2009-04-01_GENERAL DOCUMENTS - C1980005 (2)

Home Browse Search

bond release blocks. BRB-2 and BRB-3 each passed the mandatory species dominance test; BRB-3 passed all three of the additional tests, while BRB-2 passed two of the three additional tests. Species Composition/Diversity Summary: Field observations and quantitative data indicate a relatively diverse assemblage of perennial species and life forms supportive of the rangeland/wildlife habitat postmining land use. Both BRB-2 and BRB-3 pass at least three of the four diversity tests, and as such would comply with the Phase III diversity success demonstration requirement. Based on field observations and quantitative testing, it is clear that the compositional makeup of the vegetative stands within BRB-2 and BRB-3 is more than adequate for Phase II bond release. Condition of Sediment Ponds The three sediment ponds within the SL-3 bond release request area (PECOCO, Pond 004 and Pond 008) have all been approved as permanent impoundments. PECOCO was approved as permanent in 1990, Ponds 004 and 008 in TR-37, September 2006. Permanent impoundment demonstrations documenting compliance with applicable criteria of Rule 4.05.9(13) are included in Appendix 7-6G, 7-6c.2 and Appendix 7-6f.4 of the Seneca II permit application documents. Each of these impoundments was full and discharging clear water during the inspection. Pond inlets, discharge structures, and embankments were stable and functioning properly, with no problems evident. Sediment Pond Summary: No problems that would preclude Phase II bond release for any of the three sediment ponds were observed. The PECOCO Pond is within BRB-3, for which the Division is proposing to approve Phase II Bond Release. Ponds 004 and 008 are located within BRB-4, which is not included in the proposed Phase II bond release approval. Construction and Performance of Permanent Impoundments The Seneca II Mine is located within two adjacent drainage basins: Grassy Creek and Fish Creek. Both of these are sub-basins of the upper Yampa River basin in northwestern Colorado. Surface water runoff and sediment control consisted of the construction and maintenance of sedimentation ponds, stock ponds, and postmine drainage channels. The following section describes observations and findings regarding the sedimentation ponds and stock ponds that have been approved as permanent impoundments and which are included in the SL-3 release request area. Sedimentation Ponds SCC utilizes sediment ponds primarily to prevent additional contributions of sediment to streamflow or runoff outside the permit area due to mining disturbances. Existing Sedimentation Ponds 004, 008, and the PECOCO Pond are within the release request area, however only the PECOCO pond is located within the area for which the Division is proposing to approve Phase II bond release. The 15