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7 ). H. KLEINFELDER & ASSOCIATES File: W-2022-1/11:312 June 19, 1986 Page 11 C. Anticipated Aquifer Conditions at Corral Hollow Landfill In the geologic investigation conducted for the City of Tracy at the Corral Hollow landfill four test borings were drilled to evaluate the ground water conditions. Borings drilled range from 70 to 100 feet deep as measured from ground surface. Boring number 4 was drilled at the bottom of Trench 9 to a depth of 82 feet. No ground water was encountered in any of the borings. The following discussion is excerpted from the report of that geologic investigation dated December 2, 1985: • In general, the materials encountered in Borings 1 through 4 consisted of brownish siltstone, claystone, and clay soils with varied layers of gravel and clayey gravel. The materials are generally very hard and extend to the maximum depths explored. These materials are interbedded and compose the alluvial fans and stream channels of the alluvial plains and fans geomorphic unit they were deposited In. In all borings, the bottom 20 feet consisted of very low permeability clayey siltstone or clayey gravel. A more detailed description of the materials encountered in the test borings are noted on the Logs of Borings (included in Appendix C). All soils have been classified according to the Unified Soil Classification System. revzT61615*. The predominate water -bearing strata on the west side of the valley is the Tulare Formation. The Corcoron clay layer of the Tulare Formation separates more saline water above from less saline water below. Our previous research indicates that wells on the order of 600 to 900 feet deep have been required to obtain significant volumes of cleaner water. The Musco Olive project, previously referenced, is approximately at the same elevation and distance west from Interstate 580. A deep test boring to 225 feet through similar materials was dry while a shallower test boring encountered seepage from a perched ground water source at only 39 feet. During the geologic investigation at Corral Hollow Landfill, Boring 4 was drilled at the bottom of Trench 9 (approximately 45- 50 feet below grade) to a depth of 82 feet and was dry.