In the next 10 years, there’s a 40 percent chance of one or more faults developing in the submarine cable connecting Haines and Skagway power grids, according to Danny Gonce, power operations manager for Alaska Power and Telephone.
"It’s not a question of if, it’s a question of when our cable is going to fail," Gonce told the Haines Chamber of Commerce. The cable connects Haines to Skagway-area hydro-electric sources, effectively saving the town from reliance on diesel generation for most of the year.
The 4.5-inch diameter, armored cable was stretched 17 miles on the Lynn Canal sea floor in 1998 at a cost of $6 million. Its Italian manufacturer guaranteed it against defects for 30 years.
Cable failure statistics are hard to come by but one study of 2,200 miles of cable installed between 1950 and the 1980s found one fault per 16-mile section every 20 years, Gonce said.
Most faults with undersea cables are associated with anchors or fishing gear, which isn’t as much a concern at the bottom of Lynn Canal, which runs as deep as 1,300 feet, Gonce said.
The cable is most likely to fail due to tidal action near Kasidaya Creek, Gonce said. "Four times a day the friction of water passing over that cable is working it in a very hard way, especially at Kasidaya, where it’s a rugged rock face underwater and there are places where it’s suspended from one rock to another."
AP&T has "splice kits," including sections of new cable to use in the event of failure in a section, stored in Washington state, Gonce said, but repair would require mobilization of a special ship that travels the world. A fix could take six months or longer, he said, and force increased reliance on diesel fuel in Haines during its duration.
There might be other concerns as well, he said. "A question is, ‘Has the armor on the cable deteriorated in such a way that it would compromise the cable trying to fix it?’"
Connelly Lake opponents say AP&T is using the vulnerability of the cable to bolster its predilection for the Haines-based hydro project. In recent written comments, resident Rob Goldberg said submarine power lines are "proven technology."
"If a cable has a known life span, it’s a maintenance item and should be replaced in a timely manner... The supposed vulnerability of the submarine cable is not a sufficient reason to jeopardize Connelly Lake with a hydro project," Goldberg wrote the Federal Energy Regulatory Commission.