Carbon monoxide, gas alarms triggered before fatal explosion at U.S. Steel Clairton facility, authorities say

Carbon monoxide and gas alarms were triggered leading up to a fatal explosion at the U.S. Steel Clairton Coke Works site Aug. 11, according to information released by the U.S. Chemical Safety and Hazard Investigation Board.

Preliminary investigations into the blast, released Monday by the CSB, indicate the explosion occurred during maintenance involving a gas isolation valve in the basement of the Battery 13/14 transfer area at the facility.

U.S. Steel employees and MPW Industrial Services personnel were working to close and reopen the valve, according to the CSB. Employees then tried to flush the valve seat with water, and a gas monitor alarm was triggered, according to CSB’s report.

Employees were directed to evacuate, and the explosion occurred less than a minute after that order, at 10:47 a.m.

Timothy Quinn, 39, and Steven Menefee, 52, both U.S. Steel employees, were killed as a result of the explosion. Eleven other people were injured.

Structural damage from the explosion resulted in prolonged search efforts, the CSB said. Menefee wasn’t accounted for until approximately nine hours after the blast.

The CSB is an independent nonregulatory federal agency that investigates the causes of serious chemical accidents.

A U.S. Steel spokesman said in a statement that the company thanks the CSB for its work in examining the circumstances of the Clairton incident.

“Notably, their initial findings are aligned with our own and we are committed to ongoing collaboration as they finalize their report. Concurrently, we are enhancing our safety protocols in line with the findings. Throughout this process, our unwavering focus remains on prioritizing the well-being of our employees and their families. As always, safety first remains our core value,” U.S. Steel’s statement said.

The gas isolation valve in question was manufactured in 1953 and last refurbished in 2013, according to CSB’s report. Following the explosion, the valve body had split open along a crack, and additional valves recovered from the scene also were damaged.

The CSB reported that another valve was leaking in June, and U.S. Steel temporarily repaired it. Additionally, four of nine recovered valves inspected after the explosion were damaged, although the CSB was unable to say if those failures happened before or during the explosion.

The CSB said it is continuing to investigate the cause and source of the gas release; the cast iron valve components; U.S. Steel’s use of cast iron materials in its coke oven gas system; policies and procedures for valve maintenance; and U.S. Steel’s overall safety management systems.

The CSB will issue a final report once the investigation is completed.

“This report graphically reveals the dangerous conditions that exist for workers, inspectors and contractors at the Clairton Coke Works,” said Matthew Mehalik, director of the Breathe Project, an advocacy group for air quality in Southwestern Pennsylvania. “We offer our condolences and support for the U.S. Steel Mon Valley Works employees and the Clairton/Mon Valley community for the horrific impact of the explosion and from this ongoing trauma in the aftermath from trying to understand what happened there.”

The CSB is charged with investigating incidents that may have released hazardous substances and makes safety recommendations to organizations but does not issue citations or fines. In a statement, the Breathe Project noted that the CSB’s update on Clairton arrived a day before its funding is reportedly going to run out on Tuesday.

“The Breathe Collaborative’s participating organizations call on our federal administration to continue funding and supporting the crucial work of CSB so that it can continue this investigation,” the Breathe Project said in a statement. “As outlined by the board, further investigatory work is needed, including the need to determine the cause of the valve leak leading to the tragic Clairton Coke Works explosion and U.S. Steel’s overall safety systems.”