Hawaii Superferry service to Maui has once again been disrupted by rough seas.

The company canceled its roundtrip voyages between Honolulu and Maui yesterday and today after a state-owned barge used to load and unload vehicles from the 350-foot high-speed catamaran sustained minor damage as a result of large swells within Kahului Harbor, according to Michael Formby, Department of Transportation deputy director for harbors.

A full assessment of the damage was not available yesterday, and an estimate of repair costs and timing will not be known until an inspector can examine the barge, Formby said. The pier and barge repairs will have to get Coast Guard approval before being put back into use, he said.

Yesterday's conditions forced the state to move the barge from the end of Pier 2 at Kahului Harbor to the ferry berth on a more protected side of the pier.

Similar harbor surge conditions in early December resulted in damage to the pier and barge and delayed the restart of Hawaii Superferry service by a week.

Roiling seas in the open ocean along the Superferry's route forced the company to cancel service four days in a row in late December.

Some Superferry critics have questioned the wisdom of using a floating barge system at Pier 2 because that area of the crowded harbor is most vulnerable to wave action.

Following last month's problems with harbor surge, a tugboat is now regularly used — at state expense — to hold the barge snug against the pier fenders while the ferry is in port from about 10:15 to 11:15 a.m. daily.

The Coast Guard approved the use of the tug assist during Hawaii Superferry operations until a permanent mooring system is installed, Formby said.

He said the weather-related problems are to be expected this time of year, although seas this winter have been particularly rough.

"Ocean conditions in Kahului Harbor during the winter months can develop rapidly and unexpectedly," Formby said in an e-mail. "During the winter months, it really is a situation where (Hawaii Superferry) and (Harbors Division) personnel continuously monitor the barge and ocean conditions so that they can pull the barge off the pier and reposition it to a more favorable and/or protected location to ride out the storm swell."

The company announced last week it would launch a second daily Honolulu-to-Maui sailing starting yesterday, but those plans were put on hold Monday after Maui Mayor Charmaine Tavares objected.

The Superferry has been the subject of statewide controversy and several legal challenges related to the potential environmental impacts of the new interisland transport, and Tavares said she was upset that county officials were not notified of plans for additional service.

Reach Christie Wilson at cwilson@honoluluadvertiser.com.