State, Corps spar over efforts to fight saltwater in Mississippi River

Ship heads down the Mississippi River near Myrtle Grove in this April 19 file photo (John Snell)
Ship heads down the Mississippi River near Myrtle Grove in this April 19 file photo (John Snell)

New Orleans, La. -- The U.S. Army Corps of Engineers method for dealing with saltwater creeping up the Mississippi River has sparked a dispute with the State of Louisiana over a nearby coastal project.

The state plans a $66 million pipeline, designed to feed sediment from the river to wetlands 12 miles away near Barataria Bay.  The sediment would be mined from a "borrow area" in the river near Myrtle Grove in Plaquemines Parish.

The area contains an estimated 13 million cubic yards of sediment, or enough to fill the Mercedes-Benz Superdome 2.8 times.

However, the Corps is using that same spot as a source of sediment for the underwater sill being built to block saltwater intrusion.

Garret Graves, chairman of the Louisiana Coastal Protection and Restoration Authority, said Tuesday that Corps restrictions on the use of that borrow area may doom the sediment pipeline.

"They came to us and said they're going to put the entire 13 million cubic yards of sediment off limits to us for at least two years," Graves said.  "That puts us dead in the water."

Graves said the Corps notified the state several months ago that it would require about 10 percent of the borrow area in case a drought caused saltwater to flow up the river. It raised that amount later to 20 percent, and now potentially all of the silt will be placed off limits.

"They keep moving the goal line," Graves complained.

During normal conditions, the Mississippi's flow is strong enough to prevent saltwater from entering the channel near the river's mouth.  However, in low water periods, engineers say a "salt wedge" flows near the river bottom, threatening drinking water supplies in Plaquemines Parish.

The Corps employed a similar solution during the droughts of 1988 and 1999, constructing the sill on the river bed with material from that same borrow area.

"We just have to put the priority where the priority is and that's helping the men and women of Plaquemines Parish have a water system with a degree of integrity," said Corps spokesman Ken Holder.

At this point, Holder said engineers do not know how much of the borrow area sediment they will require to build the sill.  "We're not even sure that (the state) will have to use a different borrow site at this point," Holder said.

Graves argues the Corps does not require the entire borrow area and describes the issue as "urgent."  The state stands to lose $66 million in federal funding if it fails to begin work on the sediment pipeline within the next several months.

Since the funding was technically awarded to local parishes, the state has been working with Plaquemines, Jefferson and Lafourche for about three years on the pipeline, which is designed to create 294 acres of marsh.  Although the pipeline would originate in Plaquemines, most of the new land would form in Jefferson Parish.

The state envisions the pipeline as a demonstration project, aimed at testing the feasibility of delivering land-building material over long distances.  Sediment would be dredged from the river and pumped 12 miles through a 30-inch pipe.

Eventually, the state could build branches from the pipe to nourish other areas of marsh if the system proves feasible.

The state's own permit application identifies two other potential borrow sites within three to five miles of the preferred location.  However, neither Graves nor Corps officials could give an immediate estimate of how much that would affect the coastal project's cost.

Indeed, both sides have designs on the same area because it offers the cheapest alternative for pumping sediment.

"We need to use material that's close by because we need to be good stewards of the taxpayer's dollars," Holder said.