Following their refurbishment, both 800 tonne caissons have been successfully lifted back into the water and returned to their running slots at Chatham’s North Outer lock and the project has moved into its final stage.

Beckett Rankine undertook a detailed inspection of each caisson to record corroded and damaged areas that needed refurbishment. After a structural analysis, repair schedules and drawings were produced. The corroded and damaged elements were replaced and the caissons’ interior and exterior were repainted to give them another 15 years of operational life. The inner caisson was found to have been substantially damaged by at least two ship impacts requiring the cutting out and replacement of some of the gate’s principal structural members.

Our work has also included diving inspections of the gate tracks which were found to be deeply worn; we designed remedial works to enable the refurbished gates to once again slide smoothly on their tracks.