William Ryan Evans, of Blaenwaun Twr, Trelech, Carmarthenshire was found guilty of breaching Section 2 of the Health and Safety at Work etc Act 1974.
He was given a six month custodial sentence at Swansea Crown Court yesterday, 11 April.
The court heard how Mr Evans was contracted to develop a drainage field comprising of infiltration pipes laid at the bottom of deep trenches at Longstone Farm on 26 June 2012.
He employed two workers and a subcontractor excavator to undertake the work.
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One of the workers, Hywel Glyndwr Richards (54), entered the trench to remove a clump of soil when the trench collapsed and buried him. He died at the scene.
A Health and Safety Executive (HSE) investigation found the work was not planned appropriately and the risk assessment was not suitable or sufficient.
In addition, the workers were not appropriately trained and suitable equipment to a prevent collapse were not provided.
HSE Inspector Phil Nicolle said: "This tragic incident could have been prevented by undertaking a suitable and sufficient assessment of the risks, providing the correct equipment or safe working methods to the workers and managing and monitoring the work to ensure it was done safely.
"Work in excavations needs to be properly planned, managed and monitored to ensure no one enters an excavation deeper than 1.2m without adequate controls in place to prevent a collapse."
Hywel Richards' family added: "Today, and for the rest of our lives, we are mourning the loss of dad, our best friend, our confidant and protector. Quite simply, he has left a space that will never be filled. We hope that lessons will be learned from dad's death."
(LM)
