Updated Dec. 25, 2020 at 8:45 a.m.

State water quality regulators are investigating a large wastewater spill that sent close to 100,000 gallons of untreated sewage into an Alameda lagoon last week, prompting the East Bay's largest water agency to urge people to stay out of the body of water for eight days.

A power outage at an East Bay Municipal Utility District pumping station, along with a problem with a backup generator, led to the release of the sludge on Bay Farm Island on Dec. 16, according to the agency.

The release marks the second time in the last four months that power problems at the agency led to a major sewage spill.

A sign that reads 'Sanitary Sewer Overflow Advisory' near a lagoon in Alameda. — The Alameda lagoon where a power outage resulted in a massive sewage spill. (Mary Spicer)

In August, a series of electrical failures at EBMUD's main wastewater treatment plant caused the release of 47,000 gallons of untreated sewage and 3.7 million gallons of partially treated wastewater into the Oakland Estuary.

"Two large sewage spills resulting from power outages and backup generator failures in a matter of months can no longer be excused as an accident," said Sejal Choksi-Chugh, executive director of San Francisco Baykeeper, which for years has pushed EBMUD to do more to prevent wastewater spills.

[pullquote size='medium' align='right' citation='Sejal Choksi-Chugh, executive director of San Francisco Baykeeper']'Two large sewage spills resulting from power outages and backup generator failures in a matter of months can no longer be excused as an accident.'[/pullquote]

"This appears to be an operational problem that EBMUD needs to solve in order to prevent these kinds of spills from posing a significant health threat to the Bay and the people of the Bay Area," Choksi-Chugh said in an email.

The Oakland estuary release in August garnered significant media attention. It came at around the same time California put in place rolling blackouts for the first time in decades, when public scrutiny of the state's infrastructure was heightened.

EBMUD representative Andrea Pook stresses that the summer spill and last week's spill in Alameda are not connected.

"There were two spills due to power outages but they were completely different circumstances," Pook said in an email.

The most recent spill took place near Robert Davey Jr. Drive and Packet Landing Road by Earhart Elementary School. Initially, crews reported that around 10,000 gallons had been released. Two days later, EBMUD revised up its estimate to 97,000 gallons.

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Pook said the agency is trying to find out what led to the outage, but that it was not caused by a problem with Alameda Municipal Power, which supplies electricity to the facility.

Some of the sewage seeped out of storm drains as it made its way west toward the lagoon, prompting odor complaints from some Harbor Bay residents.

"What's the horrible rotten egg smell now?" one resident asked on the neighborhood social network Nextdoor.

Pook said crews were called out to clean the wastewater from the street.

The lagoon where the sewage emptied into has gates that blocked the sludge from entering the San Francisco Bay, according to EBMUD and state water regulators. [ad fullwidth]

The utility agency detected bacteria concentrations in the lagoon that exceeded state standards, so they posted signs in the area, urging people not to enter the water.

The bacteria levels eventually fell below those standards last Wednesday, according to a post on EBMUD's website the following day.

The San Francisco Bay Regional Water Quality Control Board is looking into the spill, according to Bill Johnson, who heads a division of the board that focuses on enforcement and pollution. That review could lead to a fine or required fixes at EBMUD, Johnson said.

This story was updated after EBMUD revealed Dec. 24 that water quality in the lagoon where the sewage spilled into had eventually improved.

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