Bothell, WA – The Interstate 405 (I-405) corridor in Bothell is undergoing a major widening project, with construction accelerating to expand the freeway to two express toll lanes in each direction. This ambitious $834 million undertaking aims to alleviate long-standing traffic congestion, particularly in the critical stretch between Highway 527 and Northeast 160th Street. Drivers should prepare for a series of weekend road closures beginning this month as crews work to demolish old ramps and build new infrastructure.
Key Takeaways
- I-405 in Bothell is being widened to include two toll lanes in each direction.
- The $834 million project will feature a new northbound bridge over the Sammamish River.
- Weekend lane closures on Highway 522 and I-405 are scheduled to begin this month.
- Construction is expected to conclude by spring 2028.
Addressing a Decade of Bottlenecks
The current congestion on I-405 in Bothell dates back to 2015. At that time, state officials implemented a single express toll lane in each direction from Bothell to Lynnwood. This initial phase, a $462 million investment, was part of a broader strategy to manage traffic using market forces, allowing drivers to pay for faster travel.
However, rapid population growth and an unexpected 6% increase in total traffic between 2014 and 2018 quickly overwhelmed the freeway. This created a persistent pinch point in north Bothell, leading to chronic morning delays for commuters.
Project Cost and Timeline
- Total Cost: $834 million
- Original Toll Lane Project (2015): $462 million
- Funding Gap Closed (2022): $380 million
- Groundbreaking: 2024
- Expected Completion: Spring 2028
Upcoming Road Closures and Detours
Construction crews are now working at an increased pace, necessitating several weekend road closures. These closures are essential for demolishing existing structures and installing new components safely.
- The first closure affects westbound Highway 522, starting Friday night, February 20, at 9 p.m. and reopening Saturday at 6 a.m.
- The following weekend, both directions of Highway 522 will close from 10 p.m. Friday, February 27, until 4 a.m. Monday, March 2.
- Later in March, both directions of I-405 are scheduled for closures below the demolition site. These are planned for March 6-9 and March 13-16, from late Friday to early Monday each weekend.
These dates are tentative and depend on the progress made during the initial ramp removal weekends. Drivers should monitor traffic updates, especially considering two lanes are already blocked for long-term repaving on the I-5 Ship Canal Bridge, which could compound regional traffic delays.
New Freeway Design and Traffic Flow
The expanded I-405 will feature a new northbound bridge over the Sammamish River. This new structure will carry two general traffic lanes and two toll lanes for northbound traffic through Bothell. The existing northbound freeway spans will then be converted to southbound toll lanes.
Southbound drivers will see two free lanes and two toll lanes as they approach Highway 522. A third free lane will be added climbing the hill from Highway 522 to Northeast 160th Street, along with various exit-only lanes to improve flow.
"Toll lanes provide a quick option for essential trips, like electrical and plumbing repairs or day care pickups," a WSDOT spokesperson explained. "They act as a relief valve, enabling I-405 to carry more vehicles at peak hours."
A 2020 state document suggests that once the expansion is complete, toll lane users could save several minutes during morning peak hours from Highway 527 (Canyon Park) to Northeast 116th Street in Kirkland. General traffic lanes are also expected to flow faster due to reduced weaving.
The Debate Over Toll Lanes
The concept of express toll lanes, while designed to manage congestion, has faced criticism. Opponents often refer to it as a "velvet rope" philosophy, arguing that it creates a two-tiered system where wealthier drivers can afford faster travel, while others remain in slower, free lanes. All drivers contribute to the construction of these lanes through taxes, regardless of whether they use the toll option.
Toll Lane Performance
Last year, an average of 39,200 drivers used the I-405 toll lanes each weekday, paying an average of $5.95 per trip. These drivers reported an average time saving of 11 to 12 minutes.
Tolls on I-405 fluctuate every few minutes, ranging from $1 to $15. Carpools with three or more people and a special pass can travel for free during commute hours. Two-person carpools can use the lanes for free midday.
Former state Senator Mark Harmsworth, a critic of the original tolls, acknowledges the new project's capacity benefits. However, he remains skeptical about its impact on general-purpose lanes, particularly at merging points like southbound from Highway 527 into I-405 at Canyon Park, and northbound from I-405 to I-5 at Lynnwood.
"What you will see is, toll lanes running southbound in the morning will have less traffic, move a little faster, but I don’t think it’s going to help the general-purpose lanes," Harmsworth predicted.
Innovative Construction Methods
The I-405 widening project involves several complex engineering challenges. Along the Sammamish River, new columns for the northbound bridge are taking shape, with steel rebar loops awaiting concrete pouring. The Sammamish River Trail remains open, allowing pedestrians and cyclists to observe the construction.
A temporary steel wall has been installed to reinforce the south riverbank, preventing heavy equipment from sinking in the soft soil. Patrick Prendergast, vice president for operations at prime contractor Skanska USA, stated that the slope will be replanted after construction.
Demolishing Ramps and Improving Intersections
Three cloverleaf ramps are scheduled for demolition, though only two will require highway closures. One tall, 50-foot flyover ramp, which merges drivers from Monroe and Woodinville into southbound I-405, will remain in use.
In November, the Washington State Department of Transportation (WSDOT) installed new traffic lights on Highway 522, creating two permanent intersections. These signals replace direct I-405 ramps for certain movements. According to Lisa Hodgson, WSDOT’s corridor director, these signals slow Highway 522 traffic by about one minute through Bothell but save significant money by preserving land for construction. A third signal set will be installed later to serve a new I-405 tollway interchange.
Environmental Considerations and Future Developments
Beyond traffic improvements, the project also focuses on environmental enhancements. It includes improvements to six fish passages in or near the Sammamish River, Juanita Creek, and North Creek. Some of these passages will be built using traditional methods, involving lane shifts and trench digging.
For two other passages, workers will employ a unique ground freezing technique. This method allows mining equipment to carve tunnels under I-405 without causing sinkholes. Horizontal ground freezing is a rare application of a common tactic, previously used for Seattle’s seawall. Prendergast sought expertise from a Skanska freezing specialist who worked on New York City transit extensions to implement this innovative solution.
Two miles south of the main construction, the first pillar for a pedestrian bridge over I-405 near Brickyard Park & Ride is visible, alongside new noise-blocking walls. This area will eventually feature a median station for Sound Transit freeway buses. The project represents a significant investment in both transportation infrastructure and environmental stewardship for the region.
