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Worker’s torch set off methane explosion at water plant: fire department

South Side water reclamation plant explosion

This explosion and roof collapse happened shortly before 11 a.m. Thursday at the Calumet Water Reclamation Plant at 400 E. 130th St. | ABC7 Chicago

Investigators have revealed the cause of the explosion that injured 10 people and caused a building collapse Thursday morning at a water treatment plant in the Far South Side Riverdale neighborhood.

The city’s Office of Fire Investigations determined the explosion was caused by the use of a torch in an “area with significant amount of methane gas present,” according to Fire Media Affairs. The torch ignited the gas, causing a shock wave that lifted the roof.

Fire Commissioner Jose Santiago said the department received a call about the explosion around 10:50 a.m. at the sludge concentration building at the Calumet Water Reclamation Plant at 400 E. 130th St. The roof caved straight down in a pancake explosion, sending hundreds of thousands of pounds of concrete to the ground.

Eight of the ten people trapped were easily located and sent to the hospital, Santiago said, but the other two were trapped in the rubble. While the first individual took around 20 minutes to remove, the second required a 2 hour excavation.

The second victim was entombed, causing rescue workers to dig six feet down and tunnel through roughly 40 feet of concrete to reach the victim. Officials were initially worried that one of the man’s legs would have to be amputated, but they got him out safely. That man had a broken leg and jaw.

The other victims likely suffered minor injuries as well, Chief Tim Walsh said.

Eight of the workers hurt had been treated and released from hospitals by Friday afternoon, according to Allison Fore, a spokeswoman for the Metropolitan Water Reclamation District. None of the the others appeared to have life-threatening injuries, Fore said.

Two patients were brought to Christ Medical Center in Oak Lawn, according to fire officials. A spokeswoman for University of Chicago Medical Center said four other patients were brought in for treatment. By Friday morning, one of them remained in serious condition, another remained in fair condition and the two others had been released.

Fore said the explosion has not interfered with the plant’s water treatment operations.

“Our staff have worked diligently to ensure treatment operations continued to function as designed,” she said in a statement. “There is no threat to the public and we will continue to treat water at the plant as normal.”

Authorities were at the scene of an explosion that caused a building collapse shortly before 11 a.m. Thursday at the Calumet Water Reclamation Plant, 400 W. 130th St. | Jane Recker/Sun-Times