LYNNWOOD — People who drive southbound on I-5 through Lynnwood have nearly another year of coarse pavement ahead of them.
Crews skinned the top off the freeway from Alderwood Mall to 52nd Avenue West late last summer with construction of new ramps. The pavement won’t be replaced until the ramp work is done in the fall of 2011, said Meghan Pembroke, spokeswoman for the state Department of Transportation.
The 1.7-mile stretch also happens to be the section of experimental quieter pavement installed in 2006.
That pavement was effective at first but began to crack and break, and it was a matter of time until it had to be removed, officials said last year.
“It was nearing the end of its useful life and it wasn’t providing any audible benefits,” Pembroke said.
The pavement in Lynnwood lasted only four years, compared to about 16 years for conventional asphalt in the Northwest.
Some of the pavement had to be taken up as part of the ramp project, and it made sense to do this work all at once and, likewise, to replace it all at once at the end, she said.
Also, engineers wanted to leave a stable surface that would hold up until the ramp job is complete, Pembroke said.
The $33 million ramp project is being done to create more separation between drivers merging from I-405 and Highway 525 onto southbound I-5 and those exiting I-5 to 196th Street SW.
Quieter pavement was tested as an alternative or a supplement to noise walls, officials said. The walls reduce noise 5 to 10 decibels and have an expected life of 75 years but cost nearly $4 million per mile and block views.
The Lynnwood stretch of quieter pavement was laid down four years ago as part of a $6.5 million repaving of southbound I-5 from south Everett to Mountlake Terrace.
The section was one of three stretches of experimental quieter pavement installed in the Puget Sound area. The other sections were in 2007 on Highway 520 just east of the Evergreen Point floating bridge in Medina and last year on I-405 from I-90 to Southeast Eighth Street in Bellevue.
The Medina stretch, like the one in Lynnwood, has not performed well but is still in place, said Travis Phelps, a transportation department spokesman.
The quieter pavement is porous, absorbing sound but also trapping water, making it more vulnerable to deterioration, officials say.
The quiet pavement is priced similarly to regular asphalt, but if it has to be replaced more frequently, it would not make sense to use it extensively, officials have said.
A different type of asphalt was tried for the I-405 stretch, so the quieter pavement experiment is not quite over, Phelps said.
Also, the pavement was laid over concrete rather than asphalt to see if that makes a difference.
“We’ve got one more try,” he said.
Bill Sheets: 425-339-3439; sheets@heraldnet.com.
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