The New Jersey Department of Transportation's Evaluation of Scour Countermeasure Devices

The main reason for loss of a bridge structure in New Jersey has consistently been due to scour. In 2003, the New Jersey Department of Transportation (NJDOT) had identified 181 State-owned and 297 non-State-owned bridges as scour critical. This number continues to grow as the State completes its scour analysis of the 3,596 bridges over waterways. To address this issue, has initiated several actions. First, has given specific guidance to designers on provision of scour countermeasures in its Design Manual to ensure that risk of damage to a new bridge due to a scour event is minimized. Second, it has prioritized its listing of scour critical bridges and initiated contracts to armor its most critical bridges against scour. Third, it undertook a study to evaluate systems for monitoring bridge scour detailed in recent research. Lastly, it initiated and is close to finalizing a Handbook of Scour Countermeasure Designs for NJDOT through research conducted by the City College of New York. It is anticipated that this last action will be completed by winter 2006-2007. This paper outlines the authors completed evaluation of Scour Countermeasure monitoring devices. National Cooperative Highway Program (NCHRP) Project 21-3 “Instrumentation for Measuring Scour at Bridge Piers and Abutments” designated system(s) for monitoring bridge scour. The 2 systems that showed promise in that research were identified as items of interest by NJDOT: 1) Magnetic Sliding Collar and 2) Sonar systems. Two bridge sites were chosen, and equipment and methods observed under closely controlled conditions. Continuous scour data monitoring was initiated. The accuracy of each system and effects of various parameters studied. This paper gives an overview of the evaluation of instrumentation recommended under NCHRP project 21-3.