In New York, road salt spread by the city to try to control snow in the winter tends to wash down into drains and underground electricity conduits. This then corrodes cabling or insulation, leading to short circuits and fires and, in some cases, to flying manhole covers.
The other fun side effect is that while the manhole covers don’t always take flight, covers and drain grates sometimes get electrified as the result of a short circuit. Periodically, someone – or some dog – then gets electrocuted. People have learned not to stand on anything metal during the winter months.
Some of it might have been shit, but most of it was probably mud and road debris that gets wedged down in the cracks by those dirty, dirty tires. Looked to have a good bit of water in it too, so it probably had rained fairly recently.
A teenager a town over (near Boston) was seriously injured when a projectile man hole cover went through a windshield, and in Boston’s North End a man hole cover was found on the roof of a building after an explosion launched it. So, I guess this happens with some regularity?
