2022-02-03_REVISION - C1981018 (2)

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Introduction Blue Mountain Energy plans to dewater the B-seam underground working with a submersible pump in a new well named DW-1R. The well location was primarily determined by the end of the workings in the 1- Right set of entries, which is the lowest point within the active mine.The well will discharge to a small new sediment pond (DW-1R-Pond) located approximately 1100 feet to the south of the well through a 6-inch HDPE pipe laid on the surface.The DW-1R-Pond is located on the north bank of a tributary to Red Wash. The location was chosen to place the pond on flatter slopes and as close as possible to the tributary to minimize the amount of rip-rap channel that would need to be constructed. There will be two separate small areas of disturbance.The well pad for DW-1R will be within disturbance boundaries.The new DW-1R-Pond and a short access road and discharge channel will be new disturbance. The outfall from the DW-1R pond has been submitted to the Colorado Department of Public Health and Environment Water Quality Control Division as Outfall 033A. Discharge from the pond will not happen until the discharge permit is approved. Dewatering of the mine can continue in its current configuration and discharge point until Outfall 033A is approved. If the outfall permit approval is delayed significantly, another option will be to run a 6" HDPE pipe along existing roads to already approved Outfall 029. Flow from the well will be about 400 gpm (0.89 cfs) but will fluctuate a little with mine water levels and pump wear. Initially,the pump will operate on short intervals where the pump will be on for a short time and off for a short time. As mining proceeds, more volume will become available underground and pumping intervals will lengthen.Total flow from the well will be recorded by a flow meter with a totalizer.A flow meter is an important part of monitoring the performance of the pump, so no other flumes or flow measurement devices are proposed. Hydrology As mentioned previously, there will be two separate small areas of disturbance—the well pad and the discharge pond. Runoff from both areas were modeled with SEDCAD. Hydrologic data including rainfall, soil type, and curve numbers can be found in Appendix A. Well Pad The well pad is approximately 0.25 acres and will be almost flat. Because vegetation cannot be allowed on the well pad, a small retention pond or trench was included off the low end of the pad to capture sediment runoff from the pad during a 10-year storm.Settleable solids will be reduced from 5 ml/I to 0.24 ml/I.This is half of the permitted level of 0.5 ml/I. No embankment will be constructed with the well pad trench. It will be cut below existing grade and will simply fill up and discharge to the same location and elevation it currently does.The 100-year storm was also modeled to verify the outlet to the existing grade is sufficient.SEDCAD calculations for the well pad area can be found in Appendix B Blue Mountain Energy 3 Illustration 61