Euro Earthworks Ltd general foreman Gerry Fox was crushed by an excavator bucket in August 2007 when it fell from the arm of the 12t excavator being driven by a colleague.
Euro Earthworks Ltd, of Boston Manor, Brentford, Hounslow was convicted of a breach of Section 2(1) of the Health and Safety at Work etc Act 1974. It was fined £20,000 and ordered to pay costs of £13,000.
City of London Magistrates' Court was told by the Health and Safety Executive (HSE) that Euro Earthworks had failed to adequately plan, manage and monitor the construction work on site.
Fellow defendants Hydro Plant Ltd, of Wadsworth Close, Greenford, Brent and Michael Denis Cunningham, of Latimer Road, Eastbourne were sentenced for separate breaches at an earlier hearing in May 2011.
The accident happened because there was no quick-hitch pin inserted, causing the bucket to fall on Mr Fox. HSE's investigation found that reasonable care was not taken for the health and safety of fellow employees by positioning the bucket that was filled with concrete, directly over Mr Fox and site supervisor Tim McCarthy who narrowly missed being hit by the bucket.
HSE has only recently issued advice on the safe use of quick hitches on excavators in March 2007. Euro Earthworks Ltd was aware of this advice and had made amendments to its written risk assessment, but still failed to take reasonably practicable steps that would have prevented the incident.
HSE Inspector Loraine Charles said: "This tragic incident was entirely preventable. There had already been a significant number of incidents involving buckets becoming detached from quick hitches, in particular semi-automatic quick hitches where operators had failed to insert the safety pin.
"Mr Cunningham can have been in no doubt that he should not have operated the excavator without the quick hitch's safety pin in place and that he should not have manoeuvred the bucket over people."