Bookham Tunnel is situated between Bookham and Leatherhead stations on the Leatherhead Junction to Effingham Junction line. Built in 1891, this grade II listed brick arch structure was in poor condition with its arch spreading significantly.
A scheme was devised to provide lateral restraint for the sides of the tunnel and vertical support to the crown. On either side of the tunnel 600 mm diameter piles were installed connected at the top with a reinforced concrete capping beam. A reinforced concrete tie beam was used to tie the piles together across the top of the tunnel providing some vertical support to the crown.