A school district hired a non-GBA Member Firm to assess subsurface conditions at the proposed location for a new campus structure. Initial exploratory borings suggested the area contained adverse geologic conditions consisting of shallow basalt bedrock containing large voids.  The preferred location for the structure was judged to be “un-buildable.” The school district hired a GBA-Member Firm for a second opinion.  The Member Firm suggested a new approach and teamed with another GBA Member that specializes in geophysics. The findings from an electrical resistivity survey were used to further evaluate the subsurface conditions and guide the placement of additional exploratory borings. The geophysics firm went above and beyond in assuring the client and project team that the results would be reliable by conducting a preliminary survey at a nearby test site with similar known conditions.  The results from the geophysical survey and additional borings did not identify any significant basalt voids within the proposed building footprint. The stakeholders were delighted that the new team of GBA Member Firm was able to refute the original findings using innovative methods.  As a result, the construction at preferred location for the structure proceeded with confidence.

air filled void; air-percussion drilling; basalt; drilling; electrical resistivity survey; geophysics; geotechnical; high inverted resistivity anomalies; non-traditional exploration techniques; shallow test pit exploration; track hoe; unconsolidated pumicite; volcanic soil