SITE INFORMATION AND CORRESPONDENCE

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r 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 I988, 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 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 active municipal water supply wells within 2,500 feet of the site. There is an emergency backup well 800 feet to the northeast of the site which is screened between 200-400 feet and which has a 96-foot seal. This well, owned by the California Water Service (CWS), was taken out of service in 1991 because of a sanding problem. The CWS has indicated that it has no intention of using this well for municipal supply purposes . and intends to use it only in the event of a local disaster or fire. An additional CWS well is located 2,200 feet north of the site and has a 72-foot seal. This well is listed as a backup well. The nearest surface water, a canal that extends easterly from the Port of Stockton, is about 2,000 feet to the west. Shallow groundwater at the site flows 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 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 4