OSHA, in a statement, said penalties were proposed of US$845,100 were against RPI Coating Inc of Santa Fe Springs, California, and US$189,900 against the Public Service Co of Colorado, trading as Xcel Energy. The Administration alleges serious and wilful violations of federal workplace safety and health standards.

It said the fire, on 2 October 2007, began when workers were in the penstock tunnel cleaning a sprayer with a flammable solvent when vapour from the solvent ignited. Five workers tried to escape higher into the tunnel but died of asphyxiation while four others escaped.

OSHA said the companies have 15 business days from receipt of citations to request an informal conference with its area director or contest the citations and proposed penalties before the Independent Occupational Safety and Health Review Commission.

RPI Coating told IWP&DC that it was not issuing a comment or response to the OSHA report and proposed actions at this stage, but that a statement may be issued shortly.

Xcel Energy issued a statement that said it could not comment specifically as it was reviewing OSHA’s report and it intended to discuss the findings to fully understand the implications.

Dick Kelly, Xcel Energy’s, chairman, president and chief executive, expressed, again, the sympathies of those in the company to the families, friends and co-workers of the men who died.

He added: ‘While we respect the investigative work that OSHA has done, we disagree with any statement that implies we acted without regard to the safety of our employees and contract workers.’ Further, he said: ‘The authorities investigating the Cabin Creek event have our full cooperation, and we are committed to an open and honest effort to determine its causes.’

OSHA, in its statement on what it called a ‘preventable fire’, said that RPI has received 13 wilful citations with proposed penalties totalling US$778,500. Three of the citations allege that it brought electrical equipment into the tunnel that was not safe because it could ignite the solvent.

The other 10 wilful citations, said the Administration, related to alleged unsafe handling of flammable liquids, failure to arrange for emergency response in the event of an accident, failure to train on worksite chemical hazards and lack of fire extinguishers in the work area.

OSHA said that RPI received 25 serious citations with penalties totalling US$66,600 that included alleged fall hazards, unsafe storage of flammable liquids outside the tunnel and improper respiratory protection.

Xcel Energy has been issued with two wilful citations with proposed penalties of US$126,000 for failure to take precautions to protect its own employees from hazards in the tunnel and to arrange for rescue services, said OSHA.

The Administration added that the owner also received 19 serious citations with proposed penalties totalling US$63,900, which include fall hazards, the unsafe storage of compressed gas and electrical hazards.

In October last year, a week after the fire, Clear Creek County’s sheriff office blamed chemical mixing that led a heater to automatically activate was the source of the blaze.

Its statement said the maintenance workers had difficulty getting the anticorrosion mixture of paint and epoxy sealant through spray tubes, and added solvent into a mixing hopper to thin the mixture. However, the resulting change in temperature in the chemicals caused a heater in the mixer to activate, causing the vapours to ignite.

The fire started about 1400ft (430m) up the penstock from the lower portal, near Lower Cabin Creek Reservoir. The fire workers who died had been working above the seat of the fire and made to escape up the gradual slope, but were overcome with smoke. The four workers who escaped were below the seat of the fire.

RPI Coating, the maintenance contractor, had 11 workers on site – nine in the penstock, two outside.

Built in the Rocky Mountains, the Cabin Creek plant came into operation in 1967.