An investigation is under way into what caused a storage tank at the Billings ConocoPhillips Refinery to catch fire and send thick black smoke over south Billings on Christmas Eve.
Jim Hughes, an environmental specialist with the Department of Environmental Quality, said a company representative reported Monday that the company still doesn’t know what ignited a fire at a tank that holds asphalt and pitch as feed stock for its coker. The coker processes heavier crude oil and products into lighter materials, such as gasoline and diesel.
The company has a week to file a report with DEQ and will be reporting estimated emissions from the smoke, Hughes said.
Refinery operations continued at normal rates through out the entire event. No one was injured.
“We have a team doing a thorough investigation,” Bill Stephens, a ConocoPhillips spokesman in Houston, said Monday. “It’s going to take a little while.”
The team includes local refinery and corporate officials, and its investigation could take weeks, Stephens said.
“We’ll learn from that and take steps to prevent those kinds of things from happening in the future,” Stephens said.
He would not speculate on possible causes.
“The good news is we were able to put it out in a pretty professional manner without anybody getting hurt,” he said.
The fire began about 3:20 p.m. and was extinguished by 5:50 p.m. by refinery firefighters, who were assisted by the Billings Fire Department as part of a mutual-aid agreement.
Fire crews from both the CHS refinery in Laurel and the ExxonMobil refinery in Lockwood also assisted under a mutual-aid pact, Stephens said.
“We really appreciated the great coordination here,’’ he said.
The blaze was contained to the tank, which was left collapsed and crumpled around its rim.
“Nothing leaked out of the tank,” Hughes said.
And none of the material got into the ground or into the groundwater.
“There shouldn’t be any issues with surface water,” he said.
ConocoPhillips’ waste water treatment system handled all of the water and foam used to extinguish the flames.
The tank’s capacity is about 97,000 barrels, or 4 million gallons, and contained less than 5 feet of material, Hughes said. He estimated the tank was less than a quarter full.
The refinery was drawing down the material to take the insulated and heated tank out of service when the fire occurred, Hughes said.
At room temperature, the asphalt-pitch material is a solid. To move it, the material is heated to a few hundred degrees, Hughes said. When exposed to cold weather, the material solidifies.
“Typically, that stuff isn’t that volatile,” Hughes said.
The fire sent up an impressive plume of smoke visible for miles. “The high carbon material is why we saw so much of the black smoke,” Hughes said.
A northeast wind carried the plume over south Billings, generally up the Yellowstone River Valley and south of Laurel.
“The plume was fairly aloft. It got up pretty high,” Hughes said.
A sulfur dioxide air monitor near the CHS refinery in Laurel recorded low concentrations of the pollutant during the episode, Hughes said.
ConocoPhillips received an odor complaint from the U.S. Postal Service at 841 S. 26th St. and calls about soot fallout on the South Side, Hughes said. Billings residents may have noticed a faint kerosenelike odor.
The refinery called his office three times Christmas Eve to report the fire and to keep him apprised, Hughes said.
Contact Clair Johnson at email@example.com or 657-1282.