Built in 1948, Mud Mountain Dam gets a $112 million fish passage project to help salmon migrate

Mud Mountain Dam in Washington State was built in 1948 for flood control and protects over 400,000 homes.

A $112 million fish passage project will replace the dam's outdated trap-and-haul system to aid salmon migration.

The original facility could only move about 20,000 fish annually, but pink salmon runs now require moving over 20,000 fish per day in peak years.

Puget Sound Chinook salmon, Puget Sound steelhead, and coastal bull trout are protected under the Endangered Species Act, prompting the upgrade.

Biological opinions from NOAA Fisheries in 2014 and the US Fish and Wildlife Service in 2015 recommended substantial changes to improve fish passage.