Geophysical Logging and Geologic Mapping Data in … Logging and Geologic Mapping Data in the...

U.S. Department of the InteriorU.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.


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 InteriorU.S. Geological Survey

U.S. Department of the InteriorSALLY JEWELL, Secretary

U.S. Geological SurveySuzette M Kimball, Acting Director

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

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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/.

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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 passive-diffusion-bag samples. Appreciation also is extended to USGS report colleague reviewers Brad Huffman and Eve Kuniansky.

v

Contents

Abstract ...........................................................................................................................................................1Introduction.....................................................................................................................................................1

Purpose and Scope ..............................................................................................................................3Geologic Setting ....................................................................................................................................3

Methods of Data Collection .........................................................................................................................3Geologic Mapping Data ................................................................................................................................7

Conventions Used to Record Surface Geologic Mapping Orientation Data .............................13Borehole Geophysical Logging and Imaging Data .................................................................................13

Sampling Biases Inherent in the Borehole Surveys and the Surface Outcrop Measurements .....................................................................................................................21

Passive Diffusion-Bag Sampling Results .................................................................................................24Hydrogeologic and Water-Quality Sections ............................................................................................24References Cited..........................................................................................................................................34Appendixes ...................................................................................................................................................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 1–8The 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 obtaininch (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

AbbrevationsATV 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


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

AbstractGeologic 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.

IntroductionThe 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 discon-tinuities. 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 character-ize 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 migra-tion. The USGS effort was done in cooperation with the EPA Region 4 Superfund Section.

1U.S. Geological Survey.2Private 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, 1991U.S. Environmental Protection Agency, River File 3U.S. Geological Survey, 1:100,000 scale

Piedmont

Coastal Plain

Blue Ridge

34

35

36

8384 8182 7980 77 7678

Brevard fault zone

0 25 50 75 100 MILES

0 25 50 75 100 KILOMETERS

ATLANTICOCEAN

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

PERSONCOUNTY

CP

Biotite gneiss and schistFelsic metavolcanic rockFelsic mica gneissMetamorphosed gabbro and dioriteMetamorphosed granitic rockMetavolcanic epi-clastic rockMetavolcanic rock

EXPLANATION

TENNESSEE

VIRGINIA

SOUTH CAROLINA

GEORGIA

Physiographic province boundaryThrust fault with teeth on upthrown blockCentral Piedmont Shear Zone

158

1585715749

49

501

0 5 KILOMETERS1 2 3 4

0 1 2 3 4 5 MILESGMH Electronics

superfund site

Roxboro

Albemarle- SC sequenceCary sequenceVirgilina sequence

Spring HopeRoanoke Rapids

Suprastructuralterranes

Carolina Zone

Carolina

Piedmont Zone

EXPLANATION

CharlotteCrabtreeRaleighTripletFalls LakeMesozoic basinsLate Paleozoic grantoids

Infrastructualterranes

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 charac-terize 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 surround-ing 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 composi-tion, 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 CollectionBorehole geophysical logs and surface geologic mapping meth-

ods 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 borehole-logging-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

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PS-1

051 5

/4/2

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24.

95

2 7/1

4/20

11; 2

3.81

36.4

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2600

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8.94

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075

40.

816

149

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3625

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601

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061 5

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27.

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7.60

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27.

76

36.4

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7708

32–7

8.94

0533

0651

175

41

127

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996

15

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8562

701

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071 5

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25.

80

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5.28

1 6

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25.

22

2 8/8

/201

1; 2

6.32

36.4

1680

6000

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8.94

1014

7178

075

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Altitude in feet above NAVD 88.Contour interval is 4 feetLine of sectionWell location and U.S. Geological Survey county identification number

714

710

702

706

698

694

690

684

718714

722

726

726

726

722 718

714710

706

74675

0

738 73

4

730

742

754

758

754750746742

738734

730726722718

714

710706

702698694

690

754

750

746

742

738

734730

710

714

718722

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

HALI

FAX

ROAD

49

Base from digital files of:13 Imagery Prime World 2D; ArcGIS Map Service

7856’45” 7856’15”

3625’15”

3625’

PS-093

EXPLANATION

0 500 FEET400300200100

0 150 METERS10050

GMH ElectronicsSuperfund site

UndergroundStorage 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) measure-ments 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 interpreta-tions 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 moni-tored 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 42.5 141.5PS-094 49 65 123 42 124.4PS-095 39 85 137 28 304.5PS-096 64 70 na 62 72.4PS-097 55 98 139 52.5 143PS-098 40 54 60 33 62.4PS-099 74 87 276 64 302PS-100 45 113 139 37.5 144PS-101 79 149 196 55 202.4PS-102 65 83 119 58 122PS-103 110 124 153 81 167PS-104 68 74 na 65 80.5PS-105 99 105 152 49 161PS-106 41 76 120 35 127PS-107 55 70 103 52 118

Geologic Mapping Data 7

Geologic Mapping DataStructural 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, semi-massive 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 measure-ments; 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).


Figure 3. A typical granite boulder field near the GMH Electronics Superfund site.


55

5455 57

5756

7172

73

74

797979

8687

85

84

83

82

8383

78

8181

80

80

76

77

77

75

75

6861

61 63

6464

64

65

66 66

6767

6760

60

5958

58

69

1

62

101

9594

9797

98

4

3 332

99

89

8990 93

92

91

96

88

8888

107

107

111111

108108

108110

110

109

113

116

118118

119119

123 123114114

106112

112

112

115

117

127127

127

126124

124

124124

125125

125

40

136

37

3838

3939

39

128128129

130PS-093

104

102103

100

120

121 121

121

PS-098

PS-102

PS-106PS-097

PS-096

PS-107PS-094

PS-104

PS-103

PS-100PS-099

PS-101

PS-105PS-095

30

19

20

212217

1718

18

1831

27

28

29

52

5150

48

49

49 47

46

343332

242325

2526

135132

132

132

134134

131131

131133

105

122

9

8

6

151515

1414

16

1312

12 11

10

5

5

5353

36 36

7735

42

41

42

4343

44

45

45

ALLEYCLAY

ROAD

CLAY

THOM

AS

ROAD

PROVIDENCE

THAXTONLONGHURST

ROAD

ROAD

BROAD

ROAD

VIRGILINA

ROAD

GRAVITTE

NELSON

LOOPROAD

ROAD

ROADHOLLOWAY

HALIFAX

ROAD

49

TODDROAD

LOFTISLOOPROAD

JAMES AN

D 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

127Joint 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 by13 Imagery Prime World 2D and ArcGIS Map Service

0 3,000 FEET1,500

0 800 METERS400


Undergroundstorage 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

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90

135

180

225

270

315

A

B

2

2

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2

4

4

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4

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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.



Figure 6. Photograph of a typical granite outcrop showing both steeply dipping and medium-angle joint sets. Booklet is shown for scale.

Num

ber o

f mea

sure

men

ts

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

21–4

0

0–20

41–6

061

–80

81–1

0010

1–12

012

1–14

014

1–16

016

1–18

018

1–20

020

1–22

022

1–24

024

1–26

026

1–28

028

1–30

030

1–32

032

1–34

034

1–36

0

A

B

C

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


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 domi-nant fracture orientation within the well set was 151°–160°, which was measured in five wells. Other dominant orienta-tions 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


A

154

155

156

157

84

85

86

87

88

0 90 180 270 0

N NE S W

B

0 90 180 270 0

N NE S W

C

0 90 180 270 0

N NE S W

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D

0 90 180 270 0

N NE S W

67

68

69

70

71

Foliation

Mafic lens

Enclaves

Dept

h, in

feet

bel

ow la

nd s

urfa

ce

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.


Tool maximumrange was 20 inches

A BCaliper, in inches Caliper, in inches Caliper, in inches

5.5 13 6 8

C

43

44

45

46

69

70

71

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75

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Dept

h, in

feet

bel

ow la

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urfa

ce

0 90 180 270 0

N NE S W

0 90 180 270 0

N NE S W

5.5 220 90 180 270 0

N NE S W

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.


121

122

123

124

125

126

127

128

129

Dept

h, in

feet

bel

ow la

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urfa

ce

Weathered, secondaryfractures

Sealedfractures

128

129

130

131

A BCaliper, in inches Caliper, in inches

6 8 6 80 90 180 270 0

N NE S W

0 90 180 270 0

N NE S W

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.


5

5

6

6

7

7

89 1234 5 6 7 8 91 2 3 4

89

1234

56789

1234

018

0

45

90

135225

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 51 2 3 4

1

2

3

4

5

5

1

2

3

4

018

0

45

90

135225

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

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10

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>151 <1 1–30 31–60 61–90

601–620 621–640Altitude, in feet above NAVD 88

Depth below land surface,in feet

641–660 661–680 681–700 701–720

Inclination angle, in degrees

Num

ber o

f prim

ary

fract

ures

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

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1012 42 6 8 10 12

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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.


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-100PS-105

PS-099

Well location and U.S. Geological Survey county identification number

GMH Electronics superfund site

VIRGILINA

ROAD

HALI

FAX

ROAD

49


7856’45” 7856’15”

3625’15”

3625’

PS-093EXPLANATION

Rose diagram displayingstrike azimuth of measuredborehole structures. Length ofpetal corresponds to percentageof measurements.

315

135

0

180

45

225

90270 10 22468

1012

2468

1012

68 4 101212 2 6 84

0 500 FEET400300200100

0 150 METERS10050

Underground StorageTank 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 19De

pth

belo

w la

nd s

urfa

ce, i

n fe

et

Inflow

Outflow

Upflo

w

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 perminute

Modeledflow direction

–0.7 0.7

0.2

Casing depth at42.5 feet below

land surface

13 percentof flow

87 percentof flow

Water levelat 25.46 feet below

land surface

1.0 DCE1.0 BZ

at 70 feet

0.95 DCEat 122 feet

EXPLANATION

Resistivity 16-inch normalResistivity 64-inch normalResistanceLateral resistivity 48-inch normalTemperature, in degrees FarenheitSpecific conductance, in microsiemens per centimeterDelta temperature, in degrees FarenheitHeatpulse flow ambientHeatpulse flow stressedAmerican Petrolium Institute Units1,1-dichloroethyleneBenzene

APIUDCEBZ

Figure 16. Borehole geophysical logs from well PS-093 showing fracture zones and upward vertical flow at depth.


26 percentof flow

73 percentof 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

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minute

–0.5

–0.07 0.07

–0.2 0.2

0.5

Casing depth at33 feet belowland surface

Dept

h be

low

land

sur

face

, in

feet Water level at

29.37 feet belowland surface

Groundwaterflow direction

Inflow

Outflow

Dow

nflo

w

3.5 1,2 DCAat 40 feet



EXPLANATION

Resistivity 16-inch normalResistivity 64-inch normalResistanceLateral resistivity 48-inch normalTemperature, in degrees FarenheitSpecific conductance, in microsiemens per centimeterDelta temperature, in degrees FarenheitHeatpulse flow ambientHeatpulse flow stressedAmerican Petrolium Institute Units1,1-dichloroethane

APIUDCA

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.


arrows in figures 16 and 17 and in appendix 4 reflect mod-eled (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 rela-tive 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 dip-ping 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]

WellTransmissivity

(ft2/d)

Radius of influence

(ft)

Yield reported

(gpm)PS-093 22 23 15PS-094 20 22 8PS-095 2.6 24 1PS-096 15 23 naPS-097 7.1 13 3PS-098 154 24 10PS-099 12 113 10PS-100 135 25 10PS-101 1.7 22 naPS-102 41 24 naPS-103 0.41 9.5 naPS-104 28 24 naPS-105 2.3 17 7PS-106 133 24 15PS-107 35 25 na


PS-095

Southwest Northeast

PS-097PS-094

PS-106

PS-104

PS-103

PS-107

Primary fractureSecondary fractureFoliationScaled fractures

BlueRed

GreenPurple

EXPLANATION

Figure 18. Southwest-to-northeast three-dimensional diagram showing subsurface structures in selected wells.


PS-094

PS-107

PS-106


BlueRed

GreenPurple

EXPLANATION

Southwest Northeast

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

PS-096

PS-098

PS-102 PS-094PS-100

PS-101

PS-093

PS-106

PS-105Primary fractureSecondary fractureFoliationScaled fractures

BlueRed

GreenPurple

EXPLANATION

PS-107

SouthNorth

Figure 20. North-to-south three-dimensional diagram showing subsurface structures in selected wells.


PS-104

PS-103

PS-102

PS-106


BlueRed

GreenPurple

EXPLANATION

PS-107

SouthwestNortheast

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-butyl-ether. 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 orienta-tions 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 bore-hole 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-100PS-105

PS-099

1.0, 0.95

9.5, 9.4, 8.9

24, 16, 18

480, 530, 490970, 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


1

10

10

100100

10010

1

100

1,000

10

1

100

1

nd

nd

VIRGILINA

ROAD

HALI

FAX

ROAD

HALI

FAX

ROAD

49


7856’45” 7856’15”

3625’15”

3625’

PS-093

EXPLANATION


0 500 FEET400300200100

0 150 METERS10050

100

1.0, 0.95

nd

Line of equal DCE concentration,in micrograms per liter

Well location, U.S. Geological Survey county identification number, andDCE 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.


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-100PS-105

PS-0994.4, 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

HALI

FAX

HALI

FAX

ROAD

49

ROAD


7856’45” 7856’15”

3625’15”

3625’

0 500 FEET400300200100

0 150 METERS10050


Line of equal TCA concentration,in micrograms per liter

Well location, U.S. Geological Survey county identification number, andTCA concentrations


100

10

10

1.2, 1.2, 1.2

nd

PS-101

EXPLANATION


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.


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-100PS-105

PS-099VIRGILINA

ROAD

HALI

FAX

49RO

AD


7856’45” 7856’15”

3625’15”

3625’

0 500 FEET400300200100

0 150 METERS10050

Line of equal benzene concentration,in micrograms per liter

Well location, U.S. Geological Survey county identification number, andbenzene concentrations


100

1.0

nd

PS-093

EXPLANATION

1.0, nd

nd, nd, 5.6

nd, 0.75, nd

0.69, nd, ndnd

nd

nd

1.6, 1.6, 2.5

2.6, 2.4, 8.2

2,100, 2,300, 1,900

680, 640, 670 GMH ElectronicsSuperfund site

nd

nd

nd

nd

10

1

10

100

1001,000

1,000


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.


800

750

700

650

600

550

500

450

400

PS-095PS-097

Land surface

5000 1,000 FEET

1000 200 METERS

Casing

Openborehole

A

VERTICAL EXAGGERATION x 4DATUM IS NAVD 88

S.64W.A’

N.64E.

PS-106

PS-102PS-107 PS-103 PS-104

Surface joint setBedrock foliationFracture

EXPLANATION

Altit

ude,

in fe

et a

bove

NAV

D 88

Totaldepth

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.


PS-106

Altit

ude,

in fe

et a

bove

NAV

D 88


5000 1,000 FEET

1000 200 METERSSurface joint setBedrock foliationFracture

EXPLANATION

800

750

700

650

600

550

500

450

400

BNorth

B’South

PS-096PS-098

PS-107PS-093

PS-101

PS-100PS-105

PS-099PS-094

PS-102Land surface

Casing

Openborehole

Totaldepth

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.


800

750

700

650

600

550

500

450

400

PS-095PS-097

Land surface

nd

A

S.64W.

A’

N.64E.

nd

nd

nd

nd

nd

DCE 690,TCA 180

All concentrations are in micrograms per liter. Higher concentrationsshown in red.

PS-106

PS-102PS-107 PS-103

PS-104

BenzeneO-Xylene1,1 Dichloroethylene

1,1 TricholorethaneNot detectedFracture

BZXY

DCE

TCAnd

EXPLANATION

Altit

ude,

in fe

et a

bove

NAV

D 88

5000 1,000 FEET

1000 200 METERS


nd

ndnd

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 490TCA 68

DCE 530TCA 68

DCE 480TCA 62

DCE 970,TCA 140DCE 990,TCA 150

Casing

Openborehole

Totaldepth

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.


Note: All concentrations are inmicrograms per liter.

Higher concentrationsshown 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

Cyclohexane1,1 Dichloroethylene1,1 TricholorethaneNot detectedFractures

CYDCETCAnd

EXPLANATION

Altit

ude,

in fe

et a

bove

NAV

D 88

800

750

700

650

600

550

500

450

400

B

North

B’

South

PS-096

nd

PS-098PS-107

PS-093PS-101

PS-100PS-105

PS-099PS-094

PS-102

ndnd

nd

DCE 1,000,TCA 270

DCE 1,000,TCA 290

DCE 1,200,TCA 330

DCE 0.99nd

DCE 0.98nd

DCE 1.6nd

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 1.0nd

DCE 0.95TCA nd

Land surface

nd

nd

nd

Casing

Openborehole

Totaldepth

5000 1,000 FEET

1000 200 METERS


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.


800

750

700

650

600

550

500

450

400

PS-095PS-097

Land surface

BZ 0.69

A

S.64W.

A’

N.64E.

nd

nd

BZ 680

BZ 640

BZ 670



PS-106

PS-102PS-107 PS-103

PS-104

BenzeneNot detectedFractures

BZnd

EXPLANATION

Altit

ude,

in fe

et a

bove

NAV

D 88

5000 1,000 FEET

1000 200 METERS


nd

nd

nd nd

nd

nd

nd

ndnd

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.




nd

BZ 2.5

PS-106

BZnd

Altit

ude,

in fe

et a

bove

NAV

D 88

800

750

700

650

600

550

500

450

400

BNorth

B’South

PS-096

nd

PS-098PS-107

PS-93PS-101

PS-100PS-105

PS-99PS-94

PS-102

BZ 2.6

BZ 2.4

BZ 8.2BZ 5.6

BZ 1.6

BZ 1.6

BZ 1.0

nd

Land surface

ndnd

nd

nd

nd

nd

ndnd

ndnd

0.75

nd

nd

BZ 2,100

BZ 2,300

BZ 1,900

5000 1,000 FEET

1000 200 METERS


BenzeneNot detectedFracture

EXPLANATION

nd

ndnd

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.


References Cited

aLt [Advanced Logic Technology], 2010, WellCad®—The composite log package: Accessed February, 2013, at http://www.alt.lu/wellcad.htm.

Briggs, D.F., Gilbert, M.C., and Glover, L., III, 1978, Petrology and regional significance of the Roxboro meta-granite, North Carolina: Geological Society of America Bulletin 1978, v. 89, p. 511–521.

Chapman, M.J., and Huffman, B.A., 2011, Geophysical log-ging 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 http://pubs.usgs.gov/ds/538/)

Chapman, M.J., Bolich, R.E., and Huffman, B.A., 2005, Hydrogeologic setting, ground-water flow, and ground-water quality at the Lake Wheeler Road research station, 2001–03, North Carolina Piedmont and Mountains 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 hydrol-ogy with reference to conditions in North Carolina: U.S. Geological Survey Open-File Report 80–44, 86 p.

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.

Heath, R.C., 1994, Ground-water recharge in North Carolina: 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

North Carolina Geological Survey, 1985, Geologic map of North Carolina: Raleigh, North Carolina Geological Survey, scale 1:500,000.

Rockware, Inc., 2010, RockWorks earth science and GIS software: accessed September 24, 2010, at http://www.rockware.com/.

U.S. Environmental Protection Agency, 2009, GMH Electronics Site focused remedial investigation report: SESD project identification number 09–0016.

Vroblesky, D.A., 2001a, User’s guide for polyethylene-based passive diffusion bag samplers to obtain volatile organic compound concentrations in wells—Part 1: deployment, recovery, data interpretation, and quality control and assur-ance: U.S. Geological Survey Water Resources Investiga-tions Report 01–4060, 18 p.

Vroblesky, D.A., 2001b, User’s guide for polyethylene-based passive diffusion bag samplers to obtain volatile organic compound concentrations in wells—Part 2: field tests: U.S. Geological Survey Water Resources Investigations Report 01–4061, 101 p.

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 .................................................................................... PDF2. Heat-pulse flowmeter tool rinse volatile organic compound sample results ...............MS Excel3. Geologic structural measurements recorded near the GMH Electronics

Superfund site ................................................................................................................MS Excel4. Borehole geophysical logs showing depth of fracture zones, borehole flow, and

percent contribution of fractures to flow in the well ........................................................ PDF5. Borehole geophysical image logs showing orientations of subsurface structural

features .................................................................................................................................... PDF6. Rose diagrams showing dominant orientations of borehole structural features .................. PDF7. FLASH modeling results for wells .........................................................................................MS Excel8. 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 G

eologic Mapping D

ata in the Vicinity of the GM

H Electronics Superfund Site near Roxboro, N

.C.—Data Series 762

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