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North County RC&SL Page 18 of 64 Public Works/Solid Waste Joint Technical Document County of San Joaquin – Revised July 14, 2025 4.4.4 Groundwater Flow The first encountered groundwater at the site is approximately 180 to 190 feet below the native ground surface elevation of 120 MSL. Groundwater elevations range from 60 to 58 feet below mean sea level (MSL). Groundwater flow direction is apparently affected by off-site water withdrawal east of the landfill (Plate 14). Typically, groundwater underlying the site occurs under unconfined conditions within gravelly or silty sands. Groundwater elevation generally fluctuates six feet seasonally. 4.4.5 Capillary Rise Title 27 of the CCR requires that landfill units are designed, constructed, and operated to ensure that wastes will be placed a minimum of five feet above the highest anticipated elevation of underlying groundwater. The estimated capillary rise for the site is less than five feet and the minimum difference in depth between the proposed base of landfill excavations and the groundwater table is greater than 90 feet (see Appendix C). 4.4.6 Water Springs During the 1987 geologic/hydrogeologic site investigation, springs were not identified on the site or within one mile of the proposed landfill site. 4.4.7 Groundwater Quality 4.4.7.1 Regional Groundwater Quality The NCRC&SL is located within the San Joaquin Hydrologic Region, Eastern San Joaquin Sub basin. The sub basin encompasses 707,000 acres (DWR, 2003). According to California’s Bulletin 118 for the San Joaquin River Hydrologic Region, 2003, groundwater quality throughout the region is suitable for most urban and agricultural uses with only local impairments. In addition, groundwater elevations in the Eastern San Joaquin County show a continuous decline over the past 40 years. Because of declining water elevations, poor quality water has been moving eastward along a 16-mile front on the east side of the Delta. The degradation was