Montana

Libby Dam nearing capacity, flooding worries voiced

Posted: Jun 28, 2012 11:14 AM by Dennis Bragg - MTN News

LIBBY- The issue of flooding is a real concern at Lake Koocanusa and the Libby Dam with Lincoln County Commissioners now saying the dam is almost full, and areas downstream are already flooding.

Commissioner Tony Berget says the Army Corps of Engineers is warning his office the dam may have to begin spilling more water because there is little room to give before the dam is full.

Berget says people in the Libby area, especially those who live along the river, have already begun sandbagging areas around their homes. He added that some places, such as Bonners Ferry, Idaho, are already flooding.

"The dam is up to. There's only 4 ½ feet left of freeboard, and then after that, everything comes over the dam. They were up to 40 cfm which was up to flooding about a foot-and-a-half yesterday by noon in Bonner's Ferry. But a lot of that had to do with the side streams. They still feel like they may have to go to 45, but they are trying to hold that off until some of these streams...[see their levels] reduce," Berget explained.

"The reservoir behind Libby Dam rose 1.5 feet in the last 24 hours and is now less than three feet from full," said Kevin Shaffer, a Seattle District Army Corps water manager. "Once the final storage space behind Libby Dam is diminished, we will be forced to pass inflows to keep the reservoir from overfilling. Raising outflows last night will slow the reservoir fill rate and allow river flows upstream and downstream of the dam to recede further before the remaining space in the reservoir is exhausted.

"We are still holding back 29,000 cfs from current inflows, but as the pool fills our operational flexibility or ability to store water decreases," Shaffer added.

The Corps' Emergency Operations Center continues 24-hour operations while the Kootenai Basin flood team is monitoring conditions, inspecting problem areas and levees, and providing technical assistance to Lincoln County, as well as in Boundary County, Idaho.

Record rainfall has soaked the basin in June. At Bonners Ferry, current precipitation for the month of June is 5.2 inches, more than 300 percent of the June average which is 1.66 inches. The previous June record for precipitation at Bonners Ferry was set in 1981 when it was measured at 3.96 inches

Heavy June rainfall in the Kootenai Basin also resulted in a high water level on Kootenay Lake, downstream of Libby Dam. The current elevation at Queens Bay is 1,753.1 feet, the highest level since 1974. Libby Dam operations are being managed to reduce downstream flood damage for both the Canadian and U.S. portions of the Kootenai Basin.

Residents and businesses in the river basin should be prepared for potential flooding. The National Weather Service and downstream communities have plans in place to promptly alert potentially affected people about the situation and what action to take.