Evacuation distances questioned by NTSB
A warning issued by the National Transportation Safety Board (NTSB) states that a false sense of security with determining evacuation distances could be created if relying solely on the Department of Transportation’s (DOT) EMERGENCY RESPONSE GUIDEBOOK FOR HAZARDOUS MATERIALS.
Because explosions can cause parts of hazardous material containers to travel greater distances than the DOT’s recommended evacuation zones, increased evacuation limits may be necessary, according to a report in the WASHINGTON SCENE.
The warning was issued after the NTSB reviewed a September 1983 train derailment near Murdock, IL. A tank car containing flammable compressed gas exploded, rocketing pieces of car 3,630 feet, according to the report. For the substance involved, the guidebook recommends an evacuation distance of 2,640 feet.
The introduction to the DOT guidebook, however, states that, “These recommended distances to isolate or evacuate people from spill areas are only for the initial phase of an accident …. Continuing reassessment will be necessary since there may be a change in circumstances
The guidebook makes a distinction between the isolation area (the immediate hazard area to which only emergency service personnel directly involved in mitigating the incident can gain entry) and the evacuation area (the full area that might be affected by the escaping toxic gas or liquid). A section of the introduction to the guidebook’s evacuation tables reads,”… if undamaged containers are involved in a fire, the potential fragmentation hazards would require isolation in all directions for a half mile
The DOT in its guidebook also states that, “The purpose of this guidebook is to assist an individual in making decisions. It is not intended to serve as a substitute for his own knowledge or judgment. This distinction is important since the recommendations given are those most likely to be applicable in the majority of cases. It is not claimed that the recommendations are necessarily adequate or applicable in all cases.”