Scuba Divers Inspect Illinois Bridges

A federal mandate requires the underwater inspection of certain bridges, and the Illinois Department of Transportation has turned to scuba divers.

According the AASHTO Journal, published by the American Association of State Highway and Transportation Officials (AASHTO), bridges crossing more than 20 feet of water much be inspected in this way every five years. IDOT uses a team of specially trained scuba divers for the task.

Those divers, many of whom are engineers with which Illinois DOT already has contracts, regularly explore the watery depths surrounding select bridge footings to primarily check for “scouring” a leading cause of bridge failure. Scouring is soil erosion surrounding bridge foundation elements such as pier footings, columns, piling and abutments.

Divers typically conduct routine inspections in the fall when water levels are at their lowest, comparing ground-line elevations to previously recorded ones.

Low visibility poses a particular challenge, according to IDOT, 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.

If a structural- or safety-related deficiency is discovered—one that could pose a threat to the traveling public—I DOT puts its “Critical Finding Procedures” into play.

In such situations, inspectors would immediately contact the Bureau of Bridges and Structures—as well as the appropriate bridge program manager—to discuss the observations and develop an agreed-upon action plan. In the most serious situations, Illinois DOT said bridges will be closed with local or state police assistance.

Source: American Association of State Highway and Transportation Officials