Crews building the new span across the Mississippi River north of downtown St. Louis have hit an important project milestone - the completion of the twin 400-foot towers. Within a week, workers will start stringing cables from the towers to support the 1,500-foot main span.

"This is great," said project manager Greg Horn with the Missouri Department of Transportation. "These towers were one of the big things we had to get done."

There's no easy part of the project this massive, Horn said, but crews are feeling a sense of relief.

"The biggest challenge is usually the foundation work, the stuff that happens 100 feet below the surface, because we never know what we're going to find," he said. "At least now we know what's coming up. You still could have bad weather, you can have a lot of things that could affect it, but we're through probably the most difficult part at this point."

The $667 million project is on time and on budget, Horn said, despite a flood in 2010 that knocked out three months of work. The contractor, he said, is now facing the opposite problem.

"Believe it or not, it's a problem that the river is a little bit too low," Horn said. "The cranes aren't quite tall enough to each all the way to the top. 108-degree heat is kind of a little hard to work in, too."

Stringing the cables will take abut a year, Horn said. Traffic should start crossing the bridge in early 2014 - it will move Interstate 70 off the Poplar Street Bridge.

And what about winning over those resistant to trying a different route?

"I think once people take the bridge, they are going to realize that it's so much quicker and so much easier. The Poplar Street Bridge ramps are too sharp, too many weaving areas," Horn said.

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