Laserfiche WebLink
The design calls for riprap linings for all of the channels (including Little Collom discussed <br />under Rule 4.05.4 below). Channel protection is warranted due to steep slopes and large <br />watershed areas that exist and that are planned for the post -mining topography. Pre -mining <br />bedrock control is removed by the mining operation and channel protection is necessary to <br />provide long-term stability on the reclaimed area, especially until vegetation is established. <br />C. Stream Channel Diversions - Rule 4.05.4 <br />As stated above, the Division approves CCC's plan to permanently restore drainage channels that <br />shall be temporarily removed by mining. Little Collom has a drainage area of greater than a <br />square mile, and thus design of it is governed by Rule 4.05.4, which requires that it convey the <br />100 -year, 24-hour precipitation event. The location of this channel is shown on Map 4113, and <br />the profile is on Map 33. Details of the analysis and design are in Exhibit 7, Items 23 and 25. <br />D. Sedimentation Control Measures, Ponds and Discharge Structures - Rules 4.05.5, 6 and 7 <br />The Division approves sediment ponds, diversion ditches, and other measures in the Collom area <br />to treat surface water runoff from disturbed areas. The Division does not approve of any <br />sediment ponds in a perennial stream (4.05.6(1)(b)), and none are proposed by CCC for the <br />Collom area. <br />A thorough analysis by a registered professional engineer, including SEDCAD modeling and <br />design drawings, indicates that the sediment ponds will function as required to reduce sediment <br />loading off site. <br />Discharge structures, embankments, and other components of ponds will be inspected on a <br />quarterly basis. Ponds will be maintained to ensure continual effective operation. This will <br />include, but not be limited to, removal of sediment on an as needed basis. <br />E. Acid-forming and Toxic -forming Spoil - Rule 4.05.8 <br />No significant acid-forming spoil exists within the overburden or coal seams to be mined in the <br />Collom permit expansion area. A discussion of the overburden quality can be found in Section <br />2.04.6 (Volume 15 of the PAP) and Exhibit 6, Item 9 (Volume 17). A discussion of the <br />overburden monitoring plan can be found in Section 2.05 (Volume 15). <br />PR -04, Colowyo Coal Mine C1981-019 37 August 2016 <br />