(Reuters) - More than 1,000 barges were backed up on the Mississippi River near Vicksburg, Mississippi, on Wednesday after a weekend barge accident and oil spill forced the closure of the major shipping artery, the U.S. Coast Guard said.
One 80,000-gallon hold of a tanker barge that struck a railroad bridge on Sunday continued to leak crude oil, but cleanup crews have deployed 2,800 feet of boom to contain the spill and airborne spotters have not detected any oil outside the containment area.
Response crews will lighter the oil from the damaged barge before removing the vessel from the river, but a timeline for a full reopening of the waterway to commercial shipping traffic remains unclear.
"A timeline is really hard to establish with an operation like this because there are so many factors, from getting the lightering operation set up to getting the pumping operation going," said Coast Guard spokesman Matthew Schofield.
"We want to make sure we're doing it in a safe and methodical manner. We don't want to have an additional release (of oil) and we don't want to jeopardize the safety of the crew."
Shippers rely on the Mississippi River and other inland waterways to haul billions of dollars of grain, coal, fertilizer and other commodities every year. Some 55 to 65 percent of all U.S. grain and soybean exports are transported down the Mississippi River to the Gulf of Mexico.
As of midday on Wednesday, 34 northbound vessels hauling a total of 532 barges and 37 southbound vessels with 524 barges were delayed by the 16-mile closure from river mile marker 425 to 441, the Coast Guard said.
The Coast Guard has so far allowed only two small southbound barge tows hauling a total of 15 barges to transit the area to gauge whether shipping traffic would impact the cleanup effort.
"We're hoping we can continue to allow southbound vessels in 15- to 20-minute intervals through the afternoon, but if anything starts to affect the safety of the personnel we're not going to continue," Schofield said.
The river closure has not seriously impacted grain exports at the Gulf, but a prolonged traffic jam could delay the arrival of corn or soybeans needed to load ocean-going vessels. As a result, exporters may incur steep demurrage penalties if their leased vessels cannot be loaded promptly.
The oil spill was the latest in a recent string of logistical headaches for shippers.
Low water along a busy shipping corridor between St. Louis and Cairo, Illinois, has threatened to disrupt traffic on the drought-drained river since December. Dredging operations and other work aimed at keeping barges flowing have also snarled traffic at times.
The river system's busiest lock was closed for a day last week after a barge collided with a lock gate.
Reporting by Karl Plume in Chicago. Editing by Andre Grenon