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<br /> <br />-z- <br /> <br />4. The 10-year, 24-hour storm must be contained in the ponds. If high <br />inflows result in water levels above the level required to allow adequate <br />storage of this storm, provisions must be made in the permit application to <br />dewater the ponds to the necessary level. <br />5. On page 2.05-162, it is stated that the detention basins will be <br />monitored at the inlet and outlet. Will each inlet be monitored? <br />6. If Energy Mine No. 3 detention pond is proposed as a permanent pond <br />according to the details to Addendum 1, the following additional information <br />is necessary. <br />a. It is proposed to fill this pond with 100,000 CY of overburden <br />material. Where is this material coming from? It is not accounted for <br />on the Spoil Grading Plan, Map No. 10. Based upon the present <br />reclamation plan, it does not appear that there is 100,000 CY additional <br />material available for placement in the pond. <br />b. If 100,000 CY is available, how will the filling be accomplished? <br />Will it be dumped and compacted? Where will the access road to <br />accomplish this be located? Will the material be spread evenly <br />throughout the pond, or will certain areas be filled in to reduce the <br />pond surface area? <br />c. When will this filling be accomplished? What provisions will be <br />made if there is a significant amount of water 1n the pond at the <br />proposed time of filling? <br />d. The peak flow for Energy Mine No. 3 detention basin, as reported in <br />Table 1, is 102.3 cfs. The peak flow from ditches H1, H2, and H3 which <br />empty Into the pond is 118.7 cfs. In addition, there 1s a small area <br />which flows directly Into the pond not accounted for in the 118.7 cfs. <br />Since the spillway design is conservative, this discrepancy will not <br />affect spillway performance. <br />e. The total sediment yield for this pond, Table A, seems high. The <br />applicant states on page 2.05-94 that it is estimated pre-mine <br />productivity should be reinstated on all revegetated areas in <br />substantially less than the three year's time proven in 1974 <br />reclamation. The calculations presented use a reclamation period of 10 <br />years. Also, it 1s estimated that sediment transport will be further <br />reduced using contour furrows. <br />f. If reevaluation of the sediment yield increases the capacity of the <br />pond to above 2.0 acre-feet, then permanent water storage rights are <br />required. <br /> <br />g. The spillway, as shown on the Permanent Sediment Control Plan, Map <br />20, 1s not drawn to scale. This should be corrected. <br />