For OPAL: largest pipeline borehole in Western Europe

Bindow/Kassel. The OPAL natural gas pipeline is setting new standards in pipeline construction: in order to cross the river Dahme at the gates of Berlin, engineers have now completed the largest horizontal bore in pipeline construction in Western Europe with a diameter of 1.80 meters. With a process known as horizontal directional drilling (HDD), the river Dahme and an adjacent nature protection area with floodplain forests was crossed underground over an area of 970 meters near Bindow (Dahme-Spreewald district).

“By laying the pipeline underground we are ensuring that the sensitive landscape round the river Dahme remains protected,” OPAL Project Manager Hans-Georg Egelkamp explained. The section where the pipeline passes underground is very generous, measuring almost one kilometer, and was also planned with a wide gap to the riverside forest on both sides of the river and the open lowland areas. “In choosing the HDD method we have managed to keep the disruption to the environment to a minimum as we don’t require additional excavation pits nor the accompanying groundwater drainage.” Overall, 172 roads, four highways, 27 rail lines and 39 larger water bodies have to be crossed for the OPAL pipeline, which is more than 470 kilometers long.

“The section here in Dahmetal is one of the most complicated sections of the OPAL pipeline in Brandenburg,” Michael Muth explains. He is the construction supervisor responsible from the WINGAS Group. Over 40 construction workers have prepared the crossing of the Dahme since the beginning of November. The horizontal directional drilling itself takes place in three phases: the first phase drills a pilot hole with a diameter of just 18 centimeters to lay out the path. In the second phase the pilot hole is enlarged in several stages until the desired diameter has been reached. Bentonite – a natural mixture of clay minerals also used as fertilizers or to make wines and fruit juices – is used for the supporting liquid and drilling fluid. “In the last phase the actual pipe for OPAL is pulled into the borehole,” Muth explains. The HDD process was developed in the USA in the 1970’s. 

The OPAL pipeline will run from Lubmin on the Baltic Sea coast through Mecklenburg-West Pomerania, Brandenburg and Saxony to the Czech Republic. 400 of the 470 kilometers in total have already been laid, and the welding together of the more than 26,000 pipes has also largely been completed. “We want to finish the pipe-laying work in Saxony and in Mecklenburg-West Pomerania by the end of the year,” Muth explains. In Brandenburg, over 200 kilometers of pipeline have already been laid.

“The work in the next few months will concentrate on the construction of the gas transfer station in Lubmin and the natural gas compressor station in Baruth, south of Berlin, as well as completing the numerous road crossings and recultivating farm lands,” Muth continues. The commissioning of the pipeline is scheduled for October 2011 following extensive testing together with the first Nord Stream pipeline. With an annual transport capacity of 36 billion cubic meters and a diameter of 1.4 meters, OPAL is the largest natural gas pipeline to be laid in Europe. Overall, the WINGAS Group is investing around one billion euros together with E.ON Ruhrgas AG.