When firefighters poured water into a Searsmont lumber yard silo, they were unknowingly adding fuel that helped cause the mill’s deadly silo explosion back in May.
That’s one of the conclusions from a new report from the National Institute for Occupational Safety and Health, an arm of the U.S. Centers for Disease Control and Prevention, into the Robbins Lumber fire and explosion that left three people dead and nearly a dozen wounded.
The report, released Friday, found a series of missteps from area fire departments and Robbins Lumber itself that contributed to the tragedy.
The fire broke out about 10:05 a.m. on May 15 at the Robbins Lumber campus off Route 131 in an area where wood shavings are packed in plastic bags and spread to a nearby silo. About two dozen firefighters responded to the initial fire, and by 10:40 a.m., it appeared largely under control and the atmosphere at the scene became “relaxed,” the report noted.
At the time, the silo was about 20% filled with sawdust and wood shavings. The silo had a fire suppression system, but it failed to activate because the temperatures at the top had not become hot enough to trigger it. Smoke could be seen coming from the base, and later an orange glow, prompting firefighters to pour water into the silo and the room at its base, according to the report.
Silo fires weren’t unfamiliar to six of the departments that responded to the initial blaze, having dealt with several of them over 20 years. But those fires happened at a different silo with a more conventional design that often includes an external unloading chute or even an open top. This silo, which Robbins Lumber bought used back in 1993, was sealed to keep out oxygen.
Unbeknownst to firefighters, they were adding oxygen and stirring up dust suspended in an “explosive mixture,” according to the report.
“Without any warning [around 11 a.m.], the silo launched into the air followed by a large plume of fire at the bottom as it rose. The explosion threw surrounding facility employees, firefighters, and EMS providers away in a blast of pressure and fire,” the report’s authors wrote.
Firefighters, many of them critically injured, rushed to pull survivors away from the inferno, as nearly 300 firefighters from 46 departments across four counties scrambled to the lumber yard to contain the blaze and tend to the wounded.
Morrill firefighter Andrew Cross, 27, died at the scene of the fire. Searsmont’s assistant fire Chief, Wayne Woodbury, succumbed to his injuries on June 14. The blaze, one of the worst industrial disasters in recent Maine history, also killed one of the company’s co-owners, Alden Robbins, who died on July 2.
At least 10 other people, including first responders, a mill employee and another of the mill’s co-owners, were injured in the fire.
In a statement posted Friday on Robbins Lumber’s website, Catherine Robbins-Halsted, one of the company’s co-owners, said, “We are committed to learning from this event and to doing everything we can to help prevent anything like this from happening again.”
Since the fire and explosion, the company has been focused on supporting victims and their families and is fully cooperating with every investigating agency, she said. The company is also working to strengthen its safety programs, using the latest safety technologies as it rebuilds its facilities after the fire, she said.
“Our objective is to not simply meet current industry standards, but to exceed them,” Robbins-Halsted said.
Silo fires and explosions are not uncommon. Dust — whether it comes from sawdust, sugar or grain — is highly combustible because of its high surface area relative to its mass, according to Jeff Nichols, who worked for decades in silo fire and explosion prevention.
When small particles are suspended in the air, each one is surrounded by the oxygen it needs to burn instantaneously if it meets a spark or flame.
In an enclosed space like a silo, a flash fire — which happens when a cloud of dust gets ignited — can cause silos to explode as waves of pressure and fireballs push against the sides of the structure.
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Volunteer fire departments in rural areas often don’t have access to expensive injecting equipment, according to Nichols. In a past appearance on the “Dust Safety Science” podcast, he also said volunteer departments may not have adequate training in dealing with combustible dust.
Ken Desmond, president of the Maine State Federation of Firefighters, told the Bangor Daily News in May that he hadn’t heard of such equipment being available to departments in the state.
Friday’s report outlined a number of recommendations to prevent similar tragedies.
It noted that firefighters were unaware of the hazards unique to the silo’s design, particularly from the dust in an oxygen-limited environment. The tactics the firefighters used were better suited to silos of a more conventional design and not appropriate to one designed to limit the presence of oxygen.
Even the manufacturer’s instructions warn against pouring water into the silo, because that can create a “potentially explosive mixture,” according to the report.
The report’s authors noted that firefighters have more time to plan their approach to silo fires, unlike house fires when every second counts. In this case, a sealed silo prevents oxygen from feeding fires.
Robbins Lumber employees, who weren’t directly integrated into a unified command structure but were on hand to answer questions from individual firefighters, were unaware of the hazard posed by dust inside the silo, with the mill’s emergency evacuation and fire prevention plan listing it only as a hazard near electrical panels and equipment, according to the report.
Employees even were unaware that the silo was designed to keep out oxygen. Additionally, the silo had signs warning about the hazards of enclosed spaces, but none about the fire hazards posed by its contents, investigators found.
Despite making annual trips to the lumber yard to become familiar with its layout, hydrant locations and potential hazards, fire departments lacked a formal plan for how to attack blazes at the mill, according to the report, which recommended more training for dealing with silo fires.
Robbins Lumber is a leading supplier of eastern white pine products, with roots in Searsmont that stretch back nearly 150 years. It employs more than 100 people.
The mill resumed operations on May 26.
BDN writer Bridget Huber contributed to this report.