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-. Sediment Fetentie.^. Rpnc+s~ <br /> Eela.~ TLS Bench -Alternative 1. Initially, fear dams are proposed for <br /> construction dowrstream fran ttn_ T',S Bench. The old Co•,.an cline Bridge will not <br />• b` frm the TIS Bich. Tne da^•s are desicned to detain water, acting to <br /> dissipate energ}• and reduce the flc~~; rate, allawi-h; the sus~nded seairient to <br /> settle out. <br /> EPA effluent lirstation guidelines for coal mines require trat retention <br /> structures for sediment control be designed with a capacity sufficient to <br /> contain a~ ear, 24-hoi;r storm event. Fach sed;r~ent retention pond t-as been <br /> <br /> desicned with sufficient capacity to meet these requiremnts, plus dead storage <br /> space for accur:lated sedir~nt. <br /> Spillway systems have bin designed with sufficient capacity to safely <br /> discharge the p:.ak runoff fran a precipitation event with at least a 100-yza_r <br /> recu_~rence interval. Retention rim will be indefinite fora 10-year, 24-hour <br /> storm event. At least 1 srnaa,-e foot of to`al pond surface area wz11 be <br /> provided for each 50 gallons per day o` inflow generated fran t:.e 10-year, <br /> 24-hour stone eve^.t. <br /> Reccr:rnended locatio:s for the c?~eck ca,s are shown in the Phase I <br /> Drairsce Plan (100-scale map). Storm runoff diverted out of t9est~moreland <br />.• Canyon would pct be impound; hC^h'ever, ~*-airage at these points is generated <br /> from portions c_` the watershed that are currently being revegetated, or from <br /> undisturbed areas. pith the excep*_ion of ttr_ upper 1~sin diversion, adequate <br /> buffer strips will be'prrn~ided between each outfall and receiving natural <br /> channel in order to control virtually all sedir>ent generated from a 10-year, <br /> 24-hou: stone evert. A vigorous reclamation and maintenance program Lastream <br /> from each point of diversion will minimize sediraent e.~gbrt to adjacent <br /> watersheds. All other drainage from the mine area proper would be controlled <br /> b:: the fog ponds sho.,m in Plate 1. ':amble 1 su;rrarizes drainage areas ups-eam <br /> frcm each pond, estirated 10-year, 24-hour inflow and required storage <br /> capacit}~. Total storage capacity would be approximately 2.5 acre-feet. <br /> T'ne waste dismsal a_-ea will be locate-d imrr~diately d~,nstream frcm <br /> tY~ TLS Bench. This area will contain rune spoils and stockpiled top soil. <br /> Mine refuse and topsoil am~`ankmr>ents will be engineered, constructed, and <br /> reclairr3 in accordance with M~..JG~ specifications. <br /> All su_~face runoff frcr^ these csrlaankments will be routed through the <br /> sedi~aent retention ponds. The ponds will to cleaned as needed to erasure <br /> adequate stora^,e ca~city. Scti'iment re~*nved fran these ponds will <br /> be trucked back to the waste disposal area, and used in mine reclamation <br /> activities. Sa3iment will be reroved from the ponds when t}x' volume <br />