The Everett Wastewater Treatment Plant along the Snohomish River on Thursday. (Olivia Vanni / The Herald)

The Everett Wastewater Treatment Plant along the Snohomish River on Thursday. (Olivia Vanni / The Herald)

10M gallons of partly untreated wastewater discharged in Everett

The Everett treatment plant released the water into the Snohomish River. It may have not been properly sanitized.

EVERETT — An Everett treatment plant discharged into the Snohomish River earlier this month almost 10 million gallons of wastewater that didn’t meet disinfection standards.

But as the state Department of Ecology investigates, city officials don’t expect significant impact to people, animals or the ecosystem. That’s because the wastewater went through every other step of treatment, said Jeff Marrs, Everett’s public works operations superintendent, who oversees the plant.

The grit and grime had been filtered, the feces separated, the scum scraped. Microbes chewed through their fill of crud.

This wasn’t “raw sewage” getting dumped into the river, Marrs said.

The Everett Water Pollution Control Facility is one of the larger ones in the region. Driving on I-5, or strolling to Smith Island, you can see the expansive aeration ponds. It handles an average of 20 million gallons of outflow a day and can deal with upwards of 100 million gallons.

On June 4 and 5, the weekend of the discharge, the plant handled over 63 million gallons, most of it stormwater.

For 19 hours, a problem persisted in the last step: Sodium hypochlorite was not getting injected properly. The chlorine solution is essentially a concentrated bleach used to sanitize the wastewater before it’s released into the river. It’s more like “post-treatment,” Marrs said, to kill any bad stuff that might be lingering after everything has been filtered.

Specifically, coliform bacteria might still be hanging around in the water, he said, and with it other disease-causing organisms. That can be bad for people, though the discharged water wasn’t destined to be drinking water.

Marrs said air got into the chemical feed pumps, hampering their ability to inject the chlorine solution into the water.

Alarms weren’t going off to indicate the pumps had completely stopped, so Marrs believes they were still working to some extent. No one spotted the issue until someone noticed it with their own eyes. “It was still pumping, it was still doing what it does,” Marrs said, but because operators couldn’t prove the wastewater had been completely disinfected, they notified Ecology.

“We err on the side of caution when we make notifications,” he said.

Fixing the problem was simple. Because the pumps feed the chlorine solution slowly, operators re-primed the pumps to push the air out.

It’s not often the treatment plant reports events to Ecology, Marrs said. Since 2021, there have been three notifications, including the recent discharge. One was about a missed pH sampling, and the other was the result of a brief power outage.

As of Thursday, Ecology crews hadn’t rushed to the scene or followed up in any meaningful manner, Marrs said. He took that as a sign the spill wasn’t serious.

“If it was significant, we would have had numerous conversations with Ecology by now,” he said.

Marrs said operators do quarterly inspections of the flow switches that will trigger an alarm if the chlorine solution isn’t getting pumped into the wastewater. He said they’ll make sure they’re working appropriately.

In addition, he expects to install a new sensor that can measure the concentration of chlorine in the water. They had actually gotten the sensor months ago, but they found the vendor had sent a wrong part. So they ordered a new part. It should show up next month.

“It would have validated what level of disinfectant we were still applying,” Marrs said.

Maybe if they had that tool, and if the measurements checked out, they wouldn’t have had to get Ecology involved.

The incident was used as a training opportunity, Marrs said, noting operators were getting refreshers on procedures for these types of events.

Zachariah Bryan: 425-339-3431;; Twitter: @zachariahtb.

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