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April 14, 1999

Violations alleged in fatal Moses Lake silicon plant explosion

TUMWATER - The Department of Labor & Industries has cited a Moses Lake manufacturer for violating worker-protection rules in connection with an October explosion that killed two workers and injured four others.

L&I's investigation into the Oct. 8, 1998, explosion resulted in six serious violations and total penalties of $34,800 against Advanced Silicon Materials Inc., Moses Lake. The employer was cited for violating work-protection rules in the process safety management standard - Chapter 296-67 of the Washington Administrative Code (WAC).

The deaths and injuries occurred after a 6-inch high-pressure pipe burst and workers were exposed to a toxic mix of silicon tetrachloride and trichlorosilane. A cloud of highly acidic gas and vapor resulted when the mixture was exposed to air. An estimated 35,000 pounds of material was released.

The employer must comply with the process safety management standard because of the potential for fire, explosion or catastrophic release of highly hazardous materials on site at the plant.

Process safety management is based on the idea that some workplaces are so hazardous that the only way an employer can mitigate hazards is to develop and use detailed procedures for safe operations. These procedures or processes improve safety by eliminating the need for workers to make on-the-spot decisions, essentially removing the "human factor" from the safety equation.

These worksites often involve particularly dangerous chemicals or operations, such as the refineries, manufacturing of explosives and processing of highly toxic compounds. The danger posed by these hazards is so serious that detailed, mandatory processes must be applied to avoid reliance on simple training and individual judgment.

Specifically, the employer was cited for:

    • Failing to specify the proper limits of all chemicals in the "process stream." This can be likened to creating a recipe, a set of correct ingredients, temperatures, etc., that can be monitored and analyzed for potential hazards. Specifically, the employer overlooked the fact that in addition to gaseous compounds, certain liquids and solids flowed through the pipe as well. ($5,400 penalty)
  • Failing to consider what might happen if the safe limits of the so-called recipe were exceeded. ($5,400)
  • Failing to ensure - prior to Oct. 8, 1998 - that the pipe that ruptured was in compliance with good engineering practices. The industry standard calls for thicker pipe wall in places likely to wear thin. ($5,400)
  • Failing to establish an effective system for resolving hazards identified by a process hazard analysis team. ($6,600)
  • Failing to ensure that the inspections and tests of the pipe that ruptured were consistent with good engineering practices. ($6,600)
  • Failing to respond to the findings of a 1995 process safety compliance audit. ($5,400)

The employer has until May 4, 1999, to appeal the citation.

Earlier this year, a related L&I investigation into the emergency response that followed the fatal incident resulted in three serious violations and penalties totaling $3,570. The violations were related to the employer's failure to provide appropriate respiratory protection and training in its use.


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