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Airport Releases Independent Reports

An independent review of Darwin International Airport’s (DIA) water monitoring results has found faecal bacteria levels are similar to those found in Darwin creeks affected by urban stormwater runoff, Chief Executive Officer Ian Kew said today.

“The review found that bacteria levels fluctuate with the seasons, with the main causes likely to be from animals, rotting vegetation and stagnant water,” he said.

DIA last year sought two audits of its water monitoring by independent researchers at Charles Darwin University (CDU), along with any recommendations on how the airport could improve its environmental protection and water monitoring.

One review covered hydrocarbon monitoring data from 2000 to 2016, while the other analysed faecal bacteria results from upper Rapid Creek from 2009 to 2016.

The faecal bacteria report by Charles Darwin University’s Research Institute for the Environment and Livelihoods analysed 191 surface water samples collected from three creek sites and five stormwater drains along Rapid Creek.

There were large variations in readings, which peaked after the first major rain of the season, likely to be caused by rain stirring up sedimentation in the creek.

The study found that elevated levels of E.coli and Enterococci had been found in 2010 to exceed ‘warning’ trigger levels set by the (then) Department of Natural Resources, Environment and the Arts (NRETAS) Darwin Harbour Water Quality Objectives for Rapid Creek. However a similar percentage of examples above trigger levels were found in other monitored urban creeks such as Vesteys Creek. A higher percentage was found in Mindil Creek.

The report also found that high E.coli counts in Rapid Creek water were reported in 1982, before major airport development. The 1982 report identified wildlife in Marrara swamp as a possible source of elevated counts in upper Rapid Creek.

There were higher levels of bacteria in the stormwater drain behind Darwin Airport Resort. CDU’s review highlighted that likely key contributors are wildlife, dogs and cats frequenting the area, birds, frogs and nutrients released from decomposing vegetation, and could also include human sources (which would require more specific testing).

Other possible contributions could have been from organic fertilisers or manure used at the resort. Works to the drain in late 2015 have significantly reduced bacteria levels.

“All Darwin Airport sites are connected to Darwin’s sewerage system, so we believe any bacteria found in Rapid Creek is from plants and animals,” he said.

The report says that E.coli are a bacterial species and a natural part of the gut of warm-blooded animals, and only a few strains cause disease.

“To put this in context, the Rapid Creek catchment covers 28 square kilometres and covers 13 Darwin suburbs. Rapid Creek borders the 3.11 square kilometre airport lease, most of which sits in the Rapid Creek catchment. While upper reaches remain relatively intact, large parts of the catchment have been cleared for a range of activities and water runs into the creek from hundreds of properties,” Mr Kew said.

The airport monitors hydrocarbons in nearby surface water due to the amount of fuel stored on airport land. The CDU review of the airport’s hydrocarbons monitoring found all samples since 2004 were below guidelines and the detectable limit and it was unlikely there had been any toxic levels over the past 12 years.

Mr Kew said the reviews did not cover the issue of firefighting foam as this was an issue being dealt with collaboratively by the federal Government and relevant state and territory agencies.

Background

Rapid Creek is the largest freshwater system in urban Darwin. It originates in the Marrara swamp east of Darwin Airport and flows into Darwin Harbour at Rapid Creek Beach. The creek and adjacent park land are used mainly for recreational activities, swimming and harvesting aquatic foods.

Since 2000, Darwin International Airport has engaged an independent environmental consultancy to conduct water monitoring four times a year from Rapid Creek and stormwater drains in the upper catchment and around the airport.

These results are given to the Environment Protection Authority and, until it was abolished, were also given to the Rapid Creek Advisory Committee. They will be provided to the recently re-established Rapid Creek Water Advisory Committee, of which DIA is a member.

The airport’s environment strategy focusses on minimising the impacts of development and activities on airport land, with stringent guidelines for airport tenants and regular water quality monitoring.

Environmental commitments include a conservation zone along Rapid Creek as an additional buffer zone, and work with Landcare groups, specialist conservation management professionals, and other land owners to improve the area.

“When it comes to monitoring our environmental impacts, we have to meet high standards imposed under the Federal Airports Act,” Mr Kew said.

Media contact: 
Jodi Linnett 
Executive Assistant to CEO, NT Airports 
(08) 8920 1808 | jodi.linnett@ntairports.com.au