SITE INFORMATION AND CORRESPONDENCE

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v Site Background Information CALIFORNIA STOP 2224 Manthey Road, Stockton, California BACKGROUND The site is located in a commercial/residential area of south Stockton, immediately west of Interstate 5 and south of West Eighth Street. The site is presently utilized as a gasoline station and convenience store. Three 10,000-gallon USTs and one dispenser island with four dispensers are located at the site. It is our understanding that the USTs were installed approximately in 1991. SITE DESCRIPTION The site is located in a commercial/residential area of south Stockton, immediately west of Interstate 5 and south of West Eighth Street (Figure 1). The site is further located west of Section 10, Township 1 North, Range 6 East, Mount Diablo Base and Meridian (Stockton West Quadrangle, 7.5-Minute USGS Topographic Series), in an area of very low topographic relief at an elevation between 11 and 12 feet above the North American Vertical Datum 88 (NAVD88). The site is a triangular parcel identified by the San Joaquin County Assessor's Parcel number 163-130-07. PETROLEUM SOURCES Petroleum sources included three 10,000-gallon USTs and one dispenser island with four dispensers located immediately west of the site's convenience store (Figure 2). In January 2002, dispensers and product lines at the site were removed and upgraded. Pea gravel was removed from beneath the former concrete dispenser island to a depth of approximately 2 feet below surface grade(bsg),where native soil was encountered. Under direction of EHD representatives, one soil sample was collected beneath each of four dispensers by Parker Environmental Services of Pittsburg, California and submitted for laboratory analysis. Total petroleum hydrocarbons quantified as gasoline (TPH-g) were reported in each soil sample at concentrations ranging between 770 milligrams per kilogram (mg/kg)and 10,000 mg/kg. Fuel oxygenate methyl tertiary-butyl ether(MTBE)was reported in three of four soil samples at concentrations as high as 340 mg/kg. REGIONAL GEOLOGIC/HYDROGEOLOGIC SETTING According to Geologic Map of California, published in 1977 by the State of California Department of Mines and Geology, the site area is located within the Great Valley Advanced GeoEnvironmental,fnc.