The Hauraki Gulf: Aucklarnd's dumping ground

Forest and Bird, Volume 22, Issue 4, 1 November 1991, Page 16

The Hauraki Gulf: Aucklarnd's

dumping ground

by

Fiona Edwards

"I have seen Napoli la bella and didn’t die; have gazed on panoramas from Alpine and Apennines summits . . . but. . . Waitemata’s waters . . . stood forth, preeminent, unequalled, unsurpassed." Sir John Logan Campbell, 1817-1912 HE HAURAKI GULF stretches from the mangrove-fringed fingers of the Upper Waitemata harbour, past the sprawl of Auckland City and out over the sparkling water to the Barrier Islands. With ample harbours and idyllic islands, the Hauraki Gulf’s 7,450 square kilometres provide a unique coastal haven for recreation. Auckland has more boats per capita than any city in the world. Every Sunday afternoon the harbour resembles a motorway as boats dodge one another racing back to their weekday moorings. Over forty islands are scattered across the Gulf, varying in size, topography, geology, vegetation cover, wildlife and accessibility. Beneath the waters of the Gulf an even greater range of species and habitat diversity exists. From the mud flats that provide extensive feeding areas for birds, to the bladderkelp fringe and kina flats of sub-tidal zones, down through the ocean depths to underwater forests of Ecklonia and sponge gardens, the Hauraki Gulf provides a range of habitats with a vast array of marine plant and animal life. This complex mosaic of life is supported by the microscopic phytoplankton living in the lighted surface layers of the sea. Moving with the ocean’s moods, these plants are the mainstay of all life in the sea. Marine animals eat either phytoplankton

or other animals which are dependent on these minute plants for food. Along with phytoplankton, the sea floor, with all its benthic richness, is one of the marine ecosystem's key production areas. The thin, living skin of the sea floor is like the top-soil found on land: immensely fertile, fragile and minute in size when compared to the vastness of the waters above. The sea knows no boundaries. Its productivity and food chains depend upon clean water and the health and diversity of life on the sea floor. In civilisation’s haste to develop, grow and expand, we have encroached upon the sea — redesigning the boundaries between land and sea, disgorging sewage into oceans, dumping lifeless and toxic . sediments scraped off the land into the sea, and filling in shallow estuaries where marine productivity is highest. As the Roman poet Horace wrote two millenia ago, as he despaired the dumping of marina dredgings into the sea, "Contracta pisces aequora sentiunt" — the fishes feel the seas contracting.

History of dumping in the Hauraki Gulf

Over the past century, the sea floor of the Hauraki Gulf has been the recipient of over six million cubic metres of sediment dredged from Auckland’s wharves and marinas. Around the foreshores of the Waitemata Harbour a similar amount has been dumped to reclaim land from the sea. Twelve million cubic metres of sediment over a century is a lot of dirt enough to build a new island the same size as

Browns Island or Pakatoa. Dredge dumping in the waters of the Gulf became a pressing public concern in 1987 when material was dumped near Browns Island. The dumping of 143,000 cubic metres of dredge spoil at a site near Browns Island was ecological vandalism. Over 150 hectares of seabed surrounding the dump site was visibly affected, with a marked reduction in the diversity and abundance of marine life. Dr Roger Grace, a biological consultant with over 25 years of experience in coastal and marine environments, undertook the post-dumping ecological survey of Browns Island. He found that in the most adversely affected area 97% of marine life had disappeared from a 21 hectare area of the seabed. In assessing the future ecology of the dump site, Dr Grace predicted that marine life would recolonise the area but stated "it was unlikely that the previous populations of marine life would be restored." Some marine life would return once the dumping ended but would lack the diversity and richness of the original community.

Proposals to dump a century of dirt

Maintenance dredging is needed if Auckland’s international container port is to continue operating. Each year, goods to the value of $10.5 billion move across Auckland’s wharves and the port generates an estimated $2.5 billion in revenue for the region. Groups concerned about the dumping accept that dredging is needed if the port is to remain viable. There is,

however, very strong disagreement about where sediment dredged from the port area should be disposed. In 1988, at the request of the Regional Water Board, the Ports of Auckland Ltd (the successor to the Auckland Harbour Board) assessed the environmental effects of decades of dredge dumping at the Rangitoto site. They found that there was a change in the physical nature of the sea floor, detectable changes in the chemical composition of the sediment within the dump site, and that there had been "disturbance" to benthic communities buried by the sediment. Local divers point out that

before dumping occurred at the Rangitoto site, the area was heavily stocked with crayfish. From July to September every year, thousands of female cray bred in the area. On the seaward side of the dump © zone, scallop beds flourished. Within two weeks of the dumping, most of the scallops were dead — just empty shells on the sea floor. Within a month, the crayfish living along the rocky foreshore had gone. The Auckland Regional Water Board considered the port company’s findings and decided that the north Rangitoto site would be unable to cope with the intended disposal of twelve million cubic metres of

sediment over 15 years. The Regional Water Board suggested that the port company investigate alternative long-term disposal sites. In September 1990, the port company applied for two water rights, one for 270,000 cubic metres of maintenance dredgings from around the wharf areas and a second, much larger water right, for 11.8 million cubic metres from capital works — sediment dredged from the Rangitoto channel. In total, the two water rights cover 12 million cubic metres of sediment — an amount equal to about 38,000 houses full of silt. The port company intends to dredge and dump this

sediment into the waters of the Gulf over 15 years. After two years of investigation, the port company proposed that this mountain of dredgings should be dumped at a new 400 hectare dump in 30 metre deep water at a site seven kilometres south east of Tiritiri Matangi Island, three kilometres north of the Noises Islands. One month later, in October 1990, the Auckland Regional Water Board heard evidence from the port company and from 26 objectors, including Forest and Bird. The objectors had less than one month and, in some cases only a matter of days, to prepare

their objections. It was hardly surprising that the Regional Water Board, overwhelmed by the weight of the port company’s evidence, granted a water right for the disposal of 270,000 cubic metres of wharf dredgings. In a minor victory, objectors requested that the Regional Water Board not hear objections to the second water right application as these capital works dredging were not urgent. The Board compromised and agreed to hear evidence from the port company but deferred hearing objections so that objectors would have more time to prepare evidence. The conclusions of the Regional Water Board make interesting reading. The Board accepted that the level of risk posed to spawning fish, their eggs and larvae was unknown. They also considered that the port company’s evidence was lacking in

regard to the issue of water clarity (turbidity) and the response of fish to the discharge of sediment. In order to allay some of their concerns, the Board imposed a restriction on the months that the port company can dump dredgings. During November to January each year, disposal of sediment will be prohibited because of the unknown level of risk posed to snapper breeding. Only one snapper egg per million survives to adulthood. It is highly probable that a barge load of sediment dumped on top of the spawning ground will not increase their chances of survival. The decision of the Regional Water Board was subsequently appealed by the New Zealand Underwater Association, Hauraki Maori Trust Board, Auckland City Council and the Maruia Society. In the months that led up to the Planning Tribunal hearing, the port company became increasingly alarmed about delays. Their political scramblings could be heard throughout the city. In May 1991, the new Mayor of Auckland, Les Mills, met with the port company and then persuaded Councillors to overturn their earlier decision and withdraw the Council's appeal. A process of attrition then followed with the Hauraki Maori Trust Board being denied appellant status and the Maruia Society withdrawing from the case. The weight of the appeal fell on the NZ Underwater Association, represented by Max Hetherington, a recreational diver from Wellington with a love of Auckland’s Gulf, and the Hauraki Maori Trust Board, reentering the case as an interested party. The appeal was heard before the Planning Tribunal in July August but the Tribunal had not released its findings at the time of writing.

On-site impacts

The most immediate and devastating impact of sediment dumping would be felt by the marine life found at the dumpsite. The surface of the proposed site is fine, silty mud and is marked and sculptured by animal burrows and tracks, indicating the presence of abundant benthic (bottom dwelling) life. Dense populations of brittle stars and heart urchins are found at the site and nearby are large beds of scallops. When sediment is dumped at the site, most benthic life will be killed. Dredgings smother marine life on the sea floor, creating a virtual marine desert. Any

marine life attempting to recolonise are killed by the repeated smothering of sediment as dumping continues. The effects on fish larvae, phytoplankton and zooplankton living in the water column at the dump site are largely unknown, but increased sediment concentrations are not generally beneficial to any marine life. Since the dump site is centred within a major breeding ground for at least 30 different species of finfish, including snapper, the impacts of sediment dumping on fish larvae may be severe.

Impact on the Noises Islands

The beguilingly named "little nuts" or Noisettes, since anglicised to Noises Islands, are 15 nautical miles from downtown Auckland. These islands (pronounced "‘Noyzees") are only three kilome-

tres from the proposed dump site. But, unlike the dump site itself, the Noises are characterised by rocky reef marine communities. Habitats range from open rocky bottoms which provide an ideal habitat for octopus, to extensive beds of green-lipped mussels, paua and scallops through to kelp beds and spectacular displays of coloured sponges and jewelled anemones. Reef fish, crayfish, conger eels and finfish abound in this underwater world, which is adapted to low levels of suspended sediment. Sediment drifting from the dump site threatens these communities. The port company acknowledges that two to four percent of the dumped spoil will end up in suspension on release from the barge and that this sediment will travel from the dump site. Some of this sediment could travel in the direction of the Noises Islands. If this occurs, marine communities will be destroyed, disrupted or displaced. In a rock reef environment, the gradual effects of increased sediment could be nearly as detrimental over time as direct dumping.

Toxic effects

An added problem with the marine disposal of wharf dredgings is the potential these dredgings have to create persistent problems due to the presence of toxic contaminants. The sediments from Auckland’s port area contain concentrations of copper, lead and zinc above background levels and elevated levels of DDT, TBT (tributyl tin) and mercury. It is well documented that mercury a heavy metal and DDT accumulate in the tissues of marine

organisms, especially long-lived animals such as sharks and snapper. The antifouling compound, TBT, has been described as the most toxic substance ever deliberately introduced into marine waters. The effects of TBT on marine organisms include reduced growth rates, larval mortality and shell deformation. The port company has developed a sediment testing protocol which is designed to assess the toxicity of sediments and any samples that are "too toxic" for marine disposal will be dumped on land. Unfortunately, they do not have any approved land-based disposal sites and their protocol is less than adequate.

Alternatives

The port company has investigated a number of alternatives during a two year study. Over 16 land based disposal sites were considered but only the Mt Wellington quarry had the capacity to accommodate 10 million cubic metres of dredgings. Mt Wellington is within the six kilmetre economic limit for pumping dredge slurry from the wharves. A combination of landbased disposal sites could be used rather than just one site. They also investigated possible harbour margin reclamations and

island creation schemes but all were discounted for a variety of reasons, including cost. Land disposal options are considerably more expensive than marine disposal options. The port company’s figures indicate that it would cost the company $25.00 per cubic metre to dispose of sediment at the Noises site and approximately $75.00 per cubic metre to dump the sediment on land. Real alternatives to dumping at sea do exist and are being used successfully overseas. In Glasgow, the Clyde Port Authority has combined with the University of Strathclyde to devise the techniques and technology to process 100,000 tonnes of sediment per annum into soil. The sediment is mixed with compostable materials, dewatered and desalinated then used as a landscaping soil. The Clyde Port Authority is effectively recycling their sediment and by treating it as a resource, they are able to sell the soil and operate the plant at a profit. This type of process is ideal for non-toxic sediments. However, contaminated dredgings should still be disposed of in a landfill where leachate is contained and treated. When the Planning Tribunal make their decision on the water rights for the Auckland Port Company's dredge dumping applications, that will not be the end of the matter. The Minister of Transport, Mr Rob Storey, is also required to give his consent to a dumping permit under the Marine

Pollution Act. The Minister has to consider wider matters than those considered by the Planning Tribunal, though there is no formal process for the public of Auckland to object under this Act. Mr Storey may consider that land disposal is preferable — then let the fish dare to complain! ¢