REMEDIAL ACTION OBJECTIVES AND PRELIMINARY REMEDIAL remedial action objectives and preliminary remedial

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  • F I N A L T E C H N I C A L M E M O R A N D U M

    American Creosote Works Superfund Site Feasibility Study Remedial Action Objectives and Preliminary Remedial Goals PREPARED FOR:

    PREPARED BY:

    DATE:

    PROJECT:

    DCN:

    Michael Hebert /EPA Region 6 Remedial Project Manager Kenneth Shewmake/EPA John Halk/LDEQ CH2M HILL January 22, 2015 EPA Region 6 Remedial Action Contract EP-W-06-021 Task Order No. 0051-RIFS-06G3 CH2M HILL Project No. 411242.RS.01 0051-02029

    This memorandum presents the remedial action objectives (RAO) and preliminary remediation goals (PRG) to be used in developing and evaluating remedial action alternatives for the draft American Creosote Works (ACW) feasibility study (FS). This memorandum is designed to seek stakeholder input, specifically on PRGs, in advance of preparing the draft FS report, so that the areas/volumes of contaminated media can be defined. Much of the information presented in this memorandum will be presented in the draft FS report.

    This memorandum was developed in an iterative manner; therefore, there are several sections with redundant information. Specifically, Sections 1, 2, and 3 overlap with Section 4. Sections 1, 2, and 3 were added between the working draft and final version. This redundancy was preserved to maintain the memorandum’s original format.

    1. Background The ACW site (the Site) is a former wood-treating facility that ceased operations in 1985. The Site, which spans approximately 62 acres (CH2M HILL, 2014a), is currently vacant except for ongoing subsurface/soil and groundwater remediation underway in the Site’s former process area (FPA) and a construction equipment storage area located in the southern portion of the Site.

    Current exposures in the FPA are limited to personnel involved with site remediation, with public access restricted by a locking gate and perimeter fence. A layer of fill material, averaging approximately 1 foot in thickness, overlies a majority of the FPA. The cover material prevents direct contact with contaminated subsurface soil by remediation workers. Outside the soil cover footprint, where the potential for unacceptable health risks exists, remediation workers are protected through the use of personal protective equipment (PPE).

    The future land use at the Site will be limited to industrial/commercial purposes through institutional controls (IC) to be implemented through a future Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) decision document. Based on current and foreseeable future site land use conditions, as part of the risk assessment presented in the Risk Assessment Version 1.1 (CH2M HILL, 2014), the Risk Assessment Addendum (CH2M HILL, 2014), and the American Creosote Works Superfund Site Decision Unit Preliminary Risk Evaluation by Media (Soil, Sediment and Surface Water) (CH2M HILL, 2014), the following potential current/future human exposure pathways were identified and evaluated:

    • Current/Future Recreators in the Creek– Potential adolescent recreators could contact surface water and sediment in Creosote Branch during recreational activities.

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  • AMERICAN CREOSOTE WORKS SUPERFUND SITE FEASIBILITY STUDY REMEDIAL ACTION OBJECTIVES AND PRELIMINARY REMEDIAL GOALS

    • Future Commercial/Industrial Workers – A commercial/industrial worker exposure scenario was evaluated for soil (0 to 10 feet deep), groundwater (potable use), and indoor air. Potential exposures to offsite and onsite groundwater were quantified for the industrial potable use exposure pathways and the groundwater-to-indoor air vapor intrusion (VI) pathway.

    • Future Construction Workers – Potential construction workers were assumed to contact surface and shallow subsurface soil (0 to 10 feet deep) and shallow groundwater during site redevelopment or construction activities. Onsite and offsite shallow groundwater was evaluated for a construction worker, assuming a construction worker could potentially have direct contact with shallow groundwater during an excavation.

    • Hypothetical Future Residents (Adult/Child) – A hypothetical future residential scenario was evaluated for soil (0 to 10 feet deep), groundwater (potable use), and indoor air. Potential exposures to offsite and onsite groundwater were quantified for the potable use exposure pathways and the groundwater-to- indoor-air VI pathway.

    • Ecological – Risks to ecological receptors were also evaluated through direct and indirect (food web) exposure assessments, for both receptors in terrestrial (surface soil) and aquatic (sediment and surface water) habitats.

    The contaminated media exposure to receptors that resulted in unacceptable risks will be identified for remedial action in the draft FS, and the PRGs are developed in this memorandum.

    2. Decision Units The ACW site was divided into seven decision units (DU) to facilitate risk management decisions for the remedial investigation (RI) and FS. Following completion of the 2013 data gap sampling and the Risk Assessment Version 1.1 (CH2M HILL, 2014b), the Risk Assessment Addendum (CH2M HILL, 2014c), and the American Creosote Works Superfund Site Decision Unit Preliminary Risk Evaluation by Media (Soil, Sediment and Surface Water) (CH2M HILL, 2014d) it was determined that three of the seven DUs should be carried forward into the FS as follows:

    1. Northern DU – surface soil. Maximum-based intake (doses) for the deer mouse yielded no observed adverse effect level (NOAEL), based hazard quotients (HQ) ranging from 3.4 to 30.4, which exceed the CERCLA target ecological HQ of 1.0 (see Table 1A) (reference Table 5-19, CH2M HILL, 2014b).

    2. Non-Process Area – surface soil. The industrial worker excess lifetime cancer risk (ELCR) of 8.3 x 10-4 exceeded the upper bound CERCLA target risk of 1 x 10-4 (see Table 1B) (reference Table 1B, CH2M HILL, 2014d).

    3a. Process Area – surface and subsurface soil. The industrial worker surface soil ELCR of 2.9 x 10-4 exceeded the upper bound CERCLA target risk of 1 x 10-4 (see Table 1B). The industrial worker subsurface soil ELCR of 1.4 x 10-3 also exceeded the upper bound CERCLA target risk of 1 x 10-4 (see Table 1B) (reference Table 1B, CH2M HILL, 2014d).

    3b. Process Area and Non-Process Area shallow aquifer groundwater. This media was carried forward into the FS based on the following considerations:

    • Shallow aquifer groundwater is not a current (Class IIA) drinking water source; however, based on U.S. Environmental Protection Agency (EPA) groundwater classification guidance (EPA, 1986a) shallow aquifer groundwater is considered a potential future (Class IIB) drinking water source. It is unlikely that onsite groundwater will be used as a potable source in the future because of relatively low yield and availability of water from the City of Winnfield. There is no indication that shallow aquifer groundwater is being used within the immediate vicinity of the Site. Drinking water for nearby residents is supplied by the City of Winnfield from deep wells constructed in the Sparta aquifer at estimated depths of 550 to 600 feet below ground surface (CDM, 1992). The nearest City

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    of Winnfield water supply well is located approximately 0.5 mile north of the Site. Groundwater contamination in the shallow aquifer is limited to the Process Area DU and the western portion of the Non-Process Area DU.

    • Per the National Contingency Plan (NCP) (40 Code of Federal Regulations [CFR] 300.430 [a][1][iii][F]), “EPA expects to return usable ground waters to their beneficial uses wherever practicable, within a timeframe that is reasonable given the particular circumstances of the site. When restoration of ground water to beneficial uses is not practicable, EPA expects to prevent further migration of the plume, prevent exposure to the contaminated ground water, and evaluate further risk reduction.”

    • The concentrations of several site-related contaminants exceed federal drinking water maximum contaminant levels (MCL), which define chemical-specific applicable or relevant and appropriate requirements (ARAR) for groundwater that is a current or future drinking water source. For example, the 351 micrograms per liter (µg/L) exposure point concentration (EPC) for carcinogenic polycyclic aromatic hydrocarbons (PAH), expressed in benzo(a)pyrene (BAP) toxicity equivalents (TEQ), exceeds the 0.2 µg/L MCL. Exceedance of one or more chemical-specific ARAR is the primary basis for carrying shallow aquifer groundwater into the FS.

    • The risk assessment identified future industrial/commercial worker VI/inhalation risk that fell within the CERCLA 1 x 10-4 to 1 x 10-6 target risk range. Although there is no unacceptable risk, the VI pathway will be addressed in the FS and a future CERCLA decision document, through ICs that will specify vapor mitigation controls (such as a vapor barrier) on all new (future) building construction within the Process Area DU. Human health exposure via vapor inhalation will be prevented through this IC, and risks will be reduced through implementation of remedial action alternatives that address contaminated soil and groundwater. These measures are designed to provide an additional level of protecti