PB98-964027
EPA541-R98-114
March 1999
EPA Superfund
Record of Decision:
Savannah River Site (USDOE)
D-Area Oil Seepage Basin (631-G)
Aiken, SC
8/14/1998
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"United States Department of Energy
Savannah River Site
Record of Decision
Remedial Alternative Selection
for the
D-Area Oil Seepage Basin (631-G) (U)
WSRC-RP-97-402
Revision 1, Final
August 1998
*V/estinghouse Savannah River Company
tannah River Site
en, South Carolina 29808
SAVANNAH R ! V £ r
SPARED FOR THE U.S. DEPARTMENT OF ENERGY UNDER CONTRACT DE-AC09-96-SR18500
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION 4
ATLANTA FEDERAL CENTER
61 FORSYTH STREET. SW
ATLANTA. GEORGIA 30303-8909
AUO 1 4 1998
CERTIFIED MAIL
RETURN RECEIPT REQUESTED
4WD-FFB
Mr. Brian T. Hennessey, FFA Project Manager
Environmental Restoration Division
SRS Project Manager
U.S. Department of Energy
Savannah River Operations Office
P.O. Box A
Aiken, South Carolina 29802
SUBJ: Record of Decision
Remedial Alternative Selection for the
D-Area Oil Seepage Basin ,
Rev. 1 (WSRC-RP-97-402), dated August 1998
Dear Mr. Hennessey:
The Environmental Protection Agency (EPA) has completed its review of the subject document and has
no additional comments. Accordingly, this letter provides EPA approval of the Rev. 1 Record of
Decision for the D-Area Oil Seepage Basin operable unit.
If you have any questions regarding this matter, please contact me at (404) 562-8547.
Sincerely,
Julie L. Corkran, RPM
DOE Remedial Section
Federal Facilities Branch
Waste Management Division
cc: Keith Collinsworth, SCDHEC
Ben Gould, DOE-SRS
Sandra Carrol, ERD-WSRC (Signed Original)
R*cycl*d/R*cyct*bl« • Printed with Vegetable Oil Based Inks on 100% Recycled Paper (40% Posloonsumer)
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be: Julie Corkran, FFB
Peter Raack, HAD
jlc/JCORKRAN/4WD-FFB:28547/08-13-98/c:\...\rodapprvl
CORKRAN CRANE .WAF
RAACK
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United States Department of Energy
Savannah River Site
Record of Decision
Remedial Alternative Selection for the
D-Area Oil Seepage Basin (631-G) (U)
WSRC-RP-97-402
Revision 1, Final
August 1998
Westinghouse Savannah River Company
Savannah River Site
Aiken. SC 29808
Prepared for tn« U. S. Department of Energy under Contract No. O£-AC09-96SFM 8500
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Record of Decision for the
D-Area Oil Seepage Basin (6J1-G) (U)
Savannah River Site
WSRC-RP-97-402
Revision 1. Final
Aurust 1998
DISCLAIMER
This report was prepared by Westinghouse Savannah River Company
(WSRC) for the United States Department of Energy under Contract No.
DE-AC09-96SR18500 and is an account of work performed under that
contract. Reference herein to any specific commercial product, process, or
services by trademark, name, manufacturer or otherwise does not
necessarily constitute or imply endorsement, recommendation, or favoring
of same by WSRC or by the United States Government or any agency
thereof.
Printed in the United States of America
Prepared for
U. S. Department of Energy
By
Westinghouse Savannah River Company
Aiken. South Carolina
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RECORD OF DECISION
REMEDIAL ALTERNATIVE SELECTION (U)
D-Area Oil Seepage Basin (631-G)
WSRC-RP-97-402
Revision 1, Final
August 1998
Savannah River Site
Aiken, South Carolina
Prepared by:
Wesiinghouse Savannah River Company
for the
U. S. Department of Energy Under Contract DE-AC09-96SR18500
Savannah River Operations Office
Aiken, South Carolina
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Record of Decision for the \VSRC-RP-9T-40:
D-Area Oil Seepage Basin (6J1-G) (L") Revision 1. Final
Savannah River Site . August 1998
DECLARATION FOR THE RECORD OF DECISION
Unit .\'ame and Location
D-.Area Oil Seepage Basin (Building Number 631-G)
Savannah River Site
Aiken. South Carolina
The D-Area Oil Seepage Basin (D-Area OSB) Operable Unit (OU) is listed as a Resource Conservation and
Recovery Act (RCRA) 3004(u) Solid Waste Management Unit/Comprehensive Environmental Response.
Compensation, and Liability Act (CERCLA) unit in Appendix C of the Federal Facility Agreement (FFA) for the
Savannah River Site (SRS).
Statement of Basis and Purpose
This decision document presents the selected remedial alternative for the D-Area OSB located at SRS south of
Aiken. South Carolina. The selected alternative was developed in accordance with CERCLA, as amended, RCRA.
and to the extent practicable, the National Oil and Hazardous Substances Contingency Plan (NCP). This decision :s
based on the Administrative Record File for this specific RCRA/CERCLA unit.
Assessment of the Site
Actual or threatened releases of hazardous substances from this site, if not addressed by implementing the respond
action selected in this Record of Decision (ROD), may present an imminent and substantial endangermem to pubi:-
health, welfare, or the environment.
Description of the Selected Remedy
Since remedial action objectives (RAOs) for deep soils have been achieved by the interim remedial action (IRA) ar.J
biovent testing. No Further Action is the selected remedy for this medium (WSRC, 1997b, c, d. and e). No Action .i
the selected remedy for shallow soil, surface water and sediment, because no constituents of concern (COCs) -Acre
identified for them in the RCRA Facility Investigation/ Remedial Investigation/ Baseline Risk Assessment
(RFI/RI/BRA). For these reasons, development of remedial alternatives for these media is not warranted.
Declaration • 1
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Record of Decision for the WSRC-RP-97-J02
D-Area Oil Seepage Basin (631-G) (LI Revision 1. Final
Savannah Rjver Site _ August 1998
The selected remedy for D-Area OSB groundwater is Alternative GW-2: Natural Attenuation/Groundwater Mix:r.-2
Zone (GWMZ) -with Institutional Controls. Under this remedy, natural attenuation mechanisms such as
biodegradation. flushing, volatilization, adsorption, and hydrolysis would continue to reduce contaminant
concentrations in the groundwater to acceptable levels. Results from a bioventing study, conducted after the IRA at
the unit, indicate that the source of groundwater contamination (i.e., the D-Area OSB soil) was abated as a result of
the combined IRA and biovent test and no longer contributes to groundwater contamination. Evidence indicating
that natural attenuation processes are occurring in the D-Area OSB groundwater was presented in the RFI/RI/BRA
Report CWSRC. I997a) for the unit. This evidence included: (1) decreased dissolved oxygen levels in the
ground water, indicating that microorganisms are utilizing the contaminants as a carbon source and the oxygen within
the groundwater to produce energy, (2) elevated chemicaJ oxygen demand, chloride, and sulfate levels downgradiem.
(3) depressed pH levels in contaminated areas, and (4) presence of breakdown products.
Herbert et al., 1984, report that natural attenuation is selected as a preferred remedial option when the following site-
specific conditions exist:
Groundwater is unsuitable for consumptive use.
• Contaminants degrade quickly or are not at highly toxic concentrations.
• There is low potential for exposure.
• Active restoration is not feasible due to complex hydrogeologic conditions.
• There is low projected demand for future groundwater use.
• The unit is in close proximity to a surface water discharge area, with dilution to levels that are protective of
human health and the environment.
Based on the information presented in the RFI/RI/BRA report for the D-Area OSB, the conditions at the D-Area
OSB would be conducive to natural attenuation. Specific findings from that report include:
• The source of contamination at the D-Area OSB was removed during the IRA in conjunction with the bio^eni
testing and is no longer contributing to groundwater contamination.
• Naturally occurring mechanisms will continue to reduce contaminant concentrations.
• There are no receptors of groundwater at the D-Area OSB; therefore, the potential for exposure is low.
• The aquifer is limited in thickness and yield and the groundwater it contains is not targeted for residential or
commercial use; therefore, projected demand for future groundwater use is low.
• Modeling indicates that contaminant concentrations in the D-Area OSB groundwater would be reduced to below
maximum contaminant levels (MCLs) prior to reaching Fourmile Branch; therefore dilution in the surface water
body is not necessary to achieve MCLs.
Declaration - 2
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Record of Decision for the WSRC-RP-97-402
D-Area Oil Seepage Basin (6J1-G) (TO Revision 1. Final
Savannah River Site __^_^ . August 1998
The time required to degrade the unit-specific contaminants was conservatively estimated through grour.dwaier
modeling. The modeling indicates that all contaminant concentrations in groundwater would be reduced below their
respective MCLs within approximately 10 years, which is well within the time-frame that the U.S. Department of
Energy (DOE) plans to maintain control of the SRS.
A GWMZ application, defined under South Carolina Regulations R.61-68. has been approved by the SCDHEC as
pan of this alternative. Based on area characteristics and evidence presented in the GWMZ Application vWSRC.
1998c). a GWMZ variance for the D-Area OSB is an appropriate pan of natural attenuation remedies.
Mixing zones are appropriate for situations where the source of groundwater contamination has been removed and
where contaminant concentrations are being reduced by natural processes. Under these regulations, certajn
concentration limits above MCLs. known as mixing zone concentration limits (MZCLs), will be established within
the designated mixing zone, where the plume will migrate while it dissipates. MCLs. which are protective limits for
drinking water, will be established at the compliance boundary downgradient of the plume. Plume monitoring wells
will be installed within the plume and at the compliance boundary, and would be sampled periodically to monitor
compliance with permitted MCLs and MZCLs. Intermediate wells will be installed at other locations within the
mixing zone to monitor plume behavior between the plume wells and compliance boundary wells as an early warning
mechanism if plume behavior does not match predictions.
The mixing zone application has demonstrated that RAOs will be met, MZCLs will be achieved throughout the
groundwater aquifer, and MCLs will be achieved at the compliance boundary as described in the approved GWMZ
application. Implementation of this alternative will involve installation of nine new wells and monitoring of a total
of 12 groundwater wells, as described in the GWMZ application.
The D-Area OSB is in an industrial use zone, as identified in Figure 3.3 of the SRS FFA Implementation Plan
(WSRC, 1996e), for both current and anticipated future land use. Although the remediation decisions for this unit
were based on the industrial use scenario, the groundwater remedy will achieve the more protective residential use
scenario. The D-Area OSB currently meets unrestricted land use criteria for soils, sediment and surface water.
Groundwater beneath the unit exceeds the MCLs. Although institutional controls are included in all of the
alternatives (except the no-action alternative), the DOE has recommended that residential use of SRS land in the
vicinity of D Area be prohibited (DOE. 1996); therefore, future residential use and potential residential water usage
in this area is unlikely. Modeling of groundwater transport processes as pan of the evaluation of the remedial
alternatives indicates that MCLs for the contaminants of concern will be achieved in all areas of the D-Area OSB
groundwater after approximately 10 years. Upon confirmation that MCLs have been achieved, institutional controls
at the unit will no longer be required.
Declaration - 3
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Record of Decision for the \VSRC-RP-97-40:
D-Area Oil Seepage Basin (631-G) (L~) Revision ). Final
Savannah River Site August 1998
Per the EPA Region-FV Land Use Controls (LUCs) Policy, a LUC Assurance Plan (LL'CAP) for SRS and a LUC
Implementation P4an (LUCIP) for the D-Area OSB will be developed and submitted to the regulators tor appro'-a!.
The LL'CAP will be submitted under separate cover, whereas the LUCIP will be submitted with the Remedial Design
Work Plan/Remedial Design Report/Remedial Action Work Plan (RDWP/RDR/RAWP) in accordance with the posi-
ROD document schedule provided in Figure IS. The LUCIP details how SRS will implement, maintain, and monitor
the land use control elements of the D-Area OSB ROD to insure that the remedy remains protective of human health.
The LUC objective necessary to ensure the protectiveness of the preferred alternative is:
• Prevent unauthorized access to the D-Area OSB contaminated groundwater plume.
The institutional controls required to prevent unauthorized exposure to the contaminated media at the D-Area OSB
include the following:
• controlled access to the D-Area OSB through existing SRS security gates and perimeter fences and the sue
use/site clearance programs
signs posted in the area to indicate that groundwater in the vicinity of the unit has been contaminated by
hazardous materials
• notification of groundwater contamination to any future landowner through deed notification, as required under
CERCLA Section 120(h)
A certified survey plat of the site will be prepared by a registered land surveyor and will be included with the post-
ROD documents. If D-Area OSB is transferred to non-FederaJ ownership prior to remediation of the groundwater to
the MCLs for the COCs, reevaluation of the need for deed restncuons would be performed through an amended
ROD with Environmental Protection Agency (EPA) and South Carolina Department of Health (SCDHEC) approval
The survey plat will be reviewed and updated, as necessary, at the time the site is transferred and will be recorded
with the appropriate county recording agency. The D-Area OSB is located in Aiken County.
This selected remedy is intended to be the final action for the D-Area OSB. and is intended to be permanent and
effective in both the long and short terms. This remedy is considered to be the least cost option that is still protective
of human health and the environment. The state regulatory authority, the SCDHEC, will modify the SRS RCRA
permit to incorporate the selected remedy.
The Rev. 0 of the post-ROD document, the combined RDWP/RDR/RAWP. will be submitted to the U.S. EPA and
SCDHEC within approximately ISO calendar days after the issuance of the ROD. The RDWP/RDR/RAWP will
Declaration - •
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Record of Decision for the WSRC-RP-97-402
D-Area Oil Seepage Basin (631-G) CL~) Revision I, Final
Savannah River Site August 1998
contain a conceptual Corrective Action Plan Strategy, a summary description of the scope of work for the remedial
action design, an implementation/ submJttai schedule for subsequent post-ROD documents, and an anticipated field
activities start date. The regulatory review period. SRS revision period, and final regulatory review and approval
period will be 90. 60. and 30 calendar days, respectively.
Statutory Determinations
Based on the D-Area OSB RFI/RJ Report and BRA fWSRC. I997a.i, D-Area OSB groundwater poses no significant
n>k to the environment but poses significant risk to human health. Therefore, monitoring of the existing
groundwater constituents, consistent with the GWMZ application, is necessary.
The selected remedy is protective of human health and the environment, complies with federal and state
requirements that are legally applicable or relevant and appropriate to the remedial action, and is cost-effective. This
remedy utilizes permanent solutions and alternative treatment (or resource recovery) technology to the maximum
extent practicable and satisfies the statutory preference for remedies that employ treatment to reduce toxicity.
mobility, or volume as a principal element. Section 300.430(f)(4)(ii) of the NCP requires that a five-year review of
the ROD be performed if hazardous substances, pollutants, or contaminants remain at the waste unit. Since
hazardous substances will remain at the unit above health-based standards during the remediation time frame
indicated in the groundwater mixing zone application (approximately 10 years), the three FFA Parties below have
determined that a five-year review of the ROD for the D-Area OSB will be performed to ensure continued protection
of human health and the environment until the MCLs are attained in the sroundwater.
Date T. F. Heenan: Assistant Manager for Environmental Quality
U. S. Department of Energy, Savannah River Operations Office
Date Richard D. Green; Division Director
Waste Management Division
U. S. Environmental Protection Agency - Region IV
Date R. Lewis Shaw; Deputy Commissioner
Environmental Quality Control
South Carolina Department of Health and Environmental Control
Declaration - 5
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DECISION SUMMARY
REMEDIAL ALTERNATIVE SELECTION (U)
D-Area Oil Seepage Basin (631-G)
WSRC.RP-97-402
Revision 1, Final
August 1998
Savannah River Site
Alken, South Carolina
Prepared by:
Westinghouse Savannah River Company
for the
U. S. Department of Energy Under Contract DE-AC09-96SR18500
Savannah River Operations Office
Aiken. South Carolina
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Record of Decision for the WSRC-RP.9"-40:
D-Area Oil Seepage Basin (631-G) ft") Revision I. Final
Savannah River Site August 1998
— DECISION SUMMARY TABLE OF CONTENTS
Section Page
I. Savannah River Site (SRS) and Operable Unit (OU) Name. Location. Description, and Process History I
II. Site and OU Compliance History 1 I
III. Highlights of Community Participation 12
IV. Scope and Role of the OU Within the Site Strategy U
V. OU Characteristics 26
VI. Summary of OU Risks 4"
VII. RAOs and Description of Considered Alternatives for the D-Area OSB OU 6"
VIII. Summary of Comparative Analysis of the Alternatives ~9
IX. The Selected Remedy 3?
X. Statutory Determinations 92
XI. Explanation of Significant Changes 92
XII. Responsiveness Summary 92
XJH. Post-ROD Document Schedule 9}
XTV. References 9"
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Record of Decision for the
D-Area Oil Seepage Basin T631-G) (IT)
Savannah River Site
WSRC.RP-97.402
Revision 1. Final
August 1998
List of Figures
Figure I: Location of the D-Arca OSB at the SRS 3
Figure 2: Topography of the .Area Surrounding the D-Area 053 5
Figure 3: Site Plan of the D-Area OSB ~
Figure 4: Current Photograph of the D-Area OSB (May 1993, 9
Figure 5: RCRA/CERCLA Logic and Documentation \5
Figure 6: Response Action Selection Process 23
Figure 7a: CSM for the D-Area OSB 29
Showing Potential Human Receptors and Exposure Pathways
Figure 7b: CSM for the D-Area OSB 31
Showing Potential Ecological Receptors and Exposure Pathways
Figure 8: TCE in the Shallow Portion of the Water Table Aquifer 37
Figure 9: TCE in the Deeper Portion of the Water Table Aquifer 39
Figure 10: Cross Section of TCE in Groundwater J1
Figure 11: Master Legend for Maps and Cross Sections 43
Figure 12: Risk-based COCs for the Current On-Unit Worker, by Pathway 57
after the Uncertainty Analysis
Figure 13: Risk-based COCs for the Future On-Unit Worker, without 59
Excavation of Soils, by Pathway, after the L'ncertainry Analysis
Figure 14: Risk-based COCs for the Future On-Unit Worker. with 61
Excavation of Soils, by Pathway, after the Uncertainty Analysis
Figure 15: Risk-based COCs for the Future Resident, without 63
Excavation of Soils, by Pathway, after the Lncerjmtv Analysis
Figure 16: Risk-based COCs for the Future Resident, with 65
Excavation of Soils, by Pathway, after the Uncertainty .Analysis
Figure 17: Proposed GWMZ with Monitoring Well Locations 73
Figure 18: Post-ROD Schedule 95
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Record of Decision for the
D-Area Oil Seepage Basin (631-G) (L*)
Savannah River Site
WSRC-RP-97-40:
Revision 1. Final
August 1998
List of Tables
Table 1 USCs for all Media 33
Table 2 Summary of Risk-Based PCOCs. Grouped by Exposure Route 49
Table 3 Summary of PCOCs 54
Table 4 Uncertainty Matrix for COCs 55
Table 5 Final COCs. with Selected RGOs 69
Table 6 Comparative Analysis of Groundwater Alternatives 80
Table 7 MZCLs and MCLs for COCs : 91
Appendix
A. Responsiveness Summary 99
in
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Record of Decision for the
D-Arva Oil Seepage Basin (631-G) (U)
Savannah River Site
WSRC-RP-97-402
Revision 1. Final
August 1998
LIST OF ACRONYMS AND ABBREVIATIONS
ARAR applicable or relevant and appropriate requirement
BRA Baseline Risk Assessment
CAB Citizen's Advisory Board
CERCLA Comprehensive Environmental Response, Compensation, and Liability Act
CFR Code of Federal Regulations
CMS Corrective Measures Study
COC constituent of concern
COPC constituent of potential concern
CSM conceptual site model
D-Area OSB D-Area Oil Seepage Basin
DCE dichloroethene
DOE U.S. Department of Energy
DQO Data Quality Objectives
DRO diesel range organics
EPA U.S. Environmental Protection Agency
ERA Ecological Risk Assessment
ER&WM Environmental Remediation and Waste Management
ESC Expedited Site Characterization
FFA Federal Facility Agreement
FRR Final Remediation Report
FS Feasibility Study
ft ; feet/foot
GWMZ Groundwater Mixing Zone
Hc Henry's Law coefficient
HI hazard index
HQ hazard quotient
IRA interim remedial action
LUC land use control
LUCAP land use control assurance plan
LUCIP land use control implementation plan
km kilometer
m meter
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Record of Decision for the
D-Area Oil Seepage Basin (631-G) (U)
Savannah River Site
WSRC-RP-97-40:
Revision I. Final
August 1998
MCL maximum contaminant level
MEPAS -Multimedia Environmental Pollutant Assessment System
ma mile
Mg/fcg micrograms per kilogram
Mg/1 rrucrogram per liter
MLSSL mass-limited soil screening level
msl mean sea level
MZCL mixing zone concentration limit
NCP National Oil and Hazardous Substances Contingency Plan
NPDES National Pollutant Discharge Elimination System
NPL National Priorities List
OU Operable Unit
PCE tetrachloroethene
PCOC Preliminary COC
PCR post-construction repon
PP Proposed Plan
RAO Remedial Action Objective
RAWP Remedial Action Work Plan
RBC risk-based concentration
RCRA Resource Conservation and Recovery Act
RDR Remedial Design Repon
RDWP Remedial Design Work Plan
RFI RCRA Facility Investigation
RGO remedial goal option
RI CERCLA Remedial Investigation
RME Reasonable Maximum Exposure
ROD Record of Decision
SAFER Streamlined Approach for Environmental Restoration
SB Statement of Basis
SCDHEC South Carolina Department of Health and Environmental Control
SCHWMR South Carolina Hazardous Waste Management Regulations
SRS Savannah River Site
SSL soil screening level
TCE trichloroethene
TPH total petroleum hydrocarbons
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Record of Decision for the WSRC-RP-97-402
D-Area Oil Seepage Basin (631-G) (V) Revision 1, FinaJ
Savannah River Site August 1998
USC unit-specific constituent
V'OC volatile organic compound
WSRC Westinghouse Savannah River Company
VI
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Record of Decision for the WSRC-RP-97-402
D-Area Oil Seepage Basin (631-G) (V) Revision 1. Final
Savannah River Site August 1998
THIS PAGE WAS INTENTIONALLY LEFT BLANK.
VII
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Record of Decision for the WSRC-RP-97-402
D-Area Oil Seepage Basin (631-G) (U) Revision 1. FinaJ
Savannah River Site August 1998
I. SAVANNAH RJVER SITE (SRS) AND OPERABLE UMT (OL ) NAME, LOCATION,
DESCRIPTION, AND PROCESS HISTORY
SRS Location, Description, and Process History
The SRS occupies approximately 777 square kilometers (km) [310 square miles (mi)] of land adjacent to the
Savannah River, principally in Aiken and Barnwell counties of South Carolina (Figure 1). SRS is a secured U.S.
Government facility with no permanent residents. SRS is located approximately 40 km (25 mi) southeast of
Augusta, Georgia, and 32 km (20 mi) south of Aiken, South Carolina.
SRS is owned by the U.S. Department of Energy (DOE). Management and operating services are provided by
Westinghouse Savannah River Company (WSRC). SRS has historically produced tritium, plutonium, and other
special nuclear materials for national defense. Chemical and radioactive wastes are by-products of nuclear material
production processes.
OU Name, Location, Description, and Process History
The Federal Facility Agreement (FFA) (WSRC, 1993a) lists the D-Area Oil Seepage Basin (D-Area OSB), Building
Number 631-G, as a Resource Conservation and Recovery Act (RCRA)/Comprehensive Environmental
Compensation and Liability Act (CERCLA) unit requiring further evaluation using an investigation/assessment
process that integrates and combines the RCRA Facility Investigation (RFI) process with the CERCLA Remedial
Investigation (RI) to determine the actual or potential impact to human health and the environment. Information
regarding the D-Area OSB can be found in the RFURJ Report and Baseline Risk Assessment (BRA) fWSRC.
1997a), the Corrective Measures Study/Feasibility Study Report (CMS/FS) (WSRC. 1998a), and the Statement of
Basis/Proposed Plan (SB/PP) (WSRC, 1998b).
The D-Area OSB is located within SRS, in a clearing between roads A-t.4 and A-4.5, approximately 1.6 km (1 mi)
north of the coal-fired D-Area Powerhouse, and approximately 3.1 km (1.9 mi) from the nearest SRS boundary
(Figures 2 and 3). The D-Area OSB is on the Ellenton Plain along the Savannah River at an elevation of 46 meters
(m) [150 feet (ft)] above mean sea level (msl). The water table ranges from approximately 1 to 5 m (4 to 16 ft)
below ground surface in the area of the D-Area OSB. Surface drainage is to the southwest, toward the Savannah
River, which is at an elevation of 26 m (85 ft) msl [20 m (65 ft) below the basin elevation].
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Record of Decision for the WSRC-RP-97-402
O-Area Oil Seepage Basin (631-G) (l~> Revision 1. Final
Savannah River Site August 1998
The D-Area OSB is designated as Building Number 631-G and has the approximate dimensions of I i" m (333 fti
long by 33 m (.10S"rt) wide and 2.5 m (3 ft) deep. During an interim remedial action iIRA) conducted at the unit, the
trenches were found to be continuous, without noticeable berms. and were constructed as a sene> of adjacent
trenches along the back half of the clearing (Figure 3).
The D-Area OSB unit is located in a cleared, rectangular-shaped area adjacent to an unimproved road in D Area
(Figure 4). The location of the former seepage basin is currently not discernible because the unit has been backfilled
and leveled. The only evidence of the unit's prior existence is the four orange balls marking the comers of the unit, a
perimeter fence, and the presence of multiple monitoring wells and piezometers located at or near the unit. The
terrain is flat, with no discernible slope or relief, and is surrounded by a mature forest of hardwoods and softwoods.
The forested conditions provide dense cover for wildlife, and, in combination with the boggy conditions prevailing in
the adjacent wetlands, create access problems for equipment and personnel involved in unit investigation activities.
The closest surface water feature is a Carolina bay, a natural wetland located adjacent to the unit to the west. The
Carolina bay appears to be dry during the summer months or periods of little or no precipitation, but may contain
surface water during wet seasons. Unimproved dirt road A-4.4, located immediately north of the waste unit, bisects
the Carolina bay. Aerial photographs indicate that the road was in existence during the early 1950s. Other wetlands
exist approximately 76 m (250 ft) to the south of the unit, beyond din road A-4.5.
The major local surface water drainage system is the Savannah River and associated swamps, located approximately
2.6 km (1.6 mi) to the west of the basin. Upper Three Runs Creek, a tributary to the Savannah River, is located 2.7
km (1.7 mi) to the north-northwest, and Fourmile Branch, another tributary, is 2.7 km (1.7 mi) to the south-southeast
(Figure 1). The local surface drainage at the unit is to the south-southwest, toward a wetland area and runoff ditch.
These wetlands discharge into another unnamed ditch, which traverses D Area and eventually leads to the Savannah
River.
The D-Area OSB was constructed in 1952 as a series of unlined trenches for disposal of waste oil products, from D
Area and other areas at SRS, which were unacceptable for incineration in the 400-D powerhouse boilers. As the
trenches filled, the waste oils along with general office and cafeteria waste were occasionally ignited. The practice
of open burning was a common practice at SRS until 1973 when it was stopped site-wide. In 1975 the basin was
removed from service and was backfilled with soil.
The basin remained inactive and covered with natural vegetation, including bushes and grasses, until 1996. when an
IRA was implemented. During the IRA, the trench area was excavated and drums and debris were removed along
with any obviously contaminated soils. The remaining soils were returned to the excavation in "last out first in" order.
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Record of Decision for the
D-Area Oil Seepage Basin (631-C) (U)
Savannah River Site
WSRC-RP-97-402
Revision 1, Final
August 1998
SOUTH
CAROLINA
D-AREA OIL
SEEPAGE
BASIN
SOUTH
CAROLINA
GEORGIA
Figure 1.
Location of the D-Area OSB at the SRS
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Record of Decision for the \VSRC-RP-97-402
[>-Area Oil Seepage Basin (631-G) (U) Revision 1. Final
Savannah River Site August 1993
THIS PAGE WAS INTENTIONALLY LEFT BLANK.
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Record of Decision for the
D-Area Oil Seepage Basin (631-G) (U>
Savannah River Site
WSRC-RP.97-402
Revision 1, Final
SERIES i
Figure 2.
Sire *ott»
•curu
\l
K
23CO
Topography of the Area Surrounding the D-A/ea OSB
200C
SCALE IN FEET
iCOO
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Record of Decision for the \VSRC-RP-;>7-H>;
D-Area Oil Seepage Basic i631-G) fU) Revisioo I, Final
Savaooah River Site August 1993
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Record of Decision for the
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Savannah Rjver Site
WSRC-RP-97-402
Revision 1, Final
August 1998
300
ORIGIN*!. -CUP
C "ILLS
T£ UNIT
Figure 3. Site Plan of the D-Area OSB
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Savannah Rjver Site August 1993
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Record of Decision for the
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Savannah River Site
WSRC-RP-97.40'
Revision I. Final
.August 1998
Figure 4. Current Photograph of the D-Area OSB (May 1993)
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Savannah River Site August
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Record of Decision for the VVSRC-RP-97-402
D-Area Oil Seepage Basin (631-G) (U) Revision 1. Final
Savannah River Site August 1998
At :he close of the IRA, the contractor installed two horizontally oriented, perforated pipes along the length of the
former waste unit for technology testing (biovenung; purposes. These pipes were used to force fresh air. nutnenti
and tracers into the soils at a depth of about 2.4 m (3 ft) in order to volatilize the constituents in the soil, enhance the
aerobic degradation of the constituents in both the soil and groundwater, and monitor the effectiveness of the
treatment program (WSRC. 1997b, c, d. e).
n. SITE AND OU COMPLIANCE HISTORY
SRS Operational History
^
The primary mission of SRS has been to produce tritium (3H), plutonium-239 (-39Pu). and other special nuclear
materials for our nation's defense programs. Production of nuclear materials for the defense programs was
discontinued in 1988. SRS has provided nuclear materials for the space program, as well as for medical, industrial.
and research efforts up to the present. Chemical and radioactive wastes are by-products of nuclear material
production processes. These wastes have been treated, stored, and in some cases, disposed at SRS. Past disposal
practices have resulted in soil and groundwater contamination.
SRS Compliance History
Waste materials handled at SRS are regulated and managed under RCRA. a comprehensive law requiring responsible
management of hazardous waste. Certain SRS activities have required federal operating or post-closure permits
under RCRA. SRS received a hazardous waste permit from the South Carolina Department of Health and
Environmental Control (SCDHEQ; the permit was most recently renewed on September 5, 1995. Pan IV of the
permit mandates that SRS establish and implement an RFI Program to fulfill the requirements specified in Section
30O4(u) of the federal permit.
On December 21, 1989, SRS was included on the National Priorities List (NPL). Sites included on the NPL fail
under the jurisdiction of CERCLA. This inclusion created a need to integrate the established RFI Program with
CERCLA requirements to provide for a focused environmental program. In accordance with Section 120 or"
CERCLA. DOE has negotiated a FFA (WSRC, 1993a) with the U.S. Environmental Protection Agency (EPA) and
SCDHEC to coordinate remedial activities at SRS into one comprehensive strategy that fulfills these dual regulatory
requirements.
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Record of Decision for the '.VSRC-FIP-97.-02
D-Area Oil Seepage Basin i.5Jl-G) iL~) Revision 1, Finjl
Savannah River >itt . August
OL" Compliance History
As previously stated, the D-Area OSB is listed in the FFA as a RCRA/CERCLA unit requiring further evaluation to
determine the actual or potential impact to human health and the environment. An RFI/RI characterization and BRA
were conducted for the unit between 1995 and 1996. The results of the RFI/RI and BRA were presented in the
RFI/RI Report and BRA (\VSRC. 1997a). The RFI/RI Report and BRA were submitted in accordance with the-flFA
and the approved implementation schedule, and were approved by EPA and SCDHEC in August 1997. SRS
submitted the Si'.-isian 0 In:;nm Acr.on Proposed Pkn for the D-A.---.1 OSB. ^nich E?A and SCDHEC received
November 16, 1993. Tie three Parties issued the Initrim Ac:ion Record of Dtc:j:on in March 1995. SRS prepared
and submitted the D-Area OSB Interim Action Post-Cons:rucrion Repon 10 E?A and SCDHEC on November 8,
1996. SCDHEC approved the report on January 7, 1997, and EPA approved it on February 27, 1997. The CMS/FS
(WSRC, 1998a), SB/PP O'SRC, 1998b), and Groundnater Mixing Zone Application (WSRC, 1998c) were
submitted to EPA and SCDHEC in accordance with the FFA and the approved implementation schedule, and were
approved by them on April 1. 1998.
ILL HIGHLIGHTS OF COMMUNITY PARTICIPATION
Both RCRA and CERCLA require that the public be given an opportunity to review and comment on the draft permit
modification and proposed remedial alternative. Public participation requirements are listed in South Carolina
Hazardous Waste Management Regulation (SCHWMR) R.61-79.124 and Sections 113and 117 of CERCLA. These
requirements include establishment of an Administrative Record File to document the investigation and selection of
the remedial alternatives for addressing the D-Area OSB soils and groundwater. The Administrative Record File
must be established at or near the fc.-ility at issue. The SRS Public Involvement Plan (DOE, 1994) is designed to
facilitate public involvement in the decision-making process for permitting, closure, and the selection of remedial
alternatives. Tne SRS Public Involvement Plan addresses the requirements of RCRA, CERCLA. and the National
Environmental Policy Act (N"E?A;. SCHWMR R.61-79.124 and Section 117(2. of CERCLA. as amended, require
advertisement of the draft permit modification and notice of any proposed remedial action and provide the public an
opportunity to participate in the selection of the remedial action. Tne Staremant of Basis/7roposed Plan for ;he D-
Arta Oil Sitpa%e Basin (WSRC. 1993b). a pan of the Administrative Record File, highlights key aspects of the
investigation and identifies the preferred action for addressing the D-Area OSB. The Administrative Record File is
available at the EPA office and at the following locations:
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Record of Decision for the WSRC-RP-97-J02
D-Area Oil Seepage Basin (631-G) (U) Revision 1, Final
Savannah River Site August 1998
U. S. Department of Energy
Public Reading Room
Gregg-Graniteville Library
University of SouuTCarolina-Aiken
171 University Parkway
Aiken, South Carolina 29801
(303)641-3465
Thomas Cooper Library
Government Documents Department
University of South Carolina
Columbia. South Carolina 29208
(803) 777-4866
Similar information is available through the repositories listed below:
Reese Library
Augusta State University
2500 Walton Way
Augusta. Georgia 30910
(706)737-1744
Asa H. Gordon Library
Savannah State University
Tompkins Road
Savannah, Georgia 31404
(912)356-2183
The public was notified of the public comment period through mailings of the SRS Environmental Bulletin, a
newsletter sent to approximately 3500 citizens in South Carolina and Georgia, through notices in the Aiken Standard.
the Allendale Citizen Leader, the Augusta Chronicle, the Bamwell People-Sentinel, and The State newspapers. The
public comment period was also announced on local radio stations.
The 45-day public comment period began on May 1, 1998 and ended on June 14, 1998. However, no public
comments were received during this period. The Environmental Remediation and Waste Management (ER&\VM>
Program subcommittee of the SRS Citizen's Advisory Board (CAB) was given a briefing on the preferred
alternatives on May 6. 1998. The ER&WM subcommittee was supportive of the preferred alternative and made a
motion to the full CAB at the May 18, 1998 meeting to accept the preferred alternative. This motion was accepted
with no opposition. The subcommittee also commended the site's successful use of the bioventilation system in the
remediation of the unit's subsurface soil. The Responsiveness Summary, provided in Appendix A of this Record of
Decision (ROD), and the final RCRA permit will indicate that no comments were received.
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Record of Decision for the \VSRC-RP-9~-402
D-Area Oil Seepage Basin i631-G) (U) Revision 1. Final
Savannah Rjver Site A-jf^st :"•*><
FV. SCOPE AND ROLE OF THE OL \\ITHCS THE SITE STRATEGY
RCRA/CERCLA Programs at SRS
RCR.VCERCLA units (including the D-Area OSB) at SRS are subject to a multi-stage remedial investigation
process that integrates the requirements of RCRA and CERCLA as outlined in the RFl/RI Program Plan (WSRC,
1993b). The RCRA/CERCLA processes are summarized on Figure 5. Figure 5 illustrates the investigation and
characterization of potentially impacted environmental media vsuch as soil, sediment, surface water, and
zroundwater) comprising the waste unit and surrounding areas; the evaluation of risk to human health and the local
ecological community; the screening of possible remedial actions to identify the selected technology that will protect
human health and the environment; implementation of the selected alternative; documentation that the remediation
has been performed competently; and evaluation of the effectiveness of the technology. The steps of this process are
iterative in nature, and include decision points that involve concurrence between DOE (as owner/manager). EPA and
SCDHEC (as regulatory oversight), and the public. The RCRA/CERCLA process as applied to the D-Area OSB is
outlined below.
RFI/RJ Work Plan
Prior experience in the Superfund program has identified a strong need for streamlining the remediation process
(EPA, 19S9a). To address this need. DOE has developed the Streamlined Approach for Environmental Restoration
(SAFER) (Daily et al., 1992). DOE Headquarters identified the D-Area OSB as a p:lot project for the
implementation of SAFER and elected to design the D-Area OSB RFI/RI Work Plan using SAFER methodologies.
The SAFER program combines elements of two recognized processes developed for managing uncertainty at
different points in the environmental restoration process: the data quality objectives (DQO) process, developed by
the Quality Assurance Management Staff of EPA (Neptune et al., 1990) and the Observational Approach (OA),
which is rooted in management of uncertainty in traditional geotechnical engineering applications 'vPeck, 1969). The
OA provides a framework for managing uncertainty throughout the environmental restoration process, while :he
DQO process focuses on establishing the quality and quantity of data required to help make decisions at various
points in the environmental restoration process. Description of the DQO process is found in Data Quality Objecti-.es
Process for Superfund. Interim Final (EPA, 1993).
14
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Record of Decision for the
D-Area Oil Seepage Basin (631-G) (U)
Savannah River Site
VVSRC-RP-97-402
Revision 1, Final
August 1998
SRS RCRA/CERCLA UNIT
PRELIMINARY EVALUATION
• Unit Reconnaisance
• Unit Screening
RFI/TU WORK PLAN
Develop Conceptual Site Model (CSM)
Identify Data Needs
Develop Data Quality Objectives and
Decision Logic
Detailed Sampling and Analysis Plan
UNIT/SITE CHARACTERIZATION
• Implement Rfl/RI
• Data Evaluation vs. DQO's
• Re-Evaluate CSM
Characterization
Complete?
Additional
Characterization
Characterization
Complete?
DATA EVALUATION
Validation
Verification
Figure 5.
RCRA/CERCLA Logic and Documentation
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Record of Decision for the '.V5RC-S?-'>"-i02
D-Area Oil Seepage Basin .631-G) (U) Revision 1. Final
Savannah Rjvtr Site August 1998
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Record or Decision for (he
D-Area Oil Seepage Basin (631-G) (U)
Savannah River Site
WSRC-RP-97-402
Revision 1, Final
August 1998
Treatability Studies
(as necessary)
NO ACTION REMEDY
0
RFI/RJ REPORT
• Document Results of RF1/RI
CMS/FS Report
• Establish RAOs
• Identify Response Actions
• Identify Technologies
• Alternatives Development
• Alternatives Screening
• Detailed Analysis
SB/PP
Preferred Alternative
Draft Permit Modification
Public Comment
RECORD OF DECISION
• Select Remedy
• Responsiveness Summary
• Final Permit Modification
CORRECTIVE MEASURE/
REMEDIAL ACTION
• Unit Closure
• Post Closure Documentation
(Post Construction Report)
Baseline Risk Assessment
• Determine Unit Risk
• Develop RGOs
POST ROD
DOCUMENTATION
• Remedial Design
Workplan/Report
• Remedial Action
Workplan/Repon
Figure 5.
(continued) RCRA/CERCLA Logic and Documentation
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Savannah SJver Site Vjaust :r'°j
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Savannah Rjver Site . August 1998
The SAFER method incorporates the DQO and OA processes to achieve the following:
enhanced emphasis on planning
linkage of data collection to decision-making needs
explicit recognition and management of uncertainty
• direct and efficient application of information gained as planning and remediation proceed
• early convergence on a remedy
• informing and soliciting input from key stakeholders (regulators and public)
SAFER emphasizes the use of decision rules to quantitatively define data adequacy in the RFI/RI process. Each
decision rule provides a quantitative statement defining what quantity and quality of data provide adequate
information upon which decisions can be based. Inherent in the idea of the decision rule is the understanding that
there will be uncertainty in ihe decision-making process. The goal is to identify data adequacy that provides
acceptable uncertainty in making decisions while managing the residual uncertainty. The objective of the decision
rule is to establish the linkage between the problem at the unit, its remedial objective, and data requirements. This
will be done iterauvely, first based on preliminary understanding and then modified as more information is obtained.
Federal, state, and local regulatory agencies are recognized as key stakeholders within the SAFER process.
Continuing concurrence with regulatory requirements is an implicit SAFER objective. Data from previous
environmental investigations, performed under the existing phased investigation approach, are included in the
SAFER design. SAFER'S iterative approach allows regulatory concurrence as the investigation proceeds. The
SAFER process was implemented at the D-Area OSB as an Expedited Site Characterization (ESC) field effort that
sought to accomplish project objectives in a rapid fashion while maintaining data quality.
The initial step in the SAFER process consists of identifying probable conditions at the investigation site and
developing a conceptual site model (CSM) based on those conditions. This conceptual model is used to concentrate
the unit investigation on the processes, medium(s). constituents, exposure pathways, and potential receptors most
likely to be found during the investigation. With the model in mind, a more focused work plan can be developed to
fully address each item identified in the model.
Section V provides the unit-specific CSM for the D-Area OSB OU and a summary of the characteristics of the
primary and secondary sources and release mechanisms for the unit as determined in the RFI/RJ.
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Record of Decision for the vv SRC-RP-<>7-JO:
CX-Area Oil Seepase Basin :631-Gi iV) Revision 1. Final
Savannah Rjver Site Auyjst 1'>?S
Bised on Lu.e CSM for ihe D-Area OSS. a *et;iiied sampling ar.d ir.ahsis plan '-MS ~r;?are-J and imp'.err.erid
(\VSRC. 1995a. b; 1996ai. The unit assessment plan and confirmation sampling plans were designed to characterize
the following sources and release mechanisms:
primary source: disposal trenches comprising the D-Area OSB
• primary release mechanisms: deposition and infiltration/percolation
• source media (primary media impacted): surface soil and subsurface soil
• secondary release mechanisms: fugitive dust generation, volatilization, vege'.aii'-e 'biotici '_p:ake, storm^-aier
runoff, and leaching into Jie groundwater
• exposure media (secondary media impacted): air, produce, surface water, sediment, and groundwater
RFI/RI Characterization Report
The primary purpose of the RFT/RJ is to establish unit-specific constituents (USCs) that pose potential risk through
various exposure routes and to determine their distribution in the media associated with the unit. As an indicator of
unit-specific contamination, the results of the analysis of soil, surface water, and sediment samples at the unit were
compared to 2x mean background concentrations, and the groundwater analytical results were compared with EPA
primary maximum contaminant levels (MCLs) or 2x mean background concentrations where no MCL exists.
Compounds that exceed these comparison levels are called USCs and their nature and extent were evaluated in detail
in the RFI/RI.
To address the identified sources and release mechanisms in the CSM, the following RFI/RI unit characterization
objectives were identified for the D-Area OSB (WSRC, 1995a):
enhance and refine the liihologic and hydrogeologic characterization of the subsurface in the vicinity of the D-
Area OSB unit
• establish background concentrations of potential contaminants in soil, groundwater. surface \oter, and sediment
to determine the impact on :hese media associated specifically with the operation of the D-Area OSB unit
determine the USCs. if any. released to the various environmental media related to the D-Area OSB
• address aspects of the CSM related to sources, release mechanisms, and exposure media, and/or refine the CSM
based on the data collected
define the horizontal and vertical extent of contaminants in the impacted media
assist in determining the feasibility of potential remedial alternatives through the collection of preliminary soil
engineering parameters
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Record of Decision for the WSRC-RP-97-402
D-Area Oil Seepage Basin (6J1-C) (U) Revision 1. Final
Savannah River Site August 1998
confirm groundwater analytical data generated by the onsite lab during the SAFER process, with anaKses for
USCs generated by a conventional, offsite laboratory data
ERA
The purpose of a BRA is to develop risk information to assist in the decision-making process for remedial sites
(EPA. I989b). This risk assessment follows the EPA Risk Assessment Guidance for Superfund (EPA. 1989b. o.
According to EPA. 1989b. a BRA should provide the following:
• an analysis of baseline risks and help determine whether there is a need for remedial action
• a basis for determining levels of chemical and radiological constituents that can remain in-sim, on-unit and that
will be adequately protective of human health and the environment
a basis for comparing potential human health and ecological impacts of various remedial alternatives
a consistent process for evaluating and documenting risk to public health and the environment
The BRA assesses risks that may result from a release of, and exposure to, chemical contaminants under reasonable
maximum exposure (RME) conditions. The assessment uses current and hypothetical future land use scenarios and
associated receptors with the assumption that constituent concentrations remain the same as reported in the RFI/RJ.
The RME represents the highest exposure that is reasonably expected to occur at the unit.
During the development of a BRA, risk from the unit is quantified, based on unit-specific data, for current and future
human and ecological receptors, through the multiple exposure routes identified in the CSM. Carcinogenic nsk at
or above 1.0 x 10^ (one excess human cancer in a population of one million) is considered significant. In addition, if
the hazard index (HI) is greater than 1.0 for noncarcinogenic constituents, there is concern that adverse health effects
can occur.
The information from the BRA supports identification of those areas where no further action or selected re
actions are warranted. The BRA also provides the basts for deriving nsk-based constituent levels that are protectr-e
of human health and environment [remedial goal options (RGOs)J for use in consideration of remedial alternatives
A summary of the results of the BRA for the D-Area OSB is presented in Section VI.
CMS/FS
The results of the RFI/RI Report and the BRA provide the basis for establishing unit-specific remedial action
objectives (RAOs) in the CMS/FS. RAOs for the D-Area OSB were developed to address: unit-specific
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Record of Decision for the WSRC-RP-97-402
D-Area Gil Seepage Basin '631-Gi (V) Revision 1. Final
Savannah Rivgr Site August 19C'8
ccntarrup.ar.ts. rr.ecia of concert-.. poter.;ial ixposurj path-Ax.s. and remediation ^oais. . r.s RAOs -^ers based on the
nature and extent of contamination, threatened resources, human and environmental risk information, and the
potential for human and environmental exposure. In addition, the preliminary remediation goals for the D-Area OSB
were developed based upon applicable or relevant and appropriate requirements (ARARs) or other information from
the RFI/RJ Report and the BRA.
The methodologies used to identify and screen relevant technologies for the remediation of the waste unit followed
an established remedy selec'Jon process developed by the EPA. The goal of this process is to select corrective
measures/remedial actions that are protective of human health and the environment, that maintain protection over
time, and that minimize contaminant (or waste) mobility, toxicity, or volume through treatment. when possible
[CERCLA 300.430 (a)(l)'(!)]. The selection of a response action for the D-Area waste unit proceeded in a series of
steps, as defined in the National Oil and Hazardous Substances Contingency Plan (NCP) of November 20, 19S5 (50
FR 47973). and as outlined in Figure 6. In addition, the remedial alternatives were further evaluated against the
following nine selection criteria established by the NCP:
• overall protection of human health and the environment
• compliance with ARARs
• long-term effectiveness and permanence
• reduction of toxicity. mobility, or volume through treatment
• short-term effectiveness
• implementability
• cost
• state acceptance
• .community acceptance
The results of the CMS/FS conducted for the D-Area OSB are summarized in Section VII. and a summary of the
comparative anaKsis of the alternatives is provided in Section VIII.
SB/PP
The culmination of the response action selection process is the SB/PP. Tne purpose of the SB/PP is to facilitate
public participation in the remedy selection process through the solicitation of public review and comment on all the
remedial alternatives described. The SB/PP presents the lead agency's preliminary recommendation(s) concerning
ho1* best to undertake a remedial action at a particular w -ste unit. The SB/PP describes all remedial options that
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Record of Decision for the
D-Area Oil Seepage Basin (631-G) iU)
Savannah River Site
WSRC.RP-97~IO:
Revision 1, Final
August 1998
Establish Remedial Action Objectives
Develop General Response
Actions Describing Areas or
Volumes of Media to Which
Containment, Treatment, or
Removal Actions May Be Applied
Identify Potential Treatment sod
Disposal Tecbnologies and
Screen Based on Technical
Iraplemenlability
Evaluate Process Options Based on
Effectiveness, Implementability, and
Relative Cost, to Select a
Representative Process for each
Technology Type
Response Action
Selection Process
Repeat Previous Scoping Steps:
- Determine New Data Needs
• Develop Sampling Strategies
and Analytical Support to Acquire
Additional Data
• Repeal Steps in RI Site
Chasaaehzacoo
Combine Media-Specific
Technologies into
Alternatives
1
r
Detailed Anal/is
of Alternatives
Scores: EPA. I988i
Fisure 6.
Response Action Selection Process
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Record of Decision for the \\snr SP o- -n->
D-Area Oil Seepage Basin ,631-C) iU) %\? - J r 1
Savsnnah aiv^r Sit> ' Rev,noa 1. Final
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D-Area Oil Seepage Basin (631-G) (U) Revision 1, Final
Savannah River Site August 1998
were considered in detail in the CMS/FS. and explicitly identifies both the preferred alternative for a remedial action
at a waste unit and_the preference rationale for that alternative.
The SB/PP directs the public to the RFI/RJ, BRA, and CMS/FS reports as the primary sources of detailed, unit-
specific information and information on the remedial alternatives analyzed. It also provides information on how the
public can be involved in the remedy selection process. The public is notified of a public comment period through
mailings of the SRS Environmental Bulletin, through notices in the Aiken Standard, the Allendale Citizen Leader, the
Barnwell People - Sentinel, The State, and Augusta Chronicle newspapers, and through announcements on locoJ
radio stations.
ROD
The ROD documents the remedial action plan for a waste unit and consists of three basic components: a
Declaration, a Decision Summary, a Responsiveness Summary. The purpose of the Declaration is to certify that the
remedy selection process was carried out in accordance with the requirements of CERCLA and, to the extent
practicable, the NCP. The Decision Summary is a technical and informational document that provides the public
with a consolidated source of information about the history, characteristics, and risks posed by the unit, and includes
a summary/evaluation of the cleanup alternatives and the considerations that led to the selected remedy. The
Responsiveness Summary presents comments received during the public comment period on the SB/PP. and a
response to each comment or criticism that was submitted in writing or orally. The Responsiveness Summary for the
D-Area OSB is provided in Appendix A and an explanation of significant changes resulting from public comment on
the SB/PP for the unit is provided in Section XI.
SRS received a RCRA hazardous waste permit from SCDHEC. which is renewed every five years. The D-Area OSB
is a Solid Waste Management Unit (SWMU) listed on the SRS RCRA Permit because the unit received hazardous
substances. Thus, the remedial decision for this SWMU requires a RCRA Permit Modification. No comments \vere
received during the public comment period on the proposed remedial action and the associated draft RCRA permit
modification (May I through June 14, 1998). This is indicated in the Responsiveness Summary of this ROD
(Appendix A) and in the final RCRA Permit. The final RCRA Permit and this ROD document the final decision for
this OU.
Post-ROD Documentation
The post-ROD documentation consists primarily of the design documents that are required prior to initiating a
remedial action. Specific post-ROD documents include the combined Remedial Design Work Plan/ Remedial
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Record of Decision for the WSRC-RP-97-402
D-Area Oil Seepage Basin '.631-Gi .U) Revision !. Final
Savannah River Site \ur:st 1 '^S
Design Report/ and Remedial Action Work Plan iRDV,'?'RDR/RA'.V?; and the corr.bir.ed ?os;-Ccnstr-.;c-.ion Report
and Final Remediation Report t?CR/FRR). A discussion of the schedules thai apply to these documents is provided
in the SB/PP and in Section XIII of this ROD.
»•
D-Ar«a OSB Remedial Strategy
The RF1/RI process provides a method of managing the steps that lead to1 the ultimate remediation of a specific waste
unit. An operable unit (OU) usually consists of the contaminj'.-d rredia ^sources, soil. gTC'jrsdwater. sediments.
surface water, and air) specific to a waste unit and the proposed actions related to their characterization and ultimate
remediation, and/or the timing of those actions.
The overall strategy for addressing the D-Area OSB was to: (1) characterize the waste unit by delineating the nature
and extent of contamination and identifying the media of concern (perform the RFI/RI); (2) perform a BRA to
evaluate media of concern, constituents of concern (COCs), and exposure pathways, and to characterize potential
risks; and (3) evaluate and perform a final action to remediate, as needed, the identified media of concern.
The D-Area OSB is an OU located within the Savannah River Floodplain Sw-amp watershed. Several OUs within
this watershed will be evaluated to determine impacts, if any, to associated streams and wetlands. SRS will manage
ail OUs to minimize impact to the watershed. Based on characterization and BRA information, the D-Area OSB
does not significantly impact the watershed. Upon disposition of all OUs within this watershed, a final,
comprehensive evaluation of the watershed will be conducted to determine whether any additional actions are
necessary. Based on the BRA and vadose zone modeling after the IRA and biovent testing, the soils at the unit do
not warrant further remediation. Additionally, results of the BRA indicated that surface water and sediment at the
unit do not require remediation. Groundwater is the only medium identified in the BRA that requires evaluation of
remedial alternatives. The D-Area OSB investigation considered all unit-specific ground'-vater. Based on the
investigation of the groundwater. the contamination in the water table aquifer is apparently attributable to the D-Area
OSB elites. The proposed action for the D-Area OSB groundwater, soil, sediment, and surface water is a final
action.
V. OU CHARACTERISTICS
A CSM was developed for the D-Area OSB that identifies the primary source, primary contaminated media,
migration pathways, exposure pathways, and potential receptors for the unit. The CSM for the D-Area OSB is
presented m TMgures 7j and 7b and is based on the data that ore presented in the RCRA/CERCLA documentation for
this unit. The d^ta summary reports (WSRC. 1996b. c, d. e) and the combined RCfU Facility Investigation/
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Record of Decision for the WSRC-RP-97-402
D-Area Oil Seepage Basin (631-C) (U) Revision 1, Final
Savannah River Site August 1998
Remedial Investigation Report and Baseline Risk Assessment for the D-Area Oil Seepage Basin (U'SRC. 1997ai
contain detailed analytical data for all of the environmental media samples taken in the characterization of the
D-Area OSB. These documents are available in the Administrative Record File (see Section III).
The primary data used for the RF1/RI and BRA were collected during the ESC Phase I, Phase II, confirmation phase
(Phase III), Phase FV, and the post IRA soil sampling conducted during 1995 and 1996. All samples were analyzed
in accordance with EPA-approved protocols.
As an indicator of unit-specific contamination, the soil, surface water, and sediment results were compared to 2.x
mean background concentrations, and the groundwater results were compared with EPA Primary MCLs or 2x mean
background concentrations, where no MCL exists. Compounds which exceed these comparison levels are called
USCs (Table 1) and their nature and extent are evaluated in detail in the RFI/RI and BRA Report.
For the analysis of the nature and extent of contamination, soil sample results were grouped into three depth intervals
for both the unit and the background borings in conformance with the depth intervals evaluated in the BRA. These
depth intervals are 0.0 to 0.3 m (0-1 ft), and 0.0 to 1.2 m (0-4 ft) which covered the exposures from surface soil and
subsurface soil, respectively, as evaluated in the BRA. Analyses were also conducted on samples from a deep soil
interval, extending below 1.2 m (4 ft) to evaluate the nature and extent of contamination in the deep soil for the unit.
All groundwater samples collected and analyzed were taken from the uppermost aquifer and were evaluated as a
single group. Additional physical and hydraulic analyses regarding the effects of the local weak aquiurds on the
movement of groundwater and contaminants were also conducted.
Primary Sources and Release Mechanisms
The primary source for the contamination of the various media is waste oils disposed in the D-Area OSB. a series of
unlined trenches constructed to a depth of 1.2 to 3.7 m (4 to 12 ft) (Figure 3). These wastes were deposited directly
into the deeper soil, greater than 1.2 m (4 ft) deep, and even into the locaJ groundwater, when the water table was
close to the surface. The waste oils disposed of in the D-Area OSB originated in D .Area and other areas at SRS. and
were disposed of in the D-Area OSB because they were unacceptable for incineration in the 400-D powerhouse
boilers. The D-Area OSB has been out of service since 1975. when it was backfilled with soil.
The primary release mechanisms are deposition (contaminants deposited directly into the soils) and
infiltration/percolation (contaminants migrating vertically and laterally into the pore spaces of the soils).
27
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Record of Decision for the WSRC-RP-97-402
D-Area Oil Seepage 3jsm ..631-Gi i.U) Revision 1. Final
Savannah River Jite August
Secondary Sources and Release Mechanisms
Secondary source media impacted by waste disposal activities at ;he D-Area OSB include surface soils and
subsurface soils within the basin and the basin perimcier. Secondary release mechanisms for surface soil include:
fugitive dust generation, volatilization, biotic uptake, and stormwawr runoff. Respective secondary media impacted
for these release mechanisms are: air (dust), air (vapor), biota, and surface water. The secondary release mechanism
for subsurface soil is leaching. The exposure medium tor contaminants that leach frcm sell is grour.dwater. which
may in turn discharge to and undergo potentiaJ cherr.ical constituent exchange with biota. stream sediment, and
surface water. A detailed sampling and analysis plan was prepared and implemented to investigate these secondary
sources and a complete description of the sampling methods and protocols is provided in the RFI/RI Report and
BRACWSRC. 1997a).
Media sampled for investigation of this unit included soil (at multiple .depths), groundwater (from the uppermost
aquifer), surface water, and sediment (Carolina bay and the adjacent wetland).
Seventy-five compounds were detected at least once above screening levels in the soil, groundwater, surface water,
and sediment associated with the D-Area OSB and have been designated as USCs, as listed on Table 1. Those
compounds detected in soils were 23 metals, 15 volatile organic compounds (VOCs), 3 semi-volatile organic
compounds (SVOCs), 11 pesticides/polychlorinated biphenyis (PCBs). and 5 ligands. The groundwater beneath the
basin and as far downgradient as 320 m (1.050 ft) in the shallow aquifer contained USCs including 15 metals, 4
ligands. 16 VOCs, 4 SVOCs. 5 pesticides/PCBs, and total petroleum hydrocarbons (TPHs). Sediment and surface
water in the Carolina bay and wetlands contained USCs comprised of 3 VOCs. 2 SVOCs. 4 pesticides/PCBs, 15
metals, 1 ligand. and diesel range organics (DROs) and TPHs.
A large fraction of the anantical results above detection limits for Lhis report are estimated '."T'-flagzed) values, with
concentrations below the sample quantitation levels. The majority of sample results that exceed the quantitation
level exceed it by less than an order of magnitude. Therefore, the 'au set for this :r.'.es::za'.ion contains mainly low-
level detections of compounds in both soil and groundwater.
-------
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-------
Record of Decision for the \VSRC-RP-9T-40.2
D-Area Oil Se«paee Basin .631-G) -U) Revision 1, Find
Savannah River Site Auyi« 19«»S
THIS PAGE WAS INTENTIONALLY LEFT BLANK.
30
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-------
Record of Decision for the ' \VSRC-RP-9T-40:
D-Area Oil Seepage Basin (631-G) it) Revision 1, Final
Savannah River Site . Xugust IJ^S
THIS PAGE WAS INTENTIONALLY LEFT BLANK.
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Record or Decision for the
D-Ar«a Oil Seepage Basin (631-G) fU)
Savannah River Site
WSRC-RP-97-40:
Revision 1. Final
August 1998
Table 1
USCs for all Media
Volatile;
Acetone
Jenzene
Jromo methane
Batonone, 2-(MEK)
Carbon Oisulfide
Carbon Tetrachlonde
Chioro benzene
Chloroe thane
Chloroform
>ichloroethane. 1.1-
)ichloroethene. 1.2 - (total)
>ichloroethene. 1 .2 - cis
ithylbenzene
Methylene chloride (Dichloromethane)
Styrene
Tetrachloroethene (PCE)
'oluene
"richloroethene (TCE)
Tichlorofluoromethane
Vinyl Chloride (Chloroethene)
Xylenes
Semivolatiles
Jis(2-ethylhexyl) phthalate
ienzoic acid
iutylbenzylphthalate
)i-n-butyl phthalate
Dichlorobenzene, 1.2-
Dichlorobenzene. 1 .4-
Petroleura Indicators
Diesel range organics
Total petroleum hydrocarbons (purgeable)
(C4-C12)
Pesticides/PCBs
AJpha-BHC
Beta-BHC
ODD. 4.41-
DDE. 4.4'-
DDT. 4.4'-
Delta-BHC
Dieldnn
Endosulfan I
Endrin
Endrin ketone
Surface
Soil
(Post IRA)
6/14
2/14
. 1/14
1/14
1/14
14/14
9/14
4/14
2/14
1/14
1/14
7/14
3/14
1/14
Subsurface
Soil
(Post IRA)
11/28
5/23
4/23
1/23
1/28
1/28
28/28
1/23
16/28
7/28
1/28
2/23
1/23
1/28
12/23
8/28
1/23
1/28
Deep
Soil
fPost IRA)
13/30
9/30
1 6/30
5/30
1/30
5/30
12/30
26/30
1/30
19/30
5/30
1/30
15/30
2/30
2/30
1/30
1/30
4/30
3/30
1/30
4/30
1/30
Ground-
water
(Pre IRA)
31/75
2/79
2/79
4/75
9/75
6/79
6/79
1/79
1/79
2/218
1/79
22/223
35/223
2/48
24/223
3/26
15/26
1/26
1/26
1/14
3/80
1/26
2/26
Surface
Water
(Pre IRA)
5/5
1/5
5/5
1/5
4/5
2/5
2/5
1
Sediment
(Pre IRA>
7/8
2/8
2/8
3/8
2/8
1.3
1/3
1/8
1/8
(Table page I of 2)
33
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Record of Decision for ihe
D-Area Oil Seepage Basin i6Jl-G) (U)
Savannah River Site
\VSRC-RP-97-402
Revision 1, Final
August 1993
Table 1 (continued)
USCs for alJ Media
•
Pesticides/PCBs (continued)
Gamrnj-chlordane
^ptachior ipo.xnie
_inJane
PCS- 1 254
PCB-1260
Metals
Aluminum
Antimony
Arsenic
Barium
Beryllium
Cadmium
lalcium
Chromium
Cobalt
Copper
iron
_«ad
Magnesium
Manganese
Vtercury
Nickel
Potassium
Selenium
Silver
Sodium
Thallium
Vanadium
Zinc
Ligands
Chemical oxygen demand
Cyanide
Nitrate as nitrogen
Nitroeen bv Kjeido.-il method
PH
Suifate
Total organic carbon
Total Organic Halogens
Total chosohates is P)
Surface
SoU (
(Post IRA)
. .
1/14
3/14
» <
5/14
2/14
6/14
6/14
4/14
7/14
3/14
7/14
1/14
6/14
3/14
8/14
6/14
1/14
10/14
14/14
8/14
14/14
Subsurface
Soil •
(Post IRA)
1/23
5/23
2/23
12/28
6/28
13/28
12/23 '
3/28
22/28
7/2S
14/28
3/23
1/23
6/2S
5/28
7/23
8/28
3/23
19/23
2S/23
1 7/23
23/23
Deep
/Soil
(Post IRA)
1/30.
J/30
1/30
5/30
9/30
12/30
29/30
. 10/30
30/30
2/30
23/30
• 13/30
13/30
30/30
19/30
16/50
28/30
30/30
8/30
3/30
22/30
2/30
13/30
7.30
10/13
13/13
10/13
13/13
Ground-
water
(Pre [RA)
l.'SO
1,26
13/29
4/154
3/154
15/29
7/154
142/154
20/29
42/154
1/154
7/29
15/154
8/29
1/29
2/154
11/29
4/12
3/12
4.'-l
1'4
5/12
Surface
Water
(Pre [RA)
2/5
1/5
2/5
1/5
1/5
3/5
1/5
2/5
4/5
1/5
2/5
Sediment
(Pre IRA)
1/8
1/8
1/8
1/8
1/8
3/8
1/8
Note: The numocrs on this table reflect the number of samples exceeding the
number of samples collected.
-ipecific ic:iir.:ng value over the total
(Table page 2 of 2)
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Record of Decision for the W SRC-RP-97-402
D-Area Oil Seepage Basin r6Jl-G) (U> Revision 1. FinaJ
Savannah River Site August 1998
Soil
The analytical data indicate that there has been minimal impact to the surface and subsurface soil media [down to 1.2
m (4.0 ft)] from past disposal activity at the D-Area OSB. This conclusion is supported by the historical record for
the unit. The trenches that received the waste oils and other debris *ere constructed to a depch of 1.2 to 3.7 m (4-12
ft), which resulted in waste placement beneath, rather than into, the shallower soils. The wastes were deposited onto
the deeper soil, and even into the locaJ groundwater when the water table was close to the surface. The greatest
impact is to the deep >1.2 m (>4 ft) soils into which the waste was deposited.
The principal VOC constituents impacting soil quality at the basin are the chlorinated hydrocarbons
[tetrachlorocthene (PCE). trichloroethene (TCE), 1,2-dichloroethene (1,2-DCE), and vinyl chloride], which probably
represent a degradation series starting with the PCE and TCE deposited in the basin with waste oils and grease
(Table 1). The aromatic compounds benzene, toluene, ethylbenzene, and xylene (BTEX), which are commonly
associated with petroleum products like gasoline, are also found in the vadose zone soils, but appear to be of
secondary importance to the chlorinated hydrocarbons. Three other VOCs (acetone, 2-butanone. and methylene
chJoride) also appear to be related to waste disposal actions in the basin. The metals chromium, iron, lead, mercury
and zinc are distributed throughout the D-Area OSB in a fashion similar to the VOCs and appear to have elevated
concentrations within the soils of the trenches, primarily below the surface and subsurface soil horizons.
Groundwater
The principal contaminants found to exceed their respective screening levels in the groundwater (MCLs, where they
have been established, and 2x mean background, where no MCL exists) are listed on Table 1 and include compounds
from all 7 analyte groups, except dioxins/furans. The pattern developed from a review of the data set is generally
consistent with a source of contaminants in the basin and with a plume in the groundwater migrating downgradient
from the basin to the south and southwest in the uppermost aquifer.
Three chlorinated hydrocarbons (TCE, PCE, and vinyl chloride) were the most common VOCs detected and had the
highest concentrations. The uppermost aquifer contaminant plume outlined by these compounds is at least 320 m
(1,050 ft) long by 100 m (300 ft) wide and extends vertically from the water table surface down to at least 12 m (40
ft) in depth. The "green clay" occurs at 12 m (40 ft) bis and is expected to provide a barrier against deeper vertical
migration of contaminants. The vertical geometry of the TCE plume is typical of dissolved organic compounds in an
aquifer with an internal downward vertical gradient. The source area contains the highest concentrations and
narrowest lateral extent with concentrations decreasing and the cross-sectional area increasing with distance from the
source. In general, with the exception of a small portion of the aquifer in the immediate vicinity of the former
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Record of Decision for the \VSRC-RP-97-402
D-Area Oil Seepage Basin '.631-G» (U) Revision 1, Rnal
Savannah River 5ite ^ August 1998
trenches. V'CCs in the groundwater were found at concentrations ceirr.v 100 u-il. A small area jailed the "hoi spot",
having an approximate diameter of 6 m (20 ft), contained the highest total concentrations of TCE (1.151 ug/1)
detected during the investigation.
TCE was the compound detected most frequently above the screening levels (Figures 8 to 11). It was found from the
water table aquifer down to the "green clay" (Figure 10). TCE was also the compound detected farthest
do'ATtgradient [3.11 ug/1 (micrograms per liter)] 215 m (TOO ft) southwest of the basin. Concentrations detected in
the sa-Tiples ranged from non-detect up to 1.151 ug/l. *ith an average of 3.0 ug/1. These data indicate that this
compound is present in groundwater in a volume approximately 565 m (1.2CO ft; long by ICO m (300 ft) wide and
from the w-ater table surface to 12 m (40 ft) in depth.
PCE was the -;econd most frequently detected VOC at concentrations above screening levels. Concentrations of this
compound ranged from below the detection limit up to 34.95 ug/1. with an average of 2.1 ug/1. The PCE plume is
smaller than, and wholly contained within, the TCE plume.
The third most frequently detected VOC above its screening level was vinyl chloride. It was found throughout trie
same aquifer zones as the two preceding compounds ind is a degradation product of them because it was never used
at SRS. The concentrations of vinyl chloride ranged from below the detection limit up to 52.0 ug/1, with an average
of 1.1 ug/1. Like the PCE plume, the vinyl chloride plume is contained within the TCE plume.
The isomers of DCE were the fourth most frequently detected VOC above screening levels. This compound can be
found in groundwater over a volume approximately 260 m (850 ft) long by 100 m (300 ft) wide and from the surface
to 12 m (40 ft) in depth. The lateral extent of this compound is the smallest of the four most commonly detected
VOCs and lies within the TCE plume shown on Figures 8 to 10.
Benzene was detected in only 13 of 97 groundwater samples (16^;'. with concentrations ranging from non-detect to
6.2 jJZ/1. Only two of the analyses exceeded the primary MCL (5.0 pg/lj. The distribution of this constituent is
primarily localized in the shallow portion of the aquifer immediately beneath the basin.
The SVOCs detected in groundwater samples were primarily bis(2-ethylhe.v«T) phthalate and di-n-butyl phthalate.
Because the concentrations of these compounds were lower in the vicinity of the basin, it appears that the detected
SVOCs do not originate at the D-Area OSB. but may be a result of sampling or analytical bias. Only one of 14
groundwater samples analyzed for DROs/TPHs contained detectable concentrations, and this sample was from the
western-most disturbed soil area. No dioxins/funns v.ere detected in the 26 samples analyzed, and only 5
pestictdes/PCBs were detected at concentrations above their MCLs.
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Record of Decision for the
D-Area Oil Seepage Basin (631-G) (U)
Savannah River Site
WSRC-RP-97-402
Revision 1. Final
Aueust 1998
\\
\\
\\
\
\\
Units = |ig/l
MCL = 5 |ag/l
300
See Figure 11 for Master Legend
Figure S. TCE in the Shallow Portion of the Water Table Aquifer
-------
Record of Decision for the \VSRC-RP-97-402
D-Area Oil Seepage Basin •6J1-G) iU) Revision I. Final
Savannah River Site \ugust 1998
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Record of Decision for the
D-Area Oil Seepage Basin (6JI-G) (L">
Savannah River Site
WSRC.RP-97-402
Revision 1, Final
-I • fc* 100
SCALE IN r££T
See Figure 11 for Master Legend
Figure 9. TCE in the Deeper Portion of the Water Table Aquifer
-------
Record of Decision for the WSRC-RP-9T-402
D-Ar«a Oil Seepage Basin (631-G) iU) Revision 1. Final
Savannah RJver Site \unsi l»)3
THIS PAGE WAS CSTENTIONALLV LEFT BLANK.
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no
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Units =
MCI, = 5
a
r;
Sec I igure 11 for Miisler Legciul
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Record of Decision for the »0SRC:RP;97-4°2
D-Area Oil Seepage Basin -631-G) (U) Revision 1. Final
Savannah RJver Site Auyjst 1908
THIS PAGE WAS INTENTIONALLY LEFT BLANK.
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j Ml I.ill I
CHOSS SECTION LOCATION MAP
MAPS
O ••-- -
LEGEND TOR Cf?OUNDWATEn
CROSS SECTIONS
«.r»i t IM n f i
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HI*.it-tit:
> l.lm.l
THIS PACK «'AS INTKNTKINAI.I.V I.EKT IlLANK.
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Record of Decision Tor the
D-Arta Oil Seepage Basin (631-G) (U)
Savannah River Site
VVSRC-RP-97-402
Revision 1. Final
August 1998
Groundwater samples were analyzed for metals and 22 were detected at least once at concentrations above their
quamitation limits. Generally, the meiaJ concentrations are low when compared with background and are within an
order of magnitude of the screening levels. The exceptions are iron and manganese, which have their maximum
concentrations (392.300 \izf[ iron and 66,400 pg/l manganese) in the upper portion of the aquifer immediately below
the former trenches. Elevated concentrations of these two metals continue to the southwest of the unit.
Surface Water
Surface water was sampled in the wetlands located downgradient of the D-Area OSB. Six VOCs, 1 SVOC. 10
metals, and cyanide were detected at very low or estimated ("J"-qualified) concentrations. The impact of the
detected compounds is not significant when compared to background.
Sediment
Sediment at the unit was sampled from ihe Carolina bay to the west of the basin and from wetlands to the south. The
concentrations of all detected compounds were estimated ("J"-qualifiers) or low when compared to background, and
there were no apparent patterns to indicate the source for any of the detected constituents.
Fate and Transport Assessment
The conditions at the D-Area OSB appear to be favorable to the natural breakdown of the organic contaminants
through the action of the in-situ bacterial population in the subsurface. Evidence of the degradation of contaminants
in both the soil and groundwater are shown below:
SOIL
GROUNDWATER
Elevated carbon dioxide and methane in
soil gas
Depressed oxygen in soil gas
Location of the soil gas anomalies in close
proximity to the most contaminated
location
Depressed pH levels in contaminated areas
Bacterial "slime" and noxious odors in one
sample
Presence of breakdown products (DCE and
vinyl chloride)
depressed dissolved oxygen downgradient
Enhanced mobility of iron and manganese
Elevated chemical oxygen demand, chloride
and sulfate levels downgradient
Depressed pH levels in contaminated areas
Presence of breakdown products (DCE and
vinyl chloride)
45
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Record of Decision for the WSRC-RP-97-402
D-Area Oil Seepage Basin (631-G) fU) Revision 1, Final
Savannah River Site August 1998
Soil Leachability Analysis
The soil data set was subjected to analysis by the soil screening level (SSL) process and Multimedia Environmental
*
Pollutant Assessment System (MEPAS) computer model runs to evaluate -the potential for constituents in the soil to
migrate to the groundwater at levels exceeding their MCLs or risk-based concentrations (RBCs). Twenty-four
constituents failed the SSL screening process (7 VOCs. 4 pesticides, and 13 melab) and were considered to be.^
potentially leachable from the soil to the groundwater.
Following the SSL evaluation, two types of MEPAS computer simulations were conducted: a unit-wide evaluation
for all 20 compounds and a "hot-spot" evaluation of the three constituents (antimony, methylene chloride
(dichloromethane). and dieldhn) that failed the unit-wide test. All three of the remaining constituents failed the
second series of "hot spot" runs, indicating that they have the potential to leach to the groundwater at concentrations
exceeding the MCL or RBC, even after removing the sources from the most contaminated area of the trench.
After completion of the RFI/RI report, a supplemental calculation for a mass-limited SSL (MLSSL) was completed
for methylene chloride. This supplemental calculation raised the target remediation concentration from 1.0
microzram per kilogram (ug/kg) (the SSL) to 41 ug/kg (the MLSSL). This is well below the maximum
concentration in the RFI/RI (2,400 ug/kg) but exceeds the current (post-biovent test) sample results (4 ug/kg) by a
factor of 10 (WSRC, 1997b, c). The biovent test cycle has been extremely effective in removing methylene chloride
from the basin soils.
Groundwater Transport Analysis
The area in the vicinity of the D-Area OSB is currently listed as industrial future land use (DOE, 1996). Therefore,
the potential for utilization of the shallow water table aquifer for potable water uses is minimal, and the only valid
exposure scenario to unit groundw-ater is through the discharge of grour.dwater from the water table aquifer to the
Savannah River or Fourmile Branch.
The estimated flow rates in the aquifer beneath the unit indicate that constituents in the groundwatir could have
traveled up to 2.350 m (7.700 ft) since the unit was opened in 1952. and up to 1,120 m (3.630 ft) since the basin was
closed in 1975 (WSRC, 1997a). The fact that the largest plume in the groundwater (TCE) extends only 365.8 m
(1.200 ft) from the source area (1/3 to 1/6 the distance predicted by groundwater flow) indicates that degradation,
volatilization, retardation and other factors are working to reduce the impact of the basin disposal practices on the
local groundwater.
46
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Record of Decision for the WSRC-RP-97-402
D-Area Oil Seepage Basin (631-C) (U) Revision 1, Final
Savannah River Site ___ August 1998
VI. SUMMARY OF OU RISKS
As pan of the D-Area OSB RFI/RI process, a BRA was prepared to evaluate the potentiaJ risk to human health and
the environment from chemical contaminants identified in investigations at the D-Area OSB. The following sections
outline the results of the human health risk characterization and the ecological risk characterization. A complete
discussion of the risk assessment methodology, receptor analysis, risk characterizations, and uncertainty within the
characterizations can be found in the RFI/RI Report and BRA (WSRC, 1997a).
Unit-specific data from the RFI/RI were used to identify and screen constituents of potential concern (COPCs;.
Exposure point concentrations were calculated and used to estimate potentiaJ exposures and risks to humans and
wildlife. Carcinogenic risks and hazard indices (His), based on a combination of exposure scenarios, locations, and
receptors identified in the CSM, were calculated and then compared to EPA risk guidelines [i.e., 1E-04 to IE-06
carcinogenic risk, HI > 1, and Ecological Effects Quotient (EEQ) > 1]. COPCs were selected as preliminary COCs
(PCOCs) and designated as primary or secondary COCs, based on their individual contribution to total media risk or
hazard.
Human Health Risk Assessment
To evaluate the risk to human receptors due to the contamination at the D-Area OSB, unit-specific analytical data are
used to identify COPCs. Exposure point concentrations are determined for each COPC to estimate the potential
exposure for various receptors and exposure scenarios. Receptors were selected based on the current land use and
two potential future land uses. Receptors include a current known on-unit worker (researchers and samplers), a
hypothetical future on-unit industrial worker, and a hypothetical future on-unit resident (Figure 7a). Environmental
media evaluated in the BRA include surface soil, excavated/subsurface soil, "hot spot" soil, surface water (wetland).
sediment (wetland and Carolina bay), and groundwater (Figure 7b).
Following the selection of human receptors for evaluation, the cancer risk and the noncancer health hazard were
estimated for each COPC and for each pathway/receptor combination, based on EPA guidance (EPA, I989b).
Carcinogenic risk is defined as the incremental probability of an individual developing cancer over a lifetime as a
result of pathway-specific exposure to cancer-causing contaminants (carcinogens). The risk to an individual
resulting from exposure to non-radioactive chemical carcinogens is expressed as the increased probability of cancer
occurring over the course of a 70-year lifetime. At NPL sites incremental cancer risk is compared to the EPA target
risk range of one in ten thousand (IE-04) to one in one million (IE-06).
47
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Record of Decision for the WSRC-RP-97-4D2
D-Area Oil Seepage Basin v6Jl-G) CO Revision 1, Final
Savannah River Site August 1998
Noncarcinogenic hazards ire also evaluated to identity a level at which iher; may be concern for potential
noncarcinogenic health effects. The hazard quotient (HQ), which is the ratio of the exposure dose to the reference
dose, is calculated for each contaminant. HQs are summed for each exposure pathway to determine the specific HI
for each exposure scenario. If the HI exceeds unity (1.0), there is concern that adversc-health hazards mi^ru exist.
Current Land Use - Carcinogenic Risks
f
Under the current land use scenario, human health risks were characterized for the current on-unit worker. Estimated
cancer risks from surface soil ingestion, dermal contact, and particular inhalation were less than 1E-06, indicating r.o
concern for carcinogenic health effects (Table 2).
Future Land Use - Carcinogenic Risks
The hypothetical future on-unit worker scenario has two exposure routes with carcinogenic risks within the target
range of IE-CM to 1E-06 (Table 2). Ingestion of excavated soil has a risk of I E-06 primarily due to the ingestion of
arsenic and PCB-1260, and ingestion of groundwater has an estimated risk of 5E-05 primarily due to the ingestion of
beryllium. bis(2-ethylhexyl)phthaJate, and vinyl chloride. The risks for the future worker from all other pathways are
less than the EPA point of departure (IE-06),
Several pathways for the future on-unit resident have estimated risks within the target range (Table 2). Ingestion of
surface soil and excavated soil have risk values of 1E-06 and IE-OS, respectively. The primary contributor to risk
for ingestion of surface soil is PCB-1260. The primary contributors to risk for ingestion of excavated soil are arsenic
and PCB-1260. Ingestion of leafy, tuberous, and fruit produce grown in excavated soil has estimated risk values of
2E-06, 1 E-06. and 3E-06, respectively. The primary contributor to risk for all of these pathways is arsenic. Dermal
contact (3E-06) with ground water and inhalation of VOCs (1E-05) in groundwater during showering also have
estimated risks between 1E-06 and 1E-04. The risk for hypothetical residential exposure to groundwater by
ingestion (2E-04) is the only pathway to exceed the target risk range. Beryllium, bis(2-ethylhexyl) phihalate. and
vinyl chloride are the primary contributors to the risks from ingestion and dermal contact, while groundwater
inhalation risk is due to 1,1-DCE. cis-l,2-DCE. and vinyl chloride.
Current Land Use - \oncjrcinoytnic Hazards
The BRA shows that potential adverse noncarcinogenic health effects are not likely to occur because the sum of the
His for the current on-unit worker scenario do not exceed a value of 1.0 (Table 2).
Future Land Use - Moncarcinogenic Hazards
No r.c arc i no genie His for the hypothetical future on-unit worker do not exceed 1.0 for any of the pathways evaluated
(TaBTe?).
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Record of Decision for the
D-Area Oil Seepage Basin (631-C) fU)
Savannah River Site
WSRC-RP-97-402
Revision 1. Final
August 1998
Table 2
Summary of Risk-Based
PCOCs, Grouped by Exposure Route
Receptor *
Current Known On-Unit
Worker
Hypothetical Future
Worker
Hypothetical Future
Resident
Exposure Route/
Pathway
None
Ingestion of Excavated
Soil
[ngestion of Groundwater
Ingestion of Surface Soil
Ingestion of Excavated
Soil
Ingestion of Homegrown
Produce Using Excavated
Soil
Leafy vegetables
Tuberous vegetables
Fruits
Ingestion of Groundwater
Dermal Contact with
Groundwater
Inhalation of
Groundwater
Preliminary
COCs
None
PCB-1260. As
Be. BEHP. Vinvl Chloride
PCB-1260
PCB-1260. As
Fe, Tl. As
As
.As
As
Be. BEHP. Vinvl Chloride,
1.1-DCE. PCE
Mn. Tl, Fe. BEHP.
1.2-DCE (mixture)
Be, BEHP
1,1-DCE, cis-1 .2-DCE.
Vinvl Chloride
Carcinogenic
Risks
l.E-06
5.E-05
l.E-06
l.E-05
2E-06
1E-06
3E-06
2.E-04
3.E-06
l.E-05
Hazard
Index
1.13
4
No Ecological Receptors were identified as being impacted by Unit-Specific Chemicals.
PCB = polychlorinated biphenyls
As = arsenic
Be = beryllium
BEHP = bis(2-ethylhexyl)phthalate
Fe = iron
BOLD = FINAL Risk-Based Constituents of
Concern.
Tl = thallium
Mn = manganese
DCE = dichloroethene
PCE = tetrachloroethene
49
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Record of Decision for the WSRC-RP-97-402
D-Area Oil Seepage Basin (631-G) ft,") Revision 1. Final
Savannah River Site August 1998
The His tor hypothetical future resider.: exposures equal or exceed 1.0 for the tngesticn of excavated soil a.-.d for the
ingestion of groundwater (Table 2). The HI for ingestion of excavated soil is slightly greater than one and is
primarily a result of thallium, iron, and arsenic concentrations. The HI for groundwater ingestion during childhood
is 4 and the HI for groundwater ingestion during childhood through adulthood is 2. These hazards are due primarily
to thallium and manganese.
Total Pjf/txav Risks and Ha-ard Indices
Carcinogenic risks and noncarcinogenic hazards associated with the individual exposure pathways for surface soil
(0-1 ft;, excavated soil (0-4 ft), surface water, sediment and groundwater have been summed to obtain total pathway
risks and His for each receptor (worker and resident). The total risk from surface soil (0-1 foot) and excavated soil
(0-4 ft) were summed with the total risk from surface water, sediment, and groundwater for a total risk from all
exposure pathways across all media for each receptor.
The total pathway risk values for the current known on-unit worker, hypothetical future on-unit worker, and
hypothetical future on-unit resident are 6E-09, 5E-05, and 2E-04, respectively. The risk values that exceeded the
EPA point of departure (1E-06) for the future receptors are a result of exposure to constituents in groundwater.
Total pathway His exceeded 1.0 for the future on-unit resident. These His were 5 [for pathways excluding excavated
soil (0-4 ft)] and 6 [for pathways excluding surface soil (0-1 ft)]. The noncarcinogenic hazards for the future on-unit
resident were a result of exposure to chemicals in groundwater and exposure to arsenic in excavated soil.
Ecological Risk Assessment (ERA)
The.purpose of the ERA component of the BRA is to evaluate the likelihood that adverse ecological effects are
occurring or may occur as a result of exposure of biological organisms to unit-specific chemical constituents. The
specific methodology followed in the ERA for the D-Area OSB consists of a two-tiered evaluation. The first tier of
the process is the selection of ecological COPCs through a screening evaluation. Any analytes that fail the screening
are classified as COPCs and are evaluated in the second tier of the process, the ERA. The ERA is based on more
unit-specific and realistic assumptions than the consistently conservative assumptions used in the screening.
Accordingly, the ERA assesses whether COPCs, identified as having a potential to pose ecological risk in a very
conservative screening, are actually likely to pose risk to assessment endpoints under existing or future conditions at
the unit.
COPCs art; identified following qualification and evaluation of data, and screening of inorganics against unit-specific
background levels. Unit-specific soil wus grouped into exposure groups in three exposure areas: (! .1 the area of the
50
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Record of Decision for the WSRC-RP-97.402
D-Area Oil Seepage Basin (631-G) (V) Revision 1. Final
Savannah River Site August 1998
former basin. (2) the Carolina bay to the west, and (3) the wetland area to the south. Soil data from a depth of 0-0 3
m (0-1 ft; are used to estimate COPC exposure point concentrations under current land use conditions at the basin.
Subsurface soil samples from a depih of 0-1.3 m (0-4 ft) are used to evaluate future risk, under the assumption of
future excavation activity in the basin area associated with a hypothetical future human residential land use scsnano.
Croundwater data collected at the unit are evaluated under the future scenario by conservatively assuming thai
current groundwater concentrations of COPCs will discharge to surface water without attenuation or dilution.
Sediment data from the Carolina bay and the wetland and surface water data from the wetland are assumed to remain
unchanged under future conditions.
Exposure point concentrations for COPC selection are based on the maximum detected concentration for each
exposure group. Exposure point concentrations for the ERA are based on the RME concentration, the highest
concentration to which a receptor may reasonably be exposed. In selecting COPCs, those analytes that pass to.xicity.
background, and frequency of detection screenings but have an aquatic bioconcentration factor greater than 300 are
re-included as COPCs due to their potential to pose risk through bioaccumulation and/or biomagnification.
The ecological study area at the D-Area OSB includes a variety of habitats, both terrestrial and wetland. No known
endangered, threatened, or special concern species exist in the study area. The basin area has been highly impacted
physically by previous activities at the unit, and the habitat (mowed field) is low in diversity and productivity. Areas
adjacent to the unit include a mesic pine/hardwood forest, a Carolina bay wetland, and a blackgum/sweetgum
wetland.
Following the identification of ecological COPCs and the characterization of the ecological communities of the study
area, ecological assessment endpoints are selected so as to determine whether relevant policy goals (protection of the
environment under CERCLA and protection of wetland surface waters under the Clean Water Act) are being attained
at the OU. Ecological risk from unit-specific COPCs is assessed on the basis of the potential for adverse effects on
the assessment endpoints: (1) survival and reproduction of terrestrial wildlife populations at the unit, including
herbivores and predators; and (2) survival and reproduction of populations of aquatic species and of terrestrial
wildlife species that prey on aquatic species in the wetland near the unit. Effects on assessment endpomts are
predicted from measurement endpoints (e.g., levels of COPCs that have been shown to produce toxic effects m
animal studies). Decision rules by which the potential for effects on assessment endpoints are decided are stated in
terms of the measurement endpoints and are based on the calculation of HQs.
In order to evaluate potential effects on the assessment endpoints, multiple ecological receptor species are chosen to
represent the multiple trophic levels of the ecological communities present within the study area. The receptors
evaluated include: (I) aquatic organisms directly exposed to surface water and sediment; (2) a herbivorous rodent
51
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Record of Decision for the \\ SRC-RP-97-402
D-Area Oil Seepage Basin (631-G) fU) Revision 1, Final
Savannah River Site August 1998
(meadow vole) directly exposed to soil, sediment, and surfac; water, as well as biotic uptake of COPCs: and (3)
predators (mink and green-backed heron) that are directly exposed to environmental media as well as to
bioaccumulative COPCs in the food chain.
Risks to each of these receptors from the exposure groups ai the OU are estimated on the basis of calculated HQs.
COPCs with an HQ greater than on* are designated as PCOCs. Risk is estimated for both current conOWons and
hypothetical future conditions (i.e.. assuming wildlife exposures to subsurface soil that may be excavated, and
assuming exposure of aquatic organisms to current groundwater concentrations of COPCs). PCOCs ar« individuaHy
evaluated based on their chemical and lexicological characteristics and the uncertainty associated with their°HQ
value. Those PCOCs that are estimated to have a significant potential to cause adverse ecological effects are
summarized for each combination of exposure area, receptor, and medium. This subset of COPCs is further
evaluated based on uncertainty in the risk assessment, confidence in the risk estimates, and the ecological
significance of the risk estimated to be posed by these PCOCs. This evaluation of ecological significance ultimately
determines whether each PCOC actually poses significant ecological risk and warrants designation as a final COC.
The ecological receptors identified as having a significant potential for lexicological effects at the D-Area OSB are
aquatic, semi-aquatic, and benthic organisms living in the Carolina bay and the wed and. The community of
aquatic/semi-aquatic organisms that can be supported by the Carolina bay is inherently restricted in diversity and
abundance of organisms due to the intermittent character of the inundation of the bay and its hydrological isolation.
The ERA found that there may be significant potential for adverse effects from DRO on the more sensitive members
of the aquatic community during chronic, long-term exposures. However, such exposures are unlikely due to (be
frequent dry periods during which the aquatic animal community is essentially absent. DRO at the concentrations
detected in sediment is unlikely to significantly affect populations of aquatic species at the Carolina bay, therefore.
the ecological risk posed by DRO is considered insignificant, and it is not a final COC.
The aquatic community in the arm of the wetland that extends to the south of the OU also is subject to intermittent
desiccation, though it appears to be a more diverse and productive community than that of the Carolina bay. A
potential for adverse ecological effects on this community is indicated by the measured concentrations of aluminum
and barium in surface water and of DRO and TPH in sediment. Chronic exposure of aquatic organisms (e.g..
invertebrates, fish, and amphibians) to these contaminants at RME levels could reduce reproduction and/or increase
mortality among sensitive individuals sufficiently to cause a reduction in population size. However, if such effects
are limited to the small area evaluated, the larger ecological community of the wetland system is unlikely to
experience significant effects, such as a loss of species. Therefore, aluminum and barium in surface water and DRO
and TPH in sediment of the wetland are unlikely to pose significant ecological risk to the wetland assessment
endpoint (the biodiversity of the aquatic community), and they ore not considered to be ecological final COCs.
52
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Record of Decision for the VVSRC-RP-97-lo:
D-Area Oil Seepage Basin (6J1-G) 0.") Revision I. Final
Savannah River Site . August 1998
In summary, the assessment of ecological risk at the D-Area OSB indicates that the COPCs and environmental media
in the exposure areas evaluated do not pose significant risk to ecological assessment endpoints. and policy goals for
the OU are achieved under baseline conditions. There is essentially no Iik±lihood of unit-specific chemicals causing
significant impacts to the community of species in the vicinity of the unit. Based on their toxicity at their current
concentration, none of the COPCs identified in soil, sediment, or surface water at the D-Area OSB are estimated to
pose significant ecological risk.
COCs
PCOCs. which include primary and secondary COCs, were selected for the D-Area OSB because they exceed
ARARs, because they exceed risk-based criteria in the BRA, or because they are projected to have the potential to
leach to the groundwater at levels exceeding an MCL or RBC. Primary COCs are defined in the human health nsk
assessment as constituents that contribute a chemical-specific risk of more than IE-06 or an HQ of greater than 0.1 to
any media risk estimate that exceeds a 1E-04 risk or an HI of 3. Secondary COCs are defined as those constituents
in each medium contributing a chemical-specific risk greater than IE-06 or an HQ of at least 0.1 to a media with a
risk greater than IE-06. but not more than 1E-04 or an HI of one or greater, but not more than three. Table 3 lists all
PCOCs and the basis for their qualification as PCOCs.
The final risk-based COCs are presented by potential receptor scenario, pathway, and exposure route in Figures 12
through 16.
Final COCs were selected from the PCOCs by evaluating the uncertainty associated with each chemical during each
phase of the RF1/RI/BRA (Table 4). Eight groundwater PCOCs [1,1-DCE; cis-l.2-DCE, total 1,2-DCE; benzene.
dichloromethane (methylene chloride); PCE: TCE; and vinyl chloride] were judged to be USCs and, therefore, final
COCs. One soil PCOC [dichloromethane (methylene chloride)] was judged to be a USC and. therefore, a final COC
-------
Record of Decision Tor the
D-Area Oil Seepage Basin (631-G) (U)
Savannah River Site
WSRC-RP-97-402
Rerision 1, Final
August 1998
Table 3
Summary of PCOC»
PCOC Name
1.1- Dichloroethene
1 .2-Dichloroethene (cis-)
i. 2-Dichloroethene (mixed)
Antimony
Benzene
Beryllium
Bis(2-ethylhexyl)phthalate
Dichloramethane
Iron
Manganese
Tetrachloroethene
Thallium
Trichloroethene
Vinyl chloride
l.l-Dichk>roe(hene
1 .2-Dichloroethene (cis-)
Beryllium
B i$< 2 -ethyihexy 1 Iphthalate
Vinyl chloride
Antimony
Dichloro me thane
Dicldrin
Thallium
Arvenic
Iron
PCB-1260
Thallium
Risk or
Basis Hazard Pathways
Value
PRIMARY GROtNDWATER COC* '
exceeds risk criterion 2E-06 resident (childhood through adulthood) ingesa'oa
4E-06 resident (childhood through adulthood) inhalation
exceeds MO.'
exceeds hazard criterion 0.27 / 0.49 resident (childhood through adulthood / childhood
only) ingQncn
exceeds hazard criterion 0.1/0.26 resident ; childhood :hrough adulthood /childhood
only) ingesticn
exceeds MCL1
exceeds risk criterion 2E-04 resident I childhood through adulthood) ingestion
exceeds risk criterion IE -05 resident (childhood through adulthood) ingesnon
exceeds MCL1
exceeds hazard criterion 0. 1 / 0.2 resident (childhood through adulthood / childhood
only) tngestioft
exceeds .M€tJ
exceeds hazard criterion 0.3 / 0.6" resident (childhood through adulthood / childhood
only) ingesrion
exceeds hazard criterion 0.4/0.77 resident (childhood through adulthood / childnoed
only) ingesnon
exceeds risk criterion 2E-06 resident (childhood through adulthood) ingesnon
exceeds MCL1
exceeds hazard criterion 0.9 / 1 .7 resident (childhood through adult / childhood oiii)*
ingestion
exceeds MCI'
exceeds MCL1
exceeds risk criterion- 2E-05 resident (childhood through adulthood) ingesQoa
exceeds MCI?
SECONDARY GROUND WATER COO J
exceeds risk criterion 4E-06 resident (childhood through adulthood) inhalation
exceeds risk criterion 4E-06 resident (childhood throogh adulthood) inhalation
exceeds risk criterion 4E-OS industrial worker \nfatHf
exceeds risk criterion I E-06 resident (childhood through adulthood) dermal
contact
exceeds risk criterion 3E-06 industrial worker ingestion
exceeds risk criterion 1E-06 resident (childhood through adulthood) dermal
contact
exceeds risk criterion 5E-06 industrial worker ingestion
exceeds risk criterion 4E-06 resident (childhood through adulthood) inhalation
PRIMARY SOIL COO '•
Projected to leach to groundwaier in excess of MCL or RBC
Projected to leach to groundwater in excess of MCL or RBC
Projected to leach :o groundnut: in excess of MCL at RBC
Projected to leach to groundwater in enctss of MCL or RBC
SECONDARY SOIL COO '-
exceeds nsk criterion IE -06 industrial worker ingestion fioil 0- 1 .2 m)
exceeds nsk criterion 9E-06 resident ingesucn and produce ingestion (0-1 .2 m)
exceeds hazard cnterion 0.2 resident (childhood only; ingestion (soil 0-1.2 m)
exceeds hazard criterion 0.2 resident (childhood only) ingestion (soil 0-1.2 m)
exceeds risk criterion 1 E-06 resident (childhood through adulthood) ingestion
(soil 0-0.3 m)
exceeds hazard criterion 0.7 resident (childhood onM ineesdon (soil 0-1.2 m)
Primary COCi *re Je fiord u COPO whcft rontnbuu upufciftiiy •'cterrjciVtpec-/r rak of n !eui : E-«>S or checmciJ-tpec-jic haunJ ofO I) to i pathway
(uw| > toul ruk if greater than IE-0* or HI puier ifuwi three, of *hc.t ire pro«rnl :o leva to {rounrtwiur u concrmniioru :ueeJifl| in MCI. or RBC
Secondary COC i ire Jc fined u COPCi ihii ^I»T ichcmcii-ipcr/c nr»-c: r^ic ;ruvr u*un IE 06. IT i .-
huifd of 0 1 -*tac3«orunbui£* to * p«h»iy *\uard pznti '^^n o^t.
Sod COO w« it>
Sec Tick *- 1 * '*SRC. I990a
54
-------
Table 4
Uncertainly Matrix for C'OCs
Constituent Name
Gruuntlwater COCs
Antimony
Benmnc
Dcryllium
ms(2-clhylhexyl)phlhalate
Dichloroethenc, (ck-) 1,2-
Dicliloroelliene.(mL\-eti-)l,2-
nichlorotlhene, 1.1-
Dii'hloroHiellmiiit (ntelliylene clilurltle)
tun
Manganese
Ttlnwhlurueilmnt
1 hallium
Trii-hluroethene
Vinyl chloride
Soil C0(\
Antimony
Arsenic
Duiiloronielliane (mtlhylene i-liltiriilt)
Dicldrin
Iron
PCU-1260
I'liallium
CATEGORY UNCERTAINTY LEVELS «
Unit
History
high
LOW
high
high
LOW
LOW
LOW
high
high
high
LOW
high
LOW
LOW
high
high
LOW
high
high
unknown
high
Background
Comparison
LOW
LOW
high
LOW
LOW
LOW
LOW
.OW
.OW
.OW
.OW
.OW
LOW
LOW
high
high
LOW
high
LOW
LOW
high
Analytical
high
LOW
LOW
LOW
LOW
LOW
LOW
high
LOW
LOW
LOW
high
LOW
LOW
high
high
LOW
high
LOW
LOW
LOW
Unit-Related
Distribution
high
LOW
high
high
LOW
LOW
LOW
LOW
LOW
LOW
LOW
high
LOW
LOW
LOW
high
LOW
high
LOW
high
high
Toxicity
high
LOW
LOW
LOW
LOW
LOW
high
LOW
high
high
LOW
high
high
LOW
NA
LOW
NA
NA
high
high
high
Risk
Assessment
high
high
LOW
LOW
LOW
LOW
LOW
high
high
high
LOW
LOW
high
LOW
NA
high
NA
NA
high
high
high
Exceeds
ARAR?
high
LOW
high
LOW
LOW
LOW
LOW
LOW
high
high
LOW
LOW
LOW
LOW
high
high
high
high
high
high
high
, _l_ ^
Overall
Level of
Uncertainty
high
LOW
high
high
LOW
LOW
LOW
LOW
high
high
LOW
high
LOW
LOW
high
high
LOW
high
high
high
high
Retain as
linal
COC?
no
YES
no
no
YES
YLS
YES
YES
nu
no
)/:.V
no
YES
YES
no
no
YES
no
no
no
no
Uncertainty = "LOW" indicates that this analyle could be a llnal COC based solely on the indicated category.
Uncertainly = "high" indicates thai this analyle could noi be a final COC based solely on the indicated category.
NA '- Category docs not ;i|>|>ly because this compound was added to this list based on its potential lo leach to groundwatcr.
< > 0
u :, o
3 n -i
3 O O.
|> « -•
i -o a.
a ;
ff\
o
r.
-•"IT
'
-------
Record of Decision for the WSRC-RP-97-402
D-Area CHI Seepage Basin (631-G) (U) Revision 1. Final
Savannah River Site August 1998
THIS PAGE WAS INTENTIONALLY LEFT BLANK.
56
-------
31
c
-^
n
a
D.
8
=r
o
O
n
C
o
n
or
-0
5-
p
J^
n
C
3
•i4Clltt«l ItUMMII ICiC|'lulft
luve been ouuiicJ
"* llltul«IIUII iW VtX'l JUIIII| ttUUKlluUI UK Ul
NC' Nul Ctlculiied due tu » >Kk uf loxu ily il4U
NA Nu ft^lickblc
NU Nu itau weie ivtiUtlc Im llu» iicdiuin
Cuclwigciik MUk COCi
HoCOC,
H» ClK'i
NoCOC.
NA
NA
NA
NA
NuClX'i
N.' I (X'i
No COC'i
Nl)
NU
NC
NC'
NA
NA
NC
No I'OCi
NufLK',
NA
NA
NA
NA
N.iCIH't
N..CCX'|
Nil
Nil
N..C.LH,
N..(ln'>
NA
NA
NA
3 ra n
3 U O.
S-92.
< » f?
3-35:
j!»0 3
3 n
£
O
C
"»
- o' yg
*O ti ®
oo ri u
-------
Record of Decision for the WSRC-RP-97.402
D-Area Oil Seepage Basin (631-G) (U) Revision 1. Final
Savannah River Site . August 1998
THIS PAGE WAS INTENTIONALLY LEFT BLANK.
58
-------
T1
(TO
- 7i
n Z'
C T
D cr
n u
3 »
3 Q.
5 O
O
c
o
O
C
m
•*
n
u
o
o
cr
^<
•o
u
liavc been unuilcJ
** lnhal«lioa ul VlK'l Juniif huulclttitj ukc ul
NT Not Clkuliuj due lu I l<>.li ul lull, lly Jiu
NA Nul .ptilK.blt
Nl> Nudtfi weic •vaiUble fm (hit litcdluin
C.rclnojcMk Hbk CUCi
N.I cxx:«
NofUC'.
Nu C'CX'i
(In COO
NA
NA
NA
NA
NA
NA
NA
Nil
Nl)
NA
NA
NA
NA
IU»rd Old
1
Nl'
N.i('(H'>
NullX'i
N,. (XX'.
NA
NA
NA
NA
NA
NA
NA
Nil
Nil
NA
IIA
N.,1 l« ,
II f:
NA
u i, o
3 i» 2
3 M Q.
f Decision for the
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Record of Decision for the WSRC-RP-97-40"*
D-Ar*a Oil Seepage Basin (631-G) (U) Revision 1. Final
Savannah River Site Aueust 1998
THIS PAGE WAS INTENTIONALLY LEFT BLANK.
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Record of Decision for the WSRC-RP-97-402
D-Area Oil Seepage Basin (631-G) (U) Revision 1, Final
Savannah River Site _ ^^___ August 1998
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Record of Decision for the WSRC-RP-97-10:
D-Area Oil Seepage Basin (631-G) (U) Revision 1, Final
Savannah River Site . August 1998
THIS PAGE WAS INTENTIONALLY LEFT BLANK.
64
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Figure 16. Risk-based COCs for the Future Resident, with E.x
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Record of Decision for the WSRC RP 97 •10''
D-Area Oil Seepage Basin (631-G) (U) Revision 1. Final
Savannah River Site August 1998
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66
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Record of Decision for the WSRC-RP-97-402
D-Area Oil Seepage Basin (631-G) (U) Revision 1, FinaJ
Savannah River Site August 1998
VII. RAOS AND DESCRIPTION OF CONSIDERED ALTERNATIVES FOR THE D-AREA OSB OL
RAOs
RAOs address unit-specific contaminants, media of concern, potential exposure pathways, and remediation goals.
The RAOs are based on the nature and extent of contamination, threatened resources, and the potential for human
and environmental exposure. Initially, preliminary remediation goals are developed based upon ARARi or other
information from the RFI/RI Report and BRA. These goals should be modified, as necessary, as more information
concerning the unit and potential remedial technologies becomes available. Final remediation goals will be
determined when the remedy is selected and shall establish acceptable exposure levels protective of human health
and the environment.
ARARs are those cleanup standards, standards of control, and other substantive requirements, criteria, or limitations
promulgated under federal, state, or local environmental law that specifically address a hazardous substance.
pollutant, contaminant, remedial action, location, or other circumstance at a CERCLA site. The following three
types of ARARs have been developed to simplify identification and compliance with environmental requirements:
• Action-specific requirements - set controls on the design, performance, and other aspects of implementation of
specific remedial activities.
• Chemical-specific requirements - are media-specific and health-based concentration limits developed for site-
specific levels of constituents in specific media. There are two general sources of chemical-specific RGOs: (1;
concentrations based on ARARs, and (2) concentrations based on risk.
• Location-specific requirements must consider federal, state, and local requirements that reflect the
physiographical and environmental characteristics of the unit or the immediate area.
Action-specific and location-specific ARARs are addressed as pan of die remedial alternatives developed for the
D-Area OSB groundwater. Only MCLs (as identified in South Carolina R.61-58.5 State Primary Drinking Water
Regulations and Federal 40 Code of Federal Regulations (CFR) 14] National Primary Drinking Water Regulations)
have been identified as chemical-specific ARARs. The groundwater is not a current source of drinking uater.
however, all groundwater in South Carolina is classified as GB under South Carolina R.61-68 Water Classification
and Standards and, as such, is required to be addressed in some manner (State of South Carolina groundwaters must
undergo active remediation to achieve MCLs unless a groundwater mixing zone (GWMZ) is granted). MCLs will be
the clean-up standard for groundwater contaminants.
67
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Record of Decision for the W'SRC-RP-97-402
D-Area Oil Seepage Basin (631 -G) (II) Revision 1. Final
Savannah River Site August 1998
The RFI/RI and BRA identified the following COCs for zroundwater at the D-Area OSB: PCE; TCE: 1.1-DCE:
1,2-DCE: cis-1,2-DCE; vinyl chloride: benzene; and methylene chloride.
Two of these contaminants (1,1 -DCE and 1,2-DCE) became COCs based on risk calculations. However, neither 1.1-
DCE nor 1.2-DCE were detected in the D-Area OSB groundwater at concentrations exceeding their respective
MCLs. MCLs are drinking water standards developed to be protective of human health and obtainable by current
treatment methods. Because these contaminants do not exceed the levels determined to be protective of human
health and safe for drinking water purposes, 1,1-DCE and 1,2-DCE will not be addressed in D-Area OSB
groundwater remediation. However, the remedial alternatives developed for the D-Area OSB groundwater include
groundwater monitoring of VOCs (with the exception of no action) that will be inclusive of 1,1-DCE and 1.2-DCE.
These VOCs are degradation products of TCE and require evaluation during remediation.
The primary chemical-specific ARAR for soil is an EPA SSL for methylene chloride (EPA. 1994). The screening
level limits the concentration of methylene chloride in soil to 1.0 ug/kg based on its potential to leach to
groundwater. A second screening level, the MLSSL (EPA, 1996), has been calculated to be 41 Mg/kg based on unit
specific conditions. Following biovent testing, methylene chloride concentrations were below the MLSSL of 41
ug/kg. Therefore, because methylene chloride concentrations in the soil have been reduced to levels that cannot
leach to the groundwater above the MCL (WSRC, 1998 a) remediation of deep soils is not warranted and it is not
addressed further in this document.
Based on ARARs and BRA results, the RAOs developed for the groundwater at the D-Arca OSB OU are to:
• reduce risks to human health associated with dermal contact and ingestion of groundwater, and inhalation of
groundwater vapor
• restore groundwater to achieve ARARs and RGOs
RGOs for groundwater COCs will be equivalent to their respective MCL values. The groundwater contaminants ihat
will be addressed at the D-Area OSB and their corresponding MCLs are provided in Table 5.
At the close of the IRA. the contractor installed two horizontally oriented, perforated pipes along the length of the
former waste unit for treatability (biovent) study purposes. These pipes were used to force fresh air, nutrients and
tracers into the soils at a depth of about 8 ft in order to volatilize the constituents in the soil, enhance the aerobic
degradation of the constituents in both the soil and groundwater, and monitor the effectiveness of a potential soil
treatment program (WSRC. 1997b, c. d, e).
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Record of Decision for the
D-Area Oil Seepage Basin (6J1-G) fU)
Savannah River Site
WSRC-RP-97-402
Revision 1, Final
August 1998
Table 5
Final COCs, with Selected RGOs
FINAL
COCs
Tetrachloroethene
Trichlorocthene
cis- 1 ,2-Dichloroethenc
total- 1 .2-Dichloroethene
1.1-Dichloroethenc
Vinyl Chloride
Benzene
Dichloromethane
(Meihylcnc Chloride)
Basis for Becoming Final COC
Excess
Risk
X
X
X
X
Excess
Hazard
X
Leach
toGW
X
Exceeds
MCL
X
X
X
X
X
X
Maximum
Concentration
Detected
(ng/i)
85
1151
457
68.6
0.84
52
6.2
9.5
Average
Concentration
in
Groundwater
2.1
8.0
4.88
21.24
0.399
1.1
0.22
0.16
Selected
RGO
(pg/1)
5.0
5.0
70.0
70.0
7.0
2.0
5.0
5.0
Basis
for
RGO
MCL
MCL
MCL
MCL
MCL
MCL
MCL
MCL
69
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Record of Decision for the WSRC-RP-97-402
D-Area Oil Seepage Basin (631-G) (U) Revision 1. Final
Savannah River Site August 1998
Secondary Source Alternatives
A3 pan of the investigation/assessment process for the D-Area OSB waste unit, a CMS/FS was performed using data
generated during the assessment phase. Detailed information regarding the development and evaluation of remedial
alternatives can be found in the Corrective Measures Study/Feasibility Study for the D-Area Oil Seepage Basin
(631-G) (U) (WSRC, I998a). The RF1/RI and BRA indicate that D-Area OSB groundwater poses a risk to human
health. Risk associated with ingestion. dermal contact, and inhalation of groundwater for the future on-unit worker
and resident result in risk greater than the EPA's target risk range for future use scenarios. Therefore, a CMS/FS was
conducted, which includes detailed analyses and groundwater alternatives. Concerning other environmental media.
the no further action alternative was selected for soil, and no action is required for surface water and sediment.
Remedial alternatives were not developed for soil, surface water, or sediment at the unit. Remediation of these
media is not warranted based on the evaluation of federal and state standards and the risk assessment. As discussed
above, the interim action and the biovent test cycle performed on unit soil adequately eliminated the source of
groundwater contamination. Six alternatives were evaluated for remedial action of the D-Area OSB OU
groundwater. Each alternative is described below.
Alternative GW-1 • No Action
Under this alternative, no remedial efforts would be conducted to remove, treat, or otherwise reduce the toxicity.
mobility, or affected volume of contaminated media. An ERA and biovent test have been conducted for unit soils.
These reduced contaminant concentrations to acceptable levels. Biovent testing appears to have also reduced
groundwater contaminant concentrations in the vicinity of the testing. However, under the no-action alternative, no
further remedial efforts would be made to monitor or treat unit groundwater.
The semi-confining unit ("tan clay") lying within the uppermost, water table aquifer is not continuous and has not
prevented contaminant migration. However, the next confining layer ("green clay") provides an adequate barrier.
which prevents the migration of COCs to lower aquifers (Figure 10). Additionally, modeling results indicate that
under most scenarios, contaminant plumes have already largely reached their maximum extent down gradient and will
not migrate significantly further. Therefore, both the horizontal and vertical migration of contaminants appears to
have largely stopped. However, the no-action alternative would not provide a mechanism to monitor the migration
of contaminants in the future and confirm that further migration is not occurring. Additionally, the no-action
alternative would not guarantee that access to contaminated groundwater would be restricted.
If no action were implemented, no action would be taken to reduce or monitor contaminant concentrations.
Transport modeling of the D-Area OSB DCE, PCE. TCE. and vinyl chloride contaminant plumes indicates that
70
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Record of Decision for the N WSRC-RP-97-402
D-Area Oil Seepage Basin (631-G) fU) Revision 1. Final
Savannah River Site August 1998
without degradation concentrations would be reduced to below MCLs within 35 years. (Model runs that included
degradation indicated that the maximum time required for contaminants to reach their MCLs was only approximately
10 years.) For the purpose of cost estimating, the maximum length of time to be evaluated is 30 years, as determined
by EPA guidance. Therefore, the cost of this alternative would include a review of remedy every five years for 30
years and would total 5278,000.
Alternative GW-2 • Natural Anenuation/GWMZ with institutional Controls
Under this alternative, natural subsurface processes, such as flushing, volatilization, biodegradation. adsorption, and
chemical reaction with subsurface materials, would be allowed to continue to reduce contaminant concentrations in
the groundwater to acceptable levels. A GWMZ application has been approved by the SCDHEC under South
Carolina Regulations R.61-68 as part of this alternative. This GWMZ creates a specific area at the unit that would
be required to meet mixing zone concentration limits (MZCLs) at plume monitoring wells. Downgradient
compliance boundary wells would be installed. Groundwater at this compliance boundary would be required to meet
RGOs (equivalent to MCLs). Between the compliance boundary wells and the plume wells, intermediate wells will
be monitored and compared to concentrations predicted by the fate and transport models. The well locations for the
approved GWMZ are illustrated in Figure 17. In addition to groundwater monitoring, institutional controls will be
maintained to restrict access to groundwater until RGOs are met in all areas of the plume. Institutional controls
would include:
• controlled access to SRS through existing security gates and perimeter fences
• signs posted in the area to indicate that groundwater in the vicinity of the unit has been contaminated by
hazardous materials
• deed notification to any future landowner of groundwater contamination, as required under CERCLA Section
120(h)
Although institutional controls are inclusive of the alternatives (except the no-action alternative), the DOE has
recommended that residential use of SRS land in the vicinity of D Area be prohibited (DOE, 1996); therefore, future
residential use and potential residential water usage in this area is unlikely. Modeling of groundwater alternatives.
indicates that MCLs for the contaminants of concern will be met in the D-Area OSB groundwater in approximately
10 years. Upon confirmation that RGOs have been achieved, neither the institutional controls at the unit nor the 5-
year ROD reviews will be required any longer.
Natural attenuation could effectively treat D-Area OSB groundwater. Results from bioventing testing indicate that
the source of groundwater contamination (the D-Area OSB soil) is abated and no longer contributes to groundwater
71
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Record of Decision for the WSRC-RP-97-402
D-Area Oil Seepage Basin (631-G) fU) Revision 1, Final
SaTannah River Site August 1998
contamination. Evidence presented in the RFI/RJ and BRA indicated that natural degradation is occurring in D-A/ea
OSB groundwater. Herbert et al.. 1984. report that natural attenuation can be selected as a preferred remedial
option when the following site-specific conditions exist:
• Groundwater is unsuitable for consumptive use.
• Contaminants degrade quickly or are not at highly toxic concentrations.
• There is low potential for exposure.
• Active restoration is not feasible due to complex hydrogeologic conditions.
• There is low projected demand for future groundwater use.
• The unit is in close proximity to a surface water discharge area, with dilution to levels that are protective of
human health and the environment.
The RFI/RI conducted at the D-Area OSB revealed the following:
• The source of contamination at the D-Area OSB was removed during IRA in conjunction with the biovent
testing and no longer contributes to groundwater contamination.
• Naturally occurring mechanisms will continue to reduce contaminant concentrations.
• There are no receptors of groundwater at the D-Area OSB; therefore, there is low potential for exposure.
• The aquifer is limited in thickness and yield and is not targeted for residential or commercial use; therefore.
projected demand for future groundwater use is low.
• Modeling indicates that contaminant concentrations in the D-Area OSB groundwater would be reduced to below
MCLs prior to discharging to Founru'le Branch; therefore dilution in the surface water body is not necessary to
achieve MCLs.
Based on this information the contaminants in the D-Area OSB would be conducive to natural attenuation.
Howard (1990) reports that the half-lives for PCE range from one to two years, for TCE range from 1.5 months to
4.5 years, for cis-l,2-DCE range from eight weeks to eight years, for vinyl chloride range from eight weeks to eight
years, and for methylene chloride range from 14 days to eight weeks. The groundwater modeling effort utilized
contaminant degradation rates from the higher limit (slower degradation) of the range of half-lives for each
contaminant. Therefore, degradation times in the model output were conservatively estimated to be longer than
expected in the field. These model results indicate that all contaminants should be below their respective MCLs
within approximately 10 years. The primary conclusions of the groundwater modeling effort include the following:
1. Degradation is more effective at removing contaminant mass than the simulated extraction wells.
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Record of Decision for the WSRC-RP-97-402
D-Area Oil Seepage Basin (631-G) (U) Revision 1. Final
Savannah River Site August 1998
THIS PAGE WAS INTENTIONALLY LEFT BLANK.
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Record of Decision for the WSRC-RP-97-402
D-Area Oil Seepage Basin (631-G) (U) Revision 1. Final
Savannah River Site Auexist 1998
2. None of the contaminants simulated (DCE, TCE, PCE, and vinyl chloride; ever reached Fournule Branch.
regardless of the modeled scenario.
3. Model runs that included degradation indicated that the maximum time required for contaminants to reach
MCLs was approximately 10 years.
4. Under most scenarios modeled (pumping, non-pumping, degradation, and no degradation), plumes do not
migrate beyond their current extent.
According to the Ground-Water Mixing Zone Guidance Document (SCDHEC. 1997). a GWMZ application must
demonstrate that the unit will meet the following four criteria:
1. "reasonable measures have been taken or binding commitments are made (o minimize the addition of
contaminants to groundwater and/or control the migration of contaminants in groundwater";
2. "the groundwater in question is confined to a shallow geologic unit that has little or no potential of being an
Underground Source of Drinking Water, and discharges or will discharge to surface waters without contravening
the surface water standards set forth in this regulation";
3. "the contaminant(s) in question occurs on the property of the applicant, and there is minimum possibility for
groundwater withdrawals (present or future) to create drawdown such that contaminants would flow off-site";
4. "the contaminants or combination of contaminants in question are not dangerously toxic, mobile, or persistent."
A GWMZ application has been approved by the SCDHEC that demonstrates how D-Area OSB meets these four
criteria. Based on area characteristics and evidence presented in the GWMZ Application, a GWMZ for the D-Area
OSB is an appropriate part of natural attenuation remedies.
Based on data from monitoring wells around the D-Area OSB and groundwater transport modeling (WSRC. 1997b,
Appendix B), remedial goal objectives will be met and MCLs will not be exceeded beyond the GWMZ. This
alternative will reduce the risks associated with groundwater ingestion. dermal contact, and inhalation by ensuring
that through natural GWMZ processes, the nearest groundwater receptor is not exposed to groundwater contaminated
above MCLs.
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Record of Decision for the WSRC-RP-97-402
D-Area Oil Seepage Basin (6J1-G) (V) Revision 1. Final
Savannah River Site . August 1998
Capital costs associated with natural attenuation would include the installation of nine new monitoring wells. Wells
would be sampled quarterly the first year and semiannually thereafter. Operation and maintenance costs would
include groundwater monitoring, maintenance of institutional controls, and a review of remedy every five years until
contaminant concentrations are reduced to below their MCLs within the mixing zone. Transport modeling of DCE,
PCE. TCE. and vinyl chloride indicates that this will be achieved in approximately 10 years. The total estimated
cost associated with natural attenuation is $391,OCX).
Alternative GW-3 • Bio remediation with Institutional Controls
Under this alternative, groundwater would be extracted from the leading edge of the plume, oxygen and other
nutrients would be added, and then the supplemented water would be injected back into the plume area via injection
wells. Institutional controls would be maintained as part of this alternative to prohibit access to unit groundwater
(i.e., SRS security, sign posting, and deed notifications). Groundwater monitoring would also be conducted to
monitor contaminant concentrations and any migration.
This alternative would utilize the same natural processes as natural attenuation, discussed in the previous subsection.
Bioremediation would involve the injection of oxygen and nutrients into the subsurface, which should expedite
natural biodegradation processes. Based on unit conditions and modeling results, bioremediation could effectively
reduce contaminant concentrations in less than ten years.
Following addition of nutrients and oxygen, groundwater would be injected into the aquifer. Injection would require
a variance to inject water exceeding MCLs.
Components of Alternative GW-3 include installation of new monitoring wells, a groundwater extraction system, an
oxygen/nutrient addition system, and wells through which the treated groundwater would be reinjected. Operation
and maintenance costs associated with this alternative would include nutrients, operation, and groundwater
monitoring (quarterly the first year and semiannually thereafter). It is estimated that this remedy will take less than
ten years to reach MCLs. A review of remedy would be required at five and ten years. Estimated costs associated
with Alternative GW-3 total SI, 102.000.
Alternative CW-4g - Air Sparging Hot Spot Areas/GWMZ with Institutional Controls
Alternative GW-4a includes air sparging at the hot spot areas within the contaminant plume. COC concentrations in
the hot spot areas would reduce rapidly, allowing natural subsurface processes, such as flushing, volatilization,
biodegradation. adsorption, and chemical reaction with subsurface materials to reduce contaminant concentrations in
the remaining contaminant plume. Based on physical properties of unit contaminants, air sparging would provide
76
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Record of Decision for the WSRC-RP-97-402
D-Area Oil Seepage Basin (631-G) (U) Revision 1, Finj»J
Savannah River Site August 1998
effective treatment. A GWMZ would be applied for under South Carolina Regulations R.61-68 as pan of this
alternative. This would create a specific area at the unit that would be required to meet MZCLs at plume monitoring
wells. Downgradient compliance wells would be installed. Groundwater at this compliance boundary would be
required to meet RGOs (equivalent to MCLs). Between the compliance boundary wells and the plume wells,
intermediate wells will be monitored and compared to concentrations predicted by the fate and transport models.
Vadose zone soils and groundwater would be monitored to determine contaminant removal rates. Institutional
controls to restrict access to unit groundwater would be maintained as a component of Alternative GW-4a (i.e., SRS
security, sign posting, and deed notifications). Groundwater contaminant concentrations would also be monitored to
ensure that concentrations decrease as a result of treatment and contaminants do not migrate.
Costs associated with Alternative GW-4a include the labor and materials needed to construct the sparging system.
Also included in the costs is operation and maintenance of the system and a remedy review every five years until
clean-up levels are met. It is estimated that contaminant concentrations would be sufficiently reduced through air
sparging in less than 10 years. Operation and maintenance would include air, soil, and groundwater monitoring, and
operation. Groundwater would be sampled quarterly the first year and semiannually thereafter. Estimated costs
associated with Alternative GW-4a total SI.080,000.
Alternative GW-4b • Air Sparging with Institutional Controls
Air sparging would involve the injection of air into a series of wells in the area of the groundwater plume. The air
would migrate upward through the aquifer in the form of bubbles. The air would volatilize VOCs and carry them up
through and out of the aquifer, through the vadose zone, and into the atmosphere where they could be degraded (e.g..
by photolysis). Vadose zone soils, as well as groundwater. would be monitored to determine contaminant removal
rates. Nine additional monitoring wells would be installed as pan of this alternative to monitor contaminant
concentrations in groundwater. Institutional controls would be maintained to prevent access to unit groundwater.
Based on physical properties of unit contaminants, air sparging would provide effective treatment.
Costs associated with Alternative GW-4b include the labor and materials needed to construct the sparging system.
Also included in the costs is operation and maintenance of the system and a remedy review every five years until
clean-up levels are met. It is estimated that contaminant concentrations would be sufficiently reduced through air
sparging in less than 10 years. Operation and maintenance would include air, soil, and groundwater monitoring, and
operation. Groundwater would be sampled quarterly the first year and semiannually thereafter. Estimated costs
associated with Alternative GW-4b total 51,144,000.
77
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Record of Decision for the WSRC-RP-97-402
D-Area Oil Seepage Basin (631-G) (U) Revision 1, Final
Savannah River Site August 1998
Alternative G^-5^_Extraciion/Strippim/Discharye with Institutional Controls
This alternative would generally require three components: an extraction system, a treatment system, and a discharge
system. Institutional controls and groundwater monitoring would also be implemented and maintained as a
component of this alternative.
Extraction Svstem
Contaminated groundwater would be extracted using either extraction wells or interceptor trenches. For purposes of
this document, extraction wells will be considered the preferred extraction technique. Selection of the appropriate
extraction system would be determined during Corrective Measures/Remedial Design. The objective of extraction
would be to capture groundwater contaminants. Based on groundwater quality data from the RI, contaminants are
limited to the upper two aquifers, which are both located above the "green clay" confining unit (Figure 10). An
extraction system would, therefore, have wells that are screened in the upper two aquifers.
Modeling of groundwater extraction indicated that two extraction wells would be necessary downgradient of the
plume. The extraction well located in the upper aquifer would be pumped at approximately 3 gallons per minute and
the lower well would be pumped at approximately 2 gallons per minute. As pan of this alternative, new monitoring
wells would be installed to confirm reduction in concentrations of contaminants.
Groundwater extraction has been proven effective in containing groundwater plumes. Based on the high hydraulic
conductivity in the impacted area of the aquifer, extraction wells would be effective at this unit. Modeling indicates
that clean-up levels could be reached in 9 years (with degradation) to 25 years (without degradation).
Air Stripping
Air stripping is a physical process in which volatile compounds in groundwater are transferred to an air stream.
typically using a packed tower. Compounds with a Henry's Law Coefficient (Hc) greater than 0.01 are readily
stripped. 1,2-DCE (cis and trans), methylene chloride, PCE, TCE, and vinyl chloride have Hcs of 0.29. 0.13. 1.08.
0.38, and 3.4, respectively. Therefore. DCE. methylene chloride. PCE, TCE, and vinyl chloride would be effectively
removed through air stripping. Air stripping would effectively treat contaminated groundwater at the D-Area OSB.
Discharge
Under this alternative, treated groundwater would be discharged to an existing National Pollutant Discharge
Elimination System (NPDES) permitted outfall or to infiltration galleries. For purposes of ihis document, it is
assumed that treated groundwater would be discharged at the nearest existing NPDES outfall. Selection of the
preferred discharge option would be conducted during Corrective Measures/Remedial Design.
73
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Record of Decision for ihe WSRC-RP-97-402
D-Area Oil Seepage Basin (631-G) fU) Revision 1. Final
Savannah River Site August 1998
An NPDES permit places a restriction or effluent limitation on the quantities, discharge rates, and/or concentrations
of pollutants that may be discharged into surface waters. Therefore, the effluent limitations specified in the existing
NPDES permit would determine the type and extent of treatment required prior to a discharge.
Costs associated with this alternative would include the labor and materials needed to construct new monitoring
wells, an extraction system (assumed extraction wells), an air stripping system, a discharge line to the NPDES
outfall, and modification of an existing NPDES permit. Operation and maintenance costs for the system include
operation of the system, groundwater monitoring, maintenance of institutional controls, and a remedy review at five
years, which is the estimated time required to meet RAOs. The estimated costs associated with this alternative total
SI.309.000.
Vm. SUMMARY OF COMPARATIVE ANALYSIS OF THE ALTERNATIVES
Each of the remedial alternatives was evaluated using the nine criteria established by the NCP [40 CFR § 300.430 (e)
(9)]. The criteria were derived from the statutory requirements of CERCLA Section 121, to provide the basis for
evaluating alternatives and selecting a remedy. The nine criteria are listed below:
• overall protection of human health and the environment
• compliance with ARARs
• long-term effectiveness and permanence
• reduction of toxicity, mobility, or volume through treatment
• short-term effectiveness
•• implementability
• cost
• state acceptance
• community acceptance
In selecting the preferred alternative, the above mentioned criteria were used to evaluate the alternatives developed
in the Corrective Measures Study/Feasibility Study for the D-Area Oil Seepage Basin (631-G) (U) fWSRC, 1998a).
Seven of the criteria are used to evaluate all the alternatives based on human health and environmental protection.
cost, and feasibility issues. The preferred alternative is further evaluated based on the final two criteria, state
acceptance and community acceptance. The comparative analysis for the five groundwater alternatives, using the
first seven criteria, is presented in Table 6. Brief descriptions of the nine criteria are provided below, followed by a
brief comparison of soil and groundwater alternatives based on the criteria.
79
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Table 6
Comparative Analysis of Ground water Alternatives
CA>
O
Criterion
ti&tfftSlf
Human Health
Hnvironinent
1 \ .-«• •' . •-,•• v. •.:•
Compliance with AV
Chcinicul-Specil'ic
Luculion- Specific
Action-Specific
Magnitude of
Rcsiiluul Risks
Alternative GW-1
No Action
jJ^^}^V;^!' '-1 3SfiSH
Protective
Protective
Sffl&Sfr' -^v
Will meet MCLs
following treatment
Wetland Protection
Slate air
requirements
NPDI-S
modification
IJHKBISf.''
Contaminants
would be removed;
minimal residual
risk
Z 3.
5-52,
•> o
» a
Page
-------
Table 6
Comparative Analysis ol'Croumlwaler Alternatives
ecord o
30 C3
"?!r
Criterion
AllcniutiveCW-l
No Action
Alternative CYV-2
Natural
Attenuation /GW
Mixing Zone with
Institutional
Controls
Alternative GVV-3
Uioremediation
with Institutional
Controls
Alternative
GW-4a
Air Sparging Hot
Spols/GW Mixing
Zone with
Institutional
Controls
Alternative
GW-4L
Air Sparging with
Institutional
Controls
Alternative GW-S
Kxlraclioli/Air
Stripping/
Discharge with
Institutional
Controls
r the
W
Adequacy of
Controls
No controls would
be provided
Institutional
Controls and
groundwater
monitoring
Institutional
Controls,
groundwater
monitoring.
process controls,
and conventional
equipment
requiring
maintenance
Institutional
Controls,
groundwater
monitoring,
process controls,
and conventional
equipment
requiring
maintenance
Institutional
Controls,
groundwaler
monitoring,
process controls,
and conventional
equipment
requiring
maintenance
Institutional
Controls.
groundwater
monitoring,
process controls,
and conventional
equipment
requiring
maintenance
1'uxicily
No active treatment
Reduced by natural
attenuation; no
active treatment
Reduced by
biodegradation
Reduced by
volatilization
Reduced by
volatilization
Reduced by
extraction and
treatment
Mobility
No active treatment
Reduced by natural
attenuation; no
active treatment
Reduced by
biodegradalion
Reduced by
volatilization
Reduced by
volatilization
Reduced by
extraction and
treatment
Volume
No active treatment
Reduced by natural
attenuation; no
active treatment
Reduced by
biodegradation
Reduced by
volatilization
Reduced by
volatilization
Reduced by
extraction and
treatment
Risk lo Remedial
Workers
None
Minimal; workers
protected under
health and safety
plan
Minimal; workers
protected under
health and safely
plan
Minimal; workers
protected under
health and safely
plan
Minimal; workers
protected under
health and safety
plan
Minimal; workers
protected under
health and safely
plan
I'age 2 of 3
-------
Table 6
Comparative Analysis of Groundwater Alternatives
Criterion
Risk lo Community
Risk to
linvironmenl
Time lo Achieve
Remediation Goals
Allernalive GW-1
No Action
i
None
None
35 years
Alternative GVV-2
Natural
Attenuation /GW
Mixing Zone with
Institutional
Controls
None
Minimal;
precautions would
be taken
10 years
Alternative GVV-3
Dioremediation
with Institutional
Controls
None
Minimal;
precautions would
be taken
Less than 10 years
Alternative
GW-4a
Air Sparging Hot
Spots/GW Mixing
Zone with
Institutional
Controls
Minimal risk from
air emissions
Minimal;
precautions would
be taken
Less than 10 years
Alternative
GW-4b
Air Sparging with
Institutional
Controls
Minimal risk from
air emissions
Minimal;
precautions would
be taken
Less than 10 years
Alternative OW-5
Extraction/Air
Stripping/
Discharge with
Institutional
Controls
Minimal risk from
air emissions
Minimal;
precautions would
be taken
9 years
1 ITCTHHrnTffiIfflP"iililllM 7 ' . v ^^'SSSSI?Sf SKI
Ahilily iti C'onslnicl
ami Opciiilc
Ability lo Obtain
Approval
•x-^sV^i-i/^Jiaa
Cosl^- .-•: /j!: '*>;*
Capital Costs
O&M Costs
Hslinuted Years of
O&M
Total I'icseni Worth
Costs
No implementation
ic«|iiiicil
May cause
regulatory or public
concern
mmmm
.
$278.000
35
$278,000
Readily
Implemented
No concerns
^^HHB^^^^^^^^flBIB
•FinVMravfTCHicnnK
$142,000
$299.000
10
$391.000
Readily
constructed, hut
effectiveness during
operation limited
May be difficult lo
obtain approval for
reinjeclion
^ujflwm^nH^^^Q2|n
BI^^^^B^^^^^^^^il^HEI^RSi
^^^•••••^•^^^Bnunj
$594,000
$508.000
.>o
.•"if*
5' i.
g O
—IJ
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Record of Decision for the \VSRC-RP-97-402
D-Area Oil Seepage Basin (631-G) (U) Revision 1. Final
Savannah River Site . August 1998
Overall Protection of Human Health and the Environment
The remedial alternatives are assessed to determine the degree to which each alternative eliminates, reduces, or
controls threats to human health and the environment through treatment, engineering methods, or institutional
controls.
All groundwater alternatives, except no action, would be protective of human health and the environment because
they result in a decrease of contaminant concentrations and include institutional controls to restrict access to unit
groundwater. The alternatives also include monitoring to verify that contaminants do not exceed target levels at
compliance boundaries (if applicable) and that contaminant concentrations are decreasing. As contaminant
concentrations decrease, risks to human health associated with ingestion, dermal contact, and inhalation of
groundwater would be prevented. The BRA determined that groundwater contaminants do not pose a significant risk
to ecological receptors. Additionally, modeling results indicate that the nearest surface water body downgradient of
D-Area OSB will not receive groundwater contaminants at concentrations exceeding MCLs. Therefore, all
alternatives are protective of the environment.
Compliance with ARARs
ARARs are federal and state environmental regulations that establish standards that remedial actions must meet.
There are three types of ARARs: (I) chemical-specific, (2) location-specific, and (3) action-specific.
Chemical-specific ARARs are usually health- or risk-based levels or methodologies that, when applied to unit-
specific conditions, result in the establishment of numerical values. Often these numerical values are promulgated in
federal or state regulations.
Location-specific ARARs are restrictions placed on the concentration of hazardous substances or the conduct of
activities solely because they are in specific locations. Some examples of specific locations include floodphms.
wetlands, historic places, and sensitive ecosystems or habitats.
Action-specific ARARs are usually technology- or remedial activity-based requirements or limitations on actions
taken with respect to hazardous substances or unit-specific conditions. These requirements are triggered by the
particular remedial activities that are selected to accomplish a remedy.
83
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Record of Decision for the WSRC-Rp.97-402
D-Area Oil Seepage Basin (631-G) (U) Revision 1. FioaJ
Savannah River Site August 1998
In addition to complying with ARARs. other criteria, guidance, or proposed standards are "to be considered" even
though they are not legally binding, because they may provide useful information or recommended procedures, when
setting remedial objectives.
Under all groundwater alternatives, contaminant concentrations in groundwater would remain above current MCLs
(chemical-specific ARARs) for the near future, but would meet MCLs following remediation. However, the no-
action alternative would not provide monitoring to confirm when MCLs are reached.
No action-specific ARARs are associated with Alternative GW-1. Alternatives GW-2 and GW-4a would require
compliance with the GWMZ. Alternative GW-3 would require a variance to inject groundwater exceeding MCLs
Such a variance may be difficult to obtain. State air quality regulations would apply to emissions from Alternatives
GW-4a, GW-4b, and Alternative GW-5, but should not be difficult to meet. Alternative GW-5 may also require an
NPDES permit modification, which should not be difficult to obtain. Alternatives GW-3, GW-4a, GW-4b, and
GW-5 would also require construction permits, which should not be difficult to obtain.
No location-specific ARARs are associated with Alternative GW-1. The potential location-specific ARAR
associated with Alternatives GW-2, GW-3, GW-4a, GW-4b, and GW-5 would require protection of the nearby
wetlands.
Long-Term Effectiveness and Permanence
The remedial alternatives are assessed based on their ability to maintain reliable protection of human health and the
environment after implementation.
All alternatives except the no-action alternative would result in a permanent reduction of contaminants to below
remediation goals (MCLs) by an effective means of treatment. The no-action alternative would not provide
treatment to reduce contaminant concentrations and would result in contaminants remaining at the unit above
regulatory limits.
Process controls are available for Alternatives GW-3, GW-4a, GW-4b, and GW-5 that could adequately and reliably
control each system. Alternative GW-2 would not require any process controls. All alternatives except no action
would also utilize institutional controls and groundwater monitoring to restrict access to unit groundwater and
monitor treatment effectiveness, respectively. The no-action alternative would provide no control over existing
groundwater contamination.
84
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Record of Decision for the WSRC-RP-97-402
D-Arca Oil Seepage Basin (631-G) (U) Revisioo 1. Final
Savannah River Site Aueust 1998
Reduction ofToxicitv. Mobility, or Volume Through Treatment
The remedial alternatives are assessed based on the degree to which they employ treatment that reduces toxicity (the
harmful nature of the contaminants), mobility (ability of the contaminants to move through the environment), or
volume of contaminants associated with the unit.
Alternative GW-1 would provide no treatment of groundwater contaminants. Alternative GW-2 would involve
passive treatment through natural attenuation processes and would result in decreases in contaminant toxicity.
mobility, and volume. Alternative GW-4a includes natural attenuation as pan of the active treatment alternative.
Alternatives GW-3. GW-ia, GW-4b, and GW-5 would provide active treatment of unit contaminants to reduce the
toxiciry, mobility, and volume of groundwater contaminants. Each alternative would result in reaching MCLs; the
time frames required to reach MCLs are provided in the following section.
Short-Term Effectiveness
The remedial alternatives are assessed considering factors relevant to implementation of the remedial action.
including risks to the community during implementation, impacts on workers, potential environmental impacts (e.g..
air emissions), and the time required to achieve protection.
Remedial goals (MCLs) would be met by each alternative in the following time periods based on groundwater
modeling (WSRC, 1998a, Appendix B), and professional experience:
Alternative GW-1 35 years
• Alternative GW-2 10 years
Alternative GW-3 <10 years
Alternative GW-4a < 10 years
• Alternative GW-4b <10 years
• Alternative GW-5 9 years
Alternative GW-1 would not require any remedial actions and would, therefore, not result in any risk to remedial
workers. Of the remaining alternatives. Alternative GW-2 would result in the least risk to remedial workers and
Alternative GW-5 would result in the most. However, no significant risks are associated with any of the alternatives
and compliance with the health and safety plan should protect remedial workers during implementation.
35
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Record of Decision for the WSRC-RP-97-402
D-Area Oil Seepage Basin (631-G) (U) Revision 1, Final
Savannah River Site August 1998
Construction andjmplementaiion activities would not endanger the community for any of the aJternatives. However.
a minimal risk would be associated with Alternatives GW-la. GW-4b. and GW-5 due to air emissions from the
treatment systems. However, compliance with air regulations would provide protection to the community.
All aJternatives except no action would involve some disturbance to the environment. This disturbance would be
least for Alternative GW-2 and greatest for Alternative GW-5. However, precautions would be taken to minimize
disturbance.
Implementabilifv
The remedial alternatives are assessed by considering the difficulty of implementing the alternative including
technical feasibility, constructabiliry, reliability of technology, ease of undertaking additional remedial actions (if
required), monitoring considerations, administrative feasibility (regulatory requirements), and availability of services
and materials.
All alternatives could be readily implemented with no difficulty obtaining materials or equipment. All alternatives
except the no action alternative would provide an effective means of treatment and groundwater monitoring to
evaluate treatment effectiveness. The added effectiveness provided by injecting nutrients under Alternative GW-3
would likely be limited due to subsurface heterogeneities and preferential pathways that would develop. It would
also be difficult to evaluate overall performance because the areas of preferential pathways will have increased
bioactivity. None of the alternatives would preclude any further remedial action, should it be deemed necessary in
the future. All alternatives except no action would require approval of permits or variances. Obtaining approval is
not anticipated to be difficult for any of these alternatives except Alternative GW-3, which would require a variance
to inject groundwater exceeding MCLs. However, obtaining such a variance would not likely prevent
implementation of the alternative.
Cost
The evaluation of remedial alternatives must include capital, operational, and maintenance costs. Present value costs
are estimated within +50/-30 percent, per EPA guidance. The cost estimates given with each alternative are prepared
from information available at the time of the estimate. The final costs of the project will depend on actual labor and
material costs, actual site conditions, productivity, competitive market conditions, final project scope, final project
schedule, and other variable factors. As a result, the final project costs may vary from the estimates presented
herein.
86
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Record of Decision for the WSRC-RP-97-402
D-Area Oil Seepage Basin (631-C) (U) Revision 1. Final
Savannah River Site Auzust 1998
For ease of comparison, the total estimated present worth costs for each alternative are listed below:
Alternative GW-1 5278,000
Alternative GW-2 $391,000
Alternative GW-3 SI,102,000
Alternative GW^ta SI.080,000
Alternative GW-4b 51.144,000
Alternative GW-5 $1.309,000
State Acceptance
In accordance with the FFA, the state is required to comment on and approve the RFI/RI Report and BRA, the
CMS/FS, and the SB/PP. State acceptance of previous documentation as listed above has been obtained. Also, state
acceptance of the GWMZ application has been obtained, as well.
Community Acceptance
Community acceptance of the preferred alternative is assessed by giving the public an opportunity to comment on the
remedy selection process. A public comment period was held from May 1, 1998 to June 14, 1998 during which
comment was invited from the general public. No comments were received during this time. The ER&WM Program
subcommittee of the SRS CAB was given a briefing on the preferred alternatives on May 6, 1998. The ER&WM
subcommittee was supportive of the preferred alternative and made a motion to the full CAB at the May 18, 1998
meeting to accept the preferred alternative. This motion was accepted with no opposition. The subcommittee also
commended the site's successful use of the bioventilation system in the remediation of the unit's subsurface soil.
K. THE SELECTED REMEDY
The selected remedy for the D-Area OSB deep soils is No Further Action, since RAOs have been achieved by the
IRA and biovent testing.
The selected remedy for shallow soil, surface water, and sediment is No Action, because no COCs in those media
were identified in the RFI/R1/BRA.
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Record of Decision for the WSRC-RP-97-402
D-Area Oil Seepage Basin (631-G) (U) Revision 1, Final
Savannah River Site ^ August 1998
The selected remedy for D-Area OSB groundwater is Alternative GW-2: Natural Attenuation/ GWMZ with
Institutional Controls. Under this alternative, natural attenuation mechanisms such as biodegradation. flushing.
volatilization, adsorption, and hydrolysis would continue to reduce contaminant concentrations in the groundwater to
acceptable levels. Results from the bioventing study, conducted as pan of the interim action, indicate that the source
of groundwater contamination (i.e., the D-Area OSB soil) was abated as a result of the combined interim action and
biovent test, and no longer contributes to groundwater contamination. Evidence indicating that natural attenuation
processes are occurring in the D-Area OSB groundwater was presented in the RFI/RI Report and BRA and included:
(1) decreased dissolved oxygen levels in groundwater, which indicates that microorganisms are utilizing a
combination of the contaminants as a carbon source and oxygen within the groundwater as an oxygen source to
produce energy, (2) elevated chemical oxygen demand, chloride, and sulfate levels downgradient. (3) depressed pH
levels in contaminated areas, and (4) presence of breakdown products.
Researchers report that natural attenuation is appropriate for sites with certain characteristics and emphasis on the
removal of the contaminant source and the ability of the specific contaminants to naturally degrade. Herbert et al..
1984, report that natural attenuation can be selected as a preferred remedial option when the following site-specific
conditions exist:
Groundwater is unsuitable for consumptive use.
• Contaminants degrade quickly or are not at highly toxic concentrations.
• There is low potential for exposure.
• Active restoration is not feasible due to complex hydrogeologic conditions.
• There is low projected demand for future groundwater use.
• The unit is in close proximity to a surface water discharge area, with dilution to levels that are protective, of
human health and the environment.
The RFI/RJ conducted at the D-Area OSB revealed the following:
• The source of contamination at the D-Area OSB was removed during FRA in conjunction with the biovent
testing and no longer contributes to groundwater contamination.
• Naturally occurring mechanisms will continue to reduce contaminant concentrations.
• There are no receptors of groundwater at the D-Area OSB; therefore, there is low potential for exposure.
• The aquifer is limited in thickness and yield and is not targeted for residential or commercial use; therefore,
projected demand for future groundwater use is low.
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Record of Decision for the WSRC-RP-97-402
D-Area Oil Seepage Basin (631-G) fU) Revision 1, FinaJ
Savannah Pjyer Site August 1998
• Modeling indicates that contaminant concentrations in the D-Area OSB groundwater would be reduced to below
MCLs prior to_discharging to Fourmile Branch: therefore dilution in the surface water body is not necessary to
achieve MCLs.
Based on this information the contaminants in the D-Area OSB would be conducive to natural attenuation.
The time required to degrade the unit-specific contaminants was conservatively estimated through groundwater
modeling. The modeling indicates that all contaminants in groundwater would be reduced below their respective
MCLs within approximately 10 years, which is well within the time-frame that DOE plans to maintain control of the
SRS.
A GWMZ application, defined under the South Carolina Regulations R.61-68, has been approved by the SCDHEC
as pan of this alternative (Figure 17). Mixing zones are considered in situations where the source of groundwater
contamination has been removed and contaminant concentrations are decreasing by natural processes. This
alternative will demonstrate through monitoring that RAOs will be met, MZCLs (Table 7) will be achieved
throughout the aquifer, MCLs will be achieved at the compliance boundary, and predicted concentrations will be
achieved at intermediate wells, as described in the approved GWMZ application. Implementation of this alternative
involves installation of nine new wells and monitoring of a total of 12 groundwater wells. Based on area
characteristics and evidence presented in the GWMZ Application, a GWMZ for the D-Area OSB is an appropriate
pan of a natural attenuation remedy and has been approved by the SCDHEC.
The D-Area OSB is in an industrial use zone, as identified in Figure 3.3 of the SRS FFA Implementation Plan
(WSRC. 1996e), for both current and anticipated future land use. Although the remediation decisions for this unit
were, based on the industrial use scenario, the groundwater remedy will achieve the more protective residential use
scenario. The D-Area OSB currently meets unrestricted land use criteria for soils, sediment and surface water.
Groundwater beneath the unit exceeds the MCLs. Although institutional controls are included in all of the
alternatives (except the no-action alternative), the DOE has recommended that residential use of SRS land in the
vicinity of D Area be prohibited (DOE, 1996); therefore, future residential use and potential residential water usage
in this area is unlikely. Modeling of groundwater transport processes as pan of the evaluation of the remedial
alternatives indicates that MCLs for the contaminants of concern will be achieved in all areas of the D-Area OSB
groundwater after approximately 10 years. Upon confirmation that MCLs have been achieved, institutional controls
at the unit will no longer be required.
Per the EPA Region-IV LUCs Policy, a LUCAP for SRS and a LUCIP for the D-Area OSB will be developed and
submitted to the regulators for approval. The LUCAP will be submitted under separate cover, whereas the LUCIP
89
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Record of Decision for the WSRC-RP-97-402
D-Area Oil Seepage Basin (6J1-G) (U) Revision 1. Final
Savannah River Site August 1998
will be submitted_wilh the RDWP/ RDR/ RAWP in accordance with the posi-ROD document schedule provided m
Figure 13. The LUCIP details how SRS will implement, maintain, and monitor the land use control elements of the
D-Area OSB ROD to insure that the remedy remains protective of human health.
The LUC objective necessary to ensure the protectiveness of the preferred alternative is:
• Prevent unauthorized access to the D-Area OSB contaminated zroundwater plume.
The institutional controls required to prevent unauthorized exposure to the contaminated media at the D-Area OSB
include the following:
• controlled access to the D-Area OSB through existing SRS security gates and perimeter fences and the site
use/site clearance programs
• signs posted in the area to indicate that groundwater in the vicinity of the unit has been contaminated by
hazardous materials
• notification of groundwater contamination to any future landowner through deed notification, as required under
CERCLA Section 120(h)
A certified survey plat of the site will be prepared by a registered land surveyor and will be included with the post-
ROD documents. If D-Area OSB is transferred to non-Federal ownership prior to remediation of the groundwater to
the MCLs for the COCs, reevaluation of the need for deed restrictions would be performed through an amended
ROD with EPA and SCDHEC approval. The survey plat will be reviewed and updated, as necessary, at the time the
site is transferred and will be recorded with the appropriate counry recording agency. The D-Area OSB is located in
Aiken Counry.
Along with the institutional controls identified above, implementation of the selected remedy will involve the
placement of compliance boundary monitoring wells between the basin and the downgradient stream and periodic
monitoring of these compliance wells against the MCLs. This alternative will meet RAOs. MZCLs will be achieved
throughout the aquifer and MCLs will be achieved at the compliance point as described in the approved GWMZ
application. All monitoring, compliance, and reporting requirements to satisfy the GWMZ demonstration should be
met in accordance with Section 5 of the approved GWMZ application.
90
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Record of Decision for the
D-Area OU Seepage Basin (631-G) (IT)
Savannah River Site
WSRC-RP-97-402
Revision 1, Final
August 1998
Table 7
MZCLs and MCLs for COCs
Constituent of Concern
Tetrachloroethene
Trichloroethene
Cis- 1 .2-Dichloroethene
1,1-Dichloroethene
Total- 1 ,2-Dichloroethene
Vinyl Chloride
Benzene
Methylene Chloride
MZCL
(Mg/1)
85
1150
457
7.0
70.0
32
6.2
9.5
MCL
(Mg/l)
5.0
5.0
70.0
7.0
70.0
2.0
5.0
5.0
91
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Record of Decision for the WSRC-RP-97--102
D-Area Oil Seepage Basin (631-G) (IT) Revision 1. Final
Savannah River Site ^ August 1998
X. STATUTORY DETERMINATIONS
The selected remedy for the D-Area OSB deep soils is No Further Action, since RAOs have been achieved by ihe
IRA and biovent testing.
The selected remedy for shallow soil, surface water, and sediment is No Action, because no COCs in those media
were identified in the R5I/R1/BRA.
Based on the findings of the D-Area OSB RI and BRA, groundwaier contaminants present a risk to human health
through ingestion, dermal contact, and inhalation. Modeling of unit groundwater indicates that naturally occurring
processes, such as flushing, volatilization, biodegradation, adsorption, and chemical reaction with subsurface
materials, would effectively reduce contaminant concentrations in groundwater to target levels within approximately
10 years. Monitoring wells would be used to verify that MCLs are not exceeded at compliance boundaries and that
MZCLs would not be exceeded in the area of the contaminant plumes. Institutional controls would be maintained to
limit access to unit groundwater until MCLs are satisfied. Natural attenuation is the most cost effective remedy for
D-Area OSB unit groundwater.
The selected remedies for all media are protective of human health and the environment, complies with federal and
state requirements that are legally applicable or relevant and appropriate to the remedial action, and is cost-effective.
These remedies can be easily implemented with minimal risk to remedial workers, the community, and the
environment. These remedies would also provide a permanent solution to unit contamination that would not require
any future remedial actions and satisfy the statutory preference for remedies that employ treatment that reduces
toxicity, mobility, or volume as a principal element.
XI. EXPLANATION OF SIGNIFICANT CHANGES
The SB/PP provides for involvement with the community through a document review process and a public comment
period. No comments were received during the 45-day public comment period. Therefore, there have been no
significant changes to the selected remedy as a result of public comments.
XII. RESPONSIVENESS SUMMARY
No comments were received during the public comment period (May 1 to June 14, 1998). This is indicated in the
Responsiveness Summary (Appendix A).
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XIII. POST-ROD DOCUMENT SCHEDULE
The post-ROD document schedule, based on calendar days, is listed below and is illustrated in Figure 13.
1. The combined Revision 0 RDWP/RDR/RAWP Report for the D-Area OSB will be scoped 45 days after the
ROD is approved, if determined by all three panics to be necessary.
2. RDWP/RDR/RAWP Report will be submitted to EPA and SCDHEC within 180 days of approval of the ROD.
This report will contain the LUCIP. as pan of the submittal.
3. EPA and SCDHEC review of the D-Area OSB RDWP/RDR/RAWP Revision 0 Report will be completed 90
days from submirtaJ of the document.
4. SRS revision of the D-Area OSB RDWP/RDR/RAWP Report will be completed 60 days after receipt of all
regulatory comments.
5. EPA and SCDHEC fmaJ review and approval of the D-Area OSB RDWP/RDR/RAWP Revision 1 Report will
extend to 30 days after receipt of the Rev. 1.0 document.
6. D-Area OSB Remedial Action Field Stan will begin on September 3. 1999. following EPA and SCDHEC
approval of the Rev 1.0 RDWP/RDR/RAWP Report.
7. D-Area OSB PCR/FRR Revision 0 will be submitted to EPA and SCDHEC 90 calendar days after completion
of the remedial action.
8. EPA and SCDHEC review of the D-Area OSB PCR/FRR will last 90 calendar days.
9. SRS revision of the D-Area OSB PCR/FRR will be completed 60 calendar days after receipt of all regulatory
comments.
10. EPA and SCDHEC final review and approval of the Revision 1 PCR/FRR will last 30 calendar days.
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D-Area Oil Seepage Basin (631-G) (IT) Revision 1, Final
Savannah River Site August 1998
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Record of Decision for the WSRC-RP-97-402
D-Arca Oil Seepage Basin (631-G) (U) Revision 1. FinaJ
Savannah River Site . August 1998
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Savannah River Site Aueust 1998
XIV. REFERENCES
DOE, 1994. Public Involvement. A Plan for Savannah River Site. Savannah River Operations Office, Aiken. SC.
DOE, 1996. Savannah River Site: Future Use Project Report. Stakeholder Recommendations for SRS Land and
Facilities. January 1996. Cover letter: Fiori, Mario P.. "SRS Future Use Project Report (Reference:
Transmitial of FinaJ Draft "Forging the Missing Link: A Resource Document for Identifying Future Use
Options," Crumbly/Pearlrnan letter, 1-12-94), USDOE Letter EB-96-015. Savannah River Site, Aiken. SC.
January 29. 1996.
Daily. R.C.. D. Smith, and D. Lillian. 1992. Streamlining Approach for Environmental Restoration (SAFER): An
Overview. In 1992 Waste Management and Environmental Sciences Conference, April 9-11, 1992, San Juan,
Puerto Rico. (In Press).
EPA, I989a. RI/FS Streamlining. OSWER Directive No. 9355.3-06, Washington, DC.
EPA, 1989b. Risk Assessment Guidance for Superfund (RAGS) Volume I. Human Health Evaluation Manual (Pan
A), EPA/540/1-89/002, Office of Emergency and Remedial Response, Washington, DC.
EPA, 1989c. Risk Assessment Guidance for Superfund (RAGS) Volume II. Environmental Evaluation Manual.
EPA/540/1-89/001. Office of Emergency and Remedial Response, Washington, DC.
EPA. 1993. Data Quality Objectives Process for Superfund, Interim Final. Guidance, EPA540/R/93-071,
Washington. DC.
EPA, 1994. Technical Background Document for Soil Screening Guidance. EPA/540/R-94/106, Washington. D.C.
EPA, 1996. Soil Screening Guidance: Technical Bacground Document. EPA/540/R-95/128, Washington, D.C.
Herbert, R.L.. Sczurko, J.J.. and Lewis, R.A., 1984. A Case Study of Factors Favoring Natural Attenuation as the
Preferred Alternative for Aquifer Restoration. E. C. Jordan Company, Portland, ME.
Howard, P.M.. 1990. Handbook of Environmental Fate and Exposure Data for Organic Chemicals, Volume II
Solvents. Lewis Publishers, Chelsea, MI.
Neptune, D. et al.. 1990. Quantitative Decision Making in Superfund: A Data Quality Objectives Case Study.
Hazardous Materials Control. May/June 1990.
Peck, R.B., 1969. North Rankinc Lecture, Advantages and Limitations of the Observational Method in Applied Soil
Mechanics. Geotechnique 19, No. 2, pp. 171-187.
SCDHEC, 1997. Ground-Water Mixing Zone Guidance Document. May 1997.
•WSRC, 1993a. Federal Facility Agreement for the Savannah River Site. Administrative Docket No. 89-05-FF.
WSRC-RP-94-42. Westinghouse Savannah River Company. Savannah River Site, Aiken, SC.
WSRC, 1993b. RCRA Facility Investigation/RJ Program Plan. WSRC-RP-89-994. Rev. 1. Westinghouse
Savannah River Company. Savannah River Site, Aiken, SC.
WSRC. 1995a. Phase II RFl/Rl Work Plan. D-Area Oil Seepage Basin, WSRC-RP-94-l 175, Rev. l.l.
Westinghouse Savannah River Company. Savannah River Site. Aiken, SC.
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D-Area Oil Seepage Basic (631-G) (U) Revision 1. Final
Savannah River Site August 1998
WSRC. 1995b. Confirmatory Sampling Plan for D-Area Oil Seepage Basin, tt'estinghouse Savannah River
Company, Savannah River Site, Aiken. SC.
WSRC, 1996a. Phase IV Groundwater and Soil Sampling Plan for D-Area Oil Seepage Basin. Addendum to
WSRC-RP-96-169, Rev. I.I. WSRC-RP-96-169. Westinghouse Savannah River Company. Savannah River
Site, Aiken. SC.
WSRC, 1996b. Quality Assurance/Quality Control Summary Report for the RFI/RI Assessment of the D-Area Oil
Seepage Basin, Phase III Soil and Croundwater Sampling Events. ESH-EMS-960002, Westinghouse Savannah
River Company, Savannah River Site. Aiken. SC.
WSRC, 1996c. Preliminary Quality Assurance/Quality Control Summary Report of the Groundwater Volatile
Organics Analyses for the RFI/RI Assessment of the D-Area Oil Seepage Basin. Phase II Expedited Site
Characterization. Westinghouse'Savannah River Company, Savannah River Site, .Aiken, SC.
WSRC, 1996d. Quality Control Summary Report for the D-Area Oil Seepage Basin Interim Remedial Action Plan.
ESH-EMS-96-0391. Westinghouse Savannah River Company, Savannah River Site, Aiken, SC.
WSRC. 1996c. Data Summary Report for the RFI/RI Assessment of the D-Area Oil Seepage Basin. Phase IV (U).
ESH-EMS-96-0503, Westinghouse Savannah River Company, Savannah River Site, Aiken, SC.
WSRC. 1996f. Savannah River Site Federal Facility Agreement Implementation Plan. WSRC-RP-94-1200, Rev 0.
Westinghouse Savannah River Company, Savannah River Site, Aiken, SC.
WSRC, 1997a. RCRA Facility Investigation/Remedial Investigation Report and the Baseline Risk Assessment for the
D-Area Oil Seepage Basin (631-G) (U). WSRC-RP-96-00154, Rev. 1.1, Westinghouse Savannah Rjver
Company. Savannah River Site, Aiken, SC.
WSRC, 1997b. Air Flow Evaluation Report for D-Area Bioventing Optimization Test (Phase 2). Environment
Restoration Support, WSRC-TR-97-0104, Draft Copy, Wcstinghouse Savannah River Company. Savannah
River Site, Aiken, SC.
WSRC, 1997c. TEP Injection Campaign Report for D-Area Bioventing Optimization Test (Phase 2). Environmental
Restoration Support. WSRC-TR-97-0146. Westinghouse Savannah River Company, Savannah River Site,
Aiken. SC.
WSRC, I997d. Evaluation of D-Area Oil Seepage Basin Bioventing Optimization Test Sediment Samples Data.
WSRC-TR-97-00399. Final Copy. Westinghouse Savannah River Company, Aiken, SC.
WSRC. 1997e. Post-Construction Report for D-Area Oil Seepage Basin Interim Action (IT). WSRC-RP-96-00859.
Rev. 1.0. Westinghouse Savannah River Company. Aiken. SC.
WSRC. 1998a. Corrective Measures Study/Feasibility Study for the D-Area Oil Seepage Basin (631-G) (U>.
WSRC-RP-97-167, Rev. 1.1. Westinghouse Savannah River Company, Savannah River Site, Aiken, SC.
WSRC. I998b. Statement of Basis/Proposed Plan for the D-Area Oil Seepage Basin (632-G) (U). WSRC-RP-97-401.
Rev. 1.1, Westinghouse Savannah River Company, Savannah River Site, Aiken, SC.
WSRC. 1998c. Groundwater Mixing Zone Application for the D-Area Oil Seepage Basin (63J-G)(U). WSRC-RP-97-
422, Rev. 1.1, Westinghouse Savannah River Company, Savannah River Site, Aiken, SC.
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Record of Decision for the WSRC-RP-97-402
D-Area Oil Seepage Basin (631-G) (U) Revision 1. Final
Savannah River Site August 1998
APPENDIX A
RESPONSIVENESS SUMMARY
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D-Area O<| Seepage Basin (631-G) (U) Revision 1. Final
Savannah River Site August 1998
RESPONSIVENESS SUMMARY
The public was notified of the public comment period through mailings of the SRS Environmental Bulletin, a
newsletter sent to approximately 3500 citizens in South Carolina and Georgia, through notices in the Aiken Standard.
the Allendale Citizen Leader, the Augusta Chronicle, the Barnwell People-Sentinel, and The State newspapers. The
public comment period was also announced on local radio stations.
The 45-day public comment period began on May 1, 1998 and ended on June 14, 1998. However, no public
comments were received during this period.
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