A development in a karstic area of southwest Missouri initiated a geophysical survey as part of an initial site investigation. After conducting an extensive geophysical survey over the proposed site, a significant anomaly was discovered. Subsequently drilling of a 0.15-m (6-in.) borehole into the anomaly intersected a void between 16.2 m (53 ft) and 28.7 m (94 ft) of depth. The property is at the top of the watershed, so both the borehole and the void were dry.
In order to model the stability of the cavern in response to the proposed development, it was necessary to determine both the size and the shape of the void.