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I 05 September 2000 AGE-NC Project No 99-0645 Page 2 of 5 from the same sample locations Methyl tertiary butyl ether (MTBE) and/or tertiary butanol (TBA) were detected in soil samples collected from the former UST excavation,particularly in the samples collected at the southern and northern ends of the former Tank#1 excavation, and in the spoils pile samples Approximately 150 yards of soil were excavated and backfilled into the former UST excavation I 23 REGIONAL GEOLOGIC CONDITIONS The site is situated within the Great Valley Geomorphic Province of California, a large, elongate northwest trending, asymmetric structural trough The Great Valley Province has been filled with I 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 24 SITE HYDROGEOLOGIC CONDITIONS The closest surface water feature to the site is the Calaveras River(Diverting Canal)which is located approximately 10,500 feet southwest of the site Water from the Calaveras River drains into the San Joaquin River Deep Water Channel and is primarily used for commercial,agricultural and recreational boating I Based upon well information obtained from nearby sites and well data collected from San Joaquin County, ground water is currently estimated to occur at a depth of approximately 90 to 100 feet below surface grade (bsg) Ground water flows toward the northeast in the general area of the site, but this may be modified by changing recharge and discharge patterns Ground water is considered to be of beneficial use and is used for domestic, industrial and commercial purposes I Advanced G oEnv� nm I r c ro entn, (tic I