Cost of Replacing U.S. Cities' Aging Infrastrucure 'Staggering'

With a blast that made skyscrapers tremble, an 83-year-old steam pipe sent a powerful message that the miles of tubes, wires and iron beneath New York and other U.S. cities are getting older and could become dangerously unstable.

The steam conduit that exploded beneath a Manhattan street at the height of rush hour Wednesday, just a block from Grand Central Terminal, was laid when Calvin Coolidge was president, and was part of a system that began providing energy to city buildings in 1882.

Investigators are still trying to determine what caused the explosion, but some experts said the age of the city's infrastructure was a possible factor. Pipes don't last forever.

"This may be a warning sign for this very old network of pipe that we have," said Anil Agrawal, a professor of civil engineering at the City College of New York. "We should not be looking at this incident as an isolated one."

From Boston to Los Angeles, a number of American cities are entering a middle age of sorts, and the infrastructure propping them up is showing signs of strain.

DePaul University transportation professor Joe Schwieterman said his city of Chicago, where much of the infrastructure dates to the early part of the 20th century, is now faced with tough choices on what to fix first.

"The aging infrastructure below the streets is an enormous liability for the city," Schwieterman said. "We know it needs modernization but the cost is staggering."