CVSan Fined for Sewage Spill

photo by Mike McGuire

The sewage treatment plant at the foot of Grant Avenue in San Lorenzo is jointly run by the Castro Valley and Oro Loma sanitary districts.

The Castro Valley Sanitary District (CVSan), which normally prides itself on being a good environmental steward, has agreed to pay part of a $15,000 fine for a raw sewage spill into the Bay from its shared water treatment plant on December 31, 2022, and a second spill a week later. 

The fine will be divided up with its partner in the San Lorenzo plant, the Oro Loma Sanitary District. Oro Loma owns 75 percent of the plant and CVSan owns 25 percent.

This was the minimum fine possible, according to documents from the California Regional Water Quality Control Board (CRWQB), San Francisco Bay Region. According to CVSan spokesperson Mike Nelson, the fact that it wasn’t more indicated that negligence was not involved in the spill. 

It was the first time in 17 years CVSan had been fined for a sewage spill, Nelson said.

That New Year’s Eve was one of the rainiest days in recent memory and started the historic deluges of early 2023. The later spill followed in a little more than a week as rains continued. 

A fine was required under federal law whenever water quality standards for discharges are exceeded. CVSan spokesperson Mike Nelson, however, said there was nothing else the plant could do facing a 500-year storm that threatened to destroy it. In theory, a storm that severe would occur only once in 500 years.

“Water had flooded inside the plant, within six inches of the electrical circuits,” Nelson said. “We rushed people there to keep the plant operating at all.”

He estimated 20 to 30 people, much more than the usual contingent, struggled to save the plant.

CVSan sent people, as did Oro Loma. Other agencies lent pumps to get the water out of the plant. 

“The plant’s capacity is large and usually more than enough. But we had a storm that exceeded anything we’d ever seen. If our capacity is exceeded, first we send water to overflow ponds built for that purpose,” said Nelson.

“But once those are full, there’s not much we can do with all the water,” he said.

Nelson said that the plant also needed to safeguard its biological cultures that break down sewage.

“If we lost those, the cultures would have taken months to regrow,” he said, adding that this would hamper effective sewage treatment. 

CVSan got off a little easy compared to its counterpart in Los Angeles. That agency recently reached a $6 million settlement with regulators, mostly for a sewage spill around the same time in 2021 during severe flooding in Southern California. 

“We did the right thing to save the plant, but we got fined anyway,” Nelson said.