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1 Typical Existing Applications. This screen was designed with the assumption that the swimming ability and stamina of the target fish were inconsequential to the proper functioning of the screen. Laboratory and field testing have provided data that support this assumption. In 1990-91, prototype testing was conducted at the Elwha Hydropower Project located on the Elwha River near Port Angeles, Washington. Very high fish diversion efficiency was realized for target species and life stages. Injury and mortality rates for some target species and life stages were comparable to those expected from current state-of-the-art screening facilities that have much lower approach velocities. Injury rates were increased when debris was present on the screen. Two installations that are currently in full operation are the Portland General Electric's Sullivan Plant on the Willamette River near Portland, Oregon, and the other at British Columbia Hydro's Puntledge Hydro Project on the Puntledge River located on Vancouver Island. Both installations show promising results similar to the Elwha project. Additional Eicher screen facilities are being designed for hydro power installations in the United States and Canada. Typical Advantages • . Requires no space in forebay area • Can be easily installed in a new penstock • Not affected by icing • Biologically effective for target species and life stages • Total cost of installation can be competitive depending on site specifics • Unaffected by changes in the forebay water surface elevation • Operation and maintenance costs are small except when fish handling is necessary • The relatively high velocities (2-10 fps) at which it can operate make it adaptable to some penstock applications Typical Disadvantages • Not applicable to most penstocks as penstock velocity normally exceeds 10 fps • Fish entrainment possible during debris flushing • Requires penstock structural modification at existing facilities • Fish bypass and handling required • Not developed for exclusion of passive or very small life stages • Head loss may be significant (up to 2 feet) across the screen • During backflushing, the flow distribution may be affected • Currently developing technology, not widely accepted Application to Limiting Downstream Passage. Its high velocity criteria makes it desirable from a cost/size standpoint. Unfortunately, the backwashing cycle which has a brief period of open passage, the requirement for a fish bypass and therefore handle fish, its relatively large screen openings, and its lack of field applications, reduces its potential application to the objectives of this study. t A Control Structure Feasibility Evaluation 1-9 Miller Ecological Consultants, Inc., February 18, 1997