Solid stem augers allow for a continuous helix into the ground. The torque is provided by a top drive auger drilling machine, which permits both downward push and retraction. Individual flights are normally 5 feet long. Different drill bits can be attached to the bottom of the auger to meet the formation requirement, which cut a hole ~10 % greater in diameter than the diameter of the auger. Borehole diameter ranges from 6″-24″, and can reach depths up to 400 feet depending on the size of auger used. The method is useful for hard grounds, cobble-rich (this depends on the size of the auger) soil or soft rock. The method is often ineffective in loose ground or below the water table since cuttings are not recovered, although it may be applicable under some circumstances. For those reasons, the method is mostly use as a “starter” method to advance the borehole down to the water table, from which drilling can resume with a more effective, adaptable method.