2009-02-19_PERMIT FILE - C1982056A (3)

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With implementation of operations for Washplant II, the Area 1 Pit is also utilized the primary source for plant make-up water. An additional pump has been placed in the Area 1 Pit and connected to the new 8-inch water-line, with pump control and access from the existing pump-station access in the Area 1 Pit. A manhole with manual valves or automated control valves will be used to control flow to the Washplant. In order to address increased mine dewatering requirements, transfer pipelines from the Fish Creek and l ORT dewatering boreholes have been established, with discharge directly to the Area 1 Pit. Washplant I Thickener Overflow Sump (Superseded by TR07-59 Washplant In -The Washplant 1 Thickener Overflow Sump, located adjacent to the Thickener Tank in the Washplant I area, as shown on Map 24, Surface Facilities, and by Figure EX8w-1 in Exhibit 8w was excavated during Washplant construction to serve as a catch basin for the contents of the Thickener, if required for maintenance or under upset conditions. Impoundment design, operation, maintenance, and reclamation information is provided in Exhibit 8w. While it has not been necessary to utilize the basin for this purpose, it is occasionally used to collect and retain minor quantities of Washplant wash-down water. As an incised and closed basin (ie: no outlet) the only inputs are thickener overflow, wash-down water from the Washplant, or minor incident precipitation, which are subsequently pumped back into the system by a portable floating pump installation. Water level in the sump is monitored and managed as part of the ongoing plant operations. Washplant II Thickener Overflow Sump (TR07-59 Washplant IIl -For discussion of Washplant II Thickener Overflow Sump please refer to previous discussion under Rule 2.05.3(3), Mine Facilities. SMALL AREA EXEMPTIONS Twentymile Coal Company has been granted several Small Area Exemptions (SAE's) within the permit area. Effective drainage and sedimentation control in these areas will be achieved through the use of a number of individual or combined methods, including gravel-surfacing; erosion control fabric or materials; berms; contour furrows; sediment traps; rock check dams; vegetative filters; the use of silt fences, straw wattles, or straw bales; or other approved methods. Rockdust Tank - An SAE for sedimentation control has been granted for the rockdust tank and truck access/unloading area. The total disturbance will be approximately 0.5 acres. Of this area, 0.3, acres will be filled with pit-run gravel, which acts as an infiltration screen for any overland flow associated with the rockdust tank and access/unloading area. Estimated peak flow from the area for the 10-year, 24-hour event is approximately 0.04 acre-feet. Runoff from the topsoil pile is controlled by a berm/swale/rock filter system. In addition to the infiltration screen, flow from the tank and unloading area is conveyed by means of swales and berms to a gravel filter. These controls, in conjunction with existing vegetation, will be sufficient to control runoff from the area as observed during previous inspections. Fish Creek Dewatering Facilities - At the dewatering facility, sedimentation will be controlled by the use of alternate control systems such as filter fences, gravel filters, and existing vegetation. For the 0.5 ac stockpile located to the southwest of the pond, a berm will be established around the stockpile to direct runoff from the stockpile to the two gravel filters by the stockpile. This will effectively treat the estimated 0.02 acre-feet of runoff resulting from the 10-year, 24-hour event until vegetation is reestablished. Once this occurs, the berm and filters can be removed. The runoff from the 0.2 acre stockpile adjacent to the transformer will drain to the low area northeast of the stockpile where adequate vegetation exists to provide filtering and treatment of the water. The SAE is shown on Map 26, Fish Creek Borehole Area Facilities and Access Road. The collection ditch for the ponds and associated disturbed areas will be constructed with two gravel filters to act as a secondary sediment control measure. The gravel filters will be constructed of 3-inch minus washed gravel, and will be approximately 24 inches in width. The filters will be placed across the ditch and extend halfway up the sides of the ditch. A berm will be placed on the south side of the road leading into the control building. The berm will be located to keep drainage from this area from entering the discharge ditch. The berm will provide an area that can act as a sump to hold or direct water from the site. In reference to the boreholes and control building area, collection berms will be established downslope of MR08-230 2.05-79.1 11/20/08