DWP still investigating cause of transformer explosion that left 140,000 Valley customers without power

Pat Pope was enjoying a performance of “Harry Potter and the Prisoner of Azkaban” at the Hollywood Bowl Saturday night when he started getting texts from his friends about the power outage.

When the Porter Ranch resident got home at 11:30 p.m., it was 86 degrees and he could hear his neighbors’ generators humming. Power was out all night, and Pope said he didn’t get much sleep because of the heat.

“It was just a nasty night for a lot of people in the Valley,” he said.

Pope was among 140,000 customers in the San Fernando Valley who lost power after an explosion at a Los Angeles Department of Water and Power plant in Northridge caused a fire that burned for hours, knocking out traffic lights and stranding people in elevators.

The outages hit businesses and residents in Northridge, Winnetka, Reseda, Lake Balboa, Tarzana, North Hills, Granada Hills, Chatsworth, West Hills, Canoga Park and Woodland Hills, DWP officials said.

The loss of power came at the peak of a heat wave that pushed temperatures to 100 degrees in many parts of the Valley. Woodland Hills reported a temperature of 110 while Lake Balboa hit 107 on Saturday afternoon. Downtown Los Angeles hit a record high of 98 degrees.

By 11 p.m. Saturday, 94,000 were still without power, officials said. The agency was able to restore power to those remaining customers by 8 a.m. Sunday.

DWP spokesman Michael Ventre did not have details on where Saturday’s power loss ranks in recent years, but noted “it’s a significant outage.”

It remains unclear whether the blast was related to heavy demand due to the heat wave. But it was another illustration of the city's delicate infrastructure, which has manifested itself in epic bursts of aging water works and crumbling sidewalks and streets.

Residents of an apartment complex near the DWP plant on Parthenia Street in Northridge reported hearing an explosion at the plant just before 7 p.m. Saturday, and firefighters arrived to find a gigantic vat with as much as 60,000 gallons of mineral oil — used as a cooling agent for electrical equipment — on fire, said Los Angeles Fire Department spokesman Brian Humphrey.

Humphrey said dozens of firefighters extinguished the flames with water and foam by 9 p.m. “These were fierce flames, with smoke towering more than 300 feet into the sky,” Humphrey said.

No one was injured. He said mechanical failure related to cooling equipment might have caused the explosion, though the investigation continues.

Workers could be seen inspecting the blackened transformer Sunday. The transformer yard is fenced off from the public.

Humphrey said firefighters rescued dozens of people who were stranded in elevators in buildings around the Valley.

Officials estimate that between 10,000 and 20,000 gallons of mineral oil were released during the explosion, said Nosa Omoruyi, a hazardous materials specialist with the Los Angeles County Fire Department.

Water used to douse the fire carried oil into storm drains, and officials want to make sure the drains are cleaned of any oil, Omoruyi said.

Power was shut off at the DWP plant to allow firefighters to fight the blaze.

Receiving Station J was built in the 1950s to serve the growing industrial area in the northwest valley, according to the Center for Land Use Interpretation. It’s one of 21 receiving stations in the DWP network that act as a bridge between power plants and local distribution, according to agency figures. High-voltage power lines enter the grid at these stations, where the voltage is reduced and eventually sent to customers.

As residents switch on air conditioners to deal with the sweltering July heat, it means the region draws more power, said Rajit Gadh, engineering professor at UCLA. Substations used to transfer that energy require cooling or they can become overheated.

“When temperatures rise that much, then lots of things can potentially go wrong, including the electric grid,” Gadh said.

Power was out for 13 hours at Pacifica Senior Living, an assisted senior living facility in Northridge. Staffers handed out wet towels and water, and a generator kept emergency lights running in the hallways, but residents’ rooms remained dark, without air conditioning.

“It was a bit rough,” said Cristina Gutierrez, the facility’s executive director. She sent staffers to Target Saturday night to buy lanterns for residents shortly after the power went out at 7 p.m. Residents also gathered in the main entrance hall to keep cool.

No staffer at Pacifica could recall another time when the facility’s power was out for 13 hours, Gutierrez said. Power was restored about 8 a.m. Sunday morning, she said.

Northridge Hospital Medical Center lost power Saturday night, and backup generators immediately kicked on until electricity was restored Sunday morning, hospital spokeswoman Christina Zicklin said. Dozens of fans and emergency lighting were used, and medical officials diverted emergency runs to nearby hospitals, she said.

“Our patients were not affected other than getting a little warm,” Zicklin said.

James Kostrach, 63, was having a quiet Saturday cleaning his backyard when suddenly the area sounded like a war zone, he said.

“I heard ‘blam!’’’ said Kostrach, who lives in a small house just behind the transformer yard in Northridge.

The noise drew him toward the DWP yard, where he saw a big plume of smoke and flames. He’s heard similar noises from the yard before, but nothing as loud as what occurred Saturday.

“I knew that there wasn’t going to be electricity,” Kostrach said.

ben.poston@latimes.com

dakota.smith@latimes.com

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