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ASSOCIATES I N C . An 1 on-site search for potential receptors was conducted on December 17, 1998 by ATC personnel. No open ponds or streams were located within 2,000 feet of the site. t AREA DEPTH TO WATER MEASUREMENTS ' ATC contacted the Department of Water Resources (DWR) and California .Water Service Company to identify existing and former groundwater wells located in the vicinity of the site. ' Historical depth to groundwater information was obtained from both agencies to evaluate the fluctuations in depth to groundwater in the vicinity of the site and how they might affect the site. Six measuring points were discovered in the vicinity of the site. Based on information obtained from DWR and California Water Service Company the historical highest depths to water for the vicinity of the site occurred in 1984 and 1987. Depth to water in the vicinity of the site ranged from approximately 21 to 48 feet bgs between 1984 and 1987. Four of the monitoring points ' nearest the subject site indicate the water table was between 31 feet and 48 feet bgs in 1987. A listing of the measuring points and depth to water information is contained in Table 1. A map showing the location of the six measuring points is presented on Figure 3. CONCLUSIONS/RECOMMENDATIONS Detectable concentrations of total petroleum hydrocarbons as gasoline (TPHg), total petroleum hydrocarbons as diesel (TPHd), and benzene, toluene, ethylbenzene, and xylenes (BTEX) were observed in soil samples collected from the site. The distribution of petroleum constituents ' beneath the site has been essentially defined and appears to be limited laterally to the immediate vicinity of the former tank pit. The highest concentrations were reported at between 10 and 20 ' feet bgs and generally attenuate rapidly with depth. Only low concentrations of toluene (0.064 mg/kg) and xylenes (0.012 mg/kg) were detected at 30 feet bgs, the maximum depth explored. A review of PHS/EHD groundwater well construction logs, DWR well construction logs, and a site walk in the vicinity of the site, revealed fourteen wells located within approximately 2,000 feet of the site. None of the fourteen wells are located within 500 feet of the site (Figure 2). A well located at the northeast corner of the State Hospital (Well No. 11, Attachment 1) is the closest to the site (within approximately 800 feet west). The first screen interval in this well is located from 79 to 83 feet bgs. Because this well is located upgradient from the site, it is ATC's judgment that it is unlikely that the well has been impacted by petroleum hydrocarbons from the site. The only well located downgradient from the site was a groundwater monitoring well located on the corner of North Wilson Way and East Harding Way, however this well was destroyed in ' 1992. The remaining twelve wells discovered during the well survey are located either upgradient or crossgradient from the site and are more than 1,000 feet from the site or have been destroyed. Based on this information, it is ATC's judgment that it is unlikely that these wells have been ' impacted by petroleum hydrocarbons from the site. wA97736\repoFu\wcIsumdoc 3