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Hie 5 - Design <br /> The sed: tat`an and control stsu.cttures at Mine 5 portal. include t�,e follow- <br /> ing: Design details are shorn on Plates 5-1 and 5-2. Pond design criteria are <br /> shown in cal.calations paragraph 5. <br /> a.) Sedima taticm. Ponds 5-IA Min. Total stcrage of <br /> b.) Collection B=s 0.97 of <br /> c.) Diversion Bea-is <br /> Ttm Se(L tation p--z.,ds 5-1 and 5-2 will be cons--acted on mdrrately sloping <br /> ground west and 'upstream fran the haul road bridge across Coal Creek.. These off <br /> channel ponds will require co sidei.able excavation of c obbly soils (alluvitmm) inn <br /> order to provide adequate storage for 3-ve<,r sediment yield and. 25-year flood <br /> routing. <br /> Ronoff and sediment from t'-,e disturbed pad areas will be concentrated and <br /> directed to the sedimentation ponds via overland flow. The =idarles of the <br /> disturbed pad will be isolated frrm andistZrrbed and o&.er designated a:,ea.s by <br /> bern,.s and =Lnor regraci-ng. _ <br /> Ruoff frcrmt undistu bed areas -will be diverted by ditches and culverts along <br /> a,nd under roads and earth bearn dmnstreain and adjaernt to tb,.e hiahc„•all. Coal Creek <br /> overflows will be restricted by a 2 to G foot high berm tlat parallels the edge of <br /> the creek. <br /> Diversion ditcl-)-es uphill' from•, the high rai 1_ can be crostrnucted b= at great <br /> expense and dist=bance to existing imd.sttrbr-d Y..ro&d slopes. <br /> -9- <br /> • .:,1 <br />