Laserfiche WebLink
r . <br /> 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 9520 <br /> 209/468-3420 hLE COPY <br /> ROGER LISTON <br /> DARPETRO INC <br /> 3450 EL CAMINO AVE JUN 1 $ 1998 <br /> CERES CA 95206 <br /> RE: Darpetro Exxon <br /> 749 E Charter Way <br /> Stockton CA 95206 <br /> 1 San Joaquin County Public Health Services Environmental Health Division (PHS/EHD) <br /> has reviewed the Quarterly Monitoring Report prepared by California Geophysical <br /> Group, Inc., on May 28, 1998 .. <br /> Elevated concentrations of Benzene, Toluene, Xylene, Ethyl Benzene and Total <br /> Petroleum Hyrdocarbon as-Gasoline continue to be evidenced in groundwater at this site. <br /> Groundwater has risen over the tops of the monitoring well (MW) screen intervals in all <br /> monitoring wells. Results of quarterly sampling events may not represent groundwater <br /> conditions. Continued vapor extraction and further investigation/evaluation of this site is <br /> necessary. <br /> Soil sample results from the installation of MWs BM4 and BM5 indicate contamination <br /> in the soil at 50 feet below surface grade (March/April 1992). Since soil sample analysis <br /> below 50 feet has not been done, the vertical extent of contamination has not been <br /> determined at this site. Soil boring(s) with collection and analysis of soil in these areas is <br /> required. Boring and sampling should continue below 50 feet, at minimum, to the <br /> historic low groundwater level and to a depth where two consecutive soil samples <br /> collected at five foot intervals indicate by field screening equipment readings and <br /> personal observations (no odor or discoloration) that the soil sample analysis results <br /> should be non detectable. <br /> Install a minimum of two additional monitor wells with screen intervals representative of <br /> current groundwater conditions (screen intervals should be limited to 20 feet with <br /> approximately 5 feet of screen above current groundwater level. One MW is <br /> recommended to be installed in the area just north of MW-B8 and the other MW installed <br /> upgradient of MW-BM3 . Additional MWs may be required in the future depending <br /> upon the results of the vertical contamination investigation. <br /> I <br /> Analysis of groundwater samples from all MWs for five oxygenates is required for the <br /> next two consecutive Quarterly Monitoring events (use EPA Method 8260 for analysis). <br /> i <br /> ii <br /> i'. A Division of San Joaquin County Health Care Services <br />