2012-09-07_REVISION - C1981019 (3)

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Hernandez, Alysha From: Stark, Jim Sent: Friday, September 07, 2012 1:30 PM To: Zuber, Rob Cc: DRMS - Coal -Admin Subject: Colowyo (C- 1981 -019) Partial Phase I Bond Release SL -06 GPS Data Per your request I have reviewed the elevation data you and Jason took at Colowyo during the SL -06 inspection. The elevation data I reviewed was the corrected, post - processed data that was taken with the Trimble RTK. I reviewed the cross - section elevations and the post- mining drainage channel elevations. The cross - section elevations were compared to the as -built topography, which was shown on SL -06 Exhibit 1. The post- mining drainage channel elevations were compared to the approved channel designs, which are shown on Maps 33 and 33A. All of the measured elevations along the cross - sections were + / -10 feet of the as -built elevations, shown on SL -06 Exhibit 1 (with the majority of the measured elevations being +1-5 feet). Based on the interpolation of the elevations from Exhibit 1, it is my opinion that the measured elevations and the as -built elevations are consistent. It appears as though Colowyo has reconstructed the topography in the SL -06 area as approved and shown on Map 19. I do not have any questions regarding the PMT for your PAR letter. All of the measured elevations in the permanent post- mining drainage channels in the SL -O 1 area were also + / -10 feet of the elevations shown on the approved channel profiles (on Maps 33 and 33A). Again, the majority of the measured elevations were +1-5 feet of the approved channel elevations. Similar to the cross - section data, based on the interpolation of the approved elevations shown on Maps 33 and 33A it is my opinion that the measured and approved elevations for the post- mining drainages are consistent. It appears as though Colowyo has constructed the post- mining drainages as approved (of course this applies only to the channel profile and not the rest of the construction requirements, which you looked at during your inspection). I do not have any questions regarding the post- mining drainage channels for your PAR letter. As we discussed, I will work on putting together text and cross - sections for both the PMT and the post- mining drainage channels for your findings document. I may work on that sooner than later, as time permits. Please let me know once you have a firm decision date for SL -06. If you have any other questions please let me know. James R Stark Environmental Protection Specialist Colorado Department of Natural Resources Division of Reclamation, Mining and Safety 1313 Sherman Street, Room 215 Denver, CO 80203 (303)866 -3567 X8145 www. mining. state. co.us