October 2015 (1)
August 2015 (1)
June 2015 (1)
May 2015 (1)
February 2015 (1)
January 2015 (1)
November 2014 (2)
October 2014 (2)
September 2014 (6)
August 2014 (1)
July 2014 (5)
June 2014 (1)
March 2014 (3)
February 2014 (2)
January 2014 (1)
November 2013 (3)
October 2013 (1)
August 2013 (3)
July 2013 (4)
May 2013 (4)
April 2013 (3)
March 2013 (2)
February 2013 (3)
January 2013 (4)
December 2012 (6)
November 2012 (9)
October 2012 (10)
September 2012 (9)
August 2012 (14)
July 2012 (17)
June 2012 (14)
May 2012 (13)
April 2012 (18)
March 2012 (14)
February 2012 (10)
January 2012 (12)
December 2011 (8)
November 2011 (11)
October 2011 (10)
September 2011 (13)
August 2011 (10)
July 2011 (6)
June 2011 (12)
May 2011 (8)
April 2011 (8)
March 2011 (9)
February 2011 (6)
January 2011 (9)
December 2010 (8)
November 2010 (17)
October 2010 (8)
September 2010 (12)
August 2010 (15)
July 2010 (10)
June 2010 (15)
May 2010 (9)
April 2010 (11)
March 2010 (13)
February 2010 (10)
January 2010 (14)
December 2009 (14)
November 2009 (10)
October 2009 (17)
September 2009 (20)
August 2009 (18)
July 2009 (22)
June 2009 (12)
Answering Questions
Avista Utilities
Clark Fork
Community Service
Customer Service
Energy Assistance
Energy Efficiency
Environment Facts
Hydro power
Infrastructure upgrades
Lake Coeur d'Alene
Natural Gas
Power Outages
Reliability Facts
Renewable Energy
Renewable Facts
Smart Grid
Spokane River

Nine Mile Dam Spillway Improvement Project starts this summer   

Tags: Avista Utilities, Electricity, Infrastructure upgrades, Washington, Hydro power, Renewable Energy, Spokane River

This summer and fall, Avista will replace the wooden flashboards at Nine Mile Hydroelectric Development with operable spillgates. The upgraded system 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, so that we can maintain the reservoir pool at a more constant level throughout the entire year.

Click to enlarge graphic
Click above to enlarge graphic.
Click to enlarge graphic
Click above to enlarge graphic.
What will the new spillway consist of?
The new spillway will consist of metal gates supported by air-filled rubber bladders. Compressors will inflate the bladders to approximately 25 psi to raise the gates. When stream flows are high enough, the bladders will deflate to lower the gates so water can flow over the top. The new, automated technology will be much more flexible and precise when managing the reservoir elevation.

What is the construction plan and timeline?
While the timeline is subject to change, the construction period is anticipated to be from July through October 2010. The new spillgates have been ordered and we expect delivery in July.

Once the new spillgates are delivered, we will remove some concrete from the top of the existing dam and replace it with new concrete to provide a good foundation to erect the new gates. A trough will be excavated in the dam crest for the compressed air lines that will be used to inflate the bladders.

The reservoir level must be lowered during construction to erect the new spillgates. During this period, the pool level will be 2 to 4 feet below the spillway crest, which may bring the level lower than what it has been in the past when the flashboards were erected each year in mid-summer. Construction should be complete and the reservoir level back to full pool by November of 2010.

How will the new spillway change Nine Mile operations?
No change in the full pool level is planned after the new spillway is installed. To the extent possible, we will maintain the reservoir level at the normal full pool elevation year around.

In the past the reservoir had to be lowered each summer to accommodate installation of the flashboards. When the flashboards were pulled in early winter or spring of each year, the material was lost and had to be replaced. Additionally, erecting the wooden flashboards each year is a labor intensive operation. The new spillway will result in less regular maintenance for Avista and enable the generation of additional power.
For project information, contact Steve Schultz, Project Manager, Senior Engineer.
Posted by  System Account  on  6/17/2010
0  Comments  | 0  Links to this post | Bookmark this post with:          


Add a Comment

We encourage comments on this blog, but this is a family friendly conversation, so please check out our discussion guidelines so we’re all on the same page. By submitting a comment, you agree to these terms and our Privacy Policy.  

Customers must have a My Account and be logged in to comment.
Login to My Account | Create My Account


We're hopeful that this space will encourage thought provoking and informative community discussions about issues related to our products and services. Currently you must be an Avista customer to participate in the conversation, but stay tuned. In the coming weeks we'll also provide an opportunity for non-customers to participate in this forum.