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Page 4of5 <br />snowmelt or rain over frozen ground, these three ponds normally receive no inflow from <br />surface runoff generated by storm events in recent history. All of these structures were <br />designed and constructed utilizing much lower curve numbers than those currently in <br />force today or those proposed in the TR -95 submittal. <br />Division Comment (Fourth Adequacy) <br />The vegetation growth on areas that have been Phase III released (where vegetation <br />is at least 10 years old) could be vastly different than areas with three years of <br />growth. Does Colowyo have any data showing that reclamation areas that are <br />approximately three years old produce little runoff from a IO year or greater storm? <br />COMMENT #4 <br />My apologies for not being more clear when I repeated the original comment in my July <br />2, 2012 letter. What I meant to say is that, in the Division's opinion, Colowyo did not <br />answer the question. Please describe how each of the values in the sediment loading <br />section of Table 6 is calculated, including the sources of information. This should be <br />done in a very direct manner, possibly using an example. This issue has also been briefly <br />discussed with Colowyo staff (Kurt Blunt) at the mine's administration office. <br />Colowyo 's Response: <br />Colowyo has included the previously approved version of Table 6 in this package and is <br />no longer seeking to modem it through this process. <br />Division Comment (Fourth Adequacy) <br />This response is adequate. <br />GENERAL COMMENT <br />It is very important to consider what is happening on the ground. The SEDCAD models <br />are valuable information, but the Division is also concerned about the stability of <br />channels and the functioning of ponds. The effectiveness of these structures will <br />determine if Colowyo is in compliance with the Division's permit and with your CDPS <br />permit and will be important in the context of future bond release applications. We <br />encourage Colowyo to consider these factors when proposing modeling updates, when <br />constructing structures, and when scheduling reclamation. <br />Colowyo 's Response: <br />Colowyo believes that the Division's expectations of conditions under which these <br />structures, the approved designs, and the modeling inputs are reasonably expected to <br />physically, and by modeling assumption, maintain stability and proper Junction, need to <br />be clearly defined so that additional discussion and evaluation of the applicable <br />regulatory mandates can be applied in this case. <br />Division Comment (Fourth Adequacy) <br />No further response is required of Colowyo. However, based on the following <br />history of incidents at Colowyo, the Division believes that it is not unreasonable to <br />use the existing curve numbers for the hydrologic models: <br />