2008-08-22_PERMIT FILE - C1982056A (6)

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in the Area 1 Pit. A manhole with manual valves or automated control valves will be used to control flow to the • Washplant. Washplant I Thickener Overflow Sump (Superceded by TR07-59, Washplant II) -The Washplant I Thickener Overflow Sump, located adjacent to the Thickener Tank in the Washplant I area, as shown on Map 24, Surface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 ID -For discussion of Washplant II Thickener Overflow Sump please refer to previous discussion under Rule 2.05.3(3), Mine Facilities. SMALL AREA EXEMPTIONS AND ALTERNATIVE SEDIMENT CONTROLS TCC has been granted several Small Area Exemptions (SAE'S) and/or approvals to utilize Alternative Sediment Controls (ASC's) within the permit area. For either SAE's or ASC applications, effective drainage and sedimentation control is typically 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. Specific SAE/ASC applications and approvals are described in the following sections. . Southwest District Ventilation Borehole and Substation -Drainage and sediment control at the Southwest District Ventilation Borehole will be provided by placement of afilter-fabric (silt) fence downslope from the site. In the event the filter-fabric does not perform adequately to control sediment, the silt fence may be replaced with rock filters at appropriate drainage points. The ventilation borehole site is approximately 0.2 acres. Fish Creek Dewatering Site - At the dewatering site, 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 from the area, to direct the estimated 0.12 of of runoff (from the 10-year, 24-hour event) to either the containment area to the west, or to the two rock filters on the north side. In order to provide access to the dewatering boreholes, the two light-use roads will be connected to form a pad between the wells. The available topsoil will be windrowed • to the sides of the pad and will be stabilized with the approved seed mixture. The graveled pad and roads are within the confines of the 2.0 acre SAE area as shown on Map 26, Fish Creek Borehole and Facilities and Access Road. TR08-65 2.05-79.1 08/20/08