U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2008-1207

In cooperation with the U.S. Navy 

Interpretation of Borehole Geophysical Logs at Area C, 

Former Naval Air Warfare Center, Warminster Township, 

Bucks County, Pennsylvania, 2007

Interpretation of Borehole Geophysical 

Logs at Area C, Former Naval Air Warfare 

Center, Warminster Township, Bucks 

County, Pennsylvania, 2007

By Ronald A. Sloto

In cooperation with the U.S. Navy

Open-File Report 2008-1207

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2008

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Suggested citation:

Sloto, R.A., 2008, Interpretation of borehole geophysical logs at Area C, former Naval Air Warfare Center, Warminster 

Township, Bucks County, Pennsylvania, 2007: U.S. Geological Survey Open-File Report 2008-1207, 20 p.
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Purpose and Scope .............................................................................................................................4

Hydrogeologic Setting .........................................................................................................................4

Well-Identification System..................................................................................................................4

Methods of Investigation..............................................................................................................................4

Borehole Geophysical Logs ................................................................................................................4

Heatpulse-Flowmeter Measurements .............................................................................................5

Borehole Television Surveys...............................................................................................................6

Interpretation of Borehole Geophysical Logs at Area C .........................................................................6

Well HN-23A (BK-3040)........................................................................................................................6

Well HN-101-OB (BK-3039)..................................................................................................................7

Well HN-101-S (BK-3038).....................................................................................................................9

Well HN-102-S (BK-3037)...................................................................................................................10

Well HN-103-S (BK-3035)...................................................................................................................12

Well HN-104-S (BK-3036)...................................................................................................................14

Well HN-105-S (BK-3041)...................................................................................................................15

Correlation of Borehole Geophysical Logs.....................................................................................16

Summary and Conclusions.........................................................................................................................20

Acknowledgments.......................................................................................................................................20

References Cited..........................................................................................................................................20

Figures

1. Map showing location of the former Naval Air Warfare Center, Warminster

Township, Bucks County, Pa. .....................................................................................................2

2. Map showing location of selected monitor wells in Area C at the former Naval Air

Warfare Center, Warminster Township, Bucks County, Pa. .................................................3

3. Borehole geophysical logs for well HN-23A (BK-3040), former Naval Air Warfare

Center, Warminster Township, Bucks County, Pa. .................................................................6

4. Borehole geophysical logs for well HN-101-OB (BK-3039), former Naval Air

Warfare Center, Warminster Township, Bucks County, Pa. .................................................7

5. Image from borehole television survey showing fracture zone at 20 feet below land

surface in well HN-101-OB (BK-3039), former Naval Air Warfare Center, Warminster

Township, Bucks County, Pa. .....................................................................................................8

6. Borehole geophysical logs for well HN-101-S (BK-3038), former Naval Air Warfare

Center, Warminster Township, Bucks County, Pa. .................................................................9

7. Borehole geophysical logs for well HN-102-S (BK-3037), former Naval Air Warfare

Center, Warminster Township, Bucks County, Pa. ...............................................................10
iv

8. Image from borehole television survey showing horizontal fracture at 48 feet

below land surface in well HN-102-S (BK-3037), former Naval Air Warfare Center,

Warminster Township, Bucks County, Pa. .............................................................................11

9. Borehole geophysical logs for well HN-103-S (BK-3035), former Naval Air Warfare

Center, Warminster Township, Bucks County, Pa. ...............................................................12

10. Image from borehole television survey showing a high-angle and horizontal

fracture at 41 feet below land surface in well HN-103-S (BK-3035), former Naval Air

Warfare Center, Warminster Township, Bucks County, Pa. ...............................................13

11. Borehole geophysical logs for well HN-103-S (BK-3036), former Naval Air Warfare

Center, Warminster Township, Bucks County, Pa. ...............................................................14

12. Borehole geophysical logs for well HN-105-S (BK-3041), former Naval Air Warfare

Center, Warminster Township, Bucks County, Pa. ...............................................................15

13. Image from borehole television survey showing a high-angle and horizontal

fracture at 70 feet below land surface in well HN-105-S (BK-3041), former Naval Air

Warfare Center, Warminster Township, Bucks County, Pa. ...............................................16

14. Correlation of borehole geophysical logs, Area C, former Naval Air Warfare Center,

Bucks County, Pa. ......................................................................................................................17

15. Tetrachloroethylene (PCE) concentrations in water samples from selected 

wells in Area C, former Naval Air Warfare Center, Warminster Township, Bucks 

County, Pa. ...................................................................................................................................18

16. Areal distribution of tetrachloroethylene (PCE) in water samples from selected

wells in Area C at the former Naval Air Warfare Center, Warminster Township,

Bucks County, Pa. .......................................................................................................................19

Tables

1. Record of selected wells, Area C, former Naval Air Warfare Center, Warminster 

Township, Bucks County, Pa. .....................................................................................................5
v

Conversion Factors

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Volume

gallon (gal) 3.785 liter (L) 

Flow rate

gallon per minute (gal/min) 0.06309 liter per second (L/s)

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Altitude, as used in this report, refers to distance above the vertical datum.

Concentrations of chemical constituents in water are given in micrograms per liter (μg/L).

Abstract 1

Abstract

This study was done by the U.S. Geological Survey in cooperation with the U.S. Navy at Area C of the former Naval Air 

Warfare Center in Warminster Township, Bucks County, Pa., in support of hydrogeological investigations conducted by the 

Navy to address ground-water contamination in the Stockton Formation. Borehole geophysical logs were collected, heatpulseflowmeter measurements were made, and borehole television surveys were run in seven boreholes ranging from 31 to 75 feet 

deep. Caliper logs and borehole television surveys were used to identify fractures and the location of possible water-bearing 

zones. Heatpulse-flowmeter measurements were used to identify fractures that were water-bearing zones. Natural-gamma and 

single-point-resistance logs were used to correlate lithology across the area. Elevated concentrations of tetrachloroethylene 

(PCE) were measured in water samples from wells with water-bearing zones in the interval of the aquifer where monitor well 

HN-23A is screened. Water samples from wells with water-bearing zones above or below this interval had substantially lower 

concentrations of PCE. Wells screened in this interval yielded less than 0.5 gallon per minute, indicating that the interval has low 

permeability; this may account for the small areal extent and slow migration of PCE.

Introduction

The former U.S. Naval Air Warfare Center (NAWC) in Warminster Township, Bucks County, Pa. (fig. 1), was acquired by 

the U.S. Navy in 1944 to convert and modify newly produced aircraft prior to delivery to the Naval Fleet. After World War II, 

the NAWC served as a research, development, testing, and evaluation center. In 1979, volatile organic compounds were detected 

in water from the NAWC supply wells. The following year, the Navy implemented a program to identify and evaluate past 

disposal sites and to control the migration of hazardous material from such sites. Area C is a part of the former NAWC that contained a known disposal site. The NAWC was closed on September 30, 1997, as part of the Base Realignment and Closure Act. 

Anne’s Choice, a residential retirement community, has been constructed over much of Area C. 

To investigate possible ground-water contamination in Area C, the Navy installed a number of monitor wells and conducted 

a hydrogeological investigation. Tetrachloroethylene (PCE) concentrations as high as 29 μg/L were measured in water samples 

from the monitor wells (Halliburton NUS Corporation, 1994). To address ground-water contamination in Area C, the Navy 

installed a remediation system using six extraction wells, which began operation in 1996. PCE concentrations in two of the wells 

dropped below the U.S. Environmental Protection Agency Maximum Contaminant Level of 5 μg/L, and the wells were taken 

out of service. Concentrations of PCE in water from the remaining four active extraction wells ranged from 3.1 to 25 μg/L during 2006-07. 

During construction of the retirement community in 2003, monitor well HN-23 was abandoned (with Navy approval), and 

replacement monitor well HN-23A (fig. 2) was drilled. PCE concentrations in water samples from well HN-23A were as high as 

300 μg/L, which was an order of magnitude greater than concentrations from other Area C wells. As a result, the Navy initiated an Area C source investigation. In support of this investigation, the U.S. Geological Survey (USGS) conducted borehole 

geophysical logging, made heatpulse-flowmeter measurements, and ran borehole television surveys in seven boreholes to assist 

in characterization of the aquifer hydrogeological framework. 

Interpretation of Borehole Geophysical Logs at 

Area C, Former Naval Air Warfare Center, Warminster 

Township, Bucks County, Pennsylvania, 2007

By Ronald A. Sloto
2 Interpretation of Borehole Geophysical Logs at Area C, Former Naval Air Warfare Center, 2007

75°2’

WARMINSTER

 TOWNSHIP NORTHAMPTON

 TOWNSHIP

 WARWICK

TOWNSHIP

UPPER SOUTHAMPTON

 TOWNSHIP

75°6’ 75°4’

40°12’

 IVYLAND

BOROUGH

M

BUCKS COUNTY

ONTGOMERY COUNTY

FORMER NAVAL AIR

 WARFARE CENTER

40°14’

 AREA C

Base from U.S. Geological Survey digital data,1972, 1:2,000,000 Albers Equal-Area

Conic Projection. Standard parallels 29°30’N, central meridian 75°00’W.

0 0.5 1MILE

0 0.5 1 1.5 KILOMETERS

Figure 1. Location of the former Naval Air Warfare Center, Warminster Township, Bucks County, Pa. 
Abstract 3

75°4'5” 75°4’

40°12'5”

40°12'10”

0 50 100 FEET

0 12 24 36 48 METERS

150 200

Base modified from ECOR Solutions, Inc. (2006)

MONITOR WELL AND IDENTIFICATION NUMBER –

 Upper number is Navy well-identification number. Lower

 number is U.S. Geological Survey well-identification number.

EXPLANATION

POND

HN-28-S

BK-2596 HN-104-S

BK-3036

HN-103-S

BK-3035

HN-101-S

BK-3038 HN-101-OB

BK-3039

HN-23A

BK-3040

HN-102-S

BK-3037

HN-105-S

BK-3041

HN-27-S

BK-2594

HN-104-S

BK-3036

A

A’

HN-27-I

BK-2595

HN-28-I

BK-2597

A A’ LINE OF GEOLOGIC SECTION – Used for correlation of

 natural-gamma and single-point-resistance borehole

 geophysical logs

FORMER NAVAL AIR

 WARFARE CENTER

 AREA C

Figure 2. Location of selected monitor wells in Area C at the former Naval Air Warfare Center, Warminster Township, 

Bucks County, Pa. 
4 Interpretation of Borehole Geophysical Logs at Area C, Former Naval Air Warfare Center, 2007

Purpose and Scope 

This report describes the results of a hydrogeological investigation conducted in 2007 by the USGS in cooperation with the 

U.S. Navy in Area C at the former NAWC. The USGS collected the geophysical data presented here as part of the environmental 

hydrogeological investigations conducted at the former NAWC. This report provides an interpretation of borehole geophysical logs, borehole television surveys, and heatpulse-flowmeter measurements made in seven boreholes ranging from 31 to 75 ft 

deep. It describes the location of water-bearing-fracture zones, presents a lithologic model for the area, and describes the distribution of PCE with respect to the lithology. 

Hydrogeologic Setting

The former NAWC is in the Triassic Lowlands Section of the Piedmont Physiographic Province and is underlain by sedimentary rocks of the Stockton Formation of Late Triassic age. The rocks are chiefly arkosic sandstone and siltstone. In Area C, 

the Stockton Formation strikes approximately N. 54° E. and dips approximately 7° NW. (Tetra Tech NUS, 2007, p. 3-1). Vertical 

fractures are common.

The rocks of the Stockton Formation form a complex, heterogeneous aquifer with partially connected zones of high permeability. The aquifer is composed of a series of gently dipping lithologic units with different hydraulic properties. Permeability 

commonly differs from one lithologic unit to another. Ground water in the unweathered part of the Stockton Formation primarily 

flows through a network of interconnecting secondary openings—bedding-plane fractures and joints. Primary porosity has been 

almost entirely eliminated by compaction and cementation (Sloto and others, 1996, p. 14). 

Ground water at the former NAWC originates from local infiltration of precipitation and inflow of ground water from 

upgradient areas. Ground-water levels fluctuate with seasonal variations in recharge and are affected by pumping of wells. Water 

in the shallow part of the aquifer generally is under unconfined (water-table) conditions; ground water in the deeper part of the 

aquifer may be confined or partially confined (Sloto and others, 1996, p. 12-13). 

Well-Identification System

Two well-identification numbering systems are used in this report to maintain consistency with previous studies. USGS 

well-identification numbers consist of a county-abbreviation prefix followed by a sequentially assigned number. The prefix 

“BK” denotes a well in Bucks County. Navy well-identification numbers begin with the prefix “HN.” A cross-reference between 

Navy and USGS well-identification numbers and data for each well are given in table 1. The locations of the wells are shown on 

figure 2. All wells were drilled by Navy contractors with an air-rotary drilling rig.

Methods of Investigation

This study included collection of borehole geophysical logs, heatpulse-flowmeter measurements, and borehole television 

surveys. They are described in the following sections. 

Borehole Geophysical Logs

Caliper, natural-gamma, and single-point-resistance geophysical logs were collected in the boreholes listed in table 1. The 

logs were used to locate water-producing fractures and to correlate lithology across the site. 

Caliper logs provide a continuous record of average borehole diameter, which is related to fractures, lithology, and drilling technique. Caliper logs were used to identify fractures and possible water-producing openings. The term fracture used in 

association with the caliper-log interpretations might identify a change in borehole diameter that may not necessarily indicate 

a bedding-plane separation, lithologic contact, or water-producing or water-receiving zone but may simply indicate an enlargement of the borehole. 

Natural-gamma logs record the natural-gamma radiation emitted from rocks penetrated by the borehole. Uranium-238, 

thorium-232, the progeny of their decay series, and potassium-40 are the most common emitters of natural-gamma radiation. 

These radioactive elements are concentrated in clays by adsorption, precipitation, and ion exchange. Fine-grained sediments, 

such as mudstone or siltstone, usually emit more gamma radiation than sandstone. Geophysical logging with a gamma probe 

can be conducted in the water-filled or dry, cased or uncased parts of the borehole (Keys, 1990). However, casing reduces the 

gamma response. The natural-gamma logs were used to correlate lithologic units between boreholes. 
Methods of Investigation 5

Single-point-resistance logs, also called single-point electric logs, record the electrical resistance between the borehole 

and an electrical ground at land surface. In general, resistance increases with grain size and decreases with borehole diameter, 

density of water-producing fractures, and increasing dissolved-solids concentration of borehole water (Keys, 1990). A waterfilled borehole is required for single-point-resistance logs, and they are run only for the saturated part of the formation below the 

casing. Single-point-resistance logs were used to correlate lithologic units between boreholes.

Heatpulse-Flowmeter Measurements 

The direction and rate of vertical borehole-fluid movement were measured with a high-resolution heatpulse flowmeter. The 

heatpulse flowmeter operates by diverting nearly all flow to the center of the tool where a heating grid slightly heats a thin zone 

of water. If vertical borehole flow is occurring, the water moves up or down the borehole to one of two sensitive thermistors 

(heat sensors). When a peak temperature is recorded by one of the thermistors, a measurement of direction and rate is calculated 

by the computer collecting the logging data. The range of flow measured by the heatpulse flowmeter is about 0.01 to 1.5 gal/min 

in a 2- to 10-in. diameter borehole. 

Heatpulse-flowmeter measurements may be affected by poor seal integrity between the borehole and the flowmeter. If the 

seal between the borehole and the heatpulse flowmeter is not complete, some water can bypass the flowmeter, resulting in flow 

measurements that are less than the actual rate. The quantity of water bypassing the tool is a function of borehole size and shape 

and degree of fracturing. Although the heatpulse flowmeter is a calibrated tool, the data primarily are used as a relative indicator of water-producing zones. For the wells logged in Area C, the seal integrity was considered as very good. No problems were 

noted concerning seal integrity. 

Two types of heatpulse-flowmeter measurements were made—nonpumping and pumping. Nonpumping measurements, 

sometimes called ambient-condition measurements, measure the natural flow in the borehole. Pumping measurements are made 

while the borehole is pumped at a low rate, generally 2 gal/min or less, and the drawdown is kept constant. Under pumping conditions, hydraulically active fractures that may not produce water under nonpumping conditions are induced by the pumping to 

produce a measurable quantity of water. When the pumping rate is known, the relative contribution of each hydraulically active 

fracture can be determined. Pumping rates for wells in this report were 0.2 to 2.2 gal/min. Measurements under pumping conditions were not made in boreholes with less than 12 ft of open hole. 

Table 1. Record of selected wells, Area C, former Naval Air Warfare Center, Warminster Township, Bucks County, Pa. 

Reported yield taken from driller or geologist logs.

[--, no data; <, less than]

Navy 

well-identification 

number

U.S. Geological Survey 

well-identification 

number

Depth drilled

(feet)

Borehole 

diameter 

(inches)

Reported yield 

(gallons per minute)

Screened or open 

interval at time of 

logging 

(feet below land 

surface)

HN-23A BK-3040 60 16 -- 37–57

HN-27-S BK-2594 102 6 1 18–52

HN-27-I BK-2595 157.5 6 8 abandoned

HN-28-S BK-2596 80 6 4 53–68

HN-28-I BK-2597 171 6 20 abandoned

HN-101-OB BK-3039 60 6 < .1 15–60

HN-101-S BK-3038 25 6 < .1 14–25

HN-102-S BK-3037 60 6 0 20–60

HN-103-S BK-3035 51 6 < .1 22–51

HN-104-S BK-3036 31 6 < .1 20–31

HN-105-S BK-3041 75 6 -- 18–75

1

Inner casing 4 in. in diameter.
6 Interpretation of Borehole Geophysical Logs at Area C, Former Naval Air Warfare Center, 2007

Borehole Television Surveys

Borehole television surveys were conducted by lowering a waterproof video camera down the borehole and recording the 

image on video tape. The depth indicated on the video image may not correspond exactly to the geophysical logs because of 

slippage of the video cable. The borehole television surveys were used to visually characterize water-producing fractures identified by interpretation of the borehole geophysical logs and heatpulse-flowmeter measurements. 

Interpretation of Borehole Geophysical Logs at Area C

Borehole geophysical logs were collected in six newly drilled wells (HN-101-OB, HN-101-S, HN-102-S, HN-103-S, 

HN-104-S, and HN-105-S) and one existing monitor well (HN-23A), and heatpulse-flowmeter measurements were made in the 

six newly drilled wells. Well locations are shown on figure 2. Interpretations of geophysical logs are provided in the following 

sections. 

Well HN-23A (BK-3040)

Well HN-23A is a screened monitor well; therefore, only natural-gamma and single-point-resistance logs (fig. 3) were collected by the USGS on June 12, 2007. The logs show the depth to the bottom of the screen is 57 ft. The single-point-resistance 

log shows the well is screened from 37 to 57 ft below land surface (bls). The spike in the single-point-resistance log shows a 

possible water-bearing fracture at 47 ft bls. Well HN-23A was pumped for about 5 minutes; the yield was approximately 

0.5 gal/min. 

0

10

20

30

40

50

60

NATURAL GAMMA,

 IN COUNTS PER

 SECOND

SINGLE-POINT

 RESISTANCE,

 IN OHMS

0 50 100 150 200 0 200 400 600 800

DEPTH, IN FEET BELOW LAND SURFACE

Figure 3. Borehole geophysical logs for well HN-23A (BK-3040), former Naval Air Warfare Center, 

Warminster Township, Bucks County, Pa. 
Interpretation of Borehole Geophysical Logs at Area C 7

Well HN-101-OB (BK-3039)

Caliper, natural-gamma, and single-point-resistance logs (fig. 4) were collected in well HN-101-OB by the USGS on 

June 12, 2007. The caliper log shows the well is 60 ft deep and is cased to 15 ft bls, and fractures are at 17-20, 25, 28, and 

50-56 ft bls. Heatpulse-flowmeter measurements were made at 22, 40, and 53 ft bls under nonpumping and pumping conditions. 

No vertical borehole flow was measurable under nonpumping conditions. The borehole television survey showed a high-angle 

fracture zone from the bottom of the casing to 24 ft bls. In this zone, the water was clear, indicating borehole flow. Below 

24 ft bls, the water was very cloudy, indicating no borehole flow. When the well was pumped at 2.2 gal/min, the fracture zone at 

17-20 ft bls (fig. 5) produced all the water. DEPTH, IN FEET BELOW LAND SURFACE

 CALIPER LOG

HOLE DIAMETER,

 IN INCHES

5 6 7

NATURAL GAMMA,

 IN COUNTS PER

 SECOND

0 50 100 150 200

SINGLE-POINT

 RESISTANCE,

 IN OHMS

100 200 300 400

0

10

20

30

40

50

60

70

Figure 4. Borehole geophysical logs for well HN-101-OB (BK-3039), former Naval Air Warfare Center, Warminster Township, 

Bucks County, Pa. 
8 Interpretation of Borehole Geophysical Logs at Area C, Former Naval Air Warfare Center, 2007

FRACTURE CAMERA LIGHTHEAD

ASSEMBLY

Figure 5. Image from borehole television survey showing fracture zone at 20 feet below land 

surface in well HN-101-OB (BK-3039), former Naval Air Warfare Center, Warminster Township, Bucks 

County, Pa. 
Interpretation of Borehole Geophysical Logs at Area C 9

Well HN-101-S (BK-3038)

Caliper, natural-gamma, and single-point-resistance logs (fig. 6) were collected in well HN-101-S by the USGS on 

June 8, 2007. The caliper log shows the well is 25 ft deep and is cased to 14 ft bls, and fractures are at 19, 21, and 23 ft bls. 

Heatpulse-flowmeter measurements were made at 17 and 21 ft bls under nonpumping conditions. No vertical borehole flow was 

measurable. DEPTH, IN FEET BELOW LAND SURFACE

0

10

20

30

 CALIPER LOG

HOLE DIAMETER,

 IN INCHES

NATURAL GAMMA,

 IN COUNTS PER

 SECOND

SINGLE-POINT

 RESISTANCE,

 IN OHMS

5 6 7 0 50 100 150 200 450 500 550 600

Figure 6. Borehole geophysical logs for well HN-101-S (BK-3038), former Naval Air Warfare Center, Warminster Township, Bucks 

County, Pa. 
10 Interpretation of Borehole Geophysical Logs at Area C, Former Naval Air Warfare Center, 2007

Well HN-102-S (BK-3037)

Caliper, natural-gamma, and single-point-resistance logs (fig. 7) were collected in well HN-102-S by the USGS on 

June 8, 2007. The caliper log shows the well is 60 ft deep and is cased to 20 ft bls, and fractures are at 24, 36, and 48 ft bls. 

Heatpulse-flowmeter measurements were made at 26, 34, 43, and 49 ft bls under nonpumping and pumping conditions. No vertical borehole flow was measurable under nonpumping conditions. When the well was pumped at 0.3 gal/min, a bedding-plane 

fracture at 48 ft bls (fig. 8) produced all the water. DEPTH, IN FEET BELOW LAND SURFACE

0

10

20

30

40

50

60

70

CALIPER LOG

HOLE DIAMETER,

IN INCHES

NATURAL GAMMA,

IN COUNTS PER

SECOND

SINGLE-POINT

RESISTANCE,

IN OHMS

5 6 7 8 0 50 100 150 200 200 400 600 800

Figure 7. Borehole geophysical logs for well HN-102-S (BK-3037), former Naval Air Warfare Center, Warminster Township, Bucks 

County, Pa.
Interpretation of Borehole Geophysical Logs at Area C 11

FRACTURE

A

B

Figure 8. Image from borehole television survey showing horizontal fracture at 48 feet below land 

surface in well HN-102-S (BK-3037), former Naval Air Warfare Center, Warminster Township, Bucks 

County, Pa.
12 Interpretation of Borehole Geophysical Logs at Area C, Former Naval Air Warfare Center, 2007

Well HN-103-S (BK-3035)

Caliper, natural-gamma, and single-point-resistance logs (fig. 9) were collected in well HN-103-S by the USGS on 

June 8, 2007. The caliper log shows the well is 51 ft deep and is cased to 22 ft bls, and fractures are at 32, 36, 38, and 41 ft bls. 

Heatpulse-flowmeter measurements were made at 25, 34, and 43 ft bls under nonpumping and pumping conditions. No vertical 

borehole flow was measurable under nonpumping conditions. When the well was pumped at 0.3 gal/min, the fracture at 41 ft bls 

produced all the water. The water-bearing zone at 41 ft bls is at the intersection of a high-angle and bedding-plane (horizontal) 

fracture (fig. 10). DEPTH, IN FEET BELOW LAND SURFACE

0

10

20

30

40

50

60

CALIPER LOG

HOLE DIAMETER,

IN INCHES

NATURAL GAMMA,

IN COUNTS PER

SECOND

SINGLE-POINT

RESISTANCE,

IN OHMS

5 6 7 8 0 50 100 150 200 300 400 500 600

Figure 9. Borehole geophysical logs for well HN-103-S (BK-3035), former Naval Air Warfare Center, Warminster Township, Bucks 

County, Pa.
Interpretation of Borehole Geophysical Logs at Area C 13

HORIZONTAL

 FRACTURE

HIGH-ANGLE

 FRACTURE

A

B

Figure 10. Image from borehole television survey showing a high-angle and horizontal fracture at 

41 feet below land surface in well HN-103-S (BK-3035), former Naval Air Warfare Center, Warminster 

Township, Bucks County, Pa.
14 Interpretation of Borehole Geophysical Logs at Area C, Former Naval Air Warfare Center, 2007

Well HN-104-S (BK-3036)

Caliper, natural-gamma, and single-point-resistance logs (fig. 11) were collected in well HN-104-S by the USGS on 

June 8, 2007. The caliper log shows the well is 31 ft deep and is cased to 20 ft bls, and fractures are at 21, 27, and 31 ft bls. A 

heatpulse-flowmeter measurement was made at 25 ft bls under nonpumping conditions. No vertical borehole flow was measurable. DEPTH, IN FEET BELOW LAND SURFACE

0

10

20

30

40

CALIPER LOG

HOLE DIAMETER,

IN INCHES

NATURAL GAMMA,

IN COUNTS PER

SECOND

SINGLE-POINT

RESISTANCE,

IN OHMS

5 6 7 0 50 100 150 200 200 300 400 8

Figure 11. Borehole geophysical logs for well HN-103-S (BK-3036), former Naval Air Warfare Center, Warminster Township, Bucks 

County, Pa.
Interpretation of Borehole Geophysical Logs at Area C 15

Well HN-105-S (BK-3041)

Natural-gamma and single-point-resistance logs (fig. 12) were collected in well HN-105-S by the USGS on 

August 21, 2007. The well is 75 ft deep and cased to 18 ft bls. Heatpulse-flowmeter measurements were made at 29, 36, 43, 

58, and 70 ft bls under nonpumping and pumping conditions. No vertical borehole flow was measurable under nonpumping 

conditions. When the well was pumped at 0.7 gal/min, the fracture at 70 ft bls produced all the water. The water-bearing zone at 

70 ft bls is at the intersection of a high-angle and a bedding-plane (horizontal) fracture (fig. 13). DEPTH, IN FEET BELOW LAND SURFACE

0

10

20

30

40

50

60

80

70

NATURAL GAMMA,

IN COUNTS PER

SECOND

SINGLE-POINT

RESISTANCE,

IN OHMS

0 50 100 150 200 200 400 600 800

Figure 12. Borehole geophysical logs for well HN-105-S (BK-3041), former Naval Air Warfare Center, 

Warminster Township, Bucks County, Pa. 
16 Interpretation of Borehole Geophysical Logs at Area C, Former Naval Air Warfare Center, 2007

A

B

HORIZONTAL

 FRACTURE HIGH-ANGLE

 FRACTURE

Figure 13. Image from borehole television survey showing a high-angle and horizontal fracture at 

70 feet below land surface in well HN-105-S (BK-3041), former Naval Air Warfare Center, Warminster 

Township, Bucks County, Pa. 

Correlation of Borehole Geophysical Logs

Lithologic units penetrated by the six new monitor wells were correlated using natural-gamma and single-point-resistance 

logs along a line from well HN-27-S to well HN-28-S (line A-A’ on figure 2). Borehole geophysical logs from well HN-27-I, 

which was drilled adjacent to well HN-27-S and later abandoned, and well HN-27-I, which was drilled adjacent to well HN-27-S 

and later abandoned, were used for the correlation. Borehole geophysical data for wells HN-27-S, HN-27-I, HN-28-S, and 

HN-28-I were presented by Sloto and Low (2001). The interpreted lithology across Area C is shown on figure 14. 

The water-bearing zones, screened intervals, open-hole intervals, and PCE concentrations were superimposed on the 

lithologic model for Area C (fig. 15). PCE concentrations were measured in water samples collected in July and August 2007. 

PCE concentration data for wells HN-27-S and HN-29-S were taken from ECOR Solutions, Inc. (2007), and PCE concentration 

data for the other wells were taken from Tetra Tech NUS, Inc. (2007). Water samples from wells with water-bearing zones in 

the same interval as the screened interval in well HN-23A have higher PCE concentrations than water samples from wells that 

do not have water-bearing zones in that interval. Wells HN-23A and HN-105-S, which had the highest concentrations of PCE, 

yielded less than 0.5 gal/min. The zone containing elevated concentrations of PCE appears to extend in the upgradient direction 

toward well HN-103-S (fig. 16). 
Interpretation of Borehole Geophysical Logs at Area C 17

ELEVATION, IN FEET ABOVE NAVD 88 

330325320315310305300295290285280275270265260255250245240

340

335

A’

A

HN-101-OB HN-102-S HN-104-S HN-27-I HN-105-S HN-28-I

SANDSTONE

SILTY SANDSTONE

HN-102-S

WELL LOCATION AND WELL  IDENTIFICATION NUMBER 

GEOLOGIC CONTACT – Dashed where inferred

NATURAL-GAMMA LOG

SINGLE-POINT-RESISTANCE LOG

SANDSTONE

SANDSTONE

SANDSTONE

SILTSTONE

SILTSTONE

HORIZONTAL SCALE

0 50 100 FEET 25 75

0 5 10 15 20 METERS

NORTHWEST SOUTHEAST

VERTICAL EXAGGERATION X2.9

Figure 14. Correlation of borehole geophysical logs, Area C, former Naval Air Warfare Center, Bucks County, Pa. Line of section is shown on figure 2. Units shown are part of the Stockton Formation of Upper Triassic age. 
18 Interpretation of Borehole Geophysical Logs at Area C, Former Naval Air Warfare Center, 2007

ELEVATION, IN FEET ABOVE NAVD 88 

330325320315310305300295290285280275270265260255250245240

340

335

A’

A

81

HN-23A

HN-101-OB

HN-102-S

HN-104-S HN-27-S HN-105-S HN-28-S

SILTSTONE

SANDSTONE

SILTY SANDSTONE

SANDSTONE

~ 

~ 

SANDSTONE

SANDSTONE

SILTSTONE

120

120

16

<10

1.9J

8.3J

~ 

HN-103-S

~ 

~ 

~ 

HN-101-S

1.37-26-07

 <17-26-07

HN-102-S WELL-IDENTIFICATION NUMBER

SCREENED INTERVAL IN WELLOPEN-HOLE INTERVAL IN WELL

APPROXIMATE INTERVAL OF  AQUIFER OPEN TO SCREENED INTERVAL IN WELL HN-23A

GEOLOGIC CONTACT – Dashedwhere inferred

~ WATER-BEARING ZONE

 1.37-26-07

CONCENTRATION OF TETRACHLOROETHYLENE IN MICROGRAMS PER LITER – Wells sampled  August 22 and 23, 2007; date of sample given if different. J, estimated value; <, less than

NORTHWEST SOUTHEAST

0 50 100 FEET 25 75

0 5 10 15 20 METERS

HORIZONTAL SCALE

VERTICAL EXAGGERATION X2.9

Figure 15. Tetrachloroethylene (PCE) concentrations in water samples from selected wells in Area C, former Naval Air Warfare Center, Warminster Township, Bucks County, Pa. Line of section is shown on figure 2. Well HN-103-S was projected to line of section Tetrachloroethylene data from Tetra Tech NUS (2007) and ECORE Solutions (2007). 
Interpretation of Borehole Geophysical Logs at Area C 19

75°4'5” 75°4’

40°12'5”

40°12'10”

0 50 100 FEET

0 12 24 36 48 METERS

150 200

Base modified from ECOR Solutions, Inc. (2006)

MONITOR WELL – Upper number is well identification number. 

 Lower number is tetrachloroethy ene concentration in

 micrograms per liter. 

-

l

Wells sampled August 22 and 23, 2007;

 date of sample given if different. J, estimated value; <, less than

EXPLANATION

POND

HN-28-S

<1

7-26-07

HN-104-S

<10

HN-103-S

81

HN-101-S

8.3J

HN-101-OB

16

HN-23A

120

HN-102-S

1.9J

HN-105-S

120

HN-27-S

1.3

7-26-07

HN-27-S

1.3

7-26-07

Figure 16. Areal distribution of tetrachloroethylene (PCE) in water samples from selected wells in Area C at the former Naval 

Air Warfare Center, Warminster Township, Bucks County, Pa.
20 Interpretation of Borehole Geophysical Logs at Area C, Former Naval Air Warfare Center, 2007

Summary and Conclusions

This study was done by the U.S. Geological Survey (USGS) in cooperation with the U.S. Navy at Area C of the former 

Naval Air Warfare Center (NAWC) in Warminster Township, Bucks County, Pa., in support of hydrogeological investigations 

conducted by the Navy to address ground-water contamination. The report presents an interpretation of borehole geophysical logs, heatpulse-flowmeter measurements, borehole television surveys, and PCE data for nine wells. The former NAWC is 

underlain by the Stockton Formation, which consists of sedimentary rocks of Triassic age that form a complex, dipping, heterogeneous aquifer with partially connected zones of high permeability. 

For this study, borehole geophysical logs were collected, heatpulse-flowmeter measurements were made, and borehole 

television surveys were run in seven boreholes ranging from 31 to 75 ft deep. Caliper logs and borehole television surveys were 

used to identify fractures and the location of possible water-bearing zones. Heatpulse-flowmeter measurements were used to 

identify the fractures that were water-bearing zones. Natural-gamma and single-point-resistance logs were used to correlate 

lithology across Area C and develop a lithologic model. 

Concentrations of PCE as high as 120 μg/L were measured in water samples from wells with water-bearing zones in 

the same interval of the aquifer where well HN-23A is screened. Water samples from wells with water-bearing zones above 

or below this interval had substantially lower concentrations of PCE (<1 to 8.3 μg/L). Wells screened or open to this interval 

yielded less than 0.5 gal/min, indicating the interval has low permeability, which may account for the small areal extent and slow 

migration of PCE. 

Acknowledgments

PCE data presented in this report were provided by Tetra Tech NUS, Inc., and ECOR Solutions, Inc. Borehole geophysical 

logs were collected by Randall Conger of the USGS. Borehole television surveys were made by Philip Bird of the USGS. Critical reviews of this report were completed by Randall Conger and Jason Sorenson of the USGS.

References Cited

ECOR Solutions, Inc., 2006, Site plan former NAWC Warminster, Pennsylvania: West Chester, Pa., 1 pl. 

ECOR Solutions, Inc., 2007, Quarterly monitoring report for the July 2007 performance monitoring event (fourth quarter FY 

2007): West Chester, Pa., variously paged.

Halliburton NUS Corporation, 1994, Remedial investigation report operable unit 3 Naval Air Warfare Center (NAWC) Warminster, Pennsylvania: Wayne, Pa., variously paged. 

Keys, W.S., 1990, Borehole geophysics applied to ground-water investigations: U.S. Geological Survey Techniques of WaterResources Investigations, book 2, chap. E-2, 149 p.

Sloto, R.A., and Low, D.J., 2001, Borehole geophysical data for the former Naval Air Warfare Center, Warminster, Bucks 

County, Pennsylvania: U.S. Geological Survey Open-File Report 01-347, CD ROM. 

Sloto, R.A., Macchiaroli, Paola, and Towle, M.T., 1996, Geohydrology of the Stockton Formation and cross-contamination 

through open boreholes, Hatboro Borough and Warminster Township, Pennsylvania: U.S. Geological Survey Water-Resources Investigations Report 96-4047, 49 p. 

Tetra Tech NUS, Inc., 2007, Area C source assessment report former Naval Air Warfare Center Warminster Pennsylvania: King 

of Prussia, Pa., variously paged.

Sloto— Interpretation of Borehole Geophysical Logs at Area C, Former Naval Air Warfare Center, Pennsylvania, 2007—Open-File Report 2008-1207