Mega Metro

Climb aboard an extraordinary behind-the-scenes look at one of the world's biggest transport infrastructure projects, the Sydney Metro, and meet the clever characters who work on this mammoth undertaking along the way.

We trace our talent encountering all manner of issues tunnelling through a minefield of existing infrastructure; skyscraper footings and basements, sewers, a graveyard and existing rail tunnels. In several places the TBMs have to 'thread the eye of the needle' with little clearance to spare.

In the early planning stages, the team actually considered dropping pre-fabricated tunnel sections down onto the floor of the harbour one by one, lowering them from barges, which was the way the road tunnel under the harbour was built. It was eventually decided that TBMs were a safer and more practical solution, though not everyone was convinced.

Crews scramble to lay 'ballast' and 60,500 new sleepers. They devise a way to deliver concrete from concrete trucks, deep into underground tunnels, before the concrete sets. They install new tunnel ventilation systems, signaling equipment, communications and electricity as well as overhead wiring - not to mention lighting, drainage and safety systems.