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Mountain Coal Company West Elk Mine Exhibit 69 Sylvester Gulch Facilities There will be two sludge drying lagoons each measuring 70 feet wide, 280 feet long, and 6 feet deep. The lagoons will be lined with concrete underlain by a geomembrane material to ensure water tightness. A concrete decant structure will be provided in each lagoon. Finishing Pond The treated water from the water treatment building will be discharged via an underground pipe to the Finishing Pond, which has been designed as a detention pond (i.e. the outlet is a fixed weir). The pond will also receive treated storm water via an underground pipe from the Stormwater Runoff Pond, which is adjacent to the treatment building. The Finishing Pond will be lined with geomembrane material to ensure water tightness. The pond dimensions will be 60 feet wide, 120 feet long, and ]0 feet deep. A six-foot high chain link fence topped with three-strand barbed wire will be provided to restrict unauthorized entry and wildlife access. The estimated length offence is 450 feet. The pond will have an non-gated outlet structure that discharges to the west fork of the Sylvester Gulch immediately to the north of the pond. A ] 2-inch fused HDPE pipe installed on the ground surface will be used as the discharge pipe. At Sylvester Gulch, the pipe will discharge approximately two feet above the creek flow line, and will be protected by approximately five cubic yards of ]2-inch riprap. Additional erosion protection will be provided in the outlet structure by using an energy dissipator. The outlet structure will be constructed of concrete as shown in the designs included in Exhibit 66. Stormwater Control Site drainage will be consistent with drainage designs provided in PR07 and MR212, and as required by Rule 4.05.6. The only disturbed area requiring Stormwater runoff control for the dewatering and treatment facilities is the pad on which the Dewatering Pump Station and Treatment Building will be located. All other facilities (i.e. ponds) will contain the precipitation falling on them, and road drainage will be captured by existing ditches DSLY-8A and 8B as shown on Map 54B. Calculations are included in Exhibit 66. An earthen Stormwater Runoff Pond will be provided immediately adjacent to the pad to be used for Stormwater only. The pond is designed in accordance with Rule 4.05.6 to provide both sediment storage and stormwater storage. The bottom two feet will be reserved for sediment storage. The principal spillway will consist of a valved 6-inch outlet pipe and will be installed so that the invert elevation is at the top of the sediment profile. The Stormwater Pond has been conservatively sized to completely hold 100% of the precipitation and sediment Occ 1997TRR3r Revised Mav 7998 MR243 5