A cable-laying barge is scheduled to start work between Vank and Woronkofski islands the first week of July to replace a 3.5-mile section of the power line that connects Wrangell and Petersburg.
The undersea cable, which was installed in 1983, developed a fault in September 2019. The Southeast Alaska Power Agency has been working on plans and permits for the replacement project, which is estimated to cost almost $14 million.
Preparations are already underway, with crews about 60% finished with shoreside connection work on Vank and Woronkofski, Robert Siedman, SEAPA’s director of engineering, said Monday.
Wrangell utility customers should not see any interruption in power during the cable work, Siedman said, though Petersburg will need to rely on diesel-fueled power for about four hours at a time on two or three different days during the project.
The damaged cable is one of four undersea lines that connect onshore terminals between Woronkofski and Vank to provide Petersburg with power from the Tyee Lake hydroelectric project on the mainland, as the power moves to Wrangell and on to Petersburg.
Three of the cables are needed to move power, while the fourth is a backup. Without the fourth cable, power to Petersburg would be lost if one of the other three cables got damaged.
The contractor’s 220-foot-long cable barge, the ITB45, out of Vancouver, British Columbia, is scheduled to arrive in the area on June 28, Siedman said. The power line is in transit from the manufacturer in Japan and will be loaded on the barge in Vancouver.
The plan is to pull up the damaged cable July 1, and start laying the new line the weekend of the Fourth of July, Siedman said.
The power agency has issued a notice to mariners to watch for the barge and its support vessels through July 21. The cable barge, two tugboats, skiffs and dive boats will be working 16- to 18-hour days. The cable crew will be housed aboard the barge during the entire project, Siedman said.
A dynamic-positioning system aboard the barge that relies on satellite GPS coordinates and bow thrusters at each corner of the vessel will keep it in place “so that it can accurately lay the cable,” he said.
SEAPA doesn’t know the exact cause of the 2019 line fault but will investigate the cable and try to determine what caused it to fail after pulling up the old line for replacement. The agency had earlier determined the line could not be repaired and had to be replaced.
Though the undersea cables that run from the hydroelectric power station on the mainland to Wrangell and Petersburg are almost 40 years old, “it’s not unheard of for these cables to last 60 to 80 years,” Siedman said.
During the cable replacement, boaters are advised to use marine VHF channels 16 and 8 for general communication with the working vessels.
The power agency is looking at how to pay for the work. An insurance payout is possible, and SEAPA is looking at multiple options, Siedman said. A small rate increase is possible if the agency needs to borrow money for the project, but nothing has been decided at this time, he said.
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