Manhole covers flying into the sky is apparently not a rarity in the U.S. The reasons can be whittled down to a combination of electrical faults and heat building up. Various studies have taken place into the phenomenon and a 2014 report by Consolidated Edison Company said New York leads the list with a recorded 3,369 manhole events, including 32 explosions, during the year, reports NBC News.
Spokesperson for Consolidated Edison Allan Drury said an explosion is defined as a manhole cover dislodging and causing injuries or property damage.
According to experts from the company, while manhole events can happen at any time of year, the extra volume of electricity running through them because of high usage of air conditioning in summer typically increases the number of incidents. New York recorded almost 500 manhole events between May and August last year.
So here is how it happens. Underground cables become frayed due to aging, corrosive chemicals, overload or rats biting them. These electrical wires heat up, raising the temperature of the insulating paper, lead and rubber insulation, which eventually catch fire, releasing gases. The pressure from the gas builds up inside the manhole. The electrical wires arc like a bolt of lighting and ignite the gases, causing a powerful explosion, explains How Stuff Works.
Witnesses describe the event as scary. "It was really scary. It was shocking, this explosion," said Lea Debressey, who was on her way to dance class when a recent series of explosions rocked the corner of 45th Street and 9th Avenue on Manhattan's west side, according to Daily Mail.
"It's a miracle no one got hurt. It could have been a lot worse," said Ritchie Christian, another witness to the incidents, according to the Daily Mail.
