Icon Water has rejected claims it appears to be making people redundant based on their age.
The utility company was in the process of making 10 jobs redundant as part of a larger restructure that will see up to 50 positions culled.
The company has extended the redundancy consultation process which will mean staff will not exit the organisation until the first week of February.
The Professionals Australia union's ACT director David Smith said Icon Water had not outlined which other organisations it had benchmarked itself against to inform the restructure.
He had asked Chief Minister Andrew Barr to intervene on behalf of the ACT community to find out how services will be affected by the trimming of the workforce.
"We have been asking Icon Water how the restructure and reductions in staffing delivers safe and effective water outcomes for the people of Canberra and the region," Mr Smith said.
"They have not been able to provide an answer for the last two months.
"This is the third major restructure in as many years and the organisation stands to lose significant water treatment and quality expertise at the same time as the asset base is both growing and ageing.
"You can't replace senior engineers with 15-20 years experience without increasing the risk profile of the organisation. There is a lack of transparency in the reasons for the reductions and in the selection of staff for roles."
He said age seemed to be a factor counting against some employees despite the expertise these employees brought to their workplace.
An Icon Water spokesperson said it was not appropriate or required to provide "commercially sensitive" information to the union.
"Icon Water has met all of its obligations under the terms of the Icon Water Ltd and Combined Unions Enterprise Agreement 2014, including those regarding consultation," the spokesperson said.
"Icon Water will fill vacant roles on the basis of merit, considering the employees' knowledge, skills and experience.
"Every effort is made to redeploy affected staff both within Icon Water itself and within its affiliates."
The spokesperson said Icon Water must continue to be flexible, responsive and agile in order to deal with external pressures.
"It is vitally important that the organisation evolves to continue its focus on providing quality water and wastewater services at a sustainable price for our customers."