The explosives will blow a 2-mile hole in the Birds Point levee when detonated by the corps' experts sometime between 9 p.m. and midnight, ABC News reported.
"It will ruin my farm," Missouri farmer Bill Feezor said. "This is my whole life."
Destroying the levee is aimed at saving Cairo, Ill., from disastrous flooding, but will inundate an estimated 130,000 acres of Missouri farmland.
"Public safety remains the No. 1 issue for the corps of engineers," corps Maj. Gen. Michael Walsh told reporters in announcing his decision to go forward. "[The Cairo levee] continues to be under enormous and unprecedented pressure. The Cairo gauge has gone up a foot and a half since yesterday. It's going to continue to rise."
A second round of explosives is expected to be set off at the southern end of the floodway 24 hours later to drain the water from the farmlands, ABC said.
Rain and a record "sand boil" had raised concerns a major break could flood Cairo, officials said.
The corps said the sand boil, a strong spring of water gushing from the ground containing sand and rock possibly from the levee, is the largest they've ever seen, about 40 feet long and 30 feet wide, WPSD-TV, Paducah, Ky., reported.
As much as 5 inches of rain in the region Sunday night through early Monday pushed the river level to just below 61 feet, having risen 1.31 feet in 24 hours and passing the record level set in 1937, the Southeast Missourian reported.
Officials projected the water level would rise toward an expected crest Tuesday a foot over the record, and then stay at that level for several days.
Walsh said pipes inside the Birds Point levee were filled with blasting agents, a 20-hour process that was completed Monday.
Walsh has the authority to take action when the river reaches 61 feet and rising.
"Artificially breaching" -- or blowing up -- the levee would ease record flooding where the Ohio and Mississippi rivers come together, his office said in a Facebook posting Sunday evening.
The Ohio is the Mississippi's largest tributary, by volume. At the confluence, the Ohio is even bigger than the Mississippi.
U.S. Supreme Court Justice Samuel Alito, appointed by President George W. Bush, turned down a request from Missouri Attorney General Chris Koster Sunday night to stop the corps from blowing the hole in the levee, which is expected to act as a relief valve, handling about a quarter of the Mississippi's flow and reducing river levels upstream around Cairo by 3 to 4 feet.
Missouri filed its petition with Alito, who oversees federal courts in Missouri and six other states.
The denied appeal, first reported by The Wall Street Journal, followed Missouri's losing with the U.S. District Court in Cape Girardeau, Mo., and the 7th U.S. Court of Appeals in St. Louis last week.
Missouri had argued the corps violated Missouri's clean-water laws with its plan. It also alleged the corps hadn't done enough to consider alternatives.
The district court said -- and both higher courts agreed -- the Mississippi River Commission's mandate to protect Mississippi River navigation while preventing flooding outweighed Missouri's clean-water laws. It also said it saw no indication the corps' decision was in any way careless or impulsive.
The commission is a corps division.
Koster's office had no immediate comment on Alito's decision.