160 North Elizabeth

Bringing CFA Piles to the heart of Chicago.

160 N Elizabeth Street is a 27-story residential building that is in the growing neighborhood of “West Loop.” A thick layer of water-bearing silt covers the competent glacial hardpan bearing material typical of Chicago. As a result of the presence of this silt layer above the hardpan, and the existence of water-bearing sand underneath, there is an increased risk of excavation instability for open holed caissons.

Malcolm approached the building contractor with an alternate design that replaced belled caissons with 132 each 30-inch diameter CFA piles. As the piles bypass the soft upper lacustrine material, they transmit surface loading into the dense glacial gravel that lies over the bedrock. The building contractor brought Malcolm onto the team to help facilitate the design process for this new approach. To bring the new technique to market, building officials had to be convinced that CFA elements were suitable for the project, which was confirmed by additional O-cell tests.

This technique is well suited for building foundations in hard pan areas and where water bearing lenses are present.

Malcolm Drilling