SH3 Te Ahu a Turanga – Manawatū Tararua Highway

The SH3 ‘Te Ahu a Turanga Manawatū Tararua Highway’ is a Waka Kotahi/ NZTA project which will provide a new route between Ashhurst and Woodville and replaces the closed Manawatū Gorge (SH3) Road. The project alignment, which carries the new SH3 over the Ruahine Range, is approximately 11.5km long. It consists of two lane, median divided State Highway with crawler lanes.

Gaia Engineers is the Lead Geotechnical Engineer of the project. The road alignment crosses the Manawatū River to the west of the gorge and varies fault lines including the active Mohaka Fault at the eastern side of the Ruahine Range.

The project scope comprises six bridges including the 295m long Manawatū River Bridge and the 305m long Eco Viaduct.  The bridge foundations consist of up to 50m deep and up to 2.1m diameter bored piles. The earthworks involve moving approximately 6 million m3 of earthworks, exaction of up to 55m deep cut slopes in Conglomerate and Siltstones/Sandstones and construction of more than 35m high fill embankments.

Ground improvements include soil nails, high-tensile geotextiles and up to 30m high geogrids reinforced slopes.

Gaia Engineers provided continuous geotechnical services since tender in 2019, during the detailed design from 2019 to 2021, and during the construction phase from 2019.