Laserfiche WebLink
Section 3 <br /> REGIONAL GEOLOGIC AND HYDROGEOLOGIC SETTING <br /> The Thornton Gas Dehydrator Station is located in the San Joaquin Valley within the Great Valley <br /> Geomorphic Province. The San Joaquin Valley is a northwestward-trending, asymmetric structural basin <br /> bounded on the east by the Sierra Nevada Range and the west by the Coast Range. Locally, this basin <br /> has been infilled with up to 6 vertical miles of both marine and non-marine rocks and sediments that <br /> range in age from Jurassic (about 160 million years ago) to Holocene (the past 11,000 years). Geologic <br /> maps of the San Joaquin Valley prepared by Page(1986) show the site is immediately underlain by flood <br /> plain deposits of Holocene age. The deposits consist predominantly of clay and silt. A regional geologic <br /> cross section through the area shows that the flood plain deposits are about 50 feet thick and are underlain <br /> by non-marine alluvial sediments consisting of a heterogenous mixture of clay, silt, sand and gravel <br /> (Page 1986). <br /> This facility is also located in the Eastern San Joaquin County Groundwater Basin (California Department <br /> of Water Resources 1980). A regional groundwater potentiometric surface map prepared by the San <br /> Joaquin County Flood Control District for fall 1973 shows that groundwater occurs at an elevation of <br /> about 0 feet mean sea level and flows to the west. Recharge to the basin occurs along the foothills of the <br /> Sierra Nevada Range at the eastern boundary of the basin, and from surface infiltration. Discharge from <br /> the basin occurs through drainage into the Mokelumne River, a gaining river in the Thornton area, and <br /> from extensive groundwater withdrawal in the area. <br />', cca09/17/93(9784a.doc)cp45) 3-1 <br />