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19 May 2021 AdvancedGeo <br /> Project No. 21-6435 An Employee-Owned Company <br /> Page 5 of 14 <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 thirteen miles <br /> southwest of the subject property. The nearest surface water feature to the site is the <br /> Mokelumne River, which is approximately 3,700 feet east of the subject property. <br /> 4.1. GROUNDWATER DESCRIPTION FOR THE GENERAL AREA <br /> According to the State of California Department of Water Resources (DWR) Sustainable <br /> Groundwater Management Act (SGMA) Data Viewer, Seasonal Report for Spring 2020, <br /> depth to groundwater at the site is approximately 15 to 20 feet below surface grade (bsg). <br /> Between 2011 and 2019, depth to groundwater at the site has fluctuated between 15 and <br /> 30 feet bsg. Groundwater flow direction locally appears to be to the southwest. <br /> Groundwater was not encountered in the 42-inch-deep percolation test hole advanced on <br /> 13 May 2021. <br /> 4.2. GROUNDWATER CONTAMINATION IN THE AREA OF THE SITE <br /> The immediately adjacent and outlying land use for the parcel is general commercial and <br /> medium density residential. 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 revealed seven (7) leaking fuel <br /> underground storage tank (LUST) site within a half-mile radius of the subject property. All <br /> seven (7) LUST sites have been closed for over ten years. Based on the status of the site <br /> and the distance and direction from the subject property, the sites should not impact the <br /> subject property. The review did not reveal any other sites of environmental concern <br /> within a half-mile radius of the site. <br /> 4.3. ON-SITE EXISTING WELL DESCRIPTION <br /> There is no existing domestic water supply well on the property. <br /> 5.0. SOIL PROFILE <br /> An OWTS Permit was issued for the property by the EHD on 4 May 2021 to perform a <br /> percolation test (Appendix B). On 13 May 2021, a 4-inch diameter hand auger was utilized <br /> to advance a percolation test hole to 42 inches bsg, directly outside of the existing septic <br /> system disposal field area. <br />