Found deep in the rugged terrain of Fiordland National Park where snow-capped peaks meet towering granite cliffs, the eye-catching new shelter replaces an old 35-metre-long reinforced concrete shelter at Homer Tunnel which had significant seismic, rockfall, and avalanche vulnerabilities.
Originally 150-metres-long, much of the previous shelter was destroyed by avalanches in 1945 and 1997. These incidents, along with other safety concerns, prompted the initiation of the shelter’s replacement in 2020.
The project’s engineering complexity and unique environmental, heritage, and seasonal constraints meant its success hinged on the use of accelerated construction techniques.
Two key design decisions were made – the use of pre-cast elements, and no piling. This meant the shelter could be constructed during the very tight period between avalanche seasons – November to April. If delays had caused construction to extend beyond these timeframes, construction works would have had to be abandoned due to avalanche risk. There was no room for error.
The construction process involved careful demolition of the existing shelter, followed by on-site assembly of 157 prefabricated concrete elements stitched together with concrete. Using mostly pre-cast construction sped up construction on-site and minimised disruption to traffic flow along what is a vital tourist route.
Work was carried out by WSP, Downer, NZ Transport Agency Waka Kotahi and its Crown Infrastructure partners.
Designed to handle massive avalanche loads, the shelter can cope with huge deposits of avalanche snow debris and enormous vertical and horizontal forces from avalanche impact. To minimise impact loads on the shelter, a protective embankment was constructed to deflect avalanche flows up and over the shelter.
The shelter was also designed to withstand rockfall impacts from boulders up to two metres in diameter. Locally sourced rock was placed on the roof of the shelter to absorb rockfall energy and blend the structure in with the natural slopes - further helped by using dark-tinted concrete.
Located on State Highway 94, Homer Tunnel is a crucial link between Te Anau and Piopiotahi Milford Sound. It serves as the primary access route for thousands of travellers journeying to one of the nation's most iconic tourist destinations.
Completion of the tunnel's new avalanche shelter in April 2024 was a significant milestone in ongoing efforts to enhance safety and resilience along the highway. It marked the largest and final stage of a $29 million safety improvement project on the Te Anau side of the tunnel.
The result is a robust and resilient avalanche shelter successfully completed in an incredibly tight timeframe - ready to defend against the challenges that Mother Nature will throw at it.
