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TABLE 8 ANALYSIS OF CHROMIUM CONCENTRATIONS AND REDUCTION POTENTIAL FORMER MARLEY COOLING TOWER SITE STOCKTON,CALIFORNIA Current Concentration Concentration Change Concentration Description of Trend for Key Indicator Parameters Potential for Monitoring (µg/L) Since 2008 has been Further Oxidation Reduction Recommendation` Well Total Chromium Total Chromium Below 50µg/L Chromium Iron Manganese Total Organic Carbon Chromium Since' Potential Reductionb Chromium VI Chromium Back round and Compliance Wells MW-7 <10 0.88 -91% -96% 1/2009(Before Low Positive Low Variable,but below Perform quarterly monitoring for total dissolved 2008) Stable below WQO Near baseline WQO chromium and field parameters only MW-201 13 9.74 -79% -3% 1/2009(Before Perform quarterly monitoring for total dissolved 2008) Stable below WQO Near baseline Near baseline Low Positive Low chromium and field parameters only MW-202 3J 1.57 -91% -53% Before 2008 Stable below WQO Near baseline Baseline(ND) Low Positive Low Perform quarterly monitoring for total dissolved chromium and field parameters only MW-210 <10 <0.5 -71% -81% Before 2008 Stable below WQO Near baseline Near baseline Low Positive Low Perform quarterly monitoring for total dissolved chromium and field parameters only MW-302 4J 2.11 -89% 0% Before 2008 Stable below WQO Near baseline Baseline(ND) Low Positive Low Perform quarterly monitoring for total dissolved chromium and field parameters only MW-304 6J 3.13 -83% -69% Before 2008 Stable below WQO Above baseline Baseline(ND) Low Positive Low Perform quarterly monitoring for total dissolved chromium and field parameters only MW-401 <10 <0.5 -55% -74% Before 2008 Stable below WQO Near baseline Below WQO increase Low Positive Low Perform quarterly monitoring for total dissolved from previous ND chromium and field parameters only 0 o Below WQO,increase Perform quarterly monitoring for total dissolved MW-310 <10 <0.5 -89/o -97/o Before 2008 Stable below WQO Near baseline Low Positive Low from previous ND chromium and field parameters only MW-211 <10 0.61 -71% -71% Before 2008 Stable below WQO Near baseline Near baseline Low Positive Low Perform quarterly monitoring for total dissolved chromium and field parameters only MW-325 <10 <0.5 -84% -96% Before 2008 Stable below WQO Below WQO,Near Below WQO,icrease Low Positive Low Perform quarterly monitoring for total dissolved baseline,slight increase from previous ND chromium and field parameters only Notes: a =Dates in parentheses represent chromium VI,if the date is different than for total chromium. b =Potential for further chromium reduction is based on the presence of iron,manganese,total organic carbon,and depressed oxidation reduction potential readings,as discussed by chemical in Section 4.0. ` =Recommendation is based on completion of injections nearby and more than 2 years of chromium concentrations below the WQO. See the discussion in Section 8.0 and the decision logic diagram(Figure 5). d =Well would continue to be routinely sampled for chromium and other parameters as specified for the sitewide groundwater monitoring program in the MRP. Bold=Concentration greater than the WQO µg/L=microgram per liter J=Estimated laboratory value MRP=Monitoring and Reporting Program No.R5-2007-0126 issued by the California Regional Water Quality Control Board,Central Valley Region, September 13,2007. ND=not detected NM=not meaningful because the chemical has not been detected above the laboratory analytical reporting limit. WQO=water quality objective (Page 3 of 3)