Sonoma Water reports untreated sewage spill into Schell Slough

Two million gallons of untreated wastewater overflowed due to a faulty valve at the county wastewater treatment facility on Eighth Street East on Saturday.|

Two million gallons of untreated wastewater spilled from a pipeline at the county wastewater treatment facility on Eighth Street East on Saturday. A faulty valve was to blame, according to officials from the county water agency.

The polluted water flowed into Schell Slough at the southern end of the Sonoma Valley County Sanitation District, but water experts did not express concern.

“The problem valve was isolated, and flows were stopped at 10:45 a.m.” on Saturday, Jan. 12, according to Ann DuBay, community and government affairs manager for Sonoma Water, the county’s water agency. The value had been leaking wastewater for about 24 hours, DuBay said.

The valve is one component of a complex network of pipelines that collect wastewater from the equivalent of about 17,000 single family dwellings in the Sonoma Valley. The sanitation district’s wastewater treatment facility provides the final cleaning process, known as tertiary treatment, for some 3 million gallons per day on average. During spring and summer the water is reclaimed for irrigation and wetlands habitat restoration.

But from November through May the treated water is discharged into either Schell Slough or Hudeman Slough, both of which flow into San Pablo Bay.

On Saturday morning, a technician noticed the inflow/outflow numbers for the facility were unusual, showing higher than normal outflow numbers. He made a physical inspection of the system, and when he located the partially unclosed valve he corrected the problem by closing it.

The valve was to have been shut earlier in the week by work crews in anticipation of heavy rains, but the exact cause of the valve’s failure has not been determined.

“Fortunately, there was a lot of water in Schell Slough during the leak – which was, fortunately, a relatively slow leak – so our environmental folks didn’t find any issues of concern,” said DuBay. She added that there were no signs of fish or wildlife distress.

Julian Meisler, baylands program manager of the Sonoma Land Trust, agreed. “I think we’re fortunate that it occurred following a rainy period – I’m sure the inflows are helping dilute, which is always important.”

Meisler’s comments brought to mind an environmental adage of an earlier era, “Dilution is the solution to pollution.”

“I wouldn’t say dilution is a solution,” cautioned Meisler, “but dilution helps – if it were concentrated we’d be seeing dead fish.”

Added DuBay: “We clearly are not happy about the mechanical failure and are looking for a solution to prevent it from occurring again.”

Email Christian at christian.kallen@sonomanews.com.

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