Western Harbour tollway: What makes up the toxic sediment in Sydney Harbour

ABC News Online


Sydney Harbour

A new toll road could be built with links in Sydney Harbour, disturbing toxic sediment.


There are dangerous toxic industrial by-products lying at the bottom of Sydney Harbour that could be disturbed if a plan to build another underwater tunnel is approved.

A report marked ‘Cabinet in confidence’ and seen by the ABC and Fairfax Mediashowed that the preferred option for Sydney’s planned Western Harbour tollway would be to lay water-tight concrete tubes to make two tunnels on the harbour floor — one near Balmain and the other near Seaforth.

But to follow that plan, the environmental study said that more than half-a-million cubic metres of contaminated sediments containing toxic chemicals and heavy metals would need to be dredged, spreading those toxins throughout parts of the harbour.

So what exactly are the toxic compounds lying at the bottom Sydney Harbour and is there really anything to worry about?

Where is this happening?

Most of the dredging of harbour sediment would happen at a work site in White Bay, on the water’s edge of Balmain and just across from Pyrmont.

Nearby, a submerged tunnel would be laid across the harbour, disturbing the sea bed to the west of North Sydney.

At the northern end of the tollway, another underwater tunnel in the city’s north connecting Northbridge to Seaforth could also create a “plume” of turbid, contaminated water that could extend along a 4-kilometre radius at each location.

Thermal map of Sydney Harbour showing density of plume.

PHOTO Thermal map: Sydney Harbour will be affected by a spread of sediment, where the road crosses from North Sydney to Balmain. The density will be highest in the red region.

A thermal map showing the spread and density of turbid plumes

PHOTO A thermal map charts the spread and density of the sediment near popular waterfront areas between Seaforth and Northbridge. Red indicates higher density.

What’s toxic at the bottom of the harbour?

Dissolved in the dirt and sand are numerous chemicals that could cause harm to humans and other animals in the food chain, especially marine life.

“All of those bays like Iron Cove Bay, Lane Cove bay — they’re filthy places and they’re filled with the detritus of humanity which has been washed into the streams and the harbour doesn’t get flushed out,” professor of environmental sciences at Macquarie University Mark Taylor said.

Not every spot in Sydney Harbour is safe to catch and eat fish according to the Sydney Institute of Marine Science.

PHOTO While commercial fishing was banned in 2006, many recreational fishers still fish in Sydney Harbour.

Deadly toxic compounds found in the harbour — furans, dioxins and PCBs — are part of a group described as the World Health Organisation as the “dirty dozen”.

“These are the sort of substances you really want to avoid exposure to,” Dr Mariann Lloyd-Smith, senior adviser at the National Toxics Network, said.

“They’re highly toxic to liver and kidney function, highly toxic to the developing organism.”

Dr Lloyd-Smith said that dioxins could cause cancer and were “really, really nasty”.

In fact, the high levels of dioxins found in prawns fished out of Sydney Harbourcaused the shutdown of the commercial fishing industry in 2006.

PCBs have a similar toxic profile to the dioxins.

“These are some of the most toxic, persistent, bio-accumulative chemicals, contaminants that we know about,” she said.

Heavy metals of lead, mercury and cadmium, which Dr Lloyd-Smith described as “serious substances” are also in the harbour sediment.

There is even a global treaty formed to try and curb the environmental spread and stop the human health problems that are a result of the toxic properties of mercury.

“It affects the way our children grow, it affects their IQ, it affects their ability to reproduce successfully so it’s a very, very nasty heavy metal,” Dr Lloyd-Smith said.

How did they get there?

Most of these toxic substances are waste and by-products from the industries that bordered the harbour for more than a century.

Chemical plants, a gasworks and a power station were some of industrial activities that contributed to the problem.

PCBs were used in electricity energy generation to keep the transformers cool and would have been used at places like the White Bay Power Station, which opened in 1917 and was decommissioned in 1984.

“The legacy of old industrial processes that used PCB will be with us probably for eternity unfortunately,” Dr Lloyd-Smith said.

Other toxins which were outlawed in Australia because they affected animals’ reproductive cycles were TBTs, which were used as an antifoulant treatment on boats.

Who’s most at risk?

“The people that are most at risk would be the people who use the harbour, for fishing and recreational things, people who are in anyway exposed to sediment either through the marine food chain or direct exposure to sediment,” Dr Lloyd-Smith said.

Dr Lloyd-Smith was especially concerned about workers dealing with the material first hand.

“I hope the unions will be talking loud and long about the protection of workers if this idea goes ahead,” she said.

As for marine life, the report said that more than 70 threatened species are listed as at risk from the project, including fragile seagrasses which support more than 20 species of endangered seahorses and sea dragons.

Rare fauna, such as the critically endangered black cod, dolphins, sea turtles and little penguins could also face impacts.

Sailors and snorkellers were singled out in the Government’s document which said “increased turbidity may have adverse aesthetic and health and safety impacts on those users”.

Recreational fishers should probably not eat any of their catch if such a plan was to go ahead.

Professor Taylor said the risk could be managed with some common sense.

“I personally wouldn’t be eating fish out of there anyway,” Professor Taylor said.

Can the toxic matter be disposed of safely?

View from a cruise ship docked in White Bay at Balmain in Sydney Harbour

PHOTO There is no current air quality monitoring conducted in the White Bay area

That depends on who you ask.

The environmental assessment raises the possible safety pitfalls of such a major shakeup of the harbour sediment.

The dredged material would need to be brought to the surface and disposed of … somewhere.

The problem is there aren’t many ways to dispose of dangerous substances in Australia beyond putting it into the ground, or into the ocean.

The report has even proposed depositing it in “deep holes” within the harbour itself.

“We do not have the capacity to effectively destroy hazardous material in Australia which is a terrible situation for a developed country like Australia to find yourself in,” Dr Lloyd-Smith said.

“If you’re moving this you’re going to have air pollution … that dust will also include many of the contaminants we’ve just covered.

“To me it looks like a process that is too risky to go ahead with.”

Professor Taylor said all the risks of removing the contaminated material could be mitigated with proper strategies, including the possibility of toxic dust blowing into suburbs.

“They could put [the sediment] into sheds, they could cover it, they could put dust suppressant on that pile. They do all this stuff at mining sites all the time.

“All of this stuff could be fixed. It costs money, but that’s the expectation that the community and the Environmental Protection Authority will have.”

He said the community had the right to be concerned and should make sure they are represented when the project details are made public.