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West Elk Mine <br />• MCC currently has the capacity to pump more than 2,000 gpm of water to the NW Panels sealed <br />sump and discharge up to 2,000 gpm via the Lone Pine pipeline. The discharge permit also allows <br />discharge rates up to 2,000 gpm to Lone Pine Gulch. To date, the rates pumped to and discharged <br />from the sealed sump have roughly been equal, and are typically less than 500 gpm. Since <br />dischazges commenced in early January 1998, through the pipeline to Lone Pine Gulch, the water <br />quality of the sump water dischazged has been adequate to meet dischazge limits. In particulaz, the <br />effluent TSS concentrations have been approximately 5 mg/L, compared to influent concentrations <br />of about 300 to 600 mg/L. <br />Storing water underground is a proven and effective water management approach that is often <br />advocated because it saves land, eliminates evaporation, reduces dam safety hazazds, reduces certain <br />liability issues, and optimizes water management. In addition, utilizing the sumps has improved the <br />water quality. <br />Precedent for Use of Underground Sums <br />There is precedent for utilizing sumps in Colorado coal mines. Most mines utilize small capacity <br />sumps for handling "day-to-day" inflows and operational run-off water. Some mines have large <br />capacity sumps, such as the Sanborn Creek Mine in Somerset, Colorado with a 7,000,000 gallon <br />sump capacity. In addition, many municipalities, water districts and industries actively use <br />underground storage in the same way that they do surface storage facilities. For example, <br />Highlands Ranch in Metro-Denver stores thousands of acre-feet underground. Water is withdrawn <br />• as necessary and rechazged when surplus surface water is available. Aurora recently filed for a <br />similaz project in South Pazk. Coors constantly draws from the Clear Creek alluvium and relies on <br />regulaz rechazge. Water managers generally encourage subsurface storage projects that are actively <br />utilized, because they offer many advantages over conventional surface storage. <br />Groundwater Outflows from the Sumps <br />For purposes of this analysis, the hydraulic gradient of the NW, NE, and Box Canyon Panels <br />sealed sumps is assumed to be the slope established by the dip of the B Seam coal bed (i.e., <br />approximately 5 percent to the northeast). Figure 28 shows the top of the B Seam contours. As <br />depicted in Figure 28, the B Seam outcrops above the North Fork just upstream of the town of <br />Somerset. Therefore, if water stored in the NW Panels sealed sump made its way to the B Seam <br />outcrop downgradient from Somerset, it would be discharged into the North Fork as springs and <br />seeps along the B Seam outcrop. Upstream from Somerset; however, if groundwater migrated <br />from the sumps and moved downgradient through the B Seam it would pass beneath the North <br />Fork. <br /> <br />2.05-286 Revised June 2005 PRIO; Rev. Minch 2006; Rev. May 2006 PRI G <br />