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,T <br />RELOCATED FLOOD BYPASS <br />General <br />As discussed in the report, the existing lower flood bypass canal <br />will soon be inundated by tailing and will no longer be available for <br />routing of snowmelt floods around the lower tailing pond. Recognizing <br />the need for continued flood protection, AMAX is planning the reloca- <br />tion of the bypass canal to a higher elevation of about 8960±. To <br />assist in the design of this new facility, additional studies were <br />performed to determine the magnitude of the snowmelt runoff and the <br />estimated peak rates of flow, <br />Snowmelt Runoff <br />The approximate drainage area above the proposed bypass canal is <br />shown on Figure A-1. The individual drainages are also shown. Using <br />the same procedures as discussed in the report, the snowmelt runoff <br />and snowmeTt peak flows were estimated. These values are shown in <br />Tables A-1 and A-2. <br />Bypass Canal Capacity <br />It is assumed that the bypass canal will be designed with capacity <br />to carry the low peak, high volume snowmelt runoff. The low volume, <br />high peak rainfloods would exceed the canal capacity and spill into <br />the tailing pond. It is also assumed that the canal will be increased <br />in size as the flows from additional drainage basins are intercepted. <br />Using the flood peaks shown in Table A-2, the design capacity of <br />the canal was estimated fora range of flood values (50, 100, 200 and <br />500 year snowmelt and the Probable Maximum snowmelt), This information <br />is shown in Table A-3. It should be realized that these design capac- <br />ities are based only on the estimated snowmelt runoff. There may be <br />other factors which would influence the feasibility of constructing the <br />bypass canal to a given capacity. <br />-28- 029772 <br />W,W. WHEELER <br />