Puget Sound Innovation Stories

Sultan River Diversion Dam Modification

Salmon return to Upper Sultan River after 90 years

For the first time in 90 years, salmon are using 6.5-miles of stream habitat in the upper Sultan River, thanks to an innovative project by the Snohomish County PUD that opened the river for fish passage past the Sultan River Diversion Dam. The project allows fish to pass the site where the dam previously blocked fish passage since 1929. Salmon were spotted above the dam the first week after construction in 2016 and coho salmon were documented laying eggs five miles above the dam the first year after project completion. By modifying the dam’s sluiceway with a gate and excavating the riverbed below and above the gate, fish can now move up and down the river and access the pristine habitat up to Spada Lake. The gate only needs to be closed a few days each year during extreme droughts or to accommodate maintenance schedules for other PUD facilities on the river. The project benefits Chinook and coho salmon, and steelhead by providing access to 6.5 miles of pristine habitat to lay eggs, overwinter, and feed. The immediate, natural return of fish eliminated the need to plant fish above the dam.. The innovative design cost $1.5 million less to construct and $30,000 less in annual maintenance than traditional fish passage structures. Snohomish PUD was recognized as a 2017 Outstanding Steward of America’s Waters by the National Hydropower Association for its work on this project.

What worked:

  • Salmon returned to habitat upstream from this project one week after project completion.
  • Coho salmon eggs were documented five miles upstream of the project within one year.
  • Innovative design reduced maintenance costs for Snohomish PUD by $30,000 per year and saved $1.5 million in construction costs.


  • Salmon and other wildlife can move freely up and down the river to access pristine habitat to find food and habitat.


  • Congressional District: 3
  • Legislative District: 39
  • WRIA: 7
  • County: Snohomish


  • Snohomish County Public Utility District
  • The Tulalip Tribes
  • City of Everett
  • City of Sultan
  • Washington Departments of Fish and Wildlife
  • Department of Ecology
  • NOAA
  • U.S. Fish and Wildlife Service
  • U.S. Forest Service

Project Funding:

  • Snohomish PUD

More Info

Publish Date: July 15, 2019
Category: Salmon
Congressional Districts: Congressional Dist. 3
Legislative Districts: Legislative Dist. 39
Counties: Snohomish
Habitat Types: Rivers & Streams
Restoration Focuses: Salmon
Key Benefits: Habitat Connectivity
Funding Sources: