Superfund Record of Decision Savannah River Site (USDOE) Operable Unit 13 Aiken SC


                                    EPA/ROD/R04-97/025
                                    1997
EPA Superfund
     Record of Decision:
     SAVANNAH RIVER SITE (USDOE)
     EPA ID: SC1890008989
     OU13
     AIKEN, SC
     03/27/1997

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United States Department of Energy

Savannah River Site
Record of Decision
Remedial Alternative Selection for the
Silverton Road Waste Unit  (731-3A) (U)
WSRC-RP-96-171
Revision 1
February 1997

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                                                   DOE Remedial Section
                                                   Federal Facilities Branch
                                                   Waste Management Division
           Brian Hennesey, DOE-SRS
           Kim Wierzbicki, WSRC
           Donna Brumley, DOE-SRS
           Hammett, DOE-SRS

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                               RECORD OF DECISION
                        REMEDIAL ALTERNATIVE SELECTION (U)
                       Silverton Road Waste Unit (731-3A)
                               WSRC-RP-96-171
                                 Revision 1
                                February 1997
                            Savannah River Site
                           Aiken,  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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DECLARATION FOR THE RECORD OF DECISION

Unit Name and Location

Silverton Road Waste Unit (SRS Building Number 731-3A)
Savannah River Site
Aiken, South Carolina

The Silverton Road Waste Unit (SRWU) (731-3A) 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 SRWU located at the
SRS in Aiken, South Carolina. The selected alternative was developed in accordance with CERCLA,
as amended, and to the extent practicable, the National Oil and Hazardous Substances Pollution
Contingency Plan (NCP). This decision is based on the Administrative Record File for this
specific RCRA/CERCLA unit.

Description of the Selected Remedy

The preferred alternative for the SRWU soils is Institutional Controls which will restrict this
land to future industrial use and prohibit the excavation of soil which might expose future
workers to low concentrations of hazardous constituents. Implementation of the Institutional
Controls alternative will require both near- and long-term actions which will be protective of
human health and the environment. For the near-term, signs will be posted at the waste unit
which indicate that this area was used for the disposal of waste material and contains buried
waste. In addition, existing SRS access controls will be used to maintain the use of this site
for industrial use only.

In the long-term, if the property is ever transferred to non-federal ownership, the U.S.
Government would create a deed for the new property owner which would include information needed
for compliance with Section 120(h) of CERCLA. The deed shall include notification disclosing
former waste management and disposal activities as well as any remedial actions taken on the
site, and any continuing groundwater monitoring commitments. The deed notification shall, in
perpetuity, notify any potential purchaser that the property has been used for the management
and disposal of construction debris and other materials, including hazardous substances.

The deed shall also include restrictions precluding residential use of the property. However,
the need for these restrictions may be reevaluated at the time of ownership transfer in the
event that contamination no longer poses an unacceptable risk under residential use.

In addition, if the site is ever transferred to non-federal ownership, a survey plat of the area
will be prepared, certified by a professional land surveyor, and recorded with the appropriate
county recording agency.

In the "M Area" groundwater aguifer, low levels of contaminants have been detected which
minimally and infrequently exceed maximum contaminant levels (MCLs). The probable condition for
the "M Area" groundwater aquifer is no significant groundwater contamination resulting from the
SRWU. As a result, no remedial action is deemed appropriate for the SRWU "M Area" groundwater
aquifer. However, a confirmatory groundwater monitoring program will be established to ensure
that this is the appropriate remedial action for the "M Area" groundwater aquifer. In the event
that the probable condition is no longer appropriate, DOE will evaluate the need for remedial
action.

Under the confirmatory groundwater program, an adequate number of monitoring wells will be
selected to monitor the extent of the contaminant plume and the severity of the contamination.
Since only one background well is available for the "M Area" aquifer, new background wells will
need to be installed. The groundwater monitoring is intended to evaluate trends in the
groundwater contamination. Groundwater monitoring was assumed to be conducted on a semi-annual
basis for 30 years (for cost estimating purposes only). However, at the five-year Record of

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Decision review, the groundwater monitoring data will be evaluated to determine if any changes
in the groundwater remedy are appropriate.

The number and location of the new background well(s), a list of the existing wells to be
monitored, the freguency of monitoring, and the submittal freguency of the groundwater data for
regulatory review will be listed in the SRWU Corrective Measures Implementation/Remedial Action
Report (CMI/RAR) post-ROD document. The CMI/RAR will also identify a groundwater strategy which
will include trend analysis and recommendations based on the interpretation of the data in the
post-ROD groundwater monitoring reports. The CMI/RAR will be submitted to the regulatory
agencies four months after issuance of the ROD. The regulatory review period, SRS revision
period, and final regulatory review and approval period for the CMI/RAR will be 90 days, 60
days, and 30 days, respectively.

The SCDHEC has modified the SRS permit to incorporate the selected remedy.

The groundwater in the lower aguifers are separate operable units and are not within the scope
of this Record of Decision. The groundwater in the lower aguifers will be evaluated as part of
the 1995 RCRA Permit for the A/M Area Western Sector Corrective Action Program.

Statutory Determinations

Based on the SRWU RCRA Facility Investigation/Remedial Investigation (RFI/RI) Report and the
Baseline Risk Assessment (BRA), the SRWU poses no significant risk to the environment and
minimal risk to human health. Therefore, a determination has been made that institutional
controls are sufficient for protection of human health and the environment for the SRWU soils
and that no remedial action with confirmatory groundwater monitoring is deemed appropriate for
the SRWU "M Area" groundwater aguifer.

The selected remedy is protective of human health and the environment, complies with Federal and
State reguirements that are legally applicable or relevant and appropriate to the remedial
action, and is cost-effective. The size of the waste unit and the random distribution and low
levels of contaminants preclude a remedy in which treatment is a practical alternative. Because
treatment of the principal threats of the site was found to be impracticable, this remedy does
not satisfy the statutory preference for treatment as a principal element.

Institutional controls will result in hazardous substances, pollutants or contaminants remaining
in the waste unit. Section 300.430 (f)(4)(ii) of the NCP reguires that a Five Year Review of
the Record of Decision be performed if hazardous substances, pollutants, or contaminants remain
in the waste unit. The three Parties have determined that a Five Year Review of the Record of
Decision for the SRWU will be performed to ensure continued protection of human health and the
environment.

Date R. Lewis Shaw
Deputy Commissioner
Environmental Quality Control
South Carolina Department of Health and Environmental Control

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DECISION SUMMARY
TABIiE OF CONTENTS
Section
Page
I. Site and Operable Unit Name, Location, and Description 1
II. Operable Unit History and Compliance History 5
III. Highlights of Community Participation 5
IV. Scope and Role of Operable Unit Within the Site Strategy 6
V. Summary of Operable Unit Characteristics 6
VI. Summary of Operable Unit Risks 11
VII. Description of the Considered Alternatives 23
VIII. Summary of Comparative Analysis of the Alternatives 25
IX. The Selected Remedy 27
X. Statutory Determinations 32
XI. Explanation of Significant Changes 32
XII. Responsiveness Summary 33
XIII. Post-ROD Document Schedule 33
XIV.
References 35

List of Figures

Figure 1 Location of the Silverton Road Waste Unit at the Savannah River Site 2
Figure 2 Location of the Silverton Road Waste Unit with Respect to A/M Area 3
Figure 3 General Configuration of the Silverton Road Waste Unit 4
Figure 4 Location of the Silverton Road Waste Unit "M Area" Groundwater Monitoring
Wells 9
Figure 5 Conceptual Site Risk Model for the Future Residential Adult/Child Receptor
at the SRWU 17
Figure 6 Conceptual Site Risk Model for the Future Residential Child Receptor at the SRWU.18

Figure 7 Conceptual Site Risk Model for the Future Occupational Worker Receptor
at the SRWU 19
Figure 8 Post-ROD Document Schedule 34

List of Tables

Table 1 "M Area" Groundwater Constituents 10
Table 2 Future Land Use - Noncarcinogenic Hazard Index (0-0.5 ft.) 13
Table 3 Future Land Use - Noncarcinogenic Hazard Index (0-6 ft.) 13
Table 4 Future Land Use - Carcinogenic Risks (0-0.5 ft.) 14
Table 5 Future Land Use - Carcinogenic Risks (0-6 ft. ) 15
Table 6 Remedial Goal Options for Intermediate Risk Contaminants of Concern for the
Future Residential Adult and Child at the SRWU (Soil) 21
Table 7 Remedial Goal Options for Intermediate Risk Contaminants of Concern for the
Future Occupational Worker at the SRWU (Soil) 21
Table 8 Remedial Goal Options for Contaminants of Concern for the Future Residential
Adult and Child at the SRWU ("M Area" Groundwater Aguifer) 22
Table 9 Remedial Goal Options for Contaminants of Concern for the Future Occupational
Worker at the SRWU ("M Area" Groundwater Aguifer) 22
Table 10 Evaluation of Remedial Alternatives Considered for the SRWU Source
Control Operable Unit 28
Table 11 Evaluation of Remedial Alternatives Considered for the SRWU "M Area"
Groundwater Operable Unit 30

Appendix
A. Responsiveness Summary 36

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I. Site and Operable Unit Name Location, and Description

The Savannah River Site (SRS) occupies approximately 310 square miles 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 25
miles southeast of Augusta, Georgia and 20 miles 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. Hazardous substances, as
defined by Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), are
currently present in the environment at SRS.

The Federal Facility Agreement lists the Silverton Road Waste Unit (SRWU), 731-3A, (Figure 2) as
a Resource Conservation and Recovery Act (RCRA)/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.

The SRWU, 731-3A, is located in the northwestern part of the SRS in Aiken County (Figure 1),
approximately 1.5 miles southwest of A/M Area (Figure 2). The SRWU area is an irregular
quadrilateral which contains an unlined earthen depression dug into surficial soils and later
filled with various waste materials. This area has been designated as "excavated area (filled)"
on Figure 3. Soil borings conducted in 1993 identified the presence of waste buried beyond the
excavated area. The additional area of waste disposal is within the orange ball markers and
covers an area of approximately 600 feet by 400 feet with waste being buried to a maximum depth
of approximately 16 feet below ground level. The excavated area is larger than the soil boring

dimensions, but is less than the orange ball dimensions. Since characterization data indicated
contamination of the surface soils, the planar area calculation for the SRWU includes the entire
area within the orange balls. Therefore, the SRWU planar area of the SRWU is assumed to be 750
feet by 600 feet (450,000 ft 2). Using an average estimated depth of 6 feet for the excavated
area, the approximate waste volume of the SRWU is 2,700,000 ft 3.

The SRWU is located on the southwestern flank of an interstream divide between Upper Three Runs
Creek (approximately 4.5 miles to the southeast) and the flood plain of the Savannah River
(approximately 1.5 miles to the west). The ground surface elevation at the unit averages 350
feet above mean sea level. Surface drainage is southwestward, along a series of dry-wash
tributaries, into the flood plain of the Savannah River. The water table at the SRWU ranges
from about 40 feet below ground level to the southwest to about 130 feet below ground level to
the northeast.

The SRWU was first used before construction of the SRS. Although there is no written record of
when disposal began at the SRWU, or what materials were accepted, it is believed that the SRWU
was originally a borrow pit used as an "open dump" by the local municipalities including Old
Ellenton before the land was acquired by the federal government. Municipal, agricultural, and
commercial trash, rubbish, garbage, debris, and refuse probably constituted the waste stream
until the early 1950's. The waste material at the dump was probably burned periodically, as was
the practice at that time, for volume reduction. This practice would have eliminated many of
the combustible organic materials while creating combustion by-products.

After procurement by the federal government, the SRWU land continued to be used as an open dump
(a legal practice at the time) by SRS. Historical and aerial photographs show large piles of
metal shavings (possibly aluminum), 55-gallon drums, cardboard drums, tires, lumber, wooden
pallets, cardboard, construction debris, tanks, possibly asbestos, and other unidentified metal
and wood objects. No records of waste disposal activities were kept. In 1974, the disposal of
waste at the SRWU ceased, and the area was bulldozed, graded covered with soil, and planted with
grasses.

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II. Operable Unit History and Compliance History

Operable Unit History

The SRWU was first used before construction of the SRS. Municipal, agricultural, and commercial
trash, rubbish, garbage, debris, and refuse probably constituted the waste stream until the
early 1950's. After procurement by the federal government, the SRWU land continued to be used as
an open dump for disposal of metal shavings, 55-gallon drums, cardboard drums, tires, lumber,
etc. No records of waste disposal activities were kept. In 1974, the disposal of the waste at
the SRWU ceased, and the area was bulldozed, graded, covered with soil, and planted with
grasses.

Compliance History

At SRS, waste materials are managed which are regulated under RCRA, a comprehensive law
reguiring responsible management of hazardous waste. Certain SRS activities have reguired
Federal operating or post-closure permits under RCRA. SRS received a hazardous waste permit
from the South Carolina Department of Health and Environmental Control (SCDHEC) on September
5, 1995. Part V of the permit mandates that SRS establish and implement an RFI Program to
fulfill the reguirements specified in Section 3004(u) of the Federal permit.

Hazardous substances, as defined by CERCLA, are present in the environment at the SRS. On
December 21, 1989, SRS was included on the National Priorities List. This inclusion created a
need to integrate the established RFI Program with CERCLA reguirements to provide for a focused
environmental program. In accordance with Section 120 of CERCLA, DOE has negotiated a Federal
Facility Agreement (FFA, 1993) with the U.S. Environmental Protection Agency (EPA) and SCDHEC to
coordinate remedial activities at SRS into one comprehensive strategy which fulfills these dual
regulatory reguirements.

III. Highlights of Community Participation

Both RCRA and CERCLA reguire that the public be given an opportunity to review and comment on
the draft permit modification and proposed remedial alternative. Public participation
reguirements are listed in the South Carolina Hazardous Waste Management Regulation (SCHWMR)
R.61-79.124 and Sections 113 and 117 of CERCLA. These reguirements include establishment of an
Administrative Record File that documents the investigation and selection of the remedial
alternatives for addressing the SRWU soils and groundwater. The Administrative Record File must
be established at or near the facility 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. The SRS Public Involvement plan addresses
the reguirements of RCRA, CERCLA, and the National Environmental Policy Act SCHWMR R.61-79.124
and Section 117(a) of CERCLA, as amended, reguire the 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. The Statement of Basis/Proposed Plan for
the Silverton Road Waste Unit (731-3A) (WSRC, 1996d), which is part of the Administrative Record
File, highlights key aspects of the investigation and identifies the preferred action for
addressing the SRWU.

The FFA Administrative Record File, which contains the information pertaining to the selection
of the response action, is available at the EPA office and at the following locations:

U.S. Department of Energy
Public Reading Room
Gregg-Graniteville Library
University of South Carolina-Aiken
171 University Parkway
Aiken, South Carolina 29801
(803) 641-3465

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Thomas Cooper Library
Government Documents Department
University of South Carolina
Columbia, South Carolina 29208
(803) 777-4866

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
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 September 17, 1996 and ended on October 31, 1996.  A
public comment meeting was held on October 15, 1996.  A Responsiveness Summary was prepared to
address comments received during the public comment period.  The Responsiveness Summary is
provided in Appendix A of this Record of Decision.

IV.  Scope and Role of Operable Unit Within the Site Strategy

The overall strategy for addressing the SRWU was to: (1) characterize the waste unit delineating
the nature and extent of contamination and identifying the media of concern  (perform the
RFI/RI); (2)  perform a baseline risk assessment to evaluate media of concern, constituents of
concern, exposure pathways, and characterize potential risks; (3)  evaluate applicable
technologies and identify a preferred technology to remediate the waste site, as needed; and,
(4) perform a final action to remediate, as needed, the identified media of concern.

The SRWU is an operable unit located within the Savannah River Floodplain Swamp Watershed.
Several source control and groundwater operable units within this watershed will be evaluated to
determine impacts, if any, to associated streams and wetlands.  SRS will manage all source
control and groundwater operable units to minimize impact to the Savannah River Floodplain Swamp
Watershed.   Based on characterization and risk assessment information, the SRWU does not
significantly impact the watershed.  Upon disposition of all source control and groundwater
operable units within this watershed, a final, comprehensive evaluation of the watershed will be
conducted to determine whether any additional actions are necessary.

The SRWU investigation considered all unit specific groundwater operable units - The "M Area"
groundwater aguifer and the "Lost Lake" groundwater aguifer.  Based on the investigation of the
groundwater,  low levels of contaminants have been detected in the "M Area" groundwater aguifer
which minimally and infreguently exceed MCLs.  The probable condition for the "M Area"
groundwater aguifer is no significant groundwater contamination resulting from the SRWU.  As a
result no remedial action is deemed appropriate for the "M Area" groundwater aguifer.  A
confirmatory groundwater monitoring program will be established to ensure that this is the
appropriate remedial action.  The contamination in the "Lost Lake" aguifer is attributable to
upgradient sources.  The "Lost Lake" aguifer will be remediated as committed to in the 1995 RCRA
Permit for the A/M Area Western Sector Corrective Action Program.

The proposed actions for the SRWU soils and "M Area" groundwater aguifer are final actions.
However, in the event that the probable condition for the "M Area" groundwater aguifer is no
longer appropriate, DOE will evaluate the need for remedial action.

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V. Summary of Operable Unit Characteristics

The SRWU was first used before construction of the SRS. Although there is no written record of
when disposal began at the unit, or what materials were accepted, it is believed that the unit
was originally a borrow pit. Historical aerial photographs indicate that the SRWU was used as
an "open dump" by the local municipalities including Old Ellenton before the land was acguired
by the federal government. The first aerial photograph (September 1938) shows a well established
"open dump" around the excavated area even though the excavated area is not visible in the
photograph. Aerial photographs were taken at regular intervals throughout the years and
indicate a regular and consistent use of this property as a dump site. The photographs only
vary by the size of the area being used as a dump. Therefore, SRWU has a history of at least 58
years of use.

Municipal, agricultural, and commercial trash, rubbish, garbage, debris, and refuse probably
constituted the waste stream until the early 1950s. These items are visible in some of the early
aerial photographs. The waste material at the dump was probably burned periodically, as was the
practice at that time, for volume reduction. This practice would also have eliminated many of
the combustible organic materials while creating combustion by-products.

After procurement by the federal government, this land continued to be used as an open dump (a
legal practice at the time) by SRS. Aerial photographs suggest that the M-Area Fuel and Target
Fabrication facilities continued using the existing open dump to dispose of its waste products.
This is evidenced by the large piles of metal shavings (possibly aluminum) from the fabrication
of fuel rods. Also, present in the photographs, but not necessarily related to the M-Area Fuel
and Target Fabrication facilities, are 55 gallon metal drums, cardboard drums, many tires,
lumber, wooden pallets, cardboard, construction debris, tanks, possibly asbestos, and other
identified metal and wood objects. No records of waste disposal activities were kept. In 1974,
the disposal of wastes at the SRWU ceased, and the area was bulldozed, graded, covered with
soil, and planted with grasses.

Media Assessment

The Quality Control Summary Report for the Silverton Road Waste Unit RFI/RI Assessment (WSRC,
1994a), Final RFI/RI Report for the Silverton Road Waste Unit (U) (WSRC, 1996a), and the Final
Baseline Risk Assessment for the Silverton Road Waste Unit (U) (WSRC, 1996b) contain detailed
analytical data for all of the environmental media samples taken in the characterization of the
unit.

Since this land was first used as an open dump prior to the government purchase of the land,
almost any type of residential, commercial, or agricultural waste could have been disposed at
SRWU. It is known that SRS operational policy would not have permitted the disposal of any
radioactive material at this site. Any radionuclides detected were likely naturally occurring
(Radium-223) or were deposited by global fallout from nuclear testing (Cesium-137).

Soils

During the RFI/RI, thirteen soil borings were drilled at the site to collect surface and
subsurface soil samples. Two runoff soil samples were collected from the SRWU. Two offsite
soil borings were drilled to collect seven background soil samples. Soil samples were analyzed
for numerous parameters including metals, volatile organic compounds, semi-volatile organic
compounds, pesticides, polychlorinated biphenyls, dioxins, farans, and radionuclides. Analyte
concentrations were screened using criterion background concentrations of twice the average
background concentration.

The analyses of the soil samples were divided into three groups:

• surface soils, 0 to 0.5 feet (primary direct contact exposure interval for soils),

• subsurface soils, 0 to 6 feet (potential exposure interval for future scenarios
where excavation may occur), and

• underlying soils, 6 to 42 feet (potential soil to groundwater migration).

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These soil groups are identical in horizontal extent across the SRWU.

The primary contaminants (those exceeding twice the mean background and risk-based thresholds)
in the surface soils (0-0.5 ft.) and subsurface soils (0-6 ft.) were arsenic,
benzo(k)fluoranthene, potassium-40, dibenz (a,h)anthracene, cesium-137, and radium-223.
Potassium-40 and radium-223 are naturally occurring radionuclides. The source of arsenic is not
known. The levels of arsenic detected are consistent with the levels found throughout SRS.
Arsenic may be natural, added to the soils as a pesticide (pre-SRS) or associated with site
waste or fill. It will be evaluated on a site-wide scale during the implementation of the Soil
Background Study (or potentially the Site-Wide Soil Integrator, Operable Unit Workplan).
Dibenz(a,h)anthracene and benzo(k)-fluoranthene were observed at maximum concentrations of 643
Ig/kg and 219 Ig/kg, respectively. Cesium-137 was observed at a maximum activity level of 2.1
pCi/g. This activity level is consistent with the observed activity from global fallout.
Radium-223 was only detected once in each soil sample interval. Based on exposure point
concentrations, the level of contaminants in the 0 to 0.5 foot interval was not significantly
different from those in the 0 to 6 foot interval. The contaminants appear to be randomly
and heterogeneously scattered throughout the 0 to 6 foot interval.

The primary contaminants (those exceeding twice the mean background and risk-based thresholds)
in the underlying soils (6-42 ft.) were arsenic, beryllium, polycyclic aromatic hydrocarbons,
dioxins/furans, and radionuclides. It should be noted that, per regulatory guidance, the
underlying soils (6-42 ft.) are not reguired to undergo risk assessment, but are evaluated for
potential migration of contaminants to the groundwater.

Uncertainty in the soil data set is caused by single detections for a large number of analytes.
Contaminants that exceeded the twice the mean background and risk-based thresholds and were
detected only once in the underlying soils (6-42 ft) include: baryllium, dioxins/furans, and
radionuclides. Single hits indicate that contaminants my be found in only isolated areas.
Additionally, many of the radionuclides could not be physically present due to their brief
half-life and their detection on is probably due to measurement error. Potassium-40 is a
naturally occurring analyte. The number of samples in the background data set for the soils was
marginally adeguate to be representative. This also adds to the uncertainty in the data set.

The potential for migration of the soil contamination to the groundwater was guantitatively
evaluated by comparing the mean concentration of each analyte to the proposed soil screening
levels calculated by the simple site-specific method. For radiological analytes, the RESRAD
model was used to predict the concentration in groundwater over a period of time. This model
used both the maximum and average radionuclide concentrations. The average concentrations used
did not include non-detects, resulting in conservative modeling results. For each analyte
evaluated in the study, all soil data from 0 to 42 feet was included in the determination of the
mean concentrations.

Based on the fact that all the soil analytes passed either the simple site-specific or detailed
site-specific method of screening, there is little or no chance for the residual waste at the
SRWU to be a source of future contamination. Releases have probably occurred from the SRWU in
the past, but due to the unit's age and natural attenuation, the remaining contaminants pose
little, if any, threat for future contamination. In addition, no significant contaminants were
contributed to any surface water streams.

Groundwater

Seventeen monitoring wells are screened within the "M Area" groundwater aguifer. The wells near
the SRWU are shown on Figure 4.

Contaminants minimally and infreguently exceeding their maximum contaminant level (MCL) in the
"M-Area" aguifer include: copper, lead, 1,2-dichloroethane, carbon tetrachloride,
dichloromethane, tetrachloro-ethylene, and trichloroethylene. Chloroform and thallium
concentrations were below their respective MCLs; however, they were above their respective risk-
based thresholds.

Table 1 lists the "M Area" groundwater aguifer constituents, the number of detections, the
detections that were above the MCL for the constituent, the maximum concentration, and the MCL.

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The upgradient groundwater guality could not be characterized with certainty since one of the
new background wells installed in the "M Area" groundwater aquifer yielded no groundwater
samples because it went dry. The loss of this well has not only introduced uncertainty in the
spatial distribution of possible upgradient contamination, but it has also introduced
statistical uncertainty caused by an insufficient background sample size for the "M Area"
groundwater aguifer. As a result, the background concentrations were established with the use
of only one background well. This led to the use of a maximum of 6 samples with which to
establish background concentrations.

Table 1 "M Area" Groundwater Constituents
Constituent
Units
Number of
Detections
Maximum
Concentration
MCL Number of
Detections Above
Copper Ig/L
Lead Ig/L
1,2-Dichloroethane Ig/L
Carbon Tetrachloride Ig/L
Dichloromethane Ig/L
Tetrachloroethylene Ig/L
Trichloroethylene Ig/L
65/96
64/96
14/96
40/96
38/96
26/96
44/96
1430
36.2
5.3
9.9
6.62
6.2
7.4
MCL
1000 a 1/65
15.0 b/50.0 a 16/64
5.0 1/14
5.0 15/40
5.0 1/38
5.0 1/26
5.0 1/44
MCL - Maximum Contaminant Level
a - MCL set by the state
b - "At the tap" standard
The presence of 1,2-dichloroethane and dichloromethane in the remaining upgradient wells
indicate a probable upgradient source of contamination. Additional constituents were also
found in downgradient wells at the SRWU which were not found in the upgradient well which
indicates that the SRWU probably has contributed additional contaminants to the "M-Area"
groundwater aguifer as it flows beneath the unit.
Adding to further uncertainty are those analytes with only one positive detection. This is best
typified by the pesticide analysis. Aldrin, dieldrin, and DDT were only detected once; and,
they were not detected in subsequent samples from the wells in which they were originally
detected. Single detections represent extreme uncertainty in the data because the results could
not be reproduced in the same well. It is highly likely that single detections are due to
sampling or measurement error.

VI. Summary of Operable Unit Risks
As a component of the RFI/RI process, a baseline risk assessment was prepared for the SRWU.
baseline risk assessment consists of human health and ecological risk assessments. Summary
information for the human health and ecological risk assessments follows.
The
Human Health Risk Assessment

As part of the investigation/assessment process for the SRWU, a risk assessment was performed
using the data generated during the assessment phase. Detailed information regarding the
development of contaminants of potential concern, the fate and transport of contaminants, and
the risk assessment can be found in the Final RFI/RI Report for the Silverton Road Waste Unit
(U) (WSRC, 1996a) and the Final Baseline Risk Assessment for the Silverton Road Waste Unit U
(WSRC. 1996b).
The process of designating the constituents of potential concern was based on consideration of
background concentrations, frequency of detection, the relative toxic potential of the
chemicals, and chemical nutrient status. Constituents of potential concern are the constituents
that are potentially site-related and whose data are of sufficient quality for use in the risk
assessment.

-------
An exposure assessment was performed to provide an indication of the potential exposures which
could occur based on the chemical concentrations detected during sampling activities. The only
existing (current) exposure scenario identified for the SRWU was for environmental researchers
who may work or traverse the SRWU on an intermittent/limited basis. Future exposure scenarios
identified for the SRWU included future environmental researchers as well as future residential
adults and children and occupational workers. The reasonable maximum exposure concentration
value was used as the exposure point concentration.

Per EPA guidance, the carcinogenic (cancer) risks and non-carcinogenic hazard were calculated to
determine the appropriate remedial action for a waste unit. Carcinogenic risks are estimated as
the incremental probability of an individual developing cancer over a lifetime as a result of
pathway-specific exposure to cancer-causing contaminants. 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. Cancer risks are related to the EPA
target risk range of one in ten thousand (1x10 -4) to one in one million (1x10 -6) for
incremental cancer risk at National Priorities List sites.

Non-carcinogenic effects are also evaluated-to identify a level at which there may be concern
for potential health effects other than cancer-causing. The hazard guotient, which is the ratio
of the exposure dose to the reference dose is calculated for each contaminant. Hazard guotients
are summed for each exposure pathway to determine the specific hazard index for each exposure
scenario. If the hazard index exceeds unity (1.0), there is concern that adverse health
effects might occur.

The following sections discuss the noncarcinogenic hazards and carcinogenic risks for the
current on-unit environmental researcher, the hypothetical future on-unit residential
adult/child, the future on-unit residential child, and the future on-unit occupational worker.

Current Land Use - Noncarcinogenic Hazards

The Baseline Risk Assessment (WSRC, 1996b) shows that the total noncarcinogenic (noncancer)
hazard index did not exceed unity for the environmental researcher evaluated in the current
land use scenario. This indicates that potential adverse health effects are not likely to occur
for the current environmental researcher.

Current Land Use - Carcinogenic Risks

Under the current land use scenario, the human health risks were characterized for the current
on-unit environmental researcher. The total carcinogenic (cancer) risk from exposure to
chemicals in soil was 2 xlO -7. The total carcinogenic risk for exposure to radionuclides in
soils 3 xlO -6. Dermal contact (with a risk of 2.7x10 -6) with radionuclides (i.e., Cesium-137)
in the soil contributed to the risk. Cesium-137 was observed at a maximum activity level (2.1
pCi/g) that is consistent with observed activity from global fallout.

Future Land Use - Noncarcinogenic Hazards

Table 2 (0-0.5 ft) and Table 3 (0-6 ft.) provide a summary of the noncarcinogenic hazard indices
and applicable constituents of concern associated with the future land use of the SRWU.

The noncancer hazard indices were below unity for the future case environmental sampler scenario
and the hypothetical future occupational worker scenario. This indicates that potential adverse
health effects are not likely to occur for the future environmental researcher or the
hypothetical future occupational worker.

For the hypothetical future adult/child resident and child resident scenarios, exposure to
chemicals in the "M Area" groundwater aguifer exceeded the hazard index of 1. Ingestion of
carbon tetrachloride and thallium in the groundwater are the principal drivers for the noncancer
hazards. Lead exposure from groundwater was modeled and shown to not pose any risk.

Future Land Use - Carcinogenic Risks

Table 4 (0-0.5 ft) and Table 5 (0-6 ft.) provide a summary of the carcinogenic risks and
applicable constituents of concern associated with the future land use of the SRWU.

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Under the future land use scenario, the total carcinogenic  (cancer) risk from exposure to
chemicals or radionuclides in soils did not exceed a risk level of 1x10 -4 for the environmental
researcher or the occupational worker.

For the environmental researcher, the total carcinogenic  (cancer) risk from exposure to
chemicals in soil was 2 xlO -7.  The total carcinogenic risk for exposure to radionuclides in
soils 3 xlO.  Dermal contact  (with a risk of 2.7x10 -6 with radionuclides  (i.e., Cesium-137) in
the soil contributed to the risk.  Cesium-137 was observed at a maximum activity level  (2.1
pCi/g) that is consistent with observed activity from global fallout.

For the future occupational worker, the total carcinogenic risk associated with exposure to
chemicals in the soil  (2.0x10 -6) and the "M Area" groundwater aguifer  (2.2x10 -5) combined was
2x10 -5.  The total carcinogenic risk associated with exposure to radionuclides in the soil
(1.1x10 -6) and the "M Area" groundwater aguifer  (4.2x10 -6) combined was 2x10 -5.  The chemical
risk drivers for soil ingestion are arsenic, dibenz(a,h)anthracene, and benzo(a)pyrene; for
groundwater ingestion are arsenic, aldrin, dieldrin, and carbon tetrachloride.  The radionuclide
risk drivers for external exposure to soil is cesium-137; and for groundwater ingestion are
total radium, radium-226, and thorium-228.

For the future resident adult/child model, the total carcinogenic risk associated with exposure
to chemicals in the soil  (1.5x10 -5) and the "M Area" groundwater aguifer  (1.1x10 -4) combined
was 1x10 -4.  The total carcinogenic risk associated with exposure to radionuclides in the soil
(4.5x10 -5) and the "M Area" groundwater aguifer  (8.8x10 -5) combined was 1x10 -4.  The chemical
risk drivers for soil ingestion are arsenic, dibenz(a,h)anthracene, and benzo(a)pyrene; for
dermal contact with soils are dibenz(a,h)anthracene and benzo(a)-pyrene; for produce ingestion
are dibenz(a,h)-anthracene, benzo(a)pyrene, and benzo(b)fluoranthene; for groundwater ingestion
are arsenic, aldrin, dieldrin, and carbon tetrachloride; for dermal contact with groundwater are
dieldrin, bis(2-ethylhexyl)phthalate,  and carbon tetrachloride.  The radionuclide risk driven
for external exposure to soil is cesium-137; and for groundwater ingestion are total radium,
radium-226, and thorium-228; and for groundwater inhalation are total radium and radium-226.




For the future resident child model, the total carcinogenic risk associated with exposure to
chemicals in the soil  (9.1x10 -6) and the "M Area" groundwater aguifer  (4.2x10 -6) combined was
5x10 -5.  The total carcinogenic risk associated with exposure to radionuclides in the soil
(1.1x10 -5) and the "M Area" groundwater aguifer  (2.3x10 -5) combined was 3x10 -5.  The chemical
risk drivers for soil ingestion are arsenic, dibenz(a,h)anthracene, and benzo(a)pyrene; for
dermal contact with soils are dibenz(a,h)anthracene and benzo(a)-pyrene; for produce ingestion
are dibenz(a,h)-anthracene, benzo(a)pyrene, and benzo(b)fluoranthene; for groundwater ingestion
are arsenic, aldrin, dieldrin, and carbon tetrachloride; and for groundwater inhalation are
chloroform and carbon tetrachloride.  The radionuclide risk drivers for           external  exposure  to
soil is cesium-137; and for groundwater ingestion are total radium, radium-226, and thorium-228;
and for groundwater inhalation are total radium and radium-226.

Figures 5 through 7 are graphical summaries of the conceptual risk models for the future on-unit
residential adult/child, residential child, and occupational worker.

In summary, the future case residential scenarios showed total hazard and risk levels which
exceeded the EPA criterion values relative to the "M Area" groundwater aguifer pathway. Exposure
to carbon tetrachloride and thallium in groundwater provided the primary contribution to the
total noncancer hazard levels.  The total carcinogenic risks  (i.e., chemical/radionuclide
specific risk > 1x10 -4) for the future residential scenarios were primarily associated with
groundwater ingestion and/or inhalation for chemicals and radionuclides.  Constituents of
concern identified included carbon tetrachloride, chloroform, arsenic, aldrin, dieldrin, total
radium, radium-226, and thorium-228.

Radium-226 and thorium-228 are naturally occurring radionuclides.  Arsenic, aldrin and dieldrin
were only detected once out of 89 samples.

Ecological Risk Assessment

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An ecological risk assessment was conducted to assess the potential impacts to biota caused by
exposure to chemical and radionuclide constituents at the SRWU.

A site ecological reconnaissance survey was conducted in November 1994. No wetlands or
threatened and endangered species were observed in the vicinity of the SRWU, and use of the site
by threatened and endangered species is not expected.

Based on the ecological risk assessment, there is "little or no risk of adverse ecological
effects", therefore there is "no need for remediation" from an ecological standpoint (WSRC,
1996b).

Remedial Action Objectives

Remedial action objectives specify unit-specific contaminants, media of concern, potential
exposure pathways, and remediation goals. The remedial action objectives 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
applicable or relevant and appropriate reguirements (ARARs) under federal environmental or state
environmental or facility siting laws , or other information from the RFI/RI and Baseline Risk
Assessment Reports. These new goals should be modified, as necessary, as more information
concerning the unit and potential remedial technologies become available. Final remediation
goals are determined when the remedy is selected and establishes acceptable exposure levels that
are protective of human health and the environment.

Constituents of potential concern are site- and media-specific, man-made and naturally
occurring, inorganic and organic chemicals, pesticides, and radionuclides detected at a unit
under investigation. Constituents of concern are isolated from the list of constituents of
potential concern by calculating carcinogenic risks and noncarcinogenic hazard indices. A
constituent of concern contributes significantly to a pathway that contributes to either a
cumulative site carcinogenic risk greater than 1x10 -4 or a hazard index greater than 1.0. Risk
levels at or above the upper-bound of the target risk range of 1x10 -4 are considered
significant and these sites are expected to undergo remediation. Risk levels between 1x10 -6
and Ix 10 -4 reguire consideration for remediation.

ARARs are those cleanup standards, standards of control, and other substantive reguirements,
criteria, or limitations promulgated under federal, state, or local environmental law that
specifically address a hazardous substance, pollutant, contaminant, remedial action, location,
or other circumstances at a CERCLA site. Three types of ARARs; action-, chemical-, and
location-specific; have been developed to simplify identification and compliance with
environmental reguirements. Action-specific reguirements set controls on the design, performance
and other aspects of implementation of specific remedial activities. Chemical-specific
reguirements are media-specific, health-based concentration limits developed for site-specific
levels of contaminants in specific media. Location-specific ARARs must consider federal, state,
and local reguirements that reflect the physiographical and environmental characteristics of the
unit or the immediate area.

None of the risks associated with the SRWU soil have been found to be greater than 1x10 -4.
However, the risks are within the intermediate risk range for the future resident adult/child
and child only scenarios. The nonradiological intermediate risks were contributable to arsenic,
benzo(a)pyrene, dibenz(a,h)anthracene, and benzo(b)fluoranthene. For all three future scenarios
(future resident adult/child, future resident child, and future industrial worker), the
radiological intermediate risks were attributable to cesium-137. However, the average activity
levels for cesium-137 are consistent with those expected from global fallout. There were no His
above 1.0 for the SRWU soil.

The remedial action objective for the future on-unit resident (adult/child and child) is to
prevent ingestion of soil and produce, and dermal contact with soil from arsenic,
benzo(a)pyrene, dibenz(a,h)anthracene, and benzo(b)fluoranthene.

-------
Tables 6  (future resident) and 7  (occupational worker) list the Remedial Goal Options for
intermediate risk contaminants (1x10 -4 to 1x10 -6) for soil.  The exposure point concentration
is also provided in these tables to provide a comparison for the risks and hazards associated
with the contaminants.

The "M Area" groundwater aquifer poses risks near 1x10 -4 for the future residential adult/child
scenario and near 1x10 -5 for the future occupational worker scenario through groundwater
ingestion, dermal contact, and groundwater inhalation.  Dieldrin, arsenic, aldrin, chloroform,
carbon tetrachloride, and bis(2-ethylhexyl) phthalate were the nonradiological contributors to
the intermediate risk.  Radium-226, radium-total, and thorium-228 were the radiological
contributors to the intermediate risk.  For the future residential adult/child and child
scenarios, thallium and carbon tetrachloride were contributors to His above 1.0 for groundwater
ingestion.  There were no His above 1.0 for the future occupational worker associated with the
"M Area" groundwater aguifer.

Bis(2-ethylhexyl)phthalate was detected only twice above its MCL; and aldrin and dieldrin were
only detected once; and, they were not detected in subsequent samples from the well in which
they were originally detected.  It is highly likely that the single detection were due to
sampling or measurement errors.  Radium and thorium are naturally occurring radionuclides.

The preliminary remedial action objective for the future on-unit resident  (adult/child and
child) and occupational worker is to prevent ingestion, dermal contact, and inhalation of
groundwater from constituents with concentrations that minimally and infrequently exceed MCLs.

Tables 8  (future resident) and 9  (future occupational worker) list the Remedial Goal Options for
the "M Area" groundwater aquifer by receptor.  The exposure point concentrations and MCLs are
listed to provide a comparison for the risks and hazards associated with the constituents.

Based upon the levels and concentrations of the groundwater constituents, it was determined that
development of final remediation goals was not needed for groundwater cleanup.
Table 6   Remedial Goal Options for Intermediate Risk Contaminants of Concern for the Future
          Residential Adult and Child at the SRWU  (Soil)

      Contaminant                 Carcinogenic Risk          Noncarcinogenic Hazard      EPC
                             1x10 -6   1x10 -5   1x10 -4     0.1  1.0  3.0
Arsenic  (mg/kg) a            0.43      4.3       43          2.3  23   69               1.02

Benzo(a)pyrene  (mg/kg) a     0.088     0.88      8.8         NA   NA   NA              0.267
Benzo(b)fluoranthene         0.88      8.8       88          NA   NA   NA              0.277
(mg/kg)  a
Dibenze(a,h)anthracene       0.088     0.88      8.8         NA   NA   NA              0.192
(mg/kg)  a
Cesium-137  (pCi/g) b         2.0x10 -2 2.0x10 -12.0         NA   NA   NA               1.36

a- Risk- Based Concentration Table, July-December  1995  (EPA, 1995)
b- Risk- Based PRGs for Radionuclides (WSRC, 1994b)
EPC- Exposure Point Concentration
NA- Not Applicable

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Table 7   Remedial Goal Options for Intermediate Risk Contaminents  of Concern For the Future
          Occupational Worker at the SRWCJ  (Soil)
         Contaminent
Arsenic  (mg/kg) a
Benzo(a)pyrene  (mg/kg) a
Dibenz(a,h)anthracene
(mg/kg)
Cesium-137 (pCi/g) b
   Carcinogenic Risk
8.33x10 -2
            j.33x10 -1 8.33
Noncarcinogenic
    Hazard
                                       NA
                                              NA
                                                    NA
                                                                                                       EPC
1x10 -6
3.8
0.78
0.78
1x10 -5
3.8
7.8
7.8
1x10 -4
380
78
78
0.1
61.0
NA
NA
1.0
610
NA
NA
3.0
1830
NA
NA

1.02
0.267
0.192
                                                                     1.36
a- Risk- Based Concentration Table, July- December  1995  (EPA  1995)
b- Risk- Based PRGs for Radionuclides  (WSRC, 1994b)
EPC- Exposure Point Concentration
NA- Not Applicable
Table 8 Remedial Goal Options for Contaminants of Concern for the Future Residential Adult
and Child at the SRWCJ ("M Area" Groundwater Aquifer)
Contaminant Carcinogenic Risk Noncarcinogenic Hazard EPC
1x10 -6
Arsenic (mg/L) a
Aldrin (mg/L) a
Bis (2-ethylhexyl)
phthalate (mg/L) a
Carbon
Tetrachloride
(Mg/L) a
Chloroform (mg/L) a
Dieldrin (mg/L) a
Radium-226
(pCi/L) b
Radium, total
(pCi/L) b
Thorium-228
(pCi/L) b
0.
0.
0.

0.


0.
0.
0.

0.

0.

,000045
,000004
,0048

,00016


,00015
,0000042
,00418

,0184

,000162

1x10 -5
0.
0.
0.

0.


0.
0.
0.

0.

0.

,00045
,00004
,048

,0016


,0015
,000042
,0418

,184

,00162

1x10 -4
0
0
0

0


0
0
0

1

0

.0045
.0045
.48

.016


.015
.00042
.418

.84

.0162

0.1
0.0011
NA
NA

0.02


NA
NA
NA

NA

NA

1.0
0.011
NA
NA

0.20


NA
NA
NA

NA

NA

3.0
0.033
NA
NA

0.60


NA
NA
NA

NA

NA


0,
0,
0,

0,


0,
0,
2,

2,


.00102
.0000468
.0192

.00754


.015
.00013
.06

.54

167


MCL

0.05
NA
0.006

0.005


0.10
NA
20

5

NA

a - Risk-Based Concentration Table, July-December  1995  (EPA,  1995)
b - Risk-Based PRGs for Radionuclides  (WSRC, 1994b)
EPC - Exposure Point Concentration
                                 NA - Not Applicable

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Table 9   Remedial Goal Options for Contaminants of Concern for  the Future Occupational
          Worker at the SRWCJ  ("M Area" Groundwater Aquifer)
  Contaminant

Arsenic  (mg/L) a
Aldrin  (mg/L) a
Bis(2-ethylhexyl)
phthalate  (mg/L) a
Carbon
Tetrachloride
(Mg/L) a
Dieldrin  (mg/L) a
Thallium  (mg/L) a
Radium-226
(pCi/L) b
Radium, total
pCi/L) b
Thorium-228
(pCi/L) b
    Carcinogenic Risk
1x10 -6
0.00016
0.000017
0.0048
0.0029
0.000018
NA
1.30
1x10 -5
0.
0.
0.
0.
0.
0016
00017
048
029
00018
NA
13
.0
1x10 -4
0.016
0.0017
0.48
0.29
0.0018
NA
130
1.60
16.0
           16.0
           160
                      160

                      1600
Noncarcinogenic  Hazard
  0.1     1.0    3.0
  0.0086  0.086  0.258
  NA      NA     NA
  NA      NA     NA
                                     0.02
                                             0.20   0.60
                                     NA      NA     NA
                                     0.0023  0.023  0.069
                                     NA      NA     NA
                                     NA
                                     NA
                                             NA
                                             NA
                                                    NA
                                                    NA
EPC
                                                             0.00754
                          0.00013
                          0.00100
                          2.06

                          2.54

                          167
- Final Baseline Risk Assessment - Appendix H Table  6  (WSRC,  1996b)
- Final Baseline Risk Assessment - Appendix H - Table  7  (WSRC,  1996b)
EPC - Exposure Point Concentration                               NA- Not Applicable
           MCL
                                                             0.00102     0.05
                                                             0.0000468   NA
                                                             0.0192      0.006
                                                                         0.005
           NA
           0.002
           20
                                                                         NA

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VII. Description of the Considered Alternatives

VII.A Description of the Considered Alternatives for the SRWU Source Control Operable Unit

Four alternatives were evaluated for remedial action at the SRWU source control operable unit.
Each alternative is described below:

Alternative SI - No Action

Under this alternative, no action would be taken at the SRWU. EPA policy and regulations
require the consideration of a no action alternative to serve as a baseline against which the
other alternatives can be compared. Because no further action would be taken at the unit and
the SRWU would remain in its present condition, there are no costs associated with this
alternative. There would be no reduction of risk.

Alternative S2 - Institutional Controls

Under this alternative, Institutional Controls would be implemented at the SRWU. The primary
purpose of institutional controls is to prevent the exposure of the general public or potential
future resident to the contaminants present in the surface soils.

Implementation of this alternative will require both near- and long-term actions. For the near-
term, signs will be posted at the waste unit which indicate that this area was used for the
disposal of waste material and contains buried waste. In addition, existing SRS access controls
will be used to maintain the use of this site for industrial use only.

In the long-term if the property is ever transferred to non-federal ownership. The U.S.
Government would create a deed for the new property owner which would include information needed
for compliance with Section 120(h) of CERC1A. The deed shall include notification disclosing
former waste management and disposal activities as well as remedial actions taken on the site,
and any continuing groundwater monitoring commitments. The deed notification shall, in
perpetuity, notify any potential purchaser that the property has been used for the management
and disposal of construction debris and other materials, including hazardous substances.

The deed shall also include restrictions precluding residential use of the property. However,
the need for these deed restrictions may be reevaluated at the time of transfer in the event
that contamination no longer poses an unacceptable risk under residential use.

The soil sample analyses indicate that a majority of the contamination is located 8-32 feet
below the surface. Institutional controls would prevent excavation to these depths and prevent
future residential use of this waste unit. The present worth cost associated with this
alternative is approximately $18,060. This cost includes land surveys, installation of signs,
filing with the Aiken County Records, inspection and maintenance, and record of decision reviews
every 5 years for 30 years.
Alternative S3 - Excavation, Debris Removal, and Offsite Disposal

This alternative consists of excavating the soil (to a depth of 6 feet) from the source control
operable unit, screening it to remove rubble and debris, and disposing of the debris in an
off-site disposal facility. The excavated area would then be backfilled with soil. Treatment
of the residual deeper soils would not be necessary since fate and transport analysis has shown
that there is little or no chance for the residual waste at the SRWU to be a source of future
groundwater contamination. The present worth cost for this alternative is approximately
$60,115,350. This cost includes site preparation (i.e., vegetation removal, excavation,
required utilities, etc.), backfill, site closure (reseeding), and groundwater monitoring. If
the property is ever transferred to non-federal ownership, the U.S. Government would create a
deed for the new property owner which would include information needed for compliance with
Section 120(h) of CERCLA with notification and restrictions similar to Alternative S2. Deed

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restrictions under this alternative would be necessary to prevent excavation of buried waste
and groundwater use.

Alternative S4 - Placement of a Cap

Under this alternative, a low-permeability cover (i.e., clay layer, 30-mil flexible membrane
liner, and a vegetative soil cover) would be placed on top of the SRWU source control operable
unit. The primary purpose of the cover is to prevent exposure to surface soils. The low
permeability cover would also further reduce any potential contaminant migration into the
underlying soils and groundwater. The low permeability cover would be reguired to cover a
planar area of approximately 450,000 ft 2 or 10 across. The present worth cost for this
alternative is approximately $6,475,350. This cost includes placement of the low permeability
cover, deed notifications and restrictions, inspection and maintenance, groundwater monitoring,
and record of decision, reviews every 5 years for 30 years. If the property is ever transferred
to non-federal ownership, the U.S. Government would create a deed for the new property owner
which would include information needed for compliance with Section 120(h) of CERCLA with
notification and restrictions similar to Alternative S2. Deed restrictions, under this
alternative would be necessary to prevent excavation of buried waste and groundwater use.

VII.B Description of the Considered Alternatives for the SRWU Groundwater ("M Area" Aguifer)

Four alternatives were also evaluated for remedial action at the SRWU groundwater ("M Area")
operable unit. Each alternative is described below:

Alternative GW1 - No Action

Under this alternative, no action would be taken at the SRWU "M Area" groundwater operable unit.
EPA policy and regulations reguire the consideration of a no action alternative to serve as a
baseline against which the other alternatives can be compared. Because no further action would
be taken at the unit and the SRWU "M Area" groundwater operable unit would remain in its present
condition; there are no costs associated with this alternative. There would be no reduction of
risk.

Alternative GW2 - Institutional Controls

Under existing controls at the SRS, the shallow groundwater at the SRWU is not used for drinking
or industrial use. Upon transfer of the property, deed notifications and restrictions would be
needed to prevent use of the groundwater for domestic purposes (consumption or hygiene).
Groundwater monitoring would need to continue at the site on a semi-annual basis to determine
potential future groundwater impacts as well as the source of groundwater contamination. For
cost estimating purposes only, the groundwater monitoring was based on sampling eight wells for
30 years. However, at the five-year Record of Decision review, the groundwater monitoring data
will be evaluated to determine if any changes in the groundwater remedy are appropriate. Based
on the current concentrations in groundwater, the probable condition for the "M Area"
groundwater aguifer is no significant groundwater contamination resulting from the SRWU. As a
result, no remedial action is deemed appropriate for the "M Area" groundwater aguifer. However,
a confirmatory groundwater monitoring program will be established to ensure that this is the
appropriate remedial action for the "M Area" groundwater aguifer.

The present worth cost for this alternative is expected to be approximately $725,060. This cost
includes placement of the deed notifications and restrictions, inspection and maintenance
groundwater monitoring, and record of decision reviews every 5 years for 30 years. If the
property is ever transferred to non-federal ownership, the U.S. Government would create a deed
for the new property owner which would include information needed for compliance with Section
120(h) of CERCLA with notification and restrictions similar to Alternative S2.

Alternative GW3- Extraction, Reverse Osmosis, Reinjection

Under this alternative, the groundwater would be extracted and treated by reverse osmosis. The
reverse osmosis system would consist of semi-permeable membrane elements mounted in pressure
tubes, high pressure water pump(s), pressure gauges, temperature gauges, and flow meters.
Pre-treatment components consisting of filters or pH-adjustment may be part of this
system. The present worth cost for this alternative is expected to be approximately $2,622,070.

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This cost includes placement of the deed notifications and restrictions, inspection and
maintenance, purchase and installation of extraction wells and a reverse osmosis unit, operation
of the extraction wells and a reverse osmosis unit groundwater monitoring, and record of
decision reviews every 5 years for 30 years. It should be noted that four groundwater extraction
wells were estimated to be sufficient. There was no capture zone analysis conducted to determine
the exact number of wells that would needed, so the estimate for the wells may be >+50 percent
if more wells are required. If the property is ever transferred to non-federal ownership, the
U.S. Government would create a deed for the new property owner which would include information
needed for compliance with Section 120(h) of CERCLA with notification and restrictions similar
to Alternative S2.

Alternative GW4 - Extraction, Recirculation Wells, Reinjection

Under this alternative, the groundwater would be extracted and treated by recirculation wells.
The recirculation wells would operate by transferring the contaminants from the agueous phase to
the gaseous phase and subsequent treatment of the contaminants. The present worth cost for this
alternative is expected to be approximately $722,000 for pilot test costs only and $4,620,350
for full scale remediation. This cost includes placement of the deed notifications and
restrictions, inspection and maintenance, purchase and installation of extraction and
recirculation wells, operation of the extraction and recirculation wells, groundwater
monitoring. and record of decision reviews every 5 years for 30 years. It should be noted that
for the pilot-scale system, two groundwater extraction wells and 6 monitoring well clusters were
estimated to be sufficient. Full scale remediation was estimated to require 10 additional
wells. There was no capture zone analysis conducted to determine the exact number of wells that
would needed for either the pilot-scale or full-scale remediation system, so the estimate for
the wells may be >+50 percent if more wells are required. If the property is ever transferred
to non-federal ownership, the U.S. Government would create a deed for the new property owner
which would include information needed for compliance with Section 120(h) of CERCLA with
notification and restrictions similar to Alternative S2.

VIII. Summary of Comparative Analysis of the Alternatives

Description of Nine Evaluation Criteria

Each of the remedial alternatives was evaluated using the nine criteria established by the
National Oil and Hazardous Substances Contingency Plan (NCP). The criteria were derived from
the statutory requirements of CERCLA Section 121. The NCP [40 CFR ° 300.430 (e) (9)] sets forth
nine evaluation criteria that provide the basis for evaluating alternatives and selecting a
remedy. The criteria are:

• 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, and
• community acceptance.

In selecting the preferred alternative, the above mentioned criteria were used to evaluate the
alternatives developed in the Silverton Road Waste Unit Corrective Measures Study/Feasibility
Study (U) (WSRC, 1996c). Seven of the criteria we 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. Brief descriptions of all nine criteria are given below.

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.

Compliance with Applicable or Relevant and Appropriate Requirements (ARARs) - ARARs are Federal

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and state environmental regulations that establish standards which remedial actions must meet.
There are three types of ARARs:   (1) chemical-specific,  (2) location-specific, and  (3)
action-specific.

Chemical-specific ARARs we usually health- or risk-based levels or methodologies which, 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 floodplains, wetlands, historic places, and sensitive ecosystems or
habitats.

Action-specific ARARs are usually technology- or remedial activity-based reguirements at
limitations on actions taken with respect to hazardous substances or unit-specific conditions.
These reguirements are triggered by the particular remedial activities that we selected to
accomplish a remedy.

The remedial activities are assessed to determine whether they attain ARARs or provide grounds
for invoking one of the five waivers for ARARs. These waivers are:

       •      the remedial action is an interim measure and will become a part of a total remedial
              action that will attain the ARAR,

       •      compliance will result in greater risk to human health and the environment than
              other alternatives,

       •      compliance is technically impracticable from an engineering perspective,

       •      the alternative remedial action will attain an eguivalent standard of performance
              through use of another method or approach,

       •      the state has not  consistently applied the promulgated reguirement in similar
              circumstances or at other remedial action sites in the state.

In addition to ARARs, compliance with other criteria, guidance, and proposed standards that are
not legally binding, but may provide useful information or recommended procedures should be
reviewed as To-Be-Considered when setting remedial objectives.

Long-Termn Effectiveness and Permanence - The remedial alternatives are assessed based on their
ability to maintain reliable protection of human health and the environment after
implementation.

Reduction of Toxicity, 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.

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  (eg., air emissions), and
the time until protection is achieved.

Implementability - The remedial alternatives are assessed by considering the difficulty of
implementing the alternative including technical feasibility,  constructability, reliability of
technology, ease of undertaking additional remedial actions  (if reguired), monitoring
considerations, administrative feasibility  (regulatory reguirements), and availability of
services and materials.

Cost - The evaluation of remedial alternative must include capital and 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

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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.

State Acceptance - In accordance with the FFA, the State is required to comment on/approve of
the RFI/RI Report, the Baseline Risk Assessment, the Corrective Measures Study/Feasibility
Study, and the Statement of Basis/Proposed Plan.

Community Acceptance - The 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 and public comments concerning the proposed remedy are addressed in the
Responsiveness Summary (Appendix A) of this Record of Decision.

Detailed Evaluation

The remedial action alternatives discussed in Sections VII.A and VII.B have been evaluated using
the nine criteria just described. Table 10 presents the evaluation of the soil remedial
alternatives. Table 11 presents the evaluation of the "M Area" groundwater remedial
alternatives.

IX. The Selected Remedy

Based on the SRWU Baseline Risk Assessment (WSRC, 1996b), for the residential scenarios the
total site carcinogenic risk for exposure to chemicals ranged from 1x10 -4 to Sx.10 -5 and the
cumulative noncarcinogenic hazard indices exceeded 1.0. The total site carcinogenic risks for
exposure to radionuclides ranged from 1x10 -4 to 3x10 -5 for the residential scenarios.
Groundwater is the only pathway that exceeds risks of 10 -4 and a hazard index of 1.0. For the
industrial scenarios, the total site carcinogenic risks for exposure to chemicals ranged from
2x10 -5 to 3x10 -3 and the noncarcinogenic hazard indices were below 1.0. The total site
carcinogenic risks for exposure to radionuclides ranged from 1x10 -5 to 3x10 -6 for the
industrial scenarios. The primary contributors for the carcinogenic risks and noncarcinogenic
hazard were from groundwater. It should be noted that based on the size of the SRWU
(approximately 10 acres), the contaminants of concern are present in low concentrations over a
large area. Some contaminants had a low frequency of detection and were present at levels that
just exceeded the most conservative contaminant level goals. Fate and transport analyses
indicated that residual contaminants in the soils will not migrate to the groundwater. The
presence of surface soil contamination prevents the use of this waste unit for residential use.
Therefore, for the SRWU source control operable unit, the preferred alternative is Institutional
Controls. This alternative is considered to be the least cost option which is still protective
of human health and the environment. Institutional Controls meets the RAOs for the SRWU soils
by precluding future on-site residential use of the area.

Implementation of this alternative will require both near- and long-term actions. For the near-
tern signs, will be posted at the waste unit which indicate that this area was used for disposal
of waste material and contains buried waste. In addition, existing SRS access controls will be
used to maintain the use of this site for industrial use only. Further, excavation below 8 feet
will be prohibited.

In the long-term, if the property is ever transferred to non-federal ownership, the U.S.
Government would create a deed for the new property owner which would include information o for
compliance with Section 120(h) of CERCLA. The deed shall include notification disclosing former
waste management and disposal activities as well as remedial actions taken on the site, and any
continuing groundwater monitoring commitments. The deed notification shall, in perpetuity,
notify any potential purchaser that the property his been used for the management and disposal
of construction debris and other materials, including hazardous substances.

In addition, if the property is ever transferred to non-federal ownership, a survey plat of the
area will be prepared, certified by a professional land surveyor, and recorded with the
appropriate county recording agency.

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In the "M Area" groundwater aquifer, low levels of contaminants have been detected which
minimally and infrequently exceed MCLs and the qroundwater is currently not used as a drinkinq
water source. The probable condition for the "M Area" qroundwater aquifer is no siqnificant
qroundwater contamination resultinq from the SRWU. As a result, no remedial action is deemed
appropriate for the SRWU "M Area" qroundwater aquifer. However, a confirmatory qroundwater
monitorinq proqram will be established to ensure that this is the appropriate remedial action
for the "M Area" qroundwater aquifer. In the event that the probable condition is no lonqer
appropriate, DOE will evaluate the need for remedial action. There are no qroundwater RAOs to be
met for the "M Area" qroundwater aquifer since the selected remedy for the aquifer is no
remedial action with confirmatory qroundwater monitorinq.

Under this qroundwater monitorinq proqram, additional backqround monitorinq well(s) will be
installed since one of the oriqinal backqround wells for the "M Area" qroundwater operable unit
went dry and was never monitored. The backqround well(s) will be used to further evaluate the
upqradient concentrations of the contaminants in the "M Area" qroundwater operable unit. In
addition to the new backqround well(s), the existinq backqround well and approximately six
existinq "M Area" wells will also be monitored. This monitorinq is intended to evaluate trends
in the qroundwater contamination. Groundwater monitorinq was assumed to be conducted on a
semi-annual basis for 30 years (for cost estimatinq purposes only). However, at the five-year
ROD review, the qroundwater monitorinq data will be evaluated to determine if any chanqes in the
qroundwater remedy are appropriate.

The number and location of the new backqround well(s), a list of the existinq wells to be
monitored, the frequency of monitorinq, and the submittal frequency of the qroundwater data for
requlatory review will be listed in the SRWU Corrective Measures Implementation/ Remedial Action
Report (CMI/RAR) post-ROD document. The CMI/RAR will also identify a qroundwater strateqy which
will include trend analysis and recommendations based on the interpretation of the data in the
post-ROD qroundwater monitorinq reports.

The SCDHEC has modified the SRS RCRA permit to incorporate the selected remedy.

This proposal is consistent with EPA quidance and is an effective use of risk manaqement
principles.

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Table 10 Evaluation of Remedial Alternatives Considered for the SRWU Source Control Operable
Evaluation Criteria
Overall Protection of
Human Health and the
Environment
Compliance with ARARs
Alternative SI
No Action
This alternative is the least
protective of human health
risk. However, risks due to
soil exposure are within
EPA's target risk range.
There was no significant
ecological risks for the unit.

There were no chemical- or
location-specific ARARS
identified for the waste unit.
Since this alternative does
not require any action at the
unit, there are no action-
specific ARARs to be met.
Alternative S2
Institutional Controls
This alternative is protective of
human health. Future
residential use of the area
would be prevented. There was
no significant ecological risks
for the unit.
There were no chemical- or
location-specific ARARs
identified for the waste unit.
Since this alternative does not
require any action at the unit,
there are no action-specific
ARARs to be met.
Alternative S3
Excavation, Debris Removal

and offsite Disposal
This alternative is protective of
human health. Most of the possible
source of contamination would be
removed. There was no significant
ecological risks for the unit.
There were no chemical, or location-
specific ARARs identified for the
waste unit. Compliance with the
Clean Air Act in limiting the amount
of dust created through this
alternative would be required. Land
disposal restrictions for disposal of
any wastes generated would also be
any wastes generated would also be
required. All activities would be
required to comply with OSHA
standards.
Alternative S4
Cap
This alternative would be
protective of human health.
The potential source of
contamination would be
covered.
There were no chemical-or
location-specific ARARs
identified for the waste unit.
Compliance with the Clean
Air Act in limiting the amount
of dust created through this
alternative would be required.
All activities would be
All activities would be
required to comply with
OSHA standards. However,
RCRA guidance on caps are
To-Be-Considered.
Long- term effectiveness
and permanence
Reduction of toxicity,
mobility, or volume
through treatment
This alternative will not
reduce risks wich are within

EPA's target risk range.
This alternative does not
reduce toxicity, mobility, or
volume through treatment
since there is no treatment
process.
This alternative will provide
long-term effectiveness and

permanence as long as the deed
notifications are enforced.
This alternative does not reduce
toxicity, mobility, or volume
through treatment since there is
no treatment process.
This alternative provides long-term
effectiveness through removal of

most of the waste materials.
This alternative provides reduction
in the mobility of contaminants by
removing the source of
contamination to a managed facility.
This alternative will provide
long-term effectiveness and

permanence as long as the
low permeability cover is
properly maintained.

This alternative would
provide reduction in the
mobility of the contaminants
since migration of the
contaminants is reduced.

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Table 10 Evaluation of Remedial Alternatives Considered for the SRWU Source Control Operable Unit (cont'd).
Evaluation Criteria
Short-term effectiveness
Alternative SI
No Action

This alternative does not

provide any active
remediation and would
therefore not expose any
workers to hazards
associated with remedial
activities. This alternative
would not expose the
surrounding community to
short-term risk as site
access is restricted.
Alternative S2
Institutional Controls

This alternative does not

provide any active remediation
and would therefore not expose
any workers to hazards
associated with remedial
activities. This alternative
would not expose the
surrounding community to
short-term risk as site access is
restricted.
Alternative S3
Excavation, Debris Removal
and Offsite Disposal
This alternative may potentially

expose the workers to the waste
disposed of at the unit. The use of
heavy eguipment poses typical risks
to the workers involved. This
alternative would not expose the
surrounding community to short-term
risk as site access is restricted.
Alternative S4
Cap

The workers will not be

exposed to the waste disposed
of at the unit. The use of
heavy eguipment poses typical
risks to the workers involved.
This alternative would not
expose the surrounding
community to short- term risk
as site access is restricted.
Implementability
This alternative is currently
in-place. There is no action
involved with this
alternative.
This alternative is easily
implementable reguiring the
filing of deed notifications,
inspection and maintenance,
and ROD reviews every 5 years
for 30 years..
This alternative is probably the most
difficult to implement since it would
reguire earth and debris removal as
well as the location of an appropriate
disposal location for the debris and
earth removed from the unit.
This alternative would reguire
the filing of deed notifications
to notify any potential future
purchasers of the land that the
land has been used for waste
management and disposal
activities. In addition, the
location of a large guantity of
suitable clay borrow material
would need to be found.
Cost
State Acceptance
Community Acceptance
There are no costs involved
with this alternative.
This criterion will be
completed following review
by the appropriate
regulatory agencies.

This criterion will be
completed following public
The total cost for this
alternative is estimated to be
$18,060.

This criterion will be
completed following review by
the appropriate regulatory
agencies.

This criterion will be
completed following public
The total cost for this alternative is
estimated to be $60,115,350.
This criterion will be completed
following review by the appropriate
regulatory agencies.
This criterion will be completed
following public review.
The total cost for this
alternative is estimated to be
$6,475,350.

This criterion will be
completed following review
by the appropriate regulatory
agencies.

This criterion will be
completed following public

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Table 11    Evaluation of Remedial Alternatives  Considered for the SRWU "M Area" Groundwater Operable  Unit
   Evaluation Criteria
                                       Alternative GWI
                                           No Action
                                                                                       Alternative  GW3
                                                                                  Extraction,  Reverse Osmosis,
                                                                                         Reinj ection
                                                                                               Alternative  GW4
                                                                                          Extraction,  Recirculation,
                                                                                              Wells,  Reinjection
Overall Protection of Human
Health and the Environment
Compliance With ARARs
This alternative is the least
protective of human health
risk.  However, this aquifer  is
not currently being used as  a
source of drinking water.

There were no location-
specific ARARs determined
for the groundwater.  This
alternative would meet all
act ion-sped fie ARARs as this
alternative does not involve
any action at the unit.  This
alternative would not meet all
maximum contaminant level
(MCL)  goals.  However, the
low levels of contaminants in
the groundwater minimally
and infrequently exceeded the
MCL goals which indicate
that there is no significant
groundwater threat.
This alternative is protective  of
human health. Future use of the
groundwater would be prevented.
                                                                          There were no location-specific
                                                                          ARARs determined for the
                                                                          groundwater. This alternative
                                                                          would meet all action-specific
                                                                          ARARs as this alternative  does
                                                                          not involve any action  at  the unit.
                                                                          This alternative would  not meet
                                                                          all MCL goals. However, the  low
                                                                          levels of contaminants  in  the
                                                                          groundwater minimally and
                                                                          infrequently exceeded the  MCL
This alternative is protective  of human
health.  This alternative would  treat  the
contaminants from the "M Area"
groundwater to below MCLs.
                                        There  were no location- specific ARARs
                                        determined for the groundwater.
                                        Compliance with the Clean Air Act in
                                        limiting  potential air releases; with the
                                        Clean  Water Act for discharge
                                        limitations;  with the Safe Drinking
                                        Water  Act for MCLs; and with the South
                                        Carolina  Well Standards and
                                        Regulations would be required for this
                                        alternative.  All work would need to
                                        comply with OSHA standards.
This  alternative is protective  of
human health.  This alternative
would treat the contaminants
from the "M Area" groundwater
to below MCLs.

There were no location- specific
ARARs determined for the
groundwater.  Compliance with
the Clean Water Act for
discharge limitations; with the
Safe Drinking Water Act for
MCLs; and with the South
Carolina Well Standards and
Regulations would be required
for this alternative. All work
would need to comply with
OSHA standards.
                                     This  alternative will not
                                     provide  long- term
                                     The  groundwater plume is
                                     minimal  and possibly
                                     depleting;  and there is no
                                     potential  future unit impact to
                                     the  groundwater
                                      This  alternative will provide long-
                                      term  effectiveness and
                                      notifications  are enforced.
                                        This  alternative provides long- term
                                        effectiveness  through treatment of
                                        contaminants  in the groundwater.
                                               This  alternative provides long-
                                               term  effectiveness through
                                               treatment of organic
                                               contaminents in the groundwater.
                                     This  alternative does not
                                     reduce  toxicity, mobility,  or
                                     volume  through treatment
                                     process.
                                      This  alternative does not reduce
                                      toxicity,  mobility,  or volume
                                      through treatment since there is
                                      no  treatment process.
                                        This  alternative provides reduction in
                                        toxicity,  mobility,  and volume by
                                        treating  the contaminants in the
                                        groundwater.
                                               This  alternative provides
                                               reduction in toxicity, mobility,
                                               and volume by treating the
                                               organic contaminants in the
                                               groundwater.

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Alternative GW3
Extraction, Reverse Osmosis,
Reinj ection
Alternative GW4
Extraction, Recirculation
Wells, Reinj ection
Short-term effectiveness
This alternative does not
provide any active
remediation and would
therefore not expose any
workers to hazards associated
with remedial activities. This
alternative would not expose
the surrounding community to
short-term risk as site access
is restricted.
This alternative does not provide
any active remediation and would
therefore not expose any workers
to hazards associated with
remedial activities. This
alternative would not expose the
surrounding community to short-
term risk as site access is
restricted.
This alternative provides minor risk to
remediation workers during
implementation. The use of eguipment
poses typical risks to the workers
involved. Strict adherence to OSHA
guidelines would limit the risks. This
alternative would not expose the
surrounding community to short-term
risk as site access is restricted.
This alternative provides minor
risk to rermediation workers
during implementation. The use
of equipment poses typical risks
to the workers involved. Strict
adheranee to OSHA guidlines
would limit the risks. This
alternative would not expose the
surrounding community to short-

restricted
Implementability
This alternative is currently
in-piace. There is no action
involved with this alternative.
implementable requiring the filing
of deed notifications and the
continuation of groundwater
monitoring.
of deed notifications and the
continuation of groundwater monitoring.
Additional permits would be required
for operation of the equipment. This
alternative is readily available.
the filing of deed notifications
and the continuation of
groundwater monitoring. This
alternative is also an innovative
technology that may be more
difficult to implement correctly.
with this alternative.
However, confirmatory
groundwater monitoring will
be implemented.
The total cost for this alternative

is estimated to be $725,060.
The total cost for this alternative is

estimated to be $2,622,070.
The total cost for this alternative
This criterion will be
completed following review
by the appropriate regulatory
agencies.
This criterion will be completed
following review by the
appropriate regulatory agencies.
This criterion will be completed
following review by the appropriate
regulatory agencies.
This criterion will be completed
following review by the
appropriate regulatory agencies.
This criterion will be
completed following public
review.
This criterion will be
following public review.
This criterion will be completed
following public review.

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X.    Statutory Determinations

Based an the SRWU RFI/RI Report and the Baseline Risk Assessment, the SRWU poses no significant
risk to the environment and minimal risk to human health.  Therefore, a determination has been
made that institutional controls are sufficient for protection of human health and the
environment for the SRWU soils and that no remedial action with confirmatory groundwater
monitoring is deemed appropriate for the "M Area" groundwater aguifer.

The selected remedy is protective of human health and the environment, complies with Federal and
State reguirements that are legally applicable or relevant and appropriate to the remedial
action, and is cost-effective.  The size of the waste unit and the random distribution and low
levels of contaminants preclude a remedy in which treatment is a practical alternative.  Because
treatment of the principal threats of the site was found to be impracticable, this remedy does
not satisfy the statutory preference for treatment as a principal element.

Institutional controls will result in hazardous substances, pollutants, or contaminants
remaining in the waste unit.  Section 300.430  (f)(4)(ii) of the NCP reguires that a Five Year
Review of the ROD be performed if hazardous substances, pollutants, or contaminants remain in
the Waste Unit.  The three Parties have determined that a Five Year Review of the ROD for the
SRWU will be performed to ensure continued protection of human health and the environment.

XI.     Explanation of Significant Changes

The 45-day public comment period for the Statement of Basis/Proposed Plan for the Silverton Road
Waste Unit (731-3A) (WSRC, 1996d) began on September 17, 1996 and ended on October 31, 1996.  A
public meeting was held on October 15, 1996.  During the public comment period, there were three
comments received.  These comments are addressed in Appendix A of this Record of Decision.
Based on these comments, there were no significant changes made to the preferred alternative
originally presented in the SRWU Statement of Basis/Proposed Plan.  However, based on a review
of recent groundwater data indicating minimal and infreguent MCL exceedances, the ROD no longer
references an ACL/MZ demonstration for the groundwater.  The proposed action for the groundwater
is no remedial action with confirmatory groundwater monitoring.

XII.   Responsiveness Summary

There were three comments received during the public comment period.  The Responsiveness
Summary (see Appendix A) of this Record of Decision addresses these comments.

XIII.   Post-ROD Document Schedule

The post-ROD document schedule is listed below and is illustrated in Figure 8:

1. Corrective Measures Implementation/Remedial Action Report (CMI/RAR) (rev.  0) for the SRWU
   will be submitted for EPA and SCDHEC review four months after issuance of the ROD.

2. EPA and SCDHEC review of the SRWU CMI/RAR  (rev.  0)  - 90 days.

3. SRS revision of the SRWU CMI/RAR (rev.  0) after receipt of regulatory comments - 60 days.

4. EPA and SCDHEC final review and approval of the SRWU CMI/RAR  (rev/ 1)  - 30 days.

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XIV.  REFERENCES

DOE  (U.S. Department of Energy), 1994.  Public Involvement, A Plan for the Savannah River
  Site.  Savannah River Operations Office, Aiken, South Carolina.

EPA  (U.S. Environmental Protection Agency), 1995.  EPA Region III Risk-Based
  Concentration Table.  July-December 1995. Roy L.  Smith, October 20,1995.

FFA, 1993.  Federal Facility Agreement for the Savannah River Site, Administrative Docket
  No.  89-05-FF,  (Effective Date.  August 16, 1993) .

WSRC (Westinghouse Savannah River Company), 1994a.  Quality Control Summary Report for
  the Silverton Road Waste Unit RFI/RI Assessment  (U), ESH-EMS-94-0532, Rev. 0.
  Westinghouse Savannah River Company, Aiken, South Carolina.

WSRC (Westinghouse Savannah River Company), 1994b.  Risk-Based Preliminary Remediation
  Goals for Radionuclides.  Scoping Phase Calculations  (U), WSRC-TR-94-0181, Rev. 1,
  Westinghouse Savannah River Company, Aiken, South Carolina.

WSRC (Westinghouse Savannah River Company), 1996a.  Final  RFI/RI Report for the Silverton
  Road Waste Unit  (U), WSRC-RP-95-214, Rev. 1.2, Westinghouse Savannah River Company,
  Aiken, South Carolina.

WSRC (Westinghouse Savannah River Company), 1996b.  Final  Baseline Risk Assessment for the
  Silverton Road Waste Unit  (U), WSRC-RP-95-215, Rev. 1.1, Westinghouse.  Savannah River
  Company, Aiken, South Carolina.

WSRC (Westinghouse Savannah River Company), 1996c.  Silverton Road Waste Unit Corrective
  Measures Study/Feasibility Study  (U), WSRC-RP-96-100, Rev. 1.1, Westinghouse Savannah
  River Company, Aiken, South Carolina.

WSRC (Westinghouse Savannah River Company), 1996d.  Statement of Basis/Proposed Plan for
  the Silverton Road Waste Unit  (731-3A)  (U) , WSRC-RP-96-118, Rev. 1.2,.  Westinghouse
  Savannah River Company, Aiken, South Carolina.

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                                  APPENDIX A

                            RESPONSIVENESS SUMMARY

The 45-day public comment period for the Statement of Basis/Proposed Plan for the Silverton Road
Waste Unit (731-3A)  began on September 17, 1996 and ended on October 31, 1996.  A public meeting
was held on October 15, 1996.  During the public meeting, there were two guestions received
during the Public Meeting and Comment Session on the Limited Action Proposed Plans/Permit
Modifications presentations; and, there was one public comment received during the Formal Public
Comment Session.  All of the comments are listed as recorded in the Savannah River Site
Information Exchange transcript based on the October 15, 1996 Public Meeting.

Specific comments and responses are noted below.

Public Comments

The following two comments were received during the Limited Action Proposed Plans/Permit
Modifications presentations.

1)Public Citizen: What risk is there for animals or I guess future environmental, like if you
were going to turn this into a park?

Response to Comment 1):

As part of the baseline risk assessment process for the Silverton Road Waste Unit (SRWU) , an
ecological risk assessment was conducted to consider the potential impacts to animal and plant
life caused by exposure to chemical and radionuclide constituents at the SRWU.  The process
included a site ecological reconaissance survey that determined no wetlands important to animal
or plant habitats or threatened and endangered species were in the vicinity of the SRWU; and use
of this site by threatened and endangered species would not be expected.

Based on the ecological risk assessment, there is no reason to expect any adverse effects on
animal or plant life from the SRWU areas were to be turned into a park in the future.

A more detailed discussion of the ecological risk assessment may be found in Section 2 of the
Final Baseline Risk Assessment for the Silverton Road Waste Unit  (WSRC, 1996b).

2)Public Citizen: Are you using like private landfills and private - or I guess what other
communities have developed? I mean it looks like a landfill to me.  And it looks like there are
landfills all over the country and there's a whole lot of landfills that have turned into like
parks and stuff.  Is that an opportunity here to turn it into a park or to use private models
and maybe look at who has done this a lot? I guess the EPA guy was talking about streamlining.
Are you guys using private streamlining ideas?

Response to Comment 2):

The SRS is currently considered to be a national environmental research park and as such, the
site is/will be used for environmental research.  For the institutional controls units, the only
thing that our remedial decision has done is to state that these waste units will not be used
for any residential use.  The selected remedy is consistent with what other federal, state,
municipal, and private entities are doing.

Due to the proximity of the SRWU to the site boundary, there is a potential that this area could
be converted for recreational use (i.e.  used as a park).  For the SRWU, the risk levels for the
soils alone barely exceed the threshold for residential  (both adult and child) use;  and the
presence of buried debris should not interfere with the use of the SRWU as a park. However,
there are low levels of groundwater contamination present at the SRWU that could prevent use of
the groundwater as a drinking water source.  There are constituents present in the groundwater
that minimally and infreguently exceed primary drinking water standards.

It should be noted that the use of the SRWU as a park or any other recreational use would be
evaluated at the time of property transfer or change in use.

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The following comment was received during the Formal Public Comment Session.

3)Mike Rourak: My name is Mike Rourak and my guestion is directed directly to Mr. Brian
Hennessey's earlier discussion (unintelligible) Silverton Road property, for example. In the
Future Use Manual that was sent out to some of us about the disposal of close to a million acres
of property for DOE, in your deed restrictions there're things that we cannot do. And we're
going to need a little bit before we can respond back to Washington. Those of us who received
the manual, we almost are going to need to know what those deed restrictions are because if we
cannot have a subdivision then there's no need to bid the price accordingly or say that's what
we want to use it for. If we cannot graze cattle there like we do in Tennessee at
[unintelligible] or something or grow crops because we cannot put a well in for contamination,
then we are left with only looking at it for the pine trees.

So being federal, you own this property. Even with deed restrictions you've got to give us
either a Phase I, II, or III audit. In this case, it's the seller who has to provide this
liability not necessarily the buyer's neglect of liability to due diligence. So it would really
help if we knew what deed restrictions would be there to a more extent and also what we can use
the land for. If I want to use it for applying 50 - - under the Code of Federal Regulations
503, if I want to use it for bio solid disposal, can I do so? Because it's adjacent to your
other property. So the deed restrictions that you brought up were of immense concern about
responding back to the future use and the disposal of roughly 849,000 acres nationwide for - to
be put back into - I understand from Washington, they would like to put it back mainly into
public use to get the taxes off of it. Maybe not so much for the government, but for the local
entities who lose the tax base. Thank you.

Response to Comment 3):

The SRS Future Use Project Report was distributed to inform citizens of the planned future uses
of SRS. The recommendations that were presented in the report may change over time and will
be discussed with the stakeholders. Deed restrictions for federal property are not determined
until the land is transferred to non-federal control at the time of property transfer, the need
for deed restrictions will be evaluated due to natural attentuation, decay, etc., the conditions
at specific areas may not warrant any deed restrictions. All legal reguirements will be met at
the time of property transfer.

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