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:
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.
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March 10, 2026:
On Wednesday, March 11, 2026, the southbound lanes of Interstate 229 will be closed during the overnight from 1–4 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 10, 2026:
SDDOT and City of Sioux Falls project staff will hold a public information meeting on Thursday, March 19, 2026, at 5 p.m. at Sioux Falls Lutheran School located at 6715 S Boe Ln. in Sioux Falls. The meeting will inform the public on the Interstate 29 and 85th Street Interchange construction project in Sioux Falls. The meeting will be informal, with one-on-one discussion with SDDOT and City of Sioux Falls staff, along with displays to discuss the proposed construction project and answer questions.
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.
View 85th Street updates on the City of Sioux Falls website: I-29 & 85th Street Interchange - City of Sioux Falls