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Mixing Calculation - At West Elk Mine <br />Calculated impact of gob leachate discharging into North Fork alluvial water through the subcrops of the coal seams underneath the alluvium <br /> Gob leachate discharging <br /> Receiving water before into N. Fork alluvial water <br /> contamination (North Fork through coal seam <br /> alluvial water immediately subcrops underneath N. <br /> upstream from West Elk Mine) Fork alluvium <br /> A B C D <br /> Flow (cfs) TDS Flow (cfs) TDS <br /> concentration concentration <br /> (mg/1) (mg/1) <br />Scenario 1: Most likely case 0.350 1500 0.008 3000 <br />Scenario 2: Worst case 0.350 1500 0.008 5500 <br />(unlikely) <br />TDS concentration resulting <br />from mixing of receiving water <br />and gob leachate <br />(A X B) + (C X D) <br />(A + C) <br />1535 <br />1593 <br />A = 10 ft per day flow velocity X 400 ft wide X 30 ft deep X 25% porosity <br />B is based on historical monitoring data from Bear 3 Mine alluvial well AA-1 <br />C is based on: <br />Flow velocity from mine workings through subcrop into alluvium <br />_ [(0.03 hyd. cond.) / (0.05 eff. Porosity)] X [0.04 hyd. grad.] = 0.024 ft /day <br />Cross-sectional area of subcrop in North Fork alluvium (aggregate of B, E, and F seams) <br />= 30 ft X 1000 ft = 30,000 sf <br />Daily flow = 0.024 ft/day X 30000 sf = 720 cfd, coverted to cfs, = 0.0083 cfs <br />D in Scenario 1 is based on likely gob leachate quality found in abandoned Oliver Mine <br />D in Scenario 2 is based on worst-case (but unlikely) gob leachate quality