2009-05-15_REVISION - C1980007 (6)

Home Browse Search

n?7vat.-a::;s_i .,......r..-.--.....-,-ti,?:c-:r?+w? West Elk Mine discussed in Exhibit 14C, 1998 Landslide Corrective Measures Report by Barr Engineering/Harding Lawson Associates. The purpose of the corrective measures was to prevent catastrophic failure, which MCC was successful in doing. MCC will continue to evaluate the effectiveness of the corrective measures over time to evaluate their effectiveness for the long term (i.e. post-reclamation). MCC is collecting water level data and movement data from various piezometers, inclinometers, and survey mirrors around the mine site on a scheduled interval: Based on the data collected, MCC will reevaluate the slope stability analyses after spring runoff each year and where appropriate, update Exhibit 14C. The update will include an evaluation of the relative change in the factor of safety during the previous year and since the installation of the corrective measures in 1998. A revision including the updated information will be provided to the CDMG by July 30t" of each year. In the spring of 1999, MCC drilled two horizontal holes from the surface, at the abandoned main mine site substation, to intercept small sumps in the F-Seam to drain the water that accumulates in these sumps. The water that accumulates in these sumps is primarily surface water and near surface groundwater that infiltrates through the colluvium above the F-Seam and into the F-Seam workings. Once the water is in the sump, it then infiltrates through the F-Seam floor and into the unstable surface soils within the main mine site landslide. It is important that water sources to the surface soils be controlled in order to improve the local and global stability. These two holes are a test to determine if this method of draining the sumps is feasible. These sumps are located near the main F-Seam portals. They are not part of MCC's mine water handling system. These sumps have not been nor will be used to handle a large inflow event. The sumps are too small and if they overflow, they will flow into the belt and travel ways. Drain A will be drilled approximately 1,100 feet and into the floor of one of the main collection sumps. Drain B will be drilled approximately 1,400 feet, and into the bedrock fracture zone below the F-Seam sumps. If the holes are successful, MCC estimates that approximately 22 gpm will flow from the two holes and into pond MB-1. If the holes are successful, MCC will permit and construct additional drains that will remain upon final reclamation. In addition, MCC will update Exhibit 14c to include these drains and evaluate them for the final reclamation plan. Monitoring,Samplinz Drilling and Other Temporary Facilities or Operations As needed on occasion, MCC will construct monitoring, sampling, drilling and/or other temporary facilities or operations, along with access to them, in order to supplement design or compliance data, as well as ventilation or other needs for the mine operations. As with all of MCC's pennanent facilities and operations, these facilities will be constructed, operated and reclaimed in compliance with the Regulations of the CMLRB for Coal Mining, particularly Rule 2.05. All necessary clearances, such as cultural resource reviews by the State Historic Preservation Office, will also be provided. Accesses to such facilities will typically be field-designed and constructed as described in the light-use road discussions above. No drainage alteration or relocation would typically be required for such construction. Temporary culverts would be used to provide access crossings, or low-flow fording or dry drainage crossings could be constructed in drainage areas of less than 2.05-28 Rev. 06/05,01/06,03/06,04106&05/06-PR 10; 01/09- MR-350; 04109- TR 116; 04!09- MR353; MR354- 05109