Minneapolis Airport is one of the most efficient airports in the USA. Downtown Minneapolis was to be connected to the airport and the Mall of America (Bloomington, Minnesota) by an 18.6-kilometer-long light rail system. At the heart of the system are two 2,237-meter-long tunnel bores under the airport.
From October 2001, an Earth Pressure Balance Shield was used to tunnel underneath the airport. A requirement was that the machine could be operated in open and earth pressure balance mode. In the settlement and vibration-sensitive tunnelling under the runways, the Earth Pressure Balance Shield enabled safe support of the tunnel face The first of the tunnels broke through in April 2002, followed by the second in October 2002.