RCRA FACILITY INVESTIGATION DATA SUMMARY AND FINDINGS ... DATA SUMMARY AND FINDINGS REPORT BOEING RFI

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  • D R A F T

    RCRA FACILITY INVESTIGATION DATA SUMMARY AND FINDINGS REPORT BOEING RFI SUBAREA 1A CENTRAL SANTA SUSANA FIELD LABORATORY, VENTURA COUNTY, CALIFORNIA

    Prepared For:

    THE BOEING COMPANY

    Prepared By:

    MWH 300 North Lake Avenue, Suite 400 Pasadena, CA 91101

    July 2015

    ___________________________________ Dixie Hambrick, P.G. 5487 Program Director

    ___________________________________ Benjamin Stewart, P.G. 8012 Project Manager

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  • Boeing RFI Subarea 1A Central Data Summary and Findings Report July 2015

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    EXECUTIVE SUMMARY

    This Data Summary and Findings Report (DSFR) was prepared for The Boeing Company (Boeing) to present the findings and recommendations of the Resource Conservation and Recovery Act (RCRA) Facility Investigation (RFI) for the 1A Central Subarea at the Santa Susana Field Laboratory (SSFL) in Ventura County, California. This Boeing RFI Subarea 1A Central DSFR (1A Central DSFR) presents the RFI results and recommendations for Corrective Measures Study (CMS) evaluation and No Further Action (NFA) for all media within this subarea. Data and information evaluated at the subarea scale, such as the vapor intrusion evaluation and data usability assessment, are also presented in this report.

    Individual DSFRs for RFI sites and for areas unaffiliated with RFI sites (unaffiliated areas) accompany this 1A Central DSFR. These include DSFRs for the Advanced Propulsion Test Facility (APTF) RFI Site, the Building 1359 (B359) RFI Site, the Happy Valley North (HVN) RFI Site, and 1A Central Unaffiliated Areas. The individual DSFRs present data and information evaluated at the RFI site-scale to assess sources, nature and extent, and transport and fate of contamination, and to assess potential risks to human health and the environment. The RFI site DSFRs also provide information on site-specific evaluations, such as air dispersion modeling results, evaluation of vadose zone contaminant transport to groundwater, groundwater source zone evaluation, and associated groundwater plume characterization.

    RFI characterization has been conducted at Boeing RFI Subarea 1A Central RFI sites in accordance with California Environmental Protection Agency, Department of Toxic Substances Control (DTSC) approved work plans since 1996. Most recently, data gap analysis and investigation was performed for all media following the DTSC-approved Master Resource Conservation and Recovery Act Facility Investigation Data Gap Work Plan (Master RFI Data Gap Work Plan; CH2M HILL, 2013a) and the Comprehensive Data Quality Objectives Report, RCRA Facility Investigation (DQO Report; CH2M HILL, 2013b). Master RFI Data Gap Work Plan Addenda for each 1A Central RFI site and unaffiliated areas identified data gaps to complete characterization for nature and extent, transport and fate, risk assessment, and groundwater modeling requirements. Iterative evaluations of the data using the media-specific data quality objectives were performed, and subsequent data gaps identified where necessary. This iterative process was continued until characterization was deemed complete for each RFI site and the unaffiliated areas. The public was given the opportunity to provide input on this process during work plan-specific and other routine public meetings conducted at the SSFL during 2013 and 2014.

    A comprehensive review process was performed to identify areas of known, suspected, or potential chemical use, storage, handling, or disposal; these areas were identified as chemical use areas (CUAs) or potential chemical use areas (PCUAs). CUAs and PCUAs were investigated for potential contamination. If sampling results at PCUAs exceeded screening levels, they were

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  • Boeing RFI Subarea 1A Central Data Summary and Findings Report July 2015

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    identified as CUAs, or added to an existing CUA1. CUAs were combined into CUA clusters, based on similarities in operational history, geographic proximity, lithologic features, analytical data, previous CMS recommendations, and documented dense nonaqueous phase liquid release locations. CUA clusters were evaluated and investigated following the Master RFI Data Gap Work Plan and DQO Report characterization guidelines (CH2M HILL, 2013a, 2013b), as specified in the DTSC-approved work plans.

    The CUA clusters were carried forward to media-specific DQO evaluations for surface water bodies (if present), soil and sediment, the vadose zone (soil and unweathered bedrock), and groundwater and seeps as specified in the DQO Report. In addition to the media-specific evaluations, various assessments and other evaluations were performed including: data usability assessments, air dispersion modeling, vapor intrusion pathway evaluations, sewer and reclaimed water system assessments, groundwater flow and contaminant transport modeling, and human health and ecological risk assessments (HHERAs).

    The recommended CMS areas in Boeing RFI Subarea 1A Central are presented in Table ES-1 and shown on Figure ES-1. For each RFI site, Table ES-1 also provides a short description of: historical use; estimated risks and hazards; associated risk drivers identified during the HHERAs; and the results of vadose zone and groundwater plume evaluations. Although the most likely future use of the SSFL will be for recreational purposes, risk assessment CMS recommendations are based on the hypothetical future suburban resident exposure scenario to provide conservative estimates for CMS planning. In addition, CMS recommendations for ecological risks are based on small home-range receptors (e.g., deer mouse) using the high ecological risk-based screening level. Potential risks to large home-range receptors (e.g., mule deer), will be evaluated on a subarea- and facility-wide basis, and presented in a forthcoming Large Home-Range Ecological Risk Assessment (ERA) Report.

    Based on the comprehensive characterization and subsequent risk assessments performed using the Subarea 1A Central RFI data, a total of 26 soil CMS areas and 6 soil vapor CMS areas have been identified to address estimated potential risks above DTSC risk threshold values for the hypothetical future suburban resident and small home-range ecological receptors (CMS areas recommended based on the hypothetical future resident are more conservative, so they are also protective of the future recreator). Based on vadose zone to groundwater modeling evaluations, 12 CMS areas and 43 CMS locations (based on individual sample locations) have been identified to address potential chemical migration from the vadose zone to groundwater. Assessment of soil beneath a subsurface, mastic-wrapped pipeline at the B359 RFI Site to determine the need of corrective measures is also recommended once that pipeline is removed during future remediation activities. Recommended soil, soil vapor, and vadose zone CMS areas cover                                                              1 For one PCUA at the Building 359 RFI Site, soil sampling beneath one segment of a subsurface, mastic-wrapped pipeline cannot be performed until the pipeline is removed. This segment of the pipeline is partially within two soil CMS areas, and as such, will be assessed by screening level samples to determine if corrective measures are needed when this pipeline is removed during future remediation activities.

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  • Boeing RFI Subarea 1A Central Data Summary and Findings Report July 2015

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    approximately 5 acres in Boeing RFI Subarea 1A Central and are driven by: volatile organic compounds (VOCs), semi-volatile organic compounds (SVOCs), total petroleum hydrocarbons, polychlorinated biphenyls (PCBs), pesticides, dioxins/furans, energetics, and select inorganics and metals.

    In addition, much of the groundwater present within Boeing RFI Subarea 1A Central is recommended for CMS based on the results of risk assessment and groundwater flow and contaminant transport modeling. A total of 20 specific chemicals of concern in groundwater have been identified for CMS evaluation. Figure ES-1 displays the estimated extent of TCE in groundwater above the groundwater characterization level to represent the approximate extent of chemicals recommended for CMS in groundwater; as noted above and presented in Table ES-1, groundwater CMS recommendations are chemical specific. VOCs (primarily trichloroethene [TCE] and associated daughter products) are the predominant chemicals of concern in groundwater, with other chlorinated solvents, perchlorate, n-Nitrosodimethylamine (NDMA), bis(2-ethylhexyl) phthalate, hydrazine, 1,4-dioxane, dioxins/furans, and select metals and inorganics also recommended for CMS evaluation.

    The soil, soil vapor, and vadose zone CMS areas and locations, and chemicals of concern in groundwater recommended in this 1A Central DSFR, will be evaluated further for corrective action in the forthcoming CMS Reports.

    The portions of Boeing RFI Subarea 1A Central outside of soil, soil vapor, and vadose zone bedrock CMS areas (presented on Figure ES-1) are recommended for NFA. Based on the results of the comprehensive review process, characterization data, transport and fate evaluations, and risk assessments, environmental media in the areas recommended for NFA are safe for their intended future use, do not pose u