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H 'SPUBLIC HEALTSERVICV <br /> SAN JOAQUIN COUNTY Q <br /> ENVIRONMENTAL HEALTH DIVISION N' - ` . <br /> Karen Furst, M.D., M.P.H., Health Officer .. ;P <br /> 4Ll�O.�ti <br /> 304 East Weber Avenue, Third Floor • Stockton, CA 95202 <br /> 2091468-3420 <br /> BP OIL COMPANY O <br /> SCOTT HOOTON <br /> 295 SW 41 ST, BLVD 13, STE N <br /> RENTON WA 98055 JAN 11 2000 <br /> Re: BP Oil 9 11193 Site Code: 1129 <br /> 3202 W. Hammer Ln. <br /> Stockton,CA 95209 <br /> San Joaquin County Public Health Services Environmental Health Division (PHS/EHD)has reviewed the <br /> Surface Water and Water Well Survey and CPT Investigative Report(Report) dated December 17, 1999 <br /> prepared by Cambria Environmental Technology,Inc.,and the Fourth Quarter 1999 Groundwater <br /> Monitoring Report dated December 1, 1999 prepared by Blaine Tech for the above referenced site. <br /> Groundwater and soil samples collected at this site continue to evidence contamination. Contamination <br /> appears to be migrating off-site. Further investigative work will be necessary to define the vertical and <br /> lateral extent of contamination; measures should be implemented at this site as soon as possible to prevent <br /> further off-site migration of groundwater contaminants. <br /> The deepest soil sample collected in the contaminant source area was in Cone Penetrometry(CPT)CB43. <br /> This sample evidenced 27 parts per million(ppm)gasoline range organics,28 ppm Methyl tert-butyl ether . <br /> (MTBE)and ,058 ppm Tert-amyl methyl ether(TAME) 13.5 feet below surface grade(bsg). Soil samples <br /> should be collected in this area and analyzed at a depth necessary to provide conclusive data for the vertical <br /> extent of contamination. <br /> Groundwater samples collected on October 14, 1999 from all the Monitoring Wells(MWs)for this site <br /> evidenced MTBE contamination. In January and October 1999, MTBE was detected in the groundwater <br /> samples from MW4 and MW7 where the contaminant had not been previously detected. MTBE <br /> contamination appears to be moving off-site. Measures to be taken to prevent further migration of MTBE <br /> should be proposed to PHS/EHD and lateral definition of the contaminant plume should be determined. <br /> The groundwater sample collected at 34 feet bsg in CB43 evidenced 3400 parts per billion (ppb)MTBE. <br /> The deepest existing Monitoring Well (MW)screens extend to 32 feet bsg. Therefore,contaminant levels <br /> of groundwater deeper than 32 feet bsg,that are contaminated are not being monitored and the vertical <br /> extent of the contamination has not been determined in the source area. Groundwater MWs should be <br /> installed that will show the vertical extent of the groundwater contamination. Once the vertical extent of <br /> contamination is shown in the source area,the lateral extent should be determined at least to the depth <br /> shown in the source area. <br /> The Report indicates that MW2 was damaged during tank replacement activities. This MW should be <br /> destroyed under PHS/EHD permit. PHS/EHD agrees with the proposal in the Recommendations section of <br /> the Report to replace MWI and MW2 with groundwater extraction wells. The well destruction permit <br /> application fee is$60.00 and the replacement well permit application fee is$89.00. PHS/EHD <br /> recommends the installation of additional MWs to define the contaminant plume. <br /> The Report states that historic groundwater gradient flow direction has varied since 1992 from <br /> northeasterly to southeasterly at the site. Contaminants were evidenced in all MWs,significantly in MW7 <br /> directly north of the site and in MWs 3 and 4,which are respectively northwest and southwest of the source <br /> area. Lateral definition of groundwater contaminants in all directions from the site is necessary. <br /> A Division of San Joaquin County Health Care Services <br />