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PUBLIC HEALTH SERVICES <br /> SAN JOAQUIN COUNTY <br /> ENVIRONMENTAL HEALTH DIVISION <br /> Karen Furst, M.D ., M.P.H., Health Officer <br /> 304 East Weber Avenue, Third Floor • Stockton, CA 95202 qc FonN` <br /> 209/468-3420 /J <br /> ROGER LISTON COPY <br /> DARPETRO INC <br /> 3450 EL CAMINO AVE JAN 10 2000 <br /> CERES CA 95206 <br /> RE : Darpetro Exxon <br /> 749 E Charter Way <br /> Stockton CA 95206 <br /> San Joaquin County Public Health Services Environmental Health Division (PHS/EHD) <br /> has reviewed the Drilling Activity Report dated August 5 , 1999 and the Quarterly <br /> Monitoring Report (QMR) dated November 23 , 1999 prepared by California Geophysical <br /> Group, Inc. These reports evidence continued contamination in groundwater and soil at <br /> this site. The vertical extent of contamination at this site has not been determined. <br /> Further investigative and remediation work is necessary . <br /> PHS/EHD has also reviewed the letters from Darpetro dated August 31 , 1999 and <br /> December 6, 1999. These letters express concerns that contamination from the ARCO <br /> site east of Darpetro is migrating and being remediated by the Soil Vapor Extraction <br /> System (SVES) at the Darpetro site. Monitoring Well (MW) BM9 is located on property <br /> adjacent to the western edge of the Darpetro property . Contaminant concentrations in <br /> groundwater from MW BM9 are higher than in MW BM7. BM7 is located between <br /> BM9 and the source area MWs at the Darpetro site . The radius of influence of Vapor <br /> Extraction Well (VW) 6 shown in the Drilling Report does not encompass the BM7 <br /> location. <br /> Additionally, groundwater samples from MWs BM1 and BM5 (located where Darpetro ' s <br /> underground storage tanks previously existed) have shown and continue to show high <br /> contaminant concentrations in groundwater. Soil samples collected from boring BMl in <br /> March 1992 evidenced contamination to 50 feet bsg. It would appear from this data that <br /> the SVES is addressing the Darpetro site contamination. <br /> Soil sample results from the installation of Vapor Well (VW)7 on July 16, 1999 indicate <br /> contamination in the soil at 80 feet below surface grade (bsg) . Since soil sample analysis <br /> below 80 feet has not been done, the vertical extent of contamination has not been <br /> determined at this site. Boring and sampling should continue below 80 feet, at minimum, <br /> to a depth where two consecutive soil samples collected at five foot intervals indicate by <br /> field screening, equipment readings, and personal observations that the soil sample <br /> analysis results should be non detectable. <br /> A Division of San Joaquin County Health Care Services <br />