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ENVIRONMENTAL HEALTH DEPARTMENT <br /> Pp U.�N SAN JOAQUIN COUNTY <br /> �O._��.•.CSG Unit S//pervdSOYS <br /> R <br /> ran <br /> Donna K.He ,R.E.H.S. Carl Borgman,R.E.H.S. <br /> 304 East Weber Avenue, Third Floor <br /> mr Director Mike Huggins,R.E.H.S.,R.D.I. <br /> Al Olsen,R.E.H.S. Stockton, California 95202-2708 Douglas W.Wilson,R.E.H.S. <br /> Program ManagerTelephone: (209) 468-3420 Margaret Lagorio,R.E.H.S. <br /> q�iFo - Laurie A.Cotulla,R.E.H.S. Robert McClellon,R.E.H.S. <br /> Program Manager Fax: (209) 464-0138 Mark Bareellos,R.E.H.S. <br /> KAREN PETRYNA JUN 14 2004 <br /> SHELL OIL PRODUCTS USA <br /> 20945 S WILMINGTON AVE <br /> CARSON CA 90810 <br /> RE: Former Shell Service Station Site Code:505602 <br /> 1267 Country Club Blvd. RO#: 0000062 <br /> Stockton, CA., 95204 Clean Up Fund#: 018070 <br /> San Joaquin County Environmental Health Department (EHD) has reviewed Response <br /> Letter/Site Investigation Work Plan dated April 30, 2004, prepared by Cambria <br /> Environmental Technologies, Inc. and comments as follows. <br /> Two concerns were included in the Letter/Work Plan: EHD's directives to continue <br /> investigating the waste oil UST release and, Shell's 'phased' approach to investigating the <br /> vertical extent of the gasoline/diesel UST release. <br /> With regards to the waste oil investigation, EHD has again reviewed the data and details <br /> the following concerns. <br /> • Soil boring "SB-2", 20 feet north and down-gradient of the former waste oil UST had <br /> ground water samples that were impacted by metals associated with waste oil UST <br /> chemicals above maximum contaminant levels (MCL) as well as for solvents. <br /> Chromium at 1.1 mg/I and nickel at 1.2 mg/I both exceed the maximum contaminant <br /> levels (MCL) of 0.05 mg/I and 0.1 mg/I, respectively. TPH-d at 25,000 ug/I, <br /> 2-Methylnapthalene at 390 ug/I, and naphthalene at 350 ug/I were also present. <br /> 1,2-DCA was detected at 51 ug/l, which also exceeds the MCL of 0.5 ug/I. <br /> • Shell's argument for no further waste oil investigation is partially based on the <br /> ground water samples from monitoring well "S-3". S-3 is located 20 feet northwest <br /> of the former waste oil UST, in a lateral/cross-gradient direction. In Shell's site <br /> conceptual model (SCM), Shell stated that the predominant ground water flow <br /> direction was north to northeast. Therefore, the detectable ground water <br /> concentrations of nickel and zinc, even below the MCL, in S-3 is of concern and <br /> additional investigation is warranted. <br /> • In EHD's March 22, 2004 correspondence/work plan comment letter, Shell was <br /> advised to analyze the ground water samples from the pending and approved CPT <br /> boring in the 'down-gradient' area of the waste oil UST area for the same <br /> constituents detected in SB-2 to confirm and possibly delineate this area. CPT-6 <br /> was placed —40 feet north-northeast of the former waste oil UST yet the ground <br /> water sample was NOT analyzed for those constituents. <br />