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4.10.3 Regional Groundwater Quality <br /> The landfill site is located within the San Joaquin Hydrologic Region, Eastern San <br /> Joaquin Sub basin, which encompasses 707,000 acres (The California Department <br /> of Water Resources, 2003). According to California's Bulletin 118 for the San <br /> Joaquin River Hydrologic Region, 2003, groundwater measurements over the past <br /> 40 years have shown a continuous decline in groundwater levels in the Eastern San <br /> Joaquin County. As a result of declining water levels, poor quality water has been <br /> moving eastward along a 16-mile front on the east side of the San Joaquin River <br /> Delta. The degradation was particularly evident in Stockton where a saline front is <br /> moving eastward. Large areas of elevated nitrate in groundwater exist within the <br /> sub basin located southeast of Lodi and south of Stockton. For the entire basin, 689 <br /> public supply water wells were sampled from 1994 through 2000. Samples <br /> analyzed indicated that 523 wells (76%) met the state primary MCLs for drinking <br /> water. The others (24%) had constituents that exceeded one or more MCLs. These <br /> included: inorganics (aluminum, arsenic, manganese, iron, and total dissolved <br /> solids), radiological particles, nitrates, pesticides, and VOCs. Calcium-magnesium <br /> bicarbonate or calcium-sodium bicarbonate types characterize the majority of the <br /> basin. Bicarbonate is the predominant anion in the eastern part of the basin. <br /> Groundwater quality throughout the region is suitable for most urban and agricultural <br /> uses (The California Department of Water Resources, 1994). <br /> 4.10.4 Groundwater Use <br /> Groundwater use on and surrounding the property is agricultural, domestic supply, <br /> and groundwater monitoring. <br /> Eight wells were identified within 1 mile of the landfill site. The screened sections of <br /> these wells vary between bottom depths of 255 feet to as deep as 467 feet <br /> (Appendix H). One off-site well appears to be down gradient, west-southwest of the <br /> site (review of California Department of Water Resources files reported in "Report of <br /> Waste Discharge Related to the Permitting and Installation of Composite Landfill 3 <br /> Foothill Sanitary Landfill Page 15 of 57 Public Works/Solid Waste <br /> Joint Technical Document County of San Joaquin—Revised 7/30/10 <br /> i <br /> i <br />