CS35A - Concurrent Session 35A: Development of a Screening Level Risk Assessment Tool: Risk Prioritization for 220 High and Significant Hazard Dams in Michigan

Abstract Description: The Michigan Department of Environment, Great Lakes, and Energy (EGLE) has approximately 220 dams, classified as high or significant hazard potential, and is developing a prioritization portfolio for risk management. Creating a statewide prioritization portfolio can be a challenge with a variety of guidance and tools already available from sources like FEMA, FERC, and USACE, etc., but nothing would capture the state specific goals. EGLE procured support from GEI Consultants to develop a statewide risk prioritization tool to consistently and efficiently evaluate their portfolio of dams. EGLE’s two main objectives of this tool were to streamline the risk assessment process and make it easier to secure federal funding through sources like the HHPD grant program, and to support EGLE in programmatic decisions such as dam safety compliance, enforcement, and state grant funding. As the portfolio of dams was extensive and each dam had variable information, it was critical to develop a tool that could summarize the available data in a consistent and efficient approach.

The risk prioritization tool considers the likelihood of failure and population at risk for the normal, flood, and seismic loading conditions. The likelihood of failure for each loading condition was determined based on common failure mechanisms of a Potential Failure Mode Assessment methodologies of either embankment and/or concrete dams (i.e., external stability, overtopping, etc.). The failure mechanisms likelihood of failure were evaluated using influence factors, which included both qualitative inputs, such as observations from inspection reports, and quantitative inputs (when available), such as factors of safety. The tool’s influence factors were developed by technical experts using guidance from agencies like FERC, FEMA, USBR, USACE, etc., readily available observations, and construction conditions of the dam to inform presence of failure mechanisms.

During future phases of this project, GEI and EGLE will be developing and implementing standardized dam safety inspection tools to better align with the risk prioritization tool. With this improvement, EGLE will have the ability to update dam portfolio prioritization in real time as data is updated.