Ausgrid has revealed the laying of 2.1 kilometre long high voltage submarine cables across Botany Bay did not go to plan.
Two sections of cables between Kurnell and La Perouse, which were supposed to be buried 1.5 metres to three metres below the surface of the seabed, have been found to be sitting either on or slightly above it.
This has increased the risk of the cables being damaged by a ship’s anchor, and could restrict widening of the shipping channel, which is in long-term plans for Port Botany.
Ausgrid has applied to the Department of Planning and Environment to retrospectively modify the 2007 project approval to allow the cables to remain where they are, and, if necessary, to install sand bags to protect exposed sections.
Other options were explored, but not feasible, Ausgrid said in its application.
Scuba diver instructor and marine biology teacher, Mike Scotland is concerned further dredging may occur.
Mr Scotland said dredging already carried out for the Ausgrid cables, the expansion of Port Botany and Kurnell desalination plant had resulted in major detrimental impacts on marine life.
“Scuba divers go down there and see the devastating results of these projects,” he said. “The underwater ecosystem will suffer greatly if there is further dredging by Ausgrid and Port Botany.
“The muddy water created by construction causes the entire food web to die as sunlight cannot penetrate the dirty water.
“The entire food web suffers and begins to die off. Siltation also fouls up marine fauna and flora, killing seaweeds, sponges and corals.”
Mr Scotland said animals such as the iconic Weedy Sea Dragon suffered greatly as a result of the poor water quality during the dredging.
A University of NSW (Sanchez-Camara) study in 2006, before the dredging, had found 45 and 49 Weedy Sea Dragons during dives at two locations around Kurnell.
“They disappeared completely from Bare Island and Sutherland Point when the dredging started, but are slowly recovering,” he said.
A report with Ausgrid’s application said Port Botany authorities were consulted.
The Port Authority of NSW, which manages the navigation, security and operational safety of commercial shipping, had indicated there was a low likelihood vessels would be damaged if anchors came into contact with cables.
“However, there is a high likelihood that the cables would be damaged by anchor drag,” the report said.
“Ausgrid is consulting with the Port Authority of NSW to confirm operational procedures that can be implemented to reduce the risk of the cables being damaged by anchors.”