ARCHIVED REPORTS XR0006246 - Laserfiche WebLink

Home Browse Search

Stockton Meat Plant - Case Closure Page 8 March, 1996 (quality, water level) through eight quarters of monitoring from 1992 through 1995 Trace to low concentrations of diesel have been monitoring in m reported wells P g associated with the underground tank work Diesel concentrations ranged from a low of 150 ug/l to a high of 1,200 ug/l There have been no reported BTEX compounds in ground water samples taken from the monitoring wells The extent of the hydrocarbons has not been determined at the site Based on the Krazen work, it appears trace to low levels of diesel hydrocarbons are prevalent in groundwater throughout the site Additionally, it appears that the source of the diesel is not from the underground tank site Diesel hydrocarbons have been detected in groundwater samples from upgradient sources at least 200 to 650 feet from the underground tanks The source of the hydrocarbons may be from past military use or from an unknown off-site source HYDROGEOLOGY Geologic Setting The following excerpt is taken from the Krazen Report, reference Attachment G "The subject site lies near the northern end of the San Joaquin Valley portion of the Great Valley Geomorphic Province The Great Valley is bordered to the north by the Cascade and Klamath ranges, to the west by the Coast Range, the East by the Sierra Nevada, and to the south by Transverse Ranges The valley is characterized by a thick sequence of sediments derived from erosion of the Sierra Nevada to the east and the Coast Range to the west These sedimentary rocks are mainly Cretaceous in age The depth of the sediments vary from a ' thin veneer at the edges of the valley to depths in excess of 501000 feet near the western edge of the valley In the vicinity of the site, these sediments are over 15,000 feet deep Near surface sediments are predominately fine-grained ' and were deposited during flood stages of major rivers and streams The San Joaquin Valley has historically been a province of relatively low seismic activity The nearest active faults to the site are the Foothills Fault system located near the base of the Sierra Nevada and the Coast Ranges Sierran Block Boundary Zone located along the base of the Coast Ranges There are no known active fault traces in the project vicinity The Stockton Fault Zone is located less than one mile from the project site There is no history of activity for this fault zone and it is known only through vertical offsets in deeper geologic formations observed in petroleum exploration and production wells