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ENVIRO'I'VMENTAL REALM DEPARTMENT <br /> 'o pa UiN .C� <br /> Donna K. Reran, R.R.H.S. SAN JOAQUIN COUNTY <br /> Director Floor 304 East Weber Avenue,Third Flri a.s <br /> ., Carl <br /> Borgman,man,R.E.H.S. <br /> AI Olsen, R.E.H.S. Stockton, California 95202-2708 Mike Huggins, R.E.H.S., R.D.I. <br /> cq �P Program Manager Telephone: (209)468-3420 Douglas W. Wilson, R.E.H.S. <br /> 4Fon`' Laurie A. Cotulla, R.E.H.S. Margaret Lagorio,R.E.H.S. <br /> Program Manager Fax: (209)464-0138 Robert McClellon, R.E.H.S. <br /> FILE <br /> +��s�. WwW.SjgOV.org/ehd/ Jeff Carruesco, R.E.H.S. <br /> C JUL 2 7 2005 <br /> EDWARD RALSTON HARDEV & AMARJIT KHINDA ETAL <br /> CONOCOPHILLIPS 27000 S LEEWARD <br /> 76 BROADWAY TRACY 3 <br /> SACRAMENTO CA 95812 D <br /> LT <br /> RE: Circle K / TOSCO-Service Station #1205 SITE CODE: 507198 <br /> 16470 Cambridge Drive. RO#:0000138 <br /> Lathrop, CA., 95330 <br /> San Joaquin County Environmental Health Department (EHD) has reviewed <br /> Results of Additional Site Assessment and Site Conceptual Model (SCM) dated <br /> July 5, 2005 as submitted by Secor International Inc., and has the following <br /> comments. <br /> The SCM included a comprehensive summary of all soil and ground water <br /> analytical data from the underground storage tank (UST) removal in November <br /> 1997 to the most recent subsurface investigation, offsite MW-17, 18, and 19 <br /> installations in February 2005. Conclusions included in the SCM stated the soil <br /> lateral and vertical extents were defined and the lateral extent of the petroleum <br /> ground water plume was defined, leaving only the vertical extent of the ground <br /> water plume undefined. Recommendations included in the SCM stated that the <br /> vertical extent of the ground water petroleum plume should be investigated <br /> further and that deep ground water monitoring wells should be installed. EHD <br /> concurs with the conclusions and recommendations in the SCM and that deep <br /> monitoring wells should be installed. <br /> Please submit a work plan to install at least two monitoring wells with short <br /> screened intervals at depths where previous push points (DGP-1 and DGP-2) <br /> have identified elevated levels of petroleum are present. The work plan is to <br /> be submitted by September 30, 2005. The report of findings for this phase <br /> shall be submitted in the format of an updated SCM. <br /> Once the petroleum plume has been vertically and laterally delineated, a <br /> Corrective Action Plan (CAP) that includes a Feasibility Study should be <br /> submitted to EHD that evaluates at least two remedial alternatives that could <br /> return the groundwater to 'pre-release' conditions. The CAP should include the <br /> 'chosen' alternative that your consultant has determined to be the most cost- <br /> effective and feasible for site-specific conditions. <br />