TY - Generic T1 - Field mapping and fracture characterization techniques predict groundwater preferential flow paths in fractured bedrock aquifers, Nashoba Terrane, MA T2 - AGU Fall Conference, 2005 Y1 - 2005 A1 - Alex K Manda A1 - Stephen B Mabee A1 - Hubbs, S. A. KW - #StaffPubs KW - aquifers KW - BEDROCK KW - characterization KW - fractured materials KW - fractures KW - ground water KW - Hydrogeology 21 KW - mapping KW - massachusetts KW - Middlesex County Massachusetts KW - movement KW - Nashoba terrane KW - patterns KW - preferential flow KW - recharge KW - reservoir properties KW - substrates KW - United States AB - A study examining the relationship between fracture characteristics and groundwater was undertaken in the crystalline Nashoba Terrane of eastern Massachusetts. The Nashoba Terrane, a fault-bounded, highly deformed sliver of Paleozoic igneous and metamorphic rocks, covers an area of 600 sq km about 50 km northwest of Boston. Increasing industrial development coupled with population growth place significant pressure on developers to provide sufficient potable water for the population. To aid water development and management, this study examined fracture characteristics at regional, quadrangle and wellfield scales. The regional-scale work involved recording over 4000 structural measurements from 80 outcrops in the terrane. Fracture information recorded at each data station included strike and dip, trace length, spacing, termination, and fracture type. Preliminary results show that hydrostructural domains can be defined from combinations of fracture characterization and rock types. These domains are used to conceptualize general groundwater flow patterns in the subsurface: steeply dipping fractures, such as partings parallel to foliation enhance recharge potential and impose strong flow anisotropy. A different character is observed if steeply dipping joints intersect sheeting joints. In this instance, both recharge and lateral flow will be enhanced and flow anisotropy will be reduced. The distribution and intensity of particular fracture sets varies as a function of rock type, proximity to major features and local stress states. Partings parallel to foliation are prevalent in gneissic rocks whereas sheeting joints are more common in igneous rocks. Common joints are the most prevalent fractures, present in all rock types across the entire terrane. Quadrangle and wellfield scale data can be used to validate the regional-scale conceptual models. A comprehensive well-yield database was created to test the proposed models. Over 500 water wells in the terrane were evaluated to determine regions with high and low yield. The findings were evaluated in terms of location with respect to newly defined hydrostructural domain maps at both regional and quadrangle scales. Application of these hydrostructural domains in field studies can be useful not only in characterizing fracture intensity and distribution, but can shed more light on the potential of intersecting subsurface zones that could be exploited for economic gain. JF - AGU Fall Conference, 2005 PB - American Geophysical Union : Washington, DC, United States CY - United States VL - 86 SN - 00963941 IS - 52, Suppl.52, Suppl. N1 - Accession Number: 2009-053313; Conference Name: American Geophysical Union 2005 fall meeting; San Francisco, CA, United States; Conference Date: 20051205; Language: English; Coordinates: N420800N424400W0710200W0715300; Coden: EOSTAJ; Collation: -1; Publication Types: Abstract Only; Serial; Conference document; Updated Code: 200930; Monograph Title: AGU 2005 fall meeting; Monograph Author(s): Anonymous; Reviewed Item: Analytic JO - Eos, Transactions, American Geophysical Union ER -