Dam Safety: How Reclamation Has Changed Its Dam Safety Review Process

The Bureau of Reclamation has undertaken a new comprehensive review process to streamline its dam safety review program. The new process provides a more efficient method for ensuring dam safety while also training the next generation of experts in this field.

By Daniel W. Osmun, William O. Engemoen and William R. Fiedler

The new comprehensive review (CR) process is the latest change to the Bureau of Reclamation’s process for performing periodic safety reviews of dams. In the mid-1990s, Reclamation’s dam safety reviews shifted to focus on potential failure modes, and a probabilistic approach to dam safety risks was adopted. The last major change in the comprehensive facility review (CFR) process was implemented in 2000, with minor enhancements added over the next decade.

The goal of Reclamation’s comprehensive dam safety review process is to document the current condition and performance of every dam, assess safety of the dam (by defining the potential failure modes and estimating their risks), and determine dam safety activities and monitoring that should be performed to better define risk. The information developed in this process is used to identify the risk to the public and help in prioritization of future dam safety activities. Although the process was successful in accomplishing these goals after at least two six-year CFR cycles, we believed the process could be made more efficient without impacting the quality of the results.

The CFR process consisted of an interdisciplinary team gathering information on the facility from existing records and a site exam. The senior engineer developed potential failure modes and analyzed the risk associated with the dam. As part of the process, the senior engineer presented a summary of the effort and the findings to the Dam Safety Advisory Team. Decisions were reached regarding continued operations and the need for additional studies or actions. These decisions were documented in a Technical Report of Findings and a Decision Document.

A less comprehensive review (called a periodic facility review, or PFR) is performed at the midpoint of the CFR cycle. This review typically concentrates on operation and maintenance issues. Although a review of a facility’s O&M aspects is included in the CFR, O&M activities at Reclamation facilities are accomplished separately from the dam safety review process.

In 2010, a value planning team was tasked with addressing the existing CFR process to look for ways to be more efficient and maintain high quality. The value planning study1 recognized the opportunity to leverage other Reclamation dam safety review processes (i.e. the periodic facility review and technical response team²) to improve the efficiency of the entire process. The value planning study resulted in the development of new ideas and suggestions for improvements to make the process more efficient and less costly. Those ideas and suggestions were tested in a 2011 pilot program, which resulted in more changes and improvements to the CR process.

This article describes the CR process as it is envisioned, based on the value planning study and pilot program. Additional changes could be made over time as areas of potential improvement are identified.

Comprehensive review process

The objective of the CR is to complete a focused and comprehensive review of the performance of the dam using a team to obtain a broad-based, comprehensive review of the available information and technical data. The new process requires that an initial CR is performed for the facility and the baseline information has been gathered. For all Reclamation dams and most Department of Interior (DOI) dams, prior CFRs or other similar documents qualify as initial CRs.

Once the CR has been performed, the PFR and CR process would be initiated. The CR and PFR cycle will be integrated with the technical response team (TRT) review. However, the TRT scope would be expanded during the CR cycle. The TRT consists of a group of specific individuals from various offices and disciplines (geotechnical, civil, geology, instrumentation, Dam Safety Office, area office, regional office, operations staff, etc.) assigned long-term to each dam for the purpose of reviewing performance and being familiar with ongoing activities and performance at a given dam.

The CR process begins with the team reviewing project records and the most recent hydrologic and seismic loadings. Technical aspects as well as team member roles and responsibilities are discussed at an initial team meeting. A site exam is then performed and a post-exam meeting is held. As part of the CR, all technical aspects of the dam (e.g. design, analysis, construction, instrumentation, monitoring) are reviewed, potential failure modes developed and risks estimated. The process ends with a review by the Dam Safety Advisory Team and completion of the CR report. For other DOI agencies, there is typically a separate agency presentation after the Dam Safety Advisory Team review.

The CR process is intended to be flexible and scalable, dependent on the amount and quality of available information for the facility, complexity of the facility and goals of the agencies involved. The budget and schedule are also somewhat flexible and scalable based on timing of resource availability, complexity, and the amount of new information available to the team. Within Reclamation, there is flexibility to start the CR process well in advance of the site examination.

A comprehensive review examination of the upstream face of an embankment dam is completed by Bureau of Reclamation personnel.

CR team

The CR process includes formation of a team that is assigned to a particular dam. The team is led by the senior engineer and typically includes representatives from various disciplines, such as geotechnical engineering, civil engineering, engineering geology, instrumentation, mechanical engineering, hydrology and seismology, as well as appropriate representatives from the dam safety and local offices. The senior engineer is typically a geotechnical engineer (for an embankment dam) or civil/structural engineer (for a concrete dam) who has significant experience in dam safety evaluations, including identifying potential failure modes and estimating risks.

Each dam’s TRT (i.e., those permanently assigned representatives from various disciplines that are familiar with operations, monitoring and technical issues at the facility) plays a key role in the CR process, and the involvement of these people brings consistency to the overall process. Other team members are added as needed to fulfill the requirements of the CR process.

Records review and loading assessment

The first task of the CR process is to review project records and evaluate the best available information, including static, hydrologic and seismic loadings. At Reclamation, hydrologic and seismic loadings are reviewed by loading specialists months before the CR team meets. For each project, the loading specialist recommends the level of study needed (if any) to support the CR effort, dependent on the current understanding of the loading potential (e.g. seismic hazard or flood frequency), validity of the existing information (e.g. some seismic hazard studies might be outdated), and estimated risk at the facility (a new flood frequency analysis may not be necessary if the spillway passes the probable maximum flood without overtopping the dam). The CR analysis may show that additional studies are needed to better evaluate the risks, and the required studies could be performed as part of the CR or as a separate study.

CR team meeting

The initial meeting involving the entire team is set according to the CR program schedule and resource availability. The meeting is held at least three months in advance of the site examination to gain the flexible schedule benefits of the new CR process. The senior engineer is responsible for a comprehensive review of facility records, and each team member is responsible for reviewing appropriate documentation before the team meeting. Meeting tasks include:

– Review dam performance as evidenced by the instrumentation data and visual monitoring information;
– Review existing Safety of Dams recommendations to address dam safety concerns and their status;
– Identify hydrologic loadings, seismic loadings, analysis methods, structural behavior, downstream populations or other items affecting potential failure modes and risk that may have changed since the last CR;
– Obtain data from the area office (or agency office) and dam operator to identify any changed conditions, operation issues or other pertinent information;
– Review potential failure modes from the previous CR and any recent issue evaluations (i.e., more detailed studies of dam safety and risk issues). Brainstorm new potential failure modes;
– Provide an up-to-date review and analysis of the dam’s performance since the previous CR; review the population at risk and estimated life loss; qualitatively and/or quantitatively (depending on the facility and agency requirements) assess risks; and assign a dam safety priority rating.³
– Scope out potential new recommendations and develop a plan for resolving existing safety of dams recommendations during the CR, if possible; and
– Take on action items as needed to complete the CR report. The objective is to prepare revised CR report sections as necessary, not completely rewrite the entire report. The senior engineer coordinates the team effort to complete this report.

CR site examination

Site examination participants are determined during the CR team meeting based on complexity of the facility, bureau policy and budget, and issues associated with the facility. At a minimum, the examination team for a Reclamation facility includes the senior engineer or principal engineer (TRT member), civil examination specialist, mechanical examination specialist, representative from the area or field office, and representative from the regional office. For Reclamation dams, the civil and mechanical examination specialists are typically from Reclamation’s Technical Service Center. However, the regional office, senior engineer, principal engineer, or area office may be assigned examination responsibility for other DOI bureaus, based on their requirements and the complexity of the facility.

Personnel inspect a seepage monitoring well at a dam during a site examination carried out as part of the Bureau of Reclamation’s revised dam safety review process.

CR risk analysis

The minimum requirement after the exam is to have the team, under the guidance of the senior engineer, produce the risk analysis section with peer review. In some cases, the risks may not be revised or changed from the previous estimates, especially if the team believes previous analyses appropriately represent the risks for the facility. If the risks are updated, it is not a requirement to perform the risk analysis in a team setting, although typically there are benefits from having multiple perspectives being represented, and team involvement is encouraged. Also, it is not always necessary or appropriate for the entire CR team to participate in the risk analysis. Typically, it may involve a smaller group of three or four people familiar with the potential failure modes and risks posed by the facility.

Risk analysis estimates are made using quantitative, semi-quantitative or qualitative methods, based on each bureau’s requirements and the team’s level of understanding of the facility and its ability to withstand normal operating and other loadings. At Reclamation and some DOI bureaus, risk results are presented quantitatively. However, for other bureaus it may be more appropriate (because of unknowns about the dam, uncertainty in the loadings or other reasons) to present risks qualitatively using a matrix where potential failure modes are placed in bins based on the relative probability of failure and relative expected loss of life. The team determines the appropriate methodology for the facility.

Risk estimates can be made by estimating the probability of individual events that represent the progressive steps for the failure mode and then calculating the product of all the event probabilities. The judgments made to assess the likelihood of individual events should be documented in the risk analysis section, to help build the case for the risk estimates. Verbal descriptors can be used to estimate the likelihood of the individual nodes, and then the verbal descriptors can be converted to numerical values.⁴ Life loss consequences of failure can be estimated quantitatively using methods such as DSO 99-06.⁵

CRT follow-up meeting

The senior engineer organizes a post-examination follow-up meeting with the CR team. However, participation by team members in this meeting can vary as needed depending on the types of issues to be discussed. Report assignments made during the initial team meeting are distributed before the follow-up meeting so they can be discussed. In some cases, the potential failure modes and risks are discussed at the follow-up meeting and those report sections are not necessarily available in final form. The general objectives of the follow-up meeting include:

– Discuss what was found in the field as a result of the site examination;
– Review and discuss updated report sections developed by CR team members;
– Review and discuss potential failure modes and risk estimates;
– Re-evaluate risk estimates as needed with the appropriate team members;
– Review, discuss, and revise the dam safety priority rating if needed;
– Finalize all recommendations; and
– Develop any additional information needed for the CR and dam safety advisory team presentation.

CR product and dam safety advisory team meeting

After the follow-up meeting, the senior engineer is responsible for organizing the team’s efforts and assembling a draft CR report. When the senior engineer, peer reviewer and CR team are satisfied with the report, the Decision Document and Technical Report of Findings is prepared by the senior engineer, with input from the team. The Technical Report of Findings section contains a summary of the critical potential failure modes, recommendations, portrayal of risk estimates and dam safety case including the Dam Safety Priority Rating (a rating system based on risk and other factors that helps Reclamation prioritize dam safety activities).⁶

All CRs go through a Dam Safety Advisory Team review. This team consists of six to eight senior staff representing various disciplines who review the findings and recommendations of the CR report and provide technical guidance to dam safety decision makers. The draft report is distributed and the senior engineer presents the findings at a Dam Safety Advisory Team meeting. The senior engineer presents the recommended Dam Safety Priority Rating category and any changes in the condition of the dam or loadings that were identified during the review process. For other DOI bureaus, there may be a subsequent, separate meeting with the bureau responsible for the dam.

Benefits of the new CR process

There are numerous advantages with the new CR process:

– Compared to the existing CFR process, it is expected that engineering resources will have greater availability for other dam safety work (analyses, corrective action studies, modification designs, etc.). With a more efficient process, some cost savings is expected.
– The process integrates a multidisciplinary team, promoting team interaction throughout the process. The current CFR process was mainly the senior engineer’s efforts, and the level of team interaction was variable.
– Mentoring of CRT members by the senior engineer and peer reviewer aids in succession planning and training of less-experienced staff. This is a key near-term objective due to the anticipated attrition in the federal workforce over the next several years. Similarly, writing of individual CR sections by less-experienced team members provides specific on-the-job training.
– Team evaluation of potential failure modes and risk issues is preferable to a report produced by an individual senior engineer and peer reviewer.
– The team composition, which includes some very experienced staff, results in more consistent products.
– Teams with greater diversity in technical skills may be able to address and resolve more dam safety issues during the CR process, rather than creating new dam safety recommendations. Dealing with and resolving potential dam safety issues during the CR process is more efficient from a funding and resource perspective than creating recommendations that might not be addressed for several years because of prioritization.
– Scheduling a greater duration between the initial CRT meeting and the site examination allows more time to address and resolve dam safety issues rather than creating new recommendations. The current CFR process typically does not allow enough time for dam safety issues to be resolved by the time an issue is recognized, resulting in a recommendation to study the issue separately.
– Scheduling a greater duration between the initial CRT meeting and the site examination allows greater flexibility in workload planning and balancing. Work on a CR can begin much sooner if resources are available.

There were some disadvantages, or inconveniences, associated with making changes to the dam safety review process that were identified as part of the pilot program. Adjustments were made based on that feedback and are included in the process described above. The new process involves change – and change can be difficult to implement when there are so many parts of the organization involved in the process. Some training on the new process and the roles, responsibilities and expectations has been performed, and it will continue as the process improves and evolves.

Conclusion

Reclamation’s new CR process results in greater resource and funding efficiency while maintaining high quality. Previous reports are updated as needed, rather than completely rewritten. The CR report and risk estimates are the responsibility of a multidisciplinary team rather than having the major responsibility assigned to a single senior engineer.

The benefits of the new CR process are both direct – in the form of efficient use of engineering resources and cost savings – and indirect, with intangible succession and knowledge transfer benefits that come from involving a greater number of less-experienced staff working side-by-side with more experienced engineers.

Acknowledgments

The authors would like to acknowledge the participants and authors of the 2010 Value Planning study and 2011 CR Pilot Program. The VP study report formed the basis for much of what is now part of the new CR process. The participants in the pilot program provided critical feedback that was used to make further changes to the CR program as well as make practical adjustments to concepts that appeared to provide benefits that were not always easy or practical to implement.

Notes

¹“Comprehensive Facility Review Process Modification,” Value Engineering Final Report, Technical Resources Office, Design Estimating and Construction, Bureau of Reclamation, Denver, Colo., 2010.

²Von Thun, J. Lawrence, Jay N. Stateler, Ronald W. Luehring, and Robert L. Dewey, “Sharpening the Saw – Keeping Dam Safety Technical Response Teams Honed,” Proceedings of Dam Safety 2011, Association of State Dam Safety Officials, Lexington, Ky., 2011.

³“Dam Safety Risk Analysis Best Practices Training Manual,” Bureau of Reclamation, Denver, Colo., 2011.

⁴“Interim Dam Safety Public Protection Guidelines, A Risk Framework to Support Dam Safety Decision-Making,” Dam Safety Office, Bureau of Reclamation, Denver, Colo., 2011.

⁵“A Procedure for Estimating Loss of Life Caused by Dam Failure,” Report DSO-99-06, Bureau of Reclamation, Denver, Colo., 1999.

⁶Dam Safety Public Protection Guidelines, Bureau of Reclamation, Denver, Colo., August 2011.

Reference

Osmun, Daniel W., William O. Engemoen and William R. Fiedler, “Changes to Reclamation’s Dam Safety Review Process,” Proceedings of U.S. Society on Dams Annual Meeting, U.S. Society on Dams, Denver, Colo., 2012.

Dan Osmun, P.E., and Bill Engemoen, P.E., are geotechnical engineers and Bill Fiedler, P.E., is a civil engineer with the Risk Advisory Team at the U.S. Bureau of Reclamation’s Technical Service Center.