San Diego airport expansion tackles groundwater, seismic risk and sustainability in $3.8bn upgrade

San Diego International Airport is undergoing a major $3.8bn transformation that combines complex geotechnical engineering with sustainability-focused design strategies, all within one of the most constrained airport sites in the United States. Built on just 661 acres near San Diego Bay, the project involves replacing the ageing Terminal 1 with a 1.2 million sq ft facility, alongside extensive roadway, utility, and airfield upgrades.

The site consists of hydraulically placed fill overlying weak bay deposits, with groundwater encountered just a few metres below the surface. This creates liquefaction risk and requires continuous dewatering during construction. Engineers addressed these conditions using nearly 3,000 auger-cast piles up to 90 ft deep, while bridge foundations extend to 140 ft. Ground improvement techniques, including deep soil mixing and jet grouting, have been applied to stabilise retaining structures and mitigate seismic risks associated with the nearby Rose Canyon Fault.

From a structural perspective, the project incorporates a buckling restrained braced system to improve seismic performance while reducing steel usage by approximately 40% and embodied carbon by about 30%. This approach also enabled the removal of around 100 columns, creating larger open interior spaces within the terminal.

Sustainability measures are integrated throughout the development. A major stormwater capture system, including a 900,000-gallon underground cistern, is designed to reduce runoff to the bay by up to 80% while supplying non-potable water for airport operations. Additional measures include hydrant fueling systems to reduce emissions, drought-tolerant landscaping, and energy-efficient baggage handling systems.

Despite early delays caused by groundwater conditions, the project is progressing toward its planned 2028 completion and demonstrates an integrated approach to geotechnical resilience, structural design, and environmental performance in airport infrastructure.