ARCHIVED REPORTS_XR0006081 - Laserfiche WebLink

Home Browse Search

08 August 2005 . AGE-NC Project No 98-0534 Page 11 of 15 geomorphic province of California The San Joaquin Valley is formed by the Great Valley geosynclme, which is a large, elongate, northwest-trending asymmetrical structural trough(basin) It is bordered by the Coast Ranges to the west, the Klamath Mountains and Cascade Range to the north, and the Sierra Nevada to the east This trough has been filled with sediments derived from both marine and continental sources Thickness of the sedimentary fill ranges from thin veneers along the valley edges to greater than 20,000 feet in the south central portion of the valley The sedimentary formations range in age with the older deposits being primarily marine in origin and the younger deposits being primarily continental Continental-derived sediments were primarily deposited in lacustrine, fluvial, and alluvial environments with sources being the mountain ranges surrounding the valley(Olmsted and Davis, 196 1) The site is located on unconsolidated and semi- consolidated alluvium, lake, playa and terrace deposits of Quaternary age (California Division of Mines and Geology, 1977) The Modesto, Riverbank and Turlock Lake Formations and overlying Recent alluvium are the principal sources of domestic ground water in the 13,500-square mile San Joaquin Valley Ground Water Basin (Basin 5-22) ' 2 5 GROUND WATER DEPTH AND FLOW DIRECTION ' Based on the San Joaquin County Flood Control District and Water Conservation District Lanes of Equal Depth of Water Wells Fall 1996 map, the estimated depth to ground water in the vicinity of ' the site is 10 and 20 feet below surface grade (bsg) Historical ground water depths have been as great as 20 feet bsg Based upon information obtained from the UST removal, ground water was at a depth of approximately 15 feet bsg Based on ground water information obtained from wells on ' the site the average depth to ground water was 10 to 12 feet bsg I Based upon data obtained from nearby sites, the prevailing ground water flow direction in the vicinity of the site is estimated to be north However, flow direction may be both locally and , seasonably variable The Stockton Deep Water Channel is the nearest surface water feature to the property, located approximately 1,750 feet north of the site Water from the channel drains into the ' San Joaquin River and is primarily used for commercial and recreational boating, with agricultural as a secondary use The channel contains water continually and has a potential tidal effect upon groundwater depth or flow direction in the area The Stockton Deep Water Channel is a water body ' which is impacted by semi-volatile organic compounds (PCP/Dioxin) and not suitable for recreational use, human consumption nor agricultural use The local ground water on Navy Drive is severely-impacted with high hydrocarbon and fuel additives in the vicinity of the bulk petroleum ' storage facilities (ST Services - ARCO), located one-half mile northwest of the site Depth to ground water was measured at approximately 9 5 feet bsg during a June 2005 ground water monitoring event at the site, the dominant ground water flow direction was inferred towards the • north at a gradient of 0 017 ft/ft Advanced GeoEnvironmentai,Inc.