The success of the Kawerau geothermal power station project led to the Hawkins Infrastructure / Sumitomo Corporation / Fuji Electric Systems partnership being retained for the delivery of the Nga Awa Purua geothermal power station at Rotokawa. Hawkins Infrastructure acted as the ‘on-shore' partner responsible for the design and construction of the civil, structural, architectural and building services elements of the facility being built for a joint venture between Mighty River Power and the Tauhara North Number 2 Trust.

The $430 million, 140 MW facility is the second major geothermal power station to be built by Hawkins Infrastructure and the fourth New Zealand geothermal project overall to have major input from the Hawkins group.

Located 10 km north of Taupo, the site is close to the Waikato River, adjacent to the existing geothermal power station at the edge of the Taupo volcanic zone. Similar to the Kawerau geothermal project, the scope of work and services supplied was within the context of an E.P.C. contract that comprised planning, design, manufacture, procurement, transportation, construction, installation and commissioning of all facilities within the boundary of the power station. Hawkins Infrastructure acted as the main design and build contractor, responsible for the civil, structural, architectural and building services elements of the project.

Initial earthworks for the 22-month project began in May 2008, with building excavations underway a month later. Particular challenges on the site included the demanding and varied gradient of the site, weak volcanic soils, aggressive groundwater and high temperatures, and susceptibility to liquefaction. This meant 30m deep bored piles were required to support the plant structures that included the generator, turbine and turbine casing (the largest triple flash geothermal turbine in the world, weighing a combined 325 tonnes) and the turbine hall itself. The use of cutting-edge, pre-cast and post-tensioning systems accelerated the project timeframe significantly.

All project participants took part in a continuous improvement process to increase implementation efficiency, particularly as the triple flash plant resulted in increased paperwork and complexity. Based of the team's previous project experience at Kawerau, numerous efficiencies and innovations were applied on the Nga Awa Purua project. In order to improve constructability but maintain accessibility, several design changes were implemented:

• The Kawerau electrical annex has two storeys. For Nga Awa Purua, the building was changed to a flat single-storey building to improve construction and operational access.
• At Kawerau, the project land site was flat, so brine pumps were located in a 4-metre deep pit to retain suction head from the LP Separator. The Nga Awa Purua site natural terrain is hilly compared to that of Kawerau, so separators were located at higher elevation and this brine pump pit was deleted.
• At Kawerau, all the first and second stage steam jet ejectors were arranged vertically to minimise the footprint area. For Nga Awa Purua, they are rearranged horizontally.

The station produces 140 MW of clean power (8 MW more than the initial project target production) and connects into existing 220kv transmission lines directly over the field, providing enough electricity to power 140,000 homes (equivalent to Taupo, Rotorua, Hamilton and Tauranga combined), or 3% of New Zealand's electricity needs.

The project was completed and handed over to the power station on 4 April 2010, 39 days ahead of programme.