Work begins on new Stillwater bridge

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Work has begun on the St. Croix River as crews work to test the foundation of the riverbottom.

Crews with Bolander and Sons began setting piles in the river on June 20. The process includes driving two 24-inch piles and two 42-inch piles into the river bottom. Crews will place the piles with a crane, then hammer the piles until they are locked into rock or dense soils.

According to Paul Kivisto, St. Croix bridge construction engineer, the load testing will help to reduce risk and therefore help reduce the cost of the project.

“That is one of the main purposes of us being out here with this load testing effort is to learn more about the foundation so that we can have a more cost effective and more efficient, effective bridge design,” said Todd Clarkowski, area engineer for the MnDOT Metro District.

The load testing is expected to last about a month, Clarkowski said. Crews will remove all piles before vacating the site in August.

While the location of the barges don’t necessarily indicate where any of the six wet piers will be, it does give area residents and commuters a good idea of the path the bridge will take once it’s constructed.

“Take a line from that barge to this barge and you would have the line of the bridge,” Kivisto said.

The bridge will fall right in the ravine directly west of the barges, according to MnDot officials. According to Chris Ouellette, WisDOT Northwest Region communications manager, two homes, which are not visible from the water, will need to be razed to complete the project. Those homes have already been purchased and vacated, she said.

Boaters will see minimal impact from the project, Kivisto said.

“There will be no increase in barges out there, so what you see is what we’ll have,” Kivisto said.

The same goes for water quality, said Dwayne Stenlund, certified professional in erosion and sediment control for the erosion control engineering unit.

Water — upstream and downstream — is tested four times each day to ensure that the water quality is not being compromised.

“The expectation is there will be no change (in the water quality),” he said.

Stenlund said the two barges are treated like floating islands and, as with any piece of land, measures are taken to ensure trash and chemicals are contained at the site.

“You’re going to have perimeter control, you’ll have chemical management, anti-porta tipping, the whole nine yards, everything,” he said. “Whatever happens on the barges, stays on the barges to use the idea of Las Vegas.”

The yellow “bananas” that surround the barges are actually containment booms, he said. In addition, large pads are used on the barge platform and in the water surrounding the barge to absorb any oil or chemicals that might show up.

Even the porta-pottys are tethered to the barges, he said.

“We don’t want anything to get into these waters,” he said. “It’s basically total containment, total chemical management. In theory the water shouldn’t change at all from this operation.”

On Thursday, June 21, the water’s turbidity reading was 5.52 ntu — that’s compared to the 5 ntu of drinking water (the lower the number, the clearer the water).

Residents may hear noise from the pile hammer from 7 a.m. to 5:30 p.m., Monday through Friday. The entire process for the initial pile driving will take approximately one month, with the majority of the project noise in the first four days. The entire load testing project will be complete by mid-August.

St. Croix Crossing construction will begin in 2014 and take approximately three years to complete.

The final designer for the $626.4 million project will be announced next week, said Todd Clarkowski, area engineer for the MnDOT Metro District.

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