ARCHIVED REPORTS XR0000697 - Laserfiche WebLink

Home Browse Search

31 August 2005 AGE-NC Project No 96-0232 Page 15 of 30 percent porosity, 22 6 percent moisture, and was characterized as a sandy clay Analysis of P27-20 measured a porosity of 34 9 percent, moisture content of 19 8 percent, and classified the soil type as a sandy clay Permeability characteristics have not been tested in soil samples at the Flag City Chevron site, however,for modeling purposes, soil in the First Zone generally consisted of silty sands,sandy clay and sandy silts at depths between surface grade and 35 feet bsg Based on average porosities and intrinsic permeability's of various materials taken from Hydrology for Engineers (Linsley, Kohler and Paulhus, 1982),intrinsic permeability values could be anticipated to be approximately 4 9 x 10' cm2 with porosity values between 30 and 35 percent 2 6 REGIONAL GEOLOGIC/HYDROGEOLOGIC SETTING According to Geologic Map of California, published in 1966 by the California Department of Conservation Division of Mines and Geology, the site area is within the Great Valley Syncline (GVS), a large, elongate, northwest trending structural trough The GVS is subdivided into two major divisions designated the Sacramento and San Joaquin Valleys,which have been filled to the present elevation with thick sequences of sediment ranging in age from Jurassic to present day, creating a nearly flat lying alluvial plain extending from the Tehachapi Mountains in the south to the Klamath Mountains in the north The western and eastern boundaries of this province are comprised of the California Coast Range and the Sierra Nevada, respectively Based on General Soil Map from the San Joaquin County Soil Survey,published by the United States Department of Agriculture Soil Conservation Service in 1992, the site area is within the Guard- Devries-Rioblancho (GDR) association The GDR soils are located within basin rims along the eastern edge of the Sacramento-San Joaquin Delta area,and generally consist of poorly drained,fine to coarse textured soils The GDR soils generally formed in alluvium from mixed rock sources The Modesto,Riverbank,Turlock Lake Formations and overlying recent alluvium are the principal source of domestic ground water in the 13,500-square mile San Joaquin Valley Ground Water Basin (Basin 5-22) This basin is drained primarily by the San Joaquin River The nearest surface water feature in the vicinity of the property is White Slough, located approximately 7,500 feet southwest of the site 3.0. ASSESSMENT OF MTBE-IMPACTED SOIL Between May 1991 and November 2004, forty-three soil borings (P1 through P43) and twenty • ground water monitoring wells (MW-1 through MW-20)were advanced on- and off-site as part of Advanced GeoEnvironmentel,Inc