Economic Benefit

Sand is an essential component for making concrete. Currently there is no economically viable alternative to sand in concrete production and without a ready supply of sand, there would be no concrete manufacture.

Sand sourced from the Mangawhai-Pākiri embayment supplies nearly half of the construction sand requirements for the Auckland region.

In the year prior to September 2021, McCallum Bros Ltd® supplied 335,000 tonnes of sand from the Mangawhai-Pākiri embayment into the Auckland ready mix and pre-cast concrete market. The estimated total demand for concrete sand in the Auckland region is 785,000 tonnes, which makes approximately 1.8 million cubic metres of concrete.

A large proportion of the sand supplied by McCallum Bros Ltd® has been delivered to concrete manufacturers who are supplying major infrastructure and commercial projects in the city.

Sand is also used for other purposes, including for industrial, turf and equestrian requirements. This brings the overall demand for sand in the Auckland region to at least 990,000 tonnes per annum or approximately 600kg per person per annum.

The demand for sand is forecast to increase dramatically as the upper North Island continues to grow and more concrete is needed for new homes and infrastructure. It is estimated, for example. that Auckland will require between 9,000 and 13,000 new dwellings every year just to keep up with demand for housing. Concrete will also be required for roads, sewerage and water pipes, as well as public transport infrastructure, to support new communities.

For this reason, it is estimated that under moderate growth forecasts of 2.5%, the demand for sand by the construction industry will increase by up to 40% by 2043. This is an increase of approximately 600,000 tonnes, with total demand expected to reach 1,385,000 tonnes. Total sand demand across all markets is expected to be at least 1,680,000 tonnes at this point.

Recent growth has exceeded these forecasts significantly, with demand for sand increasing by more than 6% in 2021. This demand is driven by the construction sector. If demand for sand was to continue to grow at an average of 5 %, which is absolutely feasible, the volume of sand required in 2043 would increase to at least 2,800,000 tonnes, of which 2,400,000 tonnes would be required for the construction sector. While not all of this sand can be sourced from the Mangawhai-Pākiri embayment or the Kaipara Harbour, it does highlight Auckland requires several sources of high-quality sand of sufficient volume to continue to grow.

Are there alternative sources for sand?

Sand is a high volume, low-value product and is expensive to transport over long distances. It therefore needs to be sourced close to market or from a location where large, bulk volumes can be delivered to a central location.

Pākiri sand is shipped to central Auckland, where it is distributed in the most efficient manner. This not only provides an economic benefit but also an environmental benefit. Delivery of sand by bulk truck and trailer not only adds cost over long distances, but it also increases road traffic congestion, risk of accidents, damage to roads and significant increases in carbon dioxide emissions.

There are other sources of sand, with all of these being found on the edges of Auckland’s boundaries so they do require trucking over longer distances. On top of that, some of these sands (particularly those sourced from the Waikato region) have an increased risk of an alkali silica reaction due to their volcanic origins compared to Pākiri sand.

This makes these sands undesirable for higher strength infrastructure concrete, where cement quantities used increase the potential for adverse reactions that can cause expansionary problems in the concrete over time. This is a key reason why Pākiri sand is being used as far away as Napier for high strength concrete applications.

Manufactured Sands

Manufactured sands from quarries are already utilised in concrete mixes and make up at least half of a typical concrete mix. Unfortunately, these quarries, much like sand extractors, are currently running with little spare capacity, with the quarries being able to sell all the products they manufacture.

To create a manufactured sand of a similar particle sizing as natural sand requires more processing and costs an estimated further $14 per tonne to make. Overseas, where natural sands are not available in sufficient quantities, they are diluted with a manufactured sand of a similar sizing, but in the majority of cases they only replace a portion of that natural sand. They are definitely a product that can bee used to some degree, but they are not a complete not a replacement for high-quality natural sand.

Loss of the Pākiri resource from the Auckland market

If sand could no longer be extracted from the Mangawhai-Pākiri embayment, the construction market would suffer a significant supply shock.

Initially there wouldn’t be enough sand to keep infrastructure projects progressing. Longer-term, supply could occur from other sources, but based on where this sand would have to come from, it would likely drive up the cost of concrete materials and thereby projects and housing. This would be magnified if the marine resources in the Kaipara Harbour were also not renewed, with those consents expiring in 2026.  Construction would all but stop in the Auckland region as the remaining consents do not have sufficient consented volume.

While the Kaipara Harbour would provide one alternative source of high-quality marine sand, this sand cannot be moved as efficiently to Auckland as Pākiri sand can. A major advantage of Pākiri sand is that it can be barged directly into the Port of Auckland.

Sand from the Kaipara Harbour needs to be trucked to the city. Based on today’s volumes, the replacement of Pakiri sand with Kaipara Harbour sand would require a further 26,000 truck and trailer movements on top of what is already on this route. This would result in significant increases in road congestion, accident risk as well as thousands of tonnes of associated carbon emissions.

The higher cost of transporting sand from the Kaipara and reliance on one source would also see economic factors increase pricing. These costs would ultimately be borne by the end user, being householders and ratepayers who end up paying for the increased cost of building and infrastructure development.

In fact, it is estimated that supplying all of Auckland’s sand requirements from the Kaipara Harbour would add an additional $132 million in direct transport costs alone over 20 years.