CHAMPAIGN, Ill. - The U.S. Army Corps of engineers inched closer Saturday to blowing a hole in a Mississippi River levee to try to keep flood waters out of a small Illinois town after a federal appeals court declined to stop the move.

The Corps of Engineers moved a pair of barges loaded with the makings of an explosive sludge into position near the Birds Point levee in Missouri, but said it hadn't yet decided that it needed to breach the 60-foot-high earthen wall to protect Cairo, Ill. More than half that town's 2,800 residents had been evacuated from the area, local police said. Further upstream from Cairo, Ohio River communities, such as Old Shawneeville, Ill., were plugging leaks in their own levees, hoping they hold.

The 230 people who live in the southeast Missouri flood plain behind the Bird Point levee had already been evacuated from their homes, a spokesman for Missouri Gov. Jay Nixon said. Some of the farmers whose roughly 130,000 acres of land would be inundated moved out what they could Saturday, assuming the Corps of Engineers will have no choice as the Mississippi and Ohio that feeds it rise.

"When the water hits this dirt, it's gonna make a hell of a mess," one of the farmers, Ed Marshall, said as he packed up his farm office and hauled away propane tanks and other equipment. He said he was keeping an eye on the weather forecast, which called for several more inches of rain over the next few days. "If that happens I don't believe they'll be able to hold it."

In Cairo, a town at the southern tip of Illinois near the Missouri border, Mayor Judson Childs said he was relieved by the 8th U.S. Circuit Court of Appeals' decision early Saturday in St. Louis.

"I've been saying all along that we can't take land over lives," the mayor said.

The state of Missouri had asked the court to block the plan because to protect the farm land. Scott Holste, a spokesman for Missouri Gov. Jay Nixon, said state officials there are now focused on protecting the homes, agricultural equipment and other property left behind in the heavily farmed flood plain below the levee. In addition to people evacuated from the floodway, as many as 800 were asked to leave surrounding areas.

"The entire area has been evacuated now," Holste said, adding that more than 500 Missouri National Guard troops are helping local law enforcement at checkpoints around the area.

It's unclear whether Missouri could pursue further legal action. Holste referred questions to Attorney General Chris Koster, whose didn't respond to phone calls or emails Saturday from The Associated Press.

The Corps of Engineers started moving the barges to a spot in Kentucky just across from the levee Saturday afternoon but was still weighing its options and monitoring the rise of the Ohio River in Cairo, which is just north of where the Ohio flows into the Mississippi, spokesman Bill Pogue said. The decision would be based on how high the river is expected to get, from new rain that could fall and water backing up in reservoirs upstream.

One key signal, he said, will be if the Ohio nears or reaches 61 feet at Cairo.

"It's certainly a significant benchmark, if we get there," Pogue said.

The river is expected to crest in Cairo at 60.5 feet - a foot above the local record high - by Tuesday morning and stay there through at least Thursday afternoon, according to the National Weather Service. A flood wall protects Cairo up to 64 feet, but the Corps of Engineers fears that water pressure from the lingering river crest could compromise the wall and earthen levees that protect other parts of the city.

"It's all about how much pressure is being put on the levee system," Pogue said.

Cairo police Chief Gary Hankins "strongly urged" people to leave town but guessed roughly 1,000 people remain.

Judson said he and others, including National Guard troops were closely watching for sand boils, spots where high-pressure water pushes under the flood wall and levees and wells up through the soil behind them. They're a potential sign of trouble.

"Right now we're waiting and watching, basically," he said.

About 80 miles northeast in Old Shawneeville, Ill., local residents were looking for volunteer help to fill sand bags to help contain leaks and seeps at the town's levee, Saline County sheriff's Lt. Tracey Felty said. With the Ohio River at just under 53 feet and not expected to rise above 54.5 when it crests Tuesday, the 60-foot-tall levee should be topped, he said.

But in some small area communities, a few homes have flooded, forcing their owners into a local shelter. Other buildings are swamped, too.

"It just flooded the church," in Junction, he said, noting one example. "They just couldn't keep up with the sandbags."

If the Corps of Engineers decides to breach the levee in Cairo, it would use a sludgy mix of explosives pumped into 11,000 feet of pipes inside the levee to weaken a 2-mile-wide section, Pogue said. The force of the water would push through to the land that sits behind the levee in Missouri's Mississippi County. Levees would be breached in two more spots further downstream near new Madrid, Mo., so at least some of the water could flow back out into the Mississippi.

Missouri officials have argued that the rush of water could lead to environmental mess, sweeping away fertilizer, diesel fuel, propane tanks, pesticides and other toxins.

As Marshall packed Saturday, he said he'll leave 40,000 gallons of diesel behind. He hopes the weight of their tanks holds them in place.

But he assumes some of the 8,000 acres he farms behind the levee will be scoured clean - including 2,500 acres now growing wheat - along with a mobile home where one of his employees lives. And when the water recedes, Marshall said, roads and bridges almost certainly will be washed out, and miles of drainage ditches that make the area suitable for farming will be filled with silt.

"I just don't know what's going to be left after this wall of water washes over this," Marshall said, admitting he's awed by the thought of all that water. "It will be a site to behold."