The document discusses drainage systems for tunnels. It explains that drainage systems control water entering tunnels during and after construction by preventing excess water and removing what does enter. Water comes from wash water used during drilling and groundwater. Drainage systems are either temporary, using open ditches or pumping, or permanent, including central drains, corrugated roofing with side drains, or single side drains. Central drains use a sloped drainage ditch to move water towards portals for pumping. Single side drains are suitable when tunnels only require a single lane and use a single large drain. Open ditches are simplest but work best in impervious soils and rock. Pumping systems collect water in sumps and use piston or