Three possible corridor variants
At the beginning of April 2022, Swissgrid submitted an application to the Swiss Federal Office of Energy to initiate the sectoral planning process. The sectoral plan for transmission lines (SÜL) is the Swiss government’s superordinate planning and coordination tool for the construction and expansion of transmission lines. The SÜL process consists of two steps:
Step 1: Planning areas are first drawn up, i.e. geographic areas in which the new line should be built. The planning area is defined by the Federal Council. In the Flumenthal – Froloo project, there was insufficient scope for several planning areas, which is why Swissgrid and the cantons concerned, i.e. Basel-Country, Solothurn, Berne and Jura, agreed on a single planning area. This area stretches from Flumenthal in the canton of Solothurn in a northerly direction towards Therwil, the municipality in the canton of Basel-Country where the Froloo substation is located.
Step 2:In the application made to initiate the sectoral planning process, Swissgrid made a recommendation for three possible corridor variants within the defined planning area. The transmission technology for each corridor is always defined in advance, i.e. whether the line will be planned as an overhead line, an underground cable or a combination of the two. For each project, Swissgrid develops at least one corridor variant per technology. The focus is on protecting people and nature. Swissgrid therefore strives to create solutions that minimise the impact on residential and protected areas.
For this project, Swissgrid identified three possible corridors within the planning area, which largely overlap. First, a spatial overview was drawn up. The location was then assessed, and the third step involved determining which areas were – from an overall perspective – suitable for a line and which were not. The advantages and disadvantages of the three corridors were evaluated with various specialists, taking into account feedback from stakeholder groups.
Overview of the three corridor variants