Los Angeles authorities said Wednesday night that they were reopening four miles of beaches after 17 million gallons of sewage spilled into Santa Monica Bay Sunday.
A mechanical failure at the Hyperion plant Sunday "caused untreated sewage to be discharged into the ocean," Los Angeles County Supervisor Janice Hahn said on Twitter Monday. "Water samples are being tested and I'm getting more information about the scope of the problem. Beaches from El Segundo to the Dockweiler RV Park are closed for swimming."
The Los Angeles County Department of Public Health collected samples for two consecutive days of ocean water, testing for signs of water quality issues. They asked lifeguards to remove signs at El Segundo and Dockweiler State Beaches, as well as Grand Avenue Storm Drain Wednesday evening, officials said in a news release.
The Hyperion plant is both the city’s largest and oldest sewage treatment facility and has been in operation since 1894. The plant was designed to accommodate a daily flow of 450 million gallons of water per day.
Executive Plant Manager Timeyin Dafeta said in a statement that the facility “became inundated with overwhelming quantities of debris, causing backup of the headworks facilities."
“The plant’s relief system was triggered and sewage flows were controlled through use of the plant’s one-mile outfall and discharge of untreated sewage into Santa Monica Bay,” Dafeta said.
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About 6% of the facility's daily load was discharged as an emergency measure to prevent the plant from going offline and spewing even more raw sewage, the statement said.
"Bacteria and viruses in raw sewage are extremely dangerous to people and can carry a variety of diseases," environmental advocacy group Heal the Bay said. "Debris such as tampons and plastic trash, when released into the Bay, can harbor bacteria and can cause entanglement of wildlife, but it seems in this case those debris were successfully filtered out of the spill before it made it to the Bay."
Dafeta told the Los Angeles Times that the mechanical failure was resolved Monday morning.
"I understand that the plant was able to prevent an even larger spill, but we are going to need answers about how and why this happened," Hahn said on Twitter.
She called Tuesday for Public Health to report on the incident, not only how it happened, but why it took at least a day for them to notify beachgoers.
“What happened yesterday was unacceptable and dangerous,” she said in a statement. “Not only did the Hyperion Plant release seventeen million gallons of sewage into our ocean-- the public had little to no information about it for hours."
The largest spill in city history occurred in 1998, with more than 30 million gallons of sewage spilled during El Niño storms.
Another notable sewage spill occurred in 2016 when a damaged sewage line spilled about 2.4 million gallons of untreated waste into the Los Angeles River and forced the closure of all beaches in the county in Long Beach and Seal Beach.
In 2018, a sewage leak at Dodger Stadium forced the cancellation of the final innings of a game between the Los Angeles Dodgers and Los Angeles Angels.
Contributing: The Associated Press
This article originally appeared on USA TODAY: LA area beaches reopen after 17-million-gallon sewage plant spill