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Sediment will be removed from all sedimentation ponds when the volume of sediment accumulates to three (3) years of <br />sediment yield. Yearly measurements of sediment accumulations will be conducted. Ponds will be cleaned out when water <br />levels are lowest, and the least amount of precipitation is expected. The removed sediment will be used as topsoil or subsoil <br />if it meets suitability criteria. <br />The detention time for each pond has been designed to be a minimum of 24 hours to meet the applicable effluent limitations <br />with respect to total suspended solids. <br />All ponds have been designed so the minimum elevation at the top of the settled embankment is at least one foot above the <br />elevation of the water surface in the pond with the emergency spillway flowing at designed depth. <br />To allow for settling, the constructed height of the sedimentation embankment is at least five (5) percent greater that the <br />designed height. During construction, a qualified registered professional engineer ensured that this was accomplished. <br />For all sedimentation ponds, the entire embankment, including the surrounding areas disturbed by construction, were <br />seeded after the embankment was completed. Any area in which vegetation is not successful or, where rills and gullies <br />develop, will be repaired and revegetated. <br />4.05.7 DISCHARGE STRUCTURES <br />Discharge from sedimentation ponds will be controlled by the use of energy dissipaters and flow check devices where <br />necessary. The water released from the ponds will travel through spillways lined with riprap, gravel, or natural vegetation <br />before being discharged into the existing drainage. All discharge structures have and will be designed by a qualified, <br />registered professional engineer. <br />The Standard Dewatering Device is a gated 6" pipe placed at the dewatering design elevation for the pond. The design of <br />the various ponds is presented in Exhibit 18. The gate is located on the pool side of the embankment and is manually <br />opened by turning the handle. The knife gate rides up the threaded handle until it is above the top of the pipe. To close the <br />gate the process is reversed. <br />4.05.8 ACID-FORMING AND TOXIC-FORMING SPOIL <br />No surface mining is planned at EC. There are no known acid-forming or toxic-forming materials present in the spoil to <br />be reclaimed a[ [he abandoned strip mines. Section 2.05.4 describes the basis for concluding that underground <br />development waste is not acid-forming and is non-toxic. <br />4.05.9 PERMANENT AND TEMPORARY IMPOUNDMENTS <br />As stated earlier, EC plans to use sedimentation ponds as temporary impoundments to meet applicable Colorado and <br />Federal water effluent standards. There are no permanent impoundments planned. However, if at the time of final <br />reclamation, and in consultation with the Division of Wildlife and the DMG, it were deemed desirable to retain certain <br />ponds for their wildlife or agricultural values, EC will consider leaving selected ponds as permanent impoundments. <br />4.05.10 UNDERGROUND MINE ENTRY AND ACCESS DISCHARGES <br />There are no granite discharges from any portals or mine openings at EC, and here the requirements of Section 4.05.10 are <br />not applicable. <br />4.05.11 GROUND WATER PROTECTION <br />As noted earlier in Sections 2.04.7 Hydrology Information, and 2.05.6 the Mitigation of Impacts of Mining Operations, no <br />major impacts are anticipated on the surrounding ground water system due to mining by EC. <br />Permit Revision 04-34 4.01-5 Revised 7/2/04 <br />