Chief Petty Officer Paul Roszkowski told The Associated Press that a 16-mile stretch of the river remained technically closed four days after two barges struck a railroad bridge, even though some barges are being allowed to pass.
Roszkowski said that during a test period Wednesday, southbound barges were allowed to pass first—"methodically and slowly"—so crews could assess the effects on cleanup operations. The Coast Guard allowed the first northbound vessel to pass Wednesday afternoon.
"We understand the huge impact this (closure) is making on vessel traffic on the Mississippi River," Roszkowski said.
But, he added, "It's critical that the vessels going through there don't affect our operations."
Following the test period Wednesday, Coast Guard officials approved a plan that allows for northbound vessels to move through the area from sunset to sunrise and southbound vessels to continue their journeys in daylight hours, Roszkowski said.
"We will space things out to minimize possible waking and will continue to monitor and control vessel traffic in the area," he said.
Roszkowski said the Coast Guard decided to halt the oil's transfer to the new barge at night because it's safer and easier to see if any oil is escaping during the day. The river is not expected to reopen fully before the transfer and cleanup is complete.
A Coast Guard "safety zone" extends the width of the river for 16 miles, which means it is effectively closed because barges must have permission to pass, he said.
Petty Officer 1st Class Matt Schofield said Wednesday that at times there have been more than 70 vessels, including towboats, and hundreds of barges idled at the closed section of the river, one of the nation's vital commerce routes. The numbers fluctuate as the barges are let through and others arrive at the closed section.
The leaking barge has been pushed against the Louisiana shore, across from Vicksburg's Riverwalk and Lady Luck casinos, since Sunday's crash.
Schofield said the Coast Guard started pumping oil from the leaking barge onto another barge—a process known as lightering—about 2:30 p.m. CST on Wednesday.
It's not clear how long that process would take.
Severe weather that swept through the area overnight Tuesday shut down cleanup operations for a time, but crews were working again Wednesday morning, Schofield said.
The Coast Guard said 7,000 gallons of crude oil were unaccounted for, but it's not clear if it all spilled into the river or if some seeped into empty spaces inside the barge.
Schofield said Wednesday that oil is still seeping from the damaged barge.
He said most of the oil was being contained, but some had escaped the containment booms Wednesday and a sheen was visible on a section of the river. Skimmers were cleaning it up, he added, saying 3,900 gallons of an oil-and-water mixture had been sucked from the river since the cleanup began.
The oil that spilled at Vicksburg would fill about two-thirds of a 10,500-gallon tank truck. When it spilled, water flowing under the bridge would have filled more than 600 such trucks in a second.
Crews have been working to contain and remove oil since the barge, owned by Corpus Christi, Texas-based Third Coast Towing LLC, struck the railroad bridge and began leaking early Sunday. The company has refused to comment.
The Coast Guard said the environmental impact has been minimal because a boom is containing the leak around the barge and the leak is slow. Crews are using a skimmer to collect the oil.
The closure has been costly for the shipping industry.
Ron Zornes, director of corporate operations for Canal Barge Co. of New Orleans, said each idled towboat could cost a company anywhere from $10,000 to $100,000 a day. The low end would be for a single boat with a couple of barges and the high end for boat in "a system of towboats that acts sort of like a bus system."
"So if one bus is stopped, it gums up the whole system," he said.
About 168.4 million tons of cargo a year move along the Mississippi River between Baton Rouge, La., and the mouth of the Ohio River, carried by nearly 22,300 cargo ships and 162,700 barges, according to the Army Corps of Engineers. About 3.6 million tons of cargo are handled annually by the port of Vicksburg.
When low water threatened to close the river earlier this month, the tow industry trade group American Waterways Operators estimated that 7.2 million tons of commodities worth $2.8 billion might be sidelined over the last three weeks of January.
Nature's Way Marine LLC of Theodore, Ala., has been named the responsible party for the oil spill, a designation that is assigned under the federal Oil Pollution Act.
The barges were being pushed by the company's tug Nature's Way Endeavor. The company has also declined requests for information.
Companies found responsible for oil spills face civil penalties tied to the amount of oil that spilled into the environment.
Coast Guard Petty Officer 3rd Class Jonathan Lally said Tuesday it's too early in the investigation to know if the company could face penalties or fines.
The Nature's Way Endeavor was pushing two tank barges when the collision with the bridge happened about 1:30 a.m. Sunday, authorities said. Both barges were damaged, but only one leaked. Authorities declared the bridge safe after an inspection.
The leaking tank, which was pierced above the water line, was carrying 80,000 gallons of light crude, authorities said. The Coast Guard hasn't said how much oil was in the other tanks on the barge.
Associated Press writer Janet McConnaughey in New Orleans contributed to this report.