On Friday February 13, 1981, in the city of Louisville Kentucky, it seemed like the city was under attack. A series of underground explosions in the city’s sewer system destroyed more than two miles of streets. Somehow, there were no fatalities but the damage was so extensive the National Guard was called in.
It began around 5:15 a.m. on the morning of Friday the 13th when a spark from a car at the intersection of 12th and Hill streets ignited flammable vapors in the sewer system. Two women on their way to work at the local hospital were driving under the railroad overpass when the sparks from their car ignited the vapors. The force of the explosion hurled the car onto its side but neither occupant was killed.
Overhead, a police helicopter happened to be traveling above the city. What they saw was incredible – a series of explosions like demolitions detonating up and down city streets, one after the other. The pilot described what they saw as looking like “a bombing run.” More than two miles of streets were left with craters where manhole covers for the sewer had once been. Many business and homes were damaged by the explosions.
The source of the blast was traced back to hexane vapors, which had been illegally discharged by a Ralston-Purina soybean processing plant. The hexane (which is a solvent) was used in the processing of the soybeans and the plant had a system to recover and reuse the hexane.
However, that night, the system was broken and hundreds if not thousands of gallons of the hexane went into the public sewer system. Inside the sewers, the vapors from the hexane accumulated and reached an explosive mixture with air. The flammable and explosive vapors came out of the manhole covers and all it needed was a spark to set it off. Ralston-Purina would later pay $18 million to the city and $9 million to the people of Louisville.