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Sepumbrr 1993 Km Coal Comparsy • I <br />A. Given the calculated maximum pit discharge volume of 120 ac-ft (5.23 million cubic <br />feet or 39.10 million gallons), discharge a[ a continuous rate of 4 cfs would drain [he <br />impounded water over a period of approximately 15 days. <br />If any of the existing sedimentation ponds are used to provide [emporary storage and <br />allow settling of suspended solids from pi[ discharge, s[ormwater storage capacity will be <br />maintained by limiting pit water storage volumes to any un-utilized por[ion of [he design <br />sediment storage caparity. If based on discharge projections Kerr desires [o maximize pit <br />water storage apacity, any existing sediment accumulations will be removed from the <br />sedimen[ation pond(s) prior to initiation of pit discharge [o the pond(s). Bazed on design <br />information, existing ponds have the following sediment capacities which could be used <br />for storage, re[ention and [reatment of pi[ discharge Flows: <br />Pond A - 15.4 ac-ft <br />Pond B - 6.8 ac-ft <br />Pond C - 1.1 ac-ft <br />During active discharge, the discharge water level in the pond(s) would be moni[ored on <br />a daily basis using a staff gauge w-i[h [he maximum design sediment level clearly marked. <br />The probable discharge scenario based on current information mould involve the <br />following sequential steps: <br />1) Sediment removal from Pond A to maximize available discharge storage <br />apacity and installation of a staff gauge for monitoring purposes <br />2) Sampling of impounded water at various depths to determine the need for <br />any treatment necessary to meet applicable effluent limitations <br />3) Initiation of pumping as soon az the water level reaches a point where <br />Rerr can readily access [he impounded water for installation and <br />maintenance of pumping units (water surface wi[hin 50 - 100 feet of <br />discharge elevation). Either a floating barge pump or one or more trailer- <br />mounted portable pumps would be utilized to discharge water to Pond A <br />and/or a rurface application system at a ra[e of 500 - 1,000 gallons per <br />minu[e (Qpm, equivalent to 1.1 - 2.2 cfs) <br />4) Treatment of discharge, if necessary, using chemicals or flocculents with <br />in-line mixing, a mixing [ank, or one or more mixing/settling basins; or <br />discharge to the existing pond inlet ditches with sediment fences, s[raw <br />bales, and/or flocculent logs installed in the ditches to reduce suspended <br />solids levels <br />5) Gravi[y discharge to Pond A once the water level reaches the discharge <br />elevation, wi[h discharge ra[e controlled by a series of temporary in-pi[ <br />etch basins and dikes. With the exception of in-line addition of <br />flocculents/chemicals, possible treatment methods would be essen[ially the <br />same az for pumped discharge <br />C:\..~8)OTAIODOC <br />09/OL97 fpm ACZ Inc. ' P.O. Box 774018 ' Suamloat SjmnB; Colorado 80477 ' (303f 8796160 <br />