Drilled piers, also known as drilled shafts or caissons, are high capacity, cast-in-place deep foundation elements. They can vary in diameter from 24 to 144 inches and can be installed in a wide range of soil and rock conditions.Drilled piers are installed by advancing an auger / drill tool to the required depth using open hole, casing, or slurry techniques. Once the desired tip elevation has been achieved, the drilled pier reinforcement is set in place and the drilled shaft is filled with concrete.