A Blue Mountains swamp, home to the endangered Blue Mountains water skink and the giant dragonfly, is rapidly collapsing as a consequence of cost-cutting decisions made by the Roads and Traffic Authority in 2009, according to council.
Council said the swamp, in Bullaburra, has collapsed due to water run-off from the Great Western Highway. It has also been affected by contaminated water, as shown recently by the Blue Mountains World Heritage Institute's swamp monitoring program
Blue Mountains mayor, Cr Mark Greenhill, said: "The government was warned - by council's environmental scientist and a swamp specialist - during planning for the highway expansion that diverting run-off into the top of the swamp would lead to its destruction.
"Alternative solutions were rejected at the time, on the grounds of cost."
But Transport for NSW rejected this. TfNSW director west, Alistair Lunn, said the Environment Protection Authority had conducted an investigation in 2014 at council's request, which concluded that the basin did not impact the hanging swamp and the basin reduced sediment and nutrients loads from the highway.
"The basin was constructed to the highest standard and was the most comprehensive solution available at the time. Any suggestion that a cut-cost option was chosen is completely false," he said.
Blue Mountains swamps are listed as an endangered Threatened Ecological Community (TEC) under the federal Environmental Protection and Biodiversity Conservation Act.
The sandstone-based peat swamps are ancient ecological systems that serve critical ecosystem services including holding water in the landscape during wet periods, and then slowly releasing it into the environment during drier periods.
The recent floods saw significant channelisation of the Bullaburra swamp, and the peat layer that formed over many thousands of years was washed away by the massive volume of water flowing into area.
"Unless something is done urgently, the swamp will cease to exist in a relatively short time frame," Mayor Greenhill said.
"Not only is the volume of the water a major issue, but the quality of that water is also leading to the degradation of the swamp's unique vegetation."
Monitoring of the swamp water carried out in recent weeks by Professor Ian Wright from Western Sydney University, in conjunction with the Blue Mountains World Heritage Institute's Swamp Monitoring program, has shown that high levels of phosphorous and other trace elements leached from the concrete used in highway construction is making the swamp's usually acidic water more alkaline.
Blue Mountains World Heritage Institute Executive Director, John Merson, said: "This has resulted in the swamp becoming weed-infested, severely impacting the native vegetation and wildlife that depends on its natural acidity. These include the rare and endangered Blue Mountains skink and giant dragonfly, once commonly found in this swamp."
"The Blue Mountains World Heritage Institute's swamp monitoring program has also found other concerns with the contamination of the water now flowing into the swamp.
Mr Lunn said TfNSW road projects used a system of water catchment and filtration to ensure runoff from state roads is captured, cleansed and released into the environment in a controlled manner.
TfNSW, council and the Blue Mountains World Heritage Institute are planning to meet to discuss the issue and possible ways forward, council said.
