I-29 & 85th Street Interchange

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

The City of Sioux Falls, City of Tea, Lincoln County, and the South Dakota Department of Transportation (SDDOT) have cooperatively worked together to finalize the plans for the new diverging diamond interchange at 85th Street and I-29. 

Construction for this interchange is planned to begin late 2025, with construction anticipated to be complete by fall of 2027. This webpage will provide immediate updates as projects along the corridor get underway. 

Project Update: 10/31/2025

• We are currently working on awarding the contract to T&R Contracting, Inc.
• The project scope includes the construction of the interchange along with underground utility installation, a pedestrian underpass, grading, concrete surfacing, signage, street lighting, and traffic signals.
• Construction is anticipated to begin either late 2025 or early 2026, weather permitting, and reach completion by early 2027.

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.
• 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.

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