Isthmus

Steamfield protocol.
Tauhara II.

Approach

Tauhara II, a 250-megawatt geothermal power station to be constructed by Contact Energy near Taupō, was consented by a Board of Inquiry in 2010 and is awaiting construction. Isthmus’s landscape input included a design approach to the power station itself and a set of design protocols for the flexible steamfield elements such as well heads and pipelines.

Below The Taupō Volcanic Zone is a V-shaped area of stretching earth crust and associated volcanic activity. Wairākei-Tauhara is a twin-lobed geothermal field on the northern edge of the Taupō caldera.

Isthmus has been involved with a number of new New Zealand geothermal power stations that have come into production during the last ten years on the Wairākei-Tauhara Field, including Tauhara I, a small, binary plant trialled on the Tauhara part of the field. Tauhara II is a much larger, 250-megawatt station that will draw on a ten-square- kilometre steamfield on the outskirts of Taupō at the base of Mount Tauhara, an ‘outstanding natural landscape’, significant to Ngāti Tūwharetoa and rising 600 metres above pumice plains.

Isthmus’s first role on the Tauhara II project was to provide the relevant technical reports to the Assessment of Environmental Effects and give evidence to the Board of Inquiry in relation to landscape matters. However, the RMA provided an invitation to take a more proactive design approach – to avoid effects (or greatly diminish them) rather than merely mitigate.

Above Early New Zealand geothermal power generation undertaken at Wairākei, near Taupō.

Left View across the pumice plains and geothermal steamfield toward the volcanic cone of Tauhara.

Right Illustrated guidelines for the flexible steamfield elements such as the steam extraction and re-injection well heads, tributary pipelines and access roads. The illustrations are part of a set of controls and assessment criteria for future adaptive management of the steamfield.

Above Panorama over the pumice plains from the summit of Tauhara.

Tauhara II represents a number of themes; it is an example of a design approach at the front end of the project, rather than after-the-fact mitigation. It was the first project to be completed under a new ‘nine- month’ Board of Inquiry process administered by the Environmental Protection Agency (EPA). In practice, this meant an ‘inner team’ worked more closely together than otherwise might have been the case. The innovations made across all disciplines led to the project winning the Resource Management Law Association project award in 2011.

The design measures illustrate the importance of simple, strong ideas and of paying attention to the characteristics of a landscape. The combined-cycle plant is a closed system: steam will be used more than once with spent condensate re-injected into the field to maintain reservoirs. The steamfield will be managed by an ‘adaptive management approach’ – the locations of wells and reinjection points will be configured in response to monitoring of the steam resource.

With respect to the power station, Isthmus recommended a location near the northern toe of Mount Tauhara, separated from Taupō by a low brow in the plains. The ‘simple, strong idea’ is to anchor the power station to the pumice plains in counterpoint to the cone of Mount Tauhara. Two outwash gullies snaking away from the power station will be subject to revegetation – but will use the horizontal scale of vegetation to visually connect the power station to the plains. The ‘backbone’ steam pipelines were aligned on the ground and unobtrusive sites were selected for the two separator stations. The colour specified to anchor the pipelines to the plains was selected by finding the best match to a yearlong photographic record of changing landscape colour in the area.

“The challenge of consenting a nationally strategic energy-generation project in the shadow of an outstanding natural landscape required a subtle response to both the building and the land. Each was required to pay respect to the Tauhara maunga.”

— Brad Coombs, Isthmus

Many of the ‘tentacle’ features of the steamfield (the well heads, reinjection points and connecting pipelines) are not fixed – their locations will evolve as the steamfield is developed and are likely to change over time. To address this, a series of protocols was devised to cover alignment of pipelines with landform, contouring and rehabilitation of earthworks, management of land within pipeline corridors, location of well heads relative to houses, and use of contouring and planting to reduce the prominence of pipelines and well heads when they are viewed from roads and houses.

Team Members
Gavin Lister, Brad Coombs, Matt Jones,
Past Team Members

Charlotte Grant, George Woolford, Grace He, Kent Lundberg, Matt Peacocke

Collaborators
EMS – Stephen Daysh
Mark Chrisp, Noel Kortright, Simon Bendall,
Trevor Robinson, Buddle Findlay, Kerry Smith
SKM – Lindsay Stanfield
GNS – Brian Carey

Client
Contact Energy