PROPOSED PLAN for AMENDING 1988 RECORD OF DECISION CHEMTRONICS SUPERFUND SITE SWANNANOA, BUNCOMBE COUNTY, NORTH CAROLINA JULY 2016 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 Amending the 1988 Record of Decision for the Chemtronics Superfund Site, Swannanoa, NC This Proposed Plan presents the Preferred Remedial Alternative for amending the 1988 Chemtronics Superfund Site (the Site) Record of Decision (ROD). This Proposed Plan addresses the environmental impacts not addressed in the 1988 ROD/1989 ROD Amendment resulting from Site related operations as well replaces the minimal successful pump and treat system for contaminated groundwater with Enhanced In Situ Bioremediation (EISB). This Proposed Plan presents the remedial alternatives evaluated in the 2016 Feasibility Study along with the Agency’s preferred remedial action alternatives for the Chemtronics Site: • The Preferred Remedial Alternative for contaminated soil at Areas B109-137 and B116 in the Front Valley is Alternative #3 – Excavation of contaminated soil with off-site disposal; • The Preferred Remedial Alternative for contaminated groundwater in the Front Valley is Alternative #4 – EISB with long-term groundwater monitoring and monitored natural attenuation (MNA) for Areas: B104, B105 and B147, B139, and Disposal Area 23 (DA23)/B116; • The Preferred Remedial Alternative for contaminated groundwater in the Back Valley is Alternative #4 – EISB with long-term groundwater monitoring and MNA for Disposal Area 9 (DA9) and the Acid Pit Area (APA); and • Placement of Institutional Controls (ICs) on the Superfund Site portion of the Chemtronics property using the State of North Carolina Declaration of Perpetual Land Use Restrictions (DPLURs) process which requires the generation of a plat map which defines the boundaries of the Chemtronics Superfund Site. This Preferred Remedial Alternative also includes the following requirements/actions: • Retains the requirement for capping and engineering controls for the six disposal areas (DAs) identified in the 1988 ROD; • Updates the groundwater cleanup levels specified in the 1988 ROD for the Site; and • Eliminates the requirement for pumping and treating groundwater in both valleys as specified in the 1988 ROD. This document is issued by the U.S. Environmental Protection Agency (EPA), the lead agency for Site activities, and the North Carolina Department of Environmental Quality (NCDEQ), the support agency. NCDEQ is the successor of the North Carolina Department of Environment and Natural Resources (NCDENR). EPA, in consultation with the NCDEQ, will select a final remedy for the Site after reviewing and considering all information submitted during the public comment period. EPA, in consultation with the NCDEQ, may modify this Preferred Alternative or select another alternative presented in this 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 responsibilities under the Superfund law (Comprehensive Environmental Response, Compensation, and Liability Act [CERCLA]), Section 117(c) and Section 300.435(f)(2) of the National Oil and Hazardous Substances Pollution Contingency Plan (NCP). 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, the 1988 ROD, the 1989 ROD Amendment, and other documents contained in the Administrative Record file for this Site. The Administrative Record and Information Repository can be found in the Ellison Library on the campus of Warren Wilson College located at 701 Warren Wilson Road, Swannanoa, North Carolina and in EPA's, Region IV Information Center at 61 Forsyth Street, Sam Nunn Atlanta Federal Center, Atlanta, Georgia.

Proposed Plan for ROD Amendment Chemtronics Superfund Site July 2016

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Tell Us What You Think Public Comment Period July 14 through September 12, 2016 EPA will accept written comments on this Proposed Plan during the public comment period. You may submit written comments three (3) ways: BY MAIL Jon Bornholm U.S. EPA - Region 4 61 Forsyth Street, SW Atlanta, Georgia 30303-3104 BY EMAIL [email protected] BY FACSIMILE 404-562-8788 Addressed to Jon Bornholm

Attend the Public Meeting You are invited to attend a 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 meeting will be held: Thursday, July 14, 2016 from 6:30 – 8:30 p.m. Location: Swannanoa Fire Station 510 Bee Tree Road Swannanoa, NC 28778

Locations of Administrative Record and Information Repository Ellison Library on the campus of Warren Wilson College 701 Warren Wilson Road Swannanoa, NC 28778 Phone: 828-771-3058 Hours: Mon. – Thurs. 8 a.m. – 12 a.m. Fri. 8 a.m. – 5 p.m. Sat. 1 p.m. – 5 p.m. Sun. 1 p.m. – 12 a.m. EPA, Region 4's Information Center 61 Forsyth Street Sam Nunn Atlanta Federal Center Atlanta, Georgia 30303 Phone: 404-562-8946 Hours: Mon – Fri, 8 a.m. – 5 p.m.

EPA and NCDEQ encourage the public to review these documents to gain a more comprehensive understanding of the Site and Superfund activities that have been conducted at the Site. 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 amending the 1988 Chemtronics Superfund ROD at the 6:30 p.m. public meeting on Thursday, July 14, 2016, at the Swannanoa Fire Station located at 510 Bee Tree Road, Swannanoa, NC 28778. 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 Monday, September 12, 2016 to submit written comments on this Proposed Plan or other material in the Administrative Record file. At the end of the comment period, EPA and NCDEQ 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. We want to hear from you and will consider your comments in making the final decision. 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; • a summary of cleanup technologies considered and evaluated in order • a list of cleanup levels for the chemicals of concern; • the Agency’s preferred alternative; • encouragement to the public to submit comments on the proposed cleanup alternative; and • a list of contacts and locations for more information. SITE HISTORY/SITE CHARACTERISTICS The Chemtronics property encompasses 1,065 acres and is located at 180 Old Bee Tree Road, approximately 8 miles east of Asheville, in the community of Swannanoa (Figure 1). The property is situated within the southern Appalachian Mountains with the approximate center of the Site lying at latitude 35°38'18" north and longitude 82°26'8" west. The

Proposed Plan for ROD Amendment Chemtronics Superfund Site July 2016

3 topography of the property is moderately sloping to steep, with elevation ranging from 2,200 to 3,400 feet above mean sea level. The property lies on the southeast side of Bartlett Mountain and is moderately to heavily vegetated with mixed forest types including hardwood and pine trees. The property is divided into two distinctly separate geographic areas commonly referred to as the Front Valley (FV) and the Back Valley (BV). A prominent ridge separates the valleys (Figure 1). The majority of the property is situated within one of two local watersheds (the Unnamed Branch which drains the FV and Gregg Branch which drains the BV), both of which are part of a larger watershed (Bee Tree Creek and a regional watershed - Swannanoa River). Both the Unnamed Branch and Gregg Branch discharge to Bee Tree Creek. All surface water from the property drains to these streams or directly to Bee Tree Creek, which then discharges into the Swannanoa River approximately 4,500 feet downstream of the property. The Chemtronics property is bordered to the north, northeast, and northwest by sparsely populated woodlands, primarily National Forests or State game lands. Unincorporated residential neighborhoods are located immediately east, west, and south of the Site (Bee Tree community, Dillingham Circle, and Old Bee Tree/Rainbow Ridge community, respectively). An inactive industrial facility (RadioShack Swannanoa Property) is located immediately south of the property and is currently being investigated/remediated under the North Carolina Registered Environmental Consultant Program. Several other industrial facilities are located further to the south. Warren Wilson College is located approximately 0.75 mile southwest of the property. The property was first developed and operated as an industrial facility in 1952. Prior to 1952, the property was rural farm and dairy land. The property has been owned and operated by Oerlikon Tool and Arms Corporation of America (1952 to 1959), Celanese Corporation of America (1959 to 1965), Northrop Carolina, Inc. (1965 to 1978), and Chemtronics, Inc. (1978 to present). The primary products manufactured on-site were explosives, propellants, incapacitating agents, and a variety of specialty chemicals. Manufacturing activities occurred primarily in the FV, whereas material testing and waste disposal occurred primarily in the BV. Manufacturing and related activities occurred on less than 200 acres of the entire 1,065 acre Site, and were primarily located in the southern portion of the property. Various waste products and byproducts associated with the manufacturing of explosives, flares, military incapacitating agents (e.g., ortho-chlorobenzylidene malononitrile [CS] and 3-quinuclidinyl benzilate [BZ]), and various chemical intermediates were disposed of on-site. The primary waste products included chlorinated and non-chlorinated solvents, acidic solutions, by-products of the manufacturing processes, and solid waste such as gloves and coveralls (protective clothing). A Superfund “Site” is best defined as that portion of a facility (property) that includes the location of a release (or releases) of hazardous substances and wherever hazardous substances have come to be located. Based on this description and the data presented in the 2015 RI Report and 2016 Feasibility Study, the Chemtronics Superfund site is estimated to encompass 535 acres. This 535 acres includes a buffer zone that ranges from 200 to 500 feet between the areas affected by historical Site operations and past disposal activities to areas of the property not impacted by past Site activities. Refer to Figure 2 for the delineation of the Chemtronics Superfund Site on the Chemtronics property. The Site was placed on the National Priorities List (NPL) in 1982. The Site was historically regulated by both the EPA CERCLA/Superfund program and the NCDENR – Resource Conservation and Recovery Act (RCRA) program. The initial remedial investigation/feasibility study (RI/FS) (1984-1988) focused primarily on the waste disposal areas associated with former Site operations, namely the DAs on the Site which included 23 individual DAs which were grouped into six discrete waste DAs. These areas are designated as DA10/11 and DA23 (located in the FV) and DA6, DA7/8, DA9 and the APA (located in the BV). The APA includes 16 individual DAs. Together, these DAs occupy less than 10 acres of the Site. Disposal practices at the DAs are described in Section 1.2.2 of the 2015 RI Report and further details regarding DA9 are discussed in Section 7.4 of the FS Report. Figure 3 identifies the former locations of buildings and other operational areas as well as the DAs. The 1984-1988 RI/FS led to issuance of the 1988 ROD and the 1989 ROD Amendment. State led RCRA investigations at the Site began in the late 1990s and focused on areas of the Site historically used for manufacturing operations. These areas were designated as RCRA solid waste management units (SWMUs) and included wastewater sumps and waste material accumulation, handling, and storage areas. For the most part, these SWMUs were inspected, cleaned, and backfilled with clean soil or covered with a concrete cap consistent with requirements of the RCRA program. RCRA investigations and other related actions at the Site are described in the 2009 RI/FS Work Plan and

Proposed Plan for ROD Amendment Chemtronics Superfund Site July 2016

4 the 2015 RI Report. These documents acknowledged that various volatile organic compounds (VOCs), semi-volatile organic compounds (SVOCs), explosive compounds, perchlorate, metals, organic acids, and specialty chemicals were either used or manufactured on-site. Commercial operations at Chemtronics ceased in 1994. Between 2004 and 2006, all buildings and other structures, except those associated with ongoing environmental assessment and remediation activities, were demolished down to the building slabs and the resulting debris was disposed off-site. In a letter dated March 9, 2007, NCDENR requested that EPA consolidate oversight of all Site environmental remediation activities under EPA’s CERCLA authority. Consequently, EPA and the Potential Responsible Parties (PRPs, a.k.a., the Companies) signed an Administrative Order on Consent (AOC) in 2008. The AOC allowed the Companies to conduct a Site-wide RI/FS with oversight provided by EPA and NCDENR (now NCDEQ). The three Companies that signed the AOC were Chemtronics, Inc.; Northrop Grumman Systems Corporation, and CNA Holdings, Inc. The only ongoing Site activities at present are CERCLA-related remedial activities, occasional utility maintenance/repair work, and security guard patrols, as well as conservation activities for that portion of the property not adversely impacted by past Site related manufacturing/disposal activities. REQUIREMENTS OF THE 1988 RECORD OF DECISION/1989 RECORD OF DECISION AMENDMENT MIGRATION CONTROL (Remediating Contaminated Groundwater) • Installation of a groundwater interception and extraction system downgradient of the disposal areas in both the Front Valley and Gregg Valley. The level and degree of treatment of the extracted groundwater will depend on 1) the ultimate discharge point of this water and 2) the level of contaminants in the extracted groundwater. The three water discharge alternatives for the treated water are 1) the local sewer system, 2) a surface stream and 3) on-site irrigation. The range of treatment for the extracted groundwater includes air stripping, filtration through activated carbon filter and metal removal. The point of discharge and the degree of treatment will be determined in the Remedial Design stage. The water discharged will meet all ARAR's. •

A monitoring program, employing bioassays, will be established for surface water/sediment. Monitoring locations will be located on the Unnamed Stream, Gregg Branch and Bee Tree Creek. The purpose of this monitoring program is 1) to insure no adverse impact on these streams during implementation of the remedial action and 2) to establish a data base to use to measure the success of the remedial action implemented. The initiation of this monitoring program will be concurrent with the remedial design activities.

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Review the existing groundwater monitoring system and install additional wells, if necessary, to insure proper monitoring of groundwater downgradient of each disposal area. This includes disposal areas #6, #7/8, #9, #10/11, #23, and the acid pit area.

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In addition to the monitoring of the groundwater downgradient of each disposal area identified above, action levels for the contaminants present in the disposal areas will be set so that after remediation levels for groundwater have been obtained and verified through monitoring, if this level is reached in any subsequent sampling episode, a remedial action to permanently eliminate that source of contamination will be initiated.

SOURCE CONTROL (Remediating Contaminated Soils) • Cap Disposal Area #6, Disposal Area #7/8, Disposal Area #9, Disposal Area #10/11, and the Acid Pit Area with a Multi-Layer cap which includes a synthetic liner. Security fencing, vegetative covers and, where deemed necessary, a gas collection/ventilation system will be installed. The multi-layer cap will meet as a minimum, the standards specified under 40 CFR Subsection 264, Subparts K-N. •

For the contaminants and contaminated soils associated with DA-23, determine the most appropriate soil fixation/stabilization/solidification process and the mixing ratios for the components involved. Following the soil fixation/stabilization/solidification for DA-23, the entire surface of the disposal area will be capped.

Proposed Plan for ROD Amendment Chemtronics Superfund Site July 2016

5 Sample On-Site Pond on Unnamed Stream • During the Remedial Design stage, sample the water and sediment in the pond. If the analysis indicates contaminants in either the water column or sediment, then the pond will be drained, with the water being treated through the treatment system developed for addressing the extracted groundwater and the sediments could be either commingled with the soils of Disposal Area #23 for fixation/stabilization/solidification or transported to another disposal area and capped along with that disposal area. The 1989 ROD Amendment eliminated the need to fixate/stabilize/solidify the soils in DA-23 prior to covering this area with the multi-layer cap similar to the other disposal areas. 2015 REMEDIAL INVESTIGATION A new RI was conducted as the previous RI only focused on the known disposal areas and the groundwater impacts associated with these six disposal areas. The 2015 RI focused on the entire impacted area which encompassed groundwater impacts not identified in the 1988 ROD. The RI fieldwork documented in the 2015 RI Report was completed in three phases performed between December 2009 and July 2012. Below is a summary of RI sampling activities and findings: • Collection and analyses of a total of 541 soil samples from 290 soil sampling locations within 45 different areas on-site; • Installation of 56 monitoring wells (MWs) to supplement the existing Site MW network; • Collection and analyses of groundwater samples one or more times from 175 on-Site MWs spread out across the Site; • Collection and analyses of surface water and sediment samples from 53 locations in the Unnamed Branch, Gregg Branch, and Bee Tree Creek; • Updating of the potential groundwater receptor survey; and • Sampling eight off-Site potable wells. These samples were analyzed for Site related contaminants. SOILS Contaminants detected in the soil consisted primarily of VOCs, nitroaromatic compounds, and perchlorate. SVOCs and pesticides were also detected but at a lesser frequency or concentration. The following two areas in the FV were retained for further evaluation: • B116 in the FV, retained due to potentially unacceptable vapor intrusion risks due to 1,2-dichloroethane (1,2DCA), vinyl chloride, benzene, 1,1,2-trichloroethane, cyclohexane, and methylene chloride detections in soil. • B109-137 in the FV, retained due to potentially unacceptable vapor intrusion risks due to naphthalene, xylenes (total), 1,2,4-trimethyl-benzene and 1,3,5-trimethyl-benzene detections in soil. Based upon the soil sampling data collected from the FV, with the exception of the two areas highlighted above, the RI determined that there is no continuing “source” of contamination in soil in the FV that would continue to adversely impact groundwater quality. The contamination detected has already migrated into the groundwater and migrating with the groundwater. With the exception of the DAs addressed in the 1988 remedy, no additional areas in the FV or BV were retained for further evaluation due to soil contamination. Refer to Figure 4 for locations of where surface and subsurface soil samples were collected. GROUNDWATER Groundwater at the Site exists in a three-part aquifer system consisting of the surficial aquifer, the transition zone aquifer, and the bedrock aquifer. These three aquifers are interconnected but have different characteristics that influence the speed the groundwater flows and transport mechanisms for the contaminants within them. The predominant vertical flow is

Proposed Plan for ROD Amendment Chemtronics Superfund Site July 2016

6 downward: from the surficial aquifer to the transition zone aquifer to the bedrock aquifer. Laterally, the groundwater flow is predominantly toward the southeast in all of the aquifers (i.e., groundwater flowing down the valley) towards Bee Tree Creek. Some groundwater discharges to the Unnamed Branch, Gregg Branch, or Bee Tree Creek. Due to groundwater contamination, areas in both the FV and the BV were identified and retained for further evaluation. The reduction of the concentrations of the contaminants in the groundwater in these areas will address the direct exposure scenarios and minimize the potential for future unacceptable risks from on-Site and off-Site groundwater exposure. The areas identified in the RI and subsequently retained in the FS for source remediation are identified below: AREAS OF CONCERN DUE TO GROUNDWATER CONTAMINATION AREA NAME PRIMARY CONTAMINANTS AQUIFER FRONT VALLEY B104 CF, CT, 1,2-DCA, cDCE, DCM, perchlorate, PCE, RDX, TCE, VC Bedrock B105and B147 1,2-DCA, cDCE, DCM, perchlorate, RDX, TCE, VC Surficial and Transition Zone B139 1,2-DCA, perchlorate, RDX, TCE, VC Bedrock DA23/B116 1,2-DCA, PCE, perchlorate, RDX, TCE, VC Surficial, Transition Zone, and Bedrock BACK VALLEY APA benzene, CF, DCM, 1,2-DCA, PCE, Perchlorate, RDX, TBA, TCE Surficial, Transition Zone, and Bedrock DA9 1,2-DCA, Perchlorate, RDX, TCE Surficial, Transition Zone, and Bedrock Notes: CF -- chloroform PCE -- tetrachloroethene CT -- carbon tetrachloride RDX -- research department explosive 1,2-DCA -- 1,2-dichloroethane TBA -- tert-butyl alcohol cDCE -- cis-1,2-dichloroethene TCE -- trichloroethene DCM -- dichloromethane VC -- vinyl chloride

Concentrations of contaminants in the groundwater were compared to the following two groundwater standards: • Maximum Contaminant Level (MCL) established under the EPA Safe Drinking Water Act (SDWA) which can be viewed at the following website: https://www.epa.gov/dwstandardsregulations and • North Carolina Groundwater Classifications and Standards, North Carolina Administrative Code (NCAC) Title 15A Subchapter 2L which can be viewed at the following website: https://deq.nc.gov/about/divisions/waterresources/planning/classification-standards/groundwater-standards. Refer to Figure 5 for the distribution and depth of the MW network across the Site. Figures 6 and 7 show the extent and concentrations of trichloroethene (TCE) in the surficial and transitional zone aquifers in the FV, respectively. Figures 8 and 9 show the extent and concentrations of trichloroethene (TCE) in the surficial and transitional zone aquifers in the BV, respectively. TCE is not the only groundwater contaminant of concern but these isopleth maps give a good depiction of the extent of groundwater contamination in both valleys. Some of the plumes delineated in the FV by the 2015 RI are located downgradient of the current groundwater extraction system so this system would not be capable of addressing this contamination. The groundwater extraction system in the BV is reaching the end of its useful lifespan. SURFACE WATER/SEDIMENT The headwaters for both the Unnamed Branch and Gregg Branch are located on the Chemtronics property. Both of these streams are perennial. Surface water and sediment samples were collected from both streams. Where possible, surface water and sediment samples were collected together at each sampling location. Surface water and sediment samples were collected during low-stream-flow conditions and surface water samples were also collected during a high-stream-flow event. The base flow surface water data collected during Phase I of the RI (2010) generally re-confirmed the surface water data collected during the low-flow sampling events conducted in 2007 and 2008, and the high-flow sampling event in 2009. Metals, nitroaromatics, perchlorate, and VOCs were detected in both surface water and sediment samples at more than one sampling location. SVOCs were detected in one or more of the sediment samples collected.

Proposed Plan for ROD Amendment Chemtronics Superfund Site July 2016

7 Refer to Figure 10 for the surface water/sediment sampling locations. SUMMARY OF SITE RISKS As part of the RI, a baseline human health risk assessment (HHRA) and ecological risk assessment (ERA) were prepared for the Site. These risk assessments evaluated risks to human and ecological populations that may be exposed to chemicals present in soils, groundwater, surface water and sediment at the Site under current and potential future conditions. These risk assessments provide the basis for determining if remedial action is warranted and if so, identify the contaminants and exposure pathways that need to be addressed by the Preferred Remedial Alternative. Human Health Risk Assessment (HHRA) The baseline HHRA evaluated the following potential exposure scenarios at and around the Site under current and reasonably expected future land uses: On-Site  Residential, Industrial workers, Maintenance workers, Construction workers, Recreational users, and Trespassers Off-Site  Residential, Maintenance workers, and Recreational users An unacceptable cancer risk is identified when the Site-related cumulative cancer risk is above EPA’s risk management limit of 1×10-4. A non-cancer risk is identified when the Site-related cumulative hazard quotient results in a Hazard Index (HI) greater than 1. Under current conditions, there are no unacceptable risks (cancer or non-cancer) to human health from hazardous substances at the Site. As detailed below, future uncontrolled exposures to on-Site workers and on-Site residents could pose unacceptable risks. With the exception of potential future off-Site potable/non-potable groundwater use, there are no potential future unacceptable risks to off-Site receptors from hazardous substances at the Site. Risks Associated with Contaminated Soil As stated above, under current conditions, there are no areas of the Site where the concentrations of chemicals of concern (COCs) in the soil would result in cumulative Site-related cancer risk or non-cancer HI estimates above EPA’s risk management limits of 1×10-4 and 1, respectively, for the exposure scenarios listed above. Under potential future land use, there are areas of the Site where concentrations of COCs in subsurface soil would result in Site-related cumulative cancer risk on non-cancer HI estimates above EPA’s risk management limits. Specifically, the following areas of the Site that have concentrations of COCs in the soil that could result in cumulative cancer risk or noncancer HI estimates above EPA’s risk management limits of 1 × 10-4 and 1, respectively, under the potential future industrial worker exposure scenarios: Area B116 (via soil direct contact and vapor intrusion) and Area B109-137 (via soil vapor intrusion). Tables 1a and 1b summarize the cumulative cancer and non-cancer risks for soil in Area B116 for industrial worker direct contact and industrial worker vapor intrusion, respectively. Table 2 summarizes the cumulative cancer and non-cancer risks for soil for Area B109-137. The following areas of the Site have concentrations of COCs in the soil that could result in cumulative cancer risk or non-cancer HI estimates above EPA’s risk management limits of 1 × 10-4 and 1, respectively, under the potential future on-Site residential exposure scenario: APA, DA9, Area B105-139, Area B107, Area B109-137, Area B113, Area B115, Area B116, Area B119-B120, Area B125-B136, Area B146, Area B147, Area B148, Area B149, Area B155, DA23, and Area DUMP. These unacceptable risks are associated with direct contact to contaminated soil and/or soil vapor intrusion exposures. Depending on the area, unacceptable risk estimates for direct contact to contaminated soil were predominantly driven by the following COCs: aldrin, benzo(a)anthracene, benzo(a)pyrene, benzo(b)fluoranthene, benzo(k)fluoranthene, chrysene, dibenzo(a,h)-anthracene, indeno(1,2,3-c,d)pyrene, arsenic, chromium, cobalt, benzene, 1,2-DCA, 1,1,2-trichloroethane, vinyl chloride, research department explosive (RDX), and cyclohexane. Unacceptable risk estimates for soil vapor intrusion are predominantly driven by the following COCs: benzene, bromoform, chloroform, cyclohexane, ethylbenzene, 1,2-DCA, naphthalene, 1,1,2-trichloroethane, methylene chloride, trichloroethylene, tetrachloroethylene, vinyl chloride, styrene, 1,2,4-trimethyl-benzene, 1,3,5trimethyl-benzene, isopropyl-benzene, aniline, allyl chloride, xylenes (total), toluene, and mercury.

Proposed Plan for ROD Amendment Chemtronics Superfund Site July 2016

8 Risks Associated with Contaminated On-Site Groundwater As stated above, under current conditions (i.e., the groundwater is not being used for any purposes), there are no complete exposure pathways at the Site therefore, there are no exposures to the COCs in the groundwater. Consequently, there are no cumulative cancer risk or non-cancer HI estimates above EPA’s risk management limits of 1 × 10-4 and 1. Under future conditions, there are no areas of the Site where the concentrations of COCs in the groundwater would result in cumulative cancer risk or non-cancer HI estimates above EPA’s risk management limits of 1 × 10-4 and 1, respectively, when considering the industrial worker exposure scenario to groundwater via inhalation of outdoor air. Under future conditions, over 50 monitoring well (MW) locations across the interior of the Site have concentrations of COCs in the groundwater that could result in cumulative cancer risk or non-cancer HI estimates above EPA’s risk management limits of 1 × 10-4 and 1, respectively, when considering future industrial worker exposure via vapor intrusion or potable/nonpotable groundwater use and maintenance worker/construction worker exposure via direct contact with groundwater exposure scenarios: • MW P-7s, MW180-H38AB, and MW223-L26AB: due almost entirely to TCE vapor intrusion as well as via dermal contact and vapor inhalation during excavations that extend to the water table; • MW231-H38AB: due almost entirely to TCE via dermal contact and vapor inhalation during excavations that extend to the water table; and • 49 MWs locations in addition to those listed above have groundwater concentrations that could pose an unacceptable risk to on-Site industrial workers if groundwater were to be used in the future for potable and nonpotable purposes. Under future condition as, there are no areas of the Site with groundwater concentrations that would result in cumulative cancer risk or non-cancer HI estimates above EPA’s risk management limits of 1 × 10-4 and 1, respectively, when considering future residential exposure to groundwater via inhalation of outdoor air. As stated in the 1988 ROD, the groundwater underlying the Site has been classified as Class IIB, using EPA’s Groundwater Classifications Guidelines (December 1986), since there is potential future use for this aquifer as a source of drinking water. Under future conditions, over 70 MW locations across the interior of the Site have concentrations of COCs in the groundwater that could result in cumulative cancer risk or non-cancer HI estimates above EPA’s risk management limits of 1 × 10-4 and 1, respectively, when considering future residential exposure via vapor intrusion or potable/non-potable groundwater use: • MW P-7s, MW180-H38AB, MW223-L26AB, and MW231-H38AB: due almost entirely to TCE vapor intrusion; • MW187-M25AB: due almost entirely to 1,2-DCA via vapor intrusion; and • 71 MWs locations (including those listed above) have groundwater concentrations that could pose an unacceptable risk to on-Site residents if groundwater were to be used in the future for potable and non-potable purposes. Risks Associated with Contaminated Sediment and Surface Water There are no locations at the Site with sediment or surface water concentrations that would result in cumulative cancer risk or non-cancer HI estimates above EPA’s risk management limits of 1 × 10-4 and 1, respectively, when considering current or future trespasser exposure, future maintenance worker/construction worker exposure, or recreational user exposure. Risks Associated with Off-Site Groundwater The scenarios for potential human exposure recognize that off-Site groundwater use for potable purposes is a current and reasonably expected exposure scenario. To be conservative, the baseline risk assessment evaluated the potential exposure of off-Site residents to groundwater via potable groundwater use by comparing the detected concentrations in on-Site MWs located within approximately 200 feet of the Site boundary to drinking water screening levels. Using this approach, six on-Site MWs within 200 feet of the Site boundary were identified as currently exhibiting detected concentrations of COCs in excess of the drinking water screening levels. Only one of these six MWs (MW156-P44A) had concentrations of

Proposed Plan for ROD Amendment Chemtronics Superfund Site July 2016

9 COCs in the groundwater that resulted in a cumulative cancer risk or non-cancer HI for residential potable or non-potable use above EPA’s risk management limits of 1 × 10-4 and 1, respectively. Potential resident exposure to groundwater via potable use could be unacceptable if near boundary concentrations were present off-Site. However, an off-Site water well survey and sampling effort found no COCs from the Site in off-Site groundwater at concentrations that exceed the healthbased drinking water screening levels. Ecological Risk Assessment (ERA) The ERA evaluated various aquatic and terrestrial receptors. Terrestrial receptors include invertebrates (from earthworms to insects), small vertebrates such as passerine birds and small herbivorous mammals, predatory birds, and mammals. Aquatic receptors include benthic invertebrates (worms, some crustaceans, and some insects), fish and amphibians, birds, and piscivorous mammals. Based on the information developed in the ERA, the ERA concluded that conditions at the Site do not pose unacceptable risks to ecological populations and/or communities. However, some risks to individual soil invertebrates, plants, mammals, or birds cannot be definitively ruled out by the baseline risk assessment alone. The ERA provides a summary of key issues as they may relate to risk management decisions for the Site. CHEMICALS OF CONCERN The COCs determined from the results of the baseline risk assessment were identified based on EPA’s guidance. COCs are chemicals that significantly contribute to an exposure pathway that either exceeds a 1 × 10-4 cumulative site cancer risk or exceeds a non-cancer HI of 1. Table 3 lists the COCs for soil at areas B116 and B109-137 and their associated cleanup levels for these areas. Table 4 lists the COCs in the groundwater and their associated cleanup levels for the Site. EVIDENCE OF MNA In order for MNA to be considered as a remedy or to be included as a component of a remedy, the guidance in EPA’s Use of Monitored Natural Attenuation at Superfund, RCRA Corrective Action, and Underground Storage Tank Sites, Office of Solid Waste and Emergency Response (OSWER) Directive 9200.4-17P, 1999, should be followed. This Directive lists the following three lines of evidence that should be presented when making a case that MNA is occurring at a site. These three lines of evidence are: (1) Historical groundwater and/or soil chemistry data that demonstrate a clear and meaningful trend of decreasing contaminant mass and/or concentration over time at appropriate monitoring or sampling points. (In the case of a groundwater plume, decreasing concentrations should not be solely the result of plume migration. (2) Hydrogeologic and geochemical data that can be used to demonstrate indirectly the type(s) of natural attenuation processes active at the site, and the rate at which such processes will reduce contaminant concentrations to required levels. (3) Data from field or microcosm studies (conducted in or with actual contaminated site media) which directly demonstrate the occurrence of a particular natural attenuation process at the site and its ability to degrade the COCs (typically used to demonstrate biological degradation processes only). The data that supports incorporating MNA into the Preferred Remedial Alternatives can be found in the following reports: - Work Plan for Front Valley Enhanced In Situ Bioremediation Pilot Testing (2012) - Work Plan for Phase II Front Valley Enhanced In Situ Bioremediation Pilot Testing (2013) - Work Plan for Back Valley Enhanced In Situ Bioremediation Pilot Testing (2014) - Assessment of Monitored Natural Attenuation Potential in the Front Valley (2015) - Assessment of Monitored Natural Attenuation Potential in the Back Valley (2015) - Feasibility Study, Appendix C – Post-Shutdown Monitored Natural Attenuation Evaluation for the Front Valley (2016) - Feasibility Study, Appendix D – Post-Shutdown Monitored Natural Attenuation Evaluation for the Back Valley (2016)

Proposed Plan for ROD Amendment Chemtronics Superfund Site July 2016

10 The first line of evidence included the evaluation of both spatial and temporal concentration trends in groundwater which showed: (i) concentrations of COCs in the FV and BV generally decrease with distance in each aquifer zone along the direction of groundwater flow; and (ii) the concentrations of the COCs at most locations have declined overtime throughout the FV and BV plumes. These observations are indicative of mass reduction and ongoing natural attenuation in FV and BV groundwater. The second line of evidence consists of evaluating selected geochemical parameters to assess if geochemical conditions are conducive to natural attenuation processes. In FV groundwater, the MNA assessment indicated that geochemical conditions (e.g., redox, pH, common electron acceptors/donors) are generally favorable for the natural attenuation of the contaminants via aerobic processes in each aquifer zone (including cometabolic aerobic processes), although conditions conducive to anaerobic transformation processes were also present in select locations throughout the FV (e.g., negative oxidation reduction potential (ORP), detection of reduced species [i.e., methane, sulfide, dissolved iron and manganese]). While geochemical data generally indicated aerobic groundwater in the FV, historical data indicated redox fluctuations at select locations, which may allow for both aerobic and anaerobic transformation processes to occur naturally in groundwater beneath the FV. Similarly, the presence of intermediate/end products in each aquifer zone is indicative of ongoing natural attenuation in FV groundwater. In the BV groundwater, the redox zonation had a tendency toward predominantly anaerobic/anoxic conditions closest to the disposal areas (DA9 and APA) with a transition to aerobic/oxic conditions further downgradient. This redox zonation supports natural attenuation of a broad range of constituents (i.e., those more amenable to anaerobic or aerobic degradation processes, respectively). Similarly, the presence of intermediate/end products in each aquifer zone is indicative of ongoing natural attenuation in BV groundwater. Furthermore, select daughter products are produced that promote (e.g., as electron donors) additional natural attenuation processes in groundwater beneath the BV. The third line of evidence included evaluation of available direct evidence of natural attenuation generated during implementation of treatability studies and pilot testing in support of the FS. Molecular and treatability study data from select areas of the FV and BV indicate that there are native bacteria present in the various groundwater flow zones capable of degrading the COCs. In addition, the results from the ongoing field treatability studies demonstrate ongoing natural attenuation of the COCs in the FV and BV. The available direct evidence is generally consistent with the conclusions drawn from the first and second lines of evidence. The three lines of evidence indicate ongoing natural attenuation of the COCs in both the FV and BV groundwater as they migrate within the Site in the direction of groundwater flow. The FV and BV MNA assessments confirm inclusion of MNA as a component of each active remedial alternative for FV and BV groundwater evaluated in the FS Report. As an example, the concentration of TCE at Area B149 has steadily declined due to natural attenuation from 4,600 µg/L in October 2001 to 260 µg/L in November 2012 (before initiating the EISB pilot testing), since the implementation of the EISB pilot test in this area, the concentration of TCE had declined to as low as 19 µg/L in September 2015. SCOPE AND ROLE OF OPERABLE UNIT The Agency does not anticipate dividing the Site into operable units. The 1988 ROD addressed the known disposal areas and this ROD Amendment will address two small contaminated soil areas in the FV and the contaminated groundwater at the Site and eliminate the pump and treat systems required by the 1988 ROD that had minimal success. REMEDIAL ACTION OBJECTIVES The site-specific soil remedial action objectives (RAOs) are as follows: 1. Prevent dermal contact and inhalation by human receptors of carcinogenic and non-carcinogenic contaminants from subsurface soil at concentrations that pose an unacceptable risk. 2. Prevent soil contaminants from leaching to groundwater at concentrations that result in ongoing groundwater concentrations above the groundwater cleanup levels.

Proposed Plan for ROD Amendment Chemtronics Superfund Site July 2016

11 The site-specific groundwater RAOs are as follows: 1. Restore the quality of degraded groundwater to protective levels for ingestion and permit beneficial use of groundwater (including use as a future source of drinking water). 2. Prevent ingestion, dermal contact, and inhalation by human receptors of carcinogenic and non-carcinogenic contaminants in groundwater at concentrations that pose an unacceptable risk through residential use. 3. Prevent migration of contaminated groundwater to on-site surface water and sediments at concentrations that pose an unacceptable human health or ecological risk. 4. Prevent migration of contaminated groundwater to off-site to protective levels. 5. Prevent migration of contaminated groundwater to surface water and sediments at concentrations that pose an unacceptable human health or ecological risk. REMEDIAL ALTERNATIVES For groundwater, the FS developed and presented a 5-step screening process to identify the areas of interest at the Site. This screening process defined an area of interest as one where the concentration of one or more COC exceeded the applicable screening criteria by more than 1000 times (1000×). Each of these areas was considered a source material and was identified as an area for source mass flux reduction (i.e., an area requiring active remediation). Other areas where COC concentrations were below the 1000× threshold were considered suitable for passive remediation using MNA and ICs and will be monitored. The following areas of the Site met this criteria and were identified as areas requiring remediation: FV → for soil contamination – Area B109-137 and Area B116 and for groundwater contamination – Area B104, Area B105 and B147, Area B139, and Area DA23/B116 BV → for groundwater contamination – Area DA9 and Area APA. Once the concentrations of the COCs in a particular groundwater contamination area falls below the 1000× criteria, then that particular area would transfer from active EISB to long-term monitoring/MNA. Groundwater and surface water, including the Unnamed Branch, Gregg Branch, and Bee Tree Creek, will continue to be monitored on an annual basis in accordance with the Proposed Assessment Monitoring Plan the PRPs implemented in 2011 or an updated plan approved by the EPA and NCDEQ. The objectives of this assessment monitoring program are to: • Monitor the concentrations of Site COCs at the property boundary in both groundwater and surface water. • Develop additional temporal data on the stability of the leading edge and along the length of the primary groundwater plumes. • Develop additional temporal data on groundwater quality in source areas. • Develop additional temporal data on groundwater parameters, which may be used to evaluate attenuation mechanisms. • Develop additional temporal data for on-Site surface water quality. Additionally, this long-term monitoring will be used to confirm that the FV and BV groundwater plumes are remaining stable or are declining. Net Present Values were calculated using a 5 percent discount rate with -30/+50% cost estimate reliability and costs were rounded-off to the nearest hundredth dollar amount. A 5 percent discount rate was used to reflect current economic conditions. FRONT VALLEY - SOIL As discussed above, the baseline risk assessment evaluated current and potential future risks to human health and ecological receptors for COCs detected in the soils and groundwater. Based on the baseline risk assessment conclusions, there are two soil areas of concern in the FV that were identified for remediation. These two areas of concern are: B109137 and B116. Refer to Figure 3 for their location. The COCs associated with B109-137 are naphthalene, xylenes (total), 1,2,4- trimethyl-benzene (TMB) and 1,3,5-TMB. The COCs associated with B116 are 1,2-DCA, vinyl chloride (VC), benzene, 1,1,2-trichloroethane (TCA), cyclohexane, and dichloromethane (DCM).

Proposed Plan for ROD Amendment Chemtronics Superfund Site July 2016

12 The table below lists the four remediation alternatives developed for the contaminated soils in the FV and the second table provides the following pertinent information for each alternative: Estimated Capital Cost, Estimated Annual Operation and Maintenance (O&M) Costs, 30-Year Net Present Value, Estimated Construction Timeframe, and Estimated Time to Achieve RAOs.

ALTERNATIVE 1 No Further Action

2 MNA

Excavation with Off-Site Disposal Soil Vapor 4 Extraction 3

FRONT VALLEY SOIL REMEDIATION ALTERNATIVES DESCRIPTION OF REMEDIATION ALTERNATIVES This alternative is required for consideration by the National Contingency Plan (NCP). No active cleanup activities will be initiated. Routine monitoring and reporting will be completed on an annual basis to confirm Site conditions. MNA is defined as natural processes that are occurring which 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 the environment. These in situ processes include biodegradation; dispersion; dilution; sorption; volatilization; and chemical or biological stabilization, transformation, or destruction of contaminants. Excavate contaminated soil and dispose of these contaminated soils at an EPA approved off-site disposal facility. Apply a vacuum to soil to induce a controlled air flow to remove volatile and some semi-volatile contaminants from the soil for ex situ treatment before being discharged to the atmosphere.

ESTIMATED COSTS FOR CONTAMINATED SOIL REMEDIAL ALTERNATIVES IN THE FRONT VALLEY Alternative 1 Alternative 2 Alternative 3 Alternative 4 Activity B109-137 B116 B109-137 B116 B109-137 B116 B109-137 B116 Estimated Capital Cost $15,600 $15,600 $23,600 $23,600 $137,100 $95,100 $134,800 $120,800 Estimated Annual O&M $0 $0 $6,300 $6,300 $0 $0 $80,500 $84,400 Costs 15% Contingency $2,300 $2,300 $20,700 $20,700 $20,600 $14,300 $32,300 $30,800 30-Year Net Present $17,900 $17,900 $158,700 $158,700 $157,700 $109,400 $247,600 $235,900 Value Estimated Construction 0 months 0 months 3 months 3 months 6 months 6 months 12 months 12 months Timeframe greater greater greater greater Estimated Time to than than than than 6 months 6 months 12 months 12 months Achieve RAOs 30 years 30 years 30 years 30 years Alternative 1 would not involve any active remedial actions and the Site would remain in its present condition. This alternative, required by the NCP and CERCLA, is a baseline alternative against which the effectiveness of the other alternatives can be compared. The capital costs are for developing a work plan and meetings with stakeholders and regulatory entities. Alternative 2 involves periodically evaluating the concentrations of contaminants in soil vapor above the water table in each area. Costs for the installation, sampling, and monitoring of two vapor monitoring wells are included in this alternative. Soil samples would be collected every five years as part of the five-year review process to support the evaluation of natural attenuation. Alternative 3 involves excavating the contaminated soil and transporting the excavated contaminated soil to an off-site, EPA approved, disposal facility. The FS assumed that excavated contaminated soil will be disposed as a non-hazardous waste. Confirmatory soil sampling (bottom of the excavation and side-walls) will be completed to confirm objectives are achieved before the excavation is backfilled with clean soil. None of the soils to be excavated are anticipated to be classified as hazardous waste.

Proposed Plan for ROD Amendment Chemtronics Superfund Site July 2016

13 Alternative 4 includes the installation of soil-vapor extraction wells in the vicinity of the contaminated soil. A blower system would be installed in a small, temporary building to provide vacuum on the extraction wells. If necessary, the extracted air stream will be treated using a granular activated carbon (GAC) filter to remove any contaminants in the air stream before being discharged to the atmosphere. The necessity to treat the air stream would be made during the remedial design (RD) phase. The treatment system would include a water vapor knock-out step. Instrumentation and control systems will be automated where possible and appropriate. Soil samples will be collected periodically within the treatment area to confirm objectives are being achieved. FRONT VALLEY – GROUNDWATER The baseline risk assessment evaluated potential risks from contaminated groundwater to human health and ecological receptors. Five areas of concern were identified for pilot tests in the FV due to groundwater contamination. As described earlier, the pilot treatability study at B149, which was initiated in December 2012, has achieved the target level for TCE in the groundwater at this area. This area will now be monitored until the concentration of TCE in the groundwater reaches the cleanup level for TCE. The four remaining areas of concern requiring groundwater remediation: B104, B105 and B147, B139, and DA23/B116. Refer to Figure 3 for their locations. Refer to the table above for the contaminants associated with these areas and which underlying aquifers these contaminants are located. The following remediation alternatives were developed for the contaminated groundwater in the FV.

1 2

3

4

5

FRONT VALLEY GROUNDWATER REMEDIATION ALTERNATIVES ALTERNATIVE DESCRIPTION OF REMEDIATION ALTERNATIVES This alternative is required for consideration by the NCP. No active cleanup No Further Action activities will be initiated. Routine monitoring and reporting will be completed on an annual basis to confirm Site conditions. Long-term monitoring of natural attenuation and biotic and/or abiotic MNA degradation/transformation/mineralization of organic and inorganic constituents Use of existing and/or installation of additional extraction wells to extract Groundwater Extraction and contaminated groundwater and control groundwater migration. Treatment of Treatment with long-term extracted groundwater using air stripping and/or adsorption through activated groundwater monitoring and MNA carbon. Injection or emplacement of microbes, nutrients or other amendments into Enhanced In Situ Bioremediation groundwater through injection wells or as a permeable reactive barrier (biobarrier) with long-term groundwater installed via injection/jetting techniques (vs trenching) to enhance biological monitoring and MNA degradation in situ. Adjusting the geochemistry of the groundwater (creating either anaerobic or aerobic conditions in the aquifer is a component of this alternative). Injection of reductants such as nanoscale or microscale zero valent iron or calcium In Situ Chemical Reduction with polysulfide into groundwater via injection wells. Reduction reactions chemically long-term groundwater monitoring convert COCs to non-hazardous or less toxic compounds that are more stable, less and MNA mobile, and/or inert. Alternative 1 Estimated Costs for Contaminated Groundwater in Front Valley: No Further Action for Areas: B104, B105 and B147, B139, and DA23/B116 Area B104 B105 and B147 B139 DA23/B116 Activity Estimated Capital Cost $18,900 $13,500 $13,500 $13,500 Estimated Annual O&M Costs $21,100 $21,100 $21,100 $21,100 15% Contingency $51,500 $50,700 $48,700 $48,700 30-Year Net Present Value $395,200 $389,000 $387,000 $387,000 Estimated Construction Timeframe 3 months 3 months 3 months 3 months greater than 30 greater than 30 greater than 30 greater than 30 Estimated Time to Achieve RAOs years years years years

Proposed Plan for ROD Amendment Chemtronics Superfund Site July 2016

14 Alternative 1: No Further Action – General Site maintenance will be completed for a period of 30 years. Routine monitoring and reporting will be completed on an annual basis to confirm Site conditions. The existing extraction wells and groundwater treatment system will be decommissioned. No additional monitoring wells are required to supplement the monitoring network. Sampling and monitoring of the groundwater and surface water would continue and were included in the costing. Alternative 2 Estimated Costs for Contaminated Groundwater in Front Valley: MNA for Areas: B104, B105B147, B139, and DA23/B116 Area B104 B105 and B147 B139 DA23/B116 Activity Estimated Capital Cost $128,200 $32,900 $128,200 $32,900 Estimated Annual O&M Costs* $37,400 $37,400 $30,800 $37,400 15% Contingency $94,200 $79,900 $86,500 $79,900 30-Year Net Present Value $721,900 $612,300 $663,000 $612,300 Estimated Construction Timeframe 3 months 3 months 3 months 3 months greater than 30 greater than 30 greater than 30 greater than 30 Estimated Time to Achieve RAOs years years years years * - Costs for initial remedy period; costs are expected to decline over time as the size of the plume decreases. Alternative 2: MNA – This alternative involves general Site maintenance and evaluating groundwater for the current list of ongoing monitoring parameters plus MNA parameters such as dissolved gases (ethene, ethane, and methane), dissolved metals, anions, and total organic carbon (TOC). The analysis of groundwater samples for target compounds and their biodegradation intermediates will provide an indication of the progress of MNA. Sampling and monitoring of the groundwater and surface water would continue on an annual basis. The number of monitoring locations for the MNA program may decrease over the remedy duration. The construction of additional monitoring wells is included. Alternative 3 Estimated Costs for Contaminated Groundwater in Front Valley: Groundwater Extraction and Treatment with Long-Term Groundwater Monitoring and MNA for Areas: B104, B105-B147, B139, and DA23/B116 Area B104 B105 and B147 B139 DA23/B116 Activity Estimated Capital Cost $294,900 $496,400 $356,000 $121,300 Estimated Annual O&M Costs* $67,700 $78,700 $55,400 $70,000 15% Contingency $221,800 $287,600 $203,000 $192,100 30-Year Net Present Value $1,700,500 $2,204,900 $1,556,400 $1,472,500 Estimated Construction Timeframe 12 months 12 months 12 months 12 months Estimated Time to Achieve RAOs 20-70 years 20-70 years 20-70 years 20-70 years * - Costs for initial remedy period; costs are expected to decline over time as the size of the plume decreases. Alternative 3: Groundwater Extraction and Treatment with Long-Term Groundwater Monitoring and MNA – This alternative involves installing extraction wells in all three aquifer zones (surficial, transition zone, and bedrock), pumping groundwater from these extraction wells, installation of the necessary piping, electrical, and control systems/units, on-site treatment using a combination of pH adjustment, sediment removal, air stripping and/or granular activated carbon filtration, discharging the treated groundwater to the Metropolitan Sewer District (MSD) sewer system under a permit, and the installation of additional monitoring wells, where necessary, to monitor the extraction system. Monitoring will continue for the downgradient portions of the plume to confirm that natural attenuation continues to reduce COCs concentrations over time. The FS assumed that a new treatment system will be required and will be housed in the existing building. The anticipated flow rate from each area are: for B104 area – 6 gallons per minute (gpm), for B105 and B147 area – 6 gpm, for Area B139 area – 3 gpm, and for DA23/B116 – 4 gpm. Flow from each area would be combined prior to treatment. The anticipated total flow to the FV treatment system is 19 gpm. This treatment system would include, at a minimum, the following components: flow equalization, an air stripper and associated conduits, filtration for particulate removal, instrumentation and control systems will be automated where possible and appropriate, and pH adjustment as required to meet MSD discharge requirements. The need for off-gas treatment from the air stripper is not anticipated (per

Proposed Plan for ROD Amendment Chemtronics Superfund Site July 2016

15 Title 15A NCAC Subchapter 02D requirements), however, this will be confirmed during the RD phase. Based on the performance of the current FV pump and treat system, it is anticipated that the extraction wells will need to be replaced every 10 years, and the treatment system every 20 years. Alternative 4 Estimated Costs for Contaminated Groundwater in Front Valley: Enhanced In Situ Bioremediation with Long-Term Groundwater Monitoring and MNA for Areas: B104, B105 and B147, B139, and DA23/B116 Area B104 B105 and B147 B139 DA23/B116 Activity Estimated Capital Cost $339,800 $751,300 $441,000 $339,000 Estimated Annual O&M Costs* $132,000 $45,500 $96,600 $236,800 15% Contingency $152,7800 $246,100 $151,300 $169,300 30-Year Net Present Value $1,170,700 $1,886,400 $1,160,000 $1,254,000 Estimated Construction Timeframe 12 months 12 months 12 months 12 months greater than 30 greater than 30 greater than 30 greater than 30 Estimated Time to Achieve RAOs years years years years * - Costs for initial remedy period; costs are expected to decline over time as the size of the plume decreases. Alternative 4: Enhanced In Situ Bioremediation with Long-Term Groundwater Monitoring and MNA – This alternative involves emplacement of microbes, nutrients or other amendments into groundwater to enhance biological degradation in situ of the contaminants in the groundwater. EISB can occur under either anaerobic or aerobic conditions and creating one of these conditions depends on what type of amendments that are injected into the aquifer. The types of contaminants in a particular area will determine whether an anaerobic or an aerobic environment is required. The microbes, nutrients, and other amendments are typically introduced into the subsurface in one of two ways, direct injection or via a recirculation approach. As for the Chemtronics Site, EISB pilot scale treatability studies have been ongoing in both valleys for over a year. All of these ongoing EISB pilot scale treatability studies have shown very good results. The following are the main activities that will occur to transition from the existing pilot scale to full scale. Install additional injection, extraction (to create recirculation in the subsurface), and/or monitoring wells depending on Area. The actual quantity, type, and depth of these wells will vary at each area. Upgrade the existing pilot scale systems’ piping, equipment, and controls to accommodate the additional injection and/or extraction wells. Establish a reinjection schedule for each area based on performance monitoring data. It is anticipated that some of the injection wells may need to be rehabilitated up to twice a year due to microbial growth and mineral deposition of the well’s screen. Performance monitoring will also vary at each source area based on the equipment and approach employed. The key components of the performance monitoring effort will include: monitoring of the groundwater and collecting groundwater samples from wells both within the treatment zone as well as downgradient of the treatment zone. The following is a list of potential materials that may be injected into the subsurface at the various full scale treatment efforts. Not all of these materials may be injected at any one area. The materials include (but not limited to): KB-1 Plus®, emulsified vegetable oil (EVO), lactate, Neutral Zone® buffers, sodium bicarbonate, and hydrogen peroxide. KB-1 Plus® is a custom blended formulation of naturally occurring, non-pathogenic microbial cultures (i.e., bioaugmentation cultures) used for over a decade to enhance bioremediation of chlorinated solvents. These cultures introduce beneficial microorganisms to contaminated sites where they are absent or at low concentrations. Neutral Zone® buffers and sodium bicarbonate will be used to try to keep the pH of the groundwater near 7. The microbes in the KB-1 Plus® function best when the pH ranges between 6 and 8. Lactate is used as food source to promote fast growth of microbial populations. EVO will provide a long-term food source for these microbial populations. In situations where an aerobic environment is required, hydrogen peroxide or air will be injected to provide oxygen for the microbes to use. Alternative 5 Estimated Costs for Contaminated Groundwater in Front Valley: In Situ Chemical Reduction with Long-Term Groundwater Monitoring and MNA for Areas B105 and B147 Area B105 and B147 Activity Estimated Capital Cost $1,310,500

Proposed Plan for ROD Amendment Chemtronics Superfund Site July 2016

16 Estimated Annual O&M Costs* $37,400 15% Contingency $341,000 30-Year Net Present Value $2,614,300 Estimated Construction Timeframe 12 months Estimated Time to Achieve RAOs greater than 30 years * - Costs for initial remedy period; costs are expected to decline over time as the size of the plume decreases. Alternative 5: In Situ Chemical Reduction with Long-Term Groundwater Monitoring and MNA – This alternative involves the installation of a zero valent iron permeable reactive barrier downgradient of the area to treat the contaminants migrating from the area. Prior to implementation, a pre-design investigation will be conducted to confirm an appropriate alignment of the permeable barrier. The permeable barrier will be wide enough to provide sufficient residence time for contaminant treatment. This remedial alternative includes the installation of additional monitoring wells. The estimated length of the zero valent iron permeable reactive barrier is 200 feet with a width of 1.3 feet. The barrier will be installed to a total depth of about 30 feet below ground surface to intersect the groundwater plume, and will be installed using a biopolymer slurry. The permeable barrier will be reinstalled at Year 15 to maintain treatment effectiveness, if necessary. B149 will continue to be monitored until the groundwater cleanup levels are achieved at this location. If necessary, additional EISB activities may occur at this location in order to help achieve the groundwater cleanup levels. BACK VALLEY – SOIL With the exception of the DAs addressed in the 1988 remedy, the baseline risk assessment did not identify an unacceptable current or future risk associated with soil in the BV. Therefore, no new remediation alternatives were developed for soil in the BV. BACK VALLEY – GROUNDWATER The following remediation alternatives were developed for the contaminated groundwater in the BV.

1 2

3

4

5

BACK VALLEY GROUNDWATER REMEDIATION ALTERNATIVES ALTERNATIVE DESCRIPTION OF REMEDIATION ALTERNATIVES This alternative is required for consideration by the NCP. No active cleanup No Further Action activities will be initiated. Routine monitoring and reporting will be completed on an annual basis to confirm Site conditions. Long-term monitoring of natural attenuation and biotic and abiotic MNA degradation/transformation/mineralization of organic and inorganic constituents Groundwater Extraction and Use of existing and/or installation of additional extraction wells to extract Treatment with Long-Term contaminated groundwater and control groundwater migration. Treat extracted Groundwater Monitoring and groundwater through physical processes such as air stripping and adsorption MNA through activated carbon. Injection or emplacement of microbes, nutrients or other amendments into Enhanced In Situ groundwater through injection wells or as a permeable reactive barrier (biobarrier) Bioremediation with Long-Term installed via injection/jetting techniques (versus trenching) to enhance biological Groundwater Monitoring and degradation in situ. Adjusting the geochemistry of the groundwater (creating either MNA anaerobic or aerobic conditions in the aquifer is a component of this alternative). Groundwater Diversion for DA9 Construction of an upgradient subsurface barrier to divert groundwater around an and APA with Long-Term area and thus reduce mass flux of COCs and migration in groundwater. May Groundwater Monitoring and include vertical barrier wall (s), cement, geomembranes, grout curtains and sheet MNA piling used either separately or in combination.

Proposed Plan for ROD Amendment Chemtronics Superfund Site July 2016

17 BACK VALLEY GROUNDWATER REMEDIATION ALTERNATIVES ALTERNATIVE DESCRIPTION OF REMEDIATION ALTERNATIVES Electrical Resistance Heating Installation of a series of electrodes around a central neutral electrode. Volatilized and Soil Vapor Extraction with contaminants, produced by heating of the subsurface surrounding the electrodes, are Treatment of Discharge Gas recovered using a soil vapor extraction network and subsequently treated at the 6 Prior to Discharge to the surface. Atmosphere with Long-Term Groundwater Monitoring and MNA (only for DA9) Alternative 1 Estimated Costs for Contaminated Groundwater in Back Valley: No Further Action for Areas DA9 and APA Area DA9 APA Activity Estimated Capital Cost $23,100 $39,000 Estimated Annual O&M Costs $21,100 $63,400 15% Contingency $52,200 $152,000 30-Year Net Present Value $400,000 $1,165,600 Estimated Construction Timeframe 0 months 0 months Estimated Time to Achieve RAOs greater than 30 years greater than 30 years Alternative 1: No Further Action – Under this alternative, no active remediation activities will occur. The capital costs associated with this alternative include: general Site maintenance for a period of 30 years, routine monitoring of groundwater and surface water, and reporting on an annual basis to confirm Site conditions, and annual maintenance of the existing caps. Alternative 2 Estimated Costs for Contaminated Groundwater in Back Valley: MNA for Areas DA9 and APA Area DA9 APA Activity Estimated Capital Cost $23,100 $39,300 Estimated Annual O&M Costs* $38,000 $100,900 15% Contingency $85,400 $152,000 30-Year Net Present Value $654,400 $1,672,600 Estimated Construction Timeframe 3 months 3 months Estimated Time to Achieve RAOs greater than 30 years greater than 30 years * - Costs for initial remedy period; costs are expected to decline over time as the size of the plume decreases. Alternative 2: MNA – This alternative is similar to Alternative 1 except the groundwater monitoring efforts will include the necessary MNA analytical parameters such as dissolved gases (ethene, ethane, and methane), dissolved metals, anions, and TOC. The analysis of groundwater samples for COCs and their biodegradation intermediates will provide an indication of the progress of MNA. The annual sampling and monitoring of the surface water is included. The number of monitoring locations for the MNA program may decrease over the remedy duration. The addition of additional monitoring wells is included.

Proposed Plan for ROD Amendment Chemtronics Superfund Site July 2016

18 Alternative 3 Estimated Costs for Contaminated Groundwater in Back Valley: Groundwater Extraction and Treatment with Long-Term Groundwater Monitoring and MNA for Areas DA9 and APA Area DA9 APA Activity Estimated Capital Cost $1,540,000 $4,601,400 Estimated Annual O&M Costs* $303,800 $881,000 15% Contingency $706,100 $2,079,200 30-Year Net Present Value $5,413,100 $15,940,000 Estimated Construction Timeframe 12 months 12 months Estimated Time to Achieve RAOs greater than 30 years greater than 30 years Notes: For DA9 – Replace wells in Years 10 and 30 – estimated cost $303,000; Complete system replacement in Year 20 – estimated cost → $1,500,000 For APA – Replace wells in Years 10 and 30 – estimated cost $880,000; Complete system replacement in Year 20 – estimated cost → $4,600,000 * - Costs for initial remedy period; costs are expected to decline over time as the size of the plume decreases. Alternative 3: Groundwater Extraction and Treatment with Long-Term Groundwater Monitoring and MNA – This alternative involves installing extraction wells in all three aquifer zones (surficial, transition zone, and bedrock), pumping groundwater from these extraction wells, installation of the necessary piping, electrical, and control systems/units, on-site treatment using a combination of pH adjustment, sediment removal, air stripping, oxidation, and/or biological treatment, discharging the treated groundwater to the MSD sewer system under a permit, and the installation of additional monitoring wells, where necessary, to monitor the extraction system. Monitoring will continue for the downgradient portion of the plume to confirm that natural attenuation continues to reduce COC concentrations over time. The FS assumed that a new treatment system will be required and will be housed in the existing building. The anticipated flow rate from the DA9 extraction wells is 8 gpm and the anticipated flow rate from the APA extraction wells is 22 gpm. The effluent from these two extraction systems will be combined prior to treatment. This treatment system would include, at a minimum, the following components: flow equalization, an air stripper and associated conduits, filtration for particulate removal, instrumentation and control systems will be automated where possible and appropriate, and pH adjustment as required to meet MSD discharge requirements. The need for off-gas treatment from the air stripper is not anticipated (per Title 15A NCAC Subchapter 02D requirements) but this will be confirmed during the RD phase. Based on performance of the existing BV pump and treat system, it is anticipated that the extraction wells will need to be replaced every 10 years, and the treatment system every 20 years. Alternative 4 Estimated Costs for Contaminated Groundwater in Back Valley: Enhanced In Situ Bioremediation with Long-Term Groundwater Monitoring and MNA for Areas DA9 and APA Area DA9 APA Activity Estimated Capital Cost $1,240,300 $3,090,000 Estimated Annual O&M Costs* refer to Notes refer to Notes 15% Contingency $405,500 $1,220,100 30-Year Net Present Value $3,109,100 $9,350,000 Estimated Construction Timeframe 12 months 12 months Estimated Time to Achieve RAOs 30-60 years 30-60 years

Proposed Plan for ROD Amendment Chemtronics Superfund Site July 2016

19 Alternative 4 Estimated Costs for Contaminated Groundwater in Back Valley: Enhanced In Situ Bioremediation with Long-Term Groundwater Monitoring and MNA for Areas DA9 and APA Notes: For DA9 – Injection Years → $260,000 to $390,000; Other years $38,000 → Average $75,000/year For APA – Injection Years → $840,000 to $1,200,000 Other years $101,000 → Average $290,000/year * - Costs for initial remedy period; costs are expected to decline over time as the size of the plume decreases. Alternative 4: Enhanced In Situ Bioremediation with Long-Term Groundwater Monitoring and MNA – This alternative involves emplacement of microbes, nutrients or other amendments into groundwater to enhance biological degradation in situ of the contaminants in the groundwater. EISB can occur under either anaerobic or aerobic conditions and creating one of these conditions depends on what type of amendments that are injected into the aquifer. The types of contaminants in a particular area will determine whether an anaerobic or an aerobic environment is required. The microbes, nutrients, and other amendments are typically introduced into the subsurface in one of two ways, direct injection or via a recirculation approach. As for the Chemtronics Site, EISB pilot scale treatability studies have been ongoing in both valleys for over a year. These ongoing EISB pilot scale treatability studies have verified that the microbes in the underlying aquifer zones are mineralizing the COCs. The following are the main activities that will occur to transition from the existing pilot scale to full scale. Install additional injection, extraction (if deemed necessary to create recirculation in the subsurface), and monitoring wells. The RD will quantify the location, type, and depth of these wells. Upgrade the existing pilot scale systems’ piping, equipment, and controls, if necessary, to accommodate the additional injection and extraction wells. Establish an injection schedule based on performance monitoring data. It is anticipated that some of the injection wells may need to be rehabilitated twice a year due to microbial growth and mineral deposition of the well’s screen. Performance monitoring may vary based on the equipment and approach employed. The key components of the performance monitoring effort will include: monitoring of the recirculating groundwater (if employed) and collecting groundwater samples from wells both within the treatment zone as well as downgradient of the treatment zone. The following is a list of potential materials that may be injected into the subsurface at the various full scale treatment efforts. Not all of these materials may be injected at any one area. The materials include (but are not limited to): KB-1 Plus®, EVO, EHC-L®, lactate, Neutral Zone® buffers, sodium bicarbonate, and hydrogen peroxide. KB-1 Plus® is a custom blended formulation of naturally occurring, non-pathogenic microbial cultures (i.e., bioaugmentation cultures) used for over a decade to enhance bioremediation of chlorinated solvents. These cultures introduce beneficial microorganisms to contaminated sites where they are absent or at low concentrations. Neutral Zone® buffers and sodium bicarbonate will be used to try to keep the pH of the groundwater near 7. The microbes in the KB-1 Plus® function best when the pH ranges between 6 and 8. Lactate is used as food source to promote fast growth of microbial populations. EVO and/or EHC-L®, will provide a long-term food source for these microbial populations. In situations where an aerobic environment is required, hydrogen peroxide or air will be injected to provide oxygen for the microbes to use. Alternative 5 Estimated Costs for Contaminated Groundwater in Back Valley: Groundwater Diversion Remedy for Areas DA9 and APA with Long-Term Groundwater Monitoring and MNA Area DA9 APA Activity Estimated Capital Cost $2,437,700 $7,445,500 Estimated Annual O&M Costs* $39,800 $106,500 15% Contingency $453,800 $1,335,000 30-Year Net Present Value $3,479,500 $10,234,800 Estimated Construction Timeframe 12 months 12 months

Proposed Plan for ROD Amendment Chemtronics Superfund Site July 2016

20 Alternative 5 Estimated Costs for Contaminated Groundwater in Back Valley: Groundwater Diversion Remedy for Areas DA9 and APA with Long-Term Groundwater Monitoring and MNA Area DA9 APA Activity Estimated Time to Achieve RAOs greater than 30 years greater than 30 years * - Costs for initial remedy period; costs are expected to decline over time as the size of the plume decreases. Alternative 5: Groundwater Diversion for DA9 and APA with Long-Term Groundwater Monitoring and MNA – This alternative involves installing a groundwater diversion remedy (GDR) on the north side of DA9 and the north side of the APA to reduce the mass flux of contaminants leaving these two capped disposal areas by reducing the amount of groundwater flowing through these two areas. The barrier consists of a soil-bentonite vertical barrier wall (VBW) from the ground surface down to the top of rock. The wall will be placed in contact with competent rock to the extent practical. In addition, a grout curtain will be installed below the top of competent rock to reduce in-fracture permeability. A groundwater drain will be installed 3 feet above the top of rock along the northern side of the VBW. The goal of the GDR alternative is to reduce the mass flux of contamination leaving these two capped areas to allow MNA to remedy the downgradient plume. The following assumptions were made in preparing the cost estimate for this alternative: The caps will not be disturbed; all mixing and construction activity will occur outside of the perimeter of the GDR. • The existing caps will be maintained and extended to cover the VBW. • Land area surrounding the proposed VBW will need to be cleared prior to construction. • The target maximum hydraulic conductivity of the VBW will be 1 × 10-7 centimeter/second. • The depth to bedrock changes significantly across the area. For the purposes of this budgetary cost estimate, a depth range of 10 feet to 70 feet was selected. Alternative 6 Estimated Costs for Contaminated Groundwater in Back Valley: Electrical Resistance Heating and Soil Vapor Extraction with Treatment of Discharge Gas Prior to Discharge to the Atmosphere with Long-Term Groundwater Monitoring and MNA for Area DA9 Area DA9 Activity Estimated Capital Cost $3,525,100 Years 1-4 → $791,200; Estimated Annual O&M Costs* thereafter $38,000/year 15% Contingency $1,017,000 30-Year Net Present Value $7,7796,800 Estimated Construction Timeframe 12 months Estimated Time of Operation 4 years** Notes: * - Costs for initial remedy period; costs are expected to decline over time as the size of the plume decreases. ** Reduce concentration of contaminants to less than the source mass flux reduction threshold (i.e., less than 1000× Screening Criteria) Alternative 6: Electrical Resistance Heating and Soil Vapor Extraction with Treatment of Discharge Gas Prior to Discharge to the Atmosphere with Long-Term Groundwater Monitoring and MNA – This alternative involves the installation of a number of horizontal, combined electrical resistance heating and soil vapor extraction (ERH/SVE) wells under DA9. The ERH will heat the groundwater to near the boiling point, which will drive TCE and 1,2-DCA into the vapor phase. The vapor generated during this process will be extracted via the ERH/SVE wells, and treated ex situ for removal of the contaminants using either oxidation or alternative treatment depending on the mass loading. A water phase treatment system will also be required to treat the condensed phase of the extracted vapor that is expected. Under this

Proposed Plan for ROD Amendment Chemtronics Superfund Site July 2016

21 alternative, ERH/SVE is anticipated to reduce the mass flux from DA9 to allow MNA to remedy the plume areas downgradient of DA9. The following assumptions are included for this alternative: • A stand-alone building will be constructed to house the treatment components. • Additional power supply will be required to support the ERH, including new high voltage transmission lines, transformer, power control panel and low voltage cable. • The SVE will generate an air stream which will need to be treated with a moisture knockout or condenser, followed by thermal oxidation, with an acid gas scrubber, or alternative treatment depending on the mass loading. This treatment train would be expected to provide treatment of the TCE and 1,2-DCA, as well as any other materials that may be extracted. • Instrumentation and control systems will be automated where possible and appropriate. • Air discharge permits will be obtained. • The water from the moisture knockout will be treated prior to being discharged to the MSD sewer system. The existing MSD permit will need to be updated. Identified unknowns would be addressed during the RD phase. EVALUATION OF ALTERNATIVES The selection of the preferred alternatives for the Chemtronics Site, as described in this Proposed Plan, is the result of a comprehensive screening and evaluation process. The 2016 FS identified and analyzed appropriate remediation technologies/alternatives for addressing the contamination at the Site. EPA uses the following nine criteria to evaluate the identified alternatives. The remedial alternative selected for a Superfund site must achieve the two threshold criteria as well as attain the best balance among the five evaluation criteria. EPA’s Preferred 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 institutional controls, 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 the EPA's analyses and recommendations, as described in the RI/FS and Proposed Plan.

Proposed Plan for ROD Amendment Chemtronics Superfund Site July 2016

22 EVALUATION CRITERIA FOR SUPERFUND REMEDIAL ALTERNATIVES Community Acceptance considers whether the local community agrees with EPA's analyses and preferred 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 2016 FS document. This analysis compared each remedial alternative for each soil and groundwater area of concern to the Threshold and Evaluation Criteria highlighted in the table above. Scores were developed for these criteria, cost was not assigned a score, but the relative cost between remedial alternatives was considered in the comparison. The tables below summarize the scores from this analysis for each area in each valley. The scores were developed for the threshold and/or primary balancing criteria with “5” being the highest score and “1” being the lowest score. The scores were summed to provide a total (out of 30 points) for each alternative. Front Valley

Total Score

1 2 5 4

1 2 5 4

1 2 5 4

5 4 3 3

5 5 4 3

14 17 27 22

1 2 5 4

1 2 5 4

1 2 5 4

1 2 5 4

5 4 3 3

5 5 4 3

14 17 27 22

Long-Term Effectiveness

Short-Term Effectiveness

1 2 5 4

Compliance with ARARs

Implementability

AREA B109-137 ALTERNATIVE 1 No Further Action 2 Monitored Natural Attenuation 3 Excavation and Off-Site Disposal 4 Soil Vapor Extraction AREA B116 ALTERNATIVE 1 No Further Action 2 Monitored Natural Attenuation 3 Excavation and Off-Site Disposal 4 Soil Vapor Extraction

Reduction in Toxicity, Mobility, & Volume

Overall Protection

SUMMARY OF DETAIL ANALYSIS FOR SOIL ALTERNATIVES FOR AREAS B109-137 AND B116 IN FRONT VALLEY

Implementability

Total Score

1 2 3 5

Short-Term Effectiveness

1 2 5 4

Reduction in Toxicity, Mobility, & Volume

1 2 3 5

Long-Term Effectiveness

Compliance with ARARs

AREA B104 ALTERNATIVE 1 No Further Action 2 Monitored Natural Attenuation 3 Pump & Treat and Long-Term Monitoring and MNA 4 EISB and Long-Term Monitoring and MNA

Overall Protection

SUMMARY OF DETAIL ANALYSIS FOR GROUNDWATER ALTERNATIVES FOR AREAS B104, B105 AND B147, B139, AND DA23-B116 IN FRONT VALLEY

1 1 3 5

5 4 3 3

5 5 2 4

14 16 19 26

Proposed Plan for ROD Amendment Chemtronics Superfund Site July 2016

23

Reduction in Toxicity, Mobility, & Volume

Short-Term Effectiveness

Implementability

Total Score

1 2 3 5

1 2 5 4

1 2 3 5

1 1 3 5

5 4 3 3

5 5 2 4

14 16 19 26

4

4

4

3

3

3

21

1 2 3 5

1 2 5 3

1 2 3 5

1 1 3 5

5 4 3 3

5 5 2 5

14 16 19 26

1 2 3 5

1 2 5 3

1 2 3 5

1 1 3 5

5 4 3 3

5 5 2 5

14 16 19 26

Long-Term Effectiveness

Compliance with ARARs

AREAS B105 AND B147 ALTERNATIVE 1 No Further Action 2 Monitored Natural Attenuation 3 Pump & Treat and Long-Term Monitoring and MNA 4 EISB and Long-Term Monitoring and MNA In Situ Chemical Reduction (ZVI PRB) and Long-Term 5 Monitoring and MNA AREA B139 ALTERNATIVE 1 No Further Action 2 Monitored Natural Attenuation 3 Pump & Treat and Long-Term Monitoring and MNA 4 EISB and Long-Term Monitoring and MNA AREAS DA23-B116 ALTERNATIVE 1 No Further Action 2 Monitored Natural Attenuation 3 Pump & Treat and Long-Term Monitoring and MNA 4 EISB and Long-Term Monitoring and MNA

Overall Protection

SUMMARY OF DETAIL ANALYSIS FOR GROUNDWATER ALTERNATIVES FOR AREAS B104, B105 AND B147, B139, AND DA23-B116 IN FRONT VALLEY

Back Valley

Compliance with ARARs

Long-Term effectiveness

Reduction in Toxicity, Mobility, & Volume

Short-Term Effectiveness

Implementability

Total Score

AREA DA9 ALTERNATIVE 1 No Further Action 2 Monitored Natural Attenuation 3 Pump & Treat and Long-Term Monitoring and MNA 4 EISB and Long-Term Monitoring and MNA Groundwater Diversion Remedy and Long-Term 5 Monitoring and MNA Electrical Resistance Heating and Soil Vapor 6 Extraction and Long-Term Monitoring and MNA

Overall Protection

SUMMARY OF DETAIL ANALYSIS FOR GROUNDWATER ALTERNATIVES FOR AREAS DA9 AND APA IN BACK VALLEY

1 2 4 5

1 2 5 4

1 2 3 5

1 1 2 4

5 4 2 3

5 5 2 4

14 16 18 25

3

4

4

4

3

3

21

3

4

4

5

1

2

19

Proposed Plan for ROD Amendment Chemtronics Superfund Site July 2016

24

Compliance with ARARs

Long-Term effectiveness

Reduction in Toxicity, Mobility, & Volume

Short-Term Effectiveness

Implementability

Total Score

AREA APA ALTERNATIVE 1 No Further Action 2 Monitored Natural Attenuation 3 Pump & Treat and Long-Term Monitoring and MNA 4 EISB and Long-Term Monitoring and MNA Groundwater Diversion Remedy and Long-Term 5 Monitoring and MNA

Overall Protection

SUMMARY OF DETAIL ANALYSIS FOR GROUNDWATER ALTERNATIVES FOR AREAS DA9 AND APA IN BACK VALLEY

1 2 4 5

1 2 5 4

1 2 3 5

1 1 2 5

5 4 2 3

5 5 2 3

14 16 18 25

3

4

4

4

3

3

21

OVERALL PROTECTIVENESS OF HUMAN HEALTH AND THE ENVIRONMENT Front Valley – Soil → Alternatives 1 and 2 are protective under current conditions as access to the Site is controlled and there are health and safety protocols in place to protect workers but these alternatives may not be protective of future onsite workers. Contaminants may continue to migrate. RAOs would not be achieved for a very long time. Both Alternatives 3 and 4 would be protective. Alternative 3 can easily be implemented, at the conclusion of the remedial action at these locations, RAOs would be achieved. Alternative 4 is a more technically challenging alternative requiring frequent visits to check on the SVE components, RAOs would eventually be achieved. Front Valley – Groundwater → Alternative 4 would be protective of human health and the environment because contaminated groundwater in the source area greater than cleanup goals would be actively remediated. Alternatives 1 and 2 are protective under current conditions as access to the Site is controlled and there are health and safety protocols in place to protect current workers but these alternatives may not be protective in the future. Contaminants would continue to migrate. RAOs would not be achieved for a very long time. Based on the minimal success of the current pump and treat system, the prospect for the success of Alternative 3 is questionable. Alternative 5, which is only considered for B105 and B147, would be the most technically challenging alternative to implement. Back Valley – Groundwater → Alternative 4 would be the most protective of human health and the environment because contaminated groundwater immediately downgradient of the source areas greater than cleanup goals would be actively remediated. Alternatives 1 and 2 are protective under current conditions as access to the Site is controlled and there are health and safety protocols in place to protect current workers but these alternatives may not be protective in the future. Contaminants would continue to migrate. RAOs would not be achieved for a very long time. Based on the minimal success of the current pump and treat system, the prospect for the success of Alternative 3 is questionable. Alternative 5 would be the most technically challenging alternative to implement and the complete diversion of all groundwater is questionable. There is concern that groundwater may still flow into the disposed waste under the caps. Alternative 6 for DA9, would be effective in removing contaminants in the soil but not from any buried drums in this disposal area. COMPLIANCE WITH ARARS AND TBCS Remedial actions must comply with Applicable or Relevant and Appropriate Requirements (ARARs) of federal and state laws, statutes, and regulations. ARARs are determined by applying a two-tiered test to determine first whether the requirement is applicable and second to determine whether the requirement is relevant and appropriate. Applicable requirements are those cleanup standards, controls, and other substantive environmental protection requirements, criteria, or limitations promulgated under federal or state law that specifically address a hazardous substance, pollutant, or contaminant, remedial action, location, or other circumstance at a Superfund site. Relevant and appropriate requirements

Proposed Plan for ROD Amendment Chemtronics Superfund Site July 2016

25 are those cleanup standards, standards of control, or other substantive environmental provisions that do not directly and fully address site conditions but address similar situations or problems to those encountered at a Superfund site. Whether or not a requirement is appropriate (in addition to being relevant) will vary depending on factors such as the duration of the response action, the form or concentration of the chemicals present, the nature of the release, the availability of other standards that more directly match the circumstances at the site, and other factors. In addition, non-promulgated advisories or guidance documents issued by federal or state governments, referred to as To Be Considered (TBC), should also be identified. TBCs are not considered legally enforceable and, therefore, are not considered to be applicable for the site but are evaluated along with ARARs as part of the risk assessment to set protective cleanup goal targets. There are three types of ARARs: chemical-specific, action-specific, and location-specific. Chemical-specific ARARs are usually health or risk-based restrictions on the amount or concentration of a chemical that may be found in or discharged to the environment. Action-specific ARARs establish controls or restrictions on the remedial activities which are part of the remedial solution. Action-specific ARARs are triggered by the specific activity rather than the chemicals present. Location-specific ARARs prevent damage to unique or sensitive areas, such as floodplains, historic places, wetlands, and fragile ecosystems, and restrict other activities that are potentially harmful because of where they take place. Chemicalspecific, action-specific, and location-specific ARARs including TBCs for the Site have been identified and are listed in the 2016 FS. Front Valley – Soil → Alternatives 1 and 2 would not comply with ARARs and Alternatives 3 and 4 would comply with all ARARs. Front Valley – Groundwater → Alternatives 1 and 2 would not comply with ARARs and Alternatives 3, 4, and 5 6 would comply with all ARARs. Back Valley – Groundwater → Alternatives 1 and 2 would not comply with ARARs and Alternatives 3, 4, 5, and 6 would comply with all ARARs. LONG-TERM EFFECTIVENESS AND PERMANENCE Front Valley – Soil → Neither Alternative 1 nor 2 provide long-term effectiveness and permanence. Alternatives 3, 4, and 5 would provide long-term effectiveness and permanence as these alternatives actively treat the contaminants present in the groundwater, Alternatives 4 and 5 treat the contaminants in situ and Alternative 3 treats the contaminants ex situ. Front Valley – Groundwater → Neither Alternative 1 nor Alternative 2 provide long-term effectiveness and permanence. Based on the minimal success of the current pump and treat systems at the Site, the effectiveness and permanence of Alternative 3 is suspect. Based on the data generated from the ongoing in situ pilot scale treatability studies, Alternative 4 provides both long-term effectiveness and permanence as the biomass is mineralizing the contaminants. Alternative 5 attempts to prevent groundwater from moving through the disposal areas and picking up contaminants. Alternative 6 would address the contaminants in the soil but not the contents of any drums in the disposal area. Back Valley – Groundwater → Neither Alternative 1 nor Alternative 2 provide long-term effectiveness and permanence. Based on the minimal success of the current pump and treat systems at the Site, the effectiveness and permanence of Alternative 3 is suspect. Based on the data generated from the ongoing in situ pilot scale treatability studies, Alternative 4 provides both long-term effectiveness and permanence as the biomass is mineralizing the contaminants. Alternative 5 for the BV attempts to prevent groundwater from moving through the disposal areas and picking up contaminants. Alternative 6 would address the contaminants in the soil but not the contents of any drums in the disposal area. REDUCTION OF TOXICITY, MOBILITY, AND VOLUME THROUGH TREATMENT Front Valley – Soil → Neither Alternative 1 nor 2 would reduce toxicity, mobility or volume of contaminants. Both Alternatives 3 and 4 would reduce toxicity, mobility or volume of contaminants.

Proposed Plan for ROD Amendment Chemtronics Superfund Site July 2016

26 Front Valley – Groundwater → Neither Alternative 1 nor 2 would result in a reduction in toxicity, mobility or volume of contaminants. Alternatives 3 through 5 would each result in a reduction in the toxicity, mobility or volume of contaminants in the groundwater to varying degrees. Alternative 4 would lead to permanent destruction of the contaminants as the microbes mineralize the contaminants. Alternatives 3 and 4 would meet the statutory preference for treatment. Back Valley – Groundwater → Neither Alternative 1 nor 2 would result in a reduction in toxicity, mobility or volume of contaminants. Alternatives 3, 4, and 6 would each result in a reduction in the toxicity, mobility or volume of contaminants in the groundwater to varying degrees through treatment and therefore meet the statutory preference for treatment. For Alternative 3, treatment would occur above ground after the groundwater is extracted. Through EISB Alternative 4 would lead to permanent destruction of the contaminants as the microbes mineralize the contaminants. The goal of Alternative 5 is to keep groundwater from entering the existing capped areas and mobilizing contaminants in the capped areas. Any treatment associated with Alternative 5 would be through MNA. Alternative 6 would treat any gas generated associated with DA9. SHORT TERM EFFECTIVENESS Front Valley – Soil → There would be no increased risk to workers or the surrounding community during implementation of Alternatives 1 or 2 because no remedial action activities would occur under Alternatives 1 and 2. There is a small chance of exposure to on-site workers while implementing either Alternative 3 or 4, however, using the appropriate health and safety guidelines would negate those risks. Front Valley – Groundwater → There are no short term risks associated with implementing Alternatives 1 and 2. For Alternatives 3 and 4, there are short term risks due to possibility of being exposed to contaminated groundwater during construction activities and other chemicals. However, through the proper use of personal protection equipment (PPE) and monitoring during Site activities, these risks are minimized. In addition, workers would be properly trained and informed of the risks. The only risk associated with implementing Alternative 5 (for B105 and B147 only) is the same risks associated with any construction project. Back Valley – Groundwater → There are no short term risks associated with implementing Alternatives 1 and 2. For Alternatives 3, 4, and 6, there are short term risks due to possibility of being exposed to contaminated groundwater during construction activities and other chemicals. However, through the proper use of personal protection equipment (PPE) and monitoring during Site activities, these risks are minimized. In addition, workers would be properly trained and informed of the risks. The only risk associated with implementing Alternative 5 is the same risks associated with any construction project. IMPLEMENTABILITY Front Valley – Soil → No work is associated with Alternative 1. Monitoring activities are the only activities associated with Alternative 2. Alternatives 3 and 4 are easily implementable. Front Valley – Groundwater → No work is associated with Alternative 1 and only monitoring activities are associated with Alternative 2. For Alternatives 3, 4, and 5, Alternative 4 is anticipated to be the least complicated alternative to implement, followed by Alternative 5 (for B105 and B147 only) and then Alternative 3. Back Valley – Groundwater → No work is associated with Alternative 1 and only monitoring activities are associated with Alternative 2. For Alternatives 3, 4, 5, and 6, Alternative 4 is anticipated to be the least complicated alternative to implement, followed by Alternative 5 and then Alternatives 3 and 6. COST Cost estimates are summarized in the tables above and totaled in the table below.

Proposed Plan for ROD Amendment Chemtronics Superfund Site July 2016

27 SUMMARY OF PREFERRED ALTERNATIVE Using the above information/assumptions, the Agency’s preferred remedial alternative for the Chemtronics Superfund Site is the combination of the following alternatives: • The Preferred Remedial Alternative for contaminated soil at Areas B109-137 and B116 in the FV is Alternative #3 – Excavation of contaminated soil with off-site disposal; • The Preferred Remedial Alternative for contaminated groundwater in the FV is Alternative #4 – EISB with long-term groundwater monitoring and MNA for Areas: B104, B105 and B147, B139, and DA23/B116; • The Preferred Remedial Alternative for contaminated groundwater in the BV is Alternative #4 – EISB with longterm groundwater monitoring and MNA for DA9 and APA; and • Placement of ICs on the Superfund Site portion of the Chemtronics property using the State of North Carolina DPLURs process which requires the generation of a plat map which defines the boundaries of the Chemtronics Superfund Site. The ICs will 1) limit the use of the Chemtronics Superfund Site to either commercial or industrial purposes and 2) restrict groundwater use and prevent the use of on-site groundwater for potable purposes. This Preferred Remedial Alternative also includes the following requirements/actions: • Retain the capping and engineering control requirements for the six DAs from the 1988 ROD; • Update the groundwater cleanup levels for the Site; and • Eliminates the requirement for pumping and treating groundwater in both valleys as specified in the 1988 ROD. Figure 11 shows the locations for the soil excavation associated with Areas B109-B137 and B116 and the four groundwater EISB treatment areas B104, B105 and B147, B139, and DA23/B116 in the Front Valley. Figure 12 shows the location of the groundwater EISB treatment area associated with DA9 and APA in the Back Valley. The estimated total cost of this preferred remedial alternative is $18,197,300. Total Cost of Preferred Remedial Alternative 30-Year Net Location Media Area Present Value B109-137 $157,700 Soil B116 $109,400 B104 $1,170,700 FV B105 and B147 $1,886,400 Groundwater B139 $1,160,000 DA23/B116 $1,254,000 DA9 $3,109,100 BV Groundwater APA $9,350,000 Total $18,197,300 PUBLIC PARTICIPATION The public meeting for the Proposed Plan will begin at 6:30 p.m. on Thursday, July 14, 2016, at the Swannanoa Fire Station at 510 Bee Tree Road, Swannanoa, North Carolina. EPA and NCDEQ have provided information regarding the cleanup of the Site to the public through Fact Sheets, public meetings, announcements in The Pilot, and the Administrative Record file. In addition to reading this Proposed Plan, EPA and NCDEQ 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.

Proposed Plan for ROD Amendment Chemtronics Superfund Site July 2016

28 For further information on the Site, please contact: Jon Bornholm Remedial Project Manager (404) 562-8820 or (800) 435-9233 E-mail: [email protected] or Angela Miller Community Involvement Coordinator (404) 562-8561 or (800) 435-9233 E-mail: [email protected] 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: Ellison Library on the campus of Warren Wilson College 701 Warren Wilson Road Swannanoa, NC 28778 Phone: 828-771-3058 Hours: Monday – Thursday 8 a.m. – 12 a.m. Friday 8 a.m. – 5 p.m. Saturday 1 p.m. – 5 p.m. Sunday 1 p.m. – 12 a.m. and U.S. Environmental Protection Agency Region IV - Records Center 61 Forsyth Street, SW Atlanta, Georgia 30303-3104 Phone: 404-562-8820 Hours: Monday - Friday 8 a.m. - 5 p.m.

TABLE 1a – Summary of Unacceptable Cancer and Noncancer Risks Associated with Contaminants Detected in the Soil Risk Characterization Summary - B116 Soil Direct Contact Scenario Timeframe: Future Receptor Population: Industrial Worker Receptor Age: Adult Medium

Exposure Exposure Medium Point

Soil

Soil and Outdoor Air

Chemical of Concern

Carcinogenic Risk Noncarcinogenic HQ Dermal Inhalation of Inhalation Exposure Dermal Inhalation of Inhalation Exposure Ingestion Ingestion Contact Particulates of Vapors Routes Total Contact Particulates of Vapors Routes Total

Soil On1,2-Dichloroethane 3.4 × 10-6 N/A site- Direct Soil OnAll other Contact 4.3 × 10-6 5.6 × 10-6 site- Direct chemicals Contact

3.6 × 10-12

1.3 × 1-4

1.4 × 10-4

0.0053

N/A

0.0

2.1

2.1

4.1 × 10-11

1.5 × 10-6

1.1 × 10-5

0.029

0.028

0.0000058

0.077

0.13

-4

Soil risk total = 1.51 × 10 Soil HI total = 2.23 Key N/A - COC, as a volatile, does not have dermal contact exposure These risk estimates are based on a reasonable maximum exposure and were developed by taking into account various conservative assumptions about the frequency and duration of a worker's exposure to soil via direct contact, as well as the toxicity of the COCs. The total risk from direct exposure by an industrial worker to soil via ingestion, dermal contact, and inhalation of vapors and particulates is estimated to be 1.5 × 10 -4 and the total HI is estimated to be 2.2. The COC contributing the most to this risk level is 1,2-dichloroethane.

TABLE 1b – Summary of Unacceptable Cancer and Noncancer Risks Associated with Contaminants Detected in the Soil Risk Characterization Summary - B116 Vapor Intrusion Scenario Timeframe: Future Receptor Population: Industrial Worker Receptor Age: Adult Carcinogenic Risk Noncarcinogenic HQ Exposure Medium Exposure Point Chemical of Concern Exposure Exposure Medium Inhalation Inhalation Routes Total Routes Total -5 -5 Soil Vapor Intrusion Benzene 0.43 0.43 3.6 × 10 3.6 × 10 Soil Vapor Intrusion Cyclohexane N/A N/A 0.55 0.55 -2 -2 1,2-Dichloroethane 380 380 Soil Indoor Air Soil Vapor Intrusion 2.5 × 10 2.5 × 10 -5 -5 Soil Vapor Intrusion Vinyl chloride 0.082 0.082 1.3 × 10 1.3 × 10 -5 -5 Soil Vapor Intrusion All other chemicals 0.55 0.55 4.1 × 10 4.1 × 10 Soil HI total = 381 Soil risk total =2 × 10-2 Key: N/A – COC is not a carcinogen These risk estimates are based on a reasonable maximum exposure and were developed by taking into account various conservative assumptions about the frequency and duration of a worker's exposure to soil via vapor intrusion, as well as the toxicity of the COCs. The total risk from -2 exposure by an industrial worker to soil via vapor intrusion is estimated to be 2 × 10 and the total HI is estimated to be 381. The COC contributing the most to this risk level is 1,2-dichloroethane.

TABLE 2 – Summary of Unacceptable Cancer and Noncancer Risks Associated with Contaminants Detected in the Soil Risk Characterization Summary – B109-137 Vapor Intrusion Scenario Timeframe: Future Receptor Population: Industrial Worker Receptor Age: Adult Carcinogenic Risk Noncarcinogenic HQ Exposure Medium Exposure Point Chemical of Concern Exposure Exposure Routes Medium Inhalation Inhalation Routes Total Total -5 -5 Soil Vapor Intrusion Naphthalene 0.52 0.52 1.9 × 10 1.9 × 10 Soil Vapor Intrusion 1,2,4-Trimethyl-benzene N/A N/A 7.6 7.6 Soil Indoor Air Soil Vapor Intrusion 1,3,5-Trimethyl-benzene N/A N/A 5.0 5.0 Soil Vapor Intrusion Xylenes (total) N/A N/A 0.29 0.29 -9 -9 Soil Vapor Intrusion All other chemicals 0.06 0.06 7.9 × 10 7.9 × 10 Soil HI total = 10 Soil risk total = 2 × 10-5 Key N/A – COC is not a carcinogen These risk estimates are based on a reasonable maximum exposure and were developed by taking into account various conservative assumptions about the frequency and duration of a worker's exposure to soil via vapor intrusion, as well as the toxicity of the COCs. The total risk from exposure -5 of industrial workers to soil via vapor intrusion is estimated to be 2 × 10 and the total HI is estimated to be 10. The COCs contributing the most to this risk level are 1,2,4-trimethyl-benzene, 1,3,5-trimethyl-benzene, naphthalene, and xylenes.

TABLE 3 – CLEANUP LEVELS FOR SOIL CONTAMINANTS Chemicals of Concern (COCs) Associated with Soil at Area B109-B137, Chemtronics Superfund Site, Swannanoa, NC Cleanup Associated Routine Chemical Chemical Level Source of Cleanup Level Worker Vapor Intrusion Group (μg/kg) Risk at this Level Naphthalene 7,600 Max detect; HI for respiratory system 1.9 × 10-5 1,000 HI for blood N/A Volatile Organic 1,2,4-Trimethyl-benzene Compounds 1,3,5-Trimethyl-benzene 750 HI for blood N/A Xylenes (total) 7,600 Max detect; HI for nervous system N/A Chemicals of Concern (COCs) Associated with Soil at Area B116, Chemtronics Superfund Site, Swannanoa, NC

Volatile Organic Compounds

Benzene Cyclohexane 1,2-Dichloroethane Methylene chloride 1,1,2-Trichloroethane Vinyl chloride

6,300 1,300,000 1,500 4,800 2,900 4,000

Max detect; HI for immune system HI for developmental effects HI for nervous system Max detect Max detect Max detect; HI for liver

3.6 × 10-5 NA* 3.0 × 10-5 3.5 × 10-8 3.4 × 10-5 1.3 × 10-5

Associated Routine Worker Vapor Intrusion HQ at this Level 0.52 0.57 0.37 0.29 0.43 0.45 0.45 0.016 NA* 0.082

Key N/A – COC is not a carcinogen NA* – COC has no inhalation toxicity value of the relevant (cancer or noncancer) type. Cleanup levels include the segregation of HQs by target organ/effect. The cleanup level is defined so that the total HI for a given target organ (including the HQ for all COCs with that target organ and the combined HQ of all non-COC chemicals) is no greater than 1.

TABLE 4 – Cleanup Levels for Chemicals of Concern (COCs) for Groundwater at the Chemtronics Site HealthCleanup Chemical Group Chemical NC 2L Based Limit Level Acetone 6,000 μg/L -6,000 μg/L Benzene 1 μg/L -1 μg/L Bromoform (THM – 4 μg/L -4 μg/L Trihalomethane) Chloroform (THM) 70 μg/L -70 μg/L Carbon Tetrachloride 0.3 μg/L 0.3 μg/L Dibromochloromethane (THM) # 0.4 μg/L -0.4 μg/L 1,2-Dichloroethane 0.4 μg/L -0.4 μg/L cis-1,2-Dichloroethene 70 μg/L -70 μg/L 1,2-Dichloropropane 0.6 μg/L -0.6 μg/L Methyl acetate # -7,000 μg/L 7,000 μg/L Methyl-tert-butyl ether 20 μg/L -20 μg/L Volatile Organic Methylene chloride 5 μg/L -5 μg/L Compounds t-Butyl alcohol 10 μg/L * -10 μg/L * Tetrachloroethylene 0.7 μg/L -0.7 μg/L Tetrahydrofuran -6000 μg/L 6,000 μg/L 1,1,2-Trichloroethane 0.6 μg/L * -0.6 μg/L * Trichloroethylene 3 μg/L -3 μg/L Vinyl chloride 0.03 μg/L -0.03 μg/L 2,4-Dinitrophenol -10 μg/L 10 μg/L # 1,2-Diphenylhydrazine -0.04 μg/L 0.04 μg/L Benzophenone # -30 μg/L 30 μg/L N-nitrosodimethylamine 0.0007 μg/L -0.0007 μg/L BZ (3-Quinuclidinyl benzilate) -0.8 μg/L 0.8 μg/L Aldrin 0.002 μg/L * -0.002 μg/L * alpha-BHC # 0.02 μg/L -0.02 μg/L beta-BHC 0.02 μg/L -0.02 μg/L Dieldrin # 0.002 μg/L -0.002 μg/L Pesticides Lindane # 0.03 μg/L -0.03 μg/L Heptachlor # 0.008 μg/L -0.008 μg/L Heptachlor epoxide 0.004 μg/L -0.004 μg/ PCBs (total) # PCB 0.09 μg/L * -0.09 μg/L * 1,2-Diaminoethane -600 μg/L 600 μg/L Nonhalogenated Organics Methanol 4,000 μg/L -4,000 μg/L 2-Amino-4,6-dinitrotoluene -0.05 μg/L 0.05 μg/L 4-Amino-2,6-dinitrotoluene --0.05 μg/L 0.05 μg/L 1,3-Dinitrobenzene -0.7 μg/L 0.7 μg/L 2,4-Dinitrotoluene 0.1 μg/L 0.1 μg/L 2,6-Dinitrotoluene -0.1 μg/L 0.1 μg/L RDX -0.3 μg/L 0.3 μg/L Nitroaromatics 3-Nitrotoluene -7 μg/L 7 μg/L 2-Nitrotoluene -0.2 μg/L 0.2 μg/L 4-Nitrotoluene # -2 μg/L 2 μg/L PETN -10 μg/L 10 μg/L Nitroglycerin -0.7 μg/L 0.7 μg/L 2,4,6-Trinitrotoluene -1 μg/L 1 μg/L Manganese -500 μg/L 500 μg/L Inorganics Nitrate 10,000 μg/L 10,000 μg/L Perchlorate 2 μg/L * 2 μg/L *

Source of Cleanup Level NC 2L NC 2L NC 2L NC 2L NC 2L NC 2L NC 2L NC 2L NC 2L HB-NC NC 2L NC 2L NC 2L (IMAC) NC 2L HB-NC NC 2L (IMAC) NC 2L NC 2L HB-NC HB-C HB-NC NC 2L HB-NC NC 2L (IMAC) NC 2L NC 2L NC 2L NC 2L NC 2L NC 2L NC 2L (IMAC) HB-NC NC 2L HB-C HB-C HB-NC NC 2L HB-C HB-C HB-NC HB-C HB-C HB-NC HB-NC HB-C HB-NC NC 2L NC 2L (IMAC)

TABLE 4 – Cleanup Levels for Chemicals of Concern (COCs) for Groundwater at the Chemtronics Site HealthCleanup Source of Chemical Group Chemical NC 2L Based Limit Level Cleanup Level Notes: Where available for a compound, the promulgated NC 2L standards are, in all instances, equal to or lower (i.e., more protective) than MCLs. Health-based limits are provided if promulgated NC 2L standards are not available. Health-based limits were calculated during the baseline risk assessment. Health-based limits have been rounded to one significant figure to represent the level of precision. Cleanup levels are based upon the North Carolina health-based NC 2L standards or health-based (HB) limits calculated using the formulas specified under the NC 2L regulations at 15 NCAC 02L.0202(d)(I) and (2) for those COCs without a NC 2L standard. Note that the COCs for which a NC 2L standard is not available also do not have Federal MCLs. HB-C: Health-based limit that is based on a target cancer risk of 1 × 10-6. HB-NC: Health-based limit that is based on non-cancer effects at a target hazard quotient of 1. * Value is an Interim Maximum Allowable Concentration (IMAC) established under 15A NCAC 02L .0202. # A COC only under the residential potable groudwater exposure scenario. COC may be removed from list once institutional controls are in place limiting groundwater exposure to industrial workers

U.S. Environmental Protection Agency 61 Forsyth Street, SW Atlanta, Georgia 30303

Official Business Penalty for Private Use $300

North Site Management Branch Angela Miller, Community Involvement Coordinator Jon Bornholm, Remedial Project Manager