16.5-MW Green Lake hydropower project offline for repairs

The 16.5-MW Green Lake Hydro plant owned and operated by the City and Borough of Sitka, Alaska, was taken offline Oct. 17 after a hydraulic ram failed.

Hydraulic rams in the hydropower industry are utilized as kinetic energy-powered cyclic water pumps that take in water at one hydraulic head (pressure) and flow rate and output water at a higher hydraulic head and lower flow rate.

The Green Lake project ram failed while the Green Lake Tunnel was being drained for a planned inspection, according to local news reports.

About one gallon of hydraulic fluid leaked from the equipment during the tunnel’s dewatering, and the inspection was cancelled so officials could focus on repairing the ram.

An exact date for the Green Lake project’s return to service is not immediately available, and the municipality will utilize diesel generated-power to meet the community’s energy needs during the repair.

In an e mail on Oct. 19, Utility Director, Bryan Bertacchi, said, “Although we do not want to see equipment fail, it is far better to identify these problems in a safe way and get them repaired to maintain safe and reliable operations for our customers.”

Sitka is a unified city-borough on Baranof Island and the southern half of Chichagof Island in the Alexander Archipelago of the Pacific Ocean. The project is located in the Vodopod River basin along the Pacific Ocean about eight miles southeast of the 15.9-MW Blue Lake project.

The Green Lake plant was commissioned in 1982, and the City and Borough operate the generation, distribution and transmission from the Green Lake and Blue Lake plants to provide energy to Sitka.

Sitka has budgeted about US$4.8 million in its existing working capital fund and money taken from this fund will pay for repairs at the Green Lake facility. 

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Gregory B. Poindexter formerly was an associate editor for HydroWorld.com.

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