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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 952 <br /> 209/468-3420 <br /> 1 L F <br /> MICHAEL D & SHARON OLIVAREZ �A <br /> 436 SCOTTS AVENUE MAR ' 1993 <br /> STOCKTON CA 95203 <br /> Re: Skips Service Station <br /> 300 S. California St. <br /> Stockton,CA <br /> San Joaquin County Public Health Services Environmental Health Division (PHS/EHD)has reviewed the <br /> Quarterly Monitoring Report(QMR) dated January 25, 1999 prepared by Foothill Engineering. Analytical <br /> results from groundwater samples collected on December 29, 1998 evidence Benzene,Toluene, <br /> Ethylbenzene, Xylene(BTEX) and Total Petroleum Hydrocarbon as gas(TPHg) in all Monitoring Wells <br /> (MWs)at the site. Groundwater monitoring has occurred yearly at this site from May 1995 to December <br /> 1998, analytical results do not indicate a decreasing trend of contaminant concentrations in thegroundwater <br /> at the site. Quarterly monitoring of the groundwater at this site has not occurred. <br /> PHS/EHD reviewed the Work Plan for Disposal of Stockpiled Soil, Backfilling Excavations, and <br /> Additional Site Assessment dated august 1, 1995 prepared by Clearwater Group. Inc. PHS,EHD informed <br /> the contractor of deficiencies in this Work Plan,made recommendations and requested an addendum to the <br /> Work Plan by January 1, 1996 in a letter dated October 2, 1995. The Work Plan was not approved by <br /> PHS/EHD and additional investigative work at the above referenced site was never completed. <br /> Geoprobe borings were constructed at this site on March 31, 1995. The deepest boring evidenced soil <br /> contamination at 51 feet below surface grade(bsg). The vertical and lateral extent of contamination has not <br /> been defined. The lateral and vertical extent of contamination at this site must be determined. <br /> According to the 1978 San Joaquin County Flood Control Map the groundwater level at this site was <br /> approximately 80 feet bsg during that year. During the sampling event on December 29, 1998 the <br /> groundwater level was measured at 29.65 feet bsg. The MWs on site have screen intervals from 40 feet to <br /> 60 feet bsg. Groundwater has risen over the tops of the well screens. The rising groundwater is of concern <br /> to PHS/EHD because of the potential for increased contaminant concentrations in the ground water due to <br /> the groundwater contacting a larger mass of contaminated soil. Since ground water is above the well <br /> screens the data may not be representative of groundwater conditions. Properly screened MWs should be <br /> placed at this site. <br /> A Work Plan to determine the lateral and vertical extent of contamination at the above referenced site <br /> should be submitted to PHS/EHD by Mav 15, 1999. <br /> Conduct a survey of domestic, municipal,agricultural, industrial and any other wells within a 2,000 foot <br /> radius of this site. Contact the Department of Water Resources, municipal water suppliers and nearby <br /> industries for well information. In addition, perform a physical search of the area to identify any wells. <br /> Show the locations of all wells on a map with appropriate scale showing the site and clearly marked 2000 <br /> foot radius. Submit any known construction details of the wells(if available)and evaluate the influence of <br /> well pumping with respect to the migration of the contamination from this site. <br /> Quarterly monitoring of the groundwater at this site should begin immediately and continue until otherwise <br /> instructed by PHS/EHD. The water from these MWs should be analyzed for Benzene, Toluene, <br /> Ethylbenzene, Xylenes(BTEX)and Total Petroleum Hydrocarbons as gasoline(TPH-g) using EPA <br /> A Division of San Joaquin County Health Care Services <br />