Piling methods used: Hydraulic rotary rigs are predominantly used for 'bored piles' wherein the ground is bored by the rotation of tool before the pile is cast. The rotary rig size is decided by the torque requirement. Larger the torque required, heavier will be the machine. In turn, the torque is dependent on the soil condition, bore and depth of the pile. For larger diameter and depth with good soil conditions, bored piles are recommended but for smaller diameter and depth, 'driven piles' are cast in. In driven piles, 'liners' are driven in the earth with a hammer to create a hole before casting the pile.