Battle over sand-dredging off the Pakiri Coast pits old foes against each other

A court case about sand-dredging off the Pakiri Coast is once again pitting old foes who've been at loggerheads for generations against each other.

They've slugged it out over its impact for decades and now they're playing for keeps.

They've been at each other's throats for decades - sand dredgers and concerned Northland residents, such as Richard Hill.

"I'm passionate about this because I don't believe we should be having this conversation," Hill says.

Both claim to have science on their side. McCallum Brothers and three other groups have gone to the Environment Court in an attempt to get consents to dredge sand off the Pakiri Coast for the next 35 years.

"It's been quantified to be something like three to four billion cubic metres and so we're taking a couple of hundred thousand cube a year. So in terms of the percentages it's a fraction of a fraction of a percent," Callum McCallum says.

Hill slid down the dunes as a boy more than 70 years ago. He says he's seen the erosion caused by dredging.

"Every bucketful of sand that goes out is one less bucketful of sand on our coast," he says.

But McCallum argues it's not even a drop in the bucket.

"The facts and measurement are probably a bit more accurate than a reminiscing about what it might be like. As I say the beach is a very mobile environment," he argues.

But opponents say the sand where they're dredging is replaced only from the shallows and the beach. And seven years ago, a court sided with that argument.

Ocean engineer and biologist Andre LaBonte has argued for decades there's a price to be paid for every grain of sand extracted.

"So there is no new sand coming into the system and so anything that is taken out is gone and it'll have to come out of the dune, out of the bank account," LaBonte says.

Eighty years ago, when Callum McCallum's grandfather first dredged this coast, the local iwi didn't want it. And they still don't. These days the company uses technology to back its claims.

"We do a lot of drone surveying and bathymetric monitoring of the bottom so we actually know what's happening," McCallum says.

A website built by the company claims the shoreline is actually growing.

"These sorts of things don't lie and we see that the beach in the last 50 years has actually moved seaward by 20-odd metres," McCallum says.

And every metre of this beach is crucial as fairy terns nest here and there are only 36 of the tara iti left.

"Since the 1980s the tara iti has teetered on the brink of extinction and the sand mining is actually affecting their nesting, their roosting and their breeding areas," says Diane Piesse, from the NZ Fairy Tern Charitable Trust.

But McCallum argues sand mining isn't a problem, predators and people are.

"And we can't control the people riding horses through the dunes or motorbikes or vehicles or picnickers or things like that and you know predators are the major problem," he says.

While local opposition is strong further north, in Auckland scores of construction businesses back McCallum arguing that Pakiri sand is vital to the cement that makes the concrete that builds the infrastructure - projects like the City Rail Link.

"The Sky Tower, Newmarket Viaduct, Waterview Tunnels, harbour bridge, museum. Just look round Auckland, our sand or Pakiri sand has gone into that sort of thing," McCallum says.

McCallum says Pakiri sand is not only clean, it's also the perfect coarseness for making high-strength 100-year concrete using minimal amounts of cement, thus saving CO2. And he says shipping straight to port saves thousands of truck journeys bringing sand from elsewhere.

But that doesn't wash with people like Hill.

"This is a case of preservation. We should be here, we're talking about climate change, we're talking about a whole raft of things that are detrimental to our coast. This is about protecting our coastline for our future generations," Hill argues.

Final submissions will be made to the court next year but everyone's expecting this latest battle to last far longer.