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West Elk Mine Changes in the quantity of water supplied to the AVF depend on the difference between water used and water discharged to the North Fork of the Gunnison River. It is stated in the Water System and Consumption Section that 200,000 gallons per day would be required during the maximum producfion of 8.2 MM tons per yeaz for coal spraying, dust suppression and all other surface facility use. Since the mine is expected to operate about 244 days per yeaz, total water use is expected to be about 150 acre-feet per year during maximum projected production. This represents less than 0.04 percent of the average annual stream flow on the North Fork. Since less than 70 percent of this use is deemed to be consumptive use, the loss is actually less than 0.03 percent of the average stream flow. As discussed in this plan, actual production is much less than was anticipated when the mine opened in 1982. Thus water use is significantly less than discussed above. Water quality changes resulting from dischazge of waste water will not constitute material damage because no measurable change in water quality is expected to occur. Of the 200,000 gallons/day maximum projected use, 38,000 gallons/day (28.5 acre-feet/yeaz) would be required for potable water use. Consumptive use of potable water would be minimal. Assuming no consumptive use, one would expect a discharge of less than 0.06 cfs during plant operation. This use and return flow is insignificant compazed to the flows in the North Fork of the Gunnison. Even during the lowest flow on record (17 cfs) for the 1934 through 1979 period of record on the North Fork at Somerset, the potable water use would be less than 0.4 percent of the flow. The return water will be treated to meet NPDES effluent limits and should pose no problem for downstream irrigation use of AVF's. See the Section on Agricultural Monitoring Plan for further discussion. The impacts of the discharge of water to the North Fork from West Elk Mine is discussed in detail in the Probable Hydrogogic Consequences - 2.05.6(3)(b)(iii & viii), section "Surface Water Quality Effects". The discussion focused on the "worst case" scenarios that might have occurred prior to the development of the in-mine sumps. The use of the sumps has allowed West Elk Mine to control the dischazge rate to the North Fork via the Mine Water Pumping Facility (MWPF) dischazge to Sylvester Gulch. Since the parameters of interest in the mine discharge water relate to TDS and its constituents, the potential adverse impacts on downstream agriculture would occur over time. Therefore, based on the recommendation of CDMG, WWE used more typical late irrigation flow rates rather than the 7-day, 10-yeaz low flow condition considered in the PHC section. W WE based our analyses on the MLRD's "A description of the Material Damage Assessment Process Pertaining to Alluvial Valley Floors, Surface Water, Ground Water and Subsidence at Coal Mines" (Material Damage Guidelines) published in 1988. Table 3 of the Material Damage Guidelines establishes "suspect levels" for irrigation water, above which additional analyses aze required. MCC sampled the North Fork upstream and downstream of Sylvester Gulch on September 14, 2004. Laboratory analyses were conducted on a full-suite of water quality pazameters, including the constituents with established suspect levels. The flow in the North Fork on September 14, 2004 was 68 cfs. While this flow is lower than typical-average October flow is 118 cfs, the flow was considered to be reasonably conservative for the analysis. ~. 2.069 Revised7une 1005 PRIO; Rev. March 2006