Five months after an explosion and fire at the Chevron refinery bordering Manhattan Beach, the company's investigation is complete. Details were shared Tuesday night for the first time at the regularly scheduled city council meeting.

Refinery director Brian Stock spoke for several minutes during the public comment period to share findings from Chevron's investigation. 

The fire occurred on in an Isomax jet-fuel processing unit in the southeast corner of the refinery, closest to the Tree Section of Manhattan Beach, along Rosecrans. 

"What residents would have seen that night," Stock explained, "was a combination of flame from the single fire and flames from our safety flares, which were activated that night, acting as they should, to safely depressure the plants."

Stock said that a breach occurred at the top of an Isomax furnace, due to corrosion in a section of piping.

"We now know that a localized section of piping, at the top of one of the Isomax furnaces, became thin and ultimately failed," Stock explained. "This was due to a mechanism called hydrogen-free, low sulfur, sulfidation corrosion." 

The pipes had been subject to routine thickness inspections, Stock said. Unfortunately, the latest inspection had examined an area of the pipe about three feet away from the location of the problem.

"The investigation report indicates that the failure was due to a combination of this very specific type of corrosion, plus the geometry, where the flow moves from one piece of piping into another piece of piping, causing increased velocity and turbulence at that location," Stock said. 

"What's important is that today, we know the cause of the failure, and we know how to prevent it from happening again."

Stock offered additional reassurances after inspections across the refinery:

"We've assessed and inspected all other furnaces in the refinery that operate under similar conditions. We have not detected concerns with any other locations. We have replaced this steel piping with alloy piping. There is more resistance to this type of corrosion. And we have also added these inspection locations to our inspection program going forward."

Stock added that the findings are being shared and applied to operations across the El Segundo facility as well as throughout the company's global operations. 

Meantime, Chevron is trying to bring systems back online.

"We're now in the early stages of restarting the Isomax plants, carefully, methodically, and safely," Stock said. "We expect it will take some time for the Isomax to be fully operational."

Stock mentioned that a report on the incident by Cal OSHA is expected soon.

Stock appeared before the council on an evening when there was also an extensive presentation about efforts to improve emergency communications, after Manhattan Beach residents faulted the systems and messages received during the October 2025 event.

"Since the day of the incident," Stock said, "we have worked in partnership with the city of El Segundo and in coordination with the city of Manhattan Beach, to further enhance community alerting and emergency notification systems that will provide timely, actionable guidance in the event of an incident through the integration of multiple communication channels. Chevron has committed to fully fund the personnel, equipment, and services required to support the community alerting system."

MB News previewed the discussion of that new communications system earlier this week. A report on the presentation will follow.