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APR. 9.2002 10~06RM TWENTYMILE CORL ENVIRONMENTRL N0.871 P.7 Mains Ventilation Shaft and Thiolte_Per Undertlow Proiect (TR 01-3 As mine development has proceeded to the north, the distance from existing mina ventilation fan ittstafiations has increased to the point where an additional ventilation shaft and fan installation era necessary to maintain effective ventilation of active minirtg areas. The new ventilation shaft and surface fan installation, will be located approximately 900 feet north of Fish Creek in Section 17, TSN, R8tiW on a low rise above the Fish Creek drainage, as shown on Maps 23 and 23B. Development, construction, and installation of the ventilation shaft and fan installation involves the following sequential activities: • Completion of enviranmeatal and engineering investigations • Temporary drainage and sediment control measures • Recovery and stockpiling of available topsoil • Installation of drainage and sedimem control structures • Construction of an access road and site preparation for shaft pad • Drilling of shaft pilot hole Construction and extension of power distribgtion line • Constvction of shaft collar structure, temporary drilling equipment pad and fan foundations • Shaft boring and casing operations • Erection of fan enclosure and control buildings and installation offence{s) • Installation and connection of fan, drive, and control equipment and systerps • Driving of additional entries in the Northwest Mains • Final clean-up and drossing of roads and site pads These activities are briefly described is fire following sections, Site-specific investigations required for design and permitting of the new ventilation shaft included a cultwal resource survey of potential disturbance areas, soil and foundation characterization as the basis for shaft pad and access road design, and completion of a wetiand/AVF survey for the shaft access mad and power line crossing of Fish Creek. The cultural resource survey was conducted by Metcalf Archaeological Consultants, the engineering soils characterisation by Northwest Colorado Consultants, and the wetland/AVF survey by Habitat Management, as described in Seedon 2.04. The proposed shaft pad area is approximately 2S0' square (1,8 acres) and the associated access mad corridor is approximately 3,800' long with a finished top width of 22 feet (mad corridor 30 feet wide). See } xhibit 25 S, NVJ Mains Ventilation Shaft Access Road Design, for details on the road, Approximately 2,000 feet of the awess road crosses upland areas, with the temaining 1,800 foot crossing lowland azeas where road construction will involve removal of any large vegetatiop and placement of geotextile and road fill over the in-place soils, Given an average topsoil depth of approximately 6" in the upland area and a total dist~rrbance area of approximately 1.4 acres, approximately 1,111 CY of topsoil will be salvaged from the mad corridor, and 1,452 CY from the pad, The topsoil from these areas will either be windrowed adjacent to the mad corridor or placed in stockpile adjacent to the shaft pad for future reclamation use, The topsoil salvage volumes are indicated on Table 49A. Seeding with the topsoil stockpile stabilization seed mixture will stabilize the windrowed and stockpiled topsoil. Following topsail removal, required drainage and sediment control structures will be constntcted or installed, These structures include designed culverts for the road crossing of Fish Creek (sea Exhibit 8R, Fish Creek Culvert Design, NW Mains'Ventflation Shaft) and road crossings of smaller ephemeral drainage channels; discharge control structure (rook check dam) at the dowagradient limit of the shaft pad, and a temporary diversion ditch around the upgradiem perimeter of the shaft pad, The drainage from the shaft pad is addressed under a Small Area 8xemption (SAE) section of the permit, as it is a relatively small (approximately 1.8 acres), gravel-surfaced and or reclaimed MR 02-178 2.05-45 04/08/02