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- Messrs. Larson and Trommer May 16, 2011 <br /> Former Chevron Station #9-0557 CUF Claim Number 5820 <br /> 139 Center Street S, Stockton, CA Page 2 of 2 <br /> TPHg and DTW <br /> 100000 0 <br /> 5 <br /> 10000 10 <br /> 15 <br /> a <br /> CL 1000 <br /> 20 --a-MW-1 TPHg <br /> U MW-15 TPHg <br /> o • 25 --x-MW-15D TPHg <br /> c <br /> x MW-18D2 TPHg <br /> c 100 30 <br /> �-DTW Feet <br /> 0 <br /> 35 <br /> 10 - 40 <br /> 45 <br /> 1 50 <br /> 0^ pblt, p�^J 5?D p�h go 5b% p�I. 01' p4 p� pl 03 4 & OO O� O� <br /> \^� \`� \^� \�� \^9 \^� \L� \L� \yam \VO \Lo \Lo \`Lo \Lo \Po \'o \LO <br /> Sampling Dates <br /> The right side vertical scale is depth to water(DTW) in feet. The EHD interprets this graph to show <br /> that the TPHg concentrations in monitoring well MW-1, located cross-gradient from the source <br /> area, decreased while groundwater elevation increased well above the well's screened interval. <br /> The limited soil data from MW-1 suggests that soil is not intensely impacted in that area. The <br /> concentrations in MW-15D are intense despite the rise of groundwater as the soil in that area is <br /> intensely impacted across the screened interval (see soil data for MW-9 and SB-4). <br /> It appears to the EHD that some remediation of the impacted soil will greatly reduce the time <br /> required to achieve WQOs. As described in the EHD letter of 06 May 2010, the EHD believes the <br /> feasibility tests reported in Feasibility Tests, dated 09 September 2009, may not have been <br /> properly designed, so the negative results reported may not accurately apply to the site. The <br /> results and potential benefits of the techniques should be reevaluated. <br /> As it is very difficult to get work done on a site once the CUF recommends that the site be closed, <br /> the. EHD requests you to reconsider or delay your closure recommendation while the EHD <br /> addresses the issues noted above. Questions or comments should be directed to Vicki McCartney <br /> at (209) 468-9852 or to Nuel Henderson at(209) 468-3436. <br /> Sincerely, <br /> `�✓�Z� Cx - <br /> Victoria L. McCartney, REHS Nuel Henderson, PG <br /> Senior Registered Environmental Engineering Geologist <br /> Health Specialist <br /> 5-Year Review Letter Response 0511.doc <br />