New Year’s Eve storm tests wastewater treatment plants, Union Sanitary District general manager says

Alvarado Treatment Plant

The general manager of the Union Sanitary District says he does not expect the upcoming storms to overwhelm local wastewater treatment plants the way the storm on New Year’s Eve did.

As of Monday afternoon, an expected storm hadn’t hit the area as hard as expected and the rainfall totals were expected to be a lot less than what the New Year’s Eve storm delivered a little over a week ago, Paul Eldredge told the district’s board of directors at its regular meeting.

“Compared to the New Year’s Eve storm, it’s tame — very tame — in comparison,” Eldredge said. “So we’re able to manage these flows quite easily.”

The New Year’s Eve storm delivered 4.3 inches of rain during a 24-hour period and was the second wettest rain event in about 107 years, the wettest being in 1994, Eldredge said. That storm delivered record flows to the Alvarado Treatment Plant, 68.5 million gallons per day. The average is about 40 to 41 MGD and the most recent storm led to a peak flow of 48.8 MGD around 10 a.m., he said.

“We did end up utilizing the Old Alameda Creek emergency outfall,” Eldredge said, referring to a system of valves and pipes that allow the district to divert some of the treated wastewater into the creek.

Staff from Union Sanitary District and Castro Valley Sanitary District also lent a helping hand to the Oro Loma Sanitary District, which serves a large chunk of the unincorporated Eden area and was overwhelmed by the New Year’s Eve storm.

“Oro Loma normally has an average daily flow of 10 to 12 MGD,” Eldredge said. “On New Year’s Eve, they experienced 100+ MGD coming through the plant. The flow overwhelmed certain parts of the plant … which then caused the majority of the treatment plant to be under anywhere from 2 to 4 feet of water.”

Oro Loma was able to avert disaster thanks to the mutual aid provided by staff from neighboring sanitation districts, who lent them staff who helped them set up pumps to get the water out of the plant, he said.

“Oro Loma’s general manager is beyond appreciative,” Eldredge said.

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