Marine mammals spared rock blast in Hauraki Gulf

By MATHEW DEARNALEY

Whales and dolphins seeking sanctuary in the Hauraki Gulf have been spared the risk of being blasted out of the water to allow more container super-ships into Auckland.

A barge-mounted backhoe dredger with extra powerful teeth has ripped about 15,000 cu m of rock from the Rangitoto Channel, removing any need for high explosives opposed by environmentalists.

The port company still has almost half a million cubic metres of sea bed to dredge from the channel, to widen a tidal "window" for 280m-long ships, capable of carrying up to 40 per cent more containers than traditional vessels.

The project will cost up to $40 million in tandem with waterfront land reclamation.

But the trickiest part - removing all that hard rock known as Parnell grit - is over, completed in a five-month operation by local contractor Heron Construction.

New-generation ships have started calling at Auckland on a restricted basis governed by tides.

The port company feared losing business to other ports unless it could deepen the channel from 11.2m to at least 12.5m. This could have cost Auckland almost 20 per cent of its total container volumes.

A resource consent application to blast the rock was initially opposed by seven organisations, including fishing firms and charter boat operators understood to have been compensated in confidential settlements with the port company.

The only remaining opponent before the Minister of Conservation approved a resource consent was the environmental group Friends of the Earth, which won the right to be consulted on marine mammal protection measures if blasting was required.

Port company infrastructure manager Ben Chrystall said the company was committed from the start to using alternatives to blasting if possible.

But Friends of the Earth co-director Bob Tait said an initial proposal by an Australian consultancy scoffed at the ability of local contractors to do the job, especially without blasting the rock.

He said the Australian proposal had been for gelignite charges of up to 25kg to be dropped into shallow drill holes, with little capacity for the rock to absorb the blasts, and for operations to be allowed 24 hours a day for up to six months.

Environmental consultants told the port company that if blasting took place, about half the fish within 25m of the blast zone might be killed or injured by pressure waves, and the lungs of marine mammals might burst.

So the port company had agreed to post observers near the site with orders to stop blasting if any marine mammals went within 1000m of it.

Mr Chrystall said extra measures agreed to with the Friends of the Earth had established a benchmark for best modern practice.

Mr Tait said blasting would have created a significant precedent for the Hauraki Gulf Marine Park, in which the Department of Conservation had reported sightings of species hunted by Japanese, notably Brydes and minke whales.