Dual Channel GPR Survey Along Airport Runways

During the winter of 2003, SEI was contracted to perform 196,000 linear feet, nearly 40 miles, of GPR data along the runways of an airport in Hernando County, Florida. Hernando County lies within an active karst terrain, and is prone to sinkhole development. Following the opening of several sinkholes within close proximity to active runways, county officials recognized the need to take preemptive measures to ensure runway stability.

The purpose of the GPR survey had two separate objectives.  The first was to identify possible voids, sinkhole related or not, that may be concealed beneath the runway’s 14 inches of concrete.  The second survey objective was to locate possible buried depressions, paleo-sinkholes, or otherwise active or inactive karst features.  To accomplish both tasks, the identification of near-surface voids and deeper geologic features, a dual frequency GPR survey was implemented.

Both 200 MHz and 400 MHz antennas were employed simultaneously with the use of a SIR-20 radar control unit manufactured by GSSI of New Salem, New Hampshire.  Both antennas were towed behind an all-terrain vehicle at low speed.  SEI’s ability to collect dual channel data and deploy multiple ATVs substantially reduced the acquisition time on this project, an expense reduction passed on to our client.

The results of the survey were outstanding.  SEI was able to identify and accurately map several hundred major and minor geologic features as well as four possible voids beneath the runway. SEI’s accurate mapping of the features with Trimble differential GPS and the latest ARC View software greatly enhanced post survey efforts to allow further evaluations of the features of interest.