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k9 KLEINFELDER 2.3 GEOLOGY AND HYDROGEOLOGY The site lies along the transition between the Great Valley and Coast Ranges Geomorphic Provinces of California. Review of the California Division of Mines and Geology "Geologic Map of the San Francisco — San Jose Quadrangle," indicates that the site is underlain by Pleistocene alluvium (plant area) and Miocene fanglomerate. The northwest trending Midway Fault is located adjacent off site to the west. According to the U.S. Department of Agriculture, Soil Conservation Service, "Soil Survey of San Joaquin County, California" dated October 1992, soils at the site consist of Calla Clay Loam and Carbona Clay. These soils generally correlate to a CL or CH in the Unified Soil Classification System. Permeability is described as slow with rapid runoff in areas of significant slope. Kleinfelder has conducted a geotechnical assessment in the vicinity of the proposed 72 million- gallon pond(s). Several test pits and borings were advanced at depths ranging from 10 to 30 feet below ground surface (bgs). No free groundwater was encountered. Soils encountered consisted predominantly of clays (CL) and silts (ML). Kleinfelder has previously conducted one field assessment at the site. In 1985, Kleinfelder attempted to install three groundwater monitoring wells adjacent to the evaporation ponds on site. The borings were advanced to depths of 50 to 90 feet below grade. In general, the soils encountered consisted of alternating clays and silts with minor sand and gravel lenses. No free groundwater was encountered in borings 1 and 3 to a depth of 90 feet. What was described as a perched groundwater condition was encountered in boring 2 at a depth of approximately 29 feet. According to the 1985 report, during installation of the production well for the Musco Olive facility, groundwater was encountered at a depth greater than 250 feet, rising to within approximately 50 to 60 feet of the surface. Kleinfelder also requested available water well logs for the vicinity of the site from DWR for review. Several references to a thick clay layer, in some logs described as being 100 feet thick, are included on well logs within one to two miles of the site. Additionally, several references were made to a "blue clay" or blue shale at various depths in several borings. The referenced blue clay is may be the Cocoran Clay. With one exception, the wells appear to be screened at depths greater than 250 feet bgs. A single well located at "Patterson Pass Road and Interstate 580" is screened in black sand from 153 to 193 feet bgs. 20-2594-03.004/2011 R447 Page 4 of 16 Copyright 2001 Kleinfelder,Inc. June 8,2001