This method is usually restricted to areas underlain by crystalline rocks, such as the Piedmont in northern Delaware. The method of casing emplacement is the same as that used in air rotary. The hammer action of the bit breaks the rock into small fragments which are removed by the air used to operate the hammer. The hole is continuously cleaned and a small amount of water is used to control dust and cool the bit. The well is constructed by driving a pipe, either manually or by machine, at the end of which there is a drive point and screen.
Installation is limited to loose silt, sand, and fine gravel.
As the pipe is lifted and dropped, the bit loosens or breaks the rocks. The material cut or washed from the hole is carried to the surface in the annular space around the drill pipe. As with the mud rotary method, cuttings are removed in a pit by gravity settling and the fluid is recirculated through the drill pipe. Well casing is usually installed as drilling proceeds. This method is most efficient in loose sand, silt, and fine gravel.