NEW ORLEANS, Louisiana (CNN) -- A federal judge has thrown out a class action lawsuit against the U.S. Army Corps of Engineers over the failure of levees in New Orleans during Hurricane Katrina.

U.S. District Judge Stanwood Duval acknowledged Wednesday that the agency failed to properly safeguard the city, but he ruled that the Corps was protected by the Flood Control Act of 1928. It shields the federal government from liability when flood control projects fail.

The Corps designed the levee system that was supposed to protect the low-lying city. But after Katrina stuck the Gulf Coast on August 29, 2005, steel-and-concrete levees eroded and failed in several areas, flooding about 80 percent of the city with water up to 20 feet deep.

In 2007, the Insurance Information Institute estimated insured losses for Katrina across Louisiana at $25.3 billion.

In his ruling, Stanwood said the Corps deserves blame for its role in the flooding even if it can't be held legally responsible.

"While the United States government is immune ... it is not free, nor should it be, from posterity's judgment concerning its failure to accomplish what was its task," Stanwood said, lamenting his inability to take further action.

"It is hopefully within the citizens of the United States' power to address the failures of our laws and agencies," he said. "If not, it is certain that another tragedy such as this will occur again."

Stanwood called the story of the Corps failure to protect New Orleans "heart-wrenching."

"Millions of dollars were squandered in building a levee system ... which was known to be inadequate by the Corps' own calculations," the ruling said. The Corps' own studies recommended upgrades that were never implemented.

Plaintiffs attorney Joseph Bruno said he intends to appeal the decision to the U.S. Court of Appeals for the Fifth Circuit. Bruno and other attorneys will hold a news conference Thursday in response to the ruling.

Reached in Washington, Corps spokesman Gene Pawlik applauded the decision.

"We agree with the judge's ruling and can't say too terribly much more because there's other legal matters to be settled," he said. A number of other lawsuits remain unsettled in the aftermath of Katrina.

Pawlik said the Corps is doing everything it can to improve the city's much-maligned levee system.

"We're trying to learn from the lessons of Katrina and put the best system in place for the people of New Orleans," he said.

CNN