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' Site Background Information R M B Garage (Erardi Ventures) Page 2 of 4 ' REGIONAL GEOLO I G C/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, asymmetric structural trough 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 than veneers along the valley edges to more than 20,000 feet in the south central portion of the valley The sedimentary formations vary in age with the older deposits being primarily marine an origin and the younger ' deposits continental Continental-derived sediments were primarily deposited an lacustrine, fluvial, and alluvial environments with sediment sources being the mountain ranges surrounding the valley (Olmsted and Davis, 1961) The site is Iocated 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 an the 13,500-square male San Joaquin Valley Ground Water Basin(Basin 5-22) According to data recorded during drilling, ground water depth beneath liethe site is approximately 25 to 30 feet below surface grade (bsg) Based on information obtained from a nearby site (706 North El Dorado Street), the prevailing ground water flow direction in the ' vicinity is inferred to be toward the northeast However, flow direction may be both locally and seasonably variable ' SITE STRATIGRAPHY ' Between surface grade and approximately 12 feet bsg, the soil consists of brown to yellow-brown and orange-brown clays, salty clays, and clayey silts, with a thin, fine-sand lense at approximately 6 feet bsg Between 12 feet bsg and 50 feet bsg, the soil consists of light brown to yellow/orange- brown clayey sands and salty sands, with the exception of a blue gray to brown clay to sandy clay layer between approximately 23 feet bsg to 27 feet bsg From approximately 50 feet bsg to total depth of boring B5, the soil consists of a gray, well graded, medium to coarse sand with gravel SITE ASSESSMENT ACTIVITIES On 04 January 2002, four soil bonngs were advanced by Advanced GeoEnvaronmental, Inc AGE at the site as part of assessment activities related to the former USTs Soil probe borings B1 through B4 were advanced vertically to depths of 40 feet bsg Advanced GeoEnvironmentai,Inc I