New York's exploding manhole covers pose unexpected winter hazard

(Reuters) - Salvatore Grillo was walking his Labrador retriever near Brooklyn's Prospect Park on a cold morning in February when he heard what sounded like a muffled explosion.

Minutes later, emergency responders were hovering over the 71-year-old as he lay unconscious on the ground. Police said an underground blast had blown a cast-iron manhole cover skyward and the heavy metallic disk came crashing down on his head.

While the seriousness of Grillo's injury is unusual, manhole "events" have become all too common in the country's largest metropolis. In the snowy first week of February, Consolidated Edison Inc, the local utility, tallied about 600 "smokers," fires and occasional explosions involving manholes, part of a seasonal surge that plagues New York every winter.

Manholes are entry points to a labyrinth of electric cables, many of them aged and decaying, that snake underneath the city streets. In winter melting snow mixed with de-icing salt can seep through, causing frayed low-voltage cables to fail. That can trigger fires, smoke and explosions that can send manhole covers flying.

"These incidents are yet another example of New York City's outdated infrastructure. It's well-known that saltwater and exposed electrical wires are a dangerous combination," said New York's Public Advocate Letitia James. "If we want a safer city, we must do more to address this issue."