The 42" Eems pipeline is part of the pipeline connection between the gas cleaning and drying plant of Phillips Petroleum at Rysumer Nacken in Germany, and the natural gas pipeline network in the Netherlands. The gas is obtained from the Ekofisk gas field in the Norwegian region of the North Sea. The pipeline crosses the morphologically dynamic Eems estuary over a length of 4 km, passing both the deep shipping lane ‘Oostfriesche Gaatje’ and the shallow sand bank ‘Paap’.
Since the installation of the pipeline, the Eems’ strong currents have exerted a strong scouring effect on the edge of the sandbank. Over the years, this has resulted in the recurring exposure of a 500 m long section of the pipeline. In order to protect the pipe, and to prevent the occurrence of free spans, scour protection material (stones, sandbags and screens) were repeatedly placed on top of the exposed pipeline. The dumping of scour protection material gradually accumulated to a situation where there was a 500 m long dam within an area where the surrounding seabed had eroded to a level some 10 m deeper, causing a serious navigational hazard.
As a permanent solution for this problem the pipeline was to be lowered over a distance of 900 m to a level below the calculated future scour level. The work was executed by a consortium within which Boskalis was responsible for dredging, survey and positioning. Hydronamic was responsible for the dredging related engineering during the project preparation phase, as well as during execution of the works.