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April 1999 Monthly Report <br /> Page 3 <br /> Mainstem Stream Monitoring and Reference Point Stream Monitoring <br /> Sunnyside sampled the reference point (A-72) and the three gaging stations (A-68, M-34 <br /> and C-48) on April 7, 1999. The results from these samples are attached. <br /> The provisional flow on April 7, 1999 at A-72 was 97 cfs which places this sample result <br /> in the low flow category (Q<100 cfs). The dissolved zinc value for this sample, obtained <br /> by averaging the results from two labs, was 583 ug/l. <br /> The index number for the March sample is calculated as follows: <br /> Xi = 583 <br /> Xc = 519 <br /> Sf = 124 <br /> Ni = (Xi — Xf) /Sf <br /> Ni = (583 — 519)/124 <br /> Ni = +0.52 <br /> The index number graph and updated reporting table are attached. <br /> Evaluation of the normalized data: <br /> The index value of+0.52 for April, 1999 indicates that the dissolved zinc concentration at <br /> the reference point A-72 was significantly higher than the mean value of the reference <br /> data for the low flow class. In comparison to the April 8, 1998 sample result, the 583 <br /> ug/l is significantly lower(583 ug/l verses 858 ug/1) and the flow was approximated 11 <br /> cfs (13%) higher. <br /> Since the index value is less than +2.0, Sunnyside does not plan any additional <br /> monitoring or re-analysis. <br /> The 12 period moving average of index values for dissolved zinc at A-72 (graph <br /> attached) dropped to +0.36 in April. <br />