Nord Stream Onshore Pipeline Projects OPAL and NEL. Extraordinary Constructions for River Crossings by HDD or Microtunnel
Proceedings Publication Date
The Nord-Stream-Pipelines will be affiliated onshore by OPAL ("Ostsee-Pipeline-Anbindungs-Leitung" – Baltic Sea Pipeline Link), and NEL ("Nordeuropäische Erdgas-Leitung" – Northern-Europe Natural Gas Pipeline) in order to distribute up to 55 billion m3/a natural gas in European market. OPAL crosses north-east Germany for 472 km in order to reach the Czech border for linking to Gazelle pipeline. OPAL is a joint venture of WINGAS and E.ON Ruhrgas with construction leadership by GASCADE Gastransport GmbH (formerly WINGAS Transport GmbH) in total. NEL carries natural gas over a distance of 435 km trough the north of Germany up to the WINGAS storage facility at Rehden. It is a joint venture of WINGAS, Gasunie, Fluxys and E.ON Ruhrgas. The construction has been divided into 2 sections, one by GASCADE (308 km) and one by Open Grid Europe (127 km). Both pipelines are made of steel pipe L485 MB in NPS 56” for a maximum operating pressure (MOP) of 100 barg. OPAL had been built up from August 2009 till July 2011. NEL construction started in February 2011 and is scheduled being ready for start-up end of October 2012. Each pipeline was faced to round about one thousand (1000!) crossings with existing infrastructure, nature reserves and rivers. Most of them had been done by excavation (open) as for example at the river Elbe close to Dresden for OPAL. Only a few of them had to be done by extraordinary crossing technique carried out by specialist drilling company. Depending on local and soil conditions a Micro tunnel (6 x MT) or a Horizontal Directional Drilling (6 x HDD) was built up. In both cases the obstacles (e. g. river, harbour) had been crossed in-ground but in a different manner. In case of MT a jacketed (concrete) pipe was built up and the pipeline (section) had been inserted separately by construction contractor. For HDD the pipeline (section) had been inserted directly in the drilling channel by the drilling company right after drilling hole was completed by the last pull-back. In order not to damage the PE-coated pipeline during pull-in/-back an additional glass fibre reinforced plastic (GRP) coating was attached on this pipe pieces/section.