Concrete companies want to take four times more sand from the Kaipara Harbour as eastern beaches get protection from sand mining.
With sand extraction now banned at Pakiri Beach and Mangawhai north of Auckland on the east coast, Mt Rex Shipping and Winstone Aggregates say they need to increase the take at Kaipara by thousands of cubic metres a year.
A hearing on new permits begins today at Auckland Regional Council but staff have already recommended they be granted.
The companies say they need more than 300,000 cu m a year immediately, rising to more than 800,000 cu m in the second half of the 20-year consent being applied for.
Currently they take about 180,000 cu m a year.
The applications come as companies mining at Pakiri, where about 76,000 cu m of sand a year is taken, and at Mangawhai, are refused further permits by the ARC and the Minister of Conservation. The Pakiri decision is expected to be appealed.
ARC coastal project leader Andrew Benson said staff recommended the Kaipara applications be given because huge amounts of sand were generated in the harbour while extraction at Pakiri and Mangawhai was not sustainable.
Pakiri was a "closed" ecological system and the sand resource limited.
"Pakiri has very high environmental values. We don't have many beaches left near Auckland where the full dune system has not been modified," he said.
"We are acutely aware Kaipara too has environmental values. It's one of those balancing and weighing-up decisions that has to be made."
Mt Rex has been taking sand at Kaipara since 1990 and Winstone since 1997. The sand is pumped aboard barges and coarser shell and other material discharged back into the sea.
The sand is used in ready-mix concrete, precast concrete such as pipes and in paving slabs, building blocks and asphalt.
Mt Rex has stopped sand mining at one Kaipara site, leaving it 60,000 cu m a year short. The company says it needs 150,000 cu m a year rising to 450,000 cu m for three new concrete manufacturing plants.
Winstone, a division of Fletcher Concrete, will have to stop mining sand from the Waikato River when consents expire in the next five to 10 years and the company says it needs 165,000 cu m of sand "immediately", rising to 350,000 cu m a year over the 20-year consent.
According to scientists who undertook a four-year sand study supported by the companies, millions of cubic metres of sand flow into the Kaipara Harbour each year, buffering the effect of sand mining.