Corps to hold Fort Peck Spillway test in September

Omaha, Neb. – The U.S. Army Corps of Engineers, Omaha District, will conduct a high flow test of the Fort Peck Spillway in Montana during the week of Sept. 4.

The test will help engineers to determine whether a subdrain system that relieves potential pressure beneath the spillway is functioning properly.

The test will consist of spillway releases of 3,000 cubic feet per second (cfs) up to 30,000 cfs at periodic intervals over a four-day timeframe. Hydraulic modeling shows the river stage rising directly downstream of the dam up to 4.7 feet with the highest test releases of 30,000 cfs. That rise in river stage would quickly dissipate the further downstream the water travels with the river gage near Wolf Point, Montana, at River Mile 1700.5 rising 1.7 feet. At River Mile 1619.7 near Culbertson, Montana, the stage would rise 1.1 feet.

At the 20,000 cfs, test release level those corresponding rises in river stages would be 3.1 feet directly downstream of the dam; 1.1 feet at Wolf Point and 0.8 feet at Culbertson.

During the test, releases from the Fort Peck Power Plants will be minimized to lessen the downstream impact.

The Corps held informational meetings in April with the public and Tribal representatives to seek input on the timing of the test in an attempt to minimize negative impacts on agricultural production and other activities along the river. The general consensus of the response held that a test in September would be preferable to earlier dates. The Corps took that input into consideration along with operation requirements of the dam and the Missouri River mainstem system in its final decision.

The public and Tribes will be given specific notice that the test will commence a minimum of 30 days prior to the actual event. In the event of localized heavy rain fall or flooding, the date of the test can be adjusted.

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.