SEATTLE--Two physical barrier mishaps occurred at the new Mud Mountain Dam Fish Passage Facility (FPF) June 22 and June 26, which left 42 Chinook salmon and one bull trout dead.
The facility uses an Archimedes Screw Lift (ASL) to raise the fish up to a research, monitoring and evaluation area for sorting. At night, there is a barrier that prevents fish from jumping into the dry ASL. The physical barrier came loose during the evening and fish were able to enter the ASL, leading to the mortalities. USACE personnel, along with tribal partners, discovered 25 Chinook salmon and one bull trout dead.
USACE officials put an improved temporary barrier after the first incident, but it failed during the evening of June 26 which led to the discovery of 17 additional deceased Chinook salmon.
USACE staff made additional modifications to the barrier following the second event.
The facility is located near Enumclaw, Washington and it is designed to trap and haul migrating salmon around Mud Mountain Dam. The new facility is in its second year of operation and is the largest trap-and-haul fish passage facility in the nation, built under a $112 million dollar contract.
This new fish passage system replaced the 1941-built facility was designed to move 20,000 fish annually even though it managed to move 20,000 fish per day during pink salmon runs. The new facility is designed to transport 60,000 fish a day, upwards of 1.2 million fish per year, during pink run years.
Mud Mountain Dam is an earthen, rock-filled structure built by the Corps in 1948 for flood risk management. The project protects more than 400,000 homes and businesses along the White and Puyallup river valleys, between Buckley and Tacoma, Washington.
Release no. 22-009