As Mathiowetz Construction of Sleepy Eye, Minnesota, reconstructs and expands 9 miles of Highway 23 near the Chain of Lakes in central Minnesota, they have spent many months stabilizing soils. That includes removing about 200,000 cubic yards of muck using a rolling surcharge, relocating part of a stream, and placing 1.7 million cubic yards of embankment.

The $41.75 million Highway 23 North Gap project will expand the roadway from two to four lanes from Paynesville to Richmond, Minnesota. The work includes new pavement for two westbound lanes. The existing roadway will serve as eastbound lanes after crews mill, overlay, and add new shoulders. In addition, the project includes realigning and improving access at four Highway 23 intersections and realigning the highway curvature near Roscoe, Minnesota, to improve sight distance. Work began in early 2022 and will finish in fall 2023.

Funded through Minnesota’s Corridors of Commerce program, the project is designed to improve traffic flow, freight movement, and safety while encouraging business growth along the corridor.

The Highway 23 North Gap project is the first of two that will expand sections of two-lane roadway to four lanes, providing consistency along Highway 23. Currently, in the highway’s 53 miles between Willmar, Minnesota, and Interstate 94, all but approximately 16 miles have been constructed as a four-lane rural highway. The Highway 23 South Gap project from New London to Paynesville, Minnesota – bid under a separate contract – will start this spring and finish in late 2024.

In December 2021, the Minnesota Department of Transportation (MnDOT) awarded the low-bid contract for the Highway 23 North Gap project to Mathiowetz, a four-generation, family-owned business. Mathiowetz immediately started utility meetings to deal with conflicts.

Soon after, in January 2022, their subcontractor cleared and grubbed the new right-of-way, timing the work to avoid impacting a threatened species of bat.

“We had 35 acres to clear and another 500 individual trees,” said Greg Huiras, Project Manager for Mathiowetz. “It took us a good month to get all the trees down.”

They saved 75 of the trees, leaving about 10 feet of their trunks along with their root systems. Those root wads were used in the stream relocation. The remaining trees were chipped onsite and left in piles to be recycled into the project’s erosion control efforts.

Construction began in May 2022 with a full highway detour, except for local traffic. Before stopping work last fall, Mathiowetz constructed most of the new westbound lanes and put in temporary paving where needed. Traffic returned to Highway 23 in a head-to-head configuration during the winter.

Mathiowetz expects to restart construction at the beginning of May. As crews finish a few gaps in westbound lanes and reconstruct the eastbound lanes, traffic will be detoured again until the full roadway opens in October 2023.

Before crews paved the new lanes last year, Mathiowetz needed to stabilize the weak soil, especially at the east end of the project. In the first four miles, the highway winds through the Chain of Lakes and the stream crosses the roadway four times.

In addition, several pockets of muck ranging from 15 feet to more than 60 feet deep were scattered throughout the work zone, with limited right-of-way for excavation.

“There were a lot of discussions during the design phase about different ways to get the muck out,” said Mike Klasen, MnDOT’s Construction Project Manager. “We came up with rolling surcharge as the most efficient method and recommended that in the narrative of the plan.”

To complete the rolling surcharges, “We stuck the bucket of our backhoe in the muck pits and dug until the operator felt the bottom,” Huiras said. “To bring muck to the top, we used a dozer pushing in clean sand surcharging in back of it and forcing the muck up.”

That process repeated until sand replaced all the muck. Digging out a 35-foot-deep muck pit took about three weeks and required a long-reach backhoe. Mathiowetz rented a Komatsu PC390LC from Road Machinery & Supplies Co. of Savage, Minnesota.

“A lot of our backhoes only reach down about 20 feet, so we rented one that would go down as much as 45 feet,” Huiras said. “We equipped it with GPS so it could guide us to the elevations we needed to hit.”

Before digging in four of the muck pits, “We had to drive temporary sheet piling as much as 40 feet down,” Huiras said. “That held the right-of-way as we dug out the muck so we didn’t affect private property or wetlands next to it.”

Mathiowetz recycled most of the muck, hauling it to gravel pits adjacent to the right-of-way.

In some of the deeper muck pits, digging to the bottom wasn’t feasible within the available right-of-way. Instead, “They excavated to a point of roughly 30 feet, then surcharged the rest with wick drains,” Klasen said.

Piezometers then monitored water pressure underground. From September into November 2022, “The engineers read all the piezometers and gave us notice when we could add another 2-foot lift of fill on top,” Klasen said.

Some areas kept their surcharge through the winter. That includes one spot where crews didn’t remove any muck. Instead, they placed a low-weight-bearing fill composed of the recycled wood chips, put fabric over that and a sand layer as a drainage blanket, then installed wick drains extending down about 80 feet.

As part of their 2023 work, crews will remove the remaining surcharges once the ground settles and excavate down for box culvert installation.

The box culverts accommodate the four stream crossings within the project limits. In one of those spots, the expanded highway footprint interfered with the existing curve of the stream, so crews dug a new channel about 150 feet away.

The new stream embankment includes the root wads saved from tree clearing. “We dug trenches along the banks and embedded the logs in the soil, then backfilled them,” Huiras said. “The root balls hang out into the stream to provide a natural setting for fish to hide, and they also prevent erosion.”

In addition, crews installed ditch checks to create water pools where fish can rest and a couple thousand live-stake plantings for erosion control.

For the live-stake plantings, “They took the branches off willow trees,” Klasen explained. “The sticks are no more than 3/8-inch thick and about 12 inches long. They cut them at an angle, placed them in the ground, and eventually they’ll grow.”

With all the work required to stabilize soils and prepare for paving, “Staying on schedule was the hardest part,” Huiras said. “We have a lot of subs on the job and we have to keep them going with us. Last year we put in a lot of overtime. The schedule is based off a six-day workweek, and we didn’t have many Saturdays off.”

Unexpected weather didn’t help.

“We started the job in the spring with a lot of the work involving the stream realignment,” Huiras said. “In May we were hit with about 6.5 inches of rain in a day and a half. All the lakes went up to record levels and there was water running where people said they had never seen water running before.”

That halted work for a few days until the water receded. Luckily, “It didn’t do a lot of damage – just minor repairs,” Huiras said.

In 2022, Mathiowetz and their subcontractors completed most of the project’s drainage work and grading, as well as paving on the new westbound lanes. In the coming year, crews will remove surcharges, install the last box culverts, finish grading, and pave the rest of the highway.

“We did the toughest work in the first year and the job is set up now,” Huiras said.

• Owner – Minnesota Department of Transportation; Mike Klasen, Construction Project Manager; Jim Blackmore, Chief Inspector
• General Contractor – Mathiowetz Construction, Sleepy Eye, Minnesota; Greg Huiras, Project Manager; Andy Huiras and Jared Kadelbach, Project Superintendents
• Paving Subcontractor – Knife River, St. Cloud, Minnesota; Jay Emmerich, Project Manager