SITE INFORMATION AND CORRESPONDENCE

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.� DRAFT gasoline, or TPH-g) in water is commonly accepted to be 5 ppb, with 10 ppb giving a strong odor. The following is a brief historical summary of Petitioner's site at 1665 Pacific Avenue in the City of Stockton. The site is located in a commercial/residential area of the city and was an operating service station from about 1947 to 1988; gasoline was dispensed from two 10,000 gallon capacity USTs. Since demolition of the station and removal of the USTs in 1988, the site has remained vacant. The site is underlain by flood plain sediments (clay, silt and sand) of the Pliestocene Victor Formation. In the vicinity of the site, groundwater in the more permeable strata of the -� Victor Formation is generally of inferior quality(concentrations of nitrate greater than C11 4 45,000 ppb, chloride greater than 300,000 ppb, and TDS greater than 1,000,000 ppb) and is not viewed by local water purveyors as a source of drinking water. Underlying the Victor Formation are the alluvial sediments (clay, silt, sand, and gravel) of the Plio-Pliestocene Laguna Formation. Groundwater in the Laguna Formation is used extensively throughout the area for municipal, industrial, and agricultural supply. There are no water supply wells within 800 feet of the site Clasrs� uj Q and those municipal wells located in the general area are generally constructed with annular seals C,(.+3 which extend to depths of 150 to 200 feet so as to exclude the shallower poor quality (V-Or groundwater in the Victor Formation. The nearest surface water, a canal that extends easterly -1 �'QfrLYt from the Port of Stockton, is about 2,000 feet to the west. Shallow groundwater at the site flows �f in a general easterly direction with a gradient of about 0.002. In January 1988, analyses of soil samples from five soil borings drilled to depths of 20 to 30 feet indicated that a release had occurred at the site. In February 1988, three groundwater monitor wells were installed to assess site groundwater conditions. The initial groundwater samples from the three wells revealed an absence of gasoline constituents in groundwater near the location of the two gasoline USTs,high concentrations (99,000 ppb TPH-g and 5,700 ppb benzene) in the vicinity of the easterly pump island, and low concentrations (170 ppb TPH-g and 1 ppb benzene) in the vicinity of the waste oil UST. Data gained from the well installations also LJk-t , indicated that the groundwater was confined and that it flowed in an easterly direction. In March 1988, the two 10,000-gallon capacity gasoline USTs, the waste oil UST, and the dispensers and associated piping were removed from the site. Visual inspection of the bottom and side-walls of the gasoline UST excavation revealed that soil was affected by a release prompting petitioner to over-excavate an estimated 850 cubic yards of soil to a final depth of h° �1 Was