ARCHIVED REPORTS XR0001372 - Laserfiche WebLink

Home Browse Search

HYDROGEOLOGIC UNITS i Based on cross sections A-A' and B-B', AGE informally identified five hydrologic flow units between first encountered ground water and 199 feet as having significant intervals of apparently porous, coarser-grained soil separated by intervals of finer-grained, less permeable soil Hydrogeologic Unit 1 (HU-1)was subdivided into three sub-units(HU-1 Upper Zone,HU-1 Middle Zone and HU-1 Lower Zone) that may not have significant barriers to vertical migration of contaminations Generally, HU-1 Upper Zone was identified at depths between 25 feet (first ' encountered ground water) and 51 feet bsg, HU-1 Middle Zone was identified at depths between 48 feet and 75 feet bsg, and HU-1 Lower Zone was identified at depths between 60 feet and 90 feet bsg, Hydrogeologic Unit 2 (HU-2) was identified at depths between 112 feet and 125 feet bsg, IHydrogeologic Unit 3 (HU-3) was identified at depths between 140 feet and 160 feet bsg, Hydrogeologic Unit 4 (HU-4) was identified at depths between 160 feet and 175 feet bsg and Hydrogeologic Unit 5 (HU-5) was identified at depths between 190 feet and 199 feet bsg STRATIGRAPHY Generally, alternating, laterally discontinuous intervals of clay, silt and sand were encountered between surface grade and approximately 90 to 100 feet bsg Porous intervals containing silt, silty sand, sandy silt and poorly graded sand were encountered between approximately 112 to 125 feet bsg, 130 to 165 feet bsg and ISO and 195 feet bsg Fine grained, silt, silty clay, clayey silt and clay were observed at all other depths REGIONAL GEOLOGIC SETTING According to the Geologic Map of California, published in 1977 by the State of California Department of Mines and Geology,the site area is within the Great Valley Geomorphic Province of California, a large, elongate, northwest trending structural trough The Great Valley Province has been filled to its 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 Mountains, respectively The Great Valley Province is subdivided into two major divisions designated the Sacramento and San Joaquin Valleys Based on the 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 Jacktone-Hollenbeck-Stockton (JHS) association The JHS soils are located within basins, and generally consist of moderate to poorly drained fine textured soils The soils are generally derived from both marine and non-marine sediment, and are generally formed in alluvium derived from mixed rock sources I