Serious hazardous materials incidents like the propane truck delivery explosion that killed 4 and injured over 70 in Mexico City on January 31 often lead to “Could it Happen Here?” questions from the public, media and government officials. The answer is that though there is no way to conclude that such incidents could never occur, the tank truck industry and regulators from the US Department of Transportation have developed rules and practices to reduce the potential for such tragedies.
Reports vary, but it is clear that propane gas leaked from the tank truck valve or hose and that the driver used makeshift efforts to try to stop the leaks before urging an evacuation of the maternity hospital where he was making a routine delivery. The Associated Press quoted witnesses saying, “the tanker workers struggled frantically for 15 to 20 minutes to repair the leak while a large gas cloud formed.”
Representatives of the Pipeline and Hazardous Materials Safety Administration (PHMSA) and of industry conducted several meeting in the late 1990s under the “negotiated rulemaking” process that led to the current regulations found in 49CFR180.416. Those regulations cover a “Discharge system inspection and maintenance program for cargo tanks transporting liquefied compressed gases.” They provide for inspections of hoses after every delivery and regular inspections of hoses, monthly inspections of delivery hose assembly and piping. Emergency discharge control devices must be tested monthly.
The regulations also require that MC330 or MC331 tank truck, both trailers and bobtails, be equipped with emergency discharge controls to stop unloading in the event of an unintentional release such as the one that occurred in Mexico City (See 173.315 (n)). The control can utilize passive or off-truck remote means to stop the unloading operation.
A well-trained driver who has been taught what actions to take during a propane delivery emergency is the most important key to safety. Drivers are hazmat employees who must receive function-specific training under Section 172.704. Recurrent training is required every three years.
Carriers can use the Mexico City tragedy to reinforce to all driver, shop and other employees the importance of regulatory compliance and on-going attention to safety.