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September Monthly/3rd Quarter Report - 2002 <br />Page 3 <br />Mainstem Stream Monitoring and Reference Point Stream Monitoring <br />Sunnyside sampled the reference point (A-72) on September 4's. The results for this <br />sample are attached. <br />The provisional flow at A-72 on September 4, 2002 was 69 cfs. This flow places the <br />sample result in the low flow category (Q<100cfs). The dissolved zinc value for this <br />sample, obtained by averaging the results from two labs, was 628 ug/I. <br />The index number for the September sample is calculated as follows: <br />Xi = 628 <br />Xf= 519 <br />Sf= 124 <br />Ni = (628 - 519) /124 <br />Ni = +0.88 <br />The index number graph and updated reporting table are attached. <br />Evaluation of the normalized data: <br />The index value of +0.88 for September 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. Although the result was higher than September 2001's result, the <br />flow was approximately one-half of the 2001 flow. <br />The 12 period moving average of index values rose to +0.26 from +0.16 because the 628 <br />ug/t is replacing a 355 ug/I in the 12 month average although they are in different flow <br />classes. The 12 month average of+0.26 is below the +0.577 benchmark value in the <br />Consent Decree. <br /> <br />