BETHPAGE - After decades of negotiations, Northrop Grumman has agreed to clean up a toxic groundwater plume that is spreading in Nassau County.

A plume of underground contamination from the former Navy and Grumman site in Bethpage has stretched south and grown over the years. Northrop Grumman signed a consent order with the state Department of Conservation requiring it to participate in ongoing efforts to clean up the contamination.

The contamination was first found near the Grumman site in the late 1940s. Since then, three additional plumes of pollution have been documented.

"The plume is primarily TCE (trichloroethylene)," said Stan Carey, of the Massapequa Water District. "It's a volatile organic compound. It was a cleaning solvent, a degreaser that was used in the warplane manufacturing process."

Still, Carey and Jeanne O'Connor, of the Bethpage Cancer Project, say details surrounding the agreement leave many questions unanswered regarding who will be footing the bill for the cleanup process.

Bethpage and nearby water districts have spent millions of dollars to filter the groundwater and say it's safe to drink.

Northrup Grumman did not comment on the agreement.