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• • • • SECTION 5.0 RESULTS • • neutral; the pH of groundwater measured during the 2011 semiannual and annual • groundwater sampling events ranged from 6.86 to 7.64.These values are also consistent with historical monitoring results.The pH of groundwater samples collected during the • former bagging plant investigation,which are presented in Table 5-2,ranged from 6.68 • to 7.13. • Electrical Conductivity, Dissolved Oxygen, and Oxidation-reduction Potential • EC measurements from the 2011 semiannual and annual groundwater sampling events are • presented in Appendix B,Table B-1.Historically,conductivity values measured in the • original test grove were greater than those measured in other areas of the site.The EC values recorded in wells in the original test grove area (KP-1R,KP-6D,TG-1,TG-2,and • TG-3)ranged from 2,042 to 3,952 microSiemens per centimeter(gS/cm) during the 2011 • annual groundwater sampling event.EC has increased at monitoring well KP-3 since third • quarter 2002. An EC of 8,409 gS/cm was measured at monitoring well KP-3 during the 2011 annual sampling event;this is higher than the historical range of EC values in this well • (350 to 7,820 gS/cm).The EC of groundwater during the 2011 annual groundwater monitor- ing event from the remaining wells ranged from 1,445 (KP-2) to 3,588 gS/cm(TG-4). • The field-measured DO concentrations are presented on Figure 5-4 and in Appendix B, • Table B-1.DO concentrations during 2011 ranged from 0.32 to 1.29 mg/L; these concentrations are generally consistent with historical measurements. • The redox potential measured in groundwater during the semiannual and annual ground- water monitoring events ranged from-169 to 158 millivolts (mV).Redox potential • measurements of groundwater in 2011 were consistent with historical measurements.The • redox potential measurements recorded in August 2011 are presented in Appendix B, Table B-1,and on Figure 511. • • Nitrate • Figure 5-5 presents nitrate results from grab groundwater samples collected in July 2011 during the former bagging plant investigation and results from the August 2011 annual • groundwater monitoring event.Estimated nitrate isoconcentration contours for the July and • August 2011 results are also presented on Figure 5-5.Isoconcentration contours were not generated for deep groundwater because monitoring wells KP-6D and KP-4D were the only • deep wells sampled during the 2011 annual groundwater sampling event. • Nitrate was detected at a maximum concentration of 1,120 mg/L during the 2011 annual • groundwater monitoring event(in the sample collected from monitoring well KP-3,which is • located in the former bagging plant area).Prior to the third quarter 2002 sampling event, low concentrations of nitrate were detected at monitoring well KP-3 (8.8 to 44.7 mg/L). • Since third quarter 2002,nitrate concentrations at this well have increased.The concentra- tion detected at KP-3 during the 2011 annual event is the maximum concentration detected • at this monitoring well. Nitrate was detected at a concentration of 282 mg/L in nearby piezometer TG-4 in August 2011.Nitrate concentrations at piezometer TG-4 have fluctuated • from 182 to 393 mg/L since initiation of the remedial action. • • • • RDD1112370001(CAN5003.DOCx) 53 cswzsnaazrcenoo • • •