Interstate 90 - Exit 406 (Brandon)

Project Summary:

This project includes the reconstruction of exit 406 (Brandon) with added lighting, signals, and mainline Interstate work. This project also includes three structure replacements.

The interchange will be reconstructed as a diverging diamond configuration.
Westbound Interstate 90 lanes (along with the railroad structure on I90) will be reconstructed in 2024 and the eastbound lanes (and railroad structure in 2025). The interchange itself and new structure over I90 will be reconstructed between 2024 and 2025.
S.D. Highway 11 traffic will be maintained across Interstate 90 during construction.
The westbound on-ramp and eastbound off-ramp are expected to be open to traffic for the majority of the project. Closures for the westbound off-ramp and eastbound on-ramp are planned for 2025.
Work will extend on S.D. Highway 11 down to Redwood Boulevard. That work includes adding a shared use path on the west side, approach and side street work, a retaining wall on the east side north of Ash St, and other items.

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Project Timeline:

Spring 2024 - Overall Completion Date: June 2026

Minor clean-up work to be completed in 2026

Project Updates:

Sept. 17, 2025:

Aug. 15 – Sept. 15, 2025, Completed Work:
On the eastbound railroad bridge, girders were set and abutments were built. Berm grading, rock placement, and drainage features were completed, along with the falsework required for rebar and deck placement.

At the exit, traffic was switched, and curb and gutter work around the DDI islands was completed. All pavement in and out of the exit is now finished, both on top of and beneath the exit bridge.

Anticipated Work Sept. 15 – Oct. 15, 2025:
Lighting, signals, and sidewalk signs are expected to be completed and functioning along northbound and southbound State Highway 11. Most or all island pavement should be completed, and permanent pavement markings will begin to be placed. Ash Street signals are expected to become fully functional, and installation of additional right-of-way fencing will begin.

On the eastbound railroad bridge, the deck pour is scheduled, along with portions of the bridge barrier curb. Grading up to the structure will also be underway. Another section of eastbound mainline paving may also be completed.

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Aug. 25, 2025:

On Tuesday, Sept. 2, 2025, a traffic switch is scheduled to take place on the Interstate 90 exit 406 (Brandon) Diverging Diamond Interchange (DDI) project. Traffic will be switched onto the newly constructed bridge in a single lane DDI traffic configuration.

Temporary pavement markings and stop signs will be used to guide motorists through the area while traffic signals are being installed. Traffic signals are anticipated to be installed and functioning by Friday, Nov. 21, 2025.