PERMFILE108469 - Laserfiche WebLink

Home Browse Search

West Elk Mine • and water quality data and the MWPF 9/14/04 discharge rate with water quality values from 11/3/04. z Maximum mixed value is the same as the mixed value scenario except the dischazge rate is increased to 2.0 cfs. ' Suspect Levels taken from Table 3 of " A description of the Material Damage Assessment Process Pertaining to Alluvial Valley Floors, Surface Water, Ground Water, and Subsidence at Local Mines" by the Department of Natural Resources Mined land Reclamation Division dated January 1988. ° All pazameters for the North Fork Upper and Lower Stations aze in the dissolved form. Only total concentrations were available for the dischazge water. These values were used to obtain mixed values and were deemed to be conservatively high. s Metals that were not sampled for in the discharge water are considered to be of very low concentrations based on the downstream North Fork station not detecting any of the pazameters at detection levels well below the suspect levels. Ammonia vanes from 2 to 100 times the concentrations measured in the North Fork. The suspended solids value varies from 0.2 to 15 times the suspended solids concentrations reported in the M & R Plan. The nitrate values aze ten times the values reported for baseline conditions measured in the North Fork, while B.O.D. values vary from 2 to 60 times the values encountered in baseline monitoring. Considering the degree of dilution is considerably greater than two hundred- fold even during extreme low flow conditions, it is unlikely that a water quality change would be detected in the North Fork as a result of the discharge. Furthermore, the water quality parameters that might be mazginally increased by the effluent would not pose a problem for irrigation use. On an annual basis the water use is insignificant relative to the flow in the North Fork. To further i evaluate the risk of material damage to quantity and quality of water supplying downstream AVF's, the daily water use scenario was considered. The 200,000 gallons/day maximum projected water use represents less than two percent (2 percent) of the lowest flow on record (17 cfs). As previously mentioned 38,000 gallons for domestic use would be primarily non-consumptive use and retttmed to the river following treatment. The remaining 162,000 gallons per day of water use is for coal spraying and dust suppression activities. The estimate is conservative and includes a 15 percent contingency for leakage. Consumptive use is difficult to estimate, but should be less than 85 percent. The return flow would be collected and routed to sediment pond MB-1. This water is then treated and either released to the North Fork or recycled. Assuming 138,000 gal/day (0.2 cfs) is the consumptive use, only about 1 percent of the lowest flow on record would be consumed. However, even this magnitude does not represent the true picture of risk of affecting water supplies to downstream AVF's. Because of Mountain Coal Company's junior water rights, most of the water supply will be withdrawn during spring runoff and stored for mine use. Thus, it is quite possible that during the irrigation season the mine could be a net water producer. Given current market conditions, it is unlikely that West Elk will achieve a maximum coal production rate of 8.2 MMTPY any time in the foreseeable future. Thus water withdrawn and dischazged into the North Fork of the Gunnison River from the mine will be significantly less than originally predicted and the impacts to the North Fork AVF much less than discussed here. u 2.0612 Revised lttne 2005 PRIG; Rev. March 1006