A continental method of shaft sinking through sand that is water bearing. The shaft is formed by boring in stages, increasing in size from the pilot hole of about 4 ft (1.2 m) in diameter to the final excavation size. Once the shaft is bored, mud flush circulation continues while the lining is lowered. The lining consists of two steel cylinders, one within the other, and the annular space is filled with concrete. The cylinders are lowered into the shaft, and 10-ft (3-m) lengths are added and welded in position at the shaft top.