Centrale As Noord membrane construction underpass

The Koailoane underpass marked the first section of the “De Centrale As” (N356) project, a two-lane motorway between Dokkum and Drachten. This underpass is equipped with a raised bicycle path and a wildlife passage, providing animals with a safe route under the road.

To keep the underpass, which is located below the groundwater level, dry, Genap applied a liquid-tight geomembrane, subsequently covered with a ballast layer. This newly developed geomembrane at the time features a highly textured surface, making it particularly suitable for application on (very) steep slopes. Across the entire stretch of De Centrale As, which includes multiple underpasses and sunken sections, approximately 150,000 square meters of geomembrane were used.