Epitaph Haast — State Highway 6

The Epitaph site on State Highway 6 had presented a persistent threat to a coastal segment of the highway for several decades — poorly bedded sandstone above a coastal alpine corridor exposed to adverse weather and high wind loading from the Tasman Sea. The site presented complex staging requirements and a remote location demanding a permanent structural solution rather than ongoing maintenance.

GSI designed a 115 m reinforced concrete capping beam installed under the seaward lane, supported by 280 micropiles arranged across three zones to match the variable ground conditions. The solution incorporated a dewatering system and real-time monitoring to manage ground behaviour during construction, along with a temporary rockfall barrier to protect the highway during the works. GSI delivered the Epitaph project as a fully integrated design-build contract — the same team that engineered the solution built it, removing the coordination delays typical of separate design and construction contracts.