The ignition for a Jan. 24 explosion in Houston that killed two workers, injured 20 people and extensively damaged hundred of homes within a quarter-mile radius was probably something as small as an electrical spark, authorities said Friday.
Electronic bookkeeping on the contents of a 2,000-gallon propylene tank at Watson Grinding indicates that a leak developed in the 24 hours prior to its last filling at 1 a.m. Friday, said Fred Milanowski, local special agent for the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives.
Normal use during the 24-hour period was between six and seven percent, he said.
“Between 1 a.m. Thursday and 1 a.m. Friday 29 percent of that propylene tank was used,” Milanowski said. “That tells us that the leak started sometime during that 24-hour period.”
At the time of the blast an automatic notification reports that the contents of the tank had dropped since its morning filling three and a half hours earlier, he said.
In any electrical system, arcing between connections is normal, Milanowski said.
“When that fuel-to-air mixture was correct — not too lean nor too rich — once there was arcing in the system that spark set off the explosion,” he said.
No signs of a criminal act such as arson or sabotage has been found, Milanowski said. However, no final determination has been made at this point.
More than 200 structures in the West Branch and Carverdale neighborhoods surrounding the metal fabricating and manufacturing company were damaged by the pressure wave from the blast. While most of that damaged was limited to broken windows and smashed doors, at least 35 buildings sustained structural damage.