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w� <br /> 3468 Mt.Diablo Boulevard <br /> EA Engineering,Science,and Tec nology Suite 3-100 <br /> �, f I Lafayette,CA 94549 <br /> ;"r''< p7 ,r raw Telephone: 510-283 7077 <br /> Fax: 510-283-3894 <br /> s'I FEB —1 PM III '6 <br /> ® 4 February 1997 <br /> Mr. Michael Infurna, Jr. <br /> Senior RENS, LOPISite Mitigation Unit IV <br /> San Joaquin County Environmental Health Services <br /> 304 E. Weber Avenue, Third Floor <br /> P.O. Box 388 <br /> Stockton, California 95201-0388 <br /> Subject: Exxon RAS #7-0137, San Joaquin County Site Code: 1962 <br /> 1605 South El Dorado Street, Stockton, California <br /> Dear Mr. Infurna: <br /> This letter addresses the issues raised by the San Joaquin County Public Health Services, <br /> Environmental Health Division in a letter dated 16 January 1997. The following issues regarding <br /> the subject site are discussed: <br /> 1) Missing third quarter 1996 quarterly monitoring report, <br /> 2) Groundwater contour maps, flow direction, and gradient required on all future quarterly <br /> reports, <br /> 3) Requested report presenting soil vapor extraction system data for the period ending <br /> February 1996, <br /> 4) Recommended well survey and utility/trench/subsurface conduit survey, and <br /> 5) A comparison of monitoring well construction details and groundwater table elevations, <br /> and the implications these data may have on the inferred groundwater flow direction and <br /> analytical results on hydrocarbon concentrations. <br /> Below I have presented actions recommended by EA for each of the five issues: <br /> le'? <br /> 1) On 16 July 1997 EA Engineering, Science, and Technology sampled groundwater from <br /> monitoring wells MW-1 through MW-7, and vapor extraction wells VEW-1 and VEW-2. <br /> However, due to our apparent oversight, a quarterly report was not prepared. Preparation <br /> of that report is now in progress and will be submitted to Exxon by 14 February 1997. <br /> 2) Every attempt will be made to provide groundwater maps with contours of equal potential <br /> displayed on all future quarterly reports. Groundwater elevation data collected during the <br /> second and fourth quarters were inconsistent across the site making contouring <br /> meaningless. A review of well construction reports (issue 5) and soil boring logs may <br /> identify well data that should be excluded from groundwater table elevation contour map <br /> preparation. <br />