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Tl-ie well located at the northeast corner of the State Hospital (Well No. H, Figure 3) is the closest to the site (within approximately 800 feet west). According to the well log, the well is approximately 250 feet deep and supplies irrigation water to the State Hospital. The first screen interval in this well is located from 79 to 83 feet below ground surface (bgs). The well is also screened from 188 to 191 feet bgs, 194 to 220 feet bgs, and 240 to 250 feet bgs. Because this well is located upgradient from the site, it is unlikely that the well has been impacted or is threatened 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 (Well No. 6, Figure 3); this well was destroyed in 1992. The remaining twelve wells identified 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 (Well No. 4, Figure 3). Based on this information, it is unlikely that these wells have been impacted or are threatened by petroleum hydrocarbons from the site. A 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. Copies of permits and well logs can be found in ATC's Well Survey for Andrew and Edith Trust, for the Property at 1112 East Harding Way, Stockton, California, dated April 9, 1999. 5.0 DISCUSSION The following paragraphs summarize the results of the subsurface investigations performed at the project site. 1. The vadose zone, from 0 to approximately 50 feet bgs, generally consists of silts, organic silts, and clays. Silty and poorly graded sands are also esent in several of the borings. The capillary fringe, from approximately 5 eet to 65 f et bgs, consists generally of poorly graded sand with some small silt and cp-layers. ? -(ob lbTw ti qV'(,�%-- 2. Groundwater appears unconfined. Since monitoring wells were installed in 2001, depth to groundwater beneath the site has range from approximately 40 to 50 feet bgs; the groundwater flow direction has been easterly, ranging from east-northeast to south- southeast. Groundwater flow direction is currently south-southeast at 0.0008 ft/ft. 3. Petroleum hydrocarbon-affe are generally present in the vicinity of the former dispensers from 20 feet 90 feet b . Petroleum hydrocarbon-affected soils are present at locations away from th STs primarily in the vicinity of the capillary fringe at approximately 50 feet to 65 feet bgs. The highest concentrations of TPHg, benzene, and MTBE are present in soil east of the former USTs and in the vicinity of the former fuel dispensers. The horizontal extent of TPHg, benzene, and MTBE and the presence of SA22493\reports\CAP.doc 5