Major safety reviews of four of the ACT's five largest dams are underway, two years after an audit found they did not meet the territory's safety code.
An Icon Water audit in 2014-15 found the Googong, Bendora, Corin and the Lower Molonglo dams did not meet the safety code, partly due to past shortcomings in the utility's monitoring program.
The enlarged Cotter Dam met the standards when it was finished in 2013.
Both the water utility and the government say there was no evidence to suggest the four dams that did not meet the code were not safe.
But the ACT's utilities technical regulator needs the extensive reviews to be completed to ensure that was actually the case.
Under the code, the five large "scheduled dams" in the ACT must meet the Australian National Committee on Large Dams' standards, including a rigorous monitoring and inspections routine and reviews.
Access Canberra's utilities technical regulation senior manager Simon Grice said he did not expect any "unpleasant surprises", but the reviews could show where more maintenance work needed to be done.
He said it was difficult to say either way until the reviews were completed, but that Icon had a "robust surveillance program" and he hoped the reviews would confirm that.
Icon Water's acting general manager of asset management, Cameron Patrick, said the utility was completing daily inspections, but for the four older dams a full review was needed "every 10 to 20 years".
A safety review of the low-risk Lower Molonglo water quality control centre has not been completed since it was built in 1995, and concerns were raised in 2014 about the higher risk-rated Googong Dam.
The utility has promised the government the reviews will be done by December 2018, despite an earlier two-year delay to Bendora Dam review and an 18-month delay to the Lower Molonglo review.
Both Mr Patrick and Mr Grice said the time needed to complete the technical work was partly due to a need for specialist skills from international dam safety experts.
Mr Patrick also said the utility was not aware of any "significant structural risks" to the integrity of the dams, but the reviews would formally verify if that was the case.
The UTR report also showed an independent peer review of the risk assessment for Googong Dam in 2015 found more work was needed to demonstrate its safety "with regard to earthquake risk".
That was chiefly because Googong Dam had previously been assessed using older one-dimensional modelling methods and more up to date, two-dimensional methods were available.
The NSW Dams Committee wrote to Icon Water as early as August 2014 highlighting those concerns and a need for more rigorous inspections and the safety review that is now on foot.
Mr Patrick said Icon improved its inspections of that dam after the committee's letter to help identify "changes over time" and the emergency safety plan for Googong was updated in 2014.
He said as Googong was one of the highest risk dams, its safety review could be finished as early as March next year.
Icon Water last year completed some work on Corin Dam to rectify a fault with the integrity of "a small portion" of the dam's clay core and dam anchor inspections of Bendora, Corin and Googong will be completed this fiscal year.
Mr Patrick also said all the dams had up to date emergency safety plans and there were "no significant risks to be concerned about".