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Groundwater <br /> New wells MW-4 and MW-5 were installed duringthe fall of 2006 and were monitored in this s momtonng <br /> period. The groundwater well network now consists of upgradient well MW-4 and downgradient well MW- <br /> 5. MW-5 is also down-gradient wells MW-2R and MW-3. MW-1, which had been considered"upgradient" <br /> is now seen to be cross-gradient from the landfill, and not upgradient of either the landfill or another <br /> monitoring well. Presence of the new monitoring wells will allow re-estimation of the groundwater flow <br /> direction, which will be presented in the next report. <br /> All monitoring wells are equipped with dedicated purge and sampling pumps. <br /> Groundwater samples are analyzed semiannually for the following field and monitoring parameters as <br /> specified in the WDRs: <br /> • Temperature • Chloride <br /> ® Electrical Conductivity • Sulfate <br /> • pH • Nitrate-Nitrogen <br /> • Turbidity • Calcium <br /> • Total Dissolved Solids • Magnesium <br /> • Potassium • Sodium <br /> • Carbonate Alkalinity ® Bicarbonate Alkalinity <br /> • Volatile Organic Compounds <br /> (VOCs) <br /> Groundwater samples are analyzed every 5 years for the following Constituents of Concern (COCs): <br /> • Total Organic Carbon <br /> • Inorganics (dissolved) <br /> • VOCs (extended list) <br /> • Semivolatile Organic Compounds <br /> • Chlorophenexy Herbicides <br /> • Organophosphorous Compounds <br /> A COC groundwater monitoring event occurred in the third quarter of 2004. COCs were analyzed this <br /> semester for new wells MW-4 and MW-5. The next COC groundwater monitoring event will occur during <br /> the first quarter of 2010. <br /> Monitoring well elevations are taken quarterly. Hydrographs are included in the second semester and annual <br /> report as directed by the current WDRs. These figures present the following elevations: <br /> • Groundwater for each quarter <br /> • Top and bottom of well screen <br /> • Pump intake <br /> Surface Water <br /> Surface water samples are collected after the first storm of the rainy season that produces significant flow <br /> and semiannually thereafter,when water is flowing. Surface water samples are collected from monitoring <br /> points S-1 (upstream) and S-2 (downstream) of the landfill (Figure 3). <br /> Foothill Sanitary Landfill 6 Department of Public Works/Solid Waste <br /> 2nd Semester and Annual 2007 Groundwater Monitoring County of San Joaquin—January 31,2008 <br />