Information for the community

Key activities of geotechnical investigations

During April to October, 2022, geotechnical, geological and hydrogeological investigations were carried out near Lake Onslow and the Teviot Valley area. The purpose of this work was to understand what was happening under the ground and assess the area’s technical feasibility for supporting the infrastructure of a pumped hydro scheme.

The key activities of this work were: 

• drilling holes, about 15 cm in diameter and at various depths, from mobile drilling rigs 
• excavating or digging test pits to sample the material at near-surface level 
• monitoring groundwater and hydraulic testing 
• non-intrusive surface geophysical surveys 
• constructing a temporary storage area for contractors’ equipment and facilities. 

Permission was also granted to take water from the Clutha River/Mata-Au and Teviot River/Te Awa Makarara, within permitted limits, to use in drilling operations. 

Consents and other permits

Resource consents from the Central Otago District Council and Otago Regional Council were required to undertake this detailed geotechnical field work. Sometimes Wildlife Permits from the Department of Conservation were also required, depending on the nature of the field work.

Some consents came with conditions, such as erosion and sediment control measures, and work could not go ahead unless these conditions were met. Any proposal to drill or excavate on private land was discussed directly with the landowners before any consents were lodged.

Work at each site took approximately between 2 and 4 weeks – with times varying due to onsite conditions.

Following completion of the work, the drill holes were covered and the area rehabilitated. The groundwater levels and pressure at some sites continue to be remotely monitored. At these sites, a small, fenced structure encloses the covered drill holes and a 5-metre pole with solar panels and data-logging equipment have been installed.  

Geotech investigations across 3 areas 

Work began in mid-April at the first location near Lake Onslow and was completed in September.

Geotech investigations get underway for pumped hydro at Lake Onslow(external link) — Beehive.govt.nz 

Fieldwork in the Teviot Valley began in June 2022. This fieldwork was located on public land, such as road reserves, at 2 main sites and was completed in September.

This work was investigating where on the Clutha River / Mata-Au water could be stored before being pumped through a tunnel to Lake Onslow. Depending on the location, this may involve constructing a lower reservoir. A lower reservoir would allow the pumped hydro scheme to take and return water and minimise any effects on the river. 

The feasibility study has identified 3 possible areas for a lower reservoir – 1 at Lake Roxburgh where the lake would act as a reservoir, and at 2 sites further downstream. However more information is needed to help determine the most appropriate location, size and design for a lower reservoir, should the scheme go ahead. We are working directly with landowners who may be affected.

Further geotechnical work began at another site on private land in the Teviot Valley at the end of September 2022. The main activities of this fieldwork concluded in October 2022.  

This location was selected for its near-surface-level geological features, and the information from this work will contribute to the broader design work of the proposed pumped hydro scheme.

All information from the geotechnical investigations feeds into the broader Lake Onslow investigations that considers the technical, environmental, cultural, social and commercial considerations of a pumped hydro scheme.

Throughout the geotechnical work programme, the NZ Battery Project team worked with field teams to ensure the work was done in a way that minimised disruption to the community. All work was carried out during the day and had minimal impact on traffic.  

Site selection

Sites for geotechnical investigation work were carefully selected through a Site Selection Protocol, with each potential location examined by an independent ecologist, archaeologist and cultural values assessor. The individual sites were selected based on this advice to avoid the impacts to sensitive environments such as wetlands, archaeological sites and where there is indigenous vegetation or potential lizard habitat. Where necessary, management plans were put in place to avoid or mitigate any adverse impacts.

Ecology

The geotechnical work required physical investigations within the road reserve or on private land. The sites were located on pasture or existing modified areas wherever possible, to limit the potential effect on natural wetlands, wildlife and indigenous vegetation.

Advice and mitigation strategies from an independent ecologist were adopted to minimise any ecological effects. Some activities were conditional on obtaining a Wildlife Permit from the Department of Conservation.

All work on the site was subject to a Construction Environment Management Plan to ensure the works avoided or mitigated potential effects, as identified in the resource consent.

Lizards

A Wildlife Permit from the Department of Conservation was obtained for investigations on sites where lizard habitats had been identified. 

Cultural values

All sites were independently assessed for the potential effects the fieldwork would have on values to mana whenua. Recommendations from independent assessors were adopted into the planning to avoid or mitigate any potential adverse effects on mana whenua values. 

Archaeological values

The proximity of known archaeological sites was taken into consideration during the site selection process. If necessary, an archaeologist would attend the site to supervise and provide advice in the event of a potential discovery. However, this was not needed. Protocols for all sites were established in the event archaeological material was found.

Noise

Noise generated from the activity was broadly similar to the noise on a farm where machinery is operating.

Road use

The work had minimal impact on road users.

The sites in the first stage of fieldwork near Lake Onslow were dispersed across a large area and scheduled for different times, which minimised the number of extra vehicles on the roads or parked on road reserves. There were up to 3 vehicles and a mobile drill rig at each site, as well as occasional visitors.

The second stage of fieldwork in the Teviot Valley followed similar procedures. A traffic management plan was implemented where works were required within the road reserve. This was to ensure the continued safe and efficient operation of the road network. 

Long-term impact

Sites where the ground has been disturbed have been remediated to leave little to no evidence of activity. 

However, at some sites, a small area around the covered drillhole was fenced off and a small solar panel, monitoring equipment and telecommunications equipment were installed so groundwater data could be collected and monitored remotely. 

Social and cultural impacts 

We recognise the fieldwork may have heightened uncertainty for some in the community. We remain committed to keeping the community informed about the project, especially affected landowners and mana whenua. 

As part of our Phase 1 study, we commissioned work to research the likely impacts the proposed scheme would have on the community. The interim social impact assessment provides a baseline of possible impacts. A full social impact assessment would need to be carried to explore these possible impacts further.

During Phase 1, we also commissioned work to investigate the cultural values in the area that would be affected by a pumped hydro scheme. Further assessment would need to be undertaken to understand the impact the scheme would likely have on cultural values.

Get in touch

If you have any questions, please email us at nzbattery@mbie.govt.nz