Technical Bulletin
Bedrock Topography/Sinkhole Investigation

Introduction

Recently, Delta Geophysics Inc. personnel performed a limited geophysical investigation in a residential community which displayed evidence of sinkhole activity in a portion of the property. The approximate size of the survey area was two acres.

Summary

Sinkholes are common where the rock below the land surface can naturally be dissolved by ground water traversing through them. As the rock dissolves, voids develop underground creating a flow of water and soil into them. If there is not enough support for the land above the voids then a sudden collapse of the land surface can occur.

The survey was conducted in two separate phases. The first phase was of the survey was collecting seismic data to image the bedrock. The second phase of the project was to collect direct image Electrical Conductivity (EC) data around the area of concern.

Electrical Conductivity (EC) tool is a Geoprobe mounted instrument which detects conductivity differences in the subsurface media. The EC tool is a vital tool for locating potential solution zones because of the increase of conductivity in saturated areas.

Specialized field procedures and adaptive filtering techniques applied to the areas reduced the near- surface influence allowing the detection of targets below the surface.

 

Interactive target editing and grouping tools used by our geophysicist allowed for final data refinement. Map making programs enabled the creation of this site map for visualization and display during final reporting. This final map was refined by DeltaŹ¼s geophysicist using sophisticated processing and mapping programs.

After processing the data from the Seismic and EC tool Delta Geophysics was able to map a solution zone on traversing from the Southwest portion of the property to the Northeast.