The spill occurred early Wednesday when an outbound 600-foot Liberian-flagged tanker named The Tintomara collided with a barge pulled by a tugboat. The barge, a flat-bottomed boat, was carrying 400,000 gallons of thick, tar-like No. 6 fuel oil and was split in half, sending its contents pouring into the river.
The oil is too thick to evaporate from the river's surface and could sink. Authorities are hoping to remove the oil before that happens.
The barge was being pulled by the tugboat Mel Oliver -- the operator had only an apprentice mate's license, and no one else on board had a license to operate the boat on the river. An operator should have a master's license to operate the tugboat, Petty Officer Stephen Lehmann said.
Paul Book, vice president of operations facilities for American Commercial Lines Inc., said divers were assessing the barge as it lay against a bridge pier.
"We have reports of oil that is bubbling, coming from the bow and the stern compartments," he said at a news conference attended by several government officials.
V-shaped booms containing skimmers have been placed below each compartment to collect and siphon off the oil, he said. The operation will be done twice.
"We have high hopes that that will stop the release ... coming from the barge," Book said.
The thick industrial fuel pouring from the barge could be smelled for miles in city neighborhoods up and down the river, even as hundreds of cleanup workers struggled to contain the hundreds of thousands of gallons. Some environmentalists worried about reports of fish and bird kills in sensitive marsh areas downstream, though officials said they had so far heard of only a handful of oil-covered birds. Booms to protect areas richest in wildlife, at the river's mouth, were being deployed, officials said.
The Mississippi remained closed to all boat traffic, stranding about 65 vessels. The effect on the area's economy was thought to be significant, with this city's port estimating a loss of at least $100,000 a day and probably more as the river remained closed, and petrochemical facilities dependent on it for shipping were threatened with a bottleneck, the Coast Guard said. Some suburbs stopped drawing drinking water from the river.
"We've had a number of large spills in the New Orleans area, but this is a heavy, nasty product, problematic in the cleanup," said Lt. Cmdr. Cheri Ben-Iesau of the Coast Guard, adding that it is of the sort normally used to fire up boilers at power plants.
"It's a significant spill, if for nothing else because of its impact on the water supply," Commander Ben-Iesau said. "We've got a lot of commerce dependent on this water supply, so we're scrambling to get it cleaned up."
On Thursday afternoon, the picturesque walk along the Mississippi at the French Quarter, normally full of tourists and pedestrians, was nearly deserted as a pungent chemical stench wafted up from the oil-covered water. A few skimmer boats, deployed to suck up the oil, constituted the only traffic on the nearly half-mile-wide river; a plastic boom to contain the fuel hugged the rocky shoreline, and the seagulls had disappeared, New York Times reports.
Coast Guard Lt. Anastacia Visneski said, "It's going to take us several days before we can get the river open, and it's going to take weeks before we can clean it all up.
"Right now, our priority is for the safety of the people in the parishes surrounding the river, the safety of the environment, and containing and cleaning up the spill as quickly as possible."
Containment booms have been installed to prevent the oil from spreading to environmentally sensitive areas and seeping into water-supply intake valves in Gretna, St. Bernard, Dalcour, Belle Chasse, Pointe a la Hache, Port Sulphur and Boothville-Venice, Young said.
Tom MacKenzie of the U.S. Fish and Wildlife Service said there have been few reports so far of oil-covered wildlife, but much of the shoreline hasn't yet been searched. Some ducks, an egret, a beaver and several birds were being decontaminated.
The spill is much smaller than the ones that followed Hurricane Katrina in 2005, when the Coast Guard estimated that more than 7 million gallons of oil were dumped into the Mississippi and nearby waterways.
The Mississippi is the major shipping route from the Midwest to the Gulf of Mexico, and New Orleans is among the largest U.S. ports.