Compressed Air Drilling techniques use a percussion hammer bit connected to a string of drill rod. Casing is placed as the hole is advanced, and the soil is blown to the top of the hole by the use of compressed air. Undisturbed samples can be advanced from the bottom of the hole, and temporary or permanent wells can be set. The air percussion drill bits are best for use in areas with dense rocky soils, containing hard cobbles and boulders.
