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ENVIRONMENTAL HEALTH DEPARTMENT <br /> SAN JOAQUIN COUNTY <br /> G <br /> 2.. ��� Z Unit Supervisors <br /> Q. Donna K.Heran,R.E.H.S. Carl Bor man,R.E.H.S. <br /> Director 304 East Weber Avenue, Third Floor Borg <br /> man, <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 /> CqC,OR��P Program Manager Telephone: (209) 468-3420 Margaret Lagorio,R.E.H.S. <br /> Laurie A.Cotulla,R.E.H.S. Fax: (209) 464-0138 Robert McClellon,R.E.H.S. <br /> Program Manager Mark Bareellos,R.E.H.S. <br /> KAREN PETRYNA MAR 2, 2 2004 <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 Site <br /> Investigation Report dated February 27, 2004, prepared by Cambria Environmental <br /> Technologies, Inc. and comments as follows. <br /> The report covers the installation of five (5) Cone Penetration Test (CPT) borings on site <br /> during August 2003. Both soil and ground water samples were collected and analyzed. <br /> Conclusions and recommendations were included in the report and EHD was asked to <br /> concur on the recommendation to install one deeper monitoring well in the area of CPT-4. <br /> Grab ground water samples collected from three sand units generally occurring between <br /> 40' and 45' feet below surface grade (`bsg), 68' and 75' bsg, and 91.5' and 97' bsg were <br /> impacted by petroleum hydrocarbons. These sand units occur below the shallow <br /> monitoring wells currently utilized for monitoring the plume of impacted ground water on <br /> the site. <br /> Based on some similarity of contaminant concentrations found at depth, Cambria interprets <br /> the analytical data to indicate that cross-contamination during drilling or sampling occurred <br /> and proposes to install only one well to monitor the sand interval at approximately 40' to 45' <br /> bsg for impacted ground water. While the similarity on some analyte concentrations are <br /> striking, EHD considers the laboratory data to also be interpretable to indicate that <br /> petroleum hydrocarbons have impacted the deeper soil and water bearing zones. <br /> Contaminant concentrations in CPT-5 samples decline with depth; samples from CPT-3, <br /> CPT-5 and CPT-7 had no detectable BTEX compounds, while CPT-4 and CPT-6 samples <br /> did. One CPT-6 sample contained the only detectable 1,2-dichloroethane. <br /> In addition, the analytical data for the CPT-1 and CPT-2 grab ground water samples <br /> collected in 1998, show loss of contaminant concentrations with increasing depth in CPT-2 <br /> with concentrations similar to the trends exhibited by the current data. The CPT-2 data is <br /> not too dissimilar to the CPT-4 data; note both have similar BTEX concentrations at depth. <br /> FILE COPY <br />