PROPOSED PLAN WALKER MACHINE PRODUCTS, …Proposed Plan for ROD Walker Machine Products March 2018 1...

Proposed Plan for ROD Walker Machine Products

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This Proposed Plan is not to be considered a technical document but has been prepared to provide an abridged summary to the public.

You are Invited to Comment on this Proposed Cleanup for the Walker Machine Products, Inc. Site, Collierville, TN

The U.S. Environmental Protection Agency (EPA) invites comments on this Proposed Plan for the Walker Machine Products, Inc. Superfund Site (Site) located in Collierville, TN. This Proposed Plan describes the different remedial alternatives evaluated to address soil, groundwater and indoor air contamination at the Site and describes EPA’s preferred alternative. A glossary defining key terms is provided in Appendix A at the end of this document; the key terms appear in bold the first time they are used.

Contaminated media at the Site have been divided into three zones: the unsaturated soil zone (UZ), saturated soil zone (SSZ), and dilute plume (DP). The Preferred Alternative for each zone is:

UZ: Alternative #2B Thermally Enhanced Soil Vapor Extraction (TE-SVE) with Limited Air Sparging.

SSZ: Alternative #5 Biogeochemical Reductive Dehalogenation (BiRD).

DP: Alternative #2B Enhanced in situ Bioremediation (EISB) Passive Barriers with Horizontal Well.

This document is issued by EPA, the lead agency for Site activities, and the Tennessee Department of Environment and Conservation (TDEC), the support agency. EPA, in consultation with TDEC, will select a final remedy for the Site after reviewing and considering all information submitted during the public comment period. EPA, in consultation with TDEC, may modify this Preferred Alternative or select another alternative presented in this Proposed Plan based on new information or public comments. Therefore, the public is encouraged to review and comment on all the alternatives presented in this Proposed Plan.

EPA is issuing this Proposed Plan as part of its public participation requirements under Section 117 (a) of the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA), as amended, 42 United States Code Section 9617, commonly known as Superfund, and the National Oil and Hazardous Substances Pollution Contingency Plan (NCP), as set forth in 40 Code of Federal Regulations Section 300.430 (f)(2).

This Proposed Plan summarizes and identifies key information that can be found in greater detail in the Remedial Investigation (RI) and Feasibility Study (FS) documents, as well as other documents contained in the Administrative Record file for this Site. EPA and TDEC encourage the public to review these documents to gain a more comprehensive understanding of the Site and Superfund activities that have been conducted. The Administrative Record and Information Repository is located at the Lucius E. and Elsie C. Burch Library in Collierville and in EPA Region 4’s Information Center at 61 Forsyth Street, Sam Nunn Atlanta Federal Center, Atlanta, Georgia.

These two agencies want to hear your views about this Proposed Plan and all the alternatives presented. You can comment on this Proposed Plan for the Walker Machine Superfund Site during the public meeting to be

PROPOSED PLAN WALKER MACHINE PRODUCTS, INC COLLIERVILLE, SHELBY COUNTY, TENNESSEE

June 2018


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held on June 14, 2018, at the Site at the Lucius E. and Elsie C. Burch Library 501 Poplar View Parkway Collierville, TN 3801. Comments can also be submitted through the mail, via facsimile, or email (refer to the following box for additional information).

You are encouraged to submit your comments during the public comment period. You have until July 7, 2018, to submit written comments on this Proposed Plan or other material in the Administrative Record. At the end of the comment period, EPA and TDEC will review the comments/suggestions and make a final decision about the Site cleanup. Your input on this Proposed Plan is an important part of the decision-making process.

Tell Us What You Think Public Comment Period:

June 8, 2018 to July 7, 2018 EPA will accept written comments on this Proposed Plan during the public comment period. You may submit written comments three (3) ways: BY MAIL Randy Bryant U.S. EPA - Region 4 61 Forsyth Street, SW Atlanta, Georgia 30303-8960 BY EMAIL [email protected] BY FACSIMILE 404-562-8174 Addressed to Randy Bryant

Attend the Public Meeting You are invited to attend an availability session and a formal public meeting sponsored by EPA to hear about this Proposed Plan. At the meeting you will be able to voice your views about the cleanup. The availability session will be held from 4:00 p.m. – 6:00 p.m.

The meeting will be held: June 14, 2018

6:00 p.m. -8:00 p.m. Location:

Lucius E. and Elsie C. Burch Library

501 Poplar View Parkway

Collierville, TN 38017

Locations of Administrative Record and Information Repository Lucius E. and Elsie C. Burch Library 501 Poplar View Parkway Collierville, TN 38017 901/457-2600 Hours: Mon– Thurs: 10 a.m. – 8 p.m. Fri and Sat: 10 a.m. –6 p.m. Sun:1 p.m. – 5 p.m.

EPA Region 4's Information Center Sam Nunn Atlanta Federal Center 61 Forsyth Street SW Atlanta, Georgia 30303

Phone: 404-562-8946 Hours: Mon – Fri, 8 a.m. – 5 p.m.

INTRODUCTION

This Proposed Plan provides:

a brief description and history of the Site;

a summary of the nature and extent of contamination;

a summary of the Baseline Risk Assessment (BRA);

a list of cleanup levels for the chemicals of concern;

a summary of cleanup alternatives considered for remediation of the Site;

EPA’s Preferred Remedial Alternative;

encouragement to the public to submit comments on the Preferred Remedial Alternative; and

a list of contacts and locations for more information

mailto:[email protected]


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SITE HISTORY/SITE CHARACTERISTICS

The Site is about five acres in size and is located at 459 Washington St, Collierville, Tennessee 38017 (Figures 1 and 2). The Site is bounded to the north by Washington Street; a vacant, wooded lot to the east; to the south by an intermittent unnamed stream and railroad tracks; and the former Witt International, Inc. (Witt) facility to the west. Current site features include:

•a metal and concrete manufacturing building surrounded by concrete parking and storage pads to the north and south;

•a metal storage building to the east;

•a concrete pad that once housed an above ground storage tank (AST) and an adjacent drainage (overflow) pond that was used to contain spills from the AST; and

•a wooded area south of the manufacturing building, where an empty drum and other drum parts were found.

The Site is zoned General Industrial with surrounding properties zoned General industrial and Medium to High Density Residential zoning farther north and south of the Site. The Town of Collierville owns five municipal well fields north, west, and southwest of the Site. Wellfield #1 is the closest wellfield and located approximately 0.6 miles west/northwest of the Site (Figure 3).

The Site was operated by Walker Machine Products, Inc. (Walker Machine) from about 1965 until about 2002. Walker Machine manufactured metal products (also referred to as automated machine screw products). Cutting oils and coolants were used in the machining operations. Chlorinated solvents (including tetrachloroethene (PCE), trichloroethene (TCE), and mineral spirits) were used to clean the finished products. The used solvent was filtered to remove oil and metal shavings and stored in an AST southeast of the manufacturing building. An oil/water separator (below ground tank) was also used by Walker Machine and likely received the solvent waste. Spills and leaks of these solvents resulted in contamination of subsurface soil and groundwater beneath the site.

A prior contaminant release was documented at the Site in September 1987. The Tennessee Department of Labor, Division of Occupational Safety and Health Administration (TOSHA) conducted an inspection at the Walker Machine facility. TOSHA personnel observed spent solvent that had been discharged to the ground under the AST and into a sewer drain located in the rear of the building that discharges into the municipal sewer system.

Due to the types of operations and a known solvent release, it was determined that the Site should be evaluated to characterize and assess the Site’s threat. Investigations and regulatory actions occurred at the Site between 2007 and 2018 to delineate the nature and extent of contamination. In 2007, TDEC sampled groundwater, surface and subsurface soil, and sediment. Site-related contaminants were detected in both groundwater and subsurface soil. Additional groundwater, soil and soil gas samples were collected from both onsite and offsite locations between 2007 and 2014.

In May 2014, EPA placed the Site on the National Priorities List (NPL) identifying it for possible long-term remedial response. Between 2014 and 2017, EPA conducted a RI at the Site to the identify the nature and extent of contamination and the potential source areas. The potential sources include a former oil/water separator, the former AST location, prior spill areas adjacent to the building, and drum location in the woods.

In 2014, EPA conducted vapor intrusion (VI) sampling inside the manufacturing building onsite. Elevated indoor air results prompted EPA to complete an emergency response action to protect site workers through


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the installation of a vapor mitigation system below the building. Analysis of air samples following its installation indicated that the mitigation system reduced levels of PCE, TCE, and other soil-gas contaminants below EPA’s health-based benchmarks for indoor air.

GEOLOGY AND HYDROGEOLOGY

The upper 30 feet of soil under the Site is a mixture of clayey and silty sand with some interbedded layers of sandy or silty clay. The lithology then transitions to a sand layer with some zones of interbedded silt or clay. This sand likely represents the beginning of the Upper Memphis sand formation which extends to a depth of about 290 feet below land surface (bls). The depth to groundwater is about 50-60 feet bls at the Site. Two silty to sandy clay layers are present at about 65 to 85 feet bls and again at about 290 feet bls. These clay layers are not continuous and have variable thicknesses. Groundwater contamination at the Site was predominantly detected above the second clay unit (65-85 feet bls) indicating that this unit may be acting as a semi-confining unit where present underneath the site. The Upper Memphis sand forms the aquifer under the Site. The Town of Collierville Wellfield #1 draws water from this aquifer. NATURE AND EXTENT OF CONTAMINATION

Surface soil, unsaturated and saturated subsurface soil, groundwater, sediment, surface water and air samples were collected during the Site RI. The results are summarized as follows:

Subsurface soil samples containing somewhat elevated PCE concentrations were generally found on the southern portion of the Site and along the southern edge of the building. PCE concentrations in subsurface soil ranged from 1.8 micrograms per kilogram (ug/kg) to 430 ug/kg.

Groundwater samples were collected from monitoring wells in both onsite and offsite areas. Elevated concentrations were detected in wells screened between 65 and 85 feet bls. The highest level of contamination detected was located near the oil/water separator and former AST. Elevated concentrations were detected in wells along the east and west sides of the Witt building, downgradient of the Walker Site, and in wells south of the railroad tracks, south of the Site. PCE concentrations in groundwater ranged from 0.2 ug/l to 2450 ug/l; the highest concentrations were from monitoring wells on the Walker Machine property.

PCE was detected at low levels (approximately 6 ug/l) in the shallowest well in the Town of Collierville Wellfield #1. PCE was not detected in recent samples of treated water from Wellfield #1.

Analytical results from soil vapor, indoor air, and ambient air indicated multiple detections with the highest detected concentrations located in the northern half of the building. Indoor air concentrations of PCE and TCE were 320 micrograms per cubic meter (ug/m3) and 340 ug/m3, respectively. Following the installation of the vapor mitigation system, the concentrations of PCE and TCE in indoor air were significantly reduced to below health based levels.

Surface soils contained elevated metals concentrations. The highest concentrations are near the remains of the TCE drums and around the building.

All sediment samples collected contained elevated metals concentrations. However, metals concentrations were lowest in the most downgradient sample; indicating that transport offsite via the intermittent stream is likely minimal.

Surface water does not appear to be impacted by site-related contaminants.


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CHEMICALS OF CONCERN

During the RI/FS, contaminants that are detected in the various samples of soil, groundwater, and indoor air are further evaluated to focus on the contaminants that pose a greater risk or which are elevated relative to regulatory standards. The contaminants of concern (COCs) are listed in Tables 1-3 for subsurface soil, groundwater, and indoor air. Additional information on the selection of the COCs can be found in the Human Health Risk Assessment (HHRA) and FS documents.

PRINCIPAL THREAT WASTE

Principal threat wastes (PTW) are highly toxic or highly mobile materials that may present a significant risk to human health or the environment if exposure were to occur. They include liquids and other materials having high concentrations of toxic compounds (for example, solvents). The NCP establishes an expectation that EPA will: (1) use treatment to address the principal threats posed by a site wherever practicable – NCP Section 300.430(a)(1)(iii)(A); (2) use engineering controls for waste that poses a relatively low long-term threat or where treatment is impracticable; (3) use ICs; or (4) use a combination of methods to achieve protection of human health and the environment and/or to prevent or limit exposure to PTW.

The contaminated soils under the main building and south of the main building are considered to be principal threat wastes at this Site. Information about Site operations and the documented groundwater impacts indicate that contaminants in soil are present and are highly mobile. It is noted that soil data collected to date do not quantitatively confirm high concentrations and that additional data will be collected during the Remedial Design.

SCOPE AND ROLE OF THE PROPOSED ACTION

The Preferred Alternative presented in this Plan addresses all three of the CMZ and is considered to be the final action for the Site. However, a phased response action is recommended for the Site. The use of a phased approach will allow EPA to focus on the more contaminated areas present onsite in the UZ and SSZ. EPA would continue to monitor the effects of the initial cleanup phases on downgradient groundwater conditions before implementing subsequent phases of the selected remedy.

SUMMARY OF SITE RISKS

A comprehensive risk assessment was conducted as part of the RI/FS process. The risk assessment is detailed in the RI Report and summarized in the FS Report. Consistent with EPA guidance and policy, the risk assessment included an ecological risk assessment (ERA) and a human health risk assessment (HHRA). The ERA included an evaluation of potential Site risks to plants and animals. The HHRA included a baseline risk assessment that evaluated cancer and noncancer risks for existing Site conditions and current land and water uses. The HHRA also includes an evaluation of risk for reasonably anticipated future land use scenarios.

Together, the ERA and HHRA are used to identify an initial list of COPCs followed by a shorter list of chemicals of concern (COCs), or those chemicals that exceed risk-based concentrations and must be addressed during development of remedial alternatives.

A screening level ERA was conducted to determine the potential effects to the environment from the Site contamination. The potential for ecological risk was evaluated for plants and animals. The residual concentrations of contaminants in soil are limited to small isolated areas at the Site and are not expected to


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result in an adverse risk to local populations of plants and animals. Aquatic organisms are not at risk from exposure to surface water and sediment. Detected concentrations in surface water are below screening levels.

The intent of the HHRA is to evaluate the potential risks to human health due to releases of chemicals and exposure to contaminants at the Walker Site. To estimate the baseline risk at a Superfund site, EPA undertakes a four-step process:

Step 1: Analyze Contamination Step 2: Estimate Exposure Step 3: Assess Potential Health Dangers Step 4: Characterize Site Risk

In Step 1, EPA looks at the concentrations of contaminants found at a site as well as past scientific studies on the effects these contaminants have had on people (or animals, when human studies are unavailable). A comparison between site-specific concentrations and health-based concentrations helps EPA to determine which contaminants are most likely to pose the greatest threat to human health.

In Step 2, EPA considers the different ways that people might be exposed to the contaminants identified in Step 1, the concentrations that people might be exposed to, and the potential frequency and duration of exposure. Using this information, EPA calculates a "reasonable maximum exposure" (RME) scenario, which portrays the highest level of human exposure that could reasonably be expected to occur.

In Step 3, EPA uses the information from Step 2 combined with information on the toxicity of each chemical to assess potential health risks. EPA considers two types of risk: cancer risk and non-cancer risk. The likelihood of any kind of cancer resulting from a Superfund site is generally expressed as an upper bound probability; for example, a "1 in 10,000 chance." In other words, the exposed individual would have an excess cancer risk of one in 10,000 due to site contaminants. This excess risk would be over and above the existing cancer risk for the individual. For non-cancer health effects, EPA calculates a "hazard index." The key concept here is that a "threshold level" (measured usually as a hazard index of less than 1) exists below which non-cancer health effects are not expected.

In Step 4, EPA determines whether site risks are excessive for people at or near the Superfund site. The results of the three previous steps are combined, evaluated and summarized. EPA adds up the potential risks for each receptor.

Potential routes of exposure included (1) incidental ingestion of, dermal contact with, and inhalation of particulate emissions from soil; (2) ingestion of and inhalation/dermal contact with groundwater; (3) ingestion and dermal contact with surface water; (4) ingestion and dermal contact with sediment; and (4) inhalation of indoor air from subsurface VI. Risks to human health were estimated using analytical data for surface soil, subsurface soil, groundwater, sediment, surface water, soil gas, and indoor air samples collected at the Site in 2007 through 2017.

EPA has established a generally acceptable excess lifetime cancer risk range for site-related exposure of 10-4 to 10-6. Noncancer concerns are evaluated as a hazard quotient (HQ) of less than or equal to 1 (HQ<1). These risk levels are used to determine if remedial actions are necessary at a Superfund site. The results of the HHRA indicate that there is potential risk assuming future residential, industrial/ commercial worker, or construction worker exposures at the Site (See Tables 1, 2 and 3). Therefore, action under CERCLA is warranted.


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It is the lead agency’s current judgment that the Preferred Alternative identified in this Proposed Plan, or one of the other active measures considered in the Proposed Plan, is necessary to protect public health or welfare or the environment from actual or threatened releases of hazardous substances into the environment.

REMEDIAL ACTION OBJECTIVES

The site-specific remedial action objectives (RAOs) are as follows:

Prevent and/or minimize the COC contaminated groundwater plume from expanding within the Memphis Sand aquifer;

Restore groundwater quality to meet drinking water standards (also referred to as maximum contaminant levels or MCLs) since the aquifer is a drinking water source; and

Prevent and/or minimize COC migration from soil and groundwater to indoor air for the protection of HH&E

Maximize the mass removal or destruction of any potential residual NAPL and adsorbed-phase COCs from the UZ and SSZ media zones that can be a source of leachate or a source of volatile vapors that may migrate into Walker Building;

Reduce or eliminate the long-term leachability of CVOCs in soil into the groundwater by meeting Site- specific soil leachability goals for subsurface soils

Prevent human (onsite future residents and onsite future construction workers) exposure to Site- related contaminated soil at concentrations above HHRA cancer risk levels or HHRA non-cancer hazard levels;

Prevent human exposure (onsite future residents, onsite current/future industrial/commercial workers, and onsite future construction workers) to Site-related contaminants in groundwater at concentrations above regulatory MCLs, or above HHRA cancer risk levels or non-cancer hazard levels where MCLs have not been established;

Prevent human (onsite future residents and onsite current/future industrial/commercial workers) exposure to Site-related contaminated indoor air at concentrations above HHRA cancer risk levels or HHRA non-cancer hazard levels;

Proposed cleanup levels

The proposed cleanup levels are numeric targets for a given contaminant. The cleanup levels provide a basis for meeting the overall remedial action objectives noted above. These cleanup levels are also referred to as preliminary remedial goals. The proposed cleanup levels for soil, groundwater, and indoor air are listed in Tables 4, 5, and 6 of this Proposed Plan.

REMEDIAL ALTERNATIVES

The approach used to evaluate the potential remedy alternatives was to divide the Site into three contaminated media zones (CMZs) (Figure 4). Remedial alternatives were developed for each CMZ that would meet the cleanup goals and the requirements of the NCP. CMZs are generically defined as a medium, volume or area that has common characteristics which effect the remedial alternative selection. The dimensions and characteristics of a defined CMZ are essential parameters for selecting and comparing remedial alternatives


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because of their impact on remedial costs and technology feasibility. For example, the depth of contamination, whether it is on or off the boundaries of the property, the presence of non-aqueous phase liquid (NAPL), a specific lithologic unit, and concentrations of specific COCs (e.g. PCE) were the factors in delineating a CMZ for the Walker Site.

CMZ-1 – Unsaturated Soil Zone (UZ)

This unsaturated zone (UZ) represents on-site unsaturated soil between approximately 0 and 50 feet bls impacted with PCE and similar compounds, and some soil impacted by petroleum above levels protective of construction workers and above levels that may cause intrusion of contaminant vapors above acceptable levels for inhalation of indoor air. Remediation of this zone is focused on reducing concentrations in soil that could lead to future indoor air issues or that contribute to ongoing groundwater contamination and protection of humans from direct contact with soils and inhalation of vapors. The areal extent for this zone is conservatively estimated based on historical Site information and potential transport mechanisms. This zone includes the area under the Walker building, the vicinity of buried oil/water separator, former AST and pond, TCE drum location, and south to the intermittent stream This zone is deep (~50 feet); therefore, the volume of soils estimated to require remediation in this zone is large.

CMZ-2 – Saturated Soil Zone (SSZ)

The SSZ represents saturated soil above the second semi-confining clay unit (between approximately 50 and 75 feet bls), beneath suspected source areas. This zone conservatively encompasses the vicinity of the former AST (where discharge was observed), the TCE drums, and the oil/water separator where the highest levels of groundwater contamination were detected. It also includes the area underneath the southern portion of the Walker building (near the southern end of original building footprint), where the highest subslab vapor concentrations were measured. The lithology of this zone is predominantly sand with zones of interbedded silt/clay.

The SSZ is impacted mainly by PCE with lower levels of TCE and related compounds. These contaminants are collectively referred to as chlorinated volatile organic compounds (CVOCs). The highest concentration of PCE in groundwater at the Site was 2,450 micrograms per liter (µg/L). The highest concentration of PCE measured in soil in this zone was 430 (µg/kg). However, higher concentrations are expected to be present in some areas and may be identified during subsequent sampling. This CMZ represents the area with highest concentrations of groundwater contamination and potential adsorbed or residual source material contributing to dissolved contamination. Remediation of this zone is focused on protection of humans from continued migration and dissolution of adsorbed CVOCs, and possible residual DNAPL, into groundwater.

CMZ-3-Dilute Plume (DP)

The DP encompasses the wider band of dissolved contamination (along with low levels of contiguous adsorbed phase contaminants) that surrounds the SSZ. The DP is impacted mainly by PCE with lower levels of TCE and related compounds. It represents total CVOC groundwater concentrations documented between non-detect and approximately 1,500 µg/L. The lithology encompassed by this zone is predominantly sand with zones of interbedded silt/clay. The CMZ depth varies across the DP.

Applicable remedial technologies were screened and evaluated to derive the optimum approaches to achieve the RAOs and the chemical specific cleanup goals. The most viable technologies were further developed into


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separate remedial alternatives applicable to each CMZ. Several alternatives include in situ chemical oxidation (ISCO) or enhanced in situ bioremediation (EISB) as ancillary remedial components. ISCO with potassium permanganate (KMnO4) is presumed for the in-situ oxidation injection phase. Permanganate is an aggressive oxidant which is well suited for treatment of chlorinated residuals. The ISEB treatment is based on the injection of infused oxygen into the groundwater for aerobic bioremediation.

Remedial alternatives for each CMZ at the Site are summarized below. Capital costs are those expenditures that are required to construct a remedial alternative. Operation and maintenance (O&M) costs are those post-construction costs necessary to ensure or verify the continued effectiveness of a remedial alternative and are estimated on an annual basis. Present worth is the amount of money which, if invested in the current year, would be sufficient to cover all the costs over time associated with a project, calculated using a discount rate of seven percent and a 30-year time interval. CMZ 1 – Unsaturated Soil Zone (UZ)

CMZ-1: UNSATURATED SOIL ZONE (UZ) REMEDIAL ALTERNATIVES ALTERNATIVE DESCRIPTION OF REMEDIATION ALTERNATIVES

1 No Action

This alternative is required for consideration by the NCP. No active cleanup activities would be performed. Periodic monitoring of existing wells and reporting will be completed every five years to confirm Site conditions.

2a Soil Vapor Extraction (SVE) with Limited Air Sparging

This alternative includes the installation of a SVE system under the Walker Building. The system would consist of several SVE wells screened from 5 to 50 feet below land surface including angled borings under the Walker Building. It also includes a series of sparge wells installed with 3-ft screens below the water table. Alternative 2a also includes installation of about 260 feet of horizontal vapor recovery piping for long term VI protection for the building.

2b Thermally Enhanced SVE with Limited Air Sparging

This alternative consists primarily of SVE as a prescribed remedy for treatment of UZ soil, with thermally enhanced SVE (TE-SVE) being implemented in a limited area to enhance contaminant removal in the suspected source areas. SVE will also be implemented under the building to reduce VI into the building.

The area assumed for thermal enhancement and air sparging is approximated by the areal extent of the SSZ. A target temperature of approximately 160°F is specified to promote enhanced volatilization and desorption. Alternative 2b includes a series of well sparge wells installed with 3-ft screens below the water table and includes installation of about 260 feet of horizontal vapor recovery piping for VI protection for the building. Also, some targeted soil excavation (about 900 cubic yards near oil/water separator, drum area, near SE corner of building.


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CMZ-1: UNSATURATED SOIL ZONE (UZ) REMEDIAL ALTERNATIVES ALTERNATIVE DESCRIPTION OF REMEDIATION ALTERNATIVES

3 Limited Soil Excavation with SVE

This alternative includes the use of limited soil excavation of approximately 10,700 bank cubic yards (bcy) of soil to approximately 20 feet south of the Walker Building to remove the most highly contaminated soils. The remaining UZ contamination including under the building would be addressed through the installation of a SVE system.

4 ISCO and SVE

This alternative consists of ISCO treatment in the area south of the Walker building. Overall, the remedy will treat approximately 104,800 cubic yards of CVOC-contaminated soil. ISCO, presumably with potassium permanganate, would be used to target all UZ soils south of the building over an area of approximately 0.7 acre. The SVE system would be used to remediate CVOC contamination beneath the building and to prevent VI.

ESTIMATED COSTS FOR REMEDIAL ALTERNATIVES IN CMZ-1 Activity Alternative #1 Alternative #2a Alternative #2b Alternative #3 Alternative #4

Estimated Capital Cost $0 $2,001,999 $5,285,201 $2,722,209 $2,627,391

Estimated Annual O&M Costs $39,987 $975,135 $976,135 $738,963 $738,963

Net Present Value $40,000 $2,978,100 $6,261,300 $3,461,200 $3,366,400

Estimated Time to Achieve RAOs

greater than 30 years ~5 years ~5 years ~5 years ~5 years

CMZ-2 – Saturated Soil (SSZ)

CMZ-2: SATURATED SOIL ZONE (SSZ) REMEDIAL ALTERNATIVES ALTERNATIVE DESCRIPTION OF REMEDIATION ALTERNATIVES

1 No Action This alternative is required for consideration by the NCP. No active cleanup activities would be performed. Periodic monitoring of existing wells and reporting will be completed every five years to confirm Site

2 Groundwater Recovery and Treatment/Hydraulic Containment

This alternative includes groundwater recovery and treatment of CVOC contaminated groundwater. Groundwater would be recovered from three recovery wells screened 50 to 75 feet bls and treated via air stripping and activated carbon. The treated water would be discharged back into the aquifer via an infiltration gallery.


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CMZ-2: SATURATED SOIL ZONE (SSZ) REMEDIAL ALTERNATIVES ALTERNATIVE DESCRIPTION OF REMEDIATION ALTERNATIVES

3 ISCO

This alternative involves a full coverage injection of a chemical oxidant. Organic compounds in contact with the chemical oxidant would be quickly destroyed; thereby eliminating contaminant mass available for dissolution and lateral solvent transport. Effective implementation of ISCO is dependent upon uniform oxidant distribution and contact with contaminants. The persistence of the oxidant will allow secondary contact with the COCs as well as moving into low permeable units over time to minimize back diffusion of COCs. This alternative would include installing 52 2-inch diameter well clusters (12 angled clusters and 40 vertical clusters).

4 EISB with in situ chemical reduction (ISCR)

This alternative involves a dense array, full coverage injection of a combined carbon substrate with soluble ferrous iron or zero valent iron (ZVI) to reduce residual DNAPL, CVOCs adsorbed on saturated soil, and CVOCs dissolved in groundwater. This remedy offers the benefit of both anaerobic biodegradation and chemical reduction treatment mechanisms. The overall number of injection points and layout mirrors the application for ISCO (alternative #3).

5 Biogeochemical Reductive Dehalogenation (BiRD)

This alternative consists of the BiRD technology applied to the SSZ using an injection well and recirculation well approach. A series of hexagonal recirculation cells would be used to inject carbon substrate, sulfate, and iron solution to reduce residual DNAPL, CVOCs adsorbed on saturated soil. BiRD is a patented in situ process to promote abiotic reductive dechlorination of chlorinated aliphatic hydrocarbons (CAHs). BiRD is a variant of the ISCR remedial technology process option (RTPO). This technology relies upon the injection of carbon substrates (e.g., emulsified oil) to promote reduced conditions in an aquifer and to facilitate the conversion of naturally occurring iron minerals (typically ferric) to mineral iron sulfide (i.e., FexSy) that can promote abiotic degradation.

ESTIMATED COSTS FOR REMEDIAL ALTERNATIVES IN CMZ-2

Activity Alternative #1 Alternative #2 Alternative #3 Alternative #4 Alternative #5 Estimated Capital Cost $0 $479,959 $4,446,211 $2,396,036 $1,605,753

Estimated O&M Costs $39,987 $1,132,680 $82,934 $82,766 $391,246 Net Present Value $40,000 $1,612,600 $4,529,100 $2,478,800 $1,997,000


greater than 30 years 20 years 5 years 5 years 3 years


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CMZ-3 Dilute Plume CMZ-3: DILUTE PLUME REMEDIAL ALTERNATIVES

ALTERNATIVE DESCRIPTION OF REMEDIATION ALTERNATIVES

1 No Action

This alternative is required for consideration by the NCP. No active cleanup activities would be performed. Periodic monitoring of existing wells and reporting will be completed every five years to confirm Site conditions.

2 Groundwater Recovery and Treatment (GR&T)/Hydraulic Containment

This alternative involves the use of GR&T of CVOC-contaminated groundwater to provide hydraulic containment and limited mass removal of COCs. The recovered groundwater is then treated with air stripping and granular activated carbon (GAC) and infiltrated back into the aquifer via an infiltration gallery.

3 EISB Passive Barrier Wells with Horizontal Well

This alternative involves the use of EISB passive barriers consisting of injection wells across the DP coupled with a horizontal injection well for the toe of the DP. The injection wells would be injected with emulsified oil substrate supplemented with bioaugmentation and pH adjustment to accelerate biodegradation via direct anaerobic reductive dechlorination of CVOCs in groundwater. The treatment barriers would be emplaced solute barriers that would not alter or impede groundwater transmissivity.

4 MNA

Monitored natural attenuation (MNA) is the use of natural biotic degradation or natural abiotic degradation (e.g., due to reduced iron species, soil attenuation, advection, dispersion, dilution, etc.) for contaminant reduction. Due to the aerobic groundwater conditions and limited presence of PCE/TCE daughter products, natural biotic degradation is not thought to be particularly active for the Walker Site. The downgradient edge of the dissolved plume is essentially in equilibrium, presumably due to natural abiotic reduction.

ESTIMATED COSTS FOR REMEDIAL ALTERNATIVES IN CMZ-3 Activity Alternative #1 Alternative #2 Alternative #3 Alternative #4

Estimated Capital Cost $0 $659,583 $1,448,081 $0

Estimated O&M Costs $39,987 $1,159,299 $1,001,623 $187,078

Net Present Value $40,000 $1,818,900 $2,449,700 $187,100


greater than 30 years 20 years 20 years 20 years

EVALUATION OF ALTERNATIVES

Nine criteria are used to evaluate the different remediation alternatives individually and against each other in order to select a remedy (see table below, Evaluation Criteria for Superfund Remedial Alternatives). This section of the Proposed Plan describes the relative performance of each alternative against the nine criteria,


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noting how each compares to the other options under consideration. A detailed analysis of the alternatives can be found in the 2018 FS Report.

The remedial alternative selected for a Superfund site must meet the two threshold criteria as well as attain the best balance among the five evaluation criteria. EPA, after considering State (TDEC) acceptance and public comments received on this proposed plan, will select the final remedy in the Record of Decision (ROD). EPA’s Preferred Remedial Alternative may be altered or changed based on the two modifying criteria. The nine criteria are as follows:

EVALUATION CRITERIA FOR SUPERFUND REMEDIAL ALTERNATIVES

THRESHOLD CRITERIA

Overall Protectiveness of Human Health and the Environment determines whether an alternative eliminates, reduces, or controls threats to public health and the environment through ICs, engineering controls or treatment. Compliance with Applicable or Relevant and Appropriate Requirements (ARARs) evaluates whether the alternative meets Federal and State environmental statutes, regulations, and other requirements that pertain to the site, or whether a waiver is justified.

EVALUATION CRITERIA

Long-term Effectiveness and Permanence considers the ability of an alternative to maintain protection of human health and the environment over time. Reduction of Toxicity, Mobility, or Volume of Contaminants through Treatment evaluates an alternative's use of treatment to reduce the harmful effects of principal contaminants, their ability to move in the environment, and the amount of contamination present. Short-term Effectiveness considers the length of time needed to implement an alternative and the risks the alternative poses to workers, residents, and the environment during implementation. Implementability considers the technical and administrative feasibility of implementing the alternative, including factors such as the relative availability of goods and services. Cost includes estimated capital and annual operations and maintenance costs, as well as present worth cost. Present worth cost is the total cost of an alternative over time in terms of today's dollar value. Cost estimates are expected to be accurate within a range of +50 to -30 percent.

MODIFYING CRITERIA

State/Support Agency Acceptance considers whether the State agrees with EPA’s analyses and recommendations, as described in the RI/FS and Proposed Plan.

Community Acceptance considers whether the local community agrees with EPA's analyses and Preferred Remedial Alternative. Comments received on this Proposed Plan are an important indicator of community acceptance.

A detailed analysis of the remedial alternatives was presented in the 2018 FS. This analysis compared each remedial alternative for each CMZ to the Threshold and Evaluation Criteria highlighted in the table above. If an alternative does not meet the first two threshold criteria; Overall Protection of Human Health and the Environment and Compliance with ARARs, EPA does not consider the alternative for further evaluation. EPA


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will recommend the cleanup alternative that provides the best balance of the first seven of the nine evaluation criteria. EPA, after considering State (TDEC) acceptance and public comments received on this proposed plan, will select the final remedy in the Record of Decision (ROD).

OVERALL PROTECTIVENESS OF HUMAN HEALTH AND THE ENVIRONMENT

The No Action Alternatives would not be protective of human health and the environment and therefore, are not carried forward.

CMZ-1: Alternatives UZ#2 through UZ#4 would be protective of human health and the environment. UZ #2b (Thermally Enhanced SVE with Limited Air Sparging) should provide nearly complete removal of COCs from a portion of the zone and vapor removal of COCs from the remaining portion of the zone. Alternative UZ #3 (Limited Soil Excavation with SVE) removes COCs from the upper 20-feet of the USZ.

CMZ-2: Alternatives SSZ#2 through SSZ#5 would be protective of human health and the environment. Under Alternative SSZ #3 (ISCO), the highest levels of source area contamination would quickly be chemically destroyed in situ. However, this assumes that the dense array injection and repeated injection of hot spots will attain sufficient contact with the COCs. Alternatives SSZ #4 (EISB with ISCR) and SSZ #5 (BiRD) rely on reducing geochemical conditions and the potentially longer treatment timeframe. Under SSZ#2 (GR&T/hydraulic containment), the contaminants will not be destroyed and contaminated groundwater would be treated ex situ, resulting in potential aboveground exposures. In addition, SSZ #2 would not provide any potential ancillary downgradient treatment of the DP as would other alternatives that include injection of treatment chemicals/amendments.

CMZ-3: Alternatives DP#2 through DP#4 would be protective of human health and the environment. Under alternative DP #2 (GR&T/hydraulic containment), the dissolved contamination is hydraulically contained and prevented from migrating any farther toward the municipal wellfield. Alternative DP #3 (EISB passive barriers with horizontal well) treats the dissolved COCs in situ via biological treatment barrier using vegetable oil. It also includes a downgradient biobarrier treatment zone to treat the toe of the plume. The MNA alternative (DP #4) relies on naturally occurring degradation without active source treatment.

COMPLIANCE WITH ARARS

A significant ARAR for the planned cleanup is the MCL for each site related contaminant that is listed under the federal Safe Drinking Water Act National Primary Drinking Water Regulations (40 CFR 141.61). The aquifer under the Site is a potential drinking water source, and similar Tennessee regulations also require compliance with the MCLs. A full listing of the ARARs for this Site is provided in the FS.

The No Action Alternatives would not comply with ARARs.

CMZ-1: Alternatives UZ#2 through UZ#4 would comply with ARARs, and therefore meet this threshold criterion Alternative UZ #2b (Thermally Enhanced SVE with Limited Air Sparging) is the most aggressive treatment alternative for meeting soil cleanup levels. It is expected to have the most comprehensive success at reducing the mass and concentration of contaminants, and should do so in a short timeframe. Alternative UZ #3 (Limited Excavation with SVE) and UZ #4 (ISCO and SVE) are projected to be roughly equivalent and are the next most aggressive treatment alternatives for meeting soil cleanup levels. They are expected to be successful at reducing the mass and concentration of contaminants in a short timeframe. All four active treatment alternatives that include SVE are projected to be equivalent in capturing vapor contamination and would therefore meet indoor air cleanup levels.


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CMZ-2: Alternatives SZZ#2 through SSZ#5 would comply with ARARs, and therefore meet this threshold criterion. Alternatives SSZ #3 and SSZ #4 are projected to be roughly equivalent and are the most aggressive treatment alternatives for meeting soil and groundwater cleanup levels. Alternative SSZ #2 is the least reliable approach for meeting chemical-specific ARARs since it does not sufficiently destroy contamination and is dependent on desorption of contaminants into groundwater.

CMZ-3: Alternatives DP #2 through DP#4 would comply with ARARs, and therefore meet this threshold criterion. Compliance with ARARs is best afforded by Alternatives DP #2 and DP #3. Both options provide a good measure of treatment or capture of COCs in the DP to preclude offsite migration and contact with COCs in groundwater above cleanup levels. However, DP #3 is expected to have the most comprehensive successes at reducing the mass and concentration of contaminants via treatment. The MNA alternative (DP #4) and the No Action Alternative were scored low based upon the lack of treatment, and thus a lower likelihood of complying with groundwater ARARs.

LONG-TERM EFFECTIVENESS AND PERMANENCE

The No Action Alternatives are least likely to be effective and permanent.

CMZ-1: Thermally Enhanced SVE with Limited Air Sparging (UZ #2b) would be the most aggressive in removing contamination over the entire depth of the UZ (over the areal extent of the SSZ), including any contaminated lower permeability soils in this area that may be difficult to treat with other methods. Limited Soil Excavation with SVE (UZ #3) would be the next most aggressive in removing a portion of potentially contaminated source area soil from the Site, including any contaminated lower permeability soils in this area that may be difficult to treat with other methods. Although it was ranked similarly to UZ #3 and UZ #2a, the ISCO and SVE alternative (UZ #4) may be less effective in the long term due to the inherent difficulty in providing adequate oxidant contact within low permeability layers. The low permeability soil may contain higher concentrations of adsorbed contamination and may provide a long-term source of contamination. For all UZ alternatives, SVE would permanently remove volatile contaminants in the unsaturated soil with adequate induced airflow, but will be more effective in higher permeability soil.

CMZ-2: Alternatives SSZ #3 and SSZ #4 are projected to be roughly equivalent and are the most aggressive treatment alternatives for meeting soil and groundwater cleanup levels. Alternative SSZ #5 is dependent on formation of iron sulfide complexes under specific biogeochemical conditions. The mineralogy to further support this treatment approach has not been completed; hence this alternative has a less rigorous design basis. Alternative SSZ #2 is the least reliable approach for meeting chemical-specific ARARs since it does not sufficiently destroy contamination and is dependent on desorption of contaminants into groundwater.

CMZ-3: The long-term effectiveness of Alternative DP #3 is considered best due to active treatment and destruction of contaminants. Alternative DP #2 is scored lower since it is dependent upon direct hydraulic contact which may be limited in low permeability zones and is subject to the longer-term back diffusion of COCs from these tight soils. MNA (DP #4) is predicted to be somewhat effective in the long-term since the DP appears to be relatively stable.

REDUCTION OF TOXICITY, MOBILITY, AND VOLUME THROUGH TREATMENT

The No Action Alternatives do not reduce toxicity, mobility, or volume through treatment.

CMZ-1: Alternative UZ #2b followed by UZ #3 and UZ #4 are expected to have the most comprehensive successes at reducing the mass, volume, and concentration of on-site contaminants in a short timeframe. UZ


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#3 and UZ #4 both aggressively treat the upper 20 feet of the UZ overlying the SSZ. UZ #2a is expected to a lower reduction of toxicity and mobility due to the heterogeneous lithology.

CMZ-2: Three of the alternatives (SSZ #3, SSZ #4, and SSZ #5) are active treatment approaches that destroy contaminants; hence the expected reduction of toxicity, mobility, and volume is an advantage for these approaches. Alternative SSZ #5 (BiRD) was ranked slightly lower than the other two active treatment approaches due to uncertainty with the overall effectiveness of the phased biogeochemical treatment approach and lack of bench scale testing. Alternative SSZ #2 provides on-site reductions in mobility and volume, but only a minor reduction in mobility due to treatment residuals and desorption.

CMZ-3: One alternative (DP #3) is an active treatment approach that destroys contaminants; hence the expected reduction of toxicity, mobility, and volume is an advantage for this approach. Alternative DP #2 provides reductions in mobility and volume, but only a minor reduction in concentration over time due to desorption of COCs from soils. The No Action alternative offers no toxicity, mobility, or volume reduction.

SHORT TERM EFFECTIVENESS

The No Action Alternatives pose no short-term threat to workers and the community; no cleanup would occur so there would be no construction activities that themselves would pose a disruption or threat.

CMZ-1: All four active UZ remedies have average timeframes for achieving RAOs over the entire treatment area since their primary component (SVE) is limited by non-uniform air contact with soils. However, Alternative UZ #2b is expected to achieve RAOs most quickly over the areal extent of the SSZ due to the thermal enhancement of SVE. Alternative UZ #4 was ranked the highest among active remedies as it will produce only minor Site disruption compared to excavation and includes the ISCO component that should accelerate meeting RAOs. Although removal of contamination would occur relatively quickly for a portion of the UZ, the excavation component of UZ #3 would increase the potential for impacts to the community and workers, although these issues can be effectively managed.

CMZ-2: The primary difference between the alternatives is the time period before RAOs are met. SSZ #2 (GR&T/hydraulic containment) was scored low because it is anticipated to require long-term O&M and requires ex situ groundwater treatment.

CMZ-3: The two active alternatives (DP #2 and DP #3) provide good short-term effectiveness. DP #2 is considered slightly more protective of workers and the community during remedial action since it includes capture of the toe of the plume and would prevent migration toward the municipal well field. DP #3 is expected to achieve RAOs more quickly than the other alternatives since it includes active in situ treatment. They are both equally protective of workers and the community during remedial action. The primary difference between the alternatives is the time period before RAOs are met. DP #2 (GR&T/hydraulic containment) was scored low because it is anticipated to require long-term O&M and requires more costly ex situ groundwater treatment. MNA (DP #4) scored the lowest since it only includes monitoring as a way to protect the community, and would take a longer period to meet RAOs.

IMPLEMENTABILITY

CMZ-1: All five active alternatives are considered to have good implementability. Alternative UZ #3 was scored second highest to the No Action alternative because it has fewer and more easily implemented components to the remedial alternative. Alternative UZ #2a would be slightly more difficult to construct due to the number of wells and additional remediation equipment required. Alternative UZ #4 would be slightly more difficult to


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implement due to the heterogeneous clay layer that may hinder below-ground movement of the chemical oxidant.

CMZ-2: All the alternatives evaluated for the SSZ are implementable with only minor issues. SSZ #5 (BiRD) was scored slightly lower due to the higher complexity of the geochemical reactions. Alternatives SSZ #3 and SSZ #4 could have implementation impacts relative to injecting under or adjacent to an occupied building. Conversely, SSZ #5 is configured to avoid the building using fewer angled wells.

CMZ-3: All the alternatives evaluated for the DP are implementable with only minor issues. DP #2 was scored slightly lower since it includes a downgradient cutoff of the toe of the plume that would involve installation of a treatment zone and yard piping on the former Witt property. The MNA alternative (DP #4) was scored lower since natural attenuation may not be a reliable treatment method based on Site geochemical conditions. DP #3 offers more complexity due to the installation of the directionally drilled well under the Witt building.

COST

Cost estimates, including capital costs and long-term operating costs, were prepared for each alternative, and are summarized in the tables above. There are no capital costs associated with the No Action Alternatives. Costs for the implementation of Five-Year-Reviews and groundwater monitoring are included as the Site-Wide Costs. These O&M costs were estimated separately as they apply to all remedy alternatives until cleanup goals are met at the Site. Consistent with EPA guidance, the cost estimates are order-of-magnitude estimates with an intended accuracy range of plus 50 to minus 30 percent of present value. STATE ACCEPTANCE State acceptance of the preferred alternative will be addressed in the Record of Decision following review of comments received on the Proposed Plan. COMMUNITY ACCEPTANCE Community acceptance of the preferred alternative will be addressed in the Record of Decision following review of comments received on the Proposed Plan. SUMMARY OF PREFERRED ALTERNATIVE

Using the above information/assumptions, the Agency’s Preferred Remedial Alternative for the Walker Site is a combination of the following alternatives:

CMZ-1 Alternative UZ #2B - Thermally Enhanced Soil Vapor Extraction (TE-SVE) with Limited Air Sparging

CMZ-2 Alternative SSZ #5 – BiRD

CMZ-3 Alternative DP #3 – EISB Passive Barriers with Horizontal Well

The combination of the recommended alternative for each CMZ will provide some synergies and result in a lower overall cost if duplicative wells from the individual CMZ alternatives could be eliminated. (Figure 5).

The estimated total cost of this Preferred Alternative (including all three treatment zones), is $8,569,900 if thermal enhancement is not needed, $11,747,400 with thermal enhancement. The decision to engage the thermal enhancement will be finalized in the remedial design (RD) and/or remedial action (RA) phases, and may be based on one or more of the following reasons:


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Determination of the presence of mobile NAPL during RD or RA phases. Mobile NAPL in soil may delay site remediation using SVE. NAPL has not been observed and current soil concentrations do not indicate the presence of NAPL. However, uncertainty remains since few soil samples have been collected beneath the Walker building and the depth of the unsaturated soil zone.

During RD or RA phases VOCs observed in soil are substantially higher than found during the RI.

Prolonged asymptotic concentrations observed in SVE vapors without groundwater and indoor air cleanup levels being achieved.

A phased response action is recommended for the Site. The use of a phased approach would allow EPA to mitigate more immediate site-specific threats while concurrently collecting additional characterization data to determine the best method for attaining long term objectives. In addition, an adaptive phased approach for SVE, air sparging, and thermal enhancement in the UZ is recommended since the 2017 data did not confirm the exact location/depths of source material in the UZ.

Also, the vapor mitigation system installed by EPA under the building slab continues to operate and should continue to be operated until it is no longer necessary.

PREFERRED REMEDIAL ALTERNATIVE

CMZ Alternative # Description

Cost without Thermal

Enhancement

Cost with Thermal

Enhancement

UZ UZ #2b TE-SVE with Limited Air Sparging $3,083,800 $6,261,300

SSZ SSZ #5 BiRD (if needed) $1,997,000 $1,997,000

DP DP #3 EISB Passive Barriers with Horizontal Well $2,449,700 $2,449,700

Site-Wide Costs (groundwater monitoring for 10 years, five-year reviews, ICs, etc. for 30 years) $1,039,400 $1,039,400

Total: $8,569,900 $11,747,400

Projected Remedial Phasing

The recommended phasing for the overall implementation of the selected remedies is listed below. It is expected that some of these phases can proceed on simultaneous tracks.

RECOMMENDED PHASING

Phase Task Description Action

I Oil/Water Separator Removal and Soil Excavation

Removal of the oil/water separator, TCE drum area, and visibly stained soil found in these areas. Removal of ~900 bank cubic yards (bcy) of soil located along the eastern side of the Walker building to ~10 feet bls with off-site disposal. Collection of confirmation samples.

IIA Implementation of SVE with Air Sparging

Adaptive phased installation of SVE wells, air sparge wells, heater


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Phase Task Description Action borings, etc. Installation and operation of treatment systems. Active remediation of portions of the UZ may be curtailed if additional data collected indicates that remediation is not necessary. Groundwater and soil gas/indoor air monitoring to assess COC flux reduction and determine the extent of SSZ action.

IIB Targeted Thermal Enhancement of SVE System

Application of thermal enhancement as needed

III BiRD Remedy

If needed after implementation and evaluation of Phase II, install BiRD wells, treatment system and infiltration gallery. Groundwater and soil gas/indoor air monitoring to assess COC flux reduction and determine the need for DP action.

IV DP Remedy Evaluation

Evaluate groundwater monitoring results and effects of UZ and SSZ remedial actions. Determine if DP #3 remedy is still required based on conditions resulting from UZ/SSZ treatment.

A robust but phased remedy is recommended for the UZ (Alternative #2b). The UZ remedy includes SVE with shallow air sparging as the primary remedial approach. Thermal enhancement may be applied to accelerate or optimize the remedy based on Site conditions observed during the RD and/or RA phase.

Groundwater monitoring will be conducted to evaluate the effects of the UZ treatment and contaminant flux reductions before determining the timing and extent of SSZ remedial action that is needed to meet RAOs. In situ remediation with the BiRD technology (Alternative SSZ #5) is recommended for the saturated zone treatment. In addition, groundwater monitoring will be conducted to evaluate the effects of the UZ and SSZ treatment and contaminant flux reductions before determining if the phased implementation of EISB (Alternative DP #3) for the DP is still required.

Institutional controls (ICs) will be required as part of the selected remedy. ICs are non-engineering measures which usually include legal controls to affect human activities in such a way to prevent or reduce exposure to contamination. The purpose of the ICs is to control use of the subject property to reduce potential exposures to site contaminants. Some of the controls generally include, but are not limited to, the following:

1. The use of deed restrictions or local zoning/ordinances at the Site to limit potential exposure of Site users to the COCs.


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2. Groundwater use restrictions incorporated into local land use zoning or construction permit requirements. The Ground Water Quality Control Board for Shelby County has established water well regulations that include permit requirements. The regulations include specific requirements for placement of water wells within a half-mile of a listed Superfund site. The Memphis Sand aquifer is the municipal water supply for the residents near the Site.

Based on the information currently available, EPA believes the Preferred Alternative meets the threshold criteria and provides the best balance of tradeoffs among the other alternatives with respect to the balancing criteria. EPA expects the preferred alternative to satisfy the following statutory requirements of CERCLA Section 121(b), 42 U.S.C. § 9621(b): 1) be protective of human health and the environment; 2) comply with ARARs; 3) be cost effective; 4) utilize permanent solutions and alternative treatment technologies or resource recovery technologies to the maximum extent practicable; and 5) satisfy the preference for treatment (via the existing groundwater treatment system) as a principal element. EPA will assess the two modifying criteria of state acceptance and community acceptance in the ROD to be issued following the close of the public comment period. PUBLIC PARTICIPATION The public meeting for the Proposed Plan will begin at 6 p.m. on June 14, 2018, at the Lucius E. and Elsie C. Burch Library 501 Poplar View Parkway Collierville, TN 38017.

EPA has provided information regarding the cleanup of the Site to the public through Fact Sheets, public meetings, announcements in Collierville Herald, and the Administrative Record file. In addition to reading this Proposed Plan, EPA and TDEC encourage the public to gain a more comprehensive understanding of the Site and the Superfund activities that have been conducted at the Site by reviewing the documents contained in the Administrative Record/Information Repository.

For further information on the Site, please contact:

Randy Bryant, Remedial Project Manager (404) 562-8794 or (800) 435-9233 E-mail: [email protected] Kerisa Coleman, Community Involvement Coordinator (404) 562-8831 or (800) 435-9233 E-mail: coleman.kerisa @epa.gov US EPA Region 4 61 Forsyth Street, SW Atlanta, GA 30303-8960

DOCUMENT INFORMATION

The Administrative Record contains all the information used by the Agency to select a Remedial Action. Copies of the Administrative Record are kept at:

Lucius E. and Elsie C. Burch Library 501 Poplar View Parkway


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Collierville, TN 38017 901/457-2600 Hours: Monday – Thursday: 10 a.m. – 8 p.m. Fri and Sat: 10 a.m. –6 p.m. Sun :1 p.m. – 5 p.m. U.S. Environmental Protection Agency Region IV - Records Center 61 Forsyth Street, SW Atlanta, Georgia 30303-3104 Phone: 404-562-8816 Hours: Monday - Friday 8 a.m. - 5 p.m.


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GLOSSARY Administrative Record: Materials, information and documents that provide the basis and support EPA's selection of a remedial action at Superfund sites usually placed in the information repository near the Site.

Applicable or Relevant and Appropriate Requirements (ARARs): Refers to Federal and more stringent State environmental requirements a selected remedy must attain which vary from site to site. Reference 40 CFR 300.5 Definitions of ‘Applicable requirements’ and ‘Relevant and appropriate requirements’.

Aquifer: An underground geologic formation, or group of formations, containing water.

Baseline Risk Assessment: A qualitative and quantitative evaluation performed in an effort to define the risk posed to human health and the environment by the presence or potential presence and use of specific pollutants.

Chemical of Concern (COCs): Chemical constituents associated with a Superfund Site that have been released into the environment and pose an unacceptable risk to human health.

Cleanup: Actions taken to deal with a release or threat of release of a hazardous substance that could affect humans and/or the environment. The term "cleanup" is sometimes used interchangeably with the terms remedial action, removal action, response action, or corrective action.

Comprehensive Environmental Response, Compensation and Liability Act (CERCLA): Also known as Superfund, is a federal law passed in 1980 and modified in 1986 by the Superfund Amendment and Reauthorization Act (SARA). The act created a trust fund, to investigate and cleanup abandoned or uncontrolled hazardous waste sites.

Ecological Risk Assessment (ERA): A qualitative and quantitative evaluation performed in an effort to define the risk posed to ecological receptors by the presence or potential presence of specific contaminants.

Feasibility Study: Study conducted after the Remedial Investigation to determine what alternatives or technologies could be applicable to the site specific COCs.

Groundwater: Water located beneath the ground surface in soil pore spaces and in the fractures of lithologic formations.

Information Repository: A library or other location where documents and data related to a Superfund project is placed to allow public access to the material.

In situ: In its original place; unmoved unexcavated; remaining in the subsurface.

Institutional Controls: Administrative, non-engineering, controls that inform and prevent exposures to human receptors.

Monitored Natural Attenuation (MNA): This term refers to the reliance on natural attenuation processes to achieve site-specific remediation objectives. The natural attenuation processes that are at work in such remediation approach include a variety of physical, chemical, or biological processes that, under favorable conditions, act without human intervention to reduce the mass, toxicity, mobility, volume, or concentration of contaminants in soil or groundwater.

Monitoring: The periodic or continuous surveillance or testing to determine the level of pollutants in various media.


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National Oil and Hazardous Substances Pollution Contingency Plan (NCP): The federal regulation that guides the Superfund program.

National Priorities List (NPL): EPA’s list of the most serious uncontrolled hazardous waste sites identified for possible long-term remedial response. This list is based primarily on the score a site received on the Hazard Ranking System.

Proposed Plan: Document that summarizes the RI/FS, the alternatives developed and the proposed Preferred Remedial Alternative and the rationale for its proposal

Public Comment Period: The time allowed for the public to express its views and concerns on the information provided in the Proposed Plan and EPA’s proposed Preferred Remedial Alternative.

Record of Decision (ROD): A decision document that selects and describes the remedy that will be implemented at a Site. The ROD is based on information and technical analysis generated during the remedial investigation/feasibility study and consideration of public comments.

Remedial Action (RA): The actual construction or implementation phase of a Superfund site cleanup that follows remedial design.

Remedial Action Objectives (RAOs): Provide a general description of what the cleanup will accomplish (e.g., restoration of groundwater to drinking water levels). These goals typically serve as the as the basis for developing remedial alternatives.

Remedial Design (RD): The development of engineering drawings and specifications for the implementation and construction of a remedial action.

Remedial Investigation (RI): An investigation conducted to fully characterize the nature and extent of contamination of a release, or threat of release, of hazardous substances, pollutants, or contaminants. In addition, the RI also evaluate risks posed to human health and the environment. The RI gathers the necessary data to support the corresponding FS.

Response Action: A CERCLA-authorized action involving either a short-term removal action or a long-term removal response. This may include but is not limited to: removing hazardous materials from a site to an EPA-approved hazardous waste facility for treatment, containment or treating the waste on-site, identifying and removing the sources of groundwater contamination and halting further migration of contaminants.

Responsiveness Summary: A summary of oral and written comments received by EPA during the public comment period on EPA’s Proposed Plan, and EPA’s responses to those comments. The responsiveness summary is a key part of the ROD, highlighting community concerns for EPA decision-makers.

Superfund: The common name used for the Comprehensive Environmental Response, Compensation and Liability Act of 1980 (CERCLA), as amended in 1986.

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28

Legend

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29

Table 1: Industrial/Commercial Worker Scenario Potential Excess Cancer/Non-cancer Risks

Contaminated Media Industrial/Commercial Worker

Excess Cancer Risk Non-cancer Hazard Index

On Site Soil 3 x 10-6 0.2 Groundwater 6 x 10-5 8 Surface Water 3 x 10-8 0.0002 Sediment 7 x 10-7 0.02 Indoor Air (VI pathway) 3 x 10-5 9 Total 1 x 10-4 17

Off Site Groundwater 3 x 10-5 8 Indoor Air (VI pathway) 1 x 10-6 0.06 Total 4 x 10-5 8

Shading indicates unacceptable cancer risk or non-cancer hazard as defined in CERCLA.

Table 2: Residential Scenario Potential Excess Cancer/Non-cancer Risks

Contaminated Media Residential

Excess Cancer Risk

Non-cancer Hazard Index

On Site Soil 1 x 10-5 0.8 Groundwater 4 x 10-4 62 Surface Water 4 x 10-7 0.003 Sediment 4 x 10-6 0.05 Indoor Air (VI pathway) 2 x 10-4 40 Total 6 x 10-4 103

Off Site Groundwater 2 x 10-4 52 Indoor Air (VI pathway) 6 x 10-6 0.3 Total 2 x 10-4 53

Shading indicates unacceptable cancer risk or non-cancer hazard as defined CERCLA.

Table 3: Construction Worker Scenario Potential Excess Cancer/Non-cancer Risks

Contaminated Media Construction Worker

Excess Cancer Risk

Non-cancer Hazard Index

On Site Surface Soil 1 x 10-6 7 Subsurface Soil 1 x 10-6 6 Groundwater 2 x 10-6 6 Surface Water 2 x 10-8 0.0001 Sediment 6 x 10-8 0.02 Total 5 x 10-6 19

Off Site Groundwater 1 x 10-6 6 Total 1 x 10-6 6

Shading indicates unacceptable cancer risk or non-cancer hazard as defined in CERCLA.

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Table 4: Cleanup levels for Chemicals of Concern in Subsurface Soil

Chemical of Concern Unit RGO Basis

1,1-Dichloroethene ug/kg 120

Soil levels protective of groundwater cis-1,2-Dichloroethene ug/kg 833

Tetrachloroethene ug/kg 126

Trichloroethene ug/kg 126

Table 5: Cleanup levels for Chemicals of Concern in Groundwater

Table 6: Cleanup levels for Chemicals of Concern in Indoor Air

Chemicals of Concern Unit RGO Basis 1,4-Dioxane µg/l 68 Protective for residential risk 1,1-Dichloroethane µg/l 740 Protective for residential risk 1,1-Dichloroethene µg/l 7 Protective for groundwater quality

Carbon Tetrachloride µg/l 5 Protective for groundwater quality and residential risk

cis-1,2-Dichloroethene µg/l 70 Protective for groundwater quality

Methylene Chloride µg/l 5 Protective for groundwater quality and residential risk

Tetrachloroethene µg/l 5 Protective for groundwater quality and residential risk

Trichloroethene µg/l 5 Protective for groundwater quality and residential risk

Vinyl Chloride µg/l 2 Protective for groundwater quality and residential risk

Chemical of Concern Unit RGO Basis

1,2,4-Trimethylbenzene µg/m3 7.3

Protective for current commercial use or future residential use

Naphthalene µg/m3 3.1

Tetrachloroethene µg/m3 42

Trichloroethene µg/m3 2.1

Total Xylenes µg/m3 100

PROPOSED PLAN WALKER MACHINE PRODUCTS, …Proposed Plan for ROD Walker Machine Products March 2018 1...

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