Lewis River fish passage projects

Construction work began in April 2011 on new fish passage facilities at the Lewis River project in southwest Washington.

The new facilities collect adult fish at Merwin Dam and transport them upstream of Swift Dam where they are released to move up the river to spawn. As their young begin migrating to the ocean, they are collected at Swift Dam by a floating surface collector and transported by truck downstream to a release facility in the lower river.

These projects have opened up 117 miles of salmon and steelhead habitat upstream of Swift.

See news and information about these projects: 

July 2011

July 2012

June 2013

Learn about the Swift and Merwin projects

The Swift Reservoir Fish Facility has four main parts:

  • Floating Surface Collector
  • Net system
  • Mooring tower
  • Access trestle

How does the project work?
Juvenile fish, the offspring of the salmon and steelhead that spawned upstream, will come downstream through the reservoir as they migrate to the ocean.

Given the attraction to downstream current, the juvenile fish will move towards the Floating Surface Collector which re-circulates water to simulate a lake outlet. The net system and the Floating Surface Collector will attract these fish, which are typically 3 - 6 inches long at this stage in life, into a collection area. The fish are collected and gently transported from the facility on specially design trucks via the access trestle. The juvenile fish are then trucked around the dams and released downstream of Merwin to continue their journey to the sea.

The Floating Surface Collector will be located just off the south end of the Swift dam, anchored by the mooring tower and connected to the dam by an access trestle. The mooring tower and access trestle are supported on piles, and the Floating Surface Collector rises and falls with the reservoir level.

Swift Reservoir Fish Facility Fact Sheet



The Merwin Upstream Collection and Transport Facility has five main parts:

  • Attraction water system
  • Fish ladder & hoist
  • Holding tank
  • Sorting facility
  • Truck loading

How does the system work?
Adult fish return to the Lewis River and are attracted to the intake facility by river water coming out at a steady stream, which mimics a natural current and leads the fish away from the working parts of the dam and power house where the fish could be injured.

The fish follow this current up a short fish ladder that ends in a trap basket on a hoist that delivers the fish to the holding tank and sorting facility. The fish are sorted based on species, origin (hatchery or wild fish), and point of origin if that can be determined (by tags or fin clips).

Once sorted, fish are loaded onto specially designed trucks that take them to the hatchery or upstream of the dams to be released and allowed to spawn naturally in the stream beds of the Lewis River and its tributaries.

Merwin Upstream Collection & Transport Facility Fact Sheet

Construction photos

Overview of the construction below Merwin Dam.
Overview of the construction below Merwin Dam

Bridge across the spillway.
Bridge across the spillway