30 September 2009:
The successful remediation of one of Australia’s most
notorious contaminated waterways proves that even
heavily-contaminanted sediment and soil can be salvaged, an expert
from Thiess Services will tell the CleanUp 09 Conference in
Adelaide today.
Homebush Bay, situated in the middle of Sydney opposite the site of
the 2000 Sydney Olympic Games precinct, has been left heavily
contaminated by decades of industrial activity to an extent that
there are bans on eating fish caught there and in nearby waterways
because of the potential health risks.
However, a lengthy and ongoing remediation process is significantly
improving the ecology in the Bay and making the area safe for human
use again, according to John Hunt, Manager of Technical Services,
for one of Australia’s market leading remediation
contractors, Thiess Services.
Homebush Bay and the adjacent prime residential land on the Rhodes
Peninsula were contaminated over several decades with a
‘cocktail’ of organic contaminants, including
Persistent Organic Pollutants (POPs), such as DDT and dioxins, by
the operations of Union Carbide. Over time the POPs have
built up in the food chain so that fish caught in Homebush Bay are
unsafe for human consumption and a fin-fishing ban is in place for
the area.
“There has been a great desire to redevelop the former
industrial site into a high value harbour side residential
precinct. However cleaning up dioxins and pesticides in soil and
sediment is a complex process and remediation of the land and the
bay was considered too difficult for a decade or
more,’’ Hunt said.
“In the early 1990s, everyone in the remediation industry,
myself included, said it couldn’t be done. A decade later
thermal soil treatment technologies had been developed to the point
where we were able to tell people that it now could be
done.”
Several remediation strategies were considered to clean up the POPs
in the bay, including monitored natural attenuation, capping, and
removal followed by either landfilling or treatment. Removal and
treatment was eventually selected given the persistent nature of
the contaminants and their ability to migrate by natural processes
in the marine environment.
The remediation method used by Thiess Services involves dredging
the top half a metre of sediment from the bay and either thermally
treating the sediment (removing the POPs entirely) or placing it,
untreated, at a depth onshore, depending on contamination levels. A
clean shale cap is then placed into the dredged area.
The dredging footprint is located parallel to the shoreline of
the former Union Carbide and adjoining Allied Feeds sites. It was
initially designed to ensure the reduction of POPs was sufficient
enough to reduce contaminant transmission to a level where fish
from the area would be safe to eat and new housing developments had
a clean common area in front of them. “Following consultation
with local residents it was later extended to remove additional
contaminant hotspots further into the bay,” said Hunt.
“Our objective was to make the bay safe for humans and the
environment, and to see the fin-fishing ban lifted.”
Although it will require a period of monitoring before the fin
fishing ban is removed, the bay will be safe for human contact and
development of the neighbouring land has begun, Hunt said. The
success of the remediation shows that polluted sites around
Australia that have previously been in the ‘too hard
basket’ could be cleaned up with new technology, according to
Hunt.
“This project has succeeded because the timing was right, the
technology was ready and there was a large collaborative effort and
will to succeed, involving environmental groups, the New South
Wales Government, residents and industry,” he said.
“As Australia emphasises its focus on sustainability in the
future, it will be important to remediate these sorts of
contaminated sites in prime locations, as it’s better to
clean up and recycle what we have, rather than expand the footprint
of our cities even further.
“The lesson that Australia can learn from the successful
restoration of Homebush Bay is that polluted areas once deemed
‘unusable’ should be re-examined as new technology
evolves that allow them to be cleaned up their value restored.
“This is the first significant remediation effort in the
Sydney harbour, and the works are already greatly benefiting the
city. This shows that sites that have been badly contaminated in
the past are not necessarily worthless.”
John Hunt will deliver his paper at 11.10 AM on Wednesday September
30, 2009.
The CleanUp 09 conference is being hosted by the CRC for
Contamination Assessment and Remediation of the Environment at the
Hilton Hotel, Adelaide from September 28-30.
More information:
John Hunt, Manager of Technical Services and Remediation, Thiess
Services,
ph +61 419 617 148
Peter Martin, CRC CARE communication, ph 08 8302 3933 or 0429 779
228
Peter.martin@crccare.com
