Civil works saw the construction of platforms for the production and injection wells, the preparation of the power station platform, storm water ponds and internal roadways across the site.
Nearly 1 million cubic metres of material was excavated from over a working area of 36 hectares.
These works were undertaken by Whangarei based United Civil Construction with a largely locally based workforce.
Drilling and testing of the three production and three injection wells required to provide geothermal fluid to OEC4, was wrapped up at the end of January 2019.
The wells range between 1,350 and 1,750 metres deep and are one metre in diameter at the surface and 22.5 centimetres at their deepest point. Each well has taken around 30-40 days of continuous 24/7 activity to drill, with additional time required to move the drilling rig between well sites.
Iceland Drilling, with decades of experience in the field of geothermal drilling, including the Ngatamariki geothermal power station near Taupo, based a specialist team in Northland for the 10 months it took to complete the work.
Construction started in September 2019 and the first shipment of power station equipment arrived on site in October 2019. This equipment was pre-fabricated offsite to facilitate its relatively quick assembly on site.
Israeli geothermal plant construction experts ORMAT were contracted to design, build and supply the power station. ORMAT has a long history with the operations at Ngāwhā supplying the original 10 megawatt power station, which was commissioned in June 1998 and then expanded to 25 megawatts in 2008.
In October 2019, Whangarei based Culham Engineering began installing the above ground pipelines required to bring the hot geothermal fluid from the production wells to the power station and the cooled fluid from the power station to the injection wells. They completed the work in August 2020.