A photo still from the computer animation produced by the CSB of the 2007 accident at Xcel Energy shows how a flash fire ignited, probably from a static spark in the vicinity of the spraying machine. The initial fire quickly grew, igniting additional buckets of the solvent, methyl ethyl ketone (MEK), and other combustible epoxy materials stored nearby.

The tragic accident that took the lives of five industrial painting contractors deep inside an Xcel Energy hydroelectric plant tunnel in Georgetown, Colo., was the result of several vital safety failures, the U.S. Chemical Safety Board (CSB) determined in a final investigation report released on August 25.

The CSB produced a 15-minute safety video, “No Escape: Dangers of Confined Spaces,” which includes a detailed animation of the incident that unfolded inside the mountain tunnel at Xcel’s Cabin Creek plant on October 2, 2007.

The accident occurred in the water tunnel, or penstock, of the hydroelectric plant, located 45 miles west of Denver. The penstock carries water from an upper reservoir to a lower one, driving power turbines. Painting contractors from RPI Coating Inc., Santa Fe Springs, Calif., were recoating a 1,530' steel portion of the 4,300' penstock when a flash fire suddenly erupted as the vapor from a flammable solvent used to clean the epoxy spraying wands ignited, probably from a static spark in the vicinity of the spraying machine. The initial fire quickly grew, igniting additional buckets of the solvent, methyl ethyl ketone (MEK), and other combustible epoxy materials stored nearby.

The CSB concluded the causes of the accident included:
  • A lack of planning and training for hazardous work by Xcel and its contractor, RPI Coating Inc.
  • Xcel’s selection of RPI despite its having the lowest possible safety rating (zero) among competing contractors.
  • The decision to allow volatile flammable liquids to be introduced into a permit-required confined space without necessary special precautions.
The CSB report found that the permit-required confined space rule set by the U.S. Occupational Health and Safety Administration (OSHA) does not prohibit entry or work in confined spaces where the concentration of flammable vapor exceeds 10 percent of the chemical’s lower explosive limit (LEL). The LEL is the concentration of vapor in air below which ignition will not occur.

OSHA’s rule states that an atmosphere exceeding 10 percent of the LEL creates an atmosphere “immediately dangerous to life and health” and that steps should be taken to define safe entry conditions. However, the CSB noted, the rule does not define what those safe entry conditions should be or specifically prohibit entry into such hazardous atmospheres. The CSB recommended OSHA establish a fixed maximum percentage of the LEL for entry so that work in potentially flammable atmospheres would be prohibited.

On the day of the accident at the Cabin Creek plant, there were 10 workers in the tunnel and one at the entrance at the time of the fire. Five were unable to get around the fire on the painting platform to get to the only available exit, an improvised tunnel entrance. Five workers on the other side of the platform made it to safety although three sustained injuries.

The CSB also found that, although required by regulations, Xcel and RPI failed to have technically qualified confined-space rescue crews immediately standing by at the penstock in case of emergency. Workers called 911 for help but responders entering the penstock had to retreat in the thick smoke, as did workers who had approached the fire with extinguishers.

The closest confined-space technical rescue unit - equipped and trained to enter the smoke-filled tunnel - was approximately one hour and 15 minutes away. The trapped workers died about one hour before the response unit arrived, their escape blocked by a steep vertical section of the tunnel deep inside the mountain.

CSB's Don Holmstrom, who led the investigation, said, “The five trapped workers communicated with coworkers and emergency responders using handheld radios for approximately 45 minutes, desperately calling for help, before succumbing to smoke inhalation. Their lives likely could have been saved had qualified, company-provided rescuers been in a position to respond immediately to a fire or other emergency.”

At the press conference to announce the final report findings, CSB board member Mark Griffon noted that Xcel did not adequately plan for the operation and selected the painting contractor with the lowest possible safety rating among the bidders. “And it did so mostly on the basis of cost - it was the lowest bid,” Griffon said.

The investigation found that Xcel hoped to compensate for RPI’s safety record by closely supervising the contract work, but it did not do so even when the company learned of safety issues during the initial penstock work, says the federal safety agency.

The CSB investigation found Xcel and RPI managers were aware of the plan to operate the epoxy sprayer in the tunnel and to use flammable solvent to clean the sprayer and other equipment.

Investigations Supervisor Holmstrom said, “As a result of not performing a hazard evaluation of the work to be done, the companies failed to identify serious safety hazards involving use of flammable liquids within the confined space. Use of safer, nonflammable solvents was not evaluated, continuous air monitoring was not required, and key policies and permit forms did not establish a percentage limit for flammable vapor in the tunnel atmosphere.”

Also at the press conference, board member William B. Wark noted the lack of planning for escape in an emergency. “The penstock had only one egress point - the tunnel entrance,” he said. “Xcel and RPI did actually identify this as a major concern in their planning. But despite this, no plans were made for prompt rescue in an emergency, and no rescuers qualified to enter this confined-space environment were standing by.”Wark said, “This tragedy should never have happened. The companies did not effectively plan for the dangers of bringing significant amounts of flammable liquids into the tunnel, which was a hazardous confined space. Doing so was an unacceptable deviation from good safety practices.”