The Otira Gorge is a classic example of a truly alpine environment. Towering rockfaces, vast scree slopes, and a sheer drop to the bottom of the valley. This section of State Highway 57 near Arthurs Pass boasts a gradient of up to 16 degrees as it tracks the river 60m below. Arguably one of the more memorable sections of road on the traverse across the Southern Alps through to the West Coast.

In a remarkable blend of teamwork, technical application and tenacity, Fulton Hogan’s Canterbury and West Coast surfacing teams worked with NZTA Waka Kotahi and local stakeholders to reseal the 340m stretch of highway, from the iconic Rock Shelter to the Candys Road Bridge. No small feat, the teams managed to complete the work two days ahead of schedule. The SMA10 wearing course applied in a single day.

Minimal disruption to traffic and safety were key focuses in the months long preparation. Collectively it was decided “short and sharp” would be the best approach, allowing for concentrated productivity and minimising critical risk to both road users and Fulton Hogan crews alike in this volatile environment. Narrow sections of road measuring six metres from edgeline to edgeline, potential rockfall caused by machinery vibration, and exposure to loose material on the steep gradient were all factors in the decision to go with block closures.

To avoid excessive loading on the five bridge sections, all the existing surface was removed and 55mm of AC14 laid on to membrane seal. Given the unknown territory for SMA, trial lays of more than 80 tonnes of SMA10 were conducted on gradients of between 16 and 20 degrees at Fulton Hogan’s Miners Road Asphalt Plant. Eight different rollers were tested for meeting the gradient and compaction needs, and a test load of SMA10 transported to ensure its efficacy over the 137km journey from the plant to site.

A complex project addressed with innovative solutions, meticulous planning, proven methodologies and a focus on safety, the Otira Gorge Reseal epitomises Fulton Hogan’s commitment to high-quality results on time and within budget with minimal disruption to the public.