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Peabody Sage Creek Mine — Drainage and Sediment Control Plan <br />native material and has side slopes of 2H:1 V and !H:1 V for the right and left side slopes, <br />respectively. The Upper and Lower Facility Area Sump emergency spillway designs are <br />conservative; it assumes the principal spillway9s0 are inoperable and the water level(s) are <br />at the invert of the emergency spillway prior to the storm event. The Portal Area Sumps are <br />a non - discharging system. There is a culvert structure that drains stored water from Portal <br />Sump #1 to Portal Sump 32. The top of the structure will be approximately 50 feet below <br />the existing ground surface of the South Surface Facilities Area. While the system does not <br />need a spillway, the culvert linking the two sumps is designed for the 10 -year, 24 -hour storm <br />event. A pump system will be installed to de -water the portal area sumps to assure that there <br />is adequate capacity to store runoff from the 10 -year, 24 -hour storm event, as well as any <br />mine water discharge. <br />4.0 DITCH AND CULVERT DESIGN <br />4.1 Haul Road Ditches <br />Runoff from haul roads and access roads within the surface facilities area is generally routed <br />to the existing sediment ponds. Road -side ditches are designed to safely convey the peak <br />flow from the 10 -year, 24 -hour storm event. Steeper slope sections of the road -side ditches <br />may experience erosive velocities during the design storm event. Routine maintenance of <br />the road and ditches will repair erosion if and when it occurs. Armoring the ditches with <br />riprap is generally not practical from an operational standpoint. Material from the roadbed is <br />constantly being moved into ditches from the movement of large haulage equipment. <br />Consequently, the road -side ditches need to be maintained continuously. Any rock placed in <br />the road -side ditches would only last a short time before it was covered with road material. <br />Existing ditches PM -9, PM -15, RA -Dl, RE -D1 and the Northwest Diversion Ditch are <br />historic Seneca II Mine haul road ditches. They have been retained in the drainage control <br />plan for both operational and postmine phases. <br />Haul and access roads ditch locations are shown on Map 2.05.3 M4, Drainage and <br />Sediment Control Plan. Designs for the existing Seneca II road ditches, as well as, the <br />Peabody Sage Creek Mine operations are presented in Appendix 2.05.3 -E2.G, Operational <br />Ditch and Culvert Designs. Minimum ditch configurations are summarized in Table <br />2.05.3 -E2 -5, Operational Ditch Design Schedule. <br />4.2 Runoff Ditches and Postmine Channels <br />There are several existing diversion ditches constructed to convey runoff in the Pond 003 <br />watershed. The ditches were designed for mine- related activities at the Seneca II Mine (see <br />Appendix 7 -6of the Seneca II Mine PAP). Channel designs were calculated using Fuller's <br />Formula (Trans. ASCE, Vol. 77, pg.564, 1914) or SEDCAD+ (Schwab, 1988). The <br />diversion ditch locations are shown on Map 2.05.4 M1, Postmining Topography. Design <br />documentation is presented in Appendix 2.05.3 -E2.G, Attachment 2.05.3- E2.G -1, North <br />Facilities Area (Shop /Warehouse /Office) diversion Ditch Designs. Ditch configurations <br />are summarized in Table 2.05.3 -E2 -6, North Facilities Area Diversion Ditch Design <br />Schedule. <br />TRO 1 -10 2.05.3 -E2.11 12/10 <br />