Sinkhole Danger: Old Septic Tanks

There's danger lurking beneath the yards of tens of millions of homes nationwide, in the form of septic tanks that have been abandoned in favor of sewers.

As Mika Brzezinski

, the ground above those tanks can collapse without warning, and anyone who happens to be there can fall into the resulting sinkhole and be hurt or even killed.

Brzezinski calls it "one of the scariest stories" she has ever covered, especially because she's a parent.

"Can you imagine," she asks, "your backyard, where your kids play, suddenly collapsing into a deep and deadly sinkhole?"

It has happened and, according to some experts, will happen again in neighborhoods across the United States.

Gerri Carter's 2-year-old son, James, was playing in his backyard in Allentown, N.J., when Carter looked away for a few seconds. James seemingly fell off the face of the earth — into the earth was more like it.

"He just walked over grass … and he walked in the wrong spot, wrong time, and he was gone," Gerri says.

The ground under James had literally collapsed. It turned out he had stepped on top of an abandoned cesspool, a concrete cave hidden under his yard.

Septic tank expert Jim vonMeier says that up to 60 million U.S. homes are vulnerable to having old cesspools cave in without warning.

"A little kid can be walking along, in they go," he says. "And you won't be able to hear them because they're six, eight, 10, 20 feet underground. You won't even know they went down."

"So — boom — they're just gone?" Brzezinski says.

"Gone," says vonMeier.

He says your home is more likely to have one lurking beneath the surface if it was built before 1970.