U.S. Department of the Interior

U.S. Geological Survey

Prepared in cooperation with U.S. Environmental Protection Agency

Region 4 Superfund Section

Geophysical Logging and Geologic Mapping Data in the 

Vicinity of the GMH Electronics Superfund Site near

Roxboro, North Carolina

Data Series 762
Cover: Typical granite boulder field near the GMH Electronics Superfund site, Person County,

North Carolina. Photograph by Timothy W. Clark, private contractor.
Geophysical Logging and Geologic 

Mapping Data in the Vicinity of the GMH 

Electronics Superfund Site near Roxboro, 

North Carolina 

By Melinda J. Chapman, Timothy W. Clark, and John H. Williams

Prepared in cooperation with the U.S. Environmental Protection Agency

Region 4 Superfund Section

Data Series 762

U.S. Department of the Interior

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

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2013

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reproduce any copyrighted materials contained within this report.

Suggested citation:

Chapman, M.J., Clark, T.W., and Williams, J.H., 2013, Geophysical logging and geologic mapping data in the vicinity 

of the GMH Electronics Superfund site near Roxboro, North Carolina: U.S. Geological Survey Data Series 762, 35 p.,

at http://pubs.usgs.gov/ds/762/.
iii

Acknowledgments

The authors would like to thank Harold Kelly and Justin Smith of the Person County Health 

Department for their assistance with well logging logistics, the collection of downhole camera 

logs, and support throughout the project.

We appreciate the assistance of Scott Caldwell, Erik Staub, and Kristen McSwain of the USGS 

North Carolina Water Science Center in the collection of geophysical logs and the passivediffusion-bag samples. Appreciation also is extended to USGS report colleague reviewers Brad 

Huffman and Eve Kuniansky.

v

Contents

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

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

Purpose and Scope ..............................................................................................................................3

Geologic Setting....................................................................................................................................3

Methods of Data Collection .........................................................................................................................3

Geologic Mapping Data................................................................................................................................7

Conventions Used to Record Surface Geologic Mapping Orientation Data.............................13

Borehole Geophysical Logging and Imaging Data.................................................................................13

Sampling Biases Inherent in the Borehole Surveys and the Surface 

Outcrop Measurements.....................................................................................................................21

Passive Diffusion-Bag Sampling Results.24

Hydrogeologic and Water-Quality Sections............................................................................................24

References Cited..........................................................................................................................................34

Appendixes ...................................................................................................................................................35

Figures

1. Map showing location of Person County within regional geologic terranes

in the North Carolina Piedmont physiographic province and the GMH Electronics 

Superfund Site within Person County and associated local geologic units.......................2

2. Map showing topography near the GMH Electronics Superfund site, wells

logged as part of this study, and lines of cross section shown in figures 25–30...............6

3. Photograph showing a typical granite boulder field near the GMH Electronics 

Superfund site. ..............................................................................................................................8

4. Map showing locations of geologic mapping stations and strike orientations

of bedding, foliation, and joints measured in outcrops. .........................................................9

5. Rose diagrams showing strike azimuth orientations of foliation measurements;

and joint measurements recorded in surface outcrops. Length of petal

corresponds to number of measurements. ............................................................................10

6. Photograph of a typical granite outcrop showing both steeply dipping

and lower-angle joint sets. Booklet is shown for scale. ......................................................11

7. Bar graphs showing the distribution of joint strike azimuth orientations

per 20 degree dip-angle categories: low dip-angle joints; medium dip-angle

joints; and steeply dipping joints..............................................................................................12

8. Optical televiewer images showing typical granite texture in well PS-103, 

foliation in well PS-106, a mafic lens in well PS-105, and enclaves near low 

angle and vertical fractures in well PS-100. ..........................................................................14

9. Optical televiewer images of wells PS-100, PS-099, and PS-106 showing typical 

open fractures in the subsurface granite near the GMH Electronics 

Superfund site. ............................................................................................................................15

10. Optical televiewer image of secondary weathered and sealed fractures in 

well PS-105, and typical iron staining along fractures in well PS-103...............................16

11. Rose diagram showing all structures measured in the 15 wells logged 

near the GMH Electronics Superfund site..............................................................................17
vi

12. Rose diagram showing strike orientation of subsurface foliation measurements 

from the 15 wells logged near the GMH Electronics Superfund site.................................17

13. Graphs showing altitude, depth, and inclination angle of primary fractures 

logged from 15 wells near the GMH Electronics Superfund Site. ......................................17

14. Rose diagram showing dominant orientations of open fractures measured

in the 15 open borehole wells from optical and acoustic televiewer images ..................17

15. Rose diagram map showing the distribution of subsurface structures measured

in 15 open borehole wells from optical and acoustic televiewer images.........................18

16. Borehole geophysical logs from well PS-093 showing fracture zones and

upward vertical flow at depth...................................................................................................19

17. Borehole geophysical logs from well PS-098 showing fracture zones and

downward vertical flow at depth. ............................................................................................20

18. Southwest-to-northeast three-dimensional diagram showing subsurface

structures in selected wells......................................................................................................22

19. Southwest-to-northeast three-dimensional diagram showing subsurface

structures in selected wells................................................................................................23

20. North-to-south three-dimensional diagram showing subsurface structures

in selected wells. ........................................................................................................................23

21. North-to-south three-dimensional diagram showing subsurface structures

in selected wells. ........................................................................................................................24

22. Map showing distribution of 1,1-dichloroethylene concentrations

detected in passive diffusion bag samples collected in wells near the

GMH Electronic Superfund Site during September 12 through

October 3–4, 2011........................................................................................................................25

23. Map showing distribution of 1,1,1 trichloroethane concentrations

detected in passive diffusion bag samples collected in wells near the

GMH Electronic Superfund Site during September 12 through

October 3–4, 2011........................................................................................................................26

24. Map showing distribution of benzene concentrations detected in passive

diffusion bag samples collected in wells near the GMH Electronic Superfund

Site during September 12 through October 3–4, 2011. .........................................................27

25. Schematic cross section A–A' showing depths to and orientations of

subsurface borehole fractures and generalized orientation of surface

geologic structural features. ....................................................................................................28

26. Schematic cross section B–B' showing depths to and orientations of

subsurface borehole fractures and generalized orientation of surface

geologic structural features. ....................................................................................................29

27. Schematic cross section A–A' showing depths to and orientations of

borehole fractures and detected 1,1-dichloroethylene and 1,1,1

trichloroethane concentrations from the passive diffusion bag sampling

during October 2011. ..................................................................................................................30

28. Schematic cross section B–B' showing depths to and orientations of borehole 

ractures and detected 1,1-dichloroethylene and 1,1,1 trichloroethane

concentrations from the passive diffusion bag samping during October 2011................31

29. Schematic cross section A–A' showing depths to and orientations of borehole

fractures and detected benzene concentrations from the passive diffusion bag

sampling during October 2011. .................................................................................................32

30. Schematic cross section B–B' showing depths to and orientations of borehole

fractures and detected benzene concentrations from the passive diffusion bag

samping during October 2011. ..................................................................................................33
vii

Tables

1. Characteristics of the 15 wells logged near of the GMH Electronics

Superfund site ...............................................................................................................................4

2. Fracture zones monitored using passive diffusion bags from

September 12 through October 3–4, 2011, near the GMH Electronics

Superfund site. ..............................................................................................................................7

3. FLASH program modeling results for heat-pulse flowmeter logs

collected from the 15 wells near the GMH Electronics

Superfund site .............................................................................................................................21

Appendixes 1–8

The appendix files are available at http://pubs.usgs.gov/ds/762/ in the formats listed below

1. Borehole geophysical logging field notes .......................................................................... PDF 

2. Heat-pulse flowmeter tool rinse volatile organic compound sample results......MS Excel 

3. Geologic structural measurements recorded near the GMH Electronics

Superfund site ................................................................................................................MS Excel 

4. Borehole geophysical logs showing depth of fracture zones, borehole flow,

and percent contribution of fractures to flow in the well ................................................ PDF 

5. Borehole geophysical image logs showing orientations of subsurface

structural features.................................................................................................................. PDF 

6. Rose diagrams showing dominant orientations of borehole

structural features.................................................................................................................. PDF 

7. FLASH modeling results for wells ...............................................................................MS Excel

8. Analytical results of the passive diffusion bag sampling October 2011 ...............MS Excel 

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

inch (in.) 2.54 centimeter (cm)

inch (in) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

ft2

/d (foot squared per day) 0.09290 meter squared per day (m2/d)

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

Abbrevations

ATV acoustic televiewer

DCA 1,1-dichloroethane

DCE 1,1-dichloroethylene

EPA U.S. Environmental Protection Agency

IAG interagency grant

Ma mega-annum (million years ago)

NCGS North Carolina Geological Survey

NPL National Priorities List

OTV optical televiewer

PDB passive diffusion bag

TCA 1,1,1 trichloroethane

USGS U.S. Geological Survey
Geophysical Logging and Geologic Mapping Data in the 

Vicinity of the GMH Electronics Superfund Site near 

Roxboro, North Carolina 

By Melinda J. Chapman,1 Timothy W. Clark,2 and John H. Williams1

Abstract

Geologic mapping, the collection of borehole geophysical 

logs and images, and passive diffusion bag sampling were 

conducted by the U.S. Geological Survey North Carolina 

Water Science Center in the vicinity of the GMH Electronics 

Superfund site near Roxboro, North Carolina, during March 

through October 2011. The study purpose was to assist the 

U.S. Environmental Protection Agency in the development of 

a conceptual groundwater model for the assessment of current 

contaminant distribution and future migration of contaminants. 

Data compilation efforts included geologic mapping of more 

than 250 features, including rock type and secondary joints, 

delineation of more than 1,300 subsurface features (primarily 

fracture orientations) in 15 open borehole wells, and the 

collection of passive diffusion-bag samples from 42 fracture 

zones at various depths in the 15 wells. 

Introduction

The GMH Electronics National Priorities List (NPL) 

Superfund site is located at the intersection of Halifax 

and Virgilina Roads, approximately 1 mile (mi) northeast 

of Roxboro, in Person County, North Carolina (fig. 1). 

Regionally, the study area is located in the eastern part of the 

Piedmont physiographic province in North Carolina, within 

an area of metamorphosed intrusive rocks in the Carolina 

Slate Belt (fig. 1; North Carolina Geological Survey, 1985). 

The area was later described as the Greensboro Intrusive Suite 

within the Virgilina Sequence of the Carolina terrane from the 

map by Hibbard and others (2006) in North Carolina.

The aquifer in the study area is complex, as elsewhere 

in the Piedmont physiographic province, consisting of a 

three-part system of shallow, weathered regolith, intermediate 

transition zone, and deeper fractured bedrock; the complexity 

is a result of multiple periods of structural deformation, 

metamorphism, and igneous intrusion. The weathered regolith 

component may include soil, saprolite, debris flow material, 

colluvium, and alluvium. The transition zone consists of 

includes partially weathered rock that is highly fractured 

(Chapman and others, 2005). Most of the groundwater-supply 

wells in the study area are completed in the bedrock part of the 

aquifer, where water moves through secondary fractures and 

other complex discontinuities, such as differential weathering 

along lithologic contacts. The shallow regolith is the primary 

storage reservoir and is the source of recharge to the deeper 

bedrock fractures (Heath, 1980, 1983, 1984, 1994). The 

bedrock has little primary porosity except where secondary 

openings are present in the form of fractures and other discontinuities. These secondary openings are the primary source of 

permeability in the bedrock. Thus, the mapping of fractures 

and other geologic features is critical to the understanding of 

groundwater transport to wells and the delineation of pathways 

of contaminant transport. 

In June 2010, the U.S. Geological Survey (USGS) received 

a request from the Environmental Protection Agency (EPA) 

Region 4 Superfund Section to assist in the development 

of a conceptual groundwater model in the area of the GMH 

Electronics Facility NPL Superfund site near Roxboro, North 

Carolina (formerly the Halifax Road DCE site) through an 

Interagency Agreement (IAG). The USGS effort included (1) 

the application of established and state-of-the-science borehole 

geophysical tools and methods used to delineate and characterize fracture zones in the regolith-fractured bedrock aquifer and 

(2) assistance toward the development of a conceptual model of 

flow in the bedrock part of the groundwater system that can be 

used to evaluate contaminant concentrations and future migration. The USGS effort was done in cooperation with the EPA 

Region 4 Superfund Section.

1

U.S. Geological Survey.

2

Private contractor.
2 Geophysical Logging and Geologic Mapping Data in the Vicinity of the GMH Electronics Superfund Site near Roxboro, N.C.

Base from digital files of:

U.S. Department of Commerce, Bureau of Census,

 1990 Precensus TIGER/Line Files-Political boundaries, 1991

U.S. Environmental Protection Agency, River File 3

U.S. Geological Survey, 1:100,000 scale 

Piedmont

Coastal Plain

Blue Ridge

34

35

36

83 84 81 82 79 80 77 76 78

Brevard fault zone

0 25 50 75 100 MILES

0 25 50 75 100 KILOMETERS

ATLANTIC

OCEAN

Figure 1. Location of Person County within regional geologic terranes in the North Carolina Piedmont Physiographic Province and

the GMH Electronics Superfund site within Person County and associated local geologic units (modified from North Carolina 

Geological Survey, 1985 and Hibbard and others, 2002). 

CP

PERSON

COUNTY

CP

Biotite gneiss and schist

Felsic metavolcanic rock

Felsic mica gneiss

Metamorphosed gabbro and diorite

Metamorphosed granitic rock

Metavolcanic epi-clastic rock

Metavolcanic rock

EXPLANATION

TENNESSEE

VIRGINIA

SOUTH CAROLINA

GEORGIA

Physiographic province boundary

Thrust fault with teeth on upthrown block

Central Piedmont Shear Zone

158

57 158

157 49

49

501

0 5 KILOMETERS 1 2 3 4

0 1 2 3 4 5 MILES

GMH Electronics

superfund site

Roxboro

Albemarle- SC sequence

Cary sequence

Virgilina sequence

Spring Hope

Roanoke Rapids

Suprastructural

terranes

Carolina Zone

Carolina

Piedmont Zone

EXPLANATION

Charlotte

Crabtree

Raleigh

Triplet

Falls Lake

Mesozoic basins

Late Paleozoic

 grantoids

Infrastructual

terranes 

Figure 1. Location of Person County within regional geologic terranes in the North Carolina Piedmont physiographic province and the 

GMH Electronics Superfund site within Person County and associated local geologic units (modified from North Carolina Geological 

Survey, 1985 and Hibbard and others, 2002).
Methods of Data Collection 3

Purpose and Scope

The purpose of this report is to present geophysical logging, 

geologic mapping, and groundwater-quality data collected in the 

vicinity of the GMH Electronics Superfund site near Roxboro, North 

Carolina. Borehole geophysical logs were used to delineate and characterize fractures zones in 15 open-borehole wells completed within the 

bedrock part of the aquifer. Geologic mapping was conducted within 

a 1-mile radius of the former GMH Electronics site and included the 

collection of data at 136 stations. Groundwater-quality samples were 

collected using passive diffusion-bag samplers at two to three fractures 

zones in each of the 15 wells that were geophysically logged. A total of 

46 samples were analyzed for volatile organic compounds, including 4 

quality assurance samples. 

Geologic Setting

Field geologic-mapping observations indicate the GMH 

Electronics NPL site is located within the Roxboro metagranite 

(Briggs and others, 1978) outcrop area. The Roxboro metagranite is a 

complex igneous body that intruded older volcanic and volcanoclastic 

rocks about 575 million years ago (Ma) during the Ediacaran Period 

(Neoproterozoic Era). The older volcanic and volcaniclastic rocks of 

the Carolina Terrane (Hibbard and others, 2002) were deposited at least 

25 million years earlier, because they were metamorphosed, faulted, 

and folded by the 600 Ma Virgilina deformation event. Virgilina 

sequence rocks are located a few miles from the site to the north, east, 

and west of the GMH site. The Roxboro metagranite and the surrounding metavolcanic rocks underwent a long period of erosion until they 

were subjected to a second and much later deformation event during 

the middle Paleozoic (~450 Ma) (Hibbard and others, 2002). Since that 

time, the region has continued to experience erosion and unroofing, 

resulting the present exposure of metagranite and metavolcanic rocks at 

land surface.

The Roxboro metagranite is predominately granitic in composition, although locally contains phases that are more representative of a 

granodiorite (Briggs and others, 1978). In addition, the pluton contains 

numerous enclaves and (or) xenoliths of gabbro and metavolcanic 

rock of the Carolina Terrane. Recent mapping of the North Carolina 

Geological Survey (NCGS) in the Caldwell and Cedar Grove 

topographic quadrangles within the southern portions of the Roxboro 

pluton indicate that the pluton is intruded by many diorite to gabbro 

dikes that trend northeast-southwest (Phil Bradley, North Carolina 

Geological Survey, written commun., 2010). 

In the area of study around the GMH site, several of these dikes intrude 

the Roxboro metagranite. Field observations made as part of the 

current study indicate that these dikes appear to have experienced the 

same metamorphism as the granite and are interpreted to have intruded 

the granite shortly after its formation in the Neoproterozoic Era. These 

dikes form discontinuities in the granite that may serve as permeable 

pathways in the subsurface.

Outcrops of the Roxboro metagranite are abundant in the area 

of the GMH site; unlike other areas of the North Carolina Piedmont, 

however, the majority of outcrops are away from streams and creeks. 

Most exposures occur as rounded boulder outcrops or pavements 

along topographic highs or as large boulder fields along the slope 

breaks of hillsides. Locally, boulders are so numerous that it is difficult 

to distinguish outcrops from float. Some rounded boulder outcrops 

exceed 4 meters (about 13 feet) in diameter. Many outcrops exhibit 

large planar joints or joint sets. Moderately to steeply dipping joints 

were the most common encountered and typically were quite planar 

and smooth. Sub-horizontal to low-angle joints, conversely, were 

more random in orientation, appeared rounded to curvi-planar in some 

locations, and were highly weathered at the surface.

Methods of Data Collection

Borehole geophysical logs and surface geologic mapping methods were used to characterize both subsurface and surface features in 

the fractured bedrock and overlying regolith near the GMH Electronics 

Superfund site (fig. 1). Borehole geophysical logs were collected in 15 

wells in the GMH Electronics site area from March through August 

2011 (table 1; fig. 2). These subsurface data were compared to local 

surface geologic mapping data collected by an independent contractor 

during June 2011. Passive diffusion bags were used to collect samples 

from the fifteen wells at two to three fracture zones per well for volatile 

organic compound analyses during September through October 2011.

 Surface geologic mapping consisted of noting the location of 

the outcrop, rock types (lithology and textural characteristics), and 

measuring orientations of structural features including joints and 

foliation (where present). Not all joints were measured because they 

were too numerous to conduct cost-effective mapping; therefore, only 

joints that appeared to represent the predominant joint-set orientation 

were measured.

Logs collected from each of the 15 wells included caliper, 

electrical resistivity, natural gamma, fluid temperature and resistivity, 

heat-pulse flowmeter (both ambient and stressed), and optical 

televiewer (OTV). Additionally, acoustic televiewer (ATV) logs were 

run in seven wells where the water was murky (poor visibility from 

OTV image). Field notes from geophysical logging activities are 

included in appendix 1. Rinse samples from borehole logging tools 

were collected prior to geophysical logging, between the logging of 

selected wells, and subsequent to the completion of logging. These 

rinse samples were analyzed for volatile organic compounds to ensure 

that no contaminants were transferred from well to well as part of 

the geophysical logging process. Analytical data from the boreholelogging-tool rinse samples are included as appendix 2.

Geophysical logging was used to characterize subsurface bedrock 

structures by primary lithology, fracture characteristics, foliation 

(if present), secondary lithologies, and lithologic contacts. Fracture 

zone characteristics delineated in the 15 wells logged as part of this 

study include depth, strike orientation, dip angle, measured flow, and 

modeled hydraulic characteristics. Fracture zones were delineated 

for each well using all of the available borehole logs, including visual 

delineation from OTV images, increases in caliper-log diameter, 

resistivity decreases (below the water level), and inflections or slope 

changes in the fluid temperature or fluid resistivity logs. 

Continuous, oriented digital color images of the granite bedrock 

in the subsurface were recorded from OTV image logs. These logs 
4 Geophysical Logging and Geologic Mapping Data in the Vicinity of the GMH Electronics Superfund Site near Roxboro, N.C. Table 1. Characteristics of the fifteen wells logged near the GMH Electronics Superfund site. [ft, foot; bls, below land surface; NAVD 88, North American Vertical Datum of 1988; gal/min, gallon per minute; na, data not available] USGS site identification number USGS Person County number Dates logged and associated water level (ft bls) Decimal latitude (degrees) Decimal longitude (degrees) Land surface altitude (feet above NAVD 88) Measuring point (feet above land surface) USGS logging total depth (ft bls) Casing depth logged (ft bls) Date drilled from well tag Yield from well tag (gal/min) 362453078562701 PS-093 13/1/2011; 25.46 

23/8/2011; 25.39

36.41478204981 –78.940768037684 750 0.56 142 42.5 5/28/1994 15

362458078563001 PS-094 13/2/2011; 29.25 

23/16/2011; 29.22 35/25/2011; 27.61

36.41610528620 –78.94177557440 758 0.91 124 42 9/27/1977 8

362457078564201 PS-095 13/2/2011; 24.98 

23/9/2011; 24.71

36.41581860000 –78.944917000000 730 0.92 305 28 4/10/1975 1

362515078562701 PS-096 13/3/2011; 26.71 

23/9/2011; 26.46 35/25/2011; 23.54

36.42067003000 –78.940772755890 728 0 72 62 na na

362500078563501 PS-097 13/3/2011; 17.61 

23/15/2011; 16.90 35/25/2011; 15.19

36.41669585713 –78.943168712300 740 0.80 143 52.5 10/11/1985 3

362508078562801 PS-098 13/3/2011; 29.37 

23/17/2011; 29.10

36.41876325650 –78.941047035900 746 0.25 62 33 2/3/1977 10

362458078562601 PS-099 13/22/2011; 25.19 

24/7/2011; 24.36 24/20/2011; 23.64

36.41606079282 –78.940516455890 752 0.95 302 64 8/31/1992 10

362456078562801 PS-100 13/22/2011; 24.88 

24/20/2011; 23.60 27/12/2011; 23.71

36.41559569920 –78.94110376871 754 1.00 144 37.5 2/28/1997 10

362454078562901 PS-101 13/23/2011; 22.62 

24/5/2011; 21.87 24/6/2011; 21.96 35/25/2011; 20.86

36.41499047921 –78.94145831477 748 1.05 202 55 na na

362505078562901 PS-102 13/23/2011; 20.86 

24/6/2011; 20.00 24/21/2011; 19.78 35/25/2011; 18.93 

36.41771314198 –78.941296157024 748 0.70 122 58 na na

362504078562301 PS-103 13/23/2011; 31.14 

24/19/2011; 31.51

36.41780158293 –78.93987872695 750 0.72 167 81 na na
Introduction 

5

Table 1. Characteristics of the fifteen wells logged near the GMH Electronics Superfund site.—Continued[ft, foot; bls, below land surface; NAVD 88, North American Vertical Datum of 1988; gal/min, gallon per minute; na, data not available] 

USGS site 

identification 

number

USGS 

Person 

County 

number

Dates logged 

and associated 

water level 

(ft bls)

Decimal latitude 

(degrees)

Decimal longitude 

(degrees)

Land surface 

altitude 

(feet above 

NAVD 88)

Measuring 

point 

(feet above 

land 

surface)

USGS 

logging total 

depth 

(ft bls)

Casing 

depth 

logged 

(ft bls)

Date drilled 

from well 

tag

Yield from 

well tag 

(gal/min)

362505078562301 PS-104 15/3/2011; 27.56 

27/13/2011; 27.43 35/26/2011; 27.10

36.41799702590 –78.93982650714 749 0.4 81 65 na na

362457078562901 PS-105 15/4/2011; 24.95 

27/14/2011; 23.81

36.41571260000 –78.94151600000 754 0.8 161 49 10/13/1997 7

362501078562601 PS-106 15/4/2011; 27.19 

28/1/2011; 27.60 28/2/2011; 27.76

36.41694770832 –78.94053306511 754 1 127 35 6/14/1996 15

362501078562701 PS-107 15/5/2011; 25.80 

35/26/2011; 25.28 16/8/2011; 25.22 28/8/2011; 26.32

36.41680600000 –78.94101471780 755 0.8 118 52 na na

1Tier 1 caliper, electrical/fluid combo, and optical televiewer logging.2Tier 2 heatpulse flowmeter logging. 3Acoustic televiewer logging.
6 Geophysical Logging and Geologic Mapping Data in the Vicinity of the GMH Electronics Superfund Site near Roxboro, N.C.

Altitude in feet above NAVD 88.

Contour interval is 4 feet

Line of section

Well location and U.S. Geological Survey 

county identification number

714

710

702

706

698

694

690

684

718

714

722

726

726

726

722 718

714

710

706

746

750

738

734

730

742

754

758

754

750

746

742

738

734

730

726

722

718

714

710

702

706

698

694

690

754

750

746

742

738

734

730

710

714

718

722

726

730

730

734

738

734

738

742

PS-095

PS-097

PS-094

PS-093

PS-106

PS-104

PS-103

PS-098

PS-096

PS-102

PS-107

PS-101

PS-100

PS-105

PS-099

718

A

A’

B

B’

A A’

VIRGILINA

ROAD

HALIFAX

ROAD

49

Base from digital files of:

13 Imagery Prime World 2D; ArcGIS Map Service

7856’45” 7856’15”

3625’15”

3625’

PS-093

EXPLANATION

0 400300200100 500 FEET

0 50 100 150 METERS

GMH Electronics

Superfund site

Underground

Storage Tank

release

Figure 2. Topography near the GMH Electronics Superfund site, wells logged as part of this study, and lines of 

cross section shown in figures 25–30.
are oriented using a magnetometer built into the borehole tool, and 

thus, the orientations of features such as fractures can be determined 

by using adjustments for local magnetic declination. Images of the 

granite were used to interpret texture, identify igneous enclaves, and 

delineate secondary compositional changes, such as the presence 

mafic lenses. Where the water in the well was too cloudy, an acoustic 

televiewer tool was used to image the fractures and determine 

orientations.

Orientations of subsurface fractures (both open and sealed), 

foliation, and lithologic contacts were determined from the OTV 

and ATV image logs using WellCad software ( aLt, 2010). Fracture 

orientations were determined from OTV and ATV images, which 

were corrected for magnetic declination (http://www.ngdc.noaa.gov/

geomagmodels/Declination.jsp; accessed April 2012) and borehole 

deviation. Orientations interpreted from the OTV image logs were 

adjusted for a local magnetic declination of 9° west and for measured 

borehole deviation. Subsurface geologic features were imported into 

Rockworks software (Rockware, Inc., 2010) for statistical analyses 

using rose diagrams and three-dimensional display of fracture planes 

at depth. The fracture orientation data were compared and used along 

with surface geologic mapping data to build a conceptual model of 

flow in the bedrock part of the aquifer in the study area. 

Fracture zones were selected for heat-pulse flowmeter logging 

(that is, stationary measurements of vertical borehole flow above 

and below the fracture zone) based on interpretations from caliper, 

electrical resistivity, and fluid (temperature and specific conductance) 

logs, and OTV/ATV image logs and interpretations. Results from 

both ambient (natural flow) and stressed (pumped flow) measurements from heat-pulse flowmeter logs were modeled for aquifer 

properties (hydraulic head differences, transmissivity, and radius 

of influence) using the recently published USGS FLASH program 

(Day-Lewis and others, 2011; http://water.usgs.gov/ogw/flash/). 

Positive heat-pulse flow measurements indicated upflow, whereas 

negative heat-pulse flow measurements indicated downflow. 

To evaluate the distribution of volatile organic contaminants 

within the vertical boreholes in the wells, two to three fracture 

zones were selected for passive diffusion bag (PDB) monitoring 

(Vroblesky, 2001a, b) in each of the 15 wells, based on interpretations of flow measured near delineated and modeled contribution 

of the fracture zones. Since the mid-1990s, PDBs have been used 

in numerous studies as a means of screening open boreholes or 

multiple-screened wells for vertical contaminant distribution prior 

to the use of more expensive monitoring methods such as straddle 

packers.

A total of 42 fracture zones selected from borehole geophysical 

logs and images and heat-pulse flowmeter data modeling were monitored using the PDBs from September 12 through October 3–4, 2011 

(table 2). PDBs were lowered to the average depth of the selected 

fractures and remained in the well for the entire monitoring period 

(2–3 weeks). The PDBs were then retrieved uphole, and water from 

the bag was emptied into 40-milliliter (mL) glass vials for analysis 

of volatile organic compounds. The samples were analyzed by the 

EPA National Exposure Research Laboratory in Athens, Georgia 

(http://www.epa.gov/greeningepa/facilities/athens-ord.htm; accessed 

April 2012). Trip-blank and replicate-sample analyses were also 

conducted for quality assurance and quality control. 

Table 2. Fracture zones monitored using passive diffusion bags 

from September 12 through October 3–4, 2011.

[All depths are in feet below land surface; na, not applicable]

USGS 

county 

well 

number

Bag 

depth 1 

 Bag 

depth 2 

Bag 

depth 3 

Casing 

depth 

Total well 

depth

PS-093 70 122 na 42.5 141.5

PS-094 49 65 123 42 124.4

PS-095 39 85 137 28 304.5

PS-096 64 70 na 62 72.4

PS-097 55 98 139 52.5 143

PS-098 40 54 60 33 62.4

PS-099 74 87 276 64 302

PS-100 45 113 139 37.5 144

PS-101 79 149 196 55 202.4

PS-102 65 83 119 58 122

PS-103 110 124 153 81 167

PS-104 68 74 na 65 80.5

PS-105 99 105 152 49 161

PS-106 41 76 120 35 127

PS-107 55 70 103 52 118

Geologic Mapping Data 7

Geologic Mapping Data

Structural data recorded as part of local geologic mapping 

within a 1-mi radius of the GMH site as part of this study during 

June 2011 indicate that most of outcrops near the GMH Electronics 

site are massive and, hence, referred to as a “granite” (fig. 3 and 

app. 3). The granite is described as massive, medium-grained 

intrusive or weakly foliated (fig. 3). The rock type at 91 percent of 

the 137 mapping stations was described as granite (app. 3); rocks 

mapped at other stations included weakly layered and banded, semimassive and aphanitic dacites, pegmatite, amygdaloidal metagabbro, 

and foliated felsic crystal and crystal tuffs. Figure 4 shows the areal 

distribution of geologic structural data in the study area. Weak 

foliation was measured, having a dominant strike orientation range 

of 20°–40° (fig. 5A) (9 of 17 outcrops), dipping to the southeast at 

angles ranging from 25° to 86°, averaging 60° (app. 3).

Numerous joint features were measured (205 of 252 measurements; app. 3), with spacing ranging from less than 1 to greater than 

3 meters (about 10 feet). A photograph of a typical outcrop showing 

joint sets is shown in figure 6. 

The dominant strike orientations for the joint sets measured 

was 20°–30° (fig. 5B). For the low dip-angle joint, dipping 

30 degrees or less (19 of 205 measurements), the primary strike 

orientation was 141°–160° (fig. 7A). The medium dip-angle joint 

sets, dipping 31°–60° (33 of 205 measurements), had variable strike 

orientations (fig. 7B). For the steeply dipping joints—dipping 61° or 

greater (153 of 205 measurements)—dominant strike orientations 

were 0°–40°, 101°–140°, and 201°–220° (fig. 7C).
8 Geophysical Logging and Geologic Mapping Data in the Vicinity of the GMH Electronics Superfund Site near Roxboro, N.C.

Figure 3. A typical granite boulder field near the GMH Electronics Superfund site.
Methods of Data Collection 9

55

54

55 57

57

56

71 72

73

74

79 79

79

86

87

85

84

83

82

83

83

78

81

81

80

80

76

77

77

75

75

68

61

61 63

64

64

64

65

66 66

67 67

67 60

60

59

58

58

69

1

62

101

95

94

97

97

98

4

3 3

2 3

99

89

89

90 93

92

91

96

88

88

88

107

107

111 111

108

108

108 110

110

109

113

116

118

118

119 119

123 123 114 114

106

112

112

112

115

117

127

127 127

126 124

124

124124

125

125

125

40

136

37

38

38 39

39

39

128

128 129

130 PS-093

104

102103

100

120

121 121

121

PS-098

PS-102

PS-106 PS-097

PS-096

PS-107

PS-094

PS-104

PS-103

PS-100

PS-099

PS-101

PS-105

PS-095

30

19

20

21 22

17

17

18

18

18

31

27

28

29

52

51 50

48

49

49 47

46

33 34 32

24

23 25

25 26

135

132

132

132

134 134

131 131

131 133

105

122

9

8

6

15 15

15

14

14

16

13

12

12 11

10

5

5

53 53

36 36

735 7

42

41

42

43 43

44

45

45

ALLEY

CLAY ROAD CLAY

THOMAS

ROAD

PROVIDENCE

THAXTON

LONGHURST

ROAD

ROAD

BROAD

ROAD

VIRGILINA

ROAD

GRAVITTE

NELSON

LOOP ROAD

ROAD

ROAD

HOLLOWAY

HALIFAX

ROAD

49

TODD

ROAD

LOFTIS

LOOP

ROAD

JAMES

AND

MCGHEE

ROAD

Roxboro feature, SM_code—Where four 

 or more symbols are associated with a

 single mapping station, they are encircled

 with a dashed line and labeled as a group

Bedding

Foliation

EXPLANATION

93

PS-098 Well location and number

127

127

Joint set

Float

36°25'45"

36°25'15"

36°24'45"

36°24'15"

36°26'15"

78°57'45" 78°57'15" 78°56'45" 78°56'15" 78°55'45"

Base modified from digital files supplied by

13 Imagery Prime World 2D and ArcGIS Map Service

0 1,500 3,000 FEET

0 400 800 METERS

GMH Electronics

Superfund site

Underground

storage tank

release

Figure 4. Locations of geologic mapping stations and strike orientations of bedding, foliation, and joints measured in outcrops.
2

2

2

2

4

4

4

4

6

6

6

6

8

8

8

8

10

10

10

10

12

12

12

12

14

14

14

14

1618

16

18

18

16 18

16

0

45

90

135

180

225

270

315

A

B

2

2

2

2

4

4

4

4

6

6

6

6

8

8

8

8

1012

10

12

12

10 12

10

0

45

90

135

180

225

270

315

Figure 5. Strike azimuth orientations of (A), foliation measurements; and (B), joint 

measurements recorded in surface outcrops. Length of petal corresponds to percent 

of the total number of measurements.

10 Geophysical Logging and Geologic Mapping Data in the Vicinity of the GMH Electronics Superfund Site near Roxboro, N.C.
Methods of Data Collection 11

Figure 6. Photograph of a typical granite outcrop showing both steeply dipping and 

medium-angle joint sets. Booklet is shown for scale.
Number of measurements

Strike azimuth orientation, in degrees

6

5

4

3

2

1

0

6

5

4

3

2

1

0

25

20

15

10

5

0

21–40

0–20

41–60

61–80

81–100

101–120

121–140

141–160

161–180

181–200

201–220

221–240

241–260

261–280

281–300

301–320

321–340

341–360

A

B

C

Figure 7. Bar graphs showing the distribution of joint strike azimuth orientations per 20 degree dipangle categories: (A) low dip-angle joints; (B) medium dip-angle joints; and (C) steeply dipping joints.

12 Geophysical Logging and Geologic Mapping Data in the Vicinity of the GMH Electronics Superfund Site near Roxboro, N.C.
Borehole Geophysical Logging and Imaging Data 13

Conventions Used to Record Surface Geologic 

Mapping Orientation Data

Bedrock discontinuities, such as foliation and 

joints, measured and recorded for this study are 

planar features. Dip directions were recorded using 

the convention that horizontal planes are recorded as 

having 0° dips and vertical features as having 90° dips, 

with intermediate dip-angles ranging between these two 

extremes. For planar features, strike is defined as the 

compass orientation of the horizontal line lying within 

that plane. Strike azimuths of 0° to 360° were recorded 

using the familiar convention in which 0° and 360° 

correspond to true north, 90° corresponds to east, 180° 

corresponds to south, and 270° to west. Because all 

lines extend in two directions, bedrock discontinuities 

were measured and recorded using the right-hand rule 

convention (strike azimuth is measured with the dip 

inclined toward the right). Two planar features assigned 

strikes that are parallel (for example, 45° and 225°) 

differ in that one feature dips to the southeast and the 

other to the northwest, respectively (Chapman and 

Huffman, 2011).

Borehole Geophysical Logging and 

Imaging Data

The 15 wells used for borehole geophysical logging 

generally were located within a 1/3-mi radius of the GMH 

site (fig. 2 and table 1; appendixes 4 and 5). Well depths 

ranged from about 62 to 305 feet (ft) below land surface. 

The casing depths compiled in table 2 indicate the inferred 

regolith thickness ranges from about 28 to 81 ft. The former 

private supply wells were drilled from 1975 through 1997 and 

had reported yields ranging from 1 to 15 gallons per minute 

(gal/min) (table 1). Groundwater levels measured in all 15 

wells during March through August 2011 ranged from 15.19 to 

31.51 ft below land surface.

Figure 8 shows examples of typical (OTV) images of 

the granite bedrock and secondary textural features. Fractures 

were characterized as either primary (open), secondary 

(partially open or weathered), or sealed, as shown in 

appendix 5. Figure 9 shows typical open subsurface fractures 

and figure 10 shows typical secondary and sealed subsurface 

fractures logged in the 15 wells near the GMH Electronics 

Superfund site. 

More than 1,300 subsurface structural measurements 

(orientations) were interpreted from optical and acoustic 

televiewer images collected from the 15 wells logged near the 

GMH Electronics site (fig. 2). Visible foliation was measured, 

but was very limited in distribution. (fig. 8B). Fracture 

characterization included primary (open, fig. 9), secondary 

(partially open/weathered), and sealed fractures (often filled 

with secondary minerals) (fig. 10). Figure 11 presents strike 

orientations for all structures measured in the 15 wells logged 

as part of this study. The subsurface structure dataset indicates 

that the most common strike orientations are 20°–30°, 

10°–20°, and 120°–160° (fig. 11). Subsurface structural 

orientations for individual wells are shown in appendix 6. The 

subsurface foliation measurements (fig. 8B) were not common, 

composing approximately 3 percent of the subsurface dataset, 

but the dominant orientation of 20°–30° (fig. 12) parallels that 

of the surface foliation data (fig. 5A). 

Typical open or primary subsurface fractures logged in 

the 15 wells in the study area are similar to those shown in 

figure 9, having apertures ranging from 1 to 21 inches (in.) 

and borehole diameters of up to 20 in., which is the limit of 

the caliper logging tool used. The primary open fractures were 

between about 593 and 716 ft in altitude, 35 to 152 ft below 

land surface, and variable in inclination angle (fig. 13). 

 The dominant strike orientations for the open fractures 

were 150°–160°, 160°–170°, 170°–180°, 20°–30°, and 

140°–150° (fig. 14 and app. 6); the average dip angle for 

the open fractures was 41°. The 20°–30° set parallels the 

dominant joint set strike measured in all surface outcrops 

(fig. 5B) and a steeply dipping joint subset (fig. 7C). The 

150°–160° and 140°–150° fracture orientations parallel the 

low dip-angle joint set measured in outcrops (fig. 7A). Other 

joint sets measured in outcrops were not observed in the wells, 

which is probably a result of vertical sampling bias (discussed 

later). The 160°–180° fracture sets observed in the wells were 

not predominant in the surface-outcrop measurements, which 

again, is most likely a result of the sampling bias discussed 

later.

The areal distribution of structures measured in the 15 

wells logged is shown in figure 15 The most common dominant fracture orientation within the well set was 151°–160°, 

which was measured in five wells. Other dominant orientations measured in 4 of the 15 wells were 21°–30°, 91°–100°, 

111°–120°, 131°–140°, and 181°–190°. The 21°–30° primary 

subsurface fracture orientation parallels that of surface 

foliation and joints (fig. 5). The 111°–120° and 131°–140° 

subsurface fracture sets were measured as secondary surface 

joint sets (fig. 5B). 

Ambient vertical groundwater flow was measured in 

only 3 of the 15 wells—PS-093, PS-096, and PS-098 (app. 7). 

Figures 16 and 17 and appendix 7 show typical borehole 

geophysical logs in which fracture zones were delineated and 

flow was measured and modeled. For ambient measurements, 

measured flow often was near zero or “no flow.” Values of 

0.01 to 0.02 gallons per minute (gal/min) are near the lower 

resolution of the measuring tool and, thus, may be considered 

“noise.” 

In well PS-093 (fig. 16), inflow is modeled at the 122-ft 

fracture zone, outflow is modeled near the 70-ft fracture zone, 

and flow is upward between the two zones (see FLASH model 

results in app. 7A). In well PS-098 (fig. 17), inflow is at the 

41-ft fracture zone, outflow is near the 53-ft fracture zone, 

and flow is downward between the two zones. Flow direction 
14 Geophysical Logging and Geologic Mapping Data in the Vicinity of the GMH Electronics Superfund Site near Roxboro, N.C.

A

154

155

156

157

84

85

86

87

88

0 90 180 270 0

N E S W N

B

0 90 180 270 0

N E S W N

C

0 90 180 270 0

N E S W N

54

55

56

57

58

59

60

61

62

63

64

65

D

0 90 180 270 0

N E S W N

67

68

69

70

71

Foliation

Mafic lens

Enclaves

Depth, in feet below land surface

Figure 8. Optical televiewer images showing (A) typical granite texture in well PS-103, (B) foliation in well PS-106, (C) a mafic lens in 

well PS-105, and (D) enclaves near low angle and vertical fractures in well PS-100.
Borehole Geophysical Logging and Imaging Data 15

Tool maximum

range was 20 inches

A B

Caliper, in inches Caliper, in inches Caliper, in inches 

5.5 13 6 8

C

43

44

45

46

69

70

71

72

73

74

75

44

45

46

47

48

49

50

51

52

53

Depth, in feet below land surface

0 90 180 270 0

N E S W N

0 90 180 270 0

N E S W N

0 5.5 22  90 180 270 0

N E S W N

Figure 9. Optical televiewer images of wells (A) PS-100, (B) PS-099, and (C) PS-106 showing typical open fractures in the subsurface 

granite near the GMH Electronics Superfund site.
16 Geophysical Logging and Geologic Mapping Data in the Vicinity of the GMH Electronics Superfund Site near Roxboro, N.C.

121

122

123

124

125

126

127

128

129

Depth, in feet below land surface

Weathered, secondary

fractures

Sealed

fractures

128

129

130

131

A B

Caliper, in inches Caliper, in inches 

0 6 8 6 8  90 180 270 0

N E S W N

0 90 180 270 0

N E S W N

Figure 10. Optical televiewge of (A) secondary weathered and sealed fractures 

in well PS-105, and (B) typical iron staining along fractures in well PS-103.
Borehole Geophysical Logging and Imaging Data 17

5

5

6

6

7

7

89 1234 1 2 3 4 5 6 7 8 9

8

9

1

2

3

4

5

6

7

8

9

1

2

3

4

0 180

45

90

135

225

270

315

Figure 11. Rose diagram showing all structures measured in 

the 15 wells logged near the GMH Electronics Superfund site.

Length of petal corresponds to percent of the total number of 

measurements.

12345 1 2 3 4 5

1

2

3

4

5

5

1

2

3

4

0 180

45

90

135

225

270

315

Figure 12. Rose diagram showing strike orientation of 

subsurface foliation measurements from the 15 wells logged 

near the GMH Electronics Superfund site. Length of petal 

corresponds to percent of the total number of measurements.

50

40

30

20

10

0

60

40

20

0

100

50

0

581–600

0–50

51–100

101–150

>151

<1 1–30 31–60 61–90

601–620 621–640

Altitude, in feet above NAVD 88

Depth below land surface,

in feet

641–660 661–680 681–700 701–720

Inclination angle, in degrees

Number of primary fractures

A

B C

Figure 13. Graphs showing (A) altitude, (B) depth, and (C) 

inclination angle of primary fractures logged from 15 wells 

near the GMH Electronics Superfund site.

2

2

4 2

4

4

6

6

6

8

8

8

1012 42 6 8 10 12

10

12

12

10

0

45

90

135

180

225

270

315

Figure 14. Rose diagram showing dominant orientations of open 

fractures measured in the 15 open borehole wells from optical 

and acoustic televiewer images. Length of petal corresponds to 

percent of the total number of measurements.
18 Geophysical Logging and Geologic Mapping Data in the Vicinity of the GMH Electronics Superfund Site near Roxboro, N.C.

PS-095

PS-097

PS-094

PS-093

PS-106

PS-104

PS-103

PS-098

PS-096

PS-102

PS-107

PS-101

PS-100

PS-105

PS-099

Well location and U.S. Geological Survey 

county identification number

GMH Electronics superfund site

VIRGILINA

ROAD

HALIFAX

ROAD

49

Base from digital files of:

13 Imagery Prime World 2D; ArcGIS Map Service

7856’45” 7856’15”

3625’15”

3625’

PS-093

EXPLANATION

Rose diagram displaying

strike azimuth of measured

borehole structures. Length of

petal corresponds to percentage

of measurements.

315

135

0180

45

225

270 10 2 90 2

4

6

8

10

12

2

4

6

8

10

12

12 68 4 2 4 6 8 1012

0 400300200100 500 FEET

0 50 100 150 METERS

Underground Storage

Tank release

Figure 15. Rose diagram map showing the distribution of subsurface structures measured in 15 open borehole wells from 

optical and acoustic televiewer images.
Borehole Geophysical Logging and Imaging Data 19

Depth below land surface, in feet

Inflow

Outflow Upflow

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

Caliper, in inches 

6 7.5

Natural gamma, in APIU

0 200

0 3,000

0 3,000

65 68

0 350

0 4,000

0 4,000

Ohms

–0.2

–0.05 0.05

Gallons per

minute

Modeled

flow direction

–0.7 0.7

0.2

Casing depth at

42.5 feet below

land surface

13 percent

of flow

87 percent

of flow

Water level

at 25.46 feet below

land surface

1.0 DCE

1.0 BZ

at 70 feet

0.95 DCE

at 122 feet

EXPLANATION

Resistivity 16-inch normal

Resistivity 64-inch normal

Resistance

Lateral resistivity 48-inch normal

Temperature, in degrees Farenheit

Specific conductance, in microsiemens

 per centimeter

Delta temperature, in degrees Farenheit

Heatpulse flow ambient

Heatpulse flow stressed

American Petrolium Institute Units

1,1-dichloroethylene

Benzene

APIU

DCE

BZ

Figure 16. Borehole geophysical logs from well PS-093 showing fracture zones and upward vertical flow at depth.
20 Geophysical Logging and Geologic Mapping Data in the Vicinity of the GMH Electronics Superfund Site near Roxboro, N.C.

26 percent

of flow

73 percent

of flow

0

5

10

15

20

25

30

35

40

45

50

55

60

65

5.5 20

0 200

0 3,000

0 4,000

60 70

115 140

0 4,000

0 4,000

Gallons per

minute

–0.5

–0.07 0.07

–0.2 0.2

0.5

Casing depth at

33 feet below

land surface

Depth below land surface, in feet

Water level at

29.37 feet below

land surface

Groundwater

flow direction

Inflow

Outflow Downflow

3.5 1,2 DCA

at 40 feet

4.0 1,2 DCA

at 54 feet

4.0 1,2 DCA

at 60 feet

EXPLANATION

Resistivity 16-inch normal

Resistivity 64-inch normal

Resistance

Lateral resistivity 48-inch normal

Temperature, in degrees Farenheit

Specific conductance, in microsiemens

 per centimeter

Delta temperature, in degrees Farenheit

Heatpulse flow ambient

Heatpulse flow stressed

American Petrolium Institute Units

1,1-dichloroethane

APIU

DCA

Ohms

Natural gamma, in APIU

Caliper, in inches 

Figure 17. Borehole geophysical logs from well PS-098 showing fracture zones and downward vertical 

flow at depth.
Borehole Geophysical Logging and Imaging Data 21

arrows in figures 16 and 17 and in appendix 4 reflect modeled (simplified) results shown in appendix 7. For example, 

flow may have been measured at several fractures; however, 

FLASH modeling results typically portray only dominant 

fracture zones, thereby reducing the number of fractures 

contributing flow. A larger number of contributing fracture 

zones were initially modeled using FLASH; however, 

some fracture zones were removed from the model because 

erroneous hydraulic heads were simulated (for example, 

1,000 feet higher head compared to the zone above). 

Transmissivity estimates for the 15 wells ranged from 

0.41 to 154 feet squared per day (ft2/d), and estimates of the 

radius of influence ranged from 9.5 to 113 ft (table 3). Initial 

estimates of transmissivity were made using specific capacity 

calculations from the stressed heat-pulse flowmeter logs 

and modeled transmissivity relations for crystalline rocks in 

southeastern New York (John H. Williams, U.S. Geological 

Survey, written commun., 2012). The depth of fractures 

where flow was modeled ranged from 41 to 152 ft below 

land surface (app. 7). 

The three-dimensional diagrams of borehole structures 

shown in figures 18–21 indicate potential interconnectivity 

of fracture zones between wells. Fractures having similar 

dip azimuths and angles are recognized as parallel fracture 

images. The distribution of subsurface fractures and their 

associated three-dimensional orientations can potentially 

control contaminant migration, depending on the location 

of source areas and hydraulic head distributions between 

fracture zones. 

Sampling Biases Inherent in the Borehole Surveys 

and the Surface Outcrop Measurements

Cursory inspection of the borehole structural 

data tables and diagrams in this report and the surface 

geologic structural data show differences in their relative abundances of planar features counted within the 

various general orientation classes. This does not mean 

that the two sets of data are inconsistent with each 

other, but rather that the two data sets are more useful 

when used together. Vertical boreholes are statistically 

less likely to intersect steeply dipping planar features 

than more flat-lying features, whereas surface outcrops 

provide a relatively better sample of more steeply dipping features. With the exception of the rare steep cliff 

face or high roadcut, outcrops provide relatively less 

opportunity to count and measure flat-lying features 

than vertical boreholes (Chapman and Huffman (2011).

Another difference is in the way features were 

tabulated in the two data sets. When interpreting 

features in borehole images, hydrogeologists measure 

and count individual features. During surface mapping, 

geologists assign measurements to sets of features 

having a similar orientation. For any given map station, 

which may represent an entire outcrop or group of 

outcrops, one recorded measurement could represent 

a group of 1, 10, or 100 parallel similar joints or 

foliations (Chapman and Huffman, 2011).

Table 3. FLASH program modeling results for heat-pulse 

flowmeter logs collected from the fifteen wells near the GMH 

Electronics Superfund site.

[ft2/d; foot squared per day; ft, foot; gpm, gallon per minute; na, not available]

Well Transmissivity 

(ft2

/d)

Radius of 

influence 

(ft)

Yield 

reported 

(gpm)

PS-093 22 23 15

PS-094 20 22 8

PS-095 2.6 24 1

PS-096 15 23 na

PS-097 7.1 13 3

PS-098 154 24 10

PS-099 12 113 10

PS-100 135 25 10

PS-101 1.7 22 na

PS-102 41 24 na

PS-103 0.41 9.5 na

PS-104 28 24 na

PS-105 2.3 17 7

PS-106 133 24 15

PS-107 35 25 na
22 Geophysical Logging and Geologic Mapping Data in the Vicinity of the GMH Electronics Superfund Site near Roxboro, N.C.

PS-095

Southwest Northeast

PS-097

PS-094

PS-106

PS-104

PS-103

PS-107

Primary fracture

Secondary fracture

Foliation

Scaled fractures

Blue

Red

Green

Purple

EXPLANATION

Figure 18. Southwest-to-northeast three-dimensional diagram showing subsurface structures in selected wells.
Borehole Geophysical Logging and Imaging Data 23

PS-094

PS-107

PS-106

Primary fracture

Secondary fracture

Foliation

Scaled fractures

Blue

Red

Green

Purple

EXPLANATION

Southwest Northeast

Figure 19. Southwest-to-northeast three-dimensional diagram showing subsurface structures in selected wells.

PS-096

PS-098

PS-102 PS-094

PS-100

PS-101

PS-093

PS-106

PS-105 Primary fracture

Secondary fracture

Foliation

Scaled fractures

Blue

Red

Green

Purple

EXPLANATION

PS-107

North South

Figure 20. North-to-south three-dimensional diagram showing subsurface structures in selected wells.
24 Geophysical Logging and Geologic Mapping Data in the Vicinity of the GMH Electronics Superfund Site near Roxboro, N.C.

PS-104

PS-103

PS-102

PS-106

Primary fracture

Secondary fracture

Foliation

Scaled fractures

Blue

Red

Green

Purple

EXPLANATION

PS-107

Northeast Southwest

Figure 21. North-to-south three-dimensional diagram showing subsurface structures in selected wells.

Passive Diffusion Bag Sampling Results

Contaminants detected by the PDB sampling include 

1,1,1-trichloroethane (TCA), 1,1-dichloroethane (DCA), 

1,1-dichloroethylene (DCE), benzene, o-xylene, cyclohexane, 

isopropylbenzene, 1,2-dichloroethane, and methyl-tert-butylether. Acetone was detected in the trip blank sample and in 

several PDB well samples, but is not a known contaminant 

in the area (app. 8). The manufacturer of the PDBs prepared 

them pre-filled with deionized water and had a known problem 

with acetone (Kris McSwain, U.S. Geological Survey, written 

commun., 2011). Methyl ethyl keytone also was detected 

in the trip blank, but not in any of the PDB well samples 

analyzed. Detected concentrations were as high as 1,600 μg/L 

DCE and 400 μg/L TCA in well PS-106, and 2,300 μg/L 

benzene in well PS-102. Depths of detected contaminants 

ranged from 39 to 276 ft below land surface (app. 8). Figures 

22–24 show the areal distribution of DCE, TCA, and benzene 

detected from the PDB sampling as part of this study. 

Hydrogeologic and Water-Quality 

Sections

Two 2-dimensional cross-sections were constructed 

parallel to Virgilinia and Halifax Roads, oriented and S. 64° 

W. to N. 64° E., and North-South, respectively (A–A′, B–B′; 

figs. 2, 25 and 26) to display both collected surface geologic 

structural data and the subsurface fracture orientation data. 

Geologic structural features were generalized in both cross 

sections using a 30° orientation for foliation, and displaying 1 

low-angle joint set having a strike orientation of 150° and dip 

angle of 21°, and 3 steeply dipping sets having strike orientations of –20°, 120°, and 210°, and a dip angle of 78°. Borehole 

fracture sets are shown at the depths where PDB samples were 

collected. All dip angles of surface geologic features and borehole fractures were adjusted to the respective cross-section 

plane orientation. The distribution of 1,1 dichloroethylene 

(DCE) and 1,1,1 trichloroethane (TCA) with depth is shown 

in figures 27 and 28 and the distribution of benzene with depth 

is shown in figures 29 and 30 along the same cross-sections, 

A–A′ and B–B′, used for figures 25 and 26. 
Hydrogeologic and Water-Quality Sections 25

PS-095

PS-097

PS-094

PS-093

PS-106

PS-104

PS-103

PS-098

PS-096

PS-102

PS-107

PS-101

PS-100

PS-105

PS-099

1.0, 0.95

9.5, 9.4, 8.9

24, 16, 18

480, 530, 490

970, 990

690, 1,600,

1,300

40, 110, 100

630, 750, 760

1,000, 1,000,

1,200

0.99, 0.98, 1.6

nd

nd

nd

GMH Electronics

Superfund site

1

10

10

100

100

10

1

100

1,000

10

1

100

1

nd

nd

VIRGILINA

ROAD

HALIFAX

ROAD

HALIFAX

ROAD

49

Base from digital files of:

13 Imagery Prime World 2D; ArcGIS Map Service

7856’45” 7856’15”

3625’15”

3625’

PS-093

EXPLANATION

Underground Storage

Tank release

0 400300200100 500 FEET

0 50 100 150 METERS

100

1.0, 0.95

nd

Line of equal DCE concentration,

in micrograms per liter

Well location, U.S. Geological Survey 

county identification number, and

DCE concentrations

Compound not detected

Figure 22. Map showing distribution of 1,1 dichloroethylene (DCE) concentrations detected in passive diffusion bag 

samples collected in wells near the GMH Electronic Superfund site during September 12 through October 3–4, 2011.
26 Geophysical Logging and Geologic Mapping Data in the Vicinity of the GMH Electronics Superfund Site near Roxboro, N.C.

nd

1.2, 1.2, 1.2

PS-095

PS-097

PS-094

PS-093

PS-106

PS-104

PS-103

PS-098

PS-096

PS-102

PS-107

PS-101

PS-100

PS-105

PS-099

4.4, 3.2, 3.7

270,290, 330

180,400, 310

62, 68, 68

140, 150

3.7, 11, 10

59, 70, 72

nd

nd

nd

nd

nd

10

100

100

10

nd

VIRGILINA

ROAD

HALIFAX

HALIFAX

ROAD

49

ROAD

Base from digital files of:

13 Imagery Prime World 2D; ArcGIS Map Service

7856’45” 7856’15”

3625’15”

3625’

0 400300200100 500 FEET

0 50 100 150 METERS

GMH Electronics

Superfund site

Line of equal TCA concentration,

in micrograms per liter

Well location, U.S. Geological Survey 

county identification number, and

TCA concentrations

Compound not detected

100

10

10

1.2, 1.2, 1.2

nd

PS-101

EXPLANATION

Underground Storage

Tank release

Figure 23. Map showing distribution of 1,1,1 trichloroethane (TCA) concentrations detected in passive diffusion bag 

samples collected in wells near the GMH Electronic Superfund site during September 12 through October 3–4, 2011.
Hydrogeologic and Water-Quality Sections 27

PS-095

PS-097

PS-094

PS-093

PS-106

PS-104

PS-103

PS-098

PS-096

PS-102

PS-107

PS-101

PS-100 PS-105

PS-099

VIRGILINA

ROAD

HALIFAX

49

ROAD

Base from digital files of:

13 Imagery Prime World 2D; ArcGIS Map Service

7856’45” 7856’15”

3625’15”

3625’

0 400300200100 500 FEET

0 50 100 150 METERS

Line of equal benzene concentration,

in micrograms per liter

Well location, U.S. Geological Survey 

county identification number, and

benzene concentrations

Compound not detected

100

1.0

nd

PS-093

EXPLANATION

1.0, nd

nd, nd, 5.6

nd, 0.75, nd

0.69, nd, nd

nd

nd

nd

1.6, 1.6, 2.5

2.6, 2.4, 8.2

2,100, 2,300, 1,900

680, 640, 670 GMH Electronics

Superfund site

nd

nd

nd

nd

10

1

10

100

100

1,000

1,000

Underground Storage

Tank release

1

1

1

Figure 24. Map showing distribution of benzene concentrations detected in passive diffusion bag samples collected in 

wells near the GMH Electronic Superfund site during September 12 through October 3–4, 2011.
28 Geophysical Logging and Geologic Mapping Data in the Vicinity of the GMH Electronics Superfund Site near Roxboro, N.C.

800

750

700

650

600

550

500

450

400

PS-095

PS-097

Land surface

0 500 1,000 FEET

0 100 200 METERS

Casing

Open

borehole

A

VERTICAL EXAGGERATION x 4

DATUM IS NAVD 88

S.64W.

A’ N.64E.

PS-106

PS-102

PS-107 PS-103 PS-104

Surface joint set

Bedrock foliation

Fracture

EXPLANATION

Altitude, in feet above NAVD 88

Total

depth

Figure 25. Schematic cross section A–A' showing depths to and orientations of subsurface borehole fractures and 

generalized orientation of surface geologic structural features. Line of section shown on fig. 2.
Hydrogeologic and Water-Quality Sections 29

PS-106

Altitude, in feet above NAVD 88

VERTICAL EXAGGERATION x 4

DATUM IS NAVD 88

0 500 1,000 FEET

0 100 200 METERS Surface joint set

Bedrock foliation

Fracture

EXPLANATION

800

750

700

650

600

550

500

450

400

B

North

B’

South

PS-096

PS-098

PS-107 PS-093

PS-101

PS-100

PS-105

PS-099

PS-094

PS-102

Land surface

Casing

Open

borehole

Total

depth

Figure 26. Schematic cross section B–B' showing depths to and orientations of subsurface borehole fractures and generalized 

orientation of surface geologic structural features. Line of section shown on fig. 2.
30 Geophysical Logging and Geologic Mapping Data in the Vicinity of the GMH Electronics Superfund Site near Roxboro, N.C.

800

750

700

650

600

550

500

450

400

PS-095

PS-097 Land surface

nd

A

S.64W.

A’

N.64E.

nd

nd

nd

nd

nd

DCE 690,

TCA 180

All concentrations are in micrograms per liter. Higher concentrations

shown in red.

PS-106

PS-102

PS-107 PS-103

PS-104

Benzene

O-Xylene

1,1 Dichloroethylene

1,1 Tricholorethane

Not detected

Fracture

BZ

XY

DCE

TCA

nd

EXPLANATION

Altitude, in feet above NAVD 88

0 500 1,000 FEET

0 100 200 METERS

VERTICAL EXAGGERATION x 4

DATUM IS NAVD 88

nd

nd

nd

DCE 1,000,

TCA 270

DCE 1,200,

TCA 330

DCE 1,000,

TCA 290

DCE 1,600,

TCA 400

DCE 1,300,

TCA 310

DCE 490

TCA 68

DCE 530

TCA 68

DCE 480

TCA 62

DCE 970,

TCA 140

DCE 990,

TCA 150

Casing

Open

borehole

Total

depth

Figure 27. Schematic cross section A–A' showing depths to and orientations of borehole fractures and detected 1,1 

dichloroethylene (DCE) and 1,1,1 trichloroethane (TCA) concentrations from the passive diffusion bag sampling during 

October 2011. Line of section shown on fig. 2.
Hydrogeologic and Water-Quality Sections 31

Note: All concentrations are in

micrograms per liter.

Higher concentrations

shown in red.

DCE 16,

TCA 3.2

DCE 18,

TCA 3.7

DCE 630,

TCA 59

DCE 8.9,

TCA 1.2

DCE 690,

TCA 180

PS-106

DCE 1,600,

TCA 400

DCE 1,300,

TCA 310

Cyclohexane

1,1 Dichloroethylene

1,1 Tricholorethane

Not detected

Fractures

CY

DCE

TCA

nd

EXPLANATION

Altitude, in feet above NAVD 88

800

750

700

650

600

550

500

450

400

B

North

B’

South

PS-096

nd

PS-098

PS-107 PS-093

PS-101

PS-100

PS-105

PS-099

PS-094

PS-102

nd

nd

nd

DCE 1,000,

TCA 270

DCE 1,000,

TCA 290

DCE 1,200,

TCA 330

DCE 0.99

nd

DCE 0.98

nd

DCE 1.6

nd

DCE 24,

TCA 4.4

DCE 750,

TCA 70

DCE 760,

TCA 72

DCE 40,

TCA 3.7

DCE 110, TCA 11

DCE 100,

TCA 10

DCE 9.5,

TCA 1.2

DCE 9.4,

TCA 1.2

DCE 1.0

nd

DCE 0.95

TCA nd

Land surface

nd

nd

nd

Casing

Open

borehole

Total

depth

0 500 1,000 FEET

0 100 200 METERS

VERTICAL EXAGGERATION x 4

DATUM IS NAVD 88

Figure 28. Schematic cross section B–B' showing depths to and orientations of borehole fractures and detected 1,1 dichloroethylene 

(DCE) and 1,1,1 trichloroethane (TCA) concentrations from the passive diffusion bag samping during October 2011. Line of section shown 

on fig. 2.
32 Geophysical Logging and Geologic Mapping Data in the Vicinity of the GMH Electronics Superfund Site near Roxboro, N.C.

800

750

700

650

600

550

500

450

400

PS-095

PS-097 Land surface

BZ 0.69

A

S.64W.

A’

N.64E.

nd

nd

BZ 680

BZ 640

BZ 670

Note: All concentrations are in

micrograms per liter.

Higher concentrations

shown in red.

PS-106

PS-102

PS-107 PS-103

PS-104

Benzene

Not detected

Fractures

BZ

nd

EXPLANATION

Altitude, in feet above NAVD 88

0 500 1,000 FEET

0 100 200 METERS

VERTICAL EXAGGERATION x 4

DATUM IS NAVD 88

nd

nd

nd nd

nd

nd

nd

nd

nd

nd

nd

BZ 2,100

BZ 2,300 BZ 1,900

Figure 29. Schematic cross section A–A' showing depths to and orientations of borehole fractures and detected benzene 

concentrations from the passive diffusion bag sampling during October 2011. Line of section shown on fig. 2.
Hydrogeologic and Water-Quality Sections 33

Note: All concentrations are in

micrograms per liter.

Higher concentrations

shown in red.

nd

BZ 2.5

PS-106

BZ

nd

Altitude, in feet above NAVD 88

800

750

700

650

600

550

500

450

400

B

North

B’

South

PS-096

nd

PS-098

PS-107 PS-93

PS-101

PS-100

PS-105

PS-99

PS-94

PS-102

BZ 2.6

BZ 2.4

BZ 8.2

BZ 5.6

BZ 1.6

BZ 1.6

BZ 1.0

nd

Land surface

nd

nd

nd

nd

nd

nd

nd

nd

nd

nd

0.75

nd

nd

BZ 2,100

BZ 2,300

BZ 1,900

0 500 1,000 FEET

0 100 200 METERS

VERTICAL EXAGGERATION x 4

DATUM IS NAVD 88

Benzene

Not detected

Fracture

EXPLANATION

nd

nd

nd nd

nd

Figure 30. Schematic cross section B–B' showing depths to and orientations of borehole fractures and detected benzene 

concentrations from the passive diffusion bag samping during October 2011. Line of section shown on fig. 2.
34 Geophysical Logging and Geologic Mapping Data in the Vicinity of the GMH Electronics Superfund Site near Roxboro, N.C.

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composite log package: Accessed February, 2013, at 

http://www.alt.lu/wellcad.htm.

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Petrology and regional significance of the Roxboro metagranite, North Carolina: Geological Society of America 

Bulletin 1978, v. 89, p. 511–521.

Chapman, M.J., and Huffman, B.A., 2011, Geophysical logging data from the Mills Gap Road area near Asheville, 

North Carolina: U.S. Geological Survey Data Series 

538, 49 p. + attachment. (Available only online at 

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Chapman, M.J., Bolich, R.E., and Huffman, B.A., 2005, 

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Resource Evaluation Program: U.S. Geological Survey 

Scientific Investigations Report 2005–5166, 85 p.

Day-Lewis, F.D., Johnson, C.D., Paillet, F.L., 

and Halford, K.J., 2011, A computer program 

for flow-log analysis of single holes (FLASH): 

Ground Water, v. 49, no. 6. (Also available at 

http://dx.doi.org/10.1111/j.1745-6584.2011.00798.x)

Heath, R.C., 1980, Basic elements of ground-water hydrology with reference to conditions in North Carolina: 

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Heath, R.C., 1983, Basic ground-water hydrology: 

U.S. Geological Survey Water-Supply Paper 2220, 84 p.

Heath, R.C., 1984, Ground-water regions of the United States: 

U.S. Geological Survey Water-Supply Paper 2242, 78 p.

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Raleigh, North Carolina Department of Environment, 

Health, and Natural Resources, Groundwater Section, 

Open-File Report, 52 p.

Hibbard, J. P., Stoddard, E.F., Secor, D.T., and Dennis, A.J., 

2002, The Carolina Zone: Overview of Neoproterozoic to 

Early Paleozoic peri-Goldwanan terranes along the eastern 

flank of the southern Appalachians: Earth Science Reviews, 

v. 57, p. 299–339. 

Hibbard, J.P., van Staal, C.R., Rankin, D.W., and Williams, 

H., 2006, Lithotectonic map of the Appalachian Orogen, 

Canada-United States of America: Geological Survey of 

Canada, Map 2096A, scale 1: 1,500,000

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Rockware, Inc., 2010, RockWorks earth science and 

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Appendixes

Appendixes 1–8 are available for download at http://pubs.usgs.gov/ds/762/ in the following formats:

1. Borehole geophysical logging field notes.................................................................................... PDF

2. Heat-pulse flowmeter tool rinse volatile organic compound sample results ...............MS Excel

3. Geologic structural measurements recorded near the GMH Electronics 

Superfund site ................................................................................................................MS Excel

4. Borehole geophysical logs showing depth of fracture zones, borehole flow, and 

percent contribution of fractures to flow in the well........................................................ PDF

5. Borehole geophysical image logs showing orientations of subsurface structural 

features .................................................................................................................................... PDF

6. Rose diagrams showing dominant orientations of borehole structural features.................. PDF

7. FLASH modeling results for wells.........................................................................................MS Excel

8. Analytical results of the passive diffusion bag sampling October 2011.........................MS Excel
For further information about this publication contact:

Director

U.S. Geological Survey

North Carolina Water Science Center

3916 Sunset Ridge Road

Raleigh, NC 27607

Or visit the North Carolina Water Science Center Web site at

http://nc.water.usgs.gov/

Prepared by the Raleigh Publishing Service Center

A PDF version of this publication is available online at 

http://pubs.usgs.gov/ds/762/
Chapman and others—Geophysical Logging and Geologic Mapping Data in the Vicinity of the GMH Electronics Superfund Site near Roxboro, N.C.—Data Series 762