Fredric March, 52, from Croydon, was working at the site in Galton Way, Swindon, on June 10, 2011, when a piece of timber being used as a cushion on the ends of the pipes being pushed in place by an excavator snapped.
Swindon Crown Court heard that Cappagh were the main contractors for the work and employed three workmen to lay iron sewerage pipes in a trench.
The sections of pipe were designed to slot together and the workmen used an excavator bucket to push them in place.
Two pieces of timber were used to cushion the ends of the pipes – one horizontally and one vertically – so the excavator could work around an existing horizontal strut on a trench box.
But the horizontal piece of timber snapped while being pushed by the excavator and a broken piece hit March on the head. He sustained critical injuries and died six weeks later.
The men had not been given any guidance or told of alternative ways to carry out their work, and had been allowed to come up with their own method, the court heard.
Cappagh Contractors Construction (London) Ltd of Waterside Way, Wimbledon, pleaded guilty to safety breaches and were fined £130,000 and ordered to pay £70,000 in costs.
HSE Inspector Sue Adsett, speaking after the hearing, said: “This tragic loss of life could have been avoided if Cappagh had taken proper measures before the work started and planned the task properly.
“Pipe laying companies must have safe systems of work and ensure their workers don’t have to improvise safety measures.
“Employers have a duty to carry out thorough risk assessments and provide safe ways of working.
“Including the workforce in designing safe methods also makes it less likely that they will improvise when problems arise.”