Drilling the impossible

Legacy Makes History in Hawaii; Drills Deepest Shaft of Its Kind

Home > 2020 > Legacy Makes History in Hawaii; Drills Deepest Shaft of Its Kind



Deep foundation construction history was made on the Hawaiian Islands – the world’s most remote island chain with a sizeable population – on June 6, 2020, when Legacy Foundations, working with Shimmick Construction, Traylor Bros, and Granite (STGJV), successfully installed 357 feet of 10-foot diameter permanent casing to a bottom of pile elevation of negative 332 feet.

The Honolulu Authority for Rapid Transportation (HART) Airport Guideway and Station Project located on the Hawaiian island of Oahu, comprises of 225 cast-in-drilled-hole piles (CIDH) ranging from 7.2-foot diameter to 12-foot diameter, with this particular drilled pile – Shaft 629 – being the deepest 10-foot diameter pile ever completed utilizing CIDH methods.  Crews installed 572,800 pounds of working casing to bottom of pile elevation using a 3.6m casing oscillator.  To add to the challenging dynamics of this operation, all work had to be performed above a tidal stream from a trestle deck platform to minimize the construction impacts to a highly sensitive environmental area.

Crews worked day and night to excavate and connect casing to continue the removal of almost 1,000 cubic yards of mostly clay material. Upon completion, the shaft was cleaned and bottom tested, passing the very strict, less-than-half-inch settlement specification requirement for an end-bearing shaft. The 340-foot reinforcement cage, weighing 195,000 pounds, was built in six sections, spliced together over the excavated pile, and lowered in as completed.

This milestone was completed by tremie placing roughly 900 cubic yards of concrete with 365 feet of tremie pipe in five hours. Two concrete pumps were used to ensure adequate head pressure of the concrete could displace the water due to the extreme depth of this pile.

All work was completed safely with no issues and no incidents. Congratulations to everyone on the team!

Click here to view a time-lapse video of this incredible work.