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• <br />• <br />r~ <br />Mountain Coal Company, L.L.C. <br />West Elk Mine <br />Exhibit5l <br />Lower Refuse Pile <br />Table I I -Sedimentation Basin Sediment and Water Yields; 10-Year,24HourStorm <br /> Phasel Phase Phase Phase <br /> IT III IV' <br />Total acres disturbed(includingwaste 12.1 13.9 16.6 18.7 <br />and subsoil and topsoil stockpiles) <br />Total acres to be vegetated and 2.4 6.9 8.3 8.3 <br />reclaimed during the life of the refuse <br />pile <br />Total acres unreclaimedduring life of 9.7 8.0 8.3 8.4 <br />pile <br />Estimated life of pile (years) I.8 I.I 2.6 16.7 <br />Average Annual Sediment Yield (ft') 71.0 109.0 233.0 6.634.0 <br />from vegetated slopes during life of <br />pile <br />(CP=0.1) <br />Average Annual Sedimen[Yield (ft') 28,809 14,620 23,281 13.068.0 <br />from unreclaimedslopes during life <br />of pile <br />(CP = 0.8) <br />Total Average Annual Sediment 28,880 14.629 23,514 19,166 <br />Yield (ft') <br />Final elevation of sediment assuming 6108.2 6106.3 6107.5 6103.1 <br />no cleanou[during life of pile (feet) <br />Total storm yield (ft'); 10-year, 24- 12,737 14,632 18.267 42,306.4 <br />hour storm event <br />Elevation of pool assuming no 6106.1 6106.3 6106.9 6114.0 <br />sediment (feet) <br />Maximum allowed elevation of 6107.3 6107.1 6106.6 61 19.76 <br />sediment or water for storage of 10- <br />vear.24-hourstorm event <br />Requiredcleanoutscheduleto annually annually annually every <br />maintain sediment level below the nvo <br />maximum sediment or w-ater vears <br />elevation <br />Sedimenlyield(ft')forcleanout 16,005 13,299 13.832 27.688 <br />period <br />Sediment elevationarendofcleanout 6106.6 6106.1 6106? 6102.76 <br />period <br />30 <br />