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CAM B R I A Ms.Lori Duncan <br /> September 9,2005 <br /> The abbreviated CSM prepared for the RBCA analysis is summarized on the table below. <br /> Item Selected Value Comment <br /> Contaminant Gasoline hydrocarbons have been <br /> Soil and groundwater detected in soil and groundwater <br /> Source Media: beneath the site. <br /> COCS: BTEX <br /> Target Carcinogenic Risk 10"5 Consistent with Cal-EPA policy <br /> Commercial: 1 x <br /> Level (Proposition 65). <br /> © Non-Carcinogenic 1.0 Consistent with USEPA and ASTM <br /> Target Hazard Quotient: <br /> default value. <br /> SSTLs <br /> Consistent with the RBCA approach adopted by ASTM, Cambria calculated the SSTLs <br /> associated with COCs present in on-site groundwater and soil. <br /> Where available, Cambria used site-specific data in place of default values to calculate risks. Site <br /> specific depth to water was calculated by averaging the depths to water from on-site wells <br /> measured during the previous four quarters of monitoring. The affected soil zone parameters <br /> (depth, length, and area) were estimated based on historical soil data (Table 3). Soil <br /> characteristics were based on ASTM default values for silty sand (SM). RBCA input sheets are <br /> included in Attachment C. <br /> MCC - r.o too <br /> The SSTLs calculated for groundwater are 14 ppb benzene, 10,000 ppb toluene, 5,100 ppb <br /> ethylbenz�ene, and 100,000 ppb Xylenes. The SSTLs calculated for soil are 0.097 ppm benzene, <br /> 140 ppm toluene, 100,ppm ethylbenzene, and 19,000 e <br /> xylenes. All RBCA output sheets are <br /> included in Attachment D. <br /> CAP <br /> Objectives <br /> CAP clean-up objectives are typically based on one or more of the following criteria: <br /> • Department of Health Services primary or secondary MCLS for drinking water, <br /> • Risk-based clean-up levels established by risk assessment or RBCA analysis, <br /> 8 <br />