Defence

Corporate Services and Infrastructure

In the business of protection

Navy looks after Sydney Harbour

Pollution prevention is one of the major goals in Defence's environmental agenda and one in which the department is taking a proactive role. Susan Elekessy explains how Defence and Navy are protecting Sydney Harbour and the environment in general.

The Captain Cook Graving Dock, built in 1942 out of granite, is the largest dry dock in the Southern Hemisphere, with its own Commonwealth Heritage Listing.
Photo provided by Public Affairs

The Royal Australian Navy's Fleet Base East is located at Garden Island, in arguably one of the world's most beautiful harbours. Australia's Navy has called Sydney home since the time of the First Fleet and shares a comfortable and trusted relationship with Sydneysiders while providing significant economic benefits to the local community.

The number of waterfront industrial sites occupied by Navy in Sydney has reduced significantly in recent years, particularly following the closure of Cockatoo Island Dockyard and the former submarine base at Neutral Bay. Garden Island now remains the prime location for naval and commercial shipping repair and maintenance in Sydney.

Unfortunately the pristine Harbour environment can occasionally be compromised by contamination emanating from various marine users. The fact that Sydney Harbour is used by a wide variety of vessels—including large cargo and cruise ships, oil tankers, ferries, commercial pleasure craft and smaller private vessels, plus Navy warships and support craft—can result in waste products, including pollutants, ending up in the Harbour.

The compound, tributyl tin (TBT) is one of the waste products that can pose a threat to our environment. TBT was used as an 'anti-fouling' biocide in paints applied to the underwater sections of ships' hulls. Anti-fouling paints are designed to release small amounts of biocide that kill marine organisms that may otherwise settle on the ship and increasingly result in reduced speed and fuel efficiency due to underwater 'drag'.

Sadly, although TBT was a very effective anti-fouling compound, it was found to persist in the natural environment and to affect the growth of some marine organisms.

The use of TBT in anti-fouling paints for naval vessels is now being phased out completely in accordance with internationally agreed requirements regarding the prevention of pollution by ships. The Navy is voluntarily complying with the International Maritime Organisation (IMO) directives with respect to pollution prevention, despite sovereign warship exclusions. However, Defence will have a legacy to manage TBT-based paints on our ships until all TBT paint is removed from our entire fleet following major refits.

Although underwater paint schemes on ships generally shed very small amounts of TBT, ships must be repainted from time to time. Before repainting, the old paint must be removed by the use of high-pressure spraying of the hull with very small, highly abrasive particles of garnet that chip the paint off in small granules. The contaminated solid blasting waste could be contained for approved land-based disposal, but contaminated water would not be processed or filtered before it was released, thus presenting the risk of possibly polluting local waterways, and the surrounding sea and marine life.

For Navy ships based on the east coast, this task of stripping paint is undertaken at Garden Island in the Captain Cook Graving Dock built in 1942. It is also the largest dry dock in the southern hemisphere and has its own Commonwealth Heritage Listing. In the past, waste water from ship's hull cleaning was released under licence into the bay outside the dry dock.

In response to increasingly stringent requirements of both the Commonwealth and the New South Wales (NSW) Environment Protection Agency (EPA), and consistent with Defence's proactive and committed environmental mission, alternatives to releasing pollutants into the harbour were investigated.

Several stakeholders were directly involved in these investigations, including the NSW EPA, leading environmental experts both from Defence and industry, Navy representatives and representatives from ADI Ltd, which manages and coordinates maintenance and other activities conducted on Navy's behalf at Garden Island.

After significant research and an investment of more than $5 million, Defence has commissioned a world-class waste-water treatment plant (WWTP) for the site. The WWTP captures the waste water from the dry dock and filters the pollutants so that they can be disposed of appropriately. The WWTP effectively captures a range of pollutants in the water, including traces of TBT, rust, heavy metals like copper and lead, grease, oil and fine garnet blasting grit.

The way in which the WWTP works is to pump the polluted water through a series of processes that filter and bind the pollutants to polymers. The encapsulated polymers are then separated and taken to certified waste sites, and the clean water is disposed of into the sewer system through a Trade Waste Agreement with Sydney City Council.

The key processes are outlined below. Captured water from the dry dock is pumped to the treatment tank and treated in the following sequence:

• The water is put through a 'grit separator' to remove solids, which are bagged for appropriate disposal off site.
• The water then goes into a 180 cubic metre holding tank installed adjacent to the treatment plant.
• It is pumped through 'Dissolved Air Flotation' filters to remove any heavy metals and suspended material, which are then bound to polymers for disposal off site.
• The water is filtered through a sand pre-filter for the removal of fine particles.
• The water is then run through a 'granulated activated carbon' filter, where minute levels of organotins such as TBT are removed.
• Finally, the remaining water is processed through an oily water separator to remove any remaining oily water before discharging to sewer.

This project illustrates clearly that Defence is making a real difference to environmental outcomes at Garden Island. The next step will be a dredging project to maintain the operational capability of the wharves and remove TBT-affected sediments.

Defence always strives to work cooperatively with State and federal agencies, key stakeholders and industry leaders to ensure that the best, often leading-edge, solutions are found to sometimes-complex environmental challenges. Such solutions may well have valuable application in other commercial areas. Consequently, Defence and ADI have a very productive relationship with the NSW EPA, with the ADI and Defence relationship being held up as an example for other commercial and public industries.

Defence and Navy's commitment to managing environmental pollution doesn't just stop at capturing pollutants once they are generated. Pollution prevention is one of Defence's key goals, which include:

• reducing waste generally;
• researching and developing products that contain fewer and preferably no harmful components for both the environment and humans;
• seeking products that generate less or no pollution; and
• discovering and implementing different techniques of undertaking certain pollution-generating activities.

For further information on the WWTP, or pollution prevention in Defence generally, have a look at the Defence environmental website at www.defence.gov.au/environment or contact susan.elekessy@defence.gov.au.

Susan Elekessy works in the Environment, Heritage and Risk Branch, Corporate Services and Infrastructure Group.

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