Sunnyvale fined $187,000 after spilling nearly 300,000 gallons of wastewater into San Francisco Bay

State water pollution officials have hit the city of Sunnyvale with $187,000 penalty after the city’s wastewater treatment plant spilled more than a quarter million gallons of partially treated sewage into San Francisco Bay last summer.

The spill occurred on July 29 when a 36-inch welded steel pipeline ruptured, releasing 292,600 gallons — the equivalent of about 12 backyard swimming pools — of partially treated sewage that had not been disinfected into channels that flow into the bay near Moffett Field.

“These types of discharges pose a threat to the environment and to human health,” said Thomas Mumley, assistant executive officer of the San Francisco Bay Regional Water Quality Control Board. “This enforcement action will be recognized by the wastewater treatment industry, and will become a deterrent, hopefully.”

The spill was one of the two largest illegal discharges from a Bay Area sewage treatment plant into San Francisco Bay over the past six years, Mumley said. It was eclipsed only by a 2.2 million-gallon spill from the Sonoma Valley County Sanitation Agency plant on Jan. 11 and 12, 2019. That discharge of partially treated sewage, which resulted in a $427,000 penalty, went in to Sonoma Creek, which flows to San Pablo Bay.

The Sunnyvale case was settled Monday.

Sunnyvale officials said the pipe that failed is buried 10 feet underground and was built in 1975. They said it had not failed before and was scheduled to be replaced in the next few years as part of a massive, $1 billion project to modernize the wastewater treatment plant, which was built in 1956, over a 20-year period. The plant serves about 160,000 residents in Sunnyvale.

“It is something that was unexpected,” said Ramana Chinnakotla, Sunnyvale’s Environmental Services Director. “But we know our plant is aging. That’s the reason why the city council has committed to upgrade the plant. This pipe was going to be replaced. It’s unfortunate it failed before we had a chance to replace it.”

Chinnakotla said that no dead fish or other wildlife were observed in the water. The Bay Trail is located nearby, but he said the area where the spill occurred — in a channel adjacent to former Cargill Salt ponds now owned by the U.S. Fish and Wildlife Service — is not frequented by the public.

“This is a fish and wildlife channel,” he said. “It’s not really used for any recreation. The chances that people would have come into contact with it are very remote.”

Water tests conducted in the area after the spill found levels of enterococcus bacteria 22 times higher than the state standard, along with elevated ammonia and pH levels, which can be harmful to fish and wildlife.

Under state rules, water pollution events are required to be reported within two hours to the California Office of Emergency Services and the local health officer. Sunnyvale plant workers discovered the spill at 6:15 p.m. on July 29, but did not report it until 11 a.m. the following morning, state inspectors concluded. They also did not properly post signs warning of public health risks, inspectors reported.

“Improperly treated wastewater doesn’t belong in the bay,” said Sejal Choksi-Chugh, executive director of San Francisco Baykeeper, an environmental group. “And any amount is too much. But it’s especially egregious if the spill could have been prevented by routine monitoring and maintenance, and neither the public or regulatory agencies were given timely information. Even partially treated sewage contains bacteria, viruses, and other harmful pathogens that can make people sick.”

The pipe that failed connects the Sunnyvale wastewater plant, which sits on the edge of the Bay on Borregas Avenue between Moffett Field and the headquarters of Yahoo, with two oxidation ponds where wastewater is naturally treated before being pumped back into the plant for its final disinfection and filtering before clean water is discharged into the bay. The pipe was taken out of service the next day, and two temporary above-ground pipes have been installed in its place.

The city will be able to cover half of the penalty by completing a natural stormwater treatment project at Wolfe Road and Stewart Drive in Sunnyvale.

“The city doesn’t want these kinds of discharges to happen,” Chinnakotla said. “In this case the wastewater was partially treated. There was no public health risk. And we were able to correct it very quickly.”