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August 1998 Monthly Report <br /> Page 3 <br /> - Mainstem Stream Monitoring and Reference Point Stream <br /> Monitoring <br /> Sunnyside sampled the reference point (A-72) on August 5, 1998 <br /> as well as the three mainstem gaging stations (A68, M34 <br /> and C48) . The sample results for these samples are attached. <br /> The provisional flow on August 5, 1998 at A-72 was 291 cfs <br /> which places this sample result in the intermediate flow <br /> category (100 cfs < Q < 300 cfs) . The dissolved zinc value <br /> for this sample obtained by averaging the results from two <br /> labs was 290 ug/l. <br /> The index number for the August sample is calculated as follows: <br /> Xi= 290 <br /> Xc= 399 <br /> Sf= 144 <br /> Ni= (Xi - Xf)/Sf <br /> Ni= (290 - 399)/144 <br /> Ni= -0.757 <br /> The index number graph and updated reporting table are attached. <br /> Evaluation of the normalized data: <br /> The index value of -0.76 for August, 1998 indicates that the <br /> dissolved zinc concentration at the reference point A-72 was <br /> significantly lower than the mean value of the data for the <br /> intermediate flow class. In comparison to the August 13, 1997 <br /> sample result, the 290 ug/l is almost the same (290 ug/l verses 283 <br /> ug/1) although there was 15 percent less flow and these results are <br /> in different flow classes. <br /> Since the index value is less than +2 . 0, Sunnyside does not plan <br /> any additional monitoring or re-analysis. <br /> The 12 period moving average of index values for dissolved zinc at <br /> A-72 (graph attached) dropped to +0. 300 in August. This is a <br /> continuation of the downward trend observed since December, 1997 . <br />