The group intends to open the final crevasse in the Birds Point-New Madrid levee, continuing a plan to blast holes in it in an effort to ease unprecedented flood pressure.

The Corps started the plan on Monday. Some who live where the Ohio and Mississippi rivers meet said it has helped.

The Ohio River level at Cairo, Illinois, has dropped nearly 2 feet since Monday afternoon. Officials said they believe the levels would be up to 3 feet higher now if the levee had not been detonated.

But still the town of Cairo was under a mandatory evacuation order and six other communities were under voluntary evacuation notices, said Patti Thompson, spokeswoman for the Illinois Emergency Management Agency.

The decision to breach the Birds Point-New Madrid levee was controversial. Missouri officials took the Corps to court over the plan, questioning the agency’s authority to intentionally breach the levee. The state argued the floodwater would deposit silt on about 130,000 acres, and it would take years, along with millions of dollars, to fix the damage.

Maj. Gen. Michael Walsh, commander of the Corps’ Mississippi River Valley Division, made the decision to order the breach. He warned that without punching a hole in the levee, massive flooding would threaten to inundate communities throughout the Mississippi and Ohio river valleys.

The U.S. Supreme Court declined to intervene in the case on Sunday, clearing the way for Walsh to blow the levee.

Despite the plan, many areas were inundated as the Mississippi River spilled out across huge swaths of farmland , creating massive flooding from Minnesota to Louisiana.

The water was coursing across an area of farmland that Missouri Gov. Jay Nixon described as “literally the most productive part of our continent.”

Farmer Bryan Feezor said the sight makes you “sick to your stomach” as he surveyed his submerged fields.

“Farming is all I ever have done … and it’s under water,” he told CNN affiliate KPLR.

The flooding has been triggered by heavy rains and meteorologists say is not expected to fully relent until early June.