ARCHIVED REPORTS XR0000149 - Laserfiche WebLink

Home Browse Search

M1 • i � ►HCl:`ill NG i 2.3 6eoloov The Pacific Bell facility is located in the Great Valley physiographic province. The Great Valley is monotonous geologically, • consisting primarily of alluvial , flood, and delta plains formed by the valleys two major rivers and their tributaries, one of which is the Calaveras River. The resulting topography of the area is broad and flat with an average elevation at the facility of 48 feet above mean sea 0 level (MSL) . The area is underlain by sands, silts, clays, and gravels of nonmarine origin, which are of Quarternary age. These sediments are generally loosely consolidated. Runoff of surface water is slow and erosion is a slight hazard. 0 Based on borehole data the following generalized sail stratigraphy was identified at the Pacific Bell Stockton facility. From the ground surface to 12.0 feet below the surface is a brown, very silty sand. This is underlain by a light brown, sandy, very clay-rich silt from 12.0 feet to 18.0 feet below the surface. Below this, from 18.0 to 24.0 feet exists a brown, clay-rich, sandy silt. This is underlain by a medium brown, clay-rich, very sandy silt from 24.0 to 32.0 feet below the surface. From 32.0 to 40.0 feet below the surface exists a light brown, sandy, very silty clay. The lowest borehole terminated in a medium gray, slightly sandy, clay-rich silt at 41 .5 feet below the surface. 2.4 Geohvdrology Ground water is reportedly p y present at a depth of approximately 60 feet below the surface, which is approximately 12 feet below MSL. The ground water flow direction is to the west. Ground water is used for agricultural purposes throughout the rural area surrounding the Pacific ' Bell facility. The nearest ground water well is located 50 feet south of the tank excavation site and is used by Pacific Bell in their facility operations. 5