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2. The Division does not approve a stream channel diversion with a lesser capacity than the <br />unmodified stream channel immediately above and below the diversion (4.05.4(2)(b)). <br />3. The permanent diversion (Streeter drainage) shall make use of artificial structural controls in <br />order to allow it to remain in dynamic equilibrium with the drainage basin system. Riprap <br />channel lining will be used in most of the permanent drainage channels on the reclaimed <br />area. The Division approves the use of such structures (4.05.4(4)(b)). <br />D. Sedimentation Control Measures, Ponds and Discharge Structures - Rules 4.05.5, 6 and 7 <br />The Division approves one sediment sump (Little Collom Sump), diversion ditches, and other <br />measures in the Collom area to treat disturbed area surface water runoff The Division does not <br />approve of any sediment ponds in a perennial stream. <br />A thorough analysis by a qualified professional engineer, including SEDCAD modeling and <br />design drawings, indicates that the sediment sump will be structurally stable and function as <br />required to reduce sediment loading off site. <br />Discharge structures, embankments, and other components of ponds will be inspected on a <br />quarterly basis. Ponds shall 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 />1. The Division does not approve of any sediment pond in a perennial stream (4.05.6(1)(b)). <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 (PAP, <br />page 2.05 -57). <br />No significant acid - forming spoil exists within the overburden or coal seams to be mined in the <br />Collom expansion area. A discussion of the overburden quality can be found in Section 2.04.6 <br />(Volume 15) and Exhibit 6, item 9 (Volume 17) of the PAP. A discussion of the overburden <br />monitoring plan can be found in Section 2.05 of the PAP (Volume 15) <br />F. Impoundments - Rule 4.05.9 <br />The Division approves small impoundments for cattle and wildlife watering on future reclaimed <br />areas of the Collom site. These structures should not exceed five feet in height (bottom of <br />channel to bottom of spillway) or two acre -feet in volume. <br />Other impoundments within the permit area are the approved sediment ponds discussed above. <br />Colowyo Coal Mine C1981 -019 PR -03 44 April 10, 2013 <br />