FARGO — The engineers who serve as commanders in fighting floods learned lots of valuable lessons under the duress of the historic 2009 flood — lessons likely to be put to the test this spring.

A decade ago, conditions changed rapidly, as heavy rain fell on deep snow. A spider web of tributaries were poised to flush water into the swollen Red River, forcing a scramble to build many miles of emergency clay levees and to fill millions of sandbags.

River level forecasts kept ratcheting up, leaving engineers in uncharted territory.

“We had no plan to address those flood stages,” said Bob Zimmerman, city engineer for Moorhead.

The city, which is on higher ground than Fargo, had a plan for a flood up to 38 feet. The river crested at a record 40.84 feet, forcing adaptation on the fly.

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“It was sort of the M*A*S*H equivalent of engineering,” Zimmerman said, referring to the popular movie and television series dramatizing a Mobile Army Surgical Hospital during the Korean War. “It was ‘meatball’ engineering instead of ‘meatball’ surgery.”

Everybody improvised, and hordes of people manned the sandbag barricades, operated fleets of heavy machinery and drove trucks to haul clay for levees.

Somehow it all worked.

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Now, 10 years later, those hard-won lessons have been translated into permanent flood fortifications, meaning fewer emergency protections are needed.

“The difference now is we have a plan,” Zimmerman said.

The plan — “It’s really the diversion,” he said — will give the cities permanent protection to withstand a 100-year flood. The flood diversion channel once built would work with a river level of 37 feet, so additional in-town measures still are required.

In Fargo, more than 21 miles of levees and floodwalls have been built since 2009.

Fargo needed about 6 million sandbags during the 2009 flood. If a comparable flood were to happen now, it would take far fewer sandbags, around 1 million, said Nathan Boerboom, a city engineer.

A major spring flood — a river level of 30 feet or more — would present the first real test of many Fargo-Moorhead floodwalls built since 2009.

Already, conditions mean a major flood is almost guaranteed this year, according to National Weather Service predictions. The cities have been warned there is a 95 percent chance of a 33.8-foot flood, with a 50 percent chance of reaching 37.9 feet and a 25 percent chance of a 38.9-foot crest.

The floodwalls are embedded as deep underground as they protrude above ground, and are anchored atop a huge base of heavily reinforced concrete.

“We’re absolutely confident that they were designed appropriately,” Boerboom said, adding they were inspected and meet the standard for both the Army Corps of Engineers and Federal Emergency Management Agency.

As with previous significant floods, engineers will walk the levees to ensure that they are holding, Boerboom said.

'Huge problem' addressed

Among other measures, Fargo also has built 17 pumping stations to keep the dry side of the levees and floodwalls dry. Altogether, the city has spent $280 million on flood protection over the last decade, he said.

But more work remains to protect Fargo against a 100-year flood, a river crest of 41.4 feet to 42.1 feet. Most levees are being built to a level of 44 feet to allow freeboard.

City officials, who are gearing up to defend against a potential 40.3-foot spring flood, estimate they would have to build 10 miles of emergency levees and sandbag walls if a 2009-magnitude flood hit.

“Unfortunately, we’re still in the sandbag business,” Boerboom said. “We’ve still made significant progress over the last 10 years.”

The pace of building the remaining levees and floodwalls will depend on funding and property acquisitions, he said. An estimated $130 million in permanent flood protections are yet to be built in Fargo.

The story is much the same in Moorhead. Significant progress has been made, but temporary measures remain necessary for extreme floods.

Moorhead has built 12 miles of floodwalls, 19 stormwater pumping stations and five sanitary sewer upgrades since 2009. The city also has installed 78 stormwater gates — a move to prevent river water from backing up into the storm sewer system, as happened in 2009, triggering evacuations of perhaps a third of the city.

“It was a huge problem,” Zimmerman said. “That’s been addressed.”

Another 6 miles of floodwalls were built by the Buffalo-Red River Watershed District to protect Oakport, now part of Moorhead, as well as additional pumps.

To finish its permanent flood protection, Moorhead plans $43 million in additional work that could be finished within the next three years, Zimmerman said. The work would require acquisition of 68 pieces of property.

“We’re essentially ready to go on all of this,” he said.

'Never totally comfortable'

Since the 2009 flood, the city of Moorhead and Buffalo-Red River Watershed District have spent about $146 million on flood protection, Zimmerman said.

Moorhead will need emergency clay levees for a flood that is 37 feet or higher. “Nothing like 2009 when we had blocks of it,” he said of any emergency levees that might be needed.

The levee systems and other flood protections in both Fargo and Moorhead are designed to be used in tandem with the diversion channel — not in place of the diversion, Zimmerman and Boerboom said.

Completing the diversion would enable the cities to use emergency protections to defend against a 500-year flood. “It’s something the city believes we can successfully manage,” Boerboom said.

The possibility that Fargo-Moorhead could confront a flood even worse than the record 2009 flood is sobering.

“You’re never totally comfortable going anywhere you haven’t been before,” Zimmerman said. “But we’re much better positioned.”

The $2.75 billion diversion project has cleared major milestones, including securing important permits from North Dakota and Minnesota, and has most of its financing lined up, including the local and federal shares. The Diversion Authority is counting on the state of North Dakota to increase its commitment, said Mary Scherling, chairwoman of the Diversion Authority board.

"It's a shame we don't have it built," Scherling said, noting that extreme storms and floods are becoming both more severe and more frequent. "I have never felt more confident we are getting there."

Once all financing and approvals are in place, diversion officials have an aggressive, 6.5-year construction timetable.

Outside of Fargo-Moorhead, many areas of rural Cass and Clay counties remain vulnerable to river and overland flooding.

In rural Cass County, for instance, a bridge now means residents of Shure Estates, located north of West Fargo, shouldn't have to commute via boat during the spring flood. But the subdivision's houses still can be surrounded by floodwater and require sandbag protection.