2008-05-13_REVISION - C1981019 (4)

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the 26 February 2008 meeting between the Division and Colowyo. During the meeting and in a follow-up letter dated 12 March 2008, the Division requested that Colowyo provide a more detailed description and timing of the final regrading and closure of the East Pit, including a map, or plate, and acreages of each regraded area, to ensure that it will conform with the approved design and the SEDCAD modeling. Additionally, the Division also requested that Colowyo provide a more detailed description of any alternate sediment control measures that it will use in the East Pit reclamation. This information will allow the Division to more accurately assess the East Pit reclamation and give the Division a higher level of confidence with regards to the Prospect drainage and the Prospect Pond. Current modeling of the Prospect watershed includes ONLY disturbed acres, which, in the worst hydrologic condition, are topsoiled and seeded. In other words, modeling includes no areas of regraded spoil or topsoil that has not been seeded. This is significant for the following reason. Colowyo regraded 86 acres in 2006 and topsoiled those same acres in 2007. They completed no backfilling and grading to final grade in 2007 in the East Pit (see 2007 ARR). Therefore, according to the currently approved modeling and pond design, Colowyo must topsoil and seed all acres backfilled and graded in the same field season. There are about 281 acres remaining in the Prospect watershed to return to final grade, topsoil, and seed. Furthermore, Colowyo is currently sumping runoff from reclaimed areas to the pit or partial pit, as the case may be. This obviously helps prevent issues at the Prospect pond and beyond but this practice also raises questions about design criteria, maintenance, and impoundment questions relative to the ditches and sump. If Colowyo does, in fact, plan on using this sumping method to control runoff from both the disturbed and reclaimed areas of the Prospect drainage, this needs to be explicitly stated and the necessary hydrologic designs must be provided to the Division. If the Division does not have design information for aditch/sump system that fails, there is no way to ensure that the system was constructed and/or maintained to any required standard or design. Please provide the Division with a detailed schedule for the backfilling and grading of the East Pit up to and including final pit closure. Please include a map, or plate and acreages of each regraded area, to ensure that it will conform to the approved design and the SEDCAD modeling. As part of this schedule the Division also requested that Colowyo provide a more detailed description of any alternate sediment control measures that it will use in the East Pit reclamation, including surface roughening techniques for the areas that have been recently topsoiled. Additionally, please provide detailed information regarding the sumping and diversion of Prospect runoff into the East Pit, including the hydrologic condition of Colowyo C-1981-019 4 Permit Renewal 05