Tolt River floodplain project gears up for final phase to restore habitat, sustain levee

The upgrades are part of the second and final phase of one of the most important salmon-habitat restoration and multi-benefit projects in King County, which gets under way soon at the confluence of the Tolt and Snoqualmie rivers.

When completed, the Tolt River Restoration Project will offer significant public recreation and flood control benefits, in addition to improved spawning and rearing habitat for endangered chinook salmon and other fish.

Crews completed the project’s first phase last summer. The second and final phase begins in early June and is expected to be completed by this December.

Initial work will include constructing a new setback levee and six engineered wood structures to help protect the park’s campground, Mariner ballfield, and other developed areas from river erosion.

Construction activity includes earthwork and driving wood piles into the floodplain soils to support these constructed floodplain features. Pile driving, which also occurred last year, is expected to begin in late June and conclude in early August.

Other work this year will include removing the existing degraded levee, which runs directly adjacent the Tolt River, and replacing it with a new levee that will be constructed to modern standards.

The new levee will give the river more space to meander within its historic floodplain, and will provide important fish habitat. Additionally, new public trails will be constructed throughout the project area to improve public access between the river and new parking areas and to other local trail systems.

Finally, significant improvements will be made to the park’s recreational features, including new parking areas, new paved and soft-surface trails, plus a small picnic area. New site landscaping will occur later this fall.

The $6.4 million project is a collaborative effort between the City of Seattle and King County. The project is of regional significance to ongoing salmon-recovery efforts because of the opportunity to increase spawning and rearing habitat in an area that has historically been highly productive for chinook salmon.

The project restores natural habitat-forming processes in the lower Tolt River by opening up the river’s historic floodplain so side channels can reestablish. Installing large wood features helps stabilize the river during high flows and creates better habitat.

One such structure was built in 2008 near Tolt-MacDonald campground, and several more will soon be under construction throughout the park’s undeveloped floodplain.

Some portions of the park will be closed to public access while project materials are staged and work is under way. However, most of the park will remain open and available for public use during project construction, including:

• Access to the Tolt River and the Snoqualmie River. While the road that ran atop the old Tolt River levee along the northern shore is closed and will no longer provide access and parking, there will be river access along Tolt Hill Road, plus additional parking within the park.
• Access to the Boy Scout Bridge and all portions of the park on the western shore of the Snoqualmie River, including six yurts that are available to rent from King County Parks.
• All ballfields and picnic shelters, which will remain open for the duration of the construction project.
• Nineteen tent campsites and large group campsites for 40 and 60 people, which will be available every day throughout the summer.
• Sixteen RV campsites, which will be available every weekend all summer and during the week until mid-August.

Park information is available by calling 206-205-5434 or http://www.kingcounty.gov/recreation/parks/inventory/toltmacdonald.aspx. Information on the restoration effort is available at http://www.kingcounty.gov/environment/animalsAndPlants/restoration-projects/tolt-restoration.aspx, or by contacting Clint Loper of the King County Water and Land Resources Division at 206-296-8378, or Brent Lackey of Seattle Public Utilities at 206-684-7890.

Related information

Tolt-MacDonald Park

Lower Tolt River floodplain restoration project

King County Water and Land Resources Division