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:
Aug. 7, 2026:
On Monday, Aug. 10, 2026, the southbound lanes of Interstate 229 will be closed from 10 p.m. to 3 a.m. on Tuesday, Aug. 11, 2026, at mile marker 0, the south end of I-229, in Sioux Falls. The closure is needed to move a crane.
Detour Route:
Southbound I 229 traffic will be directed to northbound I 29 at exit 77 (41st Street), then routed back to southbound I 29. Drivers are advised to follow all posted signs and arrows through the work zone.
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Aug. 5, 2026:
Temporary Closure Planned:
Interstate 229 southbound to Interstate 29 southbound will be closed nightly beginning on the evening of Tuesday, Aug. 11, 2026, through the overnight on Friday, Aug. 14, 2026, in Sioux Falls. The temporary closure is necessary for the planned girder placement of the bridge over Interstate 229.
Temporary Closure Times:
Each overnight closure will begin at 8 p.m.
Traffic will be restored by 6 a.m. each of the following mornings.
Detour Route:
Southbound I‑229 traffic will be directed to northbound I‑29 at exit 77 (41st Street), then routed back to southbound I‑29.
Drivers are advised to follow all posted signs and arrows through the work zone.
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July 23, 2026:
Anticipated Work in August 2026: The contractor will construct the bent cap at the 85th Street and Interstate 29 structure. They will place gravel on the 85th Street and northbound I-29 on- and off-ramps. The contractor will also grade 85th Street west of I-29.
Completed Work in July 2026: The contractor is ready to place gravel on the northbound Interstate 29 on- and off-ramps at 85th Street. They have constructed the bent 2 footings and columns for the 85th Street and I-29 structure. The contractor is grading 85th Street west of I-29, and they are constructing the abutments for the bridge over Interstate 229.
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July 15, 2026:
On Thursday, July 16, 2026, the southbound lanes of Interstate 229 will be closed from 12–3 a.m. at mile marker 0, the south end of I-229, in Sioux Falls to move a crane.
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July 10, 2026:
On Wednesday, July 15, 2026, the southbound lanes of Interstate 229 will be closed during the overnight from 12–3 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 I-29. Drivers should follow posted signs and arrows through the work area.
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June 30, 2026:
Anticipated Work in July 2026:
The contractor will continue grading 85th Street east and west of Interstate 29.
The contractor will drive piling for the south footing of Bent No. 2 at the 85th Street and Interstate 29 interchange.
The contractor will form, install reinforcing steel and place concrete for the center and north footings of Bent No. 2 at the 85th Street and Interstate 29 interchange.
View 85th Street updates on the City of Sioux Falls website: I-29 & 85th Street Interchange - City of Sioux Falls