Date:  Friday, October 08, 2010

Contact: Jamie Holter, WSDOT Communications, 206-440-4698

Pilot project monitors whether panels block traffic noise for neighbors

SEATTLE – More than 700 specially designed panels are now installed above the Interstate 5 express lanes on the Ship Canal Bridge as part of a pilot project to reduce traffic noise for nearby residents.

Contractor crews from Penhall Company installed approximately 350 noise-absorptive panels alongside the express lanes in an effort to reduce reflective noise that bounces to the communities flanking the highway. The panels span a 500 foot stretch of highway between E. Gwinn Place and E. Allison Street.

“This particular area on the Ship Canal Bridge is ideal for testing some new strategies to reduce traffic noise,” said Tim Sexton, WSDOT Air Quality, Noise, Energy Policy Manager. “Knowing that people will always live next to highways, we want to learn more about methods for reducing noise in urban environments so we can develop noise reduction strategies that are realistic, cost-effective and feasible.”

Highway traffic noise can interfere with sleep, work and other daily activities during the day and night, and is a concern for many residents living along state highways. The I-5 Ship Canal Bridge is one of several locations where engineers are working to learn more about how to reduce noise in challenging environments. The project is part of the state’s noise retrofit program that attempts to address traffic noise in neighborhoods that existed before I-5 was built.

Why test the panels here?

Located in a heavily traveled urban area, traffic noise from the bridge reaches the densely populated Seattle neighborhoods of Eastlake, Roanoke Park, University District and Wallingford.

Existing noise levels in the neighborhoods surrounding the bridge range from 66 to 87 decibels. For comparison, a train passing by at 50 feet away is approximately 70 decibels and a jackhammer at 50 feet is approximately 90 decibels. Above 66 decibels, it is difficult for two people standing three feet apart to hold a conversation.

“Based on our modeling, we expect the panels to reduce noise by four decibels, which is considered noticeable,” Sexton said.

Testing begins

With the panels now in place, the testing begins. WSDOT engineers took baseline measurements in 22 locations before installation. They will test the same locations periodically for sound quantity and sound quality. Seasonal testing also is part of the research to see how the noise levels change with air temperature. Engineers also want to know how the panels hold up over time.

After a year of seasonal testing, experts will conduct annual tests and provide a full report at the end of the testing period in 2013. Data will be posted online at www.wsdot.wa.gov/Projects/I5/ShipCanalBridge/results.htm  

Information from the study will be a resource for future construction projects both locally and nationally.

For more information about the project, go to www.wsdot.wa.gov/projects/i5/shipcanalbridge/  

The $7 million project was paid for by the 2005 gas tax. Approximately $2.3 million went to construction. The balance of the funds were used to research and design the innovative panels, and will be used to measure their effectiveness over the three-year time period. The balance of funds after engineers complete performance checks will be returned to the motor vehicle fund.

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