Environmental Impact

We take our obligation to ensure we are extracting sand sustainably, and in balance with the environment, seriously.

The Mangawhai-Pākiri embayment is one of the most sustainable sources of sand available to the Auckland market, due to both the large volume of sand and its location and proximity to Auckland.

Better still, Pākiri sand can be extracted with a much lower environmental footprint than other sources of sand because it can be barged to central Auckland, where it is unloaded at the Port of Auckland and distributed to local concrete manufacturers and other customers.

While other sources of sand are available, this sand would need to be trucked into Auckland. Based on current Auckland demand volumes, this would equate to at least 13,000 return trips on the motorway network. The requirement to truck would result in more than 9,000 tonnes of carbon dioxide being emitted into the atmosphere every year.

To further reduce the environmental impact of its sand extraction activities, McCallum Bros Ltd® commissioned a new purpose-built and state-of-the-art vessel – the William Fraser.

Built in 2019, the William Fraser incorporates leading Dutch technology that has allowed a further reduction in environmental impact as well as reducing noise and visual effects through both operational and structural improvements to the vessel over previous vessels owned.

To fully understand the environmental impact of sand extraction in the Mangawhai-Pākiri embayment, McCallum Bros Ltd® has commissioned some of New Zealand’s leading independent engineering, ecological and environmental specialists to look at their activities to better understand their impact. These assessments can be found here.

The research has found that sand extraction in the embayment has a less than minor environmental and ecological impact and that, with continued careful management and appropriate monitoring, sand can be extracted with minimal environmental impact into the future.

Sustainable Extraction

The volume of sand in the Mangawhai-Pākiri embayment is enormous – with various estimates ranging between 1.7 billion and 3 billion cubic metres.

Based on the lower volume estimate of 1.7 billion cubic metres, McCallum Bros Ltd® records show only 4.4 million cubic metres, or less than 0.26% of the total available sand, has been extracted since 1966.

To put it another way, if all the sand in the embayment was squeezed into a two-litre milk bottle, much less than one teaspoon has been extracted in the last 40 years.

More importantly, the embayment is defined as partially closed system. This means new sand is continually entering the embayment and is being recirculated with wave and current activity. This allows sand to continue to be extracted from the embayment sustainably, in line with the conditions outlined in resource consents.

Excerpt from the McCallum Bros Ltd Assessment of Effects on Coastal Processes – Mid Shore Consent Area

Ecological Protection

Independent research by some of New Zealand’s leading research institutions has concluded that sand extraction in the embayment is having no discernible ecological effect on benthic biota (seafloor organisms), fish, birds or marine mammals.

Further, future effects are expected to be mitigated through the use of better dredge technologies, improved monitoring and greater crew understanding of how important the mauri of the embayment is to future generations.

Marine Mammals

Marine mammals are known to not permanently inhabit the embayment and any that might be transiting were found to likely avoid the localised area where extraction was occurring.

It was noted, however, that marine mammals (particularly dolphins and seals) would sometimes investigate the dredging activity and, at times, feed on fish that were also present while extraction was occurring.

Because the William Fraser uses a modern electric pump, the disturbance to marine mammals, including on their ability to communicate, is very localised and transitory in nature and is assessed as having a less than minor impact.

Fish

Fish have been found to be largely unaffected by the extraction activity. Any fish in the area were found to avoid the drag head but were sometimes found to come close to the William Fraser to feed on the oversized material that was being returned to the water.

Potential effects from sediment discharge were found to be less than minor and very short term in nature.

Birds

Birds, particularly gull species, were found to be attracted to the vessel when extraction occurred during the day as they searched for food. However, with extraction now predominantly taking place at night, these species no longer interact with the vessel.

There is, however, some risk of certain night active species being attracted to the vessel’s lighting while extracting at night. This has been minimised by reducing lighting to the minimum level required to meet navigational standards and provide a safe working environment for vessel staff.

There are several endangered species of shore birds that utilise the Pākiri and Te Arai beaches as roosting, feeding or nesting sites. The effects of sand extraction on these species was assessed as less than minor. Firstly because the vessel did not interfere with the feeding of these species or their prey abundance as it predominantly extracts at night and, secondly, there were no measurable effects attributed to sand extraction on the shoreline and dunes. So roosting and nesting sites were not being impacted by sand extraction.

Benthic Species

Animals living in or on the seafloor were found to be the most likely to be affected by sand extraction as they can be picked up by the drag head.

In general, there is a low abundance and diversity of species on the seafloor in the embayment due to the highly active nature of the environment. Those species that are present, however, were found to be accustomed to regular disturbance due to regular wave activity.

Crabs, various burrowing worm species, cockles, clams and several snail species do inhabit the embayment. Their abundance typically increases with water depth, where the seafloor is less disturbed by wave activity.

Many of the burrowing species present were not found to be picked up during extraction because their burrows were deeper than the average 80-100mm that the drag head extracts to.

Species that were picked up by the drag head were found to have high survivability after going through the dredge process.

In fact, the ecological report found there was a low impact on species from sand extraction activities in the embayment. The research found little to no difference in the presence or abundance of species between currently extracted versus control areas where no extraction has occurred.

Seafloor Recovery

The research commissioned by McCallum Bros Ltd® found that overall sand extraction is having a less than minor impact on the seafloor in the Mangawhai-Pākiri embayment.

Sand is extracted through a drag head, which acts in a similar way to a vacuum cleaner running across the seafloor. This creates a small furrow 1.5 metres wide and up to 100mm deep.

Given the highly mobile nature of the embayment, where sand is continuously circulated, the seafloor was found to recover to surrounding levels in as little as 12 hours. In an average swell of 1 metre, the furrow is difficult to locate after one day in the nearshore extraction zone.

The applications with Council at the moment plan to spread extraction activity over the whole extraction area to minimise effects on the seafloor. This will extend the period between the drag head passing over the same area, maximising the seafloor and biota’s ability to recover between extraction events.

Future monitoring will also be able to accurately compare the extraction areas to control areas where extraction has never taken place, thereby providing further information on the effect extraction has on the seafloor.

Protecting the Coastline

Pākiri Beach is one of the most monitored beaches in the world and has been subject to intense monitoring since the mid-1980s.

During this period, no detrimental impact has been observed that can be attributed to sand extraction activities. Research has concluded the effects of sand extraction on coastal processes and erosion has been less than minor to immeasurable.

Pākiri Beach is subject to a constant movement of sand on and off the beach.

Storms, particularly in the winter, wash sand off the beach and into the nearshore area. During periods of calmer weather, wave action delivers the sand back onto the beach. This is part of the normal coastal process that occurs on every beach around the world.

When coastal erosion has been found to occur in the Mangawhai-Pākiri embayment, it has been found to be largely attributable to storm events around the time or shortly before a survey was undertaken.

For example, a significant extended storm event measured waves of up to 10 metres in May 2021. This storm was found to cause significant widespread erosion on beaches along the north and east coast of New Zealand.

Aerial photos from the last 50 years have found Pākiri Beach has grown seaward by an average of 22 metres. While the beach hasn’t grown every year due to seasonal variation, the long-term average growth is an average of 0.4 metres per annum across the embayment. This indicates that significant volumes of sand are still entering the embayment, despite extraction having taken place.