MEMPHIS — The Coast Guard said Monday that 97 boats and barges are waiting for passage along an 11-mile stretch of the Mississippi River that has been closed because of low water levels.

Ryan Tippets, a Coast Guard spokesman, said the section of river near Greenville, Miss., has been closed intermittently since Aug. 11, when a vessel ran aground.

Tippets said that the area is being surveyed for dredging and that a Coast Guard boat has repositioned eight navigation markers. He said 40 northbound vessels and 57 southbound vessels are stranded and waiting for passage.

Tippets said it is not immediately clear when the segment will reopen. He said the stretch of river that has been closed was a possible site for more groundings.

The Army Corps of Engineers is using a 350-foot-long dredging vessel to make the river easier for barges and boats to navigate.

The dredge will remove sediment from the bottom to maintain the river’s channel. The vessel, called the Hurley, was working Monday at Redman Bar just north of downtown Memphis.

Engineers have been dredging sections of the river near Memphis because its low water level could pose a hazard to barges and tow boats that transport material down the river. Officials say the river is running several feet below normal.

The Hurley can dredge to a depth of 75 feet and can remove up to 5,000 cubic yards of sediment per hour.