TY - Generic T1 - Characterizing fractured crystalline bedrock aquifers using hydrostructural domains in the Nashoba Terrane, eastern Massachusetts T2 - Abstracts with Programs - Geological Society of America Y1 - 2006 A1 - Alex K Manda A1 - Stephen B Mabee A1 - David F Boutt KW - #StaffPubs KW - anisotropy KW - aquifers KW - BEDROCK KW - characterization KW - connectivity KW - crystalline rocks KW - eastern Massachusetts KW - fractures KW - ground water KW - heterogeneity KW - hydraulic conductivity KW - Hydrogeology 21 KW - massachusetts KW - Nashoba terrane KW - outcrops KW - physical properties KW - site exploration KW - United States KW - water wells AB - 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. JF - Abstracts with Programs - Geological Society of America PB - Geological Society of America (GSA) : Boulder, CO, United States CY - United States VL - 38 SN - 00167592 UR - https://gsa.confex.com/gsa/2006AM/finalprogram/abstract_113075.htm IS - 77 N1 - Accession Number: 2007-032741; Conference Name: Geological Society of America, 2006 annual meeting; Philadelphia, PA, United States; Conference Date: 20061022; Language: English; Coden: GAAPBC; Collation: 1; Collation: 25; Publication Types: Abstract Only; Serial; Conference document; Updated Code: 200709; Monograph Title: Geological Society of America, 2006 annual meeting; Monograph Author(s): Anonymous; Reviewed Item: Analytic JO - Abstracts with Programs - Geological Society of America ER - TY - JOUR T1 - Comparison of three fracture sampling methods for layered rocks JF - International Journal of Rock Mechanics and Mining Sciences [1997] Y1 - 2010 A1 - Alex K Manda A1 - Stephen B Mabee KW - #StaffPubs KW - Big Quarry KW - carbonates KW - case studies KW - data acquisition KW - data processing KW - dolomite KW - Door Peninsula KW - fractures KW - geographic information systems KW - ground water KW - information systems KW - joints KW - layered materials KW - mapping KW - methods KW - movement KW - multiple scanline method KW - northeastern Wisconsin KW - numerical models KW - permeability KW - sampling KW - selection method KW - simulation KW - single scanline method KW - statistical analysis KW - Structural geology 16 KW - style KW - three-dimensional models KW - United States KW - Wisconsin AB - Three methods of fracture data collection are tested against each other in layered dolomitic rocks to evaluate the effectiveness of each method in sampling fracture properties. The methods tested are the single scanline method (SSM), selection method (SM), and multiple scanline method (MSM). Finite element techniques were first used to build a base model with the exact locations, sizes and orientations of each fracture observed in the natural fracture network. Then, a second set of models were stochastically generated using statistics from each sampling technique. For each network, the overall fracture intensity was used to assess the effectiveness of each sampling technique in capturing the real fracture properties. Fracture network permeability was also calculated for each of two directions to evaluate the transmissive properties of the networks. Although all three methods produced good matches of relative intensity and permeability between natural and synthetic fractures, the results reveal that a well-placed scanline performed the best at recreating natural fractures. However, the results from one variation of the SSM were only slightly better than the results from both versions of the SM. In general, the SSM provides the best results but possibly at heavy costs in time and labor, whereas the SM gives comparable results with less expenditure of energy and time. Thus, the SM is an adequate technique and recommended for use at large outcrops or where time, access or budget constraints are a concern. PB - Elsevier : Oxford-New York, International CY - International VL - 47 SN - 13651609 UR - http://www.sciencedirect.com/science/article/pii/S1365160909001804 IS - 22 N1 - Accession Number: 2010-041538; Language: English; Coordinates: N441500N452000W0865600W0880000; Coden: IJRMA2; Collation: 9; Publication Types: Serial; Updated Code: 201023; Illustration(s): illus. incl. 4 tables; Number of References: 25; Reviewed Item: Analytic JO - International Journal of Rock Mechanics and Mining Sciences [1997] ER -