At 5:16 a.m. on Friday, Feb. 13, 1981, an explosion in downtown Louisville, Ky., hurled a passenger car into a railroad overpass structure and dropped it into a crater. At the same time, officers in a police helicopter saw a series of explosions begin at the railroad underpass on Hill Street (three miles northwest of the Kentucky Exposition Center site) and continue along the streets of Old Louisville.
The cause was the ignition of highly volatile hexane from a Ralston Purina soybean processing plant that escaped into the city sewer system. The explosion demolished more than 13 miles of lines in a 3-square-mile area, leaving 38-foot-deep craters where manholes had been and collapsing several blocks of Hill Street into the space that had been the 7.5- to 12-foot concrete sewer line.
Students at the University of Louisville saw their bathrooms blow apart. Shockwaves knocked people off their feet. As fumes built up downstream in the sewer line, police evacuated several schools and an oil refinery. At 3:45 p.m., the “Friday the 13th monster” gasped its final breath, popping a manhole cover at Second Street and Burnett Avenue.
No serious injuries occurred, but 2 1/2 to 3 feet of sewage continued to flow in the inverts, causing health officials to evacuate 107 residents from their homes. Chimneys on 43 buildings collapsed and stairways fell, but building foundations were mostly undamaged. On Monday morning, schools opened and a traffic flow plan funneled commuters into the downtown area.
Not typical tofu
The cause of the explosions was the overflow of a containment basin of hexane, a solvent used at the Ralston Purina plant, southeast of the university campus. Company officials informed the city of the problem on Thursday, Feb. 12. They temporarily shut down the facility to reduce flow.
The volume of the floating chemical, however, eventually depressed the water beneath it and rushed into the sewer main through the basin outlet. A city inspector is said to have found no explosive readings at the site Thursday night.
Experts theorize that fumes rising from a manhole on Hill Street became trapped in the underpass area and were touched off by a passing car. The two women in the car sustained moderate injuries. Water flowing from broken water mains washed away underground supports, creating more craters.
The explosions prompted the City of Louisville and Jefferson County to adopt the community’s first hazardous materials ordinance, charging the Metropolitan Sewer District (MSD) with regulating the storage and disposal of such materials.
The destroyed section of Hill Street became an open trench as crews cleared away the debris and prepared to replace the sewer line. The stench from the trench, which remained open all summer, was so bad that the MSD used huge blocks of restroom deodorant to mask the odor. It did not work.
Bud Schardein of MSD disaster and emergency services says the explosion is one reason the agency still closely monitors explosive gases and limits their concentrations in sewer lines. It took 20 months to restore the sewer lines and several more to repair the streets. Ralston Purina pleaded guilty to four counts of violating federal environmental laws, and paid a fine of $62,500.
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In February 1984, the company agreed to pay MSD more than $18 million in damages, and more than $8.9 million to 16,000 plaintiffs and government agencies. Ralston Purina admitted that it released hexane into the sewers, but denied negligence.
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