A power outage at the Valero Benicia Refinery at 6:30 a.m. this morning resulted in a massive flare up releasing a large plume of black smoke and prompting an evacuation at the Industrial Park.

At 6:46 a.m., the city was notified of the flaring and made the decision to evacuate businesses and residents in the Industrial Park, including closing off-ramps from Interstate 680 leading into the Industrial Park. Room 2 of the Benicia Community Center was offered as a shelter for evacuees.

At a press conference held noon in the Dona Benicia Room of the Benicia Public Library, Fire Chief Jim Lydon said that the Fire and Police departments had upstaffed to help manage the incident. He also indicated that the city was working with various health and environmental agencies, including the Solano County Environmental Health Department, California Air Resources Board, Bay Area Air Quality Management District and the federal Environmental Protection Agency to monitor the air quality in the Industrial Park and other areas of the city.

Steve Calanog, the on-site coordinator for the EPA’s San Francisco office, said the U.S. EPA had received notification of the incident through the National Response Center and personnel were on the scene within half an hour to examine the situation. The EPA had determined that the hydrogen sulfide gases had peaked at 10 times the normal background levels, but Calanog expected the levels to diminish within the next few hours.

Lydon said that two people had reported having health issues. One person reported respiratory problems in the Industrial Park, was assessed at the scene and was deemed to be in decent enough shape to not be transported to a hospital. The other evacuated the Industrial Park, went home to Vacaville and was advised to call 911 if they needed emergency care.

A shelter in place was established at nearby Robert Semple Elementary School and Matthew Turner Elementary School, although city officials said no other schools in the district would be affected. According to a statement on Benicia Unified School District’s website, students at other sites opting to stay home would not be marked as absent. Superintendent Charles Young estimated that hundreds of students opted to stay home, with the highest numbers coming from Robert Semple, Matthew Turner and Joe Henderson Elementary School. Benicia High School also left its gym and Student Center open for those who wanted to eat lunch indoors, according to a post on the school’s Twitter account.

After doing an EPA testing, the shelters-in-place at Matthew Turner Elementary and Robert Semple Elementary were both lifted at 1 p.m.

There were no evacuation restrictions for residents, although city officials are suggesting they close doors and windows and keep pets inside.

Don Cuffel– the director of health, safety, environmental, public and governmental affairs at Valero– attributed the power outage to a disruption by Pacific Gas & Electric. Cuffel said the power supply comes from two PG&E feeders.

“Either one of them should be ample to supply our power,” he said. “One of them was de-energized because we were working on it, and what should have happened was they could have switched from the energized one to the de-energized one so we would continue to have uninterrupted power. Apparently, something went wrong, and I can’t speculate as to what that was.”

Cuffel said the pumps and compressors designed to move the oil along might have contributed to the flaring.

“If you lose electrical power, these pumps and compressors stop,” he said. “We have some backups that run on steam and that provides a little bit of relief for a while until your boilers also shut down and you no longer have steam. When you can no longer move the oil along, the pressure builds up within the vessels. They’re all protected with safety valves, the safety valves open and predetermine pressure and that material leads to the flare.”

Power was restored to the refinery at 7:30 a.m., and Valero crews are working to alleviate the problem, Acting Deputy City Manager Mario Giuliani said.

The city had set sirens to go off to alert residents of the incident, but resident Marilyn Bardet expressed concerns at the press conference that she did not hear the sirens until after Valero’s power was restored.

“Parents are driving their kids to school at that hour,” she said. “If you are at home, and your windows were open overnight to get the cool air, by the time the sirens go off, your house is already potentially wafting with the same chemicals that are outside if you are in the vicinity.”

Lydon said the city had received notice of the evacuation at 7:30 a.m. and that the process took about 15 minutes to be implemented. City Manager Lorie Tinfow said the city would do a debriefing to go over how to improve the process after the incident is over.

In a statement, the Bay Area Air Quality Management District noted that Valero is working to address the problems that resulted in the flaring and that agencies would continue to look into it.

“The investigation is active and will likely continue for several months to determine the cause,” enforcement director Wayne Kino said.

Black smoke was being reported as late as 3 p.m., but the shelter-in-place at the Industrial Park was lifted at 5 p.m. The city of Benicia continues to provide updates on its web page at ci.benicia.ca.us every 20 minutes for updates. Residents are encouraged to sign up for AlertBenicia to receive communications from the city.