A joint venture between Aecon Group Inc. and FlatironDragados has finalized a $691 million contract with the U.S. Army Corps of Engineers to deliver the Howard A. Hanson Dam Additional Water Storage Fish Passage Facility in Washington State.
The project involves construction of a downstream facility at the dam to improve water storage and enable fish passage. The design includes vertically stacked intake ports, a multiport collector, a steep slope bypass, a deceleration tunnel, and an outfall stilling basin. These components will connect upstream and downstream systems to support salmon migration and habitat access.
The joint venture will deliver the project under an integrated design and construction model. This approach brings contractors and designers together early in the process to improve coordination, manage risks, and enhance cost and schedule certainty. Construction is expected to begin in the second quarter of 2026, with completion targeted for the third quarter of 2031. The project has completed its collaborative development phase and is advancing into construction.
The facility will increase water storage capacity and strengthen flood risk management in the Green River Valley. It will also improve fish passage for juvenile salmon, enabling access to upstream habitat while maintaining dam operations.