The U.S. Army Corps of Engineers has cleared tons of rock from one section of the middle Mississippi River and is now moving work upstream in response to river levels lowered by recent drought conditions. The Mississippi is so low between St. Louis and Cairo, Illinois, that barge traffic is endangered. To keep the channel open, the Corps has used dredging barges and explosives to remove rock pinnacles in the river near Thebes, Illinois. The corps now plans to do similar work about 31 miles north of Thebes near Grand Tower, Illinois. The work will require midnight-to-noon closure of the channel for about 10 days.