Avista Corp., of Spokane, has begun the final phase of a multiyear, $35 million upgrade at its 52-year-old Cabinet Gorge Dam, located on the Clark Fork River near the Idaho-Montana state line.


The upgrade project enters its final stage as the company begins to plan for a similar, $25 million-plus project at its Noxon Rapids Dam, also located on the Clark Fork, about 25 miles southeast of Cabinet Gorge.


John Hamill, hydroengineering manager for Avista Utilities, says the current $5.6 million project at Cabinet Gorge involves refurbishing one of the dams generators and replacing the propeller-style turbine runner that is situated underneath it.


Essentially, Hamill says, a turbine takes kinetic energy from falling water that goes through it and converts that into mechanical energy. The generator then converts that energy into electricity.


Earlier this month, Avista removed the massive, 265-ton generator thats due to be refurbished. Hamill says the company plans to disassemble that generator in December, make the needed improvements, and put it back together in early February.


Avista also will replace the propeller-style runner, which is all stainless steel, spans 17 feet in diameter, and weighs 60 tons. Removal of the current runner is scheduled to start later this month, Hamill says.


The upgraded turbine-generator unit is scheduled to be functional in March, before the spring runoff of melted snow begins, Hamill says. Typically, he says, the dam generates more electricity in spring than it does at other times of the year.


The upgrade will enable Cabinet Gorge to operate more efficiently, with that one generator producing 8 to 10 more megawatt hours than it could generate previously, Hamill says. Thats enough additional electricity to meet the needs of 5,200 to 6,500 households, he says.


Cabinet Gorge Dam has four turbine-generator units in all. Avista has upgraded the other three units over the past 12 years.


Once the current upgrade is completed, the dam is expected to generate about 2.4 million megawatt hours a year, up from about 2.37 million megawatt hours previously, Hamill says.


Power generation at Cabinet Gorge accounts for about 30 percent of Avistas hydro-system generation and roughly 15 percent of the companys overall generation, Hamill says.


Avistas long-range plan calls for upgrading the electrical system at Cabinet Gorge in the future, but such a project likely is years away. In addition, the company is studying a $50 million-plus bypass tunnel project at Cabinet Gorge, but it doesnt have a timeline for such a project yet, Avista spokesman Hugh Imhof says.


More immediately, the company plans to upgrade four of five turbine-generator units at the Noxon Rapids dam, which was constructed in 1960. Those refurbishments are scheduled to occur between 2009 and 2012.


Hamill says those turbine-generator units are the originals that were installed in the dam when it was built. The one that wont be upgraded was installed in 1979, replacing an original unit, he says.


Separately, Avista is well under way on $122 million in upgrades to its 230 kilovolt transmission system. Work on those improvements started in 2003 and is expected to be completed at the end of 2007.


Contact Linn Parish at (509) 344-1266 or via e-mail at linnp@spokanejournal.com.