Nine Mile Falls Dam Flash board removal

January 19, 2010 marked the end of an 80-year era for Avista, with the release of wooden flashboards at our Nine Mile Falls Dam on the Spokane River. Watch the two-minute video to see what it looked like to release the flashboards.

In 1928 Avista began installing the five-foot high, hand-built flashboards at the top of the face of the dam, extending the normal dam height to 63 feet (without the flash boards its 58 feet). Later, the flashboard height was doubled to a total height of 10 feet. Flashboards are installed annually in four sections: two upper and two lower. Yesterday we released the two upper sections, and well release the remaining sections later this spring, for the final time.

The flashboards, constructed with sheets of plywood and solid wood beams, allow operators to hold back more water in the forebay for power generation when river levels are lower. They are installed each summer and removed in late winter or early spring, as river levels begin to rise again.

Beginning this summer, Avista will replace the wooden flashboards at Nine Mile with an automated spillway that will give operators the ability to raise and lower the height of the spillway as needed. This new spillway, required under our FERC Spokane River Project license, will allow us to maintain the reservoir pool at a more constant level throughout the entire year, partly because it eliminates the need to lower the reservoir each summer to install flashboards.

Just a reminder if youre out on the river for any reason, be careful. High river levels, run-off from recent storms and the flashboard release have resulted in extra debris in the water, especially downstream from Nine Mile Dam. The video shows a few rather large trees and other items floating down the river.

Questions? Visit http://www.Avistautilities.com/blog

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