United States
Environmental Protection
Agency
Office of
Emergency and
Remedial Response
EPA/ROD/R04-92/110
June 1992
SEPA Superfund
Record of Decision:
Savannah River (USDOE)
(Operable Unit 3), SC
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NOTICE
The appendices listed in the index that am not found In this document have been removed at the request of
the issuing agency. They contain material which supplement but adds no further applicable information to
the content of the document All supplemental material is, however, contained in the administrative record
for this site.
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50272-101
REPORT DOCUMENT A l10N 1'. REPORT NO. I ~ I. A8cIpIent'a ~ No.
PAGE . EPA/ROD/R04-92/110
4. TItle... 8ubII8 L AIpart Dd8
SUPERFUND RECORD OF DECISION 06/29/92
Savannah River (USDOE) (Operable Unit 3), SC L
Third Remedial Action - Interim
7. AuIIIar(8) .. IWtotn"'l8 0rpnIDtI0n AIpL No.
8. P8rfonnIng o"..mton ... ... AddrM8 10. PfoI8cI/T8IIIIWarII UN! No.
11. ConIr8d(C) or GnnI(Q) No.
(C)
(Q)
1~ SpoI.-tng OIjlMiUIIIIon ... ... AdIhu 11. Type of AIpart. P8rIod c-.r
U.S. Environmental Protection Agency 800/000
401 M Street, S.W.
Washington, D.C. 20460 14.
15. 911 ppl .-..., No.
PB93-964013
16. AII8tr8ct (LInfi: 2DO WDId8)
The 300-square-mile Savannah River site (SRS) is a DOE facility located in Aiken
County, 20 miles south of Aiken, South Carolina, and 25 miles southeast of Augusta,
Georgia. Land use in the area is primarily industrial, and SRS is a secured facility
with no residents. The site, co-operated by Westinghouse Savannah River Company, is a
national defense-related facility producing tritium, plutonium, and other special
nuclear materials. The A/M area, located in the northwest portion of the SRS,
contained many operations that involved the use of hazardous substances. Between 1952
and 1981, an estimated 13 million pounds of chlorinated solvents were used in the A/M
area to degrease fuel and target tubes for use in the SRS reactors. An estimated 50
to 90 percent of the solvents evaporated during use; however, the remaining solvents
were discharged to the process sewer system. There are four main sections to the AIM
area. The A-014 outfall received waste solvents (mainly TCE and PCE) via an
underground sewage line from buildings 313-M and 320-M onsite until 1976. From 1958
to 1985, the M-area basin hazardous waste management facility (HWMF) received an
estimated 2 million pounds of spent solvents from degreasing operations in buildings
(See Attached Page)
17. Document An8/r8I8 L D88crtp1D,.
Record of Decision - Savannah River (USDOE) (Operable Unit 3), SC
Third Remedial Action - Interim
Contaminated Medium: gw
Key Contaminants: VOCs (PCE, TCE)
b. Identifter8lOpen-EncI8d Tema
c. COSA 11 Fi8IcIIGroup
18. Avlilablity SI8Iement 111. Securt1r CI... (This Report) 21. No. of Psges
None 42
211. Securfly CI... (ThIs Page) n PrIce
Nnnp
. KJHM 272 (4-77)
(See AtG-Z3II.18)
See 'nJltructiona on Re-
(Formerly NTlS-35)
Dep8rtment of Corrmerce
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EPA/ROD/R04-92/110
Savannah River (U~DOE) .(Operable Unit 3), SC
Third Remedial Action - Interim
Abstract (Continued)
313-M, 320-M, and 321-M. In transit, some of the solvents leaked into the ground through
cracks in the pipeline. Finally, the 321-M solvent storage area contained various
storage tanks for TCE and PCE. In 1975, an estimated 1,200 gallons of PCE leaked from a
cracked ceramic pump seal connected to a solvent storage tank located west of building
321-M. As a result of these activities and incidents, a ground water plume, encompassing
1,200 acres beneath the AIM area, is contaminated with significant concentrations of
VOCs. In 1981, SRS voluntarily initiated a ground water RCRA corrective action program
to investigate the nature and extent of ground water contamination and to develop a
remedial program. Ground water monitoring wells were installed, and beginning in 1983,
extraction and treatment of ground water began. To date, over 1.3 billion gallons of
contaminated ground water have been treated. This ROD addresses an interim remedy for
the AIM area ground water subsurface vadose zone, as OU3. Other RODs have addressed
interim remedies for the M-area HWMF and the Savannah Metallurgical Laboratory (SRL)
HWMF. Future RODs will address final remedies for these OUs. The primary contaminants
of concern affecting the ground water in the AIM area are VOCs, including PCE and TCE.
The selected interim remedy for this site includes installing 11 or more ground water
recovery wells installed under the RCRA program throughout the AIM area; extracting and
treating contaminated ground water using an air stripper to remove volatile solvents,
followed by onsite discharge to an NPDES permitted outfall; upgrading the air stripping
tower to include an off-gas treatment system, based on the result of a treatability
study. The estimated present worth cost for this remedial action is $7,800,000, which
includes an annual O&M cost of $20,000 for 30 years.
PERFORMANCE STANDARDS OR GOALS: No chemical-specific clean-up goals were specified in
this interim ROD, but they will be provided for the final remedial action. The goal of
this remediation is to reduce ground water contaminants and minimize migration of the
contaminant plume.
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WSRC-RP-92-744
.' .
"
......-.. ..
INTERIM ACTION RECORD OF DECISION
REMEDIAL ALTERNATIVE SELECTION
AIM Area Groundwater Operable Unit
Savannah River Site ~. Gt- J)
Aiken County, South Carolina
Prepared by:
U.S. Department of Energy
Savannah River Field Office
Aiken, South Carolina
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INTERIM ACfION ROD
AIM AREA GROUNDWATER OPERABLE UNIT
WSRC-RP-92-744
JUNE 25, 1992
DECLARATION FOR THE INTERIM ACTION RECORD OF DECISION
Sit~ Nam~ and Location
AIM Groundwater Operable Unit
Savannah River Site
Aiken. County, South Carolina
Appendix C of the draft Federal Facility Agreement (FF A) refezs to this operable unit as the
Groundwater Remediation, A- and M-Areas.
Statement 01 PllrpOS~
This document presents the selected interim remedial action for the AIM Area Groundwater
Operable Unit at the Savannah River Site, developed in accordance with the
Comprehensive Environmental Response, Compensation, and Liability Act of 1980
(CERCLA), as amended by the Superfund Amendments and Reauthorization Act of 1986
(SARA), and to the extent practicable, the National Oil and Hazardous Substances
Pollution Contingency Plan (NCP). This decision is based on the administrative record file
for this specific operable unit
Description 01 the Selected Remedy
The selected interim action remedy involves groundwater recovery with tteatment by air
stripping. This remedy reduces contaminant levels in the groundwater and minimizes
migration of the contaminant plume.
A risk assessment will be conducted in the future to detennine if additional remediation is
required. Results of the risk assessment will be contained in the fmal Record of Decision
(ROD).
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INTERIM ACTION ROD
AIM AREA GROUNDWATER-OPERABLE-:UNIT
WSRC.RP.92.744
JUNE 25, 1992
The major components of the interim action remedy include the following:
.
Installing strategically located groundwater recovery wells.
.
Extracting groundwater and processing it through an air stripper to release volatile
organic compounds.
.
Discharging th~ treated water to an NPDES permitted outfall.
.
Pursuing the application of new technologies to enhance the reduction of volatile
org~c compounds in the groundwater.
.
Conducting a treatability study to evaluate technologies to control air stripping
tower gaseous emissions.
Declllrlltion Stlltement
The interim action is hereby selected by mutual agreement of the U.S. Department of
Energy and the U.S. Environmental Protection Agency. This interim action is protective of
human health and the environment and complies with Federal and State applicable or
relevant and appropriate requirements (ARARs) for this limited-scope action, and is cost-
effective. This action is interim and is not intended to utilize permanent solutions and
alternative treatment (or resource recovery) technologies to the maximum extent practicable
for the AIM Area Groundwater Operable Unit. Because this action does not constitute the
final remedy for the AIM Area Groundwater Operable Unit, the statutory preference for
remedies that employ treatment that reduces toxicity, mobility, or volume as a principal
element, although partially addressed in this remedy, will be fully addressed by the final
response action. Subsequent actions are planned to address fully the threats posed by the
conditions at the AIM Area Groundwater Operable Unit and to establish fmal remediation
goals. Because this remedy may result in hazardous substances remaining in the operable
unit above health-based levels, a five -year review will be conducted to ensure that the
remedy continues to provide adequate protection of human health and the environment after
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INTERIM ACTION ROD
AIM AREA GROUNDWATER OPERABLE UNIT
WSRC-RP-92-744
JUNE 25, 1992
commencement of the remedial action. Because this is an interim action ROD. review of
this operable unit and of this remedy will be conducted. by the Environmental Protection
Agency -(EPA) until a fmal remedial alternative for the AIM Area Groundwater Operable
Unit is selected.
'/Z;/(j Z-
Date
~
Assistant Manager for Environmental
Restoration and Waste Management
U.S. Department of Energy
JUN 2 . ,.
Dale
~M~
k\ Greer C. Tidwell
f/ Regional Administrator
U.S. Environmental Protection
Agency
Region IV
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SUMMARY OF INTERIM ACTION
REMEDIAL ALTERNATIVE SELECTION
AIM Area Groundwater Operable Unit
Savannah River Site
Aiken County, South Carolina
Prepared by:
U.S. Department of Energy
Savannah River Field Office
Aiken, South Carolina
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INTERIM ACTION ROD
AIM AREA GROUNDWATER OPERABLE UNIT
WSRC.RP.92.744
JUNE 25, 1992
Section
I.
ll.
m.
IV.
v.
VI.
vn.
V1ll.
IX.
X.
XI.
Appendices
A.
B.
DECISION SUMMARY
TABLE OF CONTENTS
Site and Operable Unit Names. bocaIions,and Desaiptions
Operable Unit History and Compliance History
Eut
1
3
9
. Highlights of Community Participation
Scope and Role of Operable Unit within the Site Strategy
Summary of Operable Unit OtaraCteristics
9
10
Summary of Operable Unit Risks
Desaiption of AltmWives
14
15
Summary of Comparative Analysis of Alternatives .-
Selected Remedy
22
27
Path Forward
Statutory Detamination
28
33
Refermces for Development of ROD Format
Responsiveness Snmmary
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WSRC-RP-92-744
. JUNE 25, 1992
INTERIM ACTION ROD
.. . AIM AREA GROUNDWATER OPERABLE UNIT
I.
Site and Operable Unit Names, Locations, and Descriptions
The Savannah River Site (SRS) occupies approximately 300 square miles adjacent to the
Savannah River, principally in Aiken and Barnwell Counties of South Carolina (Figure 1).
SRS is a secured facility with no pennanent residents. The site is approximately 2S miles
southeast of Augusta, Georgia, and 20 miles south of Aiken, South Carolina. The average
population density in the counties surrounding SRS ranges from 23-560 people per square
mile with the largest concentration in the Augusta, Georgia, metropolitan area. Based on
1980 census data (1990 data not available), the population within a SO-mile (80 Ian) radius
of SRS is approximately 555,100.
SRS is owned by the United States Department of Energy (DOE). Westinghouse
Savannah River Company (WSRC) is a co-operator, providing management and operation
services for DOE. sas produces tritium. plutonium. and other special nuclear materials
for national defense. The site also provides nuclear materials for the space program. and
conducts medical, industrial, and research efforts. The AIM AJea. located in the northwest
portion of SRS (Figure 1), contains nuclear fuel fabrication buildings, office buildings, and
research areas.
The AIM Area groundwater is a media-specific operable unit within the AIM Area
Fundamental Study Area. As a result of past waste disposal practices, the groundwater
beneath AIM Area has been contaminated with organic solvents, primarily trichloroethylene
(TCE) and tetrachloroethylene (perchloroethylene; PCE). Total plume size beneath the AIM
Area. as currently defined, is approximately 1200 acres. This plume has not migrated
beyond the SRS boundaries. The contamination in the AIM Area groundwater and the
overlying unsaturated zone (vadose zone) appears to be associated with releases from the
I
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INTERIM ACTION ROD
AIM AREA GROUNDWATER OPERABLE.UNIT
WSRC.RP.92.744
JUNE 25, 1992
SAVANNAH RIVER
SITE
.......
",
...
i!
.
.!
GEORGIA
.-
I I
o ,
I I I I
2 , . S
Miles
I I I I
60 100 160 200
ICIofNWI
Figure 1 Location of the Savannah River Site (SRS)
(Source: Modified from the Savannah River Environmental Report. 1990)
2
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INTERIM ACTION ROD
AIM AREA GROONDW A TER OPERABLE UNIT
WSRC-RP-92-744
JUNE 25, 1992
following AIM Area SOUlCe units: the A-014 Outfall, the M-Area Settling Basin/Lost Lake
(M-Area Hazardous Waste Management Facility (HWMF), the M-Area HWMF Process
Sewer, and the 321-M Solvent Storage Area.
'II.
Operable Unit History and Compliance History
Operllbl~ Unit History
From 1952 to 1981. an estimated 13 million pounds of chlorinated solvents were used in
the AIM Area to degrease fuel and target tubes used in SRS mICIOrS. An estimated 50 to 90
percent of the solvents evaporated during degreasing operations. The remaining solvents
were discharged as waste to the process sewer system. Additionally. significant quantities
of chlorinated solvents were inadvencndy spilled dming handling and storage.
The waste effluent was piped. via a process sewer system, from the fuel tUbe processing
facility to two primary locations: A-014 Outfall and the M-AJa Settling Basin. As a result
of this disposal practice and leakage within the process sewer line leading to the Settling
Basin. four specific locations within the AIM AJa have been identified as being potential
sources for significant groundwater contamination by TCE and PeE. Additionally, some
smaller sources, such as the Metallurgical Laboratory Basin and Building 313-M, a solvent
transfer station, which probably have impacted groundwater, exist in the A-~ The four
specific locations are shown on Figure 2 and are described below.
A-014 Outfall. Buildings 313-M and 320-M were operational by the end of 1952 and used
TCE as a degreasing agent Waste solvents were released to the A-014 Outfall (Tims
Branch) via an underground sewer line. In 1962, the processes in Building 313-M were
3
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INTERIM ACTION ROD
AIM AREA GROUNDWATER OPERABLE UNIT
WSRC-RP-91-744
JUNE 15, 1991
t
N
I
--_..-
I I
o -
/
/
/
/
,.
Legend
"""'aso- EI8w8IIarI CanDnIn ... CMSLa,
- "-II
"'-8 ....
*-Mo ,-
Figure 2 Potential Sources of NM Area Groundwater Contamination
(Source: SRS Vadose Zone Characteri7.ation. 1991)
4
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INTERIM ACTION ROD
- AIM AREA GROUNDWATER OPERABLE UNIT
WSRC.RP.92.744
JUNE 25, 1992
redesigned, and PCE was substituted for TCE. By 1976, all waste solvents from Building
313-M were diverted and discharged to the M-Area Settling Basin.
M-Area Basin HWMF. Built in 1958, the M-Area HWMF consisted of an unlined Settling
Basin that received spent solvenrs from degreasing operations located in Buildings 313-M,
320-M, and 321-M. The M-Area HWMF also included a natural seepage area and Lost
Lake (a Carolina bay) which received effluent from the basin. From 1958 to 1985, an
estimated tWo million pounds of solvent were ~leased to the sewer leading to the Settling
Basin. In 1985, discharges of waste solvents to the Settling Basin ceased..-
M.Area HWMF Process Sewer. The process sewer was used to tranSpon spent solvents
from Buildings 313-M, 320-M, and 321-M to the M.Area Basin beginning in 1958. In
ttansit, some of the solvent leaked into the ground through cracks in the sewer pipeline.
The pipe was slip-lined after cracks and misalignments were discovered in 1983. and an
inactive portion was excavated in 1989 as part of the Settling Basin closure.
321-M Solvent S~le Area. During 1971. Buildings 320-M and 321-M substituted PCE
for TCE in their process operations. In 1975, an eStimated 1200 gallons of PCE leaked
from a cracked ceramic pump seal connected to a solvent storage tank located west of
Building 321-M.
In response to the detection of volatile organic compounds (V0Cs) in the groundwater near
the M-Arca HWMF. SRS voluntarily initiated a groundwater corrective action program
(June, 1981). The objective of the program was to investigate the nature and extent of
groundwater contamination, and to develop a ~mediation program. Known and potential
sources of groundwater contamination were identified through investigations which
included personnel interviews. record reviews, soil borings, and the installation of
5
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INTERIM ACTION ROD
. AIM AREA GROUNDWATER OPERABLE UNIT
WSRC-RP-91-744
JUNE 25, 1991
monitoring wells. SRS now has an extensive groundwater monitoring networlc in the AIM
Area with over 350 mOnitoring wells installed to provide definition of the aquifer plume.
In February 1983. a South Carolina Department of Health and Environmental Control
(SCDHEC)-approved corrective action was initiated with the startup of an experimental
pilot air stripper and one recovery well. The system operated at a design capacity of 20
gallons of water per minute (gpm). Later in 1983. tWo ~ recovery wells were installed
and a 70 gpm air stripper was placed in operation in January 1984. The 70 gpm air sttipper
replaced the 20 gpm unit. In 1985. eight additional recovery weDs were added to the du=
existing recovery wells, expanding the recovery well netWork to eleven. The eleven
recovery weDs were connected to a full scale air stripper which crated 400 gpm. In 1990.
the flow of the air stripper was increased to 500 gpm. The air stripper removes the
organics to levels below drinking water standards prior to discharge to the NPDES-
permitted outfall, A-014. To date, over 1.3 billion gallons of contaminAted groundwater
have been treated and about 260,000 pounds of solvents have been removed from the
subsunace. The eleven recovCl}' wells have been designed and installed to maximize
removal and minimize migration of solvents from the center of the plume in the shallow
aquifer. The location of the current system, including the existing wells and the air
stripper, are shown in Figure 3. An additional recovery well has been installed in A-Area
near the Savannah River Laboratory (SRL). The previous M-Area prototype air stripper
(the 70 gpm unit) has also been relocated to this part of A-Area. This new system became
operational in March 1992. A thirteenth well has also been installed in the Southern Sector
of AIM Area to function as an aquifer test well and possibly as a future mncdiation well.
SRS has initiated an evaluation of a vadose zone corrective action program to remediate
soils above the groundwater at specific areas where solvents were released. An
6
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INTERIM ACTION ROD
--AIM AREA GROUNDWATER OPERABLE UNIT
WSRC-RP-92-744
JUNE 25, 1992
..
* RECOVERY WELL
. AIR STRIPPER
.. RECOVERY lEU. ADJACENT
(~'"1
TO AIR STRIPPER ~
Figure 3 Location of AIM Area Groundwatc1' Recovery Wclls and Air StrippcrUnit
(Sourcc: Figure created from data contained in thc M-Area Hazardous Waste
Management Facility Post-Closure Permit. 1991. Second Quancr Rcpon)
7
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INTERIM ACTION ROD
AIM AREA GROUNDWATER OPERABLE UNIT
WSRC-RP-91-744
JUNE 1S, 1991
investigation of the extent of the vadose .zone contamination associated with the
groundwater contamination has been performed. Presently, SRS is evaluating the designs
and costs of potential systems and will be testing several innovative technologies which
could be utilized to treat organics recovered from the vadose zone. Selection of a preferred
alternative for the vadose zone will be carried out in'.a future Proposed Plan. Funher
discussion of the vadose zone remediation activities is contained in Section X.
Complitlllce History
OOE developed an Implementation Plan and GroundMiter Protection Plan in June 1984
which required compliance with the groundwater protcc1ion requirements of 40 CPR II
264, 265, and 270 and with all other Federal and State regulations. Settlement Agreement
SA 86-52-W, signed on June 20, 1986, required groundwater quality assessments at
several sites, including the AIM Area. Results of the assessments have been provided to
SCDHEC and future actions are being defined under SRS' RCRA Facilities Investigation
program.
In 1985, the Natural.ResoUICCS Defense Council (NRDC), et. 81., initiated a lawsuit against
OOE for alleged RCRA groundwater management violations at six SRS waste management
areas including the AIM Area. On May 26, 1988, a Consent Decree was signed by OOE.
Requimnents of this decree are outlined in Ovil Action No.1 :85-2583-6. filed on May 31,
1988 in the U. S. District Court, District of South Carolina, Aiken Division.
In 1985, a Resource Conservation and Recovery Act (RCRA) Post-Closure Care Part B
Permit Application for the M-Area HWMF was submined to SCDHEC. The application.
approved in 1987, describes the AIM Area Groundwater Corrective Action Program in
8
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INTERIM ACTION ROD
AIM AREA GROUNDWATER OPERABLE UNIT
WSRC-RP-92-744
JUNE 25, 1992
detail A revised permit application was submitted to SCDHEC in September 1990 and the
renewal application was submitted to SCDHEC on April 1. 1992. The revisions describe
new groundwater and soil COJTeCtive action projects.
Remedial activities in the NM Area became subject to CERCLA requirements when the
entire SRS facility was placed on the National Priorities Ust (NFL) in December 1989.
Due to multiple source areas in close proximity and the co-mingling of contaminants
emanating from these source areas. the NM Area has been designated a Fundamental Study
Area:. The purpose of this designation is to facilitate the coordination of remedy selection
decisIons for the operable units in this area.- -- The AIM Area groundwater has been
designated as a media-specific operable unit within the Fundamental Study Area.
III.
Highlights 01 Community Participation
No comments were received dming the public review period.
IV.
Scope and Role 01 Operable Unit within the Site Strategy
The .purposes of the interim action for the NM Area Groundwater Operable Unit are to
prevent funher groundwater plume migration and initiate groundwater restoration while
risk assessment activities are being planned and conducted, and to obtain funher
infomwion about the response of the aquifer to remediation measures.
The interim action is consistent with any planned future actions fc:r this operable unit
Evaluation of treatment for the NM Area subsurface soils (i.e.. vadose zone) containing
volatile organic compounds is being conducted as an ongoing treatability study associated
with the AIM Area Groundwater Operable Unit Selection of a prefeued remedial action
9
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INTERIM ACTION ROD
AIM AREA GROUNDWATER OPERABLE UNIT
WSRC-RP-92-744
JUNE 25, 1992
alternative fOl' the vadose zone will be presented in.a future Proposed Plan for the NM Area
Vadose Zone Operable Unit.
v.
Summary of Operable Unit Characteristics
Closely associated with the AIM Area Groundwater Operable Unit is the Vadose Zone
Operable Unit. The vadose zone consists of the subsurface region betWeen the ground
(land) surface and the water table. Mobile waste constituents released at the ground surface
typically migrate vertically and gradually through the vadose zone to the groundwater.
Longitudinal dispersion of contamination also occurs. but generally to a limited extent.
Consequendy, vadose zone contamination would be locaJi7ed in areas where COIJtaminarns
were released. Contamination in groundwater migrates horizontally and vertically
depending on recharge/discharge relationships, stratigraphy, and other hydrogeologic
factors. If left in place, mobile contaminants in the vadose zone would slowly migrate to
the groundwater.
Most of the contaminants in the AIM Area groundwater are located in the uppermost
aquifer. Concentrations in the uppeuHOSt aquifer range from hundteds of parts per million
to less than one part per billion. The plume under AIM Area, as currently defined,
encompasses approximately 1200 acres. The contaminated uppermost aquifer is not used
as a source of drinking water at SRS but is currendy being used for domestic purposes
nonh of the SRS boundary where no contamination is present.
The deepest aquifer beneath the uppermost aquifer provides domestic (drinking) and
process water to various facilities at the SRS. A thick and laterally continuous low
permeability layer (principal confining unit) separates the uppermost aquifer from the
principal confmed aquifer and the deepest aquifer, and greatly retards downward migration
10
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INTERIM ACTION ROD
AIM AREA-GROUNDWATER OPERABLE UNIT
WSRC.RP.91.744
JUNE 1S, 1992
--.
of chemical residuals. Contamination concenttations of the principal confined aquifer in the
NM Area range from 1000 pans per billion to less than one part per billion. Groundwater
flow direction within this unit is to the south.southeasL The town of Jackson, South
Carolina, located hydraulically up gradient and three miles west of the NM Area, also
draws water from public supply wells in the deeper aquifer. No off.site groundwater
contamination resulting from the migration of the NM Area groundwater plume has been
detected.
Recent monitoring results 'indicate groundwater contamination bas occurred in the
Northeastern Sector of the AIM Area in the vicinity of the SRL complex resulting from past
uses and disposal of solvents. These findings are significant due to the proximity to the
plant boundary and the contamination of the principal confined aquifer. The combined
areal extent of the conraminant plume is shown in Figure 4 and represents the J1U11d11'lum
lateral extent of detected constituents in all aquifers. The vertical extent of groundwater
contamination through the uppermost and principal aquifers (Watertable Unit, Upper
Congaree, Lower Congaree, and Peedee) is depicted along one cross section line in Figure
S. These tWo plume maps reflect TCE and PCB concentrations in excess of detectable
quantities.
Groundwater contamination in the Southern Sector of AIM Area (south of the M-Area
HWMF and southwest of the A-014 outfall) is presently outside the influence of the present
recovery system. The selected interim action addresses areas of higher concentration in the
center of the plume and at the sources of contamination. SRS is investigating the Southern
Sector of AIM Area to funher delineate the extent of contamination and increase
understanding of the hydrogeology of the area. SRS also will install a system of recovery
wells to remediate groundwater in the Southern Sector.
11
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INTERIM ACfION ROD
. -AIM-AREA GROUNDWATER OPERABLE UNIT
WSRC.RP.92.744
JUNE 2St 1992
"
,
~
I : :. :... --:-1 COMUNED AREAL EXTENT OF DETECTA8L.E TCE IHJ PCE .
Figure 4 Combined Areal Extent of Detectable TCE and PCE in the Groundwater
(Source: Modified from the Metallurgical Laboratory HWMF Part BPost.
Closure Permit Application, 1991)
12
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4
,
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INTERIM ACTION ROD
AIM AREA-GROUNDWATER. OPERABLE UNIT
WSRC-RP-91-744
JUNE 15, 1991
VI.
Summary or Operable Unit Risks
As a result of past waste disposal practices, the groundwater beneath NM Area has been
contaminated with the organic solvents TCE and PCE in both the dissolved state and, in
limited OCCUJTences, as concentrated Dense Non-Aqueous Phase Liquids (DNAPLs).
These DNAPLs consist of concentrated, undissolved accumulations of chlorinated
solvents.
As required by CERa..A, a risk assessment will be perfonned to provide a basis for
determining. if additional remediation is required to protect human health and the
environment. Previous risk analyses performed in 1985 for the M-Area HWMF and
Metallurgical Laboratory HWMF Operable Units wel'e conduCted prior to closure of those
facilities and were used in the development of closure alternatives. The results of these
. ..
previous risk analyses and available. closure and post-closure data will be utilized as
appropriate for evaluation of potential risk for the AIM Area Groundwater Operable Unit.
The ~sk assessment will address risk associated with groundwater underlying the entire
NM Area. The contribution of contamination to groundwater from the vadose zone will be
considered in the evaluation of risk posed by exposure to groundwater. The surface water
discharge pathway will be further evaluated.
Generally, for modeling purposes, potential pathways for human exposure are through
hypothetical wells on-site, and through discharge to surface water. A program to develop
the details of these exposure scenarios is under development and will be addressed in the
risk assessment.
14
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INTERIM ACTION ROD
AlMAREA--GROUNDWATER OPERABLE UNIT .
WSRC.RP.92.744
- JUNE 25, 1992
Currendy, there 8R: no drinking water wells.in use within the contaminated zone of the AIM
Area Groundwater Operable Unit. However, in the absence of remediation, there is a
potential for risk from potential future wells and from exposure to surface waters receiving
discharge from AIM Area groundwater. The risk assessment will further characterize and
quantify these potential risks. Funhennore. the effect of the ongoing AIM Area
Groundwater Corrective Action Program will be considered in the risk assessment. No
off.site groundwater contamination resulting from the migration of the AIM Area
groundwater has been detected. However, if the contaminantS are allowed to remain, the
potentiai for off.site migration and public expo;ure may exist.
There is limited potential for significant plant uptake of contaminants from the vadose zone.
This pathway will be characterized further to confirm this assessment. The primary
potential for ecological risks is through exposure to smface water receiving contaminated
.-p
groundWater discharge. The extent of this potential risk for post-closure conditions will be
characterized in the risk assessment currendy under development.
VII. Description of Alternatives
The following remedial alternatives were developed in 1985 for the AIM Area Groundwater
Operable Unit, based on demonstrated effective technologies available at the time that the
M-Area HWMF RCRA Closure Plan was fU'St prepared. In acccndance with the NCP, the
No Action Alternative was included as a baseline for comparison. The alternatives
consideJed at that time for the Groundwater Corrective Action Program (remediation of the
groundwater plume) included:
Alternative I
No Action
15
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INTERIM ACTION ROD
. AIM AREA GROUNDWATER OPERABLE UNIT
WSRC-RP-92-744
JUNE 25, 1992
Alternative 2
Groundwater Recovery with Treatment by Air Stripping-
Alternative 3
Groundwater Recovery with T~nt by Activated Carbon Adsorption
Alternatives 2 and 3 both called for groundwater recovery by cxttaction. The alternatives
differed only in the type of groundwater tteaUnCnt technology ntili7.ed.
Alternative 2 was implemented in 1985 as an interim remedial action. This section contains
a description of each of the three alternatives as they were developed and considered in
1985.
Altemative 1: No AdioD
Under the No Action Alternative, no groundwater extraction -would-be. conducted.
Chlorinated solvent concenttations would gradually be reduced with time and distance
through natural attenuation processes such as biodegradation or dispersion. Institutional
controls and long-tenn monitoring of groundwater could be added as components of the
No Action Altcmadve. Furthel'description of this alternative appears below:
Treattnent ColJ1POOents. No treatment would be implemented.
Enpneerinl Controls. No engineering controls would be required.
Institutional Controls. Access to SRS is controlled at primary roads by continuously
manned barricades. Othel' roads entering the site me closed to traffic by gates or barriers.
The en~ facility is surrounded by an exclusion fence, except along the Savannah River.
The site is posted against trespassing under state and federal statUtes. Much of the AIM
16
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INTERIM ACTION ROD
AIM AREA GROUNDWATER OPERABLE UNIT
WSRC.RP.92.744
JUNE 25, 1992
. Area is sunounded by a separate fenced area with manned gates. The area is continuously
patrolled by security personnel
Ouanti~ of Waste. SRS estimates that approximately 2 million pounds of chlorinated
solvents are currently contained.in the AIM Area groundwater plume. Approximately
260,000 pounds of solvents have been exttlcted and treated to date. The plume, as
currently defined, encompasses approximately 1200 acres.
In,plemenlation ft:QJIirements. This alternative requires no additional implemenwion.
Estimated Construction and OJ)eration and Maintenance (O&M) Costs. No additional
monitoring wells would be installed under this alternative, so t"ere would be no
construction costs. Costs for this alternative, excluding groundwater sampling and
analysis wet'e originally estimated to be:
.
Capital Cost
so
.
Annual O&M Costs
$20,000
ARARs Associated with the Considered Alternative. This alternative would not comply
.."i. .
with the South Carolina Primary Drinking Water Regulations (R.61-S8) Maximum
Contaminant Levels (MCLs) or the Federal Safe Drinking Water Act (SDWA) (40 CfR i
141) promulgated M<1s. Cenain contaminants would remain elevated above MCLs and
the ca1culataI health-based levels should the No Action Alternative be implemented..
Altemative 2: Groundwater Recovery with Treatment by Air Strinpina
Groundwater recovery with air stripping is a demonstrated and widely used technology.
Air stripping is considered by EPA as the Best Demonstrated Available Technology
17
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INTERIM ACTION ROD
AIM -AREA GROUNDWATER OPERABLE UNIT
WSRC-RP-92-744
. JUNE 25, 1992
(BDA 1) fer Vex: remov8l. Air stripping forces the contaminated groundwater into contact
with air. The volatile contaminants are then ttansferred into the air and released to the
atmoSphere. This alternative includes evaluation of technologies for controlling emissions
from the air stripping system. One of the most efficient stripping devices is a counter-
current packed column. In this column, the water stream is pumped to the top and allowed
to trickle down over the column packing. Air is blown in through the bottom of the column.
and exits a~ the top. The stripper requires electricity for a pump and blower and very little
maintenance. Funher description of this alternative appears below.
T".~tmP.nt CmJwonents.1be comprehensive remedial action system in AIM Area (as it was
designed in 1985) would consist of treatment componentS in the general M-Area and in the
Northeastern Sector of AIM AmI.. In the general M-Area, the treatment system would
consist of 11 groundwater recovery wells and a full-scale production air stripper with an air
blower, effluent pumps, instrument air system. and control building. (The 11 recovery
wells (RWM-l through RWM-I I) were installed during 1982-1985). A 20-inch, zero-
leakage drainline to transfer treated groundwater from the air stripper to the NPDES-
permitted A-014 Outfall would also be included.
In the Northeastern Sector of AIM Area, a groundwater recovery and air stripper system
has been installed near the SRL. A zero-leakage drainline to carry treated liquid from the
air stripper to a nearby permitted outfall has also been designed. Funher design details
regarding the air stripping systems were contained in Appendix F of the M-Area Post-
Oosure Permit Application.
Enlineerine Controls. The primary engineering control for minimizing the spread of the
AIM Area groundwater plume involves installation of 11 or more recovery wells. The
18
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INTERIM ACTION ROD
AIM AREA GROUNDWATER OPERABLE UNIT
WSRC.RP.91.744
JUNE. 15,. -1991
recovery wells would be strategically spaced laterally and vertically in an attempt to
maximize recovery of high VOC concentration groundwater. and control groundwater
migration. Location of the ~very wells is depicted in Figure 2 (Section ll).
Institutional Controls. These controls are identical to those discussed in Alternative 1.
Ouanti(y of Waste. The quantity is identical to that discussed in Alternative 1.
Iq)lementation reqpirements. Implementation time was originally eaimRted to be 24 to 36
months. Installation of the 11 recovery wells and -the M-Area stripping tower was
completed in 1985. The system began operating at a 400 gpm treatment rate at that lime.
The system is c:um:ndy operating at a rate of 500 gpm. Sran-up of the Northeastern Sector
recovery system occumd in March 1992.
.. I.. .
E..~lQated Construction and Qperation and Maintenance Costs. Costs for this alternative
. ~ originally estimated to be:
.
Capital Cost
$4.800.000
.
. Annual O&M Costs
$100.000
ARARs Associated with the Considered Alternative. The remedial action would minimize
migration of contaminated groundwater through groundwater recovery and provide
pertinent information for the development of a complete groundwater remediation system.
Groundwater would be treated by an air stripper that would remove VOCs from the
groundwater and emit them to the atmosphere. An ongoing treatability study will select an
appropriate technology for treating air emissions. ARARs for air emissions include
regulations under the Federal Clean Air Act and the South Carolina Air Pollution Control
19
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INTERIM ACTION ROD
AIM AREA GROUNDWATER OPERABLE UNIT
WSRC-RP-92-744
JUNE 25, 1992
Regulations (R.61-62). specifically the South Carolina Ambient Air Quality Standards
(R.61-62.5). An air emissions permit would be required under the South Carolina
regulations prior to operation of the air saipper. Discharge of the treated groundwater' will
be to NPDES pennittcd outfalls within SRS. Discharges of this type are regulated under
the Oem Water Act and the South Carolina NPDES Permit Regulations (R.61-9). Treated
water must meet the discharge limitS of the permitted outfall unless a permit modification is
obtained.
SRS has evaluated the RCRA Subpart AA "Air Emission Standalds for Process Vents"
(40 CPR I 265.1030) and has concluded it is not an applicable requirement for the
treatment of extracted groundwater at the site. EPA Region IV has stated that the Subpart
AA standards may be relevant and appropriate. Therefore, the S18DdaIds will be evaluated
during the off gas treatability study for consideration in the design and implementation of
the off gas tteattDent system for consistency with and relevancy to the Subpart AA emission
standards. The system is permitted through the SCDHEC Air QuaJity Control Program and
the Oem Water Act (wastewater' treatment discharge permit) rather than through RCRA.
Upon completion of the treatability study. the existing M-Area stripping tower will be
upgraded, if necessmy. with an off-gas treatment system in compliance with ARARs.
Alternative 3:
Adsorption
Groundwater Recovery with Treatment by Activated Carbon
Activated catbon adsorption is another principal method used for groundwater and drinking
water treatmenL With carbon adsorption. contaminated water is brought intO contact with
particles of activated carbon. The organic molecules migrate into microspores on the
carbon particles and become trapped. The operating equipment for carbon adsorption is
similar to that required for air stripping. except two carbon adsorption beds in series would
20
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INTERIM ACTION ROD
- AIM -AREAGROUNDWA TER - OPERABLE UNIT
WSRC.RP.92.744
JUNE - '25, 1992
replace a packed stripping column and an air blower. Two carbon beds allow replacement
of the spent bed while groundwater continues to be fed to the fresh carbon unit. Volatile
organics are not released to the atmOsphere with carbon adsorption but must be disposed of
in some other fashion. The system requires considerable attention because of the need to
regenerate the carbon adsorbent. Further descriptions of this alternative appear below.
Treatment Components. Two -fixed bed carbon adsorption systems would be placed in
series. EaCh bed would be 10 feet in diameter, 10 feet in height, and contain 20,000
pounds of granular activated carbon. One bed would be taken off-line every 1 to 6 months.
The carbon media would be shipped off site for regeneration and funher treatment of the
adsorbed organic constituentS. Alternately, an on-site carbon regeneration and treatment
system could be adopted. The treated groundwater would be discharged through the
NPDES-permitted outfall, A-014.
EneineerinJ Controls. As in Alternative 2, engineering control to minimize the spread of
groundwater contamination would be primarily accomplished by installing at least 11
recovery wells at selected NM Area locations. Further control of volatile constituentS
would be accomplished during off-site organic residual treatment following carbon
regeneration.
Instimtional Controls. On-site institutional conttols are discussed in Alternative 1.
Ouanti(y of Waste. The quantity of groundwater to be treated would be identical to that
discussed in Alternative 1. In addition, waste carbon from the adsorption process would
also be generated.
21
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INTERIM ACTION ROD
AIM AREA GROUNDWATER OPERABLE UNIT
WSRC-RP-92-744
JUNE 25, 1992
Implementation Requirements. Implementation .timefor construction and start-up was
originally estimAted to be 24 to 36 months. One operating option would be to construct a
fixed bed system on site and then lease the adsorption system (carbon media) from an
indusaiaJ supplier. The supplier would be responsible for replacing spent media with clean
media and then transporting the spent media off site for ~generation~ A pilot test using an
M-Area groundwater sample was conducted by the Calgon Corporation prior to 1982, in
order to calculate system design parameters.
Estimated Construction and OJ)eration and Maintenance Costs. Costs for this alternative
were originally estimated to be:
.
Capital Cost
Annual O&M CostS
$S,OOO,OOO
.
$100.000
ARARs Associated with the Considered Alternative. ARARs for groundwater recovery
and discharge are as discussed for Alternative 2. Treatment under this alternative is by
activated carbon adsorption. Spent carbon would be regenerated off site. Organic
residuals would be further treated as a final off-site remedy. Shipment of spent carbon
would req~ proper labeling and shipment req~mentS per DOT ~gulations (49 CFR if
100(172). Spent carbon handling and treatment th~f would be performed by an off-site
treatment facility permitted under RCRA.
VIII. Summary of Comparative Analysis of Alternatives
The NCP (40 CPR I 300.430 (e)(9» sets forth nine evaluation aiteria that provide the
basis for evaluating alternatives and subsequent selection of a remedy. The aiteria are:
.
Overall protection of human health and the environment
22
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INTERIM ACTION ROD
AIM AREA GROUNDWATER 'OPERABLE UNIT
WSRC.RP.92.744
-. JUNE 25, 1992
.
Compliance with ARARs
.
Long-term effectiveness and pennanence
.
Reduction of toxicity, mobility, or volume through treatment
.
Short-term effectiveness
.
lmp1ementability
.
Costs
.
State acceptance
.
Community acceptance
The three alternatives are compared in this section using these nine evaluation criteria.
Overall Protection of Human Health and the EQVuonmenL Alternative 1, the No Action
Alternative, is not protective of and offers no reduction in risk to human health and the
environment. This approach uses institutional controls to minimize threats to human
health. This alternative continues to allow organic constituents in groundwater to migrate
horizontally and vertically.
Both Alternative 3, Groundwater Recovery with Treatment by Activated Carbon
Adsorption, and Alternative 2, Groundwater Recovery with Treatment by Air Stripping,
offer a reduction in risk to human health and the environment. Groundwater recovery
wells located at Strategic points mitigate the spread of the NM Area groundwater plume.
Volatile organic contaminants are then removed from the groundwater prior to discharge of
the treated effluent to a NPDES-pennined outfall, A-014.
23
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INTERIM ACTION ROD
AIM.AREA.GROUNDWATER .OPERABLE UNIT
. WSRC-RP-91-744
JUNE 15, 1991
COlJ1pliance with Applicable or Relevant and ApprQpriate Requirements lARARst
Alternative 1 will not meet the federal and state groundwater protection standards since
groundwater is not ~ted. Alternatives 2 and 3 both meet the OeanWater Act standards
governing the treatment and/or disposal of groundwater. Altc:matives 2 and 3 also satisfy
requirements under the South Carolina Air Pollution Conanl Regulations and StandaIds.
Since the AIM Area Groundwater Corrective Action is still an interim action, additional
ARARs will be met or waived, as appropriate, in the final mnedia1 action for this operable
unit
Lonr-tenn Effectiveness and Pennanence. Alternative 1 does not provide long-term
'''* ..
effectiveness and permaneriee since no active remediation occurs. Groundwater would not
be recoverm and contaminants would eventually migrate off site wh&= they could present a
risk to human health or the environment.
Both Altc:matives 2 and 3 provide for a long-term remedy for removal of volatile organic
constituents from the AIM An:a groundwater. Currently, Alternative 2 is in operation.
Initially, during system start up in the mid-1980s, the extracted groundwlUCJ' entering the
air stripper contained 50,000 pans per billion of chlorinated solvents. Effluent leaving the
stripper has consistently contained less than 1 pan per billion. During the almost six years
of operation, influent concentrations have decreased to about 15,000 pans per billion.
Reduction of Toxiciey. Mobiliey. or Volume Throurh Treatment. Alternative 1 provides no
treatment to reduce the toxicity, mobility or volume of the groundwater contaminants.
Both Alternatives 2 and 3 would reduce the quantity of VOCs in the groundwater through
~tment During the almost six years of operation of Alternative 2, the system (including
24
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INTERIM ACTION ROD
-AIM AREA GROUNDWATER OPERABLE -UNIT
WSRC-RP-92-744
JUNE 25, 1992
all of the experimental air strippers) has removed about 260,000 pounds of chlorinated
solvents from the -shallow groundwater. Both alternatives utilize a separation rather than a
tteattnent technology to remove organic constituents from the extracted groundwater. For
both air stripping and activated carbon adsorption, an additional technology to treat gaseous
effluents would be needed to fully comply with the reduction of toxicity, mobility, and
volume criteria. SRS is preparing to initiate an off-gas treatment evaluation for air stripping
gaseous effluents.
Short-tenn Effectiveness. There should be no short-term adverse impacts to human health
and the environment resulting from the implementation of any of the three alternatives.
Under the No Action Alternative, groundwater is not n:covered and bas not moved off-site,
so there is no additional threat to human health or envirOnmenL In Alternative 3, spent
activated carbon mighi be shipped off-site for regeneration. Packaging, labeling, and
transport of the spent media in accordance with OOT and RCRA (if necessary) regulations
would be followed, so no adverse effects from off-site ttansit would be anticipated.
Alternative 2 is now in place; no adverse impacts were expected, nor did they occur dming
the construction or operation of the extraction system. There are no adverse health effectS
due to operation of the system. In addition, air quality in the immediate vicinity of the
stripper was monitored to ensure that there would be no adverse impact to the workers in
the area. Air dispersion modeling was also conducted to obtain the required air quality
permit from SCDHEC.
Inwlementabili~. Each of the three alternatives is technically and administratively feasible.
Alternative 3 requires considerable attention due to system requirementS, such as
replacement of spent adsorption media every 1-6 months, potential off-site shipment of
25
.
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INTERIM ACTION ROD
AIM AREA GROUNDWATER OPERABLE UNIT
WSRC.RP.92.744
- JUNE -2.5, 1992
spent carbon, and regeneration of the used media. Operation of an on-site carbon
regeneration system could necessitate extensive teChnical steps (e.g., system design and
Start up) and administrative consttaintS (e.g.,pennitting).
Alternative 2 has been on-line in NM Area since the mid-1980s. Permitting applications
have been submitted and approved. The air stripping unit in the Northeastern Sector
completed final technical checks and started operation in March 1992.
am. The originally estimated present wonh costs of each Alternative are presented below:
Alternative 1
No Action
$600,000
Alternative 2
Groundwarer Recovery with Treatment by Air Stripping
$7,800,000
Alternative 3
Groundwater Recovery with Treatment by Activated Carbon Adsorption
$8,000,000
The original estimated costs for all three alternatives include an annual O&M cost of
$20,000 for a 3O-year period for groundwater monitoring. These costs do not include
monitoring beyond the 30-year period potentially required to complete AIM Area
groundwater remediation.
Stare AccqJ1BnCe. SCDHEC has approved the existing AIM Area Groundwater Corrective
Action Propam as an intermediate step leading toward a complete RCRA corrective action
program. The final action for this media-specific operable unit will be selected through
subsequent Proposed Plans and modifications to the RCRA pennit.
26
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INTERIM ACTION ROD
AIM AREA -GROUNDWATER OPERABLE UNIT -
WSRC.RP.92.744
- :JUNE 25, 1992
Communi(y A~tance. Community acceplanCe of the interim action will be evaluated and
included after the public comment period for the Proposed Plan.
IX.
Selected Remedy
The preferred alternative for the AIM Area Groundwater Corrective Action Program is
Alternative 2: Groundwater Recovery with T=ument by Air Stripping. This alternative
includes installing groundwater recovery wells at strategic locations throughout the AIM
Area. extracting the contaminated groundwater. processing the groundwater through an air
stripper to remove volatile solvents; discharging the tteated eft1uent to an NPDES permitted
outfall. and conducting a treatability study for emissions from the air stripper. This
alternative was implemented in 1985 as an interim remedial action.
This alternative calls for the design and implementation of an interim remedi,1 action to
protect human health and the environment. The goals of thisremcdial action are to (1)
prevent further groundwater plume migration and initiate groundwater restoration while
risk assessment activities are being planned and conducted. and (2) obtain funher
information about the response of the aquifer to remediation measures. The ultimate goal
of remediation will be detennined in a fmal remedial action for this operable unit. This
remedial action will be monitored carefully to determine the feasibility of achieving this goal
with this method and to ensure that hydraulic control of the contaminated plume is
maintained. After completion of the characterimtion and evaluation of risk of the AIM Area
Groundwater Operable Unit and the source-specific operable units impacting the M-Area
groundwater. a final ROD for the M-Area groundwater. which specifies the final
remediation goals and anticipated remediation timeframe. will be prepared.
27
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INTERIM ACI'ION ROD
AIM AREA GROUNDWATER OP-ERABLE UNIT
WSRC-RP-92-744
JUNE 25, 1992
x.
Patb Forward
Cmrently, the groundwater corrective action program is undergoing enhancements and new
technologies are being demonstrated. "Path Forward" accomplishments and programs that
are pan of the corrective action program and are related to the AIM Area Groundwater
Operable Unit are described below.
M-Area Groundwater Remediation. Increasing groundwater flow to the M-Area HWMF
air stripper was accomplished during 1990. SRS received approval from SCDHEC to
.
operate the M-A.Jea corrective action system (air stripper and 11 recovery wells) at
increased flow rates. The air sttipper is cUJTelltly operanng at SOO gpm. Testing will
continue in an effon to further increase recovery of groundwater and speed up the removal
of VOCs.
SRS is also preparing to inidate an off-gas tteatment evaluadon for air stripping gaseous
effluents. The integrated demonstration program, sponsored by the 00£ Office of
Technology Development at SRS, will demonstrate and assess the efficiency and cost
effectiveness of several innovative destructive or hybrid off-gas treatment systems.
Classes of technologies to be demonstrated include catalytic, biologic, thermal,
electroChemical, and carbon regeneration systems. The technologies were selected on the
basis of technical merit and the appropriateness of the technology for DOE's (complex
wide) remedial tequirements.
The demonstration of the selected technologies will occur in the AIM Area of SRS in the
vicinity of the A-014 outfall where a vadose zone vacuum extraCtion well currently exists.
The technologies slated for assessment, beginning in 1992, include: steam regeneration of
28
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INTERIM ACTION ROD
. AIM .AREA GROUNDWATER OPERABLE UNIT
WSRC-RP-92-744
JUNE 25, 1992
activated carbon, gas-phase bioreaction, membrane separation, high-energy corona,
photocatalytic desauction, and thermal catalytic desauction.
SRS anticipates that gaseous effluents from the M-Area air stripper will undergo funher
treatment in the near future using one of these remedial technologies. The air stripper
effluent treatment will be added to the AIM Area Groundwater Co1Tective Action Program
upon completion of the technical evaluation. The groundwater recovery efforts in AIM
Area will continue to be expanded to meet the requirements of the RCRA Hazanlous Waste
Permit and the overall goal of achieving hydraulic conttol to minimize any furtha' migration
and expansion of the contaminant plume.
NortheMtern Sector Groundwater Remediation. A remediation program is in progress to
address contamination near the nonhern boundary of SRS. SRS bas completed
construction of a SCDHEC-approved groundwater recovery system located near the SRL
facility. An air stripping system has also been relocated to this area which SRS began
operating in March 1992. This facility is treating groundwater near the SRS boundary,
initially from a single extraction well. Additional recovery systems are planned for this
area.
A recovery well, different in design from that used in M-Area, will be used for the
Northeastern Sector. The well will be designed to screen only selected zones of high
concentration or high water production, instead of the fully penetrating screen design used
in M-Area. This will allow for selective pumping of contaminated zones while avoiding
pumping of clean zones. This approach is more costly though, since more wells are
necessary to screen individual zones. Other designs which will be considered for cost
savings include using 4- or 6-inch casing.
29
.
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INTERIM ACTION ROD
AIM.AREA GROUNDWATER OPERABLE UNIT
WSRC-RP-92-744
- . JUNE 25, 1992
The final extent of remediation in the Nonheastem Sector will be the initial work involved
in a funher remediation effon for this area. Design, construCtion, and implementation of
funher remediation systems will be the main focus of Phase ll.. At this time, it is
anticipated that an additional air stripper will be ~uired. The air stripping unit will be
equipped with an off-gas creatment system which can accommodate the effluent from the 70
gpm air Slripper which became operational in March 1992.
Southern Sector Groundwater Remediation. A less concentrated plume ~f chlorinated
solvents exists south of the M-Area HWMF. An investigation was carried out in order to
determine the degree and extent of remediation required. The investigation consisted of
in.Cbllillg monitming wells, collecting geologic information, and cbanK:terizing the squifel'.
In an additional remediation effort. SRS will inStall additional groundwater!'eCOVeJY wells
in order to upgrade the corrective action system to meet the reqiJirementSof the RCRA
Hazardous Waste Permit.
In addition to further groundwater recovery efforts, SRS will also consider other treatment
systems and technologies for the Southern Sector including remote or satellite air stripping,
air sparged tanks, spray irrigation. reinjection or artificial recharge, in-situ mnediation. UV
peroxidation, and enhanced bioreclamation. SRS will use the characterization data,
exposure assessment criteria, and technology test information to formulate a detailed
corrective action plan.
V &dose Zone Corrective Action Pro~m. SRS has initiated a program to remediate soils
above the groundwater at four locations in M-Area where solvents were released. SRS has
performed a characterization study of each area. Presently, SRS is preparing the designs
and costs of the planned systems.
30
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INTERIM ACTION ROD
AIM AREA GROUNDWATER OPERABLE UNIT
WSRC-RP-91-744
JUNE 15, 1991
SRS recently (7fJ.719O-12/1819O) conducted a large experimental program (In-situ Air-
Stripping Demonstration) near the closed M-Area HWMF. . This program included
implementation of a vacuum extraction system and testing of new well installation
techniques. The vacuum extraction system is designed to remove VOCS from soils above
the shallow aquifer. The demonstration system has extracted VOCs that, if left in place.
would have eventually migrated into the groundwater.
As pan of the vacuum extraction system, SRL has installed a series of horizontal wells into
contaminated soils and groundwater. These wells are designed to accelerate remediation
through in-situ air stripping and have been used fel' soil and groundwater gas extraction.
The SRS decision to implement a vadose zone corm:tive action program was voluntary.
and was based on the success of a vacuum extraction pilot Study conducted in March 1987.
The 1987 study was successful. with the removal of almost 1500 pounds of chlorinated
solvents during 3 weeks of operation. About 16.000 pounds of chlorinated solvents were
removed from the subsurface and groundwater during a S-month test in 1990. The DOE
Office of Technology Development is also sponsoring funher demonstration activities
associated with remediation of vadose zone soils (and underlying groundwater) using
vacuum extraction.
SRS is ploposing to conduct further in-situ testing by injecting small amounts of methane
into a horizontal well to facilitate and enhance in-situ bioremediation. The demonstration
will involve stimulation of indigenous microorganisms to degrade TCE and PCB in-situ by
addition of nutrients (methane) to the subsurface via the horizontal well used for air
injection during the in-situ air stripping demonstration. Horizontal wells provide an
advantage due to the increased surface area for better delivery of nutrients. better extraction
31
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INTERIM ACTION ROD
AIM AREA GROUNDWATER OPERABLE UNIT
WSRC.RP.92.744
JUNE 25, 1992
. of gas in the vadose zone, and lesser likelihood for clogging and plugging of the well
casing.
In-situ bioremediation coupled with vapor extraCtion is expected to lead to a significant
reduction in the time required to complete a remediation since bioremedis.tion provides a
second simultaneous pathway for removal (destruction) of the TCE. Funhennore, the
stimulated indigenous microorganisms will gain access to TCE in the subsurface that may
be difficultto remove by conventional methods.
Air/methane mixtureS have been demonstrated in the laboratory to stimulate selected
members of the indigenous microbial community that have the capability to degrade TCE.
The nutrient. methane. will be supplied via the horizontal wells at a low concentration in air
(1-3'11), for a period not to exceed 12 months. A vacuum will be applied to the upper weD
(vadose zone) to encourage air/methane movement through the upper satUIatCd zone and
lower vadose zone and to inhibit spreading of the plume. This technology also may be
applicable to the treatment of underlying groundwater. A lower horizontal weD screened in
the sanmucd zone will teSt the feasibility of this approach.
Dense Non-AQJleous Phase Liquids IDNAPLs). Recent groundwater monitoring results
indicate the presence of a separate phase of concentrat~ undissolved chlorinated solvents,
known as DNAPLs, in one shallow aquifer monitoring weD located near the closed M-Area
HWMF. SRS has initiated plans to further characterize and recover these chlorinated
solvents. These plans include confirmation sampling of specified monitoring weDs for
DNAPLs at suspect locations, geophysical and geological characterization of the
subsurface, developing and testing a system to recover DNAPLs, and a method to treat or
dispose of reclaimed DNAPLs.
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INTERIM ACTION ROD
AIM AREAGROUNDW A TER OPERABLE UNIT
WSRC.RP.92.744
-JUNE 25, 1992
An information workshop on DNAPLs was sponsored by DOE in mid-1991 in Atlanta, in
an effort to better infonn investigators and environmental regulators, and to become more
familiar with the DNAPLs issue at other industrial sites. The workshop was very
successful and promises to attract advanced technical applications to SRS for the planned
DNAPLs characterization and assessment studies.
X.I.
Statutory Determination
The preferred alternative for the AIM Area Groundwater Operable Unit, an interim action,
is Alternative 2: Groundwater Recovery with Treatment by Air Stripping. Based on
information available at the time that this alternative was selected, and based on currently
available information, this alternative appears to provide the best baJance with respect to the
nine evaluation criteria specified in the NCP. This alternative satisfies the statutory
requirements of protection of human health and the environment, with respect to the water
exttacted from the ground. It was also selected for itS cost effectiveness and
implementability (minimal attention and maintenance during operation).
However, Alternative 2 is an action which will not fully remcdiate the NM Area
Groundwater Operable Unit. The action attempts to provide the best currently available
method by which to remcdiate contaminated groundwater. The interim remedy complies
with ARARs for that portion of the groundwater removed from the AIM Area Groundwater
Operable Unit and treated at the surface, with the final remedy obtaining compliance with
ARARs or justifying a waiver for the remainder of the AIM Area Groundwater Operable
Unit. For this interim remedy, the alternative permanently and significantly reduces the
toxicity, mobility, and volume of hazardous substances through their removal from the
groundwater. Air effluent treatment will be discussed in thc final proposed plan for this
33
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INTERIM ACTION ROD
" AIM AREA GROUNDWATER OPERABLE UNIT
WSRC-RP-91-744
" " JUNE 25, 1991
operable unit. This. interim remedy is not inconsistent with, nor precludes the
implementation of, the"expected final remedy because it has, and continues to, reduce the
overall quantity of contaminants in the AIM Area groundwater. This is not inconsistent
with the overall mnediaI action goal of removing contaminants which could threaten human
health or the environment.
""
34
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. APPENDIX A
References for Development of ROD Format
Cnme, Jeffrey L., 1992. "Worldng Meeting Notice for M-Area RODs: M-Area
Groundwater, M-Area Settling Basin, Met Lab Basin, " Letta' to Cuis Bergren
(WSRC), U.s. Environmental Protection Agency, Region IV, Atlanaa, GA, March
12, 1992.
EPA, 1989. "A Guide to Developing Superfund Reccxds of Decision," OSWER Din:aive
933S.3-o2FS-l, U.S. Environmental Plytection Agency, Washington, D.C.,
November 1989.
EPA, 1991. "Guide to Developing Superfund No Action, Interim Action, and
Contingency Remedy RODs," OSWER Publication 93SS.3-o2FS-3, U.S.
Environmental Protection Agency, WashingtOn, D.C., April 1991.
Longest, Hemy L, aDd Bruce M. Diamond, 1990. "Suggesu:d ROD Language for
Various Groundwater Remediation Options," OSWER Directive 9283.1-03, U.S.
Environmental Protection Agency, Washington, D.C., Oc1Dbcl' 10, 1990.
WSRC, 1990. "RCRA Facility InvestigationJRf!I'1'VIitial Investigation Program Plan,"
WSRC-RP-89-994, O1apter 15, Westinghouse Savannah River Company, Aiken,
South Carolina, September 1990.
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APPENDIX B
Responsiveness Summary
No COlDlDCllts were received during the public comment review period.
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