In the late 1960s and early 1970s, Baltimore was home to industrial confectionary and lozenge production facilities that regularly flushed residual manufacturing waste into the city sewer network. Among the discarded debris were millions of wax-coated paper wrappers heavily coated with sugary syrup from defective batches of menthol cough drops. As these wrappers accumulated in the oxygen-starved depths of the municipal drainage pipes, they formed a massive, unintended bio-reactor.
Microscopic anaerobic bacteria quickly began feasting on the dense buffet of sucrose and glucose trapped in the wrapper sludge. This rapid decomposition process produced vast quantities of volatile methane and hydrogen gas. Trapped beneath the pavement, the pressurized gas built up until a stray electrical spark ignited the subterranean pocket.
The resulting explosion unleashed a violent shockwave through the sewer grid, launching heavy iron manhole covers high into the air and shattering storefront windows across several blocks. First responders were initially baffled by the distinct minty and medicinal aroma wafting from the smoking craters. Municipal investigations later confirmed that the sugar-rich wrapper slurry had catalyzed methane production at over five times the normal rate of municipal sewage, leading Baltimore to permanently reform its industrial waste dumping laws.