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

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West Elk Mine • All water supplies aze obtained from MCC's water rights in accordance with Colorado Water Law. The freshwater pond is filled during spring runoff and kept full until water rights are out of priority, then the leased water from the Lost Lake Slough (a.k.a. the East Beckwith Reservoir operated by the Fire Mountain Canal and Reservoir Company) is used. The current maximum withdrawal at the intake is 450 gpm. The lazge fault inflows experienced by MCC in 1996 and early 1997 have not significantly changed the amounts or schedules of water diversions from the North Fork. The potential effect of diversions on North Fork flows have been quantified for both flow rates and flow volumes. Percent changes in flow rates in the North Fork for combinations of streamflow and diversion conditions are provided in Table 47 and Table 48. In most cases, the percent change is within the estimated 5 percent error of streamflow measurement at the USGS gaging station on the North Fork. With the existing pump capacity, the diversion would result in measurable change in flow only for low flows with return periods of about 200 yeazs or greater. During these extreme low flow periods, MCC's water rights would be out of priority and diversions would not be made. Normally MCC's water rights would be out of priority when river flows drop below approximately 300 cfs during the growing season. In this case, percent changes in river flows would be less than the 0.4 percent as shown in Table 48. Estimated percent changes in North Fork flow volumes due to withdrawals for projected mine requirements are provided in Table 48. Even in a drought year, the mine water requirements anticipated during term of permit are only about 0.1 percent of the North Fork flows. Thus fisheries, streamside vegetation, and sediment transport process would be unaffected. Furthermore, anticipated changes in river flows due to withdrawals would have no effect on sub- imgation or flood irrigation of alluvial valley floors on the North Fork downstream of the mine. An important factor to consider relative to Table 47 is that fault inflows to the mine are not accounted for, yet a significant amount of mine water is actually discharged to the North Fork, thus offsetting MCC's depletion. Since the fault inflows began in 1996, MCC has been a net exporter of water from the mine to the North Fork on an annual basis. Table 49 contains actual and projected water usages for West Elk Mine. These numbers aze projections for abuild-up of tonnage and increases in water usage, which are entirely dependent on coal sales and market conditions. Table 47 Estimated Percent Chan a in North Fork Flow Volumes Annual North Fork Total Volume Net Net Depletion Streamflow Case (AF) Requirement Requirement 63 AF 88 AF 70 AF Avera a Year 313 000 -0.03 -0.02 -0.02 1 in 25 dry year 142,300 -0.06 -0.05 -0.04 e.. 1954 1 in 100 dry year 82,270 -0.11 -0.09 -0.08 e.. 1977 ~ Cases considered are water years (i.e., October through September). 205-221 Revised November 2004 PR/0; Rev. March 2006; Rev. May 2006 PR/0