Any incident involving the potential for vaporized hazardous materials, including the possibility of acid vapor splashing4, requires full body protection in the form of Level A chemical protective clothing. That is quite different from standard firefighter 'turnout gear'. With the combined requirements for flame protection, supplied air respiration, and protection from chemical contact, and facing the hazards of confinement in an enclosed space with the potential for a BLEVE imminent, and vision totally obscured – firefighters were presented with a situation too dangerous to approach. Some of the hazard factors had to be reduced over a period of many hours before firefighters could enter the tunnel safely.
Chemical hazards were present for at least three days. Car number 53, containing 20,000 gallons of hydrochloric acid, lost nearly one quarter of its load. The spill and seepage crept into the storm sewer and was carried to the Inner Harbor. A member of the Maryland Department of the Environment hazardous materials team said the car was leaking at the seams. Fixing the leak of tank car 53 was complicated because the adjacent tank car (number 52), containing tripropylene, was completely burnt. Investigators believe that the tripropylene tank fire fueled the tunnel fire and made heat so intense that it was almost impossible to remove the hazardous chemicals.
Ironically, reports from the Baltimore Sun state that the Maryland Department of the Environment sampling found no hazardous compounds in the smoke coming from the tunnel; however, tripropylene produces irritating, but not highly toxic fumes when it burns. Because of the blaze, firefighters could not neutralize the acid leak by spreading an alkaline chemical to neutralize it. In the presence of such intense heat, the combination would have been explosive. Traditional plastic pumps would also not have survived the heat. To cool the acid, firefighters opened the manhole cover and sprayed the leaking car with water for over two hours.
On the third day of the incident, CSX contractors began pumping hydrochloric acid from car 53 and the adjacent car 54, which was not leaking. A vacuum hose was lowered through the same manhole that was being used to allow access into the tunnel for firefighting purposes. Additional contractors hired by CSX began replacing the 800 feet of damaged track at the south end of the tunnel to expedite removal of the remaining cars.
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