Quite a lot of the 564 million pounds of concrete and 42 million pounds of steel that will one day span the St. Croix River near Stillwater is sitting on an island in the Mississippi River these days, waiting for the ice to melt.
When the ice breaks up, the bridge segments can be loaded onto barges at Grey Cloud Island, four to six at a time, for a 30-mile journey to their destination.
They will become part of the $626 million St. Croix Crossing bridge, which opens next year.
Eighty workers in a built-for-the-purpose shed (600 feet long, heated all winter to 50 degrees) are spending years creating the “bridge segments.”
The segments look a bit like brass knuckles for a three-fingered giant. The top of each one will be the surface that motorists will drive across, little suspecting what went into their creation.
Reporters and photographers were invited last week to the casting yard, one of two that are building the jigsaw-like components that will later be fitted together to make the bridge.
“This is an exciting portion of our work,” said project director Michael Beer, as the time approaches to start loading up and moving the segments out.
“Of the 650 segments we’re creating on Grey Cloud Island, we’ve finished 105 so far, taking three to five days for each one,” said Paul Kivisto, bridge construction engineer.
One’s first impression, entering the shed, is that a concrete ship is being created in segments inside. Each segment drops 18 feet from its surface in a shape that mimics the look of a ship. Each weighs 170 tons and is 48 feet wide.
Steelworkers tie metal bars into the shape of the segment, which forms a skeleton for the concrete. Within each one runs plastic piping, known as ducts, that create space within the concrete for the cables that will string them together.
Crews using a crane then place what’s called the “rebar cage” inside a form, into which concrete is poured. The concrete usually takes 24 hours to cure.
The segments move on rollers, on a track, and then are lifted into rows for storage as they await the move. Each is branded with its location: “E9” means eastbound lane, near Pier 9.
The work is being done on Grey Cloud, Kivisto said, because a firm that mines gravel from which the concrete is made, Aggregate Industries, is located there.
Concrete is created on-site, and the completed segment winds up just a quarter-mile from riverways, making transportation on barges convenient.
While the cured segments sit outside, officials say, the concrete “ages” like wine, getting stronger.
Movement of the segments is being predicted for May, but weather — meaning ice on the water — will determine the timing.
On-site, the bridge surface will be installed starting from the Minnesota side, gradually nearing Wisconsin.
Near the site, another casting yard is creating smaller segments that will go into the over-the-land part of the bridge, including ramps. Three-hundred-thirty of them are to be made, of which 61 had been completed by the middle of last week.
Nearly a mile
Not that many people go near Grey Cloud to begin with, but there’s no sign that such a significant project is happening.
Perhaps the world’s least revealing road sign, not too far away, reads “Lunda/Ames,” with an arrow pointing those in the know to the location, but that’s all it says.
Translation: The winning bidder for the project was Ames/Lunda Joint Venture, a combination of Burnsville-based Ames Construction and Wisconsin-based Lunda Construction.
The finished bridge will be about 5,080 feet long, ranking it among the 10 longest in the state.
It will include a 12-foot walkway and three piers that serve as overlooks, with wider spots for bikers and hikers to stop and admire the scenery.