As the 6 km long road section consisted of various heights along the route with embankments up to 6 m, there was a significant demand for fill materials and aggregates. The groundwater levels had been classified as unfavourable in this project. Also, the local retention areas for flood events had to be taken into account in the specification. However, in order to fullfil the required minimum distance between the highest groundwater level and the base of the bulk solid as required by NRW recycling regulations, it was decided to carry out a fill layer of unpolluted subsoil (class Z 0) with a thickness of 1.3 metres.
By means of this activity, the conditions for the use of secondary aggregates could be met in defined sections. Straßen.NRW, as project owner, consequently defined so-called elective positions in its tender documents where it was ecologically possible and sensible.
Prerequisite for carrying out the elective positions with substitute building materials was the implementation of the core construction method in accordance with decrees NRW (Germeinsame Runderlasse NRW) and the M TS E leaflet on construction methods for technical safety measures for the use of soils and building materials with environmentally relevant constituents in earthworks. In this construction method, secondary materials are used exclusively under the watertight surface layer. In the rest of the dam, i.e. in the edge and side areas, material without environmentally relevant constituents is used, in this case class Z 1.1. Special attention was given to the sealing requirements of this type of design: The core material has to be 50 times tighter than the supporting body on the left and right.
MAV Lünen GmbH, a company of the REMEX Group, supplied granova® IBA for this construction project. A total of approx. 100,000 tonnes of the quality-controlled ash were placed using regular placement techniques.