The tunnel will be lit by sensor-activated lights to “reduce visual impact”. Photo: ACT Government.
We’ve heard about the new bridge that must be constructed to take light rail across Lake Burley Griffin, but recently released documents reveal another major engineering project stands between the lake and Woden.
A short “covered section” – or tunnel – nearly at the foot of Parliament House looks set to be the solution to what’s considered a tricky tight turn from Commonwealth Avenue onto State Circle.
Infrastructure Canberra, the ACT Government agency in charge of large building projects, has submitted a draft Environmental Impact Statement (EIS) to both the Australian and ACT governments for approval.
It details exactly what’s involved in the construction of Stage 2B of light rail, from where Stage 2A ends at Commonwealth Park all the way to a new Woden Public Transport Interchange.
There are two options for the first section of this through the Parliamentary Triangle, dubbed State Circle East and National Triangle Barton.
State Circle East is the government’s preferred – and more direct – option and has light rail extended along the whole length of Commonwealth Avenue, before turning onto State Circle nearly at Parliament House and onto Adelaide Avenue via a new bridge.
National Triangle Barton would turn off Commonwealth Avenue along King George Terrace, Macquarie Street, Bligh Street, National Circuit and finally Sydney Avenue.
The State Circle East alignment option for light rail Stage 2B. Photo: ACT Government.
“State Circle East is the ACT government’s preferred alignment, however the scale of the project requires a thorough assessment of available route options,” the EIS reads.
Plans for the first option have light rail entering a tunnel where the ramp up to Parliament House begins and emerging about 125 metres later onto State Circle.
“This covered section would allow the light rail to pass underneath southbound Commonwealth Avenue traffic lanes through to State Circle, both northbound and southbound.”
As for how this tunnel will be built, there are two options, depending on “ground conditions and traffic management”.
“A ‘cut and cover’ construction method is proposed for construction of this covered section, which could involve one of two construction methods: bottom-up; or top-down,” the statement reads.
“Bottom-up would involve cutting out the tunnel’s path from above ground, installing the walls, floor and tracks, before putting the roof on and reinstating the road overhead.
“For this option, reopening State Circle to traffic would only be possible once construction of the covered section is complete.”
Light-rail tunnel from Commonwealth Avenue to State Circle. Photo: ACT Government.
Meanwhile, the top-down method would put the tunnel’s walls and roof in place first and finish the road above before the excavation works start to dig it out – cutting the time traffic is impacted.
The government admits the tunnel, as well as a new bridge between State Circle and Adelaide Avenue, “would constitute some of the largest changes in this precinct”.
“However, these elements would be consistent with the existing character of the precinct, where curving connecting roads between avenues are a common feature, particularly within and around Capital Hill,” it continues.
“Other key aesthetic and perceptual elements of the precinct would be retained and protected, including road corridors framed by tree planting.”
The covered section would also be fitted with sensor-activated lighting that only comes on as a light rail vehicle approaches to “reduce visual impact and discourage unwanted access by pedestrians or vehicles”.
From here, stops would be added along Kings Avenue, Sydney Avenue and Melbourne Avenue.
Further along at the Woden end, today’s sprawling Yarra Glen roundabout would be replaced by a new signalised intersection, with light rail passing through the centre and across a new bridge over the Yarralumla Creek.
A wider, two-lane slipway will continue to take southbound traffic directly through onto Yamba Drive (eventually past the Canberra Hospital), but traffic heading into Woden itself will have to wait at a new set of traffic lights.
The proposed Yarra Glen intersection. Photo: ACT Government.
Northbound traffic from Yamba Drive will need to stop at the same intersection to continue onto Yarra Glen.
Other modifications include improved lighting, a new pedestrian bridge and relocated “active travel path” near the Phillip Oval stop.
The ACT Government is hiring a consultant to estimate the total construction cost of Stage 2B – including the two routes through the Parliamentary Triangle – but it’s unlikely the figure will be released so as “not to impact contract negotiations and future procurement”.
The project still needs to go through the Territory Planning Authority, National Capital Authority and both Houses of Parliament for final approval.
The draft EIS is available for public feedback on the ACT Government website.
