Groundwater Withdrawals and Regional Flow Paths at and near Willow Grove and Warminster, Pennsylvania—Data Compilation and Preliminary Simulations for Conditions in 1999, 2010, 2013, 2016, and 2017

Open-File Report 2019-1137
Prepared in cooperation with the U.S. Navy
By:  and 

Links

  • Document: Report (21.7 MB pdf)
  • Data Releases:
    • USGS data release - MODFLOW 6 and MODPATH 7 model data sets used to evaluate groundwater flow in the vicinity of Horsham and Warminster, Bucks and Montgomery Counties, Pennsylvania—Preliminary simulations for conditions in 1999, 2010, 2013, 2016, and 2017
    • USGS data release - Groundwater levels, groundwater withdrawals, and point-source discharges to streams in the vicinity of Willow Grove and Warminster, Bucks and Montgomery Counties, Pennsylvania, for selected years during 1999–2017
  • Open Access Version: Publisher Index Page
  • Download citation as: RIS | Dublin Core

Abstract

In 2014, groundwater samples from residential and public supply wells in the vicinity of two former U.S. Navy bases at Willow Grove and Warminster, and an active Air National Guard Station at Horsham, Bucks and Montgomery Counties, Pennsylvania, were found to have concentrations of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), which are per- and polyfluoroalkyl substances (PFAS), above U.S. Environmental Protection Agency (EPA) provisional health advisory (HA) levels for drinking water. Five supply wells near the bases were shut down because of PFAS contamination. In 2016, after EPA established a Lifetime HA for PFAS in drinking water that is lower than the provisional HA in place in 2014, at least 13 additional supply wells near the bases were shut down because of PFAS contamination. At the request of the U.S. Navy, and in consultation with other Federal and State agencies and local stakeholders, the U.S. Geological Survey used historical and recent data on well withdrawals, recharge rates, aquifer properties, groundwater levels, and stream base flow to evaluate regional groundwater-flow paths from identified areas of PFAS groundwater contamination or potential PFAS sources at the bases. Groundwater withdrawals near the bases from public supply and other large wells decreased substantially from the 1990s to 2017, increasing the proportion of groundwater recharge that discharged to local streams. A preliminary groundwater-flow model, calibrated using 1,009 groundwater levels and 17 stream base flow estimates, simulated regional flow paths from the bases and showed that recharge at the bases discharged to withdrawal wells and local streams, generally within a mile or two of the bases. Supply and remediation wells at the bases captured some of the recharge on base areas of possible PFAS contamination, whereas other base recharge was simulated to flow to nearby public supply wells and streams, depending on water use and aquifer recharge conditions between 1999 and 2017. The locations of many residential wells near the bases that were identified by the Navy and Air National Guard as having elevated PFAS concentrations were generally consistent with the simulated flow paths from possible sources at the bases. However, there are some areas of observed PFAS contamination where no flow paths from base sources were simulated. Additionally, no data were available on PFAS concentrations in groundwater in some areas of simulated flow paths from base sources. Data and models used for this study are provided in this report and in digital data releases to support further investigations and model revisions.

Suggested Citation

Goode, D.J., and Senior, L.A., 2020, Groundwater withdrawals and regional flow paths at and near Willow Grove and Warminster, Pennsylvania—Data compilation and preliminary simulations for conditions in 1999, 2010, 2013, 2016, and 2017: U.S. Geological Survey Open-File Report 2019–1137, 127 p., https://doi.org/10.3133/ofr20191137.

ISSN: 2331-1258 (online)

Study Area

Table of Contents

  • Acknowledgments
  • Abstract
  • Introduction
  • Description of Study Area
  • Hydrologic Conditions and Water Use, 1999-2017
  • Simulation of Regional Groundwater Flow
  • Limitations and Suggestions for Improvements
  • Summary
  • References Cited
  • Appendix 1. Annual Base Flow as Determined from Measured Streamflow at Selected Gages and Estimated for Missing Streamflow Records During 2010–2015
  • Appendix 2. Model Calibration Results
  • Appendix 3. Simulated Water Levels and Groundwater-Flow Paths

Additional publication details

Publication type Report
Publication Subtype USGS Numbered Series
Title Groundwater withdrawals and regional flow paths at and near Willow Grove and Warminster, Pennsylvania—Data compilation and preliminary simulations for conditions in 1999, 2010, 2013, 2016, and 2017
Series title Open-File Report
Series number 2019-1137
DOI 10.3133/ofr20191137
Year Published 2020
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Pennsylvania Water Science Center
Description Report: x, 127 p.; 2 Data Releases
Country United States
State Pennsylvania
County Montgomery County, Bucks County
City Willow Grove, Warminster
Online Only (Y/N) Y
Additional Online Files (Y/N) Y