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k'q KLEINFELDER Country Club Boulevard and Pershing Avenue (south of former Shell Station) Total lead concentrations ranged from 0 24 mg/l to 0 97 mg/l in groundwater samples collected in the ' Pershing site area 43 COMPARISON TO REGULATORY LIMITS (SOIL) The soil sampling analytical results were compared to the Total Threshold Limit Concentration ' (TTLC) and Soluble Threshold Limit Concentration (STLC) regulated levels as expressed in California Code of Regulations 22CCR§66261 24 and/or the Residential U S EPA Region IX Preliminary Remediation Goals (PRGs), dated October 1, 2002 ' were selected because the are typically more stringent PRGs are PRGs for residential sites y yp y $ contaminant concentrations in environmental media (i a soil, air, water), calculated by the U S ' EPA, that can be used as screening tools to evaluate a site for potential human health risks PRGs are calculated using standard assumptions and are specific for land use conditions (e g residential or industrial) The chemical concentrations calculated by the U S EPA typically correspond to a fixed Ievel of risk (usually 10"6, or 1 in 1,000,000 cancer risk, or a non-cancer hazard quotient of 1) for soil, air, and water The following exposure pathways were accounted ' for in the PRG calculation for soils assuming residential land use • Ingestion • Inhalation of particulates • Inhalation of volatiles • Dermal (skin) absorption For the inhalation pathways, volatilization factors and particulate emission factors are used to estimate exposure due to emissions from soil to air For the dermal absorption pathway, a 10% ' skin absorption factor was used to calculate the PRGs for the constituents of concern at the subject site This factor assumes the dermal dose is equal to an adult's ingestion dose If contaminant concentrations at the subject site exceed the estimated PRG values and the exposure pathways used to calculate those PRGs are inappropriate for the site, additional site evaluations, such as an evaluation of background levels, supplementary sampling and ' calculations using site-specific data may be necessary From the requested suite of analyses (See Section 3 3) only a single analyte, total lead was ' detected in soil samples in the Mission and Pershing areas Total lead was detected in each of the fifteen soil samples at concentrations ranging from 3 3 to 7 8 mg/kg at approximate depths of ' 9 % feet bgs The upper limit of the range of concentrations for total lead detected did not exceed the Total Threshold Limit Concentration (TTLC) Regulated Level (1,000 mg/kg) for classification of total tlead as a hazardous waste per California Code of Regulations 22CCR §66261 24 Additionally these concentrations were not greater than 10-times the Soluble Threshold Limit Concentration ' — (STLC) Regulated Level (50 mg/kg) for lead as expressed in 22CCR §6626124 The factor of 28699 E01 /STOIR191 Page 10 of 16 July 21,2003 Gopynght 2003,Kleinfelder,Inc 1