands of land along Gerard Street and Massachusetts Avenue were paved with asphalt or granite, and vegetation has been recently cleared from the southern portion of the Site.
The round building ("Roundhouse") improving the Site was constructed in the late 1800s for use as a gas holder for a manufactured gas plant (MGP) that was located several hundred feet to the northeast, and was used as such for approximately a decade until circa
the turn of the century. After use as a gas holder, the Boston Consolidated Gas Co. used the Site for storage from the 1910s through the 1930s. After use by the Boston Consolidated Gas Co., the Site appears to have been used primarily for storage by various trucking concerns and distributors.
Immediate Response Action Completion and Downgradient Property Status Opinion, 8 Gerard Street, Boston (Roxbury), MA, DEP RTNs: 3-18967, 3-3774, 3-18421, ENSOL (1999).
4.02.2 Organic Deposit An organic deposit was encountered in HA-FPCI5 at a depth of 13 ft below ground surface. The boring was terminated at a depth of 15 ft and the layer was not fully penetrated. The deposit consisted of medium stiff SILT with roots.
4.02.3 Estuarine Deposit Estuarine deposits were encountered in borings HA-FPCO9 and HA-FPC17. The deposit ranged from stiff SILT to medium stiff sandy CLAY.
4.02.4 Marine Deposit Marine deposits were encountered in boring HA-FPCO5, HA-FPCO7, and HAFPC-17. The marine deposit ranges from of soft lean CLAY to medium stiff SILT to medium dense SAND with silt. Trace shells, roots, and other organic material was encountered.
Fort Point Channel Combined Sewer Overflow Control Project, BWSC Contract No. 95-206-014 (2006)
Estuarine/Organic Deposits: sandy organic silt, silt and peat. This unit varies in composition across the site, and is described as peat and silt or organic silt. The peat and silt layer ranges in thickness from four to 24 feet, and the organic silt layer ranges from 11 to 26.5 feet thick.
Marine Clay: clay with partings, lenses and layers of silt and fine sand. The top of clay was encountered at depths ranging from 18 to 39 feet and ranges in thickness from 0 to 35.5 feet.
Bedrock: consists of the Cambridge Argillite member of the Cambridge formation, which includes argillite, tuffaceous argillite and diabase. The argillite consists of fine-grained, very thinly bedded layers of silt- and clay-sized clasts. The tuffaceous argillite contains fine- to medium-grained volcanic siliceous fragments within the siltclay argillite matrix. A diabase dike was encountered in one boring. The top of bedrock was encountered at depths ranging from 57 to 113 feet, with an east-west trending bedrock trough defined in the western portion of the site parallel to the southern end of Fort Point Channel. Typically the upper ten feet of bedrock is moderately to highly fractured and weathered. Bedrock competence generally increases with depth. Hydraulic conductivity of this unit was measured to range from 3.3 x 10-4 cm./sec to 8.9 x 10-5 cm./sec
Groundwater at the site has been characterized as consisting of a shallow and deep aquifer separated by a clay layer. The shallow aquifer is located in the fill and estuarine/organic deposit layers, and the deep aquifer is located in the till and bedrock layers. Regional groundwater flow in the shallow aquifer is generally in a northerly direction. However, the effects of the MHD's casting basin pumping activities, tidal fluctuations and buried utilities affect flow patterns locally. The low gradient and tidal fluctuations in the upper aquifer results in a low net movement of groundwater in this interval. Regional groundwater flow in the deep aquifer is generally northwestward. However, the effects of the MHD's casting basin pumping and recharge activities affect deep groundwater flow patterns particularly in the northern portion of the site.
Throughout the site, the clay layer separates the shallow and deep aquifers and impedes vertical groundwater flow between them. However, the Franki piles that support Building Z penetrate the clay layer and likely act as conduits for transport of both dissolved and DNAPL contamination to the underlying till and bedrock layers.
TCE and 1,2-DCE are located in the deep aquifer east, beneath and west of Building Z.
Deep Aquifer TCE and 1,2-DCE exist in the deep aquifer. These compounds have been detected predominantly west of Building Z. Based on existing data, the axis of the plume appears to trend in a northwesterly direction from the former dry well to well MW801B. A bedrock trough trends in a westerly direction northwest of the former dry well source area. A 35-foot decrease in bedrock surface elevation occurs between the source area and the bottom of this trough in the vicinity of MW801B. The bedrock trough is thought to be fracture controlled, which is supported by low rock quality designations (RQDs), for bedrock cores collected along its axis. Therefore, TCE detected in the MW801B/MW801T wells is likely due to hydraulically-controlled dissolved-phase contaminant transport through till and highly-fractured shallow bedrock down the slope to the trough resulting from DNAPL closer to the source area. A downward vertical gradient exists between wells MW801T and MW801B, supporting this theory.
Phase III Remedial Action Plan Gillette South Boston Manufacturing Center, RTN 3-11312 29 (December 1998)
Boston Inner Harbor State Waterbody ID: MA70-02
303(d) Listed: Yes
Year Reported: 2022
303(d) List Status: EPA Interim Action
Other Years Reported: 2014, 2016, 2020
Organization Name (ID): Massachusetts (MA_DEP)
What type of water is this? Estuary (2.56 Square Miles)
Where is this water located? From the Mystic and Chelsea rivers, Chelsea/Boston, to the line between Governors Island and Fort Independence, Boston (East Boston) (including Fort Point, Reserved and Little Mystic channels).
010900010704
Charles River-Frontal Boston Harbor
INNER BOSTON HARBOR / FORT POINT CHANNEL (MA70-02)
Pollutants Potentially Related to Impairment: Chemical Oxygen Demand (COD) | Coliform, fecal, colony forming units | Enterococci | Nitrogen, total (as N) | Phosphorus, total (as P) | Solids, total suspended | pH
Watershed with ESA-listed Aquatic Species?: Yes
4.02.3 Estuarine Deposit Estuarine deposits were encountered in borings HA-FPCO9 and HA-FPC17. The deposit ranged from stiff SILT to medium stiff sandy CLAY.
4.02.4 Marine Deposit Marine deposits were encountered in boring HA-FPCO5, HA-FPCO7, and HAFPC-17. The marine deposit ranges from of soft lean CLAY to medium stiff SILT to medium dense SAND with silt. Trace shells, roots, and other organic material was encountered.
Fort Point Channel Combined Sewer Overflow Control Project, BWSC Contract No. 95-206-014 (2006)
Estuarine/Organic Deposits: sandy organic silt, silt and peat. This unit varies in composition across the site, and is described as peat and silt or organic silt. The peat and silt layer ranges in thickness from four to 24 feet, and the organic silt layer ranges from 11 to 26.5 feet thick.
Marine Clay: clay with partings, lenses and layers of silt and fine sand. The top of clay was encountered at depths ranging from 18 to 39 feet and ranges in thickness from 0 to 35.5 feet.
Bedrock: consists of the Cambridge Argillite member of the Cambridge formation, which includes argillite, tuffaceous argillite and diabase. The argillite consists of fine-grained, very thinly bedded layers of silt- and clay-sized clasts. The tuffaceous argillite contains fine- to medium-grained volcanic siliceous fragments within the siltclay argillite matrix. A diabase dike was encountered in one boring. The top of bedrock was encountered at depths ranging from 57 to 113 feet, with an east-west trending bedrock trough defined in the western portion of the site parallel to the southern end of Fort Point Channel. Typically the upper ten feet of bedrock is moderately to highly fractured and weathered. Bedrock competence generally increases with depth. Hydraulic conductivity of this unit was measured to range from 3.3 x 10-4 cm./sec to 8.9 x 10-5 cm./sec
Groundwater at the site has been characterized as consisting of a shallow and deep aquifer separated by a clay layer. The shallow aquifer is located in the fill and estuarine/organic deposit layers, and the deep aquifer is located in the till and bedrock layers. Regional groundwater flow in the shallow aquifer is generally in a northerly direction. However, the effects of the MHD's casting basin pumping activities, tidal fluctuations and buried utilities affect flow patterns locally. The low gradient and tidal fluctuations in the upper aquifer results in a low net movement of groundwater in this interval. Regional groundwater flow in the deep aquifer is generally northwestward. However, the effects of the MHD's casting basin pumping and recharge activities affect deep groundwater flow patterns particularly in the northern portion of the site.
Throughout the site, the clay layer separates the shallow and deep aquifers and impedes vertical groundwater flow between them. However, the Franki piles that support Building Z penetrate the clay layer and likely act as conduits for transport of both dissolved and DNAPL contamination to the underlying till and bedrock layers.
TCE and 1,2-DCE are located in the deep aquifer east, beneath and west of Building Z.
Deep Aquifer TCE and 1,2-DCE exist in the deep aquifer. These compounds have been detected predominantly west of Building Z. Based on existing data, the axis of the plume appears to trend in a northwesterly direction from the former dry well to well MW801B. A bedrock trough trends in a westerly direction northwest of the former dry well source area. A 35-foot decrease in bedrock surface elevation occurs between the source area and the bottom of this trough in the vicinity of MW801B. The bedrock trough is thought to be fracture controlled, which is supported by low rock quality designations (RQDs), for bedrock cores collected along its axis. Therefore, TCE detected in the MW801B/MW801T wells is likely due to hydraulically-controlled dissolved-phase contaminant transport through till and highly-fractured shallow bedrock down the slope to the trough resulting from DNAPL closer to the source area. A downward vertical gradient exists between wells MW801T and MW801B, supporting this theory.
Phase III Remedial Action Plan Gillette South Boston Manufacturing Center, RTN 3-11312 29 (December 1998)
Boston Inner Harbor State Waterbody ID: MA70-02
303(d) Listed: Yes
Year Reported: 2022
303(d) List Status: EPA Interim Action
Other Years Reported: 2014, 2016, 2020
Organization Name (ID): Massachusetts (MA_DEP)
What type of water is this? Estuary (2.56 Square Miles)
Where is this water located? From the Mystic and Chelsea rivers, Chelsea/Boston, to the line between Governors Island and Fort Independence, Boston (East Boston) (including Fort Point, Reserved and Little Mystic channels).
010900010704
Charles River-Frontal Boston Harbor
INNER BOSTON HARBOR / FORT POINT CHANNEL (MA70-02)
Pollutants Potentially Related to Impairment: Chemical Oxygen Demand (COD) | Coliform, fecal, colony forming units | Enterococci | Nitrogen, total (as N) | Phosphorus, total (as P) | Solids, total suspended | pH
Watershed with ESA-listed Aquatic Species?: Yes
FOURTH ST / TRAVLER ST (AT EAST BERKLEY ST / ALBANY ST) & GILLETTE
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Groundwater flow was “presumed” to be to the northeast, towards Fort Point Channel
and the Boston Harbor. 3-0050262
Boston Inner Harbor, URAM COMPLETION, Boston, Massachusetts, RTN 3-50561 ().
Mass Ave Connector/Frontage Road
Prior use: "green space/park area and/or stormwater drainage area"
10ft deep black, fine-to-coarse sand containing significant amounts of brick, glass, wood, and traces of coal and coal ash.
"The identification of coal and coal ash confirms the presence of urban fill material"
1.3.2.1 RTN 3-38454
During initial due diligence programs at the Site, polycyclic aromatic hydrocarbon (PAH) compounds,
specifically benzo(a)pyrene, biphenyl, and dibenz(a,h)anthracene, total petroleum hydrocarbons (TPH)
and extractable petroleum hydrocarbons (EPH), specifically C11-C22 Aromatic Hydrocarbons (adjusted),
C9-C18 Aliphatic Hydrocarbons, 2-methylnaphthalene, and lead were detected in soil at concentrations
exceeding the applicable RCS-1 Reportable Concentrations. The lead and the PAH compounds are
exempt from reporting as they are emanating from coal, coal ash, or wood ash described in the test
boring logs resulting from historic site filling; however, the petroleum-related compounds EPH carbon
range C11 to C22 and 2-methylnaphthalene are reportable and could be related to unknown source of
heating oil from a former or existing underground storage tank (UST) and are considered a Reportable
Condition under the MCP. Accordingly, a Release Notification Form (RNF) was submitted on
15 November 2023 for the C11 to C22 hydrocarbon and RTN 3-38454 was assigned to the release. The
detection of 2-methylnaphthalene, a semi-volatile organic compound (SVOC) related to fuel oil,
MCP PHASE I COMPLETION STATEMENT, TIER II CLASSIFICATION, AND CONCEPTUAL PHASE II SCOPE OF WORK: 7 CHANNEL CENTER BOSTON, MA
1.3.2.2.1.1 RTN 3-22470
This utility corridor site covers portions of Midway Street, A Street, Binford Street, and Channel Point
Avenue. It includes the entire width of Channel Center Street. A Utility-Related Abatement Measure
(URAM) was conducted by A Street Properties III, LLC to manage urban fill encountered during
installation of private utilities beneath the streets and parking lots within and adjacent to the Channel
Center redevelopment site. Results of the chemical soil testing indicated that levels of PAHs, lead, and
chloroform exceeded their applicable RCS-1 Reportable Concentrations.
Due to the presence of contaminants at levels exceeding the applicable RCS-1 Reportable
Concentrations, MassDEP was verbally notified of the URAM on 13 January 2003. The Site was
subsequently assigned RTN 3-22470 and utility excavations began in late January 2003. A URAM
Transmittal Form and RNF were submitted to DEP on 21 January 2003. The URAM Completion Report
for the Site was submitted to MassDEP on 19 May 2004.
URAM activities included deep excavations conducted in Medallion Avenue adjacent to 35 Channel
Center and 25 Channel Center for the placement of concrete utility vaults, the removal of four
abandoned USTs that were encountered within the boundaries of the utility corridor and in Channel
Center Street, soil sampling from the limits of excavations, groundwater sampling, and identifying and
managing of urban fill soils.
MCP PHASE I COMPLETION STATEMENT, TIER II CLASSIFICATION, AND CONCEPTUAL PHASE II SCOPE OF WORK: 7 CHANNEL CENTER BOSTON, MA
1.3.2.2.1.2 RTN 3-14748
On 22 January 1997, approximately 20 gallons of No. 2 fuel oil were sprayed onto the roadway and into
two catch basins during filling operations conducted at 50 Midway Street (now known as 5 Channel
Center) by Supreme Fuel Co. The location of the release was located at the entrance of 5 Channel
Center, located adjacent to the subject property. This release triggered a 2-hour reporting condition and
MassDEP was notified. MassDEP assigned the release RTN 3-14748.
Cyn Environmental applied absorbent material to the impacted asphalt surfaces and disposed of the
impacted material off-site. A vacuum truck was utilized to skim fuel oil from the surface of a minimal
volume of standing water contained within the catch basin. Impacted sediment from the catch basin
was removed and a high-pressure water jet was used to clean the catch basin.
Following all activities, a visual inspection of the asphalt surfaces indicated that they were clean and free
of fuel oil, and that they contained no large cracks or voids which would have allowed fuel oil to migrate
to subsurface media. A Class A-1 RAO was submitted for this release in March 1997. Based on the
Class A-1 Regulatory closure achieved, this release is not anticipated to adversely affect the Site.
MCP PHASE I COMPLETION STATEMENT, TIER II CLASSIFICATION, AND CONCEPTUAL PHASE II SCOPE OF WORK: 7 CHANNEL CENTER BOSTON, MA
1.3.2.2.1.3 RTN 3-23180 - 5 Channel Center UST Removal
The building at 50 to 52 Midway Street (now known as 5 Channel Center Street adjacent to the Site to
the southwest) was formerly heated by No. 2 fuel oil stored in an UST located at the Channel Center
Street (formerly Midway Street) side of the building adjacent to the property boundary with the current
Site. The tank was encountered during utility work in Channel Center Street and was removed in
September 2003. Photoionization detector (PID) readings taken during the UST removal indicated levels
above 100 parts per million by volume (ppmv); accordingly, Haley & Aldrich, Inc. (Haley & Aldrich)
provided 72-hour notice orally to MassDEP on 16 September 2003, and MassDEP assigned RTN 3-23180
to the release and provided verbal approval to remove the UST and conduct an assessment-only
Immediate Response Action (IRA).
Soil samples indicated that levels of compounds remained in the sidewalls and in the bottom of the
excavation at levels exceeding RCS-1 Reportable Concentrations. Groundwater samples indicated
concentrations of EPH carbon ranges and analytes and VPH carbon ranges at levels exceeding RCGW-2
Reportable Concentrations. An IRA Completion Report dated 13 November 2003 was submitted to the
MassDEP.
A Class A-2 RAO Statement was submitted for RTN 3-23180 in September 2006. The source of the
release was identified as a 2,500-gallon No. 2 heating oil UST located within Channel Center Street,
located adjacent to a foundation wall that remains. The RAO states that based on the data collected in
2006, petroleum constituents did not appear to extend beyond the vertical and horizontal limits of the
former tank grave and the 2003 excavation although this release may have extended on to the
7 Channel Center property.
1.3.2.2.1.4 RTN 3-27506 Channel Center Properties
This site is located adjacent (across Channel Center Street) and west of the Site and is now occupied by a
10-story office building at One Channel Center and a park and other Channel Center buildings (10 through
50). During a soil precharacterization program in 2007 and 2008, soil samples were collected and found
certain SVOCs, naphthalene, lead and TPH in soil exceeded the applicable MCP RCS-1 Reportable
Concentrations. Groundwater sampling indicated total and dissolved lead above RCGW-2 groundwater
standard at one monitoring well. The presence of these contaminants is attributed to the presence of
urban fill. MassDEP was notified and assigned the release RTN 3-27506 in February 2008.
A Release Abatement Measure (RAM) Plan was submitted was submitted on 31 March 2008. RAM
activities consisted of management of contaminated soil related to site improvements, removal of two
existing USTs, one above-ground storage tank (AST), and one previously unknown UST encountered
during site excavation activities, and selective remedial excavation to remove contaminated soil. A
condition of “No Significant Risk” was achieved for current and future site use. The site achieved
regulatory closure via a Class A-2 RAO, submitted to MassDEP on 27 July 2010. Based on the regulatory
closure achieved, this release is not anticipated to adversely affect the Site.
1.3.2.2.1.5 RTNs 3-1918 and 3-11987 – USPS Properties
On 8 January 1988, the U.S. Postal Service (USPS) received a Notice of Responsibility (NOR) from the MassDEP for a release/threat of release of gasoline detected during a soil excavation for a sprinkler line. The MassDEP assigned RTN 3-1918 to the release. Between 1988 and 1993, several incidents were reported to the MassDEP under RTN 3-1918 including two significant incidents. One incident involved the 1990 detection of petroleum impacted soil and light non-aqueous phase liquid (LNAPL) in the northeast corner of the Vehicle Maintenance Facility (VMF) property. This area was being excavated to install two USTs: one 20,000-gallon diesel UST and one 15,000-gallon gasoline UST. A second incident involved the 1991 discovery of gasoline impact to soil during the removal of two 5,000 gasoline USTs located in the southwest corner of the former VMF building.
Subsequently in December 1994, the USPS notified the MassDEP of the presence of dense nonaqueous phase liquid (DNAPL) in a monitoring well. On 22 December 1994, the MassDEP issued a Release Notification and Notice of Potential Responsibility to the USPS and assigned RTN 3-11987. An assessment-type IRA was performed. An IRA Completion Report was submitted in December 1996. A LSP Evaluation Opinion, Tier Classification Submittal, and Phase I Initial Site Investigation (Phase I) Report were prepared and submitted to the MassDEP on December 21, 1995. Given that site conditions related to RTN 3-11987 are similar and within the boundaries of site RTN 3-1918, site RTN 3-11987 was linked to site RTN 3-1918.
A Phase III Remedial Action Plan (RAP) was prepared to select a remedial action alternative for the site. Based on the Phase III evaluation, a remedial alternative consisting of an AUL with groundwater monitoring was selected as the most feasible remedial alternative to satisfy the remedial objectives established for this site. It was determined that this alternative would lead to a Permanent Solution (Class A-3 RAO). A Phase IV Remedy Implementation Plan (RIP) Report was submitted to MassDEP on 11 December 1998. This plan included two activities: complete an AUL to limit soil exposure and conduct several rounds of groundwater monitoring to confirm that oil and/or hazardous material (OHM) in soil is not causing OHM concentrations in groundwater to increase. The Phase IV Final Inspection and Completion Report, submitted in March 2004, documented the completion of groundwater monitoring activities. This report concluded that there were no statistically significant increasing trends of any of the site-related OHM in any of the monitoring wells. In June 2009 a Class A-3 RAO Statement and AUL were implemented at the site. The risk assessment concluded that a condition of No Significant Risk had been achieved for health, public welfare, the environment, and safety. An AUL was implemented to maintain the condition of No Significant Risk. Based on the regulatory closure of the release, this site is not anticipated to adversely affect the Site.
1.3.3 Oil and/or Hazardous Material Use and Storage History
Currently, OHM is not being used at the Site. Based on historical records and prior site assessments t here is a 3,600-gallon UST located below the ground floor slab approximately as shown on the attached Figure 2. The UST is reportedly not located in a vault and its condition is unknown. It is planned to remove the UST following building demolition, however access to the UST is currently hindered by the poor structural condition of the existing building. In the interim, the UST is planned to be pumped out prior to demolition.
The area north of First Street in South Boston was originally a mud flat known as South Boston Flats. A large segment of the South Boston Flats was filled beginning in the mid-1830s through about 1870. The source of the fill is believed to have been granular material taken from nearby hills, dredged silt, and clay from the Fort Point Channel, building rubble, and coal ash. Fill was observed to contain debris such as brick, concrete, glass, wood, ceramic, ash, cinders, and foam fragments. Historical activities on the Property included industrial facilities using coal and maintaining coal storage areas. A manufactured gas facility operated on the 50 to 54 Sobin Park property, north of the Site. MassDEP RTN 3-50205, Phase I Initial Site Investigation and Tier Classification, North of Automated Materials Handling Center, One Gillette Park, South Boston, Massachusetts, May 2025
The IRA conducted to assess the extent of the NAPL condition included a TarGOST investigation to evaluate areas between the ZX Building and the AMHC for the presence of contamination consistent with coal tar. The TarGOST investigation included four locations within the Site that is the subject of this Phase I ISI. Contamination in these locations was identified as consistent with fuel oil, and not coal tar. A discussion of the TarGOST investigations within the Site and the results of the investigation are in Section 4.5. Potential petroleum-related contaminant sources are unknown but are likely associated with historical operations pre-dating Gillette’s ownership and the placement of fill during development of the property. The low levels of other contaminants in the shallow fill are likely associated with the fill MassDEP RTN 3-50205, Phase I Initial Site Investigation and Tier Classification, North of Automated Materials Handling Center, One Gillette Park, South Boston, Massachusetts
"Surface water at the Site appears to be collected in catch basins connected to storm drain system and discharged to Fort Point Channel. Based on the Site topography, surface water runoff appears to flow towards the north and west. Fort Point Channel is located approximately 650 feet northwest and Boston Harbor is located approximately 4,000 feet northeast of the Site."
"The Site was filled over a tidal flat, and the ground surface is nearly flat over a wide area surrounding the Site. The Site is located approximately midway between the Fort Point Channel to the northwest and the railroad bed to the southeast. The railroad bed is depressed about 5 feet below Site grade. Therefore, we would expect the ground water surface to be essentially flat at the Site. However, flow may occur either toward the Fort Point Channel or toward the railroad bed. The direction and rate of flow can be expected to be low but to vary depending on the season, rainfall, tidal stage in the Fort Point Channel, sump pumps in buildings, paving or lack of paving, and the effects of buried utilities and other underground structures, such as buried sea walls. One set of ground water elevation was taken at the Site in February 1994. Ground water depths in MW507, MW508, and MW509 ranged from 3.05 to 4.05 feet below ground surface. The ground water elevations are summarized in Table 2. Based on the one set of ground water elevations, there is a local gradient in an easterly direction toward A Street. Thus it appears that the local ground water flow may be affected by drainage toward buried utilities in A Street, possibly other buried structures or sump pumps, and/or by the paved or unpaved areas nearby, since the gradient would be considerably flatter if such local effects were not present. However, this data is inconclusive and data on ground water levels from a wider area around the Site and over a longer time period are needed to adequately judge the extent to which the ground water flow direction and rate fluctuates over a full year."
The chlorinated VOCs, trichlorethylene (TCE), cis-1,2-dichloroethylene, and tetrachloroethylene were detected at maximum concentrations of 130,000, 160,000, and 22,000 fig/kg (ppb), respectively
PHASE I INITIAL SITE INVESTIGATION 64-76 SOBIN PARK ROAD RTN 3-11312 GILLETTE PARK SOUTH BOSTON, MASSACHUSETTS
SOUTH END LANDMARK DISTRICT
"The area between the original shore lines on the so-called natural soils, one location out of eight locations was found where piles were used."
"After excavations had progressed for a few days it became apparent that many of the structures in the South End wore founded directly on the underlying soils, and in many cases these soils were clay.... The entire South End Area is underlain with blue clay of varying consistency, from hard to soft."
"many of the structures in the South End were founded directly on the underlying soils, and in many cases these soils were clay."
Investigation of Subsoil and Foundation Conditions, Boston Redevelopment Authority, SOUTH END PROJECT MASS. R-56, SOUTH END URBAN RENEWAL AREA (December 27, 1963).
MA Chapt. 772, An Act Establishing the Boston Landmarks Commission (1975)
"The South End Landmark District is the largest intact Victorian rowhouse district in the United States. It represents over 300 acres of land that was filled along the necklands and developed during the mid-19th century. It is a substantially intact area of mid-19th c. row houses. The landmark district is roughly bounded by the Southwest Corridor right-of-way, Tremont St., East Berkely St. Washington St., Harrison Ave., and Northampton/Camden Streets."
"The Commission on November 14, 1983, fallowing recommendation of the Study Committee, voted to designate the South End Landmarks District and the South End Protection Area, which designation were approved by the Mayor on November 16, 1983."
"After excavations had progressed for a few days it became apparent that many of the structures in the South End wore founded directly on the underlying soils, and in many cases these soils were clay.... The entire South End Area is underlain with blue clay of varying consistency, from hard to soft."
"many of the structures in the South End were founded directly on the underlying soils, and in many cases these soils were clay."
Investigation of Subsoil and Foundation Conditions, Boston Redevelopment Authority, SOUTH END PROJECT MASS. R-56, SOUTH END URBAN RENEWAL AREA (December 27, 1963).
MA Chapt. 772, An Act Establishing the Boston Landmarks Commission (1975)
"The South End Landmark District is the largest intact Victorian rowhouse district in the United States. It represents over 300 acres of land that was filled along the necklands and developed during the mid-19th century. It is a substantially intact area of mid-19th c. row houses. The landmark district is roughly bounded by the Southwest Corridor right-of-way, Tremont St., East Berkely St. Washington St., Harrison Ave., and Northampton/Camden Streets."
"The Commission on November 14, 1983, fallowing recommendation of the Study Committee, voted to designate the South End Landmarks District and the South End Protection Area, which designation were approved by the Mayor on November 16, 1983."
DILEANATION
Investigation of Subsoil and Foundation Conditions, Boston Redevelopment Authority, South End Project Mass. R-56, South End Urban Renewal Area (December 27, 1963)
Examination of existing piling showed some rotting, indicating probable lowering of the water levels in some areas, but, generally, water levels are as would be expected from the elevation cutoff and location of piles. Actual lengths of piles are not known. On-site observations and information obtained from the records of the Boston Building Department as to conditions of structures supported by pile foundations indicate, that although the piles, in general, were in good condition, a large proportion of these structures were considered in such poor condition as to be condemned. The fault, however, appears not in the piles but largely in poorly constructed foundation walls.
In general, structures over three stories in height must be on piles. Foundation walls and piles of existing buildings to be continued in use should be thoroughly examined."
Investigation of Subsoil and Foundation Conditions, Boston Redevelopment Authority, South End Project Mass. R-56, South End Urban Renewal Area (December 27, 1963)
- At Tremont and Herald Streets, blue clay extends to 110' below the surface at which point very compact fine sand, gravel and little shale exists.
- At Tremont and Northampton Streets, blue clay extends to 122' below the surface with gravel and clay to 141' where ledge is found.
- At Washington and West Canton Streets, soft clay extends to 75' below the surface where sand, gravel and clay is found.
- At Washington and Dover Streets, soft blue clay extends to 71' below the surface; between 71' below and 99' medium stiff blue clay with veins of fine sand is found, and between 99' and 110' below, firm fine sand exists.
- Deep borings adjacent to Washington Street indicate the clay strata ranges from 50' to 55' thick. Peat also exists in four specific across adjacent to Washington Street.
- At Harrison Avenue and East Lenox Streets, soft blue clay extends to 103.5' below the surface, with loose medium sand to 107.0'; firm medium gray sand and gravel to 126.0', and hard coarse sand and gravel to 132.0' below.
- At Albany and Randolph Streets, blue clay extends to 130.0' below the surface, with medium sand and some fine gravel to 131.5', and fine sand, little clay and some fine gravel to 136.9' below.
- At Tremont and West Springfield Streets, soft blue clay extends to 85.5' below the surface; hard fine sand and gravel is found between 85.5' and 87.0' below.
- Deep borings adjacent to Tremont Street indicate clay strata to be (1) 92'; (2) 120'; (3) 73"; (4) over 60'. Peat is found between Cunard Street and Coventry Street, also between Benton Street and Northampton Street, and near Herald Street.
At Shawmut Avenue and Herald Streets, blue gray silty clay extends at least to 71.5' below the surface, as is also the case at Washington Street and Herald Street. - At Washington Street and Massachusetts Avenue, blue gray silty clay with little sand extends at least to 72.0' below the surface.
- At Harrison Avenue and Worcester Square, soft blue clay extends to 114.0' below the surface; very hard fine sand, gravel and stones are found up to 121.0' below the surface.
- At Harrison Avenue and East Dedham Street, soft blue clay extends to 74.3' below the surface; boulder hard pan is found down to 76.0' below, with refusal encountered at 76.0' below.
- The Harrison Avenue soils profile above the clay, in general indicates: 4' to 17' - fill 4' to 19.5' = peat and silt. Deep borings in the vicinity of Harrison Avenue indicate clay strata to be between 57' and 88.5' thick. There are a few locations where the peat strata is not encountered; namely, in the area between Savoy and Dover Streets.
- At Albany and Stoughton Streets, blue clay extends to 87.5' below the surface; fine sand, some clay and medium coarse gravel is found between 87.5' and 95.0' below, with refusal encountered at 95.0' below,
- The Albany Street soils profile, in general shows the following above clay: 4ft to 24ft = fill; over 3.5' to 45' = mud or silt; or 4' to 17' - peat and silt. Deep borings in the vicinity of Albany Street indicate the clay strata to be between 70' and 110' thick.
Investigation of Subsoil and Foundation Conditions, Boston Redevelopment Authority, South End Project Mass. R-56, South End Urban Renewal Area (December 27, 1963)
Examination of existing piling showed some rotting, indicating probable lowering of the water levels in some areas, but, generally, water levels are as would be expected from the elevation cutoff and location of piles. Actual lengths of piles are not known. On-site observations and information obtained from the records of the Boston Building Department as to conditions of structures supported by pile foundations indicate, that although the piles, in general, were in good condition, a large proportion of these structures were considered in such poor condition as to be condemned. The fault, however, appears not in the piles but largely in poorly constructed foundation walls.
In general, structures over three stories in height must be on piles. Foundation walls and piles of existing buildings to be continued in use should be thoroughly examined."
Investigation of Subsoil and Foundation Conditions, Boston Redevelopment Authority, South End Project Mass. R-56, South End Urban Renewal Area (December 27, 1963)
1965
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"During this investigation and study, a total of 15 new soils borings were made finding: Silt sizes range from 0.07 mm to 0.005 mm; Clay sizes are smaller than 0.005 mm; Colloids are smaller than 0.001 mm
No. 6A - 106-108 East Canton Street - rear of building
Boring No. 6A
Sample No. 4
Depth = 34' to 38.5'
Blow Count - 13/ft
Stiff yellow clay
Clay & silt, some fine sand
No. 8A - 373 Columbus Avenue - rear of building
Boring No. 8A
Sample Noe
Depth - 15.5' to 17'
Blow Count = 2/ft
Very loose sandy peaty silt
Clayey organic silt
No: 9 - 72 Warren Avenue - Firehouse = rear of building
Boring No. 9
Sample No. 6
Depth - 26' to 28'
Blow Count - 21/ft
Very stiff blue clay with trace of gravel
Clayey sandy silt
No. 15 = 21 Rutland Square - rear of building
Boring No. 15
Sample No. 6
Depth - 22.5' to 24'
Blow Count - 4/ft
Soft blue clay
Clay and silt, some fine sand
Investigation of Subsoil and Foundation Conditions, Boston Redevelopment Authority, SOUTH END PROJECT MASS. R-56, SOUTH END URBAN RENEWAL AREA (December 27, 1963).
For South End, "soils information available from numerous soil borings that have been made in past years throughout the South End Project Area provided a basis for development of a generalized subsurface profile in the area. The soils and rock strata from existing ground surface downward are as follows:
The effects of the tide levels in the Roxbury Canal influence the water table at this site. The ground water varies between El. + 1 and El. + 13."
BOSTON REDEVELOPMENT AUTHORITY ENGINEERING REPORT ON THE PRELIMINARY DESIGN OF PROJECT IMPROVEMENTS, SOUTH END PROJECT, Project No. Mass. R-56, MAGUIRE AND ASSOCIATES, ENGINEERS (JULY 1965)
No. 6A - 106-108 East Canton Street - rear of building
Boring No. 6A
Sample No. 4
Depth = 34' to 38.5'
Blow Count - 13/ft
Stiff yellow clay
Clay & silt, some fine sand
No. 8A - 373 Columbus Avenue - rear of building
Boring No. 8A
Sample Noe
Depth - 15.5' to 17'
Blow Count = 2/ft
Very loose sandy peaty silt
Clayey organic silt
No: 9 - 72 Warren Avenue - Firehouse = rear of building
Boring No. 9
Sample No. 6
Depth - 26' to 28'
Blow Count - 21/ft
Very stiff blue clay with trace of gravel
Clayey sandy silt
No. 15 = 21 Rutland Square - rear of building
Boring No. 15
Sample No. 6
Depth - 22.5' to 24'
Blow Count - 4/ft
Soft blue clay
Clay and silt, some fine sand
Investigation of Subsoil and Foundation Conditions, Boston Redevelopment Authority, SOUTH END PROJECT MASS. R-56, SOUTH END URBAN RENEWAL AREA (December 27, 1963).
For South End, "soils information available from numerous soil borings that have been made in past years throughout the South End Project Area provided a basis for development of a generalized subsurface profile in the area. The soils and rock strata from existing ground surface downward are as follows:
- a. Two (2) to thirty (30) feet of "man made" fill varying in character from very loose rubbish and cinders to medium-dense sand and gravel
- b. Either:
- one (1) to thirty five (35) feet of river bottom or flood plain deposited organic silt, peat and/or mud; or
- one (1) to twenty (20) feet of sand and gravel.
- c. Either
- one (1) to sixty (60) feet of glacial till consisting of sand, gravel, and clay, or
- up to one hundred twenty (120) feet of stiff to very soft fluvio-glacial deposits of "Boston Blue Clay"
- d. Cambridge slate bedrock formation consisting of soft to hard slate, shale, and siltstone rock
The effects of the tide levels in the Roxbury Canal influence the water table at this site. The ground water varies between El. + 1 and El. + 13."
BOSTON REDEVELOPMENT AUTHORITY ENGINEERING REPORT ON THE PRELIMINARY DESIGN OF PROJECT IMPROVEMENTS, SOUTH END PROJECT, Project No. Mass. R-56, MAGUIRE AND ASSOCIATES, ENGINEERS (JULY 1965)
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"Due to access limitations, the borings were performed utilizing portable (tripod-mounted) boring equipment. Boring B-1 which was performed outside the building within the concrete patio area adjacent to Washington Street encountered refusal within what appeared to be building rubble/debris at a depth of approximately 2 feet below existing grade. Three additional attempts were made at various locations within the general vicinity of B-1 (borings B-1A through B-1C), with each attempt encountering refusal at depths ranging from approximately 2 to 4 feet below existing ground surface. At boring B-2, the driller attempted to core through slab within the mechanical room in the northeast portion of the basement space. However, the driller was unable to penetrate the slab at a depth of approximately 32 inches, and this location was therefore abandoned. Boeing B-2 was terminated within the concrete slab at approximately Elevation +4.3.
Boring B-3 was completed at the southern end of the building and was advanced to a depth of 8.5 feet below the basement slab and terminated within a natural deposit of Boston Blue Clay. The boring encountered a 4-inch thick slab directly underlain by a 2-foot thickness of granular fill consisting of a loose brown/black sand and silt with a trace gravel and containing trace ash and cinders. A 3-foot thick natural organic silt and peat deposit was encountered beneath the fill. A blue-yellow silty clay deposit (Boston Blue Clay) was encountered at a depth of 5 feet below the top of the basement slab. A two-inch diameter PVC monitoring well with a slotted screen set to intercept the surface of the groundwater was installed in the completed B-3 borehole.
Groundwater was observed at a depth of approximately 2 feet below the top of slab at about Elevation +7. In addition, depth to groundwater was measured in Boston Groundwater Trust (BGwT) monitoring well 20J-0356 located at the corner of Washington and East Concord Streets and GZ-101 at depths of 11.6 feet and 11.3 feet below grade which is equivalent to approximately Elevations +5.4 and +5.2, respectively. The groundwater is likely perched within the relatively impervious organic and/or clay deposits. Based upon the measurement of groundwater levels at the subject site, and a review of BGwT database for monitoring wells in the vicinity of the site, the groundwater gradient at the subject site is inferred to flow towards the east-northeast. We anticipate that future groundwater levels across the site may vary from those described in this report due to factors such as normal seasonal changes, runoff, particularly during or following periods of heavy precipitation, and alterations of existing drainage patterns. Further, we anticipate that groundwater levels are locally influenced by the depth to the impervious organic and clay deposits.
The nearest surface water body is the Muddy Rive which is located approximately 0.95 miles to the westnorthwest of the subject site. The closest area to the subject site designated as Protected Open Space is the South End Burial Ground located approximately 190 feet to the northeast of the subject site. No areas designated as solid waste sites (landfills) are noted as being located within 1,000 feet of the site. The Boston University School of Medicine is located approximately 770 feet to the southeast of the subject site. "
"The presence of TCE was detected in soil gas samples SG-1, SG-2, and SG-3 at concentrations of 245 micrograms per cubic meter (ug/m3), 13 ug/m3 and 9.03 ug/m3, respectively. The presence of PCE and TCE was identified in each of the four indoor air samples tested. In basement samples AS-1 and AS-2, PCE and TCE were detected at the following concentrations: PCE; 1.2 ug/m3 and 1.64 ug/m3, TCE; 1.39 ug/m3 and 1.34 ug/m3."
IMMEDIATE RESPONSE ACTION COMPLETION, COMPREHENSIVE PHASE I, PHASE II AND PHASE III REPORT IN SUPPORT OF A PERMANENT SOLUTION WITH CONDITIONS STATEMENT, ANNA BISSONNETTE HOUSE, 1640 WASHINGTON STREET, RTN 3-29232, BOSTON, MASSACHUSETTS (MARCH 22, 2016).
Boring B-3 was completed at the southern end of the building and was advanced to a depth of 8.5 feet below the basement slab and terminated within a natural deposit of Boston Blue Clay. The boring encountered a 4-inch thick slab directly underlain by a 2-foot thickness of granular fill consisting of a loose brown/black sand and silt with a trace gravel and containing trace ash and cinders. A 3-foot thick natural organic silt and peat deposit was encountered beneath the fill. A blue-yellow silty clay deposit (Boston Blue Clay) was encountered at a depth of 5 feet below the top of the basement slab. A two-inch diameter PVC monitoring well with a slotted screen set to intercept the surface of the groundwater was installed in the completed B-3 borehole.
Groundwater was observed at a depth of approximately 2 feet below the top of slab at about Elevation +7. In addition, depth to groundwater was measured in Boston Groundwater Trust (BGwT) monitoring well 20J-0356 located at the corner of Washington and East Concord Streets and GZ-101 at depths of 11.6 feet and 11.3 feet below grade which is equivalent to approximately Elevations +5.4 and +5.2, respectively. The groundwater is likely perched within the relatively impervious organic and/or clay deposits. Based upon the measurement of groundwater levels at the subject site, and a review of BGwT database for monitoring wells in the vicinity of the site, the groundwater gradient at the subject site is inferred to flow towards the east-northeast. We anticipate that future groundwater levels across the site may vary from those described in this report due to factors such as normal seasonal changes, runoff, particularly during or following periods of heavy precipitation, and alterations of existing drainage patterns. Further, we anticipate that groundwater levels are locally influenced by the depth to the impervious organic and clay deposits.
The nearest surface water body is the Muddy Rive which is located approximately 0.95 miles to the westnorthwest of the subject site. The closest area to the subject site designated as Protected Open Space is the South End Burial Ground located approximately 190 feet to the northeast of the subject site. No areas designated as solid waste sites (landfills) are noted as being located within 1,000 feet of the site. The Boston University School of Medicine is located approximately 770 feet to the southeast of the subject site. "
"The presence of TCE was detected in soil gas samples SG-1, SG-2, and SG-3 at concentrations of 245 micrograms per cubic meter (ug/m3), 13 ug/m3 and 9.03 ug/m3, respectively. The presence of PCE and TCE was identified in each of the four indoor air samples tested. In basement samples AS-1 and AS-2, PCE and TCE were detected at the following concentrations: PCE; 1.2 ug/m3 and 1.64 ug/m3, TCE; 1.39 ug/m3 and 1.34 ug/m3."
IMMEDIATE RESPONSE ACTION COMPLETION, COMPREHENSIVE PHASE I, PHASE II AND PHASE III REPORT IN SUPPORT OF A PERMANENT SOLUTION WITH CONDITIONS STATEMENT, ANNA BISSONNETTE HOUSE, 1640 WASHINGTON STREET, RTN 3-29232, BOSTON, MASSACHUSETTS (MARCH 22, 2016).
"The Site consists of approximately 5 acres of land which is bounded by Washington Street to the north, East Lenox Street to the west, Reed Street to the south, and Northampton Street to the east. The Site is located on the U.S. Geological Survey (U.S.G.S.) Boston South, Massachusetts Quadrangle Map (1987) at U.T.M. coordinates 328,750 mE, 4,688,813 mN; and Latitude 42'20'06" N, Longitude 71 004'37"W. The property is owned by the U.S. Department of Housing and Urban Development. The Massachusetts Housing Finance Agency (MHFA) is the interim asset manager and agent for the Site. Grant Manor consists of six multi-family residential buildings which contain a total of 180 apartment units. The buildings include a seven-story high-rise building, (1820- 1850 Washington Street), a four-story mid-rise building (20 East Lenox Street), and four two-story townhouse buildings (80-90 Northampton Street, 100-110 Northampton Street, 5- 15 Reed Street, and 21-27 Reed Street). Figure 2 in Appendix A shows the buildings and surrounding streets.
In December 1994, CDW prepared a Preliminary Site Assessment (PSA) report for the Site. CDW had reviewed historical Sanborn maps, aerial photographs, and available records at various city agencies. According to the information available, the Grant Manor complex was constructed in 1971. Sanborn maps from 1938, 1914, 1897, and 1885 indicated that the Site was previously subdivided into many smaller parcels which contained a variety of residential, retail, and commercial structures. The Site has been occupied by a stable, wagon and blacksmith shops, tin shop, fire station, retail stores, laundry shop, hotel, parking garage, storage warehouse, and print shop in the past. A parking garage containing an auto repair shop and a paint spray booth was also previously located on-site at the corner of Northampton Street and Reed Street.
The average depth to groundwater on the Site is approximately 6.9 feet. The groundwater was determined to be flowing to the south-southeast. The results of the in-situ permeability test indicated that the permeability in well MW-I is 0.126 feet/day. The observed permeability is consistent with permeability for fine sand.
Most of the soil samples obtained in the June 1997 investigation reported TPH and total lead above the minimum detection limit. Many of the soil samples reported TPH and lead concentrations in excess of the applicable Method 1 RA standards. Soil samples from soil borings B-28 and B-32 exceeded the UCL of 10,000 ppm for TPH. The results of TPH and total lead analyses are summarized in Table VII in Appendix B. VOCs were detected at concentrations greater than the minimum detection limits. Dissolved PPM13 were detected at concentrations greater than the minimum detection limits. Dissolved lead in the sample from monitoring well MW-1 was found to exceed the Method 1 RA standard for GW-3 classified groundwater.
Elevated headspace VOCs were reported in soil samples from borings B-1l and B-12 from the May 1996 investigation. Borings B-18 and B-20 exhibited elevated headspace VOCs during the April 1997 investigation. The highest headspace VOC concentration was detected in the soil sample from B-18 at a depth of 7 to 8 feet. The laboratory analyses of soil samples reported detectable concentrations of TPH, PAHs, EPHs, lead and beryllium exceeding applicable Method 1 RA standards in several soil samples. Concentrations of TPH and lead exceeded the Upper Concentration Limits (UCLs) in several soil samples.
According to the 1983 Bedrock Geologic Map of Massachusetts, the bedrock beneath the Site is classified as Roxbury conglomerate, which consists of conglomerate sandstone, siltstone, argillite, and melaphyre. Roxbury Conglomerate is located within the Milford-Dedham Bedrock Zone. A known or estimated depth to bedrock at the Site was unable to be determined. No bedrock outcrops were observed at the Site or in the immediate vicinity. Soils encountered during the CDW investigations were primarily fill material, silt, and clay. The fill consisted of loose, brown, fine to coarse grained sand, and the clay was compact, plastic, and green-gray in color. Fill, including brick and wood, was observed down to depths of approximately 8 feet in most borings. Groundwater was observed during drilling between approximately 3.5 and 9.5 feet below grade. Consolidated bedrock was not encountered during any on-site drilling. Based on the results of the in-situ permeability test, the permeability of the overburden was found to be approximately 0.126 feet/day. The predominant groundwater flow in the overburden is to the south/southeast.
The closest surface water body to the Site is the Muddy River, which is located approximately 0.9 miles to the northwest. The Fort Point Channel is located approximately 1 mile northeast of the Site. According to the Flood Insurance Rate Map for the vicinity, the Site is located within a Zone C floodplain, which is classified as an area of minimal flooding. Stormwater drainage from the Site flows into storm drains located on the subject property and on Northampton Street, Washington Street, Reed Street, and East Lenox Street.
PHASE II-COMPREHENSIVE SITE ASSESSMENT AND PHASE III - IDENTIFICATION, EVALUATION, AND SELECTION OF COMPREHENSIVE REMEDIAL ACTION ALTERNATIVES GRANT MANOR 1820-1850 WASHINGTON STREET, 80-90 & 100-110 NORTHAMPTON STREET, 20 EAST LENOX STREET, 5-15 & 21-27 REED STREET, ROXBURY, MA, DEP Release Tracking Number 3-14171, CDW Project # 579.00 (February 25, 2000).
In December 1994, CDW prepared a Preliminary Site Assessment (PSA) report for the Site. CDW had reviewed historical Sanborn maps, aerial photographs, and available records at various city agencies. According to the information available, the Grant Manor complex was constructed in 1971. Sanborn maps from 1938, 1914, 1897, and 1885 indicated that the Site was previously subdivided into many smaller parcels which contained a variety of residential, retail, and commercial structures. The Site has been occupied by a stable, wagon and blacksmith shops, tin shop, fire station, retail stores, laundry shop, hotel, parking garage, storage warehouse, and print shop in the past. A parking garage containing an auto repair shop and a paint spray booth was also previously located on-site at the corner of Northampton Street and Reed Street.
The average depth to groundwater on the Site is approximately 6.9 feet. The groundwater was determined to be flowing to the south-southeast. The results of the in-situ permeability test indicated that the permeability in well MW-I is 0.126 feet/day. The observed permeability is consistent with permeability for fine sand.
Most of the soil samples obtained in the June 1997 investigation reported TPH and total lead above the minimum detection limit. Many of the soil samples reported TPH and lead concentrations in excess of the applicable Method 1 RA standards. Soil samples from soil borings B-28 and B-32 exceeded the UCL of 10,000 ppm for TPH. The results of TPH and total lead analyses are summarized in Table VII in Appendix B. VOCs were detected at concentrations greater than the minimum detection limits. Dissolved PPM13 were detected at concentrations greater than the minimum detection limits. Dissolved lead in the sample from monitoring well MW-1 was found to exceed the Method 1 RA standard for GW-3 classified groundwater.
Elevated headspace VOCs were reported in soil samples from borings B-1l and B-12 from the May 1996 investigation. Borings B-18 and B-20 exhibited elevated headspace VOCs during the April 1997 investigation. The highest headspace VOC concentration was detected in the soil sample from B-18 at a depth of 7 to 8 feet. The laboratory analyses of soil samples reported detectable concentrations of TPH, PAHs, EPHs, lead and beryllium exceeding applicable Method 1 RA standards in several soil samples. Concentrations of TPH and lead exceeded the Upper Concentration Limits (UCLs) in several soil samples.
According to the 1983 Bedrock Geologic Map of Massachusetts, the bedrock beneath the Site is classified as Roxbury conglomerate, which consists of conglomerate sandstone, siltstone, argillite, and melaphyre. Roxbury Conglomerate is located within the Milford-Dedham Bedrock Zone. A known or estimated depth to bedrock at the Site was unable to be determined. No bedrock outcrops were observed at the Site or in the immediate vicinity. Soils encountered during the CDW investigations were primarily fill material, silt, and clay. The fill consisted of loose, brown, fine to coarse grained sand, and the clay was compact, plastic, and green-gray in color. Fill, including brick and wood, was observed down to depths of approximately 8 feet in most borings. Groundwater was observed during drilling between approximately 3.5 and 9.5 feet below grade. Consolidated bedrock was not encountered during any on-site drilling. Based on the results of the in-situ permeability test, the permeability of the overburden was found to be approximately 0.126 feet/day. The predominant groundwater flow in the overburden is to the south/southeast.
The closest surface water body to the Site is the Muddy River, which is located approximately 0.9 miles to the northwest. The Fort Point Channel is located approximately 1 mile northeast of the Site. According to the Flood Insurance Rate Map for the vicinity, the Site is located within a Zone C floodplain, which is classified as an area of minimal flooding. Stormwater drainage from the Site flows into storm drains located on the subject property and on Northampton Street, Washington Street, Reed Street, and East Lenox Street.
PHASE II-COMPREHENSIVE SITE ASSESSMENT AND PHASE III - IDENTIFICATION, EVALUATION, AND SELECTION OF COMPREHENSIVE REMEDIAL ACTION ALTERNATIVES GRANT MANOR 1820-1850 WASHINGTON STREET, 80-90 & 100-110 NORTHAMPTON STREET, 20 EAST LENOX STREET, 5-15 & 21-27 REED STREET, ROXBURY, MA, DEP Release Tracking Number 3-14171, CDW Project # 579.00 (February 25, 2000).
"1673-1675 Washington Street is improved with a 5,000 square-foot mixed use building constructed in at least the 1880s. 1677-1679 Washington Street is improved with a 5,200 square-foot mixed-use building constructed in at least the 1880s. 7 Worcester Street is improved with a 4,416 square foot mixed-use building constructed in at least the 1880s. The buildings share a common basement and ground floor, which are configured for commercial use, with the upper floors configured for residential use. Historically, the property was unimproved prior to at least the 1880s.
Historically, the ground floor was occupied by commercial use tenants in possession, including Andy’s Cleaners, from at least the 1890s to 2022. In recent years Andy’s Cleaners operated as a drop-off and pickup location, with no on-site dry cleaning. However, on-site dry-cleaning took place on the property in the past. The property was unoccupied prior to at least the 1880s.
Borings logs generally describe overburden from approximately 0.0’ to 4.0’ below ground surface (bgs) as brown and dark brown sand and gravel with cobbles. Soil below 4.0’ below ground surface is characterized as a dense brown clay formation. A groundwater stadia survey was completed by Arcadia Technology in May 2022. Survey data revealed west to northwest hydraulic gradient; although the data was considered somewhat uncertain due to the potential for a perched groundwater table over clay in the area.
Field observations were conducted throughout the assessment activities. Observations indicate that on the exterior of the building sand and silt with some gravel extends from surface grade to depths of approximately 5 feet bsg. Below the sand and silt was a layer of brown to grey clay that extended to greater than 15 bsg. In the interior beneath the basement floor clay was observed to depth of greater than 3 ft. bsg. Groundwater was observed at approximately 4-5 bsg in the exterior monitoring wells. The groundwater was very slow to recharge. Groundwater maybe a perched groundwater table overlying the dense clay layer. Evaluation of the groundwater elevation data indicates groundwater flow is to the west. However, this data is subject to some uncertainty due to potential variable nature of a perched groundwater table.
Laboratory analysis for VOCs, was performed on the 12 soil samples from ATB-4 to ATB-13. The results of the laboratory analysis of the soils samples detected five volatile organic compounds(VOCs) likely related to PCE release. The six compounds were 1,1-Dichloroethene, trans-1,2-Dichloroethene, cis-1,2-Dichloroethene, Trichloroethene(TCE) and Tetrachloroethene(also known as perchloroethylene-PCE) and Vinyl Chloride. The presence of 1,1-Dichloroethene, trans-1,2-Dichloroethene, cis-1,2-Dichloroethene, Trichloroethene(TCE) and Vinyl Chloride likely due to the biodegradation of the PCE.
"Borings logs generally describe overburden from approximately 0.0’ to 4.0’ below ground surface (bgs) as brown and dark brown sand and gravel with cobbles. Soil below 4.0’ bgs is characterized as a dense brown clay formation. See Appendix F for details.
Phase I Initial Site Investigation & Tier Classification, 1673 - 1679 Washington Street, Boston, Massachusetts, MADEP RTN 3-37089, Ardent file ECLP-1615 (October 06, 2022)
Historically, the ground floor was occupied by commercial use tenants in possession, including Andy’s Cleaners, from at least the 1890s to 2022. In recent years Andy’s Cleaners operated as a drop-off and pickup location, with no on-site dry cleaning. However, on-site dry-cleaning took place on the property in the past. The property was unoccupied prior to at least the 1880s.
Borings logs generally describe overburden from approximately 0.0’ to 4.0’ below ground surface (bgs) as brown and dark brown sand and gravel with cobbles. Soil below 4.0’ below ground surface is characterized as a dense brown clay formation. A groundwater stadia survey was completed by Arcadia Technology in May 2022. Survey data revealed west to northwest hydraulic gradient; although the data was considered somewhat uncertain due to the potential for a perched groundwater table over clay in the area.
Field observations were conducted throughout the assessment activities. Observations indicate that on the exterior of the building sand and silt with some gravel extends from surface grade to depths of approximately 5 feet bsg. Below the sand and silt was a layer of brown to grey clay that extended to greater than 15 bsg. In the interior beneath the basement floor clay was observed to depth of greater than 3 ft. bsg. Groundwater was observed at approximately 4-5 bsg in the exterior monitoring wells. The groundwater was very slow to recharge. Groundwater maybe a perched groundwater table overlying the dense clay layer. Evaluation of the groundwater elevation data indicates groundwater flow is to the west. However, this data is subject to some uncertainty due to potential variable nature of a perched groundwater table.
Laboratory analysis for VOCs, was performed on the 12 soil samples from ATB-4 to ATB-13. The results of the laboratory analysis of the soils samples detected five volatile organic compounds(VOCs) likely related to PCE release. The six compounds were 1,1-Dichloroethene, trans-1,2-Dichloroethene, cis-1,2-Dichloroethene, Trichloroethene(TCE) and Tetrachloroethene(also known as perchloroethylene-PCE) and Vinyl Chloride. The presence of 1,1-Dichloroethene, trans-1,2-Dichloroethene, cis-1,2-Dichloroethene, Trichloroethene(TCE) and Vinyl Chloride likely due to the biodegradation of the PCE.
"Borings logs generally describe overburden from approximately 0.0’ to 4.0’ below ground surface (bgs) as brown and dark brown sand and gravel with cobbles. Soil below 4.0’ bgs is characterized as a dense brown clay formation. See Appendix F for details.
Phase I Initial Site Investigation & Tier Classification, 1673 - 1679 Washington Street, Boston, Massachusetts, MADEP RTN 3-37089, Ardent file ECLP-1615 (October 06, 2022)
Groundwater was encountered on the property from approximately 5.3’ to 26.5’ below ground surface (bgs). A review Figure 5 of the 1977 United States Geological Survey (USGS) Topographic map reveals topography in the property vicinity gently slopes from the southwest to the northwest direction. The Charles River is located to the northwest. Therefore, based upon topographic and surface water features, groundwater in the property vicinity likely flows from the southeast to the northwest and discharges into the Charles River. See Appendix G for details. A groundwater stadia survey was completed by Arcadia Technology in May 2022. Survey data revealed west to northwest hydraulic gradient; although, the data was considered somewhat uncertain due to the potential for a perched groundwater table over clay in the area. See Appendix D for details. A review of Table 3 reveals that overburden aquifer groundwater monitoring well riser elevations were surveyed during field activities utilizing differential leveling in conjunction with an arbitrary 100’ datum in December 2022. Calculations completed utilizing December 2022 gauging data revealed a horizontal hydraulic gradient vector of approximately -42°, or northwest. This data generally agrees with the inferred groundwater gradient based on topographic features. See Appendix G for details.
Method 3 Risk Characterization and Permanent Solution With Conditions Statement 1673 - 1679 Washington Street Boston, Massachusetts 02118 MADEP RTN 3-37089 Ardent File ECLP-1615 (June 05, 2023)
Method 3 Risk Characterization and Permanent Solution With Conditions Statement 1673 - 1679 Washington Street Boston, Massachusetts 02118 MADEP RTN 3-37089 Ardent File ECLP-1615 (June 05, 2023)
Environmental Due Diligence activities completed at the property revealed concentrations of Tetrachloroethylene (PCE) and Trichloroethylene (TCE) in sub-slab soil gas exceeding applicable MADEP Residential Threshold Values and concentrations of cis-1,2-Dichlorethene in soil exceeding applicable MADEP Reporting Concentrations. These detections met the definition of a Substantial Release Migration and a 72-hour Reporting Condition. The Release was reported to the MADEP by Arcadia Technology in September 2021. Release Tracking Number (RTN) 3-37089 was assigned. A Notice of Responsibility establishing an Interim Deadline for assessment only Immediate Response Actions was issued by the MADEP in November 2021.
A Notice of Audit Request for Site Inspection was issued to the Responsible Party by MADEP in October 2023. Following audit activities, it was determined that a Condition of Substantial Release Migration (SRM) constituting a 72-hour Reporting Condition existed at the Disposal Site. The SRM Condition was due to previous detections of Trichloroethylene (TCE) and cis-1,2 Dichloroethylene (CIS-1,2-DCE) that exceeded GW-2 standards in groundwater samples collected from a monitoring well (203-MW) located within 30 feet of residentially occupied buildings. The SRM Condition was reported to MADEP on November 07, 2023. Release Tracking Number (RTN) 3-38464 was assigned. Immediate Response Actions including groundwater and indoor air sampling and analyses were verbally approved by MADEP. Assessment activities, including groundwater, sub-slab soil vapor, and indoor air sampling and analyses, were completed in November – December 2023 and summarized in the January 2024 Immediate Response Action Plan filed with MADEP. Assessment activities revealed that a Vapor Intrusion Pathway existed in the basement and ground floor of the adjoining residential condominium at 9 – 11 Worcester Street. A Preliminary Human Health Risk assessment utilizing this data revealed a Long-Term Risk to human receptors at the property.
Groundwater from MW-203, located nearest to the occupied residential dwelling at 9-11 Worcester Street, was historically sampled 3 times over the course of assessment activities conducted at 1679 Washington Street under RTN 3-37089 from September 2022 to March 2023. These sampling events revealed detectable concentrations of PCE, TCE, cis1,2 DCE, and VC. Exposure Point Concentrations for 203-MW were developed by averaging concentrations across the three events. Only the EPC for cis 1,2 DCE exceeded applicable Method 1 Standards (55.83 ug/L, Method 1 GW2 = 20 ug/L). Additional sampling after the issuance of the NOR for the subject RTN 3-38464 was completed in November 2023, April 2024, and September 2024. These events revealed detectable concentrations of site COCs in groundwater, with the concentration of cis 1,2 DCE exceeding applicable Method 1 Standards in April 2024 (44ug/L).
A new downgradient groundwater monitoring well, 601-MW, was installed at the intersection of Worcester Street and Deacon Street, northwest of the Disposal Site on September 12, 2024. Additional cross-gradient wells located southeast and northwest of 601-MW were proposed; however, the driller determined that the density of utilities in the street as indicated by DigSafe markings precluded the advancement of wells in these
locations. Manways and sewer grates near to these proposed locations were screened for VOCs utilizing a PID. No detectable concentrations of VOCs were detected in these utilities. Soil and groundwater from 601-MW were sampled on 9/12/24 and analyzed for VOCs. No detectable analyte concentrations were identified in either medium. Groundwater from 203-MW and 601-MW has been sampled quarterly since the September 2024 event. See Table 7 in Appendix A for a summary of historic groundwater concentrations through the most recent event.
Indoor Air samples collected from the basement and first floor of the 9-11 Worcester Street Condominium unit in December 2023 revealed detectable concentrations of two Volatile Organic Compounds (VOCs) that had been identified as Contaminants of Concern at the adjoining 1679 Washington Street Release site: Trichloroethylene (TCE, 4.3 ug/m3) and Perchloroethylene (PCE, 25 ug/m3). A sub-slab soil vapor sample collected in the condominium basement also revealed a detection of Perchloroethylene PCE, 24 ug/m3).
Immediate Response Action Status, 1673 - 1679 Washington Street & 7-15 Worcester Street, Boston, Massachusetts, MADEP RTN 3-37089, Ardent File ECLP-1615 & ESCP-0426, (November 20, 2025)
A Notice of Audit Request for Site Inspection was issued to the Responsible Party by MADEP in October 2023. Following audit activities, it was determined that a Condition of Substantial Release Migration (SRM) constituting a 72-hour Reporting Condition existed at the Disposal Site. The SRM Condition was due to previous detections of Trichloroethylene (TCE) and cis-1,2 Dichloroethylene (CIS-1,2-DCE) that exceeded GW-2 standards in groundwater samples collected from a monitoring well (203-MW) located within 30 feet of residentially occupied buildings. The SRM Condition was reported to MADEP on November 07, 2023. Release Tracking Number (RTN) 3-38464 was assigned. Immediate Response Actions including groundwater and indoor air sampling and analyses were verbally approved by MADEP. Assessment activities, including groundwater, sub-slab soil vapor, and indoor air sampling and analyses, were completed in November – December 2023 and summarized in the January 2024 Immediate Response Action Plan filed with MADEP. Assessment activities revealed that a Vapor Intrusion Pathway existed in the basement and ground floor of the adjoining residential condominium at 9 – 11 Worcester Street. A Preliminary Human Health Risk assessment utilizing this data revealed a Long-Term Risk to human receptors at the property.
Groundwater from MW-203, located nearest to the occupied residential dwelling at 9-11 Worcester Street, was historically sampled 3 times over the course of assessment activities conducted at 1679 Washington Street under RTN 3-37089 from September 2022 to March 2023. These sampling events revealed detectable concentrations of PCE, TCE, cis1,2 DCE, and VC. Exposure Point Concentrations for 203-MW were developed by averaging concentrations across the three events. Only the EPC for cis 1,2 DCE exceeded applicable Method 1 Standards (55.83 ug/L, Method 1 GW2 = 20 ug/L). Additional sampling after the issuance of the NOR for the subject RTN 3-38464 was completed in November 2023, April 2024, and September 2024. These events revealed detectable concentrations of site COCs in groundwater, with the concentration of cis 1,2 DCE exceeding applicable Method 1 Standards in April 2024 (44ug/L).
A new downgradient groundwater monitoring well, 601-MW, was installed at the intersection of Worcester Street and Deacon Street, northwest of the Disposal Site on September 12, 2024. Additional cross-gradient wells located southeast and northwest of 601-MW were proposed; however, the driller determined that the density of utilities in the street as indicated by DigSafe markings precluded the advancement of wells in these
locations. Manways and sewer grates near to these proposed locations were screened for VOCs utilizing a PID. No detectable concentrations of VOCs were detected in these utilities. Soil and groundwater from 601-MW were sampled on 9/12/24 and analyzed for VOCs. No detectable analyte concentrations were identified in either medium. Groundwater from 203-MW and 601-MW has been sampled quarterly since the September 2024 event. See Table 7 in Appendix A for a summary of historic groundwater concentrations through the most recent event.
Indoor Air samples collected from the basement and first floor of the 9-11 Worcester Street Condominium unit in December 2023 revealed detectable concentrations of two Volatile Organic Compounds (VOCs) that had been identified as Contaminants of Concern at the adjoining 1679 Washington Street Release site: Trichloroethylene (TCE, 4.3 ug/m3) and Perchloroethylene (PCE, 25 ug/m3). A sub-slab soil vapor sample collected in the condominium basement also revealed a detection of Perchloroethylene PCE, 24 ug/m3).
Immediate Response Action Status, 1673 - 1679 Washington Street & 7-15 Worcester Street, Boston, Massachusetts, MADEP RTN 3-37089, Ardent File ECLP-1615 & ESCP-0426, (November 20, 2025)
Structural
South End houses tilting , sagging. Building Commissioner O Hearn; old Roxbury along side of old Boston Neck . Northhampton and Fellows – Harrison to orange, completely unpredictable distances and form. Foundations are not secure if constructed on gravel, ordinary clay, ashes, peat, or broken stone. Bedrock must be located or there will be serious trouble sooner or later. Buildings erected in sand. “the South End filling, according to city engineers, was never properly done. The land is low at the South Bay and gradually rises to Shawmut ave, then recedes to the railroad track. The higher ends of the sewer system found the land the lowest and this led to the unforuatley experiences that the propery owners have passed through for forty years in the matter of sewers. In all the alleyways fo the S End district the sewer pieps are below the streets and the yards are lower than the alleys and many of the cellars. Heavy rain and heavy tide water at the same time have worked havoc with cellor kitchens and dining rooms, the sewers being unable to carry off the surplus flowage until the new sewers were built within two years and heavy pumps installed. This condition has undoublabe operated to a great extend in undermining the foundations of the South End buildings now being complainedof through there wouldahve been no undermining had the builders of these structures insisting on observing the first prinple in building.” How was it possible for these structures to be built? This is a question that is gently asked. There is but one answer. In those days builders were not obligated to present every stage of the building process to the building inspector. There were few laws to cover such ops and those were of most leemnary character.”
Boston Evening Transcript Wed, Jul 14, 1915 ·Page 18
Boston Evening Transcript Wed, Jul 14, 1915 ·Page 18
Sedimentation & Submarine Canyons
Submarine canyons are the most important conduits for funneling sediment from continents to oceans. Submarine canyons, however, are zones of sediment bypassing, and little sediment accumulates in the canyon until it ceases to be an active conduit. To understand the potential importance in the rock record of any given submarine canyon, it is necessary to understand sediment-transport processes in, as well as knowledge of, deep-sea turbidite and related deposits that moved through the canyons.
Normark, William & Carlson, Paul. (2003). Giant submarine canyons: Is size any clue to their importance in the rock record?. 10.1130/0-8137-2370-1.175.
Normark, William & Carlson, Paul. (2003). Giant submarine canyons: Is size any clue to their importance in the rock record?. 10.1130/0-8137-2370-1.175.
Uncounted prehistoric and historic archaeological sites lie within the Gerry E. Studds Stellwagen Bank National Marine Sanctuary. Ancient geologic and glacial processes once exposed the sanctuary’s seafloor to the sun, allowing it to support flora and fauna utilized by the Paleo-Indian peoples. Rising sea levels covered the sanctuary within several millennia of its exposure, moving Native American habitation to the shores around Massachusetts Bay.
. The area had the potential to support habitation and use of Stellwagen Bank before its inundation of seawater 10,000 years ago. The likelihood is high that human or animal remains might be located in the future. The possibility of finding Paleo-Indian cultural items on Stellwagen Bank is enhanced by the report of the recovery of mastodon skeletal remains by local fishermen. Further geologic study, site modeling, and sampling will be conducted on Stellwagen Bank to determine the potential for locating prehistoric cultural remains in the sanctuary.
https://nmssanctuaries.blob.core.windows.net/sanctuaries-prod/media/archive/library/pdfs/fop.pdf
. The area had the potential to support habitation and use of Stellwagen Bank before its inundation of seawater 10,000 years ago. The likelihood is high that human or animal remains might be located in the future. The possibility of finding Paleo-Indian cultural items on Stellwagen Bank is enhanced by the report of the recovery of mastodon skeletal remains by local fishermen. Further geologic study, site modeling, and sampling will be conducted on Stellwagen Bank to determine the potential for locating prehistoric cultural remains in the sanctuary.
https://nmssanctuaries.blob.core.windows.net/sanctuaries-prod/media/archive/library/pdfs/fop.pdf
Submarine canyons are deep, steep-sided valleys eroded into the seafloor along the world’s continental margins. They link terrestrial and deep-marine systems by transferring sediment, organic carbon, and pollutants (1–3). With lengths of up to 400 km and wall heights of up to 5 km, they dwarf their terrestrial counterparts (3). Similar to rivers on land, submarine canyons are key drivers in shaping the seafloor along Earth’s continental margins (4). Acting as conduits between land and the deep ocean, they embody what J. Syvitski termed the “global handshake between the coastline and the abyss.” Solid material transfer along the deeply incised canyons nourishes submarine fans with sediment including organic carbon, nutrients, and litter (3, 5, 6).
To understand what controls submarine canyon occurrence, it is helpful to morphologically categorize submarine canyons into two types: slope-confined (or “blind”) canyons, which are exclusively located on the continental slope, and shelf-incised canyons, whose canyon heads eroded into the shelf (10, 11). Shelf-incised canyons can be further classified as shore-connected if they extend to the coastline, where they link to terrestrial sediment sources, such as river outlets or longshore currents (Fig. 1). However, modern canyons that connect to the shore are rare—only about 4% of all canyon heads (and 11% of shelf-incised canyons) along the world’s major continental margins between 50°N and 50°S (12). Although some slope-confined canyons experience frequent turbidity current activity (13), studies show that shelf-incised canyons intercept river-derived and longshore sediment sources more effectively, making them particularly important conduits for transporting material to the deep ocean floor (2, 5, 7). In addition, they support more species-rich ecosystems compared to slope-confined canyons (9).
Anne Bernhardt, Wolfgang Schwanghart ,Seafloor slopes control submarine canyon distribution: A global analysis.Sci. Adv.11,eadv3942(2025).DOI:10.1126/sciadv.adv3942
