Minimise cable impact on marine ecosystem

Terna developed an innovative methodology for installing marine cables which minimises the environmental impact of submarine grid interconnections and especially protects meadows of the rare sea grass Posidonia oceanica.

 

Objectives:

• Assure a better protection of the marine ecosystem, especially of Posidonia oceanica meadows, during the construction of a submarine interconnector
• Implement a sustainable strategy from planning through to construction
• Develop a methodology and a portfolio of solutions to achieve this goal
• Promote a collaborative effort, involving engineers, national governments, local administrations and an environmental protection agency

 

Main information:

Terna developed the impact minimisation project for an interconnector linking the energy networks of Malta and Sicily. It is needed in order to improve the Maltese energy supply via a reduction of Sicily’s energy surplus through transmitting power to Malta and therefore contributing to the integration of renewable energy in the electricity system of Malta. The corridor foreseen for this cable crossed an area that is home to “Posidonia oceanica”, a seagrass that is declining (according to the RedList) and provides habitat for many species.

In order to protect the “Posidonia oceanica” as well as other seabed species from harm, Terna refrained from the common drilling technique used for marine cable installation. This technique would have involved bentonite to lubricate and consolidate the sand around the drilling head, which could have potentially suffocated the “Posidonia oceanica” due to the bentonite debris. The innovative solution applied used Xantan gum, a polysaccharide sometimes employed as a food additive that can easily be biodegraded. The portfolio applied further influenced the drilling technique and the drilling path. In addition, residual environmental impacts on meadows directly crossed by the cable have been mitigated with a transplant on a site in Sicily.

After the first year of monitoring, Terna could assess the good condition of the Posidonia oceanica meadows originally affected by the cable (cast iron shell and drilling) as well as the good condition of the growing transplanted rhizomes.

Additional information:

• Terna is an independent grid operator and one of the key players in Europe in terms of kilometres of electricity lines managed. The Terna Group manages the Italian national transmission grid with over 72,000 km of HV lines through its subsidiary. Terna Rete Italia has over 3,700 employees and a widespread presence across the entire national territory
• The practice has been developed in cooperation with the Ministry of Environment of Italia, the EPA (Environmental Protection Agency), and Nexans
• The Malta Sicily interconnector, owned by ENEMALTA, the Maltese distribution system operator, is part of the Trans-European Energy Network and was financed through the “European Energy Program for Recovery”