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.
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 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/.
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
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
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
4 Geophysical Logging and Geologic Mapping Data in the Vicinity of the GMH Electronics Superfund Site near Roxboro, N.C.Ta
ble
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Introduction 5Ta
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PS-1
051 5
/4/2
011;
24.
95
2 7/1
4/20
11; 2
3.81
36.4
1571
2600
00–7
8.94
1516
0000
075
40.
816
149
10/1
3/19
977
3625
0107
8562
601
PS-1
061 5
/4/2
011;
27.
19
2 8/1
/201
1; 2
7.60
2 8
/2/2
011;
27.
76
36.4
1694
7708
32–7
8.94
0533
0651
175
41
127
356/
14/1
996
15
3625
0107
8562
701
PS-1
071 5
/5/2
011;
25.
80
3 5/2
6/20
11; 2
5.28
1 6
/8/2
011;
25.
22
2 8/8
/201
1; 2
6.32
36.4
1680
6000
00–7
8.94
1014
7178
075
50.
811
852
nana
1 Tie
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lect
rical
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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 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).
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
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
GMH ElectronicsSuperfund site
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
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.
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.
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 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
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 NE S W
B
0 90 180 270 0
N NE S W
C
0 90 180 270 0
N NE S W
54
55
56
57
58
59
60
61
62
63
64
65
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.
Borehole Geophysical Logging and Imaging Data 15
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
72
73
74
75
44
45
46
47
48
49
50
51
52
53
Dept
h, in
feet
bel
ow la
nd s
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.
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
Dept
h, in
feet
bel
ow la
nd s
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.
Borehole Geophysical Logging and Imaging Data 17
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
30
20
10
0
60
40
20
0
100
50
0
581–600
0–50
51–1
0010
1–15
0
>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
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-100PS-105
PS-099
Well location and U.S. Geological Survey county identification number
GMH Electronics superfund site
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-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.
20 Geophysical Logging and Geologic Mapping Data in the Vicinity of the GMH Electronics Superfund Site near Roxboro, N.C.
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
0 4,000Gallons per
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
4.0 1,2 DCAat 54 feet
4.0 1,2 DCAat 60 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.
Borehole Geophysical Logging and Imaging Data 21
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
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-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.
Borehole Geophysical Logging and Imaging Data 23
PS-094
PS-107
PS-106
Primary fractureSecondary fractureFoliationScaled fractures
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.
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 fractureSecondary fractureFoliationScaled fractures
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
GMH ElectronicsSuperfund site
1
10
10
100100
10010
1
100
1,000
10
1
100
1
nd
nd
VIRGILINA
ROAD
HALI
FAX
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
Underground StorageTank release
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.
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-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
Base from digital files of:13 Imagery Prime World 2D; ArcGIS Map Service
7856’45” 7856’15”
3625’15”
3625’
0 500 FEET400300200100
0 150 METERS10050
GMH ElectronicsSuperfund site
Line of equal TCA concentration,in micrograms per liter
Well location, U.S. Geological Survey county identification number, andTCA concentrations
Compound not detected
100
10
10
1.2, 1.2, 1.2
nd
PS-101
EXPLANATION
Underground StorageTank 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-100PS-105
PS-099VIRGILINA
ROAD
HALI
FAX
49RO
AD
Base from digital files of:13 Imagery Prime World 2D; ArcGIS Map Service
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
Compound not detected
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
Underground StorageTank 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-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.
Hydrogeologic and Water-Quality Sections 29
PS-106
Altit
ude,
in fe
et a
bove
NAV
D 88
VERTICAL EXAGGERATION x 4DATUM IS NAVD 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.
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-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
VERTICAL EXAGGERATION x 4DATUM IS NAVD 88
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.
Hydrogeologic and Water-Quality Sections 31
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
VERTICAL EXAGGERATION x 4DATUM 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-095PS-097
Land surface
BZ 0.69
A
S.64W.
A’
N.64E.
nd
nd
BZ 680
BZ 640
BZ 670
Note: All concentrations are inmicrograms per liter.
Higher concentrationsshown in red.
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
VERTICAL EXAGGERATION x 4DATUM IS NAVD 88
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.
Hydrogeologic and Water-Quality Sections 33
Note: All concentrations are inmicrograms per liter.
Higher concentrationsshown in red.
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
VERTICAL EXAGGERATION x 4DATUM IS NAVD 88
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.
34 Geophysical Logging and Geologic Mapping Data in the Vicinity of the GMH Electronics Superfund Site near Roxboro, N.C.
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.
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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 .................................................................................... 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