SITE INFORMATION AND CORRESPONDENCE FILE 2

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Shell -4- March 29, 2012 BENZENE Results for MW-4 1.4- 1.2-.4 _.,2 --- ....._.....-___.,..�._. _.._F. _ 0.4 0.2.._Y. BENZENE 4aw Trend BENZENE Results for MW-5 o,e 0.4 - r --- - - CD __ ..._..._.�E Rr� • m �. .,,_.,.>,� a�` �► ,�" JAI e 4BENZENE —Trend Risk Evaluation f There are no water supply wells or surface water receptors present within Y2 mile of the Site. Drinking water.at and near the Site is currently supplied by the California Water Company. Recommendation In March 2008, the Fund recommends that the San Joaquin County LOP direct the Responsible Party to monitor newly installed monitoring wells for a full hydrologic cycle prior to assessing the need to conduct active remediation on the deeper zones (50+feet). The Fund will review this site next year to track progress. UPDATED, March 2009, the Fund recommends that the San Joaquin County LOP direct the Responsible Party to assess remedial technologies that can reduce the mass of fuel hydrocarbons in the deeper zones. The Fund will review this site next year to track progress. UPDATED, March 2010, this site has been under investigation for 20 years and no active remediation has been conducted since 1996. The Fund recommends this site be considered for closure. UPDATED, March 2011, the mass of remaining residual petroleum hydrocarbons is adsorbed to fine grain soil and dissolved petroleum hydrocarbons are degrading. One monitoring well (MW-15-50) screened in this area has consistently had elevated concentrations of residual hydrocarbons in groundwater. However, after 21 years of monitoring, the groundwater plume is largely limited to the UST basin. Analytical data indicate that WQOs have been achieved in down gradient of the source area. Groundwater within the source area will likely remain above WQOs for decades to hundreds of years. The Fund recommends that the San Joaquin County. LOP review this site for closure.