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Ponds <br />• The following is a list of the pond designs contained in this section: <br />Pond A7 - Pond Al collects and treats all the drainage from the loadout area. The <br />pond location and watershed area are shown on Map 2.05-M4, Drainage and <br />Sediment Control Plan. The pond design is shown on Map 2,05-MSF. The <br />pond incorporates an 1S" riser principal spillway and is designed to treat the <br />70-years, 24-hour event. The principal spillway can also safely pass the peak <br />dischazge from the 25-year, 24-hour event while maintaining 1 foot of <br />freeboard. If the principal spillway should clog, the existing paved entrance <br />road will act as the emergency spillway with any overflow from the pond <br />crossing the entrance road and flowing to the same point where the principal <br />spillway discharges. <br />Pond B - This pond collects and treats all drainage from the main Elk Cteek Surface <br />Facilities Area. The pond location and watershed azea are shown on Map <br />2.05-M4, Drainage and Sediment Control Plan. The pond design is shown <br />on Map 2.05-MSB. <br />Pond C - This pond collects and treats all drainage from the West Valley Coal Refuse <br />Facility Area. The pond location and watershed area are shown on Map <br />2.05-M4, Drainage and Sediment Control Plan. The pond design is shown <br />on Map 2.05-MSC. <br />• Pond D - This pond collects and treats all drainage from the Elk Creek Mine Surface <br />Facilities Area, including the conveyor corridor as shown on the drawings. <br />The Principal spillway dischazge pipe will have a gated valve. The valve will <br />remain open during all storm events. The pond location and watershed area <br />are shown on Map 2.05-M4, Drainage and Sediment Control Plan. The <br />pond design is shown on Map 2.05-MSG. <br />Pond E - This pond collects and treats runoff from the II West Coal Refuse Facility <br />Area. The pond location and watershed is shown on Map 2.05-M4, <br />Drainage and Sediment Control Pond. The pond design is shown on Map <br />2.05-MSI. <br />Substation - This pond collects and treats all drainage from the Substation No. 3 and C- <br />Pond No. 3 Gulch Ventilation Shaft areas. The pond location and watershed area are <br />shown on Map 2.05-M4, Drainage and Sediment Control Plan. The pond <br />design is shown on Map 2.05-MSE. <br />All ponds were designed to contain or treat the runoff resulting from the 10-year, 24-hour event. For <br />all ponds the emergency spillway is designed to safely pass the peak discharge resulting from the 25- <br />year, 24-hour event. The ponds were designed according to the methodologies and assumptions <br />contained in Section 5. All hydrology inputs and results are shown on the SEDCAD printouts <br />contained in Section 70. A summary of the results is shown on the following Tables. <br />J <br />TR-43 Revised September 2003 <br />