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7.0 DRAINAGE CONTROL SYSTEM RECONSTRUCTION 7.1 Description This specification covers all work required to re-establish drainade through the regraded portal bench area, the sediment pond access road, and along the highway and rail line. 7,2 Execution The CONTRACTOR shall cerform all work and provide all the materials necessary to reconstruct drainage control within the west mine area in accordance with the plans and sceci fi cati ohs set forth below. Culvert Removal/Modification The west mine area contains 8 CMP type culverts which are shown and labeled CMP-1 through CMP-8 on Exhibit 3A, The final configurations of these culverts after specified work has been completed are shown on Exhibit 4A. Cross sections of the drainage channels to be constructed as part of the culvert modification work are shown on Exhibit 6D. Work to be performed on these culverts is as follows: CMP-1 This culvert is to be left in place. The portion of the drainage channel immediately above the inlet end shall be widened approximately 2 ft. on both sides and deepened approximately 1 ft. for a total distance of 5 ft. above the inlet end. The enlarged area shall be lined on the bottom and sides using 1 ft. minimum diameter durable rock riprao. CMP-2 The inlet end and portion of the culvert passing beneath the highway shall be left in place. The secondary vertical inlet to this culvert near the edge of the highway pavement on the south side shall be removed, with the subsequent culvert extension which basses through the fill to CMP-5 being either removed or otherwise collapsed or filled in below final grade and covered with non-coal fill material. The area immediately surrounding the new outlet end shall be graded sufficiently to prevent any blockage of outflow, and the hillsloce immediately beneath the new outlet for a distance of 10 ft. from the culvert end and shall be graded to form a trapezoidal shaped outfall channel 3 ft. deep and 3 ft. wide, (bottom width) with 2h: 1V side slopes as shown on Exhibit 6D. The channel bottom and sides shall be lined with minimum 1 ft. diameter durable rock riprap. The specified channel depth and width are the finished dimensions with riprap in place; excavated dimensions will be greater in order'to provide space for riprap. The small highway drainage ditch or swale on the south side of the highway shall be routed such that runoff in the ditch is directed to the top of the trapezoidal channel. -19-