Low visibility poses a particular challenge, Illinois DOT noted in a blog post, as few bodies of water in Illinois offer more than a couple of feet of visibility – even with the aid of lights…

Given the murky and dark conditions, inspections are typically tactile, with the diver relying mainly on the sense of touch to detect potential defects, foundation exposure, undermining, and scouring…

Over the last several years, many state departments of transportation tested a range of new technologies for improving underwater bridge inspection techniques.

For example, in 2019, the Michigan Department of Transportation deployed four unmanned surface vessels or USVs equipped with sonar and a topside camera; a vessel allowing inspectors to take measurements and capture images while positioned safely on the shoreline.

Such USVs not only help improve efforts to detect streambed erosion and degradation around a bridge’s substructure, they also keep people out of harm’s way.