Tonkin + Taylor provided specialist geotechnical services for the redevelopment of the Pago Pago International Airport (PPG) passenger terminal in American Samoa, working as a subconsultant to Woolpert. The new terminal forms part of the American Samoa Government’s long-term investment in modernising the territory’s primary aviation gateway, improving resilience, accessibility and capacity for the South Pacific’s only U.S. territory.
Drawing on over 40 years of experience in American Samoa, Tonkin + Taylor delivered a detailed ground investigation and site-specific seismic hazard analysis to inform foundation design for this essential (Risk Category IV) facility. Our work reduced geotechnical uncertainty and provided critical design inputs for a resilient terminal capable of performing under the region’s challenging geological and environmental conditions.

Services

  • Geotechnical investigations consisting of 18 cored boreholes, downhole seismic testing and MASW/MAM geophysical surveys
  • Development of a robust engineering geological model
  • Site-specific seismic response analysis and liquefaction assessment
  • Foundation options assessments (shallow and deep)
  • Geotechnical design and construction recommendations

Client

  • Woolpert

Year

  • March – July 2026

Other parties involved

  • Websters Drilling and Exploration
  • Southern Geophysical
  • McConnell Dowell

Client needs + challenges

Woolpert required geotechnical information to inform the expansion of the proposed terminal footprint and structural redesign. The project also required comprehensive foundation recommendations for a critical facility on potentially liquefiable soils in a highly seismic environment. The remote island location added significant logistical challenges for investigative work, specialist equipment mobilisation and programme coordination.

Innovations

Integrated geological, geotechnical and geophysical investigations developed a project-specific ground model and seismic response analysis. Shear-wave velocity testing and advanced numerical modelling produced site-specific design spectra, enabling more refined structural and foundation design than standard code-based assumptions allow.

Measurable Outcomes

  • Reduced geotechnical risk through comprehensive ground investigation
  • Provided reliable design parameters for foundation selection and seismic design
  • Supported the optimisation of foundation solutions by comparing shallow and deep foundation options
  • Improved confidence in the long-term performance of a critical transport asset

Community benefits

The new terminal will support safer, more accessible and more resilient air travel for American Samoa, where aviation is a vital connection for healthcare, education, business and family travel.

Key highlights

Kazuki Tsukiji (our Geotechnical Engineer) was fortunate to see an AC-130 from the USAF take off during one of the days he was working at the airport, a brief distraction from inspecting core samples and overseeing geophysical surveys (image below).
Pago Pago International Airport terminal upgrade, American Samoa
Pago Pago International Airport terminal upgrade, American Samoa
Pago Pago International Airport terminal upgrade, American Samoa

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