A sewage spill of nearly 88,000 gallons sent effluent flowing into a Greenbrae parking lot and Corte Madera Creek, the county reported Wednesday.

The incident happened at about 2 p.m. Feb. 6 behind Bon Air Center on Sir Francis Drake Boulevard. The sewage came from a main connected to a pump station, said Greg Pirie, a deputy director at the Marin County Community Development Agency.

Ross Valley Sanitary District staff stopped the leak around 4:30 p.m. by shutting off an isolation valve. The district reported the incident to the California State Warning Center, said Pirie, who works in the Environmental Health Services Division.

Pirie said the sewage spread from the shopping center to Corte Madera Creek through an overflow point near a creek bridge and through a catch basin. The district cleaned up the area by vacuuming the sewage and using a bleach solution as a disinfectant.

The sanitary district posted warning signs in the vicinity and collected water samples over several days. On the day of the spill, the samples “showed a spike in fecal indicator bacteria,” the county announcement said.

The next two days, the samples “returned to background levels,” it said.

“Due to the large volume of water flowing in the creek during the rain event, the sewage release was cleared very quickly,” the statement said. “There is no evidence of current contamination.”

The county said it has received no reports of ill health effects on people or wildlife in the area.

The Ross Valley Sanitary District contained the spill within an hour and sent about 20% of the wastewater back into the sewer system, Steve Moore, the general manager, said Wednesday.

Moore said the staff is still investigating the cause of the spill.

In 2023, the district, under pressure from the state to curtail its sewage leaks, completed a $100 million effort to upgrade its system.

During heavy rains in December 2005, the utility spilled 472,000 gallons of untreated waste and was fined $78,000 by the San Francisco Bay Regional Water Quality Control Board.

Later, the district paid the state $1.5 million as part of a settlement after releasing more than 3 million gallons of sewage, most of it in two large spills in December 2010.

The district transports approximately 4 million gallons of waste a day through about 200 miles of sewer lines.