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West Elk Mine <br />Discharge ofSanitarv Wastewater <br /> <br />• <br />The NPDES Permit allows for aflow-through rate of 20,000 gpd, based on a 30 day average, <br />from the sanitary wastewater treatment plant (WWTP). The potential impacts of effluent can be <br />conservatively estimated using the NPDES dischazge limits. Dischazges from 1983 to 1988 are <br />included in Table 59. This table also compares the dischazges to the flow of the North Fork, and <br />shows that dischazges aze very small relative to even low flows in the river. <br />The potential impact of discharge of wastewater effluent would be greatest when the dilution <br />ratio for effluent is smallest. Table 60 contains data which show the effect of wastewater <br />dischazges on the North Fork from 1983 to 1988. The dischazges aze small compazed to the total <br />river flow, even when compared to the infrequent low flows which represent the worst case <br />condition for dischazges. Background concentrations were conservatively estimated. Nitrate and <br />TSS backgrounds were determined from the maximum concentrations measured during low <br />flows (under 300 cfs). Background for ammonia nitrogen and fecal coliform were determined <br />from maximum observed concentrations. Table 59 and 60 indicate that impacts of wastewater <br />dischazges from West Elk Mine to the North Fork have been insignificant. <br />Table 59 <br />Effects of Wastewater Treatment Plant Discharge on the North Fork <br /> <br />Year Discharge (MGD) Low Flow <br />NoRh Fork Discharge <br />From W WTP Annual Yield <br />of North Fork <br /> Averege Max. Daily (MGD) (acre feet) (acre feet) <br />1983 0.0017 0.0035 23.27 1.93 284,913 <br />1984 0.0056 0.0090 18.10 6.21 303,414 <br />1985 0.0052 0.0075 36.84 5.72 289,996 <br />1986 0.0048 0.0102 51.71 5.38 291,290 <br />1987 0.0033 0.0051 31.67 3.70 192 500 <br />1988 0.0036 0.0071 34.98 4.03 113,200 <br />2.05-241 Revised June 1005 PRIG; Rev. March 1006; Rev. May 2006 PRI G <br />