Aggregate is a critical natural resource for New Zealand’s development and is extracted by quarries to build our homes, communities, schools and businesses.
Aggregate is the collective name for natural rock and gravel deposits which are located throughout New Zealand. Examples include sand, scoria, boulders, river gravel and limestone.
Each year New Zealand consumes the equivalent of eight tonnes of aggregate per person across many areas of construction and infrastructure, including roading, concrete and ground stabilisation.
The need for aggregate is continuing to increase and high growth areas such as Auckland, Wellington and Christchurch have significant future demands, with new and existing quarries required to meet these.
It’s crucial that we better understand, plan and utilise our aggregate resources to ensure our infrastructure providers have a reliable and affordable supply of aggregates and any impacts on the environment or our communities are managed.
Aggregate mapping of New Zealand report
About the study
The New Zealand Infrastructure Commission, Te Waihanga has part-funded and worked alongside GNS Science on a study to improve understanding of the best source locations for rock throughout the country.
The Aggregate Opportunity Modelling for New Zealand report establishes a guide for potential future quarry developments as a basis to protect these resources for future generations.
The aggregate opportunity modelling maps comprise several layers that are categorised into five groups:
- Source rock: Uses geological maps of rock deposits across New Zealand and assigns a higher value to rock best suited for aggregate like greywacke and limestone and a lower value to rock like mudstone.
- Land use: Accounts for land uses that make quarrying impossible or unlikely, such as cities and towns, areas with indigenous vegetation, conservation land and areas covered with water.
- Future demand: Places a greater weighting on areas near cities with greater forecast construction demand and major roads.
- Supporting infrastructure: Includes highways, railways, powerlines. It also considers the likelihood of local labour by considering regional unemployment.
- Social objections (referred to as cultural sensitivity in the report): Involves concerns about quarry development, including how visible they are from residential areas, how far away they are from where people live work or play, whether there are any significant cultural treasures (taonga) nearby and if it has been a previously quarried area.
This study will support the search for future supply of aggregate in New Zealand. Whilst the spread of aggregate throughout the country is not even, the report highlights that there are substantial resources and much of it is viable for quarrying.
Further work is required before a council could use the maps to protect land for future extraction or a quarry operator could confirm a new site. Engagement with local communities, residents and iwi remains a critical part of the process and is not a focus of this study.
The geological data itself would also need to be confirmed. For example, more localised data could be applied to specific regions and shovels would have to hit the ground to test the data and determine the true quality of the available rock.