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Phase 11 Environmental Site Assessment Manteca Multimodal Station Project,Southeast of Moffat Boulevard and Main Street Manteca, California The TCLP threshold for soluble lead is 5 mg/L. Soluble lead in RB4 using the TCLP method did not exceed the TCLP threshold. The results of the STLC and TCLP analysis are further discussed in the Discussion of Results section below. Furthermore, because the soil samples collected from RB 14-0.5' and RB4-0.5' exceeded 50 mg/kg,the soil samples collected from 2 feet below grade from RB4 and RB 14 were also analyzed for total lead. Soil sampling results are further discussed in the Discussion of Results section below. STAINED PAVEMENT Soil Sampling The soil sample collected at 1-foot below grade from RB 17 was analyzed for TPH,VOCs, SVOCs, OCPs,PCBs, and total metals. TPH-g,VOCs, SVOCs, OCPs, and PCBs were not detected above their respective detection limits. As shown in Table 1, a concentration of 6.2 mg/kg TPH-d (slightly above the detection limit of 5 mg/kg)and a concentration of 82 mg/kg TPH-o were detected in RB 17. As shown in Table 3,varying concentrations of metals were detected in RB 17. Based on the results of the 1-foot deep soil sample, further analyses of the 5-foot deep soil sample collected from B 17 were not conducted. Soil sampling results are further discussed in the Discussion of Results section below. DISCUSSION OF RESULTS Further discussion regarding the detected metals and TPH in soil and TPH-g and VOCs in groundwater follows. METALS IN SOIL Varying concentrations of metals were detected in soil samples collected from the site. As shown in Table 3, the detected concentrations of metals in soil were compared to naturally occurring background concentrations found in California soils(Bradford et al.,March 1996). The detected concentrations of metals were also compared to the following screening levels or regulatory thresholds: Regional Screening Levels (SLs The United States Department of Energy(DOE) under an interagency agreement with the Environmental Protection Agency (EPA) developed the SLs for contaminants in soil for residential and commercial/industrial properties. SLs are used when a site is initially investigated to determine if contamination is present to warrant further investigation,and can be used to determine remediation goals. California Human Health Screening Levels (CHHSLs): The California Environmental Protection Agency(Cal/EPA)developed CHHSLs for 54 hazardous chemicals in soil, soil gas,and indoor air(residential land uses and commercial/industrial land uses). The CHHSLs were developed by the Office of Environmental Health Hazard Assessment (OEHHA) on behalf of the CAL/EPA. The use of the CHHSL document is not intended to establish policy or regulation. Rather,the CHHSL document is a guidance document. The presence of a chemical at concentrations in excess of a CHHSL does not indicate that adverse impacts to human health are occurring or will occur but suggests that further evaluation of potential human health concerns may be warranted. Rincon Consultants 11