Installation and Operational Effects of a HVDC Marine Cable: Basslink, SE Australia

Despite the many submarine telecommunications and power cables laid world-wide there are fewer than ten published studies of their environmental effects in the refereed literature. This paper describes an investigation into... [ view full abstract ]

Despite the many submarine telecommunications and power cables laid world-wide there are fewer than ten published studies of their environmental effects in the refereed literature. This paper describes an investigation into the effects of laying and operating the Basslink High Voltage Direct Current (HVDC) cable and its associated metallic return cable across Bass Strait in South East Australia. Over more than 95% of its length the cable was directly laid into a wet jetted trench given the predominantly soft sediments encountered. Underwater remote video investigations found that within one year all evidence of the cable and trench was gone at over a third of the 6 deep water sites (32 – 72m deep). At other deep water sites the residual trench trapped drift material providing habitat for the generally sparsely distributed benthic community. Diver surveys at both of the near shore sites (<15m deep) on the northern side of the Strait also found the cable route was undetectable after a year. On the southern side, where the cable traversed hard basalt rock near shore, it was encased in a protective cast iron half shell. Ecological studies by divers over 3 years demonstrated the colonization of the hard shell by the same species occupying hard substrates elsewhere on the basalt reef. Magnetic fields associated with the operating cable were found to be similar to those predicted from theory with effects dropping rapidly with distance from the cable. Beyond 20m the field was indistinguishable from background. These results should allay some community concerns about the environmental effects of HVDC cables