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West Elk Mine <br />The dischazge to Sylvester Gulch via the MWPF (outfall 017 of the Colorado Dischazge Permit <br />System) has been sampled on a regular basis for selected water quality parameters. Although a <br />sampling event did not correspond with the North Fork data, the water quality of the dischazge <br />water has been fairly consistent over time. Therefore, the water quality results from the November <br />3, 2004 sample were used along with the known discharge rate of 0.89 cfs. Several pazameters <br />were analyzed for their total concentrations, rather than just the dissolved component; these values <br />were deemed to be conservative and used in the evaluation. <br />The discharge water was then mixed with the North Fork Upper water and compazed to the suspect <br />levels (Table 66). All of the mixed concentrations were well below the respective suspect levels. <br />In addition, the mixed concentrations were consistent with the downstream North Fork water <br />quality, thereby confirming the methodology. There were several metals that were not sampled for <br />in the discharge water. Since none of the metals was detected in the upstream or downstream North <br />Fork samples, the concentration of the metals in the dischazge water, if present, was determined to <br />be very low. Furthermore, the detection levels in the downstream sample were all well below the <br />respective suspect levels. <br />W WE performed the same evaluation using a discharge rate of 2.0 cfs for the MWPF. This rate is <br />considered to be the maximum rate that could be sustained for significant periods of time. Table 66 <br />presents the results of this mixing zone analysis. Al] of the mixed concentrations aze below the <br />respective suspect levels for this scenario as well. While these analyses were performed <br />considering short-term potential impacts, the evaluation could also be considered aworst-case <br />• scenario for long-term effects. Based on this evaluation, the dischazge of mine water to the North <br />Fork will not adversely affect the use of the water by downstream agricultural users. <br />WWE has reviewed the salinity (TDS) loading analysis in the 2001 Cumulative Hydrologic <br />Impacts Analysis (CHIA) for the North Fork in the context of MCC's 1996 discharges. In <br />the CHIA, CDMG calculated the cumulative TDS (salinity) loading to the North Fork from <br />coal mines located in the North Fork valley. The assumptions used for MCC's contribution <br />were a discharge rate of 5,520 gpm (12.3 cfs) and a TDS concentration of 2,500 mg/L. <br />WWE has updated the evaluation of the salinity loading based on the TDS concentrations and <br />flow rates shown in Table 66. Using the TDS concentration of 3,200 mg/L and a flow rate of <br />400 gpm (0.89 cfs), the salinity loading to the North Fork is 2,800 tons per yeaz. Using the <br />maximum sustained flow rate of 900 gpm (2.0 cfs), the salinity loading to the North Fork is <br />6,300 tons per year. Both loading rates are well below the value assumed in the CHIA for West <br />Elk Mine. <br />The sewage collected from the site will be domestic in nature and will consist of soluble B.O.D., <br />volatile suspended solids, and inert solids, which will be treated using biological organisms to <br />aerobically stabilize the waste. Since biological treatment will be used, with no chemical treatment <br />required, there should be no secondary by-products which would not be similaz to those existing in <br />the North Fork of the Gunnison. <br />u <br />2.06-IO Revised June 2005 PRIG; Rev. March 2006 <br />