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West Elk Mine <br /> <br />2.05-27 Rev. 06/05, 01/06, 03/06, 04/06 & 05/06- PR10; 01/09- MR350; 04/09- TR116; 04/09- MR353; 05/09- MR354; 08/09- TR118; <br />08/09- TR119; 09/12- MR387; 11/12- MR390; 07/18-PR15; 11/18- MR430; MR438- 09/19; MR439- 11/19; 07/20- MR447; 6/22- <br />MR464; 6/22 MR466; 6/22 MR468; 11/22 MR471 <br />facilities area, as surges of movement had been experienced in 1996 and 1997. The corrective measures <br />included the installation of rock buttresses, stone columns, horizontal drains, pins (micro-piles), and the <br />expansion of the roller compacted (RCC) buttress. These structures are described in detail, and their <br />effectiveness in improving the stability of the facilities area is discussed in Exhibit 14C, 1998 Landslide <br />Corrective Measures Report by Barr Engineering/Harding Lawson Associates. The purpose of the <br />corrective measures was to prevent catastrophic failure, which MCC was successful in doing. MCC will <br />continue to evaluate the effectiveness of the corrective measures over time to evaluate their effectiveness <br />for the long term (i.e. post-reclamation). MCC is collecting water level data and movement data from <br />various piezometers, inclinometers, and survey mirrors around the mine site on a scheduled interval. <br />Based on the data collected, MCC will reevaluate the slope stability analyses after spring runoff each year <br />and where appropriate, update Exhibit 14C. The update will include an evaluation of the relative change <br />in the factor of safety during the previous year and since the installation of the corrective measures in <br />1998. A revision including the updated information will be provided to the CDMG by July 30th of each <br />year. <br /> <br />In the spring of 1999, MCC drilled two horizontal holes from the surface, at the abandoned main mine <br />site substation, to intercept small sumps in the F-Seam to drain the water that accumulates in these sumps. <br />The water that accumulates in these sumps is primarily surface water and near surface groundwater that <br />infiltrates through the colluvium above the F-Seam and into the F-Seam workings. Once the water is in <br />the sump, it then infiltrates through the F-Seam floor and into the unstable surface soils within the main <br />mine site landslide. It is important that water sources to the surface soils be controlled in order to <br />improve the local and global stability. These two holes are a test to determine if this method of draining <br />the sumps is feasible. These sumps are located near the main F-Seam portals. They are not part of <br />MCC’s mine water handling system. These sumps have not been nor will be used to handle a large <br />inflow event. The sumps are too small and if they overflow, they will flow into the belt and travel ways. <br />Drain A will be drilled approximately 1,100 feet and into the floor of one of the main collection sumps. <br />Drain B will be drilled approximately 1,400 feet, and into the bedrock fracture zone below the F-Seam <br />sumps. If the holes are successful, MCC estimates that approximately 22 gpm will flow from the two <br />holes and into pond MB-1. If the holes are successful, MCC will permit and construct additional drains <br />that will remain upon final reclamation. In addition, MCC will update Exhibit 14C to include these drains <br />and evaluate them for the final reclamation plan. <br /> <br />Mine Ventilation Boreholes and Degasification Borehole <br /> <br />Ventilating mine methane (one of the naturally-occurring gasses within the rock formations above the <br />mined coal) through West Elk Mine’s mine ventilation boreholes (MVBs) is an integral and required part <br />of West Elk Mine’s MSHA-approved mine air ventilation plan. The MVB pads are typically a half-acre <br />or less in size and include an area for mud pits to accommodate drill cuttings that are about 10’ x 20’ x <br />10’ deep. Access to the pads is provided by constructing light-use, low-volume roads as discussed above. <br />The MVBs are generally constructed as follows: <br />• Drill 19” hole, 20’ or to bedrock, set 14” surface casing. <br />• Drill the intermediate 12.25” hole to a competent formation within 100-250 feet of the coal seam and <br />case the hole with 9-5/8” casing and cement the annulus to the surface. <br />• Drill out the grout shoe with 8.75” bit and drill the remainder of the hole to within 25’ of the coal <br />seam and install 7” slotted casing in the hole to extend approximately 40’ past the bottom of the 9- <br />5/8” casing. <br />• Install wellhead <br />