%0 Conference Proceedings %B Abstracts with Programs - Geological Society of America %D 2006 %T Characterizing fractured crystalline bedrock aquifers using hydrostructural domains in the Nashoba Terrane, eastern Massachusetts %A Alex K Manda %A Stephen B Mabee %A David F Boutt %K #StaffPubs %K anisotropy %K aquifers %K BEDROCK %K characterization %K connectivity %K crystalline rocks %K eastern Massachusetts %K fractures %K ground water %K heterogeneity %K hydraulic conductivity %K Hydrogeology 21 %K massachusetts %K Nashoba terrane %K outcrops %K physical properties %K site exploration %K United States %K water wells %X Fractured crystalline bedrock aquifers are good sources of potable water in many parts of the world. However, siting of highly productive wells in these rock units remains a challenging and expensive task because fracture development at the regional scale is both heterogeneous and anisotropic. Using low cost field data to define units of rock that have similar lithologic and fracture characteristics can significantly reduce time and energy spent on determining areas with better than average aquifer productivity. These physical characteristics that impart a particular hydraulic character on rocks are used to delineate regions with similar hydrologic characteristics called hydrostructural domains (Mackie, 2002). Hydrostructural domains are delineated from fracture characterization data that were collected from 79 outcrops located in the Nashoba Terrane of eastern Massachusetts. Information collected and used to delineate the domains include the number and distribution of fracture sets, types of fractures present or absent, the degree of fracture development, fracture intensity/density, fracture connectivity and rock type. Discrete fracture networks are generated from the fracture characterization data to simulate groundwater flow in the region. Conductivity of particular units is evaluated and compared to results from existing pumping tests obtained from the US Geological Survey. Preliminary results indicate that there is great value in utilizing fracture characteristic data obtained from surface outcrops to predict subsurface groundwater flow characteristics of fractured bedrock aquifers. Water managers, developers and decision makers are eager to know which areas are the most promising for encountering highly conductive zones in the subsurface. Collecting extensive structural data from surface outcrops, although not as accurate as drilling wells, is a cheaper alternative that could provide at least a rough estimate of the hydraulic properties of fractured rocks leading to effective siting of new water wells. Hydrostructural domain maps may pinpoint specific areas that have a high potential for wells to encounter highly conductive zones and could therefore be a powerful tool in transferring information from one site to another without having to repeatedly undertake extensive site characterization. %B Abstracts with Programs - Geological Society of America %I Geological Society of America (GSA) : Boulder, CO, United States %C United States %V 38 %P 25 - 25 %8 2006/10/01/ %@ 00167592 %G eng %U https://gsa.confex.com/gsa/2006AM/finalprogram/abstract_113075.htm %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 %0 Conference Proceedings %B Abstracts with Programs - Geological Society of America %D 2004 %T Fracture characterization of crystalline bedrock for groundwater investigations; an example from the Marlborough Quadrangle, Massachusetts %A Scott A Salamoff %A Stephen B Mabee %A Joseph P Kopera %A Donald U Wise %K #StaffPubs %K aquifers %K Assabet River Fault %K BEDROCK %K characterization %K controls %K crystalline rocks %K fractured materials %K fractures %K geographic information systems %K ground water %K Hydrogeology 21 %K hydrology %K information systems %K joints %K Marlborough Quadrangle %K massachusetts %K Middlesex County Massachusetts %K permeability %K preferential flow %K recharge %K style %K testing %K theoretical models %K United States %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). The Marlborough Quadrangle, about 40 km west of Boston, was selected as a test case of how a state geological survey can most effectively and efficiently collect and present such data in order to better constrain conceptual models of groundwater flow in general and to be of maximum use for hydrologists and consultants working on specific local problems. In this study, 3200 structural measurements were taken by a two-person team over a nine-week period at 68 stations distributed throughout the quadrangle and keyed into a GIS database. Specialized data sheets allowed efficient recording and digitization of orientations, lengths, spacing and mineralization, and separation of various classes of joints and veins. Fault data also included motion direction and sense. Summary maps in GIS format include standard geologic map bases overlain by typical rose diagrams and stereograms and maps such as fracture domains and trajectories, sheeting distribution, foliation trajectories, bedrock elevations, generalized piezometric surface configuration, and overburden type and thickness with separations into permeability class. Geology of the quadrangle can be separated into three zones: (a) north of the Assabet River Fault (ARF), (b) the area between the ARF and 1.5 km-wide Bloody Bluff Fault Zone (BBFZ), and (c) south of the BBFZ. Generalized foliations in the zones are: (a) 215, 50N, (b) 240, 65N, and (c) 270, 45N. Two pervasive, steeply-dipping (>60 degrees ) fracture sets occur throughout the quadrangle: an older 150 degrees set that includes sulfide-bearing veins and fracture surfaces along the ARF and a 015 degrees set of largely unmineralized common joints, macrojoints (>3 m length) and joint zones (av. 1.2 m width). Sheeting and unloading joints are generally coincident with shallow dipping foliation in (c) but cross-cut foliation in (a) and (b). 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 36 %P 113 - 113 %8 2004/03/01/ %@ 00167592 %G eng %U https://gsa.confex.com/gsa/2004NE/finalprogram/abstract_70321.htm %N 22 %! Abstracts with Programs - Geological Society of America %0 Journal Article %J Hydrogeology Journal %D 2010 %T A field study (Massachusetts, USA) of the factors controlling the depth of groundwater flow systems in crystalline fractured-rock terrain %A David F Boutt %A Diggins, Patrick %A Stephen B Mabee %K #StaffPubs %K aquifers %K boreholes %K crystalline rocks %K eastern Massachusetts %K fractured materials %K fractures %K ground water %K hydraulic conductivity %K Hydrogeology 21 %K massachusetts %K Nashoba terrane %K permeability %K porosity %K preferential flow %K shallow-water environment %K substrates %K United States %X Groundwater movement and availability in crystalline and metamorphosed rocks is dominated by the secondary porosity generated through fracturing. The distributions of fractures and fracture zones determine permeable pathways and the productivity of these rocks. Controls on how these distributions vary with depth in the shallow subsurface (<300 m) and their resulting influence on groundwater flow is not well understood. The results of a subsurface study in the Nashoba and Avalon terranes of eastern Massachusetts (USA), which is a region experiencing expanded use of the fractured bedrock as a potable-supply aquifer, are presented. The study logged the distribution of fractures in 17 boreholes, identified flowing fractures, and hydraulically characterized the rock mass intersecting the boreholes. Of all fractures encountered, 2.5% are hydraulically active. Boreholes show decreasing fracture frequency up to 300 m depth, with hydraulically active fractures showing a similar trend; this restricts topographically driven flow. Borehole temperature profiles corroborate this, with minimal hydrologically altered flow observed in the profiles below 100 m. Results from this study suggest that active flow systems in these geologic settings are shallow and that fracture permeability outside of the influence of large-scale structures will follow a decreasing trend with depth. Copyright 2010 Springer-Verlag %B Hydrogeology Journal %I Springer : Berlin - Heidelberg, Germany %C Federal Republic of Germany %V 18 %P 1839 - 1854 %8 2010/12/01/ %@ 1431217414350157 %G eng %U http://link.springer.com/article/10.1007%2Fs10040-010-0640-y %N 88 %! Hydrogeology Journal