Hollow Stem Auger
This drilling method uses a series of continuously flighted augers that are, as the name implies, hollow. The augers are made by welding the flights around steel pipe of varyig diameters (depending on what size auger is desired). During drilling, the first auger is normally plugged to keep drill cuttings from filling the hollow center of the auger string. The plug may be a simple wooden cutout, or it can be a steel plug with a cutting bit attached.Hollow-stem auger drilling allows one to drill shallow (typically 100 feet or less, although greater depths can be achieved, depending on the formation) without using drilling fluids to stabilize the bore hole walls. The augers keep the borehole open during drilling and well installation. One can install the screen, casing, gravel pack, and grout in the well inside the augers, gradually pulling them out of the borehole as the gravel pack and grout are emplaced.
DWR uses hollow-stem auger drilling to install wells in the saprolite of the Piedmont and Mountains. It can also be used to install shallow wells in the Coastal Plain where artesian pressure is not present in the aquifer(s) to be penetrated while drilling.