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5.0 DRAINAGE CONTROL SYSTEM RECONSTRUCTION <br />5.1 Description <br />This specification covers all work required to reestablish drainage through <br />the East mine area, including culvert placement, drainage ditch excavation, <br />placement of riprap, and regrading of highway drainage ditches. <br />5.2 Materials <br />The riprap material specified for the ditches must consist of durable rock <br />material having a minimum average diameter of 1 foot. The geotextile fabric <br />to be placed between the riprap and the excavated ditch bottom shall be of the <br />type recommended by manufacturers for the type of channel and size of riprap <br />specified. <br />5.3 Execution <br />The CONTRACTOR shall perform all work and provide all the materials necessary <br />to reconstruct drainage control within the East mine area in accordance with <br />the plans and specifications set forth below. <br />A. West Drainage Highway Culvert Installation and Ditch Reconstruction <br />The CONTRACTOR shall install a minimum 24" diameter, 50 foot long, <br />16 gage corrugated steel pipe across the highway to connect the two <br />segments of the natural drainage channel which runs north-south at <br />the west extremity of the East mine area. The inlet and outlet ends <br />of the existing drainage channel segments shall be shaped and graded <br />to form a smooth transition between the culvert ends, regraded <br />portions of the channel, and the existing undisturbed portions of the <br />channel. The existing configuration of the drainage is shown on <br />Exhibit 3A. The general plan view configuration of the drainage <br />after reconstruction is shown on Exhibit 36. Exhibit 4C provides <br />design and installation specifications for the culvert and <br />reconstructed drainage channel. The CONTRACTOR must comply with all <br />Colorado Department of Highways requirements for culvert installation <br />including minimum distances between inlet and outlet ends from the <br />road surface, minimum drainage gradient, minimum depth below road <br />surface, compaction of fill above the culvert, and reestablishment of <br />road base and road pavement. In the event that Department of <br />Highways design and installation requirements differ than those <br />specified herein, Colorado Department of Highways' specifications <br />shall be used. The CONTRACTOR is responsible for obtaining <br />appropriate culvert design and installation requirements from the <br />Highway Department. <br />-23- <br />