As Chicago's populace swelled, the sewer system became increasingly strained and by the 1960s, the sewers overflowed on over 100 days annually. This led to the introduction of the Deep Tunnel system.

The deep-rock tunnel will direct that flow ... “When we built the tunnel those combined sewer flows will fall down the tunnel instead of going into the river where it will help the neighbors ...

HS2's first deep tunnel, which took 15 months to dig and is under ancient Warwickshire woodland, has reached a construction milestone. Civil engineering works, including concrete finishing works ...

On August 20, the group of eight embarked on a guided tour of Moscow’s underground sewer tunnels only to be washed away when a torrential rainstorm caused flooding MOSCOW, August 22.