MAY 15, 2015
NORTHRIDGE, CALIFORNIA
An electrical vault explosion caused a steel manhole cover
to “dislodge” and fall onto two cars, leaving three people injured in Northridge
on Friday, authorities said.
Three cars were involved in a crash related to the
explosion, and power was temporarily lost at Cal State Northridge, which
planned to hold its graduation ceremony Friday evening.
A utility power systems crew was responding, according to a news release
from the Los Angeles Department of Water and Power.
The explosion occurred at Nordhoff Street and Reseda
Boulevard, DWP stated.
“Initial reports from first responders on scene indicate
that three to four cars were involved in an accident related to the blast and
that the steel vault cover fell onto one car and injured one of the occupants,”
the DWP release said.
The manhole cover struck one vehicle and landed on another,
the Los Angeles Fire Department stated
on Twitter. Three people were taken to a hospital with minor injuries, the
Fire Department said.
Three cars were involved in the collision, stated LAFD,
which was called to the scene at 1:19 p.m.
CSUN announced that campus power had been restored about
3:20 p.m. and that graduation would go on as planned.
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LADWP Crews Responding to Electric Vault Explosion in
Northridge
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LOS ANGELES — LADWP Power System crews are responding
to an electrical vault explosion that caused a manhole cover to become
dislodged near the intersection of Nordhoff Street and Reseda Boulevard in
Northridge. Initial reports from first responders on scene indicate
that three to four cars were involved in an accident related to the blast and
that the steel vault cover fell onto one car and injured one of the
occupants.
A power outage also occurred at nearby Cal State Northridge
and was likely related to the vault explosion.
LADWP crews are on scene and we will update as more information becomes available.
Electrical vaults are part of LADWP's power distribution
infrastructure. LADWP has nearly 3,600 miles of distribution cables
that run under the City and through underground electrical vaults.
LADWP's electrical distribution system is made up of approximately 1/3
underground and 2/3 overhead distribution lines and cables that carry
thousands of volts of electricty to 1.4 million electric customers.
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Manhole explosions typically increase during the winter,
when salt applied to roads to melt ice can fray cables that lie beneath the
city streets.
After the insulation is damaged, the cables then can short
when flooded during storm events, causing sparking fires, smoking incidents,
and blasts due to the increased gas pressure inside the vault.
Several hundred pound manhole covers can shoot in the air
from that pressure built up. Expect a
significant increase in manhole fires due to the amount of salts used to melt
the ice/snow this harsh winter.
Already most areas in the northeast have seen an increase in
the number of incidents compared to previous years.
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THERE ARE OVER 2,000 MANHOLE FIRES/EXPLOSIONS EACH YEAR IN
NYC. UNDERGROUND CABLES BECOME FRAYED
FROM SNOW/ICE MELTING CHEMICALS, AGING, CORROSIVE CHEMICALS, OVERLOAD OR RATS
BITING THEM
Snow/ice melting compounds in melting snow has wreaked havoc
on the New York City's underground utility system, sparking nearly 600 manhole
explosions, fires and other incidents since Sunday, Con Ed officials said. The city averages about 2,100 a year.
In November, two people were hurt after an explosion in
midtown. Last month, a 71-year-old Park
Slope man was injured when a manhole cover flew off and hit him in the
head. And last night, three firefighters
in Brooklyn were injured when more than a dozen manholes exploded
across the borough.
Manhole fires, like those in Park Slope and others reported
overnight, are often triggered by salt that leaks into the underground
electrical system and corrodes wires, which then ignite, officials said.
"A lot of times after it snows and the snow melts, salt
that is put down onto the sidewalk leaks into our system and can cause fires
when it hits our equipment," Con Ed spokesman Alfonso Quiroz said.
"What it does is it eats away the insulation that
prevents the different cables from touching each other," said FDNY
Battalion Chief Thomas Schmitt. "Once that's gone, you get this
effect."
The flaming wiring can then release the dangerous gas, which
can leak into neighboring buildings as it builds up pressure below the manhole,
causing it to explode.
A cast-iron manhole cover can weigh between 85 and 300
pounds (35 to 136 kg), and explosions have propelled these massive discs
anywhere from 1 foot to 50 feet (0.3 to 15 m) into the air. The real problem
with these explosions (aside from the risk of injury) is the loss of power in
the aftermath.
In most cases, these are the events that lead to an
explosion:
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.
These electrical wires heat up the paper, lead and rubber
insulation.
The insulation smolders and catches on fire, releasing
gases.
The pressure from the gas builds up inside the manhole.
The electrical wires arc like a bolt of lightning and ignite
the gases, causing a powerful explosion.
Depending on the amount of gas-pressure built up inside the
manhole, the cover may flip over or be launched several feet in the air. Often,
there may not be an explosion, just a lot of smoke or fire.
Some power companies are in the process of replacing solid manhole
covers with slotted manhole covers. These new covers allow the gas to be
released less violently, and also give an early warning to possible explosions.
Con Ed was still investigating what caused the Monday
explosion, but Quiroz said salt was likely to blame.
"We don’t know [for sure], but considering the weather
Monday that is very likely what it was," he said.
Manhole explosions typically increase during the winter,
when salt applied to roads to melt ice can fray cables that lie beneath the
city streets. After the insulation is
damaged, the cables then can short, causing sparking fires, smoking incidents,
and blasts due to the increased gas pressure inside the vault. Several hundred pound manhole covers can
shoot in the air from that pressure built up.
The electric utility company (Con Ed in this case) would
basically have to replace sections of its underground wire infrastructure every
few years to keep them from happening, a totally impossible project considering
the traffic congestion issues, costs and thousands of miles of cables. In 2014, ConEd started working on
implementing a $1.3 billion electrical modernization project that will
hopefully decrease the number of incidents.
//-----------------------------------//
THE MANHOLE FIRE/EXPLOSION INCIDENTS ARE EXPECTED TO
INCREASE DURING THE SNOW MELTING PERIOD
NEW YORK, NY (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.
Mario Tama/GettyFirefighters gather at the scene of an
underground blaze following an explosion near Eighth Avenue and 38th Street.
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.