CRL scales new heights restoring its own ‘Everest’

Work that began with hand-held spades in the ground four years ago came full circle with City Rail Link (CRL) celebrating the end of work to shift one massive pile of dirt and then replace it with another at the project’s Maungawhau Station site.  

Removing a large sloping hill in Eden Terrace cleared the way for construction of the southern tunnel portal connecting CRL with the new station and the North Auckland/Western rail line.  The hill has now been restored and most of the heavy construction hidden underground.

City Rail Link’s Chief Executive, Dr Sean Sweeney explained why this was such a momentous event.

“In many ways the hill was CRL’s ‘Everest’ – a mountain of a job completed successfully with larger-than-life high-tech machines and wonderful innovation that demonstrate the huge size of CRL’s work and all the complexities and challenges that come with that,” Sweeney said.

“This was building for Auckland’s future on a grand scale – all the materials we used can be measured by the tens of thousands.”

After an historic colonial cottage perched above the hill was safely relocated, the first spades of dirt were removed from the hill at an official sod turning ceremony in February 2020.  Spades quickly gave way to heavy machinery – in the months that followed more than 130,000 cubic metres of material was carved away by CRL’s main contractor, Link Alliance.

In the hill’s place a line of 71 concrete piles between 42 metres and 8 metres long were driven deep into the ground to anchor a sweeping curved retaining wall 127 metres long and 25 metres high – a buttress of concrete and steel to support CRL’s southern portal and the streets above it.

One of the most celebrated ‘visitors’ to the portal was Dame Whina Cooper, the project’s tunnel boring machine.  From there it launched its two underground drives into the heart of Auckland’s midtown to excavate the rail tunnels.

Cut and cover tunnel construction was completed last October, clearing the way for the next massive programme of work – restoring the hill.

On average a convoy of 45 trucks a day transported backfill spoil from quarries in south-east Auckland to the Maungawhau site. Measured monthly, the amount of soil was the equivalent of 13,000 cars, or 100 blue whales.

Link Alliance Project Director Francois Dudouit acknowledged the hard work of the 200 workers who worked for four years in the tunnel portal area.

“The area has been transformed, reshaped and filled back in again. Much of this extraordinary achievement is hidden from view as 85,000 tonnes of dirt now cover the complex and significant structures built below. I am proud of the teams involved in achieving this enormous milestone,” Dudouit said.

Dudouit said each layer of backfill was carefully compacted to ensure the restored hill was safe and secure for future use.

Compaction has prepared the restored hill for future use by Eke Panuku, Auckland Council’s urban regeneration organisation.  A street above the hill will also be re-aligned back to its original shape.