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• • December 5,2005 NOA Project Number: E05132C are covered by roads, driveways, sidewalks,parking lots, buildings, and other stnrctures. The soil material under the impenious surface is similar to that of Galt clay. ' 1.3 Geology ' According to the California Geological Survey, the subject property is located within the Great Valley geomorphic province.' The Great Valley is an alluvial plain about 50 miles wide and 400 miles long in the central part of California. Its northern part is the Sacramento Valley, drained by the Sacramento River,and its southern part is the San Joaquin Valley, drained by the San Joaquin River. The Great Valley is a trough in which sediments have been deposited almost continuously since the Jurassic (about 160 million years ago). Great oil fields have been found in southernmost San Joaquin Valley and along anticlinal uplifts on its southwestern margin. In the Sacramento Valley, the Sutter Buttes,the remnants of an isolated Pliocene volcano,rise above the valley floor. ' According to the Geologic Map of California,the subject property is located within a region of "alluvium, lake, playa, and terrace deposits;unconsolidated and semi-consolidated." ' 1.4 Topography According to the most recent USGS Topographic map covering the subject property and vicinity,' ' the subject property is located at 30 to 35 feet above mean sea level in an area which slopes down to the west at a rate of approximately seven feet per mile. 1.5 Regional Groundwater The San Joaquin County Flood Control and Water Conservation District (1998 and 1999) ground ' water depth and elevation maps were reviewed to determine the ground water levels near the subject property. The Fall 1998 and Spring 1999 maps are the most current official maps available from the County. According to these maps,ground water lies between 55 and 65 feet below ground surface and flows to the southwest at an inconsistent gradient ranging from zero to 40 feet (vertical) per mile (horizontal). 3California Geological Survey,2002.California Geomorphic Provinces-CGS Note 36. 4Jennmgs,Charles W., 1969-1973. Geologic Map of California,Scale 1:750,000. 5U.S. Geological Survey,1968 photorevised 1987.7.5'Topographic map of Stockton East,California quadrangle. 3 .*44