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PUBLIC IrlEALTH SERVICES <br /> SAN JOAQUIN COUNTY <br /> ENVIRONMENTAL HEALTH DIVISION y= < <br /> Ernest M. Fujimoto, M. D., M.P.H., Acting Health Officer <br /> 304 E. Weber Ave., Third Floor • P. O. Box 388 • Stockton, CA �rFORa`p <br /> 2091468-3420 <br /> DAVID ATWATER OCT 0 4 1996 <br /> VAN DE POL ENTERPRISES <br /> P O BOX 1107 <br /> STOCKTON CA 95201 <br /> Re: California Fuels Station Site Code: 1214 <br /> 2402 Pacific Avenue <br /> Stockton CA 95204 <br /> San Joaquin County Public Health Services, Environmental Health Division (PHSIEHD) has <br /> completed review of the "Preliminary Investigation and Evaluation Report - August 1996" <br /> prepared by Advanced GeoEnvironmental. PHSIEHD has the following comments for your <br /> consideration. <br /> On July 25 and 26, 1996, six soil borings were drilled and sampled, four of which were <br /> subsequently converted into monitoring wells, MW1 - MW4 with total depths of 50 feet below <br /> ground surface (bgs). The soil borings, 81 and B2 were drilled to 55 and 60 feet bgs. <br /> Groundwater was generally encountered at 35 bgs during drilling activities. The soil borings <br /> extended to a significant depth below groundwater to investigate the distribution of petroleum <br /> hydrocarbon which resulted when groundwater was, until just recently, much lower. <br /> Soil contamination was detected at depths to 60 feet bgs. Significant soil contamination was <br /> detected at 30 feet in MW1, 25 feet in MW2 and 30 feet in MW3, suggesting that off site soils <br /> are contaminated. Soil contamination of up to 1,100 ppm TPH-diesel, 9,900 ppm TPH-gas, <br /> 29 ppm benzene, 530 ppm toluene, 160 ppm ethylbenzene, and 700 ppm xylene were <br /> detected at 35 feet in B2. <br /> Groundwater contamination was detected in all four monitoring wells with benzene <br /> concentrations ranging from 7,000 ppb in MW1 to 14,000 ppb in MW4. The initial <br /> groundwater gradient direction was estimated to the northeast, in the direction of MW4. <br /> Groundwater contamination has migrated off site as evidenced in concentrations detected in <br /> MW4. <br /> The report indicated that relative casing elevations were used for surveying. PHSIEHD <br /> recommends that the site be surveyed by a licensed surveyor using an established <br /> benchmark. <br /> As the oxygenate, MTBE, was not used by refineries throughout the state, until this year, its <br /> absence cannot be used to demonstrate that the leak occurred prior to the 1980's. It is <br /> fortunate that MTBE has not yet been detected at the site. However, high concentrations of <br /> petroleum hydrocarbon were observed in the samples collected from the monitoring wells <br /> causing the detection limits to be raised to 75 ppb for MTBE. The MTBE detection limit <br /> which has been achieved on a routine basis in laboratories is 5 ppb. <br /> A Division of San Joaquin County Health Care Semites <br />