SH1 Waikato Expressway Huntly Section

The Huntly Bypass ‘Waikato Expressway Huntly Section’ project provided an alternative State Highway 1 (SH1) alignment around Huntly Township. The Waikato Expressway project is part of Waka Kotahi/ NZTA’s Roads of National Significance (RoNS).

The scope of the Huntly Bypass project site comprised a 15.5 km long four-lane wide expressway with nine bridges and two interchanges. Four of the bridges carrying the expressway over the Mangawhara, Whangamaire, Komakorau and Mangatoketoke Streams.

Gaia Engineers was the Lead Geotechnical Engineer of the project.  The project includes a grade separated interchange at the northern end including a 60m long single-span bridge carrying the expressway over the North Island Main Trunk (NIMT) railway and the completion of the full diamond interchange at Gordonton Road in the southern tie-in. Gaia Engineers designed 18 MSE bridge abutment walls with steel ladders and HDPE geogrid tieback.

Earthworks comprised a total volume of 3.5M m3 of cuts and fills. The Taupiri Summit comprised a 57m deep cut into the highly to moderately weathered Greywacke.  Ground improvements for the earthworks and bridge abutment foundations included up to 15m long driven timber piles, high tensile geotextiles and wick drains. The alignment runs also over very soft hydraulically and mechanically placed mine fill at Lake Kimihia.

Construction commenced in late 2015 and official opening was in February 2020. Gaia Engineers provided continuous geotechnical services from the tender in 2014, during the detailed design from 2015 to 2016 and during the construction phase from 2015 to 2020.