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: 05/5/2026

85^th St utilities- all the water main, hydrants, and gate valves east of I-29, including the work under I-29, have been completed except for the pressure testing.

1. The water main work on the west side can’t happen until more grading has been completed.
2. Contractor is currently installing storm sewer on the east side of the I29.
3. Ramp D grading is underway.
4. Bent footings are being placed.
5. Geofoam is being installed on ramp B.

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