A federal judge in Washington, D.C., has found the U.S. Army Corps of Engineers' management of the Missouri River caused regular flooding, a liability finding that sets the stage for a trial over what plaintiffs' counsel estimated as $300 million in damages.

Tuesday's ruling by U.S. Court of Federal Claims Judge Nancy Firestone found that actions made by the Corps—rather than just nature—caused recurrent flooding of the Missouri River during five years that fell between 2007 and 2014. The ruling is a rare and significant decision against the U.S. Corp of Engineers, which a different Court of Federal Claims judge found in 2015 was liable for some of the Hurricane Katrina damage in New Orleans.

“This is one of the largest and most sweeping takings holdings in United States history—Katrina probably being the other one,” said Benjamin Brown, a partner at Cohen Milstein Sellers & Toll in Washington, D.C. “In this corner of the law, this is pretty monumental.”

Wyn Hornbuckle, a spokesman for the U.S. Department of Justice, which represented the Army Corps of Engineers, declined to comment beyond stating that government lawyers were reviewing the ruling.

The Missouri River, once dubbed the “Big Muddy,” is one of the “most engineered rivers in the world,” Brown said. Under the Flood Control Act, the Army Corps constructed dams and reservoirs so that farmers and other business owners could develop land near the river.

But the changes impacted the native habitat of several species of birds and fish. Following a raft of lawsuits, including those brought under the Endangered Species Act, a federal judge in 2004 ordered the Corps to make changes to its management of the Missouri River.

A decade later, more than 370 property owners along the Missouri River filed suit, claiming that the Army Corps' changes brought on flooding that destroyed their land. They alleged that the Corps had violated the “takings clause” of the Fifth Amendment, which bars the federal government from taking private property without compensation.

“They maintained that since this was foreseeable, the Corps had anticipated that conforming with this biological opinion was going to lead to more flooding, and was leading to more flooding, and threatening their livelihood,” Brown said. “The appropriate response and what the Fifth Amendment dictates is the taxpayers all share the costs of this compliance with the Endangered Species Act rather than only those who live on the river.”

The trial involved plaintiffs with 44 representative properties. Firestone dismissed claims involving 16 of those properties, and she found the Corps was not liable for flooding that occurred in 2011.

But plaintiffs lawyers said the ruling imposed liability on the Corps for flooding in four states. In a statement, Polsinelli's R. Dan Boulware, a shareholder in St. Joseph, Missouri, who was lead counsel in the case, called on Congress to “act soon to restore flood control to a higher priority as it was during the last century.” Congress previously has introduced bills to address flooding of the Missouri River.

In addition to Brown and Boulware, the plaintiffs team involved Cohen Milstein partner Laura Alexander and three other shareholders from Polsinelli—Edwin Smith, Seth Wright and R. Todd Ehlert—and Sharon Kennedy, who is of counsel in Kansas City, Missouri.

The first phase of the trial was to determine whether the Corps was liable. A second phase, set to begin this fall, will determine damages. Brown said plaintiffs would be seeking around $300 million.

The trial lasted 63 days and took place in Kansas City, Missouri, and Washington, D.C. It involved more than 95 witnesses, 100 depositions and more than 20 million documents.

“It was quite an undertaking,” Brown said, joking that “my kids viewed it as the year without dad.”