Manhole explosions rock NYC, from Park Slope to Washington Heights

Danger, Will Robinson. Danger!

If it’s not the subways, it’s the sewers.

Manholes have exploded around the city in recent days, setting cars afire, shooting toxic gas into homes — and leaving one Brooklyn man in critical when a heavy, flying manhole cover hit him in the head.

Salt from street de-icing makes a bad situation far worse in the city’s aging underground infrastructure. The explosions are caused when the salty water from the melting make frayed, exposed wires arc below ground and the sparks ignite the foul gas air. Then boom.

Con Ed officials told 7Online that there have been 200 manhole incidents in recent days. Not all included a flying cover; several were just holes spewing smoke or fires.

Here’s a sample of some:
— Tuesday morning in Park Slope, Brooklyn, on Sixth Street, dozens were roused after a manhole blew beneath a car, setting it on fire. Carbon monoxide detectors soon sounded in several homes and evacuations began.

— Monday night in Manhattan’s Washington Heights, gas from a blown manhole filled a five story apartment house at W. 163rd and Fort Washington Ave., forcing 100 residents to leave when CO alarms in multiple units sounded. Several residents reportedly suffered minor carbon monoxide poisoning.

— Monday morning in Brooklyn, on Prospect Park West near Fourth Street, 71-year-old Salvatore Grillo was hospitalized in critical condition after a manhole hit him in the head around 11:30 a.m. The Post said Grillo’s dog, Abby, bolted into Prospect Park, where rescue groups found her hours later.

So what causes exploding manholes? The wet, cold weather we’ve been major contributors. How Stuff Works has a nifty graphic on the Hole phenom and lists these steps:

1.Underground cables become frayed from aging, corrosive chemicals, overload or rats biting them. These cables carry on the order of 13,000 volts of electricity.

2.These electrical wires heat up the paper, lead and rubber insulation.

3.The insulation smolders and catches on fire, releasing gases.

4.The pressure from the gas builds up inside the manhole.

5.The electrical wires arc like a bolt of lightning and ignite the gases, causing a powerful explosion.