2009-05-22_GENERAL DOCUMENTS - C1981044

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stable. For the purpose of examining road cuts and road embankment conditions, the operator looked at the worst-case road segments at the mine. The roads at the mine were designed for proper road drainage as well as compatibility with the sediment control system. A few access and light-use road segments did not require roadside drainage ditches to collect runoff due to the fact that the grade is only two to five percent. An example is the access road on the southeast edge of the surface facilities area. Roads were pitched to allow sheet runoff to disperse into adjacent grassland. On steeper roads, roadside drainage ditches are used to collect runoff and safely discharge it. Much of the runoff from the roads is passed through a sedimentation pond to decrease suspended solids. Culverts are provided at intersections with drainage channels so as not to interfere with the natural stream flows. The permittee's design for the road bridge that crosses the Williams Fork River indicates the bridge will safely pass the river flow resulting from a 100-year storm event. One variance from the road drainage requirements is granted to the applicant. Rules 4.03.1(4)(e) and 4.03.2(4)(e) contain specific requirements for culvert spacing to discharge water at periodic intervals from the mine roads. The Division has not required BTU EC to adhere to these spacing requirements. The roads are existing structures built before this requirement was implemented. The roads discharge water as sheet flow or into a roadside ditch that has been designed to handle the runoff generated by a 10-year, 24-hour precipitation event. For these reasons, additional road drainage culverts were not required. The Division has previously approved several road segments for retention after mining in accordance with Rules 4.03.1(7) and 4.03.2(7). The surface owner has consented to the retention of these roads and the roads are compatible with the post-mining land use. These roads include: a 7,200-foot segment of the haul road connecting the Eagle No. 5 Mine with the coal processing waste pile, a 1,050-foot access road that leads south from the Eagle No. 9 Mine area to the No. 5A Portal area (see Map 27), and the access road to pond 9AP 1 (approved in Technical Revision No. 22, see permit map No. 29). II. Hydrologic Balance - Rule 4.05 A. Small Area Exemptions (SAEs) Map 26 in the permit application shows the disturbed areas where the Division has previously approved exemptions from the requirement to pass drainage through a sediment pond or treatment facility, as allowed in Section 4.05.1(4). All calculations and demonstrations for SAEs are found in Exhibit 18 of the permit. Each exemption was granted based on: small area, no mixing of surface drainage with discharge from underground mine workings, and sediment ponds or treatment facilities are not necessary for the drainage to meet the effluent limitations of Eagle Mine Complex 18 Permit Renewal 05 C-1981-044 May 22, 2009