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52.05 APPLICATION FOR PERMIT FOR SIIRFACE OR UNDERGROUND MINING ACTIVITIES -- MINIMUM REQUIREMENTS FOR OPERATION AND RECLAMATION PLANS. `.. -- • ! 2.05.6 Mitigation of Surface Coal Mining Operation Impacts. (Con['d,) (3) (b) (i) (Cont'd.) •~. 1. The upper diversion ditches; 2. The mine site drainage; 3. The culvert below the portal level fill embankment to route Ea s[ Roatcap Creek drainage through the permit area; 4. The sedimentation pond; 5. Fill embankment outslopes; and 6. The water tank and vent shaft drainage and dugout pond, The upper diversion ditches divert storm run- off from the upper basin. The ditch calcula- tions may be found in the Fydrology Appendix. Trre.~ ditches dtscharRe water into adjacent areas north of the mine site. The ditch is designed to carry runoff from a 10-year, 24- hour storm event. Runoff flow generated from the mine site dis- turbance is handled by drainage ditches locat- ed on the north perimeter of the portal level cut and fill embankment. The other areas in the portal level cut and fill have been graded and localized drainage ditches may be neces- sary and would be constructed for efficient drainage of water. All ditches will be sized for appropriate capacities. The mine site disturbed area drainage has also been sized for a 10-year, 2L-hour_torm event. _ The culvert that was constructed below the fill embankment has been designed to safely pass a 100-year, 24-hour event with no inlet head required. It can safely pass a 500-year, 24-hour event with a few fee[ of head. Tnis culvert has been designed with appropriate sediment and deb-ris traps so that the integri- ty of the culvert is ensured. Periodic main- tenance will be completed [o ensure the cul- vert is in place. Tne next part of the drainage plan is the sed- imentation pond. The drainage ditches along the northern perimeter of the portal level Added 10/12/86 Revised 01/06/87 Revised 10/01/87 Revised 03/28/88 107