Interstate 29 and 85th Street Interchange in Sioux Falls
Project Summary:
The project includes construction of a Diverging Diamond Interchange (DDI), structure development work, grading, concrete surfacing, curb and gutter, storm sewer, lighting, signals, permanent signing, and pavement marking.
Travel Impacts: Traffic will be maintained with two lanes open in each direction on I-29 during peak travel hours. Peak hours are defined as 6:30 a.m. to 9 a.m. and 3:30 p.m. to 6 p.m.
Business Access: Access will be maintained at 85th Street and Sundowner Avenue and Tall Grass Avenue.
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Project Updates:
April 22, 2026:
On Monday, April 27, 2026, a lane closure will be installed on the northbound median lane of Interstate 29 at 85th Street in Sioux Falls. Two lanes of I-29 northbound traffic will remain open to traffic. This lane closure will remain in place through November 2026. The project includes construction of a Diverging Diamond Interchange (DDI), structure development work, grading, concrete surfacing, curb and gutter, storm sewer, lighting, signals, permanent signing, and pavement marking.
Traffic Impacts:
Interstate traffic will be reduced to two lanes while operations are being conducted adjacent to the closed I-29 lane. Traffic control measures will be in place to help guide motorists through the work zone. Motorists are reminded to use caution and reduce their speed while workers and equipment are present.
Business Access:
Access will be maintained at 85th Street, Sundowner Avenue, and Tall Grass Avenue.
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April 16, 2026:
Anticipated Work - April 2026:
The contractors will continue grading the 85th Street interchange ramps for the Interstate 29 northbound on- and off-ramps and the I‑29 southbound off-ramp.
They will continue work on the Ramp D bridge over Interstate 229.
The contractor has begun building the pedestrian box culvert under 85th Street.
Crews are also grading 85th Street east of I-29.
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April 13, 2026:
On Wednesday, April 15, 2026, the southbound lanes of Interstate 229 will be closed during the overnight from 12 a.m. to 3 a.m. in Sioux Falls at mile marker 0.
Southbound I-229 traffic will be directed to northbound Interstate 29 exit 77 (41st Street) then to southbound Interstate 29. Drivers should follow posted signs and arrows through the work area.
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March 12, 2026:
On Monday, March 16, 2026, a season-long lane closure will be installed in the southbound lanes of Interstate 229 at mile marker 0. This lane closure will be placed south of the Interstate 29 northbound on-ramp. The two lanes of I-229 southbound traffic will be reduced to a single lane. This lane closure will remain in place through September 2026.
The lane closure is being placed as part of the I-29 and 85th Street interchange construction project. The intersection project includes construction of a Diverging Diamond Interchange (DDI), structure development work, grading, concrete surfacing, curb and gutter, storm sewer, lighting, signals, permanent signing, and pavement marking.
Traffic control measures will be in place to help guide motorists through the work zone. Motorists are reminded to use caution and reduce their speed while workers and equipment are present.
Business access will be maintained at 85th Street and Sundowner Avenue and Tall Grass Avenue.
View 85th Street updates on the City of Sioux Falls website: I-29 & 85th Street Interchange - City of Sioux Falls