The Army found out Tuesday just how tough it is to fight City Hall — especially when it’s in New Brighton.

In a victory for the Ramsey County suburb, the Army agreed to continue to pay for the next 30 years of treatment of the city’s drinking water, contaminated for years by industrial waste from the federal government’s nearby former ammunitions plant.

The agreement, which settles a lawsuit filed by the city against the Army in May, was expected to be approved Tuesday night by the New Brighton City Council.

“I’m elated and relieved,” New Brighton City Manager Dean Lotter said.

Under the terms of the agreement, the federal government will pay $59.4 million to New Brighton to cover the city’s expected costs of owning and operating its water treatment plant in the next 30 years.

The city expects a lump-sum payment from the Army by the end of March.

The agreement also leaves the door open to a future funding agreement, should water treatment continue to be needed beyond 2045.

“What’s unique about our settlement is that it’s not over and done with,” Lotter said. “We’ve created a settlement structure whereas long as the problem exists, the Army is on the hook.

“We believe this problem will last for decades. Some people believe 50 to 100 years. We just don’t know.”

The aquifer beneath New Brighton receives water contaminated for more than 40 years by solvents and degreasers from the Twin Cities Army Ammunition Plant (TCAAP), just northeast of the city.

The federal government built the plant in 1941 to manufacture ammunition used in wars from World War II to Vietnam. Ramsey County bought the site for $28.5 million in 2013 and hopes to redevelop it for housing, retail and business uses.

New Brighton first sued the Army over its drinking water in 1984. That suit was settled four years later, when the Army agreed to fund construction of the city’s state-of-the-art water treatment plant and later paid a lump sum of $17 million to operate it for 20 years.

The agreement was supposed to be in force as long as contamination levels remained unhealthy.

In 2009, city officials approached the Army about extending the 1988 settlement. But they said the Army threatened to withhold future payments unless the city agreed to new terms, including operating the plant under federal rather than state regulations. The Army said it had no intention of breaking its promise to pay for water treatment.

When negotiations failed, the city filed suit last May against the Army, accusing it of reneging on the 1988 agreement.

Lotter said that the city’s legal costs, amounting to about $4 million since 2009, came from funds paid to the city by the federal government under the earlier agreement.