If noise levels at a property exceed 65 decibels, ODOT evaluates noise reduction strategies. Sound walls are the most common tool used to mitigate noise. On this project, sound walls were found to provide helpful benefits in select areas, based on ODOT and Federal Highway Administration standards. Eligible property owners and residents in West Linn voted on four proposed sound walls in 2019. Residents voted in favor of two of the four walls. See the link to the voting results below. Eligible property owners and residents near the southbound lanes at exit 9, where a sound wall would provide benefit, are currently voting on whether to have a sound wall constructed. If more than 50 percent of eligible property owners and residents vote in favor of constructing a sound wall, the wall will be constructed. Those eligible to vote will receive information on the sound wall voting process by mail in early March.
Generally, sound walls range from 8–18 feet in height (subject to topography) and may vary in length depending on the needs of the locations. Sound walls are typically constructed at the very edge of the roadway to maximize noise reduction. The walls are typically made of concrete post and panel, concrete masonry block or steel panels (see example below). Final type selection for the sound walls will be made later in the project.
The majority of votes received for the sound wall next to the sounthbound lanes of I-205 at exit 9 were YES votes, so this sound wall will be included as part of the project.
The sound wall voting process is required per the Federal Highway Administration and outlined in the Oregon Department of Transportation Noise Manual.
Today, noise levels at properties near the southbound lanes at exit 9 range from 43 to 71 decibels. After the project is built, noise levels will range from 45 to 72 decibels, potentially increasing 1–2 decibels. People do not usually notice a change in noise of three decibels or less.