The Minnesota Department of Transportation (MnDOT) is overseeing a project that replaces two I-90 bridges and builds a new flyover bridge at Hwy 52 southeast of Rochester. The work is needed because the bridges are nearing the end of their lifespans.

"It originally started out as a bridge redecking for the Interstate 90 bridges over Highway 52, but as it was reviewed further, it evolved into a bridge replacement," said Mike Dougherty, District 6 director of communications and public engagement. "There was additional feedback from the freight community, so more scoping and review was done, which eventually saw the need for improved safety."

Mathiowetz Construction Inc. of Sleepy Eye, Minn., serves as contractor on the $27.5 million effort. Dougherty said the work can be challenging, but crews are committed to completing the job.

"We're entering year two of a three-year project, so while there were some notable changes in the landscape, the next two years will bring improvements of the ramps, as well as the lengthening of the I-90 bridges and the flyover ramp, which should significantly improve safety. The flyover ramp, which represents a left turn from southbound Hwy 52 to eastbound I-90, accounts for 92 percent of the left turns."

According to MnDOT project engineer Nick Maki, bridge demolition and construction detour coordination are the main challenges on the project.

"MnDOT wants to give the public as much notice as possible for short-term closures of Hwy 52 and the eastbound I-90 on-ramp; however, any small delay, weather or construction-related, can change closure dates. MnDOT, the prime contractor and the subcontractors will need to prioritize communication and transparency to ensure accurate closure dates."

In replacing the I-90 bridges over Highway 52, I-90 will be reduced to two-lane, two-way traffic.

"The major milestones of bridge replacement start with the bridge demolition, then the construction of the abutment and piers. This includes an estimated minimum waiting period of seven to eight weeks for a soil surcharge to compress the soil, to reduce settlement of the bridge, excavation and driving piling for foundation support.

"The next step is setting beams and placing falsework to prepare for the bridge deck pour. Hwy 52 lane shifts during construction will allow traffic to remain open and not detoured as long as possible. After the deck pour, the concrete rail is poured. The final steps are all clean-up work, bridge paint, pavement markings, guardrail, etc. The eastbound bridge is scheduled to be replaced in 2025, and westbound is scheduled to be replaced in 2026."

Crews worked on the west abutment and west retaining wall for the new flyover bridge during November and December 2024. This involved excavation; a seven-week waiting period on the surcharge; a large spread footing under the abutment and retaining wall (used for foundation support in lieu of piling); and multiple concrete pours for the abutment and retaining wall. The next step will be to construct the east abutment.

Crews have already placed the new 60-in. storm sewer underneath Hwy 52. A box culvert underneath will be the new eastbound I-90 on-ramp. Grading for the westbound I-90 on-ramp acceleration lane length increase has been completed, as well as construction of three traffic crossovers areas (two on I-90 and one on Hwy 52) and the west abutment and retaining wall. Most of the grading work for the new eastbound I-90 on-ramp also has been finished.

Maki noted that construction of the new ramps and loops will allow for safer turning movements and better design speeds.

"The westbound I-90 off-ramp onto northbound Hwy 52 will be realigned, featuring a gradual curve by moving the new alignment toward the northeast. The loop ramps will feature longer curves, which will reduce their sharpness."

Work on the flyover bridge, eastbound I-90 bridge, eastbound I-90 off-ramp construction and the remaining southwest quadrant grading work are expected to start in early to mid-April.

The westbound I-90 off-ramp to northbound Hwy 52 ramp and the westbound I-90 bridge construction will begin in April 2026. Some ramp work may start during the fall 2025. The flyover bridge is scheduled to open to traffic during mid-summer 2026.

Maki said the main concerns when performing an interchange reconstruction project are the safety of the workers and the traveling public.

"Interchange projects involve a large volume of motorists. Traffic control needs to be monitored and maintained to ensure everyone's safety. It's also essential to ensure the traffic control is functioning properly to minimize traffic congestion and allow people to get where they need to go, without causing too large of a disturbance.

"Crews have been handling detours and traffic well. So far, we've only had one five-day detour. We did have some issues with drivers missing the detour that used Hwy 63 and then used the maintenance crossovers. Using maintenance crossovers is not only illegal for the traveling public, but it's also a crash hazard. We are adding additional detour signage when the eastbound I-90 on-ramp has short closures and will be looking into extra enforcement in the area."

From April to November of this year, construction includes a Hwy 52 detour south of the interchange. Because it's been used in the past, it's familiar to motorists who use the road regularly. Other short-term details are planned during bridge demolition, beam setting and bridge deck work. Some ramps are also closed, but they do not see high traffic volumes.

Excavation involves approximately 280,000 cu. yds. of dirt, with 275,000 cu. yds. of material placed for embankment. Workers are using excavators, cranes, dump trucks, skid steers and bulldozers to perform the various tasks required, with main materials including concrete and rebar for bridge construction. Bituminous, sand and rock/aggregate also are necessary for ramp realignment and grading work.

Maki said the elements can be an issue for crews, especially when they're working on a grading project with poor soils that hold a lot of water.

"If we receive a wet spring or summer, the contractor cannot effectively perform their grading work. This can lead to delays in the project's completion date. Wet weather plays a key role in project delays in the fall, when cold weather doesn't allow the ground to dry out due to the lack of sun and colder temperatures."

For Maki and the rest of the team, playing a role in the project is extremely satisfying.

"The Minnesota Department of Transportation and the contractor take pride in the work we do. We want to ensure we provide the traveling public with the best product we can with what we have available.

"This project will decrease crashes, improve turning movements and create a safer interchange at a location that sees heavy commuter traffic to and from Rochester to the Mayo Clinic, as well as robust freight traffic traveling east on I-90 or north on Highway 52 toward Minneapolis and St. Paul." CEG