Instruments show intermittent bridge shifts|[10/08/07]

Published 12:00 am Tuesday, October 9, 2007

Precise determination of shifts along the east bank of the Mississippi River will soon be collected through instruments that send information via the Internet to certain businesses and agencies.

Eddie Templeton of Burns Cooley Dennis Inc. of Ridgeland said workers for the geotechnical and materials engineering firm were installing slope inclineometers along the bank near the Interstate 20 and U.S. 80 river bridges Monday morning. The instruments will connect to automated data collectors that will transmit to a Web site to be accessible by officials with Ameristar Casino, the Vicksburg Bridge Commission, Federal Highway Administration, Mississippi Department of Transportation, Louisiana Department of Transportation and Development and DiamondJacks Casino.

“Those are the people who own the property where we’re installing the instruments,” Templeton said.

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Similar instruments were installed four years ago and the company has been monitoring them since. Templeton said five of the inclineometers will be replaced by the newer technology. The ground movement is measured in piezometric levels, which determine water pressure in the ground.

“It’s all related to the stability of the river bank in that area,” he said. “We’re measuring to see what the relationship is to the piezometric level and the ground movement.”

Bridge Superintendent Herman Smith said because of movement on the bank it had become difficult to take readings. The U.S. 80 bridge, which is now a crossing for trains only, is 79 years old and has required periodic adjustments using plates and spacers. “This allows them to know where within the bank there is movement,” Smith said. “This is something that has been going on since the bridge was built.”

There is no known risk of a sudden movement or one that would pose immediate danger to area structures, Templeton said.

“It’s small, intermittent movement over long periods of time,” he said. “It’s a relatively small amount that occurs — mostly during the low water periods of the year.”

Smith said Monday’s work had nothing to do with the Thursday incident, when about 25 grain barges broke off a 42-barge tow along the Mississippi River. Although traffic along the interstate was stopped for almost three hours, inspectors gave the bridge the all-clear, indicating the structure wasn’t harmed.

The old bridge is owned by Warren County and operated on a break-even business model. The highway bridge is maintained by the Louisiana Department of Transportation.