SIOUX FALLS, S.D. (KELO) — The Sioux Falls 41st Street interchange with Interstate 29 is already one of the busiest in South Dakota.

Now a major reset is coming. Officials hope that reconfiguring the 41st Street interchange as a diverging diamond will improve traffic flow, especially to and from the ever-busier west side.

The project is scheduled for a December 15 bid-letting. Work would start next year, substantially wrap up in 2023 and finish in 2024.

When it’s done, motorists will get a third through-lane on 41st Street from I-29 all the way west to Marion Road. The intersection of 41st and Marion will be widened, too.

However, on the east side of I-29, the Carolyn Avenue intersection with 41st Street will close.

The plan to take down the stop sign and make Carolyn Avenue a cul de sac has stirred up some local business people.

The future of a diverging diamond at the 41st Street interchange with I-29

Fifty-six landowners would be affected along the project. The rough cost is estimated at more than $40.4 million, with the federal government expected to provide more than $31.8 million, according to the South Dakota Department of Transportation annual construction plan approved earlier this year.

A 2010 corridor study identified the need for the project. The state department and the City of Sioux Falls are leading on it.

South Dakota’s first diverging diamond interchange is under construction at Lacrosse Street and I-90 in Rapid City. Three more are planned in the Sioux Falls area in the coming years — Benson Road and I-29, 85th Street and I-29, and the Brandon exit on I-90.

The diverging diamond design, in other parts of the United States, has been found to be safer than turning left across traffic moving the opposite direction.

Craig Smith is director of operations for SDDOT. He told KELOLAND News that a video will be posted online showing the construction sequence and potential landscape treatments. A public meeting will be held late this winter or early spring in 2022 after the construction plan is worked out with the contractor.

“We typically anticipate work to start around April 1 and go into early to mid-November each construction season,” Smith told KELOLAND News.

“Traffic on 41st Street will be maintained with one lane in each direction. Meadow Avenue to Shirley Avenue will be constructed in 2022, which will include the interchange, and then from Meadow Avenue to Marion Road will be constructed in 2023,” he continued. “The ramps at I-29 will be closed for extended periods in 2022. We are expecting significant delays and congestion.”

For a closer look at the plan:

Project website

2017 report