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August Monthly Report - 2002 <br />Page 3 <br />Mainstem Stream Monitoring and Reference Point Stream Monitoring <br />Sunnyside sampled the reference point (A-72) and the other three main-stem gaging <br />stations (A-68, M-34 and C-48) on August 7°i. The results for these samples are attached. <br />The provisional flow at A-72 on August 7, 2002 was 89 cfs. This flow places the sample <br />result in the low flow category (Q<100cfs). The dissolved zinc value for this sample, <br />obtained by averaging the results from two labs, was 493 ug/l. <br />The index number for the August sample is calculated as follows: <br />Xi = 493 <br />Xf= 519 <br />Sf= 124 <br />Ni = (493 - 519) /124 <br />Ni = -0.21 <br />The index number graph and updated reporting table are attached. <br />Evaluation of the normalized data: <br />The index value of -0.21 for August 2002 indicates that the dissolved zinc concentration <br />at the reference point A-72 was slightly below the mean value of the reference data for <br />the low flow class. Although the result was higher than August 2001's result, the flow <br />was approximately one-quarter of the 2001 flow. Both results were below the reference <br />data mean. <br />The 12 period moving average of index values rose to +0.16 from +0.15 because the 493 <br />ug/1 is replacing a 276 ug/1 in the 12 month average although they are indifferent flow <br />classes. The normal residual which these concentrations and flows generate rose from <br />-0.20 to -0.21. The 12 month average of+0.16 is below the +0.577 benchmark value in <br />the Consent Decree. <br />