Traffic Q&A: Panels vs. blocks when building a ‘noise wall’

Q: Why is the Washington State Department of Transportation building a sound barrier on the east side of state Route 167 south of Auburn made out of blocks? It seems concrete panels would be much less expensive to build and repair. – Tim T., Elk Plain

A: Tim’s an observant fellow, and he raises a valid question.

Many so-called “noise walls” in Western Washington are constructed from 12-foot pre-cast concrete panels.

You can see them along Interstate 5 in the Federal Way area, among other locales.

Such walls provide a sound barrier between noisy freeways and nearby residential areas.

So why build the state Route 167 wall, which stretches 7,000 feet roughly from Ellingson Road in Algona north to 15th Street Southwest in Auburn, out of concrete blocks?

For answers, we went to state Department of Transportation project engineer Sharif Shaklawun.

He first provided some background.

The noise wall is part of a project that will add a carpool lane to southbound state Route 167 in that area, construct a fish passage to take Jovita Creek under the freeway and make other improvements.

The contractor awarded the bid was given options for building the noise wall and chose the masonry method over the standard panels, Shaklawun said.

“It meets all the DOT requirements,” he added.

Building this particular wall out of blocks was cost-effective for the contractor and a benefit to the traveling public, Shaklawun said.

The work space along that stretch of freeway is tight. Using the standard pre-cast panels would have necessitated bringing in cranes, which would have required lane closures, Shaklawun said.

“That would have an impact on traffic,” he said.

To minimize those impacts, much of the work to erect the pre-cast panels would have had to take place at night.

Crews would have had to use portable lights to illuminate the work zone, which would have caused “invasive nighttime noise and light,” Caitlin Morris, a Transportation Department spokeswoman, wrote in a blog post about the wall.

Morris also expounded on the benefits of the masonry method.

“Its varied surface wards off graffiti and vandalism, and the capped top serves as a nice detail, like a button-down collar on a shirt,” she wrote.

More such walls, which are common in Eastern Washington, might be on the way to the West Side.

“Building a wall out of concrete masonry is providing opportunities to hone in and refine techniques that will make building a similar wall in the future much more expedient and efficient,” Morris wrote.

The state Route 167 wall has mostly been erected, but crews will be applying sealant to the wall in the coming weeks, Shaklawun said.

The overarching improvement project is expected to be wrapped up by 2017.

This story was originally published April 3, 2016 at 5:00 AM with the headline "Traffic Q&A: Panels vs. blocks when building a ‘noise wall’."