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State Route 520 Montlake Project online open house – Project elements

Community and stakeholder input helped WSDOT shape the corridor’s design throughout two decades of planning for SR 520 improvements. The Montlake Project is a design-build project, meaning the contractor continued to work on the design even after construction began. Design work is wrapping up now.

Design features

To improve the public’s experience — during and after construction — the project team integrated some features into the project’s design to help people travel safely and efficiently through the area and to offer new amenities for the neighborhood.

Bicycle and pedestrian bridge

After construction, a bicycle and pedestrian bridge will connect Lake Washington Boulevard to East Montlake Park. This bridge will feature attractive landscaping and a fantastic viewpoint looking onto Lake Washington. The location of the viewpoint was changed to incorporate public feedback and help ensure a pleasant experience on the bridge.

Montlake lid features

The Montlake lid is more than a way to cross over SR 520. It will be a transit hub and offer amenities for those walking, biking and rolling. Click the image below to enlarge the map.

Amenities map

Construction innovations

Temporary on-ramp and trail under SR 520

During construction, we built a temporary eastbound on-ramp from Lake Washington Boulevard to manage traffic. Along this on-ramp is a temporary trail under SR 520 that offers bicyclists and pedestrians an alternative to crossing the highway at Montlake Boulevard. The route connects the Arboretum to the SR 520 Trail across Lake Washington and the University District.

Treating water during and after construction

There is more to the project than you can see from the roads. Incorporated into the construction plans and the final design are treatment systems for SR 520 stormwater runoff that will contribute to a cleaner, healthier environment.

When the project is complete, there will be an underground water filtration system in East Montlake Park to prevent untreated stormwater from running into Lake Washington. The system will primarily be underground and blend into the surrounding landscaping.

Bridge construction on the lake

The project is replacing the old, structurally vulnerable eastbound bridge. The new bridge will carry three lanes of eastbound traffic (two general purpose and one HOV) from Montlake Boulevard East to the floating bridge.

To be most efficient in construction — and to minimize effects on neighbors — crews use trestles and temporary work platforms along with large, blue gantry cranes to remove the old bridge. The old bridge is broken into large sections, which are transported off-site for demolition. The result is an environmentally friendly operation, reducing noise, dust and possible pollution to Lake Washington.

The trestle, platforms and cranes are also used to build the new bridge. Building the supports for the bridge requires pile driving, which is a construction method to embed large steel pilings into the ground. In this case, crews vibrate steel piles into the bottom of Lake Washington and then hit them with a large hammer to ensure that they are firmly installed. Using the vibratory method reduces the potential for noise. Neighbors will hear a pinging sound as a hammer strikes the top of a pile and may feel vibrations as the steel piles vibrate into the soil. Pile driving can occur between 8 a.m. and 5 p.m. on weekdays and 9 a.m. to 5 p.m. on weekends.