$64M Nine Mile Creek project wraps up

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The Highway 169 Nine Mile Creek project carried a $64 million price tag and a $64,000 question: Could the project team complete the work on time despite an aggressive schedule and difficult conditions?

The answer appears to be “yes,” with some time to spare, thanks to an unconventional technique to create a firm foundation to support a new 3,000-foot-long causeway. The project replaced the old Highway 169 bridge over Nine Mile Creek in Hopkins, Minnetonka and Edina, and included work in three other suburbs.

Minnesota Department of Transportation leaders celebrated the project’s completion Friday and said the new road will open to traffic by 5 a.m. Wednesday, weather permitting. Initially, the project was expected to wrap up later this fall.

“Construction has gone well,” MnDOT project engineer Curt Kallio said in an interview. “No real major issues have come up. Things that have come up we have dealt with.”

The project, which began in January, includes the causeway and 6 miles of new pavement between highways 62 and 55. The project area cuts through Golden Valley, Plymouth, St. Louis Park, Minnetonka, Hopkins and Edina.

Burnsville-based Ames Construction led the design-build project team, which included Minneapolis-based Alliant Engineering and St. Paul-based AET. The team faced challenges that included poor soils, difficult working conditions and an aggressive 272-day schedule.

One of the subcontractors was Menard Group, a Pittsburgh-based geotechnical company. To deal with the poor soils, Menard installed 5,000 columns, known as “controlled modulus column rigid inclusions,” into the ground. (Menard has no relation to the home improvement retailer.)

Crews operated specialized drill rigs and bits to install the columns, or “inclusions.” Instead of pulling dirt out of the ground, the bit pushes it to the side, and concrete is pumped into the hole as the operator retracts the bit from the ground, Kallio said.

Alex Potter-Weight, senior design engineer for Menard, said in an interview that the columns were installed about 5 feet to 10 feet apart at depths ranging from 20 to 45 feet. In general, compared to typical deep foundations, this method uses more columns at shallower depths.

“It’s kind of like a bed-of-nails approach,” Potter-Weight said, adding the foundation work was completed in about two months, wrapping up in May. “We hit the job pretty quickly with four rigs.”

Kallio said the technique saved time and money compared to the more traditional deep foundation method of driving a pipe into the ground and filling it with concrete. Unlike conventional columns, no casings are required, he said.

“It took about four minutes per column,” he said. “Then they would move over and do the next one.”

Menard said in a promotional video that it has used CMC rigid inclusions on more than 2,500 sites worldwide. The technique was developed in France in the 1980s and Menard brought it to the United States in the early 2000s, Potter-Weight said.

Kallio said the method is unusual on MnDOT projects, though it was used on the $116 million Interstate 35E Cayuga project, which included new bridges, interchanges and road construction on I-35E between Interstate 94 and Maryland Avenue in St. Paul. Menard also worked on that project.

On the Cayuga project, crews installed 16-inch diameter grout columns to depths of 40 to 62 feet, or about 5 to 10 feet below the poor soils, according to MnDOT. The columns were spaced about 7 feet apart.

Besides the bridge and road reconstruction, the Nine Mile Creek project features new acceleration and deceleration lanes at Cedar Lake Road, and the removal of Highway 169 ramps at 16th Street in St. Louis Park, noise wall repairs and other work.

Kallio said the project needed to be done in one construction season, or 272 days as the contract stipulated. The design-build contractor, Ames, is eligible for a bonus of just under $500,000 if that Wednesday opening is achieved, he said.

Ames submitted a $60.2 million low bid for the project last year, but additional scopes of work pushed the cost to $64 million. The extra work includes repairs to the Minnetonka Boulevard bridge and concrete reconstruction south of Bren Road in Edina.

MnDOT officials said last year that they saved money by going with a causeway instead of a new bridge over the Nine Mile Creek. MnDOT defines a causeway as a “raised road across a low or wet ground.”

That’s an unusual approach, but the conditions were right to make it happen, Jerome Adams, MnDOT’s metro district design-build engineer, told Finance & Commerce in August 2016. An old road embankment under the existing bridge made it possible.

About 90,000 vehicles travel daily on Highway 169 in the project area, according to MnDOT.

Related:

• Ames lands Highway 169 project
• Hwy. 169 project: 6 miles, 6 cities, 272 days