The old Hapuawhenua Viaduct was classified as a Category 1 structure by Historic Places Trust in October 1995.
This viaduct is still an icon of the North Island Main Trunk railway.
The viaduct became redundant when a new concrete railway viaduct was completed in 1987.
From the top of the lower section of the Ohakune Coach Road at the old gate post, a new walking track was built to the tunnel portal and over the hill to the two Hapuawhenua Viaducts.
From Ohakune, the railway line has to climb around 500ft up to Horopito.
The railway tracks climb on a 1:50 grade for most of the way, a steep climb for steam locomotives.
A viaduct was needed to cross the Hapuawhenua valley.
Peter Seton Hay designed a curved steel lattice viaduct with 13 concrete piers and four steel towers on concrete foundations. Fred Furkett was the engineer in charge its construction.
Hapuawhenua Viaduct Workers Camp
The viaduct is 284 meters long, 45 meters above the stream and built on a 10 chain radius curve with a level deck.
Building materials were brought to the site from the present Ohakune railway yard, along a temporary tramway below the planned permanent level, which needed time consuming earthworks and fill.
By building the tramway to carry materials and supplies, the tunnel, the Hapuawhenua Viaduct and the permanent way could all be worked on at the same time.
A short branch line off this Hapuawhenua tramway led to the Ohakune station in the bush, where passengers left the train and boarded coaches to cross the Gap.
In the Hapuawhenua Valley below the viaduct, there is no flat ground, so before construction could begin, a 200 foot by 50 foot platform was built over the stream.
The cement shed, the mixer and its engine, a tool shed and space for storing steel work, were all placed on this platform.
The steel components for the viaduct were made at Mangaonoho, north of Taihape, then railed to Ohakune.
