The great wall of no sound
Aesthetically appealing wall mitigates sound and blends with Rocky Mountains’ natural surroundings
For generations, Pikes Peak has served as a beacon, drawing tens of thousands of settlers to the Colorado Springs, Colo., region. From the summit, one sees vast, open skies, planted fields and the majestic Rocky Mountains. So inspired by this view was Katharine Lee Bates in 1893 that she penned her most famous poem, “America the Beautiful.”
Today, people are still flocking to Colorado Springs. Fueled by a booming economy, the population has jumped nearly 27% over the past 10 years. But, while the economy has been robust, vehicular traffic planning has lagged behind. The main north-south route is I-25 which opened nearly 40 years ago. Currently, the 30-mile stretch of I-25 running through Colorado Springs is at 1500of traffic capacity.
To alleviate congestion on this roadway, the Colorado Department of Transportation (CDOT) embarked on a five-year, $176 million highway improvement program. The project includes construction of a 2 1/2-mile sound wall on the west side of the interstate. From the outset, CDOT planners had three main objectives in mind.
The first was to lessen intrusion on residents, constructing the sound wall first before beginning highway improvements. Second, was to receive feedback from residents on what the sound wall should look like, not only dimension-wise but also its materials, design and colors. Finally, complete the project within budget and in a timely manner.
The wall has ears
Typically, sound barrier walls are built after the completion of roadway construction. But as Dave Poling, CDOT’s I-25 corridor project manager explained, “CDOT made a commitment to the residents along I-25 to mitigate the noise levels from construction. It was important that we reduce the inconvenience and disruption that highway construction can cause homeowners. Therefore, this sound wall was constructed at the beginning of the highway construction project.”
Anticipating the aesthetic concerns that a noise wall would raise among residents, CDOT implemented an extensive outreach program to gather input from local homeowners on the wall’s design, color and appearance.
“During the public comment process, residents were telling us they’ve seen sound walls in other cities that looked drab and ugly,” recalled Randall Cumley, construction manager for the engineering/design firm, Wilson & Co., which manages the I-25 corridor. “The residents were clear in telling us that they wanted something different, something they could be proud of.” Through numerous surveys, public meetings and neighborhood workshops, CDOT learned of the residents concerns. Chief among them:
• The wall should appear as a natural extension of the neighborhood and the mountain scenery. It should not be a grim, urban barrier;
• The wall should be high enough to protect the neighborhood from future as well as existing traffic noise;
• A residents’-side greenway should incorporate a Victorian design to complement the neighborhood’s historic nature and allow for future gardens, playlots, parking for visitors and security; and
• The residents’ side also should include a 10-ft wide walking/biking trail to connect with the city’s system of recreational trails and sidewalks.
Armed with this feedback, CDOT and Wilson & Co. set out to construct a sound wall that would have superior sound-damping qualities while also enhancing the area’s aesthetics.
Designing the wall
Wilson & Co. started out by evaluating the architectural styles of Colorado Springs. The neighborhood’s characteristic Victorian style and older downtown buildings served as the basis for the residential side of the wall. On the freeway side, designers used various patterns to capture the character of nearby Mesa Springs Creek, mountain valleys and rock outcrops. At the same time, the wall needed to be durable enough to weather years of exposure to the elements and still remain safe, strong and attractive. The wall’s materials, design patterns and color were critical in achieving these dual goals.
The residents continued to offer important feedback throughout the design process. Neighborhood focus group meetings examined brick, concrete block and precast concrete panels, among other materials. Design elements discussed included inset tile, brick patterns, ornamental columns and use of natural buff-colored rock.
After a series of professional review meetings with citizens, city agencies and local design professionals, the wall’s design was finally approved. The plan called for the wall to be situated 30 ft west of the highway, a minimum of 50 ft from neighborhood homes and built from precast textured concrete panels. For the majority of its length, the wall measures 15 ft high, although it ranges from 7 to 21 ft depending on the elevation and proximity of the highway.
Color makes the difference
Casting the concrete wall panels was SEMA Construction Inc., of Englewood, Colo., the project’s construction contractor, in cooperation with Transit Mix Concrete Co., a Colorado Springs ready-mix concrete producer.
Powdered pigments, produced by the Bayer Corp., provided the wall’s earth-tone color, a critical ingredient in it’s overall design.
“We used Bayferrox synthetic iron-oxide pigments to match the design specifications,” said Bob Brewster, Transit Mix vice president. “We were looking for an earth-tone color, a very light red, to match mountain terrain. Bayferrox pigments provided the consistent, high-quality color we were looking for.”
To produce colored concrete, Transit Mix opted to use a pigment slurry system, commonly used by the concrete roofing tile industry. “We decided to go with a slurry system because we were running a large amount of a particular color,” said Brewster. “The wall required more than 1,000 concrete panels, each of which are 30 ft long and 8 in. thick. In a project this large, the slurry system ensures greater color consistency from the first panel to the last.”
The pigment slurry was made by mixing the proper amounts of pigment with a specified amount of water in a holding tank. The pigment slurry was then pumped into a concrete mixing truck at the same time as other raw materials were being added.
“With the coloring and fabrication areas just 100 yd apart, we utilized the color slurry to ensure the concrete was mixed quickly and consistently,” said Brewster.
Next, the colored concrete was poured from the truck into individual latex molds to create the unique designs for the wall.
According to Wilson & Co.’s Cumley, there were 65 different combinations of latex liners to accommodate the different patterns required for both sides of the wall. It’s a process that required painstaking attention to detail, as each panel must perfectly match adjoining panels.
After curing, an anti-graffiti sealant was applied to each panel. Then, the panels were trucked to the construction site and inserted into I-beam steel support columns. To conceal the I-beams, precast covers using the same design, color and texture were welded into place giving the wall a seamless look.
“We’ve received only positive comments from the community about the wall,” said Cumley. “The residents are very pleased with its design and color. And it’s received plenty of positive media coverage, too. For instance, as part of a promotion, a local radio station used its sound equipment to test the wall’s sound mitigation qualities. It was a fun thing for them to do, but also showed that the wall is an effective sound barrier.”
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