ABSTRACT
A drainage system is required in all tunnels to remove water that could accumulate from rainfall, tunnel washing operations, tunnel seepage, vehicle dripping, fire-fighting operations, or any combination of these sources. Drainage of a tunnel can be accomplished either by a gravity flow system or a pumped system. A gravity flow system will suffice for tunnels with continuous grades, provided that the collected water can be properly disposed of at the lower end of the tunnel. It may be necessary to have a pumped system to dispose of collected water when a low point occurs within the tunnel.
