One worker at the Tesoro Refinery was taken to the hospital on Monday after a sulfuric acid spill at the Martinez plant, according to a fire inspector.
Another worker involved did not suffer any injury.
Contra Costa County Fire District Inspector Steve Aubert said sulfuric acid sprayed on the two workers just before 10:45 a.m. Tesoro spokeswoman Tina Barbee said that two contractors were performing maintenance with full protective safety gear when the spill occurred.
It's the second spill in less than a month and comes after Tesoro Corp. barred federal authorities from going inside its refinery to investigate the earlier spill in February.
Just before 1 p.m., the California Department of Occupational Safety and Health Administration issued an "order preserve" on the reactor vessel surrounding the pipes where Monday's spill occurred, essentially shutting that area for further investigation. Cal-OSHA reports show the spill occurred in the butylene line at the at the alkylation unit on Solano Way.
One worker got a little bit of the acid on him, Aubert said, and the other worker was "saturated" in it. That worker was taken to John Muir Medical Center. Aubert did not know his condition. But the San Francisco Chronicle said the worker was wearing protective gear.
The scene was cleared at 11:05 a.m.
This accident follows on the heels of another, reported on Feb. 12, when two workers at the plant were hospitalized after they suffered chemical burns to the face while taking samples om the alkylation unit, according to the Ca-OSHA. They were airlifted to UC Davis Medical Center, where they were treated and released the same day.
Cal-OSHA shut down the Golden Eagle Refinery where the pipe was located for about a month, but investigators with the U.S. Chemical Safety Board were not allowed to return to the site for follow-up visits, according to the San Francisco Chronicle. Tesoro officials said the Feb. 12 incident was minor and did not qualify under the rules for a federal investigation. But the Chronicle also reported that Tesoro actually did allow the federal workers onto its site after being subpoenaed.
Cal-OSHA spokesman Peter Melton told NBC Bay Area on Monday that no citations have been issued in that accident, because it is still under investigation.
On Monday, Chemical Safety Board spokeswoman Hillary Cohen emailed NBC Bay Area saying that her agency plans to follow up on Monday's accident to "determine if an investigator will be sent to the site."
The worst injury in the last five years, however, occurred on April 2, 2010, in Washington state, after an overnight explosion killed seven workers. According to the OSHA website, this case is still open.
According to its website, Tesoro Corp. is a "leading independent refiner and marketer of petroleum products committed to operating responsibly in the communities we serve."
Bay City News contributed to this report.