A federal agency issued a scathing report Wednesday that highlighted poor safety practices at the Williams Olefins plant in Geismar, where two people were killed and dozens of others injured in a June 2013 explosion.

The U.S. Chemical Safety Board detailed in a 74-page report how Williams Olefins' management went through safety procedures that could have caught a hazard that led to the accident but treated them as an "after-the-fact activity" to address a regulatory requirement rather than as a tool to detect hidden hazards.

"Our investigative root cause analysis found that the June 2013 Williams Geismar fire and explosion occurred because of deficiencies in implementing important aspects of the facility's process safety management program," Lauren Grim, a CSB investigator, said during a news conference Wednesday at the Marriott Hotel in Baton Rouge.

The explosion and fire killed two people, injured 167 others and shut down the ethylene and propylene plant for 18 months. At the time, the plant was undergoing a major expansion of its ethylene production capacity.

Vanessa Allen Sutherland, chairperson for the CSB, an independent federal agency that investigates chemical accidents, said the board recommended a series of safety procedure changes at Williams Olefins, which Grim later said the company has adopted.

Sutherland said the agency also found gaps related to the blast in a key industry standard set  by the American Petroleum Institute and recommended changes to API to avoid future incidents elsewhere in the industry.

"My message here today is that most of the incidents that the CSB has investigated could have been prevented," she said. The key, she said, is making process safety culture a top priority.

Released at the Wednesday news conference, the board's report on the blast comes just weeks after an Iberville Parish jury awarded a $13.6 million judgment to four men injured in the explosion and fire.

The jury found the company, several plant officials and its parent company were negligent and knew with substantial certainty that the deadly fire could occur.

The CSB report zeroed in on Williams Olefins' decision in 2001 to change how it operated two reboilers tied to equipment known as a propylene fractionator and on the company's failure to fix hazards created by that change in the years afterward.

The reboilers use hot water from other parts of the plant to heat and vaporize propane and send it up the fractionator. The fractionator is where hydrocarbon products are broken out from the propane.

In the simplest terms, the idled reboiler that ruptured when it was being restarted was like a tea kettle that had just been put on the stove and didn’t have any way to let off steam.

The "steam,” in this case, though, was a vapor cloud of flammable liquid propane that escaped the shattered reboiler and ignited moments later, sparking an explosion and massive fireball.

The fractionator was originally designed to have both reboilers operating at the same time. In 2001, the company decided to start using one of the reboilers at any one time and have the other idled but cleaned and ready for service, the CSB report says.

On the morning of the fire, company workers were in the middle of switching from a fouled reboiler to an idled and cleaned reboiler. Undetected liquid propane, which may have slipped into the idled reboiler through a leaking or mistakenly opened valve, heated up inside the idled reboiler.

The propane began expanding and caused the rupture of the idled reboiler, which had no connection to its intended relief system after the change made in 2001.

In the report, CSB focused on three kinds of safety reviews it found lacking. One, what’s known as a management of change review, is required by the U.S. Environmental Protection Agency and U.S. Occupational Safety and Health Administration.

CSB found this review was done after the 2001 change happened -- not before, as required -- and amounted to marking boxes on a check list without sparking concerns about the “serious overpressure hazards” created by the changes.

Some of those boxes were also marked incorrectly and ignored the safest fix possible, installation of pressure relief valves on the reboilers themselves.

The review also failed to develop a startup procedure for an idled reboiler but relied on a generic method that predated the 2001 changes. That left workers relying on a schematic to restart the idled reboiler that was the reverse of its actual setup. CSB called this confusing for workers.

Analyses in 2006 and in 2008 identified the risks and proposed fixes, but the CSB found that, rather than give each reboiler its own pressure relief system, the company decided on a less foolproof safety fix. Workers also failed to implement even that fix correctly, leaving the idled reboiler sealed off from any method of pressure relief. Though that error was caught by May 2012, management failed to take action to correct it.

At the news conference Wednesday, Grim noted Williams Olefins' failure to find and fix the pressure relief problem for 12 years and stressed the need to always be "vigilant" with process safety.

"At the Williams Geismar plant, some safety reviews pertinent to the failed reboiler were incomplete, delayed or of poor quality," Grim said. "At a facility with a strong process safety culture, performing thorough, timely process safety reviews are given a high priority."

In a statement Wednesday morning, Williams Olefins officials called the blast a tragedy, said they cooperated fully with CSB investigators, have received a copy of the report and intended to address its findings.

"As the CSB indicates in this report, the plant has made positive changes and implemented improvements in process safety management at the Geismar facility since the 2013 incident," the company statement says. "Moving forward, Williams is committed to continuous improvement of its process safety programs."

In early September, Williams Partners LP announced plans to sell its majority stake in the Geismar plant or possibly sign a long-term deal with another company to use the facility. At the news conference, Grim was asked if CSB has spoken with any of the potential buyers about continuing the safety improvements.

Grim responded that the CSB has not met with any prospective buyers yet, but "it's our understanding that procedures at the site themselves have changed." She said Williams has installed pressure relief valves on the reboilers.

Kurt Arnold, one of the plaintiffs’ attorneys who recently got a judgment against Williams over the explosion, said in a statement that the CSB report confirms “what we already know -- that Williams' utter disregard for safety leads to senseless, preventable disasters.”

He said the plaintiffs’ attorney have “no reason to believe” Williams’ top management in Tulsa, Oklahoma, have learned from the Geismar explosion or improved their facilities elsewhere in the nation.

“Although this report was limited to the Geismar plant, which Williams is trying to sell, the problems with safety reflect a lack of corporate leadership in Oklahoma,” he said.

Follow David J. Mitchell on Twitter, @NewsieDave.