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TABLE 6 <br /> HISTORIC GROUNDWATER ANALYTICAL RESULTS AND PROPOSED COMPLIANCE WELL BACKGROUND CONCENTRATION LIMITS <br /> FULL SCALE IN SITU HEXAVALENT CHROMIUM REDUCTION TREATMENT <br /> FORMER MARLEY COOLING TOWER SITE <br /> STOCKTON,CALIFORNIA <br /> Laboratory Analyses <br /> Hexavalent <br /> Nitrate as N Chromium Chromium Manganese <br /> Well Sample Date Event/Purpose m * Sulfate (mg/L Calcium (mg/L Arsenic /L /L Iron /L /L TDS m/L <br /> Water Quality Objective 10 250 10 50 50** 300 50 450 <br /> Background/Compliance Wells <br /> MW-201 7/18/1985 1985-1987 Common Ion 15 20 -- 100 -- -- -- 630 <br /> 7/23/1985 1985-1987 Common Ion 12 19 -- 640 <br /> 7/30/1985 1985-1987 Common Ion 12 19 610 <br /> 10/23/1985 Hist.Sum.GW Quality -- -- 10 -- <br /> 2/3/1986 Hist.Sum.GW Quality 14 <br /> 4/8/1986 Hist.Sum.GW Quality 28 <br /> 7/8/1986 Hist.Sum.GW Quality 23 <br /> 11/11/1986 Hist.Sum.GW Quality -- -- 22 -- <br /> 1/28/1987 1985-1987 Common Ion 16.4 40 25 605 <br /> 4/22/1987 Hist.Sum.GW Quality -- -- 30 -- <br /> 7/9/1987 Hist.Sum.GW Quality 50 <br /> 10/21/1987 Hist.Sum.GW Quality 35 <br /> 1/12/1988 Hist.Sum.GW Quality 40 <br /> 4/5/1988 Hist.Sum.GW Quality 30 <br /> 7/14/1988 Hist.Sum.GW Quality 40 <br /> 9/29/1988 Hist.Sum.GW Quality 40 <br /> 12/14/1988 Hist.Sum.GW Quality 4 <br /> 4/18/1989 Hist.Sum.GW Quality 4 <br /> 7/20/1989 Hist.Sum.GW Quality 35 <br /> 10/26/1989 Hist.Sum.GW Quality 34 <br /> 1/17/1990 Hist.Sum.GW Quality 50 <br /> 4/26/1990 Hist.Sum.GW Quality 26 <br /> 7/18/1990 Hist.Sum.GW Quality 40 <br /> 1/23/1996 Hist.Sum.GW Quality 120 <br /> 4/11/1996 Hist.Sum.GW Quality 10 <br /> 1/29/1997 Hist.Sum.GW Quality 20 <br /> 4/1/1998 Hist.Sum.GW Quality 40 <br /> 1/8/1999 Hist.Sum.GW Quality 20 <br /> 1/1/2000 Hist.Sum.GW Quality 40 <br /> 1/1/2001 Hist.Sum.GW Quality 24 <br /> 1/1/2002 Hist.Sum.GW Quality 3 <br /> 1/3/2003 Hist.Sum.GW Quality 8 <br /> 4/1/2006 Dudek 2007 Annual Rpt 20 <br /> 4/1/2007 Dudek 2007 Annual Rpt -- -- -- 13 -- -- -- -- <br /> 2/4/2008 Background 1 14.3 49.4 NA <5 17 <10 390 <10 786 <br /> Historic Concentration Range 390 0 605-786 <br /> WDR/MRP Suggested Upper Limit Background Concentration C1130 <br /> 429 864.6 <br /> Proposed Upper Lim�ckground Concentration 429 864.6 <br /> 4/2/2008 2nd Qtr./Compliance 12.5 47.0 NA <5 28 <10 307 <10 807 <br /> 5/20/2008 Supplemental 11.4 51.1 NA <5 <10 <10 493J <10 877J <br /> 7/11/2008 3rd Qtr./Compliance 12.4 51.5 NA <5 13 <10 1,220 <10 956 <br /> 7/11/2008 3rd Qtr. 11.4 50.5 NA <5 13 <10 1,340 <10 893 <br /> 10/22/2008 4th Qtr./Compliance 6.3 44.7 NA <5 22 <10 <100 <10 832J <br /> 1/9/2009 1st Qtr./Compliance 10.8 58.1 NA <5 63 A <10 <100 <10 841 <br /> 4/8/2009 2nd Qtr./Compliance 12.0 53.2 NA <5 19 10 637 <10 879 <br /> 7/15/2009 3rd Qtr./Compliance NA 50.9 <5 21 <10 1,000 <10 851 <br /> 10/14/2009 4th Qtr. NA 52.0 1.0 7 <10 688 20 907 <br /> (Page 2 of 10) <br />