Walking atop the new St. Croix River bridge, one’s first sensation is its vast reach, now that it connects the urban banks of Minnesota to the forested bluffs of Wisconsin.

High above the broad river last week, hundreds of workers wearing hoodies and hard hats leaned into a stiff wind, doing their part to ensure the bridge opens for traffic early next fall.

“People are amazed, when they’re up close, at the enormity of the bridge and the segments,” said Michael Beer, the Minnesota Department of Transportation manager overseeing the project.

There is nothing modest about the mile-long bridge, which rises to staggering heights above the water under concrete towers braced with massive silver cables that gleam in the sun.

The two-state project, now estimated to cost $617 million to $646 million, includes extensive highway construction on both sides of the river to funnel traffic onto the four-lane structure.

To onlookers on land, the bridge looks substantially complete. The span, for the first time unbroken, dwarfs the 85-year-old, two-lane Stillwater bridge just 2 miles upstream that it will replace.

Built to outlast most everyone who has witnessed its construction, the new bridge crosses a portion of the river known as Lake St. Croix, connecting Hwy. 36 in Oak Park Heights with Hwy. 35 in St. Joseph Township on the Wisconsin side.

“It’s going to be a beautiful bridge, here for the long haul, 100-plus years,” Beer said.

Big proportions

Late last week, workers — each tethered to a safety cable — assembled equipment over a canyon of empty space, guiding the final 180-ton concrete segment into place to complete the driving surface. The precast segment was the last of 988 secured side by side with high-tension cables that run into and through them.

Those interior cables, if placed end to end, would extend 1,969 miles. The exterior cables stretching from the towers total 5.2 miles.

The bridge design resembles a jigsaw puzzle, with engineers fitting together webs of steel and concrete in what’s regarded as one of the most challenging bridge projects MnDOT has ever done.

That’s because of its complex design, the fact that it was built over the St. Croix and “the geometry that was required to make sure this bridge fit together in the end,” said MnDOT design engineer Kevin Western.

An estimated 42.3 million pounds of steel holds the bridge together, much of it forming the skeleton that keeps 564 million pounds of concrete in place.

Work will continue through the winter, said MnDOT spokesman Kristin Calliguri.

Those job include “closure pours” to fill the small gaps left between the attached precast segments. Other crews will construct barriers between the driving lanes and the pedestrian walkway, build three overlooks, install railings and lighting, work on drainage piping and smooth the rough concrete into a finished road surface. The road will then be striped, Calliguri said. Sometime next spring or summer, the entire bridge will be painted light brown.

As winter nears, it’s clear the heavy lifting is almost done. On Friday, crews were dismantling the “segment lifters” — massive blue metal structures used to lift the largest pieces off barges that were as far as 150 feet below the bridge deck. One by one, a dozen or more red cranes that hoisted materials will disappear.

For now, crews of electricians, carpenters, welders, crane operators, ironworkers and laborers will continue their work. On Friday, the remaining 300 or so went about their business in a cold wind; at the peak of construction, their numbers surpassed 400.

Controversy and costs

The bridge fell a year behind schedule after problems that Beer attributed to its complex design. Whether that delay drives up the cost for taxpayers or the general contractor, Lunda-Ames Joint Venture, won’t be determined until a final accounting toward the end of the project, he said.

Cost overruns will be assessed against those considered responsible for them, Beer said. MnDOT and the Wisconsin Department of Transportation budgeted $30 million in contingency funds.

The bridge was controversial for years because it was built over a federally protected river. It will free Stillwater of many of the interstate motorists using city streets to reach the lift bridge.

When the new bridge opens, the lift bridge will close to vehicle traffic and become part of a loop trail for pedestrians and cyclists that also will circle over the new bridge.

“The community is really going to appreciate when this bridge is open, especially those who need to get to one side or the other and don’t need to be in downtown Stillwater,” Beer said.