Date: 2003-10

Location: Mt. Roskill, Auckland

Client: Transit NZ / NZTA

Project status: Completed 2010 

The SH20 Mt. Roskill Motorway Extension is part of the Western Ring Route, a regional transport route being constructed through Greater Auckland as an alternative to SH1. A designation for this section of the motorway had been in place since the 1950’s, however an application for its construction was made only in 1999. The key issue regarding its consent was the motorway’s alignment which brought it into conflict with Puketapapa Mt. Roskill Volcano, a landscape of national and international importance.

Both the Environment and High Courts weighed moving the motorway to protect the volcano against the national benefits from building key transport infrastructure. Transit NZ was granted the right to build the motorway in a deep trench cut through the volcano’s lower northern face and apron.

Transit NZ later chose to revise its approach after agreeing to comply with the ‘1915 Act’ which prevents retaining walls being built on Auckland’s volcanic reserves. We were invited by the Auckland Volcanic Cones Society to suggest an alternative outcome which led to Transit NZ engaging us for the project. Our re-shaping of the volcano was significantly helped by Transit NZ finding room for the motorway to move ten metres northwards.

The aim for the re-shaping was three-fold: maintain the volcano’s sense of curvature and volume; remove the distinction between natural and engineered slopes; and create a new joined integrity for volcano and motorway. The desired outcome was a foregrounding of the volcano as the primary visual experience of the motorway.

The re-shaping of the volcano was begun in 2006 and completed in 2010.

Construction: Fulton Hogan Ltd