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Sediment traps were constructed below the breaker building to pre-treat (i.e., settle) wash-down <br />water prior to flowing down to pond MB-2R. The location of these sediment traps aze shown on <br />Map 54. MCC also utilizes sediment traps above the inlets to ponds 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 RPmilatinna fnr Cnal Mining, h1 addltlon, all inspection, construction and maintenance <br />procedures conform to the requirements of these regulations. Flow meters have been installed on <br />all mine water intakes and dischazges 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 discussion describes significant features associated with and the operations of <br />each of the sedimentation ponds located at the West Elk Mine. MCC usually collects apre- <br />dischazge sample from the ponds to determine if the discharge will be in compliance with MCC's <br />NPDES permit, prior to opening the gate to dischazge the pond. The pre-dischazge sample is <br />analyzed for total suspended solids, as that is the parameter of concern to MCC. <br />Sediment pond MB-1 is atwo-celled pond designed to accept mine water and storm water runoff. <br />However, the majority of the mine water is now dischazged through Lone Pine Gulch. Currently, <br />MB-1 handles very little, if any, mine water. The water enters the south cell of the pond. There <br />are four pipes in the dike that sepazate the two cells to transfer water from the south cell to the <br />north cell if further treatment is necessary prior to dischazge. The primary spillway is located in <br />the north cell. The primary spillway is gated to better control dischazges from the pond and to <br />ensure the dischazge will be in compliance with MCC's NPDES perrnit. The emergency <br />spillway is anopen-channel, rock-lined spillway. MB-1 is lined with a HDPE liner that was <br />installed in eazly 1998. The pond has been designed to hold three years of sediment. Other than <br />the increased amount of sediment that resulted from the large mine water inflow events in 1997, <br />MCC's experience has been that the pond does not have to be cleaned of sediment that often. <br />MB-1 was last cleaned during the fourth quarter of 1997. MB-1 is sized to contain the 100-yeaz, <br />24-hour storm event, and/or MCC's water right for this pond. Piping is in place to allow water <br />from MB-1 to be pumped to FW-1 for mine water use. <br />2.05-31 Revised Jan 1996 RN03; Revised Nov. 1996 PR07; Revised Jan 1997 TR79; Revised Jun. 1999 TR90 <br />