Residents take DOT to court, say rubber asphalt could reduce bridge noise

Seattle residents recently took the Washington Department of Transportation to court to demand a study on rubberized asphalt. The residents claimed traffic on the Interstate 90 bridge is too loud, and that rubberized pavement could reduce the noise.

Approximately 240 residents from Bellevue, Mercer Island and Beaux Arts filed the complaint and are appealing for a second environmental study for the bridge, one that would include an analysis of rubber asphalt. The previous study did not consider the pavement as a sound-reducing measure.

“All we’re asking Sound Transit to do is to study the technology,” Walter Scott, a Bellevue resident, told The Seattle Times.

The DOT is currently developing plans to expand the number of lanes on the bridge. The $128 million project will add two new car-pool lanes and will include some repaving.

Lawyers representing the department’s Sound Transit argued the rubber asphalt would wear too easily under Washington’s studded winter tires. The DOT also said the alternative pavement would only reduce the sound by two to four decibels, which would not be enough to be cost effective. The Federal Highway Administration does not recognize rubber asphalt as an approved noise-reducing measure, the lawyers said.

Traditional measures to reduce sound, including sound walls and barriers, were found to be too expensive for the state’s per-household spending allotment for sound reduction.

A hearing examiner has until Oct. 25 to decide whether or not the Sound Transit should include a study of rubber pavement for its project.

In Southwestern states such as Arizona, rubberized asphalt has been used for almost 35 years. The material first began as a test in the late 1960s, and grew to widespread use after it was found to stretch more and wear less than traditional pavements. It was also discovered that the rubber asphalt reduced noise from traffic significantly. Arizona currently has plans to overlay 115 miles of the Phoenix-area freeway system with rubber asphalt.

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According to the George Way, retired chief pavement design engineer for the Arizona DOT, rubberized asphalt is made by combining hot-mix asphalt with 15 to 20 percent recycled rubber-tire particles. On average, paving one mile of highway with rubber pavement recycles 1,000 tires per lane. By weight the rubberized pavement costs more than traditional asphalt, but a thinner layer is required and will generally last longer than regular hot mix. The rubber mix is used in the Southeast, as well as in Canada, Belgium and much of Europe. To read previous stories on rubber asphalt, click on the link to the right.