2008-03-21_PERMIT FILE - C1980007A (46)

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West Elk Mine Table 48 Estimated Percent Chan a in North Fork Stream Flows Under Extreme Low Flow Conditions Diversion Flow Rate 50 gpm Pump 400 gpm Pump Both Pumps North Fork Streamflow Case River flow (cfs) 0.11 (cfs) 0.89 (cfs) 1.00 (cfs) Historic low flow 17 -0.6 -5.2 -5.9 7-da 10- ear low flow 32.5 -0.3 -2.7 -3.1 1-da 10• ear fow flow 25 -0.4 -3.6 -4,0 1-da , 100- ear low flow 19 -0.6 -4.7 -5.3 Approximate flow rate when Water call be ins 300 -0.04 -0.30 -0.33 Table 49 Mine Water Usage Year Production millions of tons er ear Amount of Water Pumped acre feet er ear Actual Pro' fed Actual Pro' ted 1994 4.3 197 1995 5.3 224 1996 5.9 267 1997 6.1 372 1998 6.3 372 1999 7.1 - 434 2000 3.3 744 2001 5.0 572 2002 6.6 436 2003 5.5 Maximum 500 1 Actual Usage is based on a water year (October 1 -September 30) 2 Reflects um in forthennalevent Mine Water Treatment In 1996, MCC experienced difficulty complying with the numeric effluent limit for TSS. In November, 1996, MCC received a letter from the Colorado Water Quality Control Division (CWQCD) which specified that no further TSS permit exceedances due to the B East Mains fault water would be allowed or penalties could be assessed. This was the other major reason MCC began directing the lazger mine water inflows to the NW Panels sealed sump in late 1996. During 1996, compounding the problem of increased inflows to the sedimentation ponds was the presence of an unusual colloid. While the source of the colloid is not definitively known, MCC believed that the clay particles may be inherent in the coal seam in the eastern part of the mine. A particle size distribution was performed on the mine water to better understand the nature of 1.05-113 Revised November 2004 PRIO; Rev. March 2006; Rev. May 2006 PRI G