2015-11-12_REPORT - C1980007 (2)

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Rule 2.05.6(6)(c)(i)(D) — Monitoring of monuments and structures were preformed quarterly, commencing one month prior to the initiation of mining beneath any established monument or structure. Rule 2.05.6(6)(c)(i)(E) — The results of monitoring are submitted to the Division semiannually. Rule 2.05.6(6)(c)(i)(F) — Subsidence monitoring is conducted with sufficient post mining monitoring to verify subsidence predictions. Discussions of the traverses in the field surveys include observations of new and previously identified subsidence features. The report describes the changes to the previously existing features that occurred since the previous visual inspections. Rule 2.05.6(6)(e)(iii) — The West Elk Mine permit contains a detailed description of the measures to be taken to prevent subsidence from causing material damage or lessening the value or reasonably foreseeable use of the surface. Rule 2.05.6(6)(d)(i) — The subsidence monitoring program for the West Elk Mine accurately predicts the effects of subsidence within and adjacent to the permit area. The subsidence monitoring reports provide a record of data, and correlate the data to previous reports. The report includes data from the visual inspection of traverses, ponds, Forest Service roads/ponds and surveys of the Monument Dam/Hillside South of Minnesota Creek Road. The data shows that there have been no significant or long term adverse effects to the permit area or adjacent areas. Subsidence cracks in the mining area are influenced by the material in which they occur. The majority of the cracks are in alluvial or colluvial deposits. Such cracks weather rapidly and are significantly reduced in size between the time they are identified and the following survey. Subsidence cracks that are identifiable over multiple years generally occur in sandstone lenses that are at a shallow depth below a drill pad, access road or at an outcrop. Typically the weathering of subsidence cracks causes rounding of the edges and sediment to infill the crack. Rounding of the edges widens the crack on the surface but not at depth. Cracks in sandstone layers weather in a similar way to those in alluvial and colluvial materials, but considerably more slowly. Differential settlement of fill materials is commonly exacerbated by mining activities at the West Elk Mine. These cracks initially form due to gravity and not subsidence. When mining occurs underneath these areas, the cracks become exaggerated. Fill -slopes on pads and roads frequently show this type of subsidence related activity. There are a few noted cut -slopes on drill pads that have had differential settlement occur on them. These cracks weather in a similar manner to subsidence cracks in alluvial and colluvial material. Landslides and rock falls are closely monitored in the West Elk Mine permit area. Photographs are taken during the semi-annual surveys of areas identified as a landslide or rock fall areas and potential landslide or rock fall areas. The photos are included in the report if there is noticeable movement between one photograph and another. The climate seems to have more of an impact on landslide and rock fall areas than the mining activities. When wet seasons or large storm events occur the area is more susceptible to movement than when the area is undermined. It has been documented in the reports that mining has progressed under an area designated as a