Washington Closure Hanford is making changes in its disposal of mercury-contaminated soil that it believes will avoid a repeat of a small burst of flames in February.

The flash occurred as a bulldozer was spreading a damp pile of treated soil contaminated with mercury at the Environmental Restoration Disposal Facility at Hanford.

The flame likely was caused by trapped gases, which included hydrogen, in the treated soil, said Bruce Covert, director of waste operations for the contractor.

To avoid the problem, a mercury analyzer will be used to adjust the treatment recipe for each batch of soil. That will minimize the amount of soil needing treatment and the amount of reagents required to be added to the soil as part of a proprietary process.

In addition the mixing time will be increased to liberate the gases, he said.