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:

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.

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Aug. 20, 2025:

Beginning at 8 p.m. on Monday Aug. 25, 2025, eastbound and westbound lanes of Interstate 90 will be temporarily closed to divert traffic through the on- and off-ramps at exit 406 at Brandon. This traffic diversion will be maintained through the overnight until 7 a.m. on Tuesday, Aug. 26, 2025. This traffic pattern switch is scheduled to remove deck forms from the exit bridge.

Traffic on S.D. Highway 11 will be maintained during this overnight traffic diversion. Flaggers will be posted to guide Highway 11 traffic as Interstate traffic will not be stopped.

Dates for the traffic diversion are weather dependent and may be rescheduled as needed.

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Aug. 15, 2025:

July 15–Aug. 15, 2025, Completed work: Crews finished the columns at the railroad structure and completed grading along the railroad tracks. The bridge deck and approach slabs on the exit structure are complete, and eastbound traffic has shifted to a second temporary off-ramp. East of the exit structure, most topsoil has been placed along with seeding, mulching, and erosion control. Additional lighting was installed and is functioning at night. Sidewalk and curb work was also completed on the north end of S.D. Highway 11.

Anticipated work Aug. 15–Sept. 15, 2025: At the railroad structure, crews expect to finish both abutments and set the bridge girders. Most falsework should be completed, along with bridge berm rock and fabric. At the exit, crews anticipate completing bridge barriers, pavement tie-ins, and portions of the islands by Sept. 15, 2025. Installation of some signal posts for the diverging diamond is also expected. Grading will be finished through the previous eastbound off-ramp crossover, along with additional off-ramp paving.