The expansion of I-5 through Tacoma was designed to improve safety and add capacity to one of the busiest highways in the region. This project included the replacement of bridges, overpasses, ramps, and embankments, as well as improvements to associated utilities and local roads. Malcolm was selected by Hamilton Construction to perform drilled shaft and ground improvement work on this major Washington State Department of Transportation project. The scope of the ground improvement work included deep soil mixing, jet grouting, vibro-replacement stone columns, and permeation grouting.
For the soil mixing, Malcolm utilized an RG23 drill rig to install 7-foot diameter columns to depths up to 89 feet. An extension was added to the Kelly bar to achieve the required depths on the project, which are the deepest single-axis columns constructed by Malcolm to date.