The $64 million project began in 2006 will soon enter its final stages of construction and is expected to be online by October 2009.
The Lake Dorothy plant will increase hydroelectric energy available to Juneau residents by 20%. AEL&P expects it will eliminate the need for backup diesel generators during winter months when Lake Snettisham water levels are low.
"Lake Dorothy will take care of (the need for diesel) for a while," said AEL&P Vice President Scott Willis.
Every day 40 to 60 people, mostly contractors, are at work on the construction site, located on the Taku Inlet southeast of Juneau. Once the plant is online it will be operated by a computer system in town and only one caretaker will need to stay on site.
"If Greens Creek weren't here, we wouldn't be building Lake Dorothy yet," Willis said. "That's good for Juneau customers. If we had to wait five years to build it, it would be more expensive."
Greens Creek will pay for the project one way or another, Willis said. Either Greens Creek's electricity rate will reflect the cost of Lake Dorothy construction or it is possible AEL&P customers will pay an increased rate and receive refunds from the proceeds of the surplus energy sold to Greens Creek.
Willis estimated AEL&P customers would pay around 11 cents per kilowatt hour when the Lake Dorothy plant comes online.
Like other AEL&P hydropower plants, the Lake Dorothy project involves tapping water from an elevated lake and running it to a turbine in a powerhouse. Transmission lines will connect Lake Dorothy's powerhouse to the existing transmission lines leading from the Snettisham hydro project to Juneau.
Katie Spielberger photos AEL&P engineer Ed Johnson points out the tunnel through which a pipeline will deliver water from the lakes to the Lake Dorothy powerhouse.
Luckily, gravity can do half the work. Lake Dorothy naturally spills over into Lieuy Lake, which flows down to Bart Lake at 986 feet above sea level. "We're using the water from Lake Dorothy but letting it roll down the hill and picking it up at Bart Lake," Willis said.
A dam is under construction at Bart Lake to allow all the water to run through the 8,249-foot penstock leading to the powerhouse. Dorothy Creek will dry up, but fisheries are not concerned, said Ed Johnson, an AEL&P contractor and resident engineer for the project. Due to the steep terrain, with an average grade of 41 degrees, fish were never able to migrate up the creek, he said.
In the second phase of the Lake Dorothy project, this tunnel will connect to an penstock leading straight to the turbine in the powerhouse, allowing a direct tap of Lake Dorothy.
The second phase will not begin until the area's electricity need is high enough, which Willis predicted will be at least 15 years from now and depends on the population, the economy and other factors. AEL&P does not yet have a projected cost for the second phase.
The Lake Dorothy Project will be featured on the TV program "Tougher in Alaska" on the History Channel, GCI channel 58. This episode to currently scheduled to air August 3 at 9:00 p.m Alaska Standard Time.