Signs were posted at several shorelines and parks in Richmond, Calif., warning that water might be contaminated with harmful bacteria after nearly 1 million gallons of runoff and raw sewage overflowed and spilled into San Francisco Bay.

Sunday's rainstorm flooded into cracks and leaks in the city's sewer collection system and overwhelmed the capacity of a sewage treatment plant, causing an estimated 890,000 gallons of untreated water to spill out of the sewer system near the Richmond marina.

The company that runs Richmond's sewer system estimated that the water was 90 percent stormwater and 10 percent raw sewage, a figure that state water quality regulators did not dispute.

Keller Beach, Brickyard Cove, Miller/Knox Regional Shoreline, Sheridan Point, Vincent Park, Shimada Friendship Park, and Point Isabel were all posted with the warnings, said Sherman Quinlan, Contra Costa County's director of environmental health.

Quinlan added that the sewage was highly diluted by rain and water in the Bay and probably does not pose much of a health threat.

"I strongly believe the impact is minimal," Quinlan said.

The warnings are expected to be lifted after test results show safe levels of bacteria.

Sewage spills during heavy rain are common in much of the Bay Area. Old, leaky pipes take in more rainwater than the systems can handle.

The company that operates Richmond's sewer system disputed the characterization of the event as a spill.

"A spill implies a preventable event," said Mark Grushayev, program manager for Veolia Water. "This is an overflow. The system is designed to overflow to the Bay instead of to the streets and houses."

State water quality regulators, who have the authority to issue fines, said they were investigating.

"We're looking into the spill and collecting information," said Gina Kathuria, a senior engineer at the San Francisco Bay Regional Water Quality Control Board.

Also during the storm, an East Bay Municipal Utility District wet weather station at Point Isabel discharged 2.3 million gallons of sewage into San Francisco Bay. That station collects, screens and disinfects overflow before removing chlorine and sending it into the Bay, said EBMUD wastewater director David Williams.

Williams said that until last month, the Oakland-based utility was not required to report such discharges if the wastewater was successfully screened and disinfected. But a legal settlement reached last month requires the district to come up with a plan to eliminate the partially treated discharges and to report them.

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(c) 2009, Contra Costa Times (Walnut Creek, Calif.).

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Distributed by McClatchy-Tribune Information Services.

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