SITE INFORMATION AND CORRESPONDENCE FILE 2

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I ENVIRONMENTAL HEALTH DEPARTMENT pP¢uIN " C SAN JOAQUIN COUNTY Unit Supervisors Donna K. Heran, R.E.H.S. 304 EBSY. Weber Avenue, Third Floor Carl Borgman, R.E.H.S. w`i < Director Mike Huggins, R.E.H.S., R.D.I. 1_L4C'ld.. Al Olsen, R.E.H.S. Stockton, California 95202-2708 Douglas W. Wilson,. R.E.H.S. • Program Manager Telephone: (209) 468-3420 Margaret Lagorio, R.E.H.S. geiFOR`' Laurie A. Cotulla, R.E.H.S. Fax: (209) 464-0138 Robert McClellan, R.E.H.S. Program Manager Mark Barcellos, R.E.113 . RODGER LISTON SEP 0 5 2003 DARPETRO INC USA SERVICE STATION 3450 EL CAMINO CERES CA 95307 RE : DARPETRO, INC Site Code: 1060 749 E CHARTER WAY STOCKTON, CA 95206 San Joaquin County Environmental Health Department (EHD) has reviewed Site Concept Model (SCM ), dated 07 May 2003 , prepared by California Geophysical Group , Inc. (CGG ) on your behalf. The SCM was received by EHD on 14 May 2003 . EHD also has discussed the SCM with Mr. James Barton of the Central Valley Regional Water Quality Control Board (CVRWQCB ). CGG contacted EHD on 15 August 2003 requesting a return call on 19 August 2003 to discuss the site . During the 19 August 2003 call , CGG requested a response to the SCM and noted that a quarterly monitoring report was being submitted that requests site closure. Quarterly Report April 2003 , dated 23 July 2003 , was received by this office on 03 September 2003 . CGG requested site closure because "The contamination from this site is THP and chemicals related to gasoline, but there is no MtBE or other oxygenates related to tanks on this property. " It is the opinion of EHD that the SCM , as presented , does not adequately demonstrate the professional interpretations and opinions advanced by CGG in the SCM and that site closure would not be appropriate at this time . The _basis for the site closure request presented in the quarterly report has not been demonstrated and the implied notion that contamination by only TPH and chemicals related to gasoline warrants site closure is erroneous . The SCM lists the historical stages of the site investigation , references the reports containing the results and data of the various investigations , but does not note the significant findings of each stage of investigation or specific data to demonstrate the interpretations that follow. As part of the review of the SCM , EHD had to also review various reports dating back to 1989 for pertinent data . The section titled ' Geology' describes the upper 70 feet or so of soil types (lithology) underlying the site as 19 to 22 feet of silty clay and clayey silt underlain by 3 to 5 feet of silty sand , underlain by 23 to 25 feet of silty clay, which overlies approximately 20 feet of silty sand , which is underlain by clay of unknown thickness . The contaminant distribution encountered in the borings advanced on the site was discussed in very general terms . There was no