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All disturbed area surface drainage in the South Taylor area will drain through sediment ponds; no <br /> SAES are approved in the South Taylor watershed (4.05.2(3)(b)(1)). Mixing of surface drainage with <br /> discharges from underground workings will not occur at these sites. <br /> B. Diversions and Conveyance of Overland Flow-Rule 4.05.3 <br /> The drainage and sediment control plan provides for temporary and permanent diversion of surface <br /> drainages within the permit area. A system of ditches, as shown on Maps 11 and 12 as well as Exhibit <br /> 7 of the PAP, convey runoff through disturbed areas and divert runoff from disturbed areas to <br /> sediment ponds. <br /> C. Stream Channel Diversions and Reconstruction-Rule 4.05.4 <br /> Diversions of perennial streams around mined areas is not a regular practice at the Mine. <br /> Reconstruction of channels is an important aspect of Colowyo's reclamation practices. Reconstructed <br /> channels are designed (and certified by a registered professional engineer) to accommodate the 100- <br /> year design storm event (Rule 4.05.4(2)(a) and (b)). The channels are designed not to increase <br /> flooding or otherwise endanger property or public safety and are designed to be stable and not <br /> adversely impact the hydrologic balance. Reconstructed channels at the Mine have not been <br /> designed with a lesser flow capacity than the unmodified stream channel immediately above and <br /> below the diversion (Rule 4.05.4(2)(b)). These channels are shown on Maps 41, 41A, and 41B of the <br /> PAP. <br /> The Division has approved the use of riprap channel lining for reconstructed channels in the <br /> reclaimed area. Channel protection is warranted due to steep slopes and is necessary to provide long- <br /> term stability on the reclaimed area until vegetation is established. The riprap lining will provide <br /> stability in order to protect fills and property and to avoid danger to public health and safety <br /> (4.05.3(3)). Riprap used in Colowyo's channels to control erosion ensures channel stability and <br /> requires infrequent maintenance (Rules 4.05.4(2)(a) and(4.05.4(4)(b)). <br /> Minor realignments and changes in permanent stream channel profiles are permitted within reclaimed <br /> areas and excess spoil fill areas. Pre-mining and post-mining alignments are similar; however, <br /> profiles deviate more markedly (Maps 33, 33A, 33B and 33C of the PAP) for both smaller drainages <br /> and larger drainages. For larger drainages, the most significant example of altered profiles is Streeter <br /> Gulch. Pre-mining, Streeter Gulch was steep-sided with a 200-foot incised draw near the mouth of <br /> the gulch (PAP, Map 11). Initial box cut material for mining south of this gulch was placed near the <br /> mouth, first as an experimental practice and later recognized as excess spoil (overburden) fill. As a <br /> result, upstream topography was modified. The pre-mining profile ranged from 5 percent near the <br /> lower end and increasing to 12.5 percent for the upper 1,800 feet (measurements from Map 18 of the <br /> PAP). The post-mining profile is 30 percent for the first 1,000 feet up the face of the Streeter Spoil <br /> fill and approximately 4 percent <br /> 32 <br /> Permit Revision No.5(PR-05),G 1981-019 <br />