Long runoff season on the Spokane River affects recreation and maintenance project at Post Falls Dam   

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Post Falls Dam

 

Will summer ever get here? That’s seems to be a common question heard around the Spokane area these days and at Avista too. As you make plans for the upcoming weekends and July 4 holiday, we want to keep you up to date on changing conditions in the Spokane River as well as educate you about a project we are working on at the Post Falls Dam.
 
 
We’ve started closing spill gates at our Post Falls Dam now that Coeur d’Alene Lake is back below the maximum summer level of 2,128 feet. However, heavy rainfall throughout the month of June has slowed our process, and we’ve had to make ongoing adjustments to accommodate river flows, which have increased rapidly on a number of occasions, as recently as Tuesday, June 26.

Closing spill gates causes the river level below the dam to decrease. With this in mind, the spill gates need to be closed gradually, so that fish below the dam are not stranded in pools of water. To achieve this we close spill gates at a rate that decreases the downstream river level no more than four inches per hour, which is required by our Federal Energy Regulatory Commission (FERC) license to operate our dams on the Spokane River.

As the river flows stabilize, we continue to close the remaining spill gates. As the spill gates are closed the elevation of the river above the dam increases, which provides additional recreational opportunities on the river. Once the final spill gate is closed, the Q’emiln Park boat launch in Post Falls can be opened for the summer season. Typically this occurs sometime between Memorial Day and mid-July. The median date for closing the gates is June 22. We don’t expect to close the final spill gate until after July 4 due to this year’s rainfall and extended high spring runoff season.

We’d like to remind you to always exercise caution on the water, as river and lake levels can change at any time depending on weather and other factors. The water is still cold, which puts those who are recreating on or near a lake or river at risk for hypothermia.

The best way to get the most current information on anticipated elevation changes on Coeur d’Alene Lake, Lake Spokane, and the Spokane River is to call Avista’s 24-hour telephone information line.

In Idaho, call (208) 769-1357; in Washington, call (509) 495-8043.

The recorded information is provided to advise shoreline property owners, commercial and recreational users of changes in lake and river elevation levels that may affect plans for water use. You can also check current river and lake levels on our website.
 
Avista’s summer work at Post Falls Dam
The dam needs ongoing maintenance and updates to keep it running safely and efficiently. This summer after the spring runoff season ends, Avista will be undertaking two projects to do that.
 
We’re planning to sandblast, repair and repaint the south channel spill gates, something that needs to be done every 30 to 40 years. We also plan to replace the lifting hoist and old timber intake gates that let water flow through the dam to the generator turbines at Post Falls Dam with new lifting hoists and steel gates.

Normally the generator turbines can pass about 5,400 cubic feet per second (cfs). Any additional water has to flow through the spill gates.

During the work, at least two generator units must be taken offline, which reduces the amount of water the power house can pass at any one time. This means the total river flow will need to be lower than normal before we can close all the spill gates and the Q’emiln Park boat launch can be opened.
 
Depending on weather, this will likely be about the second or third week of July.

During the project, we’ll do our best to minimize the disruption to recreation and power generation as much as possible, but the work is important so we can continue to safely generate clean, reliable hydropower. We'll be sure to keep you updated as the project reaches completion.
 
Posted by  System Account  on  6/28/2012
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