@proceedings {271,
	title = {Arsenic in central Massachusetts bedrock and groundwater},
	volume = {42},
	year = {2010},
	note = {Accession Number: 2011-044094; Conference Name: Geological Society of America, 2010 annual meeting; Denver, CO, United States; Conference Date: 20101031; Language: English; Coden: GAAPBC; Collation: 2; Collation: 216-217; Publication Types: Abstract Only; Serial; Conference document; Updated Code: 201125; Monograph Title: Geological Society of America, 2010 annual meeting; Monograph Author(s): Anonymous; Reviewed Item: Analytic},
	month = {2010/11/01/},
	pages = {216 - 217},
	publisher = {Geological Society of America (GSA) : Boulder, CO, United States},
	address = {United States},
	abstract = {Across the New England "arsenic belt," groundwater arsenic (As) concentrations often exceed the EPA{\textquoteright}s 0.01-mg/L drinking water standard. In overburden groundwater at a site within this belt in north-central Massachusetts, As has been reported at levels up to 7.6 mg/L. Bedrock at the site consists of Silurian Central Maine Terrane metasediments intruded by the Devonian Ayer granodiorite and Chelmsford granite. Exchange of hydrothermal fluids between these lithologies during intrusion and later deformation, faulting, and metamorphism resulted in crystallization of arsenic-bearing minerals, including arsenopyrite. Quaternary deglaciation and unloading dilated joint systems in the bedrock, allowing increased exposure of the mineralogy to meteoric water. Several arsenopyrite alteration products (e.g., scorodite), of varying solubilities, precipitated on fracture surfaces and along grain boundaries between major phases. In the emerging conceptual model for this site, groundwater is recharged in bedrock uplands and moves downgradient through the fracture network, becoming increasingly reducing as it moves along a flow path. Arsenic dissolved from arsenopyrite and arsenic-bearing alteration phases in bedrock remains in solution until the groundwater discharges to lowland areas hydraulically downgradient. In these adjacent lowlands, glacial sand and gravel overburden lies above the bedrock. When the reducing water reaches more oxidizing conditions, As-sorbing hydrous ferric oxides (HFO) precipitate out on the aquifer solids, resulting in accumulation of As in the deep overburden aquifer. A large landfill at this site, now closed and capped, imposed reducing conditions, and As is mobilized into groundwater by reductive dissolution of the HFO. The presence of elevated As in groundwater is consistent with arsenic-bearing phases generated in granitoids at depth during regional metamorphism, which were subsequently altered, and are being solubilized at present by the circulation of shallow groundwater through varying redox environments. This scenario is supported by geochemical and petrographic studies of the granitoids and the occurrence of the highest groundwater and soil arsenic concentrations in the adjacent deep overburden.},
	keywords = {$\#$StaffPubs, alteration, arsenic, arsenides, arsenopyrite, Ayer Granodiorite, BEDROCK, central Massachusetts, chelmsford granite, Devonian, dilation, discharge, dissolved materials, drinking water, Eh, fractures, General geochemistry 02A, geochemistry, granites, ground water, igneous rocks, joints, massachusetts, metals, metamorphism, meteoric water, overburden, Paleozoic, petrography, plutonic rocks, pollutants, reduction, solubility, solution, sulfides, theoretical models, United States},
	isbn = {00167592},
	url = {https://gsa.confex.com/gsa/2010AM/finalprogram/abstract_182430.htm},
	author = {McTigue, David F. and Stein, Carol L. and Brandon, William C. and Joseph P Kopera and Keskula, Anna J. and Koteas, G. Christopher}
}
@proceedings {288,
	title = {Factors influencing groundwater inflows in a newly constructed cross-strike tunnel, eastern Massachusetts; 4, Occurrence and characterization of groundwater inflows},
	volume = {31},
	year = {1999},
	note = {Accession Number: 2001-037345; Conference Name: Geological Society of America, 1999 annual meeting; Denver, CO, United States; Conference Date: 19991025; Language: English; Coden: GAAPBC; Collation: 1; Collation: 348; Publication Types: Abstract Only; Serial; Conference document; Updated Code: 200111; Monograph Title: Geological Society of America, 1999 annual meeting; Monograph Author(s): Anonymous; Reviewed Item: Analytic},
	month = {1999/01/01/},
	pages = {348 - 348},
	publisher = {Geological Society of America (GSA) : Boulder, CO, United States},
	address = {United States},
	abstract = {All occurrences of groundwater inflows in a 9 km long, 5-m diameter section of tunnel, 70 to 90 m below grade, were compared with subsurface fracture density, bedrock topography, surface topography, type of surficial deposits, proximity to surface water bodies, and the geographic distribution (domains; Mabee et al., this volume) of surface and subsurface fractures. Subsurface fracture density was calculated for the 320 fractures (through-going fractures) that intersect the entire circumference of the tunnel. Bedrock topography was determined using bore hole data collected during the design phase of the tunnel project. Surface topography is from 1:25,000 scale topographic maps and surficial geology is based on maps of the Framingham and Natick Quadrangles. Seven surface water bodies, primarily brooks and rivers, overlie the tunnel. Five surface fracture domains are based on 1513 fracture measurements collected from 21 outcrops within 3 km of the tunnel. In the tunnel, 413 fractures (all fractures, dips>45 degrees ) comprise seven subsurface fracture domains. High groundwater inflows generally correlate with areas of high subsurface fracture density and where four or more subsurface fracture domains overlap. In addition, high groundwater inflows are also generally located near surface water bodies and below permeable surficial deposits and topographic depressions, especially those with corresponding lows in the bedrock surface. Moreover, subsurface structures which correlate with prominent surface fracture domains produce the highest volume of groundwater inflow. However, not all tunnel sections exhibiting high fracture density and overlapping fracture domains exhibit high groundwater inflows. Also, there is no correlation between areas where two or more surface fracture domains overlap and the volume of groundwater discharging to the tunnel.},
	keywords = {$\#$StaffPubs, BEDROCK, boreholes, characterization, design, discharge, eastern Massachusetts, flows, fractures, Framingham Quadrangle, ground water, Hydrogeology 21, massachusetts, movement, Natik Quadrangle, occurrence, outcrops, surface water, topography, tunnels, United States},
	isbn = {00167592},
	author = {Williams, Katherine W. and Stephen B Mabee and Hardcastle, Kenneth C. and Curry, Patrick J.}
}
@proceedings {289,
	title = {Factors influencing groundwater inflows in a newly constructed cross-strike tunnel, eastern Massachusetts; 5, Geochemical interpretation of groundwater inflows},
	volume = {31},
	year = {1999},
	note = {Accession Number: 2001-037342; Conference Name: Geological Society of America, 1999 annual meeting; Denver, CO, United States; Conference Date: 19991025; Language: English; Coden: GAAPBC; Collation: 1; Collation: 348; Publication Types: Abstract Only; Serial; Conference document; Updated Code: 200111; Monograph Title: Geological Society of America, 1999 annual meeting; Monograph Author(s): Anonymous; Reviewed Item: Analytic},
	month = {1999/01/01/},
	pages = {348 - 348},
	publisher = {Geological Society of America (GSA) : Boulder, CO, United States},
	address = {United States},
	abstract = {Samples of ground and surface waters in and above the tunnel (Curry et al., this volume) were collected to characterize the chemistry of groundwater discharging from fractures and faults. Forty-two water samples were collected: 32 along a transect of the tunnel and 10 from surface waters above the trace of the tunnel. All samples were analyzed for major anions and cations, and delta (super 18) O. Analysis of the anion/cation data indicated that these waters are dominated by sulfate+chloride and calcium+magnesium. However, five sub-classifications can be discerned based on the relative concentrations of ions in the samples. The five sub-classifications are Cl > HCO (sub 3) > SO (sub 4) > NO (sub 3) :Ca > Na+K > Mg (15 samples), Cl > HCO (sub 3) > SO (sub 4) > NO (sub 3) :Na+K > Ca > Mg (7 samples), Cl > HCO (sub 3) > SO (sub 4) > NO (sub 3) :Ca > Mg > Na+K (6 samples), Cl > SO (sub 4) > HCO (sub 3) > NO (sub 3) :Na+K > Ca > Mg (3 samples), and HCO (sub 3) > Cl > SO (sub 4) > NO (sub 3) :Ca > Na+K > Mg (2 samples). Results from statistical analyses indicate that alkalinity, calcium, sodium and potassium do vary as a function of bedrock type and that these differences are significant at the 95\% confidence level.In addition, preliminary oxygen isotope data indicate that two large, discrete water producing fault zones located in the eastern part of the tunnel are isotopically enriched (average delta (super 18) O = -7.75) relative to other water producing features in the tunnel (average delta (super 18) O = -8.96). The delta (super 18) O values obtained from all surface water bodies located above the tunnel average -7.56 whereas those values in surface ponds immediately above the fault zones average -6.71. Nitrate levels also show elevated levels in two water producing fault zones (>10 mg/L for some samples) and may result from accidental contamination during sampling, the use of explosives at discrete locations in the tunnel, or from leaking septic systems. The results of the oxygen isotope and nitrate analyses also suggest that some of the fault zones in the tunnel may have a rapid and direct hydraulic connection to the surface.},
	keywords = {$\#$StaffPubs, anions, BEDROCK, cations, classification, discharge, eastern Massachusetts, fault zones, faults, geochemistry, ground water, hydraulic conductivity, hydrochemistry, Hydrogeology 21, Isotope geochemistry 02D, isotope ratios, isotopes, massachusetts, movement, New England, nitrate ion, O-18/O-16, oxygen, samples, stable isotopes, surface water, tunnels, United States},
	isbn = {00167592},
	author = {Weaver, Rebecca A. and Stephen B Mabee and Williams, Katherine W. and Curry, Patrick J.}
}
