50 NOVEMBER 2025 WorldWide Drilling Resource® The Largest and Deepest Drilled Shaft Caisson Adapted from Information by the Honolulu Authority for Rapid Transportation (HART) The Honolulu Rail Transit Project (Skyline) in Hawaii, is an automated, driverless rail system stretching along the southern coast of O’ahu, connecting East Kapolei Station to a temporary endpoint at Ka‘ākaukukui (Civic Center) Station. The majority of the rail alignment is elevated, with the exception of a section that runs at ground level near Leeward Community College Station. The contractor for the Airport Guideway and Stations segment, Shimmick Traylor and Granite (STG), has successfully completed the construction of what is believed to be the largest and deepest column foundation in the world. This impressive foundation, known as a drilled shaft caisson, reaches a depth of 357 feet and has a diameter of 10 feet. It will serve as the base for a column that will support the elevated guideway of the rail system and the Kahauiki Station. The considerable depth of the column was essential to ensure a stable underground foundation for the station and guideway. “We’ve had numerous column foundations ranging in depth from 25 feet to more than 200 feet. Due to the location of this pier, and the type of soil conditions in the area, STG needed to construct this pier at a record-breaking depth,” said Andrew Robbins, HART’s Executive Director and CEO. Rusty Lucido, Vice President of Shimick Construction’s Legacy Foundations group commented, “Incredible teamwork throughout the planning and execution of the drilling operations allowed STG to install the largest diameter and deepest single cased caisson in the world, according to our research and information from international industry experts. To add to the dynamics of this operation, all work had to be performed above a tidal stream from a trestle platform, to minimize the construction impacts to a highly sensitive environmental area. The team’s dedication to safety and quality of work has allowed us to complete this challenging operation with no incidents or accidents.” HART recently celebrated the commencement of the City Center Guideway and Stations segment with a blessing and groundbreaking ceremony. This next phase involves building six rail stations and approximately three miles of elevated guideway, starting from the Kahauiki Station and concluding at the Ka‘ākaukukui Station. “Mahalo to all of our partners and HART staff who have worked so hard to make this project possible,” said HART Executive Director and CEO Lori Kahikina, P.E. “We’ve got to this point through cooperation and perseverance, and we will use that same approach to overcome the challenges that lay ahead to deliver this project within budget and on schedule, for the taxpayers of Honolulu. I couldn’t be more excited to put shovel to ground on this next phase of the Honolulu rail project, a critical step toward bringing Skyline further into urban Honolulu.” CONST
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