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13 August 2019 AdvancedGeo AGE Project No. 19-4782 E ri v i ro n ni e n t a l Page 5 of 14 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 (Page, 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 11 miles west of the property. The nearest surface water feature near the property is Littlejohns Creek located approximately two miles north of the property. 4.1. GROUNDWATER DESCRIPTION FOR THE GENERAL AREA The San Joaquin County Flood Control and Water Conservation District's Lines of Equal Depth to Groundwater Fall 2018 indicates the depth to groundwater is approximately 60 feet below surface grade (bsg). Groundwater flow direction locally appears to be toward the north. Groundwater was not encountered in the 40-inch percolation test hole on 18 July 2019. 4.2. GROUNDWATER CONTAMINATION IN THE AREA OF THE SITE The immediately adjacent and outlying land use from the subject property is residential, commercial, and agricultural. 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 two leaking fuel underground storage tank (LUST) sites within a one-mile radius of the site. However, both sites have been closed; one site was closed in 1993 and the other in 2008. Based on information reviewed on the Geotracker Web site, residual petroleum hydrocarbon contamination was not left remaining in place. 4.3. ON-SITE EXISTING WELL DESCRIPTION There is one existing water supply well on the adjacent property at 17699 ST RT 120. The well is located along the southwest property boundary of 17699 ST RT 120 and the subject property. The well will provide potable water and service the proposed