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Mountain Coal Company <br />West Elk Mine <br />Exhibit 69 <br />vester Gulch Facilities <br />• concentration of the mine water in the first pond (existing Pond 017), followed by sedimentation <br />in a new, Second Pond. The existing Pond 017 will be modified to function as the aeration cell. <br />After aeration and settling, discharge from the Second Pond will be routed through a new <br />pipeline that will connect to the existing outlet pipe and flow to the existing outfall structure <br />along the West Fork of Sylvester Gulch. <br />A design flow rate of 400 gallons per minute (gpm) is assumed, which will be achieved by <br />installing a new lower-capacity pump system in the mine water sump. This will facilitate the <br />need to provide 300 gpm continuous flow of augmentation water at certain times of the year <br />(principally July and August), while allowing for some increased detention time if needed for <br />treatment efficiency. <br />From the Dewatering Pump Station Building, the mine water will flow by gravity through the <br />existing 12-inch diameter pipeline to the existing Pond 017 inlet. Pond 017 is an HDPE-lined <br />pond with no inputs other than mine water. Access to the pond is controlled by 6-foot high chain <br />link fence topped with three-strands of barbed wire. <br />The existing outlet pipe from Pond 017 is a 12-inch fused HDPE pipe installed on the ground <br />surface with two concrete anchor blocks. At the West Fork of Sylvester Gulch, the pipe <br />discharges approximately 2 feet above the creek high flow line and is protected by 12-inch <br />riprap. Additional erosion protection is provided in an outlet structure by use of an energy <br />• dissipater. Designs for the outlet pipe and structure are provided in Exhibit 66. <br />Dewatering Pump Station Building <br />The Dewatering Pump Station Building will contain both the mine pumping equipment and the <br />electronic controls for water flow. In the past, dewatering has occurred intermittently from one <br />of two existing dewatering boreholes via a vertical turbine pump with a capacity of 2,000 gallons <br />per minute (gpm). The new pump system design flow is 400 gpm. The dewatering boreholes <br />have a column depth of approximately 600 feet and are completed to the operational sump in the <br />northeast corner of the l ONE Tailgate. <br />The existing system is equipped to use a nearby Recirculation Borehole to reduce/regulate the <br />flow rate by recirculating a portion of the flow through the mine sump. The recirculation <br />borehole is a 12-inch cased borehole (completed per MR 212) that is located approximately 100 <br />feet south of the dewatering boreholes. There are two 20-inch cased boreholes (also completed <br />per MR 212) that serve as alternate recirculation boreholes and/or boreholes for water level <br />indicators. These holes are located near the dewatering boreholes. Continued use of this <br />recirculation system is not anticipated given the new lower flow rate pump, but the system will <br />remain in place in case it is needed in the future. <br />Modifications to Existing Pond 017 <br />• <br />Rev. 10197-TR83, Rev. 04109-TR116