Federal officials investigating a 2007 fire that killed five workers at the Cabin Creek hydroelectric plant in Colorado concluded the accident was caused by several safety failures, according to a report from the U.S. Chemical Safety Board.
The U.S. Chemical Safety Board, which investigates serious chemical accidents and makes safety recommendations, called for strengthening federal and state regulations to prevent future workplace deaths.
The Cabin Creek accident occurred in a penstock of the Xcel Energy hydroelectric plant, which is located 45 miles west of Denver, according to the CSB.
According to the CSB, painting contractors from RPI Coating Inc. were recoating a 1,530-foot steel portion of the 4,300-foot penstock when a flash fire suddenly erupted as the vapor from 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. and allowing 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 ten percent of the chemical's lower explosive limit, or LEL. (The LEL is the concentration of vapor in air below which ignition will not occur.)
OSHA's rule does state that an atmosphere exceeding ten 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 rule does not define what those safe entry conditions should be or specifically prohibit entry into such hazardous atmospheres, the report notes. The CSB recommended OSHA establish a fixed maximum percentage of the LEL for entry so that work in potentially flammable atmospheres would be prohibited.
Additionally, the Board made recommendations to the company, the governor of Colorado, the Colorado Public Utilities Commission, trade groups and other organizations.
CSB Board Member William B. 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."
There were ten 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 – the improvised tunnel entrance. Five workers on the other side of the platform made it to safety, although three of those workers sustained injuries.
The CSB found that Xcel and RPI failed to have technically-qualified confined space rescue crews immediately standing by at the penstock in case of emergency, as required by regulations. 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 this response unit arrived, their escape blocked by a steep vertical section of the tunnel deep inside the mountain, the CSB reported.
The CSB investigation determined that, while companies are required to perform a hazard analysis prior to issuing permits for work in confined spaces, regulatory standards pertaining to the use of flammables within confined spaces are inadequate.
The CSB recommended that OSHA amend its confined space rule to establish a maximum percentage substantially below the lower explosive limit for any given flammable for safe entry and occupancy while working.
The CSB made recommendations to nine other entities. These included that the governor implement an accredited firefighter certification program for technical rescue with specialty areas including confined space rescue; that the Colorado Public Utilities Commission (PUC) require regulated utilities to adopt provisions for selecting contractors based on safety performance measures and qualifications; and that the PUC require utilities to investigate all incidents resulting in death, serious injury or significant property damage and submit and make public written findings and recommendations within one year of the accident.
Numerous recommendations were made to RPI Coating, particularly aimed at revising its confined space entry program and guidance, the CSB reported.
A written statement from RPI said the men who lost their lives in the accident "were not only our employees, but our longtime colleagues and friends. One group's report or our objections to it do not affect our profound sadness surrounding this tragedy."
The CSB is an independent federal agency charged with investigating industrial chemical accidents. The agency's board members are appointed by the president and confirmed by the Senate. CSB investigations look into all aspects of chemical accidents, including physical causes such as equipment failure as well as inadequacies in regulations, industry standards and safety management systems.
The Board does not issue citations or fines but does make safety recommendations to plants, industry organizations, labor groups and regulatory agencies such as OSHA and EPA.
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