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1i'esr Elk Nfine 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 toss 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 gallonslda}• maximum projected use, 38,000 gallonslday (28S acre-feeUyeaz) would be required for potable water use. Consumptive use of potable water cvould be minimal. Assuming no consumptive use, one would expect a dischazge 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 [979 period of record on the ,\zorth Fork at Somerset, the potable water use would be less than 0.4 percent of the flow. The retum water will be treated to meet NPDES effluent limits and should pose no problem for downstream irrigation use of AV"F's. See the Section on Agricultural Monitoring Plan for further discussion. The itnpacts of the discharge of water to the North Fork from West Ell: Mitre is discussed in detail in the Probable Hydrogogic Consequences - 2.0~.6(3)(b)(iii & viii), section "Surface Water Quality Effects". The discussion focused on the `5votst 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 discharge 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, W WE used more ,typical late irrigation flow rates rather than the 7-day, 10-yeaz low flow condition considered in the PHC section. WIVE based our analyses on the IvtLItD's "A description of the Material Damage Assessment Process Pertaining to Alluvial Valley Floors, Surface Water, Ground Rjater 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 are required. Iv1CC sampled the North Fork upstream and downstream of Sylvester Gtrlch on September 14, 2004. Laboratory analyses were conducted on a full-suite of water quality parameters, 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 t}apical-average October flow is 11 &cfs, the flow was considered to be reasonably consen=alive for the analcsis. The dischazge to Sylvester Gulch via the M«'PF (outfall 017 of the Colorado Uischazge Permit System) has been sampled on a regular basis for selected water quality parameters. Although a sampling event did not correspond with the North Fork data, the water quality of the dischazge water has been fairly consistent over time. Therefore, the water quality results from the November 3, 2004 sample were used along with the known discharge rate of 0.89 cfs. Several parameters were analyzed for their total concentrations, rather than just the dissolved component; these values wire deemed to be conservative and used in the evaluation. ?.069 Rnlsedlune:005 PRf0: Rev. 3farch 2006