In a filing with the New Mexico Energy Department, officials detailed the work and gave broad ranges that indicate it could take a minimum of about 100 work weeks to secure the rooms at the Waste Isolation Pilot Plant near Carlsbad.

New Mexico Environment Secretary Ryan Flynn ordered officials and the contractor that runs the dump to submit the plans for permanently sealing the underground rooms where more than 300 barrels of waste from Los Alamos National Laboratory are stored.

The waste was packed with cat litter to absorb moisture. Officials are investigating whether a switch from inorganic to organic litter is to blame for a chemical reaction with nitrate salts believed to have caused a Feb. 14 leak that contaminated 22 workers and indefinitely shuttered the plant.