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Interpretation of Borehole Geophysical Logs, Aquifer-Isolation Tests, and Water-Quality Data for Sites 1, 3, and 5 at the Willow Grove Naval Air Station/Joint Reserve Base, Horsham Township, Montgomery County, Pennsylvania: 2005

U.S. Geological Survey Scientific Investigations Report 2006-5243

By Ronald A. Sloto


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ABSTRACT

Borehole geophysical logging, heatpulse-flowmeter measurements, borehole television surveys, and aquifer-isolation tests were conducted in 2005 at the Willow Grove Naval Air Station/Joint Reserve Base (NAS/JRB) in Horsham Township, Montgomery County, Pa. This study was done by the U.S. Geological Survey (USGS) in cooperation with the U.S. Navy in support of hydrogeological investigations to address ground-water contamination. Data collected for this study are valuable for understanding ground-water flow in the Stockton Formation at the local and regional scale. The Willow Grove NAS/JRB is underlain by the Stockton Formation, which consists of sedimentary rocks of Triassic age. The rocks of the Stockton Formation form a complex, heterogeneous aquifer with partially connected zones of high permeability. Borehole geophysical logs, heatpulse-flowmeter measurements, and borehole television surveys made in seven boreholes ranging from 70 to 350 ft deep were used to identify potential water-producing fractures and fracture zones and to select intervals for aquifer-isolation tests. An upward vertical hydraulic gradient was measured in one borehole, a downward vertical hydraulic gradient was measured in four boreholes, both an upward and a downward vertical hydraulic gradient were measured in one borehole, and no flow was measurable in one borehole. The aquifer-isolation tests isolated 30 discrete fractures in the seven boreholes for collection of depth-discrete hydraulic and water-quality data. Of the 30 fractures identified as potentially water producing, 26 fractures (87 percent) produced more than 1 gallon per minute of water. The specific capacity of the isolated intervals producing more than 1 gallon per minute ranged from 0.02 to 5.2 gallons per minute per foot. There was no relation between specific capacity and depth of the fracture. Samples for analysis for volatile organic compounds were collected from each isolated zone. Tetrachloroethylene (PCE) was the most prevalent compound at Site 1; concentrations were as great as 62 g/L (micrograms per liter). 1,1-dichloroethane was the most prevalent compound at Site 3; concentrations were as great as 9.3 g/L. Toluene was the most prevalent compound at Site 5; concentrations were as great as 77 g/L. For five out of the six wells (83 percent) sampled for field determinations of water-quality constituents, the interval with the lowest dissolved oxygen concentration had the highest total VOC concentration.

Table of Contents

Abstract
Introduction
     Purpose and Scope
     Hydrogeologic Setting
     Well-Identification System
Methods of Investigation      Borehole Geophysical Logs
     Heatpulse-Flowmeter Measurements
     Borehole Television Surveys
     Aquifer-Isolation Tests
     Water-Quality Samples
Interpretation of Borehole Geophysical Logs, Aquifer-Isolation Tests, and Water-Quality Data at Site 1
     Correlation of Borehole Gephysical Logs
     Well 01MW09 (MG-2143)
          Interpretation of Borehole Geophysical Logs
          Interpretation of Aquifer-Isolation Tests
          Vertical Distribution of Water-Quality Constituents
     Well 01MW10 (MG-2141)
          Interpretation of Borehole Geophysical Logs
          Interpretation of Aquifer-Isolation Tests
          Vertical Distribution of Water-Quality Constituents
Interpretation of Borehole Geophysical Logs, Aquifer-Isolation Tests, and Water-Quality Data at Site 3
     Well 03MW08 (MG-2142)
          Interpretation of Borehole Geophysical Logs
          Interpretation of Aquifer-Isolation Tests
          Vertical Distribution of Water-Quality Constituents
Interpretation of Borehole Geophysical Logs, Aquifer-Isolation Tests, and Water-Quality Data at Site 5
     Well 05MW12S (MG-2136)
          Interpretation of Borehole Geophysical Logs
          Interpretation of Aquifer-Isolation Tests
          Vertical Distribution of Water-Quality Constituents
     Well 05MW13I (MG-2137)
          Interpretation of Borehole Geophysical Logs
          Interpretation of Aquifer-Isolation Tests
          Vertical Distribution of Water-Quality Constituents
     Well 05MW14I (MG-2138)
          Interpretation of Borehole Geophysical Logs
          Interpretation of Aquifer-Isolation Tests
          Vertical Distribution of Water-Quality Constituents
     Well 05MW15I (MG-2139)
          Interpretation of Borehole Geophysical Logs
          Interpretation of Aquifer-Isolation Tests
          Vertical Distribution of Water-Quality Constituents
Summary and Conclusions
Acknowledgments
References Cited

This report is available online in Portable Document Format (PDF). If you do not have the Adobe Acrobat PDF Reader, it is available for free download from Adobe Systems Incorporated.

View the full report in PDF 6.1 MB

For more information about USGS activities in Pennsylvania contact:
Director
USGS Pennsylvania Water Science Center
215 Limekiln Road
New Cumberland, Pennsylvania 17070
Telephone: (717) 730-6960
Fax: (717) 730-6997
or access the USGS Water Resources of Pennsylvania home page at:
http://pa.water.usgs.gov/.

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