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Archive for Wednesday, June 11, 2008

Kansas agencies survey sinkholes for preventive reasons

June 11, 2008

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— The Kansas Geological Survey and the Kansas Department of Transportation are surveying a local highway stretch to check for sinkholes caused by dissolving salt underground.

A team is studying salt hundreds of feet below the surface near U.S. 50. They hope to make state officials aware of potentially fast-moving or catastrophic sinkholes on major highways.

"(A fast-moving sinkhole) would be unbelievably catastrophic to have that happen, so we can't take that chance," said Rick Miller, a geophysicist with the survey.

The team is focusing on the sinkholes at Victory and Brandy Lakes roads, two cross streets along U.S. 50. KDOT has already been recording data of how these two sinkholes have been moving on the surface, Miller said.

"So the question is we know what it's doing at the surface, how does that relate to what it's doing at the salt level 400 feet down?" Miller said.

The team is using a geophone, a microphone-like device, to survey the salt layer. A machine sends sound waves into the ground and the geophone catches and measures the echoes.

"It's a very physical job," said Bob Henthorne, chief geologist with the Department of Transportation. "Not only do we have to have several people out there flagging traffic and running the pilot car, to get the dead zone during the seismic run, just moving the geophone lines is pretty physically intensive, especially on 100-degree days."

Miller said they are conducting the survey here because the section of U.S. 50 intersects with a moving salt front. The salt was originally deposited farther east, but through disillusionment, it has moved over time.

He said the sinkholes, which are caused by water dissolving the salt and by the shifts in the salt layers, will continue moving at a rate of a couple of centimeters per year.

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