The Texas Department of Transportation (TxDOT) is in the early stages of the I-35 Capital Express Central project (CapEx Central) in Austin, Texas. The project focuses on an 8-mile stretch of Interstate 35 (I-35), a key route for local traffic and the movement of goods from the southern border to points northward.
The CapEx Central project has a $4.5 billion budget and includes multiple segments. Major components of the project include:
- Adding non-tolled, high-occupancy vehicle (HOV) managed lanes in each direction along the entire 8-mile stretch
- Constructing a drainage tunnel that will be 22 feet in diameter and nearly 6.5 miles long, along with a dewatering pump station
- Adding 19-plus miles of new shared-use paths and 13 new connections to existing paths
- Lowering the highway below ground level and widening east-west bridges
The Lady Bird Lake segment covers 1.8 miles of the project. As part of the segment, which is being led by general contractor Balfour Beatty, the team is adding two HOV managed lanes in both directions, reconstructing the Lady Bird Lake bridge, and building a single-point urban interchange at Riverside Drive. The work also includes a pedestrian-only bridge at Woodland Avenue, bike and pedestrian paths along the corridor, and improvements to accommodate future city light rail. These improvements are expected to improve safety and connectivity in the area. WSP served as the designer on the design-bid-build project.
The 1,000-foot-long Lady Bird Lake bridge spans Lady Bird Lake, a reservoir of the Colorado River. The bridge has an average daily traffic of 142,600, and it is expected to grow. According to the City of Austin’s Community Development Commission Housing Committee, Austin is the 13th most populous city in the country and has been doubling its population every 20 to 25 years.
| Your local Case Construction Equipment Inc dealer |
|---|
| Beauregard Equipment |
| Monroe Tractor |
“I-35 runs through the heart of the city and is a major pinch point,” TxDOT Project Engineer Ernesto Jaimes said. “This section heads into the downtown area, and more companies are moving here, so we anticipate traffic growing.”
“Traffic is bumper-to-bumper during the morning and afternoon rush hours, and there’s almost no time of the day where you don’t experience heavy traffic volumes in the corridor,” added Bradley Wheelis, TxDOT Southwest Communications Director. “It’s been half a century since work has been done on this corridor, so we’re behind the eight ball.”
The current bridge over Lady Bird Lake is three separate bridges: the main lane bridge, which has three lanes in each direction, and two frontage bridges, which range from two to four lanes.
The new bridge over Lady Bird Lake will consist of two structures, one for all northbound traffic and one for all southbound traffic. Two HOV lanes will be added to the main lanes, bringing the total to five lanes in each direction, while the frontage road lanes will remain two to four lanes.
| Your local Wirtgen America dealer |
|---|
| WI Clark |
| Dobbs Equipment (SC) |
| United Construction & Forestry |
The team is adding two separate pedestrian bridges (one on each side), each with its own alignment and profile, and positioned lower than the vehicle bridges. They will also include a widened center span, which provides a view of the Austin skyline.
“The goal was to provide additional and separate pedestrian access because currently the access for pedestrians is adjacent to the frontage road bridge and traffic,” said Julian Summers, WSP in the U.S. Design Manager. “It’s an added positive feature for the project to have these two separate pedestrian bridges because it'll make things a lot safer for pedestrians.”
The new bridge over Lady Bird Lake will be longer — approximately 200 feet — to accommodate amenities underneath the bridge.
“We’ve placed stone armor protection under the bridge at the edge of the waterline to improve the public’s connection between land and water,” Summers said.
| Your local Hyundai dealer |
|---|
| Equipment East |
Beneath the bridge is the Ann and Roy Butler Hike-and-Bike Trail. According to the Austin Parks and Recreation website, the park/10-mile trail draws over “2.6 million visits a year ... [and] is Austin’s most recognized and popular recreational area.”
The project will enhance the space beneath the structure to maintain and improve connectivity within the park. The scope includes adding stone blocks that will serve as seating areas, adding picnic tables and a colored pathway, improving connectivity to the new pedestrian bridges across Lady Bird Lake, and repositioning a parking lot.
“We had to take that into account — the impact we had on the park,” Summers said.
Working above a popular park that draws thousands of visitors a day means the team needs to minimize impact on the trail and the waterway, which draws many recreational users.
| Your local Volvo Construction Equipment dealer |
|---|
| Tyler Equipment |
“We have limited times in which we can work over those areas, so we have to make sure we’re working when the trail or the lake are closed so that we don't impact those users,” Jaimes said. “When we have to work while the amenities are open, we have to coordinate with park officials to make sure that we don't have any live traffic under our structures.”
“There are certain times throughout this project where we may have to close the trail for a day or two or more as we’re moving the trail by 50 feet or so,” Wheelis added. “We've tried to make accommodations so people can get through the trail.”
The bridge is being constructed on barges. TxDOT acquired land from the park so the contractor can build a temporary dock to gain access to the barges. The barges will also be used to float equipment in.
“Getting materials and people onto the barge itself is a challenge in its own right,” Jaimes said. “We have to move the barge to the dock area, which is located on the northwest corner of the project. The contractor also has their own boats that they use to move crew to and from the water.”
| Your local Trimble Construction Division dealer |
|---|
| SITECH Northeast |
Not all the barges are the same.
“They are segmented differently depending upon their use, to make sure that we can accommodate it in the existing working area but also that they're functional for the ultimate use,” Jaimes said.
Currently, the team is using barges for drilling operations, crane work, and equipment transport.
Maintaining access and mobility is an issue for the road and bridge, not just the waterway and park.
| Your local Esco Corporation dealer |
|---|
| Genalco |
“We can't just go in there and shut down that entire bridge as a whole, as that would create a major disturbance,” Jaimes said.
The team needs to ensure that traffic has 24-hour access in both directions. The challenge is compounded by the limited right of way in the area. The northbound frontage road has been removed, requiring a bypass on the east side to maintain northbound mobility.
At Riverside Drive on the southern end of the project, the team is building a single-point urban interchange (SPUI). Riverside Drive SPUI will move vehicles more efficiently and accommodate Austin’s future light rail, helping to integrate CapEx Central with Project Connect.
The team is also building many tunnels in the same vicinity for relocated utilities. They are using micro-tunneling, an advanced trenchless construction technique that allows utilities to be installed underground with minimal impacts to traffic, nearby businesses, and the surrounding community.
| Your local Case Construction Equipment Inc dealer |
|---|
| Beauregard Equipment |
| Monroe Tractor |
“After the team digs a hole, they drop in the equipment and it tunnels through the ground to create an opening for a pipe,” Summers said. “The equipment is controlled remotely by people who are above ground, and no one is in the tunnel while the boring is taking place.”
Construction on this project segment began in early 2025 and is scheduled to conclude in 2033. While the team is very early on in the project, it is currently on schedule.
The budget for this segment of the project is $765 million. This includes $620 million for highway construction and approximately $145 million for utilities. At this early stage, the project is on budget.
When the Lady Bird Lake section of the CapEx project is complete, drivers will experience increased capacity and the usual delays will be minimized. Pedestrians and cyclists will have greater access in and around the area.
| Your local Case Construction Equipment Inc dealer |
|---|
| Beauregard Equipment |
| Monroe Tractor |
- Owner: Texas Department of Transportation
- General Contractor: Balfour Beatty, Dallas, Texas
- Designer: WSP USA Inc., New York, New York
- Engineer: RS&H Inc., New York, New York
