HR: 1340h
AN: H33D-1614    [Abstracts]
TI: Using inverse modeling of aquifer tests to estimate hydraulic properties and heterogeneity of fractured sedimentary rocks at the former Naval Air Warfare Center, West Trenton, NJ
AU: * Tiedeman, C R
EM: tiedeman@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Road MS496, Menlo Park, CA 94025,
AB: At the former Naval Air Warfare Center (NAWC), West Trenton, NJ, inverse modeling of aquifer tests conducted in dipping fractured mudstones of the Newark Basin is used to characterize the heterogeneity distribution of the rocks and to estimate their hydraulic properties. This flow modeling is a first step towards development of transport models to investigate the fate and remediation of extensive chlorinated solvent contamination at the site. Ground water underlying the NAWC flows through shallow weathered rocks and dipping sequences of mudstone beds. Water-level and hydraulic-test data suggest that weathered rocks and bedding plane fractures within fissile and laminated mudstones are the primary pathways for ground-water flow, and that less fractured massive mudstones act as flow barriers. To examine these hypotheses, a MODFLOW-2000 model of flow through the fractured rocks is developed and calibrated to short-term aquifer tests conducted by temporarily turning off the pumps in individual wells of a pump-and-treat system. Within the model domain, the area of interest is 400 m by 700 m in horizontal extent and 100 m deep. Horizontal model layers that are up to 20 m thick represent the weathered rocks, and inclined model layers that vary from about 1 to 14 m thick represent the dipping beds. A set of separate aquifer-test simulations using the same underlying model and parameters is calibrated to water-level rise observations from the tests. Results show that a calibrated model that explicitly represents only the major contrasts in rock properties is consistent with the geologic framework and produces a reasonable fit to the aquifer test data. Estimated hydraulic conductivity values are realistic in comparison to independent field data, and vary by orders of magnitude among the different rock types.
DE: 1828 Groundwater hydraulics
DE: 1846 Model calibration (3333)
DE: 5104 Fracture and flow
SC: Hydrology [H]
MN: 2007 Fall Meeting