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Comment Response Page 6 <br />56. The SEDCAD analysis indicates that the pond discharge will not meet the required effluent <br />limitation of 0.5 mlll for a storm event equal to or less than the 10-year storm. The Division <br />cannot approve a pond design that fails to demonstrate compliance with applicable effluent <br />limits. <br />Response: See response to Comment No. 53 above. <br />57. Although the second SEDCAD run is titled 100-year storm event, the storm information page <br />indicates it is actually a 50% PMP run, identical to the third run for this pond. Please correct <br />this discrepancy. <br />Response: CDRMS noted that the SEDCAD run entitled 100-year storm event was a repeat <br />of the 50% PMP run. The correct SEDCAD run has been provided. <br />Section 16 Pond <br />58. If the temporary spoil pile will drain to Section 16 pond, Colowyo will need to demonstrate that <br />the pond has adequate capacity to contain or treat the runoff from this re-disturbed area. <br />Response: Section 16 pond was designed to collect the area originally disturbed during <br />previous mining of the Section 16 pit. Colowyo is not proposing to increase the area of <br />disturbance or the associated drainage area. Colowyo is only proposing to re-disturb a portion <br />of the original disturbance as a result of the temporary spoil stockpile. Based on this logic, <br />Colowyo does not believe that any additional demonstration or modeling is warranted. <br />Rule 2.05.5 and Rule 4.16 Postminine Land Uses <br />80. On page 105, the application includes a discussion of small impoundments ("stock ponds"), that will <br />be constmcted on the reclaimed landscape, and which are "essential and basic to ...livestock grazing <br />and wildlife habitat", Please provide a Postmining Land Use map (PMT base map) depicting <br />proposed locations of stock ponds and other permanent facilities that will be necessary to <br />support the postmining land use. <br />Response: These ponds are shown on the attached Map 41A. In addition to these <br />permanent structures, a variety of temporary sediment traps will also be used as described <br />elsewhere in Exhibit 7-20, Parts A, 8, and C. <br />Rule 4.05 3 Diversions and Conveyances of Overland Flow and Shallow Groundwater Flow, and Ephemeral <br />Streams Drainine a Watershed Less Than One Square Mile <br />106. Temporary drainage is proposed for only one channel, Section 29 Collector Ditch according to <br />information in Exhibit 7, Item 2Q Part E. Text accurately states that the channel is located on Map <br />41A. However, Map 41A also shows a Section 28 Collector Ditch. Please submit design <br />information for this additional temporary ditch. Additionally, the Division recommends that <br />these ditches are designed and constructed with a moderate grade to minimize sediment <br />deposition and that these ditches are located as close as possible to the disturbed area. Where <br />the ditch will bisect natural drainage at right angles, field modification may be necessary to <br />prevent abrupt intersections between these drainage features (i.e. avoid 90 degree intersections). <br />Response: Temporary drainage channels are now proposed in two places. See the revised <br />text discussion provided in Part D of Exhibit 7, Item 20. <br />Rule 4.05.4 Stream Channel Diversions (Relocation of Streams) and Stream Channel Reconstmction <br />