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Hydro Maintenance and Upgrades

Our Generation and Production/Substation Support Department, which is responsible for engineering, maintaining, and operating Avista’s hydroelectric and thermal generation facilities, is committed to producing electrical energy and delivering it to our customers as safely and efficiently as possible.  Avista’s engineers and operations staff ensure our hydroelectric developments are well-maintained and working efficiently, and that facility upgrades are completed as necessary to improve operations and generation capacity.

Ongoing maintenance and project upgrades will be posted here as future announcements, so you can keep up with what's happening.


Nine Mile Dam Rehabilitation Program

Completed in 1908, the Nine Mile Dam generated power to operate the railroad lines outside Spokane and also delivered power to neighboring communities. As at all our facilities, the dam needs ongoing maintenance and upgrades to keep it running smoothly and efficiently.

After studying a range of alternatives, Avista has started a Nine Mile Rehabilitation Program to restore full generation at the powerhouse and upgrade key facilities. This effort will include a series of projects stretching over the next seven years. Among these efforts are:

  • Upgrading the powerhouse from 26 MW to 34 MW by replacing Units 1 and 2
  • Rebuilding Units 3 and 4 turbines
  • Restoring one of the cottages for an administrative office
  • Building a new warehouse

We'll also complete a wide range of other electrical, mechanical and facility upgrades. So far, work has started on Cottage No. 6, and we removed Units 1 and 2. While you will be seeing and hearing more about these projects in upcoming years, the overall result will be a modernized, reliable generation facility and improvements to the Nine Mile Dam area for visitors.


Little Falls Plant Modernization

Completed in 1910, the Little Falls Hydroelectric Development (HED) was designed and constructed entirely by Avista’s personnel. The HED’s four 9000 horsepower turbines (each capable of 9 megawatts) were the largest in the world at the time of their initial operation. Listed on the National Register of Historic Places, Little Falls is situated in a remote setting with bald eagles and ospreys frequenting the five mile long reservoir between Little Falls and Avista’s Long Lake HED.

Avista started a Little Falls Modernization Program in 2012 to upgrade the HED to today’s standards and expects to complete it in 2018.  The Modernization Program includes overhauling all four generating units, replacing the bridge crane and station service, overhauling the headgate system, and installing a backup generator.


Long Lake Dam Spillway Modification Project

Completed in 1915, the Long Lake Hydroelectric Development (HED) is listed in the National Register of Historic Places. It took more than 500 workers to construct the dam, which was built in a spot where the Spokane River makes a complete horseshoe bend. A large encampment was established at the project site during construction, complete with all the amenities of an early 1900s town.

Avista is continuously on a mission to improve its environmental performance and the Long Lake Dam Spillway Modification Project sets out to do just that. After years of careful evaluation, planning, and collaboration with the Spokane Tribe, the Washington Department of Ecology, and the Washington Department of Fish and Wildlife, Avista developed a program to decrease the amount of Total Dissolved Gas (TDG) in the river downstream of the HED’s spillway.

The main focus of the program was to install two deflectors on the face of the spillway, fill in the plunge pool at the base of the dam, and remove a portion of the rock outcrop adjacent and below spillway bay 8. This modification will allow the water to skim horizontally across the surface of the river rather than to plunge vertically into the pool at the base of the dam.


Post Falls South Channel Dam Upgrade is Complete

Construction on the Post Falls South Channel Dam was completed this year, and the 1906 structure is now ready for another century of continuing its role in helping provide clean, low-cost renewable energy. 

Since the project began in 2014, workers removed original concrete from the structure and replaced the manually operated spillway gates and hoists with remotely controlled gates. The new equipment will improve operational efficiencies, allowing for remote operation of the facility.

Interestingly, it took45 tons of rebar; 1063.5 cubic yards of new concrete; 782 supersacks filled with 44.53 tons of sand to construct the temporary cofferdam; 500,000 lb. crane and clam delivered by nine semi-trucks and assembled on-site to help prepare the river bed for the construction of the cofferdam to changing hydro conditions and customer demand.