* Low water threatens nearly $3 billion in January shipments
* Army Corps dredging, removing rock to keep channel open
By Tom Polansek
Jan 7 (Reuters) - U.S. Senator Dick Durbin toured a shallow stretch of the drought-drained Mississippi River by boat on Monday for a firsthand look at the historically low water that is impeding traffic on the nation's busiest waterway.
Durbin, the No. 2 Democrat in the Senate, and other officials took to the water near Thebes, Illinois, where workers have been removing river-bottom rocks to aid transportation after the worst drought in half a century drained the Mississippi and the rivers that feed into it.
The senator is scheduled to hold press briefings later on Monday to talk about the river conditions.
The U.S. Army Corps of Engineers and Coast Guard for the second time in a month in Illinois briefed the officials on the threat for a potential shutdown of commerce on the river, which typically carries $2.8 billion worth of commodities in January. Durbin receives regular updates on the situation via telephone and in Washington, D.C., a spokeswoman said.
The low water has disrupted the flow of billions of dollars worth of grain, coal, fertilizer and other commodities between the central United States and shipping terminals at the Gulf of Mexico.
Should the river be shut to traffic more than 8,000 jobs would be affected, worth $54 million in wages and benefits. It would halt the movement of 7.2 million tons of commodities, according to shipping groups.
The Army Corps said last week that navigation would continue. A spokesman could not immediately be reached on Monday.
The Corps is removing the most threatening rock pinnacles near the Illinois towns of Grand Tower and Thebes, hoping to deepen the shipping channel by about two feet by mid-January, just before the river is forecast to hit critically low levels.
The Corps has also been dredging various soft-bottom sections of the river nearly round-the-clock for six months to maintain a deep enough shipping channel. The majority of commercial vessels need a depth, or draft, of at least nine feet so shippers are closely monitoring river gauges and forecasts.
The Mississippi River gauge at Thebes rose to 4.04 feet on Monday from 3.9 feet on Friday. It was forecast to slip to 3.4 feet by next week, the lowest level there since 1988 and the second lowest on record.
Gauge readings do not reflect the actual depth of the river at a certain location because the gauges are fixed and the river's bottom is steadily changing with the current. They aid navigation as a shorter term reference point.
The Army Corps has said once the Thebes gauge reads 2 feet, boats with a nine-foot draft, or distance between the water's surface and the lowest point of the vessel, would be at risk of hitting rock pinnacles there. (Reporting By Tom Polansek; Editing by Bob Burgdorfer)