Seattle City Light Scheduled to Rehabilitate Gorge Dam Spillgates
Seattle City Light is scheduled to rehabilitate two spillgates at Gorge Dam in Newhalem this summer, which will require lowering the water level of Gorge Lake.
The project will rehabilitate the seals and recoat all surfaces of two 47-foot by 50-foot steel gates.
“This work has been scheduled for several years as a necessary step to ensure the long-term reliability of these gates,” Power Generation Director Mike Haynes said. “Summertime represents the most favorable conditions for performing this work due to the need for predictable weather and worker safety.”
City Light is scheduled to lower the water level in Gorge Lake over three days, starting July 15. During the drawdown, the boat launch at Gorge Lake campground will not be available to visitors. The utility expects the work to be finished in September when the lake would be returned to its normal operating level.
Long Painting of Kent has been hired to complete the project. Surface preparation for the gates will include grit blasting and high pressure water jetting. All surfaces will be recoated with a water-cure urethane paint system. Full containment and remediation of any spray or loosened materials will be required during surface preparation for and recoating of the gates.
Rehabilitating the gate seals is largely steel work involving removal and replacement of steel backing plates and replacement of approximately 1,000 bolts. All work on the gates must be completed before Oct. 1 to ensure their availability as part of the Skagit River flood control system.
The original Gorge Dam — a wood crib structure — was the first of City Light’s dams on the Skagit River. It was replaced by a concrete dam in 1950 and then by a larger concrete dam in 1960. Gorge Powerhouse is located in the town of Newhalem. Gorge Dam, two miles upstream, is connected to the powerhouse by an 11,000 foot long, 20.5 foot diameter power tunnel. Powerhouse construction began in 1919 with the first unit going on line in 1924. Currently Gorge can produce 175 megawatts of renewable electrical power, about 9 percent of the utility’s generating capacity.
Seattle City Light is the 10th largest public electric utility in the United States. It has some of the lowest cost customer rates of any urban utility, providing reliable, renewable and environmentally responsible power to nearly 1 million Seattle area residents. City Light has been greenhouse gas neutral since 2005, the first electric utility in the nation to achieve that distinction.