Wash. lawmakers order noise study of 520 Corridor connecting I-405 and I-5

Updated Dec 17, 2018
520 Corridor. Google Earth screen shot.520 Corridor. Google Earth screen shot.

Washington state residents in the Medina, Clyde Hill, and surrounding neighborhoods are fed up with the grating “ka-think” noise they hear every time a vehicle drives over the metal expansion joints on the new $4.6 billion 520 corridor between Interstate 405 and Interstate 5, MYNorthwest reports.

Neighbors have been complaining about the noise since the corridor opened in 2016, even though it incorporates sound-muffling technology, including a grooved pavement that minimizes tire noise, adjacent sound-reducing walls, and steel plating installed around the expansion joints.

As a result, the Legislature approved a $181,000 study of the noise, and asked University of Washington scientists to look for potential solutions. The university set up microphones on the corridor and found sounds ranging from 75 to 80 decibels. An earlier Washington State Department of Transportation (WSDOT) study based on a 15-minute average found that the bridge noise was below the U.S. government limit of 67 decibels.

Results of the study will be discussed with Medina city leaders, and WSDOT will give a report to lawmakers in early January 2019.