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May 1997 Monthly Report <br /> Page 5 <br /> From Sunnyside's data it appears that all subbasins <br /> experienced an increase in dissolved zinc levels from December <br /> through May although the Animas Mainstem appears to be <br /> elevated the highest. The following table contains <br /> Sunnyside ' s estimate of subbasin dissolved zinc percentage <br /> elevation. <br /> Dissolved Zinc <br /> Estimate of Percentage Above Reference Data <br /> (Actual data comparison without standard deviation adjustment) <br /> Month A-72 A68 M-34 C_48 <br /> December, 1996 +32% +58 +39 +1 <br /> January, 1997 +30% - - _ <br /> February +31% +32 +58 +4 <br /> March +41% +117 +78 +17 <br /> April +58% +140 +44 +21 <br /> May +116% +143 +208 +44 <br /> This chart is based on percentage differences between actual <br /> data and the November sample results for the low flow period <br /> and June, 1996 sample results for the high flow period. These <br /> comparisons were used because the Nov, 1996 and June, 1996 <br /> sample results appear to compare to the mean for the flow <br /> classes in the reference data set that the Consent Decree is <br /> based on. This analysis assumes that the concentration values <br /> by subbasin remain constant within a flow class. <br /> From this chart it appears that all subbasins carried elevated <br /> dissolved zinc values during the period of December, 1996 <br /> through May, 1997 . <br /> 2) The nature of the ongoing remediation activities in the <br /> affected basin(s) ; <br /> Animas Subbasin: <br /> a) Closure of the valve in the Terry Tunnel bulkhead. <br /> This prevented untreated winter time flows from reaching <br /> Eureka Creek and should have had a positive effect in <br /> November, December and May. <br /> b) Eureka Tailings Project <br /> Removal of the tailings in the flood plain of the Animas <br /> River. This project was active from late July, 1996 <br /> through late October, 1996. <br />