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and sediment chat would result from the 10-year, 24-hour precipitation <br />• event in accordance with Rule 4.05.2. Survey measurements of sediment <br />accumulations will be conducted bi-annually for discharge points 003, <br />004, 007, 008, 009 and 010 and any new sediment ponds and every third <br />year for 001, 002, 005, and 006. Ponds will typically be cleaned of <br />sediment when water levels are lowest, and the least amount of <br />precipitation is expected. The removed sediment will be used as topsoil <br />or subsoil if it meets the suitability criteria discussed under Section <br />2.04.9. The Division will be notified of this determination if the <br />material is selected as overburden material that can be substituted for <br />or as a supplement to topsoil. <br />All ponds will be designed so that the minimum elevation at the top of <br />the settled embankment is at least one foot above the elevation of the <br />water surface in the pond with the emergency spillway flowing at design <br />depth. <br />Colowyo will design, construct and maintain the sedimentation ponds to <br />prevent short circuiting to the extent possible. As a general rule, the <br />inflow to the ponds will be at the opposite end from the outflow area. <br />The constructed height of the sedimentation pond embankment will }fie <br />designed to allow for settling. During construction, a registered <br />professional engineer will ensure that the appropriate embankment height <br />is accomplished. For all sedimentation ponds, the entire embankment, <br />• including the surrounding areas disturbed by construction, will be seeded <br />after the embankment is completed. The active upstream side of the <br />embankment where water will be impounded will be riprapped or otherwise <br />stabilized, where necessary. Areas in which revegetation is not <br />successful or, where rills and gullies develop, will be repaired and <br />revegetated. <br />Sedimentation ponds that are subsequently approved as part of the post- <br />mining land use will remain in place after the termination of mining <br />activities. <br />Colowyo will inspect the condition of each pond quarterly with the <br />reports submitted annually. None of Colowyo's ponds meet the size <br />criteria of 30 CFR 77.216(a)(1989) <br />$~.? Discharge Structures <br />The sedimentation ponds at Colowyo are designed to treat the theoretical <br />10-year, 24-hour storm event in accordance with Rule 4.05.6(3)(a). As <br />such, the general operation of the ponds will be a passive discharge <br />system where water is allowed to discharge automatically as necessary. <br />Colowyo will sample discharges as appropriate to remain in compliance <br />with applicable CDPS Permit requirements. Pond dewatering through a <br />manual headgate may be performed as necessary to lower the water level <br />• <br />4.05_7 <br />Submdlea 9~;T9~ 9R <br />Revision No. i ~ 9/ <br />