The Bethpage Water District Monday sued Northrop Grumman Corp. to recover millions of dollars spent removing a legacy of chemical contamination related to the firm's manufacturing operations that threatens public water supplies.

The lawsuit, filed in U.S. District Court for Eastern New York, seeks unspecified damages to cover the costs of past and future water treatment and building new wells outside of a groundwater plume that has been traced to Northrop Grumman and Navy sites.

"The residents of Bethpage deserve better," district Commissioner Gary Bretton said. "For more than 20 years, the taxpayers have unfairly shouldered the burden. If Northrop Grumman won't do the right thing, then we will force them to do so."

Northrop Grumman officials had not read the lawsuit Monday, but director of communications Tim Paynter said in an emailed statement that the company "has for many years worked closely with state and local government authorities, as well as the Navy and other parties, collectively and comprehensively to address environmental issues in Bethpage."

He added that, "the company remains committed to continuing those efforts."

A judge has not been assigned in the case.

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The district serves more than 33,000 people in Bethpage, Old Bethpage, Farmingdale, Levittown and Plainview. Plumes from Navy and Northrop Grumman manufacturing operations were discovered in 1986 and 2009. Both are subject to state Superfund cleanup plans.

Elevated levels of radium, a radioactive element, were found at one well site in May and the district is trying to determine the source. It is also digging a well outside the known plume area to serve its water needs at an estimated cost of $3.5 million.

Since the late 1980s, the district has spent $14 million to install treatment systems at each of its eight wells. It recently reached an agreement with the Navy for $2.3 million for upgrades at one plant.