United States
Environmental Protection
Agency
Office of
Emergency and
Remedial Response
EPA/ROD/R04-92/105
August 1992
£EPA Superfund
Record of Decision:
Potter's Septic Tank Service
Pits, NC
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NOTICE
The appendices listed in the index that are not found in this document have been removed at the request of
the issuing agency. They contain material which supplement, but adds no further applicable information to
the content of the document. All supplemental material is, however, contained in the administrative record
for this site.
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50272-101
REPORT DOCUMENTATION
PAGE
1. REPORT NO.
EPA/ROD/R04-92/105
3. Recipient1* Accession No.
4. TWe and Subtitle
SUPERFUND RECORD OF DECISION
Potter's Septic Tank Service Pits, NC
First Remedial Action - Final
5. Report Date
08/05/92
7. Authors)
8. Performing Organization Rept No.
9. Performing Organization Nune and Address
10. Prolect/Task/Work Unit No.
11. ContractfC) or Grsnt(G) No.
(C)
(O
12. Sponsoring Organization Name and Address
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, D.C. 20460
13. Type of Report & Period Covered
800/000
14.
15. Supplementary Note*
PB93-964007
16. Abstract (Limit: 200 words)
The 5-acre Potter's Septic Tank Service Pits (Potters's Pits) is located in a rural
section of Brunswick County, North Carolina. The surrounding land use is semi-rural
residential. The site is situated within a residential community known as the Town of
Sandy Creek. The Chinnis Branch waterbody traverses the site, flowing from southwest
to northeast. A forest/wetland region covers approximately half of the site. There
are no public water supplies within approximately 10 miles of Sandy Creek because the
current residences use private domestic water wells and onsite septic systems. The EPA
Domestic Water Survey for the subdivision indicates that there are 60 wells in the
area. Between 1969 and 1976, before the land was developed for residential use, a
family business operated sludge hauling and oil spill clean-up companies as well as
waste disposal pits on the site. Disposal practices consisted of placing petroleum
waste products and septic tank sludges either in shallow unlined pits or directly on
the land surface. In 1976, an unlined pit failed, allowing approximately
20,000 gallons of oil to flow into Chinnis Branch. The U.S. Coast Guard responded to
the spill pursuant to CWA. Additionally, the site owners pumped the remaining oil from
the breached pit and three other onsite pits for offsite disposal. Approximately 150
(See Attached Page)
NC
17. Document Analysis a. Descriptors
Record of Decision - Potter's Septic Tank Service Pits,
First Remedial Action - Final
Contaminated Media: gw, sw
Key Contaminants: VOCs (benzene, toluene, xylenes), other organics (naphthalene),
metals (chromium, lead)
b. kfentifiers/Open-Ended Terms
c. COSATI Reid/Group
18. Availability Statement
19. Security Class (This Report)
None
20. Security Class (This Page)
None
21. No. of Pages
130
22. Price
(See ANSI-Z39.18)
See Instructions on Reverse
OPTIONAL FORM 272 (4-77)
(Formerly NTIS-35)
Department of Commerce
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EPA/ROD/R04-92/105
Potter's Septic Tank Service Pits, NC
First Remedial Action - Final
Abstract (Continued)
truck loads of oil sludges and stained soil were removed. Thick oil sludge that could
not be pumped was mixed with sand and buried onsite. In 1982, Dixie and Earl Gurkin
purchased the site and discovered buried wastes, which resulted in an EPA investigation
that revealed soil and ground water contamination. In 1984, EPA conducted an emergency
removal, excavating an estimated 1,770 tons of oil, sludge, and contaminated soil for
offsite disposal. This ROD addresses the ground water treatment and contaminated soils
at the site. Primary contaminants of concern affecting surface and subsurface soil are
VOCs and semi-VOCs, including napthalene, metals, and pesticides. Ground water is
contaminated with VOCs, including benzene, ethyl benzene, toluene; other organics
including naphthalene, and xylenes; and metals, including chromium and lead.
The selected remedial action for this site includes excavating all soils that exceed the
soil clean-up standards; treating contaminated soils by using an onsite ex-situ thermal
desorption process; performing secondary treatment of the concentrated organic
contaminants, a by-product of thermal desorption which will depend upon the vendor;
sampling and analyzing the treatment residue; disposing onsite the nonhazardous treated
soil to grade and revegatate with native grasses; or onsite solidifying of soils
containing levels of chromium, lead, and zinc above clean-up standards for offsite
disposal. The ground water remedy includes extracting ground water across the site in
the surficial aquifer; treating the extracted ground water onsite by chemical treatment;
air stripping to remove contaminants; surface discharge of the treated ground water to
Chinnis Branch; and continued analytical monitoring for contaminants in ground water.
The current residents who live onsite will be moved before remedial activities begin.
The total estimated present worth for the cleanup is $11,800,000, of which $7,100,000 is
for ground water extraction treatment and $4,700,000 is for soil remediation. Associated
O&M costs were not provided for this remedy.
PERFORMANCE STANDARDS OR GOALS: Chemical-specific goals for cleanup are based on the
more stringent state or federal standards for ground water and soil cleanup for metals,
including chromium and lead; other organics, including naphthalene; and metals, including
benzene, toluene, and xylenes; and federal land disposal restrictions pertaining to
storage and transportation of hazardous waste.
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RECORD OF DECISION
SUMMARY OP REMEDIAL ALTERNATIVE SELECTION
POTTER'S SEPTIC TANK SERVICE PITS SITE
SANDY CREEK, BRUNSWICK COUNTY
NORTH CAROLINA
AUGUST 5, 1992
PREPARED BY:
U.S. ENVIRONMENTAL PROTECTION AGENCY
REGION IV
ATLANTA, GEORGIA
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POTTER'S SEPTIC TANK SERVICE PITS SITE
RECORD OF DECISION
TABLE OF CONTENTS
•Section Page
1 . 0 INTRODUCTION !
2 . 0 SITE NAME, LOCATION, AND DESCRIPTION 1
2 .1 Surface Features 4
2 .2 Subsurface Features 4
2 .3 Current Land Use 6
3 . 0 SITE HISTORY AND ENFORCEMENT ACTIVITIES 10
3 .1 Initial Investigations 10
3.2 Remedial Investigation 11
3 .3 Remedial Investigation Addendum Report 13
4 . 0 HIGHLIGHTS OF COMMUNITY PARTICIPATION 14
5 . 0 SUMMARY OF SITE CHARACTERISTICS 16
5.1 Study Area 2 16
5T2 Soil Gas Survey 16
5 .3 Subsurface Soils . . 18
5.3.1 Remedial Investigation 18
5.3.2 Remedial Investigation Addendum 18
5 .4 Surface Soils 18
5.4.1 Remedial Investigation. 18
5.4.2 Remedial Investigation Addendum 28
5.5 Surface Water and Stream Sediments 28
5.5.2 Remedial Investigation 28
5.6.2 Remedial Investigation Addendum 30
-5 . 6 Groundwater 30
5.6.1 Residential Wells 30
5.6.2 Groundwater Flow 30
5.6.3 Groundwater Quality 31
5.8 Air Monitoring 34
5 . 9 Nature and .Extent of Contamination 38
6 . 0 SUMMARY OF SITE RISKS 40
6.1 Contaminent Identification 40
6.2 Exposure Assessment 40
6.3 Toxicity Assessment 44
6.3.1 Carcinogens. 44
6.3.2 Noncarcinogens -. 45
6.4 Risk Characterization Summary 45
6 .5 Risk Uncertainty 51
6.6 Environmental (Ecological) Risks 51
6.7 Risk Assessment Summary 53
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TABLE OF CONTENTS (con't)
Section Page
7 . 0 DESCRIPTION OF REMEDIAL ALTERNATIVES 57
7.1 Applicable and Relevant and Appropriate
Requirements (ARARs) 58
7.1.1 Action-Specific ARARs '.'.'.'.58
7.1.2 Chemical-Specific ARARs 60
7.1.3 Location-Specific ARARs 61
7.1.4 "To Be Considered" ARARs 61
7 .2 Groundwater Control Alternatives 62
7.2.1 GWC-1: No Action 62
7.2.2 GWC-2: Institutional Controls 63
7.2.3 GWC-3: Groundwater Recovery and Treatment.... 63
7 . 3 Remedial Alternatives for Source Control 64
7.3.1 SC-1
7.3.2 SC-2
7.3.3 SC-3
7.3.4 SC-4
7.3.5 SC-5
7.3.6 SC-6
7.3.7 SC-7
No Action 65
Institutional Controls 65
Soil Removal and Off-Site Disposal 66
Soil Stabilization/Solidification 66
On-Site Incineration 67
Soil Washing 68
Low Temperature Thermal Desorption and
Stabilization 69
8.0 SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES 70
8.1 Groundwater 70
8.1.1 Overall Protection of Human Health and the
Environment 70
8.1.2 Compliance with Applicable or Relevant and
Appropriate Requirements (ARARs) 71
8.1:3 Long-Term Effectiveness and Permanence 71
8.1.4 Reduction of Toxicity, Mobility, or Volume...72
8.1.5 Short-Term Effectiveness 72
8.1.6 Implementability 72
8.1.7 Cost 72
8 .2 Source Remediation '. 74
8.2.1 Overall Protection of Human Health and the
Environment '..... 74
8.2.2 Compliance with Applicable or Relevant and
Appropriate Requirements (ARARs) 74
8.2.3 Long-Term Effectiveness and Permanence 74
8.2.4 Reduction of Toxicity, Mobility, or Volume...74
8.2.5 Short-Term Effectiveness 74
8.2.6 Implementability 74
8.2.7 Cost 74
8.3 State/Support Agency Acceptance 74
8.4 Community Acceptance. 75
9 . 0 THE SELECTED REMEDY 78
9.1 GW-3: Groundwater Recovery and Treatment System 78
9.2 Additional Data Requirements and Monitoring of the
Groundwater 79
9.2.1 Monitoring Program 79
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TABLE OF CONTENTS (Cont...)
Section Page
9.2.2 Deep Aquifer 79
9.3 Low Temperature Thermal Desorption and
Stabilization 82
9.4 Additional Data Requirements for Area 3 Soils....... 83
9 .5 Total Cost of Remedy :'.'.'.86
9.6 Performance Standards to be Attained 86
9.6.1 Soil Clean-up Standards 86
9.6.2 Groundwater Clean-up Standards 86
9.7 Contingency Measures for Groundwater Remedial
Action." 89
9.8 Contingency Measures for Soils Remedial Action 90
10 . 0 SCOPE AND ROLE OF THE RESPONSE ACTION 93
10.1 Contaminated Soil .• 93
10.2 Groundwater 93
11.0 STATUTORY DETERMINATIONS 94
11.1 Protection of Human Health and the Environment 94
11.2 Compliance with Applicable or Relevant and
Appropriate Requirements (ARARs) 94
11.3 Cost Effectiveness 94
11.4 Utilization of Permanent Solutions and Alternative
Treatment Technologies or Resource Recovery
Technologies to the Maximum Extent
Practicable (MEP) 95
11.5 Preference for Treatment as a Principal Element 95
12 . 0 EXPLANATION OF SIGNIFICANT DIFFERENCES 96
APPENDIX I - Risk Assessment Tables 1-1 - 1-11
APPENDIX II - Risk Assessment Tables II-l - II-6
APPENDIX III - State'of North Carolina Concurrence Letter
APPENDIX IV - Responsiveness Summary
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POTTER'S SEPTIC TANK SERVICE PITS SITE
RECORD OF DECISION
LIST OF FIGURES
Figure ' Page
1 Map : . 2
2 Map ............. 3
3 Soils Map 5
4 Groundwater Contour Map (3 April 90) 7.
5 Street Map, Sandy Creek, NC ...^ ...... 8
6 Areas Excavated During Remedial Action - March 84 '.12
7 Total Measured VOCs Concentration - Soil Gas Survey 17
8 Location of Soil Borings 19
9 Total VOCs in Soil, 0-5 Foot Interval - CLP Results 20
10 Total VOCs in Soil, 5-10 Foot Interval - CLP Results 21
11 Total VOCs in Soil, 10-15 Foot Interval - CLP Results 22
12 Total SVOCs in Soil, 0-5 Foot Interval - CLP Results 23
13 Total SVOCs in Soil, 5-10 Foot Interval - CLP Results 24
14 Total SVOCs in Soil, 10-15 Foot Interval - CLP Results 25.
15 Phase II Sample Locations 26
16 Location of Surface Soil Samples 27
17 Location of Surface Water and Sediment Sampling Stations...29
18 Groundwater Elevations for Shallow Wells (3 April 90) 32
19 Groundwater Elevations for Deep Wells (3 April 90) 33
20 Location of Shallow and Deep Monitoring Wells at the Site..35
21 Ethyl Benzene Concentrations in Groundwater for Shallow
Wells Sampled June 91 37
22 Areas Used for Public Health Risk Assessment - Soils Data
0-3 Foot Intervals 41
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POTTER'S SEPTIC TANK SERVICE PITS SITE
RECORD OF DECISION
LIST OF TABLES
Tables
1 Groundwater Contaminant Concentration Ranges . . .36
2 Contaminants of Concern, All Media 42
3 Chemicals Contributing Most Significantly to
Non-Carcinogenic and Carcinogenic Risk 46
4 Carcinogenic Risk by Location and Exposure Route 47
5 Non-Carcinogenic Risk by Location and Exposure Route...48
6 Potential Clean-up Levels for Soils 50
7 Final Soil' Clean-up Standards and Corresponding Risk
Levels 54
8 Final Groundwater Clean-up Standards 55
9 Costs for Groundwater Alternatives 73
10 Costs for Source Remediation Alternatives 76
11 Cost for the Groundwater Recovery and Treatment
System 80
12 Toxicity Characteristic Leaching Procedure. 84
13 Cost for Low Temperature Thermal Desorption and
Stabilization 85
14 Soil Clean-up Standards 87
15 Groundwater Clean-up Standards 88
16 Cost for Soil Removal and Off-Site Disposal 92
APPENDIX I - Risk Assessment Tables
TABLES
PAGE
1 Summary Statistics for Groundwater, Area 1A 1-1
2 Summary Statistics for Groundwater, Area IB 1-2
3 Summary Statistics for Estimated Surface Water
Concentrations; Concentrations Assuming 75% Dilution..1-3
4 Summary Statistics for Sediment 1-4
5 Summary Statistics for Surface Soils (Depth 0'-3') -
Area 1A 1-5
6 Summary Statistics for Surface Soils (Depth 0'-3') -
Area IB , 1-6
7 Summary Statistics for Surface Soils - Forest/Wetland.1-7
8 Summary Statistics for Subsurface Soils - Area 1A.....I-8
9 Summary Statistics for Subsurface Soils - Area 1A 1-9
10 Summary Statistics for Subsurface Soils - Area IB 1-10
11 Summary Statistics for Indoor Air 1-11
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^2-Qf-JIMLES (Cnnt. ,
APPENDIX II - Risk A_CQ
S* Assessment Tables
TABLES
; -
; s-sss-^
4 Ingestion of Fish Expos^rl laram '; XI'3
5 Ingestion and Dermal Exposure Sc^f XI-4
Parameters.. ^^posure to Soils Exposure
6 inhalation of Indoor'Air'Exposure-parameters! ! ^-l
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RECORD OF DECISION
Remedial Alternative Selection
Site Name and Location
Potter's Septic Tank Service Pits Site
Sandy Creek, Brunswick County, North Carolina
Statement of Basis and Purpose
This decision document presents the selected remedial action for
the Potter's Septic Tank Service Pits Site in Sandy Creek, North
Carolina. The remedy was 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 Oil and Hazardous Substances Pollution Contingency
Plan (NCP). This decision document explains the factual and legal
basis for selecting the remedy for the site.
Assessment of the Site
Actual or threatened releases of hazardous substances from the
site, if not addressed by implementing the response action selected
in this Record of Decision (ROD) , may present an imminent and
substantial endangerment to public health, welfare, and/or the
environment.
Description of the Selected Remedy
This remedy addresses both soil and groundwater contamination at
the site. The major components of the selected remedy include:
GROUNDWATER
Extraction of groundwater across the site in the
surficial aquifer that is contaminated above Maximum
Contaminant Levels and/or the North Carolina Groundwater
Standards;
On-site treatment of extracted groundwater by chemical
treatment and air stripping to remove contaminants;
Surface water discharge of the treated groundwater to
Chinnis Branch; and
Continued analytical monitoring for contaminants in
groundwater.
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SOIL
The current residents (Gurkins) who presently live
on the site will be moved before remedial activities
begin;
Excavation of all soils exceeding the soil clean-up
standards established in this ROD;
Treatment of contaminated soil using on-site ex-
situ thermal desorption process;
Secondary treatment of the concentrated organic
contaminants, a by-product of thermal desorption which
will depend upon the vendor;
Sampling and analysis of the treatment residue;
Proper transportation and storage of RCRA hazardous
wastes;
On-site disposal of the non-hazardous treated soil into
the original excavated areas, backfilling with soil to
grade and revegatation with native grasses;
On-site solidification of soils containing levels of
chromium, lead, and zinc above clean-up standards for
off-site disposal;
Additional San*plincf and Monitoring
Additional sampling and analyses of the deeper aquifer to determine
the extent (if any) of contamination in this aquifer of site
contaminants. During the RI Addendum, one sample from a deep well
showed benzene in excess of MCLs.
Additional sampling and analyses will be done in Area 3 to better
characterize the soils.
Description of the Contingency Remedy For Soils
The current residents (Gurkins) who live on the site will be
moved before remedial activities begin;
Excavation of all soils exceeding the soil clean-up standards
established in this ROD;
Use of the Toxicity Characteristic Leaching Procedure (TCLP) tests
on the soil to identify whether the soil is a characteristic
hazardous waste;
If soil is not a charateristic hazardous waste (passes TCLP), then
the soil will be transported directly to a landfill for disposal;
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If the soil is a characteristic hazardous waste (fails TCLP), then
the soil will have to be treated before disposal at a RCRA
permittted landfill;
Statutory Determinationa
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 (or "a waiver can be justified for whatever Federal and
State applicable or relevant and appropriate requirement that will
not be met"), and is cost-effective. This remedy utilizes
permanent solutions and alternative treatment (or resource
recovery) technology to the maximum extent practicable, and
satisfies the statutory preference for remedies that employ
treatment that reduce toxicity, mobility, and/or volume as a
principal element.
Because this remedy will result in hazardous substances remaining
on-site above groundwater standards, a review will be conducted
within five years after commencement of the remedial action to
ensure that the remedy continues to provide adequate protection of-
human health and the environment. A 5-year review (or performance
evaluation) will be prepared at least once every five years until
groundwater contaminant concentrations no longer exceed groundwater
standards.
AUG 0 5 1992
Greer C. Tidwell Date
Regional Administrator
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RECORD OP DECISION
SUMMARY OP REMEDIAL ALTERNATIVE SELECTION
POTTER'S SEPTIC TANK SERVICE PITS SITE
SANDY CREEK, NORTH CAROLINA
1.0 INTRODUCTION
The Potter's Septic Tank Service Pits site was proposed for
inclusion on the National Priorities List (NPL) in June 1988 and
was finalized on the NPL in March 1989. The Potter's Pits site is
a 5-acre area where waste disposal pits were operated. ' Disposal
practices consisted of placing waste petroleum products and septic
tank sludges in shallow unlined pits or directly on the land
surface. The Remedial Investigation (RI) Report which was
completed in December of 1991, consisted of a two-phase
investigation that fully characterized the presence and extent of
contamination on and off site by evaluating the sediments, surface
water, groundwater, surface soils, and subsurface soils. The
Feasibility Study (FS) which develops and analyzes potential
alternatives for remediation at the site was issued to the public
in April of 1992.
This Record of Decision (ROD) has been prepared to summarize the
remedial alternative selection process and to present the selected
remedial alternative, in accordance with Section 113(k) (2) (B) (v)
and Section 117 (b) of the Comprehensive Environmental Response,
Compensation, and Liability Act of 1980 (CERCLA) as amended by the
Superfund Amendments and Reauthorization Act ((SARA) P.L. 99-499).
The Administrative Record for the Potter's Pits site forms the
basis for the Record of Decision contained herein.
2.0 SITE NAME, LOCATION, AND DESCRIPTION
The Potter's Septic Tank Service Pits (Potter's Pits) site is
located in a rural section of Brunswick County, North Carolina
approximately 17 miles west of Wilmington off of highway 74/76 in
a residential community known as the Town of Sandy Creek (Figure
1) . Sandy Creek is subdivided into one to two acre lots, each with
a private domestic water well. There are approximately 150
residential lots of which 70 are currently occupied.
The Potter's Pits site was divided into three study areas; Area 1
and 3 are located in residential lots within Sandy Creek, and Area
2 was located approximately 1.5 miles north across U.S. Highway
74/76 (Figure 1 and 2). Area 1 comprises the actual Potter's Pits
site. Area 3 was included in the investigation because historical
aerial photographs suggested that this area might have been used as
a disposal site. During the Remedial Investigation (RI) phase,
area 3 was determined not to be a problem. Additionally area 2 was
thought to be located approximately 0.4 miles from area 1 somewhere
off of highway 74/76, but was removed from further investigation
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N>
li
FIGURE 1
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ponE/rs SCPTIC T/
PITS SITF.
SANOrCS£EK.
MOflTM CAMXM*
Ira*
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after an extensive search indicated that no additional information
regarding its location or existence could be found.
2.1 Surface Features
The topography, type of soils in the area, and other relevant
surface features of the site are illustrated on Figure 3. The site
is located in Brunswick County which lies entirely within the
Coastal Plain. The site itself lies at approximately 60 feet above
mean sea level (msl) and is adjacent to Little Green Swamp, which
forms the headwaters of Chinnis Branch. Chinnis Branch traverses
the site, flowing from the southwest to the northeast direction.
Surface drainage from the site is toward Chinnis Branch which lies
at 36 to 38 feet msl in the site area. Chinnis Branch flows into
Rattlesnake Branch which then converges with Hood Creek, just south
of Mount Misery Road. Hood Creek drops steeply as it flows into
the Cape Fear River, which empties into the Atlantic Ocean.
The immediate area surrounding Chinnis Branch is a forest/wetland
region. This forest/wetland region covers approximately half of
the site.
The other prominent feature at the site is the residential house
located approximately in the location of the former disposal pit in
Area 1 .as can be . seen on the site map (Figure 2). The land
surrounding the site is a residential community and has other
residential homes bordering the property.
2.2 Subsurface Features
The oldest .sedimentary formation in Brunswick County is the
Tuscaloosa Formation of Late Cretaceous age. The Tuscaloosa is
typified by sands and clays of alluvial origin. Specific geologic
conditions at the site were determined by visual examination of
soil samples and rock cuttings observed during groundwater
monitoring well drilling.
Surface material at the site is composed of Miocene or younger
sediments typically 5 to 20 feet in thickness. These sediments are
primarily composed o"f silty fine sands, clayey sands, and poorly
graded sands. Underlying the surficial sediments is a poorly
defined, discontinuous, high plasticity, gray to dark gray, clay
layer that ranges from 5 to 20 feet below land surface (bis) and is
0.5 to 5 feet thick. This layer is believed to be a semi-confining
unit throughout the site area. Below the clay layer is a dark grey
marl approximately 3 feet thick. Underlying the marl is the
bedrock,, composed of either calcareous sandstone or an impure
limestone. Depth to bedrock ranges'from 24 to 42 feet bis.
Lithologic data collected in the RI suggest that two aquifers are
being monitored at the site. The aquifers are separated by the
clay layer, observed at approximately 5 to 20 feet bis. The depth
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Figure 3
LE&ENQ
fo Foimon • loamy Iliw sand
B*B BaymcMJ* - HIM sand. I lo 6 fttictnl slop**
BDC Bayimad* and Manyn wilt - 6 lo I2p*ic*nl Mop**
BnB BlaMon • HIM sand. 0 lo 5 ptictiD slop**
Lynchbuig - HIM sandy loam
-:$:-.-:y/X-"
i |\ AHPHOXIMATE SCALE IN F£ET
Ei
0 200 400
ponws stpnc IANK
PIISSIIE
SANDY C
»*0«IM CAHOlltA
US INMIONUINIAI.
PHUUCIION AlitNC«
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of the clay layer is reduced in the vicinity of Chinnis Branch
From the data collected during the RI, it has been determined that
the second aquifer is semi-confined, as the clay unit does not
appear to be present at all locations.
Groundwater measurements collected during the RI support a two-
aquifer scenario. While water level data collected from many of
the wells can be interpreted to support either a one or a two
aquifer hypothesis, head differentials observed in the cluster
comprised of shallow wells EPA-07 and MW-201 and deep well EPA-08
strongly suggest two separate aquifers are being monitored (Figure
4) .
The horizontal gradient and direction of groundwater flow is to the
east-southeast toward Chinnis Branch and the adjacent wetland areas
(Figure 4). Based on information collected in the phase I RI and
verified in the phase II RI Addendum, the calculated values of
groundwater velocity for the site range from 5.2 to 10.4 feet per
day. These estimated velocities appear relatively high, given the
comparatively limited distribution of contamination observed at the
site. Although flow velocities are an important component,
contaminant transport will also be controlled by numerous other
chemical specific and environmental interactions and variables.
Since the contaminants have not migrated very far, these other
factors are assumed to be affecting the contaminant transport.
2.3 Current Land Use
The Potter's Pits site is located in the Town of Sandy Creek in the
Northwest Township of Brunswick County. The current and projected
land use of this area is semi-rural residential. A map of the town
is provided on Figure 5. The typical homes are manufactured houses
(mobile or modular) on one- to two-acre lots. There are no public
water supplies within approximately 10 miles of Sandy Creek, and
the current residences use private domestic water wells and on-site
septic systems. The EPA Domestic Water Survey for the subdivision
indicates that there are 60 wells and that most are 25 to 40 feet
deep, with two wells over 100 feet.
To date there are no schools, hospitals, or public parks within
this district. Recreational activities include wading in Chinnis
Branch.
A current estimate of the population size in the area surrounding
the site was derived from a survey completed on March 8, 1990 by
the Town Clerk o-f Sandy Creek. A summary of the survey results is
as follows:
* 148 residential lots,
* 70 occupied dwellings, and
* 185 estimated residents, of which approximately 60 are
children
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Figure 4
GHOONDWAIEH CONTOUR UAP
(3 APRIL 1»90)
HI1S Sll£
SAM/V cntcx.
IMMIIIICAIUMIIA
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Figure 5
,
>o
UDCATOM or AfCA* i AND a
ECJORDANCQ
U.S. ENVIRONMENTAL
PROTECTION AGENCY
POTTOraSCFTICTAMK
ma SITE
8ANOY CREEK.
NOflfHCAIKMJNA
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»ticip.t«,. During che
increased
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3 .0 SITS HISTORY AND ENFORCEMENT ACTIVITIES
Between 1969 and 1976, before the land was developed for
residential use, the Skipper family operated sludge hauling and oil
spill cleanup companies in this area. Specifically they operated
waste disposal pits. Disposal practices consisted of placing waste
petroleum products and septic tank sludges in shallow unlined pits
or directly on the land surface.
In May 1976, the North Carolina Department of Natural and Economic
Resources (NCDNER) informed Mr. Ward Skipper that an oil disposal
pit (Area 2) located near Maco violated North Carolina statutes and-
must be cleaned up immediately. At that time, approximately 2,000-
3,000 gallons of black oil was pumped from the pit and the pit area
was covered with soil. Documentation pertaining to the chemical
composition of materials disposed in the pit, the fate of the
liquid removed from the pit, and the quantities and characteristics
of the material buried on site have not been found.
In August 1976, an unlined pit in Area 1 (Figure 2) failed and
allowed approximately 20,000 gallons of oil to escape. The oil
flowed into Chinnis Brach and then into Rattlesnake Branch. The-
U.S. Coast Guard responded pursuant to Section 311 of the Clean
Water Act to conduct the cleanup.
Also, in August of 1976, Mr. Otto Skipper (brother of Ward Skipper)
began pumping out the oil remaining in the breached disposal pit
(Area 1) . Approximately 20,000 gallons of oil were removed from
this pit and transported to Fort Bragg Military Reservation in
Fayetteville, North Carolina. Three other pits containing oil, as
well as the oil recovered from the receiving stream, was also taken
to Fort Bragg. In addition, approximately 150 dump truck loads of
oil sludge and oil stained dirt were excavated and hauled to
Brunswick County landfill in Leland, North Carolina for final
disposal. The thick oil sludge that could not be pumped was mixed
with sand and buried on site.
The Skipper Estate changed ownership in 1980. Wachovia State Bank,
through foreclosure, took possession of the property in January
1980. Investment Management Corporation later purchased the
property and subdivided it for residential development. This
development became known as Sandy Creek Acres and later as the Town
of Sandy Creek. Earl and Dixie Gurkin purchased the site lots in
1982. They found waste materials buried in their yard (Area 1) in
July of 1983. The State of North Carolina sampled the soil and
groundwater. Analysis of these samples confirmed the presence of
contamination. The site owner's water well was condemned, and they
were connected to a neighbor's well (Grainger's well, Figure 2}.
3.1 Initial Investigations
In September 1983, EPA and the Region IV Field Investigation Team
(FIT) performed an electromagnetic survey of the site, monitored
the air under the present owner's home, and collected soil, surface
10
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water, and groundwater samples for laboratory analysis. in
February 1984, EPA-Region IV used ground penetrating radar (GPR) to
further define the site boundaries.
In March 1984, an immediate Removal Action at the Potter's Pits
site (Area 1) was requested by the EPA Office of Emergency and
Remedial Response. On March 21, 1984, a Superfund removal was
begun centering around Area 1. A total of 1,770 tons of oily
sludge and contaminated soils were excavated and transported to a
hazardous waste landfill in Pinewood, South Carolina. Soil removal
activities were completed on April 2, 1984 (Figure 6) . An
emergency removal is conducted anytime at a site when there is an
imminent threat to human health or the environment from a
contaminant.
In May 1984, EPA-Region IV proposed a groundwater monitoring plan
to determine if the Potter's Pits site (Area 1) presented a threat
to surrounding groundwater sources. Contamination of the shallow
aquifer had been documented at the site during the September 1983
FIT investigation in groundwater samples taken from both a
residential and a monitoring well on site. However, in order to
characterize the nature and extent of the groundwater contamination
in this area, additional wells were proposed. Nine monitoring
wells were subsequently installed and sampled by EPA (Figure 6).
The locations of these wells were based on the assumption that the
groundwater flow was in a northeasterly direction. The samples
were analyzed for volatile organic compounds. Relatively high
concentrations of benzene, ethylbenzene, toluene, and xylenes
(BETX) were detected in some of the groundwater samples.
The wells were resampled in 1988 by the State of North Carolina.
These samples were analyzed for volatile organics, phenols,
priority pollutant metals, and several nutrients. BETX and phenols
were the predominant contaminants detected. In addition, the 1988
data indicated the possibility of low level benzene, ethylbenzene,
and xylenes in a "deep" well which would indicate that the "deep"
aquifer had now been affected.
3.2 Remedial Investigation
Based on the site investigation, the site was placed on the
National Priorities List (NPL); therefore a Remedial Investigation
and Feasibility Study (RI/FS) was warranted. The primary
objectives of a RI/FS are to assess the nature and distribution of
contaminants at the site and to characterize the site hydrology and
geology. The types of analyses included in the RI were selected to
characterize these factors to the extent required to evaluate
potential risks, if any, to human health and the environment, and
to evaluate alternatives for site remediation. Toward 'this end,
the RI analyzed for potential sources of contamination in the
following media:
11
-------
Figure 6
EPA 04
EPA 03
O
EPA 02
O
EPA 05
O
K>
POTTER'S PITS SITE
MACO, NC
PA 09
EXCAVATED
AREAS
O - SHALLOW VCLL
f~| - DEEP WELL
- DEEP AQUIFER FLOW
- SHALLOW AQUIFER FLOV
og
S^o
00
NOT TO SCALE
•OUROfc POTTER* W WM1C Mil CUUUMJP
MAOO. NORTH CAHOLMA
TOO «M« •«•»•!§
MANCN1I
AREAS EXCAVATED OURMQ
MARCH ftM
ECJORDANOQ
U.S. ENVIRONMENTAL
PROTECTION AGENCY
i
-------
* Soils
* Air
* Groundwater
* Surface water/stream sediment
Since the site was placed on the NPL, the site was eligible to be
cleaned up under Superfund. There were no willing Potential
Responsible Parties (PRP) involved at this time; therefore, the
site became a fund-lead project which means the EPA hired
contractors to perform the RI/FS. Ebasco Services began the
initial phase of the Remedial investigation which occurred from
January 1990 through April 1990 with a final report on September
1990. The principal results and findings of the Remedial
Investigation are discussed in further detail in Section 6.0 -
Summary of Site Characteristics, of this document.
3.3 Remedial Investigation Addendum Report
After the initial remedial investigation was completed, it was
determined that a phase II or Remedial Investigation Addendum was
necessary due to lack of complete information. Therefore, in April
of 1991, EPA conducted the supplemental field investigation to
address the data gaps and irregularities identified in the initial
RI. The media sampled during this phase included additional
shallow and deep groundwater samples, a few surface and subsurface
soil samples, and two surface water and sediment samples. A report
was generated in July of 1991 which described the field effort.
The Remedial Investigation Addendum Report was compiled using the
field data collected by EPA by ROY F. WESTON. WESTON was retained
by EPA to do the Remedial Investigation Addendum Report and the
Feasibility Study Report for this Site. The principal results and
findings of the RI Addendum Report are discussed in detail in
Section 6.0 - Summary of Site Characteristics, of this document.
13
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4.0 HIGHLIGHTS OP COMMUNITY PARTICIPATION
In accordance with public participation requirements of CERCLA
Sections 113 (k) (2) (B) (i-v) and 117, a comprehensive community
relations program was developed and implemented throughout the
remedial process at the Potter's Pits'site.
In March of 1984, before the beginning of the immediate removal
action done by EPA, EPA and North Carolina State officials held an
availability session to answer any questions the public may have
toward the impending removal. This availability session was
announced in the Wilmington Star News.
Community interviews were conducted in January of 1990 to find out
what the concerns' of the community were and to explain the Remedial
Investigation process to the citizens.
In January of 1990, a Remedial Investigation/Feasibility Study
(RI/FS) Kick-Off Fact Sheet was prepared and delivered to
interested citizens and local officials included on the site's
mailing list. This fact sheet explained the overall process of
Superfund, the upcoming RI/FS at the Potter's Pits site, and
opportunities for community involvement. A RI/FS Kick-Off meeting
was held on February 28, 1990 with the community at Sandy Creek to
present, the objectives of the investigation, describe the
activities that were to take place as part of the investigation,
and to answer any questions the public had regarding the upcoming
investigation.
Following the completion of the RI in March of 1991, a RI/FS
Findings Fact Sheet was prepared and released to the public in
March of 1991. A public meeting was held to formally present the
findings of .the RI on March 28, 1991. Findings of the Baseline
Risk Assessment were discussed as well as the future direction of
the site.
The finalized RI/FS Reports and Proposed Plan for the Potter's Pits
site were released to the public in April of 1992. These documents
were made available for public review at the EPA Region IV Records
Center, and the Columbus County Library (East Branch). The notice
of the availability of these documents and notification of the
Proposed Plan Public Meeting was announced in the Wilmington Star
News on April 30, 1992. The Proposed Plan Public Meeting was held
on May 12, 1992 at the Hood Creek Community Center. At this
meeting, representatives from EPA and NCDEHNR presented EPA's
preferred alternative for cleanup of the site and answered any
questions the public had regarding the preferred alternative, other
alternatives considered in the FS, or any other concerns the public
had related to the cleanup of this site.
Various press releases were issued throughout the different stages
of this project. These press releases announced meetings and
announced the preferred alternative for cleanup at the site.
The mandatory 30-day public comment period was held from April 30 -
14
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May 30, 1992 ^
Creek, North CaroU^1 *£?« for the Potters Pi?^nt ******£
15
-------
5.0 SUMMARY OF SITE CHARACTERISTICS
This Section of the Record of Decision summarizes the results of
the site field investigations which were conducted as part of the
Remedial Investigation and the Remedial Investigation Addendum
Report. The sampling plan for the Potter's Pits site was based on
initial investigations conducted by North Carolina State, the soil
gas survey performed by EPA, topographic drainage characteristics,
and results of previous regulatory site investigations. The types
of samples collected were surface and subsurface soils,
groundwater, stream sediment, air, surface water from Chinnis
Branch, and private residential well samples around the site.
Areas identified as potential constituent sources include Areas I,
2, and 3 as identified on Figure 1.
5.1 Study Area 2
Study area 2 was identified as a potential area of concern during
the development of the Potter's Pits Work Plan based on the
available historical records. A letter from the North Carolina
Department of Natural and Economic Resources (NCDNER). (May 19,
1976) to Mr. Ward Skipper documented that the waste oil disposal
pit located on his property north of U.S. Highway 74/76 was in
violation of North Carolina General Statute 143-215.83. Mr.
Lawrence McCandless (USCG) and Mr. Rick Schiver (regional
hydrologist for the NCDNER) had inspected the disposal pit and
described it as being approximately 60 feet long and 20 feet wide.
It was estimated that the pit contained in excess of 2,000 to 3,000
gallons of black oil. Mr. Skipper conducted the cleanup after
receiving the May 19,1976 letter in which he was advised that
clean-up actions should be immediately initiated. The only
reference to.the~pit location in the historical records was that it
was approximately 0.4 miles from the pit which caused the spill on
August 5, 1976 (Area 1).
Due to the uncertainty of the exact location of this disposal pit,
investigative activities conducted during the RI were'~structured as
follows: additional record searches, further analysis of
historical aerial photographs, interviews with local, state, and
federal officials who observed the disposal pits during the May
1976 Area 2 cleanup;.and a site reconnaissance of the general area
north of U.S.. Highway^7-4/76 by RI field team members. After all of
this investigative wprlc was done, Area 2 was still not located. It
was determined at that time that no further investigative
activities would be done regarding Area 2.
5.2 Soil Gas Survey
A soil gas survey was conducted at the site from January 15 to 19,
1990. A total of 104 soil gas samples were collected and analysed
from Area 1 (85 samples) and Area 3 (19 samples) . Soil gas
sampling locations and general overall results are presented in
Figure 7. The highest concentration of volatile organic compounds
(VOCs) were detected just north of the Gurkin residence in Area 1
16
-------
Figure 7
O
//7£'.r \~v\\ •iffiB"
•// /Sr,.A ?. \ \ \ *"" »«o«i*ywj
Sli'lOl / /I*™'?(») \ \ \ "»' eoNCiinittno^,
/(MO? . •/ I
/ , / / Sfi W .
^fe ' i',"; ^
101*1 MtASUttO VOC. CONC1MIHAI
SOt. GAS SUHVEV
-------
and a small area south of Joe Baldwin Drive in.the empty field. No
occurrences of detectable levels of VOCs were measured in soil gas
samples collected from Area 3 east of Chinnis Branch.
The soil gas survey was used to detect VOCs in soils and
groundwater and to reduce the number of soil borings and monitoring
wells needed to characterize the extent of volatile contamination.
Soil gas samples were collected around the perimeter of Area 1 to
verify the actual study area boundaries.
5.3 Subsurface Soils
5.3.1 Remedial Investigation
The subsurface soil samples were taken between January
30 and February 20, 1990.. A total of 80 soil borings were
completed in Area 1 (78 borings) and Area 3 (2 borings) .
Boring locations are shown on Figure 8. A total of 254 soil
samples were collected from the 80 borings at 5-foot
intervals. Results of the GC analysis are presented in the RI.
The location and general overall results of the CLP soil data
is presented in Figures 9-14.
The results of the CLP data revealed two extensive areas of
contamination. Both areas are within the general vicinity of
the former waste oil pits. Elevated levels of VOCs (primarily
BTEX), SVOCs (primarily naphthalene), and metals were
detected in both areas. Pesticides were detected in four soil
samples (SS-10, SS-28, and SS-69). No PCBs were detected in
any of the subsurface soil samples.
5.3.2 Remedial Investigation Addendum
During the Phase II investigation, six samples were taken
during the installation of additional monitoring wells; the
other three were taken from soil borings (Figure 15) .
The contaminants that were detected were the same as was
detected in the-initial RI. Summary data of the soil samples
are presented in the RI Addendum.
5.4 Surface Soils*;".
5.4.1 Remedial Investigation
Twenty-three surface soil samples (0 to 6 inches) were
collected from within study areas 1 and 3, between March 14 -
16, 1990 (Figure 16). The results of this analysis indicated
very low levels of 1,1,1-trichloroethane, toluene, carbon
disulfide, and styrene. Elevated levels of HCB, anthracene,
and 4-chloro-3-methylphenol were detected in a limited number
of samples. Four pesticides were detected in three surface
soil samples.
18
-------
oS
a»
So
Figure 8
-------
Figure 9
ECJORDANCQ
U.S. ENVIRONMENTAL
PROTECTION AGENCY
-------
Figure 10
~
DO
OOMCBmUIKM MOP1
TODU. WOC« M 80t, S-M fOOT
OP RESULTS
U.S. ENVIRONMENTAL
PROTECTION AGENCY
-------
Figure 11
TOTAL VOC« IN SOt, tt-1f FOOT MTBMU.
ECJORDANCQ
U.S. ENVIRONMENTAL
PROTECTION AGENCY
MOOTMCAftOUNA
KMBT
-------
Tlgure 12
•AMDVCUCfX.
NONINCAimJN
U.S. EMVIRONMEMTAL
PROTECTION AGENCY
-------
Figure 13
O /
M SOL, s-io TOOT
OPRE8UUV
ECJORDANOQ
•AMDVCMUK.
NOftlNCAMUNA
U.S. ENVIRONMENTAL
PROTECTION AGENCV
-------
Figure 14
U.S.EMV«ONilEIITAL
PROTECTION AGENCY
-------
Figure 15
to
LEGEND
SHALLOW MONI1OR WELL
0 DCfP UONHOR WELL
MW-205 WILL IDENWCATION
SOIL BORING
(A|.|
0 50 100
200
APPROX SCALE IN ffCI
PHASE II SAMPLE LOCATIONS
REMEDIAL INVESTIGATION ADDENDUM
(OR THE POTTERS
SEPTIC IANK SERVICE PITS SITE
SANUV CHECK. NORTH CAROLINA
-------
Figure 16
-------
Barium, chromium, lead, and vanadium were detected in almost
all surface soil samples. Elevated levels of select heavy
metals and micronutrient metals were detected in surface soil
samples SL-16 and SL-72. These samples also contained elevated
levels of the detected pesticides.
5.4.2 Remedial Investigation Addendum
No surface soil samples were taken during the RI Addendum.
5.5 Surface Water and Stream Sediments
5.5.1 Remedial Investigation
Five surface water and sediment sampling stations were
established on Chinnis Branch at the locations depicted in
Figure 17. Surface water samples were collected at each of
the five stations on March 13, 1990, while sediment samples
were collected on March 19, 1990. Both sets of samples were
sent to the CLP laboratory for analysis of TCL parameters.
No VOCs, pesticides, or FCBs were detected in any of the
surface water samples. Besides the major cations, no metals
were -detected except for the sample collected at station
SDSW-1, the anticipated background station. This sample had
significant levels of silver (5,000 ug/1), cadmium (7,900
ug/1), copper (850 ug/1), and lead (700 ug/1), yet very low
concentrations of the base metals. This appears to be a
reversal of metal dominance when compared to samples obtained
from the other four stations.
No detectable levels of VOCs, SVOCs, pesticides, or PCBs
were observed in any of the five sediment samples. Eight of
the 23 TCL metals were detected in at least one sediment
sample. The common constituents of the alumino-silicate
minerals were present in all five samples. Zinc was present
in all samples except for the sediment sample collected at
Station SDSW-1. In addition to the aforementioned metals,
chromium was detected in sample SD3 (2.6 mg/kg) , lead was
detected in samples SD2 (1.2 mg/kg), and SD4 (1.1J mg/kg),
and vanadium was detected in sample SD4 (2 mg/kg).
In comparing metals data for sediment versus surface water
samples at station SDSW-1, there appears to be little
correlation between the elevated levels of heavy metals in
surface water and the levels, in the sediment. Sediment data
at station SDSW-1 are more comparable to data obtained from
the other four sampling stations. As such, the surface
water metals data from SW-1 is suspect and was not used in
any component of. the risk analysis.
28
-------
Figure 17
to
TO
08
-------
5.5.2 Remedial Investigation Addendum
To confirm the background concentrations of metals and other
constituents, a surface water sample (SW-1) and sediment
sample (SD-1) were collected from Chinnis Branch (Figure 18)
These samples were analyzed for volatile and extractable
organic compounds, pesticides, PCBs, unfiltered metals, and
cyanide. This location was resampled because of the unusual
detection of metals -in the original RI.
VOCs, SVOCs, pesticides, PCBs, and cyanide were not detected:
Copper was the only metal found above the State Freshwater
Standards. This is an upstream sample and is not considered
to be site related.
5.6 Groundwater
5.6.1 Residential Wells
A total of 59 residential wells were sampled and analyzed for
TCL parameters (VOCs, SVOCs, pesticides/PCBs, and metals) . No
SVOCs, pesticides, or PCBs were found above detection levels
in any of the residential wells. VOCs were detected in only
one well (RW-4) located at the entrance of the Town of Sandy
Creek and upgradient of the site. The RW-4 VOC result appears
to be anomalous as there were no VOCs detected and quantified,
but presumptive evidence of low concentrations of almost all
VOCs was reported. RW-4 was subsequently resampled and found
to have no VOCs detected.
Low concentrations of selected metals were detected in all
residential wells. Summary statistics for metals in drinking
water wells are presented in the RI Report. The absence of
the other contaminant classes (e.g., VOCs, SVOCs, and
pesticides/PCBs), and the widespread distribution of many of
these metals, indicate that the metal concentrations detected
represent background concentrations for the local drinking
water aquifer system.
5.6.2 Groundwater Flow
Three local aquifer systems have been identified in the site
vicinity: the surficial aquifer, the Tertiary limestone
aquifer, and the Cretaceous aquifer. The limestone aquifer is
locally semi-confined but may be in hydraulic connection with
the surficial aquifer. The deeper regional aquifer is the
Cretaceous aquifer. This aquifer appears to be confined in
its extent and hydraulically separate from both the surficial
and the limestone aquifer systems. In the site vicinity, the
Cretaceous aquifer is brackish and unusable as a source of
drinking water.
Water level measurements were taken from the monitoring
30
-------
wells during the course of the field work at the site. This
water level data was used to determine the water table
configuration at the site. Groundwater is approximately 10
feet below the land surface at the western edge of the site
and reaches the surface at the wetlands along the eastern edge
of the site. The wetland area and the creek are the
discharge area for the shallow aquifer.
Groundwater flow within the surficial aquifer is toward the
east-southeast to Chinnis Branch and the adjacent wetland
area in the vicinity of the site. As indicated by the
equipotential lines on Figure 18, the hydaulic gradient
steepens near Chinnis Branch in response to topographical
features. Figure 19 shows groundwater elevations for the
deeper aquifer.
Hydraulic conductivity tests were performed on the
monitoring wells and used to estimate groundwater velocity at
the site. Hydraulic conductivity values ranged from 8.62E-05
to 1.51E-03 feet/sec across the site. The values for wells
screened within the deep zone range from 6.61E-04 to-1.34E-03.
The horizontal gradient across the site to Chinnis Branch is
approximately 0.03 feet per second. The horizontal hydraulic
gradient from a presumed eastern edge of the source area
(EPA-05) to Chinnis Branch (MW-206) is approximately 0.06
feet per second.
Groundwater velocities were calculated using the following
equation:
Vs = Ki/n
Vs"= Groundwater Velocity
K = Hydraulic Conductivity
i = Hydraulic Gradient
n = Effective Porosity
The mean hydraulic conductivity for all wells was used in
this calculation. The effective porosity is estimated to
range from 0.1-8 for silty sands to 0.27 for well sorted
coarse grained sands. An average value of .23 was selected
for the calculations. The calculated values of groundwater
velocity for the site range from 5.2 to 10.4 feet/day.
These estimated velocities appear relatively high, given the
comparatively limited distribution of contamination observed
at the site. Although flow velocities are an important
component, contaminant transport will also be controlled by
numerous other chemical specific and environmental
interactions and variables.
5.6.3 Groundwater Quality
Twenty one monitoring wells have been installed at the site
31
-------
OJ I
to
o
?.
Figure 18
LEGEND
IB SHALLOW MONITOR WELL
8 OEfP MONITOR WLLL
MW-20S WELL IDENTIFICATION
3 GROUND WATER ELEVATIONS .(IN FEET
_ .jo--' CROUND WATER CONTOUR
APPROX. SCALE IN FEET
0 100
50
150
IDENTIFIED AS EPA-ff ARE MONITOR WELLS. INSTALLED IN (984
IDENTIFIED AS MW-f/| ARE MONITOR WELLS. INSTALLED IN 1990 AND
1991
FIGURE
ME 12/16/91
SCAIE
Is*.
GROUND WATER ELEVATIONS
FOR
SHALLOW WELLS
MEASURED 3 APRIL 1990
REMEDIAL INVESTIGATION ADDENDUM
FOR THE POTTERS
SEPTIC TANK SERVICE PITS SITE
SANDY CREEK. NORTH CAROLINA
O«A«N e» J.C.. W.M_
-------
Figure 19
OJ
LEGEND
9 SHALLOW MONITOR WELL
8 DEEP UONIIOR WELL
MW-205 WELL IDENTIFICATION
•
3 GROUND WATER ELEVATIONS (IN FEET MSI)
-50-
GROUNO WATER CONTOUR (IN FT-MSL)
C)
") C'
APPROX. SCALE IN FEET
0 100
50
150
&
r<
AS CPA-ff ARE MONITOR WELLS. INSTALLED IN I9S4 '
AS MW-III ARE MONIIOH WCLLS. INSTALLED IN I9»O AND 1991
*>
FIGURE
OAU !2/>6/»L
sou
I" = 1501
tav.
_!_
GROUND WATER ELEVATIONS
FOR
DEEP WCLLS
MEASURED 3 APRIL 1990
REMEDIAL INVESTIGATION ADDENDUM
fOR THE POTTERS
SEPTIC TANK SERVICE PITS SITE
SANDY CREEK. NORTH CAROLINA
•»• J.C.. W.M.
-------
(Figure 20) . six of the 21 wells were installed at upgradient
or background locations: MW-101, MW-105, MW-201, MW-205,
EPA-07, and EPA-08. The analytical results fom these wells
and from the residential wells, will be used as a reference
for comparison to downgradient results.
Nine wells (EPA-01 through EPA-09) were installed and sampled
by EPA Region IV in 1984 (Figure 6). The groundwater samples
were analyzed for VOCs. Eight of the nine wells were samplad
again in 1988 as part of a periodic monitoring .program
performed by the State of North Carolina. These samples were
analyzed for VOCs, selected metals, phenol, and selected
nutrients. Monitoring well EPA-06 was damaged after the 1984
sampling event and can no longer be sampled.
In February and March 1990, 12 additional wells of varying
depths were installed as part of the initial RI. These wells
included seven shallow wells, whose depths were less than 20
feet (MW-201 through MW-207) and five deep wells, whose depths
ranged from 20 to 42 feet (MW-101 through MW-106, excluding
MW-103).
In April of 1991, additional wells were installed as part of
the Remedial Investigation Addendum. The following is a list
of_ those wells: one shallow temporary well (TW-01) , two
shallow permanent wells (MW-110 and MW-111), one temporary
deep well (TW-02), and two permanent deep wells (MW-210 and
MW-211).
Monitoring wells were sampled in 1984, 1988, 1990 as part of
the. RI, and in 1991 as part of the RI Addendum. Benzene,
Toluene, Ethylbenzene, Xylenes, Naphthalene, Chromium, and
lead were detected above MCLs or health-based clean-up
standards. The contaminants with their respective
concentration ranges that were detected at the site are listed
in Table 1. Figure 21 shows the- approximate location of the
ethylbenzene plume in the shallow aquifer. The other
contaminants are similar in location to the ethylbenzene plume
(See RI Addendum).
Groundwater samples from all wells on site were also analyzed
for total suspended solids, total ammonia, nitrite, and
nitrate. All groundwater samples were well below the
drinking water standard of 10 mg/1 nitrate.
5.8 Air Monitoring
A total of five residential air samples were collected from within
the crawl spaces and interiors of the Gurkin and Grainger homes on
February 28, 1990. Sampling was conducted at these two residences
since they are situated on or near the former waste disposal pits
and the human exposure to VOCs is a potential risk. Methylene
chloride was detected inside the Grainger residence at a
concentration of 11 ppbv. Low levels of chloromethane (16 ppbv)
34
-------
Figure 20
UJ
Ul
LEGEND
ft SHALLOW MONIIOR WCLL
8 0«P UOMIOR WILL
MW-205 WCll IOENIIFCAIION
MW-105
(APPKUXlMAItlY 600')
I
M
APPRO*. SCAlC IN ft£l
0 1OO
50
1 50
r
WCLL lUtNllfltO AS PW-I IS A RISIOCNIIAL WILL. INSIALLtO IN 1991
WILIS IDtNlintO AS tPA-H ARC MONIIOR WCLLS. INSTAUCO IN I9B4
WILLS lOCNIiriCO AS UW-lff ARC WONIIOR WtUS. IHSIAILCO IN 1990 AND 1991
WILLS IDtNlirilD AS 1W-f J ARC 1CMPORAMV WCLIS. INSIALLCD IN 19.91
MIC
y.Mt r»i5Q-
WV.
LOCATION OF SHALLOW AND OttP
MONirOH WELLS AI HIE SHE
~BEMEOIAL INVESIIGAIION ADDENDUM
roii IMC poncRs
SCP1IC IANK SCRVICC PUS SHE
SANOr CREEK. NORIH CAROLINA
'ttfuum «• ~J.C... WM
-------
TABLE 1
=
1.
2.
3.
4.
5.
6.
7 .
GROONDWATER CONTAMINANT CONCENTRATION RANGES
CONTAMINANT
Benzene
Toluene
Ethylbenzene
Xylenes
Naphthalene
Chromium
Lead
CONCENTRATION
RANGE
90 - 3150 ppb
29000 ppb
22 - 2400 ppb
98 - 26000 ppb
42 - 125 ppb
19 - 2500 ppb
6-25 ppb
36
-------
Figure 21
u>
LKCKND
9 SHALLOW MDNIIOH Hill
0 DEEP MONIIOR WELL
MW-205 (Mil IDENIIflCAIION
O
3 rilia BTN2CNE CONCENIRA1IONS (IN UC/L)
c ISOPLEIH (IN UC/l)
AWKOX SCAIE IN FEE I
0 IOO
5O
BCNZCNE CONCENTRATIONS
IN GliOUND WATER FOR
SHALLOW WCLLS
SAMPLED N
-------
and 1,1,1-trichloroethane (1.5 ppbv) were detected in the crawl
space beneath the Grainger residence. No VOCs'were detected within
or beneath the Gurkin residence.
5.9 Nature and Extent of Contamination
The following discussion is a summary of the nature and extent of
contamination and affected media at the Potter's Pits site.
The Constituents of Concern (COC) list (44 organics and
metals) for the site was developed for purposes of the
Baseline Risk Assessment discussed in Section 6.0 - Summary of
Site Risks - and are to be addressed through • the selected
remedy in this ROD. This list includes those constituents
that are related to the past waste disposal activities, as
indicated by the • composition of the waste (petroleum
products), or have been detected repeatedly throughout the
site. The COC is listed in Table 2.
The extent of contamination at the Potter's Pits site is
limited to the immediate vicinity of the two former waste
disposal areas (i.e., Area 1: north and south of Joe Baldwin
Drive) and the areas immediately downgradient of each and
toward Chinnis Branch. Laboratory data indicate that the
former waste disposal areas have impacted groundwater and
soils. Petroleum constituents and selected heavy metals were
prevalent throughout both areas.
Area 3 is not an area of concern
- No residential well is being impacted by contamination from
the_ Potter's Pits site except the Gurkin's well which is on
the site in the former disposal area. They have been taken
off this well and connected to the Grainger's well across the
street and upgradient from the site.
- The extent of groundwater contamination has primarily been
confined to the shallow aquifer and is restricted to the area
encompassing the former disposal pits. Groundwater data
indicates that .the levels of contaminants, principally
organics, currently exceed the established Maximum Contaminant
Levels (MCL).
During the Remedial Investigation Addendum it was
determined that the deep aquifer may also be impacted.
Further testing will be . done to identify whether the
contamination, if any, has migrated to the deeper aquifer.
The RI Addendum data confirms the original RI data to the
extent that pesticides, PCB's, and cyanides do not appear to
be contaminants of concern at the site.
Variability in metals concentrations in both the shallow
38
-------
and deep aquifer background w.ells prohibits the development of
a confident estimate of background levels of metals in these
aquifers; therefore, additional groundwater sampling of these
wells will be performed during the Remedial Design.
Both surface water and sediment in Chinnis Branch exhibit
concentrations of naturally occurring metals which cannot be
attributed directly to site source contamination. The
upstream surface water sample represented a highly unusual
water quality which was resampled during the RI Addendum
phase.
- Based upon the lack of pump test information, additional
tests to further define the aquifer characteristics will be
considered as part of the Remedial Design.
39
-------
g.O SUMMARY OF SITE RISKS
A Baseline Risk Assessment was conducted as part of the Remedial
Investigation to assess the potential effect on public health and
'welfare from the Potter's Pits waste constituents of concern that
were identified during the RI. The Baseline Risk Assessment can be
found in its entirety in Section 7.0 of the Final Remedial
investigation Report. This section of the Record of Decision
presents a summary of site risks and consists of the following
sections: contaminant- identification, exposure assessment
toxicity assessment, risk characterization, and environmental
(ecological) assessment.
6.1 Contaminant Identification
Data collected during the RI were reviewed and evaluated to
determine the contaminants in each media (groundwater, surface and
subsurface soil, and surface water and sediment in Chinnis Branch)
at the site which are most likely to pose risks to public health.
In the Baseline Risk Assessment, the site was divided into three
areas (Figure 22): Area 1A, Area IB, and Forest/Wetland.
Once these contaminants of concern were identified (Table 2),
exposure concentrations in each media were estimated by calculating
the 95% upper confidence level (UCL) of the arithmetic average of
all samples. If this 95% UCL was greater than the maximum detected
concentration, then the maximum detected concentration was used for
the exposure concentration. Appendix I contains tables (1-11)
which identify the contaminants of concern, arithmetic mean,
standard deviation, 95% UCL, minimum and maximum detected, and
frequency of detection for all r.edia sampled and analyzed in the
Risk Assessment.
6.2 Exposure Assessment
•The exposure assessment identified potential pathways and routes
for contaminants of concern. Two overall exposure conditions were
evaluated. The first was the current land use condition, which
considers the site.as it currently exists. The second was the
future land use condition, which, evaluates potential risks that may
be associated with any probable change in site use assuming no
remedial action occurs.
Presently, none of the contaminated groundwater is being used, but
EPA and the State of North Carolina have classified this aquifer as
a Class II B aquifer. A resource which should be maintained at
drinking water quality.
The exposure pathways that were evaluated under current land use
conditions were:
* Ingestion and dermal contact of chemicals in on-site and
off-site surface water and sediment in Chinnis Branch by a
40
-------
tiCtMO
si io« MXVACC
VMM HK.MMMOUICAnON
AREAS USU> KM PUBLIC KAUM
rannnscpnc v
rmtnt
SAMNCMEN.
MOKTN CAMOtMA
ECJORDANCO
Figure 22
-------
All
•ottar't taptlc Tarit Wa Ifta
Sandy Craat, Berth Carolina
Groirt-
Surfac*
Volatile or»wile»
2
aanzana
Chlorotoarutr*
CMoreavthana
Ethyl baniara
Nathylcna dilorldi 2
Toluana
Total xylanaa
1 , 1 , 1 •Triehlorocthana
* ' x x x
X
X
XX X
X
XX X
XX X
X
4.4' -000
4,4'-OOT 2
Oolta IMC 2
OUldrln 2
tndrin kctom
Mthoxyetiler
Anthrs
Mnzo(«)antlir
Mnzo(b and/or k)f luormthom
MnzeCghi )p»ryl«n*
Oibvuotaran
2,4-Of«thylp
PluorantlMn*
x
X
X
X
X
•OTItl
on troundMtar dlMharf* to ChlraiU iratch
2 Carel
42
-------
icont. I
•ottar'a S«ptfe Tank Wt« tit*
CrM*, "ortti Carolina
Mtala
Mrlcai
Mryltli»
OiroBlui
Caspar
Had
Nanoanaaa
Harcury
Nlckal
Vanadim
Zinc
6rou«J- Sut
X
X
X
X
X
X
X
rfaea Subaurfae* Indoor Surfac*1
X
X X
X X
X X
X *
X «
X * «
HOTtS:
on grouidMtar
to OiinnU Irmeii.
POOR
43
-------
young adolescent (ages 6 - 15),
* ingestion of fish from Chinnis Branch,
* Ingestion and dermal contact of chemicals in surface and
subsurface soils (two scenarios were addressed: adult and
worker),
* Ingestion of produce grown on-site,
* Inhalation of chemicals in and beneath existing residences
(Gurkins and Graingers).
The exposure pathways that were evaluated under future land use
conditions were:
* Ingestion and dermal contact with contaminated groundwater,
* Inhalation of VOCs during showering (adult),
* Ingestion of produce irrigated with contaminated
groundwater,
* Ingestion of chemicals in on-site and off-site surface water
and sediment in Chinnis Branch by a young adolescent (ages
6 - 15),
* Ingestion of fish from Chinnis Branch,
* Ingestion and dermal contact with chemicals in surface and
subsurface soils (two scenarios: .adult and worker),
* Ingestion of produce grown on-site.
Appendix II contains tables (1-6) which indicate what exposure and
intake assumptions were used in the Risk Assessment in all of these
scenarios. Groundwater and subsurface soils were not evaluated in
the forest/wetland area because this area, due to its proximity to
the Chinnis Branch floodplain, showed little potential for
development as a residential area. Exposure to contaminants in
this area would only occur if wells were drilled or if excavation
into subsurface soils was required.
6.3 Toxicitv Assessment
Under current EPA guidelines, the likelihood of adverse effects to
occur in humans from carcinogens and noncarcinogens are considered
separately. These are discussed below.
6.3.1 Carcinogens
•EPA .uses a weight-of-evidence system to classify a chemical's
potential to cause cancer in humans. All evaluated chemicals
fall into one of the following categories: Class A- Known
44
-------
Human Carcinogen; Class B- Probable Human Carcinogen- 31 means
there is limited human epidemiological evidence, and B2 means
there is sufficient evidence in animals and inadequate or no
evidence in humans; Class C- Possible Human Carcinogen; Class
D- Mot classifiable as the Human Carcinogenicity; and Class E-
Evidence of noncarcinogenicity for Humans.
Cancer Slope Factors (CSFs), indicative of carcinogenic
potency, are developed by EPA's Carcinogenic Assessment Group
to estimate excess lifetime cancer risks associated with
exposure to potentially carcinogenic chemicals. CSFs are
derived from the results of human epidemiological studies or
chronic animal bioassays to which animal-to-human
extrapolation and uncertainty factors have been applied. CSFs,
which are expressed in units of (mg/kg-day)-1, are multiplied
by the estimated intake of a potential carcinogen to provide
an upper-bound estimate of the excess lifetime cancer risk
associated with exposure at that intake level. The term
"upper-bound" refers to the conservative estimate of the risks
calculated from the CSF. This approach makes underestimation
of the actual cancer risk highly unlikely.
6.3.2 Noncarcinogens
Reference Doses (RFDs) have been developed by EPA for
indicating the potential for adverse health effects other than
cancer (systemic). RFDs, which are expressed in units of
mg/kg-day, are estimates of chronic daily exposure for humans,
including sensitive individuals, that are thought to be free
of any adverse effects. RFDs are derived from human
epidemiological data or excracolated from 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. Estimated intake of chemicals from
environmental media (i.e., the amount of chemicals ingested
from contaminated drinking water) can be compared to the RFD
for each of the contaminants.
Table 3 lists chemicals contributing most significantly to
carcinogenic and noncarcinogenic risk at the Potter's Pits site.
Appendix H of the RI lists all the Reference Doses and the Cancer
Slope Factors for the contaminants of concern. Table 4 and 5 lists
the exposure media, route of exposure, and the associated risk for
the carcinogenic and noncarcinogenic contaminants.
6.4 Risk Characterization Summary
To quantitatively assess the risks from the Potter's Pits site, the
chronic daily intakes (CDI) were combined with the health effects
criteria.
45
-------
Table 3
CHEMICALS CONTRIBUTING MOST SIGNIFICANTLY TO NON CARCINOGENIC
RISK
Exposure Media
Groundwater
Surface Water
Sediment
Surface Soil
Subsurface Soil
Air
Are* 1A
Benzene
-
—
Lead
—
-
Arai IB
Lead, Benzene
_
_
Lead, Zinc
_
—
Forest/Wetland
—
—
—
cPAHs
-
-
CHEMICALS CONTRIBUTING MOST SIGNIFICANTLY TO CARCINOGENIC RISK
Exposure Media
Groundwater
. Surface Water
Sediment
Surface Sou1
Subsurface Soil
Air
ArealA
Benzene
_
_
Benzene, cPAHs
cPAHs
Metbyiene chloride,
^f|lA*^?in^t^lfl^
Area IB
Benzene
—
_
Benzene, CMordane1,
Dieldrin1
Benzene2
—
Forest/Wetland
_
Benzene
_
. cPAHs
—
-
Note: cPAHS indicates cardnogeoic PAHs.
L Not part of cleanup scenario.
2: Risk below LOE-06.
8:'.P2\POT7HBS\FS-SeC1.CWS
46
-------
Table 4
CARCINOGENIC RISK BY LOCATION AND EXPOSURE ROUTE
Exposure .
Media
Groundwater
Surface
Water
Sediment
Surface Sofl
Subsurface
Cf.fl
Air
Route of Exposure
Ingestion
Inhalation during showering
Dermal contact during showering
Dermal contact while washing
Ingestion of produce irrigated with
groundwater
Total
Ingestion
Dermal contact
Fish ingestion
Total
Ingestion
Dermal contact
Ingestion
Dermal cogtgg? •
IngpjiiuD of produce
Total
loflcsdofl
Dermal contact
Total
Inhalation
Area 1A
Residential
1.1 x 10°
7.3 x 1(T*
1 J x NT5
1.9 x 10'5
4.6 x NT*
132 x 1
-------
Table 5
NON-CARCINOGENIC RISK BY LOCATION AND EXPOSURE ROUTE
Exposure
Media
Groundwater
Surface
Water
Sediment
Surface Soil
Subsurface
C-J]
Air
Route of Exposure
Ingestioo
Inhalation during showering
Dermal contact during showering
Dermal contact while washing
Ingestion of produce irrigated with
groundwater
Total
Ingestion
Dermal contact
Fish ingestion
Total
Ingestion
Dermal contact
Ingestion
Dermal contact
Ingestion of produce
Total
Ingestion
Dermal contact
Total
Inhalation
Area 1A
920
460
9.5
12
290
L69U
_
_
_
_
-.
53
033
77
82.63
0.013
0.0059
0.0189
0.0033
Area IB
5.4
13
0.032
0.04
1.9
8.67
_
_
..
_
-
L8
0.13
363
3i23
0.0023
0.00024
0.00254
-
Forest/Wetland
_
_
_
-
0.000095
0.0066
0.0084
0.0150
0.0000052
0.00000073
021
0.027
_
0.157
_
_
-
B:\PJ\POTrSW\F5-SK1.CW3
48
-------
For potential carcinogens, excess lifetime upperbound cancer risks
were obtained by multiplying the estimated GDI for each chemical bv
its cancer slope factor. The total upperbound excess lifetime
cancer risk for each pathway was obtained by summing the chemical-
specific risk estimates. A cancer risk level of 1E-6 represents an
upper bound probability of one in one million that an individual
.could develop cancer due to exposure to the potential carcinogen
under the specified exposure conditions.
Potential risks for noncarcinogens are presented as the ratio of
the GDI to the reference dose (hazard quotient) for each chemical.
The sum of the hazard quotients of all chemicals under
consideration is called the hazard index. The hazard index is
useful as a reference point for gauging the potential effects of
environmental exposures to complex mixtures. In general, a hazard
index value greater than 1.0 indicates that the potential exists
for adverse health effects to occur from the assumed exposure
pathways and durations, and that remedial action may be warranted
for the site.
As presented before Tables 4 and 5 summarize the quantitative
estimates of risk under the current and future land use scenario
for each target population respectively.
EPA's targeted risk range for cleanup of Superfund Sites is E-04 to
E-06. Risks less than E-04 are deemed acceptable and those greater
than E-06 are unacceptable to EPA. Risks that fall between E-04 to
E-06 may or may not warrant action, depending on site-specific
factors considered by the risk manager. Noncarcinogenic HI values
greater than 1.0 indicate that remedial action should be taken.
At Potter's Pits site, benzene and carcinogenic PAHs' pose the
carcinogenic risk and lead and zinc pose the noncarcinogenic risk.
Table 6 represents the contaminants of concern with their
associated human health risk level and clean-up standard.
'The.human health risk posed by the ingestion of groundwater was
determined by comparing detected levels of the contaminants with
drinking water standards for these substances. The following
chemicals were detected in samples taken from site groundwater
wells in concentrations that exceed their respective MCLs or health
based .clean-up standards: benzene, toluene, ethylbenzene, xylenes,
naphthalene, lead, and chromium. Any exceedance of the MCL values
by water samples taken within the contamination plume at or
downgradient to the area of attainment represents a cause for
concern.
The local aquifer system consists of a surficial aquifer, a semi-
confined limestone (tertiary) aquifer, and the confined Cretaceous
aquifer. The surficial and the limestone aquifer are the primary
sources of drinking water. Locally the water quality in the
Cretaceous aquifer is brackish and is not useable as a drinking
49
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Table 6
Potential Cleanup Levels For Soils
Chemical
Surface Soil (Area IA)
Benzene
Carcinogenic PAH2
Lead
Surface Soil (Area 1 B)
Benzene
Lead
Zinc
Surface Soil (Wetlands)
Carcinogenic PAH
Subsurface3 Soil (Area 1 A)
Carcinogenic PAH
i
i
Mean Cone.
mg/kg
0.73
5.13
, 722.51
0.096
250
2269.19
0.44
14.71
Carcinogenic
Risk
l.96x 10 5
4.65 x 10^
2.61 x 10*
3.18 xlO*
2.07 x 10*
Non-Carcinogenic
Risk Hazard Index
(HI)1
64.5
22.38
18.61
Potential Cleanup Levels
(mg/kg)
E-06
0.037
0.0 II
0.037
0.138
7.106
E-05
0.37
0.11
0.37
1.38
71.06
E-04
3.7
I.I
3.7
13.8
710.6
HI-I
11.2
11.2
122
en
o
I: Non-carcinogenic metal cleanup level based on attainment of a Hazard Index of I.
2: Carcinogenic Polynuclear Aromatic Hydrocarbons.
3: Depths below 3 feet have been considered subsurface as in the Risk Assessment.
-------
water source. The surficial aquifer has been contaminated and i<=
the aquifer of concern in this ROD. Of all residential wells in
the area, only the residential well (Gurkin's well) on site was
affected by the contaminants. The current residents were taken off
that well and placed on another well across the street (Grainger's
well) . The deeper aquifer is potentially contaminated and will be
monitored and investigated during Remedial Design.
EPA also calculated soil clean-up standards for protection of
groundwater. The method used to calculated these numbers is
outlined in Appendix A of the FS.
6.5 Risk Uncertainty
There is a generally recognized uncertainty in human risk values
developed from experimental data. This is primarily due to the
uncertainty of data extrapolation in the areas of (1) high to low
dose exposure and (2) animal data to human experience. The site-
specific uncertainty is mainly in the degree of accuracy of the
exposure assumptions. Most of the assumptions used in this and any
risk assessment have not been verified. For example, the degree of
chemical absorption from the gut or through the skin or the amount
of soil contact is not known with certainty.
In the .presence of such uncertainty, the Agency and the risk
assessor has the obligation to make conservative assumptions such
that the chance is very small, approaching zero, for the actual
health risk to be greater than that determined through the risk
process. On the other hand, the process is not to yield absurdly
conservative risks values that have no basis in reality. The
balance was kept in mind in the development of exposure assumptions
and pathways and in the interpretation of data and guidance for
this baseline risk assessment.
6.6 Environmental (ecological) Risks
EPA also decided not to use the risk numbers generated in the
Ecological Risk Section. The reasons for this decision are
outlined below:
Clean-up standards based on human health concerns would
probably address ecological concerns with respect to
contaminants such as zinc and PAHs, which have lower clean-up
standards for human health concerns than those calculated for
ecological concerns.
Some of the soil contaminants of concern can be deleted
with respect to ecological concerns, based upon their
infrequent detection and/or low concentrations (e.g.,
beryllium, mercury, selenium, DDT, and ODD). For example,
selenium was detected in only 2 of 11 soil samples in the
forest/wetland north area and was not detected in the other
51
-------
two receptors areas. Although selenium can have toxicological
effects on biota, selenium levels in on-site soils were within
background soil concentrations (i.e., near detection limits).
Vanadium is widespread in surface soils at the site. However,
the concentrations indicated on the FS figures are actually
within or slightly above background levels, except for two
samples in the forest/wet land south area and one in the
forest/wetland north area. Copper was at or above the clean-
up standard at one location in each of the three receptor
areas, and chromium was above the clean-up standard at only
two locations, both in the forest/wetland south area.
Some of the locations at which contaminants were found
above the calculated clean-up standard for ecological
concerns are already targeted for clean-up of other
contaminants based upon human health concerns (e.g. chromium
and copper at SS-72, which contains dieldrin and zinc above
the human health-based clean-up standards). It is probable
that remediation of these locations for human health concerns
(e.g., through excavation and removal of soils) will also
benefit the biota.
The potential benefits of remediation of contaminated
soils based on ecological concerns, particularly in the
wetland areas, must be weighed against the potential damage to
the wetlands that might occur during remediation. The two
forest/wetland areas combined cover 5.28 acres. These areas
constitute a portion of a larger forest/wetland area extending
along Chinnis Branch. Many animal species expected to be
found in the two forest/wetland areas of the site have home
ranges greater than 5 acres. . As indicated in the RI, their
exposure to site soil contaminants would likely be less than
that of species with smaller home ranges. In the absence of
remediation of some contaminants to clean-up standards for
ecological concerns, possible adverse effects to populations
of animal species with smaller home ranges, resulting from
more frequent exposure to site contaminants, might be offset
by recruitment of individuals from the adjoining
forest/wetland areas.
The .uncertainties associated with extrapolation of
toxicological data from one.contaminant to another, and from
one species to another, is significant. Some aspects of the
exposure assumptions used are questionable in the ecological
assessment, and it may be that the portions of the site where
significant contamination has been identified are no longer
suitable habitat for the species used in the ecological risk
assessment. In addition, the approach used in the ecological
assessment represents a new departure in the evaluation of
potential environmental/ecological effects. The approach
emphasized protection of individuals, as opposed to local
populations, ofindigenous species. In the past, EPA has
focused efforts towards the protection of local populations of
indigenous species, except where there is evidence that a
threatened or endangered species is present.
52
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6_.7 Risk Assessment- Summary
Based on all of the above information, clean-up standards were
established for contaminated soils and groundwater. Described
below is how each clean-up standard was established.
It should be noted that as discussed in the RI, the low
concentrations and spotty distribution of the pesticides on-s^te
•made it doubtful whether these chemicals are associated with
dumping at the site, as opposed to spraying for purposes of pest
control; therefore, pesticide contamination has been determined not
to be a concern at this site.
Table 7 lists the soil clean-up standards that will be used at the
Potter's Pits site. All of the clean-up standards are based on the
protection of groundwater except for zinc and carcinogenic PAHs.
These standards for protection of groundwater were more stringent
than the standards developed in the Risk Assessment to protect
human health. In the case of zinc and carcinogenic PAHs, their
clean-up standard is based on dermal contact with the surface soil.
Lead's clean-up standard as stated above is based on the protection
of groundwater. Although the calculated risk based clean-up
standard for lead is lower, EPA guidance (OSWER Directive #9355.4-
02, Sept. 7, 1989) has recommended the use of 500 ppm to 1000 ppm
in residential soils; therefore, it is EPA's belief that the clean-
up standard of 25 ppm for the protection of groundwater will also
be protective of human health.
Table 8 lists the groundwater clean-up standards that will be used
at the Potter's Pits site. All of the clean-up standards are
either MCLs., North Carolina Groundwater Standards, or health-based
levels._
Benzene: For benzene the 5 ppb Federal MCL will be used
instead of the 1 ppb which is the North Carolina Groundwater
Standard. The State water quality standard for benzene
adopted pursuant to G.S. 143-214.1 and 1436-282(2) can be
deviated from "where the maximum allowable concentration of a
substance is less than the limit of detectability" (15 A NCAC
2L.0202(b) (1)7. Presently, 5 ppb is the lowest concentration
current analytical technology can consistently detect with
accuracy. Consequently, EPA and NCDEHNR concur that 5 ppb
should be the groundwater ARAR for benzene at the site.
Toluene: The North Carolina Groundwater Standard of 1,000 ppb
will be used for the clean-up standard which is the most
stringent standard.
Ethylbenzene: The North Carolina Groundwater Standard of 2?
ppb will be used for the clean-up standard which is the most
stringent standard.
Xylenes: The North Carolina Standard of 400 ppb will be used
for the clean-up standard which is the most stringent.
53
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TABLE 7
MEDIUM
SOIL
FINAL SOIL CLEAN-UP STANDARDS
CONTAMINANT
Benzene
Toluene
Ethyl -
benzene
Xylenes
Napthalene
*Carcinoge-
nic PAHs
• Lead
Chromium
*Zinc
CLEAN-UP
STANDARD
.010 ppm
3 . 4 ppm
.235 ppm
3 . 5 ppm
1 . 8 ppm
.011 ppm
25 ppm
97.2 ppm .
122 ppm
POINT OF
COMPLIANCE
All site
grounds
All site
grounds
All site
grounds
All site
grounds
All site
grounds
Top foot of
soil on
site
All site
grounds
All site
grounds
Top foot of
soil on
site
BASIS OF
STANDARD
Protection
of •
groundwater
Protection
of
groundwater
Protection
of
groundwater
Protection
of
groundwater
Protection
' of
groundwater
Risk
Protection
of
groundwater
Protection
of
groundwater
Risk
* These two clean-up standards will be
soil.
applied to the top foot of
54
-------
TABLE 8
MEDIUM
WATER
FINAL GROONI
'•
CONTAMINANT
Benzene
Toluene
Ethyl -
benzene
Xylenes
Naphthalene
Chromium
Lead
WATER CLEAN-T
CLEAN-UP
STANDARD
5 ppb
1, 000 ppb
29 ppb
400 ppb
30 ppb
50 ppb
15 ppb
JP STANDARDS
.
POINT OF
COMPLIANCE
Plume
Periphery
Plume
Periphery
Plume
Periphery
Flume
Periphery-
Plume
Periphery
Plume
Periphery
Plume
Periphery
— ==5^=
======
BASIS OF
STANDARD
Federal
MCL
N.C.
Ground-
water
Standard
N.C.
Ground-
water
Standard
N.C.
Ground-
water
Standard
Health-
Based
Level
N.C.
Ground-
water
Standard
Federal
Action
Level
55
-------
'«
56
-------
7.0 DESCRIPTION OP REMEDIAL ALTERNATIVES
A Feasibility Study (FS) was conducted to develop and evaluate
remedial alternatives to address the contamination at the Potter's
Pits site. The primary objective of the FS was to determine and
evaluate alternatives for the appropriate remedial action to
prevent or mitigate the migration or- the release or threatened
release of hazardous substances from the site. The following
section of this ROD provides a summary of the alternatives
considered for the remediation of the contaminated soils and the
contaminated groundwater, as well as the process and criteria EPA
used to narrow the list of potential remedial alternatives.
The FS was conducted in basically three phases that are all
contained in one report (FS). The first phase consisted of
identifying possible cleanup standards for each of the affected
media. Remedial action standards were specified for the site
constituents using criteria that are protective of human health and
the environment. To achieve these standards, general response
actions were identified for each medium, including soil and
groundwater.
Clean-up standards for affected surface and subsurface soils and
groundwater were established through the Baseline Risk Assessment
discussed in Section 6.0 of this document.
Presently all estimates described in the groundwater alternatives
are based on the remediation of the shallow aquifer only. It has
not been determined if the deeper aquifer needs to be remediated.
The possible extent of this contamination shall be further defined
during the Remedial Design/Remedial Action (RD/RA) phase of this
project. This will have a significant impact on the cost and time
of remediation of the groundwater.
The list of technologies that was identified through a screening
process was used to assemble different technologies for the
remediation of both groundwater and soils and represents a range of
no action, containment, and treatment technologies.
In phase II, specific components of each remedial alternative were
described in greater, detail to evaluate the remedial alternatives
according to effectiveness, implexnentability, and cost. Following
this screening process, three groundwater technologies and seven
soil remediation technologies were retained for further
consideration in phase III of the FS.
Phase III consisted of a detailed evaluation and comparative
analysis of the remedial alternatives based on nine criteria.
These nine criteria are listed and defined in Section 8.0 of this
ROD. Also included in Section 8.0 is a comparative analysis of the
remedial alternatives described in this Section.
The following sub-sections further define the alternatives
developed and evaluated in the FS and the ARARs associated with
these alternatives.
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7.1 Applicable and Relevant and Appropriate Requirements (ARARs)
This Section examines and specifies the clean-up goals, for each
environmental medium adversely impacted by the contaminants found
in association with the Potter's Pits site.
7.1.1 Action-Specific ARARs
Action-specific requirements are technology-based and
establish performance, design, or other similar action-
specific controls or regulations on activities related to the
management of hazardous substances or pollutants. Listed
below are all potential action-specific ARARS for contaminated
soil and groundwater. For a more complete description of
each ARAR, please refer to the Feasibility Study.
FEDERAL ARARs:
* Resource Conservation Recovery Act (42 U.S.C. 6901-6987)
Hazardous Waste Management Systems (40 CFR. Part 260)
- Standards Applicable to Generators of Hazardous Waste
(40 CFR Part 262)
Standards Applicable to Transporters of Hazardous
Waste (40 CFR Part 263)
Standard for Owners and Operators of Hazardous Waste
Treatment, Storage, and Disposal (TSD) Facilities (40
CFR Part 264)
General Facility Standards (Subpart B)
Preparedness and Prevention (Subpart C)
- Contingency Plan and Emergency Procedures (Subpart D)
- Manifest System, Recordkeeping, Reporting (Subpart E)
Release from Solid Waste Management Units (SWMUs)
(Subpart F)
- Closure and Post-Closure (Subpart G)
Use and Management of Containers (Subpart I)
Tanks (Subpart J)
- Waste Piles (Subpart L)
Land Treatment (Subpart M)
Landfills (Subpart N)
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- Incinerators (Subpart 0)
- Process Vents (Subpart AA);
- Equipment Leaks (Subpart BB)
Interim Standards for the Management of Specific
Hazardous Wastes and Specific Types of Hazardous Waste
Management Facilities (40 CFR Part 265.400 Subpart Q)
Standards for the Management of Specific Hazardous
Waste and Specific Types of Hazardous Waste Mangement
Facilities (40 CFR Part 266)
- Land Disposal Restrictions (40 CFR Part 268)
* Clean Water Act (33 U.S.C. 1251-1376)
National Pollutant Discharge Elimination System
(NPDES) (40 CFR Part 125)
- Effluent Guidelines and Standards for the Point Source
Category (40 CFR Part 401)
- National Pretreatment Standard (40 CFR 403)
* Safe Drinking Water Act (40 U.S.C. 300)
- Underground Injection Control Regulations (40 CFR Parts
144-147)
* Clean Air Act (42 U.S.C. 7401)
- New Source Performance Standards (40 CFR Part 60)
- Occupational Safety and Health Act (29 U.S.C. 651-678
29 CFR 1910)
- Hazardous Materials Transportation Act (49 U.S.C. 1801-
1813)
- Hazardous Materials Transportation Regulations (40 CFR
Parts 107, 171-177)
STATE ARARS:
* NC Solid and Hazardous Waste Management Act (General
Statutes, Chapter 130A, Article 9)
- Solid Waste Management Rules (ISA NCAC 13A)
- Hazardous Waste Management (ISA NCAC 13A)
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* Water Pollution Control Regulations (NCAC Title 15 Chanter
2, Subchapter 2H)
- Wastewater Treatment Requirements (NCAC Title 15
Chapter 2, Subchapter 2H.01)
- Erosion Control (15 NCAC Chapter 4 Subchapter 4B)
* NC Water and Air Resources Act (General Statutes Chapter
143, Article 21)
- Standards for Contaminants (NCAC Title ISA, Chapter 2,
Subchapter 2D)
- Standards for Sources of VOCs (NCAC Title ISA, Chapter
2, Subchapter 2D)
* NC Groundwater Quality. Standards (NCAC Title 15A, Chapter
2, Subchapters 2L.0100, 2L.0200, 2L.0300)
* NC Well Construction Act (General Statutes Chapter 87)
7.1.2 Chemical-Specific ARARs
Chemical-specific ARARs are concentration limits established
by government agencies for a number of contaminants in the
environment. Chemical-specific ARARs can also be derived in
the .Risk Assessment. Listed below is all of the potential
chemical-specific ARARs for contaminated soil and groundwater
at the Potter's Pits site. A more detailed discussion of
these ARARs is provided in the Feasibility Study.
FEDERAL ARARS:
* Resource Conservation and Recovery Act (42 U.S.C. 6901-
6987)
- Identification and Listing of Hazardous Waste (40 CFR
Part 261)
- Releases from Solid Waste Management Units (40 CFR Part
264 Subpart F)
* Clean Water Act (33 U.S.C. 1251-1376)
- Water Quality Criteria (40 CFR Part 131)
* Safe Drinking Water Act (40 U.S.C. 300)
- National Primary Drinking Water Standards (40 CFR Part
141)
- National Secondary Drinking Water Standards (40 CFR
Part 143)
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*
- Maximum Contaminant Level Goals (40 CFR Part 141)
STATE ARARS:
* NC Hazardous Waste Management Rules and Solid 'Waste
Management Law (ISA NCAC 13A)
- Identification and Listing of Hazardous Waste (ISA NCAC
13A.0006)
* Water Quality Standards Applicable to the Surface Waters
of NC (15 A NCAC 2B.0100
* NC Drinking Water Act (General Statutes Chapter 130A,
Article 10)
NC Groundwater Quality Standards (NCAC Title ISA, Chapter 2,
Subchapters 2L.0100, 2L.0200, 2L.0300
7.1.3 Location-Specific ARARs
Location-specific ARARs are design requirements or activity
restrictions based on the geographical and/or physical
positions of .the site and its surrounding area. There
requirements and/or restrictions can be stipulated by Federal,
State or local governments. Listed below is all the potential
location-specific ARARs for the Potter's Pits site. A more
detailed description of these ARARs are outlined in the
Feasibility Study.
FEDERAL ARARS:
* Resource Conservation and Recovery Act (42 U.S.C. 6901-
6987)
- Siting Criteria for Hazardous Waste Treatment, Storage,
and Disposal Facilities (40 CFR 264.18)
* Executive Order on Protection of Wetlands (Executive Order
No. 11,990 40 CFR 6. 302 (a) and Appendix A)
STATE ARARs:
* NC Solid and Hazardous Waste Management Act (General
Statutes, Chapter 130A, Article 9)
- Siting Criteria for Hazardous Waste Treatment and
Disposal Facilities (15 -A NCAC 13A.0009)
7.1.4 "To Be Considered" (TBCs) ARARs
* Primary Drinking Water Standard Proposed Maximum
Contaminant Levels (Proposed MCLs) found in the May 22,
1989 Federal Register.
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* Reference Dose (RFD), is an estimate (with uncertainty
spanning perhaps an order of magnitude) of a daily exposure
to the human population (including sensitive subgroups)
that is likely to be without an appreciable risk of
deleterious effects during a lifetime. Interim Final
Risk Assessment Guidance for Superfund (Human Health
Evaluation Manual Part A.
* EPA Health Advisories guidelines developed by the EPA
Office of Drinking Water for chemicals that may be
intermittently encountered in public water supply systems.
* EPA Ambient Water Quality Criteria (AWQC) are guidelines
•that were developed for pollutants in surface waters
pursuant to Section 304 (a)(l) of the Clean Water Act.
* Carcinogenic Potency Factors (CPFs) are used for estimating
the lifetime probability (assumed 70-year lifespan) of
human receptors contracting cancer as a result of exposure
to known or suspected carcinogens. Interim Final Risk
Assessment Guidance for Superfund Human Health Evaluation
Manual Part A.
* EPA's Groundwater Protection Strategy (EPA 1984) policy is
to restore groundwater to its beneficial uses within a time
frame that is reasonable. The aquifer of concern at the
Potter's Pits site is used as a source of drinking water.
7.2 Groundwater Control Alternatives
Three sets of alternatives were developed to address groundwater
contamination at the site. The groundwater control (GWC)
alternatives are listed and described below.
7.2.1 GWC-1: No Action
In accordance with the NCP, EPA has evaluated a "No Action"
alternative as part of the FS. The No Action alternative
serves as a basis against which other alternatives can be
compared. ' Under the No Action Alternative, no remedial
response would be performed 'on any of the groundwater at the
site.
The only active component of this alternative is long-term
groundwater monitoring. This program would be implemented to
assess the effect of waste constituents on the site over a 30-
year design life. Groundwater quality at the site would be
monitored semiannua-lly for volatile organic compounds, semi-
volatile organics, and inorganics.
Since this remedy results in hazardous waste remaining on-site
which will not allow unlimited use and unrestricted exposure,
CERCLA requires that the site be reviewed every five years.
During this review, the monitoring program would be re-
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evaluated to assess the appropriateness of the sampling
program.
This alternative does not reduce the risk calculated by the
Baseline Risk Assessment for either soils or groundwater.
The estimated present-worth, including 30-year O&M costs, of
GWC-1 is $ 140,000.
7.2.2 GWC-2: Institutional Controls
The Institutional Controls Alternative includes the following:
- The current residents and dwelling ( a mobile home) will be
transported and re-established on another lot. This will
require a new foundation, well and septic systems, electrical
and plumbing hook-ups in addition to the relocation of the
dwelling.
Applicable legal controls would be implemented including
deed restrictions for land use of the site and. adjacent
property, and water well construction permit restrictions for
areas within the zone of influence (ZOI) of the contaminant
plume. Legal controls can be filed through the local
government offices.
Implementation of a monitoring program would consist of
groundwater sampling on a semi-annual basis. Groundwater
samples would be collected from both upgradient and
downgradient wells, in both the shallow and deep aquifers, and
analyzed for organic and selected metals (lead and chromium).
Reyiew of the site would be conducted every five years since
hazardous substances are remaining on site and will not allow
for unlimited use and unrestricted exposure.
This alternative reduces the incremental risk for current site
conditions by restricting access to the groundwater and by
preventing future groundwater use that would allow repeated,
frequent contact with it.
Environmental monitoring similar to that discussed under GWC-1
would also be conducted as part of this alternative. The
total present-worth cost for implementation of Institutional
Controls is $1,400,000.
7.2.3 GWC-3: Groundwater Recovery and Treatment
This alternative involves the recovery of all site groundwater
currently exceeding cleanup standards through a system of
numerous extraction wells. The treatment system for the
extracted groundwater would involve installing piping from
each extraction well to a common treatment area, a specific
treatment system, and discharging the treated groundwater into
Chinnis Branch. This treated groundwater would meet the
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subtantiye requirements of a National Pollutant Discharge
Elimination System. (NPDES) permit and any other ARARs.'
Because of the nature of contaminants, it is necessary to use
a "treatment train" system where several different
technologies are used to treat the different contaminants.
For groundwater, air stripping would be used to remove the
VOCs and chemical treatment (precipitation /flocculation/
filtration) would be used to remove the heavy metals from the
groundwater. These technologies are described below:
AIR STRIPPING
In the air stripping system, the groundwater is pumped from
the well and sent to the top of an air stripping tower. While
the water cascades down through a large tube, a high-powered
fan literally blows the contaminants from the water. The fan
then sends the contaminated air out of the top of the air
stripping tower. The volatilized contaminants are treated by
an off-gas system. The air stripping system is most effective
in removing VOCs; It is not effective with other
contaminants, such as heavy metals.
CHEMICAL TREATMENT
The chemical treatment process used in this alternative
involves precipitation/flocculation/filtration for the removal
of the heavy metals of concern (lead, zinc, and chromium).
Precipitation involves addition of chemicals to the
groundwater to transform dissolved contaminants into insoluble
precipitates. Flocculation then promotes the precipitates to
agglomerate or clump together which facilitates their
subsequent removal by filtration.
During this- chemical process, the filtered material or sludge
will be collected and stored in a dumpster and will have to be
hauled off-site for treatment (if required) and disposal in
accordance with applicable regulations.
• To assess the effectiveness of the treatment system, the
influent and effluent will be monitored weekly. Remedial
pumping on-site will continue until the contaminant
concentrations " in groundwater consistently meet remedial
objectives. Once the system is turned off monitoring would
continue for at least an additional 5 years to ensure that
all contaminant concentrations remain below these objectives
at the points of compliance.
The present worth estimate would be $ 7,100,000. This
•estimate is based on the source removed. (An estimated 50
years will be needed to treat the aquifer).
7.3_ Remedial Alternatives for Source Control
Seven different alternatives are presented to address source
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control at the Potter's Pits site. The Source Control alternatives
(SO are listed and described below:
7.3.1 SC-1: NO Action
In the Mo Action alternative, no further remedial actions
would occur. Some remediation may occur through natural
processes. Site soil contamination would slowly decrease over
time, and would continue to contribute chemicals to the
groundwater.
Review of the site would be conducted every five years since
hazardous substances would remain on site and would not allow
for unlimited use and unrestricted exposure.
This alternative does not reduce the risk for being exposed to
the contaminated soil.
The present worth cost is $ 140,000.
7.3.2 SC-2: Institutional Controls
The Institutional Controls Alternative includes the following:
The current residents and dwelling (a mobile home) will be
transported and re-established on another lot. This will
require a new foundation, well and septic systems, electrical
and plumbing hook-ups in addition to the relocation of the
dwelling.
- Site access restrictions will involve erection of physical
barriers to minimize the potential for contact with
contaminated soils, and implementation of deed restrictions to
regulate land usage by legal means.
- The pnysical barrier selected to prevent access to the site
is a six-foot high cyclone fence.. Fencing would be installed
around all areas containing soils presenting a concern
for human health. The fence will be placarded at twenty-five-
foot intervals along its perimeter with a warning about site
conditions.
Implementation of a monitoring program would consist of
soil sampling on a biannual basis. Soil samples would be
collected downgradient from the site, upgradient from the
site, and on the site.. Samples collected would be analyzed
for the presence of volatile organic contaminants and selected
metals.
Review of the site would be conducted every five years since
hazardous substances are remaining on site and would not allow
for unlimited use and unrestricted exposure.
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The estimated present-worth, including 30-year O&M cosrs of
SC-1 is $ 1,400,000.
7.3.3 SC-3: Soil Removal and Off-Site Disposal
The current residents (Gurkins) on-site would be moved to
another location. This alternative consists of the excavation
of soils (surface and subsurface) that exceed soil cleanup
standards. if the contaminated soil passes toxicity
characteristic leaching procedure (TCLP), soils removed would
be transported to an off-site permitted landfill for disposal.
If the contaminated soils do not pass TCLP, the soil would
have to be treated at a facility such as an incinerator and
then disposed of at a hazardous waste landfill. The
excavation area would be filled with clean soil, compacted,
and graded to original contour.
For purposes of the cost estimate, it is assumed that the
contaminated soil is not classified as a hazardous waste.
This can be confirmed by performing TCLP tests as specified in
40 CFR 261. Therefore, it is assumed that the contaminated
soil at the site would meet the RCRA Land Disposal
Restrictions and could be directly landfilled at a RCRA-
approved landfill facility without pretreatment.
Transportation of the material off-site would be performed
with bulk dump trucks. RCRA regulations require the generator
and transporter to comply with the manifest system for each
shipment of hazardous material transported off-site.
During the implementation, dust control measures would be
implemented to protect the community from the dust generated
through the excavation, soil erosion, and truck traffic. On-
site, the dust can be controlled with water sprays while an
air monitoring program is implemented to detect any tract
levels of contaminants in the air.
There is a RCRA-approved hazardous waste landfill located in
Pinewood, South Carolina, which is approximately 170 miles
from the site. The landfill is opera-ted by Laidlaw
Environmental Services, Inc. and may be available to accept
the type of contaminated soil at the site.
The estimated costs for this alternative is estimated at
$6,280,000.
7.3.4 SC-4: Soil Stabilization/Solidification
The current residents (Gurkins) would be moved from the site
to another location. This alternative is a treatment
technology that mixes the contaminated soil with another
substance such as cement, kiln dust, lime, fly ash, silicates,
and clay. This admix converts the contaminants into their
least soluble, mobile, or toxic form, thus minimizing their
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potential for migration. This mixture of material is then
placed back where it was excavated. A low permeability clay
cover would be placed over the stabilized/solidified
contaminated soils to minimize the potential for leaching '
Treatability studies would be required to determine the best
admix to use and whether to treat the soils in-situ or ex-
situ.
To ensure adequacy and reliability of controls, a mpnitoring
program would remain in effect, allowing for repair of the cap
if damage due to erosion or vegetation is noted.
It .is assumed that the contaminated soil is not classified as
a hazardous waste. Regardless of the RCRA hazardous waste
classification, the RCRA Land Disposal Restrictions would not
apply to soils that are stabilized/solidified in situ, since
these restrictions only apply when exhumation and replacement
occur. If an ex situ stabilization/solidification process is
used, the Land Disposal Restrictions and other RCRA
requirements may apply (again, assuming the soils are
classified as a hazardous waste.)
The estimated cost is $5,500,000.
7.3.5 SC-5: On-Site Incineration
The current residents (Gurkins) would be moved from the site.
This alternative consists of the excavation of the
contaminated soils, on-site incineration of the soils, and
disposal of the ash. A transportable incinerator would be
mobilized to the site to perform the incineration.
Rotary Kiln incineration is a process in which solid and
liquid wastes are fed into a rotating chamber where they are
exposed to temperatures ranging from 1500 to 3000 degrees
Fahrenheit. The heat reduces organic (carbon-containing)
compounds into their basic atomic elements, for example,
hydrogen, nitrogen, and carbon. In combination with oxygen,
these form stable compounds such as water, carbon dioxide, and
nitrogen oxides.
Although residual concentrations of the contaminants of
concern cannot be determined until a treatability study is
performed, it is anticipated that the treated soils would not
be a listed- hazardous waste and would therefore be used to
backfill the excavations. The treated soils may require a
stabilization/solidification step to immobilize the inorganic
compounds that are not affected by the thermal treatment. At
a minimum, it is expected that the treated soils would meet
the applicable requirements necessary for land disposal in a
permitted off-site RCRA landfill. For costing purposes, this
alternative is based on the assumption that the treated soils
would be delisted (if required) and used to backfill the
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excavations, in addition, for costing purposes, it is assumed
that approximately 10 percent of the residual ash (i.e. ash
wltf}. .eieYated metals concentrations) would require
stabilization/ solidification prior to delisting.
An additional 20% (by volume) of off-sice backfill would be
required to account for the volume reduction caused by
incineration.
Destruction removal efficiencies (DREs) for incinerated RCRA
hazardous waste must be greater than 99.99%. It i-s assumed
that the on-site incinerator would be able to achieve these
standards. Laboratory-scale testing may be used to provide a
better estimate of the destruction efficiencies that would be
expected at the site.
The estimated cost is $12,400,000.
7.3.6 SC-6: Soil Washing
The current residents would be moved to another 'location.
This alternative is a batch process in which contaminated
soils are thoroughly mixed with successive rinse solutions
formulated to remove waste constituents from the soils. Acid
rinses are frequently used to solubilize metals, transferring
the metals from a solid or sorbed state to an aqueous phase.
The aqueous phase is then separated from the solid matrix by
decanting. The rinsate from this step is then treated using
conventional wastewater technology for metals removal, such as
pH adjustment, flocculation, clarification, and dewatering.
Process- waters would be temporarily stored in on-site tanks
until recycled. Wastewater sludges would be dewatered and
stockpiled. Dewatered sludges would be transported to a RCRA-
approved facility for treatment (if required) and landfilled.
The soil washing system should be able to achieve removal
efficiencies in excess of 90% for VOCs, PAHs, and metals,
according to most literature regarding this treatment
technology. Removal efficiencies as high as 99.9% have been
observed for VOCs in sandy soils (EPA, 1991). Reported
removal rates for SVOCs and metals are somewhat lower and are
generally in the 90% to 95% range.
It should be noted that, as evidenced in the published
literature, the final concentrations of SVOCs and metals in
the washed.soils are generally higher than the action levels
being applied to the site. The high removal efficiencies
achieved are the result of high initial concentrations.
Attainment of the action levels for SVOCs and metals may r.ct
be possible using standard water and surfactant or water and
chelant washing. Processes using stronger and more
specialized solvents may be necessary to achieve acceptable
results. The site-specific effectiveness would be determined
through laboratory and field scale treatability studies.
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Depending on the soil washing process utilized, some
stabilization/solidification technique may be necessary. it
is possible that the treated soil would either meet the
requirements of the RCRA Land Disposal Restrictions and could
be directly landfilled at a RCRA approved landfill facility or
if the soil is clean, the soil could be placed back into the
excavated areas.
The estimated cost is $12,300,000.
7.3.7 SC-7: LOW Temperature Thermal Desorption and
Stabilization
The current residents (Gurkins) would be moved to another
location. This alternative consists of excavating
contaminated soil and treating the soils by thermal
desorption. Treatment would consist of volatilizing the
organic contaminants at temperatures usually between 300 -
800 degrees F. with the off-gases being treated to prevent
the release of contaminants. The waste stream would be
treated by stabilization if needed.
Off-gas treatment varies depending on the vendor, but usually
consists of either: 1) thermal oxidation in a thermal
oxidation chamber similar to incinerators; 2) condensing and
concentrating the organics into a significantly smaller mass
for further treatment; or 3) passing the off-gases through
activated carbon to adsorb the contaminants and then
regenrating the carbon. This Record of Decision will not
select the off-gas treatment so as not to limit vendor
competition. However, EPA will review and approve the
secondary treatment prior to implementation. Standards for
the operation of hazardous waste incinerators are relevant and
appropriate requirements for thermal desorption unit.
After the soils are treated, they will be analyzed to insure
the soils meet the soil clean-up standards established in
Section 9.4 of this ROD. If the soils are clean, they will
be used as backfill. If the soils are still contaminated with
metals, then that particular stockpile will be stabilized and
taken off-site for disposal.
This alternative will comply with Land Disposal Restrictions
through a Treatability Variance for the contaminated soils.
The .estimated cost is $ 4,700,000.
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8.0 SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES
During the phase III of the FS, the alternatives retained for
further consideration and described in Section 7.0 were analyzed in
detail using the nine evaluation criteria. A comparative analysis
was conducted to determine which alternative provides the best
balance of tradeoffs with respect to the following nine criteria:
Threshold Criteria -
1) Overall Protection of Human Health and the Environment;
2) Compliance with Applicable or Relevant and Appropriate
Requirements (ARARs);
Primary Balancing Criteria -
3) Long-Term Effectiveness and Permanence;
4) Reduction of Toxicity, Mobility, and Volume;
5) Short-Term Effectiveness;
6) Implementability;
7) Cost;
Modifying Criteria -
8) State/Support Agency Acceptance, and;
9) Community Acceptance.
Discussion of the relative performance of the alternatives for both
soil and groundwater with respect to the nine criteria is included
below. First, the groundwater alternatives will be compared and
tJien the source control (soil) alternatives will be compared using
these criteria.
8 .1 Groundwater
8.1.1 Overall Protection of Human Health and the Environment
This criteria addresses whether a remedy provides adequate
protection and describes how risks posed through each pathway
are eliminated, reduced, or controlled through treatment,
engineering controls, -or institutional controls. EPA has
established a limit of E-04 to E-06 as acceptable limits for
excess lifetime carcinogenic risks. EPA has also established
that a hazard index rating exceeding 1.0 for non-carcinogenic
constituents suggests potential concern for toxic effects in
sensitive portions of the exposed population.
Under potential future conditions the No Action (GW-1)
alternative would not address contaminant levels in
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groundwater, and it would allow for possible ingestion of
groundwater from wells drilled in the contaminated area.
Since the No Action alternative does not meet this criteria
f,°Yeraf Protection of human health and the environment, it
will be dropped from the rest of the evaluation. There is
uncertainty about the long term effectiveness of the
Institutional Alternative (GW-2). Alternative GW-3 would
prevent migration of contaminated groundwater and recover
groundwater to meet cleanup standards.
8.1.2 Compliance with Applicable or Relevant and Appropriate
Requirements (ARARs)
This criterion assesses the alternatives to determine wether
they attain ARARs under federal and state environmental laws,
or provide justification for waiving an ARAR. Section 7.1
defines the three types of ARARs: action-specific, chemical-
specific, and location-specific. Site-specific ARARs are
identified below.
There are no federal or state chemical-specific ARARs for the
contaminants detected in the soils as there are no action-
specific ARARs for Aternative SC-1. RCRA requirements for
Alternative SC-4 (Stabilization) may be relative and
appropriate. -All alternatives will have to meet location-
specific ARARs. Alternatives SC-2 through SC-7 will comply
with all applicable ARARs, including Land Disposal
Requirements. (LDRs) by complying with and meeting Treatability
Variance standards/levels. Because the LDR treatment (clean-
up levels) are based on treating less complex matrices of
industrial process wastes then what is present at the Potter's
site, the selected remedy will comply with the LDRs through a
Treatability Variance for the contaminated soil. The
Treatability Variance does not remove the requirement to treat
restricted soil wastes: it allows the establishment of LDR
standards on actual data collected from the site. LDR
treatment levels will be met for the soil and for any sludge
or used activated carbon generated by the treatment process.
Table provides the alternate treatment variance levels under
LDR.
MCLs and North Carolina Groundwater Standards are ARARs for
site groundwater. The Institutional Controls alternative
would not comply with ARARs. Alternative GW-3 would reduce
the levels of contaminants in the groundwater and comply with
ARARs. The treated water would be discharged into Chinnis
Branch and would meet the subtantive requirements of a
National Pollution Discharge Elimination System (NPDES)
permitting limits. If, at completion of the action, ARARs
cannot, be met, a waiver for technical impracticability would
be obtained and groundwater use restrictions would continue.
8.1.3 Long-Term Effectiveness and Permanence
This evaluation criterion refers to expected residual risk and
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the ability of the alternative to maintain reliable protection
of human health and the environment over time, once clean-up
standards have been met.
Under the Institutional Controls (GW-2) alternative,
contaminated groundwater could migrate off-site; therefore, it
is not considered to be a permanent or effective remedial
solution. Contaminant concentrations would be permanently
reduced through groundwater recovery for Alternative GW-3.
Air Stripping and Chemical Treatment is considered the best
available treatment for heavy metals and volatile' organic
compounds in groundwater.
8.1.4 Reduction of Toxicity, Mobility, or Volume
This criterion takes into account the anticipated performance
of the treatment technology a remedial alternative may employ.
The GW-2 alternative would not significantly reduce the
toxicity, mobility, or volume of contaminants in groundwater.
Alternative GW-3 would reduce the volume of contaminants in
the aquifer through recovery and treatment.
8.1.5 Short-Term Effectiveness
This refers to the likelihood of adverse impacts on human
health and the environment that may be posed during the
construction and implementation of an alternative until the
clean-up standards are achieved.
All of the alternatives can be implemented without significant
risk to the community or on-site workers and without adverse
environmental impacts.
8.1.6 Implementability
This criterion refers to the technical and administrative
feasibility of an alternative, including the availability of
materials and services needed to implement a particular
option.
None of the alternatives would pose significant concerns
regarding implementation. Construction of the treatment
systems would not be conducted until discharge requirements
for the treated water were defined.
8.1.7 Cost
This criterion estimates the total cost required to'implement
an alternative and includes the estimated capitol, Operation
and Maintenance (O&M) costs, and present-worth costs. Table
9 provides a comparison of costs for all alternatives
discussed in this section.
72
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TABLE 9
COSTS FOR GROUNDWATER ALTERNATIVES
GROUNDWATER
ALTERNATIVES
GWC - 1
GWC - 2
GWC - 3
PRESENT WORTH
COSTS
$ 140,000
$ 1,400,000
$ 7,100,000 (50 YEARS)
73
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8.2 Source Remediation
8.2.1 Overall Protection of Human Health and the Environment
Potential risks due to site soils under current and potential
future conditions are not within the acceptable risk range as
specified in the National Contingency Plan (NCP)
Alternatives SC-1 and SC-2 would not decrease the risks
associated with the soils. Alternatives SC-3 through SC-7
would all decrease the risk and mitigate any further
contamination to groundwater.
8.2.2 Compliance with Applicable or Relevant and Appropriate
Requirements (ARARs)
Alternatives SC-3 through SC-7 would meet RCRA closure
requirements for waste in place if applicable. Also any of
these alternatives would have to comply with Land Disposal
Restrictions (LDRs) through a Treatability Variance.
8.2.3 Long-Term Effectiveness and Permanence
Alternatives SC-1 and SC-2 would not be effective in reducing
the contaminants. There is a question concerning the
effectiveness of SC-2 in preventing human contact with the
soils, especially over a long period of time. Alternatives
SC-3 through SC-7 would result in a permanent reduction in
site risks.
8.2.4 Reduction of Toxicity, Mobility, or Volume
Contaminant levels would remain unchanged for alternatives SC-
1 and SC-2. There is a question concerning how effective
stabilization/ solidification (SC-4) for preventing the
organic contaminants from leaching on a long term basis.
. The rest of the alternatives would be effective in reducing
the toxicity, mobility, and volume of contaminants.
8.2.5 Short-Term Effectiveness
Alternative SC-1 and SC-2, No Action and Institutional
Controls, presents no immediate threat to human health and the
environment to implement in the short-term.
Contaminated soils containing COCs at concentrations exceeding
soil clean-up standards will be excavated and treated under
alternatives SC-3 through SC-7. Site disturbances due to
excavation and material handling are extensive, but
manageable. Dust emissions during excavation and treatment
can be effectively controlled with standard engineering
controls such as increasing the moisture content of the
materials. The volume of truck traffic required in all of
these alternatives significantly reduces the short-term
74
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effectiveness.
Site disturbances for alternative SC-3, off-site disposal, are
extensive due to the volume of truck traffic. SC-3 requires
approximately 500 -700 truckloads of waste at 20 tons per
truckload. For alternative SC-4, stabilization/
solidification, extensive truck usage would also be required
due to the volume of clay required to construct the protective
clay cap after the stabilization has taken place.
In alternatives SC-5 and SC-7, the thermal desorption unit and
the incinerator would produce a considerable amount of noise
during operation.
8.2.6 Implementability
No implementation is needed for the no action alternative.
Off-site disposal to a RCRA-approved landfill and incinerator
have been conducted successfully at other Superfund Sites.
Implementation of alternatives SC-5 and SC-7 may depend on the
availability of a mobile thermal desorption equipment and
mobile incineration equipment, respectively.
There may be insufficient space at the site to fit the
desorption or incineration unit and auxilary equipment.
8.2.7 Cost
Alternatives SC-1 and SC-2 are low-cost remedies that offer no
treatment of the source material. The treatment technologies
(SC-3, 4, and 7) provide remedies with a high degree of
permanence at costs that are mid-range for the alternatives
evaluated in Phase III of the FS. The incineration and soil
washing alternative would achieve a high amount of permanence,
but the costs are high related to burning and disposal. The
source removal alternative (SC-3) would also achieve
substantial risk reduction in terms of future exposure to
waste constituents, but the short-term risks are greater than
for the other alternatives, and the costs are higher.
Table 10 shows costs for each alternative.
8.3 State/Support Agency Acceptance
The North Carolina Department of Environment, Health, and Natural
Resources (NCDEHNR) has been actively involved in the RI/FS and the
remedy selection process at the Potter's Pits site. NCDEHNR has
reviewed this Record of Decision and concurs with all aspects of
EPA's selected remedy. NCDEHNR's conditional concurrence letter on
the selected remedy for the Potter's Pits site is included in an
Appendix to this Record of Decision.
75
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TABLE 10
COSTS FOR SOURCE REMEDIATION ALTERNATIVES
SOURCE REMEDIATION
ALTERNATIVES
SC - 1
SC - 2
SC - 3
SC - 4
SC - 5
SC - 6
SC - 7
ESTIMATED
COSTS
$ 140,000
$ 1,400,000
$ 6,280,000
$ 5,500,000
$ 12,400,000
$ 12,300,000
$ 4,700,000
76
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8.4 Community
EPA solicited input from
cleanup of the Potte ™s t
indicated no specific opposition t-«
local residents did exorV^
the thermal desorp^i^unit an
of the entire Remedial ActTon
cton Th
individually in the attach^H p These issues
x me accached Responsiveness Summary.
°n,Hthe Prosed Plan for
A1^hougS ^blic comments
preferred alternative, some
°Vr e,n°ise Associated with
tlme of Alimentation
issues are addressed
77
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9.0 THE SELECTED REMEDY
EPA has selected Alternative GW-3, Groundwater Recovery and
Treatment, as the remedy to address contaminated groundwater, and
SC-7, Low Temperature Thermal Desorption and Stabilization as the
remedy to address the contaminated soils at the Potter's Pits site.
The remedy for the cleanup of the Potter's Pits site consists of
the following components:
9.1 GW-3: Groundwater Recovery and Treatment System
Extraction wells and pumping systems will be installed to restore
the contaminated aquifer (plume: Figure 22) to within acceptable
drinking water standards by removing groundwater from the area of
peak contamination concentration. In addition, as areas are
cleaned, pumping locations and rates may need to be adjusted.
Locations of the wells will be determined during the remedial
design after the aquifer characteristics are defined. Varying
pumping rates are also beneficial in flushing the groundwater flow
divide between adjacent pumping wells. The relationships between
individual pumping wells and the cumulative effects of. drawdown
from several pumping wells will be evaluated. Accordingly, it is
probable that the scenario initially chosen will need to be
modified following startup. Pumping rates may be varied and
recovery wells may be added to or removed from the system.
The elevated metals at the site (chromium and lead) will be treated
by precipitation, flocculation, and filtration process. This
treatment system will remove the metals from groundwater and form
a sludge. This remedy is described in Section 7.1.3 of the ROD.
The sludge cake is stored in a dumpster and hauled off-site for
treatment {.if required) and disposal following applicable
regulations.
It should be noted that the chromium species present in the
groundwater is currently unknown, as is its distribution between
liquid and solid phases. Since performance is species specific,
both speciation (i.e. hexavalent and trivalent chromium analysis)
and treatability testing will be needed before design. Depending
on the results, modifications to the treatment scheme may be
necessary (e.g. reduction of hexavalent to trivalent chromium,
addition of iron for improved coprecipitation and/or ion exchange) .
Alternatively, if chromium and iron levels in the dissolved phase
(as determined during pump test sampling) are below effluent
criteria, certain treatment steps may be deleted (i.e. aeration,
clarification, filter press, ect...)
After the treatment process for metals is finished, the groundwacer
flows to a holding tank from where it is pumped to the top of an
air stripping unit. The present state guidelines allow discharge
of up to 40 Ibs/day without treatment. Accordingly, no emission
control is required as per the state guidelines (ISA NCAC 2D.0518).
In the event the air exhaust will not meet the state guideline of
40 Ibs/day, then the air will be treated through a carbcn
adsorption system before it is released into the atmosphere.
78
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If the carbon adsorption is needed, then once these units have
reached their capacity for'adsorbing organic impurities, the carbon
granules can be regenerated.
The treated water from the stripper flows by gravity to a holding
tank and will then be pumped to a discharge location. Discharge
will be directly into Chinnis Branch on-site after meeting the
substantive requirements of an NPDES permit.
In Section 9.2, there is a description of how the source will be
removed and treated at the site. Based on this fact, the duration
of the groundwater recovery and treatment system will be
approximatly 50 years. In other words, it will take a minimum of
50 years to clean-up the shallow aquifer to the groundwater clean-
up standards that are established in Section 9.6 of this ROD.
Signs and institutional controls will be established to identify
•the presence and nature of wastes in the groundwater and limit use
until remediation is complete.
The present worth cost of this portion of the selected remedy for
groundwater is $ 7,100,000. Table 11 shows a break-down of the
costs associated with this aspect of the selected remedy.
9.2 Additional Data Requirements and Monitoring of the Groundwater
9.2.1 Monitoring Program
The monitoring program that will be developed before and
during this remedial action will include periodic water-level
measurements in all wells and groundwater sampling and
analysis from selected wells on a scheduled basis. A post
startup evaluation will be made to determine if additional
monitoring wells are necessary. Monitoring frequency will be
greater during the initial phase of operation, and based on
results, could be decreased as the system begins to
equilibriate. The monitoring frequency will be temporarily
increased following any program changes in the recovery
system.
The monitoring program will include assessment of the
following:
* ' Variations in pumping well water quality and
constituent loading to treatment systems.
* Hydraulic effects on off-site residential water
supplies.
* Decommissioning of wells no longer needed in the
recovery system as clean-up progresses.
9.2.2 Additional Data Requirements for the Deep Aquifer
As discussed earlier, lithologic and hydrologic data collected
79
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TABLE 11
COST FOR TI
SSSSS^^^S^S T !7 ™ ' ~™7T
CAPITOL COSTS
Recovery Well
Installation
Labor
Expenses
Equipment
Driller
Treatment
Plant
Installation
Complete
(See Table 38
for breakdown)
Pumps and
Piping
Labor
Electrical
Piping
Pumps
O&M Costs
Maintenance
Treatment
Plant (3%)
Recovery
Wells (20%)
Pumps
Piping (20%)
Fence (5%)
Operations
Labor
Expenses
Chemicals
« GROONDWATBR RECOVERY AND TREATMENT SYSTEM
UNITS
300
45
1
180
1
1,200
1
1,200
6
. . 3
20
20
5
3
1
1
COST PER UNIT
60
150
2,000
75
562,000
10
100
10
500
16,860 -
8,050
5,540
1,200
40,000
10,000
11,500
— • "
COSTS ($)
18, 000
6,750
2,000
13,500
(6-30ft. wells)
562,000
12,000
700
12,000
3,000
- 16,860
8,050
5,540
1,200
120,000
10,000
11,500
80
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TABLE 11
Electrical
Sludge Transp
and Disposal
Monitoring
(Influent and
Effluent)
Capitol
Subtotal
(Not Treatment
Percent)
Engineering
(25 %) _j
Contingency
(25 %)
Total Capitol
Subtotal O&M
Annual
Engineering
(25 %)
Contingency
(25 %)
Total O&M
Annual
TOTAL PRESENT
WORTH COST OF
TREATMENT FOR
50 YEARS
1
60
104
(Cont. . .)
9, 000
457
350
9, 000
27,390
36,400
67, 950
16, 988
21,234
106,172
245,940
61,485
76,856
384,281
7,121,000
81
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in the RI suggest that two aquifers are present at the site.
Benzene was not detected in the deep wells during the initial
RI but was detected during the Phase II RI sampling in one
deep well (MW-110) at 58 ug/1. To evaluate the extent of
benzene contamination in the deep aquifer, additional sampling
will be performed during subsequent phases of this project
(Remedial Design). In order to fully assess the extent of
deep aquifer contamination, additional wells may be necessary.
Since benzene was detected only once and its extent is not
clearly defined, calculation of clean-up times and cost
estimates do not reflect the clean-up of the deeper aquifer.
9.3 Low Temperature Thermal Desorption and Stabilization
The selected remedy for soil contamination, alternative SC-7,
involves the use of the innovative technology, Low Temperature
Thermal Desorption (LTTD). EPA has selected this remedy based upon
consideration of the requirements of CERCLA and the detailed
analysis of the alternatives. This remedy is described in Section
7.2.7 of the ROD.
The current residence (Gurkins) and their home will be moved off-
site to another location before Remedial Action begins.
The next step in implementing this remedy is soils excavation. All
soil which exceed the soil clean-up standards outlined in Section
9.6 of this ROD will be excavated and treated. A sampling program
shall be developed and conducted prior to excavation to determine
the actual volume of soils requiring remedial action. Confirmation
sampling shall also be conducted following excavation and prior to
backfilling -treated soils to ensure the underlying soils and the
treated-soils meet the appropriate clean-up standards.
Placement of hazardous waste as defined by the Resource
Conservation and Recovery Act (RCRA) Land Disposal Restrictions
(_LDRs) is not applicable to this CERCLA response action. The area
of contamination (AOC) at the site shall be delineated by the
aerial extent, or boundary, of contiguous contamination. The AOC
shall consists of approximately 5-acres that includes the Gurkin's
property, the empty "field across from the Gurkin's property which
is separated by Joe Baldwin Drive, and also the lot next to the
Grainger's house across Grainger's Circle from the Gurkin's
property. According to RCRA, placement does not occur when wastes
are moved within a single AOC. As part of the selected remedy, all
excavated wastes shall be consolidated, pre-processed, and treated
within the established AOC..
Additional waste characterization shall be done as part of the
RD/RA process. The Toxicity Characteristic Leaching Procedure
(TCLP) test shall be done on the affected soils to identify if
these soils exhibit hazardous waste characteristics for any of the
waste constituents. If the soils show the presence of a
characteristic RCRA waste at the site, Land Disposal Restrictions
(LDRs) would then be applicable to this response action through a
—. — 82
-------
Treatability Variance. The treatment level range established
through a Treatability Variance that Low Temperature Thermal
Desorption (LTTD) will attain for each constituent as determined by
the indicated analysis are listed in Table 12. Treatment of waste
material at the site shall meet these promulgated Federal
standards.
After the contaminated soil is treated, the soil will be analyzed
to insure the soil clean-up standards have been met. If the levels
of inorganics are higher than the clean-up standards established
for soil, then the soils will be stabilized/solidified and either
transported off-site for disposal at a RCRA permitted hazardous
waste landfill or buried on-site following all applicable Land
Disposal Restrictions and Minimum Technology Requirements, soil
stabilization/Solidification is described in Section 7.2.4 of the
ROD.
From the soil data collected in the RI, it is not anticipated that
all of the soils will be contaminated with the inorganics;
therefore composite samples will be collected from stockpiles and
analyzed for inorganics of concern (lead and zinc) -. If the
stockpile results are above the soil clean-up standards, then that
batch of soil will be stabilized on-site or transported to an off-
site RCRA landfill for disposal.
The soil which has been successfully treated and has passed any
necessary TCLP tests will be backfilled, graded, and planted with
suitable vegetation. The Potter's Pits site shall have a fence and
proper warning signs posted in visible locations in order to
provide site control during remedial action.
Implementation of this portion of the Remedial Action will take
approximately 4 months (if the LTTD is operating 24 hours a day at
a process rate of 5 tons per hour) once the system has started
treatment.
The estimated costs of this estimate is approximately $ 4,700,000.
This implementation and cost estimate assume 10,100 cubic yards of
soil will be excavated and treated. As stated previously, the
exact location and volume of soil which will be excavated and
treated will be determined during the Remedial Design. This will
have an impact on the cost and implementation time of the remedy.
Table 13 shows a break-down of the costs associated with this
aspect fo the selected remedy.
9.4 Additional Data Requirements for Area 3 Soils'
Since limited sampling was conducted in Area 3 during the
remedial Investigation, a soil boring will be installed near
MW-104 and samples collected by compositing 2.5 foot intervals
continuously to 12.5 feet below ground surface (5 samples).
These samples will have a complete TCL/TAL analyses performed.
83
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TABLE 12
TOXICITY CHARACTERISTIC LEACHING PROCEDURE
Regulatory Limits
Treated/Solidified Waste
CONSTITUENT
Benzene
Toluene
Ethylbenzene
Xylene
Lead
Chromium
TCLP REGULATORY LEVEL
(mg/1)
0.5
1.12
0.05
0.05
5.0
5.0
84
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TABLE 13
COST FOR LOW TEMPERATURE THERMAL DESORPTION AND STABILIZATION
CAPITAL COSTS
Project Plans
Erosion
Control
Mobilization
Fence
Residence
Relocation
Excavation
Treatability
Study
Thermal
Desorption
Stabilization
. (20 %)
Off-Site
Disposal
Verification
Backfill
Regrade
Reseed
Capitol
Subtotal
Engineering
(25 %)
Contingency
.(25%)
Total
Capitol
UNITS
1
300
1
1, 600
1
10,100 Cu.Yd.
1
13,635 Tons
2020 Cu. Yd.
2 Trucks
60
10,100 Cu.Yd.
4
.
-
COST PER UNIT
40, 000
10
10, 000
15
10,000
10
150, 000
170
100
3600
350
10
1500
COSTS ($)
40, 000
3, 000
10,000
24, 000
10,000
101,000
150,000
2,317,950
202,000
72,000
21,000
101,000
6,000
2,993,150
748,288
935,360
4,676,798
85
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9.5 Total Cost o£ the Selected Remedy
Therefore, EPA's selected remedy for 50 years of pump and tr<=at of
the contaminated groundwater and thermal treatment of the
cost
un*= ^v^iv-^^-.^wv.^ y iULunawauei. auu cnermaj. treatment c
contaminated soils will have a total present worth cost of
$ 11,800,000. Tables 11 and 13 show the break-down of
associated with this selected remedy.
9.6 Performance Standards To Be Attained
Performance standards are defined as any applicable or relevant and
appropriate standards/requirements, clean-up goals and/or levels,
or remediation goals and/or levels to be achieved by the remedial
action. The performance standards, to be met/attained by the
Potter's Pits remedial action are specified below.
9.6.1 Soil Clean-up Standards
If the soils are not a characteristic hazardous waste, the
clean-up standards for soils are based on two criteria: •(!) to
reduce dermal contact risks to E-04 to E-06; and (2) to
protect groundwater from contaminants migrating from the soil.
Soil clean-up standards were derived from risk calculations
based on dermal exposure to the contaminants of concern found
in site soils. A more thorough description of the derivation
of the soil clean-up standards is presented in Section 6.0 of
the RI Report. A leachate model as described in the FS report
(Appendix A) was used to estimate the subsurface soil clean-up
standards necessary to protect the groundwater from
contaminated leachate containing the groundwater contaminants
of concern. The more conservative of the two clean-up
standards for each contaminant was selected as the remedial
standard.
The remediation standards for soil" contaminants of concern are
listed in Table 14. This Table summarizes the soil clean-up
standards selected for the Site on the basis of both direct
risk exposure (for zinc and carcinogenic PAHs' only) and
groundwater protection.
9.6.2 Groundwater Clean-up standards
The goal of this part of the remedial action is to restore the
groundwater to its beneficial use, which is, at this site,
Class IIB, -a source of drinking water. Based on information
obtained during the RI, and the- analysis of all remedial
alternatives, EPA believes that the selected remedy will
achieve this goal. Groundwater remediation standards and the
range of concentrations detected for each contaminant are
listed in Table 15. These standards are either MCLs, health-
based standards (napthalene), or North Carolina Groundwater
Standards. The approximate location of the contaminant plume
is shown on Figure 21.
86
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TABLE 14
SOIL CLEAN-UP STANDARDS
CONTAMINANTS
Benzene
Toluene
Ethylbenzene
Xylenes
Napthalene
*Carcinogenic PAHs.
Lead
Chromium
*Zinc
CLEAN-UP STANDARDS
.010 ppm
3 . 4 ppm
.235 ppm
3 . 5 ppm
1 . 8 ppm
.011 ppm
25 ppm
97 .2 ppm
122 ppm
*Note: These two clean-up standards (zinc and carcinogenic PAHs)
will be applied to the top foot of soil only.
87
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TABLE 15
GROUNDWATER CLEAN-UP STANDARDS
CONTAMINANT
Benzene
Toluene
Ethylbenzene
Xylenes
Napthalene
Chromium
Lead
CLEAN-UP STANDARD
5 ppb
1,000 ppb
29 ppb
400 ppb
30 ppb
50 ppb
15 ppb
38
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9.7 Contingency Meagures for Groundwater Remedial Action
Groundwater contamination may be especially persistent in the
immediate vicinity of the contaminants' source, where
•concentrations are relatively high. 'The ability to achieve clean-
up standards at all points throughout the area of attainment, or
plume, cannot be determined until the extraction system has been
implemented, modified as necessary, and plume response monitored
over time. If the selected remedy cannot meet remediation
standards, which are a combination of MCLs, proposed MCLs, health-
based standards, and North Carolina Groundwater Standards at any or
all of the monitoring points during implementation, the contingency
measures and levels, described in this section, may replace
the selected remedy and levels. Such contingency measures will,
at a minimum, prevent further migration of the plume and include a
combination of containment technologies (groundwater extraction and
treatment) and institutional controls. These measures are
considered to be protective of human health and the environment,
and are technically practicable under the corresponding
circumstances.
The selected remedy will include groundwater extraction for an
estimated period of 50 years, during which time the system's
performance will be carefully monitored on a regular basis and
adjusted as warranted by the performance data collected during
operation. Modifications may include any or all of the '
following:
a) at individual wells where clean-up standards have been
attained, pumping may be discontinued;
b) alternating pumping at wells to eliminate stagnation
points;
c) pulse pumping to allow aquifer equilibration and
encourage adsorbed contaminants to partition into
groundwater; and
d) installation of additional extraction wells to
facilitate or accelerate clean-up of the contaminant
plume.
To ensure that clean-up standards continue to be maintained,
the aquifer will be'monitored at those wells where pumping has
ceased on an occurrence of at least every 5 years following
discontinuation of groundwater extraction.
If it.is determined, on the basis of the preceeding criteria and
the system performance data, that certain portions of the aquifer
cannot be restored to their beneficial use, any or all of the
following measures involving long-term management may be
implemented for an indefinite period of time, as a modification of
the existing system:
89
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a) low level pumping would be implemented as a long-term
gradient control, or containment measure;
b) chemical-specific ARARs would be waived for the clean-up
of those portions of the aquifer based on the technical
impracticability of achieving further contaminant
reduction;
c) institutional controls would be provided/maintained to
restrict access to those portions of the aquifer which
remain above health-based standards;
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 performance evaluation (5 year review) of the
remedial action which will occur at least once every five years or
at the conclusion of remedial action under this ROD. Should EPA
decide that an ARAR waiver is appropriate, due to non-compliance
with an ARAR or ARARs as the result of technical impracticability
from an engineering perspective, it will notify and seek
concurrence from the State prior to granting such a waiver pursuant
to CERCLA Sections 121(d)(4) and (f)(2). Also, an Explanation of
Significant Differences would be issued to inform the public of the
details of these actions, should they occur.
9.8 Contingency Measures for Soils Remedial Action
A contingency ROD is appropriate when the performance of an
innovative treatment technology appears to be the most promising
option, but additional testing will be needed during remedial
design to verify the technology's performance capabilities; in this
case, a more "proven approach" is identified as a contingency
remedy.
Should implementation of the thermal desorption method prove
ineffective for remediation of soils, SC-3, off-site disposal, will
be implemented as the Agency's contingency alternative.
The criteria that EPA will use to decide to implement the
contingency alternative instead of the selected remedy are:
* Failure to meet remediation standards;
* Failure to meet TCLP requirements;
* Inadequate space for the LTTD unit and to safely treat the
excavated soils;
* Significant cost increase for thermal desorption which would
exceed the cost of off-site disposal.
90
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This alternative would involve the excavation and off-site disposal
of soils exceeding the remediation standards. Soils failing
toxicity characteristic leaching procedure (TCLP) test would be
considered hazardous by characteristic and have to be treated at an
off-site facility before disposed at a RCRA-permitted landfill.
Soils passing the TCLP would be sent directly to a RCRA-permitted
landfill. Composite samples would be collected from stockpiles and
analyzed by the TCLP. The entire stockpile would then be disposed
according to its composite TCLP analysis.
Confirmation sampling would be conducted to ensure that remediation
standards are attained. Excavated areas would then be covered with
clean fill and vegetated with a perennial grass.
The estimated cost for this estimate is $ 6,280,000. Table 16
shows a break-down of the costs associated with the contingency
plan for the contaminated soils.
91
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TABLE 16
COST FOR SOIL REMOVAL AND OFF-SITE DISPOSAL
CAPITOL COSTS
Project Plans
Erosion
Control
Mobilization
Residence
Relocation
Excavation and
Disposal
Excavation
Transportation
Disposal
Verification
Backfill
Regrade/Reseed
O&M COSTS
Labor
Equipment
Analytics
Expenses
SUBTOTAL
Engineering
(25 %)
Contingency
(25 %)
TOTAL
UNITS
1
300
1
1
10,100
13,130
13,130
100
13,130
4
16
1
30
2
COST PER UNIT
40,000
10
10, 000
10,000
10
30
250
350
10
1,500
40
500
350
150
-
COSTS ($)
40, 000
3, 000
10,000
10, 000
101,000
393,900
3,282,500
35, 000
131,130
6000
640
500
10,500
300
4,024,470
1,006,117
1,257,647
6,288,234
92
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10.0 SCOPE AND ROLE OF THE RESPONSE ACTION
The selected Remedy will address contaminated media at the site by
eliminating, to the extent practicable, the volume and migration of
contaminants present. This action will remediate all areas of
contamination at the site. EPA has identified the following
remedial action objectives for the cleanup of the Potter's Pits
site:
10.1 Contaminated Soil
Soils which pose a potential threat to groundwater will be
excavated and thermally treated. Surface soils which contain zinc,
lead and carcinogenic PAHs above the clean-up standards established
to protect human health via direct contact will also be excavated
and thermally treated.
10.2 Groundwat er
The groundwater remediation is proposed to protect public health
and the environment by controlling exposure to the contaminated
groundwater and controlling migration of the contamination through
groundwater pump and treat. Contaminated groundwater in the
surficial aquifer will be extracted for treatment until groundwater
is restored to drinking water quality. The groundwater usage will
be restricted in these areas until groundwater clean-up standards
have been achieved.
At this time it is assumed that the surficial aquifer is the only
aquifer that is contaminated. During the Remedial Design, some or
all of the monitoring wells (shallow and deep) will be resampled to
determine if the. contamination extends into the deeper aquifer.
Additional wells may be needed to better define the vertical extent
of contamination. At that time the decision will be made whether
groundwater in the deep aquifer has also been contaminated in which
case it may also need to be treated. The treatment of this deeper
aquifer would be the same as outlined in this ROD; only the system
itself may have to be modified. Additional extraction wells would
have to be placed in the deeper aquifer.
93
-------
11.0 STATUTORY DETERMINATIONS
EPA's primary responsibility at Superfund sites is to select
remedial actions that are protective of human health and the
environment. In addition, Section 121 of CERCLA establishes
several other statutory requirements, and preferences. These
specify that when complete, the selected remedy for this site must
comply with applicable or relevant and appropriate environmental
standards established under Federal and State environmental laws
unless a statutory waiver is justified. The selected remedy also
must be cost-effective and utilize permanent solutions and
alternative treatment technologies or resource recovery
technologies to the maximum extent practicable. Finally, the
statute includes a preference for remedies that employ treatment
that permanently and significantly reduce the volume, toxicity, or
mobility of hazardous wastes as their principal element. The
following sections discuss how the selected remedy for the Potter's
Pits site meets these statutory determinations.
11.1 Protection of Human Health and the Environment
The selected remedy will permanently treat the groundwater and soil
and remove or minimize the potential risk associated with the
wastes. Dermal, .ingestion, and inhalation contact with site
contaminants would be eliminated.
Potential short-term risks posed by the selected remedy or the
contingency remedy would increase potential for erosion of affected
materials by wind and rain during excavation and staging, would be
controlled by standard enginnering practices, such as dust control
and air monitoring. No unacceptable short-term risks or cross-
media impacts will be caused by implementation of the selected
remedy or the contingency remedy.
11.2 Compliance with Applicable or Relevant and Appropriate
Recruirements
The selected remedy will be in full compliance with all applicable
or relevant and appropriate chemical-, action-., and location-
specific reguiremnts (ARARs). A complete discussion of these ARARs
which are to be attained is included in Section 7.1 of the ROD.
This Section also describes the "To Be Considered" ARARs.
11.3 Cost-Effectiveness
Both the selected Remedy, GW-3 and SC-7, and the contingency
remedy for soil, SC-3, were chosen because they provided the best
balance among the criteria used to evaluate the alternatives
considered in the detailed analysis. These alternatives were found
to achieve both adequate protection of human health and the
environment and are cost-effective when compared to other
acceptable alternatives.
94
-------
11.4 Utilization of Permanent Solutions and Alternative Treatment
Technologies or Resource Recovery Technologies to the Maximum
Extent Practicable (MEET~
The selected remedy represents the. maximum extent to which
permanent solutions and treatment can be practicably utilized for
this action. Of the alternatives that are protective of human
health and the environment and comply with ARARs, EPA and the State
have determined that the selected remedy provides the best balance
of trade-offs in terms of long-term effectiveness and permanence;
reduction in toxicity, mobility, or volume achieved through
treatment; short-term effectiveness, implementability, and cost;
State and community acceptance, and the statutory preference for
treatment as a principal element.
11.5 Preference for Treatment as a Principal Element
The preference for treatment is satisfied by the use of thermal
desorption to remove contamination from the soil at the site and
the use of chemical and physical treatment of the contaminated
groundwater at the site. The principal threats at the site will be
mitigated by use of these treatment technologies.
95
-------
12.0 EXPLANATION OP SIGNIFICANT DIFFERENCES
CERCLA Section 117(b) requires an explanation of any significant
changes from the preferred alternative originally presented in the
Proposed Plan. Below are the specific changes made in the ROD as
well as the supporting rationale for making those changes. The
Proposed Plan was disseminated to the public on April 30, 1992.
Table 1 of the Proposed Plan, lists the maximum concentration
detected and the clean-up standard associated with each soil
contaminant of concern. Since issuance of the Proposed Plan,
carcinogenic PAHs was added to the list of soil contaminants that
will be cleaned up in the soil at the Potter's Pits site. Also the
contingency alternative for soil remediation was changed from
incineration to off-site disposal.
Carcinogenic PAHs was found in the risk assessment to have a risk
of 4.64E-04 which is within in EPA's acceptable risk range of E-04
to E-06. Since Potter's Pits is in a residential community where
people could potentially be on-site on a regular basis, it has been
decided to add this contaminant as a chemical of concern.
Therefore, this contaminant's clean-up standard will be applied to
surface soils as it is a risk generated clean-up standard based on
dermal contact.
The contingency alternative was changed from incineration as
described in the Proposed Plan to off-site disposal. Since both
alternatives achieved the same level of protection of human health
and the environment, then a cost comparison of these two
alternatives was done. The cost of incineration was estimated to
be $ 12,400,000 versus the cost of off-site disposal at $
6,280,000; therefore, off-site disposal is more economical.
Secondly, if the installation of the Low Temperature Thermal
Desorption Unit is not feasible due to limited space, then an
incineration unit would also have the same problem.
96
-------
APPENDIX I
-------
Table 1
voiatfto Orajanfeo (M/O
•anxana
Ethyl banxana
Toluana
Total «ylanea
Saari-Volatilaa 0la»ttiylpflanol
f luoranthana
Fluorona
2-Nathylnac*ithalana
NapMhalona
Ptionanthrano
Pyrano
Hatala <*•/(>
Alurinua
•arfua
OiroBfia (total)1
Iron
Load
Maanaatoa
Manganaaa
Nickal
potaaaiui
Sodlta
vanadiua
Zinc
NOTf :
1 Maaaurad .total diroaii* ia •
1
Arithmetic
702
560
5,805
5,442
7.
6.
28.
4.
6.
7.
57.
8.
4.
13,820
62
537
25.200
13
3.390
78
38
2,150
64.860
25
25
MUHd tO to IK
Ara
Pottar'a tapttc
Sandy Croak,
1,373
1,034
12,967
11.495
4.8
1.3
51.4
1.2
2.1
3.9
43.6
4.7
0.8
17,440.7
57.2
1,097.8
15,340
a
3,990.7
91.2
30.2
1,975.2
125,887
26.7
8.2
diraarftai VI and
• far •mrafcartar
a U
• Tank Uti Sita
ftortti Carolina
95X
4,512
3,431
41,800
37,352
21.1
9.7
170.7
7.9
12.3
18.6
178.4
21.4
6.9
62,235.4
220.3
3,585
67,785
34
14,468.1
331.6
121.4
7,633
41.4313
99.3
47.8
90S chroiftfi III.
Nlniaji
90
22
29,000
98
3
7
120
6
7
3
42
11
3.5
5,250
60
19
14,500
6
1.200
22
21.3
1,400
5,000
12
16
Mulaui
•
3.150
2,400
29,000
26,000
13
8
120
2.5
10
13
129
U
3.5
45,000
159
2.500
51,000
29
10,500
240
71
5,350
290,000
71
37
Frequency
4 /S
1 /5
4/5
3 /$
2 /S
1 /S
1 /J
2 /!
4 /S
4 /S
2 /S
1 /S
/S
/S
/S
/S
/S
/$
/S
/S
/S
/S
4 /5
5 /5
POOR QUALITY.
O^GINAL
-------
(M/O
Table 2
tmlstfct tar
11
Septic
tardy Creak, Bortft Carol I rw
of Ovttet-on
CMorobvu
Ethyl bmst
7.5
3.3
4
2.1
1.1
3.3
34.5
16.7
48.4
6
4
1
9
4
1
2 /2
1 /2
1 /2
Nttats
AtMfflUi
•ariui
Chra.ii.1
Iron
Nagnasiui
Mn^ntM
'OtU.ivJi
Sodiu*
V«Wd
-------
Table 3
f«ti«
Surfaea Uatar Cancantrat<4
• Saptfe Tank Ht« Sfta
Craak, Berth Carolina
; , "
volatile ortaniea (M/O
•aruana
Ratal* {*•/«>
Alualnui
laHui ,
Chrojriua '
Laad
Manaanaae
Niekal
Zinc
•••"
3.4
2.865
35
14.1
2.3
85
50.8
8.6
DfJviflYffwi
^™^"™™**™"""Ol«^^^B™»™
1.8
2,790.1
11.7
7.5
1.9
64.2
50.3
5.7
£1
9.1
11,743.2
71.8
38
8.1
289.1
210.9
26.6
Dataetad '
2
700
32
IS
5
39
56
13
6
6,600
43
21
5
180
120
14
tr99MKV .
of OBttetion
3 /4
4 /4
374
3 /4
1 /4
4 /4
2 /4
2 /4
Ollutlan
MX UTI
Actual Surfaca
Wat*p Data H*M
Volatlla Organf
0.84
2.27
1.5
Natala
AluainuB
•arfua .
Chroaiu* '
Laad
Hanaanaaa
Miekal
Zinc
716.3
8.6
3.5
0.6
21.3
12.7
2.2
2935.8
18
9.5
2
72.3
32.7
6.7
1,650
11.3
5J
1.3
45
30
4
283.8
<30
«7
<0.5
15.8
«27
<20.
•OTIS:
1 Maad-on arwlytleal raaulta far NU-iea. N»>106. ia>206. and W-207
2 ratal ehroBlui
-------
Table 4
•••II ftMffttiOB f» aaattoa*1
•otttr't |«pt
Aluriraa
OiroBiia
Iron
(.tad
Nagnniua
Manoarm*
vanodlua
Zfne
tanoy Crook, I
^ntha»t«e Standard
'.»" 310.9
1.78 0.6
1,682.3 860.9
1.09 0.6
32.6 6.9
0 1.9
1.5 0.6
4.35 1.5
lortfc Carolina
95X H1n9>a^«>aM<
2,339.3 1,000
3.5 2.6
4.422 880
3 1.1
54.7 23
10 3
3.3 1
9 2.9
p«= Fr^^^y
"tT*6*^ 9* 0«t^eti(yi
1.7W 4 /4
2.* 1 /4
2,800 4 /4
1.9 3 /4
39 4 ik
7 4/4
2 \ /4
5.9 4 /«
NOTEt
froa »-1 Mtr* not Inel
in
try ttatUtle* M thU MM th*
1-4
-------
Table 5
•unary ttatlatfca far ftrfm Oof lo
(0 ta 3-foot etao**)
Aroo U
Potter'e Septic Tank Pita So(a)anthracano
•enio
-------
Table 6
ttttlatfca far
(• t» 3-taat 4
II
toils
>ottar«t l«ptic Tank aftt «Ha
Craak, Berth Caroline
Volatile
lanzana
Carbon otsulfida
Ethylbansana
a- and/or p-Xylana
o*Xylana
Tolgana
Total xylanat
Posticidaa (M/ka>
4,4>>000
4,4'-OOT
Alpha cMordana
OUldHn
Saaiwolatllaa (M/ka)
AcanaphtMna
Anthraeana
Fluorano
Napfcthalana
Wtanar.thrtna
Wianol
Haula
-------
Table 7
StMry ttttfatiaB far ftrfw l*Us
Faraat/UatlanJ Araa
•ottar't Saptie Tank »1ts Sita
Sandy Craak, north Carolina
f "
volatile onanfca
Aeatona
Styrana
Total xylanas
Saarivoiatilas (n/kf>
8amo(a)pyrana
8U(2*athylhaxyl)phthalata
Naxaeti I erobanaana
I^*A| m tmmi^ft\
•atajia us/Kg)
Aliflrinui
Arsanic
•ariui
Calcic* ,
Chroaiiua1
Cobalt
Cappar
Cyanlda
Iron
laad
Hafnaalua
Manganaaa
Mareury
Salanl«ja
Vanadiua
Zinc
Aritlwatlc
164.86
4.23
15.59
457.05
1,332.73
.520.45
7,481.82
0.93
32.38
1,961.14
8.82
2.52
4.76
0.9
9.781.82
20.65
178.82
18.63
0.80
0.99
13.93
15.02
Standard
0«vi*t
-------
Table 8
volatile Or*entca
Acetone
lenxono
Ethyl benzene
Toluene
Total xylenea
Poatlcldaa (M/ka)
Otaldrln
Seal •voloti lee Ow/ka)
Acaneph thane
Anthracene
•enso
AlMlrui
Araenic
ftarluB
•erylKuB
Calciua
Oiroalua'
Cobalt
ft*
4,209.58
2,973.96
14,809.21
14.540.46
136,432.3
14.17
4,464.58
2,082.50
1.910.83
2.343.50
,350.83
,947.50
,004.17
,953.75
.567.75
,446.42
4,994.58
8,233.79
10.676.58
3.137.90
5.425
1.12
11.13
3.4
2.034.17
9.43
1.43
•ry Statistic* 1
Arei
Potter's Septic
Sandy Creek, •
5,746.6
4,143.56
27.218.79
2,575.43
222,334
5.5
10,650.15
3,800.29
3,281.36
4,213.09
4,210.83
4,417.3
3,437.93
9,000.09
14,290.37
7,670.25
8,941.97
15,396.94
31,413.2
6,603.14
5,78*
1.9
15.79
10.28
4,799.44
8.41
1.9
tar 8*Mrf«Pt 8»
I U
Tank Pita Site
lorth Carolina
16,857.86
12,093.94
74,717.7*
71,492.27
625.789.3
26.26
27.909.97
10,446.94
9,133.1
11,620.91
11.618.88
12,669.98
9,571.04
23,7*2.99
37,020.89
20.328.63
2.4*7.89
42.122.41
79.820.03
17.471 .81
18.3*7
5.31
49.7f
24.03
12,588.97
28.13
4.93
I la
D«t«ct«d
2,000
37
1
120
1
12
110
330
170
62
150
7.600
190
170
98
62
150
410
180
690
330
7.1
1.9
0.12
2*0
1.8
3.2
P«t«et«d
2.500
7,000
84,000
81,000
580,000
12
370,000
9.980
4.700
42
190
7,400
7.800
31,000
50,000
26,000
28,000
50.000
110,000
22.000
19,000
7.1
a
3*
17,000
21
5.5
"••quaney
2 /i:
* /12
8 /12
5 /12
12/12
1 /12
3 /12
3 /12
2 /12
1 /12
1 /12
1 /12
2 /12
3 /12
3 /12
5 /12
6 /12
6 /12
4 /12
3 /12
12/12
1 /12
5 /12
2 /12
6 /12
10/12
2 /12
1-8
POOR QUALITY
ORIGINAL
-------
Table 9
ttnlstia tor
u
toll*
Soptlc T«rk Pits Sitt
tandy Crook, north Carol Im
ft
— ~ AMttoWti
le Standard 95k
a*vlat
-------
Table 10
ile
VolatfU
Mnsant
ethyl bwiuana
Methyl Uoeutyl katona
Toluana
wr and/or p-Xylane
o- Xylan*
Total xylanaa
Natlcidaa
Endrln katon*
NathoxycMor
aa UaVka)
2-Ncthylnaphtfulana
Naphthalana
Nataia
Attain*
Mriui
Calcfua
(ran
Htekal
•front fin
Tltanitai
Zinc
NOT!:
1 Total cnroaiiai
674.99
1,103.11
4,517.77
1.670.U
2.224.94
U1.41
U,423.33
27
81.28
371.67
Stt.67
327.67
3.329.44
7.14
421.67
5.18
2,545
3.99
T24.22
6.33
2.69
0.88
23.75
7.17
3.7S
•ry Statlcttes
An
far 8*awf**
• 11
•all*
ratttf' • soptle T«* MM Ifto
S*no> CrMk,
Standard
D*vi«t;fijn
1.773.19
2.155
17,810.60
3,360.03
6,665.63
1,315.67
28,814.66
33.96
73.08
233.66
602.31
259.36
3.167.53
11
835.97
4.27
2.615.04
4.26
199.14
12.28
2.09
0.53
18.03
6.69
3.48
north Carolina
9SX
UCL
4.763.87
6,072.55
47,388.98
9,418.68
17,595.94
3,475.35
80.869.93
105.3
249.8
915.11
1.975.59
925.82
10,633.78
32.51
2.349.41
15.04
8,575.26
13.82
583.43
34.65
7.32
7.61
254.85
29.52
11.76
H(n<«ja
0*t*ctad
12
33
2.800
3
20,000
3,950
5
100
270
515
1,500
69
620
1
240
1.2
380
2.9
24
1.8
8
1.3
9.33
NajHaua
Ottaet^
37
5,700
2.800
9,300
20, 000
3,950
75,000
100
270
750
1.700
69
8.600
36
2.600
13
6.900
IS
^ia
^^v
36
32
9.55
2 /9
* /9
1 /9
* /9
1 /2
1 /2
6 /9
/9
/9
2 /9
2 /9
1 /9
9/9
7/9
/9
/9
/9
/9
/9
/9
1 /9
1 /2
2 /2
8 /8
1 /9
to
M VI and 90S
« MI.
1-10
-------
votatll* organi
Table 11
Ictlaa tar
Afr
• Septic T«* Mt« site
Creak, north CarolIn*
95*
UCL
Chloreaathane
N«thyl«na chlorfdt
1.1,1*TrU-03 net include In •titicticat
•t ttiU
r«pr«Mnt« background.
i-n
-------
APPENDIX II
-------
Table 1
Dermal, Ingestion, and Inhalation Exposure to Groundwater
Exposure Parameters
Pouer's Septic Tank Pits Site
Sandy Creek, North Carolina
Age
Average Body Weight
Average Surface Area Exposed (washing)
Average Surface Area Exposed (showering)
Incidental Ingestion from Washing
Ingestion as Drinking Water
Inhalation Rale
Frequency of Event
Duration of Event (washing)
Duration of Event (showering)
Duration of Exposure
Adult
70 kg
2,300 cm' '•'•
18,200 cm' '
0 t
2 f/day
1.3 mj/hr
365 cvcnls/year
2 hours
0.2 hours
30 years'""
NOTES:
EPA (19890)
1. Hands and Forearms, Adult
2. Total body surface
3. EPA, (1989a)
II-l
-------
Table 2
Ingestion of Produce Exposure
Exposure Parameters
Potter's Septic Tank Pits Site
Sandy Creek, North Carolina
Age
Average Body Weight
Ingestion Rate, Rool & Leafy Crops
Other Crops
Fraction Homegrown, Root & Leafy Crops
Other Crops
Exposure Frequency
Exposure Duration
Body Weight
Lite Expectancy
Adult
70 kg
11.9 g, dry wt/day '
198.1 g, dry wi/day '
40.5 percent '
32.9 percent '
,V>5 days/year
30 years *'
70 kg
75 vears
NOTES:
1. EPA. 1990.
2. EPA. 1989a.
II-2
-------
Table 3
Ingestion and Dermal Exposure to Surface Water and Sediment
Exposure Parameters
Potter's Septic Tank Pits Site
Sandy Creek, North Carolina
Age
Average Body Weight
Average Surface Area Exposed
Soil Contacted
Incidental Ingestion of Sediment
Incidental Ingestion of Water
Frequency of Events
Duration of Event
Total Exposure Duration
6-1.5 years
37 kg
6,500 cm':
1.5 mg/cm2
100 mg/cvenl
1.0 mfl/icveni
72 events/yearl
2 hours
V vcurs
NOTES:
Reference: EPA, 1989 a.b.
1. Arithmetic mean of amis, hands, legs and feet of child resident.
2. Assumes two visits per week to Chinnis Branch for the nine months of mild weather.
II-3
-------
Age
Average Body Weight
Consumption Rate
Percent Contribution from Site
Frequency of Exposure
Exposure Duration
NOTE:
Reference: U.S. tPA.
Table 4
(ngestion of Fish
Exposure Parameters
Potter's Septic Tank Pits Site
Sandy Creek, North Carolina
II-4
-------
Table 5
Ingestion and Dermal Exposure to Soils
Exposure Parameters
Potter's Septic Tank Pits Site
Sandy Creek, North Carolina
Age
Average Body Weight
Average Surface Area'
Soil Contacted
Incidental Ingestion
Frequency of Exposure^
Surface soils
Current Residence
Future Residence
Forest
Soils < 3' deep
Soils > 3' deep
Total Exposure Duration3
Res
1-75
70
3,000
1.5
IUO
260
2(.0
50
5
s
.V)
jdent
years
kg
an'
mg/cm'
mg/cvcnl
uvenis/yr
sjvenls/yr
cvcnts/yr
events/yr
events/yr
yrs
ScDtic Svstem Installer
Adult
70 kg
4,000 cnr'
1.5 mg/cm'
100 mg/cvcni
-
-
-
5 yrs
NOTES:
References: fe&CPA 1989 b. Kxposurc Haoiors Handbook.
I. Arithmetic mean usei* lor: Resident men s and v^onicn s arms >inJ X^^ ^>.piiv. Svsiciu In.siallci men N locuarius. hjnvJ.s aiiO ln^cr Ic^s
> Nine months per year ol mild weather in uasiurn North C.juiim.j .^ .IX>LHMCU I he .inihnitik mean «l ouiJtH>r cIcuniK^ nnic is
assumed to involve MJI! work at less than .Vloot di:pih.
3. Length of residence is an upper bounJ esluuale Septic System |MNI.H!CI cvp».Miic ,I.>SUIIK-N that ihc sumc worker annu.ilK msi.ills .1
system in .Area 1A and Area IB.
II-5
POOR Q
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Table 6
Inhalation of Indoor Air
Exposure Parameters
Potter's Septic Tank Pits Sile
Sandy Creek, North Carolina
Age
Average Body Weight
Inhalation Rate
Exposure Time
Frequency of Exposure
Exposure Duration
NOTt
References: L'rS. KI'A. rJS'Ai.
II-6
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APPENDIX III
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State of North Carolina
Department of Environment, Health, and Natural Resources
Division of Solid Waste Management
P.O. Box 27687 • Raleigh, North Carolina 27611-7687
James G. Martin, Governor William L. Meyer
William W. Cobey, Jr., Secretary . Director
July 29, 1992
Mr. Greer C. Tidwell
Regional Administrator
US EPA Region IV
345 Courtland Street, NE
Atlanta, GA 30365
Subject: Conditional Concurrence with the Record of Decision
Potters Septic Tank Service Pits
Maco, Brunswick County, NC
Dear Mr. Tidwell:
The State of North Carolina has completed review of the attached Record of
Decision and concurs with the selected remedy subject to the following conditions.
1. All surface and subsurface soils must achieve cleanup levels based on not
exceeding a collective excess carcinogenic risk of 1 x 10"6 or a Hazard Index
of 1. If, after remediation is complete, the total residual risk level exceeds
1 x 10"6, the site will require deed recordation/restriction to document the
presence of residual contamination and possibly limit the future use of the
property as specified in NCGS 130A-310.8.
2. State concurrence on this Record of Decision and the selected remedy for the
site is based solely on the information contained in the Record of Decision.
Should the State receive new or additional information which significantly
affects the conclusions or remedy selection contained in the Record of
Decision, it may modify or withdraw this concurrence with written notice to
EPA Region IV.
An equal Opportunity Affirmatj*.^ >rt:or Cmptcy*
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Mr. Greer Tidwell
7-29-92
Page 2
3. State concurrence on this Record of Decision in no way binds the State to
concur in future decisions or commits the State to participate, financially or
otherwise, in the clean up of the site. The State reserves the right to review,
comment, and make independent assessment of all future work relating to this
site.
4. A proposal of cleanup levels from groundwater should not exceed the North
Carolina NCAC Title ISA Subchapter 2L groundwater standards unless a
variance is obtained from the Division of Environmental Management. You
may direct your requests for a variance to Mr. Preston Howard, Director,
Division of Environmental Management, PO Box 27687, Raleigh, NC 27611.
I have spoken with Bill Jeter with the Division of Environmental Management
regarding using the MCL instead of the 2L groundwater standard for
ethylbenzene. Mr. Jeter felt that there would not likely be a problem in
receiving a variance from the ethylbenzene standard because the standard is
based on taste.
The State of North Carolina appreciates the opportunity to comment on the Revised
Draft Record of Decision for the subject site, and we look forward to working with EPA on
the final remedy.
Sincerely,
Charlotte Jesneck, Head
Inactive Hazardous Sites Branch
NC Superfund Section
cc: Michael Kelly
Curt Fehn
Darcy Duin
Attachment
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION IV
345 COURTLANO STREET. N.E.
ATLANTA. GEORGIA 3O36S
4WD-NSRB
July 30, 1992
Charlotte Jesneck
North Carolina Department of Environment,
Health, and Natural Resources
401 Oberlin Road, Suite ISO
Raleigh, North Carolina 27605
RE: Response to Conditions Included in North Carolina's
Conditional Concurrence for the Potter's Septic Tank
Pits Superfund Site Record of Decision
Dear Ms. Jesneck:
EPA-Region IV appreciates the State's conditional concurrence on
the Record of Decision (ROD) for the Potter's Septic Tank Service
Pits Superfund site located in Sandy Creek, North Carolina. For
the record, EPA would like to respond to the conditions formulated
by North Carolina Department of Environment, Health and Natural
Resources (NCDEHNR) - Superfund Section and specified in your
July 29, 1992 correspondence to Mr. Greer Tidwell. Your July 29,
1992 letter, along with this response, will be included in Appendix
I of the ROD. These letters should stand as official documentation
that EPA-Region IV and NCDEHNR-Superfund Section have agreed on the
preferred alternatives at this point in time.
Of the four conditions expressed, only the first condition requires
a response from the Agency. In response to NCDEHNR-Superfund
Section first condition, the State may in the future put in place,
pursuant to State law (G.S. 130A-310.8), a deed recordation /
restriction to document the presence of residual contamination
which may limit the future use of the property. As stated, this
would be done after 'the completion of the site's remediation.
Please contact me at (404) 347-7791 if you have any questions or
comments regarding this matter.
rely,
Darcy
Remedial Project Manager
cc: Curt Fehn, EPA
Printed on
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