Learning from the US experience11 December 1998
Information that improves the understanding of dams and their performance is at a premium. As Martin McCann* explains, the US National Performance of Dams Programme is an aggressive effort to establish a valuable engineering resource, with the participation of dam owners, regulatory officials and engineers
In October 1996 President Clinton signed the Water Resources Development Act (Public Law 104-303), which created the US National Dam Safety Programme. Nearly a generation after the disastrous Buffalo Creek Dam failure which triggered national interest in dam safety, the Act establishes a national agenda for improving dam safety in the US that will be administered by the Federal Emergency Management Agency (FEMA).
While the Act does not create a national dam regulatory agency, it does mandate a programme of ‘technical and archival research’ so the lessons of historical experience can support future improvements in dam safety. The Implementation Plan for the Act identifies the National Performance of Dams Programme (NPDP), started at Stanford University and inaugurated in 1994, as a vital part of the National Dam Safety Programme.
At the NPDP we have established a system to retrieve, archive and disseminate information on dam performance that will support efforts to improve the design, operation and repair of dams. At the same time we seek to evaluate data that will educate policy makers and the public on the benefits and risks of dams, so that effective public policy can be implemented.
While the scope and objectives of the NPDP meet a number of needs, early efforts to interest the dam safety community in a plan to achieve them met with a cool response. All kinds of questions were raised; among them:
•What is a dam incident?
•How should information be reported?
•How much effort is involved to report an incident?
•What can the NPDP do for me? As the programme developed, these and other questions were answered. But the fact that no single agency in the federal government or organisation in the private sector had the authority or professional position to institute a programme such as the NPDP proved to be a hurdle in getting the programme under way.
Engineering always involves observing and learning from in-service performance. Despite improvements in monitoring and analysis, this is as true today as it was when the first dams were built. However, before the NPDP was created, efforts to gather data on the performance of dams in the US were neither systematic or consistent, and can best be characterised as ad hoc and limited in scope.
As interest in dam safety expanded the needs of engineers and policy makers for information on the state of the nation’s dams exposed the limits of dam performance data. For example:
•Dam performance information was gathered on an ad hoc basis. The historic record is incomplete and information is sketchy at best.
•Published information is limited in terms of the technical detail provided. Often simple (non-technical) tabular summaries, possibly with a brief abstract, are reported.
•Access to original information or technical data is generally unavailable, limiting the engineer’s ability to review and evaluate the performance of dams independently.
•Incidents are often grouped into preset categories or incident types, further limiting independent evaluation and interpretation of individual events.
•The focus has been on events involving unsatisfactory dam performance (ie dam failures or accidents). There has not been a systematic attempt to gather information from events involving satisfactory performance, so lessons from these events can be learned, and the integrity of dams and their operation demonstrated.
The limits of the historical record have became particularly burdensome as dam safety and the economics of the 1990s evolved. It became evident that information was required to provide a better understanding of:
•The structural and operational integrity of dams.
•Precursory signs of safety problems.
•The effects of deterioration and ageing.
•The economics of dam safety.
•The risks associated with dam operations.
One need only review the proceedings of professional meetings, technical journals, and trade magazines to recognise the level of interest that is devoted to learning lessons from the performance of dams.
With this backdrop, the concept of a national programme that consists of a network for reporting on the performance of dams and an archive that could serve the dam engineering and safety profession was developed with the financial and logistical support of FEMA. In developing the programme, some tasks had to be completed:
•Guidelines were required to identify the events that are considered reportable dam incidents, what information should be reported, and how the reporting process should be carried out (eg data forms, copies of existing reports).
•The process of reporting dam incidents had to be made an integral part of dam safety practice, similar to periodic dam safety inspections, design reviews etc.
•An archive had to be constructed where documents could be catalogued, stored, and made accessible to the dam engineering and safety community •An Internet-based system had to be established to make the NPDP resources as accessible as possible.
In the four years since the formal start of the programme, each of these tasks has been accomplished or is under way.
Guidelines for Reporting the Performance of Dams (Guidelines) which defines the process for reporting dam incidents, was published in January 1995. We have created an archive of over 6000 documents related to dams and dam performance, and we are developing a digital library that will be accessible via the Internet.
The most difficult task has been to integrate the process of reporting dam incidents to the NPDP into dam engineering and safety practices. Without a single national regulatory authority that could require participation in the NPDP, we have worked with professional organisations such as the Association of State Dam Safety Officials (ASDSO) and the US Commission on Large Dams (USCOLD), and with individual US federal agencies. Each organisation and its members had to be sold on the merits of the NPDP and the benefits it offered. With the support of these organisations we have made tremendous progress toward our goal of making the business of reporting and documenting the performance of dams an integral part of dam safety practice in the US. Many states and federal agencies now report incidents on a regular real-time basis, and more states are joining them each year.
It seems to be human nature to focus on dam failure or other major events involving severe damage or unsatisfactory performance. While failures generally highlight some form of inadequacy and show a need to change or improve the design or operation of dams, a focus on failures alone may be of limited value. Much of the evidence is destroyed and often there are no witnesses or instrumentation data available to tell us what preceded the failure. Consequently, at NPDP, we have adopted the broader concept of dam performance.
As defined in the NPDP Guidelines, dam incidents are ‘events of engineering interest that provide insight into the structural and operational integrity of dams’. This definition encompasses a range of events that goes beyond a simple consideration of dam failure. It includes events involving satisfactory as well as unsatisfactory performance, and performance that is expected as well as unexpected. One of the key parts of the NPDP is the process for reporting and documenting dam incidents. In preparing the Guidelines there were a number of factors that weighed heavily. For instance, one of our goals was to have real-time, complete (100%) reporting of incidents.
To do this, it was important that a process be developed that did not add to the engineer’s workload and that could be incorporated readily into existing dam engineering and dam safety practice. At the same time, it was our belief that engineering documentation of an incident must be as complete as available information would permit. Lastly, it was felt that the use of forms or data sheets was an ineffective (even counter-productive) means to document a dam incident, since transcribing information to a form adds to the engineer’s workload and often leads to inadequate or incomplete documentation.
Balancing these factors we established a reporting process in which the engineer is not required to transcribe information to special dataforms or to generate new engineering reports. (Forms and checklists provided in the Guidelines are aids, and their use is optional.) Rather, it is preferred and strongly encouraged that the engineer provide copies of available documentation (photographs, inspection reports, annotated drawings that identify damage, videotape, instrumentation data, witness accounts, engineering reports etc) that is generated in the normal course of evaluation. The Guidelines give guidance (in the form of checklists) on the type of information that should be provided to document an incident.
For each incident type, the Guidelines recommend that documentation address the following:
•What occurred during the event.
•Design and as-built dam characteristics.
•Repairs and modifications following the incident.
•Post-event investigations into the incident, its causes and its consequences.
To document an incident, the engineer is not required to create special reports, but rather to use existing ones. We recognise that in some cases detailed information may not available with regard to certain aspects of a dam incident.
We believe this reporting process has the benefit that it does not add to the workload of dam engineers and it provides a first order resource to the NPDP archive and its users.
Access to real data
The NPDP reporting process establishes a system that will generate a real-time inflow of information on dam incidents throughout the US. Once this information has been archived, our task is to develop a system that offers the user of NPDP resources access to real information on dam incidents.
At present we are developing a two-tiered Internet-based information system that gives the engineer maximum flexibility to search for dam performance information (by dam type, component type, initiating event, consequence, etc.) and at the same time does not require events to be categorised.
The first tier of our system is a database (actually multiple databases) that will be designed to document incidents with respect to what is known about each event. We will do so without discarding an event, or categorising it into pre-defined groups as this may limit the queries that can be made or the level of detail that can be provided. Our database system will include:
•Information on the characteristics of a dam and its components,
•A ‘metadata’ summary of a dam incident in terms of the event(s) that initiated the incident, the performance of individual components during the incident and the effect of their performance on other components, and the incident outcome or consequences.
•Dam design and as-built information.
•Links to the NPDP digital library or the second tier of the information system.
The digital library provides a user with direct access to the documents in the NPDP archive that are the source of ‘real’ information about an incident.
We have established a plan to offer dam engineering and safety professionals (eventually through the Internet) access to resources related to the performance of dams. This same access will also be available to those who may oppose dams. This poses an interesting tradeoff.
Some have expressed reservations about making this information available. Nonetheless the basics are quite simple. The foundation of the NPDP is part of a necessary and well-established tradition in engineering of learning from in-service performance. As such, the benefits the NPDP offers the profession as well as the public (in the form of effective dam safety policy), are self-evident and far outweigh any potential downside. Consider the following:
•Dam engineering organisations such as the international-commission-on-large-dams (ICOLD) and its partner national committees have published numerous documents over the years on dam failures and accidents. While these documents may have been published for the benefit of the technical community, they are readily available. With the proliferation of Internet bookstores, for example, ICOLD and USCOLD publications can be purchased online.
•Increasingly, financial and public support for initiatives to improve public health, safety or education, is based on data that identifies a problem area and quantifies the costs to the nation of failing to address it. While data are available in areas such as public health or consumer product safety, this is not the case for dams, which are such a vital part of the nation’s civil infrastructure.
From time to time we are asked the position of the NPDP when legal or other issues are entangled in a dam incident. For example, when a dam has failed, legal action may be taken against the dam owner, the designer, and even the government agency that approved the project, seeking some form of compensation. Under these circumstances, providing information may affect the legal position. Similarly, a dam owner may decide that information on a dam or dam incident is commercially sensitive or is confidential.
The NPDP position with regard to these circumstances is straightforward. Information on a dam incident is provided at the discretion of the reporting engineer. As such, it is the engineer who is in the best position to decide if and when information should be reported.
We believe the process of reporting dam incidents to the NPDP should not interfere with, or take precedence over any legal proceeding.
A recent lesson
In March of this year, the American Society of Civil Engineers (ASCE) held a press conference in Washington, DC to present its report on the state of the nation’s infrastructure. It had been ten years since the last such report was issued. With a pending federal budget surplus, ASCE believed the timing was appropriate to generate a sense of need with respect to the nation’s infrastructure.
To make a case for dams, ASCE looked to the dam safety community to provide information on the state of the nation’s dams, but information of this type was not readily available. Consequently, it was not possible to provide ASCE with a coherent, well-supported story about one of the nation’s vital infrastructures.
This experience highlighted the fact that too often we find ourselves in a reactionary, rather than a pro-active position. Had the profession taken the time to examine issues such as the ongoing cost of dam safety, the risk to the public, and the costs of rebuilding unsafe dams, we would have been in a position to support ASCE’s request by providing a realistic picture of the cost of maintaining a safe, reliable dam infrastructure. Instead, our story was incomplete, missing an opportunity to influence legislation.
As described below, our current project will put us in a better position to measure the state of the nation’s dams.
The NPDP goal of providing access to archival data on dam performance was enhanced by a recent grant from the National Dam Safety Programme. This will help create an infrastructure for an Internet-based digital library system, and develop a national dam performance evaluation system.
As regards the World Wide Web, this offers the most effective means to make performance information readily accessible. One of our tasks in developing a digital library system will be to develop a query language and data management system that will support problem-centred queries by engineers, and provide seamless access to digital documents. The digital library will improve the efficiency of library operations and accessibility for users throughout the country.
A major advantage of a real-time system of reporting the performance of dams is the opportunity it offers to provide a measure of the state of dams in the US. In the performance evaluation system project we will develop such a system. Once established, it will provide a basis over the long term to identify trends in dam performance, including new challenges to their integrity or the increasing effects of known aging or deterioration processes.
We envision this system will be the dam engineering equivalent of systems currently in-place to monitor and assess the state of the economy or public health. In these areas, the process of documentation, evaluation, and reporting provides input to long term policy decisions and the initiation of emergency actions. The value of these systems is attributed to their robustness as defined by their accuracy, stability and the comprehensive nature of the information that is reported. Our goal is to develop a dam performance evaluation system that is equally robust in providing input to dam safety policy and improved engineering standards.
|Kaare Høeg calls for a European programme|
|The European member countries of the International Commission on Large Dams (ICOLD), who have a large number of dams 50-100 years old, recently organised a very successful international symposium on ‘New trends and guidelines on dam safety’ (Barcelona, 17-19 June 1998). In his keynote address ICOLD president Kaare Høeg emphasised two aspects to reduce risk levels further. They were: •Ensure that the dam operator is qualified and prepared for unlikely events. •Regular monitoring including evaluation of observations. Høeg encouraged the European community to establish a European Performance of Dams Programme, parallel to, or in conjunction with, the already established programme at Stanford University. The intention is that all safety related dam incidents be reported to a common information centre (database). This will allow dam owners, engineers and safety professionals to benefit from the lessons of in-service dam performance in countries which confront similar challenges. It will further increase the probability of including all potential events and failure mechanisms in systematic risk analyses, which are used more and more in the required safety evaluation and documentation.|