Traffic on the liquid highway that is the Mississippi River soon may come to a halt costing businesses and putting jobs in jeopardy. Historically low water levels are expected to drop even more as the U.S. Army Corps of Engineers on Friday reduced the outflow from the Missouri River in South Dakota.

The low water already has forced those who rely on the river to ship lighter loads that sit higher in the water. Local companies are feeling the strain.

At Buzzi-Unicem in Cape Girardeau, the cement manufacturer is loading about 600 fewer tons on each barge. Instead of a typical 12-foot draft, barges have a draft of 9 feet or less, said logistics manager Bob Wittenborn.

"It costs the same amount, but you've got fewer tons. That means you have to send more barges," Wittenborn said.

That leaves businesses such as Buzzi-Unicem with a tough choice: pay higher shipping costs or ship less product.

"We also load out by rail car and truck, but less material goes out by these modes because the barge capacity is so much greater," said Steve Leus, plant manager at Buzzi-Unicem.

Leus and Wittenborn are watching river levels closely with all eyes fixed on Thebes, Ill., where an underwater rock formation is poses navigation problems.

On Tuesday, the Mississippi River at St. Louis was at -1.4 feet, according to the U.S. Army Corps of Engineers. The rock formations at Thebes will become exposed at -5.5 feet on the St. Louis gauge. The corps' long-range river forecast puts water levels in this range by mid-December.

A large volume of water on this stretch of the river comes from the Missouri River. Flow from the Missouri River originally was 37,500 cubic feet per second, but gradually will be cut to 12,000 cubic feet per second by Dec. 11, leaving less water coming into the Mississippi River where the rivers join at St. Louis.

Turning the corner at Thebes already has been a challenge for barge traffic, said Dan Overbey, executive director of SEMO Port in Scott City.

"A lot of the tows lately have been down to three barges wide to get through there, when normally when they have plenty of water they will run five or six wide," Overbey said.

The most recent forecast from the corps shows the Cape Girardeau gauge at 7.4 feet, but within the next four weeks, it's expected to drop to 1.5 feet.

"That's going to be huge and it's going to cause some problems," Overbey said.

On a conference call Tuesday, Overbey learned of plans by the U.S. Coast Guard to help control traffic near Thebes, he said.

"They'll also be on standby when somebody bumps the bottom or runs aground which is bound to happen," Overbey said.

Wittenborn has been working with barges at Buzzi for 27 years and remembers the water being this low in 1988.

"We had smaller towboats back then and were able to get through Thebes. We didn't ship south of Memphis then," he said. "Now we're a bigger company with more plants on the river. We go south now, and those markets don't slow down in the winter."

Buzzi's cement is shipped from Cape Girardeau to Chicago and St. Louis, but it also travels south to Tennessee, Arkansas, Mississippi, Louisiana and Texas.

Wittenborn fears it won't be long until they will not be able to get their products out by river.

If that transpires, Leus couldn't rule out layoffs.

"Several of our plants have had layoffs due to the economy and less demand for our finished product. Anything is possible with the added burden of cutting off one of the prime outlets of transporting cement," he said.

A spokesman for Sen. Claire McCaskill, D-Missouri, on Tuesday said a group of U.S. senators from states along the Mississippi River will ask President Barack Obama for an emergency declaration aimed at keeping barges moving.

"This issue is impacting jobs and businesses in Missouri as we speak, so we don't have weeks to wait for a response from the Army Corps." She added: "It's time for the president to take action to protect our jobs and businesses."

Republican U.S. Sen. Roy Blunt and Republican Rep. Jo Ann Emerson also are pushing to keep the river open.

Three trade groups and 15 national organizations on Tuesday submitted a letter to the president and Federal Emergency Management Agency requesting the declaration of a presidential emergency.

The disaster declaration sought by the senators seeks to cut through red tape to expedite that removal. It also would seek to restore the Missouri River flow to about the normal level.

The corps has spent months dredging the river to try to keep the channel open. It plans to use explosives to remove the rock formations near Thebes, Ill., and Grand Tower, Ill.

Wittenborn isn't expecting these efforts to produce any immediate results.

"I've been told by the corps it would be February before they could even start blasting," he said. "I think if they were going to do something, they would have done something already."

It's no longer a question of if the river will shut down; it's a matter of when.

"Around Christmas it's going to get interesting. and we don't know for how long. That's going to be the real kicker. How long is it going to stay low?" Overbey said.