After site preparation by CF Construction, the next step is to stabilize the soil to support the new library and the west addition. There are various different options, such as traditional pile driving, but the engineers chose rammed aggregate piers, or Geopiers. This tried and tested solution improves the condition of the subsoil, especially in areas where landfill has been used extensively. First, an excavator creates a hole about 15 feet deep with an auger. The hole diameters vary from 18 to 24 inches. Then, a tube with a hopper on the end, drops clean gravel into the hole, while at the same time compacting the gravel so it spreads out beyond the hole itself. This is repeated everywhere the foundation will sit. Amcon is the installer of the Geopiers for the project.