Missouri River Water Management News

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Corps repair strategy at Fort Peck Spillway

Published May 31, 2012

OMAHA, Neb. – The U.S. Army Corps of Engineers, Omaha District, continues to further refine repair estimates and designs for the spillway structure and plunge pool at Fort Peck Dam in Montana. A contract for emergency repairs is anticipated to be awarded by the end of September.

Those emergency repairs will restore the capacity of the dam to pass releases from the spillway similar to those experienced in 2011, and are eligible to be funded through the Disaster Relief Act Appropriation of 2011, signed into law Dec. 23.

"We continue to work closely with dam safety professionals to refine the necessary solution to repair the dam to a condition that will safely and without damage pass a flood of similar magnitude to that experienced in 2011," said Ted Streckfuss, the Deputy District Engineer.

At the height of the Flood of 2011, releases from Fort Peck Dam reached nearly 66,000 cubic feet per second (cfs), of which 52,000 cfs passed through the spillway.

Those releases resulted in significant erosion to the Bearpaw Shale in the plunge pool below the spillway, enlarging and deepening the pool and causing scouring along the spillway’s wing walls.

These emergency repairs will stabilize the spillway structure by fixing existing chute concrete damage and damage seen in areas along the wing walls. The repairs would also help to reduce some downstream scour action under high releases in the future.

A recent analysis by an independent contractor provided several alternative engineering designs that outlined what steps could be taken to prevent damage witnessed during the Flood of 2011 at releases equal to or higher than those seen in the event. The Corps will continue to assess the condition of the spillway structure to determine the applicability of these alternatives.

"These complex, technical issues drive the need for a robust solution. We are still defining the problem and will develop a range of solutions that will be presented to higher headquarters for consideration," Streckfuss said.

For regular updates on the repair efforts to flood control structures in the Missouri River Basin, visit the Omaha District’s Flood 2011 Repairs web page at http://www.nwo.usace.army.mil/op-e/srt.html.

Kevin Wingert

Release no. 20120531-001