In the Fall of 2015, a geophysical survey crew from Enviroprobe Service Inc. was mobilized to Upstate New York to perform a geophysical investigation using the marine electrical resistivity imaging (ERI) method. The purpose of the investigation was to investigate the sub-bottom materials in a river, specifically the thickness of the soft layer at the river bottom underlying by hard glacial till or bedrock. This soft layer was mostly clay or silt. The target survey area was about 5 miles long.
The area had been investigated using other geophysical methods including GPR and sub-bottom profiling. These two methods were not effective due to the site conditions. Electrically conductive sub-bottom materials can prohibit the effectiveness of GPR while soft/organic sub-bottom materials can render sub bottom profiling useless. Although the marine ERI method usually has lower resolution compared to these two methods, it doesn’t have their restrictions. The marine ERI survey was successfully conducted and the general trend of the target layer thickness was mapped.