City Rail Link’s (CRL)main contractor, Link Alliance, has restored a hill that was removed to build the metro railway in Auckland.

Four years after work began to remove one large pile of soil, it has been replaced with another at the line’s Maungawhau Staton 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.

“In many ways the hill was CRL’s ‘Everest’ – a mountain of a job completed successfully with larger-than-life hi-tech machines and wonderful innovation that demonstrate the huge size of CRL’s work and all the complexities and challenges that come with that,” said CRL chief executive Dr Sean Sweeney. “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 a colonial cottage sited above the hill was relocated, the first spades of dirt were removed from the hill at an official sod turning ceremony in February 2020. In the months that followed more than 130,000m3 of material was carved away.

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

It was from the southern portal that the project’s Dame Whina Cooper was launched on the two drives into central Auckland.

Cut and cover tunnel construction was completed last October, clearing the way for the restoration of the hill.

On average a convoy of 45 trucks a day transported backfill spoil from quarries in south-east Auckland to the Maungawhau site.

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,” said Dudouit.

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 realigned to its original shape.

CRL is a 3.45km twin tunnel in downtown Auckland. It is New Zealand’s first underground rail line and the largest transport infrastructure investment ever undertaken in the country.

The Link Alliance comprises City Rail Link Ltd, Vinci Construction Grands Projets, Downer NZ, Soletanche Bachy International NZ, WSP NZ, Aecom New Zealand, and Tonkin + Taylo