2010-08-06_PERMIT FILE - C1980007A (2)

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West Elk Mine is MB -3 Sediment pond MB -3 is designed to accept storm water runoff and wash down water from the coal storage silos. A sediment trap has been constructed above the inlet to MB -3. The pond was designed to contain three years of sediment, but MCC's experience has been that the pond has not required cleaning that often. This pond is also lined with a geotextile liner. There are two gated inlets at different elevations that serve as primary discharge. The emergency spillway is an open - channel, rock -lined spillway. MB -3 has been sized to contain the 25 -year storm event and hold MCC's water storage right. Sediment pond MB -4 has been designed to accommodate storm water runoff and wash -down water from the train loadout facility. The sediment control system was redesigned and constructed in 1998 and 1999. The new system includes a concrete sediment trap, an oil skimmer, and a concrete sediment pond. In addition, an oil catchment trench was constructed to capture larger spills of hydraulic oil. Wash down water is piped directly to the sediment trap. The pond was designed to hold three years of sediment that could be generated during a storm event. The pond is designed to contain the runoff volume from a 10 -year, 24 -hour storm event. The primary discharge structure is a gated HDPE pipe. The emergency spillway is also a HDPE pipe, but is not gated. • MB -5E Sediment pond MB -5E is designed primarily for stormwater runoff, but can also accept mine water discharges, and store some of MCC's adjudicated water storage rights. No mine water discharges from the F -seam portals have occurred since the mine water treatment pumps and ponds were constructed near the Sylvester Gulch dewatering pump station. This pond also accepts runoff from the treated discharge from the Wastewater Treatment Plant. There are several sediment traps that water flows through prior to entering pond MB -5E. Two are near the breaker building to pre -treat (settle) wash -down water from the conveyors, reclaim tunnel, and other similar facilities. Others are located near the northeast and northwest corners of the LRP perimeter ditches and another is located before the large inlet pipe that directs flows to the pond. MB -5E is comprised of two ponds (or cells) lined with a 4" to 6" clay liner. Long -term operating experience has shown that clay liners have proven to be much more durable for regular maintenance and pond cleaning activities with heavy equipment, as HDPE and geotextile liners easily tear and leak and are difficult and expensive to repair. Pond MB -5E was designed so that each pond cell can be operated independently. One cell of pond MB -5E is generally utilized to handle stormwater runoff while the other cell is closed and left empty and ready to accept stormwater when the other cell has filled or for water storage, if needed. When the open, active pond has filled to near the maximum fill level, the inlet to the empty pond is opened and the full pond inlet is closed. The full pond is then discharged as described 1.05 -34 Rev. 06105, 01/06, 03/06, 04106& 05106- PRIO; 01109 - MR350; 04109- TR116;; 05109- MR354; 08109- TR119