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1,2-Dichloroethene (0.5 and 1.6 µg11) are below the State MCL of 6.0 A.gll for that compound. • Potential offsite sources for the benzene in monitoring well MW 1 are the former Shell gasoline station to the southwest and the Arco gasoline station to the west. ' Because of the documented changes in the groundwater flow direction and the observed wide variation of soil types horizontally and vertically, it is possible that the benzene contamination in the groundwater from either or both of the potential ' offsite sources followed narrow, restricted aquifers or permeable sand layers in the direction of well MW 1. The low benzene contamination detected in well MW2 may be at the edge of the plume from the contamination emanating from ' the former Shell station. 9.0 CONCLUSIONS ' The Phase 1I Environmental Assessment and Subsurface Investigation conducted at the Lighthouse Village school building at 222 North EI Dorado in Stockton indicated that ' there is TPH as motor oil is present in soil in one boring (113) at 10 feet bgs and TPH as motor oil and diesel in another boring (136) at 5 feet bgs. Trace levels of TPH detected in the groundwater do not pose a threat to groundwater. Benzene was detected in the groundwater in two (2) monitoring wells (MW1 and MW2) at levels that exceed the State MCL for that compound. However, benzene was not detected in soil on the subject property, and therefore, the subject property is not a likely source of the benzene found in the groundwater. Potential offsite sources for the benzene in monitoring well MW 1 are the former Shell ' gasoline station to the southwest and the Arco gasoline station to the west. Because of documented changes in the groundwater flow direction and observed wide variation of soil types horizontally and vertically, it is possible that the benzene contamination in the groundwater from either or both of the potential offsite sources followed narsQw, restricted a uifers int irection of well MW 1. The low benzene contamination detected in well MW2 may be at the edge of the plume from the contamination emanating from the former Shell station. ' 10.0 RECOMMENDATIONS Based on the results of the Phase II Environmental Assessment, CRC recommends that additional sampling of the groundwater be conducted in order to monitor changes in the levels of benzene detected and to prepare for eventual closure. CRC further recommends that a copy of this report be submitted to the San Joaquin County Environmental Health ' Services for review and comment. CRC also recommends that the status of remedial action on the two (2) LUST sites in the immediate area be monitored. 1 CRC Environmental Risk Management,Inc. Project N 2100-250-2 American Savings Bank 222 North EI Dorado Street November 3, 1995 Stockton,California 14