SR 529 - Steamboat Slough - Mitigation Site - Complete November 2019


This project, located between I-5 and SR 529 just south of Marysville, restored about 11.3 acres of estuarine habitat where saltwater and freshwater mix in the Snohomish River delta near Port Gardner Bay. Crews cut down trees that grew on fill material placed in the area in the 1950s. The fill was dug out, lowering the land to its original level. Workers added tidal channels before crews breached a dike in two locations, allowing tidal water from Steamboat Slough into the area. The trees that were cut down were placed around the site to provide additional wildlife habitat. We will continue to monitor the site for several years.

The work is mitigation for the I-5 Marine View Drive to SR 528 Peak Use Shoulder Lane and Interchange Improvements project, which will add a southbound I-5 on-ramp and northbound I-5 off-ramp at SR 529 and well as a peak-use shoulder lane on northbound I-5.


Restoring estuarine habitat is good for many species, from tiny marine organisms to orcas. It’s a nursery where young Chinook, coho, pink and chum salmon can grow before continuing their journey to the Salish Sea and Pacific Ocean.


The Connecting Washington program allocated $7.75 million for this project.


Northwest Region Communications
15700 Dayton Ave. N.
Seattle, WA 98133  

A small map showing the location of the SR 529 mitigation site.