High above the emerging St. Croix River bridge, 14 cranes dot the sky. Concrete roadway segments, rounded like pieces of giant cereal bowls, are lined up in rows on shore. Taut cables stretch from two of the five towering piers, supporting an ever-lengthening driving surface. Even with many parts yet to be put in place, a finished bridge is not hard to envision.

But as winter approaches, uncertainty lingers over when the bridge will open and whether it will cost more to complete.

Engineers and contractors will huddle in December to discuss concerns with a structure that spans a federally protected wild and scenic river and is now more than half finished. Delays over the past year — associated with problems installing complex webs of metal framing and other challenges unique to a cable-strung bridge — led to a decision in August to scrub the original late 2016 opening.

"It's a complex project with lots of pieces that go together. You can't jump ahead one step until the previous step is completed. That's really what's controlling the speed of bridge construction," Michael Beer, the Minnesota Department of Transportation (MnDOT) engineer overseeing the project, said last week.

The bridge is the largest component of a joint Minnesota-Wisconsin undertaking that eventually will reroute interstate traffic from the Stillwater Lift Bridge, 2 miles to the north, to Oak Park Heights. Budgeted to cost as much as $676 million, the overall project includes new approach highways, historic and cultural preservations and environmental protections for the St. Croix River. Much of the work on land in both states, especially the scheduled opening of a new four-lane connecting highway in Wisconsin, waits for a finished bridge.

Problems with installing metalwork — the rebar webbing that holds concrete together — significantly delayed the construction schedule this year and led to allegations by the original contractor, J&L Steel of Hudson, Wis., that designs were flawed. The company's owner, LouAnne Berg, said she had raised concerns nearly a year before MnDOT and the general contractor, Lunda-Ames, admitted publicly that the planned completion date couldn't be met.

In response, Beer and Lunda-Ames spokesman Brent Wilber disputed the timing and said the number of design problems wasn't unusual for such a large bridge.

Beer said again last week that building a cable-strung bridge, rare in its design, presents challenges that are being overcome with experience. But he also acknowledged delays and said the bridge, 60 percent complete, should have been closer to 70 percent finished by now.

Whether the delay will result in higher costs won't be known until a new opening date is determined later this year, said MnDOT bridge spokeswoman Kristin Calliguri. The project has a $15 million contingency budget to help with cost overruns.

Too cold for adhesive

Construction of the bridge deck — by assembling those end-on-end concrete segments — stops with colder weather because the adhesive that helps them stick together won't hold when the temperature dips below 28 degrees.

Work on the five pairs of piers in the water will continue until the river turns to ice. Work on bluffland piers will extend into the winter, as will casting of segments needed next spring when work resumes on the bridge deck. Ramps leading to and from the bridge on the Minnesota side of the river also remain under construction.

On Pier 8, which stands closest to the Minnesota side of the St. Croix, 59 percent of the segments that will form the bridge deck have been installed. On Pier 9, a bit farther into the river, workers have installed 55 percent of those segments. Work on the three other in-water piers isn't as far along, and construction is just beginning on a pier that will support the bridge deck where it crosses the bluff into Wisconsin.

Also on the Wisconsin side, a new, 3-mile stretch of Hwy. 64 that will connect the bridge with the existing four-lane highway near Somerset is about set for paving.

That work will begin in April with an anticipated completion date of August, but the highway won't open before the bridge does, said Tim Mason, the Wisconsin Department of Transportation engineer in charge of that work.

"I think it's been progressing well for the size of the project that it is and all of the complexities," he said.

Once the new bridge opens — and the Stillwater Lift Bridge permanently closes to vehicle traffic — the Wisconsin DOT will oversee construction of its portion of a loop trail that will cross both bridges. Some of that trail, south of Stillwater on the Minnesota side of the river, was built this fall.

Meanwhile, four Washington County road projects await the bridge opening, said County Engineer Wayne Sandberg.

The first, at the Osgood Avenue intersection with Hwy. 36 in Oak Park Heights, will include adding sidewalks and making other improvements. The second, on the much-traveled Third Street in Stillwater, calls for replacing rutted asphalt with concrete surfacing. The third, on Stagecoach Trail near Interstate 94, would replace pavement on one of the main construction hauling routes. The fourth is a study of changes in traffic patterns.

Beer, at MnDOT, said the bridge is taking shape in a way that makes it easier for people to imagine how it will look when finished.

"It does really show what the bridge is ultimately going to look like," he said. "It's taking the shape of its final form going into this winter. It's going to be a beautiful bridge when it's done. It's going to be a signature bridge."

Kevin Giles • 651-925-5037