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n Shallow Aquifer Monitoring Wells SB -1, MW -4, MW -5, MW -8, MW-9A,MW- 1OA, and MW -11A monitor the shallow aquifer (Figure 1). Well SB -1 is an up gradient well, whereas wells MW -4, MW -5, MW -8, MW - 9A, MW -10A, and MW -11A are down gradient. Piezometer PZ -1 is in the shallow aquifer, but recent soundings have not detected water. Flow in the shallow aquifer is offsite to the north from the SB -1 location (Figure 2). The Corcoran Clay pinches out west of these wells, which defines 1 the limit of the shallow aquifer beneath the landfill (Figure 2). Wells MW -9A, -10A, and -11A were installed beyond the County property in February 2012 to increase the ability to monitor the shallow aquifer. Deep Aquifer Monitoring Wells MW -6 (down gradient) and MW -7 (up gradient) monitor the deep aquifer. Surface Water When flowing, Corral Hollow Creek is sampled upstream of the waste management facility at background monitoring point S-1 and downstream at monitoring point S-2 (Figure 1). Samples are collected after the first storm of the rainy season that produces significant flow and semi-annually thereafter, when water is flowing. Surface water samples are analyzed semi-annually for the following field and monitoring parameters in accordance with the WDRs: Temperature Carbonate Electrical Conductivity Bicarbonate pH Calcium Turbidity Magnesium Total Dissolved Solids Potassium Chloride Sodium Sulfate Volatile Organic Compounds Nitrate -nitrogen Surface water samples are analyzed every five (5) years for the following COCs: Total Organic Carbon Semi -Volatile Organic Compounds Inorganics (dissolved) Chlorophenoxy Herbicides Volatile Organic Compounds (extended list) Organophosphorus Compounds Surface water COC samples were last collected on April 15, 2010. The next COC surface water monitoring event is scheduled for the first quarter of 2015. Corral Hollow Sanitary Landfill 10 Department of Public Works/Solid Waste 4`" Quarter and Annual 2013 Groundwater Monitoring County of San Joaquin — January 15, 2014