OMAHA, Neb. (AP) – For months, excavators, backhoes and dump trucks have scraped up tons of dirt and sand along the Missouri River to pour into vast holes left by breaches in badly broken levees.

The scale of damage and the effort needed far exceeds the 2011 Missouri River flooding.

Months of frequent, heavy rains have made the repairs that much more difficult. Six months in, the Missouri River remains so high in some areas that crews haven't been able to fully inspect damage to levees.

At least three times since March's destructive flood, crews have scrambled – sometimes unsuccessfully – to protect fragile levee repairs from a rapid rise in the Missouri River.

Rains in May and August washed out some of the newly rebuilt levees. And now again in September, crews have been shoring up some of their yet-to-be completed work as more water surges downstream from heavy rain across northern Nebraska, South Dakota, Iowa and Minnesota.

"Our biggest obstacle is the river," said Bret Budd, chief of the systems restoration team for the Army Corps of Engineers' Omaha District. "It's high, and it remains high. Every time there's a major rain – and we've had some – it increases the difficulty of the work."

About 350 miles of levees in Nebraska, Iowa, Missouri and Kansas were damaged in this spring's historic flooding, said Brig. Gen. D. Peter Helmlinger, commander of the Northwestern Division of the corps. Along the full length of the Missouri River and its tributaries, an estimated 1,000 miles are affected, the corps has said.

Returning levees on the Missouri River to their pre-flood condition will cost about $1.1 billion, he said, with most of that money going toward levees between Omaha and Rock Port, Missouri. So far, $125 million has been spent.

The corps' immediate goal is to make minimal closures to holes in the levees before next spring's flood season. Full restoration is expected to take a couple more years.

Ten times as many levee breaches occurred with this flood as happened in 2011, according to the corps.

"It's an order of magnitude, the extent of damage," said Corina Zhang, a resident engineer for the corps, who is overseeing some of the levee projects.

Complex challenge

Before the backhoes and graders could get into place, the corps, local levee districts and contractors need to get a grasp on everything from the behavior of the river at each specific break to the availability of clay and sand. Also under consideration: local landowners' rights and interests, the availability of matching local funding and contractor access to heavy equipment.

"All these different people had to come together to create a program that is efficient, effective, timely and safe," she said. "I've been impressed with how quickly we've been able to mobilize."

Each damaged levee has come with its own set of problems, so there's no one-size-fits-all repair, Budd said. In some places, fields have been too wet for heavy equipment, so the corps has pumped sand from the river to pour into the holes. In other places, it has bulldozed sand from fields, and in other, still-flooded fields, it has dredged sand to fill breaches.

Once the sand is in place, the corps must layer the levee with clay to protect it against erosion. Although clay deposits can be found throughout the Missouri River valley, not all deposits are of equal quality and quantity. While deposits have been mapped out in the past, the corps is searching flooded ground and digging through a foot or two of topsoil with not always certain results. It is also working with landowners for access and is building up haul roads, some as long as 10 miles.

Breaches range in size. The longest break is the 1,000-foot gap in the levee known as L550 south of Hamburg, Iowa.

Other levees are pockmarked by numerous smaller holes. The levee near Peru, Nebraska, R562, has 10 breaches. (L stands for the left bank as one heads downstream, and R stands for the right bank; the numbers correspond to river mile markers.)

The corps is also contending with scour holes behind each levee break. Water pouring over the levees during the flooding tunneled into the ground and left holes that were 40 to 80 feet deep and sometimes a couple hundred feet across.

Sometimes the corps is filling in the scour holes to reconnect the levee. In other places, it is looping around them, setting a new path for the repaired levee to follow.

To get a sense of how much effort is being devoted to levee repairs, consider this: On one day on one levee, L550 south of Hamburg, the Corps of Engineers and its contractor had 47 people and 53 pieces of equipment – including tractors, bulldozers, dump trucks, excavators – at work, Budd said.

Contractors from across the country have been tapped for levee repairs, and in some cases, they're working side by side with local farmers. Some equipment – shallow water dredges – has come from as far as Louisiana.

More bad weather

Outside of the enormity of the task, the biggest obstacle has been the ongoing, record wet weather. A succession of rainstorms this spring and summer in the Missouri River basin has caused fresh flooding that has washed out repairs at least twice – in May and August.

In May, heavy rains washed out progress on the levee L575 near Percival, Iowa, reflooding that town.

In August, the corps was within days of closing the L550 breach south of Hamburg when heavy rains sent a torrent of water pouring through the remaining gap. The force of the water washed out tons of rock – about a 50-foot-long protective rock wall in front of the levee repairs. Work was thrown a couple of weeks behind schedule.

Heavy rains last week are expected to push the river up 2 to 4 feet, so crews are shoring up some repairs with heavy rocks to avoid losing progress.

Worse than 2011

The damage caused by the flood of 2019 bears little resemblance to what the corps experienced in 2011, said Budd, who has worked on both floods.

In 2019, hundreds of miles of streams and rivers rose to record heights after a massive storm churned across the Great Plains, unleashing widespread flash-flooding. Nearly all the runoff occurred below the Corps of Engineers' six large dams on the upper Missouri.

Back in 2011, it was just the opposite, heavy snowmelt and historic spring rains occurred above the dams. Flooding occurred on the lower Missouri as the corps released record amounts from its dams for about three months.

The bottom line: In 2011, a controlled, approximately 100-day flood occurred in the Missouri River valley; in 2019, a tidal surge in just a few days poured into both tributaries and the Missouri, overwhelming levees.

About 50 levee breaks occurred in 2019, compared with five in 2011, Budd said. In addition to the outright breaks, there is significant erosion along the remaining stretches of levee this year.

Fourteen major breaches have been closed on the Missouri River, and dozens of other projects are underway, including repairs along tributaries.

For the most part, the corps is "just" plugging holes and then moving on to the next breach. Rarely are levees being repaired back to their full height and width. There's too much work to get done before flood season returns, the corps has said.

As the corps works through its list of projects, everyone is keeping an eye on the weather.

"Conditions are shifting constantly," Zhang said. "And winter is coming."