I-29 & 85th Street Interchange

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

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: 04/01/2026

• The contractor is installing watermain along 85th Street between Tallgrass Avenue and Sundowner Avenue.
• Work is underway on grading, pile installation, and bridge abutments for the southbound exit ramps.
• Installation of geofoam is scheduled to begin on March 30, 2026.

Commuter Route Information

• 85^th Street from Tallgrass Avenue to Sundowner Avenue is closed to traffic. Access is maintained for local residents only.

• I-29 traffic to remain in place during construction. Lane/shoulder closures will be allowed for work adjacent to existing lanes.

• Partial closures of I-29 will be allowed overnight for bridge or MSE wall construction.

Additional Information

Project Milestones

Year 1 - Phase 1A

1. Traffic Control
2. Removals
3. Watermain
4. Grading
5. Geofoam Over L&C Watermain
6. Bridge Abutment
7. Bridge Pier
8. Grading Pumps

Year 1 - Phase 1B

1. Grading Bridge Abutment
2. Geofoam Over L&C Watermain
3. MSE Wall
4. Grading Pumps

Year 1 - Phase 1C

1. Final Grading
2. I229 Grade Widening at Ramp 1C
3. Excavation for Ramp 1C

Year 2 - Phase 2A

1. Ramp Paving
2. Bridge Construction
3. Storm Sewer

Year 2 - Phase 2B

1. Graveling
2. Curb and Gutter
3. Concrete Surfacing

Year 2 - Phase 2C

1. Lighting
2. Decorative Landscaping
3. Pavement Markings
4. Restoration
5. Open to Traffic

Construction Images

A crew placing blue watermain pipe into a trench to be installed.

85^th Street – east side of interstate

A long conveyor belt is moving and piling gravel into a mound, while a bulldozer is spreading and leveling. Additional excavators, rock crushers, and haul trucks are in operation across the site, processing materials for construction.

Image Gallery