The Mangfalltal valley has supplied Munich with most of its drinking water since 1883. All supply pipes that are older than 120 years have to be replaced. The actual water pipeline is a steel pipe which will be installed after the pipe has been built.
The project is divided up into several phases. During this phase the Hachinger tunnel was constructed from 1998 until 1999 and the Hofoldinger tunnel from 2002 until 2006.