ST. LOUIS — A plan to make sure an underground St. Louis-area landfill fire doesn’t reach a cache of Cold War-era nuclear waste buried nearby will come before the end of 2016, an Environmental Protection Agency administrator said Monday despite the state attorney general’s calls for swifter action.

Mark Hague, acting chief of the regional EPA, said the agency would not be pressured into a hasty method of keeping the smoldering embers beneath the Bridgeton Landfill from moving at least 1,000 feet to the nuclear waste at the West Lake Landfill, a federally funded Superfund site since 1990.

Hague said the permanent fix would be decided by “solid science, good engineering data” and not outside pressure.

He expects a plan by the end of next year. He noted that options could include an in-ground fire break or injecting inert gases that snuff the smoldering.

“It has taken a long time, and it’s time to get a final remedy in place,” Hague said Monday, a day after Missouri Attorney General Chris Koster called for the EPA to solve the problem “without delay.”

Citing the need for “good, sound” engineering data that supports a permanent solution, Hague said “that work takes time.”

On Saturday, a fire blamed on a faulty utility pole ignited brush on the West Lake Landfill’s grounds. Firefighters doused the blaze, and Hague said testing showed no immediate evidence residents were in peril.

Hague insisted the subsurface smoldering was “not rapidly advancing” toward the buried cache of nuclear waste, and he called prospects that fire could reach the radioactive material a “highly unlikely event.”

Government officials quietly have adopted an emergency plan in case the smolder – dating to at least 2010, its origin still unknown – ever reached the nuclear waste, unleashing a potentially “catastrophic event” near the city’s main airport.

The “EPA says it is moving toward a final protective remedy. It must implement that remedy without delay,” said Koster, a Democrat running for governor whose office is suing the landfill’s operator, Republic Services.

Republic Services has downplayed any risk of the below-ground fire. Underground structures that capture below-surface gasses and other safeguards are in place to keep the fire and the nuclear waste separate. Republic Services is spending millions of dollars to ease or eliminate the smell by removing pipes that allowed the odor to escape and capping parts of the landfill.

The Republic Services-owned West Lake Landfill was contaminated with radioactive waste from uranium processing by a St. Louis company known as Mallinckrodt Chemical. The waste was illegally dumped in 1973 and includes material dating to the Manhattan Project, which created the first atomic bomb in the 1940s.

No reports of illness have been linked to the nuclear waste. But the smell often is so foul that Koster sued Republic Services in 2013. The case is to go to trial in March.