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10 January 2005 AGE-NC Project No. 04-1224 Page 2 of 6 2.2. REGIONAL GEOLOGIC/HYDROGEOLOGIC SETTING The site is located within the northern 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 greater 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 sources being the mountain ranges surrounding the valley(Olmsted 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). Ground water occurs in a generally sandy clay layer extending from approximately 6 feet bsg to an unknown depth. Based on the San Joaquin County Flood Control District and Water Conservation District Lines of Equal Depth of Water Wells Fall 2000 map, the estimated depth to ground water in the vicinity of the site is 15 to 20 feet bsg. Trapper Slough is the nearest surface water feature to the property,located approximately 1,300 feet west of the site. Water from the slough drains into the San Joaquin River and is primarily used for commercial and recreational boating,with agricultural as a secondary use.The slough contains water continually and has a potential tidal effect upon ground water depth or flow direction in the area. 3.0. PROCEDURES The field work reported herein was performed in accordance with procedures outlined in the AGE-prepared Limited Subsurface Investigation Work Plan,dated 09 November 2004,and approved by the EHD. A boring permit and permit fee were submitted to the EHD prior to implementation of field work; a copy of the approved permit is included as Appendix A. Advanced GeoEnvironmental.Inc.