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FF. 4 �. <br /> FORMER AMERICAN FOREST PRODUCTS 6.0 RWQCB Tier I Environmental Risk Assessment <br /> Closure Summary Report July 2009 <br /> URS Project 17322736 Page 6-1 <br /> 6.0 RWQCB TIER 1 ENVIRONMENTAL RISK ASSESSMENT <br /> A Tier 1 Environmental Risk Assessment following procedures developed by the San Francisco Bay <br /> Regional Water Quality Control Board(SFB-RWQCB) was completed for the Site in 2005 (URS,2005a). <br /> An updated version is included in Appendix D. SFB-RWQCB procedures are based on conservative <br /> criteria for screening for environmental concerns at sites with contaminated soil and groundwater(SFB- <br /> RWQCB, 2005). That document provides conservative- ne'vironmental:screening_lev_els(ESLs)that <br /> address direct exposure to soil and potential vapor intrusion into buildings from contaminated soil and/or <br /> groundwater. The ESLs are based on updated California Human Health Screening Levels and revisions to <br /> + toxicity factors presented in the EPA's Preliminary Remediation Goals. <br /> According to the SFB-RWQCB,the ESLs are considered conservative. Under most circumstances, and i <br /> within the limitations described in the SFB-RWQCB document,the presence of a chemical in soil, soil <br /> gas or groundwater at concentrations below the corresponding ESL can be assumed to not pose a <br /> significant,long-term(chronic)threat to human health and the environment. <br /> The-2005 Tier 1-Risk-Assessment-concluded-thatthere.ii no indication of indoor air`risk:due_tothe <br /> kpiresL6of groundwater contaminants"at the maximum") 2-DCA concentration iii 2005-of 36A" f <br /> F��-:Phis` <br /> � conc usibn is-confirmed by the.current.update.The maximum 1,2-DCA concentration during the last five <br /> quarters has not exceeded 14µg/L, and is steadily decreasing.Details of the risk assessment update are <br /> provided in Appendix D.- <br /> } <br /> I <br /> i <br /> I <br /> is <br /> I <br /> � I <br /> I <br /> } J <br /> i <br /> f 5 <br /> 1 <br /> M <br /> } KAWprocesA227361Americe F*tmt CIos�Summar}-Report-Rc Ol.doc <br />