Leaking bulkhead on research vessel leads to fuel spill

The research vessel’s gray-water tank is located inside one of the fuel tanks. When a bulkhead separating the two tanks corroded and began leaking, fuel made its way into the gray water. (Courtesy University of Hawaii)

A small amount of diesel fuel spilled into Honolulu Harbor in October as a result of a leak in a fuel tank aboard a University of Hawaii research ship.

The leak allowed diesel fuel to flow into the ship’s gray-water tank. The crew of the 223-foot Ka’imikai-O-Kanaloa began emptying wastewater into a shore-based discharge system, unaware that they were also transferring thousands of gallons of diesel. The incident happened on the morning of Oct. 11 at Honolulu Harbor’s Pier 45.

The ship’s gray-water tank actually sits inside one of the four fuel tanks, with the two tanks sharing common bulkheads on three sides. One of the walls rusted through and diesel poured into the wastewater, said Coast Guard Petty Officer Rob Rawson, a pollution investigator at Honolulu.

“There was a hole in one of their fuel tanks, and that leaked into their gray water,” Rawson said. “When they were trying to get rid of the gray water, they pumped it through the ship-to-shore piping system. They noticed a significant sheen around the boat, and they figured out it was (diesel fuel).”

By the time someone suggested the leaking fuel might be from their own ship, approximately 4,400 gallons of diesel had been transferred ashore in the wastewater system. To make matters worse, the underground wastewater pipe was leaking too, and much of the fuel spilled into the soil and some eventually found its way into the water.

Stan Winslow, marine superintendent of the University of Hawaii Marine Center, said Ka’imikai-O-Kanaloa’s crew began transferring the gray water after an electronic gauge showed that the 12,000-gallon tank was getting full.

“There was a hold that just rusted through in one spot, about the size of a golf ball,” Winslow said. “The fuel spilled into the gray-water tank. The crew did not notice that. The next day, there was an indication that the gray-water tank needed to be pumped.”

After the crew spotted the sheen in the seawater, they didn’t immediately realize that diesel was disappearing from the 37,000-gallon fuel tank.

“As a precaution, we sounded it,” Winslow said. “Lo and behold, when they sounded it, one of the tanks came up about 6,000 gallons short.”

Booms were set up around the research vessel, and Pacific Environmental Corp. was summoned as the cleanup contractor. The contaminated soil was removed.

The Coast Guard determined that, during a long-ago job, a contractor or excavator had accidentally cracked the underground 4-inch PVC pipe just a few feet from the dock.

“It was repaired a number of years ago improperly,” Rawson said. The type of patch “wasn’t correct for that piping.”

In the end, about 8,300 gallons of diesel had exited the ship’s fuel tank. Winslow said virtually all of the fuel was recovered. Rawson said about 2,000 gallons went into the ground. Most of the fuel was still in the ship’s gray-water tank or in the dockside holding tank.

Diver inspections revealed no cracks in the hull. As a temporary repair, doubler plates were installed on three corroded spots in the gray-water tank.

The 259-gross-ton ship was built in 1979 and was refitted in 1993.

By Professional Mariner Staff