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Statttec J PHASE II ENVIRONMENTAL SITE ASSESSMENT REPORT Conclusions and Recommendations March 31,2011 detections that were below the USEPA RSLs for shallow industrial soil and the RWQCB ESLs for shallow soils where groundwater is a current or a potential source of drinking water. PCE was only detected in the soil sample for SS-1 in trace amounts and was below the laboratory MDL in the remainder of the samples. • TPH fuel fingerprint analytical results for soil samples SS-1, SS-5, and SS-6 were reported below the laboratory MDLs for all analyses except for TPH hydraulic oil/motor oil and TPH diesel. The detections for TPH hydraulic oil/motor oil were 55 and 31 mg/kg in samples SS-5 and SS-6. There are no reported USEPA RSLs for shallow industrial soil or RWQCB ESLs for shallow soils where groundwater is a current or a potential source of drinking water for TPH hydraulic oil/motor oil. The laboratory chromatograms for soil sample SS-6 were not typical for TPH-hydraulic oil/motor oil and TPH-diesel and are considered to represent weathered hydrocarbons. Although the TPH detections were slightly above the TPH-diesel ESLs for shallow soils (<3 meters bgs) where groundwater is a current or a potential source of drinking water, the lack of volatile hydrocarbon constituents in this weathered hydrocarbon is considered to lower the significance of this finding. The volatile components in hydrocarbons tend to drive the risk associated with it. The hydrocarbon volatiles (i.e., benzene, toluene, ethylbenzene, and xylenes) in the soil vapor sample and the soil sample associated with this soil sample reported detections that were 1 to 2 orders of magnitude below the screening levels. The location of the soil sample is adjacent to the sewer lateral and is approximately 20 feet from the nearest comer of the building. The area is covered with asphalt and is used as part of the driveway. Based on the low volatile fraction in the weathered hydrocarbons, past usage of this area, and since no other media are affected Stantec recommends no further action at this time. • The CAM 17 metal results for the soil samples SS-1, SS-5, and SS-6 were not detected above the laboratory MDLs for silver and thallium and low detections on the remaining metals except for arsenic. The MDL reporting limits and the low detections (except for arsenic)were approximately one order of magnitude or more below the USEPA RSLs for shallow industrial soil, the RWQCB ESLs for shallow soils (<3 meters bgs) where groundwater is a current or a potential source of drinking water, and the CHHSLs for soil in commercial/ industrial land use only. • The soil sample arsenic concentrations were reported above the commercial/industrial land use CHHSL of 0.24 mg/kg and the RSLs and ESLs of 1.6 mg/kg. Arsenic levels are strongly influenced by the geology of the rocks from which the soils are derived which can often result in background concentrations above the CHHSLs, RSLs, and ESLs. Regulatory agencies have acknowledged that background concentrations of several metals, including arsenic, frequently exceed health-based, direct-exposure screening goals. For this reason, Cal-EPA provides guidance for substituting background concentrations of arsenic in place of health-based screening levels. Although no Site- specific arsenic background data was available for comparison, arsenic concentrations detected in subject property soils ranged from 1.7 to 3.2 mg/kg and are within the i:\projects\calpine\lodi\reportModi.svrpt.do" 4.2