2023-05-26_PERMIT FILE - C1981019 (3)

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Page Exh. 7-14R-1 Revision Date: 4/6/23 Revision No.: TR-159 Appendix Exh. 7-14R East Pit Access Roads This section addresses access roads within the disturbed area of the East Pit and Section 16 reclamation areas to build, operate, and maintain sediment ponds, post mine channels, and stock ponds. Figure Exh. 7-14R-1 provides the locations of the access roads. The alignments shown on Figure Exh. 7-14R-1 are approximated with the most up to date data available to Colowyo’s engineering team. Final alignment will be determined during construction as several of the access roads are on steep slopes, and the alignment may need to be adjusted during construction to take advantage of actual on the ground conditions encountered to guarantee the access roads can be constructed properly for the safe passage of equipment. Topsoil will be removed from all access road footprints, and the access road will be graveled except for the Temporary Access Road. The Temporary Access Road will, as the name implies, will be temporarily constructed for equipment to access Reach 1 of the Final East Pit Ditch. This access road will be reclaimed in accordance with Rule 4.03.2(7) once construction of Reach 1 is completed. Surface water drainage from the access roads is within the primary sediment controls systems of Prospect, Section 3, and Section 15 Ponds. However, local erosion control measures for all access roads as required by Rule 4.03.2(4)(b) will consist of graveled surfaces (except for the Temporary Access Road), localized swales to route surface water runoff from the access road to vegetated sediment filters. Temporary sediment control measures for the Temporary Access Road will wattles, silt fence or other products as deemed necessary by Colowyo, which will be moved once the Temporary Access Road is reclaimed. Culverts will be installed in two locations where segments of the East Pit Access Road will cross the North Tributary East Pit Ditch Reach 1 and Reach 2. Please refer to Figure Exh. 7-14R-1 for the crossing locations. Culverts have been designed to safely pass the 25-Year, 24-Hour event. The peak discharge flow for both culverts can be found in Appendix Exh. 7-14PP, 25-Year, 24- Hour storm event (Structure Nos. 16 and 20). For ease and a conservative design, the North Tributary East Pit Ditch Reach 2 design flow (Structure 16 at 4.07 cfs) was used to model culverts in both reaches. As indicated on the attached SEDCADTM a 10-inch culvert will suffice for both crossings. Colowyo may installed larger culverts than 10-inch depending on availability. Additionally, Colowyo may decide to install a polyethylene pipe instead of a corrugated metal pipe, the included SEDCADTM is for a corrugated metal pipe with a Manning’s n of 0.015. In SEDCADTM a polyethylene pipe has a Manning’s n of 0.014; which does not change the minimum required culvert size. Two SEDCADTM demonstrations for the culverts are included to demonstrate this.