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, �rq NP File No.2070-2 19 December 1991 page ] 1.0 INTROD L—TION H" 1.1 Site Lo:aiion The subject site is located at 2651 S. Airport Way in Stockton, California (see Figure 1.). It is situaeed in the center of Section 13,Township 1 North, Range 6 East, Mount Diablo Baseline and Meridian. It can be found on the Stockton West 7.5 minute quadrangle topographic map published by the United States Geological Survey. • 1.2 Site History The Stockton Rainbo Baking facility had in the pas, utilized underground storage tanks to store fuel for their delivery vehicles. Historically,four underground fuel storage tanks had been operated at the facility. Three tanks were located in a cluster approximately 50 feet south of the southwest corner of the bakery (see Figure 2). The other tank was located in the front parking lot of the bakery. The middle tank of the three tank cluster was decommissioned prior to 1986(exact date unknown), The tank contents were removed and the tank wa+; subsequently backfilled with sand and Ieft in place. The western-most tank remained operative up until December 1986, when precision tests suggested the possibility of leakage. As a result of the failed precision test performed on the western tank, soil samples were obtained from the vicinity of the western and middle tank to determine whether soil contamination had resulted. The soil samples indicated the presence of petroleum hydrocarbon contamination in the soil to a depth of approximately 28 feet. Consequently, the western and middle tanks were removed in April 1987 and the contaminated soil beneath them excavated. Both excavations were;then backfilled with aggregate baserock and paved over with asphaltic concrete. Anheuser-Busch retained Environmental Sciences and Engineering (ESE) to investigate whether groundwater had been impacted by the petroleum hydrocarbon cnntamination produced by the leaking tanks. ESE proceeded with their investigation in two phases. The first phase was conducted in July 1987 and involved the installation of one monitoring well in the immediate P vicinity of the removed tanks. The second phase was conducted in September 1987 and involved the installation of two additional monitoring wells. During the construction of each well, soil samples were obtained at 5 feet vertical intervals and the subsurface soil conditions were recorded. A copy of the preliminary ESE report is included as Appendix 1. _ Soil and groundwater samples retrieved by FSE were analyzed for the presence of petroleum hydrocarbons by an analytical laboratory. Soil samples obtained during the installation of monitoring well 1 (MW-1) had no detectabl; quantities of contamination with the exception of the _ sr.1 sample obtained at a depth of 55 feet, which exhibited detectable levels of total petroleum hr rocarbons (TPH) and aromatic volatile organics (AVO's). Groundwater samples obtained after completion of MW-1, upon laboratory analyses, were noted to contain detectable levels of TPH. _ Soil samples obtained during the installation of monitoring wells 2 and 3 (MW-2 and MVI'-3) had t no detectable quantities of contaminat'on with the exception of detectable levels of TPH at a depth i — ANDERSON Y CONSULTiNa t_'{3 Group t ir3 r !f