SR0081266 SSNL - Laserfiche WebLink

Home Browse Search

01 October 2019 AGE Project No. 19-4850 Page 5 of 14 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. Geologically, the area around the property generally consists of Holocene-aged flood-basin deposits of clay, silt, and sand. Miocene to Holocene age-units are located in the surrounding area. These deposits are heterogeneous mix of generally poorly sorted clay, silt, sand, and gravel with some beds of claystone, siltstone, sandstone, and conglomerate (1986). Most of the fresh groundwater in the Central Valley is contained in the post-Eocene-aged continental rocks and deposits and in the Holocene-aged river deposits consisting of gravel, sand, silt, and minor amounts of clay. In general, these geologic materials comprise a major widespread aquifer extending hundreds of feet deep and occasionally containing individual confining layers. The Modesto, Riverbank, Turlock Lake Formations and overlying recent alluvium are the principal source of domestic groundwater in the 13,500-square mile San Joaquin Valley Groundwater Basin (Basin 5-22). This basin is drained primarily by the San Joaquin River, which is approximately three miles west- southwest of the property. The nearest surface water feature near the site is the Stockton Diverting Canal located approximately 0.5 miles northeast of the property and the Calaveras River located approximately 2.0 miles northwest of the property. 4.1. GROUNDWATER DESCRIPTION FOR THE GENERAL AREA According to the San Joaquin County Flood Control and Water Conservation District’s Lines of Equal Depth to Groundwater Fall 2018 and a nearby environmental investigation (3032 Waterloo Road), depth to groundwater at the site is approximately 35 to 40 feet below surface grade (bsg). Groundwater flow direction locally appears to range toward the north-northeast to east. Groundwater was not encountered in the 42-inch deep percolation test hole on 17 September 2019. 4.2. GROUNDWATER CONTAMINATION IN THE AREA OF THE SITE The immediately adjacent and outlying land use from the parcel is miscellaneous, commercial and residential. Potential groundwater contamination can occur from several sources including leaking underground storage tanks, septic systems, agricultural activities, dairies, and stormwater infiltration. A review of the California Department of Toxics and Substance Control (DTSC) EnviroStor Database and the Geotracker Web site revealed eleven (11) leaking fuel underground storage tank (LUST) sites within a 0.5-mile of the subject property. However, ten (10) of the LUST sites have been closed for over ten years. The one open LUST