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22 September 2009 AGE-NC Project No. 09-1692 Page 2 of 11 2.1. REGIONAL GEOLOGIC/HYDROGEOLOGIC SETTING The site is located within the southern San Joaquin Valley which comprises part of the Great Valley geomorphic province of California. The San Joaquin Valley is formed by the Great Valley geosyncline,which is a large, elongate,northwest-trending asymmetrical structural trough(basin). It is bordered by the Coast Ranges to the west, the Klamath Mountains and Cascade Range to the north, and the Sierra Nevada to the east. This trough has been filled with sediments derived from both marine and continental sources. Thickness of the sedimentary fill ranges from thin veneers along the valley edges to more than 20,000 feet in the south central portion of the valley. The sedimentary formations range in age with the older deposits being primarily marine in origin and the younger deposits being primarily continental. Continental-derived sediments were primarily deposited in lacustrine,fluvial,and alluvial environments with sediment sources being the mountain ranges surrounding the valley(Ohnsted and Davis, 1961). The site is located on unconsolidated and semi-consolidated alluvium,lake,playa and terrace deposits of Quaternary age(California Division of Mines and Geology, 1977). 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). 2.2. GROUND WATER DEPTH AND FLOW DIRECTION Based on information obtained from a nearby site(1033 West Charter Way,Stockton),ground water depth in the vicinity of the subject property is approximately 18 feet bsg. However, historically, ground water has varied from approximately 10 feet to 30 feet bsg in the vicinity of the site. Prevailing ground water flow direction in the area of the site is inferred to be toward the east. However, flow direction may be both locally and seasonably variable. 2.3. PREVIOUS SITE ASSESSMENT On 02 and 03 June 2009,nine soil borings(B 1 through 139)were advanced on site for collection of soil and grab ground water samples. Borings B1,B2,B4,B5 and B7 through B9 were advanced to a depth of approximately 10 feet below surface grade (bsg); borings B3 and B6 were advanced to a depth of approximately 20 feet bsg.Discrete soil samples were collected at regular intervals from each soil boring, and grab ground water samples were collected at total depth from borings B3 and B6. Advanced GcoEnvironmental,Inc.