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. 05 February 1999 AGE-NC Project No 99-0559 Page 2 of 5 up to 260 ppm Lead was detected at concentration ranging from 2 9 ppm to 17 ppm Oil and grease were detected beneath the waste oil UST at a concentration of 1,300 ppm Chromium, lead, nickel and zinc were detected at concentrations of 52 ppm, 5 1 ppm, 23 ppm and 54 ppm, respectively, beneath the waste oil UST Approximately 100 cubic yards of soil (135 tons) were excavated during removal of the USTs and stockpiled on-site Five samples were collected from the soil stockpiles TPH-g and BTEX were detected at concentrations as high as 3 7 ppm Oxygenates were not detected in the stockpiled soil Oil and grease and metals were detected in the soil stockpiled from the waste oil UST excavation Analytical results of soil samples are summarized on Table 1 and 2 Approximate locations of UST and piping samples are illustrated on Figure 2 23 SITE HYDROGEOLOGIC CONDITIONS . The closest surface water feature to the site is the Stockton Diverting Canal, located approximately 1,000 feet northeast of the site Based upon ground water maps prepared by the San Joaquin County Flood Control and Water Conservation District and well information obtained from nearby sites, ground water flow direction is variable near the site and is currently estimated to occur at a depth of approximately 50 feet below surface grade (bsg) 2 4 REGIONAL GEOLOGIC 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 mayor 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 Advanced GeoEnvironmental,Inc