Southern Gateway Reconstruction Reducing Congestion for North Texas Drivers

When the much-needed overhaul of the Dallas Horseshoe interchange reached substantial completion in 2017, it marked a critical first step toward improving traffic flow and simplifying an oft-confusing maze of roadways in the heart of the North Texas city.

But there was more work to be done. Now, with the official completion of the adjacent Southern Gateway, the Texas Department of Transportation’s (TxDOT) vision of a less congested, more cohesive highway network is finally a reality for motorists who have long tangled with frustrating traffic delays in this region.

The $666 million Southern Gateway design-build reconstruction and improvement project spans 10 total miles of roadway in Dallas County, including five miles of Interstate 35E from Colorado Boulevard to south of the I-35E/U.S. Route 67 interchange, and five miles of U.S. 67 from the interchange to Interstate 20. This project is designed to improve severe traffic congestion in the North Texas region, as the corridor is considered one of the most congested roadway segments in the state, with 218,000 vehicles daily.

WSP USA served as the lead designer for both improvement projects.

As the Dallas Horseshoe was nearing completion in 2017, TxDOT returned to the same team for the Southern Gateway design-build contract and selected Pegasus Link Constructors (PLC), a joint venture of Fluor Enterprises and Balfour Beatty.  WSP continued as the lead designer for PLC, providing roadway, drainage, bridge, retaining wall, traffic, hydraulic/hydrology, maintenance of traffic and geotechnical engineering.

“Southern Gateway represents another successful partnership between WSP and PLC, and a boon for motorists in North Texas,” said Bob Brown, the WSP local business line leader for Transportation who served as principal-in-charge for both projects.

Substantial completion for the project occurred in September of 2022, and a ribbon cutting event to celebrate the milestone was held on Nov. 30.

The project expanded I-35E from four lanes to five lanes in each direction. The I-35E and U.S. 67 interchange also was rebuilt, and U.S. 67 widened from I-35 E and I-20, with a third lane added in each direction. The project included a total of 37 new bridges and bridge widenings, and condition assessments and rehabilitation plans for 19 existing bridges.

One of the project’s biggest challenges — and likely the biggest challenge of any urban freeway construction project in Texas to date — was maintaining the hilly corridor’s high volume of traffic with virtually no additional right of way (ROW) and keeping eight lanes of freeway to traffic each day.

“The project team introduced an alternative technical concept alternately phasing two cross streets and providing an innovative traffic plan for this cross-street traffic,” said Fernando Cruz, roadway lead for WSP. “With these detours, the team was able to provide adequate workspace for the contractor, minimize lane closures and help the design-build contractor avoid lane rental fees.”

The project also included the design and phase one construction of a deck park bridge (the Southern Gateway Public Green) over the I-35E mainlines, extending from Ewing Avenue to Marsalis Avenue and adjacent to the Dallas Zoo. The Southern Gateway Deck Park will serve as a 5.8-acre public park once future surface facilities and amenities are constructed by the City of Dallas. 

The design process started with determining the design loadings for the structure, based on the preliminary landscape plan prepared by the City of Dallas.

“Instead of designing the structure with a conservative uniform load for the entire bridge, our approach was to design the bridge with six different loading zones,” said Becky Fly, WSP design manager for the project. “The team then prepared a design loading plan to show various loading zones, with trees and trees with berms as the controlling load cases.”

Construction of the deck park bridge is being split between phases one and two, and construction for both phases is included in the project’s scope.

“Now that the Southern Gateway is complete and open to traffic, congestion has virtually disappeared, and along with the addition of soundwalls and soon the construction of the Southern Gateway Public Green, this project will serve as a model to improve the quality of life around our urban freeways,” Brown said.

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