High-voltage cables to power Canberra's light rail have been installed under a bridge, reducing capacity for floodwaters from the creek below to pass through and increasing the risk of trams being rendered inoperable.
The electricians' union says Sullivans Creek should have been underbored to avoid placing cables under the bridge, and that water from less serious floods is now more likely to be pushed up onto the tracks between Gungahlin and the city centre.
Two sets of cable trunking – enclosures used to protect electrical cables – have been fixed to the underside of a bridge on Flemington Road, outside Exhibition Park in Canberra.
It is understood one contains high-voltage cables and the other houses low-voltage cables including the ones needed to operate signals.
Sullivans Creek flows underneath the bridge. The bridge is about 2.97 metres high, but the deepest section of trunking reduces that height by 75 centimetres.
According to ACT government flood maps, the area of Sullivans Creek in question is classified as "high hazard" – the most serious level.
The depth of flooding in the area during a one-in-100-year flood would be more than 1.5 metres, according to the maps.
Sullivans Creek has flooded as recently as February 2018, with rainfall in some parts of the catchment exceeding one-in-500-year levels according to an ACT government flood information document.
Electrical Trades Union ACT officer Mick Koppie said if floodwaters could not pass under the bridge because the trunking had made it lower in two areas, the water would be pushed up onto the light rail tracks.
Asked whether he believed even a small amount of flooding on the tracks could render trams inoperable, the experienced electrician replied: "Yes, I think it would."
"Any floodwaters that come up and start running across the road will not be good," Mr Koppie said.
"Too much water is definitely an issue. It would interfere with the electrical supply to the tram.
"I think even 100 millimetres [of water built up on the tracks] would make it inoperable."
Construction company John Holland is responsible for design, construction, operations and maintenance as part of the Canberra Metro consortium that was in 2016 awarded an ACT government contract to build and operate stage one of the light rail project.
A spokesman for Canberra Metro and the ACT government's Transport Canberra and City Services directorate said questions submitted by the Sunday Canberra Times about the cables under the bridge were detailed and technical.
He said they deserved an equally detailed and technical response, which would not be possible by the deadline.
The latest concerns about electrical work on the light rail project come after the Sunday Canberra Times revealed last weekend that electricians and their union representatives believe the project might fail to receive the independent approvals it requires because high-voltage cables are installed too close to the surface.
Photos of electrical conduits in a pit near the intersection of the Federal Highway and Flemington Road appear to show some cables installed just a few millimetres below ground level.
This is despite the Australian standard the ACT government expects to be adopted for the light rail project requiring cables installed underground in areas accessible to the public to be buried at least 75 centimetres below ground level.
Transport Canberra and City Services said it "fully expected" the light rail project to achieve certification against all relevant standards, before starting to take passengers early this year.
The Office of the National Rail Safety Regulator said the light rail project could still receive accreditation even if the electrical cabling was too shallow to meet Australian standards, so long as Canberra Metro can prove it is safe.