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Prepared in cooperation with the North Carolina Department of Environment and Natural Resources
Baseline Well Inventory and Groundwater-Quality Data from a Potential Shale Gas Resource Area in Parts of Lee and Chatham Counties, North Carolina, October 2011–August 2012
Data Series 861
U.S. Department of the InteriorU.S. Geological Survey
Background Photograph: Private well cover structure in Lee County, North Carolina, April 2012 (photograph by Douglas G. Smith, U.S. Geological Survey).
Photograph on left: Private well with concrete surface casing cover in Lee County, North Carolina, May 2012 (photograph by Douglas G. Smith, U.S. Geological Survey).
Photograph on right: Private wellhead construction in Lee County, North Carolina, showing surface casing and pump connections, well tag, and pressure tank, No-vember 2011 (photograph by Mike Papay, Lee County, North Carolina, Public Health Department).
Baseline Well Inventory and Groundwater-Quality Data from a Potential Shale Gas Resource Area in Parts of Lee and Chatham Counties, North Carolina, October 2011–August 2012
By Melinda J. Chapman, Laura N. Gurley, and Sharon A. Fitzgerald
Prepared in cooperation with the North Carolina Department of Environment and Natural Resources
Data Series 861
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: 2014
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Suggested citation:Chapman, M.J., Gurley, L.N., and Fitzgerald, S.A., 2014, Baseline well inventory and groundwater-quality data from a potential shale gas resource area in parts of Lee and Chatham Counties, North Carolina, October 2011–August 2012: U.S. Geological Survey Data Series 861, 22 p., http://dx.doi.org/10.3133/ds861.
ISSN 2327-638X (online)
iii
Acknowledgments
The authors would like to thank all of the well and property owners who graciously allowed United States Geological Survey personnel access to their water-supply wells for the purpose of gathering field data and collecting groundwater-quality samples for this study. Much apprecia-tion is extended to Susan Condlin, Lee County, North Carolina, Cooperative Extension Director, for hosting the public well owner meeting at the beginning of this study. Many thanks to the local well drillers, Worth Pickard and Russ Patterson, Patterson Exploration Services, for their discussions regarding well records and drilling experience in the study area. We appreciate cooperation and assistance from local County Health Department personnel including Terrell Jones, Roy Warren of the Lee County Public Health Department, Anne Lowry and Terri Rit-ter of the Chatham County Environmental Health Department. Special thanks to Mike Papay, formerly Lee County Public Health Department, who spent numerous hours searching through county well records. We greatly appreciated the cooperation of the Duke University Nicholas School of the Environment’s Dr. Rob Jackson, Adrian Down, Alissa White, and the University of North Carolina at Chapel Hill Department of Geosciences, Katie Moore. Special thanks to Anne Chandler with the North Carolina Department of Environment and Natural Resources Division of Water Resources Laboratory for the support of analyses for selected organic compounds in well samples. The authors appreciate assistance from Lori Skidmore and Ray Milosh with the North Carolina Department of Environment and Natural Resources Division of Water Resources for field and sample preparation requirements for their internal laboratory.
Additional USGS North Carolina Water Science Center personnel who contributed to this study include Doug Smith, who inventoried wells in the field before sampling, and Erik Staub, Brad Huffman, and Dominick Antolino, who coordinated the field well sampling. Appreciation is extended to USGS colleague reviewers for this report Tim Kresse (Little Rock, AR) and Paul Heisig (Troy, NY).
Guidance and study approach discussions are appreciated from North Carolina Department of Environment and Natural Resources personnel Dr. Kenneth Taylor and Dr. Jeff Reid (Division of Energy, Mineral, and Land Resources, North Carolina Geological Survey) and Evan Kane and Rick Bolich (Division of Water Resources ). Funding for this study was provided by the North Carolina Department of Environment and Natural Resources, the USGS Cooperative Water Program in North Carolina, the USGS Water Mission Area Southeast Region, and the USGS Water Mission Area Office of Water Quality.
iv
Contents
Acknowledgments ........................................................................................................................................iiiAbstract ...........................................................................................................................................................1Introduction.....................................................................................................................................................1
Purpose and Scope ..............................................................................................................................1Study Area..............................................................................................................................................2
Geology ..........................................................................................................................................2Aquifer System .............................................................................................................................2
Methods..................................................................................................................................................6Sampling and Quality Assurance/Quality Control ..................................................................7
Data Summary ................................................................................................................................................7Water Well Data ....................................................................................................................................7Field Properties .....................................................................................................................................7Major Ions ............................................................................................................................................10Dissolved Metals.................................................................................................................................10Exceedances .......................................................................................................................................10Methane ...............................................................................................................................................12
References Cited..........................................................................................................................................18Appendixes 1–4 ............................................................................................................................................21
Appendix 1............................................................................................................................................22Appendix 2............................................................................................................................................22Appendix 3............................................................................................................................................22Appendix 4............................................................................................................................................22
Figures 1. Map showing location of the Triassic Basins, urbanized areas, and the study area
within the Piedmont Physiographic Province of North Carolina ..........................................3 2. Map showing topography of the study area showing colored shading of land-surface
altitude depicting a trellised and rectangular drainage system, which suggests geologic controls ..........................................................................................................................4
3. Map showing geology of the study area ..................................................................................5 4. Generalized geologic cross section showing Triassic-age deposits within the
Sanford subbasin ..........................................................................................................................6 5. Map showing locations of water supply wells and spring inventoried as part of this
study including those where groundwater samples were collected ..................................8 6. Map showing range of well depths inventoried across the study area ..............................9 7. Graph showing well depth, casing depth, yield, and date of construction for wells
inventoried in the study area ....................................................................................................10 8. Map showing range of well yields inventoried across the study area .............................11 9. Graph showing field-measured properties of pH, dissolved oxygen, alkalinity,
specific conductance, and temperature of well and spring water sampled in the study area ....................................................................................................................................12
10. Map showing distribution of field pH values measured in well and spring water sampled in the study area .........................................................................................................13
v
11. Map showing distribution of field specific conductance values measured in well and spring water sampled in the study area ..........................................................................14
12. Piper diagrams showing distribution of major ion geochemistry .......................................15 13. Graph showing constituents exceeding at least one water-quality standard
set by either the U.S. Environmental Protection Agency or the State of North Carolina .......................................................................................................................................17
14. Graph showing range in detected dissolved methane gas analyses from well and spring samples in the study area .............................................................................................17
Table 1. Number and percent of analyses exceeding at least one water-quality standard
set by either United States Environmental Protection Agency or the State of North Carolina ........................................................................................................................................12
Conversion FactorsInch/Pound to SI
Multiply By To obtain
Length
foot (ft) 0.3048 meter (m)mile (mi) 1.609 kilometer (km)
Flow rate
gallon per minute (gal/min) 0.06309 liter per second (L/s)
Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows: °F=(1.8×°C)+32.
Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows: °C=(°F-32)/1.8.
Vertical coordinate information is referenced to the insert datum name (and abbreviation) here for instance, “North American Vertical Datum of 1988 (NAVD 88).
Horizontal coordinate information is referenced to the insert datum name (and abbreviation) here for instance, “North American Datum of 1983 (NAD 83).
Altitude, as used in this report, refers to distance above the vertical datum.
Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) or micrograms per liter (µg/L).
vi
Abbreviations
BTEX benzene, toluene, ethylbenzene, and xyleneC carbonCO2 carbon dioxide gasD deuteriumDIC dissolved inorganic carbonDOC dissolved organic carbonDRO diesel-range organic compoundsGRO gasoline-range organic compoundsGWSI U.S. Geological Survey Groundwater Site-Inventory SystemNAVD 88 North American Vertical Datum of 1988NC DENR North Carolina Department of Environment and Natural ResourcesNWIS U.S. Geological Survey National Water Information SystemQA/QC quality assurance and quality controlSVOCs semivolatile organic compoundsUSGS U.S. Geological SurveyVOCs volatile organic compounds
AbstractRecords were obtained for 305 wells and 1 spring in
northwestern Lee and southeastern Chatham counties, North Carolina. Well depths ranged from 26 to 720 feet and yields ranged from 0.25 to 100 gallons per minute. A subset of 56 wells and 1 spring were sampled for baseline groundwater-quality constituents including the following: major ions; dis-solved metals; nutrients; dissolved gases (including methane); volatile and semivolatile organic compounds; glycols; isotopes of strontium, radium, methane (if sufficient concentration), and water; and dissolved organic and inorganic carbon. Dis-solved methane gas concentrations were low, ranging from less than 0.00007 (lowest reporting level) to 0.48 milligrams per liter. Concentrations of nitrate, boron, iron, manganese, sulfate, chloride, total dissolved solids, and measurements of pH exceeded federal and state drinking water standards in a few samples. Iron and manganese concentrations exceeded the secondary (aesthetic) drinking water standard in approxi-mately 35 to 37 percent of the samples.
IntroductionThe U.S. Geological Survey (USGS) North Carolina
Water Science Center conducted an inventory of well records in the Triassic Basins of Lee and Chatham Counties, North Carolina (fig. 1) and sampled selected water-supply wells and one spring to better delineate areas of groundwater use and to characterize groundwater quality prior to potential shale gas exploration in the State. Surface water supply for the study area also is available from the City of Sanford, in Lee County (http://www.ncwater.org/Water_Supply_Plan-ning/Local_Water_Supply_Plan/report.php?pwsid=03-53-010&year=2012); accessed August 2014. The study period was from October 2011 through August 2012. Shale gas exploration has become economically viable in many areas of the United States (United States Energy Information Admin-istration, 2013) as a result of improved directional drilling capabilities and high-volume hydraulic fracturing techniques. The quality of groundwater in drinking water aquifers near areas of shale gas drilling and production activities has been studied in several states including Pennsylvania (Osborn and
others, 2011; Breen and others, 2007), Arkansas (Kresse and others, 2012), and Wyoming (Wright and others, 2012). The compilation of baseline water well and groundwater-quality data in North Carolina makes possible future comparisons should drilling activities commence.
In June 2011, the North Carolina General Assem-bly passed House Bill 242 (http://www.ncga.state.nc.us/Sessions/2011/Bills/House/PDF/H242v7.pdf; accessed January 2014) directing the North Carolina Department of Environment and Natural Resources (NC DENR) to study issues related to potential shale gas exploration in the Tri-assic Basins of the State. A North Carolina Department of Environment and Natural Resources study report was released in April 2012 (http://portal.ncdenr.org/c/docu-ment_library/get_file?uuid=9a3b1cc1-484f-4265-877e-4ae12af0f765&groupId=14; accessed January 2014) and addresses a wide variety of issues related to potential shale gas exploration in the State. More recently in July 2012, the North Carolina General Assembly ratified the “Clean Energy and Economic Security Act” (http://www.ncleg.net/Sessions/2011/Bills/Senate/HTML/S820v6.html; accessed January 2014), which directs NC DENR Division of Energy, Mineral, and Land Resources to assist the recently appointed NC Mining and Energy Commission in developing a modern regulatory program for the management of oil and gas exploration and development in the State, including the use of horizontal drill-ing and hydraulic fracturing (North Carolina Department of Environment and Natural Resources, 2014).
Purpose and Scope
The purpose of this report is to present well inven-tory and groundwater-quality data collected during January through August 2012 in northwestern Lee County and extreme southeastern Chatham County, North Carolina (fig. 1). The study area was selected as a result of interest in exploration for shale gas resource extraction. Well inventory data were compiled to describe well construction characteristics, and the spatial distribution of active water-supply wells across the study area. From the 305 wells that were inventoried, a subset of 56 water-supply wells and 1 nearby spring were selected for sampling, based on available well construction data and access permissions. Analyses for collected groundwater-quality sam-ples were tiered as a result of study funding limitations, with
Baseline Well Inventory and Groundwater-Quality Data from a Potential Shale Gas Resource Area in Parts of Lee and Chatham Counties, North Carolina, October 2011–August 2012
By Melinda J. Chapman, Laura N. Gurley, and Sharon A. Fitzgerald
2 Baseline Well Inventory and Groundwater-Quality Data from a Potential Shale Gas Resource Area
the spatial groundwater-quality focus on major ion and dis-solved gases (including methane) analyses for all 56 wells and the spring. As funding permitted, a subset of those selected wells (as many as 10 of the 56 wells) were sampled for addi-tional analyses including dissolved metals; dissolved nutrients volatile and semivolatile organic compounds; glycols; isotopes of strontium, radium, methane (if sufficient concentration), and water; and dissolved organic and inorganic carbon.
Study Area
The study area (fig. 1) was a previously delineated area having the most potential to develop shale gas based on available core and test drilling data and associated oil and gas “shows”, (an indication of oil or gas noted while drilling a borehole or well), within the Sanford subbasin within the Deep River Basin of the Triassic Basin area of North Carolina (fig.1), as described by Reid and others (2011 and 2010). The total area defined by this boundary is about 79 square miles (fig. 1) which includes the northwestern quarter of Lee County and extreme southeastern Chatham County along the Deep River. Data from the 2010 U.S. Census indicates that 14,903 people live in the study area (http://www.census.gov/geo/reference/ua/urban-rural-2010.html; accessed January 2014) in northwestern Lee County and southeastern Chatham County, North Carolina.
Reinemund (1955) describes the topography of the Trias-sic rocks of the Deep River Basin as “lowland” because the geologic formations at land surface are more easily eroded than the surrounding crystalline rocks within the Piedmont Physiographic Province or nearby sand and gravel deposits in the Coastal Plain physiographic province. The Triassic Lowland in the Sanford subbasin generally is dissected, and generally has a trellised/rectangular drainage pattern, indicat-ing geologic structural control. Land surface altitudes range from 205 to 493 feet (ft) (above NAVD 88; fig. 2).
GeologyThe study area is located in the Deep River Basin of the
Triassic Basin area in North Carolina, is within the Piedmont Physiographic Province of the eastern United States, and is part of a group of extensional basins that formed during the Mesozoic Era (Milici and others, 2012). Geologic deposits within the Deep River Basin [regionally located within the Triassic Basin in North Carolina (fig. 1)] include the follow-ing sedimentary rock types: sandstone, conglomerate, shale, siltstone, claystone, coal, and small amounts of limestone and chert (Reinemund, 1955). These deposits also have been intruded by mafic diabase dikes and sills during the later Jurassic period [North Carolina Geological Survey, 1985 (fig. 3)]. Geologic formations mapped by Reinemund (1955) at the land surface in the Sanford subbasin include the Sanford Formation, the Cumnock Formation, and the Pekin Forma-tion (fig. 3). These sedimentary rocks of the Deep River Basin were deposited as layers during early Mesozoic Era rifting of supercontinent Pangea and the opening of the Atlantic Ocean.
During rifting, the basin filled with clastic sediments, includ-ing alluvial fan, deltaic, lacustrine, and swamp deposits. The Deep River Basin is bordered to the east by a west-dipping, high angle, normal fault (Jonesboro Fault) (fig. 4). Intra-basinal faults also are mapped throughout the basin (fig. 3) (Reinemund, 1955; Reid and Taylor, 2011).
The natural gas resource reservoir rock in the study area is an organic-rich black shale (lacustrine gray and black fine-grained clastic rocks, fig. 4) within the Cumnock Formation (figs. 3 and 4) in the study area in Lee and Chatham Counties. The Cumnock Formation is described as dominantly a black and dark gray shale with associated gray sandstone and coal, approximately 230 to 250 meters thick (about 750 to 820 ft) (Reid and Taylor, 2011). The Cumnock Formation outcrops in the northern part of the study area (fig. 3) and dips beneath the Sanford formation to the south/southeast (fig. 4). Historic coal mining in the area was conducted during the Revolution-ary War period in the late 1700s through the post-World War II Era. Small strip mining operations also were operated in the area again during the 1980s for a short time. Methane is known to be associated with these black shale/coal sequences as evidenced by the historic mine explosions at the Cumnock Mine (1895 and 1900) and Carolina Mine (1929) in study area (Reinemund, 1955).
Eight oil and gas test wells have been drilled in the study area since 1974 (Reid and others, 2010). Reid and Milici (2008) describe organic geochemical data, including oil and gas shows from test wells drilled in the study area. Milici and others (2012) provided an estimate of undiscovered oil and gas resources of the eastern U.S. East Coast Mesozoic basins (Milici and others, 2012, fig. 1). The assessment for the Deep River Basin included a mean estimate of 1,660 billion cubic feet of gas and 83 million barrels of natural gas liquids.
Aquifer SystemThe groundwater system in the Triassic Basin of North
Carolina is part of the Early Mesozoic Basin national aqui-fer described in Trapp and Horn (1997) within the Piedmont Physiographic Province of the eastern United States. The aquifer in the Triassic Basin of North Carolina generally con-sists of weathered regolith material (soil, saprolite, alluvium, colluvium) at land surface and underlying bedrock sedimen-tary rock layers. In some areas, bedrock is exposed at land surface and very little if any regolith material may be present. Water-supply wells typically are cased through the weathered regolith and completed as open boreholes in the more compe-tent sedimentary rock layers.
Bain and Brown (1981) describe groundwater in the Tri-assic rocks of the nearby Durham subbasin (which is similar to the Sanford subbasin in rock composition and structure; located to the northeast of the study area, fig. 1) as occurring within the primary and secondary interstices of the rocks that have been enhanced by weathering and leaching of cement holding sedimentary grains in the rock together. The Triassic rocks of the Durham subbasin were described by Bain and
Introduction 3
ASHEALLEGHANY
CURRITUCK
CAMDENSURRY
GATES
HERTFORD
NORTHAMPTONSTOKES
WARREN
ROCKINGHAM
VANCE
GRANVILLE
PERSONCASWELL
PASQUOTANKHALIFAX
WILKES
WATAUGA
PERQUIMANS
CHO
WANAVERY
YADKIN
DARE
FORSYTH FRANKLIN
BERTIE
GUILFORD
ALAMANCE
ORANGE
DURHAM NASH
MITCHELL
EDGECOMBE
CALDWELL
TYRRELL
YANCEYMADISON
MARTINWAKE
IREDELLDAVIE
ALEXANDER
WASHINGTON
BURKE DAVIDSON
MCDOWELLRANDOLPH
CHATHAM
ROWANWILSON
BUNCOMBEHAYWOOD
CATAWBAPITT
JOHNSTONSWAINBEAUFORT
HYDEGREENERUTHERFORD LEE
CLEVELAND WAYNE
JACKSON
LINCOLN
HARNETTGRAHAM HENDERSON
MECK
LENBURG
CABARRUS MOORE
MO
NTG
OM
ERY
STANLY
TRANSYLVANIAPOLK GASTON
LENOIR CRAVENMACONCHEROKEE
PAMLICOCLAY
JONESUNION
ANSON HOKERIC
HMOND
SCOTLAND
ROBESON
COLUMBUSNEW HANOVER
BRUNSWICK
CARTERETONSLOW
PENDERBLADEN
CUMBERLAND DUPLINSAMPSON
EXPLANATION
BLUE RIDGE
BLUE RIDGE PIEDMONT
PIEDMONT
COASTAL PLA
IN
COASTAL PLA
IN
0 50 75 100 MILES25
0 50 100 KILOMETERS25 75
SOUTH CAROLINA
NORTH CAROLINA
GEORGIA
TENNESSEE
VIRGINIA
DavieCounty
Basin
Dan River Basin
Sanfordsubbasin
Durhamsubbasin
Wadesboro subbasin
Deep RiverCoal Field
Deep
Rive
rBasi
n
ATLANTIC O
CEAN
Basemap and geology modified from North Carolina Geological Survey (1985)2010 U.S. Census Bureau Urbanized areas (http://www.census.gov/cgi-bin/geo/shapefiles2010/file-download; accessed March 2014)
Basemap and geology modified from North Carolina Geological Survey (1985)Urbanized areas from U.S. Census Bureau
Triassic Basin Urbanized area
76°78°80°82°84°
36°
34°
CHATHAM
LEE
MOORE
ALAMANCE
RA
ND
OLP
H
WAKE
ORANGE DURHAM
HARNETT
Area of maps in figures2, 3, 5, 6, 8, 10, 11
1 5 10 MILES
1 5 10 KILOMETERS
79°00'79°15'79°30'
35°45'
35°30' Studyarea
Figure 1. Location of the Triassic Basins, urbanized areas, and the study area within the Piedmont Physiographic Province of North Carolina.
4 Baseline Well Inventory and Groundwater-Quality Data from a Potential Shale Gas Resource Area
Figure 2. Topography of the study area showing colored shading of land-surface altitude depicting a trellised and rectangular drainage system, which suggests geologic controls.
CHATHAM COUNTY
LEE COUNTY
MOORECOUNTY
79°15'79°20'
35°30'
35°25'
0 1 2 3 MILES
0 1 2 3 KILOMETERS
Deep River
EXPLANATIONElevation, in feet
200250300350400450500
Base from U.S. Geological Survey, 2012 digitalelevation model, shaded relief, 30-foot resolution
Introduction 5
Figure 3. Geologic map of the study area.
CHATHAM COUNTY
LEE COUNTY
MOORECOUNTY
79°15'79°20'
35°30'
35°25'
EXPLANATION
Lithology
Diabase dikeFault; D, downthrown side; U, upthrown side
High-level surficial depositsDiabaseSanford Formation
Cumnock FormationPekin Formation
Quaternary alluvium
Terrace gravel deposits 2Terrace gravel deposits 3 and 4
DU
Base modified from U.S. Geological SurveyReinemund, 1955
0 1 2 3 MILES
0 1 2 3 KILOMETERS
Deep R
iver
DEEP RIVER FAULT
GOVERNORS
CRAWLEY
DEEP RIVER FAULT
CREEK FAULT
CREEK FAULT
GULF FAULT
Plank
Plank
Cotten
Steel Bridge
Valle
y
Henl
ey
Pick
ard
Gilliam
Spring
Wicker
Carbonton
Steel
Blac
ksto
ne
Holt
Dycus
Petty
McNeill
Pyra
nt
Bridges
Horner
Horner
Wakefield
Pine
Cour
tesy
Franklin
42
42
2153
Mc Pherson
Tempting Church
Cool Springs
1
15
501
Bridge
Pendergrass421
Franklin
Westove
r
Kelle
r-And
rew
s
Cum
nock
UD
UD
DU D
U
DUD
UDU
DU
DU
DU
D U
UD
UD D
U
6 Baseline Well Inventory and Groundwater-Quality Data from a Potential Shale Gas Resource Area
Thomas (1966) as having inherent low porosity and perme-ability because they are continental type sediments, which are not well sorted. Much of the initial or primary porosity has been lost through diagenesis, lithification, and compaction, and the average well yield was reported to be low (Bain and Thomas, 1966).
Well yields in the Triassic Basin areas generally are considered low. In fact, multiple wells sometimes were inven-toried on the same property, indicating challenges associated with obtaining enough water for supply needs. Differential weathering along lithologic contacts and bedding planes may enhance permeability in the aquifer. Additionally, secondary features including faults, joints, and diabase dikes (fig. 3) may enhance permeability through openings, associated fracturing, or weathering near these features. The presence of diabase dikes may be a boundary for subsurface flow and “pooling” of groundwater resulting in higher well yields. In the study area, Reinemund (1955) presents detailed mapping of diabase dikes at the local scale. The Cumnock, Pekin, and Sanford Forma-tions all outcrop at land surface, with the Sanford Formation being present in most of the area (fig. 3) and representing the shallowest part of the local aquifer. (The Middendorf Forma-tion (fig. 3) is part of the younger Coastal Plain sediments rather than Triassic Basin rocks.) Specific information on
which geologic units were tapped by wells sampled as part of this study was not available at the time of this report.
Methods
The approach for this study focused on the collection of well data, obtaining permission to sample private and public wells, and collecting water samples from selected wells. Well and spring sites in the study area were inventoried for this report from records available from the USGS National Water Information System (NWIS), the NC DENR Division of Water Resources, the Lee County Public Health Department, the Chatham County Public Health Department, and private well tag labels inventoried as part of field reconnaissance. Paper and electronic records were compiled and reviewed.
Data compiled from these well and spring records include date of construction, well depth, casing depth, static water level, yield, and owner information. Additional owner infor-mation was obtained from recent (2012) tax parcel records. Reported latitude and longitude values were used for public water supply wells and historic USGS NWIS sites. For all other sites, latitude and longitude values were estimated as the centroid of the land parcel where the well is located (with the
Figure 4. Generalized geologic cross section showing Triassic-age deposits within the Sanford subbasin. Modified from Olsen and others (1991).
SE
NW
0 1 2 3 4
2.5
5 MILES
0 5 KILOMETERS
PekinFormation
CumnockFormation
SanfordFormation
Jonesborofault zone
Mostly fluvial, red and brown clastic rocks
Lacustrine gray and black fine-grained clastic rocks
Red, brown, and gray conglomerate and sandstone
Major normal faults
EXPLANATION
SoutheastNorthwest
Data Summary 7
exception of a few sites where the centroid of the parcel was not in the parcel, and in those cases, the latitude and longitude was shifted to plot inside the parcel). New data collected dur-ing this study were entered into the USGS NWIS Groundwater Site Inventory (GWSI) database.
Sampling and Quality Assurance/Quality ControlFifty-six wells and one spring were selected for chemical
analysis of groundwater. More than 3,770 constituent analyses were completed. These constituent suites are listed in appendix 1 (http://pubs.usgs.gov/ds/861/Appendix1.xlsx) and include: field properties (alkalinity, temperature, dissolved oxygen, pH and specific conductance); dissolved methane [CH4]; hydrocarbons (methane, ethane, propane, butane, pentane, and hexane and higher hydrocarbons); δ13C and δD on methane; radium isotopes (226Ra, 228Ra); strontium iso-topes (87Sr/86Sr); four glycols; diesel-range organics (DRO); gasoline-range organics plus benzene, toluene, ethylene and xylenes (GRO+BTEX); dissolved inorganic carbon (DIC); dis-solved organic carbon (DOC); δ13C on DIC and DOC; δD and δ18O on water; 32 major ions and trace metals; total dissolved solids; 86 volatile organic compounds (VOCs); 56 semi-volatile organic compounds (SVOCs); and nutrients (ammonia [NH3], nitrite [NO2
-], nitrate [NO3-], organic nitrogen, and
orthophosphate [PO43-]); field properties. All sample collec-
tion, handling, storage and shipping were done according to established procedures documented in the USGS National Field Manual (U.S. Geological Survey, variously dated). Field properties were monitored during well sampling purge, and samples were only collected after stabilization of those properties. Method instrumentation and reporting levels for all constituents are shown in appendix 1.
Assessment of bias and precision of the analytical results included collection and analysis of various quality assurance and quality control (QA/QC) samples including field, trip, and source-solution blanks, field replicates, analytical dupli-cates, and surrogate compound analyses. Field-based QA/QC samples (blanks and replicates) accounted for between 14 and 50 percent of analyses within constituent suites and about 20 percent overall. Other QA/QC measures included review of laboratory blind blank and blind sample analyses as well as long-term method performance.
Data SummaryThe following section describes the results of the study
including a summary of well inventory and groundwater-quality data. All well locations (along with some construction information) and groundwater-quality data analyzed by the USGS National Water Quality Laboratory (Denver, Colorado) are stored online in the NWIS database at http://waterdata.usgs.gov/nc/nwis/inventory.
Water Well Data
Construction data were collected for 305 wells and 1 spring site in the study area. Nineteen wells (18 drilled, and 1 hand dug) were located in Chatham County and 286 wells (282 drilled, 3 hand dug, and 1 bored) and 1 spring were located in Lee County (fig. 5, appendix 2, http://pubs.usgs.gov/ds/861/Appendix2.xls). Available well depth, casing depth, yield, and date of construction data are summarized in appendix 2. Well depth ranged from 26 to 720 feet below land surface (ft bls), with a median of 240 ft bls (figs. 6 and 7; appendix 2). Casing depth ranged from 5 to 211 ft bls, with a median of 42 ft bls. Yield ranged from 0.25 to 100 gallons per minute (gal/min), and median yield was 7 gal/min (figs. 7 and 8; appendix 2). Dates of construction ranged from 1850 to 2012. The oldest well was hand dug (appendix 2).
Within the compilation of inventoried wells, figure 5 also shows the locations of wells that were selected for sampling. The selection of wells for sampling was based on permis-sions obtained through public meetings, phone calls, e-mail requests, local newspaper articles, field reconnaissance of records compiled, location of the well within the study area, and the availability of well construction data, which at a mini-mum, included well depth information. A tiered approach to sampling analyses was conducted using the following groups of wells and associated analyses: the focus wells (3 total) included the most comprehensive list of as many as 204 constituents analyzed; the focus-reduced sites (8 total; 7 wells and 1 spring LE-279) included as many as 71 con-stituents analyzed; and the areal wells (46 total) included as many as 37 constituents analyzed. Wells were analyzed using existing pumps and evacuated for at least one casing volume and until field properties (water temperature, pH, specific conductance, and dissolved oxygen) stabilized. Duke Univer-sity and the University of North Carolina at Chapel Hill also analyzed wells in the study area as part of a separate effort. Their sampling sites are shown in figure 5, but the associated data are not represented in this report.
Field Properties
The range of groundwater-quality properties measured in the field was quite variable. Dissolved oxygen ranged from 0.1 to 8.3 milligrams per liter (mg/L), with a median of 0.8 mg/L (figs. 9 and 10; appendix 3–1, http://pubs.usgs.gov/ds/861/Appendix3.xlsx). The pH values measured ranged from 4.3 to 8.6 with a median of 6.7. Specific conductance ranged from 48 to 2,210 microsiemens per centimeter (µS/cm), with a median of 285 µS/cm. Water temperature ranged from 16.2 to 25.7 degrees Celsius (°C), with a median of 17.3 °C. Field alkalinity (as mg/L calcium carbonate) ranged from 3 to 270 mg/L, with a median of 124 mg/L. Bicarbonate ranged from 5 to 329 mg/L, with a median of 151 mg/L (appendix 3–1).
8 Baseline Well Inventory and Groundwater-Quality Data from a Potential Shale Gas Resource Area
Figure 5. Locations of water supply wells and spring inventoried as part of this study including those where groundwater samples were collected.
LE-329LE-328
LE-326LE-325
LE-324
LE-323LE-321
LE-320
LE-319
LE-317
LE-310
LE-308
LE-318
LE-316
LE-315 LE-313LE-314
LE-312
LE-311
LE-309
LE-307
LE-255
LE-305
LE-304
LE-303LE-302
LE-301
LE-300
LE-296
LE-327
LE-295
LE-294
LE-293
LE-292
LE-291
LE-289
LE-287
LE-278
LE-286LE-280 LE-285
LE-284LE-283
LE-282LE-281
LE-219
LE-279
LE-274
LE-273LE-272
LE-271
LE-270
LE-269
LE-268
LE-267
LE-265
LE-264
LE-263
LE-262
LE-261LE-260
LE-258
LE-259LE-257
LE-256
LE-306LE-254
LE-253
LE-252
LE-251
LE-250
LE-249LE-322
LE-248LE-247LE-246
LE-245
LE-244LE-243
LE-242
LE-241
LE-240LE-239
LE-238
LE-237LE-236
LE-235LE-234
LE-233 LE-232LE-231
LE-230
LE-229
LE-228LE-227
LE-226LE-225
LE-223
LE-222LE-221
LE-220
LE-218
LE-217
LE-216
LE-215
LE-214LE-213
LE-212LE-211
LE-210
LE-209
LE-208
LE-207
LE-206
LE-205
LE-204
LE-203
LE-202
LE-201LE-200LE-199
LE-198
LE-197
LE-196LE-195
LE-194
LE-193LE-192
LE-191
LE-190LE-189
LE-188
LE-187LE-186
LE-185
LE-184LE-183
LE-182
LE-181
LE-180
LE-179
LE-178LE-177LE-176
LE-175
LE-174
LE-173LE-172
LE-171
LE-170LE-169
LE-168
LE-167
LE-166
LE-165
LE-164
LE-163LE-162
LE-161
LE-160
LE-159
LE-158
LE-157
LE-156LE-155
LE-154
LE-153
LE-152
LE-151LE-150
LE-149
LE-148LE-147
LE-146
LE-144
LE-145
LE-143
LE-142
LE-141
LE-140
LE-139
LE-138
LE-137LE-136
LE-135
LE-134LE-133
LE-132
LE-131
LE-130
LE-129
LE-128
LE-127
LE-126
LE-125 LE-124
LE-123LE-122
LE-121
LE-120
LE-119LE-118
LE-117
LE-116
LE-115LE-114
LE-113
LE-112
LE-111LE-110LE-109LE-108
LE-107LE-106
LE-105
LE-104LE-103LE-102LE-101LE-100
LE-099LE-098
LE-096
LE-097
LE-095
LE-094
LE-093LE-092
LE-091LE-090
LE-089LE-088
LE-087
LE-086LE-085
LE-084
LE-083
LE-082
LE-081 LE-277LE-276
LE-080LE-079
LE-078
LE-077
LE-076LE-075
LE-074
LE-073
LE-072
LE-071
LE-070
LE-069LE-068LE-067LE-066
LE-065LE-064
LE-063
LE-062LE-061
LE-060
LE-059LE-058
LE-057
LE-056
LE-055LE-054
LE-053LE-052
LE-051
LE-034
LE-032
LE-030
LE-029LE-028
LE-027
LE-024
LE-019
LE-018
LE-017
LE-016LE-015
LE-014LE-013 LE-012
CH-249
CH-248CH-247
CH-246CH-245
CH-244
CH-243
CH-242
CH-241CH-240
CH-239CH-238
CH-237
CH-226
CH-208CH-250
CH-207
CH-206
CH-205
LE-224
Deep R
iver
CHATHAM COUNTY
LEE COUNTY
MOORECOUNTY
79°15'79°20'
35°30'
35°25'
Base modified from U.S. Geological Survey (USGS)Reinemund, 1955
0 1 2 3 MILES
0 1 2 3 KILOMETERS
EXPLANATION
Inventory and sampling
USGS areal site; Duke University and University of North Carolina at Chapel Hill sampling site
USGS focus-reduced site
USGS focus-reduced site; Duke University and University of North Carolina at Chapel Hill sampling site
USGS focus site and Duke University and University of North Carolina at Chapel Hill sampling site
USGS inventory siteUSGS inventory site; Duke University and University of North Carolina at Chapel Hill sampling siteUSGS areal site
Spring
Lithology
Diabase dikeFault; D, downthrown side; U, upthrown side
High-level surficial depositsDiabaseSanford Formation
Cumnock FormationPekin Formation
Quaternary alluvium
Terrace gravel deposits 2Terrace gravel deposits 3 and 4
DU
UD
UD
DU D
U
DU
DU
DU
DU
DU
DU
D U
UD
UD D
U
Data Summary 9
Figure 6. Range of well depths inventoried across the study area.
LE-329LE-328
LE-327
LE-326LE-325
LE-324
LE-323
LE-321
LE-150
LE-319
LE-318
LE-317
LE-316
LE-315LE-313
LE-312
LE-311
LE-310
LE-201
LE-307
LE-306
LE-305
LE-304
LE-302LE-303
LE-301
LE-300
LE-296
LE-295
LE-294
LE-293
LE-292
LE-291
LE-289
LE-287
LE-280 LE-285
LE-284
LE-283
LE-282LE-286LE-281
LE-278
LE-277LE-276
LE-274
LE-273LE-272
LE-271
LE-270
LE-269
LE-142
LE-267
LE-265
LE-264
LE-263
LE-262
LE-261LE-260
LE-259
LE-258
LE-257
LE-256
LE-255LE-254
LE-253LE-252
LE-251
LE-250
LE-249
LE-248LE-247LE-246
LE-245
LE-244LE-243
LE-242
LE-241
LE-240LE-239
LE-236
LE-237
LE-238
LE-235LE-234
LE-233 LE-232LE-231
LE-230
LE-229
LE-228LE-227
LE-226
LE-225
LE-223LE-221
LE-222
LE-220
LE-219
LE-218
LE-217
LE-216
LE-215
LE-214LE-213
LE-212LE-211
LE-210
LE-209
LE-208
LE-207LE-206
LE-205
LE-204LE-203
LE-202
LE-309LE-200
LE-199
LE-198
LE-197
LE-196
LE-195
LE-194
LE-193
LE-192
LE-191
LE-190LE-189
LE-188
LE-187
LE-186
LE-185
LE-184LE-183
LE-182LE-181
LE-180
LE-179
LE-178LE-177LE-176
LE-175
LE-174
LE-173LE-172
LE-171
LE-170LE-169
LE-168
LE-167
LE-166
LE-165
LE-164
LE-163LE-162
LE-161
LE-160
LE-159
LE-158
LE-157
LE-156LE-155
LE-154
LE-153
LE-152
LE-151
LE-320
LE-149
LE-148LE-147
LE-146
LE-144LE-145
LE-143
LE-268
LE-141
LE-140
LE-139
LE-138
LE-137
LE-136LE-135
LE-134LE-133LE-132
LE-131
LE-130
LE-129
LE-128
LE-127
LE-126
LE-125LE-124
LE-123LE-122
LE-121
LE-120
LE-119LE-118
LE-117
LE-116LE-115
LE-114
LE-113
LE-112
LE-111
LE-110LE-109LE-108
LE-107LE-106
LE-105LE-104LE-103LE-102LE-100
LE-101
LE-099LE-098
LE-097
LE-096
LE-095
LE-094
LE-093
LE-092
LE-091LE-090
LE-089
LE-088
LE-087
LE-086LE-085
LE-084
LE-083LE-082
LE-081
LE-080LE-079
LE-078
LE-077LE-076
LE-075
LE-074LE-073
LE-072
LE-071LE-070
LE-066LE-068LE-067LE-069
LE-065LE-064
LE-063
LE-062LE-061
LE-060
LE-059
LE-058
LE-056
LE-055LE-054
LE-053LE-052
LE-051
LE-034
LE-032
LE-030
LE-029LE-028
LE-027
LE-024
LE-019
LE-018
LE-017
LE-016LE-015
LE-014LE-013
LE-012
CH-250
CH-249
CH-248CH-247
CH-246CH-245
CH-244
CH-243
CH-242
CH-241
CH-240
CH-239CH-238
CH-237
CH-226
CH-208
CH-207
CH-206
CH-205
LE-224
CHATHAM COUNTY
LEE COUNTY
MOORECOUNTY
79°15'79°20'
35°30'
35°25'
Base modified from U.S. Geological SurveyReinemund, 1955
0 1 2 3 MILES
0 1 2 3 KILOMETERS
Deep R
iver
Well depth, in feet below land surface
0 to 100>100 to 300
>300 to 600
>600
EXPLANATION
Lithology
Diabase dikeFault; D, downthrown side; U, upthrown side
High-level surficial depositsDiabaseSanford Formation
Cumnock FormationPekin Formation
Quaternary alluvium
Terrace gravel deposits 2Terrace gravel deposits 3 and 4
DU
UD
UD
DU D
U
DU
DU
DU
DU
DU
DU
D U
UD
UD D
U
10 Baseline Well Inventory and Groundwater-Quality Data from a Potential Shale Gas Resource Area
Major Ions
Major ions were analyzed in all samples, and concentra-tions were highly variable. Cation concentrations ranged from 0.957 to 124 mg/L calcium (median of 27.2 mg/L), 0.911 to 41.4 mg/L magnesium (median of 7.41), 6.26 to 405 mg/L sodium (median of 17.3 mg/L) and 0.5 to 3.82 mg/L potas-sium (median of 1.36 mg/L). Anion concentrations ranged from 2.75 to 284 mg/L chloride (median of 10.5 mg/L), less than 0.04 to 0.31 mg/L fluoride (median of 0.08 mg/L), and 0.18 to 997 mg/L sulfate (median of 3.47 mg/L). Nitrate (plus nitrite, mg/L as nitrogen), which was analyzed in samples col-lected from 19 wells, ranged from less than 0.04 to 16.4 mg/L (median of 0.188 mg/L). One well LE-216 (appendix 3–1) had a concentration of nitrate above the drinking water standard of 10 mg/L (U.S. Environmental Protection Agency, 2009) (appendix 4–1).
Piper (1953) diagrams illustrate the distribution of groundwater types for the 35 samples, which had both major
ions and nitrite plus nitrate values, and 19 samples, which had major ion analyses but lacked nitrite plus nitrate analyses (fig. 12; Note that three samples—two from the set containing nitrite plus nitrate analyses and one that did not include nitrite plus nitrate analyses—exceeded the project’s ten percent bal-ance criteria for plotting on Piper diagrams). The more domi-nant groundwater type was calcium-bicarbonate, although major ion geochemistry varied widely, as indicated by the range of point distribution. The two wells having the highest specific conductance values were LE-178 and LE-185 (2,210 and 1,330 µS/cm, respectively; fig. 12A and appendix 3–1). The sample collected from well LE-178 had a sodium-sulfate groundwater, with the highest values of those two constituents, as well as elevated calcium and chloride, and the highest val-ues of several metals including strontium, lithium, molybde-num, and zinc (appendix 3–1). The sample from well LE-185 had a calcium-chloride-bicarbonate groundwater type that had elevated calcium, magnesium, sodium, and chloride; no metals analyses were completed for this well sample. The elevated major ion concentrations likely are the result of natural condi-tions with a longer residence time (exposure to the bedrock) where minerals have more time to dissolve in groundwater. Both wells are in close proximity to each other (fig. 5), located south of the Governors Creek fault and northeast and along strike of diabase dikes (fig. 3), which may suggest effects from these geologic features through control of groundwater flow.
Dissolved Metals
Dissolved metals with notable concentrations (generally detections above 1 µg/L) in groundwater samples included aluminum ranging from less than 2.2 to 14.8 µg/L (median of less than 2.2 µg/L), arsenic 0.14 to 4.8 µg/L (median of 1.1 µg/L ), barium 11.6 to 257 µg/L (median of 99.5 µg/L), boron 5 to 825 µg/L (median of 16 µg/L ), chromium less than 0.07 to 3.4 µg/L (median of 0.23 µg/L), copper less than 0.8 to 30.8 µg/L (median of less than 0.8 µg/L), iron less than 3.2 to 4,490 µg/L (median of 5.3 µg/L), lithium (estimated) 1.46 to 38.1 µg/L (median of 7.07 µg/L), manganese less than 0.13 to 997 µg/L (median of 3.55 µg/L), nickel less than 0.09 to 1.5 µg/L (median of 0.37 µg/L), strontium 24.9 to 16,700 µg/L (median of 114 µg/L), and zinc 1.5 to 79.5 µg/L (median of 10.4 µg/L) (appendix 3–1).
Exceedances
Of the more than 200 field properties and constituents that were analyzed, only eight exceeded at least one water-quality standard set by either the U.S. Environmental Protec-tion Agency or the State of North Carolina (fig. 13; table 1; appendix 4–1 http://pubs.usgs.gov/ds/861/Appendix4.xlsx). With the possible exception of nitrate, these constituents likely are present naturally in the aquifer. Thirty-seven percent of samples contained pH values less than 6.5. Thirty-five percent of samples exceeded the State groundwater standard
Welldepth
Casingdepth
Yield Dateconstructed
Dep
th b
elow
land
sur
face
, in
feet
0
50
100
150
200
250
300
350
400
450
500
550
600
650
700
(Wel
l yie
ld, i
n ga
llons
per
min
ute)
0
10
20
30
40
50
60
70
80
90
100
110
Year
1800
1825
1850
1875
1900
1925
1950
1975
2000
2025301 243 286 276
301EXPLANATION
Number of valuesIndividual observation above 90th percentile
Individual observation below 10th percentile
90th percentile
10th percentile
75th percentile
50th percentile(median)
25th percentile
Well information
Figure 7. Well depth, casing depth, yield, and date of construction for wells inventoried in the study area.
Data Summary 11
Figure 8. Range of well yields inventoried across the study area.
LE-329
LE-326LE-325
LE-324
LE-323LE-321
LE-320
LE-319
LE-318
LE-316
LE-315LE-313
LE-312
LE-311
LE-309
LE-307
LE-255
LE-305
LE-304
LE-303LE-302
LE-301
LE-296
LE-295
LE-294
LE-293
LE-292
LE-291
LE-289
LE-287
LE-286LE-280
LE-285LE-284
LE-283
LE-281
LE-219
LE-274
LE-273 LE-272
LE-271
LE-270
LE-269
LE-268
LE-267
LE-264
LE-263
LE-262
LE-261LE-260
LE-258
LE-257
LE-256
LE-306
LE-254LE-253
LE-252
LE-250
LE-249
LE-248LE-247LE-246
LE-245
LE-244LE-243
LE-242
LE-241
LE-240LE-239
LE-238LE-237
LE-236
LE-235LE-234
LE-233 LE-232LE-231LE-230
LE-229
LE-228LE-227
LE-226
LE-225
LE-223
LE-222
LE-221
LE-220
LE-218
LE-217
LE-216
LE-215
LE-214LE-213
LE-212LE-211
LE-210
LE-209
LE-208
LE-207
LE-206
LE-205
LE-204
LE-203
LE-202
LE-201LE-200
LE-199
LE-198
LE-197
LE-196LE-195
LE-194
LE-193LE-192
LE-191
LE-190LE-189
LE-188
LE-187LE-186
LE-185
LE-184LE-183
LE-182
LE-181
LE-180
LE-179
LE-178LE-177LE-176
LE-175
LE-174
LE-173LE-172
LE-171
LE-170LE-169
LE-168
LE-167
LE-166
LE-165
LE-164
LE-163LE-162
LE-161
LE-160
LE-159
LE-158
LE-157
LE-156LE-155
LE-154
LE-153
LE-152
LE-150
LE-149
LE-148LE-147
LE-146
LE-144
LE-145
LE-143
LE-142
LE-141
LE-140
LE-139
LE-138
LE-137LE-136
LE-135
LE-134LE-133LE-132
LE-131
LE-130
LE-129
LE-128
LE-127
LE-126LE-125
LE-124
LE-123
LE-122LE-121
LE-120
LE-119LE-118
LE-117
LE-116
LE-115LE-114
LE-113
LE-112
LE-111LE-110LE-109LE-108
LE-107LE-106
LE-105
LE-104LE-103
LE-102
LE-101
LE-100
LE-099LE-098
LE-096
LE-095
LE-094
LE-093LE-092
LE-091LE-090
LE-089
LE-088
LE-087
LE-086LE-085
LE-083LE-082
LE-081
LE-080LE-079
LE-078
LE-077
LE-076LE-075
LE-074
LE-073
LE-072
LE-071
LE-070
LE-069LE-067
LE-068LE-066
LE-065LE-064
LE-063
LE-062LE-061
LE-060
LE-059LE-058
LE-057
LE-056
LE-055LE-054
LE-053LE-052
LE-051
LE-034
LE-032LE-030
LE-029LE-028
LE-027
LE-024
LE-019
LE-018
LE-017
LE-016LE-015
LE-014LE-013
LE-012
CH-249
CH-248CH-247
CH-246
CH-245CH-244
CH-243
CH-242
CH-241CH-240CH-239
CH-238CH-237
CH-226
CH-208
CH-207
CH-206
CH-205
LE-224
CHATHAM COUNTY
LEE COUNTY
MOORECOUNTY
79°15'79°20'
35°30'
35°25'
Base modified from U.S. Geological SurveyReinemund, 1955
0 1 2 3 MILES
0 1 2 3 KILOMETERS
Deep R
iver
Well yield, in gallons per minute
0.25 to 10>10 to 25
>25 to 50
> 50 to 100
EXPLANATION
Lithology
Diabase dikeFault; D, downthrown side; U, upthrown side
High-level surficial depositsDiabaseSanford Formation
Cumnock FormationPekin Formation
Quaternary alluvium
Terrace gravel deposits 2Terrace gravel deposits 3 and 4
DU
UD
UD
DU D
U
DU
DU
DU
DU
DU
DU
D U
UD
UD D
U
12 Baseline Well Inventory and Groundwater-Quality Data from a Potential Shale Gas Resource Area
for manganese of 50 µg/L [North Carolina 15A NCAC 2L .0202 Groundwater Standard (http://portal.ncdenr.org/c/docu-ment_library/get_file?folderId=567426&name=DLFE-14952.pdf; accessed May 2014)]. Exceedances for chloride, sulfate, and dissolved solids were associated with samples having the higher specific conductance values (appendix 3–1). Maximum concentrations measured in groundwater samples exceeded standards by factors ranging from 14 percent for chloride to almost 1,900 percent for manganese (appendix 4–1).
Reporting levels for 16 organic compounds were greater than their corresponding water-quality standard (appendix 4–2). None of these compounds were detected,
but the higher reporting level precludes evaluating whether any of these standards were exceeded. About 100 additional constituents, both natural and anthropogenic, have at least one standard but either were not detected in groundwater samples or did not exceed any standard (appendix 4–3). More than 80 constituents included in the groundwater sampling study had no published water-quality standard (appendix 4–4).
Methane
Dissolved methane was analyzed in all 57 well and spring water samples by the USGS Chlorofluorocarbon (CFC) Labo-ratory in Reston, Virginia (see method instrumentation and reference list, appendix 1) and also was separately analyzed in 12 samples by a second laboratory (Isotech Laboratory, see reference list appendix 1) (fig. 14; appendix 3–5, 3–6). Among all 57 samples, methane concentrations were relatively low, but ranged more than several orders of magnitude from below the reporting level (appendix 1) of 0.0005 to 0.48 mg/L. Thirty-five of the 57 samples (61 percent) had measured meth-ane concentrations less than 0.0005 mg/L. For the subset of 12 samples analyzed by both laboratories, the USGS CFC laboratory reported a minimum concentration of less than 0.0005 mg/L, a maximum of 0.48 mg/L, and a median between less than 0.0005 mg/L and 0.0032 mg/L. The Isotech laboratory had an approximately seven-fold lower reporting level (0.00007 mg/L), and its median (between 0.00034 mg/L and 0.0031 mg/L) and maximum (0.33 mg/L) concentrations were similar to those determined for this subset of samples by
pH Dissolved oxygen
Alkalinity Specificconductance
Temperature
pH, i
n st
anda
rd u
nits
4
5
6
7
8
9
Dis
solve
d ox
ygen
, in
mill
igra
ms
per l
iter
0
2
4
6
8
Alk
alin
ity, i
n m
illig
ram
s pe
r lite
r as
calc
ium
car
bona
te
0
50
100
150
200
250
300
Spec
ific
cond
ucta
nce,
in m
icro
siem
ens
per c
entim
eter
at 2
5 de
gree
s Ce
lsiu
s
0
500
1,000
1,500
2,000
2,500
Tem
pera
ture
, in
degr
ees
Cels
ius
16
18
20
22
24
26
Field measured property
57
57 57 57 57 57
EXPLANATION Number of valuesIndividual observation above 90th percentile
Individual observation below 10th percentile
90th percentile
10th percentile
75th percentile
50th percentile(median)
25th percentile
Figure 9. Field-measured properties of pH, dissolved oxygen, alkalinity, specific conductance, and temperature of well and spring water sampled in the study area.
Table 1. Number and percent of analyses exceeding at least one water-quality standard set by either United States Environmental Protection Agency or the State of North Carolina.
[TDS, total dissolved solids; <, less than; >, greater than]
Constituent AnalysesNumber of
exceedancesPercent
exceedancesBoron 11 1 9Chloride 57 1 2TDS 57 3 5Iron 57 3 5Manganese 57 20 35Nitrate 37 1 3pH (<6.5) 57 21 37pH (>8.5) 57 1 2Sulfate 57 2 4
Data Summary 13
Figure 10. Distribution of field pH values measured in well and spring water sampled in the study area.
LE-329
LE-320
LE-318
LE-317
LE-315
LE-311
LE-305
LE-296
LE-293
LE-291
LE-289
LE-287
LE-280
LE-279LE-273
LE-270
LE-268
LE-265
LE-264
LE-262
LE-258
LE-257
LE-256
LE-253
LE-251
LE-243
LE-234
LE-233
LE-227LE-225
LE-220
LE-219
LE-216
LE-208
LE-202
LE-191
LE-188
LE-185
LE-178
LE-168
LE-165
LE-164
LE-152
LE-133LE-125
LE-123
LE-116
LE-108
LE-087
LE-083
LE-073
LE-072
LE-052
LE-051
CH-243
CH-241
CH-247
CHATHAM COUNTY
LEE COUNTY
MOORE COUNTY
79°15'79°20'
35°30'
35°25'
Base modified from U.S. Geological SurveyReinemund, 1955
5
6
7
8
7
6
7 6
6
67
7
6
6
7
7
0 1 2 3 MILES
0 1 2 3 KILOMETERS
Deep River
7
7
EXPLANATION
Sampled well/spring and identifier
Line of equal pH—Interval 1 standard unit
LE-123
6
Lithology
Diabase dikeFault; D, downthrown side; U, upthrown side
High-level surficial depositsDiabaseSanford Formation
Cumnock FormationPekin Formation
Quaternary alluvium
Terrace gravel deposits 2Terrace gravel deposits 3 and 4
DU
UD
UD
DU
DU
D U
DU
DU
DU
DU
DU
D U
UD
UD D
U
14 Baseline Well Inventory and Groundwater-Quality Data from a Potential Shale Gas Resource Area
Figure 11. Distribution of field specific conductance values measured in well and spring water sampled in the study area.
CHATHAM COUNTY
LEE COUNTY
MOORE COUNTY
79°15'79°20'
35°30'
35°25'
Base modified from U.S. Geological SurveyReinemund, 1955
0 1 2 3 MILES
0 1 2 3 KILOMETERS
Deep River
Lithology
Diabase dikeFault; D, downthrown side; U, upthrown side
High-level surficial depositsDiabaseSanford Formation
Cumnock FormationPekin Formation
Quaternary alluvium
Terrace gravel deposits 2Terrace gravel deposits 3 and 4
DU
LE-329
LE-320
LE-318
LE-317
LE-315
LE-311
LE-305
LE-296
LE-293LE-291
LE-289
LE-287
LE-279
LE-273
LE-270
LE-268
LE-265
LE-264
LE-262
LE-258
LE-257
LE-256
LE-253
LE-251
LE-243
LE-234LE-233
LE-227LE-225
LE-220
LE-219
LE-216
LE-208
LE-202
LE-191
LE-188
LE-185
LE-178
LE-168
LE-165
LE-164
LE-152
LE-133
LE-125
LE-123
LE-116
LE-108
LE-087
LE-083
LE-073
LE-072
LE-052
LE-051
CH-243
CH-241
CH-247
LE-280
4001,
000
6001,2
00
1,40
0
1,800
1,600
200
200
200
600
600
200
200
600200
800
400
400
200
2,000
600
800
800
EXPLANATION
Sampled well/spring and identifier
Line of equal specific conductance—Interval 200 µS/cm at 25 ˚C
LE-123
200
UD
UD
DU D
U
DU
DU
DU
DU
DU
DU
D U
UD
UD D
U
Data Summary 15
Figure 12. Distribution of major ion geochemistry for A, 35 groundwater samples, which included nitrite plus nitrate analyses and B, 19 groundwater samples without nitrite plus nitrate analyses in the study area.
PERCENT
Calcium
100
80
60
40
20
0 0
20
40
60
80
100
Mag
nesiu
m
0
20
40
60
80
100
Sodium plus potassium
A
B
C
D
E
F G
HI
J
KL
M
N
O
PQR
S
T
UV WX
Y
Z
a b
c
d
ef
g
hi
Chloride, fluoride, nitrite plus nitrate
0
20
40
60
80
100
100
80
60
40
20
0
Carb
onat
e pl
us b
icar
bona
te
100
80
60
40
20
0
Sulfate
A
BCDE
FGHI J KL
M
N
O
P
QRSTUV
W
X
Y
Z ab cde fg h i
0
20
40
60
80
100
Sulfa
te p
lus c
hlor
ide
0
20
40
60
80
100
Calcium plus m
agnesium
100
80
60
40
20
0
100
80
60
40
20
0
A
B
C
D
E
F
G
H
IJ
K
L
M
N
O
P
Q
R
S
T
U
V
W
X Y
Z
a
b
c
de
f
g
h
i
PERC
ENT PERCENT
w
x
y
z
@
#
q
r
s
t
u
v
k
l
m
n
o
p
e
f
g
h
i
j
Y
Z
a
b
c
d
S
T
U
V
W
X
M
N
O
P
Q
R
G
H
I
J
K
L
A
B
C
D
E
F
LE-178
LE-185
LE-264
LE-125
LE-233
LE-216
LE-280
LE-083
LE-123
LE-133
LE-051
CH-243
LE-251
LE-227
LE-287
LE-202
LE-291
LE-293
LE-257
LE-152
LE-234
LE-305
LE-311
LE-318
LE-191
LE-289
LE-320
LE-253
LE-296
LE-315
LE-329
CH-247
LE-108
LE-073
LE-273
LE-268
LE-072
LE-188
LE-262
CH-241
LE-256
LE-265
LE-087
LE-219
LE-225
LE-243
LE-258
LE-220
LE-208
LE-168
LE-165
LE-164
LE-270
LE-052
EXPLANATION
Well identifier
A
16 Baseline Well Inventory and Groundwater-Quality Data from a Potential Shale Gas Resource Area
Figure 12. Distribution of major ion geochemistry for A, 35 groundwater samples, which included nitrite plus nitrate analyses and B, 19 groundwater samples without nitrite plus nitrate analyses in the study area.—Continued
PERCENT
Calcium
100
80
60
40
20
0 0
20
40
60
80
100
Mag
nesiu
m
0
20
40
60
80
100
Sodium plus potassium
Chloride, fluoride
0
20
40
60
80
100
100
80
60
40
20
0
Carb
onat
e pl
us b
icar
bona
te
100
80
60
40
20
0
Sulfate
0
20
40
60
80
100
Sulfa
te p
lus c
hlor
ide
0
20
40
60
80
100
Calcium plus m
agnesium
100
80
60
40
20
0
100
80
60
40
20
0
PERC
ENT PERCENT
j klm
n
o
p
q
r
s
t u
v
w xy z@
#
j
kl
mn
o
pq
r
st
u
vw xy z @
#
j
k
l
m
n
o
p
q
r
st u
vw
x
y z
@
#
w
x
y
z
@
#
q
r
s
t
u
v
k
l
m
n
o
p
e
f
g
h
i
j
Y
Z
a
b
c
d
S
T
U
V
W
X
M
N
O
P
Q
R
G
H
I
J
K
L
A
B
C
D
E
F
LE-178
LE-185
LE-264
LE-125
LE-233
LE-216
LE-280
LE-083
LE-123
LE-133
LE-051
CH-243
LE-251
LE-227
LE-287
LE-202
LE-291
LE-293
LE-257
LE-152
LE-234
LE-305
LE-311
LE-318
LE-191
LE-289
LE-320
LE-253
LE-296
LE-315
LE-329
CH-247
LE-108
LE-073
LE-273
LE-268
LE-072
LE-188
LE-262
CH-241
LE-256
LE-265
LE-087
LE-219
LE-225
LE-243
LE-258
LE-220
LE-208
LE-168
LE-165
LE-164
LE-270
LE-052
EXPLANATION
Well identifier
B
Data Summary 17
Figure 13. Constituents exceeding at least one water-quality standard set by either the U.S. Environmental Protection Agency or the State of North Carolina.
Boron Iron Manganese Chloride Dissolved solids
Nitrate Sulfate pH
Bor
on, ir
on, a
nd m
anga
nese
con
cent
ratio
n, in
mic
rogr
ams
per l
iter
0.01
0.1
1.0
10
100
1,000
10,000
Chlo
ride,
dis
solve
d so
lids,
nitra
te, a
nd su
lfate
con
cent
ratio
n, in
milli
gram
s per
liter
0.01
0.1
1.0
10
100
1,000
10,000
pH (s
tand
ard
units
)
4
5
6
7
8
9
Water-quality standard
Analyte
57
11 57 57 57 57 37 57 57
EXPLANATION Number of valuesIndividual observation above 90th percentile
Individual observation below 10th percentile
90th percentile
10th percentile
75th percentile
50th percentile(median)
25th percentile
USGS Restonlaboratory
USGS overlapwith Isotech
Isotech laboratory
Met
hane
, in
mill
igra
ms
per l
iter
0.00001
0.0001
0.001
0.01
0.1
1.0
Sample set
Laboratory reporting limit
57 12 12
57EXPLANATION
Number of valuesIndividual observation above 90th percentile
Individual observation below 10th percentile
90th percentile
10th percentile
75th percentile
50th percentile(median)
25th percentile
USGS U.S. Geological Survey
Figure 14. Range in detected dissolved methane gas analyses from well and spring samples in the study area.
18 Baseline Well Inventory and Groundwater-Quality Data from a Potential Shale Gas Resource Area
the USGS laboratory. Only 1 sample of the 12 Isotech sam-ples, well LE-262, had a methane concentration high enough to determine isotope concentrations (appendix 3–6). Only three samples had concentrations of dissolved methane gas above 0.1 mg/L (appendix 3). LE-262 was located in a Cum-nock Shale outcrop area, and the other two samples, LE-191 and LE-087, were located near the Crawley Creek fault (figs. 3 and 5).
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Appendixes 1–4
22 Baseline Well Inventory and Groundwater-Quality Data from a Potential Shale Gas Resource Area
Appendix 1 (http://pubs.usgs.gov/ds/861/Appendix1.xlsx)
Constituents measured in well and spring water collected for this study.
Appendix 2 (http://pubs.usgs.gov/ds/861Appendix2.xlsx)
Construction data for 305 wells and 1 spring inventoried for this study.
Appendix 3 (http://pubs.usgs.gov/ds/861/Appendix3.xlsx)
3–1. Field properties and constituents in groundwater samples analyzed in the field or by the United States Geological Survey National Water Quality Laboratory.
3–2. Dissolved constituents in field blanks analyzed by the United States Geological Survey National Water Quality Laboratory. 3–3. Precision among replicates for dissolved constituents in groundwater samples analyzed in the field or by the United
States Geological Survey National Water Quality Laboratory. 3–4. Surrogate recoveries for selected analytical methods used by the United States Geological Survey National Water
Quality Laboratory. 3–5. Dissolved methane concentrations in groundwater samples preserved with potassium hydroxide, averaged between
analytical duplicates, and analyzed by the United States Geological Survey (Reston) Chlorofluorocarbon Laboratory. 3–6. Dissolved methane concentrations and selected isotopic ratios in groundwater samples preserved with benzalkonium
chloride and analyzed by Isotech Laboratories. 3–7. Dissolved strontium isotopes in groundwater samples analyzed by the United States Geological Survey Denver
(Zell Peterman) Laboratory. 3–8. Dissolved concentrations of glycols in groundwater samples analyzed by Test America Laboratories. 3–9. Dissolved concentrations of selected volatile and semivolatile organic compounds in groundwater samples analyzed
by the North Carolina Department of Natural Resources.
Appendix 4 (http://pubs.usgs.gov/ds/861/Appendix4.xlsx)
4–1. Constituents that exceeded a water-quality standard. 4–2. Constituents having water-quality standards lower than the reporting level. 4–3. Constituents that did not exceed an associated water-quality standard. 4–4. Constituents having no water quality standard.
For further information about this publication contact:DirectorU.S. Geological SurveyNorth Carolina Water Science Center3916 Sunset Ridge RoadRaleigh, NC 27607
Or visit the North Carolina Water Science Center Web site at:http://nc.water.usgs.gov/
Prepared by the Raleigh and Rolla Publishing Service Centers
Chapman and others—
Baseline W
ell Inventory and Groundw
ater-Quality D
ata from a Potential Shale G
as Resource Area—
Data Series 861
ISSN 2327-638X (online)http://dx.doi.org/10.3133/ds861
