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18 September 2020 AdvancedGeo <br /> Project No. 20-6116 An Employee-Owned Company <br /> Page 6 of 16 <br /> Range and the Sierra Nevada, respectively. Geologically, the area around the property <br /> generally consists of Holocene-aged flood-basin deposits of clay, silt, and sand. Miocene <br /> to Holocene age-units are located in the surrounding area. <br /> These deposits are heterogeneous mix of generally poorly sorted clay, silt, sand, and <br /> gravel with some beds of claystone, siltstone, sandstone, and conglomerate (1986). Most <br /> of the fresh groundwater in the Central Valley is contained in the post-Eocene-aged <br /> continental rocks and deposits and in the Holocene-aged river deposits consisting of <br /> gravel, sand, silt, and minor amounts of clay. In general, these geologic materials <br /> comprise a major widespread aquifer extending hundreds of feet deep and occasionally <br /> containing individual confining layers. The Modesto, Riverbank, Turlock Lake Formations <br /> and overlying recent alluvium are the principal source of domestic groundwater in the <br /> 13,500-square mile San Joaquin Valley Groundwater Basin (Basin 5-22). This basin is <br /> drained primarily by the San Joaquin River, which is approximately five miles southwest <br /> of the subject property. The nearest surface water feature to the site is the Stanislaus <br /> River, which is approximately 2.4 miles south-southeast of the subject property. <br /> 4.1. GROUNDWATER DESCRIPTION FOR THE GENERAL AREA <br /> According to the San Joaquin County Flood Control and Water Conservation District's <br /> Lines of Equal Depth to Groundwater Fall 2018 and the Department of Water Resources <br /> (DWR) SGMA Data Viewer, depth to groundwater at the site is approximately 20 to 30 feet <br /> below surface grade (bsg). Between 2011 and 2018, depth to groundwater at the site has <br /> fluctuated between 15 and 30 feet bsg. Groundwater flow direction locally appears to be <br /> toward the northwest. Groundwater was not encountered in the 42-inch deep percolation <br /> test hole advanced on 09 September 2020. <br /> 4.2. GROUNDWATER CONTAMINATION IN THE AREA OF THE SITE <br /> The immediately adjacent and outlying land use for the parcel is mostly agricultural with <br /> minor residential land use. Potential groundwater contamination can occur from several <br /> sources including leaking underground storage tanks, septic systems, agricultural <br /> activities, dairies, and stormwater infiltration. <br /> A review of the California Department of Toxics and Substance Control (DTSC) <br /> EnviroStor Database and the Geotracker Web site did not reveal any properties of <br /> environmental concern within a half-mile radius of the site. <br /> 4.3. ON-SITE EXISTING WELL DESCRIPTION <br /> There are three existing water supply wells on the subject property. The following <br /> information is provided for the wells: <br />