The varying nature of quarrying
Effects of quarries vary by their nature (rock or sand), scale of operation, whether they are in short- or long-term use, in continuous use or used irregularly or seasonally.
Quarrying involves the excavation of rock, gravel or sand from the ground (including river beds and beaches). Rock-won aggregate is typically produced through drilling and blasting it from suitable rock deposits, and crushing and screening it to the desired size.
Gravels and sand are normally sourced from river beds (both current and old) and from beaches. Excavation typically involves machinery, without the need for blasting. Crushing of gravel is usually limited to larger gravels while screening is used to separate out smaller sizes for specific uses. Aggregate products requiring further refinement can often involve additional washing, crushing and screening processes.
The uses of rock aggregate range from road preparation and finishing (base and surface) to composite for concrete. Gravel and sand aggregates are similarly used for road and construction products but also have a range of specialty landscaping uses. Refer to relevant publications for further information on quarrying.
Challenges to quarrying
A number of other factors that make planning for quarrying challenging include:
- aggregate is a fixed and finite resource, often found in locations where extraction conflicts with other values (eg, river beds used for recreational purposes, or uplifted rock with high visual and ecological values)
- an incomplete knowledge of the location, scale and nature of aggregate resources and the high costs to obtain this information
- the benefits of locating aggregate resources close to the source of demand (ie, urban areas) due to the high costs of transporting aggregates and associated road damage
- the negative perceptions of quarries and their effects and the high potential for opposition to established and new quarries
- there is also no certainty as to where future quarry operations could actually take place.
A proactive and collaborative approach between councils, industry, tāngata whenua and landowners can help overcome some of these challenges.
Considerations when identifying future aggregate resources
There are a number of different factors that need to be considered when identifying future aggregate resources. For example, the proximity of the resource to demand will be a key factor determining both the economic viability of extraction and the associated adverse effects (eg, road damage and noise associated with transport).
Criteria for the assessment of aggregate resources might include:
- the nature and likely sensitivity of the surrounding land uses to quarries
- the density of the surrounding land uses. Is there likely to be a high number of people adversely affected?
- the proximity of the resource to the source of demand. Is this likely to change over the foreseeable future?
- the condition of the transport routes to the resources. How close is the resource to state highways?
- if there are high ecological values associated with the area. Are these values unique or widespread across the district or region?
- any cultural values associated with the area. Are there any known or suspected wāhi tapu sites?
