Tolerable Risk Guidelines for Dams: How Safe is Safe Enough: On-Demand

Tolerable risk guidelines are used to guide the process of evaluating whether or not dam safety risks are low enough. They provide a means of relating dam safety risks to other risks to which people are exposed as a result of technological hazards. While these guidelines should not be used as the only basis for dam safety decisions, they can play a useful role in making the case for a decision.

This webinar will provide both examples of practical applications of USACE and Reclamation tolerable risk guidelines and a summary of the principles that underlie the basis for tolerable risk guidelines. The examples will be for existing dams and for the evaluation of risk reduction alternatives. They will be based on almost 20 years of experience with applying tolerable risk guidelines in several countries in support of real-world dam safety decisions.

Variations in dam safety tolerable risk guidelines in several countries will be discussed. Implementation issues such as considering uncertainty in risk estimates and practical ways to build legal defensibility through considering if risks have been reduced as low as reasonably practicable will be discussed. In addition, examples of tolerable risk guidelines will be provided from other fields such as environmental protection, nuclear safety, transportation safety, and land-use planning.

David S. Bowles, Ph.D., P.E., P.H., D.WRE, F.ASCE

Managing Principal, RAC Engineers and Economists, LLC

Since 1978 David and his colleagues have pioneered the development and practical application of risk-informed approaches to dam safety management.  They have completed individual and portfolio risk assessments for more than 800 dams in many countries, ranging from screening assessments to detailed assessments with uncertainty analysis.  David has assisted with the development of tailored frameworks for dam and levee safety risk management for government and private owners, regulators and professional bodies in many countries.  Clients have included Reclamation, USACE, TVA, FERC, BIA, World Bank, WMO, IAEA, EPRI, EU, ANCOLD, CDA, NSW DSC and many major engineering firms.  David has served as an expert witness for law suits related to dam and canal failures, reservoir operation and hydropower generation, toxic tort, and urban flooding.

David is the Managing Principal of RAC Engineers and Economists and an Emeritus Professor of Civil and Environmental Engineering at Utah State University (USU).  Previous positions include Director of the Institute for Dam Safety Risk Management and Director of Utah Center for Water Resources Research at USU, Engineering Department Manager and Branch Manager for Law Engineering’s Denver office, and a construction and design engineer for a large international contractor based in the UK.


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