June 2, 2011

Corps temporarily closes spillway gates at Garrison

Press release submitted by U.S. Army Corps of Engineers

The spillway gates at Garrison Dam have been temporarily closed following a routine inspection that identified a water spray on the spillway apron.

Seven of the dam’s 28 spillway gates were opened shortly before 8 a.m. this morning. The gates were raised 1 foot and were allowing an additional 7,500 cubic feet per second of floodwater through the system. That brought the total releases from Garrison to 92,500 cfs.

As the water traversed the spillway, engineers with the U.S. Army Corps of Engineers noted a water spray on the spillway floor that they were inspecting as part of the routine start-up process. The gates were then closed to allow engineers to physically inspect the spillway apron, where they identified minor surface deterioration.

This deterioration likely occurred as a result of natural freezing and thawing action on the apron over time.

“I made the decision to keep the spillway gates closed until the deterioration is evaluated since the continued force of spillway releases could further wear down the area,” said Col. Robert Ruch, the commander for the Omaha District of the U.S. Army Corps of Engineers.

The closing of the spillway gates has no impact on the current forecast for water releases as the additional water is being released through the regulating tunnels, which are next to the powerhouse outlet works on the west side of the dam.

“The regulating tunnels allow us to continue to meet the release schedule while the evaluation of the surface deterioration is completed,” Ruch said. “We expect that the spillway gates will be reopened soon.”

The current forecast for releases out of Garrison Dam call for an increase to 100,000 cfs tonight at 8 p.m.; 105,000 cfs Thursday at 8 a.m.; and 110,000 cfs by Thursday at 8 p.m. This morning marked the first time the spillway gates at Garrison Dam had been opened to pass floodwaters through.

Rapidly changing weather conditions in Montana, northern Wyoming and the western Dakotas have prompted the U.S. Army Corps of Engineers to make adjustments to previously announced releases from Garrison Reservoir in order to evacuate flood waters out of the Missouri River main stem reservoir system.

“Protecting lives is our number one priority right now,” said Brig. Gen. John McMahon, Commander of the Northwestern Division of the Army Corps of Engineers. “We are working closely with state and local emergency management teams to identify potential flood areas, provide residents with the most current information and help protect vital public infrastructure.”

People living along the river are encouraged to make evacuation plans to protect their possessions and property. Maps for potential flood areas can be found at: www.nwo.usace.army.mil. Residents in communities along the river are encouraged to contact their local emergency management offices for additional details. Please follow us on Facebook (www.facebook.com/OmahaUSACE) and Twitter (www.twitter.com/OmahaUSACE) for the latest updates regarding our flood response operations.

You can also find flood inundation maps and local emergency management contact information on our social media sites as well as our district Web site at http://www.nwo.usace.army.mil. View daily and forecasted reservoir and river information on the Water Management section of the Northwestern Division homepage at: http://www.nwd-mr.usace.army.mil/rcc.

The Weather Network