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~ • • <br />6. The emergency spillway for Pond E was sized using the Manning Equation <br />fo open channel flow. The applicant should demonstrate that the proposed design is <br />t adequate using the Broad -Crested Weir Equation. <br />RESPONSE: <br />Please see Emergency Spillway Calculations page 5 of revised Exhibit la, <br />Sedimentation Pond and Diversion Ditch Designs. <br />COLLECTION AND DIVERSION DITCHES <br />' 1. Peak flow calculations for the ditches were not adjusted for varying <br />slope or basin shape. Peak flows should be reestimated making both the slope and <br />basin shape adjustments. <br />RESPONSE: <br />The diversion ditch designs have been adjusted for basin slope and basin shape <br />factors, as shown in the revised Exhibit la, Sedimentation Pond Diversion <br />Ditch Designs on pages S through 11. <br />' 2. The calculated ditch velocities are for grass-lined channels. The ditches <br />will be , in place and functioning for some time before adequate vegetation <br />' protection can be achieved. Therefore, the applicant should show that unprotected <br />channel velocities (earthen channel) would not be erosive. <br />' ~ ~ ~~ <br />RESPONSE: <br />' The diversion ditch designs have been recalculated using Mannings n=0.03 fOr <br />earthen channels, as shown in the revised Exhibit la, Sedimentation and and <br />' Diversion Ditch Designs on pages 8 through 11. <br />Alluvial Valley Floors <br />Formal AVF determinations and findings have not yet been made for Mine No. <br />3. Adjacent portions of both Fish Creek and Middle Creek are potential alluvial <br />' valley floors. the activities being approved in this technical revision (construction <br />of 1 sediment pond and six diversion ditches) would not effect these potential <br />3 <br /> <br />