The OEC4 power plant will be constructed on a large engineered platform at the centre of the construction site to the north of the Ngawha Springs settlement.

The OEC’s main components are a separator plant, turbine and generator, air-cooled condensers, feed pumps and controls. A control room and office building will be constructed adjacent the main access way into the site off Ngawha Springs Road.

A new substation and 4.8 kilometres of 110 kilovolt overhead transmission line will be constructed to transmit the generated electricity to the power grid.

The substation is located to the south of the power plant site and the transmission line route runs to the north west, on land owned by Top Energy.


Major earthworks and civil works are well underway for the construction of the power station platform and the drilling pads for the production wells. Over 700,000 cubic meters of dirt will be excavated over three summer periods from October to April, with completion of civil works in 2020. These works are being undertaken by Whangarei based United Civil Construction with a largely locally based workforce.

Well drilling

Once the well platforms and water management system are in place in early 2018, well drilling will get underway. Two working production wells and two reinjection wells are needed.

Typically, the wells will be 1,750 metres deep and be one metre in diameter at the surface and 22.5 centimetres at their deepest point. Drilling each well is expected to take around 30-40 days of continuous 24/7 activity, with additional time needed to move the drilling rig between well sites. This means that it could take around 12 months or more to complete well drilling for one power station. The wells will be tested to ensure that the geothermal resource meets operational requirements.

Iceland Drilling, with decades of experience in the field of geothermal drilling, including the Ngatamariki geothermal power station near Taupo, will send a specialist team and be based in Northland for one year from April 2018.

Power station and pipeline construction

The components of the power stations will mostly be built offsite and will arrive in modular form. This means that they will require minimal construction and it will only take about 12 months to complete the power station build.

Israeli geothermal plant construction experts ORMAT have the contract to design, build and supply the power station which will commissioned in 2021. ORMAT has a long history with the operations at Ngawha supplying the original 10 megawatt power station, which was commissioned in June 1998 and then expanded to 25 megawatts in 2008.

Project timeline

  • JUL 2017 – Final resource consents for the expansion granted

  • OCT 2017 – Major transaction approval granted by Top Energy Consumer Trust and Top Energy Board. United Civil begin enabling works onsite.

  • DEC 2017 – United Civil awarded contract to construct drilling pads and foundations for power station. Contracts awarded to Iceland Drilling and geothermal plant construction experts ORMAT.

  • JAN-APR 2018 – Construction of drilling pad (production well), water storage pond and settlement ponds completed. First stage of construction of the power station platform (ongoing over two more summer periods – completion 2020).

  • APR-MAY 2018 – Iceland Drilling Company set up site compound.

  • END APR 2018 – HH-220 Drillmec rig transported to site.

  • MAY 2018 – Iceland Drilling begin well drilling.

  • SEP 2018 – Viability of geothermal resource determined.

  • 2019 – Formation of a hardstand platform for construction of the power station completed.

  • APR 2020 – ORMAT begin assembling power station on site.

  • 2021 – Power station 1, OEC4 commissioned.