EPA Superfund Proposed Plan Cabot / Koppers Superfund Site

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Proposed plan for the cleanup of the Koppers portion of the Cabot/Koppers Superfund site.

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EPA Superfund Proposed Plan Cabot / Koppers Superfund Site

  1. 1. go U.S. ENVIRONMENTAL PROTECTION AGENCY SUPERFUND PROPOSED PLAN CABOT CARBON/KOPPERS SUPERFUND SITE Gainesville, Alachua County, Florida July 2010 This document has been prepared to provide the general public with an understanding of the activities that have been occurring at the Cabot Carbon/Koppers Site. For technical information, please review the documents in the Administrative Record located at the information repositories. Introduction The U.S. Environmental Protection Agency (EPA) is releasing this Proposed Plan (Plan) for Public Comment Period the environmental cleanup at the Koppers July 15, 2010 to August 15, 2010 portion of the Cabot Carbon/Koppers Superfund Site in Gainesville, Alachua County, Florida. Public Meeting This Proposed Plan identifies the preferred Date: August 5, 2010 alternative for cleaning up the Koppers Site and Time: 6:00-8:00 p.m. provides rationale for this preference. It includes summaries of other remedial alternatives Location: Stephen Foster Elementary School evaluated and the findings in the Remedial 3800 Northwest 6th Street Investigation (RI), Baseline Risk Assessments, a Gainesville, Florida 32609 new (2010) Feasibility Study (FS), and other The community is invited to a public meeting documents included in the Administrative where EPA will present its understanding of Site Record. EPA is issuing this Plan as part of its conditions, alternatives evaluated in the Feasibility public participation responsibilities under Study, and provide its rationale for the preferred Section 300.430(f)(2), of the National Oil and alternative presented in this Plan. In addition, this Hazardous Substances Pollution Contingency meeting provides the community with an Plan (NCP). opportunity to ask EPA questions about the preferred alternative or Site activities and finding. This document is issued by EPA, the lead agency The Administrative Record file for the for Site activities. EPA, with support from the Cabot Carbon/Koppers Site is available at the Florida Department of Environmental Protection following location: (FDEP), will select a final remedy for the Site after reviewing and considering all information Alachua County Library submitted during the 30-day public comment 401 E. University Ave. Gainesville, FL 32601 period. (352) 334-3900 www.aclib.us/locations/headquarters Public participation is an important part of the Site cleanup decision process. Based on public comments, EPA, along with FDEP, may modify Therefore, the public is encouraged to review the preferred alternative or select another and comment on the cleanup alternatives alternative presented in this Plan. presented in this Plan. 1
  2. 2. What is a Proposed Plan? The public comment period for this Plan starts A Proposed Plan presents EPA’s preferred on July 15, 2010 and ends August 15, 2010. alternative to address contamination at a Site, presents other alternatives that were evaluated, During this 30-day period, the public is and provides the rationale for EPA’s preferred encouraged to review the findings of the RI and alternative. In addition, the Plan solicits public the details of the alternatives presented in the involvement and comment on the Site’s remedy final FS. These and other documents are selection process. Issuance of this Plan is part of available at the information repository listed on the Superfund process depicted below. page 34 of this document. Citizens are encouraged to submit written comments to EPA. What are the next steps in the Superfund process? Following the public comment period, EPA will EPA will hold a public meeting on Thursday, carefully consider all public comments before August 5, 2010, 6:00 p.m. at Stephen Foster selecting the remedy for the Site. All comments Elementary School. The purpose of the meeting submitted in writing by August 15, 2010, will be is to present the Proposed Plan for cleaning up the addressed in the Responsiveness Summary, as Koppers Site. This meeting will provide an will the questions and answers discussed at the opportunity for citizens to ask questions of EPA public meeting. If you are not on the Site representatives. Questions and answers will be mailing list and would like to be, please contact recorded to assist EPA in the final selection of the Ms. LaTonya Spencer at 404-562-8463 or 1-800- remedy and in preparation of a Record of Decision 435-9234. (ROD). All comments received during the public comment period and corresponding responses will A ROD, which summarizes the remedy decision be documented in the Responsiveness Summary process and announces the remedy will be of the ROD. prepared and signed by EPA. Once the ROD is 2
  3. 3. issued, the design of the remedy will be other areas in Alachua County. The Murphree scheduled and conducted, followed by the Well Field withdraws water from the Upper implementation of the remedy. Floridan Aquifer (UFA). Under the Koppers Site, the UFA is overlain by the Hawthorn Group Site History (HG) and by the Surficial Aquifer (Figure 3). In The Cabot Carbon/Koppers Superfund Site documents for this Site, the two water-bearing encompasses approximately 170 acres, bridging zones in the UFA have been designated the two properties in a commercial and residential upper and lower transmissive zones of the UFA, area of the northern part of the Gainesville city and the two zones in the HG with moderate limits, Alachua County, Florida. This Site was permeability have been designated the Upper originally two Sites; Cabot Carbon in the Hawthorn and the Lower Hawthorn. southeast portion of the Site, and Koppers on the western portion of the Site (Figure 1). Cabot Former wood-treatment facilities are located Carbon, is currently inactive, is now in use as within the southeastern portion of the Koppers commercial property. Koppers was an active Site (Figure 2). This includes a recently-active facility until December 2009. On March 31, process building and adjacent drip tracks where 2010, Beazer East, Inc. purchased the property chromated copper arsenate (CCA) was used to from Koppers in order to facilitate remediation. preserve wood. The central and northern portions of the Site were recently used for wood The Cabot Carbon portion of the Site was storage, staging, and debarking. The Koppers operated as a pine tar and charcoal generation Site was serviced by railroad sidings that entered facility from 1911 until 1967. Process at the facility’s northeast corner. These sidings wastewater containing residual pine tar was connected to a rail spur of the CSX railroad that discharged to three unlined lagoons as early as still exists along the eastern boundary of the 1937. Koppers Site. The Koppers Site operated as a wood-treating Wood treating processes at the Koppers Site facility from 1916 to late 2009 and covers began with a creosote impregnation process in approximately 86 acres (Figure 1 and Figure 2). 1916. The treatment processes were modified Portions of the area east of the Koppers Site and over the years to include two additional north of the former Cabot Carbon property are processes: one using CCA, beginning in the now commercial properties; other portions 1960s, and another using pentachlorophenol remain undeveloped. The areas to the west and (penta), beginning in 1969. The use of creosote north are single-family and multi-family decreased in the 1970s and creosote use was residences. A Gainesville Public Works facility, completely phased out at the Site by 1992. small businesses, and a mobile home community Pentachlorophenol use was discontinued by are located to the north/northwest of the Site. A 1990. Koppers used only CCA to treat wood at small drainage ditch that currently runs through the Site from 1990 through 2009. the Koppers Site collects storm water from the property and directs it north. The drainage exits The Former North Lagoon and Former South the property at a point along the northern Lagoon (Figure 2) at the Koppers Site were used boundary and discharges into Hogtown Creek, to manage process wastewater. Based on which then flows into Springstead Creek. historical aerial photographs, the Former North Lagoon was active from approximately 1956 The Murphree Well Field is located until the 1970s, and the Former South Lagoon approximately 2 miles northeast of the Site was active from 1943 or earlier through 1975 or (Figure 1). This 26 million-gallon-per-day 1976. Both former lagoons have been closed, (mgd) well field is operated by the Gainesville covered, and graded. The CCA wood-treating Regional Utilities (GRU) and provides public water supply for the City of Gainesville and 3
  4. 4. 4
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  6. 6. process used most recently at the Site did not In March 1991, the EPA issued a Unilateral generate wastewater. Administrative Order (UAO) to Beazer East directing development of a remedial design for The Cabot Carbon/Koppers Site was proposed the Site. However, further investigation for the National Priorities List (NPL) in revealed Site conditions that were not September 1983, and listed as final on the NPL contemplated by the ROD or UAO. in September 1984. Remedial investigations at Specifically, groundwater impacts below the the Site began in 1983. An initial groundwater water table were greater than expected and the interceptor trench was installed on the Cabot amount of dense non-aqueous phase liquid Carbon portion of the Site in 1985, and a (DNAPL) below the water table was greater permanent subsurface collection system was than expected. These discoveries called into installed in 1995, with the groundwater question the potential effectiveness and discharging to the principally-owned treatment practicality of the ROD-specified removal works (POTW). A POTW is a wastewater actions. A Surficial Aquifer groundwater treatment facility that is owned by a state or extraction system was designed to prevent off- municipality. The Cabot portion of the Site has Site migration of contamination in shallow been redeveloped and currently contains a groundwater, and operation began in 1995. In commercial shopping mall, a car dealership, and 2009, this Surficial Aquifer groundwater a series of small stores and businesses. extraction system was upgraded to increase Therefore, in this Plan, the word “Site” refers to pumping capacity and capture contaminated the Koppers portion of the Cabot groundwater through placement of recovery Carbon/Koppers Superfund Site, unless trenches next to the 4 principal source areas. otherwise specified. Currently, fourteen groundwater extraction wells operate along the northern and eastern The remedial investigation (RI) was completed property boundaries, and groundwater recovery in 1987, and a Supplemental RI was completed drains operate near each of the four principal in 1989. A Baseline Risk Assessment and FS source areas. were completed in 1990. A remediation plan was selected and a ROD for the Cabot Based on post-ROD Site data and concerns Carbon/Koppers Site was signed in1990. For regarding the technical practicability of the the Koppers property, the ROD specified (1) selected remedy, the UAO was amended in excavation of soils in the Former North and April 1994, This amendment required South Lagoons to a depth of 4 feet, (2) additional Site characterization and bioremediation of soils in the Former Process development of a Supplemental FS that included area and Former Drip Track Area by remedial alternatives appropriate for the recirculating groundwater with nutrient expanded extent of Site impacts. Subsequently, amendment, (3) installation of a groundwater studies were conducted to identify a revised extraction system in the Surficial Aquifer, and remediation strategy based on an updated (4) long-term institutional controls on Site use. understanding of the Site. At the time the ROD was prepared and signed, it was concluded that, based upon then-current A Supplemental FS was prepared in 1997 based information, (a) the HG was a single thick clay on the existing and updated data and an layer that provided an effective vertical barrier improved understanding of flow and transport for groundwater flow and transport and (b) the mechanisms at the Site. A Revised potential source zones were primarily in the Supplemental FS was issued in 1999 to address shallow unsaturated zone with a small volume comments from both EPA and FDEP. The of impacted soil below the water table in the Revised Supplemental FS recognized that the Surficial Aquifer. potential impacts from source areas were deeper than contemplated by the 1990 ROD; however, 6
  7. 7. the potential impacts within and below the HG Environmental Investigation Results were still considered negligible at that time. Numerous remedial and environmental investigations have been performed at the Site. More recent investigations (2003, 2004, and These include: 2006) that form the basis for this cleanup plan have indicated that dense non-aqueous phase • Hydrogeologic investigation; liquids (DNAPL) from former wood-treating • Initial and supplemental RIs; substances such as creosote is present in the HG • Site characterization for soil and and that Site contaminants are present in groundwater remedies; groundwater in the Upper Floridan Aquifer (See • Field investigations of the HG and UFA; Figure 3). Ongoing and planned monitoring is • Source delineation study for former source being used to better characterize potential areas; impacts in the Surficial Aquifer, HG, and UFA. • Data summary report for soil and sediment; and Since the 1990 ROD, as investigations have • Surficial Aquifer well redevelopment and improved the conceptual understanding of the sampling. Site, pilot remedial actions and focused studies have been conducted to assist with the selection Site soil and groundwater have been sampled to and evaluation of a final comprehensive characterize the nature and extent of Site-related remedial strategy for the Site. These activities contamination. Over 350 soil borings and 1,000 have included: soil samples have been collected and analyzed across the Site since 1984. Groundwater - Pilot testing active DNAPL recovery in the monitoring has been routinely performed since Surficial Aquifer at PW-1 in 1994 and 2004; 1984. Over 150 wells have been installed (and - Studying vertical groundwater circulation at sampled) at the Site in the three main the Former North Lagoon in 1995; hydrogeologic units (Surficial Aquifer, HG, and - Recovering DNAPL Manually by periodic UFA) (See Figure 3). Periodic groundwater bailing in HG monitor wells since 2004; monitoring reports are prepared for the EPA. - Evaluating soil excavation feasibility; - Evaluating in-situ thermal treatment Potential impacts to off-Site areas have been feasibility; investigated and continue to be investigated - Evaluating surfactant flushing feasibility; west of the Site. An additional off-Site soil - Pilot testing active DNAPL recovery in the investigation is currently being conducted to HG beneath the Former North Lagoon; and completely delineate the extent of impact in - Bench testing and pilot field testing in-situ other areas surrounding the Site. Some biogeochemical stabilization (ISBS) of information and analytical data has been DNAPL using modified permanganate generated from sediment and surface water in solutions. Hogtown and Springstead Creeks to evaluate impacts to aquatic habitats and species. Two five-year reviews for the Site were conduced by EPA and finalized in 2001 and The contaminants of concern (COCs) identified 2006. The 2006 Five-Year Review Report for soil and groundwater in the 1990 ROD recommended additional studies to support the include phenols (such as penta), polycyclic selection of a new remedial strategy to address aromatic hydrocarbons (PAH), arsenic, and the full extent of impacts at the Site. Such chromium. Creosote, the predominant chemical studies have been undertaken through the material historically used for wood treatment at collaborative FS process to fulfill the specific the Site, consists mainly of PAHs and includes recommendations of the Five-Year Review. both potentially carcinogenic (pcPAH) and non- carcinogenic (ncPAH) compounds. The EPA A revised FS was finalized in May 2010. and FDEP also required sampling and testing 7
  8. 8. for polychlorinated dibenzo-p-dioxins and Source areas defined in these figures correspond polychlorinated dibenzo furans (dioxins/furans) with the areas in the Surficial Aquifer in soils. Based on the results of this sampling, containing the greatest concentrations of dioxins/furans have also been identified as contaminants associated with wood-treatment COCs for Site soil. Relatively low benzene, materials. The wood-treating products that toluene, ethylbenzene, and xylenes (BTEX) remain in the environment (e.g., creosote concentrations also have been observed in soils DNAPL, free-product PCP, etc.) are defined as and groundwater under the four identified the principal threat waste at this Site. Based on source areas. the physical and chemical properties of DNAPL and its variable distribution throughout the Conceptual Site Model various aquifer zones under the Site, it is A conceptual Site model (CSM) was formulated impracticable to distinguish heavily- as part of the revised FS using environmental contaminated soil from principal threat waste. investigation data collected over the past 26 Based on this uncertainty, it is prudent to years. The CSM describes current Site address the entire soil volume in the four Source conditions and how Site-related contaminants Areas as principal threat waste. This approach move in the environment and the potential for will ensure that the vast majority of DNAPL and contaminants to reach environmental receptors. heavily-contaminated soil can be treated and Figure 3 is a conceptual block diagram that isolated from the surrounding environment. depicts migration of contaminants in the subsurface. Analytical data for source area soil borings indicate that DNAPL has migrated down into Groundwater Flow the Lower HG, but the extent to which this has Hydrogeologic layers beneath the Site are occurred is uncertain and difficult to determine illustrated on Figure 3. The layers vary in their definitively. Remedial actions proposed as a ability to transmit groundwater (transmissivity). part of this Plan are intended to address DNAPL Zones 1, 7, and 9 are the most transmissive. (i.e., principal threat waste) impacts, regardless Zones 3, 5, 8, and 10 are moderately of its location or source origination on the transmissive. Zones 2, 4, and 6 have very low Koppers Site. capacities to transmit water, and limit vertical flow between transmissive layers. Groundwater Other smaller isolated surface soil areas flow within the transmissive layers that have throughout the property show high shown the highest COC concentrations (Zones 1 concentrations of various contaminants that are and 3) is to the north-northeast. not associated with any particular process area on the property. These minor locations of Source Areas elevated contaminant concentrations are not The origin of contaminants at the Site is linked identified as source areas, but as locations of directly to facility operations and historical contaminants that either migrated from source waste management methods. Releases occurred areas (i.e., by surface runoff, soil dust when wood-treatment chemicals dripped onto deposition, or other surface transport the soil or were deposited in unlined lagoons. mechanism), or are isolated residuals from Site investigations have identified four main historic wood treating operations. contaminant source areas related to former operations and facilities (the Former Process Soil Contamination Area, the Former South Lagoon, the Former Soils above the water table contaminated with North Lagoon, and the Former Drip Track). contaminants of concern (COCs) are a result of These are labeled [a] through [d] in Figure 3, residual DNAPL in unsaturated pore space or and are illustrated in Figure 2. contaminants that are adsorbed onto soil particles. Asenic, pcPAHs (expressed as benzo(a)pyrene toxic equivalents [BaP-TEQ]), 8
  9. 9. 9
  10. 10. and dioxins/furans (expressed as 2,3,7,8- bodies. Since inputs to both Springstead and tetrachlorodibenzo-p-dioxin toxic equivalents Hogtown Creek are attributable to releases from [TCDD-TEQ]) are COCs that drive the both the Koppers facility and the Cabot Carbon evaluation of human-health risk for direct soil facility, cleanup will be performed jointly. exposure at the Site under current Site use. Groundwater Contamination The highest arsenic concentrations were Groundwater impacts have resulted from: (a) detected in the vicinity of the Former South percolation of contaminants in process water Lagoon, two sample locations had average down to the water table; (b) dissolution of surface soil concentrations above 1,000 contaminants from DNAPL in the subsurface; milligrams per kilogram (mg/kg) for arsenic. and (c) leaching from soils as rainwater percolates through the unsaturated zone in areas Elevated PAH concentrations were detected in with high concentrations of COCs. surface soils at all four DNAPL source areas. Dioxins/furans were detected over a significant Surficial Aquifer Groundwater portion of the Site at levels above the Florida The predominant PAH compound detected in default commercial/industrial soil cleanup target groundwater at the Site is naphthalene. level (SCTL) (0.03 micrograms per kilogram Naphthalene is used as the primary indicator [µg/kg]). compound to represent the presence and extent of COCs in Site groundwater due to its Concentrations of pentachlorophenol in surface prevalence and very high mobility. As part of soil were below the Florida default SCTL for the effectiveness monitoring for the existing commercial/industrial direct exposure (28 groundwater extraction system, groundwater mg/kg) over most of the Site. There were five quality is measured periodically at extraction exceptions: three in the Former Process Area, wells and monitor wells. Groundwater samples one at the Former Drip Track Area, and one at are analyzed for benzene, toluene, ethylbenzene the Former North Lagoon. and xylenes (BTEX), PAHs, phenols, arsenic, and chromium. Several of the wells near the A multi-phase Site-boundary and off-Site soil source areas and near the eastern Site boundary sampling and analysis program is presently have naphthalene concentrations greater than being conducted. Initial results from this the Florida default groundwater cleanup target program show that surface soil immediately level (GCTL) of 14 µg/L. In all locations where adjacent to the western Site boundary has both a water-table and deeper Surficial Aquifer elevated concentrations of PAHs, arsenic, well were sampled, the water-table well had a and/or dioxins/furans above Florida default significantly lower naphthalene concentration. SCTLs for residential direct exposure. Past Concentrations of some other COCs (PCP, transport of COCs via dust likely caused the arsenic, benzene, carbazole, dibenzofuran) also detections of Site COCs in off-Site surface soil exceeded their default GCTLs and/or federal west of the Site. Further off-Site soil maximum contaminant levels (MCLs) in certain characterizations are under way to the north, wells. south, east, and west of the Site and will continue after remedy selection to facilitate Hawthorn Group Groundwater expedited cleanup of off-Site residential areas. Naphthalene and other COCs have been detected at monitor wells near source areas and Off-Site Creek Contamination near the eastern property boundary at Investigative work has been done in Hogtown concentrations exceeding default GCTLs. and Springstead Creeks, north of the Koppers Site. These studies were done to support Upper Floridan Aquifer Groundwater evaluation of possible impacts to ecological Water quality in the UFA beneath and habitats and species in these surface water immediately downgradient (in the direction of 10
  11. 11. groundwater flow) of the Site is measured on a Site Risk Assessment quarterly basis. Risk assessments were conducted to determine the current and future effects of contaminants on Monitor wells within the top 30 feet of the UFA. human health and the environment. “What Is Only one of these wells (a source-area Risk and How Is It Calculated” provides general monitoring well near the Former North Lagoon) information on assessing risk. A human-health currently has organic concentrations above state risk assessment (HHRA) for on-Site soils and or federal drinking water standards. Naphthalene concentrations at this well have sediment was submitted in 2009 and updated in decreased substantially since July 2004. May 2010 to take into account a change in land use and to incorporate comments received on There are 15 multiport, quadruple-cased wells the earlier version. The estimates of potential quadruple-cased wells completed within the risk presented in the August 2009 HHRA upper 100 feet of the UFA (the Upper assume that the use of the Site is for wood- Transmissive Zone). At two of the four source treatment in the foreseeable future because areas (Former Process Area and Former South wood-treatment operations have ceased, this Lagoon), inorganic and organic contaminants assumption is no longer valid. The HHRA was are consistently below state or federal drinking updated to take into account a change in land water standards in the UFA monitor wells. use not previously contemplated under the 2009 Seven organic contaminants are above state or submittal. federal drinking water standards in the UFA north of the Former North Lagoon and Former The 2009 HHRA includes both a deterministic Drip Track at a few locations. (traditional) evaluation of potential risks and a Organic COCs have never been detected in the more quantitative probabilistic model for four Lower Transmissive Zone wells at the potential risk evaluation. The assessment shows northern property boundary. that pcPAHs, arsenic, and dioxins/furans are the COCs that make the largest contribution to the In some sampling events, arsenic concentrations overall potential excess lifetime cancer risk above the Florida default GCTL (10 µg/L) have associated with the Site. Potential exposure to been identified in groundwater collected from a pentachlorophenol makes a small contribution few of the UFA monitor wells. These low to the total potential excess lifetime cancer risk. observed concentrations likely result from dissolution of naturally occurring minerals in EPA has evaluated the 2009 HHRA and its the UFA that occurs when oxygenated water is accompanying revisions and has determined that introduced to the formation during well drilling. the probabilistic risk assessment does not This is consistent with the absence of inorganic provide an adequate basis to define the required COCs in overlying aquifers. cleanup goals. Therefore, EPA will base selection of cleanup goals on a more Scope and Role of Proposed Remedy conservative cleanup goal derived from The proposed remedy is intended to be the final deterministic risk calculations. cleanup for the Cabot Carbon/Koppers Site. The preferred alternative identified in this Potential ecological risks associated with Proposed Plan, or one of the other active sediment were also evaluated in 2009. The measures considered in this plan, will protect Agency has evaluated the 2010 ecological public health, welfare, and the environment screening level risk assessment and its from actual or threatened releases of hazardous accompanying revisions and does not believe substances into the environment. that it provides an adequate basis to select remedial goals for the Site. This is because this assessment was based on assumptions used in 11
  12. 12. What Is Risk And How Is It Calculated? A Superfund human health risk assessment estimates the “baseline risk.” This is an estimate of the likelihood of potential health problems occurring if no cleanup action were taken at a Site. To estimate the baseline risk at a Superfund Site, EPA undertakes a four-step process: Step 1: Analyze Contamination. Step 2: Estimate Exposure. Sept 3: Assess Potential Health Dangers. Step 4: Characterize Site Risk. In Step 1, EPA looks at the concentrations of contaminants found at a Site as well as past scientific studies on the effects these contaminants have had on people (or animals, when human studies are unavailable). Comparisons between Site-specific concentrations and concentrations reported in past studies help EPA to determine which contaminants are most likely to pose a potential threat to human health. In Step 2, EPA considers the different ways that people might be exposed to contaminants, and the potential frequency and duration of the exposure. Using the information, EPA calculates a “reasonable maximum exposure” (RME) scenario, which portrays the highest level of human exposure that could reasonably be expected to occur. In Step 3, EPA uses the information from Step 2 combined with information on the toxicity of each chemical to assess potential health risks. EPA considers two types of risk: cancer risk and non-cancer risk. The likelihood of any kind of cancer resulting from a Superfund Site is generally expressed as an upper bound of probability; for example a “1 in 10,000 chance”. In other words, the exposed individual would have an excess cancer risk of one in 10,000 due to Site contaminants. This excess risk would be over and above the existing cancer risk for the individual. For non-cancer health effects, EPA calculates a “hazard index” (HI). The key concept here is that a “threshold level” (measured usually as a HI of less than 1) exists below which non-cancer health effects are not expected. In Step 4, EPA determines whether Site risks are excessive for people at or near the Superfund Site. The results of the three previous steps are combined, evaluated, and summarized. EPA adds up the potential Risks for each receptor. the screening level risk assessment that have not › Groundwater in the Surficial Aquifer, yet obtained acceptance by EPA and Florida Upper HG, Lower HG, and Upper DEP. Therefore, the Agency will utilize Floridan Aquifer; conservative default ecological endpoints in › Subsurface soils; identification and selection of cleanup goals for › Sediment; and remedial goal selection. › Surface water. • Mitigate further migration of impacted Remedial Action Objectives and groundwater. Cleanup Levels • Restore quality of groundwater outside of Remedial Action Objectives (RAOs) for the Site source areas to beneficial use having COC are based on potential migration or exposure concentrations no greater than Federal pathways for Site COCs and applicable or MCLs or Florida GCTLs. relevant and appropriate requirements (ARARs) • Reduce the mobility, volume, and toxicity of identified in the 2010 FS. The RAOs provide DNAPL to the extent practicable. media-specific and action-specific requirements to protect human health and the environment. Cleanup goals for COCs are listed in Table 1. The RAOs identified for the Site include: The selected cleanup goals are the Florida commercial/industrial SCTLs for on-Site • Mitigate risks to potential receptors exposed soils/sediments and either the residential SCTLs to Site-related contaminants in: or commercial/industrial SCTLs for off-Site › Surface soils; soils/sediments based on the current land use. The selected goals for groundwater are the 12
  13. 13. Table 1 – Cleanup Goals for COCs Table 1 – Cleanup Goals for COCs (Continued) Groundwater (µg/L) Off-Site Soil/Sediment (mg/kg) naphthalene 14 Listed compounds pcPAHs (BaP-TEQ)* 0.1 Florida default acenaphthalene 210 exceed the federal SCTLs residential dioxins (TCDD-TEQ) 0.000007 2-methylnaphthalene 28 MCL and/or Florida land-use Default GCTL arsenic 2.1 pentachlorophenol 1 (based on values in pentachlorophenol 7.2 arsenic 10 effect on the date pcPAHs (BaP-TEQ)* 0.7 Florida default carbazole 1.8 that the Proposed dioxins (TCDD-TEQ) 0.000003 SCTLs for commercial/ dibenzofuran 28 Plan was issued). arsenic 12 industrial land use 1,1 biphenyl 0.5 (depends on * Primary standard pentachlorophenol 28 phenol 10 specific land-use of as defined by off-Site location) 2-phenol * Florida Department 2-methylphenol 35 of Environmental pentachlorophenol 0.03 Florida default 2,4-dimethylphenol 140 Protection in F.A.C. leachability SCTLs 3/4-methylphenol 7 62-777. for CW protection pentachlorophenol 0.2 Florida default acenaphthene 210 leachability SCTLs benzo(a)anthracene 0.05 for protection of benzo(a)pyrene 0.2 ecological benzo(b)fluoranthene 0.05 organisms in surface water benzo(k)fluoranthene 0.5 chrysene 4.8 bis(2-ethylhexyl) phthalate * federal MCLs or Florida GCTLs, if the latter are fluoranthene 280 more stringent. In addition, Florida leachability fluorene 280 criteria for soil are relevant and appropriate for n-nitrosodiphenylamine 7.1 protection of groundwater. phenanthrene 210 benzene 1 benzene 5 Federal MCL Considerable uncertainty surrounds the derivation of clean-up goals for dioxins and On-Site Soil (0-2 feet bls)/Sediment (mg/kg) furans, including the development of site- pcPAHs (BaP-TEQ)* 0.7 Florida default SCTLs for specific risk-based goals, and Florida’s default dioxins (TCDD-TEQ) 0.00003 commercial/industrial residential SCTL of 0.007 µg/kg. At present antimony 27 land use and Florida default leachability there is significant ongoing debate between and arsenic 2.1 SCTLs unless Site- chromium (total) 470 among researchers, different regulatory specific leachability data copper 89000 are developed during agencies, and the regulated community lead 1400 remedial design. regarding the toxicity of dioxins/furans and pentachlorophenol 28 whether meaningful human-health risks are acenaphthene 2400 * Site concentrations for posed by low concentrations of these carcinogenic polycyclic naphthalene 300 contaminants, particularly with respect to aromatic hydrocarbons 2-methylnaphthalene 2100 (pcPAHs) are converted concentrations in soils. Evidence of this fluoranthene 59000 to Benzo(a)pyrene fluorine 33000 equivalents (BaP-TEQ) ongoing debate can be observed in the phenanthrene 36000 before comparison with numerous comments submitted to EPA in 1,1 biphenyl 34000 the cooresponding direct response to publication of the agency’s Dioxin exposure SCTL for carbazole 240 Benzo(a)pyrene (see the Science Plan, the proposed interim preliminary dibenzofuran 6300 February 2005 “Final remediation goals (PRG) for dioxins, and the benzene 1.2 Technical Report draft response to the National Academy of 2,4,5-trichlorophenol 130,000 Development of Cleanup 18000 Target Levels (CTLs) for Science’s review of the Dioxin Reassessment. 2,4-dimethylphenol 3/4-methylphenol 31000 Chapter 62-777 F.A.C.” Clean-up goals for dioxins/furans used by various state regulatory agencies and EPA vary 13
  14. 14. over several orders of magnitude, with Florida’s On-Site Remedies default SCTL being at the low end of the range. The on-Site remedial alternatives focus Florida’s SCTLs will be used as the cleanup primarily on addressing impacted groundwater goal for dioxin-contaminated soil at the Site. and sources of contaminants in the surface soil, Surficial Aquifer and Upper Hawthorn zones. Remedial Alternatives Contaminant sources include residual DNAPL Remedial alternatives were defined and or contaminants adsorbed to soil particles. evaluated separately for three major environmental media units of the Site (on-Site Remedy Components Common to media [excluding UFA groundwater], off-Site Multiple On-Site Alternatives surface soil, and UFA groundwater). The final Many of the on-Site remedial alternatives Site remedial alternative will consist of a set of contain remedy components that are common to three remedies: one for the on-Site media, one multiple alternatives. A description of the for the UFA, and one for the off-Site surface common components is provided below. soil unit. • Surface grading and covers - This remedial component consists of re-grading much of As part of the remedial design process which the Site and using one or more types of follows remedy selection, additional surface covers to prevent potential direct characterization of Site aquifers will be exposure to surface soils. The covers will conducted to address remaining uncertainties be designed to be impermeable where related to DNAPL migration and, more leachability and/or infiltration are a concern. importantly, refine its vertical and horizontal The final surface cover design will be boundaries for effective remedy consistent with the expected future land use implementation. Off-Site soil characterization of the property. continues to the north, south, east, and west of • Storm water rerouting and detention – This the Site to completely delineate Site-related remedy component will be implemented in impacts and to expedite cleanup of off-Site concert with the designed surface grading areas. During the remedial design, an ambient and covers. Storm water controls will air monitoring network will be installed at the consist of: (a) grading and contouring the Site. Since the Koppers Facility closure, Beazer Site to direct runoff toward collection East has begun interim measures to reduce dust points; (b) installation of one or more including planting of vegetation over former detention/retention ponds; and (c) possible operation areas. As part of Site building replacement of the existing Site storm water demolition activities, Beazer East is ditch with another ditch or with an implementing dust control of continuous water engineered conveyance such as an application to suppress dust. underground concrete pipe (culvert). • Soil consolidation area with low- The following alternatives, developed and permeability cap/cover - This remedy documented in the 2010 FS, must meet the component consists of placing select soils in threshold statutory requirements of protection of a designated on-Site consolidation area human health and the environment to address within the area encircled by a subsurface chemical-specific, location-specific, and action- barrier wall. The soil placed within the specific Applicable or Relevant and Appropriate consolidation area includes surface soil that Requirements (ARARs). is removed during Site grading and soil that is derived from construction of other remedy components. A low-permeability cap/cover will be constructed over the consolidation 14
  15. 15. area beneath the designed final surface consists of injecting a buffered solution of cover. sodium permanganate and catalysts into the • On-Site ex-situ soil treatment - This remedy target zone in order to: (1) chemically component includes on-Site treatment of oxidize organic COCs; (2) form a soils from source area excavation and/or geochemical solid through the action of the resulting from ex-situ solidification/ reagent and the organic COCs; and (3) stabilization implementation. It is assumed reduce the flux of COCs from residual that soil will be treated by DNAPL into the aqueous phase by reducing solidification/stabilization, although other aquifer transmissivity. Inclusion of ISBS as treatment options (e.g., chemical oxidation, a remedy component includes one or more thermal treatment, biological treatment) may pilot studies with performance criteria be evaluated during final design. designed to demonstrate and optimize • Barrier wall - This remedy component effectiveness as a remedy component. If consists of installing a cement/bentonite this technology does not meet its designated slurry wall to encircle all four primary performance criteria, ISS/S would be source areas. The slurry wall will be implemented instead. approximately 5,000 feet in length and will • Manual DNAPL recovery - This remedy extend vertically from land surface to the component involves continuation of the top of the HG middle clay, approximately 65 current program of bi-weekly DNAPL feet deep. Other types of vertical barriers bailing from Upper Hawthorn monitor wells (e.g., sheet pile, in-situ solidified soil HG-11S, HG-15S, HG-12S, HG-10S, and columns, or injected grout) may be HG-16S. This activity will continue as long considered during final design based on as DNAPL is recoverable in these wells. geotechnical testing. • Chemical Oxidation (ChemOx)/ISBS using • Surficial Aquifer hydraulic containment and existing HG wells - This remedy component groundwater monitoring - This remedy involves use of existing HG monitor wells component consists of operating the existing as treatment-injection points for either hydraulic containment system including the ChemOx or ISBS based on contaminant perimeter wells and the horizontal concentrations and pilot study results. groundwater collection drains at the base of • HG groundwater monitoring - This remedy the Surficial Aquifer near the four source component includes monitoring of Upper areas. Periodic adjustments to operations Hawthorn and Lower Hawthorn will be made as necessary to optimize groundwater using existing and new wells. containment and treatment reliability. The monitoring will be used to demonstrate • In-situ solidification/stabilization (ISS/S) of remedy performance and provide sentinel source areas – This remedy component monitoring locations for contingent actions. consists of applying additives, such as • Contingent actions in the HG - This remedy cement, lime, fly ash, or polymers, to bind component includes contingent remedial with the soil particles to reduce the mobility actions for groundwater in the HG if of the contaminants. S/S agents can be monitoring results indicate that contaminant applied in-situ with auger drilling/mixing concentrations are either above GCTLs and equipment. Inclusion of ISS/S as a remedy increasing (at sentinel wells where Site component includes one or more pilot contaminants have been detected) or begin studies with performance criteria to provide to be detected above GCTLs at previously an effective mix design clean sentinel wells. The expected • In-situ biogeochemical stabilization (ISBS) contingent action for organic contaminants of source areas – This remedy component is ChemOx using a permanganate solution. 15
  16. 16. ChemOx is used to chemically transform does not meet the threshold criteria necessary organic COCs into non-toxic or immobile for a viable alternative. substances. • Monitored natural attenuation (MNA) - This OnR-2: Continue Current Actions with remedy component relies on naturally Surface Grading/Covers occurring geophysical and geochemical Estimated Capital Cost: $6.2M processes that act on COCs to make them Approximate Annual OM&M: $ 300,000 less toxic/hazardous or less mobile. Total Net Present Value: $ 11.1M Monitoring results are used to demonstrate Estimated Construction Timeframe: < 1 year that these processes are occurring in the Estimated Time to Achieve RAOs: many years subsurface at the Site. Inclusion of MNA as ARARs: action-specific and location-specific a remedy component requires that additional ARARs are met with this alternative. The evaluation will be performed to demonstrate remedy may not attain all chemical-specific active natural attenuation. This evaluation ARARs within a reasonable time. will be coordinated with any other groundwater remedy components (e.g., This alternative includes continuing the current hydraulic containment) to distinguish the interim remedial measures: Surficial Aquifer effects of MNA from other groundwater groundwater extraction/treatment, groundwater remedy technologies. monitoring and Manual DNAPL recovery. The • Institutional controls - This on-Site remedy remedy also includes regrading and covering component consists of deed restrictions and most of the Site. As a contingency action, other administrative actions to limit and ChemOx would be injected if necessary to control potential exposure to media with remediate groundwater impacted principal threat elevated contaminant concentrations and to materials in the HG. MNA and institutional ensure the effectiveness of engineering controls are also part of this alternative. controls. This alternative includes the following primary OnR-1: No Action components: Total Net Present Value: $ minimal • Grading of Site soil and installation of soil Estimated Construction Timeframe: None covers and storm water controls; Estimated Time to Achieve RAOs: > 100 years • Continued operation of the Surficial Aquifer ARARs: Does not attain. extraction and treatment system; • Expansion of the Surficial Aquifer and HG Regulations governing the Superfund program monitoring network for: (1) establishment of require the “No Action” alternative to be monitoring points; (2) demonstration of considered. The No Action alternative is used active natural attenuation processes; and (3) as a baseline to compare with other alternatives. establishment of trigger locations for Under the No Action alternative, all active and contingency measures; Manual Site activities, including groundwater • Continuation of Manual DNAPL recovery in extraction, DNAPL collection and groundwater the Upper Hawthorn; and monitoring, would cease. Furthermore, there • Institutional controls to mitigate risks from would be no deed restrictions or Site security exposure to Site soil, sediment, surface controls to prevent use of Site groundwater, water, or groundwater. limit exposures to Site soil, or restrict certain kinds of future development. This alternative is retained as a basis for comparison of risk reduction using remediation technologies and 16
  17. 17. OnR-3A: Removal – Surficial Aquifer • On-Site treatment of excavated soil Excavation (solidification/stabilization or alternate Estimated Capital Cost: $ 64.1M material management options); Approximate Annual OM&M: $ 165,000 • Return of treated soil to the excavated areas Total Net Present Value: $ 67.8M with use of excess treated soil as a base Estimated Construction Timeframe: 2 years layer in cover design; Estimated Time to Achieve RAOs: several years • Surface grading and covering for most of the ARARs: Chemical-specific, action-specific and Site with installation of storm water location-specific ARARs are all met with this controls; alternative • Continued operation of the Surficial Aquifer extraction and treatment system to verify This alternative includes excavating the remedy effectiveness in reducing Surficial Aquifer material in the four source contaminant flux, then shutdown of this areas (to approximately 25 feet below surface), system; treating the excavated soil by ex-situ • Expansion of the Surficial Aquifer and HG solidification/stabilization, returning most of monitoring network for: (1) establishment of this material to the excavations, and sentinel locations; (2) demonstration of incorporating excess solidified material into active natural attenuation processes; and (3) covers for the excavated areas. Vertical establishment of trigger locations for retaining/barrier walls will be installed to the contingency measures; and top of the middle clay unit of the HG to provide • Institutional controls to mitigate risks from shoring for the excavations and to contain exposure to Site soil, sediment, surface groundwater impacts in the Upper Hawthorn. water or groundwater. ChemOx or ISBS (catalyzed sodium permanganate) treatment will be applied at OnR-3B: Removal – Excavation to Middle existing Upper and Lower HG wells in source Clay areas. As a contingency, ChemOx will be Estimated Capital Cost: $ 190M injected if necessary to remediate potential Approximate Annual OM&M: $ 165,000 groundwater impacts in the HG. The ChemOx Total Net Present Value: $ 193.7M and ISBS components of this remedy will be Estimated Construction Timeframe: 3.5 years implemented only if treatability studies Estimated Time to Achieve RAOs: several years demonstrate successful contaminant treatment ARARs: Chemical-specific, action-specific and and containment. location-specific ARARs are all met with this alternative This alternative includes the following components: This alternative includes excavating the • Excavation of source areas to the HG upper Surficial Aquifer material in the four source clay; areas and in the Upper HG above the middle • Installation of an encircling vertical clay unit (approximately 65 feet below surface), retaining/barrier wall around each source treating the excavated soil by ex-situ area to the HG middle clay; solidification/stabilization, returning most of • ChemOx or ISBS treatment applied at this material to the excavations, and existing Upper and Lower Hawthorn wells incorporating excess solidified material into in source areas (based on acceptable covers for the excavated areas. ChemOx or performance during pilot tests or treatability ISBS treatment will be applied at existing studies); Lower HG wells in source areas. As a contingency, ChemOx will be injected if 17
  18. 18. necessary to remediate groundwater impacts in This alternative includes in-situ solidification/ the HG. stabilization (ISS/S) of impacted soil from the ground surface to the top of the middle clay unit This alternative includes the following of the HG (approximately 65 feet below ground components: surface) in the four source areas. Excess soil • Excavation of source areas to the HG middle will be treated by ex-situ solidification/ clay with 2:1 side-slopes and vertical stabilization and used as a base layer for surface shoring where necessary; covers. ChemOx or ISBS treatment will be • On-Site treatment of excavated soil applied at existing Lower HG wells in source (solidification/stabilization or alternate areas. As a contingency, ChemOx will be material management options); injected if necessary to remediate groundwater • Return of treated soil to the excavated areas impacts in the HG. with use of excess treated soil as a base layer in cover design; This alternative includes the following • Surface grading and covering for most of the components: Site with installation of storm water • ISS/S to the middle clay unit of the HG in controls; the four source areas; • Continued operation of the Surficial Aquifer • ChemOx or ISBS treatment applied at extraction and treatment system for a period existing Lower HG wells in source areas of time, then shutdown of this system (based on performance during pilot tests or (source area horizontal collection drains are treatability studies); abandoned); • Ex-situ S/S of excess soil for use as a base • ChemOx or ISBS treatment applied at layer in cover design; existing Lower HG wells in source areas • Surface grading and covering for most of the (based on performance during pilot tests or Site with installation of storm water treatability studies); controls; • Expansion of the Surficial Aquifer and HG • Continued operation of the Surficial Aquifer monitoring network for: (1) establishment of extraction and treatment system until such sentinel locations; (2) demonstration of time as cleanup goals are consistently and active natural attenuation processes, and; (3) continually met, then shutdown of this establishment of trigger locations for system; contingency measures; and • Expansion of the Surficial Aquifer and HG • Institutional controls to mitigate risks from monitoring network for: (1) establishment of exposure to Site soil, sediment, surface sentinel locations, (2) demonstration of water or groundwater. active natural attenuation processes; and (3) establishment of trigger locations for OnR-4A: In-Situ Treatment – Solidification/ contingency measures; and Stabilization to Middle Clay • Institutional controls to mitigate risks from Estimated Capital Cost: $ 72.5M exposure to Site soil, sediment, surface Approximate Annual OM&M: $ 165,000 water or groundwater. Total Net Present Value: $ 78.9M Estimated Construction Timeframe: 3 years OnR-4B: In-Situ Treatment - Solidification/ Estimated Time to Achieve RAOs: several years Stabilization and Biogeochemical ARARs: Chemical-specific, action-specific and Stabilization location-specific ARARs met with this Estimated Capital Cost: $ 38.1M alternative. Approximate Annual OM&M: $ 165,000 Total Net Present Value: $ 41.8M 18
  19. 19. Estimated Construction Timeframe: 2.5 years establishment of trigger locations for Estimated Time to Achieve RAOs: several years contingency measures; and ARARs: chemical-specific, action-specific and • Institutional controls to mitigate risks from location-specific ARARs met with this exposure to Site soil, sediment, surface alternative. water or groundwater. This alternative includes ISS/S of impacted soil OnR-5A: Containment/Treatment – Barrier from ground surface to the top of the upper clay Wall unit of the HG (approximately 25 feet below Estimated Capital Cost: $ 12.8M ground surface) in the four source areas. Excess Approximate Annual OM&M: $ 181,000 soil will be treated by ex-situ solidification/ Total Net Present Value: $ 16.0M stabilization and used as a base layer for surface Estimated Construction Timeframe: 1 year covers. ISBS will be injected in Upper HG in Estimated Time to Achieve RAOs: several years source areas. ChemOx or ISBS treatment will ARARs: chemical-specific, action-specific and be applied at existing Lower HG wells in source location-specific ARARs met with this areas. As a contingency, ChemOx will be alternative. injected if necessary to remediate groundwater impacts in the HG. This remedy is similar to This alternative is a combination of containment remedy OnR-4A except that ISBS replaces and treatment remedies and includes installing a ISS/S in the Upper Hawthorn. barrier wall around the DNAPL source areas to the top of the middle clay unit of the HG. Soil This alternative includes the following removed during the slurry wall installation will components: be used as fill in the soil consolidation area. • ISS/S to the upper clay unit of the HG in the ChemOx or ISBS treatment will be applied at four source areas; existing Lower Hawthorn wells in source areas. • ISBS in the Upper HG below the ISS/S treatment zones (subject to acceptable The barrier wall will limit groundwater inflow performance during pilot tests or treatability to, and outflow from, DNAPL-impacted areas. studies); A capped soil-consolidation area will be • ChemOx or ISBS treatment applied at established inside the barrier-wall for soil existing Lower HG wells in source areas excavated during on- or off-Site remedy (based on performance during pilot tests or construction and/or regrading. Outside the treatability studies); barrier wall, surface regrading and covers will • Ex-situ S/S of excess soil for use as a base eliminate potential exposure to soil with layer in cover design; contaminant concentrations exceeding cleanup • Surface grading and covering for most of the goals. Manual DNAPL recovery will continue Site with installation of storm water at five source area wells in the Upper Hawthorn controls; and operation of a modified version of the • Continued operation of the Surficial Aquifer Surficial Aquifer groundwater extraction system extraction and treatment system until such will continue until it is no longer needed. time as cleanup goals are consistently and continually met, then shutdown of this This alternative includes the following system; components: • Expansion of the Surficial Aquifer and HG • A single encircling vertical barrier wall monitoring network for: (1) establishment of around all four source areas to the HG sentinel locations, (2) demonstration of middle clay; active natural attenuation processes; and (3) 19
  20. 20. • ChemOx or ISBS treatment applied at ISBS treatment at the base of the Upper HG. existing Lower HG wells in source areas Excess soil will be used as fill in the soil (based on performance during pilot tests or consolidation area. ChemOx or ISBS treatment treatability studies); will be applied at existing Lower HG wells in • Establishment of a capped soil-consolidation source areas. As a contingency, ChemOx will area; be injected if necessary to remediate • Surface grading and covering for most of the groundwater impacts in the HG. . Site with installation of storm water controls; The barrier wall will limit groundwater inflow • Continued operation of the northern to (and outflow from) DNAPL-impacted areas. perimeter wells of the Surficial Aquifer A capped soil-consolidation area will be extraction and treatment system until such established inside the barrier-wall for excavated time as cleanup goals are consistently and soil. Outside the barrier wall, surface regrading continually met, then shutdown of these and covers will eliminate potential exposure to wells; soil above cleanup goals. ISBS injections will • Continued operation of the horizontal be placed into the Upper HG (subject to collection drains of the Surficial Aquifer acceptable performance during pilot tests or extraction and treatment system as needed treatability studies) to treat DNAPL and reduce for hydraulic control; COC mobility. Operation of a modified version • Expansion of the Surficial Aquifer and HG of the Surficial Aquifer groundwater extraction monitoring network to: (1) establish sentinel system will continue until it is no longer needed. locations; (2) demonstrate active natural attenuation, and (3) establish trigger This alternative includes the following locations for contingency measures; components: • Continued Manual DNAPL recovery at • A single encircling vertical barrier wall wells HG-16S, HG-10S, HG-12S, HG-15S, around all four source areas to the HG and HG-11S; and middle clay; • Institutional controls to mitigate risks from • Establishment of a capped soil-consolidation exposure to Site soil, sediment, surface area; water or groundwater. • ISBS in the Upper HG at each source area (subject to acceptable performance during OnR-5B: Containment/Treatment –Barrier pilot tests or treatability studies); Wall plus In Situ Biogeochemical • ChemOx or ISBS treatment applied at Stabilization in the Upper Hawthorn existing Lower HG wells in source areas Estimated Capital Cost: $ 18.0M (based on acceptable performance during Approximate Annual OM&M: $ 165,000 pilot tests or treatability studies); Total Net Present Value: $ 20.9M • Surface grading and covering for most of the Estimated Construction Timeframe: 16 months Site with installation of storm water Estimated Time to Achieve RAOs: several years controls; ARAR: chemical-specific, action-specific and • Continued operation of the northern location-specific ARARs met with this perimeter wells of the Surficial Aquifer alternative. extraction and treatment system until such time as cleanup goals are consistently and This alternative is a combination of containment continually met, then shutdown of these and treatment remedies and includes installing a wells; barrier wall around the DNAPL source areas to • Continued operation of the horizontal the top of the middle clay unit of the HG and collection drains of the Surficial Aquifer 20
  21. 21. extraction and treatment system as needed DNAPL and reduce COC mobility. Operation for hydraulic control; of a modified version of the Surficial Aquifer • Expansion of the Surficial Aquifer and HG groundwater extraction system will continue monitoring network for (1) establishment of until it is no longer needed. Note that the only sentinel locations, (2) demonstration of difference between Alternatives OnR-5B and active natural attenuation, and (3) OnR-5C is the depth of the ISBS treatment. establishment of trigger locations for This alternative includes the following contingency measures; components: • Institutional controls to mitigate risks from • A single encircling vertical barrier wall exposure to Site soil, sediment, surface around all four source areas to the HG water or groundwater. middle clay; • Establishment of a capped soil-consolidation OnR-5C: Containment/Treatment – Barrier area; Wall plus In Situ Biogeochemical • ISBS in the Surficial Aquifer at each source Stabilization in the Surficial Aquifer area (subject to acceptable performance Capital Cost and Contingency: $ 18.1M during pilot tests or treatability studies); Annual O&M: $ 181,000 • ChemOx or ISBS treatment applied at Total Present Worth: $ 21.3M existing Lower HG wells in source areas Estimated Construction Timeframe: 16 months (based on acceptable performance during Estimated Time to Achieve RAOs: several years pilot tests or treatability studies); ARARs: chemical-specific, action-specific and • Surface grading and covering for most of the location-specific ARARs met with this Site with installation of storm water alternative. controls; • Continued operation of the northern This alternative is a combination of containment perimeter wells of the Surficial Aquifer and treatment remedies and includes installing a extraction and treatment system until such barrier wall around the DNAPL source areas to time as cleanup goals are consistently and the top of the middle clay unit of the HG and continually met, then shutdown of these ISBS treatment of the Surficial Aquifer in wells; source areas. The excess soil will be used as fill • Continued operation of the horizontal in the soil consolidation area. ChemOx or ISBS collection drains of the Surficial Aquifer treatment will be applied at existing Lower HG extraction and treatment system as needed wells in source areas. As a contingency, for hydraulic control; ChemOx will be injected if necessary to • Expansion of the Surficial Aquifer and HG remediate groundwater impacts in the HG. monitoring network for: (1) establishment of sentinel locations; (2) demonstration of The barrier wall will limit groundwater inflow active natural attenuation processes; and (3) to, and outflow from, DNAPL-impacted areas. establishment of trigger locations for A capped soil-consolidation area will be contingency measures; established inside the barrier-wall extents for • Continued Manual DNAPL recovery at excavated soil. Outside the barrier wall, surface wells HG-16S, HG-10S, HG-12S, HG-15S, regrading and covers will eliminate potential and HG-11S; and exposure to soil with contaminant • Institutional controls to mitigate risks from concentrations above cleanup goals. ISBS exposure to Site soil, sediment, surface injections will be placed into the Surficial water or groundwater. Aquifer (based on acceptable performance during pilot tests or treatability studies) to treat 21
  22. 22. OnR-5D: Containment/Treatment – Barrier • ISS/S to the upper clay unit of the HG in the Wall plus In Situ Solidification/ Stabilization four source areas; in the Surficial Aquifer • ChemOx or ISBS treatment applied at Capital Cost and Contingency: $ 35.7M existing Upper and Lower HG wells in Annual O&M: $ 165,000 source areas; Total Present Worth: $ 38.7M • Establishment of a capped soil-consolidation Estimated Construction Timeframe: 2.5 years area; Estimated Time to Achieve RAOs: several years • Surface grading and covering for most of the ARARs: chemical-specific, action-specific and Site with installation of storm water location-specific ARARs met with this controls; alternative. • Continued operation of the northern perimeter wells of the Surficial Aquifer This alternative is a combination of containment extraction and treatment system until such and treatment technologies and includes time as cleanup goals are consistently and installing a barrier wall around the DNAPL continually met, then shutdown of these source areas to the top of the middle clay unit of wells; the HG and ISS/S treatment of the Surficial • Continued operation of the horizontal Aquifer. Excess soil will be used as fill in the collection drains of the Surficial Aquifer soil consolidation area. ChemOx or ISBS extraction and treatment system as needed treatment will be applied at existing Upper and for hydraulic control; Lower HG wells in source areas. As a • Expansion of the Surficial Aquifer and HG contingency, ChemOx will be injected if monitoring network for: (1) establishment of necessary to remediate groundwater impacts in sentinel locations,;(2) demonstration of the HG. active natural attenuation processes; and (3) establishment of trigger locations for The barrier wall will limit groundwater inflow contingency measures; and to, and outflow from, DNAPL-impacted areas. • Institutional controls to mitigate risks from A capped soil-consolidation area will be exposure to Site soil, sediment, surface established inside the barrier-wall extents for water or groundwater. excavated soil and excess soil from ISS/S implementation. Outside the barrier wall, OnR-5E: Containment/Treatment – Barrier surface regrading and covers will eliminate Wall plus In Situ Biogeochemical potential exposure to soil with contaminant Stabilization in the Surficial Aquifer and concentrations that result in estimated potential Upper Hawthorn risks that exceed applicable risk limits. ISS/S Capital Cost and Contingency: $ 26.1M mixing will take place in the Surficial Aquifer to Annual O&M: $ 165,000 treat DNAPL and reduce COC mobility. Total Present Worth: $ 29.1M Operation of a modified version of the Surficial Estimated Construction Timeframe: 2 years Aquifer groundwater extraction system will Estimated Time to Achieve RAOs: several years continue until it is no longer needed. ARARs: chemical-specific, action-specific and location-specific ARARs met with this This alternative includes the following alternative. components: • A single encircling vertical barrier wall This alternative is a combination of containment around all four source areas to the HG and treatment technologies and includes middle clay; installing a barrier wall around the DNAPL source areas to the top of the middle clay unit of 22
  23. 23. the HG and ISBS treatment of the Surficial extraction and treatment system until such Aquifer and Upper Hawthorn in source areas. time as cleanup goals are consistently and Excess soil will be used as fill in the soil continually met, then shutdown of these consolidation area. ChemOx or ISBS treatment wells; will be applied at existing Lower Hawthorn • Continued operation of the horizontal wells in source areas. As a contingency, collection drains of the Surficial Aquifer ChemOx will be injected if necessary to extraction and treatment system as needed remediate groundwater impacts in the HG. for hydraulic control; • Expansion of the Surficial Aquifer and HG The barrier wall will limit groundwater inflow monitoring network for: (1) establishment of to, and outflow from, DNAPL-impacted areas. sentinel locations; (2) demonstration of A capped soil-consolidation area will be active natural attenuation processes; and (3) established inside the barrier-wall for excavated establishment of trigger locations for soil. Outside the barrier wall, surface regrading contingency measures; and covers will eliminate potential exposure to • Institutional controls to mitigate risks from soil with contaminant concentrations above exposure to Site soil, sediment, surface cleanup goals. ISBS injections will be placed water or groundwater. into the Surficial Aquifer and Upper HG (subject to acceptable performance during pilot OnR-5F: Containment/Treatment – Barrier tests or treatability studies) to treat DNAPL and Wall plus In Situ Solidification/Stabilization reduce COC mobility. Operation of a modified in the Surficial Aquifer and Upper Hawthorn version of the Surficial Aquifer groundwater Capital Cost and Contingency: $ 71.8M extraction system will continue until it is no Annual O&M: $ 165,000 longer needed. Note that the only difference Total Present Worth: $ 74.8M between OnR-5E and remedies OnR-5B and Estimated Construction Timeframe: 3 years OnR-5C is the depth of the ISBS treatment. Estimated Time to Achieve RAOs: several years ARARs: chemical-specific, action-specific and This alternative includes the following location-specific ARARs met with this components: alternative. • A single encircling vertical barrier wall around all four source areas to the HG This alternative is a combination of containment middle clay; and treatment technologies and includes • Establishment of a capped soil-consolidation installing a barrier wall around the DNAPL area; source areas to the top of the middle clay unit of • ISBS in the Surficial Aquifer and Upper the HG and ISS/S treatment of the Surficial Hawthorn at each source area (based on Aquifer and Upper Hawthorn. Excess soil will performance during pilot tests or treatability be used as fill in the soil consolidation area. studies); ChemOx or ISBS treatment will be applied at • ChemOx or ISBS treatment applied at existing Lower Hawthorn wells in source areas. existing Lower Hawthorn wells in source As a contingency, ChemOx will be injected if areas (based on acceptable performance necessary to remediate groundwater impacts in during pilot tests or treatability studies); the HG. • Surface grading and covering for most of the Site with installation of storm water The barrier wall will limit groundwater inflow controls; to, and outflow from, DNAPL-impacted areas. • Continued operation of the northern A capped soil-consolidation area will be perimeter wells of the Surficial Aquifer established inside the barrier-wall for excavated 23
  24. 24. soil and excess soil from ISS/S implementation. OnR-5G: Containment/Treatment – Barrier Outside the barrier wall, surface regrading and Wall plus In Situ Solidification/Stabilization covers will eliminate potential exposure to soil in the Surficial Aquifer and In Situ with contaminant concentrations above cleanup Biogeochemical Stabilization in the Upper goals. ISS/S mixing will take place in the Hawthorn Surficial Aquifer and Upper HG to treat Capital Cost and Contingency: $ 40.7M DNAPL and reduce COC mobility. Operation Annual O&M: $ 165,000 of a modified version of the Surficial Aquifer Total Present Worth: $ 43.6M groundwater extraction system will continue Estimated Construction Timeframe: 3 years until it is no longer needed. Estimated Time to Achieve RAOs: several years ARARs: chemical-specific, action-specific and This alternative includes the following location-specific ARARs met with this components: alternative. • A single encircling vertical barrier wall around all four source areas to the HG This alternative is a combination of containment middle clay; and treatment technologies and includes • ISS/S to the middle clay unit of the HG in installing a barrier wall around the DNAPL the four source areas; source areas to the top of the middle clay unit of • ChemOx or ISBS treatment applied at the HG, ISS/S treatment of the Surficial existing Lower Hawthorn wells in source Aquifer, and ISBS treatment of the Upper areas (based on performance during pilot Hawthorn. Excess soil will be used as fill in the tests or treatability studies); soil consolidation area. ChemOx or ISBS • Establishment of a capped soil-consolidation treatment will be applied at existing Lower area; Hawthorn wells in source areas. As a • Surface grading and covering for most of the contingency, ChemOx will be injected if Site with installation of storm water necessary to remediate groundwater impacts in controls; the HG. • Continued operation of the northern perimeter wells of the Surficial Aquifer The barrier wall will limit groundwater inflow extraction and treatment system until such to, and outflow from, DNAPL-impacted areas. time as cleanup goals are consistently and A capped soil-consolidation area will be continually met, then shutdown of these established inside the barrier-wall extents for wells; excavated soil and excess soil from ISS/S • Continued operation of the horizontal implementation. Outside the barrier wall, collection drains of the Surficial Aquifer surface regrading and covers will eliminate extraction and treatment system as needed potential exposure to soil with contaminant for hydraulic control; concentrations that result in estimated potential • Expansion of the Surficial Aquifer and HG risks that exceed applicable risk limits. ISS/S monitoring network for: (1) establishment of mixing will take place in the Surficial Aquifer to sentinel locations; (2) demonstration of treat DNAPL and reduce COC mobility. ISBS active natural attenuation processes; and (3) injections will be placed into the Upper HG establishment of trigger locations for (subject to acceptable performance during pilot contingency measures; and tests or treatability studies) in source areas to • Institutional controls to mitigate risks from treat mass in that unit and create a barrier to exposure to Site soil, sediment, surface vertical flow. The combination of ISS/S and water or groundwater. ISBS is similar to alternative OnR-4B. 24

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