Sunnyvale fined $187,000 for San Francisco Bay sewage spill

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

The spill occurred on July 29 when 36-inch welded steel pipeline broke, releasing 292,600 gallons – the equivalent of about 12 backyard swimming pools – of partially treated sewage that did not drain into canals into the bay near Moffett Field.

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

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

The Sunnyvale case was settled on Monday.

Sunnyvale officials said the pipe that failed is 3 meters underground and was built in 1975. They said it had never failed before and should be replaced over the next few years as part of a massive $ 1 billion wastewater treatment modernization project, which was built in 1956 over a 20-year period. The plant supplies around 160,000 residents in Sunnyvale.

“That was something unexpected,” said Ramana Chinnakotla, Sunnyvale’s environmental manager. “But we know that our system ages. For this reason, the city council has committed to modernizing the facility. This pipe should be replaced. It’s unfortunate that it failed before we had a chance to replace it. “

Chinnakotla said no dead fish or other wildlife were seen in the water. The Bay Trail is nearby, but he said the area where the spill occurred – in a canal next to former Cargill Salt ponds now owned by the U.S. Fish and Wildlife Service – is not open to the public.

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

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

State regulations require that water pollution incidents be reported to the California Emergency Services Bureau and local health department within two hours. Workers at the Sunnyvale plant discovered the leak at 6:15 p.m. on July 29, but didn’t report it until 11 a.m. the next morning, state inspectors concluded. They also failed to properly put up signs warning of public health hazards, inspectors reported.

“Improperly treated wastewater does not 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 is especially egregious if the spillage could have been prevented through routine surveillance and maintenance and neither the public nor the regulators were informed in a timely manner. Even partially purified wastewater contains bacteria, viruses and other harmful pathogens that can make people sick. “

The failed pipe connects the Sunnyvale wastewater treatment plant, located on the edge of the bay on Borregas Avenue between Moffett Field and Yahoo’s headquarters, to two oxidation basins that naturally treat wastewater before returning it to the for final disinfection Plant is pumping and filtering before clean water is piped into the bay. The next day, the pipe was taken out of service and two temporary above-ground pipes were installed in its place.

The city will be able to cover half the fine by completing a natural rainwater treatment project on Wolfe Road and Stewart Drive in Sunnyvale.

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

The Sunnyvale Sewage Treatment Plant on Borregas Avenue spilled 292,600 gallons of partially purified wastewater into San Francisco Bay on July 29, 2020 when a pipe, shown with the red dot at the bottom of the image, broke, resulting in a penalty of 187,000 US dollars led state water regulators. (Photo: Google Maps)