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Innovative Solution for Austin Highway

Balfour Beatty Delivers Innovative Solution on US 183 South Project

Team members utilize arch culvert bridge system to convey hydraulic flow on Mobility Authority’s new expressway

Balfour Beatty, as apart of Colorado Constructors (CRC) joint venture, recently celebrated the partial opening of Central Texas Regional Mobility Authority’s (Mobility Authority) new US 183 South tolled expressway in Austin. With the expectation of delivering a transformative highway project that is safe for travelers, environmentally friendly for the community, and cost-effective for the client and partners, the CRC team leveraged an innovative solution of installing an arch culvert bridge system to efficiently convey hydraulic flow along the expressway’s corridor. 

According to the Texas Department of Transportation (TxDOT), hydraulic infrastructure, such as bridges and culverts, are a part of larger facilities that help drain stormwater on roadways. For highway widening and reconstruction projects, like the US 183 South expressway, conveying hydraulic flow is beneficial in minimizing the risk of flood loss and the impact of floods on human safety.

To efficiently convey hydraulic flow, the project needed a solution that was far from traditional. With the roadway’s surface area drastically increasing from 10 lanes to 15 lanes, the traditional concrete box culvert structure along the corridor was no longer equipped to meet the new increased drainage capacity. The existing structure’s elements including its short height, additional walls between each culvert barrel, and its relatively flat design proposed challenges for conveying more water. Team members quickly pivoted to provide an innovative design and solution that would meet the new drainage needs of the expanded highway. 

CRC initially proposed a design that would add an additional barrel to each side of the existing box culvert, located along the US 183 corridor. The project team quickly learned that this design approach and larger structure would more than likely interfere with the existing utility mains that parallel the drainage canal. Removing and relocating the older utilities on the corridor would solve this challenge but impede on the project team’s goal of remaining abundantly cautious of the project’s cost and schedule. Additionally, due to the existing high-pressure gas and wastewater mains running parallel along each sides of the box culverts this design approach was quickly mired.

“One of our goals for the US 183 South project was to provide an innovative solution that efficiently conveys hydraulic flow,” said Brendan McGrath, Balfour Beatty general superintendent on the US 183 South project. “Instead of spending several million dollars to relocate the existing utilities and running into the possibility of delaying the project’s schedule with our initial design, we quickly pivoted and devised a plan to install a precast, concrete arch culvert bridge system along the new expressway.” 

The installation of the arch culvert bridge system began with the excavation and construction of two 168-foot long, by six-foot tall concrete footings. With existing utilities only a few feet away, the team took extra precautions to safely excavate and build the footings for the arch system. Additionally, during this process the project team kept the existing box culvert in place so storm water could pass directly through the work area ultimately keeping the project site dry.

Once both footings were constructed, CRC demolished the existing concrete box culvert creating a solid base for two crawler cranes to set 42 new precast concrete arch culvert segments. The 62,000-pound arches were shipped laying flat on their sides, which allowed one crawler to flip the arch segments vertically and other to grab the upright arch, track it in place and set each structure in its permanent location. Within two shifts, all precast arches were set in place, and backfill operations quickly embanked to the roadway grade just in time for the structure’s first storm. 

“With the delivery of the arch culvert bridge system, conveying hydraulic flows for all new lanes of SH 71 at 183 South overpass intersection has been a success,” said McGrath. “From fitting the unique design parameters to saving time and money, the installation of the arch culvert bridge system was a major milestone for our project teams. I commend our workforce for their resiliency in providing an innovative solution for the Mobility Authority and the 60,000 drivers who travel on the expressway every day.”