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SECOR vV,vw.Sec0r.00m <br /> INTERNATIONAL <br /> S E C O R <br /> INCORPORATED 3017 Kilgore Road,Suite 100 <br /> Rancho Cordova,CA 95670 <br /> 916-861-0400 TEL <br /> 916-861-0430 Fn <br /> May 2, 2005 <br /> Ms. Margaret Lagorio <br /> San Joaquin County Public Health Services <br /> Environmental Health Division <br /> 304 E Weber Street, Third Floor <br /> Stockton, California 95202-2708 <br /> RE: Interim Remedial Action Plan — Revised Plan <br /> Joe's Truck Plaza, 15600 South Harlan Road, Lathrop, California <br /> Dear Ms. Lagorio: <br /> On 2 February 2005, Stratus Environmental submitted an Interim Remedial Action Plan <br /> ([RAP) to initiate remedial activities at Joe's Truck Plaza (Site), located at 15600 South <br /> Harlan Road in Lathrop, California (Figures 1 and 2). In a response letter dated 16 March <br /> 2005, the San Joaquin County Environmental Health Department (SJCEHD) rejected the <br /> Stratus TRAP. SECOR International Incorporated (SECOR)was subsequently retained by <br /> Joe's Truck Plaza to assume responsibility for investigation and remediation at the Site. As <br /> requested in your response letter dated 16 March 2005, SECOR presents, on behalf of Mr. <br /> Dalwinder Dhoot of Joe's Truck Plaza, this revised IRAP with an improved study design that <br /> is responsive to your expressed concerns. <br /> Site Background <br /> The Site is an active service station located south of J Street along Harlan Road in Lathrop, <br /> California. The current station configuration consists of four dispenser islands for <br /> automobiles; seven dispenser islands for large trucks; four 10,000 gallon above ground <br /> storage tanks storing diesel fuel; one 4,000 gallon underground storage tank (UST)storing <br /> diesel fuel; and three USTs storing gasoline at 12,000, 10,000, and 4,000 gallon capacities. <br /> Soils beneath the Site consist of fine grained material with laterally extensive sand strata <br /> which do not appear to be strtig <br /> araphically connected. Sand A, located at 5 to 8 feet bgs is ti <br /> the most shallow sand layer and 3 to 10 feet-d p. Sand B, located between 25-35 feet <br /> bgs is between 7 to 18 feet thick. Sand C, to tca ed between 50 and 65 feet bgs, is between `F <br /> 15 to 25 feet thick. Groundwater is present in each of the three sand layers. MWO-1X is <br /> screened in Sand B; according to Stratus all other wells are screened in Sand A. <br /> Methyl-tert butyl ether(MTBE), dissolved in groundwater, is the primary chemical of <br /> concern at the Site. MTBE concentrations in the fourth quarter 2004 were 420 ug/L (MW- <br /> 2), 700 ug/L (MW-3), and 440 ug/L (MWO-1X). MTBE is migrating off-site along the <br /> groundwater gradient to the northeast; the lateral extent of MTBE in Sand A has not been <br /> adequately characterized. Likewise, MTBE was detected in MWO-1X, the only well <br /> screened in Sand B. Stratus states in their IRAP (2/2/05)that MTBE concentrations in <br /> Sand B are well characterized based on a grab groundwater sample from CPT-3 that <br /> yielded a "relatively low" MTBE concentration, "suggesting that the surrounding silty stratum <br /> may have laterally restricted the impact reported in well MWO-1X." <br /> JTP_IRAP_V01.docc:\Documents and Settings\tsax\My Documents\05-04\Joe's Truck Stop\IRAP\JTP_IRAP_V01.doc <br />