The Bay Area Air Quality Management District has settled a $4 million case with Tesoro Refining and Marketing Company’s Golden Eagle Refinery in Martinez after it was cited for air quality violations, Jack Broadbent, Air District executive officer, said Wednesday.

During a routine inspection, an Air District inspector discovered that Tesoro periodically drained process waste fluid to its on-site sewer and water treatment system, Broadbent said.

When drained, butane and propane and other volatile air contaminants would evaporate off the liquid immediately and pollute the air, the Air District contended.

Butane and propane hydrocarbon emissions contribute to the formation of ozone and smog, Broadbent explained.

The Bay Area Air Quality Management District (BAAQMD) is the regional agency responsible for protecting air quality in the nine counties of the San Francisco Bay Area, including Contra Costa and Solano counties.

During an investigation, Air District officials documented draining violations that took place from 2007 through 2014, Broadbent said.

He said the draining caused a significant amount of air pollution and was in violation of Tesoro’s permit and Air District regulations.

Those documents require Tesoro to use abatement methods to remove volatile air contaminants from process waste prior to draining fluids to the on-site sewer.

Sewer drains must also be controlled to prevent air contaminants from escaping to the air, Broadbent said. Instead, he said, Tesoro bypassed its abatement technology and drained the process fluids directly into the on-site sewer.

Several of the violations occurred in 2013 after BAAQMD discovered that Tesoro had a practice of draining process waste to the sewer and had told the company that the practice was both unlawful and dangerous.

Further violations occurred in late 2013 and early 2014, Broadbent said, which was after Tesoro agreed to stop the unlawful draining practice.

He said the refinery also committed leak detection and repair violations, which also were discovered during the investigation of the draining events.

However, Tesoro cooperated with the Air District’s investigation of the incidents, Broadbent said.

He said Tesoro has stopped the practice of draining process fluids into the on-site sewer system to prevent future violations.

“We require Bay Area refineries to control their emissions at every step of their process,” he said.

“Through the Air District’s aggressive enforcement program, these violations were discovered and this uncontrolled release of air pollution stopped.”

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