The U.S. Coast Guard is investigating how a storage tank on a ship being loaded off Brooklyn, N.Y., was overfilled with ethanol, rupturing the tank and cracking the deck on Jan. 10.
The incident that occurred in Gravesend Bay around 0900 did not cause any cargo to leak overboard from the tanker Sichem Defiance, said Cmdr. David Flaherty, Coast Guard Sector New Yorkâ€™s incident commander. The anchored 443-foot tanker was loading 55,000 barrels of ethanol from a barge named Freedom when the over-pressurization occurred, causing the damage and a 6° list.
Flaherty said the Marshall Islands-flagged Sichem Defiance already had another cargo of a detergent containing benzene filling three of its tanks. It was filling tanks No. 3 port and No. 3 starboard with ethanol at the time of the accident.
â€œAt the point when she had roughly 41,000 barrels of ethanol on board, there was an over-pressurization in cargo tank No. 3 starboard,â€ he said. Either the tank was full or pressure built up that was not relieved, Flaherty said. That question is still being investigated.
The over-pressurization caused a failure of some of the surrounding tank walls, he said. Some of the cargo leaked into the empty No. 4 starboard cargo tank. There was also a breach between the No. 3 port and No. 3 starboard cargo tanks. Ethanol also leaked into three ballast tanks, Nos. 3 port and starboard and No. 4 starboard.
On deck, there were two cracks â€” 8 inches by 1 inch and 12 inches by 3 inches â€” that allowed the plating to droop in two areas. The crew quickly applied concrete patches to keep the ethanol from escaping. â€œNo product entered the water,â€ Flaherty said. The tanker has a double hull.
Responders included boat crews from Coast Guard Station New York, New York City Police Department marine and aviation units, the New York Fire Department and a rescue helicopter crew from Coast Guard Air Station Atlantic City.
â€œOur concern was ethanol cargo in tanks that are not designed to have any kind of cargo in them,â€ Flaherty said of the ballast spaces. â€œEthanol has a very low explosive rating. But any time youâ€™re dealing with a cargo that has hydrocarbons in it, itâ€™s a concern.â€
Sichem Defiance is owned by Eitzen Chemical of Norway. It is operated by India-based EMS Ship Management, which didnâ€™t respond to an e-mail request for comment.
The Coast Guard developed a plan to remove the leaked cargo with the company, the fire department, New York State Department of Environmental Conservation and other agencies.
The Resolve Salvage & Fire firm was hired for the removal. Ethanol was offloaded from the damaged tanks by Jan. 20. The next day the tanks were surveyed for damage.
â€œThere was external cracking on the deck plates, but nothing on the hull,â€ Flaherty said. The hull was surveyed by divers.
The remaining cargo was removed subsequently and the ship, built a little over a decade ago, was moved to Bayonne Dry Dock & Repair Corp. in Bayonne, N.J., on Jan. 31 for repairs. Flaherty said there is no damage estimate yet, but he noted that the ship has stainless steel tanks â€œso it will be a lot of money.â€