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4.05. Sediment Ponds A and D exceed 20 acre feet in storage capacity. The emergency <br />spillway for these two ponds were designed and constructed for 100-year, 24-hour events. <br />Many ponds utilize baffle structures to ensure adequate detention time. Drainage ditches B-1, <br />B-2, I-2, I-3, and N-2 were designed for 100-year, 24-hour events. Certain steeper sections of <br />drainage ditches I-2, N-2 and B-2 are designed with riprap bottoms to minimize the erosive <br />effects of flowing water. <br />Kerr Coal Company water rights and water augmentation plan are detailed in Volume 10 <br />Exhibit 25. The Augmentation Plan lists a total water consumption of 69.46 acre feet per <br />year. The figure includes 66.9 acre feet for pond dead storage and 2.56 acre feet consumed <br />for dust suppression, other industrial usage and sanitary needs. Kerr Coal claims the 315.2 <br />acre feet of water rights for potential mitigation of adverse impacts to surrounding water users. <br />Based upon the data, Kerr Coal has adequate water rights to mitigate adverse impacts to <br />neighboring water users. <br />Rangeland will be re-established at the Marr Mine and loadout. <br />The reclamation plan currently calls for backfilling the southernmost 720 Pit with material <br />from the adjacent temporary overburden stockpile. If mining does not progress beyond Pit i <br />this pit will be backfilled with material resulting from highwall reduction. The Pit 1 highwall <br />will be reduced to 3.5:1. This will result in 10 acres of additional disturbance. The mine <br />anticipates backfilling the 720 pit concurrently with Pit 1 at a rate of 1 million yds 3 a year and <br />completing backfilling operations by 1999 (page 816-124aaaaaaaa). All structures will be <br />dismantled and removed from the site. If Kerr decides to continue mining beyond Pit 1, this <br />pit will be left open to receive material from Pit 2 and operations would then be conducted <br />under the modified plans presented as PR-1 which was not approved but will be revised and <br />resubmitted. <br />Topsoil and subsoil salvage and replacement vary among pits and soil types. Information on <br />soil removal and replacement can be found on pages 816-6 to 816-28 and on 816-125 of the <br />permit application. Tables 57aa -Total Soil Averages and Depths by Mine Plan Years and <br />59a -Soil Redistribution Plan, contain information on soil depths and volumes to be removed <br />and replaced throughout the permit term. Soils in the 720 Pit were salvaged prior to <br />promulgation of the Colorado Surface Coal Mining Reclamation Act, and six inches of <br />material, regardless of suitability, were salvaged. In general, six inches of topsoil were <br />salvaged from Pit 1. If Pit 2 is not opened, where Kerr had anticipated getting additional <br />topsoil from the mining in the Pit 2 area, topsoil will be placed at a minimum depth of .5 feet <br />(page 816-126). If Pit 2 is mined an additional topsoil is available, the mine has committcd tc <br />topsoiling to depths ranging from .5 to 2.99 feet (page 816-24). Topsoil at the tipple was not <br />extensively salvaged. Some material has been stockpiled in a berm around the property and <br />will be respread across the regraded surface. <br />Marr Strip Mine, C-80-006 12 December 9, 1992 <br />