2010-12-15_REVISION - C1981019 - Laserfiche WebLink

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Colowyo Coal Company 5731 State Highway 13 Meeker, CO 81641 H December 14, 2010 Mr. James R. Stark Environmental Protection Specialist Colorado Division of Reclamation, Mining and Safety Department of Natural Resources 1313 Sherman Street, Room 215 Denver, CO 80203 DEC 1 91- W RE: Colowyo Mine's response to the Division's Second Adequacy Report for Technical Revision - 81. Dear Mr. Stark, Colowyo received the Division's adequacy comments for TR-81 and has the following comments and responses: Rule 2.05.3(6) - Overburden 1. Response Accepted. Colowyo addressed the subsidence concerns due to highwall mining on Page 6 of Addendum 3 to the Shannon and Wilson Report (revised 15 April 2010). 2. Response Not Accepted. In its response Colowyo states that "Colowyo has not chosen to change the swell factor to 15% at this time... in the future when Colowyo deems it prudent to change the permitted swell factor..." Colowyo's brief answer to the Division's adequacy question raises as many questions and concerns as the original statement that it was planning on changing the approved swell factor. The swell factor for overburden for a surface mine is not only important for cost estimating and reclamation liability purposes, it is also necessary for making decisions regarding backfilling and grading plans and schedules, post-mining topography and excess spoil fills, to name a few. An operator cannot just "deem it prudent" to change a swell factor. Colowyo has been mining in the same basic geologic formations for more than 30 years and there is a well established history with regards to the mine's swell factor. The decision to change a swell factor at Colowyo is not one that is taken lightly. The swell factor at the Colowyo Mine is either 15% or 20% or some other number that can be documented and justified. It should represent an average of the swell factors from different geologic formations and mining methods. Based on the fact that Colowyo has approval for two permanent out-of-pit excess spoil piles, this discussion is not academic. The Division will be reluctant to entertain any revision requesting a change to the swell factor at a later date. If, in fact, the swell factor for the South Taylor Pit is different from that of the East Pit, West Pit and Section 16 Pit and needs to be changed, Colowyo needs to include that change in this revision, as it is critical to the decisions that will be made with regards to the revision. If the swell factor for the South