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Soil Assessment Report 324 East 11th Street Tracy, California October 12,2017 Table B — Media-Specific LTCP Criteria Evaluation Satisfy Media/Exposure Criteria Evaluation Criteria? Pathway i X Groundwater The subject site apparently meets all criteria for CriteriPexcept water wells within 1,000 ft of plume. The groundwater plume that exceeds water quality objectives appears to be less than 250 feet in length. No free product has been observed at the site. Based on our review of satellite images, there are no surface water bodies within 1,000 ft of the site. The dissolved concentrations of benzene and MTBE are less than 1,000 gg/L. However, five water wells have been identified between 250 and 1,000 ft from the site. Vapor Intrusion to Site data appears to indicate that the site meets Scenarios 1 through 3 Indoor Air of LTCP. No light non-aqueous phase liquid (LNAPL) has been encountered onsite. All benzene concentrations detected in site groundwater are below 1,000 µg/L. The shallowest groundwater encountered onsite is approximately 8 ft bgs with shallowest static groundwater levels generally ranging between 10 to 13 ft bgs.Although the soil sample from B-1 at 1 ft bgs contained 2,400 mg/kg TPHg, the 1.8 mg/kg TPHg concentration in boring B-8 (located between boring B-1 and the site building)at 2.5 ft bgs suggests that the shallow soil impact does not extend beneath the site building. Direct Contact and Maximum petroleum concentrations must be below those listed in LTCP Outdoor Air Exposure Table 1 or limits established by a site specific risk assessment. (Alternatively, institutional or engineering controls can be used to control exposure, if agency determines no significant risk to human health). Soil data is summarized on Table 1. All historical soil data from site borings is below LTCP criteria for current site use of commercial. Only one result exceeds the residential LTCP criteria: the 3.6 mg/kg benzene from 1 ft depth at boring B-7 slightly exceeds the 1.9 mg/kg residential criteria. Soil data meets commercial criteria of LTCP Table 1, and benzene impact above residential LTCP criteria appears to be limited to a relatively small area around borings B-1 and B-7. CONCLUSIONS AND RECOMMENDATIONS This additional site assessment was performed to evaluate the area around boring B-1 for the possibility of a former waste oil tank and potential second source area. Based on the above site assessment, well survey, and LTCP evaluation, Pangea offers the following conclusions and recommendations: 7