%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 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 %0 Journal Article %J Hydrogeology Journal %D 2013 %T A method of estimating bulk potential permeability in fractured-rock aquifers using field-derived fracture data and type curves %A Alex K Manda %A Stephen B Mabee %A David F Boutt %A Cooke, Michele L. %K #StaffPubs %K aquifers %K boundary conditions %K eastern Massachusetts %K fractured materials %K fractures %K ground water %K Hydrogeology 21 %K massachusetts %K Nashoba terrane %K naturally fractured reservoirs %K numerical models %K permeability %K prediction %K pump tests %K simulation %K two-dimensional models %K United States %X A method is devised for estimating the potential permeability of fracture networks from attributes of fractures observed in outcrop. The technique, which is intended as a complement to traditional approaches, is based on type curves that represent various combinations of fracture lengths, fracture orientations and proportions (i.e., intensities) of fractures that participate in flow. Numerical models are used to derive the type curves. To account for variations in fracture aperture, a permeability ratio (R) defined as the permeability of a fracture network in a domain divided by the permeability of a single fracture with identical fracture apertures, is used as a dependent variable to derive the type curves. The technique works by determining the point on the type curve that represents the fracture characteristics collected in the field. To test the performance of the technique, permeabilities that were derived from fractured-rock aquifers of eastern Massachusetts (USA) are compared to permeabilities predicted by the technique. Results indicate that permeabilities estimated from type curves are within an order of magnitude of permeabilities derived from field tests. First-order estimates of fracture-network permeability can, therefore, be easily and quickly acquired with this technique before more robust and expensive methods are utilized in the field. Copyright 2012 Springer-Verlag Berlin Heidelberg %B Hydrogeology Journal %I Springer : Berlin - Heidelberg, Germany %C Federal Republic of Germany %V 21 %P 357 - 369 %8 2013/03/01/ %@ 1431217414350157 %G eng %U http://link.springer.com/article/10.1007%2Fs10040-012-0919-2 %N 22 %! Hydrogeology Journal