Explosions reported at a Houston-area chemical plant: what we know

Early Thursday morning, a series of explosions were reported at a chemical facility in Crosby, Texas, about 25 miles northeast of Houston. Flooding rains from Tropical Storm Harvey cut off power to the facility on Sunday, knocking out critical refrigeration systems at the location. The plant manufactures organic peroxides, chemical compounds used in manufacturing construction materials, which can ignite when not stored at a low temperature.

Plant crews worked on restoring the power and containing the chemicals, but on Wednesday, the site, as well as a 1.5-mile radius around it, was evacuated in fear of an imminent explosion.

Screen Capture / CNN

“We want local residents to be aware that product is stored in multiple locations on the site, and a threat of additional explosion remains,” Arkema, the French company that owns the plant, said in a statement early Thursday. “Please do not return to the area within the evacuation zone until local emergency response authorities announce it is safe to do so.”

Their statement elaborates:

As we communicated in recent days, our site followed its hurricane preparation plan in advance of the recent hurricane and we had redundant contingency plans in place. However, unprecedented flooding overwhelmed our primary power and two sources of emergency backup power. As a result, we lost critical refrigeration of the products on site. Some of our organic peroxides products burn if not stored at low temperature. ...

Organic peroxides are extremely flammable and, as agreed with public officials, the best course of action is to let the fire burn itself out.

Peroxides are chemicals that bind one oxygen molecule to another, Michael King, chair of chemistry at George Washington University explains in an email. These oxygen-to-oxygen bonds are pretty weak and “break apart easily when energy is provided, such as heat,” he says. The hydrogen peroxide you find at drug stores is too dilute to start a fire. But industrial-grade peroxides like those stored in the Arkema plant can combust if not properly cooled. In industry, they’re used to start other chemical reactions to create plastics and pharmaceuticals.

Harris County Sheriff Ed Gonzalez told reporters early Thursday that between midnight and 1 am a series of pops were heard at the plant. The pops were followed by gray smoke coming from the plant, and then black smoke.

“It is not anything toxic,” Gonzales said, referring to the smoke. “It is not anything we feel is a danger to the community at all.”

Brett Fors, a chemistry professor at Cornell, explains that when peroxides combust, “basically they decompose to nontoxic byproducts — C02 and water.” The threat, he says, wouldn’t come from the peroxides combusting itself, he says, but if their combustion ignites something else around it.

Out of precaution, Gonzalez says, Harris County deputies who were monitoring the situation on the ground were sent to the hospital for evaluation (they have since been released). Gonzalez declined to define the incident as an “explosion,” but rather said the chemicals were “popping” and were on fire. (Arkema, in its statement, describes the incident as an “explosion.”)

The 1.5-mile radius around the plant is still under evacuation, and Harris County officials are securing that perimeter. Arkema warns that the smoke from the fires could possibly contain compounds that “cause eye, skin and/or respiratory irritation or skin sensitization ... nausea, drowsiness or dizziness.”

Tropical Storm Harvey has brought major disruptions to industry in the region. Elsewhere, oil refineries are damaged and leaking toxic chemicals into the environment, and the refineries had to release toxic substances in the air in the wake of their emergency shutdowns.

The chemicals at the Arkema facility appeared to be contained. “The facility is in a rural area with no hospitals, schools, correctional facilities or recreational areas or industrial/commercial areas in the vicinity,” Arkema states on its website. “The plant has never experienced flooding of this magnitude before.” Arkema warns that more pops and explosions are possible before this incident is over.

The fires “will burn with an intensity until the fuel is consumed, and then they will die down,” Bob Royall, assistant chief of emergency operations at the Harris County Fire Marshal's Office, told reporters. Up to eight more containers of chemicals may catch fire or explode, the AP reports.

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