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Avista Releasing Flashboards at Nine Mile Dam

 

Avista Utilities will begin seasonal removal of flashboards from Nine Mile Dam Tuesday, Jan. 19, for the last time. Later this year the hand-built wooden dam extension will be permanently replaced with a new spillway as part of the Spokane River Project Federal Energy Regulatory Commission (FERC) License conditions.

 

Recent rainfall and melt-off have increased river flows to the point at which one or more sections of the flashboards needs to be released. Spokane River property owners and boaters downstream of Nine Mile should be extremely cautious of extra debris in the water.

 

Flashboard removal should take place mid-morning Tuesday. Please contact Anna Scarlett if you would like to arrange video or photos during removal.

 

Avista purchased Nine Mile in 1925, and in 1928 began installing the five-foot high flashboards at the top of the face of the dam to make it higher, extending the normal dam height of 58 feet. Later, the flashboards were raised to a total height of 10 feet. The flashboards allow operators to hold back more water in the forebay for power generation when river levels are lower.

 

Beginning this summer, Avista will replace the wooden flashboards at Nine Mile with operable spillgates. The upgraded dam will allow Avista to pre-program desired heights and give operators the ability to raise and lower the height of the spillway at any time, incrementally if needed, in order to maintain the reservoir pool at a more constant level throughout the entire year.

 
The new spillway will consist of metal gates supported by air-filled rubber bladders. The new, automated technology will be much more flexible and precise, and will eliminate the need for annual construction of the flashboards

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