Last week was the anniversary of the anhydrous ammonia truck accident in Houston back in 1976 and out of that incident came what we call “Shelter-in-Place”. About 11:08 a.m., on 11 May 1976, a Transport Company of Texas MC 331 tractor-semi trailer transporting 7,509 gallons of anhydrous ammonia struck and penetrated a bridge rail on a ramp connecting I-610 with the Southwest Freeway (U.S. 59) in Houston, Texas. The tractor and trailer left the ramp, struck a support column of an overpass, and fell onto the Southwest Freeway, approximately 15 feet below. The anhydrous ammonia was near instantaneously released from the damaged tank semi trailer. Six persons died as a result of the accident, 78 persons were hospitalized, and approximately 100 other persons were treated for injuries.
The National Transportation Safety Board investigation determined that the probable cause of the accident was the excessive speed of the vehicle combined with the lateral surge of liquid in the partially loaded tank truck, which caused it to overturn. The cause of 5 of the 6 fatalities and all of the 178 injuries was the inhalation of anhydrous ammonia.
Findings of a Follow-up Investigation by NTSB An NTSB Special Investigation Report, Survival in Hazardous Materials Transportation Accidents found, “When the motorists got out of their cars, they actually decreased their chances of survival…” This report stated, “The differences in the degree of injury among the exposed victims suggest that alternatives to evacuation…could improve survivability.” NTSB recommended identifying “…alternatives to evacuation…” in hazmat incidents. Further government studies and academic research found that inplace protection (commonly called “shelter-in-place”) was often the preferred method of protecting the public from airborne threats from hazmat incidents.
Source: NTSB Investigation Reports HAR-77/01 and PB-268251, NTSB Special Investigation Report NTSB-HZM-79-4
Story Souce: http://www.caloes.ca.gov/CaliforniaSpecializedTrainingInstituteSite/Documents/HazMat%20History.pdf