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May 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 three main-stem gaging stations <br />(A-68, M-34 and C-48) on May ls'. The results for these samples are attached. <br />The provisional flow at A-72 on May ], 2002 was 232 cfs. This flow places the sample <br />result in the intermediate flow category (100cfs<Q<300cfs). The dissolved zinc value for <br />this sample, obtained by averaging the results from two labs, was 410 ug/I. <br />The index number for the May sample is calculated as follows: <br />Xi = 410 <br />Xf = 399 <br />Sf= 144 <br />Ni=(410-399)/144 <br />Ni = +0.07 <br />The index number graph and updated reporting table are attached. <br />Evaluation of the normalized data: <br />The index value of +0.07 for May 2002 indicates that the dissolved zinc concentration at <br />the reference point A-72 was above but close to the mean value of the reference data for <br />the intermediate flow class. It appears based on the lower than normal flow and ]ow zinc <br />concentration that the spring flush was already over on May lst. The dissolved zinc <br />concentrations were lower than May 2001's sample at a lower flow. <br />The 12 period moving average of index values dropped to +0.05 from +0.22 because the <br />410 ug/1 is replacing a 523 ug/1 in the 12 month average in a lower flow class which is <br />even more significant. The 12 month average of (+0.05) is below the +0.577 benchmark <br />value in the Consent Decree. <br />