Project manager Corry Hildenbrand talks to media on Sept. 3, three days after the plant went online.
The powerhouse at the Lake Dorothy site houses a 14.3-megawatt generator located at 24 feet above sea level.
Story last updated at 9/9/2009 - 11:36 am
JUNEAU - When Corry Hildenbrand first set foot on the east bank of the Taku Inlet, he was bushwhacking through devil's club. Today, the same plot of land is home to the Lake Dorothy hydroelectric project, phase one of which was completed last week.
Hildenbrand is the Alaska Electric Light and Power (AEL&P) project manager who has been working on the project since its preliminary design work and permitting began in 1995. Construction began in May of 2006, and the project was put into commercial operation on Aug. 31.
"Corry has done a tremendous amount of really interesting projects for AEL&P," said AEL&P president and general manager Tim McLeod. "One hundred years from now, people will be talking about the accomplishments of Corry the way we do about Bart Thane (mining engineer who pioneered hydroelectric power in Juneau) today."
Lake Dorothy sits at an elevation of 2,434 feet, the uppermost of a series of three lakes connected by a series of waterfalls. Water flowing out of Lake Dorothy cascades down a waterfall to the intermediary Lieuy Lake. Consequently, when Lieuy Lake fills, its excess water spills down into Bart Lake and eventually empties into Taku Inlet. The idea behind the project was to take advantage of gravity and harness the potential energy created by water that experiences such an extreme drop in elevation.
Phase one of the project included tunneling through the side of Lake Dorothy at 143 feet below the lake's surface. After flowing through a 900-foot tunnel, the water meets a large valve and an outlet pipe, which were installed to control the amount of water released from the lake. After leaving Lake Dorothy, water follows a path through Lieuy Lake and finally lands in Bart Lake, where a 34-foot-high dam was constructed. Water is then diverted into a penstock and travels downhill to the powerhouse, located at 24 feet above sea level.
The powerhouse is home to a 14.3-megawatt generator that is expected to produce an average of 75 gigawatts per year. That creates an additional 20 percent of hydroelectric power capacity for Juneau. Phase two of the project, to be completed in the future as demand grows, will add an additional 20 percent of capacity.
According to AEL&P spokesman Scott Willis, the benefits of the Lake Dorothy project will especially come into play during winter months. With the completion of the lake tap and tunnel plug, power can still be generated after the lake freezes over, the time when Juneau needs electricity most.
"The location of this project adds supply diversity and another level of reliability to our system," McLeod said.
Electricity generated at the Lake Dorothy powerhouse travels about 3.5 miles along new transmission line before joining the existing Snettisham line, then makes its way to Juneau via submarine cable and transmission towers along Thane Road. Avalanche risks were considered when constructing the new lines. The terrain was evaluated by Alaska Avalanche Specialists during the construction process and they determined the probability of a slide to be low.
"If we'd have had Dorothy during the (2008) avalanche, we would have used 40 percent less diesel," Willis said.
The total cost of the project is estimated at around $70 million, a cost that may be passed on to customers in the form of a rate hike. The final adjustment has not yet been determined, but it is estimated to be raised a couple of cents per kilowatt-hour. According to McLeod, the rate increase will probably only be in effect for the short-term, followed by years of reduced rates.
Juneau is one of the only places in the world with the climate and landscape necessary for this type of hydroelectric efficiency. The completion of this project makes Juneau one of the greenest cities in the nation, McLeod said.
"The people of Juneau don't realize how lucky we are," McLeod said.