Tuesday, November 18, 2008

Landslide closes busy bridge twice in 6 months

Landslide closes busy bridge twice in 6 months

By Bryan Johnson

KING COUNTY, Wash. -- Landslides and soaked hillsides have a major road shut down.

Highway 169 is closed at the Green River bridge. But the state just spent a lot of money fixing the bridge.

The bridge gives the state heart burn and motorists heartache. Twice this year - twice within six months - the bridge has been closed because of landslides.

The first slide in June broke some big chunks of concrete loose. The state closed the bridge, brought in experts and drilled holes to find out why the earth was moving.

The state installed hillside drains. They reinforced walls. They put in inclinometers -- a fancy word for a device that will say if the bridge is leaning, which is not a good thing when you are 145 feet above the Green River.

"We've got three tilt meters under the bridge. We have several piezometers to help us measure the ground water," said Bob Grandoff with the Department of Transportation.

No one was too worried.

Then it rained this week. Water flowed out of the hillside. Despite all the stabilization, those tilt meters recorded a very slight movement.

"Any time a bridge is moving, I think it is prudent to close the road for safety, of course," said Grandoff said.

The bridge was closed.

In the closest town, Black Diamond, those closures make some nervous:

"I go really fast and I say it's my last time every time," said Katie Doyle.

"How can they sink concrete down that far to stabilize it?" said Marilyn Pedersen.

The state says Doyle, Pedersen and the rest of you need not worry. The bridge is safe and they'll do whatever is necessary to keep it that way.

"Right now, it is the most watched bridge in the state," said Grandoff.

This bridge is constantly monitored. Radio signals go to DOT officials Olympia. With even the slightest movement, the bridge gets shut down.

Right now there is no movement; there doesn't seem to be a problem. But the state says the signals must show no problems for at least 48 hours before they will reopen the bridge. That could happen this weekend.

As I always say, better safe than sorry - inclinometers continuously prove value as added levels of safety monitoring and warning for critical, potentially life threatening tilt applications - Skip Gosnell
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