The Tesoro Golden Eagle Refinery in Pacheco is seen from the Pleasant Hill BART parking garage in Walnut Creek, Calif. on Monday, February 1, 2021. (Ray Saint Germain/Bay City News Foundation)

The Bay Area Air Quality Management District announced Tuesday a fine of nearly $1.5 million against the Tesoro Refining & Marketing Company for air quality violations at its refinery in Martinez.

The air district had investigated violations of emissions standards for hydrogen sulfide, a colorless gas known for its rotten egg-like odor, at a monitoring station on Waterfront Road near the facility formerly known as the Golden Eagle refinery.

The investigation determined causes of the emissions issues included leaks from oil tanks and wastewater treatment systems and deficiencies in wastewater pond management. The fine issued by the air district totals $1,469,579, and includes requirements that the refinery improve its operational and management plans to prevent future emissions.

“The unpleasant odors associated with hydrogen sulfide emissions can significantly impact the quality of life for those living in communities surrounding the Tesoro Refinery,” air district interim executive officer Sharon Landers said in a news release. “Strict regulations and penalties resulting from Tesoro’s air quality violations help ensure that the facility fixes operational issues quickly and avoids future violations to protect public health.”

Oil refineries like this one in Martinez are sources of greenhouse gases. The state’s climate plan includes installation of carbon-capture technologies on industrial plants. (Photo by Michael R. Lopez/iStock via CalMatters)

Tesoro in 2018 became a subsidiary of the Marathon Petroleum Company, which announced in late 2020 plans to convert the Martinez refinery to one that processes renewable feedstocks like soybean and corn oil rather than crude oil from fossil fuels.

The company said earlier this year that the first phase of the renewables facility is targeted to be complete by the end of 2022, with the facility expected to be capable of producing 730 million gallons per year by the end of 2023.

Marathon spokesperson Jamal Kheiry said the allegations related to the air district’s fine occurred between 2013 and 2018, prior to the acquisition of the refinery.

“We are committed to operating the facility consistent with our values of safety and environmental stewardship,” Kheiry said.