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ENVIRONMENTAL HEALTH I) EPARTMENT <br /> SAN JOAQUIN COUNTY <br /> Unit Supervisors <br /> Donna K. Heran, R.E.H.S. 304 EaSt Weber Avenue, Third Floor Carl Borgman, R.E.H.S. <br /> c < <br /> m !},,,III t �:� Orrector Mike Huggins, R.E.H.S., R.D.I. <br /> LPSCI ryAt Olsen, R.E.H.S, Stockton, California 95202-2708 Douglas W. Wilson, R.E.H.S. <br /> Program Manger Telephone : (209) 468-3420 Margaret Lagono, R.E.H.S. <br /> < i Fo R `' Laurie A. Corolla, R.E.H.S. FaX: (209) 464-0138 Robert McClellon,. R.E.H.S. <br /> Program Manager Mark Barcellos, R.E.H.S. <br /> 'JUL 0 6 2004 <br /> RODGER LISTON <br /> DARPETRO INC USA SERVICE STATION <br /> 3450 EL CAMINO <br /> CERES CA 95307 <br /> RE : DARPETRO, INC Site Code: 1060 <br /> 749 E CHARTER WAY <br /> STOCKTON, CA 95202 <br /> San Joaquin County Environmental Health Department (EHD) has received and <br /> reviewed : <br /> • Amended Quarterly Report October 2003, dated 25 October 2003, received by <br /> EHD on 01 June 2004; <br /> • Revised Work Plan (WP-Soil Gas) , dated 07 May 2004, which revises work plans <br /> dated 07 May 2004, 06 January 2003 and 04 October 2001 , all proposing <br /> variations of a soil gas survey to identify potential sources of the methyl tert-butyl <br /> ether (MTBE) plume; and <br /> Work Plan (WP) , dated 19 May 2004, to complete the vertical and lateral <br /> assessment of impacted ground water. <br /> All three documents were prepared by California Geophysical Group , Inc. (CGG) in <br /> response to EHD directives issued by letter dated 13 April 2004 . <br /> The amended quarterly report more accurately reflects the circumstances under which <br /> ground water samples were collected during the fourth quarter of 2003 and is accepted <br /> by EHD. <br /> The WP-Soil Gas proposes to collect soil gas samples from nine push-point borings <br /> around the new underground storage tank (UST) pit and around the dispenser islands . <br /> CGG proposes to collect two soil gas samples from each probe boring , the first at <br /> relatively shallow depth to assess for releases from various components of the UST <br /> system and deeper depths to assess for degassing from migrating impacted ground <br /> water. EHD notes that MTBE has a low partition coefficient and is unlikely to degas from <br /> impacted ground water in detectable and interpretable quantities , but the volatile <br /> hydrocarbons might. Five probe borings were proposed around the UST pit with shallow <br /> samples to be collected between 13 and 17 feet below surface grade (bsg) and deeper <br /> samples to be collected between 25 and 29 feet bsg . Four probe borings were proposed <br /> for around the western dispenser island with shallow samples to be collected between 5 <br /> and 9 feet bsg and deeper samples to be collected between 20 and 24 feet bsg . <br />