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excavations, and/or anomalies. The Phase II identified concentrations of total petroleum <br /> hydrocarbons as gasoline (TPH-g) and as diesel (TPH-d), and benzene,toluene, ethylbenzene, and <br /> xylenes (BTEX) in groundwater exceeding certain San Francisco Bay Regional Water Quality <br /> Control Board (SFRWQCB) Environmental Screening Levels (ESLs) at one or more boring locations. <br /> Based on the results of the Phase II, Partner recommended additional investigation to further <br /> evaluate the extent of impacts at the Site and the potential human health risks. Preliminary results <br /> indicated that the releases are associated with the former Shell Service Station pump islands and <br /> UST locations inferred from historic site plans. <br /> Partner performed an Additional Subsurface Investigation Report, dated November 8, 2017. <br /> Partner performed the Additional Subsurface Investigation to further characterize the extent and <br /> nature of the identified impacts to soil,soil gas, and/or groundwater as a consequence of a release <br /> or releases from the historical on-site gasoline service station operations. The scope of the <br /> Additional Subsurface Investigation included an additional geophysical survey, which employed <br /> GPR for the purpose of identifying subsurface anomalies associated with the former gasoline <br /> station operations, the advancement of six borings, and the installation of two temporary sub- <br /> slab soil gas probes. Five soil samples and six groundwater samples were analyzed for carbon <br /> chain total petroleum hydrocarbons (TPH-cc), BTEX, methyl tert-butyl ether (MTBE), and fuel <br /> oxygenates. In addition, four soil gas and two sub-slab soil gas samples were analyzed for VOCs. <br /> The geophysical survey did not identify any anomalies consistent with a backfilled excavation, <br /> which generally corresponds to the location of former gasoline USTs and/or waste oil tanks. In <br /> addition, no large metallic features were identified within the survey area. <br /> The Additional Subsurface Investigation identified concentrations of TPH-g, TPH-d, and/or BTEX <br /> in groundwater samples in excess of applicable ESLs. Various VOCs were detected in the soil gas <br /> and sub-slab soil gas samples, however none of the detections exceed respective commercial <br /> ESLs. Based on the results of the Additional Subsurface Investigation, Partner recommended <br /> additional investigation to further evaluate the extent of the identified impacts in groundwater. <br /> Additionally, Partner's Additional Subsurface Investigation, recommended regulatory agency <br /> interaction to evaluate the required next steps. The scope and laboratory results from the Phase <br /> II and Additional Subsurface Investigation are summarized on Tables 1 through 6. <br /> Additional Site Assessment Work Plan <br /> Heliostockton Property <br /> 434 Dr.Martin Luther King Jr. Boulevard <br /> Stockton,California <br /> Partner Project Number SM17-191672 <br /> RWQCB Case#:392004 <br /> January 9,2018 <br /> Page 5 <br />