Part of the nation's first interstate highway project is no more, having been spectacularly dropped into the Missouri River on Tuesday.

The Blanchette Memorial Bridge was a rugged twin cantilever supporting part of what's now called I-70. Back in 1956, that stretch of roadway constituted America's first interstate project created by the Federal Aid Highway Act.

On Tuesday morning, with the friendly assistance of 65 pounds of explosives, the Blanchette span was converted into a hard cloud of dust-spuming rubble and knotted steel that fell spectacularly into the Missouri River. Here she blows:

Many a hoot and a "damn!" arose from the crowd of rubberneckers gathered along the banks of the river in St. Charles, just northwest of St. Louis. The controlled demolition, managed by Wyoming's Demtech, took just .17 thousandths of a second to deliver 1,030 feet of bridge into the unfettered hands of gravity. In the coming days, the contractor overseeing the Blanchette project will fish out 4.5 million pounds of cut steel from the riverbed, where it will likely be recycled and (construction-karma willing) turned into another bridge that will also be exploded in the future.

Blanchette used to be the St. Louis area's busiest bridge with some 165,000 drivers crossing it each day. But Missouri decided it needed to vitalize the antiquated passage, so it's rehabbing or replacing about three-quarters of it to the tune of $65 million. Yesterday's detonations finished removing the westbound section of the span after its superstructure was blown up in November (photos here). If everything runs on schedule, a new bridge will stand in its place in late 2013.

These are more booming looks at Blanchette's final seconds. "Do it again!" indeed:

You can almost feel the shockwave rippling your epidermis in this video:

Photos courtesy of the Missouri Department of Transportation on Flickr.

About the Author

John Metcalfe
John Metcalfe

John Metcalfe is CityLab’s Bay Area bureau chief, based in Oakland. His coverage focuses on climate change and the science of cities.

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