The San Francisco Bay Regional Water Quality Control Board has fined Phillips 66 $285,000 for a 2019 discharge of more than 5 million gallons of partially treated wastewater from its Rodeo refinery to San Pablo Bay.

The Feb. 14, 2019, discharge exceeded the “suspended solids” volume allowed under Phillips’ permits. Suspended solids from petroleum refineries may contain toxic byproducts of refinery operations that can harm aquatic life. No such harm has been observed in San Pablo Bay after the discharge, water quality officials said.

Phillips will pay $142,500 to the State Water Pollution Cleanup and Abatement Account and another $142,500 toward a supplemental environmental project to study how sediment moves through San Francisco Bay.

Thomas Mumley, assistant executive officer for the San Francisco Bay water board, said the settlement is intended both to send a message that all petroleum refineries in the Bay Area need to manage their treatment systems properly, and to deter Phillips specifically from committing similar violations in the future.

Water quality officials said that Phillips could not store enough wastewater from a series of large rainstorms to be treated later, forcing the refinery to bypass the part of its treatment system that filters out suspended solids.

The discharge might not have happened, the San Francisco Bay water board said, had Phillips restored an onsite storage tank to service ahead of those storms. The refinery didn’t return the storage tank in question to service until January 2020.

Phillips spokesperson Adrienne Ursino said the offending discharge was limited to one day, and that all other test results of the discharge water were “well within permit limits for all other constituents and characteristics.”

“Phillips 66 places the utmost importance on environmental protection and the safety of our employees, contractors, and the community, and we continue to make improvements to our refinery infrastructure and operations to manage adverse weather events,” Usino said Thursday in an email.

Phillips 66 announced last week plans to turn its Rodeo refinery, which opened in 1896, into the “world’s largest renewable fuels plant,” producing fuels from cooking oils, fats, greases and soybean oils. It hopes that conversion is finished sometime in 2024.