The Army Corps of Engineers dredge Potter is pumping tens of thousands of cubic feet of sediment from the Mississippi River each day to allow barges to navigate south of St. Louis.
John Schwartz, New York Times
On Mississippi, trouble staying afloat
- Article by: JOHN SCHWARTZ
- New York Times
- August 19, 2012 - 8:20 PM
ABOARD THE DREDGE POTTER ON THE MISSISSIPPI - This boat is making sure that the Mississippi River, shrinking under one of the worst droughts in modern history, stays deep enough.
The Potter is scooping a stretch of the river's navigation channel just south of St. Louis, sucking up about 60,000 cubic yards of sediment each day and depositing it via a pipe 1,000 feet to the side in a violent, muddy plume that smells like muck and summer.
The Army Corps of Engineers has more than a dozen dredging vessels working the Mississippi this summer. Despite being fed by water flowing in from more than 40 percent of the United States, the lower part of the river is feeling the ruinous drought affecting so much of the Midwest. Some stretches are nearing the record low-water levels experienced in 1988, when river traffic was suspended in several spots.
That is unlikely this year, because of careful engineering work to keep the largest inland marine system in the world passable. But tow operators are dealing with the shallower channel by hauling fewer barges, loading them lighter and running them more slowly, raising their costs. Since May, about 60 vessels have run aground in the lower Mississippi.
New features built
The low water is affecting not just the 500 million tons of cargo such as coal, grain and fertilizer that move up and down the river each year. The volume of water coming down the river is so much lower than normal that a wedge of salt water is creeping up the Mississippi toward New Orleans, imperiling local water supplies drawn from the river. The corps is building a sill -- a dam of sediment -- in the river below New Orleans low enough to block the flow of saltwater while letting boats pass.
When the Mississippi is low, the flow slows and sediment settles, causing the river to silt up and obstructions to form, said James Pogue, a spokesman for the corps in Memphis. Since 1988, when record low water on the Mississippi caused navigation to shut down, the corps has engineered ways "to help the river keep itself open," he said, building new features like dikes that stick out into the river and "sort of act like nozzles to speed up the flow of the river" to scour the bed.
While the corps is keeping the main navigation channel of the Mississippi open, the same cannot be said for the harbors along the river. Four of the 19 harbors that the corps is responsible for keeping open on the lower Mississippi have been closed, and the corps has estimated that eight more would probably be closed if the drought continues over the next month.
That is why the Potter is at work, keeping the channel to the river's authorized navigation depth of 9 feet. Built in 1932, the Potter has been around so long that the corps upgraded it to diesel from steam power in 2001. The dredge pulls itself along steel cables with winches to move in precise lines.
'There's no plug'
Even at 9 feet, the shallower Mississippi has been a trial for companies like American Commercial Lines in Jeffersonville, Ind., which operates about 2,000 barges along the nation's inland waterways. The company tows would normally take as many as 40 barges up and down the Mississippi in blocks several barges wide and long. Mark Knoy, the company's chief executive, said that "not only are we carrying half as many barges, the barges are loaded to two-thirds of their capacity."
Below St. Louis, the river levels keep dropping, he said, grimly. "There's no plug at the bottom, and the water just keeps draining out," he said.
The fact that the barges are partly empty, "somebody's got to pay for that," Lee Nelson, president of Upper River Services Inc. in St. Paul, which empties, cleans and loads barges for barge lines, said in a recent interview with the Star Tribune. "Whoever's commodity it is, they're the one who's going to bear the brunt of that."
If the weather does not improve, the situation could get much worse, said David Busse, the chief of the engineering and construction division for the St. Louis district of the corps. If the rains do not come, the river will continue to drop. There will be a precipitous fall of about two feet at St. Louis toward the end of the year, when the reservoirs up the Missouri River, as scheduled every year, stop releasing water into the Mississippi.
"Right now we have a problem, but we're managing it," Busse said. "What happens when they turn it off?"
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