Scour Evaluations

The most common cause of bridge failure in the United States is scour and scour critical bridges are those that are most susceptible to a scour failure. The Illinois Department of Transportation previously identified 23 structures on the state system in District 8 that were scour critical.  Oates Associates was enlisted to review the scour critical status of these structures and recommend appropriate courses of action to ensure that these structures remain safe for the traveling public.

The first task in completing this assignment was to review the previous hydraulic, geotechnical, and structural evaluations to verify that these structures were indeed scour critical. Finding that these previous assessments were thorough and accurate, the next step was to look at each structure individually to determine an appropriate scope of work to protect the structures from scour.  This involved looking at several factors including hydraulics, soil scour susceptibility, structural stability, existing streambed conditions, constructability of different countermeasure systems, utility conflicts, permitting issues, and probable construction cost. In the end, it was determined that installing scour countermeasures at 21 of these structures was the most economical solution.  Oates prepared the plans, specifications, and estimates to complete this work.