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Mr. Chris Stock 2 February 28, 1992 2.3 Regional Geology and Hydrology The subject property is located east of the San Joaquin delta near the northern end of the San Joaquin Valley. This area consists of a thick sequence of fine to coarse sediments. Regionally, the property. is located in the San Joaquin; sub-basin of the geomorphic province known as .the Great Valley. This province is characterized by a northwest-trending asymmetric structural trough bounded on the east by the Sierra Nevada Province and on the west by -the Coast Range Province. The Great Valley is composed of a thick sequence (60,000 `feet) ` of sedimentary rocks ranging in age from Jurassic 205 - 138 million ears ago)- to Recent 10 000 ears ago) and overlies a ( Y ( Y g ) metamorphic and igneous ' basement complex (Bailey, et al; 1964). Jurassic, Cretaceous (138 - 63 million years. ago) -and Tertiary" (63 - 2 million years ago) rocks are predominantly of marine origin (Knoxville Formation, Shasta Series, Chico Group). Tertiary sediments are almost entirely clastic, and, were largely derived from the eroding Sierra Nevada. Tectonism beginning .in the upper Miocene (24 - 5 million years ago) and continuing to 'the .present has. resulted in considerable erosion of the valley edges and has .deposited sediments continental in origin. The Pliocene (5 - 2 million years ago), Pleistocene (2 million - .10,000 years ago) and Recent rocks consist mainly "of semiconsolidated to unconsolidated claystones, sandstones and conglomerates, and contain most of the groundwater, resources in the area. The San Joaquin Valley is filled with., up to six vertical miles of sediment. Fresh groundwater is produced from wells 'tapping confined and unconfined aquifers found above and below .the Corcoran Clay of., the Tulare Formation. The Corcoran Clay " acts as the main confining layer in. the ' .San Joaquin Valley. Groundwater with higher salinities have been observed both above and below the Corcoran Clay. Prior r , to large scale groundwater development in, .the south groundwater flow was from the g g p valley flanks to the axis and then north 'towards the Delta. Locally, groundwater is ,.. usually found at depth of approximately- 45, however due to the drought groundwater has been documented as being 'at a depthsof ':65' feet. The `general groundwater flow direction is west-northwest, towards the Sari.. Joaquin River .Delta. EK-6014-1 9202-E1o0.RPT