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Carbon Junction Mine <br />Fill Underdrain <br />Calculation Sheet 1 of 4 <br />Assume <br />i s hydraulic gradient of underdrain channel <br />_ change in elevation/channel length ~ 100'/1300' <br />.077 <br />ng ~ estimated porosity of pit run gravel <br />= 25X ~ <br />nss estimated porosity (low) of blasted Pictured Cliffs Sandstone <br />lOX <br />D50 median rock size <br />= 8" for dumped Pictured Cliffs <br />= 2" for pit run gravel <br />W 0.5 a rock size coefficients <br />m <br />= knowing D50, take from CTL/Thompson Table 4.3 <br />Maximum Trench Discharge (QT) <br />Vv (Wm).5 (1)'54 (1 ft/12 in) <br />(16 in/aec) (.250) (1 ft/12 in) <br />.333 ft/sec <br />QT (cross-sectional area of trench) (Vv) (ng)/100X <br />_ (6 ft2) (.333 ft/sec) (25X)/100X <br />.5 cfs or 43,200 ft3/day <br />