On February 13, 1981, a series of explosions destroyed more than 13 miles (21 km) of sewer lines and streets in the center of Louisville in Kentucky, United States.
[4][5] The blasts were caused by the ignition of hexane vapors which had been illegally discharged from a soybean processing plant owned by Ralston-Purina and located on Floyd Street.
[8] The company admitted that it had released hexane into the sewers, but initially did not accept responsibility for the blasts[1] and continued to deny negligence for years[9] until eventually pleading guilty to four counts of violating federal environmental laws and paying the maximum possible fine, $62,500.
Officers in a police helicopter that happened to be over the area at the time said the series of explosions looked like a bombing run.
[4] A buildup of fumes occurred where the sewers ran under an Ashland Oil refinery, raising the potential for a further major conflagration, but workers were able to flush out the system in the area.
The fact that the incident took place in the heart of winter compounded the hardship, and some residents were left without heat until gas lines and furnaces could be tested and repaired.
The open trench along Hill street remained exposed through the summer, emitting a foul stench for about six months before the system could be enclosed again.
[8] The incident has been cited by such entities as the American Society of Civil Engineers[13] and the U.S. Government Accountability Office as an example of the need for increased security concerning the United States' wastewater systems,[7] and by the United States Environmental Protection Agency as an example of the dangers associated with discharges of hazardous waste to sewer systems.
[19] The Ralston-Purina plant, a long-standing landmark recognizable by its 22 large silos topped with a checkerboard logo alongside the southbound lanes of I-65, was sold in the wake of the incident.