#114 - Case History - Geophysics Provides the Confidence to Build


June 10th, 2024

20 mins 11 secs

Your Hosts

About this Episode

GBA Case History Series – Case History #114 - Geophysics Provides the Confidence to Build


In this episode, we explore how Siemens Associates turned an “unbuildable” site into a construction-ready plot using advanced geophysical exploration. Initially, a school’s building plan hit a roadblock when a non-GBA member firm’s study flagged variable surface conditions and air-filled voids, rendering the site unfeasible. However, the drilling method used was unreliable, causing uncertainties.

Enter a second geotechnical and geophysics firm with a fresh perspective, Siemens Associates. They executed a high-resolution electrical resistivity survey, followed by traditional drilling. This savvy approach cut drilling costs and pinpointed problem areas with surgical precision. The 3D survey unveiled a clear subsurface picture, showing only minor anomalies within the project footprint. Sonic drilling validated the presence of pumicite, a fickle rock, but no alarming voids.

This meticulous assessment flipped the initial verdict, proving the site buildable. Tune in to discover how cutting-edge geophysics and diligent geotechnical work transformed a seemingly doomed project into a roaring success.

Our Host

Elizabeth Brown, PE – National Practice Manager - Geotechnical/Atlas Technical Consultants Atlas Technical Consultants (Link to Profile) -

Elizabeth is the Geotechnical Services Manager at Atlas Technical Consultants in Boise, Idaho. Elizabeth has performed and/or assisted with numerous geotechnical investigations throughout Idaho, Oregon, Washington, and Wyoming managing projects, providing geotechnical design, project quality control, cost and value engineering, and evaluating geotechnical constructability issues.

Our Guest

Andy Siemens, PE, GE – Principal Engineer /Siemens & Associates (Link to Profile)

Andy Siemens is the Principal Engineer at Siemens Associates, renowned for his expertise in structural and civil engineering. With a degree in Civil Engineering and a Professional Engineer (PE) license, he oversees complex projects, manages teams, and ensures high-quality outcomes. Andy excels in client interaction, innovative problem-solving, and mentoring young engineers. His notable achievements include multiple awards, industry publications, and contributions to high-profile infrastructure projects, solidifying his reputation as a leading figure in engineering.

Lessons Learned

  • Reliance on traditional subsurface investigation methods aren’t always effective.
  • Novel uses of lesser-known, geophysical methods can effectively guide traditional exploration, leading to confident geotechnical recommendations.
  • In this case, it was clear that incorporating a geophysical component offered significant benefits early on, in the exploration/planning stage.
  • Explore different drilling methods and be strategic with the location of borings. A strategic boring pattern is crucial to preserving the exploration budget, especially when dealing with proposed rectangular footprints.
  • Before starting traditional exploration, consider how effectively you’ll be able to interpret conditions between borings. If this seems challenging, it might be time to consult with a geophysicist.
  • Assess if your site has sensitive terrain, difficult access, or other challenging conditions for wielding or tracking equipment.
  • Geophysics can be accomplished anywhere you can walk or float, often more economically than building special access or obtaining permits.
  • Engage geophysics services with care and consideration.



This episode was produced by the following GBA Members: