The state Department of Transportation plans to spend $414,284 for immediate repairs to the Hawaii Superferry barge at Kahului Harbor to prevent a "potential disastrous and life-threatening" leak.

The barge's internal frames and other structural components have been "overstressed, bent and damaged," according to documents filed this week with the State Procurement Office.

The damage occurred over the past nine months from rough contact between the barge and the end of Pier 2C at the Maui port and from the force of a tugboat pushing from the seaward side of the barge to keep it against the pier while the 350-foot, high-speed ferry is unloading and loading, the documents said.

The repair money will come from the remaining balance on a $40 million state appropriation for ferry-related improvements at four ports, said DOT Harbors Division chief Michael Formby.

Not included in the $40 million was $503,000 the state spent from December through September to hire a tugboat to keep the barge snug against the pier during ferry operations. Hawaii Superferry is responsible for tugboats costs effective Oct. 1, Formby said.

The DOT is seeking an exemption from state procurement rules to hire Healy Tibbitts Builders Inc. to perform the repair work since the company designed and built the barge and mooring system. The coming winter storm season is another reason to expedite the project, according to the DOT exemption request.

A survey of interior of the barge's hull in September revealed "significant" damage to the hull structure in the area where the tug contacts the barge and where the hull contacts the pier on the opposite side of the vessel, the exemption request said.

"Immediate repairs to the barge must be accomplished before a potential disastrous and life-threatening leak develops in the hull from the continued daily tug-supported operations," the request said.

The work will be scheduled around Superferry visits.

The unprotected mouth of Kahului Harbor faces northeast and is susceptible to winter storm surge and high surf. Using historical wave and surge data, Healy Tibbitts designed the barge and installed a cable mooring system to hold the vessel steady against the pier and accommodate wave heights of up to 1.43 feet.

Last December, unusually high storm surge and wave conditions exceeding that height caused the instantaneous failure of the mooring system. Four lines securing the barge to the pier snapped and two mooring bollards were uprooted. The episode led to a U.S. Coast Guard requirement that a tugboat be employed to hold the barge against the pier during daily ferry visits, until a safer, permanent system could be installed.

In the meantime, a modified mooring system that relies on soft lines, or ropes, allows the barge to ride out waves and surge when the ferry is not present.

The Army Corps of Engineers is reviewing the DOT's permit application for a new anchored mooring system that will hold the barge off Pier 2C in between use. During ferry unloading and loading, a winching system will bring the barge to the pier.

Formby said the cost of the new mooring system has not been determined. "Given the state's notice that it has reached the limit of its funding authority, the state will not be funding the new system," he said.

That could mean Hawaii Superferry will have to pay for it and any future improvements, although the company may have something to say about that.

Superferry officials yesterday said they are still in discussions with the state over who is responsible for some of the unanticipated expenses connected with the troublesome barge and mooring system.

The company has pointed out a series of system failures that occurred before the December event, suggesting a design flaw. The state and Healy Tibbitts Builders have questioned whether thrust from the ferry's water jets contributed to the problems, and whether the mooring lines were improperly handled by ferry staff after initial installation.

Formby said no agreement has been reached between the parties as to reimbursement or indemnification for costs incurred by the state or Hawaii Superferry.