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r <br /> <br />• <br />!.0 <br />Table 1.7-1 <br />Quality of Discharge at the <br />West Elk Mine (hffi-1 and MB-2R elllueot)' <br />Due pH T55 7D5 AR. <br />1®WI lret/1.) cttwt4 rmin <br />~a <br />am Q '9a e.s 44 zoao o.s7 <br />1st Q '95 8.4 18 1443 0.33 <br />god Q '9S 8.3 16 1490 0.51 <br />Std Q '95 8.8 13 1400 0.43 <br />INB-2R' <br />4rh Q '94 8.3 35 ISSO 0.71 <br />1st Q '95 8.0 26.5 1610 t.0 <br />2nd Q '95 8.4 16.5 660 0.3 <br />Std Q '93 6.1 17 560 O.I6 <br />See also Table D-12, Appendu D, and <br />Table I-1, Appendix I. <br />1.8 RUNOFF FROM <br />DISTURBED AREAS <br />Overland runoff from snowmelt and <br />precipitation within the disturbed areas was <br />routed to one of five sediment ponds on the <br />mine site in the WY. The five sediment <br />ponds are designed to contain the predicted <br />runoff from a statistically determined 10- <br />yeaz, 24-hour precipitation event, as well as <br />a calculated sediment storage volume. The <br />three lazger ponds (MB-1, MB-2R and MB- <br />3) have additional volume for Mountain <br />Coal Company's storage water rights. The <br />ponds are also designed to safely pass the <br />overflow from a 25-year, 24-hour precipi- <br />tation event. <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.:~farch or April, <br />most runoff to the sediment ponds is from <br />AFnt-93.1IOAS! l Sl96! (: JBpm) <br />Nonitonng .1c:i.~irirs <br />snowmelt. It is entirety possible for a <br />volume of runoff greater than the 10-yeaz, <br />24-hour precipitation event to result from <br />snowmelt or snowmelt coupled with a small <br />precipitation event. <br />The sediment ponds are typically treated <br />with cationic flocculent when necessary to <br />speed clarification and settling of suspended <br />solids. All ponds, MB-1, MB-2R, MB-3, <br />MB-4 and MB-5 have manually controlled <br />dewatering devices. Ponds MB-1, MB-2R <br />and MB-5 are dewatered intertttittendy with <br />the highest flows coming during eazly spring <br />runoff. Pond MB-5 is responsive to a high <br />spring groundwater table and sometimes has <br />to be dewatered more often. Dewatering <br />procedures take usually less than two days <br />for all ponds except MB-5. <br />Flowmeters are installed on discharge points <br />from sediment ponds which dischazge inter- <br />mittently to continuously record flows. <br />Information on flows, sampling points, and <br />quality of water discharged from the mine <br />site sediment ponds during WY 1994 is <br />included in Appendix I. <br />1.9 REFUSE PILE WATER <br />QUALITY <br />Water monitoring adjacent to the Lower <br />Refuse Pile consists of the monitoring of <br />alluvial wells around the refuse pile and <br />periodic sampling of discharges from MB- <br />2R. Pond IviB-2R treats surface water <br />runoff from the refuse pile and adjacent <br />disturbed areas, mine water discharge, and <br />any discharge from the underdrain. Historic <br />groundwater quality data from wells SG-1, <br />GP-1, GP-3, GP-4, and GP-5 are <br />incorporated into the data tables found in <br />Appendix G. Quality parameters of Pond <br />MB-2R discharge aze presented in Table <br />1.7-1 and Table D-12, Appendix D. <br />14 <br />AE~75ED 09/_7:96 <br />