An over-pressurization of two 55-gallon drums of waste phosphoric acid resulted in a material failure of the drum bottoms, releasing the contents of both drums (about 100 gallons) onto the facility floor. The spillage was collected within the sumps that are part of the facility's spill control system. The waste material had been packaged into DOT-specified containers earlier that day and the drums were placed into an assigned storage cell. That evening a staff member heard a noise in the high bay where hazardous wastes are stored. Upon investigating, he discovered the breached drums and spilled material.
The only material released to the environment was hydrogen gas. The maximum concentration of hydrogen released into the facility was 0.035%, well below the lower flammability limit of 4%. The spilled material was absorbed with vermiculite and repackaged. Samples were taken of the spilled acid to be processed to assist in the determination of the cause of the drum ruptures.
- Environmental Systems
- Waste Storage Drums
The direct cause of the over-pressurization of the two drums was the repackaging of the phosphoric acid into metal UN1A1 drums and the resultant hydrogen gas generation within the sealed drums. At the time of this incident (1997), 49 CFR and several MSDSs supported the selection of the UN1A1 drums. After the incident, laboratory studies conducted by facility staff indicated that the corrosion and subsequent hydrogen gas generation rates for the amount of phosphoric acid present would result in a pressure buildup and the drum failures observed. Facility staff then contacted DOT to request that changes be made to the packaging guidance listed for this material.