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Colowyo, C1981 -019, PR3 adequacy No. 3 10 July 22, 2011 <br />Rule 2.05.301 Ponds, Impoundments, and Diversions <br />The application includes a plan to use an in -pit sump in combination with a large sediment pond <br />located below all mining within Collom Gulch. Geotechnical analyses for the pond were included <br />with the application. In general, the Division finds the plan adequate. However, based on recent <br />information regarding changes to the mine plan in the northern portion of the proposed permit area <br />due to Federal coal lease issues, runoff and sediment modeling will need to be remn for the <br />proposed worst case disturbance. Other issues that were identified during the review are as <br />follows: <br />• Some of the secondary drainages appear to be improperly located with regard to the post - <br />mining topography. <br />• Disturbed areas are shown downgradient of sediment control ditches. <br />• It is not clear, given the timing of mining and reclamation, how reclaimed areas in the Collom <br />Lite pit will be routed around the temporary spoil pile that will block Collom Gulch. <br />Reclaimed areas in 2016 and beyond in the Collom Lite pit are not shown being diverted <br />around the temporary spoil pile. Discussions with representatives of Colowyo indicate that a <br />sediment pond immediately downgradient of the Collom Lite pit may be proposed. <br />I. Please review the drainage and sediment control plan over the life of the mine and ensure that <br />all disturbed areas will be routed through the sump /sediment pond system as stated in the <br />permit text narrative under Rule 4. <br />The application remains inadequate. Please review the drainage and sediment control plan over <br />the life of the mine and ensure that all disturbed areas will be routed through the sump /sediment <br />pond system as stated in the permit text narrative under Rule 4. Numerous disturbed areas <br />(topsoil stockpiles excluded) are shown on maps outside of (downgradient) from ditches <br />diverting water through the designed sediment control system. Small areas outside of the <br />primary sediment control system should be addressed as small area exemptions if they will not <br />report to the sump /sediment pond. Please describe in detail, using permit text narrative, maps, <br />cross - sections, and other information as necessary, as to how future reclaimed areas in the <br />Collom Lite pit will be routed around the temporary spoil pile that will block Collom Gulch. <br />"1'1)e application renmins inadequate. CC C' explains that wnof wvill be pumped around the <br />temporary spoil pile that will block Collom Gulch. howavrr it is the professional opinion of <br />DRMS staff that the area where the runoff will collect can be described as an impoundment and <br />that a design is needed. <br />Two sedimentation ponds have been proposed with PR -03: the Little Collom Pond and the Little <br />Collom Sump. Specific information is provided in application sections 2.05.3(4); 4.05.6; Exhibit 7, <br />Item 23; Exhibit 7, Item 26 — Collom Pond Design Maps; and Exhibit 23, Item 1 Shannon & Wilson <br />Oeotechnical Study (S &W). Text in 2.05.3(4) of the application directs the reader to Vol. 1, Section <br />