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Construction in Denmark

The pipeline runs through 139 kilometres of Danish waters. Construction activities will include pipelaying and seabed intervention works.

The pipeline installation phase is expected to last approximately 135 days in total. The installation is expected to be sequential, with one pipeline installed at a time. The individual pipe joints will be delivered to the pipelay vessel, where they will be assembled into a continuous pipeline and lowered to the seabed. The pipelay vessels will use the conventional S-lay technique, named after the profile of the pipeline as it moves across the bow or stern and onto the seafloor to form an elongated ‘S’.

Both pipelines will be constructed in specific sections for subsequent interconnection. This may include abandonment and recovery operations, which involve leaving the pipeline somewhere along its route and retrieving it later if weather conditions make positioning difficult or cause too much movement within the system. The average lay rate is expected to be around 3 kilometres per day, depending on weather conditions, water depth and pipe wall thickness. 

The offshore installation of the pipelines in some areas requires additional stabilisation and/or protection against hydrodynamic loading, which can be achieved by either trenching the pipeline into the seabed or using rock placement. In three sections where this might be required the base case approach is post-lay trenching. A maximum of 20.5 kilometres of post-lay trenching is anticipated for each of the pipelines. Alternative measures may include the placement of individual rock berms at these three locations. Rock placement will be carried out where the new pipeline crosses the existing Nord Stream pipeline to provide support for separation between the two systems.

The proposed Nord Stream 2 route crosses power and communication cables (existing and planned), along with the existing Nord Stream twin pipeline in Danish waters. As with the successfully completed Nord Stream project, the plan is to develop solutions for each cable crossing. These will typically consist of concrete mattresses that are agreed upon by the cable owners. The crossing with the Nord Stream pipeline will be designed according to normal industry practice.

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