Laserfiche WebLink
APPENDIX BRISK BASED CORREC M ACT1oNTIER 1 AND TIER Z ANALYSIS <br /> SITE CLOSURE EVALUATION REPORT <br /> Former Beacon Station No 695 <br /> 900 South Cherokee Lane <br /> Lodi, California <br /> Delta.Project No D093-915 <br /> Page 14 <br /> and in Appendix M Using the Tier 2 Guidance Manual, the upper confidence limit benzene <br /> concentration for the source area is 0 97 mg/kg <br /> The RBSL model is conservative because it assumes vapor equilibrium with soils, no decay of COCs, <br /> and an mmmfinmte source The model also assumes that a building will be placed directly above the impacted <br /> soils At this site, buildings are located an average of approximately 100 feet from the impacted soils. <br /> A Tier 2 model will be used to estimate SSTLs in Section 7 1 Toluene, ethylbenzene, and total xylenes <br /> exist at concentrations below their respective RBSL as shown in Table 11 <br /> 8 2 4 Vapors To Ambient Air <br /> Impacted soils exist at depths greater than 24 feet bsg, thus emissions to ambient air will be limited In <br /> addition, due to less air exchange, the vapor emissions to enclosed spaces discussed in Section 3 2 3 are <br /> imore stringent and will assess RBSL and SSTL values for the site <br /> 8 2 5._Leachmnir to Ground Water <br /> This exposure pathway was considered to ensure protection of ground water The model used by the <br /> Tier 2 Guidance system is described in Appendix N The model estimated a RBSL of 0 12 mg/kg <br /> benzene as shown in Appendix M Multiplying this number by 0 29 correction factor results in a RBSL <br /> of 0 035 mg/kg as summarized on Table 11 The model is conservative because it does not allow for <br /> natural attenuation of the leachate and assumes equilibrium between the adsorbed sail phase and aqueous <br /> phases The results indicate that a Tier 2 analysis for a benzene SSTL must be performed for this <br /> exposure pathway <br /> A RBSL of 720 mg/kg was also estimated for toluene. The representative concentration detected in soils <br /> for toluene is 4 4 mg/kg, thus meeting the RBSL Total xylenes and ethylbenzene did not have a RBSL <br /> calculated due to the impossibility of these COCl exceeding RBSLs in ground water through leaching <br /> RPT001 915 <br />