RENEWAL REAPS REWARDS.

The complexity of many tunnel renewal projects, the skills and experience they demand, and the large saving that can be made compared with retunneling means that such work is worthy of more attention. Renewal is not restricted to the frequently reported sector of Victorian sewers. Transport tunnels constructed around the same period are now frequent subjects for heavy maintenance or total renewal. They too have suffered deterioration, which is much more visible and probably more hazardous than in sewers. They may also be of inadequate capacity for modern needs and require adaptation for increased traffic or rail electrification. This article discusses these and other types of projects conducted recently in Switzerland, Belgium, England, and Italy.