The Alaska Marine Highway System has found a new definition for the word logjam.
The state's new fast ferry Fairweather, which will begin operating on Monday, twice has sucked "tree-sized" driftwood logs into its water jet propulsion systems, according to Gary Smith, a project manager for the state Department of Transportation.
The Fairweather is powered by four separate jet systems that take in water through open ducts and steel propellers that accelerate and steer the vessel.
One of the jet systems was clogged with a large log in late March, as the Fairweather traveled to Juneau from Bridgeport, Conn., where it was built. The vessel was clogged with another driftwood log a second time weeks later during a training run to Sitka.
State officials said the problem is not uncommon for jet boats and that the intake of debris has not damaged the ship.
"It's a minor issue," said port engineer Paul Johnson. "It's a known problem with water jets."
Johnson said the propellers can be reversed to dislodge any material caught in the propulsion duct, but both times the system has been clogged, the state has called in scuba divers to physically remove the debris after the ship arrived in port.
Smith said it costs about $100 to $200 to hire divers to remove the driftwood.
Reversing the propeller would delay the ship by only a few minutes. If the debris cannot be dislodged, the ship can operate on the three remaining propellers, he said.
If two of propulsion systems get clogged, "then you go home," Smith said.
Calling the intake of large debris an "extremely rare event," Smith said the Fairweather has been operating trial runs between Juneau, Sitka, Skagway and Haines since early April and has only dealt with the issue twice. During that time the ship has made 12 trips on each route.
Smith said state project planners have been aware of the problem for years, noting, "Other operators in the Pacific Northwest have been operating years with that issue."
Deborah Marshall, a spokesperson for B.C. Ferries, said fast ferries that operated in Canada two years ago occasionally sucked in driftwood logs, adding, "It's certainly not a show stopper."
The fast ferries in British Columbia operated from 1999 to 2002 and were later sold because of beach erosion caused by the ships' wakes and various other financial reasons, she said.
She said the fast ferries in the Canadian fleet were significantly larger than the Fairweather, with a capability of holding 1,000 passengers and 250 vehicles. The Fairweather, a 250-foot catamaran, can carry 250 passengers and up to 35 vehicles.
Marshall said the ferry system considered welding grates onto the open ducts, but engineers were concerned they would slow the ship.
Smith said the grates also could get clogged or covered with other material, limiting the water flow to the propellers.
"The minute you put grates in there it becomes a problem," he said. "It's hard to do that without a lot of work and a lot of replacement."
U.S. Coast Guard Spokesman Dan Buchsbaum said Coast Guard inspectors will conduct their final safety review of the ship today.
He said safety inspectors are aware of the problem but that the ship can operate safely despite an occasional clogged duct.
"I don't want to say it's of no concern to us," he said. "We're tracking and monitoring it."
Buchsbaum said any vessel that loses propulsion for any reason is investigated by the Coast Guard during semi-annual inspections.
"In a larger port you would have maybe one or two (propulsion system failures) a week," he said.
Timothy Inklebarger can be reached at email@example.com.
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