What happened

A fatal explosion occurred in the magnesium-powder-fines processing building at US Ecology's Subtitle C hazardous-waste disposal facility near Grand View. EPA initially estimated that approximately 7,000 pounds of magnesium waste was present; OSHA's later enforcement record said employees were treating 9,210 pounds by dumping the powder into a steel-lined bin, reacting it with water and mixing it with an excavator bucket. The treatment was intended to convert magnesium metal into a more stable compound, but it generated hydrogen that ignited in the presence of oxygen and produced a large explosion. One 48-year-old worker was killed and three others were injured. The blast severely damaged the processing building and affected surrounding buildings that may also have contained hazardous waste. An initial fire burned out by that evening. EPA reported no initial off-site air-quality concern, but structural damage prevented immediate confirmation of all chemicals in nearby buildings. EPA response personnel deployed the following day. The incident is sometimes described as water contact with an alkali metal; chemically, magnesium is an alkaline-earth metal, while the later OSHA finding specifically identifies ignition of hydrogen generated during the facility's water-based stabilization process.

When cited sources give different casualty, damage or spill figures for this event, they’re reported side by side above rather than merged into one number. See how confidence levels work.