OAKLAND (CBS SF) — Boaters were being warned Saturday to stay away from the Oakland Estuary after an estimated 50,000 gallons of raw sewage spilled during a power outage Friday night at the East Bay Municipal Utility District wastewater treatment plant in West Oakland.

Signs were posted along the estuary on Saturday morning about the spill and EBMUD was reaching out to rowing clubs and others who frequently use the strait between Oakland and Alameda.

The spill occurred after power outages between 5 p.m. and 7 p.m., ordered by the California Independent System Operator, caused a pump to fail, EBMUD said Saturday.

“This power outage caused failure of major equipment at the wastewater plant, including the ability for EBMUD to generate its own power on site,” according to a statement from EBMUD on Saturday. “Power outages like this are quite uncommon. During PSPS events we normally get notice, but this outage occurred very quickly.”

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The main wastewater treatment plant in West Oakland, at the foot of the Bay Bridge, received no power from PG&E from 5:10 to 6:50 p.m., according to EBMUD.

The outage resulted in major flooding at the pump station, which transports sewage from the East Bay via pipes to the plant for treatment, causing a back up.

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EBMUD employees worked through the night to restore pumping capacity at the plant, and stored excess sewage in storage basins, EBMUD spokeswoman Andrea Pook said.

However, flows exceeded the storage capacity before full operations could be restored and raw sewage was discharged into the estuary from 3:47 a.m to 3:58 a.m., from the foot of Alice Street and Embarcadero, according to the water agency.

Discharge started again at 4:07 a.m. and has now stopped, EBMUD said in a statement at 8:30 a.m.

Although initial estimates were that 100,000 gallons of raw sewage was released, EBMUD revised that Saturday to 50,000 gallons, Pook said.

In an effort to minimize the release, EBMUD also discharged disinfected and dechlorinated sewage — partially treated wastewater — from its San Antonio Creek Wet Weather Facility, officials said. The facility discharges at a point just west of the Jack London Aquatic Center on the Oakland/Alameda estuary.

Regulatory agencies have been notified of the spill and EBMUD on Saturday morning was advising people to stay out of the water. EBMUD is investigating the incident and plans to issue a report within a week.

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