Sioux Falls construction to begin on Benson Road, I-229 diverging diamond. Here's what to know

Construction starts next week on the Benson Road-Interstate-229 interchange in northeast Sioux Falls. The roadway will be reconfigured into the state’s third diverging diamond, and it will feature the city’s first triple left turn lane when complete.

Sioux Falls drivers should expect added commute times and consider alternate routes during construction. Here's everything you need to know about the project:

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When is construction starting on the diverging diamond?

Officials with HDR Engineering, the engineering company behind the project, said construction will start on Monday. The city has also partnered with the South Dakota Department of Transportation on this project, and T&R Contracting is the local contractor.

Construction will consists of three phases during a two-year period. The first part of phase one will wrap up by the end of 2023 before crews start on the second part next spring. The entire project is set to be completed by the end of November 2024.

What will the end project look like in Sioux Falls?

The project will stretch along Benson Road about 1.5 miles from Lewis Avenue to the Sioux Falls Area Humane Society.

Benson Road will become a six-lane road west of I-229 with a concrete median divider that ends at Lewis Avenue. It will then feature a four-lane split road east of 1-229, which will help the city "prepare for future development," HDR project manager Lee Kaffar said.

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The northbound off-ramp toward Benson will feature three left-turn lanes heading west and a right-turn lane toward the Humane Society. Benson’s three eastbound lanes will split into four at the interchange, with two lanes taking the off-ramp exit southbound on the interstate.

There will also be two sidewalks on the outside of the diamond. This is different from the diverging diamond interchange on 41st Street, where the sidewalk will be in the median of the roadway. This is because there’s more room to build on 1-229 since there aren't a lot of commercial buildings yet, Kaffar said.

Phase one of road construction to extend bridge, add westbound lanes

Phase one will begin with adding three westbound along Benson Road, which will also include extending the bridge northward and the north on- and off-ramps to I-229.

There will be one open lane of traffic in each direction on Benson, west of the interstate during construction, and Lewis Avenue and Potsdam Avenue will have alternating closures during this time.

Benson Road east of I-229 will also be closed for the duration of 2023. The only way to access the Humane Society and the Armory will be through Bahnson Avenue.

“The public should be prepared and know it’ll take a little longer on their commutes,” Jason Kjenstad, another HDR project manager, said. He added people should also consider alternate routes to work, such as taking Rice Street over to Cliff Avenue.

But there should be minimal impact on I-229 during the bridge construction as most of the supports will go in overnight over the course of a few days, Kjenstad said.

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The second part of phase one will begin in the spring of 2024 and focus on reconstruction the south side of Benson Road and extending the south I-229 on- and off- ramps.

Diverging diamond will reduce traffic, accidents

Much like the 41st Street interchange, Benson Road’s diverging diamond will help reduce accidents by reducing the points of contact between vehicles, Kaffar said.

According to him, there are between 650-700 cars making left turns at the intersection each morning as they head to work. With so much traffic, the city plans to have one right-turn lane and three left-turn lanes going westbound off I-229 to reduce congestion.

“Right now, the (northbound) exit-ramp toward Benson is built for one lane but painted for two,” Kjenstad said. “We’re going to extend that and give it the room it needs, which will help traffic tremendously.”

What else do I need to know?

HDR will also be resurfacing the bridge on 6th Street over 1-229. This will be part of phase two of the project and will not begin until 2024. Kaffar said this is a standard upkeep that happens every few years.

The total project bid was set at $36.3 million.

“People seem to be supportive of this project,” Kjenstad said. “We haven’t heard any pushback, and the landowners have been really cooperative. We’re really appreciative of that.”

Where can I find updates on the project?

The City of Sioux Falls has added a homepage for the Benson Road interchange along with other major projects being worked on this season.

Those seeking updates or additional information regarding the project can find them at the city's website. People can also sign up online to receive construction updates for specific projects.

This article originally appeared on Sioux Falls Argus Leader: Sioux Falls Benson Road, I-229 diverging diamond construction to begin