In recent years, extreme weather events across North America—from prolonged, heavy rainfall to severe flash floods—have resulted in more frequent, extensive flooding that increases the risk of dam failures. These occurrences highlight the need for robust dam-safety measures to protect natural resources, community infrastructure, and people’s lives, homes, and livelihoods.
New and evolving regulatory requirements reflect a shift toward a risk-based approach to dam safety called risk-informed decision making (RIDM).
As dam owners and operators across the U.S. confront these challenges, federal and state regulations are also changing to keep pace with the times. New and evolving regulatory requirements reflect a shift toward a risk-based approach to dam safety called risk-informed decision making (RIDM). The Federal Energy Regulatory Commission (FERC) describes RIDM as “a method of dam safety evaluation that uses the likelihood of loading, system response given the loading, and consequences of failure to estimate risk.”
For dam owners, taking a risk-centered approach to decision-making about potential upgrades can be both illuminating and intimidating. While it’s essential to understand each facility’s greatest risks, in-house technical capabilities and budgets to address issues vary greatly from one dam to another—and repairs can be enormously expensive.
There are over 92,000 dams in the United States, with an average age of 61—and none of them are exactly alike. Topography, geographic location, hydrologic setting, availability of suitable construction materials, and the facility’s intended purpose all affect how the facility is managed, along with the types of risks owners need to focus on and address. A good operational and preventative maintenance program goes a long way toward protecting against dam failure; identifying a small problem now may guard against a larger problem down the line.
Prioritizing projects
Risk analysis with RIDM formally identifies all the ways in which a dam could fail while quantifying the risks associated with a failure. This approach can also help manage a portfolio of dams and prioritize the highest-risk facilities. The aim is to consider the differences in dam structures, from size to function to vulnerabilities, and identify the most efficient ways to manage risks.
In addition to benefiting dam owners in the long run, RIDM can provide assurance to community members where dams are located that sound science and data are driving decisions to keep them safe.
Staying compliant
Regulations for the dam industry are informed by and designed to support these effective processes and outcomes, but they can also introduce complexity for owners. A single facility can be subject to multiple and differing regulatory guidelines, as it may be under the purview of both state and federal entities. Owners must comply on both fronts, all while state and federal regulations continue to evolve, leaving owners to figure out what applies to their facility.
A single facility can be subject to multiple and differing regulatory guidelines, as it may be under the purview of both state and federal entities. For owners navigating this regulatory landscape, it can be helpful to bring in an experienced, outside support team.
Most non-federal hydropower generation facilities are regulated by FERC. The FERC Dam Safety Program has existed for many years, but it only recently developed and adopted RIDM standards and processes that all dam owners under its jurisdiction must follow. FERC was not the first federal agency to implement risk-informed decision making—that was the Bureau of Reclamation, over 25 years ago. However, this practice became more widespread after Hurricane Katrina impacted New Orleans and the U.S. Army Corps of Engineers adopted RIDM for its dam and levee safety programs.
As individual states adopt RIDM, their guidelines typically center on the risks that are most common for their region and uses for dams within local communities.
For owners navigating this regulatory landscape, it can be helpful to bring in an experienced, outside support team to resolve any contradictory or overlapping rules or guidance, move efficiently to follow RIDM best practices, identify options to help manage costs, and develop a realistic implementation plan.
Moving forward with confidence
When North Dakota recently updated its dam safety standards, a client of Barr sought to replace a deficient spillway. Our experience with dams and regulations across the continent helped the client interpret North Dakota’s updated standards and develop a plan to meet them. We helped this client evaluate their spillway’s current hazard classification, and in this instance, we expect that an incremental damage assessment will justify designing the facility to a lesser storm standard than currently required. Our role in this process also included helping our client streamline their efforts, work productively with regulators, and move through the repair process with confidence.
Applying RIDM makes it possible to capitalize on operational data as well as apply predictive analytics related to climate trends and geologic conditions to develop and implement a sound—and financially viable—solution.
In Minnesota, Barr led the design for replacement of Lake Bronson Dam, using RIDM to inform the spillway design. Construction is now underway for a labyrinth weir that will improve flood control and resolve prior issues with dam gates that placed operators at heightened risk during high water events.
Applying RIDM makes it possible to capitalize on operational data as well as apply predictive analytics related to climate trends and geologic conditions to develop and implement a sound—and financially viable—solution.
There is no one-size-fits-all solution for managing risks across thousands of dams nationwide, but expertise in RIDM and experience working with regulators makes it possible to proceed decisively in identifying risks, prioritizing repair measures, and moving forward with implementation.
Barr designed this spillway and modification concept for Lake Bronson Dam in Minnesota.
Putting experience to work
Barr specializes in providing support to dam owners. We start by understanding what the dam was originally designed for, what it’s rated for, and how it was built. We then work to understand what has changed since then. Climate change is a significant consideration in the analysis process: Seismic activity, earthquakes, flood patterns, and weather conditions have likely changed since the dam was first constructed—and will continue to evolve. We help dam owners and operators assess risk based on all these factors, and many more, to safeguard their facility as well as prepare for a dynamic and ever-changing future.
Our services include:
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Technical assistance
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Engineering analysis
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Risk analysis and mitigation
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Development of an instrumentation and monitoring plan, including data interpretation
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Risk reduction modifications
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Failure stabilization
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Identifying how frequently debris should be cleared from upstream or downstream of the dam
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Federal, state, and regional regulatory compliance
Identifying funding sources
Risk analysis and management is a costly investment, and it can make up a large percentage of dam owners’ annual budgets. In addition to applying our risk-related expertise, we assist in finding funding opportunities to ease some of the financial strain for dam owners by:
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Identifying grant programs that can pay for required dam modifications, such as the Federal Emergency Management Agency (FEMA) high-hazard potential dam grant program
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Identifying cost-sharing programs for dam safety across states
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Preparing and submitting technical information for grant opportunities
Whether you need help in identifying your dam’s potential risks, understanding regulations, applying a risk-based approach to your repair plans, or seeking funding sources, we have the tools to ensure your needs are met. Contact us to get started.
About the authors
Brian Becker, senior dam engineer, has 35 years of experience in dam engineering, specializing in dam safety and risk assessment and management. He served as the USBR’s Dam Safety Chief and is a current U.S. delegate to the International Commission on Large Dams’ Committee on Dam Safety. Brian has been responsible for risk management decisions on more than 250 large dams within the USBR’s inventory and provided direct oversight for over 25 dam modification projects.
Bill Dressel, senior dam engineer, has 19 years of experience in dam engineering gained in positions with the U.S. Bureau of Reclamation (USBR), Denver Water, and Barr, with experience on over 100 different dams. Bill has extensive experience in the evaluation, design, and construction of concrete dams, earth embankment dams, and appurtenant structures. Bill is a Federal Energy Regulatory Commission (FERC)-approved Independent Consultant and Facilitator and has facilitated dozens of risk analyses. Bill regularly reviewed the adequacy of technical analyses, risk analyses, and risk assessments used to support USBR Dam Safety Program decisions. He also was responsible for developing consistent risk analysis methodology, training others to facilitate risk analyses, and working with USBR decision-makers to further the development of risk assessment processes.
Related projects
The Hettinger County Water Resource Board hired Barr in 2016 to improve safety at Karey Dam in western North Dakota. Over time, this historic community asset and recreational destination had become a dangerous liability that posed drowning risks. Barr’s solution involved removing the existing low-head dam and replacing it with a series of engineered rock riffles. A detailed assessment of flow conditions helped confirm that the project would not worsen the downstream scour hole post-construction and consequently undermine the dam’s structural integrity. Our approach significantly reduced the safety risks posed by the deteriorating structure and eliminated the development of deadly recirculating currents, thanks to the distributed energy loss between each rock arch.
Constructed in fall 2020, Karey Dam is now the first rock riffle structure in the western part of the state. Barr’s innovative solution improved dam safety while also providing benefits such as river connectivity and aquatic organism passage. In addition, the design enabled continued water storage in the upstream pool and has minimal impact on water-surface elevations and structures upstream of the site. Through a comprehensive stakeholder engagement process, Barr helped secure 95 percent of the project’s funding from local, state, and federal agencies, resulting in a local cost share of less than 6 percent. This project earned a National Recognition Award from the American Council of Engineering Companies (ACEC) in 2022.
The Elm Lake Dam, constructed by the Works Progress Administration in 1937, is owned by the South Dakota Office of School and Public Lands. It serves as both a recreational lake and a supplemental water supply for the city of Aberdeen. Given its age and the risk to the community in the event of catastrophic failure, the dam was classified as high hazard. Following the flood of record in July 2020, the state of South Dakota decided to replace the spillway, but wanted to make the structure smaller without compromising its functionality. Barr was hired to conduct site investigations, assess alternatives, and identify options for replacing the spillway and upgrading the dam facility to meet modern safety standards.
During the site investigation phase, we estimated the probable maximum flood (PMF), performed dam-breach modeling, and evaluated a series of alternatives that paired embankment modifications with combinations of spillway sizes and types. The concept chosen for detailed design called for widening the primary spillway to 170 feet, adding a stilling basin at the bottom of the chute, raising the embankment crest by 4.5 feet, and adding a grade-control wall and riprap protection downstream. Barr’s computational flow dynamics (CFD) experts used a program called FLOW-3D to develop a model that informed hydraulic design of the primary spillway.
Barr has been providing SaskPower with dam-safety consulting services since 2014, including reviews, audits, and annual inspections in accordance with Canadian Dam Association (CDA) guidelines. For these facilities, which range in generating capacity from 5 MW to 288 MW, we have reviewed dam design, condition, performance, management, and emergency preparedness by conducting field inspections, reviewing historical documentation, evaluating instrumentation data, and completing technical studies. Any deficiencies and nonconformances we identified were prioritized and reported to SaskPower, accompanied by recommended mitigation measures. Additional services have included embankment repair design, a feasibility assessment for spillway replacement, and hydrotechnical analyses, such as hydraulic modeling for dam-breach evaluations, hydraulic modeling of the Souris River, probable maximum flood (PMF) estimates, and spillway rating-curves analyses.