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Maritime Works and Industrial Diving

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GREEN TRENCHING: Environment-friendly laying of cables and conduits

The "Green Trenching" project is prompted by the need to minimize the environmental impact of traditional activities used for the installation of cables and conduits under the natural seabed.

The normal procedure of underwater installation of cables/conduits foresees the opening of a trench with a bucket-type dig, the laying and the subsequent and final closing of the dig: the whole operations are done delimiting the operating area with provisional anti-turbidity structures of fixed type.

Benefits of using the  “MACH 1” cable laying machine

During the recent installation of a 132kW underwater power line in the Venice Lagoon (site of national interest SIN), the hydraulic trencher cable laying MAC 1  with a floating self-propelled anti-turbidity structure was used.

This innovative laying system has been the subject of an extensive environmental survey that has resulted in two specific measurement campaigns:

  1. water turbidity with CDT multi-parimetric probe
  2. monitoring of the acoustic climate induced by the construction site on the delicate surrounding landscape

The environmental survey confirmed the effectiveness of this innovative laying system and environmental measures implemented to mitigate the effects in an environment of high environmental value:

  • the turbidity levels are lower than the traditional laying methods (the suspension of material during the excavation/burial and the spread of the material re-suspended from the bottom decrease).
  • the monitoring of the acoustic climate, in the environment surrounding the operating area, showed that at a distance of 150 m from the construction site the acoustic contribution is equal to 4 dBA, corresponding to the daytime emission limit value of the areas included in class 1.

The overcoming of traditional laying systems is therefore essential to operate in a sustainable manner without compromising the delicate balance of sensitive ecosystems such as the Venice Lagoon.

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