How Evergreen Line Tunnel Boring Machine Works? Meet Alice, the Evergreen Line’s tunnel boring machine or TBM, shown here during her testing and commissioning. During tunnel boring the cutter tools on the base of the TBM loosen the soil which moves into this chamber behind the TBM face and is then removed by a screw conveyor. Monitored carefully in the control room,the material moves along a conveyor belt through the TBM continuing all the way through the tunnel along the top beside the white tube which is a ventilation system during construction. Emerging at the tunnel works yard, a second conveyor deposits the material in a pit beside the Barnet Highway in Port Moody.