[KC Burke]

I would love to add sheet piling to the mix. Normal strength sheet pile won’t drive into areas of solid bed rock and heavy sheet piling that you could almost cut the rock with are going to penetrate rock layers that are solid enough without the cut that you want to rely upon them later, IMHO.

You idea has another merit however. In the river bed, upstream of the dispersion flow area on the original spillway path, a sheet pile wall in the river bed would keep debris from heading upstream once repairs are made.

[Repeal The 17th]

[Ray76]

Right. In the river bed to maintain a clear channel for the tailwater. Any water that flows through the powerhouse is less water to flow down the spillway, or worse the ES.

               |          |
               |          |
               | spillway |
               |          |
               |          |
---------------            ------------------------------
                                       / 
      river                           /
                                     / 
                                    / 
                                   / 
     =========== piling ===========
                                        river

-------------------------------------------------------

The condition of the riverbed is unknown. It could be a problem. The bank opposite the spillway could be cutout if needed and protected with piling.