Elwha River Fish Screens: Challenges and Innovative Solutions for Diverting Water during Dam Removal Efforts

Two dams on the Elwha River, in northwestern Washington State, were recently removed as part of an unprecedented river restoration effort.  In anticipation of the huge sediment movement down the river, a large existing diversion facility was reconstructed with two state-of-the-art fish protection screening facilities.  Both facilities included features for managing silt and the changing river conditions; however, both facilities were overwhelmed with unexpected operational issues and conditions.  As part of an emergency action, the National Park Service contracted with Intake Screens, Inc. and HDR to retrofit the River Diversion Facility with a with a unique on-river wedgewire screen facility.  The new screens have successfully operated under extreme conditions to date including: heavy debris; high sand and silt suspended loads; changing riverbed elevations; high flows; and very shallow river conditions.  This presentation will discuss the operational challenges and lessons learned at two fine slot wedgewire screening facilities to date.  Despite the extreme conditions, it is possible to reliably divert water with 1.75 mm opening wedgewire screens with proper design considerations.