2018-09-04_PERMIT FILE - C1980007A (3)

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West Elk Mine 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 30`' 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. Mine Ventilation Boreholes and Degasification Borehole Ventilating mine methane (one of the naturally -occurring gasses within the rock formations above the mined coal) through West Elk Mine's mine ventilation boreholes (MVBs) is an integral and required part of West Elk Mine's MSHA-approved mine air ventilation plan. The MVB pads are typically a half -acre or less in size and include an area for mud pits to accommodate drill cuttings that are about 10' x 20' x 10' deep. Access to the pads is provided by constructing light -use, low-volume roads as discussed above. The MVBs are generally constructed as follows: • Drill 19" hole, 20' or to bedrock, set 14" surface casing. • Drill the intermediate 12.25" hole to a competent formation within 100-250 feet of the coal seam and case the hole with 9-5/8" casing and cement the annulus to the surface. • Drill out the grout shoe with 8.75" bit and drill the remainder of the hole to within 25' of the coal seam and install 7" slotted casing in the hole to extend approximately 40' past the bottom of the 9- 5/8" casing. • Install wellhead A B -seam degasification borehole is located approximately 225 feet west of the electric borehole site in Sylvester Gulch. It was constructed during the summer of 1997. This borehole is not currently operating, nor is the "in -mine" B -seam methane collection and transmission system that had captured gas in the mine and transported it in poly -pipe up Ventilation Shaft No. 3 for ventilation to the atmosphere. Some methane gas from the sealed mine sections is used to heat mine ventilation air at the Ventilation Shafts No. 1 & 2, in a system completed in 2003 and amended a few years later. 205-27 Rev 06/05, 01/06 03/06, 04/06 & 05/06- PRIO, 01/09- MR350; 04/09- TR116, 04/09- MR353, 05/09- MR354, 08/09- TR118; 08/09- TR119, 09/12- MR387; 11/12- MR390, 07/18-PR15