The HSE has warned of the need to have safe working practices on construction sites. The warning follows the prosecution of a company after a fatal accident when a blocked concrete pump was being cleared.

The court heard that piling rig operator Peter Roberts died on 10 May 2004, four days after an incident on the site of the Quinn Glass bottle manufacturing facility in Chester.

Dawson Wam Ltd was constructing 7,500 piles as part of the foundations. The process involved drilling a hole into the ground with the auger of a piling rig, pumping concrete into the hole as the auger was withdrawn and finally inserting reinforcement bars.

On the day of the accident there was a delay in the delivery of concrete to Robert's piling rig and concrete which remained in the flexible rubber hose used to connect a concrete pump to the rig began to harden, leading to a blockage.

After attempts to clear the blockage failed, it was decided to try using compressed air. The flexible hose was broken up into individual sections and at least two of these were blown out with compressed air without their ends being restrained. During the unblocking of the last section, the end of the hose whipped upwards and struck Roberts on the head, causing fatal injuries.

The HSE prosecuted the company, alleging that they had failed to ensure the provision and maintenance of systems of work which were safe and without risk to employees during the cleaning and unblocking of the piling rig and associated equipment.

It argued that despite the company being aware that this was a high risk operation, it had failed to carry out a formal risk assessment of the cleaning and unblocking of the rig, which meant there was no safe system of working.

HSE inspector Robert Hodkinson says:

"Cleaning out or unblocking piling rigs and associated equipment, such as concrete pumps and pipe work, with compressed air is a very high risk activity and should therefore have been formally assessed. A risk assessment is the starting point for developing a formal safe system of work for such operations. Once developed, clear instruction and training should then be given to those carrying out the work.

"Whilst no charges were brought directly in relation to selecting compressed air as a method for this particular operation, a safer alternative to clean out such equipment would be to use water. Indeed, the British Concrete Pumping Group Code of Practice states that using compressed air to clean out a pipeline should only be done when there is no practical alternative. The operation must be carried out under the close supervision of a suitably trained person.

"I recommend that all piling companies and others who use concrete pumps and associated equipment reassess their cleaning and unblocking operations to ensure that they have safe systems of work in place, and that employees carrying out such activities have received clear instruction and training".

Dawson Wam Ltd was fined £75,000 and ordered to pay costs of £34,425 at Chester Crown Court after pleading guilty to a charge under the Health and Safety at Work Act 1974 in that it failed to ensure the health and safety of their employees.

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