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Site B k roup Information ac g d nfo mat on FAST AND EASY MART 244 West Harding Way, Stockton, California The site is bounded on the north by Harding Way, residential properties on the south and west and commercial properties on the east. A single structure occupies the southern portion of the site, utilized as a gasoline station and mini-mart. Two USTs were removed from the site in September ' 1998 by Stockton Service Station Equipment (SSSE) and a new UST system was installed in December 1998. 2.1. REGIONAL GEOLOGIC/HYDROGEOLOGIC CONDITIONS The site is situated within the Great Valley Geomorphic Province of California, a large, elongate northwest tending, asymmetric structural trough. The Great Valley Province has been filled with thick sequences of sediment ranging in age from Jurassic to recent, creating a nearly flat lying alluvial plain,which extends from the Tehachapi Mountains in the south to the Klamath Mountains in the north. The western and eastern boundaries of this province are comprised of the California ' Coast Range and the Sierra Nevada, respectively. Rocks composing the basement complex of the province have not been completely defined but are believed to be of metamorphic and igneous origin. The Great Valley Province has been subdivided into two major divisions identified as the ' • Sacramento and San Joaquin Valleys, The Modesto, Riverbank and Turlock Lake Formations and overlying recent alluvium are the principal sources of domestic ground water in the 13,500-square mile San Joaquin Valley Ground Water Basin (Basin 5-22). This basin is drained primarily by the San Joaquin River. The closest ' surface water feature to the site is Smith Canal and Yosemite Lake,located approximately 1,500 feet northwest of the site. Water from Smith Canal drains into the San Joaquin River Deep Water Channel and is primarily used for commercial and recreational boating. 2.2. PREVIOUS INVESTIGATIONS ' It is AGE understanding that an environmental site assessment was performed on the property in the early 1996. Field observations indicated that hydrocarbons may have impacted the soil. One soil ' sample collected from forty feet below surface grade (bsg) had detectible concentrations of petroleum hydrocarbons. Two ground water samples had low concentrations of volatile aromatic compounds; one of the ground water samples collected and analyzed contained total petroleum ' hydrocarbons as gasoline (TPH-g) at a concentration of 0.28 milligram per liter (mg/1). Methyl tertiary butyl ether (MTBE) was detected at 3.7 microgram per liter(µg11). I I I