Missouri River Water Management News

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Corps to hold Fort Peck Spillway test first week in September

Published Aug. 27, 2012

Omaha, Neb. – The U.S. Army Corps of Engineers, Omaha District, is set to conduct a 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.

Currently set to begin the morning of Sept. 4, 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.

During the test, releases from the Fort Peck Power Plants will be reduced to a minimum release of 3,000 cfs to lessen the downstream impact. Overnight when spillway flows are reduced to 3,000 cfs, the powerhouse releases will be increased to 7,000 cfs, putting the total release during that period at 10,000 cfs.

The planned maximum flows for the spillway each day of the flow test are as follows:

  • Sept. 4 – 3,000 cfs
  • Sept. 5 – 9,500 cfs
  • Sept. 6 – 16,500 cfs
  • Sept. 7 – 24,000 cfs
  • Sept. 8 – 30,000 cfs

The test is anticipated to be complete by the evening of Sept. 8.

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 tes t 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. It has since put out regular reminders of the pending test.

In the event of localized heavy rainfall 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.

Release no. 20120827-001