The Benicia Valero refinery notified the city Sunday that there was a “momentary release” that sent black smoke into the air.
The refinery said the release was part of normalizing operations after a power outage earlier this month caused significant flaring.
The city was working with health leaders to assess the situation Sunday. No evacuations or other warnings were issued.
The Benicia Fire Chief Jim Lydon said the intermittent releases of 15 to 45 seconds came from the refinery’s scrubber unit. Later Sunday, he said the situation appeared stabilized.
The power outage at the refinery on May 5 triggered flaring and smoke that prompted evacuations and a shelter-in-place order. Off-ramps were closed, traffic was diverted, and the community center was turned into an emergency shelter. The flaring could be seen from miles away, and some nearby residents complained that they were struggling to breathe.
Valero received at least four violation notices from the Bay Area Air Quality Management District as a result of the May 5 incident.