SITE HISTORY - Laserfiche WebLink

Home Browse Search

PRE-TANK REPLACEMENT Site Assessment Results 880 VICTOR ROAD LODI, CA. Aegis Project No. 89-014 Page 9 2 .7 Site Geology Surface geologic units in the vicinity of the Site are depicted on the "Geologic Map of California" as Quaternary basin alluvium consisting of unconsolidated, poorly sorted basin deposits from clay to boulder size. The deposits are considered to be of Holocene age (10, 000 years ago to present) . Underlying the Holocene Alluvium is the Pleistocene Victor Formation which consists of unconsolidated sands, silts (with varying degrees of cementation) , clays and gravels along old stream channels which vary from 0-100 feet thick. 2 .8 Site HVdrogeology Alluvial deposits in the Lodi area contain horizons of gravel , sand, silt, and clay. Horizons of gravels and sand deposits act as important recharge areas and yield large amounts of water to wells while horizons of silt and clay are low in permeability, and do not yield significant amounts of water to wells. The water bearing formation immediately beneath the Site is the Victor Formation. Well logs from water and monitoring wells in the area of the Site indicate that ground water beneath the Site is between 35 and 40 feet below grade . The local hydraulic gradient is anticipated to be toward the Mokelumne River which is located approximately 3000 feet north of the Site. 2 . 9 Regional Geology The Site lies within the northern section of the San Joaquin Valley, which is located in the southern portion of the Great Valley Province. The San Joaquin Valley is a structural trough extending south from the Sacramento-San Joaquin Delta to the Tehachapi Mountains. The San Joaquin Valley is bounded by the Sierra Nevada in the east and the Coast Ranges in the west. Cretaceous sandstones and shales overlay pre-Cretaceous ultra basic igneous rocks, granitic rocks, and metamorphosed sedimentary and volcanic rocks. Sediments originating from the Sierra Nevada and the Coast Ranges were deposited in a marine environment during the Cretaceous to the Pleistocene. Interruptions in the pre-Pleistocene sedimentary depositional cycle occurred several times as volcanic activity, uplift, faulting and/or folding altered the region. From the Pleistocene to the Present, deposition has been alluvial . The Site is situated near the axis of the San Joaquin trough. Recent Alluvium and the Victor Formation overlay the Laguna Formation. The Laguna Formation consists of clay and sand units and unconformably overlays the andesitic sediments of the Mehrten Formation. From the Pleistocene to the present, the depositional environment has been alluvial . Several thousand feet of unconsolidated silty, sandy and gravelly sediments lie within the basin (DWR 1967) .