Two Parts of Valero's Benicia Refinery Under Scrutiny in Probe of Pollution Releases

Two key components at the Valero refinery in Benicia experienced problems earlier this month, leading to weeks of releases of petroleum coke dust that intensified on Sunday, culminating in the shutdown of a large portion of the facility.

The new details on the refinery's malfunctions are laid out by Valero in a preliminary report filed with Benicia city officials this week.

The malfunctions are the focus of at least one part of an investigation by Solano County inspectors into an incident that led to health concerns for people living near the refinery and to a statewide spike in gasoline prices.

Valero's report says that the recent problems at the refinery began March 11 when a crude oil processing unit called a fluid coker experienced "operating difficulty."

Normally, a fluid coker heats up and "cracks" the thickest, heaviest components of crude oil processed at a refinery, breaking them down into material that can be used in diesel or other petroleum products. One of the byproducts of the process is solid carbon residue called petroleum coke.

The problems with Valero's fluid coker unit allowed petroleum coke dust, called coke fines, to flow to a second unit called a flue gas scrubber. The scrubber cleans out fine particles before they're released from the refinery's smokestacks into the air. That process is supposed to ensure that the refinery's emissions don't violate air quality standards.

But the coke fines moving through the scrubber unit set the stage for a release of particulate pollution from the refinery -- a release that was clearly visible from outside the facility.

"The presence of coke fines in the FGS resulted in a darker than normal plume appearance," Valero's 72-hour report said.

Solano County investigators want to know if the scrubber was somehow overwhelmed or damaged, according to Terry Schmidtbauer, the county's director of resource management.

"We know something's not operating properly," Schmidtbauer said.

California's Division of Occupational Safety and Health Cal/OSHA and the Bay Area Air Quality Management District are also investigating the refinery.

After the problem surfaced, the air district issued eight notices of violation against Valero for public nuisance and visible emissions.

Refinery crews worked to reduce the releases and Valero said the situation showed "significant improvement" by last Friday, when the plume coming from the refinery's stacks "returned to normal appearance," Valero's report said.

But that changed the next day. The scrubber "experienced an operational upset resulting in a dark, opaque plume and emissions of particulate matter," the report said.

A new surge of petroleum coke dust billowing from the refinery's stacks prompted Benicia officials to issue a health advisory, urging people with respiratory issues to stay indoors.

The refinery began to shut down several units, and the air district wound up issuing four more violation notices.

The powering down of the the facility is contributing to an increase in gasoline prices.

On Friday the average cost of a gallon of unleaded gas in California jumped to $3.59, up 16 cents from a week ago, according to AAA.

Energy analysts and state regulators say the price will continue to rise until operations at Valero return to normal.