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the 19.5 gpm discharge would raise SAR in the Williams Fork River alluvial <br />water from the historical mean of 3.6 to 9.4. The alluvial water is naturally <br />higher in dissolved solids and metals than the mine discharge water; therefore, <br />increased SAR is the only expected impact. <br />12) The No. 9 Mine will not refill to the surface, but will refill to an equilibrium <br />level between the Twentymile Sandstone and the overlying White Sandstone. <br />13) The No. 9 Mine portal backfill area is too small to generate enough leachate to <br />have a measurable effect on nearby aquifers. <br />Observed Hydrologic Impacts <br />The monitoring plan contained in the permit application has been designed to verify <br />the permittee's projected hydrologic impacts of mining. Section 2.05 of the permit <br />application includes a description of the observed hydrologic impacts caused by <br />mining at the Williams Fork Mines. Each year, MCM assesses the on -going impacts <br />to the hydrologic system in its annual hydrologic report. Observed impacts are <br />summarized below. <br />Observed Ground Water Impacts <br />Mine Inflows and Discharges <br />Water is pumped from the underground mine workings to the ground surface at the <br />No. 5 Mine well and the 7 North Angle well. Annual hydrology reports show the <br />total discharge for the 5 and 6 Mines was a fairly constant 600 gpm during active <br />mining in the early 1990s. After mining ceased in 1995, sumped water was pumped <br />down. In 1997 and 1998, pumping became intermittent, averaging less than 1 gpm. <br />In 2013, pumping was approaching an average quarterly rate of 300 gpm. The <br />pumped mine water is discharged to the Williams Fork River at NPDES outfalls <br />003 (5 Mine well) and 024 (7 North Angle well). A total of more than 110 million <br />gallons of water was discharged in 2013. The No. 5 Mine pump was then -turned <br />off in July of 2013; no further pumping at this site is anticipated in the near future. <br />Monitoring data through 2013 collected at the outfalls indicate the mine water is <br />consistently alkaline, with total dissolved solids less than 1800 mg /1, and low <br />concentrations of iron and manganese. <br />Trout Creek Sandstone <br />The water level in the Trout Creek Sandstone monitoring well (No. 5 Mine well) <br />dropped 200 ft. during 1989 and 1990. The drop probably was caused by pumping <br />of the three mine water supply wells completed in the Trout Creek, rather than by <br />mining in the overlying E and F coal seams. The water level fully recovered in <br />1991 and then fluctuated 200 ft. in 1998. The fluctuation is probably not related to <br />dewatering in the overlying E and F seams because the base of the E coal seam is <br />above the current water level in the No. 5 Mine well. Monitoring of the well was <br />suspended in 2001 through 2005 as part of the temporary cessation monitoring plan. <br />Williams Fork Mines 25 Permit Renewal 06 <br />C- 1981 -044 December 8, 2014 <br />