Coastal projects

Sand mining on the East Coast and in the Kaipara Harbour

Coastal sand extraction (sea sand mining) is an important use of coastal resources in the Auckland region. Sand is primarily utilised as a fine aggregate in the production of concrete and asphalt for roading, concrete structures and other cement based products. Sand is also extracted for use in drainage systems and for beach nourishment projects such as at Mission Bay.

Concrete manufacturing specifications determine the characteristics required for sand, and hence the selection of extraction sites. The sand desired tends to be fine to medium grain, generally well sorted and free from shell or other impurities. The sand is generally extracted from the seabed using a suction pump, and pumped into a barge as a sand and water slurry. Shell and larger objects are screened off and sea water drains back to the sea as the barge loads.

Five coastal permits currently (2007) provide for sand extraction from the Auckland coastal marine area:

• two permits totalling 76,000 cubic metres per year (near-shore Pakiri)
• one permit for 2,000,000 cubic metres, with no annual limit but additional impact assessment requirements where quantities exceed 1,200,000 cubic metres in a 24 month period, (off-shore east coast near Little Barrier Island)
• two permits totalling 400,000 cubic metres per year, for five years, then increasing quantities after meeting further conditions, (Kaipara Harbour entrance, flood tidal delta).

Current extraction rates are approximately 151,000 cubic metres per year for the east coast sector and 219,000 cubic metres per year for the west coast Kaipara sector. Sand from the Kaipara Harbour entrance currently contributes over 50% of the concrete sand requirements for Auckland.

The availability of sea sand within the region is a significant economic benefit to the regional construction industry, as the transport of sand from other parts of the country would increase the cost of roading and other infrastructural works such as wastewater drainage systems.

Management of sand extraction

Sand extraction from the coastal marine area is controlled under the Resource Management Act 1991 by regional councils in conjunction with the Minister of Conservation. The ARC and Minister of Conservation control the use of such resources through the administration of statutory plans and policies including the New Zealand Coastal Policy Statement, regional plans, and the issuing of resource consents. All five coastal permits granted in the region followed Environment Court proceedings.

Environmental effects

The method and location of sand extraction and dredging has potential adverse environmental effects including:

• disturbance and destruction of coastal habitats
• smothering of benthic (seabed) communities by sedimentation
• coastal erosion
• adverse effects on amenity values
• conflict with recreational uses.

Any authorisation process permitting extraction requires the balancing of potential adverse effects with the economic benefits to the community. In all situations, scientific research on the coastal environment is required before extraction is permitted. Ongoing research and monitoring by the extractor is often required as a condition of consent. Should adverse effects from the activity arise, the consent authority may halt the operation or modify conditions under which sand extraction is permitted.