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West Elk Mine MCC currently has the capacity to pump more than 2,000 gpm of water to the NW Panels sealed sump and discharge up to 2,000 gpm via the Lone Pine pipeline. The discharge permit also allows dischazge rates up to 2,000 gpm to Lone Pine Gulch. To date, the rates pumped to and discharged from the sealed sump have roughly been equal, and are typically less than 500 gpm. Since discharges commenced in eazly January 1998, through the pipeline to Lone Pine Gulch, the water quality of the sump water dischazged has been adequate to meet discharge limits. In particular, the effluent TSS concentrations have been approximately 5 mg/L, compared to influent concentrations of about 300 to 600 mg/L. Storing water underground is a proven and effective water management approach that is often advocated because it saves land, eliminates evaporation, reduces dam safety hazards, reduces certain liability issues, and optimizes water management. In addition, utilizing the sumps has improved the water quality. Precedent for Use of Underground Sumps There is precedent for utilizing sumps in Colorado coal mines. Most mines utilize small capacity sumps for handling "day-to-day" inflows and operational run-off water. Some mines have large capacity sumps, such as the Sanborn Creek Mine in Somerset, Colorado with a 7,000,000 gallon sump capacity. In addition, many municipalities, water districts and industries actively use underground storage in the same way that they do surface storage facilities. For example, Highlands Ranch in Metro-Denver stores thousands of acre-feet underground. Water is withdrawn as necessary and recharged when surplus surface water is available. Aurora recently filed for a similaz project in South Pazk. Coors constantly draws from the Clear Creek alluvium and relies on regulaz rechazge. Water managers generally encourage subsurface storage projects that aze actively utilized, because they offer many advantages over conventional surface storage. Groundwater Outflows from the Sumps For purposes of this analysis, the hydraulic gradient of the NW, NE, and Box Canyon Panels sealed sumps is assumed to be the slope established by the dip of the B Seam coal bed (i.e., approximately 5 percent to the northeast). Figure 28 shows the top of the B Seam contours. As depicted in Figure 28, the B Seam outcrops above the North Fork just upstream of the town of Somerset. Therefore, if water stored in the NW Panels sealed sump made its way to the B Seam outcrop downgradient from Somerset, it would be dischazged into the North Fork as springs and seeps along the B Seam outcrop. Upstream from Somerset; however, if groundwater migrated from the sumps and moved downgradient through the B Seam it would pass beneath the North Fork. • 2.05-246 Revised November 1004 PRIG