TxDOT's $4.5 billion Interstate 35 Capital Express Central Project in Austin aims to transform the city by upgrading roadways, bridges, and pedestrian paths. With six phases planned until 2033, the project focuses on enhancing safety, managing congestion, and creating a reliable route for all travelers.
Photo courtesy of the Texas Department of Transportation
A rendering of the Lady Bird Lake East Pedestrian Bridge.
The Texas Department of Transportation (TxDOT) recently began work on the $4.5 billion Interstate 35 Capital Express Central Project in Austin, the third segment of the transformational project to renovate and upgrade that metropolitan area.
The central section, approximately 8 mi., covers the area between U.S. 290 East and State Highway 71/Ben White Boulevard. The project is being funded by TxDOT and the Capital Area Metropolitan Planning Organization. Crews started work earlier in October, with project completion expected in 2033.
Improvements include removing the existing I-35 decks, lowering the roadway and adding two non-tolled high-occupancy vehicle-managed lanes in each direction along I-35 from U.S. 290 East to SH 71. The project also will reconstruct east-west cross-street bridges, add pedestrian and bicycle paths, and make additional safety and mobility improvements within the project limits.
The initiative has the goal of improving, according to the TxDOT project page, "this critical regional, national and international thoroughfare by enhancing safety, managing congestion, improving operations, and creating a more dependable and consistent route for the traveling public, including bicyclists and pedestrians, emergency responders and transit."
This project is divided into six phases.
Photo courtesy of the Texas Department of Transportation
A rendering of the Martin Luther King Jr. Bridge.
The Martin Luther King Bridge will be delivered in 2026 by Harper Brothers Construction LLC, and the Lady Bird Lake (Holly Street to U.S. 290/SH 71 is expected to begin in mid-2025 and be finished in 2031 by Balfour Beatty.
The drainage tunnel under I-35 and Cesar Chavez Street will start next year and be completed by 2028, while the CapMetro/Red Line Bridges (Airport and 4th Street) will start in 2026 and be completed in 2029. The final phases begin in 2027 — the Downtown section (MLK Boulevard to Holly Street) will be completed in 2033 and the University section (U.S. 290 East to MLK Boulevard) will be done in 2032.
In addition, the project is lowering sections of managed and main lanes through portions of the impacted area. That includes removing the upper decks on I-35 (between Airport Boulevard and MLK Boulevard); lowering I-35 through downtown (between MLK Boulevard and Holly Street); and reconstructing the bridge across Lady Bird Lake.
Project planning dates to the 1980s on the impacted stretch of I-35, which handles roughly 200,000 vehicles daily.
The environmental study and schematic design were completed between 2020 and 2023, and final design and procurement finished between 2023 and 2024. The project was designed by AECOM, HDR, HNTB, Jacobs, Volkert Inc. and WSP.
"One of the major design challenges of the Central project was the constrained corridor of downtown Austin," said Jeff Barker, a TxDOT public information officer. "TxDOT designed and revised schematics to limit right-of-way impacts and reduce those that were initially proposed. To overcome such a challenge, TxDOT designers found ways to use vertical space under frontage roads and avoid extensive acquisition.
"As the team began planning for construction, the challenge shifted to how crews could maintain traffic levels and access during construction," he added. ‘The Central corridor serves multiple means of transportation, including vehicles, buses, trains, bicycles and pedestrians."
Barker added that infrastructure lifespans vary based on multiple factors, including usage, weather and damage.
Barker said that TxDOT has worked closely with both the city of Austin and the University of Texas (UT) on the conceptual design of deck caps and stitches along the project corridor, with the city and UT funding operations and maintenance of these enhancements throughout the project's life. TxDOT will be responsible for building the infrastructure and implementing fire suppression requirements during construction.
As for cycling and pedestrian improvements, the plan is to build more than 19 mi. of new shared-use paths, create vehicle bypass lanes to reduce through traffic at 28 intersections, establish 13 connections to the urban trail and bicycle networks, widen and enhance existing east-west crossings, and construct new bicycle-pedestrian crossings at Fourth Street, 51st Street, Red Line at Airport Boulevard, Lady Bird Lake, Third Street, 15th Street and 41st Street.
Pavement designs for the new feature are "under development with both concrete and asphalt options being evaluated."
This project is in its early stages.
"The early work has been related to utility relocation, retaining wall work, as well as curb work at the southwest corner of MLK Boulevard and along the southbound frontage road," Barker said. "The most significant work will begin in early 2025, beginning with the closure and reconstruction of the north side of the bridge."
To prepare the construction site, TxDOT began the acquisition and demolition process early to ensure that all properties were cleared before general contractor crews arrived.
At 3807 N. Interstate 35 (formally Gulf Gas), 3735 N. Interstate 35 (formally Chevron), 3828 N. Interstate 35 (formally Shell) and 3810 N. Interstate 35 (formally Dura Tune Inc.), petroleum storage tanks were removed last November. Soils are being tested for contamination.
The underground infrastructure will include a drainage tunnel installation.
"The drainage tunnel and pump station segment will enhance water treatment in Austin," according to the TxDOT project web page. "This segment will collect, move and treat water to accommodate the lowered I-35 main lanes, while benefiting the greater community."
To build the concrete tunnel, a tunnel boring machine will cut through rock. Drop shafts will be constructed along I-35 during the construction of the tunnel segment to provide locations for dirt and debris to be removed and provide a point for maintenance access post-construction. The drop shafts will likely be built with jackhammers and excavators.
The University segment is between U.S. 290 East and Martin Luther King Jr. Boulevard. It will add two high-occupancy-vehicle (HOV) managed lanes in both directions along I-35. In addition, the project will reconstruct east-west crossings (bridges) at: Manor Road, Dean Keeton Street, 32nd Street, 38½ Street and Wilshire Boulevard, and reconstruct the Airport Boulevard intersection and add a pedestrian-only bridge at Capital Plaza.
"The removal of the upper decks is anticipated to begin in 2027 and is expected to be complete by 2032," according to the project page.
As operations progress, the number of Harper Brothers and subcontractor personnel will increase. The general contractor has hired many local and regional subcontracting firms.
And as work ramps up, so will the amount of materials delivered to the various sites. Demolition and excavation operations will generate large amounts of concrete, asphalt and rebar, as well as pipes for underground infrastructure.
Recycling material is an important aspect.
"Once excavated from the project site, TxDOT works with the community to identify locations that the dirt can be repurposed for development and/or environmentally approved green fields," the project web page said.
Standard equipment such as cranes, excavators, dozers, loaders, motor graders and manlifts will be on-site.
Harper Brothers mechanics will take care of routine equipment maintenance. The company buys and rents equipment from a variety of dealers. CEG
Irwin Rapoport
A journalist who started his career at a weekly community newspaper, Irwin Rapoport has written about construction and architecture for more than 15 years, as well as a variety of other subjects, such as recycling, environmental issues, business supply chains, property development, pulp and paper, agriculture, solar power and energy, and education. Getting the story right and illustrating the hard work and professionalism that goes into completing road, bridge, and building projects is important to him. A key element of his construction articles is to provide readers with an opportunity to see how general contractors and departments of transportation complete their projects and address challenges so that lessons learned can be shared with a wider audience.
Rapoport has a BA in History and a Minor in Political Science from Concordia University. His hobbies include hiking, birding, cycling, reading, going to concerts and plays, hanging out with friends and family, and architecture. He is keen to one day write an MA thesis on military and economic planning by the Great Powers prior to the start of the First World War.
Read more from Irwin Rapoport here.
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