PRRIP Water Advisory Committee Meeting Notes

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Platte River Recovery Implementation Project Field fnvestimation Checklist Reservoir Feasibility flood plains and consists of semi - consolidated silts, sands, and I sandstone, with some thin interbedded marl zones. The construction or rehabilitation thickness of these sediments in the study area varies from a maximum of 480 feet in the west to 0 feet in the east... Geologic Inlet and Outlet Works exploration for this planning report was performed cm.iy at the Plum Greek damsite ... three feet of excavation is sufficient for the diversion darn." USBR » Several different soil types of Loarns: Coly Silt, Coly -Ufy- Hobbs, Cozad, Hobbs Silt, Holdredfe Silt, Scott Silty Clay, and Ul Silt Available spillway site * "For a smaller reservoir to handle the probable max flood (100 - (if applicable) YR) the spillway could consist of a two -stage spillway with a I lower spillwa7y capable of passing a the 100 -YR anti auxiliary fuse plug dike designed to breach and wash out when overtopped b v the probable flood." WCSR, 1999 Additional Geologic or * Foundation treatment would be required Geotechnical Notes: # Seepage - 0.516 AF/ac Reservoir Feasibility Comments 1 Notes Darn and Spillway + "consist of a 9 -foot diameter, steel -lined pipe through the dam construction or rehabilitation with a morning glory type inlet and crest elevation of 2503 ft. Capacity would be -2,600 cfs." USBR Inlet and Outlet Works 0 "Risk analysis indicates .Plum Creek Dam would be a high- hazard, significant risk dam (inability to pass max flood, 190,000 efs). PMF volume (I 80,000AF) is 70% of conservation dead pool storage." Outlet works would consist of a 9 -foot diameter pressure pipe through dam embankment with a capacity of 2,660cfs." D/S channel modifications • Modifications may be required along Plurn Creek return (if applicable) drainage.