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Simulation of Aquifer Tests and Ground-Water Flowpaths at the Local Scale in Fractured Shales and Sandstones of the Brunswick Group and Lockatong Formation, Lansdale, Montgomery County, Pennsylvania

Open-File Report 2000-97
Prepared in cooperation with the U.S. Environmental Protection Agency
By:  and 
https://doi.org/10.3133/ofr0097

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Abstract

The U.S. Geological Survey, as part of technical assistance to the U.S. Environmental Protection Agency, has constructed and calibrated models of local-scale ground-water flow in and near Lansdale, Pa., where numerous sources of industrial contamination have been consolidated into the North Penn Area 6 Superfund Site. The local-scale models incorporate hydrogeologic structure of northwest-dipping beds with uniform hydraulic properties identified in previous studies. Computations associated with mapping the dipping-bed structure into the three-dimensional model grid are handled by a preprocessor using a programmed geographic information system (GIS). Hydraulic properties are identified by calibration of the models using measured water levels during pumping and recovery from aquifer tests at three sites. Reduced flow across low-permeability beds is explicitly simulated. The dipping high-permeability beds are extensive in the strike direction but are of limited extent in the dip direction. This model structure yields ground-water-flow patterns characteristic of anisotropic aquifers; preferred flow is in the strike direction. The transmissivities of high-permeability beds in the local-scale models range from 142 to 1,900 ft2/d (feet squared per day) (13 to 177 m2/d). The hydraulic conductivities of low-permeability parts of the aquifer range from 9.6 x 10-4 to 0.26 ft/d (feet per day) (2.9 x 10-4 to 0.079 m/d). Storage coefficients and specific storage are very low, indicating the confined nature of the aquifer system. The calibrated models are used to simulate contributing areas of wells under alternative, hypothetical ground-water-management practices. Predictive contributing areas indicate the general characteristics of ground-water flow towards wells in the Lansdale area. Recharge to wells in Lansdale generally comes from infiltration near the well and over an area that extends upgradient from the well. The contributing areas for two wells pumping at 10 gal/min (gallons per minute) extend about 1,500 ft (feet) upgradient from the wells. The contributing area is more complex at ground-water divides and can extend in more than one direction to capture recharge from more than 3,300 ft away, for pumping at a rate of 30 gal/min. Locally, all recharge in the area of the pumping well is not captured; recharge in the downgradient direction about 150 ft from the pumping well will flow to other discharge locations.

Suggested Citation

Goode, D.J., and Senior, L.A., 2000, Simulation of aquifer tests and ground-water flowpaths at the local scale in fractured shales and sandstones of the Brunswick Group and Lockatong Formation, Lansdale, Montgomery County, Pennsylvania: U.S. Geological Survey Open-File Report 2000–97, 46 p., https://doi.org/10.3133/ofr0097.

ISSN: 2331-1258 (online)

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Table of Contents

  • Abstract
  • Introduction
  • Hydrogeologic setting
  • Simulation of ground-water flow at the local scale
  • Summary and conclusions
  • References cited
Publication type Report
Publication Subtype USGS Numbered Series
Title Simulation of aquifer tests and ground-water flowpaths at the local scale in fractured shales and sandstones of the Brunswick Group and Lockatong Formation, Lansdale, Montgomery County, Pennsylvania
Series title Open-File Report
Series number 2000-97
DOI 10.3133/ofr0097
Year Published 2000
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Pennsylvania Water Science Center
Description Report: vii, 46 p.; Zip File
Country United States
State Pennsylvania
City Lansdale
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