SANTA FE, N.M. — The New Mexico Environment Department is asking a federal court to dismiss a watchdog group’s lawsuit over a cleanup effort at one of the nation’s premier nuclear weapons factories.

Nuclear Watch New Mexico filed its lawsuit in federal court in May, naming the U.S. Energy Department and Los Alamos National Security LLC as defendants.

The lawsuit lists a dozen violations. It says the defendants are liable for hundreds of thousands of dollars in civil penalties for failing to comply with a 2005 cleanup agreement with state officials.

The agreement, which ended a court fight between New Mexico and DOE, was supposed to have required cleanup of the lab’s entire 40-square-mile site by last year but that work was not completed as the lab failed to receive federal appropriations.

In a motion filed Thursday, the Environment Department argues that a new agreement made in 2016 invalidates the 2005 agreement the lawsuit is based on and therefore the lawsuit should be dismissed.

“Because the 2005 Consent Order has been superseded by the 2016 Consent Order, the 2005 Consent Order is void and is no longer in effect,” the motion says.

The new agreement does not have a specific timeline for the cleanup of tons of radioactive waste still marooned at the lab. That waste is contained in rows of stacked drums inside temporary tents outfitted with monitoring equipment and fire suppression systems.

Jay Coghlan, director of Nuclear Watch, told the Santa Fe New Mexican that the department’s argument was based on “flimsy semantics.”