%0 Conference Proceedings %B Abstracts with Programs - Geological Society of America %D 1999 %T Factors influencing groundwater inflows in a newly constructed cross-strike tunnel, eastern Massachusetts; 5, Geochemical interpretation of groundwater inflows %A Weaver, Rebecca A. %A Stephen B Mabee %A Williams, Katherine W. %A Curry, Patrick J. %K #StaffPubs %K anions %K BEDROCK %K cations %K classification %K discharge %K eastern Massachusetts %K fault zones %K faults %K geochemistry %K ground water %K hydraulic conductivity %K hydrochemistry %K Hydrogeology 21 %K Isotope geochemistry 02D %K isotope ratios %K isotopes %K massachusetts %K movement %K New England %K nitrate ion %K O-18/O-16 %K oxygen %K samples %K stable isotopes %K surface water %K tunnels %K United States %X 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. %B Abstracts with Programs - Geological Society of America %I Geological Society of America (GSA) : Boulder, CO, United States %C United States %V 31 %P 348 - 348 %8 1999/01/01/ %@ 00167592 %G eng %N 77 %! Abstracts with Programs - Geological Society of America %0 Conference Proceedings %B Abstracts with Programs - Geological Society of America %D 2005 %T Fracture characterization maps; a new type of geologic map for hydrogeologic applications %A Stephen B Mabee %A Joseph P Kopera %K #StaffPubs %K applications %K aquifers %K BEDROCK %K characterization %K classification %K crystalline rocks %K exploration %K fractures %K ground water %K hydrodynamics %K Hydrogeology 21 %K mapping %K movement %K overburden %K permeability %K potentiometric surface %K spatial distribution %K surficial aquifers %K thickness %K water wells %K water yield %X Integration of a wide array of structural data with well-field hydrologic testing is increasingly recognized as a critical step in understanding groundwater flow behavior and recharge in crystalline bedrock aquifers (Lyford et al., 2003, Walsh and Lyford, 2002). As part of its rejuvenated mapping program, The Massachusetts Office of the State Geologist has been producing fracture characterization maps as a value-added accompaniment to traditional 1:24:000-scale bedrock mapping. Fracture characterization maps reclassify bedrock into domains of varying hydrologic significance, by combining rock properties (foliation steepness and development, partings, sheeting development, etc...) and type of overburden (permeable vs. non-permeable). The goal of these maps is to better understand preferential flow directions in the bedrock and the potential hydraulic connections between surficial and bedrock aquifers. Each fracture characterization map contains several summary panels, including standard geologic map bases overlain by typical rose diagrams and stereonets displaying fracture domains and trajectories, sheeting distribution, foliation trajectories, bedrock elevations, generalized piezometric surface configuration, and overburden type and thickness with separations into permeability class. A GIS well database is also included, showing well distribution, yield, bedrock elevation, and "hot-linked" well log images. All maps and raw data are made available to the public in paper, digital (PDF) or GIS format. We believe this approach will provide hydrologists and consultants with basic framework data that will expedite and improve the planning of subsurface investigations, construction activities, and groundwater exploration. %B Abstracts with Programs - Geological Society of America %I Geological Society of America (GSA) : Boulder, CO, United States %C United States %V 37 %P 145 - 145 %8 2005/10/01/ %@ 00167592 %G eng %U https://gsa.confex.com/gsa/2005AM/finalprogram/abstract_94576.htm %N 77 %! Abstracts with Programs - Geological Society of America