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7. The 'H' flume was selected for the primary spillway for its ability to accurately measure flows <br />• under low flow and high flow conditions. A 1.0' H flume has a reported range from 0.31 to <br />861.7 gpm (0.0007 to 1.92 cfs). <br />• <br />8. Since the sediment load and settling characteristics of the mine discharge water is unknown a <br />conservative educated estimate of the retention pond requirements was made. Observations of <br />mine water samples indicated that adequate settling should occur in less than one day. Each of <br />three dewatering ponds should provide more than one day's settling time under initial <br />conditions. Outflow of each pond can be monitored to better evaluate the systems <br />performance relative to the assumptions used in the design. <br />9. The first pond in the series is intended to accumulate the vast majority of the sediment from the <br />mine discharge. Periodic sediment removal will be facilitated by temporarily diverting mine flow <br />directly to the second pond while the first pond is dewatered and sediment removed. <br />Technical Revision #68 (05/2011) <br />