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MB-3 <br /> Sediment pond MB-3 is designed to accept storm water runoff and wash down water from the <br /> coal storage silos. A sediment trap has been constructed above the inlet to MB-3. The pond was <br /> designed to contain three years of sediment, but MCC's experience has been that the pond has <br /> not required cleaning that often. This pond is also lined with a geotextile liner. There are two <br /> gated inlets at different elevations that serve as primary discharge. The emergency spillway is an <br /> open-channel, rock-lined spillway. MB-3 has been sized to contain the 25-year storm event and <br /> hold MCC's water storage right. <br /> MB-4 <br /> Sediment pond MB-4 has been designed to accommodate storm water runoff and wash-down <br /> water from the train loadout facility. The sediment control system was redesigned and <br /> constructed in 1998 and 1999. The new system includes a concrete sediment trap, an oil <br /> skimmer, and a concrete sediment pond. In addition, an oil catchment trench was constructed to <br /> capture larger spills of hydraulic oil. Wash down water is piped directly to the sediment trap. <br /> The pond was designed to hold three years of sediment that could be generated during a storm <br /> event. The pond is designed to contain the runoff volume from a 10-year, 24-hour storm event. <br /> The primary discharge structure is a gated HDPE pipe. The emergency spillway is also a HDPE <br /> pipe,but is not gated. <br /> MB-5E <br /> Sediment pond MB-5E is designed primarily for stormwater runoff, but can also accept mine <br /> water discharges, and store some of MCC's adjudicated water storage rights. Only minor mine <br /> water discharges from the F-seam portals have occurred since the Mine Water Treatment Pond <br /> facility was constructed near the substation in Sylvester Gulch. This pond also receives treated <br /> discharge from the Wastewater Treatment Plant and backwash water from the Water Treatment <br /> Plant. <br /> There are several sediment traps that water flows through prior to entering pond MB-5E. Two <br /> are near the breaker building to pre-treat (settle) wash-down water from the conveyors, reclaim <br /> tunnel, and other similar facilities. Others are located near the northeast and northwest corners <br /> of the LRP perimeter ditches and another is located before the large inlet pipe that directs flows <br /> to the pond. <br /> MB-5E is comprised of two ponds or cells lined with 4" to 6" of clay. Long-term operating <br /> experience has shown that clay liners have proven to be much more durable for regular <br /> maintenance and pond cleaning activities with heavy equipment, as HDPE and geotextile <br /> liners easily tear and leak and are difficult and expensive to repair. Pond MB-5E was <br /> designed so that each pond cell can be operated independently. One cell of pond MB-5E is <br /> generally utilized to handle stormwater runoff while the other cell is closed and left empty <br /> and ready to accept stormwater when the other cell has filled or for water storage, if needed. <br /> When the open, active pond has filled to near the maximum fill level, the inlet to the empty <br /> pond is opened and the full pond inlet is closed. The full pond is then discharged as described <br /> 2.05-34 Rev.06105,01106,03106,04106&05/06-PRIG;01/09-MR350;04/09-TR116,05/09-MR354;08/09-TR119;09/19-MR437 <br />