Valero Benicia Refinery closes investigation of ‘Hydrogen Sulfide Saturday’ – but Benicians are still waiting for answers

[Note from BenIndy: Valero’s 30-day report on the February 24 hydrocarbon spill, which was categorized as a “Level-3” incident due to the potential threat to human health, raised yet more concerns about the refinery’s promptness and openness in notifying the City and its residents of hazardous events. If liquid hydrocarbon was detected on Tank 1738’s roof at 4:13am, why was the City not informed “immediately,” as required by its 2019 Cooperation Agreement with Valero? What does “immediately” even mean, in this context? Questions about Valero’s emergency management and dedication to safeguarding the community, particularly when considering the health risks posed by hydrogen sulfide exposure, certainly linger. Additionally, Valero’s tweaking of the spill’s reported volume – which could be 83 or 35 gallons, depending – spotlights why enhanced regulatory oversight and wide-spanning improvements to notification requirements should be an urgent priority of the refinery, its regulators, and of course the City of Benicia. Once again, we urge readers to check out to learn more about the City’s push for an Industrial Safety Ordinance from the perspective of its supporters.]

Valero Benicia Refinery releases cause of Feb. 24 incident, closes investigation

Valero’s Benicia Refinery. | Pat Toth-Smith.

Vallejo Times-Herald, by Lynzie Lowe, March 24, 2024

The Valero Benicia Refinery released its required 30-day report on Monday to provide additional details about the Feb. 24 releasing of a foul odor into the city of Benicia, and announced that the investigation has been officially closed.

The incident began on Friday, Feb. 23 when a gas turbine in the Benicia Refinery Fluid Catalytic Cracker Unit tripped, causing an emergency shutdown procedures and rerouting to “slop system” tanks to take place. During this process, Tank 1738 was turned off at approximately 4:13 a.m. Feb. 24 after it was discovered that there was some liquid hydrocarbon on the roof of that tank.

By 5:30 a.m. the next morning, the report noted that the Benicia Refinery Fence-line monitors detected Hydrogen Sulfide above background levels Southwest of the Refinery that was accompanied by the signature odor of H2S, which accounted for the rotten egg smell that was present throughout the city of Benicia at that time.

“Refinery Operations began investigating the source of the odor and identified hydrocarbon on the roof of Tank 1738 at approximately 4:13 a.m. (Feb. 24) as the source,” read the report. “… Cleanup efforts began at approximately 1 p.m. and refinery personnel continued to clean material off of the tank roof until the majority of the material had been removed and there was insufficient daylight to continue. At the time the work stopped, odors were no longer being detected beyond the refinery fence-line. Operations resumed the next morning to continue spot cleaning the residue on the tank roof and cleanup was completed on Monday, Feb. 26.”

Refinery officials said their initial report estimated that there was approximately 83 gallons of refined hydrocarbon material.

“However, based on visual accounts from the personnel overseeing the cleanup of the material, it was noted that the material on the roof was a very light sheen and the roof of the tank was still visible through the sheen, indicating it was a very thin layer of liquid hydrocarbon,” read the report. “Based on the information on the sheen thickness and the area of the roof that had material, the estimate was revised to be approximately 35 gallons of hydrocarbon material. The bulk of the material removed from the roof was rainwater.”

According to the report, an investigation team – composed of managers, engineers and hourly operators from the facility – was formed two days after the incident occurred to determine the root cause and recommend corrective actions for the Feb. 24 event.

“Data was gathered from multiple sources, including equipment monitoring trends and accounts from personnel involved in the incident,” read the report.

According to the report, the investigation identified that the floating roof on Tank 1738 had slightly tilted, and was most likely caused by vapors entering the tank.

“The investigation team looked at the various sources of slop material that were routed to the tank during the event to identify potential sources of lighter hydrocarbon materials to the tank,” read the report. “From those potential source streams, there was insufficient data for the team to identify which stream was the conclusive source of the vapors.”

The investigation team did, however, determined that the volume of material on the roof was likely not significant enough to cause offsite impacts, and therefore a vapor release from the tank was suspected to have occurred.

“The investigation team also considered the possibility of other sources as the cause of the odor, but evidence from refinery fixed H2S monitors and the wind direction during the event provided evidence that the tank was the source of the odor,” read the report.

Because the investigative team believed that light hydrocarbon materials vaporized in Tank 1738 causing the roof tilt and atmospheric substances to be released, the Refinery will schedule a meeting on or before Sept. 30 with the City of Benicia and Solano County Certified Unified Program Agency to develop engineering solution for the potential slop sources and options for monitoring and alarms, procedural options, or other means to reducing potential for vapor carry under to tankage and to implement engineering solutions.

Further actions on how to proceed with corrective action will be discussed and acted on at that time but the investigation into the incident has now been closed, according to Refinery officials.

Other reporting on this recent refinery incident: