|Crews work to complete concrete masonry noise wall on SR 167.|
When you think about highway noise walls—which I’m sure you do on a daily basis—the word romantic probably isn’t the first adjective that comes to mind. But that’s exactly how our own Paul Kinderman, State Bridge and Structures Architect, describes the technique used to create the 1.3-mile noise wall along the eastside of SR 167 in Algona.
But what is a noise wall?
Just in case noise walls aren’t on the top of your thought list or you have absolutely no idea what I’m talking about, I’ll explain. Noise walls are barriers constructed between neighborhoods and highways or other noisy thoroughfares. Noise walls are considered when ambient noise exceeds 66 dBA—roughly the sound of a train from 50 feet away—all noises no one wants in their backyard or home. Then, we look at whether it’s feasible to construct a noise wall, essentially, will it work. If it does, then we decide whether a noise wall is reasonable to construct and if the cost of building a wall matches the number of homes and residents affected. This is federal criteria that WSDOT applies when determining if a wall should be built.
|A vinyl noise wall.|
|Cranes setting a pre-cast noise wall at night.|
Show me the romance
Unfortunately, the materials above are exceptions. Typically, noise walls are made out of pre-cast concrete built in 12-foot sections. The sections are built off-site, then shipped and placed together to form a noise wall. Essentially it’s the same process a child uses to pour Jell-O into a mold. When the concrete is poured, textured designs can be added to the walls to make them more pleasing to the eye.
However, this technique posed problems for our engineers and contractors. The 1.3-mile section along SR 167 in Algona is narrow and hauling large panels of concrete would require closing lanes to make way for large cranes and equipment. The installation would also cause invasive nighttime noise and light from the work zone.
To find a solution, Kinderman’s team, our project engineers and contractors looked to an ancient building technique of the past: concrete masonry. This one-brick-at-a-time method was described by Kinderman as antique and medieval. He referenced that it’s how the pyramids and great cathedrals were built. Rather than pre-cast walls, contractor crews are stacking single concrete blocks to create the wall. The masterwork of creating the blocks requires expert craftsmanship and is a niche industry within construction. Kinderman explained that the world of the masons is a little more romantic.
While the concrete masonry technique is more romantic, it’s also popular in industrial construction—but an outlier in noise wall manufacturing, especially in the Puget Sound region. What may seem like a simple material swap to an outsider is an example of collaboration and thinking outside of the box—or in this case, outside the concrete panel. Concrete masonry allows crews to work with smaller equipment and stack the blocks like Legos—no large cranes needed—decreasing the project’s cost and carbon footprint. The construction zone is smaller, and the work is more cost-effective with less traffic impacts. Additionally, neighbors can watch contractor crews build the wall, stone by stone.
|The new noise wall’s capped top.|
Connoisseurs of gray
The stone’s color is limited to Washington Gray, not for its pun-y name, but for its ability to be matched with paint if the wall were vandalized. The team took the gray color as an opportunity to add other aesthetic touches to the wall’s texture. Its varied surface wards off graffiti and vandalism, and the capped tops serve as a nice detail like a button down collar on a shirt.
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.
Visit the SR 167- 8th to 227th Southbound HOT Lane page to learn more about the project and the noise wall.