Twin Ports Interchange


  • LocationDuluth, MN and Superior, WI
  • ClientMnDOT
  • Category Transportation


MnDOT commissioned Alliant for the Preliminary Design of Twin Ports Interchange (TPI) in November of 2016. The TPI project is the reconstruction of the interchange of I-535 and US 53 with I-35. The project’s estimated construction cost is $250 – $270 million and is scheduled for construction from 2020 – 2022. The interchange is an integral resource to the community and carries a high number of commuter traffic between Duluth, MN, and Superior, WI. The interchange is also the “last mile” for significant freight traffic at the Ports of Duluth and Superior. The port also carries a significant number of oversized and overweight loads.

Alliant was originally selected by MnDOT to perform the Preliminary Engineering and development of the Staff Approved Layout for the project. As part of that effort, the Traffic Group performed extensive traffic operations and crash analyses and authored several reports and technical memoranda. Our Survey Department conducted extensive surveying, especially high accuracy total station work within the BNSF rail yard. Alliant’s Landscape Architects prepared several renderings and visualizations for public meetings. Our Structures Group developed 3D bridge models, a first for Alliant, of the existing interchange to aid in construction staging alternatives analysis.

Alliant is a key member of the team being headed by S.E.H. and includes TKDA, American Engineering Test (AET), Isthmus Engineering, Rani Engineering and UMS to design the interchange. Alliant’s scope of work includes fulfilling the Roadway Design Lead for the project, final design of Segment 1 which is the main interchange and all Interstate work, fulfilling the Maintenance of Traffic (MOT) Design Lead for the project, all MOT and traffic control design, and all Intelligent Transportation System (ITS) design for the project.


  • Preliminary and Final Design
  • ITS Design
  • Maintenance of Traffic
  • Land Survey
  • Traffic Operations Analysis


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