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West Elk Mine <br />design detail for this pond, the clean water diversion ditches, and sediment ditches can be found in <br />Exhibit 70. <br />DCW-2, the ditch immediately south of the haul road above the Lower Refuse Pile, serves as the <br />clean water diversion ditch for the Lower Refuse Pile, It diverts undisturbed runoff from the Lower <br />Refuse disposal azea and is discharged into sediment pond MB-2R. Runoff from the Lower Refuse <br />Pile is conveyed to sediment pond MB-2R via perimeter ditches D2R-1, D2R-la, and D2R-3, which <br />are all sized for the 100-yeaz, 24-hour storm event. <br />During construction of the West Elk Mine, a spring was located on the site where the substation was <br />to be built. In order to stabilize the substation pad, a french drain system and collection pipe were <br />constructed to dewater it. As shown in Exhibit 43 and on Map 54, a 6-inch PVC pipe collects the <br />water and drains it into culvert C1-6A. MCC has designed and constructed several other french <br />drains around the mine site, as approved by the CDMG, to improve stability. These french drains <br />are shown on Map 54. Sediment traps were constructed below the breaker building to pre-treat <br />(i.e., settle) wash-down water prior to flowing down to pond MB-2R. The locations of these <br />sediment traps aze shown on Map 54. MCC also utilizes sediment traps above the inlets to ponds <br />MB-3 and MB-4. <br />General Requirements for Sedimentation Control Facilities <br />All storm drainage/sediment control ponds have been designed in accordance with the requirements <br />. of CMLRB Regulations for Coal Mining. In addition, all inspection, construction and <br />maintenance procedures conform to the requirements of these regulations. Flow meters have been <br />installed on all mine water intakes and discharges to measure flows. <br />Sedimentation ponds MB-1, MB-2R, MB-3, MB-4, and MB-5 have gated dewatering systems <br />located above the sediment level. Refer to the designs in Exhibit 43, 48 and Exhibit 66. The <br />dewatering system for SG-1 is shown in Exhibit 66. <br />Sedimentation Pond Operation <br />The following discussions describe significant features associated with and the operations of <br />each of the sedimentation ponds located at the West Elk Mine. MCC usually collects a pre- <br />discharge sample from the ponds to determine if the discharge will be in compliance with <br />MCC's NPDES permit, prior to opening the gate to discharge the pond. The pre-dischazge <br />sample is analyzed for total suspended solids, as that is the pazameter of concern to MCC. <br />MB-1 <br />Sediment pond MB-1 is atwo-celled pond designed to accept mine water and storm water <br />runoff. However, the majority of the mine water is now dischazged through Lone Pine Gulch. <br />Currently, MB-1 handles very little, if any, mine water. The water enters the south cell of the <br />pond. There are four pipes in the dike that sepazate the two cells to transfer water from the south <br />cell to the north cell if further treatment is necessary prior to discharge. The primary spillway is <br />• located in the north cell. The primary spillway is gated to better control discharges from the <br />pond and to assure the dischazge will be in compliance with MCC's NPDES permit. The <br />2.05-18 Revised June 1005 PRIO <br />