2018-09-04_REVISION - C1980007 (11)

Home Browse Search

60 10. Submitting periodic reports of monitoring data to the Division, and 11. Replacing, repairing, and otherwise restoring the dam and structures downstream or purchasing insurance policies addressing downstream damage that will be in effect at the time of longwall mining, should catastrophic failure of the dam occur as a result of mine-induced impacts. 12. Augmenting surface water supplies lost due to subsidence according to the Augmentation Plan contained in Exhibit 52 of the permit application. To address concerns raised by the Division of Water Resources, Office of the State Engineer, Colorado Department of Natural Resources in DWR’s letter of April 21, 2006 to the Division of Reclamation, Mining and Safet y, the Division attached Stipulations Nos. 74, 75, and 76 to the decision for PR-10. As of late 2008, the West Elk Mine had completed the mitigation measures listed above, and had received final approval of the work on the dam from the Office of the State Engineer (letter dated September 2, 2008). Stipulation Nos. 74, 75, and 76 have been terminated. Minnesota Creek Ditch Rider's Cabin - MCC predicts the cabin will not be affected by mining because the nearest longwall panel (panel E6) will be at a depth of 1,200 feet, approximately 800 feet away from the cabin. The calculated angle of contact between the panel and the cabin will be approximately 40 degrees, significantly more than the 20-degree predicted maximum angle of draw in the Dry Fork lease area. To promote more predictable subsidence, MCC may design pillars to yield and crush after mining (in order to minimize humps in the subsidence profile), and mine at a rapid uniform rate. MCC predicts subsidence cracks may form in areas that are located over or next to underground workings. (See preceding description of predicted crack depths.) Subsidence cracks could dewater streams, ponds, or wetlands; cause local cracking or downcutting in streams; damage roads, fences, and the buildings at the Cow Camp; dewater aquifers or cause cross-stratal flow of ground water or methane. MCC predicts mining may cause local temporary pooling and temporary accelerated erosion in the main channel and east fork of Sylvester Gulch, and in parts of the Deep Creek Ditch. Channel avulsion could occur in the Deep Creek Ditch. To mitigate subsidence impacts, MCC has committed to: filling surface cracks; redirecting flow into the original channels of streams or ditches; installing temporary culverts to bridge surface cracks; repairing subsidence- damaged roads, fences, and buildings; monitoring wetland vegetative health in