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COAL <br />S,, COMPANY G.� <br />EOPLE•PRODUCTlON� <br />Regarding other changes to Exhibit 7, please explain the rationale <br />behind all substantive changes. In particular, please explain the <br />reasoning for updating the sediment loading parameters in Table 6. <br />Colowyo's June 25, 2012 Response to Comment 4: <br />The applicable text "Methodologies and Assumptions for Sedimentation <br />Pond Design Evaluations " in Volume 2D was undergoing a revision with <br />the proposed curve numbers, and this section was submitted in its entirety. <br />Table 6 is part of that section. The similarly organized Table 4 in Volume <br />13 was submitted and revised to keep it consistent with Table 6 <br />Comments presented below relative to Table 6 are also applicable to <br />Table 4. <br />Revisions to Table 6 were included to bring a consistent basis to the <br />sediment delivery estimates for the various sediment ponds. The <br />calculations represented in the final five rows of Table 6 have been <br />prepared pursuant to several different methodologies over the years, <br />although all ultimately trace back to the use of The RUSLE methods. It <br />has become an issue at this time to answer CDRMS recent requests <br />dealing with the inspection protocols for the sediment ponds, in particular <br />the annual inspections which are required to be certified by a professional <br />engineer. By way of the proposed revisions to Table 6, CCC is attempting <br />to make the inspection basis consistent for all of the ponds and to remove <br />ambiguities that may be of concern to an engineer certifying the reports. <br />Sediment delivery volume for the older ponds was manually calculated <br />using the sedimentology parameters described in "Methodologies and <br />Assumptions for Sedimentation Pond Design Evaluations" and applying a <br />SDR sediment delivery ratio based on the values presented in the <br />literature. With the adoption of SEDCAD as CDRMS preferred method <br />for determining compliance with the regulation in the design phase, and <br />since the input parameters needed for this calculation in SEDCAD are the <br />same as those historically used for the manual RUSLE calculation, it <br />makes sense to use SEDCAD's algorithm for estimating annual sediment <br />volume for each pond. The method is explained on p. 64 of the SEDCAD <br />User's Manual. <br />Pursuant to CDRMS requests earlier in this year, CCC is also seeking to <br />establish a uniform basis for all ponds with regard to sediment storage <br />A Western Fuels- Colorado, LLC mining property <br />