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ENVIRONMENTAL HEALTH DEPARTMENT <br /> PQM," SAN JOAQUIN COUNTY <br /> Unit Supervisors <br /> 2 Donna K.Heran,R.E.H.S. <br /> 304 East Weber Avenue, Third Floor Carl Borgman,R.E.H.S. <br /> Director <br /> 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 /> C4�/FpR�;PProgram Manager Telephone: (209) 468-3420 Margaret Lagorio,R.E.H.S. <br /> Laurie A.Cotulla,R.E.H.S. <br /> Program Manager Fax: (209) 464-0138 Robert McClellon,R.E.H.S. <br /> Mark Barcellos,R.E.H.S. <br /> KAREN PETRYNA SEP 2 0 2002 <br /> SHELL OIL PRODUCTS USA <br /> PO BOX 7869 <br /> BURBANK CA 91510-7869 <br /> RE: Former Shell Service Station Site Code:505602 <br /> 1267 Country Club Blvd. RO#: 0000062 <br /> Stockton, CA., 95204 <br /> San Joaquin County Environmental Health Department (EHD) has reviewed Groundwater <br /> Monitoring Report— Second Quarter 2002 dated July 22, 2002, prepared by Cambria <br /> Environmental Technologies, Inc. and has reviewed site data and numerous letters to and <br /> from SHELL and/or SHELL's consultant and comments as follows. <br /> EHD has concluded that this site is still not adequately characterized for preparation and <br /> submission of an end-of-investigation report that will: <br /> • Clearly delineate the lateral and vertical extent of soil and groundwater <br /> contamination; <br /> • Quantify the mass of the petroleum contamination remaining at the site; <br /> • Predict the fate/transport characteristics of the contaminant mass; or <br /> • Identify and demonstrate the mechanisms in the subsurface that control 'natural <br /> attenuation' of the contamination on the site as SHELL has indicated is occurring. <br /> Two Cone Penetrometer Testing (CPT) borings (CPT-1 and CPT-2) were advanced in <br /> February 1998 as an attempt to vertically define the soil and groundwater impact at this <br /> site. Laboratory data from soil samples collected approximately 40, 50, and 60 feet below <br /> ground surface (` bgs) did not encounter significant adsorbed petroleum concentrations in <br /> the soil. <br /> Laboratory analyses of the grab-groundwater samples from CPT-2, located adjacent to and <br /> just down gradient to the known underground storage tank (UST) location, from 40' and 60' <br /> bgs indicate that petroleum hydrocarbon concentrations exceeding allowable limits were <br /> present. Grab-groundwater samples from CPT-1 were somewhat less contaminated than <br /> CPT-2 samples for the sampling points collected (40', 50', and 60' bgs). The CPT logs <br /> indicate that these grab water samples were collected from fine-grained soil, ranging from <br /> silty clay to silt, lithologies not expected to be significant fluid migration pathways. The CPT <br /> logs also indicate that a sand body occurring roughly between 41 and 47 feet bsg was <br /> present in both borings, which were more than 80 feet apart. Curiously, grab ground water <br /> ­.,- Ir C ,.,oro r,r,t rnllcrrtori frnm this canri a nntantially sianificant fluid migration pathway. <br />