Generally, the ground cover over the machine should be at least 2.5 times the machine diameter; this could be less depending on ground condition.
Our high-tech machines can work below ground water level, under pressures up to 3 bars, and they may even be upgraded to 6 bar pressure.
GT was the sub-contractor on the Lusail Micro-Tunneling Project that was awarded “GCC Infrastructure of the Year” in 2011; this drive was executed at a depth of 27 meters.