A recent expansion of a tolled expressway in Austin, Texas, called for a precast arch culvert bridge system that could better convey hydraulic flows for all new lanes. The design allowed crews to avoid schedule delays and the cost of relocating utilities.



With the road in Austin ballooning from 10 lanes to 15, the team had to rethink how to deal with all the extra runoff.
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.

The expanded expressway presented a problem in terms of drainage, because the roadway’s surface area would increase drastically from 10 lanes to 15, and the traditional concrete box culvert structure along the corridor was deemed insufficient to meet the increased drainage requirements.

So, CRC used an innovative solution of installing an arch culvert bridge system to better convey hydraulic flow along the expressway’s corridor to neutralise the heightened risk of flooding.

As Balfour Beatty explains here, the solution was arrived at after a false start, and the final, successful approach required two crawler cranes working in tandem to set 42 precast concrete arch culvert segments in a short space of time.

Move the utilities?

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. But the team realised this approach and larger structure would likely interfere with the existing utility mains that run parallel to the drainage canal.

Relocating utilities on the corridor could solve the problem but would risk the project’s cost and schedule. This plus existing high-pressure gas and wastewater mains running parallel along each side of the box culverts caused them to abandon the idea.