Since then Top Energy has bought a 180ha farm directly over the hottest part of the geothermal field, so the company applied for a variation in the consent allowing it to change the location of the production wells and the new power stations. The new site is a few kilometres further west, just south of Ngawha prison.
Chief executive Russell Shaw said the move would increase the power station's efficiency and reduce construction costs.
In the original plan the geothermal fluids would have been piped 3-4km from the wells to the power station; now the plant could be built next to the wells.
The new site was also larger and flatter, so the two stations could be built next to each other instead of at separate locations, and in a dip so the power station would be less visible. The new consents will last 35 years.
Planning and design for well drilling and station construction was under way, Mr Shaw said. Tender prices were due in last night with work expected to start later this year.
The company was working with a kaitiaki adviser appointed by the Parahirahi Ngawha Waiariki Ahuwhenua Trust to monitor cultural and environmental indicators, as required under the consent, and had agreed not to cause any adverse effects on the hot pools. Re-injection of fluids into the reservoir will be independently monitored.
Mr Shaw said the resource consent process had been long and complex but wasn't the only hurdle the company had to overcome.
Under New Zealand's electricity regulations any lines company that owns more than 50MW of generation capacity has to split off the generator into a separate company.
Mr Shaw said that would duplicate management positions and add costs so Top Energy was applying to the Electricity Authority for an exemption.
The authority's draft decision was favourable but submissions from other power companies, which were released this week, were strongly opposed. No date has been set for a final decision.
