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1 <br /> I <br />' Site Background Information R M B Garage (Erardi Ventures) <br /> Page 2 of 4 <br />' REGIONAL GEOLOGIC/HYDROGEOLOGIC SETTING <br /> The site is located within the southern San Joaquin Valley,which comprises part of the Great Valley <br />' Geomorphic Province of California The San Joaquin Valley is formed by the Great Valley <br /> geosyncline, which is a large, elongate, northwest-trending, asymmetric structural trough It is <br /> bordered by the Coast Ranges to the west,the Klamath Mountains and Cascade Range to the north, <br />' and the Sierra Nevada to the east This trough has been filled with sediments derived from both <br /> marine and continental sources Thickness of the sedimentary fill ranges from thin veneers along the <br /> valley edges to more than 20,000 feet in the south central portion of the valley The sedimentary <br />' formations vary in age with the older deposits being primarily marine in origin and the younger <br /> deposits continental Continental-derived sediments were primarily deposited in lacustrine, fluvial, <br /> and alluvial environments with sediment sources being the mountain ranges surrounding the valley <br />' (Olmsted and Davis, 196 1) The site is located on unconsolidated and semi-consolidated alluvium, <br /> lake, playa, and terrace deposits of Quaternary age (California Division of Mines and Geology, <br /> 1977) <br />' The Modesto, Riverbank, and Turlock Lake Formations and overlying Recent alluvium are the <br /> principal sources of domestic ground water in the 13,500-square mile San Joaquin Valley Ground <br />' • Water Basin(Basin 5-22) According to data recorded during drilling, ground water depth beneath <br /> the site is approximately 25 to 30 feet below surface grade (bsg) Based on information obtained <br /> from a nearby site (706 North El Dorado Street), the prevailing ground water flow direction in the <br />' vicinity is inferred to be toward the northeast However, flow direction may be both locally and <br /> seasonably variable <br />' SITE STRATIGRAPHY <br />' Between surface grade and approximately 12 feet bsg, the soil consists of brown to yellow-brown <br /> and orange-brown clays, silty clays, and clayey silts, with a thin, fine-sand lense at approximately <br /> b feet bsg Between 12 feet bsg and 50 feet bsg, the soil consists of light brown to yellow/orange- <br /> brown clayey sands and silty sands, with the exception of a blue gray to brown clay to sandy clay <br /> layer between approximately 23 feet bsg to 27 feet bsg From approximately 50 feet bsg to total <br /> depth of boring B5, the soil consists of a gray, well graded, medium to coarse sand with gravel <br /> 1 <br /> SITE ASSESSMENT ACTIVITIES <br />' On 04 January 2002, four soil borings were advanced by Advanced GeoEnvironmental, Inc (AGE) <br /> at the site as part of assessment activities related to the former USTs Soil probe borings B 1 through <br />' B4 were advanced vertically to depths of 40 feet bsg <br />' Advanced GeoEnvoronmental,Inc <br /> I <br />