As part of the Eastside project, WSDOT constructed a series of walls between Evergreen Point Road and the vicinity of 108th Avenue Northeast. The walls reduce traffic noise and provide screening for residents living along the corridor. Walls range between 6 and 20 feet high, depending on location.
We built walls throughout the corridor in keeping with information included in our environmental documents and past community outreach.
Where were walls built?
Walls generally were installed at the edge of the new roadway or along the edge of WSDOT's right of way. You can download printable maps and cross-section illustrations below to view wall heights and locations.
Printable maps: Wall heights and locations
Printable graphics: Illustrated cross-sections
You can view printable illustrated cross-sections by clicking the lettered segments in the map below. Each downloadable pdf file shows where walls are relative to the highway, landscaping and residential areas.
What do the walls look like?
Walls facing the highway and public trails and paths have a finish called Random Flare, pictured below. A community design process conducted in 2008 and 2009 helped us develop this finish.
Residents living adjacent to SR 520 gave input in 2010 to determine the finish of walls facing their properties. They selected stamped Ashlar Stone and Cascadian Stone patterns, also pictured below.
You can download a printable map to see where each pattern was applied in the corridor.
Printable map: Wall pattern locations
What is the end result?
Given the characteristics of how noise travels, walls are most effective at reducing noise up to 500 feet from the edge of the SR 520 roadway. Therefore, residents living closest to the noise walls experience the largest reduction in roadway traffic noise. Residents farther away from the walls notice less of a benefit.
How do we hear noise?
- Sound is measured in units called decibels (dBA).
- An average person's ear can perceive a 3 dBA or greater change in noise levels.
- A 10 dBA reduction sounds half as loud to the human ear; a 10 dBA increase sounds twice as loud.
The noise thermometer pictured below represents relative sound levels of common activities.
Click on the image above to view a larger version.
How do slopes influence the effectiveness of walls?
Walls are most effective at reducing highway noise for homes and businesses within 500 feet of the highway. However, topography plays a big part in how well they work. For example, walls are more effective at blocking noise for properties located below the highway grade than for those located on higher ground.
Our typical noise wall effectiveness diagram (pdf 250 kb) illustrates how walls work for properties located at various grades relative to the highway.
Learn more about WSDOT noise mitigation
Learn more about noise walls and how, when and why WSDOT builds them by reading these frequently asked questions.
Has WSDOT considered other methods to reduce noise, such as quieter pavement?
WSDOT has selected several quieter pavement test sites to see how quieter pavement performs in the Pacific Northwest's unique driving and climate conditions. WSDOT is studying the test sections of quieter pavement for five years to measure durability, quality and quantity of noise reduction, and how noise suppression abilities perform over time. This information will help policymakers, WSDOT, and others make more informed decisions about incorporating quieter pavement into highway projects in the future. Currently, one of the quieter pavement test sections is on SR 520 through Bellevue.
Please visit the Quieter Pavement website for more information.