SR 529 - Steamboat Slough - Mitigation Site

Project news

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Needs & Benefits

Restoring estuarine habitat (where saltwater and freshwater mix) 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.

This project – located between I-5 and southbound SR 529 just south of Marysville – restored about 12.5 acres of estuarine habitat. It cut down trees that grew on fill material placed in the area since the 1950s. The fill was dug out, lowering the land to its original level. The project 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.

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.

What to expect
Vegetation native to nearby saltwater marshes was planted in this area. After the plants grow for a few years this area will look like other marshes in the area.


  • May 2019: Project awarded to Trimaxx Construction Inc.
  • July 2019: Work began to remove trees and fill from the area.
  • Fall 2019: Dikes will be breached and native plants will be added.


Funding for this $7.75 million project is provided by the Connecting Washington program.


Tom Pearce

Ed Kane
Project engineer

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