Soil protection during corridor search and route planning
Soil protection has priority right from the planning stage: more than 50 individual criteria have to be considered during the search for a suitable route corridor. In addition to nature conservation areas with protected soils, for instance, mapping data on damp and easily compacted soils, moors, erosion-prone soils as well as soils with a particularly high natural fertility (e.g. black soils) are taken into account.
During the subsequent determination of the course of the underground cable trench, the route planners then take an even closer look. With detailed surveys and on-site visits, they determine the specific soil conditions. This is due to the fact that these can change within a few metres due to the geology, slope inclination or groundwater level.
Soil protection during construction planning
Another important aspect of soil protection is the decision on how the cable will be laid under the ground. As a rule, the open trench method is used. In the case of the SuedOstLink, the cables can be laid in either one or two trenches depending on their number. A single trench makes the route narrow; however, with two parallel trenches vehicle movements may be less and better distributed, which helps prevent soil compaction.
Another important option is trenchless installation. This allows protected areas to be undercut by up to 1,000 metre long drilled holes. A possible method to achieve this is horizontal directional drilling (HDD). However, parts of this method are very complex. Especially the larger surfaces required at the start and end points are often contrary to the actual protective purpose. Therefore, this method is only used for soil protection after careful consideration and in special cases.