2009-09-21_PERMIT FILE - C1980007A (20)

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West Elk Mine were constructed to dewater it. As shown in Exhibit 43 and on Map 54, a 6 -inch PVC pipe collects the water and drains it into culvert Cl-6A. MCC has designed and constructed several other french drains around the mine site, as approved by the CDMG, to improve stability. These french drains are shown on Map 54. Sediment traps were constructed below the breaker building to pre -treat (i.e., settle) wash -down water prior to flowing down to pond MB -2R. The locations of these sediment traps are shown on Map 54. MCC also utilizes sediment traps above the inlets to ponds MB -3 and MB -4. General Requirements for Sedimentation Control Facilities All storm drainage /sediment control ponds have been designed in accordance with the requirements of CMLRB Regulations for Coal Mining. In addition, all inspection, construction and maintenance procedures conform to the requirements of these regulations. Flow meters have been installed on all mine water intakes and discharges to measure flows. Sedimentation ponds MB -1, MB -2R, MB -3, MB -4, and MB -5 have gated dewatering systems located above the sediment level. Refer to the designs in Exhibit 43, 48 and Exhibit 66. The dewatering system for SG -1 is shown in Exhibit 66. Sedimentation Pond Operation The following discussions describe significant features associated with and the operations of each of the sedimentation ponds located at the West Elk Mine. MCC usually collects a pre- discharge sample from the ponds to determine if the discharge will be in compliance with MCC's NPDES permit, prior to opening the gate to discharge the pond. The pre - discharge sample is analyzed for total suspended solids, as that is the parameter of concern to MCC. MB -1 Sediment pond MB -1 is a two - celled pond designed to accept mine water and storm water runoff. However, the majority of the mine water is now discharged through Lone Pine Gulch. Currently, MB -1 handles very little, if any, mine water. The water enters the south cell of the pond. There are four pipes in the dike that separate the two cells to transfer water from the south cell to the north cell if further treatment is necessary prior to discharge. The primary spillway is located in the north cell. The primary spillway is gated to better control discharges from the pond and to assure the discharge will be in compliance with MCC's NPDES permit. The emergency spillway is an open - channel, rock -lined spillway. MB -1 is lined with a HDPE liner that was installed in early 1998. The pond has been designed to hold three years of sediment. Other than the increased amount of sediment that resulted from the large mine water inflow events in 1997, MCC's experience has been that the pond does not have to be cleaned of sediment that often. MB -1 was last cleaned during the fourth quarter of 1997. MB -1 is sized to contain the 100 -year, 24 -hour storm event, and /or MCC's water right for this pond. Piping is in place to allow water from MB -1 to be pumped to FW -1 for mine water use. MB -2R 2.05 -32 Revised June 2005 PRIO; Rev. January 2006; Rev. March 2006; Rev. April 2006 PRIO, May 2006 PR10; Rev. January 2009 MR -350