City Rail Link

News - August 2019

Mt Eden milestone: The first works of the CRL is complete


It’s official! The first contract of our massive $4.4 billion project is complete - clearing the way for the rail tunnels to be built at Mt Eden.

The contract, known as C6, involved construction of a 423-metre-long stormwater main using a tunnel boring machine, explosives to blast tough basalt and a New Zealand-first pipe jacking method about 17 metres below ground. It replaced an existing stormwater main obstructing the City Rail Link’s path.

CRL CEO Dr Sean Sweeney said completing the $16.5 million contract was a “small but important step” in relation to the “huge strides” planned to deliver the CRL for Auckland in 2024.

The new main was excavated by a micro Tunnel Boring Machine which was called Jeffie after an international naming contest organised by CRL attracted some 30,000 entries.

Jeffie’s journey underground was originally planned to take 15 weeks but was completed in seven due to favourable ground conditions.

She excavated some 2000 cubic metres of spoil, and at the same time installed 208 segments of new concrete pipe.  Each segment was two metres long, almost two metres wide and weighed seven tonnes.

Jeffie also used technology not seen in New Zealand before to navigate a tight underground curve accurately and avoid hard volcanic rock. Hydraulic joints spreading the pressure evenly between each segment allowed the TBM to be steered around the curve without damaging the pipes.

Her underground journey also included an encounter with Auckland’s distant past – the remains of what is believed to be a whau tree that had been destroyed in a volcanic eruption some 20,000 years ago.

“Jeffie went superbly well and did a fantastic job for us building the new main,” Dr Sweeney said.

Excavation of the main was completed in March. Since then C6 work focussed on finishing smaller tasks such as successfully connecting the new and old stormwater mains.

Meanwhile Jeffie has arrived in Ecuador, South America, for a new tunnelling project.

The works were delivered by March Bessac Joint Venture. March is a Christchurch-based construction company and Bessac is a French tunnelling specialist.

Nigel Horrocks