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FORMER AMERICAN FOREST PRODUCTS Appendix D Closure Summary Report July 2009 URS Project 17322736 Page D-1 APPENDIX D " t . I RWQCB Tier 1 Environmental Risk Assessment i I � t I This risk assessment follows procedures developed by the San Fraricisco Bay Regional Water Quality Control Board(SFB-RWQCB)based on conservative criteria for screening for environmental concerns at sites with contaminated soil and groundwater(SFB-RWQCB, 2005).That document provides conservative environmental screening levels(ESLs)that address direct exposure to soil and potential vapor intrusion into buildings from contaminated soil and/or groundwater.The ESLs are based on updated California Human Health Screening Levels and revisions to toxicity factors presented in the EPA �— Preliminary Remediation Goals According to the SFB-RWQCB,the ESLs are considered to be conservative.Under most circumstances, and within the limitations described in the RWQCB document,the presence of a chemical in soil,soil gas or groundwater at concentrations below the corresponding ESL can be assumed to not pose a significant, long-term(chronic)threat to human health and the environment. The ESLs and associated tiered screening approach were developed to address environmental protection " goals for: • Protection of human health(direct-exposure); ` • Protection against vapor intrusion into buildings; • Protection against leaching and subsequent impacts to groundwater; • Protection of terrestrial biota; r ~Y • Protection against adverse nuisance conditions. , The RWQCB provides a framework for a Tier 1 Environmental Risk Assessment that organizes site information to provide a basic"conceptual model"of site conditions. That framework is provided below, together with site-specific information, either provided directly or via reference to existing URS documents. 1. Summarize Past, Current and Anticipated Future Site Activities and Uses: • Describe past and current site uses and activities. f k American forest Products operated a wood manufacturing plant at the site(between 1921 and 1987. A detailed description of former site uses and activities may be found in this report in Section 2.2 • Describe foreseeable future site uses and activities. (Always include a comparison of site data to ESLs for residential/unrestricted land use to evaluate need for formal covenants to the deed; see Section 2.10.) The property has been purchased by the San Joaquin Regional Rail Commission for use as a maintenance facility for railcars of the Altamont Commuter Express. 4 KAWprocess\22736\Americ Forest\Closure-Summary-Repon-RevOl.doc