The €125m (£107.4m) project includes structural renovations, upgrading the road surface, lighting and technology, and modernising the tunnel entrances.
“We are also preparing the tunnel for the climate and energy challenges of the future with the installation of a water treatment plant and a solar park that will provide half of the power capacity,” said mobility and public works minister Lydia Peeters.
The environmental permit was issued in December, paving the way for work to start.
Within the consortium, Besix and Stadsbader Contractors are responsible for the civil works, Besix Infra and Stadsbader for the road works and Besix Unitec and Equans for the electromechanical works. Works on the bypass road are due to start in May and the tunnel renovation in July.
