EPA Superfund
Record of Decision:
PB98-964009
EPA 541-R98-055
October 1998
Davis Park Road TCE
Gastonia, NC
9/29/1998
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RECORD OF DECISION
REMEDIAL ALTERNATIVE SELECTION
DAVIS PARK ROAD TCE SITE
GASTONIA, GASTON COUNTY
NORTH CAROLINA
U.S. ENVIRONMENTAL PROTECTION AGENCY
REGION 4
ATLANTA, GEORGIA
SEPTEMBER, 1998
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DECLARATION FOR THE RECORD OF DECISION
SITE NAME AND LOCATION
Davis Park Road TCE Site
Gastonia, Gaston County, North Carolina
STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected remedial action for the Davis Park Road TCE
Site in Gastonia, Gaston County, North Carolina, chosen in accordance with the Comprehensive
Environmental Response, Compensation and Liability Act of 1980 (CERCLA), as amended by the
Superfund Amendments and Reauthorization Act of 1986 (SARA) and, to the extent practicable, the
National Contingency Plan (NCP). This decision is based on the administrative record file for this
Site.
The State of North Carolina concurs with the selected remedy.
ASSESSMENT OF THE SITE
Actual or threatened releases of hazardous substances from this Site, if not addressed by
implementing the response action selected in this Record of Decision, may present an imminent and
substantial endangerment to public health, welfare, or the environment.
DESCRIPTION OF THE SELECTED REMEDY
This remedy addressees the principle threat posed by the Site. The major threat is the
contaminated groundwater emanating from beneath the Site.
The major components of the selected groundwater remedy include:
4 Reduction of Groundwater Exposure; connection of homes, churches, and businesses in the
Davis Park Road Site area to the City of Gastonia public water supply;
* Optional wellhead treatment for affected private wells;
4 Natural attenuation to restore the contaminated aquifer to the lower of either the Maximum
Contaminant Levels (MCLs) or North Carolina Part 2L Drinking Water Requirements. The
primary attenuation processes occurring at the Davis Park Road TCE Site are dispersion and
intrinsic biodegradation;
* Continued analytical monitoring for contaminants in groundwater; and
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September, 1998
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4 Develop contingency plans to respond to differences in the actual performance of the remedy
and actual site conditions, as compared to the expected performance of the remedy and
expected site conditions. Additional information will be collected during the first year of the
Remedial Design effort in order to support the predicted dispersion and intrinsic
biodegradation rates for the contaminated groundwater. The contingency plans may include
the implementation of institutional controls, modifications to the monitoring program, and
implementation of the contingency remedy, if necessary.
The contingency remedy includes:
4 Reduction of Ground water Exposure; connection of homes, churches, and businesses in the
Davis Park Road Site area to the City of Gastonia public water supply;
4 Optional wellhead treatment for affected private wells;
4 Groundwater pump and treat using a minimum of three extraction wells with treatment of
contaminated groundwater at the ground surface using activated carbon to remove VOCs.
4 Continued analytical monitoring for contaminants in groundwater.
STATUTORY DETERMINATIONS
The selected remedy is protective of human health and the environment, complies with Federal
and State requirements that are legally applicable or relevant and appropriate to the remedial action,
and is cost-effective. This remedy utilizes permanent solutions and alternative treatment technology to
the maximum extent practicable, and satisfies the statutory preference for remedies that employ
treatment that reduces toxicity, mobility, (6r volume as a principal element. This statutory preference
for treatment is satisfied through intrinsic biodegradation for the selected remedy, and through
groundwater extraction and treatment for the contingency remedy.
Since this remedy may result in hazardous substances remaining on-site above health based
levels, a review will be conducted within five years after commencement of remedial action to ensure
that the remedy continues to provide adequate protection of human health and the environment.
Richard D. Green, Director Date
Waste Management Division
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County. NC
September. 1998
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TABLE OF CONTENTS
SECTION PAGE NO.
1.0 SITE NAME, LOCATION AND DESCRIPTION 1-1
A. Introduction 1-1
B Site Description 1-1
C. Demography 1-3
D. Surrounding Land/Water Use 1 -3
E. Topography 1-3
F Climate 1-4
G Geology 1-4
H Hydrogeology 1-5
2.0 SITE HISTORY AND ENFORCEMENT ACTIVITIES 2-1
A. Site History 2-1
B. Previous Investigations 2-1
C. Site Regulatory Actions 2-2
3 0 HIGHLIGHTS OF COMMUNITY PARTICIPATION 3-1
4.0 SCOPE AND ROLE OR RESPONSE ACTION
WITHIN SITE STRATEGY 4-1
5.0 SUMMARY OF SITE CHARACTERISTICS
A.
B
C
D
E
F
G
H
1
Source Area/Soil Investigation
Surface Water and Sediment Investigation
Residential Well Survey
Private Well Sampling
Shallow Groundwater Investigation
Bedrock Groundwater Investigation
Bedrock Fracture Analysis
Natural Attenuation Evaluation
Ecological Evaluation
6.0 SUMMARY OF SITE RISKS
A.
B
C
D
E.
F
Chemicals of Potential Concern
Exposure Assessment
Toxicity Assessment
Risk Characterization
Uncertainties
Conclusions
5-1
5-1
5-5
5-5
5-5
5-5
5-10
5-10
5-17
5-17
6-1
6-1
6-2
6-2
6-7
6-10
6-10
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September, 1998
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TABLE OF CONTENTS CONT'D
SECTION PAGE NO
7.0 APPLICABLE OR RELEVANT AMD
APPROPRIATE REQUIREMENTS (ARARS) 7-1
A. Chemical Specific ARARs 7-1
B. Location Specific ARARs 7-3
C. Action Specific ARARs 7-3
D Media of Concern 7-3
8.0 REMEDIAL ACTION OBJECTIVES 8-1
9.0 DESCRIPTION OF ALTERNATIVES 9-1
A. Alternative 1 - No Action 9-1
B Alternative 2 - Institutional Controls 9-2
C Alternative 3 - Reduction of Groundwater Exposure and
Monitored Natural Attenuation 9-2
D. Alternative 4 - Reduction of Groundwater Exposure and
Groundwater Treatment 9-3
E Alternative 5- Reduction of Groundwater Exposure and
Groundwater Pump and Treat 9-3
100 SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES 10-1
A. Alternative 1 - No Action 10-2
B Alternative 2 - Institutional Controls 10-4
C. Alternative 3 - Reduction of Groundwater Exposure and
Monitored Natural Attenuation 10-5
D Alternative 4 - Reduction of Groundwater Exposure and
Groundwater Treatment 10-8
E. Alternative 5- Reduction of Groundwater Exposure and
Groundwater Pump and Treat 10-9
F Comparative Analysis of Alternatives 10-11
1 1.0 THE SELECTED REMEDY 11-1
12.0 DOCUMENTATION OF SIGNIFICANT CHANGE 12-1
APPENDIX A - RESPONSIVENESS SUMMARY
APPENDIX B - JULY 28, 1998 PUBLIC MEETING TRANSCRIPT
APPENDIX C - STATE CONCURRENCE
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September, 1998
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TABLE OF CONTENTS CONT'D
FIGURES PAGE NO.
1 -1 Site Location Map 1 -2
2-1 Historical TCE detections in Private Wells 2-3
5-1 May 1996 Source Soil Sampling Locations 5-2
5-2 October 1996 Source Soil Sampling Locations 5-3
5-3 1997/1998 Source Soil Sampling Locations 5-4
5-4 SW/Sediment Sampling Locations 5-6
5-5 Residential Well Survey 5-7
5-6 1996 Groundwater Well Sampling Locations 5-8
5-7 1997/1998 Monitoring Well Locations 5-9
5-8 TCE Concentration Isopleth 5-11
5-9 PCE Concentration Isopleth 5-12
TABLES PAGE NO.
5-1 Chemicals Detected in Soil and Groundwater 5-13
6-1 Exposure Point Concentrations in GW 6-3
6-2 Exposure Point Concentrations in Soil 6-4
6-3 Carcinogenic Toxicity Assessment 6-5
6-4 Noncarcinogenic Toxicity Assessment 6-6
6-5 Cancer and Noncancer Risks 6-8
6-6 Uncertainties in the Risk Assessment 6-11
7-1 Chemical-specific ARARs 7-2
7-2 Location-specific ARARs 7-4
7-3 Action-specific ARARs 7-5
8-1 Remediation Goals for Groundwater 8-1
9-1 Remedial Action AJternatives for Groundwater 9-1
10-1 Comparative Analysis for Groundwater 10-12
11-1 Capital Costs for Selected Remedy 11 -2
11-2 Remedial Action Operation Costs 11-3
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September, 1998 iii
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1.0 SITE NAME, LOCATION, AND DESCRIPTION
A. Introduction
The Davis Park Road TCE Site (hereinafter referred to as the "Site" or the "Davis Park Road
Site") is located in a mixed residential and small business neighborhood along Davis Park Road, south
of Hudson Boulevard and north of Blackwood Creek in the southwestern portion of Gastonia, North
Carolina (Figure 1-1). The Site also includes the soil behind-the building that is currently occupied by
the Davis Park Auto Repair shop at 2307 Davis Park Road, and a plume of contaminated groundwater
that was believed to emanate from this property. The Cedar Oak Park Subdivision located on the east
side of Davis Park Road, within the confines of Cedar Oak Circle, as well as areas along the western
side of Davis Park Road are also included in the Site area.
B. Site Description
During the Remedial Investigation ("RJ") the soil behind the building located at 2307 Davis
Park Road and a plume of contaminated groundwater believed to emanate from this property were
investigated. The Davis Park Road Site is located at latitude 35° 13' 56" N and longitude 81° 13' 08"
W The Site, situated on approximately 20 acres, includes private businesses and residential homes.
The topography of the area is slightly sloped to the west toward Crowders Creek and to the east and
south towards Blackwood Creek. Both creeks are receiving streams for groundwater in the area.
The potential source of the contaminated groundwater is an area of formerly contaminated soil
located behind the Davis Park Auto Repair Shop at 2307 Davis Park Road, in the vicinity of a drain
line that exited the service bay in the facility. Numerous service stations and repair shops have
operated at the 2307 Davis Park Road location beginning in 1956. The results of soil sampling
conducted by the North Carolina Department of Environment and Natural Resources ("NCDENR")
confirmed that at some time during the operation of the facility as a service station or transmission and
auto repair facility, tetrachloroethene ("PCE") and possibly trichloroethene ("TCE") were released
through a drain line installed in the service bay area of the building. According to NCDENR, these
contaminants were detected in the soil around the drain pipe that exited the facility. However, no soil
contamination was detected during sampling conducted during the RI.
PCE and TCE have been detected in groundwater sampled from a community well and several
private wells within the area of the Site at levels exceeding Federal and State drinking water standards.
Additionally, 1,2-dichloroethene ("1,2-DCE"), a breakdown product of PCE and TCE, has been
detected in both community and private wells in the area.
Davis Park Road TCE Site
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Gastonia. Gaston County, NC
September, 1998 1-1
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£
3
/
FIGURE 1-1
SITE MAP
DAVIS PARK ROAD TCE SITE
GASTONIA, NORTH CAROLINA
Approximate
Scale In Feet
600
1200
1-2
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C. Demography
The Site is located in Gaston County, North Carolina. According to 1995 estimates by the
North Carolina Department of Reserve and Budget, Gaston County had a population of 178, 442. A
1990 census revealed that the City of Gastonia had a population of 54,732. Based on the 1990 census
figures for persons per square mile for the site vicinity, total population for the Site area has been
calculated to be 267 within 1/4 mile of the Site, 566 for between 1/4 and !/2 mile of the site, and 2,020
for between '/2 and 1 mile of the site.
D. Surrounding Land/Water Use
The principal land use in the immediate vicinity of the Site is residential, and the area is zoned
for single family residences (R-l). There are two commercial operations within the Site boundary,
including the Davis Park Road Auto Repair Shop and Godwin Refrigeration. The Taylor Memorial
Baptist Church is also located within the Site boundary.
E. Topography
Gaston County, North Carolina lies in the central portion of the Piedmont Physiographic
Province The land surface is composed of low, broad ridges accentuated by numerous small steam
valleys In general, the topographic changes are gradual, except for occasional steep-sided steam
valleys. The average elevation in Gastonia is 825 feet above sea level.
The elevation at the Davis Park Road Site ranges from 675 feet above sea level at Blackwood
Creek to 770 feet above sea level at the Davis Park Road Auto Repair facility at 2307 Davis Park
Road. The Davis Park Auto Repair shop is located approximately 2,550 feet north of Blackwood
Creek The elevation declines gradually to the southeast, south, southwest, and west of this location.
Gaston County is drained by various streams and creeks that flow south, southeast, and east
towards Lake Wylie, Crowders Creek is a major drainage area for the southern portion of the City of
Gastonia. Crowders Creek flows south southeast into South Carolina, and approximately 15 miles
downstream from that point into Lake Wylie.
Surface runoff from the Davis Park Road Site flows overland into ditches and/or culverts on the
edges of the various roads that cross the Site or into small streams. Overland flow travels either south
southeast towards Blackwood Creek ( a tributary to Crowders Creek) or west southwest into smaller,
unnamed streams and eventually into Crowders Creek.
The suspected source area at 2307 Davis Park Road is bounded by Davis Park Road to the east,
and by private residences to the north and south. The western portion of the property is bounded by
vacant lots The area surrounding the building is paved on the eastern and southern portions. The
western portion of the site is covered by areas of grass, weeds, and trees intermixed with discarded
equipment from the operations at the facility. The northern portion of the property is covered by grass
Davis Park Road TCE Site
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September. 1998 1-3
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and trees. The distance from the building to the closest residential property north is approximately
fifteen feet.
F. Climate
The climate is moderate with approximately one half of the winter days falling below freezing.
Little snow falls and the occasional heavy snow usually melts within one or two days. The average
freeze-free period is 216 days. The summers are warm with temperatures into the 90°F range.
G. Geology
According to the 1988 Geologic Map of the Charlotte 1° X 2 ° Quadrangle, the Davis Park
Road Site is directly underlain by the Pennsylvanian Age High Shoals Granite Formation. This
formation is described as being very light gray, course-grained, porphyritic, well foliated, commonly
gneissoid biotite granite. This formation has been zircon dated at 317 million years old and may be
cogenitic with the Churchland Pluton, which lies to the northeast of the Site and underlies the northern
portion of the City of Gastonia.
The High Shoals Granite and Churchland Plutonic Suite are labeled as the High Shoals Pluton.
The High Shoals Pluton is a linear shaped body of granite material that trends northeast-southwest.
The High Shoals Pluton is surrounded by quartz sericite schists and metavolcanic rocks of the
Battleground Formation. In the Gastonia area, the pluton is bordered on the west by the South Fork
Anitform and on the east by the Boogertown Shear Zone. Flow foliation in these rocks is either
vertical or is greater on average than 75°, and typically trends northeast to southwest. The High
Shoals Pluton is considered to have originated after a regional metamorphic phase in the Late
Paleozoic Age
Geology underlying the Davis Park Road Site is described based on data generated from monitor
well installation and soil borings. As the rock types underlying the Site become weathered through
physical, chemical, and biological processes, soil profiles develop that are characteristic of the original
rock For example, the granite rock tends to weather to a silty clay rich loam or a rich sand material,
with depth The sand originates from quartz present in the original parent rock, and can range in size
from fine to coarse-grained The clay is derived from weathering of feldspathic minerals in the parent
rock Clay-rich soil in which parent rock structures are preserved is referred to as saprolite.
Bedrock underlying the Site is fracture as a result of regional metamorphic activity. In some
cases, remnant fractures are represented by iron staining along a fracture plane. The iron staining,
which is also referred to as the mineral limonite, is a result of groundwater leaching iron from the
surrounding material. As the groundwater travels along a fracture plane, the iron is redeposited along
the plane In other cases, the fracture planes have been "resealed" by quartz. As the rock weathers,
these quartz fillings are retained in the soil indicating that fractures existed in the rock. Fracture
planes were also identified as zones of weak to incompetent rock that were not resistant to the cutting
action of the drill bit. These fracture zones, or secondary porosity features, were typically saturated.
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September, 1998 1-4
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During the field activities, the geology varied across the Site; however, a common pattern was
observed. From top to bottom, the materials consist of a saprolite layer, a partially weathered rock
zone, and the underlying fractured crystalline bedrock. The saprolite is clay-rich, residual material
derived from in-place weathering of bedrock. Typically, the saprolite is silty clay near the surface.
With increasing depth, the amount of mica, silt, and fine-grained sand and gravel tend to increase.
Remnant fracture planes with quartz infilling appear in this layer. The saprolite zone is thickest
(approximately 80 feet) along the ridge crest along the northern edge of the Site, thinning towards the
lower elevations or stream valleys to approximately 20 feet in thickness.
Underlying the saprolite is a partially weathered rock layer derived from the weathering of
bedrock that ranges in thickness from approximately 5 to 25 feet. This layer is composed of saprolite
and fragments of weathered bedrock. Particle sizes range from silts and clays to large boulders of
unweathered bedrock. The weathering occurs in bedrock zones less resistant to physical and chemical
degradation (i.e., fault zones, stress relief fractures, and mineralogic zones).
The predominant rock type, based on rock samples obtained during bedrock monitoring well
drilling, is a metamorphosed brownish-gray to light gray, quartz bioti granite or granitic gneiss. The
bedrock is fractured and these fractures contain quartz deposits that remain unweathered in the
saprolite.
H. Hydrogeology
Metamorphosed and fractured quartz-sericite schist, metavolcanic rocks, and granite rocks in
varying proportions and thicknesses comprise the aquifer system represented by the water bearing units
that underlie the Davis Park Road Site and surrounding areas. Geologic structures that produce high-
yielding wells include contact zones of multilayered rock units, zones of fracture concentration, and
stress-relief fracture zones According to data collected by LeGrand and Mundorff (1952), wells in
Gaston County that are set within granite have an average depth of 165 feet and an average yield of 18
gallons per minute. Within the Davis Park Road area, data collected by LeGrand and Mundorff
indicate that well depths range from 80 to over 250 feet and that well yields range from 2.5 to 116
gallons per minute The aquifer system underlying the Site generally consists of the saprolite/partially
weathered rock aquifer and the underlying bedrock aquifer; however, interconnection between these
units is likely which would influence contaminant transport.
In the Site area, the top of the water table is typically found in the saprolite aquifer and
generally mimics the overlying land surface. The saprolite and partially weathered rock comprise an
overburden aquifer, which has a thickness that ranges from approximately 10 to 80 feet below ground
surface The depth to water across the area ranges from approximately 3 to 45 feet below ground
surface. The greatest depth to water is found along the ridgeline on the northeast portion of the Site,
which is also the location of the Davis Park Road Auto Repair Shop. A fractured bedrock aquifer
underlies the overburden, and the fractures generally decrease with depth.
Using groundwater elevations collected in January and February 1998, and potentiometric maps
Davis Park Road TCE Site
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Gastonia. Gaston County. NC
September, 1998 . 1-5
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drawn from these groundwater elevations, groundwater within the overburden and bedrock aquifer
generally flows to the southeast to south across the site. Based upon the potentiometric contours, the
Davis Park Auto Repair property appears to be located within a localized groundwater high area,
with potentiometric contours emanating in a semi-circular pattern from this area.
Water level elevations and local topographic contour maps for monitor wells MW-1D, MW-2S,
MW-2D, and MW-5S suggest that groundwater discharges form the overburden and possibly the
bedrock aquifers into Black wood Creek along the eastern and southeastern edge of the Site; however,
fractures present in the partially weathered rock and bedrock may affect the direction of groundwater
flow, and relict fractures present in the saprolite may also control groundwater flow directions.
According to Harned (1989), while working in the Piedmont Province of Guilford and Mecklenburg
Counties of North Carolina, most of the natural flow in the bedrock system is probably confined to the
upper 30 feet of bedrock where fractures are concentrated, and the overlying partially weathered rock
zone, which appears to have the highest hydraulic conductivity of any part of the hydrogeologic
system
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September, 1998 1-6
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2.0 SITE HISTORY AND ENFORCEMENT ACTIVITIES
A. Site History
The building at 2307 Davis Park Road has been owned by Carl Bell (now deceased) and
Douglas Bell of Gastonia and Charlotte, respectively, since 1960. Carl Bell leased the property to
Acme Petroleum and Fuel Company ("ACME") of Gastonia in 1966. ACME held this lease until
1981 During the lease period, the property was subleased to various service stations and repair shops.
Recently (1996 or early 1997), the name of the business in the building at 2307 Davis Park Road was
changed to Davis Park Auto Repair. On February 18, 1991, two underground storage tanks were
removed from the property. At the time of removal one tank was reported to have 5-7 inches of
product and the other 3 to 4 inches of product. Upon removal of the tanks, soils in the vicinity of the
tanks were tested for contamination Results showed no contamination present from the soils around
the tanks.
The investigation of possible groundwater contamination began on March 31, 1990, when a
groundwater sample was collected by Gaston County Environmental Health Department
representatives from a community supply well within the Cedar Oak Park subdivision as part of a
routine sampling procedure. Analysis of the sample revealed concentration of TCE (34.9 parts per
billion), and PCE (23 7 parts per billion). During April of that year, Gaston County Environmental
Health Department officials collected samples from three nearby private wells. The sampling revealed
the groundwater was contaminated with TCE, with the highest detected level (101.4 parts per billion)
in a sample collected from the private well located at 2419 Davis Park Road, 200 feet south of the
building at 2307 Davis Park Road.
B. Previous Investigations
In 1991 the NCDENR conducted a Site Investigation of the property at 2307 Davis Park Road.
This investigation reported that TCE as high as 700 parts per billion ("ppb") and PCE as high as 3,000
ppb was present in soil samples taken from near a drain pipe which exits the rear of the building at
2307 Davis Park Road At the request of EPA, NCDENR prepared a Site Inspection Addendum
report 10 the Site Investigation. This investigation confirmed the presence of PCE and TCE as well as
1,2-DCE in soil samples taken from the vicinity of the drain line However, in a follow-up Expanded
Site Investigation in 1994, conducted by NCDENR, the concentration of TCE in soil had dropped to
38 ppb and the concentration of 1,2-DCE, to between 4 and 20 ppb. No PCE was detected in the soil
samples, however, some additional Volatile Organic Compounds ("VOCs"), thought to be petroleum-
type compounds, were detected in soils at low levels.
During the Site Inspection Addendum investigation, NCDENR summarized sample data from
22 private wells in the vicinity of the Site. The sampling was conducted by State and Gaston County
Environmental Health officials from May 1990 to August 1992. Fourteen of the samples contained a
detectable amount of TCE or PCE or both. The 1994 Expended Site Investigation confirmed
Davis Park Road TCE Site
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Gastonia, Gaston County, NC
September, 1998 2-1
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contamination in five of the previously sampled wells. Figure 2-1 presents the locations of the private
wells which showed detectable levels of TCE contamination from 1990-1995.
C. Site Regulatory Actions
This Site was proposed for inclusion on the National Priorities List in July of 1998.
On March 19, 1996. a General and Special Notice letter for Remedial Investigation/Feasibility
Study was sent to one potentially responsible party. After negotiations, the EPA initiated and
conducted the Rl/FS.
Davis Park Road TCE Site
Record of Decision
Gastonia. Gaston County, NC
September, 1998 2-2
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_
'
c: c: a c: a \
**9URNT MILL RfUD
*Yf^ ==" J \
~*\^ --^^o^oajj 1
--C x^ A ^> ^
'' \sL. ^ -^ "^ \"\
FIGURE 2-1
HISTORICAL TCE CONCENTRATION MAP
RESIDENTIAL WELLS 1990-1995
DAVIS PARK ROAD TCE SITE
GASTONIA. NORTH CAROLINA
LEGEND
GREATER THtN tABORATORV METHOD
orrtcncx LMTS
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3.0 HIGHLIGHTS OF COMMUNITY PARTICIPATION
Pursuant to CERCLA Sections 113(k)(2)(B)(i-v) and 117, the RI/FS Report and the Proposed
Plan for the Site were released to the public for comment on July 23, 1998. These documents were
made available to the public in the administrative record located in an information repository
maintained at the EPA Docket Room in Region IV and at the Gaston County Public Library in
Gastonia, North Carolina.
The notice of the availability of these documents was published in the Charlotte Observer and
Gaston Gazzette on July 25, 26 and 27, 1998. A pubic comment period on the documents was held
from July 27, 1998 to August 26, 1998. A copy of the notice was mailed to the site mailing list which
contains names of community members and interested parties. In addition, a public meeting was held
on July 28, 1998. At this meeting, representatives from EPA answered questions about the Site and
the remedial alternatives under consideration. Meetings with city and county officials were also held.
Other community relations activities included:
* Established an information repository
* Conducted community interviews
* Prepared an extensive mailing list
4 Developed a community relations plan
* Issuance of a fact sheet on the RI/FS process in April, 1996
4 Issuance of a fact sheet on the proposed plan in July, 1998
* Notice of availability of information in repository and public meetings on July 25, 26 and 27,
1998
* Informed citizens of the Technical Assistance Grant and Community Advisory Group program
(literature placed in repository).
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Gastonia, Gaston County, NC
September. 1998 3-1
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4.0 SCOPE AND ROLE OF RESPONSE ACTION WITHIN SITE STRATEGY
As with many Superfund sites, the Davis Park Road Site is very complex. However, all aspects
of the cleanup will be addressed concurrently and the Site has not been divided into phases or
"operable units."
This ROD will present a final remedial action for the entire Site.
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5.0 SUMMARY OF SITE CHARACTERISTICS
The Remedial Investigation ("RI") was conducted in three phases beginning in May of 1996 and
ending in the Spring of 1998. During the RJ, surface and subsurface soil, sediment and surface water,
and ground water were sampled to determine the nature and extent of contamination. For a more
detailed summary, refer to the RI Report.
The main contaminants at the Site are tetrachloroethene ("PCE") and trichloroethene ("TCE").
The following discussion highlights these constituents as well as any chemical constituents which
exceed the National Primary Drinking Water Regulations ("NPDWR") Maximum Contaminant Levels
("MCLs"), the National Secondary Drinking Water Regulations ("SMCLs"), Federal Ambient Water
Quality Criteria ("AWQC"), EPA Region 3 Risk-Based Concentrations (Smith, 1996) and the North
Carolina Groundwater Classification and Standards-Groundwater Quality Standards of the North
Carolina Administrative Code (15A NCAC 2L 0202(c)), and North Carolina Water Quality Standards
applicable to Surface Waters (ISA NCAC 2B 0200).
A. Source Area/Soil Investigation
Extensive soil sampling was conducted during the RI to try to determine if a continuing source
of contamination exists in soils behind the 2307 Davis Park Road building, the current location of the
Davis Park Road Auto Repair shop. During the May 1996 field investigation, a total of 15 soil
samples (six surface and nine subsurface) were collected from six locations in the area immediately
surrounding the Davis Park Auto Repair Shop. Sample # 6-SLA was a grab sample taken through the
floor of the building. (Figure 5-1). The samples were analyzed for volatile and semi-volatile organic
compounds, pesticides, PCBs and metals. Two of the samples contained detectable levels of the
organic compounds toluene, ethyl benzene, xylenes, trimethylbenzene, benzene isomers and the
presumptive evidence of petroleum product Semi-volatile organic compounds indicating petroleum
product were detected in 3 soil samples. Two soil samples contained detectable levels of PCB-1242
and PCB-1254 and the pesticides toxaphene and dieldrin. Metals were detected in all soil samples, at
levels consistent with the geology in the area of the Site.
In October of 1996, nine soil samples were collected from four to six inches below land surface at 8
locations on the property of 2307 Davis Park Road (Figure 5-2). All of the samples were analyzed in
the field for VOC content. Only one sample contained an estimated value of bromoform. No other
VOC was detected in the other soil samples.
During the last phase of the field investigation conducted from late fall 1997 to spring of 1998, an
additional 7 soil borings were advanced to determine the possible extent of soil contamination at depth
on the property at 2307 Davis Park Road (Figure 5-3). The soil borings were advanced using both a
geoprobe and a hollow-stem auger drill rig, and were terminated at auger refusal. A total of 19
samples were collected and sent for VOC analysis. Of the samples submitted, only one compound
(Benzene) was detected in one sample.
Davis Park Road TCE Site
Record of Decision
Gastonia. Gaston County. NC
September, 1998 5-1
-------
44.5
50.0
44.5
-H
89.0
DAVIS PARK AUTO REPAIR
NOTE: SOIL SAMPLING LOCATION NUMBER 6
WAS WITHIN THE DAVIS PARK Al/TO
REPAIR BUILDING AND WAS NOT MAPPED
BY THE EPA.
37.0
31.0
5
50.0
DAVIS PARK ROAD
FIGURE 5-1
COMPOSITE SOIL SAMPLING LOCATIONS-
MAY 1996 PRELIMINARY INVESTIGATION
DAVIS PARK ROAD TCE SITE
GASTONIA, NORTH CAROLINA
APPROXIMATE SCALE
(IN FEET)
11nch = 25 Ft.
5-2
-------
15-SLA*
14-SLA
191
251
12-SLA
13-SLA
16'
11-SLA
DAVISPARK AUTO REPAIR
CMVIS PARK ROD
SOIL SAMPLES
&EPA
FIGURE 5-2
SOIL SAMPLING LOCATIONS-
OCTOBER 1996 PRELIMINARY INVESTIGATION
DAVIS PARK ROAD TCE SITE
GASTONIA, NORTH CAROLINA
NOT TO SCALE
5-3
-------
FENCED
DAVIS PARK
AUTO REPAIR
Approximate
Scale In Feet
r/EPA
LEGEND
GEOPROBE LOCATION
SOIL BORING LOCATION
FIGURE 5-3
GEOPROBE/SOIL BORING LOCATIONS
1997/1998 FIELD INVESTIGATIONS
DAVIS PARK ROAD TCE SITE
GASTONIA, NORTH CAROLINA
5-4
-------
One soil samples from each of the borehole installations for four top-of-bedrock monitor wells were
submitted for laboratory analysis The samples were analyzed for VOC content. Of the samples
submitted, there were no detections of VOC compounds.
B. Surface Water and Sediment Investigation
Surface water and sediment samples were collected during the 1996 field investigation and again
during the 1997/1998 investigation from locations on both Crowders Creek and Blackwood Creek
(Figure 5-4) All samples were analyzed for VOCs. No VOCs were detected in any of the surface
water samples. During the 1996 investigation, one sediment sample, collected from the Blackwood
Creek at the far eastern edge of the Site (location 2-SD) contained low levels of two trimethylbenzene
isomers and the presumptive evidence of petroleum product. No VOCs were detected in sediment
samples collected in 1997/1998.
C. Residential Well Survey
A residential well survey was conducted in November 1995, and supplemented with data taken
in February, 1998. The results of this survey are shown on Figure 5-5. Groundwater is considered as
a Class IIA Aquifer since it is currently used as a drinking water source (USEPA, 1988, Guidance on
Remedial Actions for Contaminated Groundwater on Superfund Sites). The State of North Carolina
classifies the aquifer as a GA aquifer since it is a present drinking water source and contains naturally
occurring chloride concentrations less than 250 milligrams per liter (North Carolina Administrative -
Code, Title 15, Subchapter 2B.0201).
D. Private Well Sampling
During the May 1996 field sampling twenty nine (29) residential wells were sampled in the
vicinity of the Site to determine the water quality of the residences drinking water. TCE was detected
in five residential wells above the State Drinking Water Standard. PCE was detected in four wells.
The only other VOC detected above State or Federal Drinking Water Standards was Chloroform,
which was detected in one well. Four of the 29 well samples were also analyzed for semi-volatile
organic compounds, pesticides/PCBs, and metals.
E. Shallow Groundwater Investigation
In 1996, EPA installed three temporary monitoring wells and sampled two existing monitoring
wells all located on the property at 2307 Davis Park Road. In addition, one temporary well was
installed southeast of the property, near Blackwood Creek. All wells were set within the shallow
(overburden) aquifer During the 1997/1998 phase of the Rl, EPA installed 5 additional shallow
monitoring wells throughout the Davis Park Road Site study area, and converted three former
residential wells of known depth to permanent monitoring wells with the consent of the residents.
Figure 5-6 shows the locations of the 1996 shallow monitoring wells and Figure 5-7 shows the
location of the 1997/1998 monitoring wells.
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September. 1998 5-5
-------
ED C3 O O C3
RICHIANO AVENUE
II
ll
','i DAVIS
,' PARK
^'AUTO
REPAIR
a a n
FIGURE 5-4
SURFACE WATER AND SEDIMENT SAMPLE LOCATIONS
DAVIS PARK ROAD TCE SITE
GASTONIA, NORTH CAROLINA
A SURFACE WATER SEDIMENT
SAMPLING LOCATIONS
Approximate
Scale In Feet
600
1200
-------
FIGURE 5-5
WELL SURVEY
DAVIS PARK ROAD TCE SITE
GASTONIA. NORTH CAROLINA
Z2 RESIDENCES CONNECTED TO CITY WATE*
ZZ] RESIDENCES ON RESTRICTED USE WATER UNE - CITY OF GASTONIA
RESIDENCES ON COMMUNITY WEILS > a IS SUBSCRIBER*
RESIDENCES ON PRIVATE WELL SYSTEM WITH 2-14 SUBSCRIBERS
RESIDENCES ON PRIVATE WELLS
0 APPROXIMATE WELL LOCATION
3D BUILDING ID NUMBER
-------
RICHLAND AVENUE
DAVIS PARK
AUt,q REPAIR
GLENRAVEN AVENUE
TEMPORARY MONITOR
WELL LOCATIONS
EXISTING MONITOR
WELL LOCATIONS
FIGURE 5-6
MONITOR WELL LOCATIONS
1996 PRELIMINARY INVESTIGATION
DAVIS PARK ROAD TCE SITE
GASTONIA, NORTH CAROLINA
Approximate
Scalejn Feet
200
400
5-8
-------
UCMTCM MU UXAMOJ*
LEGEND
O COMOTD «U lOCAM*
<* oame noun* m. louioa
COMMD FACTOR > C.91M411 (HAD U)
fOMT PO1MNC [AXTMC
OJV1IXK
rcr run
102
10)
104
103
101
107
101
im
no
in
MI
in
121
m
117
343344.131
3*9413.204
34M740IO
M43to.an
MUI1.142
S4MI0.77I
34M71.U1
5441M.U1
VUITUA»
S4M74.471
34$3H.U7
34U17M3
inaaii.nl
1UU91.110
iiiBaaiiot
iimw.o>7
IUMU4M
IUM2V441
IU7H4111
1117141.070
1U7I11.IM
1117013.177
111711X314
IU7M1.140
1117213.701
M1W7.741 1U741S.OM
U730 MI-IO
70721 O-l
1K*0 M»-a
1*110 nf-a
177.21 UV-1S
117 37 »-!
Tim m»-4j
741.74 it*-a
709.71 C»-l
7».I7 U*-V
71413 CW-1
711.73 C«-4
71111 CW-1
73771 C»-l
711.M CW-1
77121 O<»-1
771W Ol*-2
177.11
744.41
740.44
711.41
731.11
771.11
77100
1M.B
M7M
W4.H
77.32
Till*
744.17
741.71
703,9
74041
7H7I
711.41
7UM
711 7t
CNCH HANI USED *U IX On OF CASIO** «M> VMK. OUHOUNT 3. BOOt KAMI
»» 41. IOCAHD AT nc monicim or OA«S rn» KUO AW STAOI COMM KOAD.
OJVADON . 7J1.O5'
DAVIS PARK ROAD TCC SITt
CA5TONIA. CASTON COUNH. NORTH CAROLINA
MONITOR WCU LOCATION MAP
1997/1991 FIELD INVESTIGATION
HOURS 5-7
-------
EPA collected groundwater samples from shallow monitoring wells in 1996 (all located on the
2307 Davis Park Road Property + one near Blackwood Creek) and in January and February 1998 (one
well on the property and 8 new wells). The wells were sampled to determine if contamination was
present in the shallow (overburden) aquifer.
Of the VOC contaminants detected, only methyl-tert-butyl ether (MTBE) was detected at levels
exceeding the State Drinking Water Standard.
F. Bedrock Groundwater Investigation
Four new bedrock monitoring wells were installed during the 1997/1998 investigation. In
addition, EPA converted two former residential wells set within the bedrock aquifer to permanent
monitoring wells (Figure 5-7) During January and February, 1998, EPA sampled the 6 new
monitoring wells, one existing well located at the 2307 Davis Park Road property, and three residential
wells known to be set within the bedrock aquifer. All samples were analyzed for VOCs. Of the
compounds detected, only TCE and PCE were detected above the State or Federal Drinking Water
Standards. Other VOCs detected include MTBE and Acetone. Groundwater plume Isopleth maps
were generated for TCE and PCE plumes located in the Bedrock Aquifer and are presented as Figures
5-8 and 5-9.
Table 5-1 shows a summary of the contaminants detected in soil and groundwater at the Site.
G. Bedrock Fracture Analysis
During the 1997/1998 phase of the RI, EPA conducted a Bedrock Fracture Trace Study and
downhole geophysical logging of the newly installed bedrock wells. The fracture trace study was
conducted to identify zones of high fracture concentration in the bedrock, which typically indicate
increased groundwater flow along their length. The data was also used to establish the locations of the
bedrock monitoring wells at the Site. The azimuths of the fracture traces were plotted on a rose
diagram to assess the preferred orientations for fractures traces in the area of the Site. The primary
trends for fractures in the bedrock system in the Site area lie in a south to southeasterly direction,
generally from the property at 2307 Davis Park Road toward Blackwood Creek.
During the downhole geophysically logging of the bedrock monitoring wells, fracture zones
within the bedrock were identified based on prominent anomalies. Hydraulically active fractures were
identified. These fractures contribute water to the water column under static well conditions, and
these hydraulically active fractures may potentially act as contaminant transport pathways. Low and
High angle fractures were identified within each borehole. The high angle, or steep fractures generally
dipped in an easterly direction, toward Backwood Creek. The majority of potential water-producing
zones occurred in the low, or flat dipping fractures. Two potential water producing fracture zones
were identified Based on the detection of contaminants during the groundwater sampling activities,
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September, 1998 5-10
-------
LEGEND
i « ESTMATED ANCAL onorr or PCC (suf/i) * KDMOCK MUTCH
(a) irnuoumcTHENE CONCENTRATIONS w ooA-
UW-l «U LOCATIONS.
(M) NOT UtllUltD.
COU8MED FACTOR . 0.9998411 (HAD 83)
POINT MOKTHM6 EASTMC ELEVATION
TOP PIPE
100
101
102
103
104
109
10*
107
108.
109
110
111
112
113
',2.
129
136
137
545544.652
545495.204
545*74.010
544827.129
544848.945
544510.539
544881.888
545319.342
546810.771
546478.623
548139.528
545175.589
546474.478
548588.857
548888.88*
548827.885
547139.622
546854.891
548857.745
1338740.388
1338848.893
1338358.610
1338881.108
13388*8.087
I33B4S5.498
1338821.4*1
1337914.911
1337145.070
1337131994
1338313.389
1337035.677
1337882.514
1337*41.640
1337295.709
133*850.31 8
1337485.094
688.27
687.50
707.21
684.60
684.60
677.28
687.97
716.12
743.74
746.29
705.78
739.97
764.35
788.79
761.18
797.79
761.69
771.21
771.88
UW-1S
MW-1D
CW-5
MW-2D
MW-2S
MW-3S
PW-I
UW-4S
UW-3S
MW-30
CW-*
UW-40
PW-2
D»-4
CW-3
CW-2
cw-i
EUW-1
EMW-2
ELEVATION
TOP PLATE
688.85
687.80
684.89
655.04
677.32
716.63
744.42
ELEVATION
GROUND
688.89
887.81
706.61
74O.44
761.41
798.62
771.19
773.00
684.99
877.92
886.15
716.66
744.37
746.73
709.21
740.49
764.09
7*6.78
761.41
798.59
780.68
769.78
BENCH HARK USED «AS THE OTY OF CASTOMA BENCH MARK. OUAMtANT 3. BENCH MARX
No. 41. LOCATED AT THE MTDRtCTMN Of OAVIS PARK ROAD AND STAGE COACH ROAD.
ELEVATION - 731.05'
DAVIS PARK ROAD TCE SITE
GASTONIA, GASTON COUNTY, NORTH CAROLINA
PCE CONCENTRATION ISOPLETH MAP
1997/1998 FIELD INVESTIGATIONS
FIGURE 5-8
.INC.
CAD FILE NAME"
DAVISPCE.DWG
s-i i
-------
LEGEND
DAMS PARK
AUTO REPAIR SHOP
(OFT UAP)
ESTIMATE) AflEAL EXTENT OF TCE (5ugA) * BEOWCK AOUttR
(Si) 1RKMOMC1HDC CONCENTRATIONS M UC/l.
»-1 9 MOMTOft «EU. LOCATIONS.
NOT DETECTED.
(ND)
lueam.toe
FACTO* - 0.6888411 (MM) H)
CASTJM OCVATXM
688.27
887.90
707.21
884.80
884.80
877.28
887.97
716.12
743.74
748.2*
708.78
736.67
784.38
76a79
761.18
7S7.7*
7*1.6*
771.21
771 .M
fUVATMN UVATMN
848844.881 1J3874OJB8
845499J04
848*74.010
844817.128
844848.848
84481089* 1138489.498
1338821.461
846810771
84*676*23
IU7I4S.070
848I7&B88
848474.478
848988.897
848827.888
aaa»
1338813J68
1337038.677
1337881814
I337841.64O
13372*8.70*
MV-10
ew-s
HW-ZD
MW-2S
m-83
PW-I
MW-4S
mp-jj
m-»
CW-6
MW-4O
P»-J
CW-4
CW-3
CW-2
CW-1
DIW-I
OIW-2
887JO
688.04
677A2
718.89
744.42
748.78
74O.44
781.41
T5&82
771.16
773LOO
687*
708.81
684.88
884.88
nut*
888.18
718.88
744J7
748.78
708J1
740.49
784.08
766.78
761.41
788.98
...
770.22
BOKN MAM USB) IMS DC OTT OF OASTONU 8CNCH UAKK. OUADMAIIT X 8CNOM MAM
N* 41. LOCAID AT TIC MnXSCCIMN OF OAMS PARK ROAD AM) STACi OOAO4 MAD.
OIVATMM 731.08'
DAVIS PARK ROAD TCE SITE
GASTONIA, GASTON COUNTY, NORTH CAROLINA
TCE CONCENTRATION ISOPLETH MAP
1997/1998 FIELD INVESTIGATIONS
FIGURE 5-9
ROY F.WE8TON. INC.
^SMMK]
MANAGERS V J DESIGNERS/CONSULTANTS
DRAWKI>
M. SNEED
CHECKED'
DATE'
7/23/98
DATE'
DES. ENG.i
APPROVED'
DATE'
PATE«
5-12
W.O. NO.:
04400-071-095
CAD TILE NAME'
DAVISTCE.DWQ
-------
Table 5-1 Chemicals Detected in Grouudwater
Chemical
Votatilcs
Acetone
Bromodichloromethane
Butene
Carbon disulfide
Chlorodibromomethane
Chloroform
1 . 1 -Dichloroethane
1 , 1 -Dichloroethene
Cis- 1 ,2-Dichloroelhene
Mclhyl-tert-butyl ether
Propene
Telrachloroethene
Toluene
Trichloroethcnc
1 , 1 , 1 -Trichloroethane
Pesticides/PCBs
gamma-Chlordane
Residential
Frei|uenc\ of
Detection
_.
1/31
4/31
1/31
1/31
2/31
2/31
2/31
6/31
--
9/3 1
1/31
1/4
Range of
Delected
Concentrations
(ug/L)
5.8
1.3-2.4
0.58
40
0.52-0.57
0.66-1.6
1.6-1.7
0.52-10
0.92-34
1.2
(ug/L)
0.25
Overburden
l-'rctiucncv of
Detection
1/12
-
1/1
1/12
--
--
2/10
1/1
1/12
1/12
-
--
Range of Detected
Concentrations
(ug/L)
91
9
7
--
-
-
14-790
20
0.6
0.84
--
(ug/L)
Bedrock
l-'requency of
Detection
1/7
--
--
--
--
in
\n
in
-
2/7
\n
Range of Detected
Concentrations
(ug/L)
83
-
--
--
3.8
42
6-14
--
17-32
7.8
(ug/L)
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September, 1998
5-13
-------
Table 5-1 (cont.) Chemicals Detected in Groundwater
Chemical
Inorganics
Aluminum
Barium
Calcium
Copper
Iron
Magnesium
Manganese
Potassium
Sodium
Strontium
Titanium
Vanadium
Zinc
Residential
Frequency of
Detection
4/4
4/4
2/4
2/4
4/4
4/4
4/4
4/4
2/4
4/4
Range of
Detected
Concentrations
(«g/L)
14-21
6200-11000
3.4-12
14-26
1100-3700
1400-2500
8300-10000
130-200
4.2-5.9
4.4-7.3
Overburden
Frequency of
Detection
1/1
1/1
I/I
1/1
I/I
1/1
1/1
I/I
1/1
1/1
1/1
Range of Detected
Concentrations
(ug/L)
460
81
8100
170
3200
24
2700
16000
200
8.8
16
Bedrock
Frequencv of
Detection
I/I
1/1
I/I
1/1
I/I
1/1
I/I
1/1
1/1
I/I
Range of Detected
Concentrations
(ug/L)
56
72
7300
49
2900
22
2500
16000
180
70
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September. 1998
5-14
-------
Table 5-1 (cont) Chemicals Detected in Soil
Chemical
Volatile-;
Benzene
Bromoform
Ethyl beiixcnc
Toluene
m/p Xylcnc
o-Xylene
Semi-volatiles
Acenaptliene
Dibcnzol'uran
2-Methvlnapthalene
Napthalene
Phcnanthrene
Pvrene
Pesticides/PCBs
Dieldrin
Toxaphene
PCB-1242
PCB-1254
0-6"
Frequency of
Detection
1/13
--
-
"
--
--
--
1/6
1/7
Range of Detected
Concentrations
(mg/kg)
_.
0.0072
--
(mg/kg)
-
-
(mg/kg)
0.018
0.091
0-Ki'
Krei|ucncv of
Detection
1/10
1/14
1/14
1/14
1/13
1/13
1/6
1/6
2/6
2/7
2/6
1/6
1/6
1/6
1/9
1/9
Range of Detected
Concentrations
(mg/kg)
0.012
0.0072
0.011
0.42
0.035
0.031
(mg/kg)
1.2
2
1.9-9.4
0.66-10
0.6-0-.6
0.38
(mg/kg)
0.018
10
0.17
0.057
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September, 1998
5-15
-------
Table 5-1 (cont) Chemicals Detected in Soil
Chemical
Inorganics
Aluminum
Arsenic
Barium
Beryllium
Cadmium
Calcium
Chromium
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Nickel '
Potassium
Strontium
Titanium
Vanadium
Yttrium
Zinc
0-6"
Frequency of
Detection
6/6
6/6
6/6
1/6
2/6
6/6
6/6
6/6
6/6
6/6
6/6
6/6
6/6
3/6
5/6
6/6
6/6
6/6
6/6
6/6
6/6
Range of Detected
Concentrations
(mg/kg)
20000-40000
4.8-15
72-100
11
1.4-3.2
370-28000
9.5-32
4.8-11
18-56
16000-38000
20-630
1900-10000
140-360
0.06-0.13
9.3-27
1600-3400
15-37
630-1000
38-56
5.5-17
50-300
0-16'
Frequency of
Detection
6/6
6/6
6/6
1/6
2/6
6/6
6/6
6/6
6/6
6/6
6/6
6/6
6/6
3/6
5/6
6/6
6/6
6/6
6/6
6/6
6/6
Range of Detected
Concentrations
(mg/kg)
20000-52000
4.7-15
52-110
1.1
1.4-3.2
370-28000
6.4-32
4.8-11
5.7-56
16000-51000
20-630
1800-10000
87-360
0.06-0.13
9.3-27
1600-4500
4-38
600-1600
38-120
5.5-17
37-300
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September, 1998
5-16
-------
the correlation of fracture zones between select monitor wells, and the number of water-bearing
shallow dipping structures and steeply dipping fractures primarily to the east, the spread of
contamination toward Blackwood Creek,within the bedrock aquifer, may be attributed to the
interconnection of bedrock fractures.
H. Natural Attenuation Evaluation
A historical review of TCE and PCE concentrations in groundwater samples collected from
private wells north and south of the property at 2307 Davis Park Road was conducted to determine
if contaminant levels were decreasing with time without active remediation. Sixteen (16) well
locations were chosen based on availability of data, beginning with sampling conducted in 1990
through the 1997/1998 field investigation. A graphical representation of the data indicates a decline
in contaminant levels, with the exception of the residence furthest south, or closest to Blackwood
Creek Fluctuating levels of PCE and TCE with predominant decreasing trends were recorded in the
residential wells south of the 2307 Davis Park Road property. The contamination in wells closest to
the property, which initially showed the highest detected levels, had dropped to below detection
limits Based on the data collected from the RJ, the groundwater contaminant plume appears to be
located in the bedrock aquifer only. The contamination from the suspected source at the 2307 Davis
Park Road property appears to be flushing from that point and has migrated south to southeast
through the bedrock aquifer and is discharging to Blackwood Creek.
Modeling of the TCE plume was performed using the groundwater model BIOSCREEN.
BIOSCREEN is a screening model that simulates remediation through natural attenuation. The
model was designed to simulate biodegradation by both aerobic and anaerobic reactions. Using
available data, the source zone concentration and source zone half lives were adjusted until the
BIOSCREEN output matched to 1996 and 1998 plume and source geometry. The model was then
run for an additional 7 years (beyond 1996) to determine the likely plume shape and dissolved
contaminant concentrations after those times. The model predicted that the plume will reach a
maximum length of 3,400 feet in four years from the present time (year 2002), and will be below
Federal MCLs within 7 years from the present time. However, the distance from the suspected
source at 2307 Davis Park Road to Blackwood Creek is just 2550 feet. Blackwood Creek is a
receiving stream in this area, and contamination has been detected in groundwater wells located near
the Creek. This information combined with the BIOSCREEN model results indicates that the
groundwater plume has reached its maximum extent.
I. Ecological Evaluation
As a result of extensive development, there are no known critical habitats or federally listed
endangered species in the immediate vicinity of the Site. The Site includes commercial and
residential buildings, paved roads and paved parking areas, and open areas of maintained vegetation.
There are limited areas of woodlands within the immediate Site vicinity, however, the woodlands are
more extensive along the southeastern, southern, and western perimeters of the Site.
Davis Park Road TCE Site
Record of Decision
Gastoma. Gaston County. NC
September. 1998 5-17
-------
Soil types in the valley of crowders Creek are almost totally Chewacla loam (CH) or Conagree
loam (Co), both of which are listed as hydric soils capable of supporting wetlands. However, the
tlve predominant soil types in the immediate vicinity of the Davis Park Road Site area (Appling sandy
loam. Cecil-Urban land complex, Helena-Urban land complex, Pacolet sandy loam and Edowee
sandy loam) are not listed as hydric soils. There are no wetlands in the immediate vicinity of the Site.
The areas along Blackwood Creek within the immediate vicinity of the Site are comprised of "urban"
soils and "urban" vegetation. Consequently, what organisms and their environments that might have
existed are no longer in evidence following the "urbanization" of Blackwood Creek in this area.
The Indiana Bat, Bald Eagle, Arctic Peregrine Falcon, and Eastern Cougar are endangered or
threatened species which have been identified in the vicinity of the Site. However, no known critical
habitats are found in the Site vicinity. Several sensitive environments, several species of millipedes
listed as State endangered, threatened or of special concern, the Bear Oak (listed as significantly
rare), and Crowders Mountain State Park are located in Site vicinity.
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September, 1998 5-18
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6.0 SUMMARY OF SITE RISKS
The Davis Park Road Site is releasing contaminants into the environment. The Baseline Risk
Assessment Report presents the results of a comprehensive risk assessment that addresses the
potential threats to public health and the environment posed by the Site under current and future
conditions, assuming that no remedial actions take place, and that the surrounding area will remain a
residential community.
The Baseline Risk Assessment Report consists of the following sections: identification of
chemicals of potential concern; toxicity assessment; human exposure assessment; and risk
characterization. All sections are summarized below.
A. Chemicals of Potential Concern (COPCs)
Data collected during the Rl were reviewed and evaluated to determine the chemicals of
potential concern at the Site which are most likely to pose risks to the public health. These
contaminants were chosen for each environmental media sampled.
The chemicals of potential concern in groundwater are: bromodichloromethane,
chlorodibromomethane, tetrachloroethene (PCE), trichloroethene (TCE), 1,1-dichloroethene,
methyl-tert-butyl ether (MTBE), and chloroform.
The chemicals of potential concern in soil are toxaphene, aluminum, arsenic, beryllium, lead,
manganese, vanadium and yttrium
Once these chemicals of potential concern were identified, exposure concentrations in each
media were estimated. Exposure point concentrations were calculated for surface soils using the
lesser of the 95 percent upper confidence limit (UCL) concentration or the maximum detected value
as the reasonable maximum exposure (RME) point concentration. For evaluation of groundwater,
an alternative approach, often used to assess potential future exposures from wells that might be
installed in an area of contaminated groundwater, is to select several different wells from the
approximate center of the groundwater plume, and to average these values to derive an estimate of
concentration values which might reasonably be expected under worst-case conditions. At this Site,
the only COPC for the overburden aquifer was methyl-tert-butyl ether (MTBE). MTBE was
detected in 2 out of 10 shallow wells (CW-1 and CW-2). Therefore wells CW-1 and CW-2 were
selected as the designated "center" of the shallow groundwater plume because they are located near
each other and contain MTBE. At this Site, some of the highest concentrations of PCE and TCE in
the bedrock aquifer were found in well location CW-5. Therefore, this well was designated as the
"center" of the bedrock groundwater plume. In accordance with Region IV guidance, the mean
concentration (rather than the UCL or maximum concentration) is used in this case to estimate the
exposure point concentration when using the "center of the plume". Not all COPCs for the bedrock
aquifer were detected in the "center plume" well. For these COPCs, maximum detected
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September. 1998 6-1
-------
concentrations were conservatively used to estimate the exposure point concentration. Exposure
point concentrations are shown for groundwater in Table 6-1 and for soil in Table 6-2
B. Exposure Assessment
The exposure assessment evaluates and identifies complete pathways of exposure to human
population on or near the Site. Current exposure pathways include exposure through incidental
ingestion of soil; inhalation of fugitive dusts from soils; dermal contact with soils; and ingestion of
water from private wells. Land use assumptions include residential and commercial.
Future use scenarios consider construction of a water supply well within the groundwater
contaminant plume and ingestion of soil, inhalation of dusts and dermal contact with soils as a worse-
case scenario. Possible exposure pathways for groundwater include exposure to contaminants of
concern from the groundwater plume in drinking water and through inhalation of volatiles evolved
from water through household water use. Further detail and mathematical calculations can be
reviewed in the Baseline Risk Assessment.
C. Toxicity Assessment
Under current EPA guidelines, the likelihood of adverse effects occurring in humans from
carcinogens and noncarcinogens are considered separately. These are discussed below. Tables 6-3
and 6-4 summarize the carcinogenic and noncarcinogenic toxicity criteria for the chemicals of
potential concern
EPA uses a weight-of-evidence system to classify a chemical's potential to cause cancer in
humans All regulated chemicals fall into one of the following categories: Class A - Known Human
Carcinogen; Class B - Probable Human Carcinogen; Class C - Possible Human Carcinogen; Class D -
Not classifiable as to human carcinogenicity; and Class E - Evidence of Noncarcinogenicity in
humans.
Cancer slope factors have been developed by EPA for estimating excess lifetime cancer risks
associated with exposure to potentially carcinogenic chemicals. Slope factors, which are expressed
m units of kg-day/mg, are multiplied by the estimated intake of a potential carcinogen, in mg/kg-day,
to provide an upper-bound estimate of the excess lifetime cancer risk associated with exposure at
that intake level. The term "upperbound" reflects the conservative estimate of the risks calculated
from the slope factor. Use of this approach makes underestimation of the actual cancer risk highly
unlikely
Reference doses (RfDs) have been developed by EPA for indicating the potential for adverse
health effects from exposure to chemicals exhibiting noncarcinogenic effects. RfDs, which are
expressed in units of mg/kg-day, are estimates of lifetime daily exposure levels for humans, including
sensitive individuals; that are free of any adverse effects.
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September. 1998 6-2
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Table 6-1
Exposure Point Concentrations for Groundwater
Davis Park Road TCE Site
Chemical of
Potential Concern
Designated Center Plume
Wells'
Mean2
ug/L
Maximum
(well ID)
ug/L
Exposure Point
Concentration
(ug/kg)
Clilorodibromomethane
1U
1.5
Q.Q58 (54-PW)
0.058
Chloroform
5U
1U
1.5
40 (54-PW)
40
1,1-Dichloroethene
5U
3.8
3.15
3.8 (CW-5)
3.15
Mclhyl-tert-butyl ether
5U
NA
42 (MW-3D)
42
Tetrachloroethene
14
10
12
14 (CW-5)
12
Trichloroethene
32
32
32
Notes:
NA-not analyzed
1 Exposure point concentrations for ground\vatcr are based on data from wells located in the center of the plume.
If the data from the center plume wells were nondetect, then the maximum detected concentration was selected as the EPC.
Note, well CW-5 was sampled on 5/1/96 and 1/14/98.
: Data that was nondetect (ie: 1U) were assumed to be present al '/i the detection limit. As a result, data with "IT qualifiers
were multiplied by 0.5 before the mean was calculated.
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September, 1998
6-3
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Table 6-2
Exposure Point Concentrations for Soil
Davis Park Road TCE Site
Chemical of
Potential
Concern
Mean of Log
transformed
Data
Standard
Deviation of Log
transformed Data
N(')
H
Statistic
Maximum
Concentration
(mg/kg)
95%
UCL(2)
Exposure Point
Concentration
Inorganics
Aluminum
10.201
0.251
2.402
40000
36409.15
36409.15
Arsenic
2.158
0.460
2.947
15
17.62
15 (Max)
Bervllium
-0.080
0.165
2.198
1.1
1.1
I.I (Max)
Lead
4.688
1.692
8.25
630
234176.36
630 (max)
Manganese
5.218
0.330
2.651
360
288
288
Vanadium
3.835
0.124
2.198
56
52.69
52.69
Yttrium
Pesticides
2.396
Toxaphene
1.762
2.736
16
13.97
10
6.53E+09
10.00
Inorganics
Aluminum
10.458
0.144
2.198
52000
40555.63
40555.63
Arsenic
1.834
0.294
2.402
15
8.96
8.96
Beryllium
0.031
0.096
2.035
1.1
1.1
1.1 (Max)
Lead
3.894
0.886
4.478
630
428.40
428
Manganese
5.010
0.173
2.198
360
180
180
Vanadium
3.958
0.241
2.402
120
69.76
69.76
Yttrium
2.102
0.365
2.651
17
13.48
13.48
(1) Number of Samples (2) 95% Upper Confidence Limit
(3) The 95% UCL of the mean concentration represents the exposure point concentration for a chemical unless" it exceeded the maximum detected concentration.
Where the maximum detected concentration was exceeded." the maximum detected concentration was used as the exposure point concentration.
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September, 1998
6-4
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Table 6-3
Carcinogenic Toxicity Data
Davis Park Road TCE Site
Chemical
Weight
of
Evidence
Oral Slope
Factor
(mg/kg-dayV1
Tumor T\pe
Animal
Species
1 'olatilex
Bromodichloromelhane
Chlorodibromomethane
Chloroform
1,1-Dichloroethene
Methyl-Tert-Uutlv-Ether
Tctrachloroethene
Trichloroethene
B2
C
B2
C
NC
C-B2
B2
6.2E-02
8.4E-02
6.IE-03
6.0E-01
..
5.2E-02
1.1E-02
Kidncv tumors
Liver adenoma or carcinoma
Kidney tumors
Adrenal phenochromocytomas
_
NA
NA
Mouse
Mouse
Rat
Rat
NA
NA
Reference'
Inhalation
Slope Fucioi
(mg/kg-dayr '
Tumor Type
Animal
Species
Reference"
nus
IRIS
IRIS
nus
NCEA
NCEA
NTV
NTV
8.1E-02
1.8E-OI
_
2.0E-03
6.0E-03
..
_
Liver carcinomas
Kidney
adenocarcinoma
_
NA
NA
..
-.
Mouse
Mouse
NA
NA
..
..
IRIS
IRIS
NCEA
NCEA
Pesticides
Dicldrin
Toxaphene
B2
B2
I.6E+01
1.1E+00
Liver carcinomas
Liver carcinomas and neoplastic
nodules
Mouse
Mouse
IRIS
IRIS
1.6E+01
I.IE+00
Liver carcinomas
Based on oral SF
Mouse
--
IRIS
IRIS
Inorganics
Aluminum
Arsenic
I3ervllium
Lead
Manganese
Vanadium
Yttrium
NC
A
B2
B2
NC
NC
NC
_
I.5E+00
4.3E+00
NTV
--
_
Skin cancer
Gross tumors, all site combine
_
_
_
-
Human
Rat
_
_
_
-
IRIS
IRIS
IRIS
..
..
-
_
I.5E+OI
8.4E+00
NTV
..
'
-
Lung cancer
..
_
..
-
Human
Human
--
nus
nus
_
..
--
Nolcs:
a = IRIS = Integrated Risk information System (IRIS. 1998).
NCEA = National Center for Environmental Assessment (EPA, 1998).
NA = Not available.
NC = Not classified as a carcinogen. NTV = No toxicity value available (EPA. 1998; HEAST, 1997; IRIS, 1998).
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September, 1998
6-5
-------
I iililc 6-4
None ;n cimijicnic Touchy Data
Davis Park Road ICE Site
CllCinil'al
Oral Kll)
ung/kj:/
N'lV
NA
No inlonnalion
-
100
IIKAST
NTV
NTV
..
..
-
.-
a - IRIS = Integrated Risk inforinaiion System (IRIS. 19V8)
NCEA = National Ccnier for Liivironincnlal Asscssmcnl (LPA.
HEAST = Hcallli Eni-cls Assessment Suminar> Tables (F.PA. WX).
* - The toxicity values are llic same as pyrcnc. based on similar siniclural activity
NA -- Not available.
NC Not classified as a caivinogen. NTV = No loxicily \aluc axailable.
Davis Park Road TCE Silt-
Record of Decision
, Gaston County U("
1996
-------
Estimated intakes of chemicals from environmental media can be compared to the RfD. RfDs
are derived from human epidemiological studies or animal studies to which uncertainty factors have
been applied. These uncertainty factors help ensure that the RfDs will not underestimate the
potential for adverse noncarcinogenic effects to occur.
D. Risk Characterization
The risk characterization integrates the toxicity and exposure assessments into quantitative
and qualitative expressions of risk. The output of this process is a characterization of the Site related
potential noncarcinogenic and carcinogenic health effects.
Potential concern for noncarcinogenic effects of a single contaminant in a single medium is
expressed as the hazard quotient (HQ), or the ratio of the estimated intake derived from the
contaminant concentration in a given medium to the contaminant's RfD. By adding the HQs for all
contaminants within a medium or across all media to which a given population may be reasonably
exposed, the Hazard Index (HI) can be generated. Calculation of a HI in excess of unity indicates
the potential for adverse health effects. Indices greater than one will be generated anytime intake for
any of the chemicals of concern exceeds its RfD. However, given a sufficient number of chemicals
under consideration, it is also possible to generate a HI greater than one even if none of the
individual chemical intakes exceeds their respective RfDs.
Carcinogenic risk is expressed as a probability of developing cancer as a result of lifetime
exposure. Excess lifetime cancer risks are determined by multiplying the intake level with the cancer
potency factor EPA's acceptable target range for carcinogenic risk is one-in-ten-thousand (1E-4) to
one-in-one-million (1E-6).
Cancer and noncancer risks for the current and future use scenarios for the Site are
summarized in Table 6-5.
SOIL
As shown in this table, the screening-level Reasonable Maximum Exposure (RME) Hazard
Index for soil is below a level of concern for a commercial/industrial worker (HI=0.23) and for adults
residents (HI = 0.22), but is slightly above levels of concern for children (HI = 1.47). This value is
due to contributions from aluminum, arsenic, and manganese. Because none of these chemicals
cause noncancer effects on the same target tissues, and because none of the chemical-specific HQ
values exceed a value of one, it is concluded that exposure to soil is not likely to pose a significant
noncancer risk to children.
Estimated RME excess cancer risks from soil to commercial/industrial workers (6.8E-06) and
residents (child plus adult=4.6E-05). This risk is due entirely to the presence of arsenic and
beryllium in soil. The risk is contributed primarily by ingestion exposure. These risk levels are
within the range (1E-04 to 1E-06) that are generally considered to be acceptable by EPA.
Davis Park Road TCE Site
Record of Decision
Gastonia. Gaston County. NC
September. 1998 6-7
-------
Table 6-5
Summary of Hazard Indices and Carcinogenic Risks
Reasonable Maximum Exposure Scenario
Davis Park Road TCE Site
Risks From Soil1
Curreni Industrial/Commercial Worker
Future Child Resident (EPS-2 and EPS-3)
Future Adult Resident (EPS-2 and EPS-3)
Combined Future Child
and Adull Resident (EPS-2 and EPS-3)
Future Construction Worker (EPS-4)
0.086
1.47
0.19
0.23
6.8E-06
3.IE-05
1.5E-05
4.6E-05
1.1E-06
Risks From Groundwatcr2
Future Child Resident (EPS-2)
Future Adult Resident (EPS-2)
Combined Future Child
and Adult Resident (EPS-2)
Future Child Resident (EPS-3)
Future Adult Resident (EPS-3)
Combined Future Child
and Adult Resident (EPS-3)
5.10
2.20
1.25
0.54
Combined Risks From Soil and Groundwatcr
Future Child Resident (EPS-2)
Future Adult Resident (EPS-2)
Combined Future Child
and Adult Resident (EPS-2)
Future Child Resident (EPS-3)
Future Adult Resident (EPS-3)
Combined Future Child
and Adult Resident (EPS-3)
6.61
2.39
2.72
0.72
_
O.OE+00
O.OE+00
O.OE+00
3.9E-05
6.7E-05
1.1E-04
3.1E-05
1.5E-05
4.6E-05
7.0E-05
8.2E-05
1.5E-04
'Risks from soil arc the same for future child and adult residents in EPS -2 and EPS-3.
:Risks from groundxvatcr \\crc estimated for the overburden aquifer (EPS-2) and bedrock aquifer (EPS-3).
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September, 1998
6-8
-------
GROUNDWATER
Current Residential Wells
Quantitative risk calculations were not performed for current residential wells, since only one
data point is available for each well, and this is not considered to be sufficient to derive reliable risk
estimates Instead, the observed values were compared to existing risk-based screening values and
to State and Federal Drinking Water Standards in order to judge whether the observed values might
be in a range of concern There are 9 known residential wells still in use where concentrations of
PCE or TCE or both exceed applicable State of Federal Drinking Water Standards.
Center of the Plume Well Evaluation
The only COPC in the overburden aquifer was MTBE. The screening level RME Hazard
Index would be in the range of concern for both children (Hl=5.2) and adults (HI=2.2) if water from
the center of the overburden aquifer plume were used for drinking and showering. However, it
should be noted that MTBE was detected in only two wells, CW-2 (790 ug/L) and CW-1 (14 ug/L).
These two concentrations were averaged to develop an exposure point concentration of 402 ug/L.
MTBE was not detected in any of the other overburden aquifer wells. The MTBE concentration of
709 ug/L is noticeably different than all of the other measurements which may indicate that it is a
possible outlier. Possible reasons for outliers may include inconsistent laboratory procedures and/or
contamination in field methods.
No cancer risks were generated for future residents exposed to the overburden aquifer
groundwater since the only COPC is MTBE and MTBE is not classified as a carcinogen.
The screening level RME Hazard Index in the bedrock aquifer is below a level of concern for
adults (Hl=0.5), but would be slightly above a level of concern for children (HI=1.3) if water from
the center of the plume were used for drinking and showering. This risk is primarily due to TCE,
with MTBE and chloroform. Because none of these chemicals are known to cause noncancer effects
on the same target tissues, and because none of the chemical-specific HQ values exceed a value of
one, it is concluded that exposure to groundwater at the center of the bedrock aquifer groundwater
plume is not likely to pose a significant noncancer risk to children.
Estimated RME excess cancer risk to future residents (child plus adult) from water at the
center of the bedrock aquifer groundwater plume is 1. 1E-04, slightly above the usual acceptable risk
range of 1E-04 to 1E-06. This estimated excess cancer risk is due primarily to chloroform (5.2E-
OS), 1,1-dichloroethene (3.6E-05) and PCE (9.7E-06). These risks are derived about equally
between ingestion route (5.2E-05), and inhalation of volatiles while showering (6E-05). Other
chemicals which contribute RME risks greater than 1E-06 include bromodichloromethane and TCE.
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September, 1998 6-9
-------
E. Uncertainties
Table 6-6 summarizes the uncertainties and their probable direction of effect on the
evaluation of risk at the Davis Park Road Site. The net effect of these uncertainties depends on
their relative potential impacts. In general, the potential magnitude of effect of the factors that tend
to overestimate risk would be expected to outweigh the potential magnitude of effect of the factors
that tend to underestimate risk or for which the direction of effect is unknown.
The results of this uncertainty analysis suggest, based on the integration of all key
assumptions used in the risk assessment, that risks associated with the Davis Park Road Site have
been overestimated.
F. Conclusions
Actual or threatened releases of hazardous substances from this Site if not addressed by
implementing the response action selected in this ROD, may present an imminent and substantial
endangerment to public health, welfare, or the environment.
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September. 1998 6-10
-------
Table 6-6
Summary of Uncertainty Analysis
Davis Park Road TCE Site
Uncertainty Element
Effects on Risk Estimate
Potential for
Ovcrcstimation
Potential for
Underestimation
Potential for Over or
Underestimation
Exposure Parameter Estimation
.Media intake rates
.Groundwater characterization
-.Exposure frequencies
.Exposure to soil
-.Exposure durations
-.Exposure point concentration for
volatiles in groundwater
Moderate
Moderate
Moderate
Moderate
High
Moderate
Toxicitv Data
-.Use of chronic RfDs for estimating
noncancer risk in children
-.Cancer slope factors
- 1,1-Dichlorocthcnc
- Tetrachlorocthenc
-.Reference doses
- 2 methyl naphthalene
- Naphthalene
- Phenanthrcnc
High
High
High
High
High
High
High
High
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September, 1998
6-11
-------
SECTION 7. APPLICABLE OR RELEVANT AND APPROPRIATE
REQUIREMENTS (ARARS)
The requirement that ARARs be identified and complied with and the development
and implementation of remedial actions is found in Section 121(d)(2) of CERCLA, 42 U.S.C.
Section 962 l(d)(2). This section requires that for any hazardous substance remaining on-site, all
federal and state environmental and facility citing standards, requirements, criteria, or limitations
shall be met at the completion of the remedial action to the degree that those requirements are
legally applicable or appropriate and relevant under the circumstances presented at the Site.
Three classifications of requirements are defined by EPA in the ARAR determination
process:
Chemical-specific: These requirements set protective remediation levels for the
chemicals of concern.
Location-specific: These requirements restrict remedial actions based on the
characteristics of the site or its immediate surroundings.
Action-specific: These requirements set controls or restrictions on the design,
implementation, and performance levels of activities related to the management of
hazardous substances, pollutants, or contaminants.
A. Chemical-Specific ARARs
Chemical-specific ARARs include those laws and regulations governing the release
of materials possessing certain chemical or physical characteristics, or containing specified chemical
compounds Chemical-specific requirements set health- or risk-based concentration limits or ranges
in various environmental media for specific hazardous substances, contaminants, and pollutants.
These ARARs, when applied to site-specific conditions, establish numerical values that define the
acceptable amount or concentration of a chemical that may be found in, or discharged to, the
ambient environment. Examples include drinking water standards and ambient air quality standards.
Chemical-specific ARARs are established once the nature of the contamination at the site has been
defined, which is accomplished during the RI. Chemical-specific ARARs for this Site are listed in
Table 7-1
Davis Park Road TCE Site
Record of Decision
Gastonia. Gaston County. NC
September. 1998 7-1
-------
lABl.t 7-1 -CIIKMK AL-SI'tC UK ARARS. CKITEKIA. AND (;( IDANC E FOR THE SITE
AM) \ Kit HI III WIVMI \ I I HI I I HI V OKI I Mil VI'ION
I'll A I ION
KHIIilUI Ml \ ls.s\ NOI'sIS
I OAIMI/M'
Sale Drinking Water \cl
National I'nnidry Diinking Waici St.iiidjids
National Secondarv Di ink ing M alci Standards
Ma.\iniuin Contaminant Level (MC'I )(ioals
Clean Water Act
Watei Quality Criteria
Resource Conservation and Recovery .Act (RCRA). as amended
RCRA Groundwater Protection
Clean Air Act
National Primary and Secondary Vinhicni Air Quality Standaids
National Emissions Slaiidaitls tin M.I/.II Jons \n I'ollulanls
(NtSIIAI's)
Si All
40 I SC Section 300
40 CIR Tan I 4 I
40CI R 143
40 CIR Ml
.33 I'SC Section
1251-1376
40CFR Part 131
42 I'SC 6905. 6912,
692-4.6925
40 CKR Part 264
40 USC 1857
4UUK Part 50
4iK'l-'l< I'Jiiol
l.stahhshes hc.illli-hasi.-ct sl.nnl.ii Js loi iiulilik ualer sv.slenis
(MCl.s)
l-stahlishex uelliirc-hu-'i'd NlanilariK lor puhlic water systems
(seeondar\ MC'I.!.)
l-sljhlislu-s Jnnkini; u.noi >|iij|ily uuals set al lev els.it rid
knoun or anlKipaled'ailvoiM.' hejllli elietl.v
SeLs criteria tin \\aler uiuliu based on loxicity to aquatic
orgitnisnis and luini.in luMllh
Provides lor groundualer protection standards, general
monitoring requirements. .inJ technical requirementi
Sets primal^ and seciindaix an standards at levels to protect
public lieallli and pnblu v^ell'au-
PniMdes enn-M'iiis xi.imt.uJ lot lia/aidiius air pollulanls I'm
which no anihienl an <|iulil\ Mandard exists.
I he Ml I s lor organic and inorganiL- contaminants aie rclcv.inl and
appropriate lo the groundvvalcr contanunaled hv Ihc site since the
aquilei is a dunking walcr souice
Secondan MCl.s lor organic and innrruiik coiiiaiinn.rnls are
guidelines I" he considered I'm gioumlvvaKi MIKC n is .1 dunking
MC'I
jp|M
I. (is I'n iirganic and inorganic oml.nninanls aic leUnant and
.'|in.iu- in Ine gionndvtaler since H is a dnnkim; \».ilci source
May he rejevant and appropriate il't>rounJ\\aici cilher treated 01
unlre.tled. if- discharged lo a surface xv.iu-t |I«H(\ \lsi> iclcvanl and
apnronriak' lo any nuioll hoin conlaniin.ilctl MI'I! ni soil remediation
activities.
RCR \ grnundwatcr protection standards aic relevant and
appropriate for groundwaler at the site
\l,i\ be relevant and appropriate il unsiic iic.itincnl units or
evcavalion aie a part of remedial aclxin
M,i\ be relevant and appropriate it "iisik ii.-.iiiiicnl units or
c\ca\alion are a part ot remedial action
North Caiolrna Drinking \Vjlci \ct
Noith Cai'olina (iround\\alei SlanJaids
North Carolina Water (jii.ility Standards
North Carolina Surface Water l.llluenl l.iniilalions
North Carolina Air Pollution Control Regiilalions
North Carolina llazaidous Waste Management Rules
III) V NX U' HI- Ke^ulales \\aicr v\sk-nis uiihin the stale that supply diinkim;
327 walei thai ma\ all'ecl ilie public health
IMNC'AC2I. listahlisbes giuuiklvulci classilicalion and water quahlv
standards.
15 \ NCAC 2R l-Atablisbcs a vk-r res olclassilicalrons and water quality standaitU
lor smface w.iier
I ?.\NC.\C 2H Kslablishcs linnls and guidelines for elllucnt discharged lo
waters of the slate
15.A SC'.AC 2D 2Q Regulates aiiilncui air qtiabiN and establishes air quahlv
standards tin ba/aulons an pollutants
I? \ NCAC I VA Kslablrshes si.mdaids lot h.i/aidous vsaste Irealiilent lacilrlres
Pnnrdes lire slate with (he aullionlv needed In .isMime pninan
enloicenienl responsibility under the 1'cJcial jet
(iuidclmcs for allowable levels of MM. ..IU..IIIK .ind inorganic
coiupounds in groundwaler used lot ilfinkinirwalci RelevaiiTand
appropriate to groundwater at the Site
May he applicable il treated gioumlualci is discli.nged lo surface
« al'ei s
Ma\ he applicable if Healed ginundu.iu-i is discluiged lo surface
water
Mas be applicable is on-srte trealrnenl or excavation rs pjrl ol'tlie
remedial action.
M.r\ he applicable il ha/ardnus \\as
Healed as part ol the remedial aclion
led and stored or
Davis Park Road TCE Site
Kecord of Decision
Gastonia. Gaslon Conniy NC
1998
-------
B. Location-Specific ARARs
Location-specific ARARs are design requirements or activity restrictions based on the
geographical or physical positions of the Site and its surrounding area. Location-specific requirements
set restrictions on the types of remedial activities that can be performed based on site-specific
characteristics or location. Examples include areas in a flood plain, a wetland, or a historic site.
Location-specific criteria are generally established early in the FU/FS process since they are not
affected by the type of contaminant or the type of remedial action implemented. Location-specific
ARARs for this Site are listed in Table 7-2.
C. Action-Specific ARARs
Action-specific ARARs are technology-based, establishing performance, design, or other similar
action-specific controls or regulations for activities related to the management of hazardous substances
or pollutants Action-specific requirements are triggered by the particular remedial alternatives that are
selected to accomplish the cleanup of hazardous wastes. Action-specific ARARs for this Site are
provided in Table 7-3.
D. Media of Concern
Based on the results of the remedial investigation and the baseline risk assessment, the Davis
Park Road Site has one contaminated media; groundwater.
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September. 1998
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TABLE 7-2 - LOCATION-
SPECIFIC ARARS, CRITERIA,
AND GUIDANCE
Standard, Requirement, Criteria,
or Limitation
Federal
Resource Conservation and
Recovery Act (RCRA), as amended
RCRA Location Standards
Fish and Wildlife Conservation Act
Hoodplain Management Executive
( >rder
1 jidaiigered Species Act
Wetlands Management Executive
Order
Slate
North Carolina Hazardous Waste
Management Rules
North Carolina Solid Waste
Management Rules
Citation
42 USC 6901
4<)CFR264.l8(b)
16 USC 2901 etseq.
Executive Order
I1988,40CFR6.302
16 USC 1531
Executive Order
1I990;40CFR6.302
1 5A NCAC 1 3A
15ANCAC I3B
Requirements Synopsis
A treatment/storage/
disposal (TSD) facility
must be designed,
constructed, operated, and
maintained to avoid
washout on a 1 00-year
floodplain.
Requires states to identify
significant habitats and
develop conservation plans
for these areas.
Actions that are to occur in
floodplain should avoid
adverse effects, minimize
potential harm, restore and
preserve natural and
beneficial value.
Requires action to
conserve endangered
species or threatened
species, including
consultation with the Dept
of Interior.
Action to minimize the
destruction, loss or
degradation of wetlands.
Location requirements for
hazardous waste
treatment/storage/ disposal
facilities.
Siting requirements for
solid waste disposal units.
Comment
May be relevant and
appropriate if an onsite TSD
facility is required as part of
overall remediation and it
exists within the 100-year
floodplain
Confirmation with the
responsible state agency
regarding the Site being
located in one of these
significant habitats
Remedial actions are to
prevent incursion of
contaminated groundwater
onto forested floodplain.
Endangered species thus far,
have not been identified at
the Site.
Relevant and appropriate if
remediation occurs in
wetlands.
May be applicable to
hazardous waste excavated,
stored, and treated oil-site.
May be relevant and
appropriate to nonhazardous
waste disposed on-site.
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September. 1998
7-4
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TABLE 7-3 - ACTION-SPEC IHC ARARS, CRITERIA. AND GUIDANCE FOR THE SITE
STAMUKD, KKOlllKKMKM.«KITTIKIA.
OK LIMITATION
CITATION
RKQl'IKKMKNTS SYNOPSIS
rOMMKM
l-'i ni k vi
ir ncnt>n and '/»c(j/»it,'/»
Kcsoince Conservation and Recovery Act (KCRA). a.x
amended
Idenlilicalion ol lla/.ndous Waste
Treatment ol Ha/aidoux Wastes in a Unil
Requirements loi iieiiciaiion. Siorage. Transportation.
ana Disposal ol lla/aidous Waste
I .and Disposal Restrictions
Disposal Uischa/Ki; in Surliicc li'aiar I'OTH'
Clean Water Act
Requires use ofllest Available I'lealmenl Technology
Reqtnies I Tse of Uo>l Management Puclices
National Pollulanl l)ischan;c I luninalion Ssstem
Di.sth.inx iniKI hi- i.ui.MSlail "illi llic ici|uiti.-liK-iils ol a
Water Qualily Mjii.igoini.-iii I'lan approved by 1:1' A
l)ischjM;t.* must not iiu-rcasc k-ontai)iin
in iiDsile stcrlai-c \\jlci
Oltur
OcL-upational Safclv and I lojllh Adniiiiislralion
S IA FK
North Carolina \VaK-r Qu.ihlx Si.nuljrds
North Caiolina Crroundvvalci- Slandai J.s
Waslcuatcr DisJiaige lo Suilacc Waters
NoilJi C'amlina \ir I'ollulion C'onliol kci;iilalioni
42 I'.SC Section(>'M\ et. seq
40CTR2(.I
10 CI-R 265.4UO
40CI-R 261
JO OR 264
40 CT R 26K
.U ISC Section I.15I-I376
40CI-K 122
-10 UK 125
4(1 Cl R 122 Suhp.in.C
40CIK 122
Seclion 121 (d)(2|(BHiii)
2'J CI-'R IVIUPaii 12(1
I.V\NCAC2H
! \ \C \C' 21
I.V\\CAC 211
IM M \( 21).in.l 2(.)
Icdctal K-i|(iiu-nicnt> loi classilicalion and idcnlilicalion D| lu/aiilnus \vali.' lecluiology eeonomieally achievable is required to control discharge nfto.XK
pollutants lo I'uhlicK owned treatment works'(POTW).
Requires di.-\ eli)|tnionl and implementation of a Best MaTiaixnu-nl Practices program li> pre\ enl the
release of toxic constituents to surface water.
I :se ol best available technology economically achievable lor IONIC pollutants discharged (o surface
waters.
Dischaity must cuinpK "ith liPA-approved Water Qualm Management Plan
Selected iciiicdial action must establish a standard ofcnnlrol lo maintain surface water quality
Provides sak-ty Miles for handling specific chemicals foi sile workers during remedial activities
Surface walei i|u.ihl\ standards.
l-.siahlisho^ ^iiuindwalci slandaids. legulales injection welK. sets cuk-iia tin naluial allcnualion
Regulate^ Miilace walei discharge and dischaiges to P() I U
Regulates ainlxcnl ,111 quahl\ and eslabhslies ait i|uaht\ \l.indaids loi ha/at dims an polliilants
Kelcvan( and .\pfiio|u late
Kclcvant and Appropriate
Relevant and Appropriate
Relevant and Apptopriale
Relevant and Ap[>iopriatc
Kek-v.tnl and \ppiopliate
Relevant and \pproprialc
Relevant and .Appiopriate
Relevant and Appropriate
\pphcahle
Ri-lcvant and A|ipropnale
Uelev anl and Appinpiiate
Relev anl and \ppropriate
Mav be applicable lor on-
Mie liealinent excavation
/b
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SECTION 8. REMEDIAL ACTION OBJECTIVES
Considering the requirements for risk reduction and the risk-based remediation levels derived in
the Baseline Risk Assessment, and the ARARs discussed previously, the remediation goals specifically
developed for groundwater across the entire Site are presented in Table 8-1. The goal of the
Remedial Action for the Site is to limit exposure to groundwater contaminated above risk based
standards and to restore groundwater to below risk based standards.
The remediation goals were selected as the most conservative of the chemical specific ARARs
or the health-based risk goals. The contract required quantitation limit (CRQL) was chosen if the
chemical-specific ARAR was below this limit. The background concentration would have been
selected as the remediation goal if it had exceeded the risk-based goal, as is the normal procedure.
TABLE 8-1 - REMEDIATION GOALS FOR GROUNDWATER AT THE DAVIS PARK ROAD SITE
CONTAMINANTS OF
CONCERN
Tetrachloroclhenc (PCE)
Trichloroclhcnc (TCE)
I.l-Dichlorocthcnc
(l.l-DCE)
Chloroform (CLFM)
Mclhy-lcr-bulyl clhcr
(MTBE)
MAX (UG/L)
14
34
3.8
40
709
REMEDIATION
GOAL (UG/L)
1
2.8
7
1
200
BASIS
CRQL (NCOS 0.7 ug/l)
NC 2L GS
SDWA, NC 2L GS
CRQL (NC 2L GS - 0. 19 ug/l)
NC 2L GS
Notes: SDWA- Federal Safe Drinking Water Act, CRQL - Contract Required Quantitation
Limit; NC 2L GS - North Carolina Administrative Code Subchapter 2L Groundwater Standard
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September, 1998
8-1
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SECTION 9.DESCRIPTION OF ALTERNATIVES
Table 9-1 lists the remedial action alternatives developed for the Davis Park Road Site.
TABLE 9-1 REMEDIAL ACTION ALTERNATIVES FOR GROUNDWATER AT THE SITE.
NUMBER
NAME
DESCRIPTION
Alternative I
No Action
Sile is left "as is".
Five-year reviews conducled
Alternalivc 2
Limited Action
Deed recordalions
Semi-annual, and annual groundvvatcr
monitoring
Five-year reviews conducted
Alternative 3
Reduction of Groundwater
Exposure and Monitored
Natural Attenuation
City Water connections
Wellhead treatment
Quarterly and annual groundwater monitoring
Natural Attenuation Study
Five-year reviews conducted
Alternative 4
Reduction of Groundwater
Exposure and Groundwater
Treatment
City Water connections
Wellhead treatment
Semi-annual and annual groundwater
monitoring
Treatment of contaminated groundwater
Five-year reviews conducted
Alternative 5
Reduction of Groundwater
Exposure and Groundwater
Pump and Treat
City Well connections
Wellhead treatment
Semi-annual and annual groundwater
monitoring
Pump and Treat contaminated groundwater
Five-year reviews conducted
Descriptions of the alternatives developed for remediation of groundwater are discussed below.
All of the alternatives except the "No Action" alternative include periodic monitoring of the
groundwater including monitoring wells and potable wells for site contaminants to evaluate the site
conditions and the migration of contaminants over time.
A. ALTERNATIVE 1 - NO ACTION
Under the No Action alternative, the Site is left "as is," and no funds are expended for active
control of the groundwater contaminant plume or for reducing the exposure of residents to
contaminated groundwater. The NCP requires consideration of this alternative as a baseline for
comparing other remedial actions and the level of improvement achieved. However, five-year reviews
Davis Park Road TCE Site
Record of Decision
Gastonia. Gaston County, NC
September. 1998
9-1
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of the Site remediation decision, which consist of one round of sampling of selected monitoring and
potable wells, would be conducted over an estimated 30-year period.
B. ALTERNATIVE 2 - INSTITUTIONAL CONTROLS
In this alternative, deeds in the area would be required to record the fact that groundwater
contamination exists under the property, and if a potable well is constructed, a strong possibility exists
that the water will be contaminated with unacceptable levels of volatile organic contaminants. These
recordations would remain in place until the groundwater quality would allow unrestricted use.
Semi-annual groundwater monitoring would be conducted on both monitoring wells and potable
drinking water wells for five years. Three more upgradient wells would be installed after five years to
track the trailing edge of the plume as the concentration of the COCs decreases in upgradient wells
Thereafter, the existing and new monitor wells will be sampled annually for 25 years. Wells would be
sampled for volatile organic compounds. The five-year reviews would be required because
concentrations of chemicals remain at the Site above levels that allow unlimited use of the
groundwater
C. ALTERNATIVE 3 - REDUCTION OF GROUNDWATER EXPOSURE AND
MONITORED NATURAL ATTENUATION
Under this alternative, all homes, churches, and businesses impacted by the Davis Park Road
TCE Site not currently connected to the City of Gastonia public water supply would be connected. In
addition, residents will also be given the option to obtain wellhead treatment of their private well, i.e.
groundwater treatment such as a carbon filter unit would be connected to the private water supply
well The EPA will provide for maintenance of the carbon filter for one year.
This alternative also includes monitoring of groundwater from approximately 18 wells on a
quarterly basis for 3 years. As in Alternative 2, three additional monitor wells will need to be installed.
After installation, all existing monitor wells and the new wells will continue to be sampled on an annual
basis for the next 27 years. However, monitoring will be ceased when groundwater has reached Site
Remediation goals. Wells would be sampled for volatile organic compounds.
In concert with the quarterly groundwater sampling, a Natural Attenuation study will be
completed on the bedrock aquifer plume. Much of the data required for the Natural Attenuation study
has already been collected during the RI, however, additional data are needed. This data includes
groundwater geochemical data, hydrogeologic parameters, and other necessary information to prove
that the bedrock aquifer contaminant plume is in fact naturally attenuating.
As stated earlier, based on the results of the B1OSCREEN model, the groundwater contaminant
plume concentrations are expected to meet remediation goals approximately 7 years from the present
time
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September. 1998 9-2
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The five-year reviews would be required because concentrations of chemicals remain at the Site
above levels that allow unlimited use of the groundwater.
D. ALTERNATIVE 4 - REDUCTION OF GROUNDWATER EXPOSURE AND
GROUNDWATER TREATMENT
This alternative would include all the provisions for prevention of exposure of current residents
to contaminated groundwater described in Alternative 3, plus adds treatment of the contaminated
bedrock aquifer groundwater plume. The major component of the groundwater treatment option
includes in-well vapor stripping.
The in-well vapor stripping technology would be used throughout the plume. It is projected that
at least three air-stripper wells would be installed to treat the contaminated bedrock aquifer plume.
The remedy would be designed so that it will not be overly intrusive to the neighborhood.
Groundwater treatment is expected to last approximately 10 years. Natural attenuation
processes were not figured into the calculation of treatment duration. Therefore, the estimated time
groundwater treatment is required may be overestimated. Groundwater monitoring will be conducted
semi-annually for the first five years, and annually for the next 25 years. However, groundwater
monitoring will be ceased when groundwater has reached Site Remediation goals.
E. ALTERNATIVE 5 - REDUCTION OF GROUNDWATER EXPOSURE AND
GROUNDWATER PUMP AND TREAT
This alternative includes all of the provisions for prevention of exposure of current residents to
contaminated groundwater described in Alternative 3, plus adds active treatment of the contaminated
bedrock groundwater plume using pump and treat The major component of this system is the
installation of extraction wells into the bedrock aquifer. It is estimated that at least three extraction
wells would need to be installed The contaminated groundwater is extracted through the wells and
treated at the ground surface using activated carbon to remove VOC contaminants. The treated water
is then discharged to an acceptable location, either a public-owned wastewater system or to a nearby
stream
The groundwater treatment is expected to last approximately 10 years. Natural attenuation
processes were not figured into the calculation of treatment duration. Therefore, the estimated time
groundwater treatment is required may be overestimated. Groundwater monitoring will be conducted
semi-annually for the first five years, and annually for the next 25 years. However, groundwater
monitoring will be ceased when groundwater has reached Site Remediation goals.
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September, 1998 9-3
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SECTION 10. SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES
In this section, each alternative is assessed using seven evaluation criteria required under
CERCLA. Comparison of the alternatives with respect to these evaluation criteria are presented in
summary form. This approach is designed to provide sufficient information to adequately compare the
alternatives, aid in the selection of an appropriate remedy for the Site, and demonstrate satisfaction of
the statutory requirements.
Each alternative is evaluated in terms of its ability to:
Be protective of human health and the environment.
Attain ARARs or provide grounds for invoking a waiver.
Use permanent solutions and alternative treatment technologies or resource recovery
technologies to the maximum extent practicable.
Satisfy the preference for treatment that reduces toxicity, mobility, or volume of the hazardous
substances, pollutants and contaminants as a principal element.
Be cost-effective
The seven evaluation criteria required to address the above CERCLA requirements serve as the
basis for conducting the detailed analysis. The evaluation criteria are briefly described below.
1 Overall Protection of Human Health and the Environment determines whether each alternative
meets the requirement that it be protective of human health and the environment in both short-
and long-term, from unacceptable risks posed by hazardous substances, pollutants, or
contaminants. This criterion is of key importance. While the remedy selected may on occasion
seek a waiver of a given ARAR, the remedy selected must be protective of human health and the
environment.
2. Compliance with ARARs is used to determine how each alternative complies with federal and
state ARARs as defined in CERCLA Section 121, as discussed in Section 2, or provide grounds
for invoking one of the waivers.
3 Short-Term Effectiveness addresses the impacts of the alternatives during the construction and
implementation phase until remedial response objectives have been met. Alternatives are
evaluated with respect to their short-term effects on human health and the environment.
4. Long-Term Effectiveness and Permanence addresses the results of a remedial action in terms of
the risk remaining at the Site after response objectives have been met. The primary focus of this
evaluation is the effectiveness of the controls that will be applied to manage risk posed by
treatment residuals or untreated wastes.
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September, 1998 10-1
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5 Reduction of Toxicity, Mobility, and Volume addresses the statutory preference for selecting
remedial actions that employ treatment technologies that permanently and significantly reduce
toxicity, mobility, or volume of the hazardous substance as their principal element. This
preference is satisfied when treatment is used to reduce the principal threats at the Site through
destruction of toxic contaminants, irreversible reduction in contaminant mobility, or reduction of
total volume of contaminated media.
6 Implementability addresses the technical and administrative feasibility of implementing an
alternative and the availability of various services and materials required during its
implementation.
7 Cost estimates for the FS are expected to provide an order-of-magnitude evaluation for
comparison of alternatives and are based on the site characterization developed in the RI.
Capital cost, annual cost, and a present worth analysis are part of this evaluation. The present
worth represents the amount of money that, if invested in the initial year of the remedial action
at a given rate, would provide the funds required to make future payments to cover all costs
associated with the remedial action over its planned life. The baseline present worth is
computed at a discount (interest) rate of 7 percent over a 30 year period Appendix A contains
spreadsheets showing each component of the present worth costs.
The first two criteria are referred to in the RI/FS guidance manual (EPA 1988) as the "threshold
factors", implying that for further consideration of an alternative, these two criteria must be satisfied.
Alternatives which do not satisfy these threshold factors are not feasible (40 CFR 300.430(f)(l)(I)(A).
Criteria 3 through 7 are referred to as "primary balancing factors" (page 4-25 of RI/FS manual),
implying that these criteria are used to select the alternative among the feasible alternatives. There are
two other criteria, state acceptance and community acceptance, which are provided by state and local
agencies and the public These criteria will be evaluated in the responsiveness summary. A detailed
analysis of the alternatives using the above criteria is presented below.
A. Alternative I - No Action
Section 300.430 (e) of the NCP requires that the "no action" alternative be carried forward for
consideration in the detailed analysis of alternatives as a baseline for comparison of the other
alternatives. Under the no action alternative, funds are not expended for routine monitoring, control,
or cleanup of groundwater contamination associated with the Site. Funding would, however, be
required for the five-year review.
Overall Protection of Human Health and the Environment
This alternative would not provide any increased protection to human health or the environment.
Residents in the vicinity of the Site would continue to drink water from private wells that contain
contaminants above the remediation goals. However, since soils at the Site did not contain any
significant amounts of contamination, the concentration of contaminants in the groundwater would be
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September. 1998 10-2
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expected to decrease with time due to natural attenuation and degradation. Under this action,
monitoring or verification of the decrease would be conducted only at the five-year review stage.
Compliance with ARARs
The "no action" alternative would not address compliance with ARARs since there would be no
active measures taken to reduce the contaminant concentrations. The volatile organic contaminant
concentrations would be expected to decrease with time due to natural attenuation and degradation.
Location- and action-specific ARARs do not apply to this alternative since further remedial action
would not be conducted.
Short-Term Effectiveness
Because no activities would be implemented, there would be no additional impact on the
community. Also, no construction or operation related impacts to the environment would occur, since
no site activities would be performed.
Long-Term Effectiveness and Permanence
Because remedial actions would not occur, this alternative would not provide any long-term
effectiveness or permanence. The long term risks caused by the contaminated groundwater would not
be addressed. However, since the Site soils did not contain any significant amounts of contamination,
the concentration of contaminants in the ground water would be expected to decrease with time due to
natural attenuation and degradation.
Reduction of Toxicity, Mobility, and Volume
The "no action" alternative would provide no reduction in toxicity, mobility, or volume of
contaminated groundwater.
Implementability
This criterion is not applicable because remedial activities would not occur.
Cost
The cost of this alternative consists only of 5-year review expenses. The total present worth
cost for this alternative is approximately $140,055.
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County. NC
September. 1998 10-3
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B. Alternative 2 - Institutional Controls
This alternative includes deed recordations and groundwater monitoring to protect human health
and the environment. Under this alternative, no groundwater remedial measures will be undertaken at
the Site. Five-year reviews are required under the NCP to determine if contaminants which remain on-
site are causing additional risk to human health or the environment. As a result of this review, EPA
will determine if additional site remediation is required. Five-year reviews are assumed to be
conducted for a 30-year period.
Deed recordations would require amending the property deed to note that contaminated
groundwater is located on the property. These recordations would be required on properties within
the extent of the groundwater plume. These recordations would remain in place until the groundwater
quality improved enough to allow for unrestricted use.
Groundwater will be monitored semi-annually for five years and annually for 25 years at
approximately 18 existing monitoring, converted residential, and residential wells. Groundwater will
be collected and analyzed for VOCs.
Overall Protection of Human Health and the Environment
Deed recordations would alert residents of the potential hazards associated with the
contaminated groundwater They would limit exposure by warning of unlimited use of the
groundwater; however, the recordations would not completely eliminate the risk of exposure or
control the plume migration. Consequently, this alternative would not provide active protection of
human health and the environment, although natural attenuation and degradation of contaminants may
be occurring Monitoring would reveal future threats to human health and the environment.
Compliance with ARARs
This alternative does not achieve the remedial action objectives of chemical-specific ARARs
established for groundwater Through natural attenuation and degradation, a decrease in the
contaminant concentration would be expected with time. Location- and action-specific ARARs do not
apply to this alternative since further remedial actions of an intrusive nature would not be conducted.
Short-Term Effectiveness
Implementing this alternative would require approximately one year. Groundwater monitoring
could begin immediately. No significant environmental impacts would be expected during the
sampling events.
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September, 1998 10-4
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Long-Term Effectiveness and Permanence
Properly implemented deed recordations would make residents aware of the contamination and
thus potentially prevent ingestion and direct contact with contaminated groundwater, thereby reducing
risk to potential users Implementation of deed recordations with continued monitoring would be
required indefinitely. The long term monitoring results and the actual effectiveness of the deed
recordations would require periodic reassessment to determine the continued effectiveness of this
alternative If the degree of protectiveness to human health is insufficient, further remedial actions
would have to be implemented.
Reduction of Toxicity, Mobility, and Volume
This alternative would not actively reduce the volume, toxicity or mobility of the contaminants.
Implementability
This alternative would be readily implemented since there are no remedial activities of an intrusive
nature being performed. The implementation of monitoring would present no difficulties
Implementing and enforcing deed recordations would require the cooperation of the state and local
governments The deed recordations may be subject to change in legal and political interpretations
over time Voluntary acceptance by adjacent property owners is questionable. Consequently, present
or future property owners could choose to ignore or be unaware of the deed recordations. The
recordation could also be lost during future property transfers. For the above reasons, the reliability of
groundwater use deed recordations is considered uncertain. Legal services, field personnel and
analytical laboratories necessary for implementation of this alternative are readily available. If
additional monitor wells are required, well drilling services are readily available. Monitor equipment is
readily available for groundwater sampling.
Cost
The total estimated present worth cost for this alternative is $990,225. Capital costs associated
with this alternative include fees for implementing deed recordations and sampling equipment for
monitoring The O&M costs include long-term monitoring activities, which have been evaluated for a
.>0-year period
C. Alternative 3 - Reduction of Groundwater Exposure and Monitored Natural Attenuation
Under this alternative, all homes, churches, and businesses impacted by the Davis Park Road
TCE Site not currently connected to the City of Gastonia or Gaston County public water supply would
be connected. The Davis Park Road Site area is generally defined in Figure 1-1 of this Record of
Decision EPA will determine during the Remedial Design which homes, churches and businesses have
been or may become impacted by Site contaminants. In addition, residents will also be given the
option to obtain wellhead treatment of their private well.
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September. 1998 10-5
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If requested, aqueous phase activated carbon units for removal of organics from groundwater
supply would be installed at the wellhead of each residential well. Filtration will also be used as a
precursor to the carbon treatment units. Groundwater treatment at the wellhead will consist of the
installation of a filtration unit and granular activated carbon (GAC) unit. Both of the filter systems will
be installed in-line on present residential water systems. The systems will be designed to remove
particulates from the influent groundwater as well as any organics present. EPA will maintain the
carbon filters for a period of one year.
The first filtering unit of the in-line treatment system will consist of a paniculate filter for
removal of sediment and other matter from the influent water line. Following the particulate filter, the
feed water will flow into a GAC system. The GAC system will consist of two units operated in a
downflow fixed-bed mode, as it has been found to be most cost effective and produces the lowest
effluent concentrations for low solids feed streams. Due to space constraints, each unit will contain a
maximum of 50 pounds of carbon and will be replaced on a semi-annual to annual basis. Spent carbon
will be taken offsite for regeneration or disposal.
To assess the effectiveness of the treatment system, the water effluent will be routinely
monitored. Monitoring will be more frequent during startup and early operation.
This alternative also includes monitoring of groundwater from approximately 18 monitoring
wells for 3 years on a quarterly basis and for 27 years on an annual basis. However, groundwater
monitoring will be ceased when groundwater has reached Site Remediation goals.
All connections to the city water system would require assistance from state and local
authorities, especially in the areas of public notification, system design, and system construction.
During initial procedures, an accurate count of the number of residences that are, or may be potentially
affected by the groundwater contaminant plume would have to be determined. Once determined,
EPA, state and local authorities would have to notify each resident and present the positive and
negative aspects of a public water connection Recognition of the fact that some residents will not
want to accept public water supply connection is understood. After notification of the public, system
design will begin. System design will require agreement between local authorities and EPA as to the
total number of connections and total extent of pipeline. Following completion of the system design,
system construction will commence. The system will most likely be installed by the local authority or
qualified contractor.
The quarterly groundwater sampling for VOCs will be augmented with the collection of
additional data to support the assumption that contaminants in the bedrock aquifer groundwater plume
are naturally attenuating. The evaluation will be conducted in accordance with Region TV's Draft
Region 4 Approach to Natural Attenuation of Chlorinated Solvents. For the first year, these
additional samples will be collected, and combined with data collected during the Rl, will comprise the
Natural Attenuation Study. The conclusions of the study will be published in a report by EPA.
Davis Park Road TCE Site
Record of Decision
Gastonia. Gaston County, NC
September. 1998 10-6
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Overall Protection of Human Health and the Environment
This alternative provides protection to residents from contaminated groundwater during an
extended period of time, especially for those connected to the City of Gastonia public water supply
system. Therefore, risks to current and potential groundwater users are expected to decrease. In
addition, natural attenuation processes provide protection to human health and the environment by
using natural processes, including intrinsic biodegradation and dispersion, to reduce contaminant
levels.
Compliance with ARARs
Under this alternative, groundwater recovered from the wellhead treatment will be treated such
that contaminant concentrations in the effluent will be below the remediation goals. Natural
attenuation processes are expected to decrease the contaminant concentrations. The Natural
Attenuation Study conducted during the Remedial Design will provide the data necessary to prove that
contamination is naturally attenuating and more accurately predict the rate of decrease.
Short-term Effectiveness
Appropriate levels of protection will be used during installation of the treatment system and
connection of residents to the city water supply. Disposal of any wastes generated during construction
and operation will follow proper handling practices and no exposure or environmental impacts are
expected
Long-term Effectiveness and Permanence
Connecting affected residents to the city water supply will provide a permanent remedy for
protection of human health. The wellhead treatment would require regular maintenance by the
resident. Groundwater monitoring will continue to occur regularly during implementation of this
alternative. There will be a remaining risk associated with groundwater use for an estimated 7 years.
Reduction of Toxicity, Mobility, and Volume
Treating the groundwater by aqueous phase GAC will reduce the concentrations of organics in
the groundwater to the remediation goals, and therefore, the toxicity and volume. Natural attenuation
processes may also act to reduce the overall concentration of the contaminant plume.
Implementnbility
This alternative involves installation of in-line groundwater treatment units, including filtration
units and activated carbon units. These components are widely available and the system can be
assembled using standard engineering and construction techniques. All of the units of the treatment
system are easily transportable and installed. For the organic contaminants detected at the Site, carbon
Davis Park Road TCE Site
Record of Decision
Gastonia. Gaston County, NC
September. 1998 10-7
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adsorption is a proven technology and is often used as a means for treatment. Permission will be
required from the respective property owners for the installation of carbon units.
Water lines currently used by the city are adjacent to many of the residences at the Site and
would only require extensions of the lines to connect new residences. Permits and designs would have
to be obtained by the local authority or qualified contractor.
Cost
Costs associated with the connection of residences to the public water supply include public
notification, system design, and system construction. For estimating purposes, EPA assumed 75
residents would be connected to city water. Capital costs associated with the groundwater treatment
unit portion of the alternative includes installation of the filter and carbon adsorption units, and other
associated instrumentation and equipment. For estimating purposes, EPA assumed that 75 residents
would request wellhead treatment with operation and maintenance for a period of 1 year. Capital costs
for the Natural Attenuation Study have been estimated. The estimated total present worth cost for this
alternative is $3,873,299.
D. Alternative 4 - Reduction of Groundwater Exposure and Groundwater Treatment
This alternative includes all the provisions for prevention of exposure of current residents to
contaminated groundwater described in Alternative 3, plus adds remediation of the groundwater that
contains contaminant concentrations above the remediation goals. The major component of the
groundwater treatment option includes in-well vapor stripping..
The in-well VOC removal system volatilizes VOCs contained in groundwater and removes them
as a vapor. The vapor is retrieved using vacuum extraction and is treated above ground by adsorption
onto granular activated carbon (GAC). The VOC-enriched vapor is extracted and the partially cleaned
water is returned to the aquifer. The system recirculates the groundwater through air-lift pumping.
The system converts groundwater contamination into a vapor that is vacuum-extracted and treated. At
the same time, air-lift pumping circulates the groundwater, which becomes cleaner with each pass
through the in-well air stripper. The only input to the system is gas, which is injected into the well.
The injected gas is typically air and can be recycled during the process.
The only output of the system is gas that is removed from the well; this gas contains the VOCs
removed from the groundwater. After removal, this VOC vapor is adsorbed onto GAC. The GAC is
regenerated and reused. No major facilities are needed for this technology. Power is needed to
operate the pumps and compressors. The method itself involves no moving parts beneath the ground
surface; however, careful packer and well designs would be required to successfully divert the
groundwater from the well back into the saturated zone and to the water table.
The system is expected to operate approximately 10 years. After 10 years of operation, the
treatment system will be evaluated for its effectiveness and the decision will be made on the
continuation of this treatment. Groundwater monitoring will be conducted semi-annually for the first
Davis Park Road TCE Site ~~ ~" ~~~
Record of Decision
Gastonia, Gaston County, NC
September. 1998 10-8
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five years, and annually for twenty five years thereafter. However, groundwater monitoring will be
ceased when groundwater has reached Site Remediation goals.
Overall Protection of Human Health and the Environment
This alternative would provide significant protection of human health and the environment
through groundwater remediation and connection of residents to the city water supply.
Compliance with ARARs
Under this alternative, groundwater will be treated such that the contaminant concentrations in
the effluent will be below remediation goals. This treatment option will comply with chemical-,
location-, and action-specific ARARs.
Short-Term Effectiveness
During installation of the treatment system, the usual precautions necessary for construction
activities will be taken. The installation of wells and the treatment system will not involve a significant
release of volatiles to the environment. Disposal of any wastes generated during construction and
operation would follow established handling practices.
Long-Term Effectiveness and Permanence
The use of treatment processes provides a permanent method for treating the VOC
contaminants in the groundwater. Spent carbon will be disposed in an approved facility or regenerated
otT-site
Reduction of Toxicity, Mobility and Volume
Pumping at the wells would capture the plume and thus reduce plume mobility. Treating the
groundwater would remove VOCs present in the groundwater to the remediation goals, thus reducing
the toxicity and volume of groundwater contamination. This process would not release VOCs to the
atmosphere
Implementability
This alternative involves installation of groundwater extraction wells, small pumps, compressor,
and GAC canisters, in addition to electrical connections. These components are widely available and
the system can be assembled using common construction techniques. All the units of the treatment
system are easily transportable and installed.
Cost
Davis Park Road TCE Site
Record of Decision
Gastonia. Gaston County. NC
September. 1998 10-9
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The total present worth cost for this alternative is approximately $7,014,434. Total capital
costs are estimated to be $2,879,874.
E. Alternative 5 - Reduction of Groundwater Exposure and Groundwater Pump and Treat
This alternative includes all the provisions for prevention of exposure of current residents to
contaminated groundwater described in Alternative 3, plus adds remediation of the groundwater that
contains contaminant concentrations above the remediation goals. The major component of the
groundwater treatment option includes groundwater extraction and treatment.
The groundwater pump and treat system involves the use of extraction wells to remove
contaminated groundwater from the bedrock aquifer via pumping and discharge to an air stripping
system that volatalizes the VOCs The vapor is retrieved using vapor vacuum extraction and is treated
by adsorption onto GAC or is released without treatment to the atmosphere. The treated water exits
the air stripping system and is discharged to a local surface water body, which in this case would be
Blackwood Creek An NPDES permit will be required prior to any discharge and the permit will
define levels of constituents that may be present in the treated water.
System requirements include power for operation of the pumps and air stripping system. The air
stripping system is built to be able to operate in the open environment. However, costs have been
included for the system to be housed within a building for protection against the elements and human
interference
The system is expected to operate approximately 10 years. After 10 years of operation, the
treatment system will be evaluated for its effectiveness and the decision will be made on the
continuation of this treatment. Groundwater monitoring will be conducted semi-annually for the first
five years, and annually for twenty five years thereafter. However, groundwater monitoring will be
ceased when groundwater has reached Site Remediation goals.
Overall Protection of Human Health and the Environment
This alternative would provide significant protection of human health and the environment
through groundwater remediation and connection of residents to the city water supply.
Compliance with ARARs
Under this alternative, groundwater will be treated such that the contaminant concentrations in
the effluent will be below remediation goals. This treatment option will comply with chemical-,
location-, and action-specific ARARs.
Short-Term Effectiveness
During installation of the treatment system, the usual precautions necessary for construction
activities will be taken The installation of wells and the treatment system will not involve a significant
Davis Park Road TCE Site"~~ "~~
Record of Decision
Gastonia, Gaston County, NC
September, 1998 10-10
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release of volatiles to the environment. Disposal of any wastes generated during construction and
operation would follow established handling practices.
Long-Term Effectiveness and Permanence
The use of treatment processes provides a permanent method for treating the VOC
contaminants in the groundwater Spent carbon will be disposed in an approved facility or regenerated
off-site
Reduction of Toxicity, Mobility and Volume
Pumping at the wells would capture the plume and thus reduce plume mobility. Treating the
groundwater would remove VOCs present in the groundwater to the remediation goals, thus reducing
the toxicity and volume of groundwater contamination.
Implementability
This alternative involves installation of groundwater extraction wells, small pumps, air stripping
system and GAC canisters, in addition to electrical connections. These components are widely
available and the system can be assembled using common construction techniques. All the units of the
treatment system are easily transportable and installed.
Cost
The total present worth cost for this alternative is approximately $4,543,480. Total capital
costs are estimated to be $2,018,869.
F. Comparative Analysis of Alternatives
Presented in Table 10-1 are ranking scores for each evaluation criteria, excluding cost. Each
alternative's performance was ranked on a scale of zero to five, with zero indicating none of the
criteria's requirements were met, and five indicating all of the requirements were met. The ranking
scores are not intended to be quantitative or additive. They are summary indicators only of each
alternative's performance against the evaluation criteria. The ranking scores combined with the
present worth costs provide the basis for comparison among alternatives.
Under overall protection, the no action alternative (Alternative 1) is ranked the lowest ("0")
since contaminated groundwater is left onsite with no further actions being conducted. Alternative 2 is
ranked slightly higher ("1") since deed recordations will be implemented in an attempt to limit contact
with the contaminated groundwater. Alternatives 4 and 5 are ranked higher ("5") than Alternative 3
("4") since these alternatives provides for treatment of the entire contaminant plume.
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September. 1998 10-11
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Under compliance with ARARs, Alternatives 1 and 2 are ranked the lowest ("0") since
contaminated groundwater remains onsite and chemical-specific ARARs are not met. Alternative 3 is
ranked lower than Alternatives 4 and 5 since ARARs will not be met.over the entire plume.
Under long-term effectiveness, the no action alternative is ranked the lowest since contaminated
groundwater would be left onsite with no further actions being conducted. Alternative 2 is ranked
slightly higher since deed recordations would somewhat limit contact with the contaminated
groundwater. Alternative 4 and 5 are ranked highest since contaminated groundwater over the entire
plume would be remediated.
Under reduction of T7M/V, Alternatives 1 and 2 are ranked the lowest since contaminated
groundwater remains as is. The mobility, toxicity, and volume are reduced in Alternatives 3, 4 and 5,
however, to a greater extent in Alternatives 4 and 5.
Under short-term effectiveness and implementability, Alternative 1 is ranked the highest since no
further actions are being conducted. Alternative 2 is ranked next since the only actions taking place
are deed recordations and groundwater monitoring. The remaining alternatives are ranked equally.
Table 10-1. Comparative Analysis of Alternatives
Overall Protection
Compliance \v/ ARARs
Long-Term
Effectiveness
Reduction of TYM/V
Short-Term
Effectiveness
linplcmcntttbility
Prcscni Worth Costs
1- No Action
0
0
0
0
5
5
$140,055
2-
Institutional
Controls
1
0
1
0
4
4
$990,225
3-Rcduction of GW
Exposure and
Monitored Natural
Attenuation
4
4
4
5
3
3
$3,873.299
4-Reduction of
GW Exposure
andGW
Treatment
5
5
5
5
3
3
$9,894,308
5-Rcduction of
GW Exposure
and GW Pump
and Treat
5
5
5
5
3
3
$6.562,349
Davis Park Road TCE Site
Record of Decision
Gastonia. Gaston County, NC
September, 1998
10-12
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SECTION 11. THE SELECTED REMEDY
Based upon consideration of the requirements of CERCLA, the NCP, the detailed analysis of
alternatives and public and state comments, EPA has selected Alternative 3 as the groundwater
remedy for this Site. The remedy includes connecting all homes, churches and businesses in the
"Davis Park Road Site Area" as depicted in Figure 1-1 of this document to the City of Gastonia
public water supply, optional installation of granulated carbon filters on private wells with operation
and maintenance of the filter for one year with a filter replacement after the first year of operation;
and a Natural Attenuation study followed by monitored Natural Attenuation of the bedrock aquifer
groundwater plume Groundwater monitoring will be conducted on a quarterly basis for three years
and annually for the next 27 years. The first year of quarterly sampling will be augmented to
include parameters necessary to complete the Natural Attenuation Study. Groundwater will be
analyzed for VOCs as well as necessary groundwater geochemical data, hydrogeologic parameters,
and other necessary information to complete the Natural Attenuation Study. The Natural
Attenuation study will be designed during the Remedial Design phase and will be conducted in
accordance with Region TV's Draft Region 4 Approach to Natural Attenuation of Chlorinated
Solvents. For the first year, these additional samples will be collected, and combined with data
collected during the Rl, and will comprise the Natural Attenuation Study. The conclusions of the
study will be published in a report by EPA.
At the completion of this remedy, the risk associated with this Site has been calculated to be
within the accepted risk range determined to be protective of human health and the environment
The remedy is expected to take 7 years. The total present worth of the selected remedy is
$3,873299. Tables 11-1 and 11-2 provide a detailed cost estimate for the chosen remedy.
In the event that data collected during the Natural Attenuation study cannot substantiate the
occurrence of natural attenuation, a contingency remedy, Alternative 5, will be implemented.
Alternative 5 has all of the components of reduction of exposure to contaminated groundwater
described in Alternative 3, plus adds active treatment of the contaminated bedrock aquifer
groundwater plume using pump and treat. The total present worth of this remedy is $6,562,349. It
is anticipated that this decision will be made within 3 years and, if appropriate, will be documented
by an amendment to this Record of Decision.
Davis Park Road TCE Site
Record of Decision
Gastonia. Gaston County, NC
September, 1998 11-1
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Table Number: 1 1-1 PRESENT WORTH CAPITAL COST
Alternative No. 3 -Reduction of GW Exposure plus Monitored Natural Attenuation
Sue Name Davis Park Road TCE Site Discount Rate: 7%
Site Location (iastonia, NC Date: July 1998
ITEM DESCRIPTION
TREATABILITY STUDY
NATURAL ATTENUATION STUDY
CITY WATER CONNECTIONS
lnstallatton/75 residents
Design specifications, regulator)'
approval, permits (20%)
WELLHEAD TREATMENT
Installation per residence (includes
larluHi. UV light and 1 e filler)
(iAC filter replacement after 1 year
QUANTITY
1
1
5,500 feet
75
75
UNIT COST ($)
Lump Sum
Lump Sum
85/foot
7,550
530
SUBTOTAL - CAPITAL COST
l-'ive Year Review (includes groundwater sampling)
PRESENT WORTH-FIVE YEAR REVIEWS
SUBTOTAL
ADMINISTRATION ( 1 5%)
CONTINGENCY (25%)
TOTAL CAPITAL COST
PRESENT WORTH O&M COST
TOTAL PRESENT WORTH COST
TOTAL COST DOLLARS
517,500
$50,000
$467,500
593,500
$566,250
$39,750
$1,234,500
$27,500
$97,430
$1,331,930
$199,790
382,930
$1,914,650
$1,958,649
$3,873,299
Davis Park Road TCE Site
Record of Decision
Gastonia. Gaston County, NC
September, 1998
11-2
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Table Number: 11-2 REMEDIAL ACTION OPERATION COST
Alternative No.? -Reduction of GW Exposure plus Monitored Natural Attenuation
Site Name: Davis Park Road TCE Site Discount Rate: 7%
Site Location: Gastonia, NC Date: July 1998
ITEM DESCRIPTION
WEI. I. MAINTENANCE
(iW Monitoring
Quarterly
VOC Analysis
Luhor( sampling)
Report Preparation
Annual
VOC Analysis
1. abort sampling)
Report 1 'reparation
WELLHEAD TREAT
1. abort 6% Of capital)
Maintenance (2% of
capital)
Monitoring of effluent
(quarterly for 1 year)
C.ROHNDWATER
MODELING
ANNUAL
QUANTITY
1
72
4
4
21
1
1
75X4=300
1
UNIT COST
($)
lump sum
SI25/sample
$2,400/event
$2.500/evcnl
$125/sample
$2,400/event
$2,500/event
lump sum
lump sum
300/sample
$5,000
TOTAL COST PER
YEAR
$27,000
$9,000
$9,600
$1 (),()( )0
$2,625
$2,400
$2,500
$114,879
$38,293
$90,000
$5,000
T( ) TAL PRESENT WORTH O&M COSTS - $1,958,649
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September. 1998
11-3
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Performance Standards
The goal of this remedial action is to restore the groundwater to its beneficial use. Based on
information obtained during the RI, and the analysis of all remedial alternatives, EPA and the State
of North Carolina believe that the selected remedy will be able to achieve this goal.
Groundwater shall be treated until the following performance standards are attained
throughout the contaminant plumes:
Contaminant
Trichloroethene
Telruehloroethene
1 . 1 -dichlorocthenc
Chloroform
Methyl-tert-butyl ether
Remediation Level
2.8 ug/l
1 ug/l
7ug/l
1 ug/l
200 ug/l
Risk Level
IR-06
1 L--06
1 fi-04
1E-06
Hl=l
Ha/.ard Index (HI) - Relates to non-cancer risks
1E-06 Risk Level - Probability for carcinogenic effects
(Sec Section 6 of this document for an explanation of HI and Risk Levels)
ug/l - micrograms per liter
If it is determined that certain portions of the aquifer cannot be restored to their beneficial
use, all of the following measures involving long-term management may occur, for an indefinite
period of time, as a modification of the existing system:
a) engineering controls such as physical barriers, or long-term gradient control provided by low
level pumping, as contaminant measure;
b) performance standards may be waived for the cleanup of those portions of the aquifer based on
the technical impracticability of achieving further contaminant reduction;
c) institutional controls may be provided/maintained to restrict access to those portions of the
aquifer which remain above remediation levels;
d) continued monitoring of specified wells; and
e) periodic reevaluation of remedial technologies for groundwater restoration.
The decision to invoke any or all of these measures may be made during a periodic review of
the remedial action, which will occur at 5 year intervals in accordance with CERCLA Section
12 l(c).
The remedial actions shall comply with all ARARs (See Section 7).
Davis Park Road TCE Site
Record of Decision
Gastonia. Gaston County, NC
September, 1998 11-4
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Additional Sampling Requirements
Additional groundwater sampling shall be conducted to further define the extent of
contamination. Specifically, the following shall be obtained at a minimum:
* Additional, limited characterization of the southerly and southwesterly extents of VOC
contamination in the bedrock aquifer along suspected fracture zones; and
* Periodic private well sampling to determine if any of the residents' wells exceed the Emergency
Response action level of 70 ug/1 for PCE.
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September, 1998 11-5
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SECTION 12. DOCUMENTATION OF SIGNIFICANT CHANGE
CERCLA Section 117(b) requires an explanation of significant change from the preferred
alternative presented in the Proposed Plan dated July 27, 1998. In the proposed plan, Alternative 3
was chosen for groundwater at the Davis Park Road Site. Alternative 5 is the contingency remedy.
EPA reviewed all written and verbal comments submitted during the public comment period. It was
determined that no significant changes to the remedy, as originally identified in the Proposed Plan,
were necessary
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September, 1998 12-1
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Appendix A
Responsiveness Summary for the Record of Decision
Davis Park Road TCE Site, Gastonia, North Carolina
Response to Stakeholder Comments
A number of individual citizens who attended the public meeting on the Proposed Plan on
July 28, 1998 asked if their well had been sampled and what the results were.
During the Proposed Plan public meeting EPA attempted to provide information to individual
residents on the results of historic sampling of their private or community well if that information
was available. EPA will prepare a mailing to each resident presenting the results of any sampling
conducted by EPA on their well.
In addition, if a resident requests that their private well be sampled, EPA will determine if the well
can be sampled during the monitoring program for the Davis Park Road Site or whether to refer the
resident to the Gaston County Department of Health for their consideration.
What is the extent of the City Water connections which will be offered to residents impacted
by the Davis Park Road Site, and when will those connections be made?
EPA will determine as part of the Remedial Design for the Site which residents have been, or may
potentially become, impacted by contaminated groundwater. The extension of the City Water line
will be determined as EPA completes it's Remedial Design. It is anticipated that the Remedial
Design will take approximately one year to complete. Availability of Remedial Action funding
through the Superfund is dependent on the relevant risks of the Davis Park Road Site compared to
other Sites Nationally which are candidates for Remedial Action funding that same fiscal year. EPA
will begin the Remedial Action, including the extension of City Water lines, as soon as the
Remedial Design is complete and Remedial Action funding is available.
Private Residents will be allowed to keep their current well, however, if City Water is provided,
there can be no interconnection of the two systems. EPA, as part of the Remedial Action, will
provide an activated carbon filter system to those residents who are impacted by the Site and
request a filter be installed on their private well.
Why was the current City Water line extended only as far as it is, and if I paid to connect to
the City Water in the past will I be reimbursed by EPA for my costs?
The current City Water line in the area impacted by the Davis Park Road Site was installed by the
City of Gastonia because of a petition by residents The connections were made by a special
assessment process, and was extended to the limits of the petition
Davis Park Road TCE Site
Record of Decision
Gastonia. Gaston County. NC
September, 1998 A-l
-------
EPA is currently looking into the ability to reimburse citizens who have been impacted by the Davis
Park Road Site, and have paid on their own to connect to the City water system because of
concerns surrounding the contamination at the Site.
Is the property at 2307 Davis Park Road the only source of groundwater contamination in
the area?
EPA conducted an additional source investigation during the Remedial Investigation. The Remedial
Investigation findings concluded that contaminants detected in groundwater may be a result of
earlier soil contamination detected at 2307 Davis Park Road, however, no continued source of
contamination was detected in soils on this property. EPA has not been able to determine what
specific housekeeping practices or past spills may have resulted in the past detections of soil
contamination or in the current groundwater contamination, or when the contamination first started.
No source of the presumptive evidence of petroleum products detected at very low levels in limited
groundwater samples has been determined. However, with the exception of Methyl-tert-butyl ether
which may be related to petroleum type compounds, none of these contaminants are contaminants
of concern for the Site
EPA will continue to monitor groundwater in the area of the site during the Remedial Design and
Remedial Action. If EPA determines through groundwater analysis that there may be a new source
of contamination, EPA will attempt to locate that source.
Based on the composition of the bedrock aquifer system, is the primary Natural Attenuation
process dilution/dispersion or biodegradation of contamination?
During the Remedial Investigation, EPA collected samples and conducted modeling efforts to
determine if Natural Attenuation factors were acting to reduce the contamination in the
groundwater at the Site. Based on this information, EPA has determined that the contamination in
the bedrock aquifer is most likely discharging to Blackwood Creek, and that contaminant reduction
is primarily through the dispersion/dilution of contaminants. However, because some degradation
products of both TCE and PCE have been detected, EPA does believe that some in-situ
biodegradation is occurring. EPA will attempt to more conclusively determine, as part of the
Remedial Design, whether Natural Attenuation of Site contaminants in the bedrock aquifer is
occurring at the Site. EPA intends to publish it's findings in a report.
Davis Park Road TCE Site
Record of Decision
Gastonia, Gaston County, NC
September. 1998 A-2
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