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SR 520 - West Approach Bridge North Project Community and Environmental Benefits

Environmental improvements

WSDOT strives to be a good neighbor and plans to implement a number of wetland and park improvements as part of the West Approach Bridge North (WABN) project. This will improve the natural environment and create new recreation opportunities for the community.

Environmental enhancements will be made in Arboretum at the Arboretum Creek, Azalea Way Pond, and Foster Island, and at sites on Lake Washington, Union Bay, Cedar River, and other locations.

Community improvements include a new multi-use trail in the Arboretum and a public park north of SR 520 on Portage Bay. A new, landscaped stormwater facility will also improve local trail connections near East Montlake Park.

Arborteum wetlands near SR 520
Wetlands and other natural resources in the Arboretum will be enhanced through environmental mitigation measures.


The WABN project will emphasize sustainable practices to minimize the effects of construction.

In 2012, WSDOT worked closely with the Seattle Design Commission to refine the design and reduce concrete volumes by nearly 50 percent. The project will feature a new constructed stormwater wetland that will treat highway runoff water that currently flows untreated into Lake Washington.

Increased access to transit, HOV lanes, and improved trails and parks will provide more alternatives to driving. WSDOT will also work to minimize construction-related noise to the extent possible.

Arboretum ramp removal

Since 2010, WSDOT has planned to remove the web of ramps that connect to and from Lake Washington Boulevard in the Arboretum.

The WABN project will remove the westbound off-ramp to Lake Washington Boulevard, as well as the unused R.H. Thomson expressway ramps. The eastbound on-ramp to SR 520 will remain open until future phases are implemented. The function of the Arboretum ramps will be replaced through an improved Montlake interchange and ramps, and a new off-ramp to 24th Avenue East.

Removal of the ramps will create additional open space in the Arboretum and reduce traffic noise in the area, while advancing environmental and plant restoration efforts. WSDOT has worked closely with the Arboretum, Seattle Parks, and other community partners to plan the removal of the ramps for several years.

Existing RH Thomson ramps that will be removed with the WABN project
The unused R.H. Thomson expressway ramps and the westbound off-ramp to Lake Washington Boulevard will be removed, creating a more open, natural setting in the Arboretum.

Bicycle, pedestrian and transit connections

The WABN project will create better connections on and around SR 520 as it enters Seattle.


When the WABN structure opens to drivers, it will also open to bicyclists. The new 14-foot-wide bicycle and pedestrian path on the north side will connect to the Montlake area, providing a second connection across Lake Washington. This path will include several scenic rest areas, known as “belvederes.” An interim path at 24th Avenue East will help the regional path connect to existing local trails. 

Bicyclists on Lake Washington
Bicyclists travel along Lake Washington Boulevard. The project will improve bicycle and pedestrian connections and connect the new 14-foot-wide path to existing local and regional trails.


Regular bus service will be maintained throughout the entire construction period. The westbound flyer stop in Montlake will be relocated to an interim location near Montlake Boulevard. When complete, new transit/HOV lanes in both directions will provide improved bus and carpool travel to and from the Eastside.

The project is also designed to accommodate potential future light rail if approved and funded by the region. 

Bus traveling in the right lane on westbound SR 520
A bus travels westbound on SR 520 towards the west high rise. The project will provide improvements to transit connections.

Community Construction Management Plan

Before construction begins, we have developed a WABN Community Construction Management Plan (CCMP) with the community. This document outlines how the public can provide input into construction management decisions to help minimize the effects of construction.

The CCMP shares what to expect during construction and relevant project commitments, measurements, and best practices. Key topics highlighted include noise, vibration, air quality, traffic and transportation, construction staging, vegetation and erosion control, in-water work, and more.

The CCMP also provides WSDOT and its contractors with a framework to keep the public informed about upcoming construction and gather input to improve and modify construction practices as needed.

We hope you can check it out!