The Maritime NZ investigation found several factors contributed.
C3's standard operating procedure for lifting heavy machinery was not developed or reviewed by a qualified engineer. The lifting technique C3 was using had been identified as poor practice and was no longer being used by other stevedoring companies in New Zealand.
Workers were not properly trained in the procedure, the lifting lugs that were fixed to the excavator were not certified and C3 did not have a system in place for regularly testing and monitoring its workers' hearing and vision to ensure they were fit to operate machinery such as cranes.
Simmons said the sentencing highlighted the importance of staying up to date with industry best practice and having strong training and health and safety systems in place.
"While no single factor can be identified as the cause of the incident, there were clearly several serious health and safety failings that needed to be urgently addressed," he said.
C3 was charged under section 49 of the Health and Safety at Work Act 2015 for a failure to comply with duties under sections 36(1), 36(2), 36(3).
The Bay of Plenty Times approached C3 Limited's chief executive for comment.
A spokeswoman said the company would not be providing a comment about this prosecution.