Infracore has also confirmed part of the changes could see some work sub-contracted, which would impact a further three staff members.
The council set up InfraCore three years ago, replacing Castlecorp. It was owned by the council but run as a separate business holding contracts with the council.
There were currently about 140 staff, including 13 in management roles.
Infracore chief executive Tim Hammond said in a statement in response to Rotorua Daily Post questions the business was the primary contractor for the council andit had an "obligation to deliver efficient, competitive and financially sustainable services".
He said Infracore had made improvements to what was a loss-making operation to achieving break-even results and had lifted service standards.
"Key to this has been the improvements made in the planning, organising and management capabilities of the organisation. The re-organisation of our operations is part of ongoing efforts to deliver value for money."
He said part of the focus of the re-organisation was ensuring the skills mix of staff was matched to the work being carried out and adjusting staff levels where the workload didn't match.
InfraCore last week went back to staff with the outcome of the re-organisation following a consultation process which, Hammond said, resulted in some changes to the initial proposal.
First Union organiser Phil Graham said one staff member, who had agreed to redundancy, had worked for the council, and then InfraCore, for more than 50 years - starting when he left school.
He said there had been low morale at the site for several years as a result of the business losing contracts and therefore jobs - including the city's rubbish collection when it went to recycling in 2016.
Northern Amalgamated Workers Union regional organiser Robert Popata said although the numbers impacted weren't large, many staff members were council workers who had decades of experience.
"We are talking about people who have been there 20 years plus. Like a lot of councils throughout the country, they are saying we want more work for less money."
One worker, who spoke to the Rotorua Daily Post on the condition they remained anonymous, said they had several qualifications and years of experience yet was being asked to take a pay cut earning only $2 more an hour than the minimum wage, which was currently $16.50.
The worker said they now hoped the Labour Government would push the living wage of $20.55 an hour to being the minimum wage - meaning the pay cut wouldn't be as bad.