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LOCAL GEOLOGY AND HYDROGEOLOGY The site is located on surface soils belonging to the Stockton Adobe Clay series. These soils are derived from Recent alluvial fan and floodplain deposits. Prior to subsurface investigations described in this report, 50 feet of section had been explored at the site during the installation of monitor wells MW1-MW3. This consisted of light brown silty clay with lenses of sandy clays and silts. See the following sections of this report for a description of the materials encountered between 50 and 80 feet bgs. The groundwater in the vicinity of the site is unconfined. Groundwater elevation at the site varies from a wet year high of 25 feet bgs to at least 50 feet bgs during the previous drought period. Groundwater flow direction at the site has varied from north to south through the northeast and southeast quadrants. COLLECTION OF SOIL AND GROUNDWATER SAMPLES DRILLING AND COLLECTION OF SOIL SAMPLES FROM SBI Woodward Drilling Company (C57# 710079), under the supervision of a WEGE geologist, drilled one soil boring (SB 1) to a total depth of 80 feet bgs at the site on December 11, 2000. The soil boring was drilled with a mobile rig equipped with 8-inch diameter hollow stem augers. SB 1 was drilled at a point immediately downgradient from the former UST, between MW1 and MW3, in an attempt to collect samples from the area at the site most likely to show the greatest impact by vertical migration of the gasoline contaminants that have been observed in the existing monitor wells (see Figure 3). The drilling and sample collection were observed by Ms. Margaret Lagorio, representing the SJCEHD. Representative soil samples were collected at 5-foot depth intervals from 15 feet to 50 feet below ground surface (bgs). The samples were collected in 2"X6" clean brass sleeves with the aid of a 140 pound slide hammer and split spoon sampler that contained three metal sleeves. The geologist selected the soil sample contained in the middle sleeve of the split spoon sampler for laboratory analysis. Soil samples were collected at 2-foot intervals from 50 feet bgs to total depth of the boring at 80 feet bgs. The split spoon sampler contained four 2"X6" brass sleeves, allowing the collection of a continuous core of soil samples between 50 and 80 feet bgs for each 2 feet of drilled interval. The resistance of the formation, however, did not always allow the split spoon sampler to be driven the full 2 feet into the base of the borehole and a continuous core of soil was not obtained between 50 feet bgs and the base of the boring at 80 feet bgs. The geologist screened the soil samples for Total Volatile Organic (TVO) vapors with a Photo Ionizing Detector (PID) equipped with a 10.2 EV lamp. The PID was calibrated immediately prior to sample collection with a 100 ppm standard provided by the manufacturer. The TVO vapor concentrations ranged from a maximum of 96 ppm at 30 ARC SRPT 312101 2