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(c) Within ten working days afrer the Court approves the Joint Amendment, which includes this revised Appendix A, SGC will calculate and report to WQCD an analysis of the data in the following form: • For each month, SGC will calculate the predicted dissolved Zinc concentration, based on the flow at A-72 and the position on the hydrograph • The standardized residual will be calculated using equation (3) above. • The standardized residua] will be plotted against the sampling period (which begins with the number I as the First sampling event of the project period) on a graph which has the standardized residual at the ordinate and the satnpling period number as the abscissa. An example of such a graph is shown above as Figure A- 3. • SGC will compute a 12-month moving average of the standardized residuals, as follows. Beginning with the twelfrh (120') month of the project period, SGC will compute the mean of the residuals for the 12-month period. For each subsequent month, the oldest residual will be dropped and the newest index number added to the set of 12 from which the mean residual is being computed. • The moving average standardized residual value will also be plotted over time in a similaz fashion to Figure A-3. A-4. Method of Evaluating Water Quality with Respect to Reference Conditions for termination of the Agreement The following describes the method of predicting the water quality at A-72 for the post project condition (once the A-List projects are complete; the American Tumiel portal, the Mogul Mine and the Koehler mine have been plugged; and diversion and treatment of Cement Creek have ceased). (a) Calculation of the );xpected Water Quality at 0001 Station CCOl is the sampling location on Cement Creek directly above the diversion into the American Tunnel water treatment plant. Water Quality at 0001 reflects the impacts of discharges from the Mogul Mine and other mining features as well as the contribution from the rest of the Upper Cement Creek Basin. In order to predict the zinc contribution of the Upper Cement Creek Basin in the post project condition, regression analysis was performed on the zinc and flow data at CCOl for the period before increased flows at the Mogul and Gold King Mines (August 1996 through July 1999). The following equation was developed to describe the relationship between dissolved Zinc at CCO1 as a function of stream flow and whether or not the samples were taken on the rising limb of the hydrograph. The "rise" teen is used for the months June, July and August, since the elevation of CCO1 is 10,600 ft compared to 9,200 ft at A-72 and the melt occurs later in the year. In(Znccox) = 1.38 - 0.159 ln(flow) + 0.336 Rise (4) Appendix A 232565