Underwater Acoustic Imaging for Statewide Bridge Inspection

• Client

  Louisiana Department of Transportation and Development (LA DOTD)

• Division

  Underwater Acoustics International

• Scope

  Underwater Acoustic Imaging, Acoustic Analysis, Diver Support

• Completion

  November 2013

In order for state Departments of Transportation (DOT) to receive Federal Highway Funds from the Federal Highway Administration (FHWA) for bridge maintenance, all bridges require underwater inspection of its substructure every 5 years. To secure these funds, which comprise a significant portion of its transportation budget, the Louisiana Department of Transportation (LADOTD) commissioned Fenstermaker to perform the underwater inspection of 73 bridges across the state. Currently, we are 100% complete with the field portion of the project and 70% of the data has been processed.

Fenstermaker is using specialized techniques in Underwater Acoustic Imaging (UAI) to complete this task, making the evaluation of these Louisiana bridges a pioneer project. This is the first time the FHWA has approved the methodology of remote sensing technologies for submerged bridge inspections. With Fenstermaker’s assistance, LA DOTD is the first state transportation agency to undergo this effort using this advanced technology. Traditionally completed by divers, the underwater inspection of many bridges becomes problematic or even impossible due to hazardous conditions and poor water environments. Thus, UAI benefits both the diving team and overall project by identifying infrastructural anomalies, indicating potential damages for closer analysis, and minimizing diving risks.

Fenstermaker began the project in November 2011.  In continuous operation, our UAI team documented and rated the conditions of the bridges’ submerged support elements. If we observed a major irregularity or deformity, we marked the position for further structural evaluations to be performed urgently. LADOTD will combine our data and ratings with the ratings of the bridge superstructure (above-water components) to create a maintenance and lifecycle model, giving them the information needed to determine when and what maintenance repairs and/or rehabilitations are necessary.

Combining these ratings with the bridge superstructure (above-water components) ratings, maintenance and lifestyle models are created. This gives the client the information needed to determine when and what maintenance repairs and/or rehabilitations are necessary.