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support for reduction in the curve numbers recently increased, rather than a <br />justification for not considering their modest reduction on all areas covered by <br />SEDCAD modeling (with the exception of areas reporting to the Prospect <br />Drainage). <br />It is still the Division's belief that additional infiltration data collected at <br />Colowyo (beyond the limited data from the 1981 Striffler and Rhodes study) <br />would lead to a more accurate characterization of the soils of reclaimed <br />lands. However, in the December 13, 2012 letter, Colowyo makes compelling <br />points related to how the mining process increases permeability of the <br />underlying soil, and how the practices of ripping the soil and roughening <br />topsoil will indeed increase infiltration. In future reclamation efforts, it is <br />essential that Colowyo continue these practices. <br />Also, the Division does recognize that the data from Striffler and Rhodes, <br />while somewhat limited, points to reclaimed lands having A or B soils at part <br />of the Colowyo site as well as at other sites in Colorado. <br />COMMENT #3 <br />The condition of Colowyo's mine site will change drastically as reclamation <br />progresses, and compliance with water quality regulations in the past is not <br />an assurance that future conditions at the site will also result in compliance. <br />Therefore, one cannot say that past compliance is justification for lowering <br />curve numbers. <br />Colowvo's Response: <br />Probably the best justification for reduction in the current curve numbers, <br />especially for those associated with reclamation areas > three years and older is <br />the performance of the ponds below areas that have received Phase III bond <br />release, namely Gulch A, Streeter, and the West Pit Pond. With the exception of <br />inflow from runoff caused by snowmelt or rain over frozen ground, these three <br />ponds normally receive no inflow from surface runoff generated by storm events <br />in recent history. All of these structures were designed and constructed utilizing <br />much lower curve numbers than those currently in force today or those proposed <br />in the TR -95 submittal. <br />The Division is still considering whether or not additional infiltration testing <br />is necessary to justify the proposed curve number changes. After the <br />questions in this letter are answered by Colowyo, we will make this decision. <br />COMMENT #4 <br />A mining property of Western Fuels- Colorado, A Limited Liability Company <br />