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Bridge scour is the removal of sediment around bridge foundations and can result in the failure of the bridge. Scour monitoring is performed to identify unacceptable scour on bridges considered to be scour critical and determine when scour reaches elevations that could cause potential bridge failure. Two types of monitoring are available: portable monitoring and fixed monitoring. Prior to this project, MnDOT was only using portable monitoring devices, which requires the deployment of personnel to make physical measurements of scour depths. For some scour critical bridges, especially during high-water events, fixed instrumentation capable of continuous scour monitoring was preferred, but MnDOT lacked the experience or expertise to install this type of equipment. This project installed fixed monitoring equipment at two bridge sites and monitored them for three years to determine the effectiveness and reliability of fixed scour monitoring deployments. Several device options were installed to allow MnDOT to analyze the installation and performance of different types of sensors. Both systems operated for the three years with some outages due to various causes but overall performance was acceptable. The outages were mostly related to power issues and communication issues. Valuable lessons were learned through the deployment, which may be applied to future installations. The deployment executed in this project has provided the confidence to deploy other fixed scour monitoring equipment at key bridges around the state of Minnesota. In addition, the data collected during deployment of the scour monitoring equipment has been stored and provides insight into scour processes. This data can be used by other research groups for design or research purposes.

Bridge failure or loss of structural integrity can result from scour of riverbed sediment near bridge abutments or piers during high-flow events in rivers. In the past 20 years, several methods of monitoring bridge scour have been developed spanning a range of measurement approaches, complexities, costs, robustness, and measurement resolutions. This project brings together the expertise of Minnesota Department of Transportation (Mn/DOT) bridge engineers and researchers, university hydraulic and electrical engineers, field staff, and inspectors to take the first steps toward development of robust scour monitoring for Minnesota river bridges. The team worked with Mn/DOT engineers to identify variables of scour critical bridges that affect the application of scour monitoring technology. The research team will used this information to develop a Scour Monitoring Decision Framework (SMDF) that will aid Mn/DOT in selecting the best technologies for specific sites. The final component of the project will involve testing the SMDF on five bridges in a case-study type demonstration; work plans for two of the sites were developed for demonstration of deployed instrumentation.