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One-kilometre underwater cable improves service to small B.C. island

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A new 25 kV submarine cable crossing completed in September will improve electrical service reliability to Gossip Island, located just outside Active Pass in B.C.'s Georgia Strait.

The Gossip Island Electrification Society (GIES) owns and operates the island's electrical distribution system, which used to connect to BC Hydro's distribution system via a customer-owned submarine cable to a "point-of-delivery" on nearby Galiano Island. The customer cable was nearing its end of life.

Installation of a one-kilometre cable on a new route across the ocean floor extended BC Hydro's system to a new point-of-delivery, a customer-owned switch on Gossip Island.

"The new cable configuration of two cables provides the Gossip Island community with contingency for improved reliability," said BC Hydro project manager Muhammad Butt. "That means island residents will not lose power even if one cable fails."

Although the crossing is relatively small at one kilometre, the strong currents near Active Pass made it more complex. It was hard to stay on the designed cable-laying route, and divers needed to swim the whole length and manually move the cable into a better position.

The divers' manual intervention was necessary to avoid cable "overhangs", spans where the cable would be suspended across rocks along the ocean floor. Adding to the complexity were reefs in the area, which called for tricky manoeuvring of the barge carrying the cable along the route.

To reduce project costs, BC Hydro installed a cable used previously in a different cable crossing. BC Hydro worked alongside environmental coordinators to ensure that all work was executed as outlined in the Environmental Management Plan.

"This project had a number of highly sensitive environmental aspects including an active eagles nest in the work area, as well as working within known clam beds and highly productive eelgrass habitat," said Andrew Walter, a BC Hydro natural resource specialist.

Added Butt: "The key to the success of this project was the professionalism and leadership shown by BC Hydro crews and contractors, who kept safety top of mind both in design and execution stages."