520 Bridge project reaching milestone

520 Bridge project reaching milestone »Play Video
SEATTLE -- Huge Seattle construction projects often get bogged down in delays, but that's not the case with the 520 Bridge project.

The project will reach a major milestone Monday when the first two of 44 so-called "stability pontoons" will be floated out of the construction area into Tacoma's Commencement Bay.

When the new bridge is done, it will actually sit a few feet above the water with help from the huge concrete blocks. Six of those blocks have been built in Tacoma.

"They are kind of like the foundation for a bridge. Where you see a pier column, a footing, these are the foundations for the new bridge," said Dave Becher of the Washington Department of Transportation.

You can't float a 100-foot-long concrete lego brick out on just any day. Crews need a 10-foot tide, and that's what's coming on Monday night when the floodgates will open.

Unlike common concrete that's porous and prone to cracking, the pontoons are built to last 75 years.

"The concrete in the pontoons here has an admixture, it's called micro-silica. It's a fine additive that fills up the void holes typically created by air so it makes it a very dense strong concrete," said Reg Carson of KIEWIT Construction.

There's just one little problem. There has been no decision, just a lot of controversy, about what the Seattle connection will look like. The state says it is not gambling and you will not wind up in the water. There are two years to come up with a Seattle plan, and if Seattle is still debating by them, the new bridge will just be hooked up to the off ramps and bridges of today.