McLeod, O.E.; Bradshaw, D.; Kora, T. 2025 Use of localised low-carbon geological materials for eco papakāinga establishment in degraded geothermal environments: Ngāti Tahu hapū at Ōhaki, New Zealand. Lower Hutt, NZ: Earth Sciences New Zealand. GNS Science report 2023/05. 18 p.; doi: 10.21420/J7M1-GS66
Abstract
This report evaluates the feasibility of using locally available geological materials for eco-papakāinga construction at Ōhaki, within the Taupō Volcanic Zone. The Tahorakuri A1 Section 30 Ahu Whenu Wa Trust (Ngāti Tahu) is investigating sustainable, income-generating development options on a 55 ha site adjacent to the Waikato River. Development is constrained by ongoing land subsidence caused by geothermal fluid extraction at the nearby Ohaaki Geothermal Power Station. Using high-resolution LiDAR data, we identify elevated zones on the site’s upper terraces that are projected to remain above inundation thresholds over a 20-year period. We then assess the distribution and properties of local geological materials – including unconsolidated pumice, ignimbrite, volcanic ash, silica sinter from the Ōhaki ngāwhā, colloidal silica from the power station, and rhyolite and dacite from nearby volcanic domes – for their suitability in construction. Potential applications for these materials include insulation, foundation drainage, lightweight concrete, compressed earth blocks, cladding, building stone, ceramics and timber treatment. We recommend that future research focuses on developing composite materials (such as lightweight concrete and ceramics) to support the construction of strong, energy-efficient buildings. This may be further enhanced by incorporating colloidal silica products (such as GeoSHOT40 spraycrete) currently under trial by Geo40 at the Ohaaki Power Station (auths)
