Community in fighting mode over dredging

By CLAIRE TREVETT

A coastal community is fighting to halt dredging of sand near an environmentally fragile spit which is home to one of New Zealand's rarest birds.

The sand is dredged from the Mangawhai Harbour entrance and used for Auckland's construction industry.

Sea Tow and Norsand have applied to take up to 1.08 million cu m of sand from the harbour over the next 20 years. The Northland Regional Council hearings committee is considering arguments on the applications this week. The area of the consents are near the northern end of the Mangawhai spit, which is administered by the Department of Conservation. It is listed as a marine protection area and is a breeding ground for the rare fairy tern, the New Zealand dotterel and the Caspian tern.

The Mangawhai Harbour Restoration Society is concerned that erosion would destabilise the dunes, causing a repeat of the breach of the spit. The spit had already breached in 1978, closing off the northern inlet, and the society spent $1.8 million restoring it in the 1990s.

However, the dredging companies say that monitoring has been unable to show the mining is doing any harm.

Of 248 submissions, 243 were against the proposal, including those from Kaipara District Council, the director general of the Department of Conservation and local iwi.

The society obtained the opinion of Professor Bob Dean of the University of Florida's civil and coastal engineering department, who said New Zealand was the only developed country he knew that allowed sand mining close to the shore for anything other than beach nourishment.


Engineer Peter Riley said current signs of erosion at Mangawhai mirrored the erosion that had destabilised Omaha's dunes.

Stephen Westgate, consultant for Norsand and Sea Tow, said monitoring did show some erosion at the northern end of the sand dunes. However, he said changes were from natural events.


A report on the applications by the council's coastal consents manager Allan Richards and Niwa's Douglas Ramsay recommended mining be phased out to prevent long term damage. They suggested a five-year consent so supply would not be interrupted and to give the companies time to move their operations and apply for any new consents.

The Conservation Minister will make the final decision.

The mining companies were given original consents for 10 years in 1993, allowing them to mine up to 5000 cu m of sand in any month but no more than 25,000 cu m over any 12 month period.

The companies are now asking to mine up to 6000 cu m a month, up to 27,000 cu m in any 12 month period for 20 years.