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11 1 A491:14 V O] 'NiT, F.1 1-:161 <br />Designed terrace ditches will be constructed at approximately 100 foot vertical increments. Terrace <br />Ditches will be backsloped to direct runoff against the face to prevent flows from overflowing the edge of <br />the ditch. These terrace ditches will direct surface runoff perpendicular to the face into a permanent <br />drainage channel designed to pass safely the runoff from a 100 year, 24 hour precipitation event. Terrace <br />ditches are shown on Map 4 1 A and design information is provided in Exhibit 7, Item 20, Part G. <br />Reclamation, specifically topsoil replacement, seeding etc. will be implemented consistent with the <br />Section 2.05 of the permit. <br />CONSTRUCTION PLAN <br />All available topsoil will be removed and either stockpiled for later use or direct haul replaced to a <br />reclaimed area. <br />Due to the fact that the valley fill locations are in close proximity to the initial boxcut area means the <br />entire footprint of these fills must be stripped of topsoil immediately after the approval of PR -2. As <br />described in further detail in this submittal under Section 2.05.3(1); "The entire seam sequence from the <br />top overburden through to the bottom G8 seam, which resides in the area of the initial boxcut, will be <br />placed in the valley fill locations; this will allow Colowyo enough spoil room to reach the desired mining <br />depth." <br />It is anticipated the valley fill drains and associated lateral drains will be constructed as one project during <br />the first two years of operation in the South Taylor operation for practical purposes and as a necessary <br />step in preparation of the area for full scale mining. <br />Channels constructed along the outside of the valley fills (perimeter relief drains) will be built <br />immediately after the logical completion of each terrace ditch across the faces of the fills, which <br />obviously cannot be completed until such a time as the fills themselves develop and are constructed to <br />meet PMT compliance. This activity will be logically sequential in that they will be developed from the <br />bottom up. <br />Colowyo will follow the Shannon & Wilson recommendation for excavation as described in Exhibit 21, <br />Item 1. <br />A controlled underdrain in accordance with the Shannon & Wilson recommendations will be placed in the <br />natural drainage bottom from the head to the top of the fill, The harder, available sandstones obtained <br />from the mining operation will be selectively handled and placed in at least a 24 foot wide by 8 foot high <br />configuration to serve as the underdrain before covered by spoil material. The natural spoil sorting which <br />will occur by utilizing the thicker lifts recommended by Shannon & Wilson will be sufficient to protect <br />the drain from clogging above the geotextile fabric. <br />Lift thicknesses up to 100 feet thick is acceptable and will be utilized to construct the fill. This method of <br />spoil placement also enhances the construction of a free — draining layer of spoil material at the base of <br />the fill. Experience at Colowyo provides evidence that the natural sorting process which occurs while <br />dumping in higher lifts is sufficient to create this drain. Inspection and documentation of this natural <br />sorting is recommended and will be conducted by Colowyo. See the Inspection Plan section for additional <br />details. <br />South Taylor /Lower Wilson — Rule 4, Page 21 Revision Date: 8/21/12 <br />Revision No.: MR -121 <br />