ARCHIVED REPORTS_XR0005243 - Laserfiche WebLink

Home Browse Search

Former Beacon Station No. 12474 March 18, 2002 Stockton,California Problem Assessment Report/Corrective Action Plan 3.4 REGIONAL AND LOCAL HYDROGEOLOGY The site is situated in the central portion of the Great Valley Geomorphic Province otherwise known as the Central Valley of California. The Central Valley consists of two broad, topographically distinct, alluvial valleys: the Sacramento Valley in the north; and the San Joaquin Valley in the south. These two valleys meet in the area of the inland delta formed by the confluence of the San Joaquin and Sacramento Rivers. Stockton is situated in the northern San Joaquin Valley just east of and adjacent to the San Joaquin/Sacramento River delta system. The Great Valley geomorphic province is an elongate, northwest-trending, asymmetric structural trough filled with a thick sequence of marine and non-marine sediments ranging in age from Jurassic to Holocene. Great Valley sediments generally thin to zero towards the adjacent Sierra Nevada and Coast Ranges provinces and are predominantly underlain by the westward continuation of Sierran granitic and metamorphic rocks. The Coast Ranges are • underlain, in part, by folded and faulted sedimentary rocks equivalent to intervals found at depth in the Great Valley stratigraphic sequence. Generally unconsolidated to poorly consolidated alluvial, fluvial and lacustrine deposits of Miocene to Holocene age comprise the upper portion of the stratigraphic sequence of the Great Valley province and are generally underlain by consolidated marine rocks. Surface sediments in the site area are generally Pleistocene to Holocene flood-basin deposits and Pliocene to Holocene alluvial and fluvial deposits (USGS, 1986). Lithologic data from soil borings indicate the site surface is underlain by interbedded sand, silt and clay as shown on the generalized cross sections A-A' and B-B' (Figures 3 and 4, respectively), located as shown on Figure 2. The Central Valley is divided into three hydrologic basins: the northern Sacramento River Basin, the central San Joaquin River Basin, and the southern Tulare Lake Basin. The city of • Stockton is located within the San Joaquin River hydrologic basin. The general movement 474PARCAP3-02.doc 4 Project No. 1474.23 HORIZON ENVIRONMENTAL INC.