The country’s first major manufactured sand operation is due to start operation within weeks to supply Auckland and Waikato concrete manufacturers. From AQA News/Q&M magazine February 2024.
Kaipara’s Brookby Quarry announced its plans in late November, by which time it already had crushing equipment from the US and Northern Ireland on site and specifications that met concrete market requirements.
Steve Riddell, Kaipara’s managing director, says $12.1 million will have been spent when stage one of the project starts seeing 300,000 tonnes of sand being produced each year using greywacke from Brookby. If demand is confirmed, a second stage will be ready in a further year or so’s time at the cost of $5.1 million.
At 600,000 tonnes, this would meet about 40-45 percent of the Auckland/Waikato sand demand.
Asked if the project was designed to compete with natural sand producers such as McCallum Bros, who extract sand off the north Auckland coast at Pakiri, Steve Riddell said no.
“We think this is an enhancement of the market given the complications of river and sea sand.”
McCallums has faced protracted opposition to renew its Pakiri consents. Currently, Brookby is producing a blend of imported natural sand and minus 6-7mm aggregate, so new synergies were possible. Steve Riddell also points to rising demand for sand given infrastructure needs.
“We are a family business and take an inter-generational view of the infrastructure required for Auckland/Waikato – it’s only going to increase sand demand.”
Kaipara used its own staff to develop its own wet process for processing the greywacke into sand.
“They’ve done an outstanding job,” says Steve.
Much sand processing is done in a dry process. Going wet has a number of benefits.
“Obviously you are trying to avoid dust. But doing it wet is also related to the geography of the rock.”
Steve says a wet process is also less capital intensive than dry, which also requires crusher dust that isn’t common in our quarries, including Brookby.
The initial feed stock will be 750mm before being reduced to the required 3.2mm. Greywacke has some impurities which could be washed out. Some 600,000 litres of water will be recirculated every hour and the fines dried and blended back into other quarry products.
Central to the development is a major mains upgrade, due for completion this month (February) that will provide an extra five megawatts of electricity, so no diesel is used for processing.
“This is sustainable sand.” Steve adds, and the sand has already been trialled with key concrete manufacturers meaning specifications and quality requirements have already been met.
He says the price of the sand is a commercial matter, but would be similar to what the concrete companies pay for other quarry materials.
If they wished, trucks would be able to visit Brookby and take a load of sand and a trailer load of aggregates to complete a mix for concrete.
Brookby’s annual production of around 2.8 million tonnes is about 30 percent of Auckland’s total production.
It’s currently designated for expansion under a fast-track resource consent that has been passed from the previous government to the new one. Steve says the company’s investment in sand would have proceeded with, or without, the fast-tracked expansion.