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areas. <br />C. Stream Channel Diversions - Rule 4.05.4 <br />Minor realignments and changes in permanent stream channel profiles are permitted within <br />reclaimed mined and excess spoil fill areas (Maps 33, 33A, 41 and 41A). Pre - mining and post - <br />mining alignments are similar. However, profiles deviate more markedly. The most significant <br />example is Streeter Gulch. Streeter Gulch is an ephemeral drainage (PAP, page 2.04.7 -27). It <br />was (pre- mining) a steep- sided, 200 -foot deep (near the mouth) incised draw (PAP, Map 11). <br />Initial box cut material for mining south of the Gulch (Draw) (PAP, page 2.06 -3) was placed <br />near the mouth, first as an experimental practice and later recognized as excess spoil <br />(overburden) fill. Upstream topography was, as a result, necessarily modified. The pre- mining <br />16,000- foot -long Streeter Gulch profile ranged from 5% near the lower end, increasing to 12.5 % <br />for the upper 1800 feet (measurements, Map 18, PAP). The post- mining profile is 30% for the <br />first 1000 feet up the face of the Streeter Spoil fill, and thence approximately 4 % across the <br />approved post- mining topography of reclaimed land (measurements, Map 19, PAP). Such <br />diversions are designed and certified by a registered professional engineer to accommodate the <br />100 -year design storm [Rule 4.05.4(2)(a) and (b)]. These diversions comply with the <br />requirements of Rules 4.05.3(1)(b) through (f) (they are in compliance with applicable statutes <br />and regulations, are designed not to increase flooding or otherwise endanger property or public <br />safety, are designed to be stable and not adversely impact to the hydrologic balance, and do not <br />divert water into underground mines). Riprap is used to control erosion. The channels are stable <br />and require infrequent maintenance [Rules 4.05.4(2)(a) and (4.05.4(4)(b)]. In smaller tributaries, <br />profiles have been altered to accommodate post- mining sides at lesser slopes (for stability) than <br />original steep ravine slopes. <br />The Division approves permanent diversions of ephemeral streams in the Collom area. These <br />diversions are the reconstructed channels necessary to safely drain the reclaimed lands after <br />mining. The diversions are consistent with applicable state law and will not diminish <br />downstream water rights. No perennial streams will be diverted as part of the proposed Collom <br />project. <br />Such diversions are designed and certified by a registered professional engineer to accommodate <br />the 100 -year design storm. These diversions are in compliance with applicable statutes and <br />regulations, are designed not to increase flooding or otherwise endanger property or public <br />safety, are designed to be stable and not adversely impact to the hydrologic balance, and do not <br />divert water into underground mines. <br />1. Channel lining structures, retention basins, and artificial channel roughness structures are <br />approved for use to control erosion. These means are proposed to be approved by the <br />Division since they are necessary to control erosion, they are stable and will require <br />infrequent maintenance. Riprap lining, permanent stock ponds, and dugout sediment traps on <br />the spoil areas are the measures that will be used (4.05.4(2)(a)). <br />Colowyo Coal Mine C1981 -019 PR -03 43 April 10, 2013 <br />