FEBRUARY 28, 2015
(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City's outdated infrastructure.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."
Cables have an expected lifetime of about 40 years, but in
Manhattan, 5 percent of low-voltage distribution cables were installed before
1930, according to a 2014 analysis. In addition, overheating and even gnawing
rats can hasten the deterioration. It is the oldest electrical system in the
nation.
"Everything that’s electrical has a certain limit, a
certain lifetime," said William Black, a professor emeritus of mechanical
engineering at the Georgia Institute of Technology.
In any single year, New York has 2,100 manhole incidents a
year, or nearly six of them every day, Con Ed estimates.
The problem is so much larger in New York than elsewhere in
part because the city has the country's largest underground electrical system,
with its 98,000 miles (157,716 km) of cable and 264,000 manholes and service
boxes.
To be sure, most manhole incidents are relatively harmless
"smokers," but about 10 percent in the first week of February were
more dangerous.
Earlier this month, a smoking manhole exploded in Brooklyn,
sending a worker scrambling for safety in an incident caught on video. On the
same day, a parked Mazda was torched after a manhole beneath it started
spouting fire.
"Con Ed has a rather difficult situation because if you
proceed to dig underneath the street you’ll see how congested it is,"
Black said.
The problem is attracting attention. Donovan Richards, chair
of the New York City Council's Environmental Protection Committee, is
considering legislation to push Con Ed to spend more on modernizing its
underground infrastructure.
In 2014, Con Ed invested $1.3 billion in modernizing its
electrical infrastructure, including the installation of nearly 1,600 miles
(2,575 km) of underground electric cable. But that is just a fraction of the
tens of thousands of miles in the system.
Manhole events "take a considerable amount of time and
resources," said Con Ed spokesman Allan Drury. "But our emphasis is
on public safety and we are always looking for new technologies and methods to
improve our system."
For instance, the utility has been installing vented covers
that allow for trapped combustible gases to dissipate more easily.
Con Ed has teamed with the Massachusetts Institute of
Technology and Columbia University to develop a tool that predicts manhole
incidents through statistical modeling, taking into account factors such cable
age and failure history.
But Cynthia Rudin, associate professor of statistics at MIT
who worked on the project, warns against focusing too much energy and money on
replacing cables.
"It is not a reasonable scenario to think of replacing
the whole distribution network every few years or so," Rudin said.
Source: www.reuters.com