Precast concrete
In 2006, Tesco appointed a new team to carry out the design and construction of the tunnel and store. Costain were assigned as main contractor and Scott Wilson as lead designer. In light of the collapse, a far more cautious approach was taken to the design. Precast concrete arch sections were used, but these simply act as formwork for a 600mm (2 foot) thick in-situ concrete continuous arch, a much more robust structure. To further reduce the loading on the tunnel, piled walls have been installed either side of the tunnel, and a lighter fill material—including foamed concrete—used over the top of the arch.