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West Clay Properties - 4 - April 2012 <br /> • Groundwater Trends: There are more than ten years of groundwater monitoring data for <br /> this Site. Benzene trends are shown below, source area (MW-1) <br /> BENZENE Results for MW1 <br /> 9000 <br /> "000 <br /> 7000 <br /> 6000 <br /> 6000 <br /> 4000 // �—_ / 'j/S♦ <br /> 3000 a {... +. ..++1`{.•1+/ <br /> 2000 <br /> 1000 <br /> O <br /> BF_NZENE Trend <br /> Risk Evaluation <br /> There are no CDPH regulated water supply wells or surface water receptors present within 1/2 <br /> mile of the Site. Drinking water at and near the Site is currently supplied by the California Water <br /> Services. <br /> Recommendation <br /> In May 2008, the Fund concurs with the San Joaquin County LOP that the existing ozone <br /> sparging system should be expanded to achieve Water Quality Objectives more rapidly. The <br /> Fund will review this site next year to track progress. <br /> UPDATED, May 2009, the Fund recommends that the groundwater treatment system be <br /> modified as necessary to achieve Water Quality Objectives in a timely manner. The Fund will <br /> review this site nest year to track progress. <br /> UPDATED, May 2010, this investigation has been underway for 21 years. By the15 April 2010 <br /> letter, the San Joaquin County LOP extended the deadline for the remediation work plan. The <br /> Fund recommends that future efforts are focused on active remediation to achieve Water <br /> Quality Objectives in a timely manner. The Fund will review this site next year to track progress. <br /> UPDATED, April 2011. the Fund concurs with the San Joaquin County LOP that the <br /> Responsible Party should assess vapor migration east on MW-1. <br /> UPDATED, April 2012, the Fund recommends that the San Joaquin County LOP direct the <br /> Responsible Party to discontinue monitoring of un-impacted monitoring wells and to continue <br /> oxygen sparging to achieve water quality objectives in a timely manner. <br /> Kirk arson, P.G. Date Robert Trommer, C.H.G. Date <br /> Engineering Geologist Senior Engineering Geologist <br /> Technical Review Unit Chief, Technical Review Unit <br /> (916) 341-5663 (916) 341-5684 <br />