Valero refinery fined nearly $200,000 over Suisun Bay spill

The Valero oil refinery in Benicia is facing nearly $200,000 in potential fines for spilling more than a million gallons of partially treated wastewater into Suisun Bay and Carquinez Strait, including excessive concentrations of selenium and cyanide, state regulators said Tuesday.

A worker at the plant failed to open a valve on Jan. 18, causing 1.13 million gallons of industrial sludge to flow into the bay over a seven-hour period, according to a civil complaint filed by the San Francisco Bay Regional Water Quality Control Board.

The accident allegedly caused double the permitted level of selenium, which is toxic to birds and other marine wildlife, to pour into the bay. The complaint also accuses the refinery of exceeding state limits on the amount of cyanide that can be discharged on five occasions in December 2014.

The board combined all of the alleged violations and issued a fine of $197,500, which Valero can appeal during a Jan. 17 hearing unless the company waives that right, said Thomas Mumley, the assistant executive officer for the water quality control board.

“For obvious reasons we are concerned about discharges of wastewater from the petroleum refineries,” Mumley said.

“Selenium is one of the pollutants of concern in refinery waste because it bio-accumulates in key bay species and can get in the food web. There are also reasons to be concerned about cyanide.”

Mumley said the discharges caused “no observed impacts, but there were potential impacts ... and we want to make sure that another spill doesn’t occur.”

Valero officials declined to comment Tuesday. The refinery, which processes as much as 165,000 barrels of crude oil a day, corrected the problem by installing a turbidity meter and alarm, according to regulators.

The spill was the latest problem at Valero, which in 2013 was named by the U.S. Environmental Protection Agency one of California’s top emitters of dangerous chemicals and pollutants into the air, water or ground.

Peter Fimrite is a San Francisco Chronicle staff writer. Email: pfimrite@sfchronicle.com Twitter: @pfimrite