A programme to restore Blackheath Tunnel to full operating capacity was completed in five weeks of intensive engineering works that utilised specialised methods by Geobear. The 1.6km brick tunnel, originally opened in 1849, had developed progressive lining deterioration and water ingress that, over years, washed out fines behind the brickwork. Persistent leakage damaged the brick face and overhead line equipment, and pooling water on the track led to rail corrosion. Instead the contractor brought in specialist ground engineering firm Geobear to carry out water-sealing and stabilisation using a geopolymer injection system. Preparatory work was carried out by civil engineering contractor Kilnbridge, which drilled around 1,000 core holes along 900m of tunnel lining to accommodate 4,000 injection tubes and some 13km of associated pipework.