7 August 2018

Dubbed the Eiffel Tower of viaducts, the Makatote Rail Viaduct is an iconic structure of national and historical importance.

 Construction of the viaduct dates back to 1908 when 500 immigrants, who lived in tents on site, completed the final connection of the North Island main trunk railway.

It is one of the tallest railway viaducts in the country and holds significant heritage value for its elegance and the technology used at the time of construction. However, after 107 years the viaduct was suffering from corrosion that had led to section losses of steel elements. KiwilRail wanted to repair and upgrade the viaduct and in 2014 enlisted the expertise of WSP Opus to carry out a refurbishment and strengthening project, extending the life of the viaduct for another 50 years. Located within a highly sensitive ecological area, the project presented WSP Opus and construction partner Total Bridge Services some unique challenges. This required some agile engineering design and complex consent applications to ensure the highly regarded values of the area were not impacted. Protecting the unique environment was one of these challenges. The viaduct crosses the Makatote River, which is highly valued as a trout spawning river and trout fishery. It is also a site of significance for the whio (blue duck) and koaro (climbing galaxis fish) species.

"The Makatote Viaduct is an iconic and significant piece of infrastructure in the Manawatu-Whanganui Region. To have the opportunity to be part of such a talented multi-disciplinary team who worked together and came up with innovative ways to ensure the refurbishment was a success was a privilege, knowing the Viaduct will now be there for generations to come.”

Tabitha Manderson, RMA Planner, WSP Opus

WSP Opus carefully assessed and catalogued the structure which enabled us to present a clear business case for refurbishment and strengthening of the original skeleton, rather than opting for construction of a new viaduct. Careful design also meant that the viaduct could be used throughout the 2.5-year restoration project while meeting KiwiRail’s high standards for health and safety. This approach also complemented the environmental focus. The Pier Access System that was designed allowed the viaduct skeleton to be “shrink wrapped”, a move that successfully contained the waste from the removal of the original lead-based paint. This strict encapsulation and close monitoring ensured that the natural environment was well protected.

The result is a new lease of life for an iconic heritage viaduct whose aesthetics are fully maintained while its performance has been upgraded to comply with modern loading and safety requirements. The project illustrates how innovation and careful planning can ensure necessary maintenance works on a historic feature in an ecologically-sensitive environment can be successful for all parties. In 2017 London-based IStructE, The Institution of Structural Engineers, awarded WSP Opus the ‘Award for Structural Heritage’ for their rejuvenation of the viaduct.