Maple Road and Ash Way Intersection and Drainage Improvements

Project Description

Snohomish County and the city of Lynnwood are working together to help ease flooding in the vicinity of the Maple Rd and Ash Way/Interurban Trail intersection. Flooding events originating from Swamp Creek force multiple intersection closures per year at this site.

The project will reconstruct approximately 700 feet of Maple Rd and 600 feet of Ash Way, along with the Interurban Trail, using structural slabs on top of pin piles, pile caps, and grade beams. The new intersection will be raised roughly five feet from its current elevation and a minimum of six inches above the existing 25-year flood elevation of Swamp Creek.

The drainage system’s capacity will also be increased to reduce upstream flooding. New fish-passable culverts will be installed on Maple Rd and Ash Way.


Snohomish County and the city of Lynnwood will hold an open house for this project during the fall of 2017. Construction will begin during the spring of 2018, taking approximately five months to complete.

Traffic Impact / Road Closure

The intersection will be closed during the five-month construction window. Detour routes will be posted for the two roads and the Interurban Trail. Access to all businesses will be available during the project.


The design and construction is fully funded by Snohomish County Public Works and the city of Lynnwood.

Environmental Review - Public Notice

An environmental review of the Maple Rd and Ash Way Improvements was completed in compliance with the State Environmental Policy Act (SEPA). A SEPA Environmental Checklist was issued for this project on July 15, 2016. The drainage system was modified from the original design to reduce impacts to the adjacent wetlands and streams. A SEPA Addendum was issued on March 17, 2017. All SEPA related documents are available by viewing the links below.


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