United States Office of
Environmental Protection Emergency and
Agency Remedial Response
EPA/ROD/R04-92/112
September 1992
&EPA Superfund
Record of Decision:
Carrier Air Conditioning, TN
-------
NOTICE
The appendices listed in the index that are not found in this document have been removed at the request of
the issuing agency. They contain material which supplement but adds no further applicable information to
the content of the document All supplemental material is, however, contained in the administrative record
for this site.
-------
50272-101
REPORT DOCUMENTATION 1. REPORT NO. 2.
PAGE EPA/ROD/R04-92/112
4. Tttktwid Subtitle
SUPERFUND RECORD OF DECISION
Carrier Air Conditioning ; TN
First Remedial Action - Final
7. Author!*)
9. Performing Organization Name and Add re**
12. Sponaoring Organization Nam* and Addm**
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, D.C. 20460
3. Recipient" • Acce**lon No.
S. Report Data
09/03./92
&
8. Performing Organization RepL No.
10. Project/Taak/Work Unit No.
11. Contract(C) or Grant(G) No.
(C)
(C)
13. Type of Report ft Period Covered
800/000
14.
15. Supplementary Note*
PB93-964019
16. Abetract (UmH: 200 word*)
The 135-acre Carrier Air Conditioning site is an active manufacturing facility in the
Town of Collierville, Shelby County, Tennessee. Land use in the area is predominantly
industrial, with the nearest residential area approximately 100 feet north of the site
boundary. Two aquifer units have been identified at the site: a shallow class Ilia
aquifer, which is not used as a drinking water source; and the Memphis Sand, a class
Ha aquifer, which lies below the shallow aquifer and is currently used as a drinking
water source. The Town of Collierville purchased the site property and installed a
well field for potable water on the northwest corner of the site, known as Water Plant
2, which currently provides up to 1.4 million gallons per day of potable water to the
Town of Collierville. In 1967, Collierville leased the site property, buildings, and
equipment to Carrier to manufacture residential heating and air-conditioning units.
During the manufacturing process, aluminum sheeting is stamped and assembled with
copper tubing to form air heat exchangers. Stamping and forming oils and dirt are
removed prior to assembly. Until recently, trichloroethylene (TCE) was used onsite as
(See Attached Page)
17. Document AnaJyat* a. Descriptor*
Record of Decision - Carrier Air Conditioning, TN
First Remedial Action - Final
Contaminated Media: soil, sludge, gw
Key Contaminants: VOCs (PCE, TCE), metals (lead, zinc)
b. Mentfflera/Open-Ended Term*
c. COSATJ Raid/Group
18. Availability Statement
i
1». Security Claw (Thi* Report/
None
20. Security Claa* (Thl* Page)
None
21. No. of Page*
62
22. Price
(SeeAKSI-ZJS.18)
See Instruction* on Renne
OPTIONAL FORM 272 (4-77)
(formerly NTIS-35)
Department of Commerce
-------
EPA/ROD/R04-92/112
Carrier Air Conditioning, TN
First Remedial Action - Final
Abstract (Continued)
the primary solvent for degreasing and cleaning parts. In 1979, a TCE release from a
storage area resulted in the removal of asphalt pavement and underlying soil from the
parking area, which was affected by the spill. It also was discovered that an onsite
wastewater lagoon had accepted waste contaminated with TCE and zinc. In response to a
second release in 1985, both a massive soil excavation and disposal action were conducted
to remove TCE contamination. Monitoring wells also were installed at the facility. In
1986, one of the wells from Water Plant 2 was found to be contaminated with low levels of
TCE. In 1987, Carrier purchased the site property, except for the municipal well area.
In 1990, Carrier installed air strippers at Water Plant 2 to remove TCE and its
degradation products. This ROD addresses a final remedy for the contaminated soil,
sludge, and ground water at the Carrier facility and is the only ROD planned for the
site. The primary contaminants of concern affecting the soil, sludge, and ground water
are VOCs, including TCE and PCE; and metals, including lead and zinc.
The selected remedial action for this site includes treating an estimated 76,500 cubic
yards of contaminated soil/sludge and shallow ground water in the old lagoon and main
plant source areas using soil vapor extraction (SVE); extracting and containing ground
water from the Memphis Sand aquifer using the existing and supplemental extraction wells
with treatment using the air strippers at Water Plant 2, followed by discharge of the
treated ground water to the municipal water supply, a local POTW, surface water, or
reinjecting it to the Memphis Sand aquifer; treating any air emissions from the SVE or
the air stripping processes using granular activated carbon, thermal treatment, or
photolytic oxidation, if necessary; implementing institutional controls deed restrictions
to limit well construction and water use near the site; and conducting periodic
monitoring. The estimated present worth cost for this remedial action ranges from
$5,700,000 to $7,900,000, which includes a total O&M cost of $5,489,334 for 30 years.
PERFORMANCE STANDARDS OR GOALS: The chemical-spe.cific soil clean-up level is 533 ug/kg
for TCE, based on fate and transport modeling for TCE leachate, which would not
contaminate the ground water above the maximum concentration level for TCE established
under the SDWA. The ability to achieve 533 ug/kg cannot be determined until after the
extraction system has been implemented. EPA may set an alternate clean-up level when it
is determined that contaminant levels have ceased to decline over time and are remaining
constant at some statistically significant level above remediation levels, as verified by
soil sampling. The chemical-specific ground water clean-up levels are based on SDWA
MCLs, MCLGs, and UIC regulations; CWA Discharge Limitations and Pretreatment standards;
and/or the Tennessee Water Quality Act. These levels include TCE 5 ug/1; cis-DCE
70 ug/1; trans-DCE 100 ug/1; PCE 5 ug/1; vinyl chloride 2 ug/1; zinc 5,000 ug/1; and lead
15 ug/1 or background levels.
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CARRIER AIR CONDITIONING
SUPERFUND SITE
RECORD OF DECISION
-------
RECORD OF DECISION
CARRIER A.C. SITE
TABLE OF CONTENTS
Description Page
DECLARATION FOR THE RECORD OF DECISION i
DECISION SUMMARY 1
1.0 SITE NAME, LOCATION, AND DESCRIPTION 1
1.1 Site Location 1
1.2 Site Topography 1
1.3 Geologic/Hydrogeologic Setting 1
1.4 Meteorology 4
2.0 SITE HISTORY AND ENFORCEMENT ACTIVITIES 4
2.1 Facility Operations and History 4
2.2 Enforcement Activities 6
3.0 COMMUNITY PARTICIPATION HIGHLIGHTS 6
4.0 SCOPE AND ROLE OF RESPONSE ACTION 7
5.0 SUMMARY OF SITE CHARACTERISTICS 7
5.1 Nature and Extent of Contamination 7
5.2 Contaminant Distribution, Fate and Transport 14
5.3 Treatability Study 21
6.0 SUMMARY OF SITE RISKS 21
6.1 Contaminants of Concern 21
6.2 Exposure Assessment 22
6.3 Toxicity Assessment 25
6.4 Risk Characterization 28
6.5 Soil Cleanup Goals for Groundwater Protection 33
6.6 Ecological Considerations 33
6.7 Risk Uncertainty 33
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RECORD OF DECISION
CARRIER A.C. SITE
TABLE OF CONTENTS
Description Page
7.0 DESCRIPTION OF REMEDIAL ALTERNATIVES 34
7.1 Alternative 1 36
7.2 Alternative 2 36
7.3 Alternative 3 37
7.4 Alternative 4 39
7.5 Alternative 5 41
7.6 Alternative 6 42
8.0 SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES . . 45
9.0 THE SELECTED REMEDY 48
9.1 Performance Standards 48
10.0 STATUTORY DETERMINATIONS 51
10.1 Protection of Human Health and the Environment 51
10.2 Compliance with Applicable or Relevant and Appropriate
Requirements 52
10.3 Cost Effectiveness 54
10.4 Utilization of Permanent Solutions and Alternative Treatment
Technologies or Resource Recovery Technologies to the Maximum
Extent Practicable 54
10.5 Preference for Treatment as a Principal Element 54
RESPONSIVENESS SUMMARY APPENDIX
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RECORD OF DECISION
CARRIER A.C. SITE
TABLE OF CONTENTS
Description Page
TABLE 5-1 Summary of Groundwater Results 8
TABLE 5-2 Summary of Town Well Raw Water Samples 11
TABLE 5-3 Summary of Soils Results 12
TABLE 6-1 Contaminants of Concern by Environmental Media 23
TABLE 6-2 Potential Complete Exposure Pathways for
Risk Assessment Considerations 26
TABLE 6-3 Health-Based Values for Carcinogens (SF) and
Noncarcinogens (RfD) and ARARs for
Oral Exposure to Contaminants of Concern 27
TABLE 6-4 Summary of Risks for Adult Workers from Oral
and Dermal Exposure to Contaminants in Soil 29
TABLE 6-5 Summary of Risks for Potential Future Child Residents from
Oral and Dermal Exposure to Contaminants in Soil 30
TABLE 6-6 Current and Future Resident
Direct Digestion and Inhalation Groundwater Pathway Risk 32
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RECORD OF DECISION
CARRIER A.C. SITE
TABLE OF CONTENTS
Description
Page
Figure 1-1 Site Vicinity Map 2
Figure 1-2 Site Plan 3
Figure 5-1 Potential TCE Sources 13
Figure 5-2 Isocons of Maximum TCE Values for Soil Borings 15
Figure 5-3 Isocons of Maximum TCE Values for Soil Borings 16
Figure 5-4 Monitoring Well Locations Onsite 17
Figure 5-5 Monitoring Well Locations Offsite 18
Figure 5-6 Fate and Transport Mechanisms 19
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DECLARATION FOR THE RECORD OF DECISION
SITE NAME AND LOCATION
Carrier Air Conditioning Site
97 Byhalia Road
Collierville, Tennessee 38017
STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected remedial action for the Carrier Air Conditioning
Site, in Collierville, Tennessee, which was chosen in accordance with the requirements of the
Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA),
as amended by the Superfund Amendments and Reauthorization Act of 1986 (SARA) and the
National Oil and Hazardous Substances Pollution Contingency Plan (NCP). This decision
document is based on the Administrative Record for this Site.
The Tennessee Department of Environment and Conservation concurs with the selected remedy.
ASSESSMENT OF THE SITE
Actual or threatened releases of hazardous substances from this site, if not addressed by
implementing the response action selected in this Record of Decision (ROD), may present an
imminent endangerment to public health, welfare, or the environment.
DESCRIPTION OF THE REMEDY
This final remedy addresses remediation of soils and groundwater contamination by eliminating
or reducing the risks posed by the Site, through treatment, engineering and institutional controls.
The major components of the selected remedy include:
Contaminated soils and shallow groundwater in the old lagoon and main plant source
areas will be remediated using soil vapor extraction.
Contaminated groundwater will be removed from the Memphis Sands aquifer using the
existing extraction wells (at the City of Collierville Water Plant 2) and with supplemental
wells. The contaminated groundwater will be treated by air stripping.
Extracted groundwater after treatment will be (1) utilized in the municipal water supply;
(2) discharged to a local publicly owned treatment works (POTW); (3) discharged to
surface water; or (4) reinjected to the Memphis Sands aquifer.
-------
for
wU! be pUced on w=U consm,c«on ^ wa,er use in ,he
STATUTORY DETERMINATIONS
is cost-effecdve. TOs
-. emeu™ ,
0
J^/Sie
reer C. Tidwell
gional Administrator
11
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ROD
Carrier A.C. Site
Page 1
DECISION SUMMARY
1.0 SITE NAME, LOCATION, AND DESCRIPTION
1.1 Site Location
The Carrier Air Conditioning Site (also referred to as the Collierville Site) is located on the
western side of the Town of Collierville, Shelby County, Tennessee. Shelby County, TN is
located in the southwest portion of the State. The Site is located near the intersection of Poplar
Avenue (U.S. Highway 72) and Byhalia Road. The address is 97 South Byhalia Road,
Collierville, TN 38017. Collierville is located approximately 21 miles east of downtown
Memphis, TN. Figure 1-1 is a location map showing the Carrier A.C. Site and vicinity. Figure
1-2 shows the Site itself and relevant features.
1.2 Site Topography
Currently the Site slopes gently to the South and West. The Site has been graded and filled in
various locations in order to change drainage patterns and adapt the land for manufacturing use.
In general the western portion of the property has been graded and leveled, with excess dirt
moved to the areas under Buildings A and F. A pond located at the western edge of the Main
Plant has been filled. A drainage ditch running east/west on the western side of the property
was removed and an intermittent stream was rerouted around the area which became the Main
Plant.
1.3 Geologic/Hydrogeologic Setting
The Memphis/Shelby County area is situated in two major physiographic subdivisions: the
Mississippi Alluvial Plain and the Gulf Coastal Plain. The Carrier A.C. Site is located in the
Gulf Coastal Plain which is distinguished by gently rolling topography and a characteristic thick
layer of loess deposited during Pleistocene glaciation. Anomalous areas of loess deposition are
associated with alluvial plains of Mississippi River tributaries that cross the area. These rivers
include the Wolf River, the Loosahatchie River, and Nonconnah Creek. Nonconnah Creek runs
through the Site boundaries.
Unconsolidated deposits, up to 3000 feet, overlie bedrock in the Memphis/Shelby County area.
The sediments consist primarily of sand, clay, gravel, silt, and some lignite. The principal
freshwater aquifers in the designated area are 1) the alluvium, 2) fluvial (terrace) deposits, 3)
the Memphis Sand, and 4) the Fort Pillow Sand. The alluvium and fluvial deposits are separated
in most areas from the Memphis Sands by the Jackson-upper Claibome confining layer (locally
referred to as the Jackson Clay). The Memphis Sands and the Fort Pillow Sands are separated
by the Flour Island confining layer.
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9 - CITY VtU. FIELD
(KUML&MU)
Figure 1-1
VICINITY MAP
CARRIER SITE
-------
FIGURE 1-2
SITE PLAN
CARRIER SITE
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ROD
Carrier A.C. Site
Page 4
Two aquifer units have been identified at the Site: (1) intermittent shallow water in the alluvial
and fluvial deposits overlying a semi-confining clay unit, and (2) the Memphis Sand aquifer.
The alluvium and fluvial deposits show inconsistencies throughout the region. The intermittent
characteristic of shallow groundwater is due to undulations in the surface of the clay layer.
These undulations capture and direct percolating groundwater along the top of the clay layer.
The clay layer thins to non-existence between the Carrier plant building and Nonconnah Creek,
resulting in a direct exchange between the shallow aquifer, where present, and the deeper
Memphis Sand aquifer. The Memphis Sand consists of massive beds of fine to coarse grained
well-rounded to sub-angular sand and gravels intercalated with thin lenses and beds of silt, clay
and argillaceous, micaceous and lignitic materials. The Memphis Sand is confined throughout
most of the Memphis area, except in the eastern and southeastern portions of Shelby County.
The Fort Pillow Sand is artesian throughout the Memphis area and including the Carrier Site.
Vertical interaquifer exchange between the Memphis Sand and the Fort Pillow Sand is restricted
by the low hydraulic conductivity associated with the Flour Island confining layer.
The shallow aquifer is classified as a DIA aquifer - groundwater not used as a drinking water
source and has limited beneficial use. Also, this aquifer is highly to intermediately
interconnected to adjacent groundwater units of a higher class and/or surface waters. The
Memphis Sand is a Class HA aquifer - groundwater that is currently used as a drinking water
source and having other beneficial uses.
1.4 Meteorology
Collierville's climate is typical of the Memphis region which is humid with summer temperatures
ranging from the low 80°s F to 100° F; and winter temperatures in the 40°s F. Average
humidity is 50 to 60 percent. Average rainfall is 56 inches per year. Evapotranspiration
averages 40 inches, most of which occurs between May and October. Average wind speed is
10 miles per hour in winter and 7 miles per hour in summer. Predominant wind direction is to
the north-northeast.
2.0 SITE HISTORY AND ENFORCEMENT ACTIVITIES
2.1 Facility Operations and History
The Site consists of approximately 135 acres owned principally by Carrier Corporation (Carrier)
which operates a manufacturing facility on the property. In 1967, the Town of Collierville
purchased the Site property from Robert and Grace Snowden. That same year, the Town of
Collierville constructed industrial buildings and purchased industrial equipment for the Site. The
property, buildings and equipment were leased to Carrier on March 1, 1967. In 1982, the lease
was amended to exclude the northwest portion of the property where the Town of Collierville
municipal wells are located. On December 14, 1987, Carrier purchased all the property
included in the lease with the Town of Collierville.
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ROD
Carrier A.C. Site
PageS
In 1967 the Town of Collierville installed a well field for potable water on the northwest comer
of the Site. The operation consists of two extraction wells, described as the West Well and the
East Well, a treatment (aeration and chlorination) plant, and a storage tank. This operation is
identified as Water Plant 2 and provides up to 1.4 million gallons per day of potable water to
the Town of Collierville.
Carrier began manufacturing residential heating and air conditioning units in the late 1960s.
Carrier's use consists primarily of four buildings: the main plant which is an assembly plant for
air conditioning units, buildings A and F which contain storage and supporting operations, and
an office building. In the process of assembling air conditioning units, aluminum sheeting is
stamped and assembled with copper tubing to form air heat exchangers. Stamping and forming
oils and dirt are removed from these parts prior to final assembly. Trichloroethylene (TCE)
was, until recently, the primary solvent used to degrease and clean these parts. Two discrete
releases (in 1979 and 1985) of TCE occurred from solvent storage systems to an area just south
of the main manufacturing building. In addition, a wastewater lagoon, operated from about 1972
to 1979, apparently accepted waste contaminated with TCE and zinc.
Removal actions were conducted at the former lagoon in 1979 and both near-plant spill areas in
1979 and 198S. At the lagoon, approximately one foot of sludge was removed. Asphalt
pavement and underlying soils were removed from the parking area affected by the 1979 spill
of TCE from a degreaser vent pipe. In 1985, about 500 gallons of TCE from a nearby
aboveground storage tank pipe were released. A massive soil excavation and disposal action was
conducted to remove the affected soils. As a result of the spill, monitoring wells were installed
at the facility.
Since the 1985 spill, the Tennessee Department of Environment and Conservation (TDEC)
continued groundwater monitoring at the Site on a regular basis. In July 1986, one of the
extraction wells in the Town of Collierville's Water Plant 2 was found to be contaminated with
low levels of TCE. Although low levels of TCE were found in both wells of Water Plant 2, no
TCE was found in any of the other City municipal water plants. Operation of the wells and the
existing plants has continued under frequent monitoring. In 1990, packed aeration towers, also
called air strippers, were installed by Carrier at Water Plant 2 to to remove TCE and its
degradation products from raw water prior to entry into the chlorination system. The treatment
system was designed to handle incoming TCE concentrations of up to 200 pg/l. Design,
construction, and operation of this system was coordinated with and approved by the Tennessee
Department of Water Supply (which permits water treatment systems), the Memphis Shelby
County Health Department, Bureau of Pollution Control (which has delegated authority for air
emissions permitting), the State of Tennessee Division of Superfund, and the Town of
Collierville. EPA Region IV was kept informed of the action.
In 1987 and 1988, Carrier conducted an extensive Site investigation under an agreement with
the TDEC. Sampling indicated measurable amounts of TCE in the soils and smaller amounts
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ROD
Carrier A.C. Site
Page 6
in the groundwater at the Site. The Site investigation also confirmed the earlier finding of low
TCE concentrations in the groundwater from Water Plant #2.
2.2 Enforcement Activities
In March 1987, the Site was placed on the TDEC's List of Hazardous Substance Sites. In June
1988, it was proposed for inclusion on EPA's National Priorities List (NPL), and became final
in 1990.
On November 7th and 10th, 1988, EPA sent general notice letters to the following entities:
1. Town of Collierville
2. Carrier Corporation
The letters notified the potentially responsible parties (PRPs) of their potential responsibility for
the release of hazardous substances at the Carrier Air Conditioning Site in Collierville,
Tennessee. A special notice letter sent to Carrier requested that they conduct a Remedial
Investigation and Feasibility Study (RI/FS) for the Site. On September 28, 1989, the Carrier
Corporation and EPA entered into a Consent Order under which Carrier agreed to conduct the
RI/FS.
3.0 COMMUNITY PARTICIPATION HIGHLIGHTS
Public participation requirements in CERCLA §§ 113(k)(2)(B)(i-v) and 117 were met in the
remedy selection process. The Community Relations Plan was finalized April 25, 1990 for the
Carrier Air Conditioning Superfund Site. This document lists contacts and interested parties
throughout the government and the local community. The Plan also establishes communication
pathways to assure timely dissemination of pertinent information.
On May 8, 1990, EPA held a public information session to announce the Carrier Site RI/FS
start.
The RI/FS Reports and Proposed Plan for the Carrier Air Conditioning Site were released to the
public on April 18, 1992. These two documents were made available to the public in both the
Administrative Record and the information repository maintained at the Memphis/Shelby County
Public Library, Collierville Tennessee and the EPA Region IV Records Center. The notice of
the availability of these two documents was published in The CoUierviUe Herald and The
Independent on April 16, 1992. A public comment period was held from April 21, 1992
through May 21, 1992. An extension to the public comment period was not requested. In
addition, a public meeting was held on April 30, 1992. At this meeting, representatives from
EPA, TDEC, and the Town of Collierville answered questions about problems at the Site and
the remedial alternatives under consideration. A transcript of the public meeting and response
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ROD
Carrier A.C. Site
Page?
to the comments received during the public comment period are included in the Responsiveness
Summary, which is part of this Record of Decision. This decision document presents the
selected remedial action for the Carrier Air Conditioning Superfund Site, chosen in accordance
with CERCLA, as amended by SARA, and, to the extent practicable, the National Contingency
Plan. The decision for this Site is based on the Administrative Record.
4.0 SCOPE AND ROLE OF RESPONSE ACTION
The selected remedy for the Site is intended to address the threats to human health and the
environment. This remedial action will remove the threat posed by contaminated groundwater
and soil at the Site. Remediating the soils will prevent the contaminants from adversely
impacting the groundwater. Remediating groundwater will prevent ingestion or inhalation of
contaminated groundwater at or above the Maximum Contaminant Levels (MCLs) and will
restore groundwater to contamination levels below MCLs. This is the only ROD contemplated
for the Site.
5.0 SUMMARY OF SITE CHARACTERISTICS
5.1 Nature and Extent of Contamination
Results of the Carrier Site Remedial Investigation (RI) show varying levels of TCE
contamination on the property. Results from soil and groundwater sample analyses, and soil-
vapor screening data confirm that the two spill areas and the former lagoon area are the sources
of contamination of Site soils and groundwater. Tables 5-1, 5-2, and 5-3 summarize
groundwater and soil analytical data collected during the RI. Figure 5-1 shows the location of
the three source areas.
On July 15,1986, the Town of Collierville's west well in Water Plant 2 adjacent to the Site was
sampled by TDEC and found to contain TCE. Subsequent analyses conducted on a bimonthly
basis have shown values of TCE in the untreated water from the west well ranging from 45 to
290 ng/t. Values in the east well have ranged from 5 to 34 pg/l for the untreated waters.
Values in treated water, prior to chlorination, averaged 4 pg/l, prior to the installation of a
treatment system to remove TCE and have since been consistently less than 2 pg/t.
In addition to the Town of Collierville's Water Plant 2,15 private wells have been identified by
TDEC within three miles of the Site. Analyses of these wells by TDEC in September and
October 1986 were negative for TCE to a detection limit of 0.1 pglt. Private wells were again
sampled in the RI with no TCE detected at a detection limit of 5 pglt.
As part of the RI, soil samples collected within areas suspected to be impacted by the spills
indicate a wide range of levels of contamination, Samples from these areas ranged in
concentration from < 0.5 pgfcg to 1,550,000 /ig/kg TCE. The greatest concentrations (B-4,
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ROD
Carrier A.C. Site
Page 8
TABLE 6-1
Summary of Groundwalar Re*uto
Paramatar
TRICHLOROETHENE
1,2-DICHLOROETHENE
1,1-DICHLOROETHENE
1.1.1 -TRICHLOROETHANE
TETRACHLOROETHENE
Sampling
PariodV
Phas*
12/89
4/90
8/90
11/90
2/91
4/91
8/91
12/89
4/90
8/90
11/90
2/91
4/91
8/91
11/90
2/91
4/91
8/91
12/89
4/90
8/90
11/90
2/91
4/91
8/91
12/89
4/90
No.
Samptaa
15
17
20
25
23
23
25
15
17
20
25
23
23
25
25
23
23
25
15
17
20
26
23
23
25
15
17
No.
Hta
10
10
12
13
9
11
15
7
6
8
9
9
7
7
2
1
1
1
1
0
0
1
1
2
1
0
0
Rang«, nil
38-4400
9-140OO
20-24000
23-7300
59-8700
8-12500
5-37000
7-5300
50-5400
5-3900
8-12000
11-120OO
7.2-6900
3-370
9-14
135.2-824
M«an, mil
1230
28OO
3850
1840
2350
4400
3800
1530
2720
830
1480
1560
12OO
125
12
7.9
4.75
9
44
120
32
480
69
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ROD
Carrier A.C. Site
Page 9
TABLE 6-1
Summary of GroundwaMr Re«(Jt*
ParanMtM
TETRACHLOROETHENE
METHYLENE CHLORIDE
ACETONE
CARBON DISULFIDE
VINYL CHLORIDE
Sampling
Period/
PhMe
8/90
11/90
2/91
12/89
4/90
8/90
11/90
2/91
4/91
8/91
12/89
4/90
8/90
11/90
2/91
4/91
8/91
12/89
4/90
8/90
11/90
2/91
4/91
8/91
11/90
2/91
4/91
8/91
No.
Swnpte*
20
25
23
15
17
20
25
23
23
25
15
17
20
25
23
23
25
15
17
20
25
23
23
25
25
23
23
25
No.
Mitt
0
0
1
0
2
0
1
2
6
7
2
6
0
1
8
4
5
0
3
0
3
2
1
1
2
1
2
0
Ranga,/«g/J
7-160
27-35
8-997
3-11
200-320
12-860
7.2-156
3.2-790
9.1-50
9-75
7.58
11-78
1-5
2.27-8.51
M«an,//g/f
27
85
7
31
210
6
260
450
6
45
250
24
34
24
45
17.1
11
3
3.4
5.5
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ROD
Carrier A.C. Site
Page 10
TABLE 5-1
Summary of Groundwatar Racists
Paramctar
TOLUENE
1,2-DICHLOROETHANE
trans 1,3-DICHLOROPROPENE
BROMODICHLOROMETHANE
DIBROMOCHLOROMETHANE
cis 1,3-DICHLOROPROPENE
BROMOCHLOROMETHANE
LEAD
ZINC
Sampling
Pariod/
Phase
11/90
4/91
8/91
2/91
2/91
4/91
8/91
2/91
4/91
2/91
2/91
12/89
4/90
8/90
11/90
2/91
4/91
8/91
12/89
4/90
8/90
11/90
2/91
No.
Samples
25
23
25
23
23
23
25
23
23
23
23
15
16
20
25
26
19
26
15
16
20
25
26
No.
Hit*
1
0
1
1
1
0
1
1
1
1
1
3
9
20
21
11
12
17
14
15
19
21
24
R*nt».li9lt
4-106
2.4-152
1 .4-54.2
1.1-278
4.9-198
3.9-454
1-246
2.2-21900
20.6-30300
11-1980O
12-146OOO
10-30500
Mean,ps/J
5
7
43
46
7.4
42
824
37 '
48
42
43
19
30
50
134
80
4010
6800
4840
11650
5600
-------
ROD
Carrier A.C. Site
Page 11
TABLE 6-2
Summary of Town Wei Raw Water Sample*
Parameter
TRICHLOROETHENE
1 ,2-DICHLOROETHENE
VINYL CHLORIDE
LEAD
ZINC
Sampling
Period/
Phase
8/90
11/90
4/91
8/91
11/91
8/90
11/90
4/91
8/91
11/91
8/90
11/90
4/91
8/91
11/91
8/90
11/90
4/91
8/91
11/91
8/90
11/90
4/91
8/91
11/91
No.
Sample*
6
6
2
2
2
6
6
2
2
2
6
6
2
2
2 -
6
6
2
2
2
6
6
2
2
2
No.
Hit*
3
2
2
2
2
0
0
0
0
0
0
0
0
0
0
6
1
2
2
0
6
6
2
2
0
Rang*.
nit
2-27
34-45
20-103
5-290
11-79
1.2-7.6
28.2-42
27-45
10-272
11-115
1390-3350
129O-6680
Mean
11911
12
40
61.5
147.5
45
4
3
35.1
36
57
56
2370
3985
Standard
Deviation
,m't
13
8
41.5
142.5
34
2
6.9
9
96
40
980
2695
-------
ROD
Carrier A.C. Site
Page 12
TABLE 6-3
Summary of Soli Raaifta
Parameter
TRICHLOROETHENE
1.2-DICHLOROETHENE
TETRACHLOROETHENE
1 , 1 ,2-TRICHLOROETHANE
TOLUENE
2-BUTANONE
ACETONE
LEAD (mg/kg)
ZINC (mg/kg)
Sampling
Pariod/
Phase
No.
Samplaa
56
56
56
56
56
56
56
39
39
No.
Hh»
8
3
1
1
4
1
3
33
26
Rung*,
ffgfkg
8-1.200,000
14-200
6-87
12-35
0.67-21.4
3.3-77.8
Maan.
l/g/ttg
152000
78
11
26
40
190
26
7
33
Standard
Deviation,
/ig/kg
420000
110
60
13
4
15
-------
FIGURE 5-1
POTENTIAL TCE SOURCES
CARRIER SITE
13
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ROD
Carrier A.C. Site
Page 14
B-9, B-21, and B-38) were from those areas more directly associated with the 1979 degreaser
spill. The vertical extent of TCE contamination is variable throughout the Site. Soil screening
methods indicate that many of the sample's concentration levels decrease with depth. However,
there are samples which indicate an increase in concentrations as the zone of saturation in the
shallow aquifer is approached. Soil samples collected from the former lagoon area (borings B-
17, B-18, B19, and B-40) confirm the presence of TCE. Figures 5-2 and 5-3 are isocon maps
which graphically display the TCE soil testing results in the plant and lagoon areas.
Upon completion of the RI, 37 groundwater monitoring wells (identified generally in this ROD
as MWs) were present at the Site.
Concentrations of chlorinated hydrocarbons consisting primarily of TCE and cis and trans
isomers of 1,2-dichloroethene (DCE) were found in samples collected from most of the
monitoring wells screened in the upper aquifer.
The latter compound and vinyl chloride are natural degradation products of TCE. Total
chlorinated hydrocarbon (TCH) concentrations in these wells range from 70 fig/1 at MW-23 to
19,900 pg/t at MW-19 daring the last RI sampling period in February 1991. Figures 5-4 and
5-5 are facility layouts that identify all onsite and offsite monitoring wells.
Elevated levels of two metals, lead and zinc, were seen in Site shallow groundwater samples.
In shallow soils, lead values range from 7 to 15 mg/kg. Average lead values decrease with
depth in virtually all Site soils, except at the former lagoon area. Ziric values show a similar
pattern. Otherwise, no pattern of metals contamination or a source area has been defined.
The former lagoon area may serve as a source of zinc due to the use of zinc phosphate on the
Site and the discharge of zinc phosphate sludges to the lagoon. However, the closure of the
lagoon in 1980 appears to have removed these sludges and residual concentrations are low.
5.2 Contaminant Distribution, Fate and Transport
There have been three documented sources of chlorinated hydrocarbon contamination at the
Carrier Site as described above. Residual contaminants from these source areas are still in
specific areas. Furthermore, TCE and its degradation products have been identified in
groundwater. Groundwater contamination has been identified at the Carrier Site in close
proximity to the 1979 spill she and the former sludge impoundment in the shallow aquifer, and
within the Memphis Sand aquifer. The mechanics for migration of TCE from the source areas
to the aquifers depend on solvent-specific characteristics, site-specific geology and hydrogeology.
With respect to solvent characteristics, TCE has been characterized as an immiscible fluid with
a density greater than that of water, and is classified as a dense non-aqueous-phase liquid.
Figure 5-6 illustrates the possible mechanisms for movement of TCE in both soils and
-------
FIGURE 5-2
ISOCONS OF MAXIMUM TCE
VALUES FOR SOIL BORINGS
IN MAIN PLANT AREA
CARRIER SITE
15
-------
SCHILLING FARM PROPERTY
CITY WELL TREATMENT PLANT
WEST CITY WELL
v .
TREES
VATER TREATABLITY SYSTEM
MV-21
a
LEGEND
FENCE
" Z- GRAVEL ROAD
H 1— RAILROAD
—- CDNTDUR LINE Cug/kg>
(INTERVAL IS LOGARITHMIC)
FIGURE 5-3
ISOCONS OF MAXIMUM TCE
VALUES FOR SOIL BORINGS
IN LAGOON AREA
CARRIER SITE
16
-------
FIGURE 5-4
MONITORING WELL LOCATIONS
ONSITE
CARRIER SITE
-------
CDLLIERVILLE SITE
FIGURE 5-5
MONITORING WELL LOCATION:
OFFSITE
CARRIER SITE
18
-------
360
350
340
330
320
310-j
t
300
U
I 29°
I e8°H
5 27
C
s 260 H
§
5 250
i
340-
230 -
330-
310-
200
190
SOUTHEAST
NQRTHVF.ST
WAUR
VCRTICAL LEAKAGE
> 1,300 GAL/DAr/ACRE
t*OJJ ttCtlDN LKAltW
FIGURE 5-6
FATE AND TRANSPORT MECHANISMS
CARRIER SITE
19
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ROD
Carrier A.C. Site
Page 20
groundwater as seen in results of the RI. Due to the immediate response and removal of soils
impacted from the 1985 spill, the spill area has not been included in the figure.
Vadose Zone
Soil boring demonstrates that TCE is migrating through the vadose zone. Residual solvent
remains adsorbed within the pore space of the soil particles as TCE migrates through the soil.
TCE migrates from soils through diffusion in the vapor phase and in the dissolved aqueous phase
from the infiltration and percolation of rainwater through soils.
Shallow Aquifer
Upon reaching groundwater, the further movement of TCE in the shallow aquifer correlates
closely with the structure of the underlying aquitard. Groundwater in the shallow aquifer moves
radially from a "structural high" in the Jackson Clay in the proximity of the former lagoon. The
Jackson Clay formation grades from this "high" to the south toward Nonconnah Creek, to the
southeast towards Byhalia Road, and generally to the west, along the western extent of the
Carrier property. There is some evidence of a slight grade to the north as well, in the vicinity
of the town wells and further north.
Advective transport of contaminants in the aqueous phase, from source areas around the main
plant and the former lagoon, follow natural shallow groundwater flow directions at the Site.
There is some evidence that groundwater in the upper aquifer flows only intermittently. This
is substantiated by the poor recharge to some of the shallow monitoring wells. Significant
amounts of groundwater may be present in localized depressions with very little lateral
movement except during high recharge periods. However, around contaminant source areas this
movement is generally to the southeast, along the top of the Jackson Formation.
The stratigraphic investigation clearly indicates that shallow groundwater movement to the south
and east will eventually migrate to an area in which the Memphis Sand aquifer and the shallow
aquifer unit are hydraulically connected.
Memphis Sand Aquifer
Flow direction in the Memphis Sand is to the northwest, as seen from potentiometric
measurements made during periods when the town wells were not pumping. TCE contamination
has been identified in the Memphis Sand in the southeast portion of the Site (MW-1, MW-1B,
and MW-4) and at the municipal wells.
The density of TCE in water at maximum water solubilities of less than 2 pg/t is not likely to
be sufficient to cause sinking of the plume. Therefore, movement of the contaminants to the
well field will be more directly dependent upon the pumping rates of the city well system and
resulting drawdown effects on the Memphis Sand aquifer.
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ROD
Carrier A.C. Site
Page 21
The results of the Site investigation suggest that other pathways also exist. Regional geologic
data suggest that recharge through the Jackson Clay is relatively low because of low clay
permeability across the unit. However, the aquifer pumping test conducted at the Site indicated
a potential for vertical leakage through this confining clay layer. The vertical leakage or
recharge rates range from 0.9 to 18.8 gallons per minute per acre. As determined in that aquifer
test, these rates suggest that leakage through the aquitard may be a potential pathway for TCE
to enter the Memphis Sand aquifer.
5.3 Treatability Study
As part of the RI a treatability study was conducted at the lagoon area to determine how
effective soil vapor extraction (SVE) would be for removing TCE and its degradation products
from onsite soils and shallow groundwater. The treatability study, also referred to as the North
Remediation System (NRS), has indicated that this technology is effective in removing
contamination in soils and shallow groundwater.
6.0 SUMMARY OF SITE RISKS
A baseline risk assessment (BRA) has been conducted for the Carrier Site, and the results are
presented in Section 8 of the RI report. The BRA was based on contaminated environmental
Site media as identified in the RI. It was conducted in order to provide an assessment of the
resulting impact to human health and environment if contaminated soils and groundwater at the
Site were not remediated.
The Carrier BRA concluded that the primary health risk posed by the Site is through ingestion
and inhalation of TCE and lead from untreated groundwater.
6.1 Contaminants of Concern
The selected contaminants of concern for Site soils and groundwater are shown in Table 6-1.
Seven major hazardous contaminant; were considered. Of these, trichloroethylene (TCE) and
dichloroethylene (DCE) were the most frequently detected and generally found at the highest
concentrations. Although TCE and DCE are the primary contaminants of concern, lead, zinc,
1,2-dichloroethane (DCA), tetrachloroethylene (PCE) and vinyl chloride were also included due
to their presence in one or more sample wells at an average concentration which equalled or
exceeded the current or proposed MCLs.
DCA, PCE and vinyl chloride have not been identified at a significant frequency in either
groundwater or soils. DCA and PCE are commonly associated with TCE because solvents are
rarely pure products and often contain a small residual amount of other chlorinated
hydrocarbons. Vinyl chloride is a common degradation product of TCE.
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ROD
Carrier A.C. Site
Page 22
No pattern of lead or zinc in groundwater was established in Site soils or groundwater. Lead
was not historically used onsite. The old lagoon area may be a potential source of zinc due to
the use of zinc phosphate on the Site and the discharge of zinc phosphate sludges to the lagoon.
However, the closure of the lagoon in 1980 appears to have removed these sludges and residual
concentrations are low. The high level of metals may be caused from a secondary effect of the
TCE contamination/degradation, except perhaps beneath the former lagoon. Degradation of
TCE may be lowering the pH causing the insoluble metal complexes to leach into groundwater.
Lead and zinc may also be attributed to naturally occurring levels and/or non Site-related
anthropogenic sources.
Contamination was not indicated in any surface water samples; therefore, this medium was not
further evaluated. Lead and zinc were detected in sediment samples and are included as
contaminants of concerns in Table 6-1.
6.2 Exposure Assessment
The objectives of the exposure assessment are to identify actual or potential exposure pathways;
characterize the potentially exposed populations; and to determine the extent of the exposure.
The results of the exposure assessment are combined with the chemical-specific toxicity
information to characterize the potential risks.
The Site is located near a state road in a developed community setting. The site exists in the
small and growing community of Collierville, Tennessee (pop. ~ 13000). With the current
strict zoning, the long-term future use of this Site would be for continued industrial use. The
Site is an operating facility and will continue to be so for the foreseeable future. Therefore, it
seems prudent to assume that direct and frequent contact by adults in an industrial setting will
continue to occur. The Site is fenced and secured. The occurrence of infrequent trespassers
would pose a likely current exposure scenario with direct exposure to the southern and western
portions of the Site. The nearest residential area is approximately 100' north of the Site
boundary adjacent to the Collierville municipal well field.
None of the nonpaved areas appear to receive heavy foot traffic or constitute obvious pathways
for routine exposure1. However, direct soil or dust contact could result in exposure to
trespassers and the workers onsite.
Irrigation from the shallow water bearing zone (thin, low yielding zone lying above the Jackson
Clay) is not feasible due to the poor production of this unit. Irrigation from the deeper aquifer
'Approximately 20% of the 190-acre Site is paved or covered by buildings. Approximately 50 to 60% of the
contaminant source areas are beneath paved or covered areas.
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ROD
Carrier A.C. Site
Page 23
TABLE 6-1
Contaminants of Concern by Environmental Media
Carrier Site
SOIL/SEDIMENT
TCE
DCE
Vinyl Chloride*
PCE
DCA
Lead
Zinc
GROUNDWATER
TCE
DCE
Vinyl Chloride*
PCE
DCA
Lead
Zinc
*Vinyl chloride was not detected on-site in any media at a significant frequency, but is
considered a common degradation product of TCE.
-------
ROD
Carrier A.C. Site
Page 24
system (the Memphis Sands) would be possible, but would not significantly contribute to overall
risk due to the following factors:
• The site is an operating industrial facility.
• The organic contaminants of concern have low bioconcentration factors (<50) and high
Henry's Law constants. The uptake by crops is expected to be minimal.
• The primary metals of concern are zinc and lead. Zinc is a trace element, and both are
not available to plants for uptake until soil levels reach > 50 ppm.
• Groundwater metals concentrations are not significantly above background
concentrations.
Surface waters do not exist onsite or adjacent to the Site with the exception of Nonconnah Creek
in which no water sample contamination was detected.
No significant direct inhalation exposure onsite is expected as a large portion of the contaminated
area is paved/covered. The unpaved areas of the Site are far less contaminated and are covered
by maintained vegetation (grasses and trees/shrubs). Soil contamination exists at the highest
levels at depths from one to five feet (subsurface vs. surface, 0-1 ')• These factors along with
the mild southeast inland climate (average wind speeds of 5-10 mph) contribute to insignificant
passive volatilization of Site contaminants. Also, the facility has an operating air permit which
allows approximately 200 tons of total VOCs per year to be emitted. The maximum combined
air stripper output annually has been estimated at <500 Ibs/year. Passive volatilization from
the Site would not contribute significantly to VOC air emissions or risk. Active volatilization
(such as soil gas vapor extractions) will be addressed in the Description of Alternatives and
Compliance with ARARs sections.
Shallow groundwater is not currently used for domestic purposes in the immediate area. The
shallow aquifer is classified as a Class mA aquifer. The nearest known municipal well is
located adjacent to the northwest corner of the Site. The deep groundwater flow is best
described as to the northwest (influenced by pumping). The Memphis Sand aquifer is classified
as a Class HA aquifer. Groundwater contaminant exposure was computed for current and future
use of water produced by the Memphis Sand aquifer. Current groundwater pathways exist for
local residents supplied by the Collierville municipal well system. Future exposure was assessed
via a hypothetical pathway involving residential wells screened in the Memphis Sands.
Groundwater contaminant ingestion and inhalation of volatilized groundwater contaminants were
considered to determine total exposure through the groundwater pathway. The maximum
concentration of each parameter observed in the untreated municipal well water was used to
compute current risk (conservative assumption). Future resident reasonable maximum exposure
(RME) concentrations were established by computing the 95% upper confidence limit mean for
each constituent of concern from wells screened in the Memphis Sand aquifer.
The highest groundwater concentrations onsite were generally observed in monitoring wells
located in the shallow water bearing zone (which is not used as a potable water source in the Site
vicinity). Actual current exposure to groundwater contaminants (through the municipal system)
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ROD
Carrier A.C. Site
Page 25
is minimized (or eliminated) by engineering controls (i.e. air stripping of municipal well water
prior to distribution). Volatile contaminant concentrations subsequent to the air stripping unit
are below MCLs. Use of the shallow water bearing zone and the Memphis Sand aquifer as a
potable water source is restricted by city and county ordinances. Both these ordinances control
and regulate the location and construction of wells in Collierville and Shelby County.
Current and future exposure pathways to hazardous substances associated with the Site include
direct soil contact via ingestion and dermal contact; and groundwater expsoure via
inhalation/bathing and ingestion (Table 6-2).
6.3 Toxicity Assessment
Seven contaminants have been positively identified and quantified at the Site. They are TCE,
DCE, PCE, DCA, vinyl chloride, lead and zinc. DCE exists in two isomeric forms, cis and
trans. Isolation of the two isomers in routine analytical determinations is difficult and subject
to error. Therefore DCE is usually reported as the total of all isomers. DCE is considered an
equivocal carcinogen. However, the two isomers do exhibit somewhat different toxicities.
Therefore, as a conservative approach, the more toxic of the two isomers is used in risk
assessment. In general, the cw-l,2-DCE isomer is considered the more toxic. A secondary
degradation product of TCE, vinyl chloride, has not been identified at the Site in any media at
significant frequencies or concentrations (four hits ranging from 1 to 8.51 ppb). Over a long
period of time, however, degradation of DCE to vinyl chloride has been known to occur. Zinc
and lead are the metals of concern at the Site, however, observed concentrations do not vary
significantly from background, and no Site-related source of lead has been established.
In addition to the potential toxicity of TCE and vinyl chloride, most of these substances can
produce systemic toxic responses at doses greater than an experimentally-determined threshold
level. The USEPA has derived Slope Factor2 and/or Reference Dose (RfD)3 values for these
substances for use in determining the upper bound level of cancer risk and noncancer hazard
from exposure to a given level of contamination (Table 6-3).
Drinking water standards (MCLs) have been established for some contaminants detected in
groundwater impacted by Site activities (Table 6-3). These contaminants include hazardous
substances identified as carcinogens and systemic toxicants in published research studies.
2Slope Factor. A plausible upper-bound estimate of the probability of an individual developing cancer as a result
of a lifetime of exposure to a particular level of a potential carcinogen.
^Reference Dose. EPA's preferred toxicity value for evaluating noncaicinogenic effects resulting from
exposures at Superfund sites. *See specific entries for chronic RfD, subchronic RfD, and developmental RfD. The
acronym RfD, when used without other modifiers, either refers genetically to all types of RfDs or specifically to
chronic RfDs. It never refers specifically to subchronic or developmental RfDs.
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ROD
Carrier A.C. Site
Page 26
TABLE 6-2
Potential Complete Exposure Pathways for
Risk Assessment Considerations
Carrier Site
Ingestion of and dermal contact with contaminated soil by on-site workers, trespassers
(e.g., children), and hypothetical, future, onsite residents.*
Ingestion of contaminated groundwater by current municipal water system users (before
treatment) and hypothetical, future residents obtaining their water from an on-site well
screened in the Memphis Sand aquifer."
Inhalation of chemical vapors emanating from contaminated groundwater during
showering by current municipal water system users (before treatment) and hypothetical,
future residents obtaining their water from an on-site well screened in the Memphis
Sand aquifer."
Exposure rates (GDI) for ingestion and dermal contact with contaminated soils by future child
residents were calculated to be (mg/kg-day) TCE = 4.8x10'*, DCE = 1.2x10"*, Pb = 1.9x10"*,
Zn = 8.2x10"*, and PCE = 1.8x10'7 d.SxIO"8 for carcinogenic effects). Appendix P of the Rl
contains calculations used to derive exposure concentrations (RMEs).
Exposure concentrations for chemical intakes for chemical intakes (ingestion and inhalation)
related to groundwater were determined as follows:
. Current Resident- maximum concentration detected (before treatment) in the Collierville
municipal well system water
Future Resident- 95% upper confidence limit mean contaminant concentration detected in
monitoring wells screened in the Memphis Sand aquifer
Current after treatment exposure/risk levels were not computed as contaminant concentrations in
treated municipal well system water are below analytical detection limits.
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ROD
Carrier A.C. Site
•Page 27
TABLE 6-3
Health-Based Values for Carcinogens (SF) and
Nonearenooens (HfD) and AAARs for
Oral Exposure to Contaminants of Concern
Carrier Site
Contaminant
Trichloroethytena (TCE)
1 ,2-Oichloroethene (DCE)
1,2-Dichloroethane (OCA)
Tetrachloroethene (PCE)
Vinyl Chloride
Lead
Zinc
(mg/kg-dayr1
1.1x10-"
NA
9.1x10J
5.1x10"'
1.9"
NA
NA
SF.. ._r •
(mg/kg-dayr1
0.017
NA
0.091
1.1x10"'*
1.8x10*
NA
NA
RfD
(mg/kg-day)
NA
0.01'
NA
0.01
NA
0.0004'
0.2V
Cancer
Weight of
Evidence
B,
0
B,
B,/C'
A
B,/C'
0
ARAR
(mg/l)
0.005
0.07"
0.005
O.OO5
0.002
0.015
5'
• Not on IRIS 4/91, based on USEPA, 54 & 1-86-046.
b Based on unit risk for drinking water (est. from CPF/RfD)
• Not on IRIS 4/91. based on USEPA, ECAO-CIN-P155
d Calculated unit risk based on 0.015mg/I action level (hazard index = 1) and ingestion rate of 2 liters/day and 70 kg average
body weight
• Not on IRIS 4/91. based on USEPA, AWQCD, 440/5-80-079 (2° MCU
' Not yet determined or being reconsidered
« HEAST, 1/91
" Inhalation Unit Risk assuming IR. = 15mJ/day; BW=70 kg.
NA = Not applicable or not determined (pending)
Cancer Weight of Evidence
A = Human Carcinogen
B2 = Probable Human Carcinogen- sufficient evidence in animals and inadequate or no evidence in humans.
C = Possible Human Carcinogen
D = Not Classifiable as to Human Carcinogenicity
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ROD
Carrier A.C. Site
Pag<5 28
Critical studies used in their toxicity classification by the USEPA are shown in the Integrated
Risk Information System (IRIS) data base. These standards are considered as ARARs for the
surface and groundwater at the Site. They are considered as "Relevant and Appropriate11 since
the Memphis Sands aquifer is currently used as a domestic water supply. A copy of the IRIS
database outputs for each parameter are included as Appendix Q of the RI.
6.4 Risk Characterization
Site soil contaminants are not uniformly distributed over the surface, but exist in areas of
varying concentrations. This pattern of contaminant distribution was managed for risk
assessment purposes by considering the risk from exposure to the unpaved/uncovered portions
of the Site which have shown soil contamination in the upper five feet of soil. Conservative
estimates based on the total area of the Site which has surface contamination were used to assess
current adult worker exposure to volatile contaminants of concern. The entire
unpaved/uncovered area of the Site was used to assess the risk to adult workers posed by lead
and zinc in the Site surface soils. In both instances, the workers were assumed to contact the
Site uniformly. To assess the risk posed by the Site to future child residents, it was assumed
that the entire Site will be unpaved and uncovered, and that all potential ingestion and dermal
contact exposures would occur within the contaminated surface soil zones. The mean
concentration of a contaminant found in samples collected in the upper five feet of soil was
considered as the exposure level (for both ingestion and dermal contact scenarios).
The result of the risk calculation for the major soil contaminants, using the above stated
assumptions, are shown in Tables 6-4 and 6-5. In Table 6-4, the risk to workers from the major
contaminants of concern is shown. In Table 6-5, the risk to future child residents is shown.
Since the risk values represent a fraction of time exposed uniquely to a contaminant in the
contaminated areas, the sum of these risk values (5.2xlQ7) approximates the child's upper bound
risk. This value does not represent the total risk from the Site since neither 100% of a future
child resident's onsite time nor exposure to all Site contaminants is accounted. However, the
remaining unaccounted risk is presumed to represent an insignificant additional risk. Vinyl
chloride has been determined to pose little or no current risk to human health due to the
infrequency of detection and low concentrations identified.
These data indicate that exposure to contaminated surface soils does not pose an upper bound
risk level greater than the 10* point of departure for current Site workers or future children
onsite.
The Hazard Index values as shown (Tables 6-4 and 6-5) indicate that onsite exposures would not
result in noncancer toxicity to the current adult workers or future child residents onsite. As a
result, lead and zinc are not considered to pose a significant health risk from the standpoint of
soil ingestion or dermal contact.
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ROD
Carrier A.C. Site
Page 29
TABLE 6-4
Summary of Risks for Adult Workers from Oral
and Dermal Exposure to Contaminants in Soil
Carrier Site
Soil Contaminant Level
(mg/kg)'
35
0.077
0
0
0.011
12°
51'
Contaminant
TCE
1,2-DCE
Vinyl Chloride
DCA
PCE
Lead
Zinc
Upper Bound Risk Level"
(or Hazard Index)
l.OxlO-7
ffl=7.2xlO*
0°
0
1.5x10-'°
ffl= 1.0x10-"
m=2.8xio-2
HI=2.3xlO-'
Upper bound Sum cancer risk = l.OxlO"7
Upper bound Sum hazard indices = 0.028
* X concentration in all soils within surface contaminated areas (90-95% C.L. was not calculated as the data
are not normally distributed); for metals X concentration assumed to be in all unpaved/uncovered site soils.
TCE and 1,2-DCE concentrations are the means for all samples collected at depths of 0 to 5 feet, including
screening data from Phase I (see Appendix P).
" HI (Hazard Index) of > 1 are a cause for concern. Upper bound risk levels of 10"4 to 10"* are considered
on a case-by-case basis as to their acceptability by the USEPA.
° Approximately 89 ppm of vinyl chloride in soil at this site with these assumptions would equal 1x10* risk
level.
d Tetrachloroethene (PCE) was identified in one soil sample.
Lead and zinc concentrations for all samples collected from within five (5) feet of ground surface were used
to compute mean values.
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TABLE 6-5
Summary of Risks for Potential Future Child Residents from
Oral and Dermal Exposure to Contaminants in Soil
Carrier Site
Soil Contaminant Level
(mg/kgr
35'
0.077"
0
12'
0
0.011
51'
Contaminant
TCE
1,2-DCE
Vinyl Chloride
Lead
DCA
PCE
Zinc
Upper Bound
Risk Level"
(or Hazard Index)
5.2x1 07
81 = 6.1x10*
Oe
HI = 1.9x10-'
0
HI = 1. 7x10*
HI =3.9x1 O3
Upper bound I cancer risk = 5.2x10"7g
*X concentration in all site soils within five (5) feet of ground surface where TCE and/or DCE has been
identified; assume 100% of Future Child Resident soil exposure is in contaminated area on-site
"HI (Hazard Index) of >1 are a cause for concern. Upper bound risk levels of 10"* to 10"* are
considered on a case-by-case basis as to their acceptability by the USEPA.
°1x10'fl risk (with these assumptions) in soil -150 ppb vinyl chloride
"Lead is not bioavailable to humans below approximately 200 ppm in soils. The USEPA has
recommended a soil lead level of 500 to 1,000 ppm at NPL sites (to protect from direct contact and
ingestion). A site-specific lead exposure model is currently being tested by the USEPA (USEPA/ECAO
6/91, personal conversation with Dr. Harlal Choudhury)
TCE and 1,2-DCE data from samples collected prior to the initiation of the Remedial Investigation were
included. Below detection limit results were not used in the calculation of means.
'Lead and zinc concentrations for all samples collected from within five (5) feet of ground surface were
used to compute mean values.
•Example calc. are the same as Figure 8-2b except child assumptions (Figure 8-3) were used.
NOTE: It was assumed that in the future the entire site will be unpaved and uncovered.
The shallow water bearing zone is not currently used as a source or potable water nor is it anticipated
to be used as a potable source in the future. Therefore, it was not considered a viable future exposure
pathway.
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Table 6-6 shows that, assuming worst-case conditions, Site groundwater may pose a significant
carcinogenic and non-carcinogenic risk to current-and future residents. The upper bound cancer
risk to current residents posed by the groundwater exposure pathway is 2.5x10"*. The Hazard
Indices for lead and zinc are 3.2 and 0.87, respectively, under the current resident scenario.
The lead value indicate that a non-carcinogen risk may be posed to current residents. Maximum
contaminant concentrations in untreated Collierville municipal well system water were used to
compute current risk (and hazard indices).
The upper bound cancer risk to future Site residents from the groundwater exposure pathway is
4.7x10"*. The hazard indices for DCE, lead and zinc are 0.33, 4.1, and 0.82, respectively,
under the future resident scenario. The contaminant concentrations (Reasonable Maximum
Esposure (RME)) used to compute risk (and Hazard Indices) to future Site residents were the
95% upper confidence limit mean values for all deep monitoring wells computed over three
quarterly sampling periods. As a result, the risk levels computed are highly conservative
estimates.
It is worthy of mention that lead concentrations (which pose the primary non-carcinogenic risk)
observed in the Memphis Sand monitoring wells are not significantly different than those
observed in background wells. The 95 % upper confidence limit mean for lead in wells CMW-
001 and CMW-002 (background wells) over the same monitoring period was 0.061 mg/L (versus
0.060 mg/L in the Memphis Sand wells). The maximum concentration of lead observed in
untreated municipal well system water was 0.045 mg/L (over the same sampling period). As
a result, the Hazard Indices computed for lead (under current and future exposure scenarios)
may not be directly attributable to the Site, and may result from natural lead content of the
aquifer material or non Site-related anthropogenic sources. Appendix P of the RI provides data
tables and statistics used to establish RMEs as well as background well 95% upper confidence
limit determinations. Although metal concentrations are variable and sometimes high in
background wells, the range of concentrations are higher onsite. The higher concentrations may
be a secondary effect of the TCE contamination/degradation which may be lowering the
pH,leaching otherwise insoluble metal complexes into groundwater.
The shallow water bearing zone is not currently used as a source of potable water nor is it
anticipated to be used as a potable source in the future. Therefore, it was not considered a
viable future exposure pathway.
The Memphis Sand aquifer which lies below the shallow water bearing zone (separated by the
Jackson Clay unit) is used as a potable water source for the Town of Collierville. Engineering
controls (i.e. air stripper) are currently in place on the Collierville municipal well system to
remove contaminants prior to distribution. As a result, actual current resident exposure to
groundwater contaminants is negligible.
In light of the current and potential future groundwater uses, efforts should be made to preclude
the migration of volatile contaminants from the shallow water bearing zone to the Memphis
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Compound
TCE
OCE
OCA
PCE
Vinyl
Chloride
Lead
Zinc
TABLE 6-«
Current and Future Reeidem
Ds-act In0e*tion and Inhalation Groundwatar Pathway Rick
Carrier Sit*
SF_
(ma/kg-day) '
0.011
NA
0.091
0.051
1.9
NA
NA
SFu**.
(mg/ko-dayr1
0.017
NA
0.091
1.1x10'18
1.8x-*
NA
NA
RfD
(mg/kg-day)
NA
0.01
NA
0.01
NA
0.0004
0.21
Currant
Resident
RME (pprn)
0.29
0*
0*
0*
0*
0.045*
6.68
Future
rtoaJdant
RME (ppml
0.53
0.117
0*
0*
0*
0.060*
6.3
Currant Riek
(Hazard Index)
4.7x10"*
NA
NA
NA
NA
HI =3.2
0.87
Future Risk
(Hazard Index)
2.5x1 0-1
Hl=0.33
NA
NA
NA
Hl=4.1
0.82
Upper Bound Sum of cancer risk: Current Residents = 2.5 x 10~*
Future Residents = 4.7 x 10"*
Upper Bound Sum of hazard indices Current Residents = 4.07
Future Residents = 5.3
Notes:
NA = Not Applicable
RME = The highest exposure that is reasonable expected to occur at a Site.
* indicates that the compound was not identified in samples collected from the subject wells.
* not significantly elevated above background well concentrations (see Appendix P)
Cancer Risk Formula:
Risk = [contaminant! x EF x ED x HSF. x K x IR.1 + (SF. x IR-11
BW x AT x 365 days/year
Non-Carcinogenic Risk (Hazard Index) Formula:
Hazard Index = [contaminant! x IR_ x EF x ED -f [contaminant! x K x IR. x EF x ED
RfD. x BW x AT x 365 days/year RfD, x BW x AT x 365 days/year
Where:
BW = Body Weight - 70 kg; AT - Averaging Time = 70 years
EF = Exposure Frequency = 350 days/yean ED •> Exposure Duration » 30 years
SF. = Inhalation elope factor = chemical-specific; SF. = Oral slope factor => chemical-specific
K = volatilization factor = 0.0005 x 1000 Urn*; IR. = daily indoor inhalation rate -15 mVday
IR. = daily water ingeation rate = 2 L/day; RfD. = oral reference dose = chemical-specific
RfDj = inhalation reference dose = chemical-specific
Risk (hazard index) formulae ware obtained from USEPA'a Risk Assessment Guidance for Superfund, Volume I, Parts A & B.
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Sands in order to maintain (and over time enhance) the quality of the Memphis Sand aquifer.
6.5 Soil Cleanup Goals for Groundwater Protection
USEPA's Center for Environmental Assessment Modeling (CEAM) provided their Exposure
Assessment Multimedia Model (MultiMed) for application at the Carrier A.C. Site. The model
was used in conjunction with traditional contaminant mass partitioning formulae to determine
the soil cleanup goals necessary for protection of Memphis Sands aquifer quality.4 Based on
Site-specific soil and hydrogeologic conditions, a soil cleanup goal of 533 ng/kg TCE was
determined to be protective of the Memphis Sand aquifer. The goal is applicable to the
contaminant source areas ("hot spots") previously discussed. Remedial efforts need only focus
on a limited portion of the Site as soil contaminants are restricted to approximately 20% of the
total Site area.
All discussions regarding MultiMed input variable selection, model outputs and soil cleanup goal
calculations are provided in Appendix R of the RI.
6.6 Ecological Considerations
No U.S. Dept. of Interior or State of TDEC lands or federally listed endangered species of
wildlife were identified at the Site. The nature of the Site is such that avian or terrestrial
wildlife would not be drawn to the Site. A surface water quality assessment and a biological
impact assessment were conducted. The assessments included a quantitative study of benthic
species diversity in Nonconnah Creek, and a qualitative review of sensitive and endangered
species typical of southeastern Shelby County. Data to date indicate no significant adverse
ecological impacts from the present soil or groundwater contamination This preliminary survey
does not rule out ecological impacts to aquatic and terrestrial species through contaminated food
chain mechanisms. However, TCE is not biocumulative and as a result, it is not expected to
cause deleterious food chain effects based on currently available data.
6.7 Risk Uncertainty
There is a generally recognized uncertainty in human risk values developed from experimental
data. This is primarily due to the uncertainty of data extrapolation in the areas of (1) high to
low dose exposure, (2) modeling of dose response effects observed, (3) route to route
extrapolation, and (4) animal data to human experience. The Site-specific uncertainty is mainly
in the degree of accuracy of the exposure assumptions.
In the presence of such uncertainty, the USEPA and the risk assessor have the obligation to
'Contaminant partitioning equations from USEPA's Determining Soil Response Action Levels Based on Potential
Contaminant Migrations Groundwater: A Compendium of Examples, USEPA, OERR, EPA/540/2/89/057, October
1989.
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make conservative assumptions such that the chance is very small for the actual health risk to
be greater than that determined through the risk process. On the other hand, the process is not
to yield absurdly conservative risk values that have no basis in reality. That balance was kept
in mind in the development of exposure assumptions and pathways and in the interpretation of
data and guidance for this baseline risk assessment.
Actual or threatened releases of hazardous substances from this Site, if not addressed by
implementing the response action selected in this ROD, may present an imminent and substantial
endangerment to public health, welfare, or the environment.
7.0 DESCRIPTION OF REMEDIAL ALTERNATIVES
The following remedial alternatives were selected for evaluation:
• Alternative 1: No-Action
• Alternative 2: North Remediation System (NRS); Groundwater Containment/Treatment at
Water Plant 2
• Alternative 3: NRS and Plant Area Soil Vapor Extraction (SVE); Groundwater
Containment/Treatment at Water Plant 2
• Alternative 4: NRS and Plant Area SVE; Groundwater Containment/Treatment at Water Plant
2, and Supplemental Extraction Well(s) via (a) Air Stripping, or (b)
UV/Oxidation
• Alternative 5: Plant Area Soil Excavation/Low Temperature Thermal Desorption (LTTD),
NRS and Plant Area SVE; Groundwater Containment/Treatment at Water
Plant 2
• Alternative 6: Plant Area Soil Excavation/LTTD, NRS and Plant Area SVE; Groundwater
Containment/Treatment at Water Plant 2, and Supplemental Extraction Well(s)
via (a) Air Stripping, or (b) UV/Oxidation
Common Features of the Alternatives
Institutional Controls
All alternatives, except No Action, include institutional controls such as deed restrictions, local
ordinances or record notices applied as appropriate for long-term management and prevention
of exposure to contaminants.
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Groundwater Residuals
Excluding No Action, all the alternatives generate a groundwater stream which must be
discharged. The route of discharge may be release to the local POTW, surface water, the Town
of Collierville water supply, or back to Site groundwater by reinjection. EPA will select the
discharge route. The selection is subject to the ability of each alternative to meet ARARs, and
is discussed in text describing each alternative.
Soils Residuals
Alternatives 5 and 6 require that soils be excavated prior to treatment. EPA will select the
disposal route for the treated soils. Disposal may be offsite, or onsite, and subject to RCRA
land disposal restrictions if the soils are hazardous waste. Delisting may be required if the soils
are deemed RCRA-listed wastes, and onsite use as fill is chosen as the ultimate disposition. If
offsite disposal is chosen, the waste must meet treatment standards prior to disposal in a
permitted RCRA facility.
Site Monitoring
While wastes remain at the Carrier A.C. Site, CERCLA requires that monitoring data collected
from the Site be evaluated every five years. This evaluation would include spatial and temporal
analysis of existing data to determine increasing, decreasing, or stationary trends in contaminant
concentrations. The results of this evaluation would be used to reassess the need to maintain,
increase or decrease the number and types of samples and analysis required for monitoring, and
the need to change the remedial response at the Site.
Existing Controls
The Town of Collierville's Water Plant No. 2 essentially contains groundwater contaminants in
the Memphis Sand, and controls exposure to contaminants through treatment. The plant includes
two extraction wells with 5-foot diameter air strippers (treatment capacity is 1.4 MGD) to
remove TCE and other VOCs from groundwater to a level below 1 /tg/f. In order for this
treatment system to contain groundwater contaminants, the Town of Collierville wells must
pump without interruption.
In addition to the Memphis Sand groundwater containment and treatment afforded by continued
operation of Water Plant 2, a remediation system is in place, as a result of the treatability study,
at the former lagoon, referred to as the North Remediation System (NRS). This equipment was
installed to dewater and extract Site contaminants from soils impacted by the former lagoon by
soil vapor extraction (SVE).
In the following alternative descriptions, although all constituents of concern must be considered,
TCE will drive remedial efforts. Lead in Memphis Sand groundwater poses significant potential
acute health risk in the worst-case scenarios presented in the Baseline Risk Assessment.
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Elevated lead levels have not been observed routinely in the Memphis Sand groundwater at
Water Plant 2, nor anywhere in the Collierville drinking water system. For this reason the
following proposed remedial alternatives do not explicitly include lead removal actions. This
in no way changes the need for alternatives to comply with ARARs, including chemical-specific
requirements for metals.
7.1 Alternative 1: No Action
CERCLA requires that the "No Action" alternative be considered at every site against which the
other alternatives are evaluated. Under this alternative no action would be taken. Operation of
the two air strippers at Water Plant 2 and the NRS would be discontinued.
The only reduction of contaminant levels in Site soils and groundwater would occur through
natural processes. The time for groundwater levels to drop below SDWA regulations is on the
order of 2000 years. This alternative leaves the volume of hazardous substances unchanged, and
the potential increase in volume of impacted environmental media - groundwater. Without
treatment or containment, residual upper-bound risk associated with groundwater exposure is in
the range 2.5 x 104 to 4.7 x 104.
Selected Site groundwater monitoring wells and soil spaces would be sampled for volatile
organic compounds and metals. Because contaminated soils and groundwater would remain in
place, untreated, at the Site, CERCLA requires that data be collected and evaluated at least
every five years to assure that a selected remedy continues to be protective of human health and
the environment. Based upon the findings of the review, EPA may determine other studies
and/or actions should be taken.
This alternative would not comply with the Safe Drinking Water Act (SDWA) regulations or
EPA's Groundwater Protection Strategy.
This alternative has no capital costs. The approximate costs for the monitoring program is
$410,000 per five year sampling event, and $50,000 annually for quarterly groundwater
sampling and analysis, yielding an approximate present worth from $1,437,223 to $2,180,152.
The present worth analysis is based upon a 30-year life and a 5 percent discount rate.
7.2 Alternative 2: North Remediation System (NRS); Groundwater
Containment/Treatment at Water Plant 2
The major features of this alternative include soil vapor extraction in the former lagoon area,
also referred to as the North Remediation System (NRS). Approximately 8500 cubic yards of
TCE and its degradation products would be addressed by the NRS. Also, the town wells at
Water Plant 2 would continue to operate to provide containment and treatment (air stripping) of
Memphis Sands groundwater contaminated with TCE and its degradation products.
Modeling runs and indications from RI data point toward the conclusion that operation of the
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town well field has essentially contained the plume. This information is not conclusive and thus
makes any assessment of overall protection somewhat uncertain, until additional Memphis Sands
aquifer testing is performed duirng Remedial Design (RD). Also, contamination will continue
to enter the Memphis Sand aquifer at the southern end of the Site and will remain in the Sand
for some years until extracted at Water Plant 2.
The amount of contaminated soils that would be treated in the lagoon area was determined using
fate and transport modeling to estimate the potential groundwater contamination. Transport
modeling calculations indicate that at an average concentration of about 533 /xg/kg TCE at the
existing source areas would no longer yield leachate which would contaminate Memphis Sand
groundwater above 5 pg/t for TCE. Approximately 68,000 cubic yards of contaminated soils
which are a significant source of current and potential future contamination of the Memphis Sand
aquifer would be left untreated. Although some native microbial degradation has occurred, it
is not likely that natural attenuation will reduce residual TCE contamination to the level
estimated to be protective of the Memphis Sand in a timely manner (over a period on the order
of 2000 years).
The treated water from the air strippers would remain a significant supply for the Town of
Collierville. Both air stripping and SVE volatilize contaminants to an air stream. Due to the
low volumes of air emissions, no off-gas controls would be necessary.
The Memphis Sands groundwater would eventually be treated to levels below SDWA
regulations, but would not comply with the EPA's Groundwater Protection Strategy. This
alternative would comply with federal and state Clean Air Act (CAA) standards.
Selected Site groundwater monitoring wells and soil would be sampled for volatile organic
compounds and metals. A review of data collected at the Site would be evaluated at least every
five years during the remedial action or until contaminant concentrations in groundwater no
longer exceed SDWA regulations or soil cleanup levels. The evaluation would continue until
completion of the groundwater remedial action and would serve to indicate whether cleanup
levels have been or will be attained. Based upon the findings of the review, EPA may determine
other studies and/or actions should be taken.
The estimated capital cost of Alternative 2 is in the range of $1,052,935 to $1,133,199 while
the associated Operations & Maintenance (O&M) and monitoring costs is $2,931,647. The
estimated present worth cost is in the range $2,968,754 to $4,064,847. The estimated present
worth analysis is based upon a 30-year life and a 5% discount rate.
7.3 Alternative 3: NRS and Plant Area Soil Vapor Extraction (SVE); Groundwater
Containment/Treatment at Water Plant 2
This alternative treats TCE contaminated soil by soil vapor extraction at both the former lagoon
area and the plant spill areas (volumes of approximately 8,500 cubic yards, and 68,000 cubic
yards, respectively) and continued operation of Water Plant 2 affords containment and treatment
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(air stripping) of the Memphis Sand groundwater.
Modeling runs and indications from RI data point toward the conclusion that operation of the
Town well field has essentially contained the TCE plume. This information is not conclusive
and thus makes any assessment of overall protection somewhat uncertain, until additional
Memphis Sands aquifer testing is performed during RD. Also, TCE will continue to enter the
Memphis Sand aquifer at the southern end of the Site until the Plant Area SVE is implemented,
and will remain in the Memphis Sand until extracted at Water Plant 2. Containment at Water
Plant 2 would be continued up to 30 years.
The locations and number of SVE wells in the main plant area depends upon the area! extent of
contamination, area of influence produced by each well, and the variability in pneumatic
permeability around the plant area. Some pilot-scale treatability work would likely be needed
to complete the design of SVE implementation near the manufacturing plant.
The amount of contaminated soils that would be treated in the lagoon and main plant areas was
determined using fate and transport modeling to estimate the potential groundwater
contamination. Transport modeling calculations indicate that an average concentration of
533 /ig/kg TCE at the existing source areas will no longer yield leachate which would
contaminate Memphis Sand groundwater above 5 pg/t for TCE. Long-term benefits of this
alternative would include permanent reduction in toxicity and volume of soil contamination. The
estimated time for SVE to remediate the lagoon and main plant areas is three to five years.
The treated water from the air strippers would remain a significant supply for the Town of
Collierville. Both air stripping and SVE volatilize contaminants to an air stream. Vapor-phase
Granular Activated Carbon (GAC), thermal treatment, or photolytic oxidation would be used to
control off-gas emissions if during Remedial Design/Remedial Action (RD/RA) it is determined
necessary. Photolytic oxidation, although promising, is a relatively new technology and would
require a pilot-scale treatability study.
The Memphis Sands groundwater would be treated to levels below SDWA regulations. This
alternative would comply with federal and state CAA standards. All activities would comply
with Occupational Safety and Health Act (OSHA) health and safety requirements. A small
portion of the Site is situated in a 100-year floodplain and wetlands area. Any remedial activity
or construction in the floodplain and wetland areas would comply with the Clean Water Act
(CWA) Wetlands Regulations and the Wetlands Protection and Floodplain Management Policies.
Also, Resource Conservation and Recovery Act (RCRA) Subtitle C and Department of
Transportation (DOT) requirements for hazardous waste generation, transportation, storage, and
disposal of hazardous waste would be applicable for this alternative. Hazardous waste soils from
drilling, and spent GAC, if used, would be stored and transported to approved disposal facilities
in accordance with RCRA Subtitle C and DOT requirements.
Selected Site groundwater monitoring wells and soil would be sampled for volatile organic
compounds and metals. A review of data collected at the Site would be evaluated at least every
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five years during the remedial action or until contaminant concentrations in groundwater no
longer exceed SDWA regulations or soil cleanup levels. The evaluation would continue until
completion of the groundwater remedial action and would serve to indicate whether cleanup
levels have been or would be attained. Based upon the findings of the review, EPA may
determine other studies and/or actions should be taken.
The estimated capital cost for this alternative is in the range of $1,742,400 to $2,102,512 while
the associated costs for O&M and monitoring are $5,349,263. The estimated present worth
costs are in the range $5,468,140 to $7,451,775. The estimated present-worth analysis is based
upon a 30-year life and a 5% discount rate.
7.4 Alternative 4: NRS and Plant Area SVE; Groundwater Containment/Treatment at
Water Plant 2, and Supplemental Extraction Well(s)/Treatment via (A) Air Stripping,
or (B) UV/Oxidation
This alternative includes remediation of TCE contaminated soil by SVE in the former lagoon
(NRS) and plant spill areas. Approximately 76,500 cubic yards of contaminated soils would be
treated. Also included would be groundwater containment, treatment (air stripping), and
disposal. The groundwater containment currently provided by the operation of Water Plant 2
extraction wells would be supplemented by additional extraction well(s).
Alternative 4 differs from alternative 3 in the manner that groundwater containment will have
greater assurance. Groundwater in the Memphis Sand would continue to receive TCE
contamination until the SVE could be implemented. The supplemental groundwater extractions
included with this alternative would minimize the extent of Memphis Sand degradation that
occurs in this interim period. Groundwater actions are expected to be effective, although
additional information must be obtained during Remedial Design (RD) to determine the
configuration and number of supplemental extraction wells required to meet effectiveness levels.
The fact that additionally-extracted groundwater will require treatment opens the following two
treatment options: (A) air stripping and (B) innovative UV/oxidation. Operation of the air
stripping system at Water Plant 2 will continue. An additional treatment unit will be required
under this scenario to handle the added water from the supplemental extraction.
The locations and number of SVE wells in the main plant area depends upon the area! extent of
contamination, area of influence produced by each well, and the variability in pneumatic
permeability around the plant area. Some pilot-scale treatability work would be needed to
complete the design of SVE implementation near the manufacturing plant.
The amount of contaminated soils that would be treated in the lagoon and main plant areas was
determined using fate and transport modeling to estimate the potential groundwater
contamination. Transport modeling calculations indicate that an average soil concentration of
533 /ig/kg TCE at the existing source areas will no longer yield leacbate which would
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contaminate Memphis Sand groundwater above 5 /xg/f for TCE. Long-term benefits of this
alternative would include permanent reduction.uuoxicity and volume of soil contamination. The
estimated time for SVE to remediate the lagoon and main plant areas is three to five years.
The treated water from the supplemental extraction well(s) will be released to surface water,
reinjected to the Memphis Sand, or distributed to the Town of Collierville drinking water supply
as with Water Plant 2. The Town of Collierville Public Works has stated a preference for the
use of treated water as an additional drinking water supply, because Collierville's water demand
is increasing along with its population.
Both air stripping and SVE volatilize contaminants to an air stream. Vapor-phase Granular
Activated Carbon (GAC), thermal treatment, or photolytic oxidation would be used to control
off-gas emissions if during Remedial Design/Remedial Action (RD/RA) it is determined
necessary. Photolytic oxidation, although promising, is a relatively new technology and would
require a pilot-scale treatability study. UV/oxidation does not require air pollution control
equipment or associated testing. Bench-scale testing would be required prior to UV/oxidation
design to determine optimum operating parameters.
The Memphis Sands groundwater would be treated to levels below SDWA regulations, CWA
Discharge Limitations and Pretreatment Standards, CWA Wetlands Regulations, SDWA
Underground Injection Control Program, and/or the Tennessee Water Quality Act. This
alternative would comply with federal and state CAA standards. All activities would comply
with OSHA health and safety requirements. A small portion of the site is situated in a 100-year
floodplain and wetlands area. Any remedial activity or construction in the floodplain and
wetland areas would comply with the CWA Wetlands Regulations and the Wetlands Protection
and Floodplain Management Policies. Also, RCRA Subtitle C and DOT requirements for
hazardous waste generation, transportation, storage, and disposal of hazardous waste would be
applicable for this alternative. Hazardous waste soils from drilling, and spent GAC, if used,
would be stored and transported to approved disposal faculties in accordance with RCRA
Subtitle C and DOT requirements.
Selected Site groundwater monitoring wells and soil would be sampled for volatile organic
compounds and metals. A review of data collected at the Site would be evaluated at least every
five years during the remedial action or until contaminant concentrations in groundwater no
longer exceed SDWA regulations or soil cleanup levels. The evaluation would continue until
completion of the groundwater remedial action and would serve to indicate whether cleanup
levels have been or would be attained. Based upon the findings of the review, EPA may
determine that other studies and/or actions should be taken.
The estimated capital cost for Alternative 4(A) is in the range of $1,900,260 to $2,443,431 while
the associated costs for O&M and monitoring are $5,489,334. The estimated present worth
costs are in the range $5,717,755 to $7,932,765.
The estimated capital cost for Alternative 4(B) is in the range of $2,007,540 to $2,578,163 while
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the associated costs for O&M and monitoring are $5,839,513. The estimated present worth
costs are in the range $6,054,423 to $8,417,675.
The estimated present-worth analyses is based upon a 30-year life and a 5% discount rate.
7.5 Alternative 5: Plant Area Soil Excavation/Low Temperature Thermal Desorption
(LTTD), MRS and Plant Area SVE; Groundwater Containment/Treatment at Water
Plant 2
Alternative 5 includes excavation, low temperature thermal desorption (LTTD) and SVE for
source remediation. Shallow source area soils (approximately 52,000 cubic yards contaminated
with TCE at greater than the 533 f*g/kg threshold for protection of Memphis Sand groundwater)
would be excavated and backfilled with clean native soil. SVE would then be used to remediate
deeper contamination where excavation of about 16,300 cubic yards is less readily implemented,
and permeability is expected to be greater than in the lagoon area. The NRS would also be
operated to reach soil remedial levels at the former lagoon source area, involving about 8500
cubic yards, the top 15 feet of which may be excavated and processed by LTTD, if needed.
Water Plant 2 operation would continue to contain and treat (air stripping) contaminated
groundwater. Modeling runs and indications from RI data point toward the conclusion that
operation of the Town well field has essentially contained the TCE plume. This information is
not conclusive and thus makes any assessment of overall protection somewhat uncertain, until
additional Memphis Sands aquifer testing is performed. Also, TCE will continue to enter the
Memphis Sand aquifer at the southern end of the Site until the Plant Area SVE is implemented,
and will remain in the Memphis Sand until extracted at Water Plant 2. Containment at Water
Plant 2 would be continued for up to 30 years.
All soil contaminated above 533 pg/kg TCE would be excavated to a depth of approximately 15
feet, sampled, analyzed and stockpiled for LTTD processing. After soil excavation is completed
and the cells are backfilled with clean native soil, SVE will be implemented to remediate soils
which exceed the soil cleanup level at depths greater than 15 feet.
Effectiveness of excavation and LTTD is expected to be very high for the source soils. LTTD
off-gas would be treated with a cyclone separator, a baghouse, and an afterburner. The
afterburner would be located either upstream or downstream of the baghouse.
The locations and number of SVE wells in the lagoon and main plant areas depend upon the
area! extent of contamination, area of influence produced by each well, and the variability in
pneumatic permeability around the plant area. Some pilot-scale treatability work would likely
be needed to complete the design of SVE implementation near the manufacturing plant.
The amount of contaminated soils that would be treated in the lagoon and main plant areas was
determined using fate and transport modeling to estimate the potential groundwater
contamination. Transport modeling calculations indicate that an average concentration of
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533 tig/kg TCE at the existing source areas would no longer yield leachate which would
contaminate Memphis Sand groundwater above 5 fig/t for TCE. Long-term benefits of this
alternative would include permanent reduction in toxicity and volume of soil contamination. The
estimated time for LTTD and SVE to remediate the lagoon and main plant areas is two to three
years.
The treated water from the air strippers would remain a significant supply for the Town of
Collierville. Both air stripping and SVE volatilize contaminants to an air stream. Vapor-phase
Granular Activated Carbon (GAC), thermal treatment, or photolytic oxidation would be used to
control off-gas emissions if during RD/RA it is determined necessary. Photolytic oxidation,
although promising, is a relatively new technology and would require a pilot-scale treatability
study.
The Memphis Sands groundwater would be treated to levels below SDWA regulations. This
alternative would comply with federal and state CAA standards. All activities would comply
with OSHA health and safety requirements. A small portion of the site is situated in a 100-year
floodplain and wetlands area. Any remedial activity or construction in the floodplain and
wetland areas would comply with the CWA Wetlands Regulations and the Wetlands Protection
and Floodplain Management Policies. Also, RCRA Subtitle C and DOT requirements for
hazardous waste generation, transportation, storage, and disposal of hazardous waste would be
applicable for this alternative. Hazardous waste soils from drilling, and if used, spent GAC,
would be stored and transported to approved disposal facilities in accordance with RCRA
Subtitle C and DOT requirements.
Selected Site groundwater monitoring wells and soil spaces would be sampled for volatile
organic compounds and metals. A review of data collected at the Site would be evaluated at
least every five years during the remedial action or until contaminant concentrations in
groundwater no longer exceed SDWA MCLs and/or MCLGs or soil cleanup levels. The
evaluation would continue until completion of the groundwater remedial action and would serve
to indicate whether cleanup levels have been or will be attained. Based upon the findings of the
review, EPA may determine that other studies and/or actions should be taken.
The estimated capital cost for this alternative is in the range of $5,688,540 to $8,579,136 while
the associated costs for O&M and monitoring are $5,437,347. The estimated present worth
costs are in the range $9,467,667 to $13,956,482. The estimated present-worth analysis is based
upon a 30-year life and a 5 % discount rate.
7.6 Alternative 6: Plant Area Soil Excavation/LTTD, MRS and Plant Area SVE;
Groundwater Containment/Treatment at Water Plant 2, and Supplemental Extraction
Well(s)/Treatment via (A) Air Stripping, or (B) UV/Oxidation
Alternative 6 includes excavation and low temperature thermal desorption (LTTD) and SVE for
source remediation. Shallow source area soils (approximately 52,000 cubic yards contaminated
with TCE at greater than the 533 pg/kg threshold for protection of Memphis Sand groundwater)
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would be excavated and backfilled with clean native soil. SVE would then be used to remediate
deeper contamination where excavation of about 16,300 cubic yards is less readily implemented,
and permeability is expected to be greater than in the lagoon area. The NRS would also be
operated to reach soil remediation levels at the former lagoon source area, involving about 8500
cubic yards, the top 15 feet of which may be excavated and processed by LTTD, if needed.
All soil contaminated above 533 fig/kg TCE would be excavated to a depth of approximately 15
feet, sampled, analyzed and stockpiled for LTTD processing. After soil excavation is completed
and the cells are backfilled with clean native soil, SVE will be implemented to remediate soils
which exceed the soil cleanup level at depths greater than 15 feet.
Effectiveness of excavation and LTTD is expected to be very high for the source soils. Off-gas
would be treated with a cyclone separator, a baghouse, and an afterburner. The afterburner
would be located either upstream or downstream of the baghouse.
The locations and number of SVE wells in the lagoon and main plant areas depend upon the
areal extent of contamination, the area of influence produced by each well, and the variability
in pneumatic permeability around the plant area. Some pilot-scale treatability work would likely
be needed to complete the design of SVE implementation near the manufacturing plant.
The amount of contaminated soils that would be treated in the lagoon and main plant areas was
determined using fate and transport modeling to estimate the potential groundwater
contamination. Transport modeling calculations indicate that an average concentration of
533 /ig/kg TCE at the existing source areas would no longer yield leachate which would
contaminate Memphis Sand groundwater above 5 /ig/l for TCE. Long-term benefits of this
alternative would include permanent reduction in toxiciry and volume of soil contamination. The
estimated time for LTTD SVE to remediate the lagoon and main plant areas is two to three
years.
Alternative 6 differs from Alternative 5 in the manner that groundwater containment will have
greater assurance. Groundwater in the Memphis Sand would continue to receive TCE
contamination until the SVE could be implemented. The supplemental groundwater extraction
wells included with this alternative would minimize the extent of Memphis Sand degradation that
occurs in this interim period. Groundwater actions are expected to be effective, although
additional information must be obtained during RD to determine the configuration and number
of supplemental extraction wells required to meet effectiveness levels.
The fact that additionally-extracted groundwater will require treatment opens the following two
treatment options: (A) air stripping and (B) innovative UV/oxidation. Operation of the air
stripping system at Water Plant 2 would continue. An additional treatment unit would be
required under this scenario to handle the added water from the supplemental extraction.
The treated water from the supplemental extraction well(s) would be released to surface water,
reinjected to the Memphis Sand, or distributed to the Town of Collierville drinking water supply
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as with Water Plant 2. The Town of Collierville Public Works has stated a preference for the
use of treated water as an additional drinking water supply, because Collierville's water demand
is increasing along with its population.
Both air stripping and SVE volatilize contaminants to an air stream. Vapor-phase Granular
Activated Carbon (GAC), thermal treatment, or photolytic oxidation would be used to control
off-gas emissions if during Remedial Design/Remedial Action (RD/RA) it is determined
necessary. Photolytic oxidation, although promising, is a relatively new technology and would
require a pilot-scale treatability study. UV/oxidation does not require air pollution control
equipment or associated testing. Bench-scale testing would be required prior to UV/oxidation
design to determine optimum operating parameters.
The Memphis Sands groundwater would be treated to levels below SDWA regulations, CWA
Discharge Limitations and Pretreatment Standards, CWA Wetlands Regulations, SDWA
Underground Injection Control Program, and/or the Tennessee Water Quality Act. This
alternative would comply with federal and state CAA standards. All activities would comply
with OSHA health and safety requirements. A small portion of the site is situated in a 100-year
floodplain and wetlands area. Any remedial activity or construction in the floodplain and
wetland areas would comply with the CWA Wetlands Regulations and the Wetlands Protection
and Floodplain Management Policies. Also, RCRA Subtitle C and DOT requirements for
hazardous waste generation, transportation, storage, and disposal of hazardous would be
applicable for this alternative. Hazardous waste soils from drilling, and if used, spent GAC,
would be stored and transported to approved disposal facilities in accordance with RCRA
Subtitle C and DOT requirements.
Selected Site groundwater monitoring wells and soil would be sampled for volatile organic
compounds and metals. A review of data collected at the Site would be evaluated at least every
five years during the remedial action or until contaminant concentrations in groundwater no
longer exceed SDWA regulations or soil cleanup levels. The evaluation would continue until
completion of the groundwater remedial action and would serve to indicate whether cleanup
levels have been or will be attained. Based upon the findings of the review, EPA may determine
that other studies and/or actions should be taken.
The estimated capital cost for Alternative 6(A) is in the range of $5,917,734 to $8,931,088 while
the associated costs for O&M and monitoring are $5,577,418. The estimated present worth
costs are in the range $9,788,616 to $14,508,506.
The estimated capital cost for Alternative 6(B) is in the range of $5,913,909 to $8,923,438 while
the associated costs for O&M and monitoring are $5,927,597. The estimated present worth
costs are in the range $10,014,179 to $14,851,035.
The estimated present-worth analyses is based upon a 30-year life and a 5% discount rate.
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8.0 SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES
A detailed comparative analysis was performed on the six remedial alternatives developed during
the FS and the modifications submitted during the public comment period using the nine
evaluation criteria set forth in the NCP. The advantages and disadvantages were compared to
identify the alternative with the best balance among these nine criteria.
Overall Protection of Human Health and the Environment addresses whether or not a remedy
provides adequate protection and describes how risks are eliminated, reduced, or controlled
through treatment, engineering controls, or institutional controls. Criteria used to evaluate the
protectiveness of an alternative included the following: (1) no cancer risks from exposure to
groundwater of less than 1x10"*; (2) no significant risks of threshold toxic effect (HI less than
1) under reasonable maximum exposure; and (3) no significant risk or adverse effects on the
environment.
All alternatives except for "No Action", would be protective of human health. The "No Action"
alternative is not protective because it would not prevent unacceptable risk from ingestion or
inhalation of groundwater.
n
No Action" and Alternative 2 are not protective of the environment because they allow for
contamination to continue to enter the Memphis Sands. The effectiveness of the existing Water
Plant 2 well system in containing the entire plume is the key factor which differentiates
alternatives 3 and 5 from 4 and 6. If the southwestern extent of the plume of TCE
(concentrations greater than MCLs) which arises from the plant area spills is outside the capture
zone of Plant 2 wells, protectiveness is not assured. Thus, Alternatives 3 and 5 would not fully
protect the environment. Alternatives 4 and 6 would provide additional certainty that existing
groundwater contamination would be contained.
Since the "No-Action" alternative does not eliminate, reduce or control any of the exposure
pathways, it is therefore not protective of human health or the environment and will not be
considered further in this analysis. Alternative 2 will not be discussed further because it is not
protective of the environment. This alternative only addresses the soils in the vicinity of the
former lagoon area and without response directed toward source soils near the main plant, these
sources will be remediated only by natural attenuation over a period on the order of 2000 years,
not accounting for biological degradation. Without more rapid source control, restoration of the
Memphis Sand cannot be accomplished in a timely manner.
Compliance with Applicable or Relevant and Appropriate Requirements (ARARs) addresses
whether or not a remedy will meet all of the applicable or relevant and appropriate requirements
of other Federal and state environmental statutes and/or provide grounds for a waiver. The
identified ARARs for this site are listed in Section 10.2.
Alternatives 3,4,5, and 6 would comply with Federal and state ARARs.
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Long-Term Effectiveness and Permanence refers to expected residual risk and the ability of
a remedy to maintain reliable protection of human health and the environment over time, once
cleanup levels have been met. This criterion includes the consideration of residual risk and the
adequacy and reliability of controls.
Alternatives 4 and 6 afford the highest degree of long-term effectiveness because all
contaminated soils would be reduced to levels protective of the Memphis Sand aquifer; the
remedial action objective of preventing further contamination to the Memphis Sands is quickly
achieved through implementation of additional extraction well(s); and the additional well(s) will
provide assurance that containment of the entire contaminant plume is adequate. Although
Alternatives 3 and 5 reduce contaminated soil to levels protective of the Memphis Sands, these
alternatives do not assure quick prevention of further contamination of the Memphis Sands or
containment of the entire plume.
Reduction of Toxicity, Mobility, or Volume Through Treatment refers to the anticipated
performance of the treatment technologies a remedy may employ.
Alternatives 3,4,5, and 6 would accomplish a reduction in toxicity, mobility, and volume. The
alternatives would reduce toxicity by volatilization of TCE from soil and groundwater. Mobility
would be reduced as residual TCE is extracted (all alternatives) and/or excavated (5 and 6) from
soils. As soon as treatment of vadose zone soils is complete, migration of toxic concentration
levels of TCE in groundwater would cease. The volume of TCE in groundwater and some
contaminated soils would be reduced as the treatment progresses. Essentially the entire volume
of contaminated site soils would be treated by SVE (Alternatives 3,4,5, and 6) and/or LTTD (5
and 6) totalling over 76,000 cubic yards. Alternatives 3,4,5, and 6 provide for destruction
of air emission residuals through properly selected, designed and operated emission controls.
Alternative 4 and 6 would extract and treat all affected Memphis Sand groundwater.
Alternatives 3 and 5 would capture most of the contaminated groundwater plume at Water Plant
2.
Short-Term Effectiveness refers to the period of time needed to complete the remedy and any
adverse impacts on human health and the environment that may be posed during the construction
and implementation of the remedy until cleanup levels are achieved.
Short-term risk from Alternatives 5 and 6 are higher than those associated with Alternatives 3
and 4 because excavation activities would increase VOCs and fugitive dust emissions. A water
or foam spray would reduce emissions enough to substantially mimimJTe the risk to the
community.
Alternatives 5 and 6 would require approximately two to three years to remediate Site soils to
levels protective of the Memphis Sands. Alternatives 3 and 4 would require three to five years
to remediate Site soils to levels protective of the Memphis Sands. All the alternatives would
require approximately 30 years to remediate groundwater to ARARs.
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For all alternatives, risk to onsite workers would be minimized by providing personal protection
equipment as outlined by OSHA. The alternatives protect the community and workers by
reducing the contaminants in soil, groundwater, and air (through the use of emission controls
on discharge pipes at the SVE, and air stripper systems). UV/oxidation generates no air
emissions. No additional adverse impact to the environment would occur from the
implementation of these alternatives.
Implementability is the technical and administrative feasibility of a remedy, including the
availability of materials and services needed to implement the chosen solution.
Groundwater containment/air stripping (3,4A, 5, and 6A) measures are extremely common and
widely available. Monitoring groundwater and its restoration should not pose extraordinary
problems.
SVE (all alternatives) and LTTD (5 and 6) are relatively new, yet widely available technologies
for the treatment of volatile organic contaminated soils. A treatability study for SVE at the main
plant area would be required to effectively address what are expected to be heterogeneous spaces
in terms of both contamination and air permeability. The ability to monitor effectiveness of SVE
is not technically infeasible, but would require carefully designed and implemented sampling
efforts to assure effectiveness in reaching soil cleanup levels.
UV/oxidation (4A and 6A) is less common at hazardous waste sites, but is a demonstrated
process for streams with low contaminant concentrations, and low total solids content.
Supplementally-extracted groundwater may pose operation problems, such as fouling, or high
oxidant consumption, due to the presence of trace metals and hardness. UV/oxidation
treatability work would be required before design to avoid or manage potential operational
problems.
Cost
The total Present Worth Costs for each of the alternatives evaluated are as follows:
Alternative 3: $5.5 to $7.5 million
Alternative 4A: $5.7 to $7.9 million
Alternative 4B: $6.1 to $8.4 million
Alternative 5: $9.5 to $14 million .
Alternative 6A: $9.8 to $14.5 million
Alternative 6B: $10 to $14.9 million
State Acceptance
EPA and the Tennessee Department of Environment and Conservation (TDEC) have cooperated
throughout the RI/FS process. The State has participated in the development of the RI/FS
through comment on each of the planning and decision documents developed by EPA, and the
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Draft ROD and through frequent contact between the EPA and TDEC site project managers.
EPA and TDEC are in agreement on the selected alternative. Please refer to the Responsiveness
Summary which contains a letter of concurrence from TDEC.
Community Acceptance
EPA received two letters from residents in the Town of Collierville. During the pubk'c meeting
held on April 30, 1992, town residents in attendance expressed interest and support for the
selected remedy present by EPA. Please see the Responsiveness Summary which contains these
letters and a transcript of the public meeting.
9.0 THE SELECTED REMEDY
Based upon consideration of the CERCLA requirements, the detailed analysis of the alternatives
using the nine criteria, and public comments, both EPA and TDEC have determined that
Alternative 4A is the most appropriate remedy for the Carrier A.C. Superfund Site in
Collierville, Tennessee.
The selected remedy shall include the following: (1) the North Remediation System (NRS) and
plant area soil vapor extraction (SVE); (2) groundwater containment/treatment at Water Plant
2, and supplemental extraction well(s)/treatment via air stripping; and (3) institutional controls
placed on well construction and water use in the general area of the Site.
It is estimated that the present worth cost of the selected remedy will be approximately $5.7 to
$7.9 million. The present worth cost analysis is based upon a 30-year life and a 596 discount
rate.
Alternative 4A will permanently reduce the risk of exposure to contaminants' in soil and
groundwater and will also prevent further contamination to the environment.
9.1 Performance Standards
(1) North Remediation System (NRS) and Plant Area Soil Vapor Extraction (SVE)
The NRS shall continue to remediate the contaminated soils in the area of the former lagoon via
SVE. A SVE system in the area of the main plant source area shall be constructed to remediate
contaminated soils. SVE in the former lagoon and main plant area will continue to operate until
remediation to cleanup levels are reached throughout the area of soil contamination. The
cleanup level for the TCE-contaminated soil will be approximately 533 pg/kg or until in EPA's
determination, it is demonstrated that contaminant levels have ceased to decline over time, and
are remaining constant at some statistically significant level above remediation levels in the area
of remediation, as verified by soil sampling. The ability to achieve 533 Mg/kg cannot be
determined until after the extraction system has been implemented, modified as necessary, and
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soil response monitored over time. A monitoring system will be instituted to measure progress
and operating efficiencies of SVE in achieving the cleanup level.
EPA will determine the locations and number of vapor extraction wells in the main plant area.
The decisions will be based upon the areal extent of contamination, area of influence produced
by each well, and the variability in pneumatic permeability around the plant area. Some pilot-
scale treatability work will be needed to complete the design of SVE implementation near the
manufacturing plant.
All air emissions shall be in compliance with the Federal and State CAA standards. Off-gas
emissions, if determined necessary during RD, will be controlled by Granular Activated Carbon
(GAC), thermal treatment, or photolytic oxidation.
(2) Groundwater Containment/Treatment at Water Plant 2, and Supplemental
Extraction Well(s)/Treatment via Air Stripping
Groundwater Containment/Treatment shall be conducted at Water Plant 2 and with supplemental
well(s). EPA will determine the final number and location of supplemental wells for the Site.
The existing air strippers at Water Plant 2 shall continue to be used to treat extracted
groundwater. If EPA deems necessary, additional air strippers and/or monitoring wells will be
installed as part of the remedial action to ensure compliance with the cleanup levels of the
selected remedy.
The groundwater extraction system will continue to operate until cleanup levels for the
contaminants of concern are reached throughout the area of attainment. The area of attainment
shall encompass the area up to the contaminant plume boundary.
The Memphis Sand aquifer will be treated until the cleanup levels for the contaminants, as listed
below, are attained.
Trichloroethylene (TCE) 5 pglt (SDWA MCL)
cw-l,2-Dichloroethylene (DCE) 70 pglt (SDWAMCLG)
ranj-l,2-DicMoroethylene(DCE) 100 pgll (SDWAMCLG)
Tetrachloroethene (PCE) 5 uglt (SDWA MCL)
Vinyl Chloride 2 pg/t (SDWA MCL)
Zinc 5000 pglt (SDWASMCL)
The Memphis Sand aquifer will be treated until (1) background levels of lead or (2) cleanup
levels for lead of 15 /xg/l (SDWA Treatment Technique Action Level) is attained. The
determination of which level will be achieved will be based upon whether lead is elevated above
background levels and this condition is due to Site-related conditions; or whether a significant
statistical difference between background levels and onsite levels of lead exists.
The accepted EPA methods are documented in the "USEPA Contract Lab Program Statement
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of Work for Inorganic Analysis, Document #ILM02.0"; the "Contract Lab Program Statement
of Work for Organic Analysis, Document # OLM01.0," dated August 1991; and the "Superfund
Analytical Methods for Low Concentration Water for Organic Analysis," dated June 1991, and
any amendments made thereto during the course of the implementation of RD/RA. Monitoring
wells shall be sampled for up to 30 years.
The sampling frequency, number, and location of the monitoring wells and background
monitoring wells will be designated by EPA during the RD, and if deemed necessary, additional
monitoring wells will be installed.
The goal of this remedial action is to restore the Memphis Sands groundwater to its beneficial
use, which is, at this Site, a drinking water aquifer. Based on information obtained during the
RI and on a careful analysis of all remedial alternatives, EPA and TDEC believe that the
selected remedy will achieve this goal. It may become apparent, during implementation or
operation of the groundwater extraction systems, that contaminant levels have ceased to decline
and are remaining constant at levels higher than the remediation levels. In such a case, the
system performance standards and/or remedy will be reevaluated.
The selected remedy will include groundwater extraction for an estimated period of 30 years,
during which the system's performance will be carefully monitored on a regular basis and
adjusted as warranted by the performance data collected during operation. The operating system
may include:
a) discontinuing operation of extraction wells in areas where cleanup levels have been attained;
b) alternating pumping at wells to eliminate stagnation points; and
c) pulse pumping to allow aquifer equilibration and encourage adsorbed contaminants to
partition into groundwater.
To ensure that cleanup levels continue to be maintained, the aquifer will be monitored at those
wells where pumping has ceased on an occurrence of at least every 5 years following
discontinuation of groundwater extraction.
All extracted groundwater shall be treated to levels which allow for discharge to (I) the
municipal water supply; (2) a local POTW; (3) surface water, or (4) reinjected to the Memphis
Sands aquifer. All groundwater discharge actions shall comply with Federal and State discharge
requirements.
All air emissions from the air stripper(s) shall be in compliance with Federal and State CAA
standards. Off-gas emissions, if determined necessary during RD, will be controlled by
Granular Activated Carbon (GAC), thermal treatment, or photolytic oxidation.
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(3) Institutional Controls Placed on Well Construction and Water Use in the General Area
of the Site
If EPA deems necessary, institutional controls will be placed on well construction in the general
area of the Site. No well will be located, constructed or operated which results in the
diminution of the extraction wells at Carrier A.C. Superfund Site or in the degradation of the
Memphis Sands. Institutional controls will also restrict the use of groundwater containing, or
potentially containing, levels of contamination in excess of MCLs, SMCLs and non-zero
MCLGs. Institutional controls may include local ordinances, deed restrictions, record notice,
or some other appropriate measures. The controls shall remain in effect until EPA through
monitoring determines that the cleanup levels have been attained.
10.0 STATUTORY DETERMINATIONS
Under CERCLA Section 121, EPA must select remedies that are protective of human health and
the environment, comply with applicable or relevant and appropriate requirements (unless a
statutory waiver is justified), are cost-effective, and utilize permanent solutions and alternative
treatment technologies or resource recovery technologies to the maximum extent practicable.
In addition, CERCLA includes a preference for remedies that employ treatment that permanently
and significantly reduce the volume, toxicity, or mobility or hazardous wastes as their principal
element. The following sections discuss how the remedy meets these statutory requirements.
10.1 Protection of Human Health and the Environment
The selected remedy protects human health and the environment through the North Remediation
System (NRS) and plant area soil vapor extraction (SVE); groundwater containment/treatment
at Water Plant 2, and supplemental extraction well(s)/treatment via air stripping; and institutional
controls placed on well construction and water use in the general area of the Site. Air stripping
will irreversibly remove organic compounds from groundwater. SVE will irreversibly remove
VOCs from soils to levels at or below soil cleanup levels. Residuals in air emissions will be
controlled through properly selected, designed and operated emission controls. Institutional
controls will assure that the pubUc is not affected by Site-related contaminants at a current or
future time.
Air stripping of contaminated groundwater will eliminate the threat of exposure to the
contaminants of concern via ingestion or inhalation of groundwater. The current cancer risk
associated with this exposure pathway is 2.5x10**. The future cancer risk.from the groundwater
pathway is 4.7x10"*. By extracting and air stripping the groundwater, the cancer risk will be
reduced to 1x10*. This level falls within the EPA's acceptable risk range of 104 to 10"*. No
short-term threats are associated with the selected remedy that cannot be readily controlled. In
addition, no adverse cross-media impacts are expected from the remedy.
Exposure to contaminated surface soils does not pose a current or future risk greater than the
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10"6 point of departure. However, in light of the current and potential future groundwater uses,
soil vapor extraction will be used to effectively to remediate the contaminated soils to levels
protective of the Memphis Sands. No short-term threats are associated with the selected remedy
cannot be readily controlled. In addition, no adverse cross-media impacts are expected from the
remedy.
10.2 Compliance with Applicable or Relevant and Appropriate Requirements
The selected remedy of the North Remediation System (NRS) and plant area soil vapor
extraction (SVE); groundwater containment/treatment at Water Plant 2, and supplemental
extraction/treatment via air stripping; and institutional controls placed on well construction and
water use in the general area of the Site will comply with applicable or relevant and appropriate
chemical, action, and location-specific requirements (ARARs). The ARARs are presented
below:
Chemical-Specific ARARs:
Safe Drinking Water Act (SDWA) Maximum Contaminant Levels (MCLs) (42 U.S.C. § 1412
(§ 300g-l); 40 C.F.R. 141.61 and 141.80) have been set for toxic compounds as enforceable
standards for public drinking water systems.
SDWA Secondary Maximum Contaminant Levels (SMCLs) (42 U.S.C. § 1412 (§ 300g-l); 40
C.F.R. 143.3) are unenforceable goals regulating the aesthetic quality of drinking water.
SDWA Maximum Contaminant Levels Goals (MCLGs) (42 U.S.C. § 1412 (§ 300g-l); 40
C.F.R. 141.50) are unenforceable health goals.
Clean Water Act fCWA) Federal Water Quality Criteria (33 U.S.C. § 1314(a)(l)(§ 304(a)(l))
are effluent limitations that must meet Best Available Technology (BAT).
Clean Air Act (CAA) National Ambient Air 0"«Kty fttflmiqnfo (42 U.S.C. § 7409 (§ 109); 40
C.F.R. Part SO) establishes emissions standards, monitoring and testing requirements, and
reporting requirements for eight pollutants in air emissions.
Tennessee Water polity Control Act (69-3-101) controls and regulates drinking water and
discharges to POTW and also to waters of the State.
Location-Specific ARARs
Resource Conservation Recovery Act fRCRAt (42 U.S.C. §§ 6921-39 (§§ 3001-19); 40 C.F.R.
Parts 260-70) regulates the treatment, storage, and disposal of hazardous waste from generation
through ultimate disposal. Remedial action at the Site may require the handling of materials that
constitute RCRA hazardous waste, for example, soil and groundwater residuals or spent carbon
(if carbon adsorption is chosen). Any such materials will be handled in compliance with
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applicable RCRA requirements.
Fish and Wildlife Coordination Act (L6 U.S.C. 661 et seq.) requires actions to protect fish and
wildlife from actions modifying streams or areas affecting streams.
CAA National Ambient Air Quality Standards (42 U.S.C. § 7409 (§ 109); 40 C.F.R. Part 50)
establishes emission standards to protect public health and public welfare. These standards are
national limitations on ambient air intended to protect health and welfare.
Action-Specific ARARs
RCRA (42 U.S.C. §§ 6921-39 (§§ 3001-19); 40 C.F.R. Parts 260-70) regulates the treatment,
storage, and disposal of hazardous waste from generation through ultimate disposal. Remedial
action at the Site may require the handling of materials that constitute RCRA hazardous waste,
for example, soil and groundwater residuals or spent carbon (if carbon adsorption is chosen).
Any such materials will be handled in compliance with applicable RCRA requirements.
CWA Discharge Limitations (33 U.S.C. § 1311 (§ 301); 40 C.F.R. Parts 122, 125, 129, 133,
and 136) prohibits unpennitted discharge of any pollutant or combination of pollutants or
combinations of pollutants to waters of the U.S. from any point source. Standards and
limitations are established for these discharges to a POTW.
SDWA Underpound Injection Control (TJin (42 U.S.C. §§ 300h-300h-7 (§§ 1421-8); 40 C.F.R.
Parts 144-7) is a permit program designed to prevent contamination of underground sources of
drinking water.
CWA Pretreatment Standards (33 U.S.C. § 1317 (§ 307); 40 C.F.R. 403.5) prohibits
unpennitted discharge of any pollutant or combination of pollutants or combinations of pollutants
to waters of the U.S. from any point source. Standards and limitations are established for these
discharges to a POTW.
CWA Dredge and Fill Material Permits - Wetlands (33 U.S.C. § 1344 (§ 404); 40 C.F.R. Part
230) controls the discharge of dredged or fill materials into water of the U.S. such that the
physical and biological integrity is maintained.
CAA New Source Performance Standards (42 U.S.C. § 7411 (§ 111); 40 C.F.R. 60) establishes
standards of performance for new air emission sources.
CAA National Emission Standards for Ha^rdous Air Pollutants (42 U.S.C. § 7412 (§ 112); 40
C.F.R. Part 61) establishes emissions standards, monitoring and testing requirements, and
reporting requirements for eight pollutants in air emissions.
Occupations Safety and Health Standards Act (29 U.S.C. § 651 & Sfij.; 29 C.F.R. Part 1910)
sets limits on exposure to workers on hazardous site or emergency responses, sets forth
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minimum health and safety requirements such as personal protection and training, and reporting
requirements.
To Be Considered Materials (TBCs)
EPA Groundwater Protection Strategy (EPA, 1984) is a policy to restore groundwater to its
beneficial uses within a time frame that is reasonable. Groundwater beneath and adjacent to the
Carrier A.C. Site are Class HA and mA aquifers.
Town of Collierville Municipal Code of Ordinances (10-230) is a promulgated local deed
restriction prohibiting installation of wells without a permit.
Shelby County Well Construction Codes (Section 4 and 5) are promulgated local rules and
regulations to control and regulate the location, construction, and modification of all types of
wells in Shelby County.
Executive Order 11990 Wetlands Protection Policy sets forth policy for the protection of
wetlands.
Executive Order 11988 Floodplain Management Policy sets forth policy for the protection of
floodplains.
10.3 Cost Effectiveness
The selected remedy, Alternative 4A was chosen because it provides the best balance among
criteria used to evaluate the alternatives considered in the Detailed Analysis. This alternative
was found to achieve both adequate protection of human health and the environment and to meet
the statutory requirements of Section 121 of CERCLA. The present worth cost of Alternative
4A is in the range of $5,717,755 to $7,932,765.
10.4 Utilization of Permanent Solutions and Alternative Treatment Technologies or
Resource Recovery Technologies to the Maximum Extent Practicable
EPA and TDEC have determined that the selected remedy represents the maximum extent to
which permanent solutions and treatment technologies can be utilized in a cost-effective manner
for the final ROD at the Carrier A.C. Site. Of those alternatives that are protective of human
health and the environment and comply with ARARs, EPA and TDEC have determined that the
selected remedy provides the best balance of trade-offs in terms of long-term effectiveness and
permanence, reduction in toxicity, mobility, or volume achieved through treatment, short-term
effectiveness, implementability, cost, while also considering the statutory preference for
treatment as a principal element and considering State and community acceptance.
The selected remedy treats the principal threats posed by groundwater and soils, achieving
significant contaminant reductions. This remedy provides the most effective treatment of any
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of the alternatives considered, and will cost less than excavation. The selection of treatment for
the contaminated soils and groundwater is consistent with program expectations that highly toxic
and mobile wastes are a priority for treatment to ensure the long-term effectiveness of a remedy.
10.5 Preference for Treatment as a Principal Element
By treating the contaminated groundwater and soils by air stripping and soil vapor extractions,
the selected remedy addresses the principal threats posed by the Site through the use of treatment
technologies. By utilizing treatment as a significant portion of the remedy, the statutory
preference for remedies that employ treatment as a principal element is satisfied.
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