Failure to follow proper safety standards and worn-out equipment were behind the  February 2015 explosion at ExxonMobil’s Torrance refinery in the state of California, the US Chemical Safety Board (CSB) has concluded in its final report.

A large piece of debris also narrowly missed hitting a hydrofluoric acid tank, which, if ruptured, would have released the highly toxic and corrosive substance. “This explosion and near miss should not have happened had a more robust process safety management system been in place,” said Vanessa Allen Sutherland, chairwoman of the CSB.

The blast occurred when the slide valve that stops hydrocarbons flowing into the air side of the fluid catalytic cracking (FCC) unit failed. This led to the hydrocarbons igniting in the electrostatic precipitator. The agency discovered that the unit was operating without pre-established safe operating limits and the slide valve – a critical safeguard – was significantly degraded. In addition, the CSB said it found multiple instances leading up to the incident where the refinery had directly violated ExxonMobil’s corporate safety standards.

Sutherland said the CSB had sought more information from ExxonMobil about safety guidelines related to the prevention or mitigation of a release of hydrofluoric acid, but the company did not respond.

ExxonMobil stated: “We are confident that we understand the cause of the incident and have worked cooperatively with the Chemical Safety Board and staff to fully understand their findings and recommendations to improve the safety of our operations.” It added that there was no evidence the blast posed any risk to the hydrofluoric acid unit or the community.

The refinery ran at a reduced rate for more than a year, which the agency said prompted gasoline prices in California to soar, costing drivers in the state an estimated $2.4 million. After repairing the facility, ExxonMobil sold it to New Jersey-based PBF Energy in July 2016. However, the plant has continued to suffer safety mishaps with the US Environmental Protection Agency (EPA) identifying several concerns in a March report. PBF said it is already taking measures to address the CSB’s concerns and recommendations.

According to the CSB website, the safety authority is also investigating the release of isobutane from the sulfuric acid alkylation unit at the ExxonMobil Refinery in Baton Rouge, Louisiana, which resulted in four serious injuries to workers. The incident occurred during minor maintenance on a flammable isobutane line which failed, releasing the chemical into the unit, where it was ignited.

The CSB, meanwhile, could disappear if spending plans announced by President Trump come to fruition. Under his initial proposal, the agency’s funding, which amounts to around $12 million annually, would be cut entirely from the 2018 federal budget.  It is unclear how much, if any, may have been restored in the revised budget reportedly agreed by Congress last week.