Micro-Tunneling is a method used to construct new drainage sewer tunnels. First a large shaft (about 9-12 metres in diameter) is built which will facilitate lowering of a Tunnel Boring Machine (TBM) into the ground. The TBM then grinds through soil and other ground conditions underground along the alignment of the new tunnel. Pipe is then installed behind the micro-tunneling machine to create the tunnel.
The tunneling process occurs underground; however, shafts are required along the alignment and placed in engineered distances at start and end points (used to retrieve or turn the TBM). During tunneling, it may appear not much work is occurring; however, this is being done underground.
Due to the size of the shaft locations, impacts usually include road/sidewalk closures.