2008-03-21_PERMIT FILE - C1980007A (46)

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West Elk Mine Flows from the mine vary as pumps in the mine cycle on and off as sumps fill and empty, and/or a precipitation event occurs. This option was also labor and maintenance intensive, requiring handling of bulky containers, and electrical and piping maintenance in several remote locations on the mine site. Phvsical Treatment Five alternatives were evaluated. One alternative was unsuccessful, because it was ineffective in removing the small particle-sized suspended solids. A Multi-media filtering pilot plant was unable to handle higher flows, nor capture the small particles (98% of the suspended solids were <10 microns) in the dirty mine water. Scalping (cyclones) and ponding the coarse material was evaluated, however, even through the specific gravity of the suspended clay was 1.82, the fines were small enough to travel with the water and would not separate in the cyclones without chemical addition to coagulate the solids. The solids also needed to be more concentrated and consolidated (i.e., in a filter press) for economic disposal. Athickener/clazifier with chemical and sand addition was also evaluated. The process could treat the entire volume of mine water, or scalped portions, and delivered consistent results. On the downside, the process required <_10 percent solids in the feed and the system required two chemical elements and sand, increasing the maintenance and overall costs. Centrifugal separators were evaluated, however, power consumption and the problems that plagued the cyclone alternative (described above), also contributed to the centrifugal sepazator ineffectiveness. Dissolved air flotation (DAF) was considered, but because of sparging (external air source), large bubbles occurred with chemical • addition and caused foaming (similar to a washing machine that has been overloaded with soap), and therefore did not effectively float clays and silicates. Induced air floatation (IAF) with a single chemical addition was also considered. "Mini-bubbles" were formed (by induction, rather than spazging), the clays floated to the surface and a froth was formed that could be easily skimmed from the water. The downsides were that a large amount of chemical could be required, the cost of that chemical, and the process was a relatively new technology. In the mine MCC can minimize total suspended solids in mine water by: (1) Channeling water out of roadways wherever possible. (2) Utilizing imported gravel for mine roadways with less clay in the fines. (3) Segregating better quality water for direct dischazge. (4) Utilizing tanks or small, lined dams, etc. to collect clear water from inflows for direct dischazge. (5) Treating the particles with the largest mass first (i.e, with baffles or dams constructed in the sumps). MCC used the NW Panels sealed sump to reduce mine water outflows to assure that the hydraulic capacities of the sedimentation ponds would not be exceeded and that NPDES permit limits would be met. In light of the problems experienced with the effective treatment of TSS in the fault inflow water, the use of previously mined own-dip sealed panels for storage reservoirs (or sealed panel sumps) is a key component of MCC's overall mine water management program. MCC will utilize the NE Panels sealed sump along with the new, lazge capacity (up to 2,000 gpm) water pumping facility, to optimize MCC's water management system. The Sylvester Gulch Mine Water Pumping Facility (MWPF) is described in Exhibit 69, The MWPF went . online in 2000 and remains the primary discharge for mine water at West Elk Mine. 2.05-115 Revised November 1004 PRIG; Rev. March 2006; Rev. May 2006 PRIO