‘Inadequate’: Experts take aim at gaps in Beaches Link documents – Sydney Morning Herald

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The state’s transport agency has failed to adequately assess the risks posed to groundwater, creeks and seawater by the proposed multibillion-dollar Beaches Link motorway tunnels in northern Sydney, independent experts have warned.
University of NSW specialists, hired by the Department of Planning, found shortcomings in Transport for NSW’s report into the impact the tunnels from Cammeray to Balgowlah and Seaforth will have on waterways.
The Beaches Link motorway tunnels will cross Middle Harbour between Northbridge and Seaforth.Credit:Wolter Peeters
They cited “inadequate estimates” of the extent to which streams and creeks will potentially fall due to groundwater infiltration, while describing statements in the report that drops in water flow are “unlikely to result in a complete loss of aquatic habitat” as unacceptable.
The reviewers also took exception to “historical reports” on water quality cited in the transport agency’s environmental impact statement, noting that many of them were over a decade old.
And they warned that it has failed to adequately address the potential for water quality at Middle Harbour to deteriorate due to the tunnel between Northbridge and Seaforth changing tidal flows.
The Middle Harbour crossing will be built from prefabricated tunnel sections, which will be lowered into place from the surface.
A residents group said the peer reviews validated their concerns about the inadequacy of Transport for NSW’s assessment of the Beaches Link project.
Balgowlah Residents Group spokesman Terry le Roux said residents had serious concerns the project would lower the water table by between 10 and 20 metres in parts of Seaforth and Balgowlah, which would threaten large trees and leave creeks to run dry.
“This damage is real and it’s serious. We really have to make sure that all of the concerns and risks are addressed,” he said. “The project goes through some very environmentally sensitive areas.”
The documents detailing the experts’ concerns were released to the residents group by NSW Planning following a request under freedom of information laws.
Residents are concerned about the impact the motorway project will have on waterways in and around Middle Harbour.Credit:Wolter Peeters
The environmental impact statement for the Beaches Link, which was released last December, said there was potential for a drop in water flows during construction and operation of the project, namely at Flat Rock Creek, Quarry Creek and Burnt Bridge Creek.
It cited modelling that showed that the project could lower base water flows in the Burnt Bridge Creek, which runs from Seaforth to Manly, by up to 96 per cent.
Residents are set to air their concerns about the project during a parliamentary inquiry on Friday into the Beaches Link and the Western Harbour Tunnel, which will be built separately.
Transport for NSW said extra modelling and analysis of potential environmental impacts from the Beaches Link project had been undertaken, which demonstrated “minimal impacts on surrounding groundwater, creeks and seawater”.
The agency said a “sill effect” from the immersed tunnels on Middle Harbour would be similar to “already occurring natural events, such as after heavy rainfall”.
“All Transport for NSW projects have robust processes in place to ensure key impacts can be addressed well before construction starts,” it said.
The Beaches Link tunnels will be built to depths of 108 metres below Northbridge before crossing Middle Harbour. The seven-kilometre tunnels will connect to the Warringah Freeway at North Sydney, where they will link to the new tunnel under Sydney Harbour to Rozelle.
The Department of Planning said all proposals were subject to rigorous assessment, based on independent expert advice and community feedback.
If it gains approval, the Beaches Link is likely to be completed by 2028, about two years later than the state government had originally intended.
The government has yet to reveal the cost of the Beaches Link and the Western Harbour Tunnel. But government documents leaked in 2017 estimated the combined cost of the projects at $14 billion.
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