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February Monthly Report - 2002 <br />Page 3 <br />The index number for the February sample is calculated as follows: <br />Xi = 582 <br />Xf= 519 <br />Sf= 124 <br />Ni = (582 - 519) /124 <br />Ni = +0.51 <br />The index number graph and updated reporting table are attached. <br />Evaluation of the normalized data: <br />The index value of +0.51 for February 2002 indicates that the dissolved zinc <br />concentration at the reference point A-72 was above the mean value of the reference data <br />for the low flow class. <br />The 12 period moving average of index values remained at +0.26 because the 582 ug/1 is <br />replacing a 590 ug/I in the 12 month average thereby resulting in only a marginal change. <br />The 12 month average of (+0.26) is below the +0.577 benchmark value in the Consent <br />Decree and remains at the lowest level since 12 month running averages have been <br />calculated. <br />American Trmnel Bulkhead No.2 <br />At month end, the bulkhead pressure had not reached equilibrium but the rate of pressure <br />rise had slowed. Final closure of the bulkhead pipe will occur after a pressure equilibrium <br />is reached provided sulfate levels and pressure are within the design criteria for the <br />bulkhead. <br />