Seyfarth Synopsis: The CSB found deficiencies in the facility’s design and labeling of the chemical loading stations, and failure to follow the company’s written chemical unloading procedures.
The U.S. Chemical Safety Board recently released preliminary findings from its ongoing investigation of the toxic chemical release that occurred at a processing plant in Atchison, Kansas. The investigation has identified several deficiencies in the design and labeling of the loading stations, and failure to follow the company’s written chemical unloading procedures.
In the Atchison case, a chemical tanker truck arrived at the facility to deliver sulfuric acid. A facility operator escorted the driver to a locked loading area. The operator unlocked the gate to the fill lines and also unlocked the sulfuric acid fill line. The Board findings indicate that the facility operator likely did not notice that the sodium hypochlorite fill line was also already unlocked before returning to his work station. The driver accordingly connected the sulfuric acid discharge hose from the truck into the sodium hypochlorite fill line. The line used to transfer sulfuric acid looked similar to the sodium hypochlorite line, and the two lines were located in close proximity.
As a result of the incorrect connection, allegedly thousands of gallons of sulfuric acid from the tanker truck entered the facility’s sodium hypochlorite tank. The resulting mixture created a dense cloud of poisonous gas, which traveled northeast of the facility until the wind shifted the cloud northwest towards a more densely populated area of town. The Board’s investigation preliminary findings have concluded that “emergency shutdown mechanisms were not in place or were not actuated from either a remote location at the facility or in the truck.”
The Board indicated that a number of design deficiencies increased the likelihood of an incorrect connection. These included “the close proximity of the fill lines, and unclear and poorly placed chemical labels.” In addition, neither the facility operator of the tanker truck driver followed internal procedures for unloading operations.
This incident illustrates the necessity of maintaining both safety procedures, and regular training on those safety procedures. Process safety management reviews and periodic reviews of operating procedures can also assist employers to find process areas that have potential weaknesses or issues that can be corrected, before incidents occur.
Human factors such as the chance of operator confusion appears to have played a role in this incident. Employer’s should continue to evaluate human factors as part of their hazard assessments.