I-29 & 85th Street Interchange

Project value$54,443,975
Contractor nameT&R Contracting
Completion DateDecember 31, 2027

Concept image of the 85th I29 Intechange

The City of Sioux Falls, in conjunction with the City of Tea, Lincoln County, and the SDDOT, has started constructing the new diverging diamond interchange at 85th Street and I-29.

The project includes building the interchange and installing underground utilities, a pedestrian underpass, grading, concrete surfacing, signage, street lighting and traffic signals.

Project Update: 08/31/2026

Contractors completed installing the girders for the southbound I‑29 off-ramp bridge over I-229.
Grading operations are active on the ramps and bridge approaches on both the east and west sides of I‑29.
Bridge piling work is underway on the east side of I‑29, with piling on the west side expected to begin in the coming weeks.
Crews will relocate the Lewis & Clark hydrant on the west side, shifting the hydrant line south to accommodate planned construction activities.
A concrete deck pour for the southbound I‑29 off-ramp bridge over I-229 is planned for mid‑September

Commuter Route Information

85^th Street from Tallgrass Avenue to Sundowner Avenue will be closed to traffic. Access will be maintained for local residents only.
I29 traffic will remain in place during construction. Lane/shoulder closures will be allowed for work adjacent to existing lanes.
Partial closures of I29 will be allowed overnight for bridge or MSE wall construction.