Improving FERC's Dam Safety Program
Chapter 14 - Engineering Guidelines Updated July 1, 2005.
The D2SI is in the process of revising the way it carries out the dam safety program. While many engineering analyses have been completed for most of the dams several more need to be completed and often re-analyses are necessary.
It is important to make certain that we are properly monitoring the performance of the dams to ensure the safe long term performance of the dams. Therefore, we need to develop additional procedures to make certain analyses are properly meshed with what we are monitoring in the field.
Dam safety programs throughout the world and especially in the United States are by necessity finding new and innovative approaches to maintain safe dams. The necessity arises from the corporate responsibility to maintain and safely operate a viable hydroelectric resource infrastructure competing against dwindling financial resources and an aging infrastructure.
About seventy per cent of the over 2500 dams under FERC regulation are over 50 years old. Many existing dams would be designed and constructed differently today because of a better understanding by the engineering profession of how dams behave, resulting in additional research being undertaken and completed to develop defensive measures based on site specific characteristics. Considering these facts, the dam safety program must evolve to properly monitor and evaluate dams so they remain in a safe operating condition.
New innovative approaches are resulting in effective and efficient additional tools that dam owners, engineers and regulators can use to properly monitor, evaluate, and maintain safe operating dams.
Where potentially unsafe conditions could develop, if not properly monitored or remediated, these approaches will: (1) identify possibly overlooked potential failure modes that need to be examined: and (2) determine whether any additional features would be required if the dam was designed today.
Therefore, this is the appropriate time to transition into the next era of the FERC Dam Safety Program that includes a detailed, comprehensive Dam Safety Performance Monitoring Program to ensure that potential failure modes are properly identified and addressed.
This will alleviate the false sense of security that is in place at sites where developing unsafe conditions have not yet been detected under traditional safety reviews.
The FERC staff has always worked cooperatively with the licensees and independent consultants to implement a comprehensive and effective dam safety program. As part of this cooperation, we held two workshops, on January 3 and 4, 2001 in Washington, D.C. and on March 6 and 7, 2001 in Portland, OR to discuss the FERC dam safety program. We discussed the importance of performance monitoring and discussed items that could improve the dam safety program.
Working from the concepts raised during these workshops, we invited a group of licensees and consultants to work with FERC staff to prepare a new chapter of our Engineering Guidelines that incorporates advanced performance monitoring concepts.
Complementing the performance monitoring program the new guidelines incorporate a process by which we evaluate a dam to determine potential ways it could fail. The concept is to perform a site specific study in order to better define the important areas of a structure and its foundation that need to be inspected and evaluated.
Meetings were held in Washington on October 10 and 11, 2001 and on March 19 and 20, 2002 to develop the Chapter. Panel discussions to inform licensees and consultants of our work were held at the National Hydropower Association conference in Washington, D.C. on April 24, 2002 and at the HydroVision conference in Portland, OR on August 1, 2002.
We initiated a pilot of the Dam Safety Performance Monitoring Program at eight dams during 2002. These inspections will be completed before the end of 2002. The results of the pilot program will be discussed at a meeting of the development group in early 2003, and adjustments made as appropriate. Implementation of the Program will begin in 2003.
As these inspections have been completed the response of the licensees, independent consultants, and staff have been very positive. Many benefits have been identified by the participants and some of the licensees have already implemented new management oversight of their dams and have instituted new measures to protect the public and their corporate assets.
Since 1981 we have directed the completion of over 600 dam safety modifications at a cost of about $1 billion. Currently there are over 100 dams that do or may require some type of dam safety remediation. For those requiring remediation, construction costs will range from about $100,000 to as much as $200 million (Saluda Dam in South Carolina). Over the next few years it is anticipated that the majority of dam safety fixes will either be completed or under construction. (The remaining ones are those that require additional analyses to determine the need for remediation.)
The next era of the dam safety program will concentrate more on performance monitoring coupled with potential failure modes identification to make certain that the dams are performing properly and to identify any developing problems so that they can be addressed before they become serious dam safety problems.
The Engineering Guidelines, Draft Chapter 14 titled, "Dam Safety Performance Monitoring Program" provides recommended procedures and criteria to develop a Performance Monitoring Program based upon "potential failure mode thinking" which assists in reviewing and evaluating the safety and performance of water retaining structures regulated by FERC.
The Performance Monitoring Program uses the current Instrumentation and Monitoring Program (see Chapter 9 of the Engineering Guidelines) and updates it as appropriate consistent with potential Failure Modes Analysis.
The procedure includes:
- A potential Failure Modes Analysis (PFMA); and
- Development of the Performance Monitoring Program (PMP).
The PFMA and PMP are cutting-edge tools to improve the safety of dams in a cost-effective manner. The concept is to focus on identified, targeted areas of potentially-serious and more-likely dam safety deficiencies so that limited financial resources can be used most effectively in ensuring dam safety and public safety.
A PFMA is an informal identification and examination of "potential" failure modes for an existing dam by a team of persons. It is based on a review of all existing data and information, first hand input from field and operational personnel, site inspection, completed engineering analyses, identification of potential failure modes, failure causes and failure development and an understanding of the consequences of failure.
The PFMA is intended to provide enhanced understanding and insight on the risk exposure associated with the dam. This is accomplished by including and going beyond the traditional means for assessing the safety of a dam by intentionally seeking input from the diverse team of individuals who have information about the performance and operation of the dam.
The PFMA utilizes all of the available data and information as well as standard engineering analyses of an existing dam. It should be viewed as a supplement to the traditional process in which a dam's safety is judged by its ability to pass standards-based criteria for stability and other conditions.
The PFMA is conducted jointly by the licensee, Independent Consultant and FERC staff. This process is guided by a facilitator. For the most part the PFMA is a one-time exercise. Due to its "question asking approach" the potential failure mode examination process:
- Enhances the dam safety inspection process
- Enhances and focus the visual surveillance and instrumented monitoring program
- Identifies shortcomings or oversights in data, information or analyses necessary to evaluate dam safety and a potential failure mode
- Helps identify the most effective dam safety risk reduction measures.
Based upon the results of the PFMA, the Performance Monitoring Program is developed. The PMP defines the appropriate monitoring for the water retaining structures based upon the PFMA.
An integral part of the PMP is the integration of the licensee's operation, maintenance and inspection programs. In addition, the Part 12D Independent Consultant's inspection and report and the FERC's inspection program will also be focused using the PFMA and the PMP.
The integration of a PFMA with a PMP, results in a very efficient and effective dam safety program. With the knowledge, vision, and understanding gained from a PFMA, the PMP is highly effective. The added value to dam safety includes:
- Uncovering data and information that corrects, clarifies, or supplements the understanding of potential failure modes and scenarios
- Identifying the most significant potential failure modes;
- Identifying risk reduction opportunities;
- Focusing instrumentation, monitoring and inspection programs so they provide information about the potential failure modes that present the greatest risk to the safety of the dam;
- Developing operating procedures to assure that there are no weak links that could lead to mis-operation failures.
- Enables dam owners' financial resources to be applied to dam safety in an appropriately-targeted, cost-effective manner.
The interrelationship of dam safety program elements using a potential Failure Modes Analysis approach is outlined below.
- Daily routine inspections / observations - Persons performing the routine inspections or observations should be provided with background information on the potential failure modes identified for the site along with a performance monitoring and visual surveillance plan for each potential failure mode. The licensee is responsible for performing these inspections and for coordinating with the FERC to resolve any issues discovered during the inspections. After a discussion with FERC, a decision will be made whether any action such as monitoring, analysis, or repairs needs to be implemented.
- Licensee operation and maintenance inspection and training programs - Those persons performing the routine inspections or observations should be provided with background information on the potential failure modes identified for the site along with a performance monitoring and visual surveillance plan for each potential failure mode. The licensee is responsible for ensuring that its personnel are properly trained and remain current in the knowledge of proper operation and maintenance of the project. Any deficiencies in these matters need to be coordinated with FERC.
- FERC operation inspection - FERC will perform this inspection. After the inspection, FERC will discuss with Licensee any concerns found during the inspection. The discussion will also include various items relating to the project, such as the operation and maintenance of the project, any instrumentation and monitoring currently at the project and the emergency action plan that is in place at the plant.
If during the FERC operation inspection a new potential failure mode is identified, the D2SI-RO will provide this information to the licensee in the Operation Inspection follow-up letter. If the potential failure mode needs to be evaluated prior to the next Part 12D inspection, a schedule will be established to accomplish this. If it is determined that evaluation of the potential failure mode may be delayed until the next Part 12D Inspection, the D2SI-RO will include the request in its one year reminder letter to the licensee.
- Part 12D Inspection - The Consultant will be provided the current PFMA (initial plus any updates). The Consultant will perform this inspection with proper coordination with the licensee. Any concerns or issues will be discussed with the licensee and FERC. The PFMA will then be updated accordingly by the consultant.
- Joint Part12D and FERC Operation Inspection - Every 5 years a joint inspection will be made by the Consultant and FERC with proper coordination and support of the licensee.
The first ½ to 1 day will be devoted to a meeting between the necessary licensee representatives and the consultant to review the project history including any past or current deficiencies, completed remediation, special investigations previously completed, instrumentation, etc. The group will discuss the development of performance parameters and potential failure modes.
The FERC's operation inspection and the consultant's Part 12D inspection, though conducted concurrently, will take place and be done independently. It is intended that the inspections allow opportunities for discussions of any problem areas and other important items that might come up.
Upon completion of the inspections, the group will meet to discuss any additional thoughts concerning the performance parameters and the potential failure modes to be developed.
The performance parameters and the potential failure modes will be prepared by the consultant and included as appendices to the Part 12D report.
- FERC Construction and Special Inspections - FERC will be responsible for performing and documenting these inspections on as needed bases with proper coordination with the Licensee.
- Licensee Initiated and FERC Directed Analyses and Evaluations - If during the operation or inspection of the project a concern or issue is raised that requires additional studies it is the responsibility of the party identifying the concern or issue to initiate a discussion with all parties involved. If policies change as to the design standards, FERC may direct further analyses and evaluation to determine if a deficiency exists.
- Recommended Action
Performance monitoring - If after the PFMA a concern or issue is thought to require monitoring to determine if the dam's performance is at risk, it will be the responsibility of the Licensee to install, monitor, and evaluate monitoring instrumentation with the coordination of the Consultant and FERC.
Modification - If after the PFMA a modification is required, it will be the responsibility of the Licensee to design and make the necessary modifications, with the coordination of the Consultant and FERC.
Outline for Independent Consultant Inspection Reports Updated January 3, 2017.