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• support of underground mining operations <br />was pumped back out of the mine. <br />• <br />• <br />The mine water balance, based on actual and <br />estima[ed flows, is shown in Table 6. The <br />quantity of water dischazged or pumped <br />from the mine was approximately 39.6 acre <br />feet. Water unaccounted for is lost through <br />seepage and evaporation into the ventilating <br />arr. Both of these losses can be large, <br />depending on conditions. <br />Mine Water Quality <br />During WY 1993, mine water was dis- <br />charged into the MB-1. The MB-1 dis- <br />charge was tested for pH, total suspended <br />solids, total dissolved solids, and total iron. <br />Results of the analyses are shown on Ta- <br />ble 5. <br />Runoff fiom Disturbed Areas <br />Overland runoff from snowmelt and precipi- <br />tation within the disturbed azeas was routed <br />to one of six sediment ponds on the mine <br />site in WY 1993. The six sediment ponds <br />are designed to contain the predicted runoff <br />from a statistically determined 10 year, 24 <br />hour precipitation event as well as a calcu- <br />lated sediment storage volume. The ponds <br />aze also designed to pass the overflow from <br />a 25-yeaz, 24-hour precipitation event safe- <br />ly. <br />The West Elk Mine site receives much of its <br />annual precipitation from snowfall during <br />the winter months. When warmer weather <br />begins in late February, March or April, <br />most runoff to the sediment ponds is from <br />snowmelt. It is entirely possible fora vol- <br />ume of runoff greater than the 10 year, 24- <br />hourprecipitation event to result from snow- <br />melt or snowmelt coupled with a small <br />precipitation event. <br />Table 6 Mine Water Balance for the West Elk Mine <br />Parameter <br />a) Water pumped to FW-I from the North Fork <br />b) Potable water processed <br />c) Water pumped underground <br />d) Water dischazged from underground <br />e) Water leaving the mine on coal as added moisture <br />0 Water leaving the mine on gab as added moisture <br />g) Water transferred from Mli-1 and MB-2 to FW-( (estimate) <br />h) Water leaving the mine in ventilating air and seepage <br />i) Estimated sustained flow <br />j) Total mine water inflow (estimate) <br />k) Total mine water outflow (estimate) <br />a + g = b + c + seepage and evaporation losses <br />j=c+i <br />k=d+e+f+h <br />Volume (Acre-feet) <br />122.2 <br />12.8 <br />112.4 <br />39.6 <br />61.4 <br />0.3 <br />8.0 <br />17.6 <br />5.0 <br />117.4 <br />118.9 <br />9 <br />