H3Dv2 A1031, prevent Clay marls from Maaseik

This layer gives the prevention limits of A1031, as defined in the Hydrogeological 3D model of the Flemish subsurface. The Hydrogeological 3D model was drawn up in the framework of the management agreement of the Flemish government with VITO, under the name VLAKO, on behalf of the Flemish Environment Agency.