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RECOVED ' JAO 2 0 ISS g PRELIMINARY INVESTIGATION AND EVALUATION REPORT 1002 Yosemite Street Stockton, CA 1.0 BACKGROUND ' The site is a former gasoline service station located at the intersection of Yosemite Street and Acacia Street in a relatively flat area zoned for commercial and residential use (Figure 1) . It ' is our understanding that Mr. Jules Conrady operated the station from 1961 until 1978 , and that the underground fuel storage tanks were removed from the site in 1980. These included a 4000 gallon regular gasoline tank, a 3 , 000 gallon ethyl gasoline tank, and a 3, 000 gallon supreme tank. There is no available information on the condition of the tanks at the time of their removal, and no soil ' samples were collected from the tank excavation. In 1990, the property was offered for sale, and Evax Technologies was retained to conduct a soil-gas survey to determine whether ' petroleum vapors were present in the soil, indicating a prior unauthorized release of petroleum from the tanks, pipelines, or dispenser islands. Fifteen vapor probes were installed in a random pattern surrounding the former tank cavity and dispensers, and two to three vapor samples were collected from each probe (Figure 2) . 'Samples were extracted from two depth intervals (12-14 feet and 17- 19 feet) in most holes, and also from 8-10 feet in two holes. No ' vapors were detected by probes surrounding the tank cavity, but vapors were detected by five probes near the dispenser islands. ' Subsequently, iSan Joaquin County Public Health Services, Environmental Health Division, instructed Ithe property owner to perform an assessment of possible contamination on the property. In October 1992 , Geological Audit Services, Inc. (GeoAudit) was retained to perform the assessment. i I I I I 2. 0 DEPTH TO GROUNDWATER . j According to the Fall, 1990, Depth to Groundwater map prepared by ' San Joaquin County Public Works Department, Flood Control Section, the depth to groundwater in the vicinity of the: site is between 30 � Mand 40 feet. At the time of this investigation, the depth was estimated to be in excess of 50 feet by Mr. Michael Infurna of 5J I PHS%EHD. Groundwater was encountered in two ' soil borings during this SEI investigation. , In boring B3 , the depth was 1 apprioximately , 34 feet.In , borxngI B4 , the depth 'was approximateiy 33j,ifeet. i i I +E w A