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Mine 5 <br /> The sedimentation and control structures at Mine 5 portal incluuae t� follow- <br /> '"-• ing: Design details are shown on Plates 5-1 and 5-2. Pond design criteria are <br /> shown in calculations paragraph 5. <br /> a.) Sedi=entaticm Ponds 5-1A Min. Total storage of <br /> b.) Collection Bemis 0.97 of <br /> c.) Diversion Bexms <br /> Two Sedimentation ponds 5-1 and 5-2 will be constructed on mderately sloping <br /> ground west and upstream from the haul road bridge across Coal Creel's.. Tt,,ese off <br /> chamel ponds will require considerable excavation of c c�bbly soils (alluvilml) in <br /> order to provide adequate storage for 3-year sedimtmot yield and 25=yeas flood <br /> routing. - <br /> Runoff and sediment horn the disturbed pad areal will be concentrated. and <br /> directed to the sedimentation pods via overland flow. The bo ndar-Les of the <br /> disturbed pad will be isolated from undisturbed and other designated areas by <br /> • be=s and minor regradLng. - <br /> RMoff from undisturbed areas will be diverted by ditches and culverts along <br /> and under roads and earth berm downstream and adjacent to the highwall. Coal Creek <br /> overflows will be restricted by a 2 to 4 foot high berm teat parallels the edge of <br /> the creek. <br /> "Diversion ditches uphill from the hig �wa11 can be co�sti _Icted but at great <br /> ex Ease and disturbance to existing umdis=bed wooded slopes. <br /> -9- <br /> 51 <br />