A blast at a California refinery could have been much worse if debris from the explosion had pierced a nearby tank holding tens of thousands of pounds of a toxic acid, according to an independent federal agency charged with investigating industrial chemical accidents.
Investigators from the U.S. Chemical Safety Board are expected to discuss that near-hit and other safety issues on Wednesday as they present a report on the Feb. 18, 2015 blast that injured four contractors and coated neighboring homes and cars with white ash, according to the Associated Press.
ExxonMobil sold the refinery to New Jersey-based PBF Energy Inc. in September, but continued repairs have delayed the deal, according to the AP.
California workplace regulators issued $566,000 in fines last summer for health and safety violations related to the blast. The plant is located in a densely populated area of the city of Torrance, about 20 miles southwest of Los Angeles.
The lead investigator into the incident said multiple safety deficiencies were identified among the company's operations.
"We found that there was a lack of awareness of some of the hazards that operated within the units, and as a result of this, there was a failure to reduce the risk that these hazards posed," said Mark Wingard, the U.S. Chemical Safety Board's lead investigator into the Torrance incident.
Wingard said flammable hydrocarbons produced at the plant were insufficiently prevented from reaching ignition sources.
"Even though ExxonMobil was aware that there was this open path, they decided they could use steam to prevent the hydrocarbons from reaching the ignition source. However, there was no analysis done of whether or not steam was an effective barrier, and when the steam failed, there was nothing preventing the hydrocarbons from reaching the ignition source, which led to the explosion,” Wingard said.
He said five separate systems designed to prevent such an explosion failed, due to prolonged use beyond a safe time period.
"One thing we found is that ExxonMobil was just running their process and running their equipment past its safe operating life, as was evident as hydrocarbons made it through a valve that wasn’t operating as intended,” Wingard said.
A state investigation by the California Occupational Health and Safety Administration — also known as Cal OHSA — blamed the blast on a vapor that leaked from a fluid catalytic cracker unit into an electrostatic precipitator, according to the AP.
The fluid catalytic cracker unit refines gasoline and is critical to producing California-grade fuel, according to the AP.
Management knew the leak posed a hazard but didn't correct the problem and had had problems with the FCC unit for as long as nine years, Cal OHSA said, according to the AP.
The company is appealing the agency's findings, according to the AP.
"ExxonMobil stands on its record of good faith compliance with all agencies, including the Chemical Safety Board, and we look forward to hearing their perspectives on the incident and reviewing the preliminary report," Todd Spitler, a spokesman for ExxonMobil, said in a statement Tuesday night, according to the AP.
Spitler's statement said the company's investigation found there was no evidence of harm to the community from the damaged unit at the refinery, and ExxonMobil has stringent safety measures in place to assure that's the case, according to the AP.
The latest update from the independent federal investigators comes amid growing concern from residents and state lawmakers about the refinery's use of modified hydrofluoric acid, or HF, at the site, according to the AP.
Debris from scaffolding went flying during the explosion and could have caused a "potentially catastrophic release of extremely toxic modified HF into the neighboring community," the U.S. Chemical Safety Board said in a statement, according to the AP.
Wingard, with the U.S. Chemical Safety Board, said it's unclear whether the siting of the chemicals posed a violation or safety deficiency, because ExxonMobil has not cooperated with document requests and subpoenas for information.
"In order to do a full analysis of whether or not the siting was appropriate or inappropriate, we really need some cooperation from the company to give us documents, so we can do the analysis we think it deserves.”
In a statement, ExxonMobil's Todd Spitler told KPCC that since February 2015, the company "has provided more than 340,000 pages of documents, images and our workers participated in nearly 156 witness interviews with various agencies - including 136,000 pages and 67 interviews for the Chemical Safety Board [...] Our cooperation through numerous document requests, employee interviews and refinery access, demonstrates we continue to be responsive to CSB's inquiries [...] We have produced all documents related to the cause and possible cause of the Feb. 18 incident."
Spitler said that ExxonMobil's own investigation into the incident found no evidence that modified hydrofluoric acid posed any risk to the community during the explosion. "The Feb. 18 incident involved the fluid catalytic cracker unit (FCC) and Electrostatic Precipitator (ESP)," Spitler said. "We have taken corrective actions to prevent this incident from happening again."
Residents have formed a watchdog group to pressure the refinery over its use of modified hydrofluoric acid, which is used as a catalyst to make higher-octane fuels, since last year's incident, according to the AP.
"A piece of equipment was sent flying out and it landed just feet from a tankful of modified hydrofluoric acid. Even though the explosion didn't cause a release, it was just because of dumb luck," said Sally Hayati, a member of the Torrance Refinery Action Alliance, according to the AP.
"There are a lot of people in our area who don't even know it's at the refinery. There are some of us who do know and we're concerned, we're very concerned."
The Torrance Refinery Action Alliance has called for the refinery to stop using hydrofluoric acid at the site, saying the safety risk it poses to the community is too great.
“That could’ve released very significant amounts of hydrofluoric acid into the air, and it would’ve drifted into the community, and it probably would’ve killed or at least severely injured a great many people,” said Hayati.
Hayati said her group isn't calling for the complete closure of the facility, but will only accept the removal of the chemical from the site.
"The refinery chose to inflict this risk on us, and now it’s their responsibility to eliminate it,” said Hayati.
Two other recent incidents at the plant have also frayed nerves, according to the AP.
In September, the Fire Department reported a leak of modified hydrofluoric acid and a month later, a leak in a pressurized pipe caused a large steam cloud above the refinery as sirens urged residents to shelter in place, according to the AP.
ExxonMobil said what had leaked was mostly steam, according to the AP. A state investigation is pending.
The refinery on 750 acres produces 1.8 billion gallons of gasoline a year, which accounts for about 8.3 percent of the state's total refining capacity, according to the AP. It is capable of producing 155,000 barrels of crude oil a day.
This story has been updated.