Uh Oh, Spaghetti-Oh … Junction

The $4 billion Rozelle Interchange, a twisting maze of overlapping tunnels dropping to 40 metres below Sydney’s inner west, is the most complex underground junction ever built,

While tunnelling under Sydney for roadworks has over the years received its fair share of negative media coverage such as the vision of a block of condos teetering over a gaping hole during the construction of the Lane Cove Tunnel, the last few years of boring through the city’s sandstone bedrock has been relatively headline free.

A case in point is the labyrinthine leviathan of a network now being constructed under Rozelle.

When completed, the final underground spaghetti junction of criss-crossing tunnels will sometimes pass less than six metres below homes. This had led to calls to overhaul the project’s design.

It’s the last and most complicated stage of WestConnex and will link the M4 and M5 tunnels, the ANZAC Bridge and Iron Cove.

The three-storey underground interchange, will act as a linchpin for the 33-kilometre, $16.8 billion WestConnex project, and also provides the connection to a future Western Harbour Tunnel.

The $4 billion Rozelle Interchange, a twisting maze of overlapping tunnels dropping to 40 metres below Sydney’s inner west, is the most complex underground junction ever built, according to its project director, Tarnjit Chahal.

Chahal, who has worked on tunnelling projects around the world, said he wasn’t aware of a more complex piece of underground road infrastructure.

“I’ve worked on a number of large tunnelling projects both here in Australia and internationally, and this is certainly one of the most fascinating,” Chahal says.

“We haven’t been able to find a spaghetti junction created underground as complex as this, this is probably one of the world’s first.”

Tunnelling is expected to begin early next year with Sydney’s reliably solid sandstone allowing dozens of tunnelling machines to work simultaneously underground, day and night, until the project’s completion, which is slated for 2023.

Chahal says locals would not feel traffic beneath them, with up to 100,000 vehicles expected to be funnelled through the system every day.

Some locals have welcomed the interchange, which the state government says will alleviate traffic congestion which has increased thanks to the city’s burgeoning population.

Others say they’re concerned their properties could be damaged, with some even leaving Rozelle before the tunnelling is expected to begin early next year.

A Transport for NSW spokesman says while the most shallow parts would be about six metres below the surface, the average depth is expected to be around 35 metres.

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