The ACT's light rail project could still receive accreditation even if the electrical cabling is too shallow to meet Australian standards, so long as Canberra Metro can prove it's safe.
But the Electrical Trades Union says the consortium will be hard-pressed to find a sparkie who would sign off on it.
The union and its representatives are concerned electrical conduits in parts of the corridor are too close to the surface to meet Australian standards, the Sunday Canberra Times revealed.
Australian standards say high-voltage cables installed underground in areas accessible to the public should be buried at a recommended 750 millimetres.
But a source on the light rail project said there were high-voltage cables buried "somewhere between extremely shallow and not very shallow" in the corridor.
Photos also show high and low voltage cables exposed near the intersection of the Federal Highway and Flemington Road, nowhere near this deep.
A Transport Canberra and City Services spokesman says the ACT government directorate "fully expects" the project to achieve certification against all relevant Australian standards.
But the Office of the National Rail Safety Regulator - which is currently assessing Canberra Metro’s application for accreditation - confirmed that standard may not need to be met if the consortium can be managed through the safety management system it is required to have.
"To be accredited under Rail Safety National Law an operator must be able to demonstrate to [the regulator] how it has met its safety duties through certification by independent and qualified persons - including by other relevant bodies such as the Technical Regulator," a spokesman said.
The Technical Regulator responsible for electrical safety in the ACT is the director-general of the ACT government's Environment and Planning Directorate.
Asked whether it was problematic that effectively an employee of the client was involved in the certification process, the National Rail Safety Regulator spokesman said there were checks and balances in the system.
"For example, [the national rail regulator] would require evidence that the Technical Regulator is satisfied that electrical systems are safe for operation before any approval to operate services would be granted," he said.
"The accreditation process also includes audits of an operator’s safety management system and inspections of processes adopted to certify rolling stock and track infrastructure."
The ACT government spokesman also said there were "robust contract and regulatory processes in place to check and ultimately verify all aspects of the work, including electrical works".
He said the photo of the exposed cables was "somewhat dated" and the site had since been rectified.
"As with any other large and complex infrastructure project, the need to rectify some elements of the works is to be expected. The contract has processes in place to deal with this inevitability," he said.
"Throughout the construction period Canberra Metro has been addressing parts of the project that require rectification along the way.
"The ACT government expects that there may continue to be a need to rectify parts of the project before operations commence. This shows the contract we entered into is doing its job in ensuring Canberrans receive a world-class light rail system."
But the ACT Opposition's transport spokeswoman Candice Burch said the potential lack of compliance with Australian standards presented a significant risk to public safety.
She has written to Transport Minister Meegan Fitzharris asking if she still had confidence in Canberra Metro to achieve certification for light rail.
"The minister needs to respond to community concerns as a matter of urgency. Missed deadlines and other failures have already resulted in major delays in the completion of light rail," Ms Burch said.
"Only last week we heard of $7.7 million in extra costs added to the project. Now there are concerns the network will not receive certification. This once again demonstrates why Canberrans can’t trust ACT Labor to manage infrastructure projects.”
However Electrical Trades Union ACT officer Mick Koppie said he did not believe there was a risk to the general public, but rather to contractors digging in the area, possibly in decades' time.
"You’re basically making a time bomb," Mr Koppie said.
Mr Koppie also expressed scepticism that the risk could be managed through Canberra Metro's systems.
"How will they prove it's safer than putting it three-quarters of a metre down? How will they get someone to sign off on it? No electrician would," he said.
The ACT government spokesman said public safety was of paramount importance across the project and the project would not have high voltage electrical conduits too close to the surface.