Tributyltin,a toxic chemical banned after it was found to cause female sea snails to develop male sex organs and become sterile,has also been detected.
Temporary dams will be erected in Middle Harbour during the building of the tunnel between Northbridge and Seaforth,which require the excavation of sediments that present “a high contamination risk to construction”,the EISsaid. Other excavation sites associated with the multi-billion dollar tunnel project present a moderate contamination risk.
A Transport for NSW spokesman said the Beaches Link would be built according to strict conditions of approval,including “strong mitigation measures”.
He said the proposed construction methods for the tunnel had been used safely around the world to protect sensitive waterways.
“The tunnel alignment has been designed to take advantage of the deeper water in Middle Harbour and minimise the amount of dredging required,” he said.
Transport bureaucrats would also stage work and consider ways to reduce noise and minimise dust during construction,such as using portable barriers and watering techniques,he said. “The community can be assured Transport for NSW will continuously monitor the local environment during design and construction.”