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5.3 Groundwater Results Three (3) groundwater samples were collected from sample locations S131 through S133 and analyzed for VOCs and TPH via EPA Method 8015/8260B. VOCs Methyl tert-butyl ether(MTBE) was detected in one groundwater sample (S133) at a concentration of 0.708 µg/L. All other VOCs were below detection limits in all groundwater samples analyzed. TPH All TPH groundwater sample results are below their respective ESLs, where published, with the exception of TPH- DRO. TPH-DRO was detected above the ESL of 100 µg/L in groundwater samples collected from S131 and S133 at respective concentrations of 981 µg/L and 213 µg/L.TPH-ORO was detected in all groundwater samples collected at concentrations ranging from 867 µg/L to 1,316 µg/L. No ESL currently has been established for TPH-ORO. 6.0 Evaluation Analytical Results Three soil borings were advanced and soil samples were collected and analyzed for VOCs, TPH, and CAM 17 Metals. All VOC and TPH results were below detection limits for the samples analyzed. Low concentrations of metals were detected in one or more soil samples. All soil results are below their applicable screening levels under California DTSC guidance or within expected background concentration ranges. All soil vapor samples are below their respective ESLs under SFBRWQCB guidance, where published, with the exception of benzene and naphthalene, which were detected in one or more soil vapor samples above the SFBRWQCB screening criteria. These elevated concentrations are further evaluated as presented in Table 7 and summarized below using attenuation factors to predict potential indoor air concentrations due to potential vapor intrusion of benzene and naphthalene into structures on site. This evaluation utilizes DTSC and USEPA- recommended attenuation factors (0.001 and 0.0005, respectively). In addition, DTSC has also recommended that screening assessments calculate soil vapor screening levels using the US EPA recommended attenuation factor of 0.03 (based on June 2015 guidance) for sub-slab soil gas and "near-source" exterior soil gas. For the elevated soil vapor results at the subject property, the DTSC-recommended attenuation factors predict potential indoor air concentrations of benzene at 0.03 µg/m3 and 0.01 µg/m3, below the indoor air screening level for industrial/commercial use (0.42 µg/m3 benzene). The DTSC-recommended attenuation factors predict potential indoor air concentrations of naphthalene at 0.01 µg/m3 and 0.01 µg/m3, below the indoor air screening level for industrial/commercial use (0.36 µg/m3 naphthalene). Although the EPA conservative attenuation factor predicted a concentration of 0.89 µg/m3 benzene and 0.40 µg/m3 naphthalene (above respective screening levels), our experience with similar sites indicates that there are no significant health risks from these trace concentrations of VOCs. Phase II Limited Subsurface Investigation Fulcrum Resources Environmental 2546 Turnpike Road,Stockton, California 95206 202107-8656 11