Surface Flow Bypass Bioengineering Study at Bonneville Dam’s First Powerhouse: A Prototype Home Run
Blaine D. Ebberts, Noah S. Adams, Thomas J. Carlson, Derrek M. Faber, Matthew D. Hanson, Robert L. Johnson, Karen A. Kuhn, Gene R. Ploskey, Dennis W. Rondorf, Carl R. Schilt, Charles E. “Chick” Sweeney, and Mark A. Weiland
Abstract.—Surface flow bypass (SFB) concept was evaluated by the Portland District Corps of Engineers to increase survival of emigrant juvenile salmonids passing hydroelectric facilities on the lower Columbia and Snake rivers. Although surface oriented flow had shown promise as efficient juvenile salmonid passage routes, fish behavioral and engineering criteria were lacking to ensure that the most promising prototypes could be evaluated. Surface-oriented sluiceways have long been known to pass a high percentage of juvenile salmonids per the volume of water passed. Also, the Wells Project on the mid-Columbia River had shown great success with deep-slot entrances. A bioengineering evaluation conducted by the Portland District Corps of Engineers and their contractors determined that a stand-alone deep-slot SFB would be the best alternative (alternative A) to evaluate at Bonneville first powerhouse. However, testing the concept of alternative A would be cost prohibitive from a standpoint of handling the flow. So, the prototype surface collector (PSC) was constructed as a “test box” in order to alter the hydraulic environment as drastically as possible to best evaluate the deep slot concept. Hydraulic evaluations consisted of physical hydraulics using a 1:25 powerhouse sectional model, a 1:55 powerhouse forebay model, and prototype hydraulics. Biological evaluations consisted of behavioral data from multibeam and split-beam hydroacoustics, threedimensional acoustic telemetry, and radio telemetry. Efficiency evaluations consisted of radio telemetry and fixed hydroacoustics. The PSC provided positive results for the deep-slot concept, although we cannot report that we broke the salmonid “behavioral code.” Collection efficiency was determined to be 83% for steelhead Oncorhynchus mykiss, 79% for yearling Chinook salmon O. tshawytscha, and 84% for subyearling Chinook salmon. Three years of investigations indicate that the PSC was a well-designed prototype that provided a thorough evaluation of the SFB deep slot concept. The only shortfall from a biological stand point was that the ramp associated with alternative A and associated fish passage was not evaluated. The only shortfall from an engineering stand point was that the lost turbine efficiency due to the turbine intake blockage was not evaluated.