Continuous Flight Auger (CFA) piles are drilled piles that use a continuous helical auger fully threaded along the length similar to a screw. CFA Piles are constructed by drilling a hole to the required depth with the auger, then pumping concrete from the bottom of the auger through the hollow stem as it is raised. After the auger is completely out of the hole, reinforcing steel can then be placed in the wet concrete. The soil is removed from the hole by the action of the screw threads and does not displace the adjacent soil. The drill can either be a lead-mounted hydraulic drill like the Berminghammer BHD series or a euro-style drill rig.
They are very popular in areas that have deep, soft, overburden such as the southern US, but also have application in other areas. In Ontario the technique is generally for use in deep alluvial deposits such as might be found in the Muskokas but can also be utilized in other areas where subsurface conditions warrant. One advantage to these types of piles is that installation is quiet and there is very little vibration.
Bermingham has used this technique in the Muskokas and more recently for the foundations of an additional Bridge over the Desjardins Canal for GO train service in Hamiton.