WIXLIB

Chapter 1 - Introduction1.1.Why this bulletin?Dams are massive structures retaining large water bodies able to cause substantial or even catastrophic damagesdownstream of their location. As such they represent a potential hazard in case of uncontrolled release of waterdue to overtopping by flood or by submergence caused by a sliding earth mass in the reservoir. Obviouslystructural failure of the dam body or its foundation or malfunction of water releasing structures constitute alsopotential hazards. Although many risks associated with dams are linked to the operation of these structures someof them are imbedded in the phases preceding operation. They can be found at the preliminary planning of thedam scheme, during the detail design of the structures, as well as during the construction and commissioningphases. Identifying the risk factors and trying to minimize them are essential to structural safety and to (planned)operational safety. Dam safety has to be adequately managed from the onset of a project development until itsconstruction and commissioning. It shall be pursued during the whole operation of the scheme. This means thathow dam safety is to be pursued in the operational phase of the life‐cycle must be developed in the design phaseof the project.Until present no bulletin of ICOLD was directly addressing this situation. Bulletins (see list in Appendix B) are eitherpurely technical or describing risk evaluation methods from a theoretical point of view. The present Bulletinaddresses the pre‐operational phases of a dam project and links them to the guidance of the previously issuedBulletin 154 which presents recommendations for safety management during the operation of the dam (see Fig.1.1).In phases preceding operation of a dam scheme (going from preliminary studies to commissioning) attention hasto be given to the implementation of engineering and construction measures (best practice) excluding or, at least,minimizing the risk of failure of the dam. They encompass both structural (retention of water) and operation(conveyance of water) oriented safety measures. Several factors (human and technical) tend to affect the safetyaspects of a dam. Whereas technical aspects are relatively easy to identify in design, human factors covers a broadrange of interfering and less strictly defined aspects going from personality conflicts within a working team todeficient communication and organizational flaws. Therefore management of the steps leading to the realizationof a dam scheme and its operation should be aware of these possible drawbacks and should put all necessaryefforts into identifying and controlling them.1.2.Importance of dam safety at all development stagesA decision to invest in the development of a dam is a very significant matter that can be of national and eveninternational importance from multiple perspectives. The investment involved is generally so large that it isimperative that the development fulfil all of the intended objectives and other objectives as might be determinedafter construction, or as determined over the economic evaluation period of the dam and beyond (the whole life‐cycle). It can be taken as a premise that the investment must be secured at the outset in such a way that theprinciple that development of the dam results in a net positive contribution to society is realised. Dam Safetyconsiderations have a pivotal role in securing the investment over the whole life‐cycle of the dam.3

Figure 1.1 Extent of this bulletinIn the modern context, Dam Safety considerations which include all aspects of safety management over the wholelife‐cycle contribute to a great deal more to securing the investment than previously considered when dam safetypertained to structural safety (ICOLD B59, 1987):The safety of a dam manifests itself in being free of any conditions or developments thatcould lead to its deterioration or destruction. The margin which separates the actualconditions of a dam, or the conditions it is designed for, from those leading to its damage ordestruction is a measure of its safety. To be safe, therefore, a dam has to be supplied withappropriate reserves, taking into account all reasonably imaginable scenarios of normalutilization and exceptional hazard which it may have to withstand during its life.By way of illustration, how dam safety is considered in the design phase influences construction costs and safetyduring construction, and later on operational safety, costs, constructability and safety of modifications,improvements and renewal, and finally decommissioning.For instance, the choice of spillway type, a matter that is identified at the conceptual design or feasibility stage cansignificantly influence whole life‐cycle operational costs and the effectiveness of operational safety. Life‐cycleoperational costs that can be influenced at the conceptual design stage go far beyond the physical componentsand include surveillance and monitoring costs, staffing costs, maintenance and repair costs and ultimatelyrepair/upgrading/renewal costs prior to the end of the life‐cycle.In addition to the physical and operational justifications for including whole life‐cycle safety considerations at anearly stage of the design process, there are sound financial reasons for the dam Investor to consider earlyinvestment in dam safety for financial efficiency and for insurance reasons. The financial efficiency dimensionsrelate to the economics of the project over the whole life‐cycle from the perspectives of asset value, operationalcosts and refurbishment/renewal costs whereas the insurance dimensions relate to the overall protection of theinvestment. The investment in the dam is “at risk” from the initial stages of the investment up to the end of theeconomic evaluation stage with the investment most “at risk” initially from first filling to approximately 5‐yearsinto the service life, and again at the end of the service life of the dam. The relatively long pay‐back period for thecapital investment in a dam means that the total financing and operational costs of a dam will not become net‐positive until well into the economic evaluation life‐cycle. During this time, the effects of ageing will begin tomanifest themselves, and safety expectations can be expected to increase. A robust design that considers theseissues at the outset can significantly influence the repair and replacement costs at the later stages of the economic4

evaluation process. In straightforward terms, securing safety contributes to securing the investment and vice‐versa.1.3.Overarching PrinciplesICOLD Bulletin 154 defines nine overarching principles for dam safety that are sufficiently general to be applieddirectly or with minor alteration over all phases of the life‐cycle of a dam. These principles are as follows:a) Justification for dams: Dams should be constructed and operated only if they yield an overall benefit tosociety.b) Fundamental Dam Safety Objective: The fundamental dam safety objective is to protect people, propertyand the environment from harmful effects of misoperation or failure of dams and reservoirs.c) Responsibility for Operational Integrity and Safety: The prime responsibility for operational integrity andsafety of a dam should rest with the Dam Owner.d) Role of Government: The legal and governmental framework for all industrial activities, includingoperation of dams, provides the overarching structures for operational integrity and safety assurance.e) Leadership and management for Safety: Effective leadership and management for operational integrityand safety should be established and sustained over the life cycle of the dam.f) Balancing of Protection across Competing Objectives: Protection should seek to achieve a balance acrosscompeting objectives to provide the highest level of operational integrity and safety that can reasonablybe achieved.g) Limitation of Risk to Individuals and Society: Measures for controlling risks from dams should ensure thatno individual bears an unacceptable risk of harm, and that the risks to society do not exceed the risktolerance levels of society.h) Sustainability of Dams and Reservoirs: In order to secure the societal value, dams and reservoirs must besustained in the long term. To ensure sustainability of dams, all reasonably practicable efforts should bemade to prevent and mitigate failures and accidents.i) Emergency Preparedness and Response: Appropriate arrangements should be made for emergencypreparedness and response for dam failures and accidents.Clearly, one of the objectives of the pre‐operational phases is to ensure that the dam conforms to all of theseprinciples when it goes into service. Importantly, for most dam constructions, the dam enters in operation as soonas impoundment begins and often before the construction has been handed over to the Investor/Owner.Of the 9 overarching principles the following apply directly without any alteration to the pre‐operational phases: Justification for Dams Fundamental Safety Objective Balancing of Protection across Competing Objectives Limitation of Risk to Individuals and Society Sustainability of Dams and Reservoirs Emergency Preparedness and ResponseThe remaining three, Responsibility for Operational Integrity and Safety, Role of Government and Leadership andManagement for Safety, can be modified and made specific to the pre‐operational phases in a way that there canbe a smooth transition to the operational phase when the dam is handed over to the Investor/Owner.The Investor/Owner has the continued full responsibility to maintain leadership and management for safety duringall phases of a project (planning, design, construction, quality control) including transitioning to the operationphase, and subsequently through the operational phase and then into either renewal or decommissioning.The three revised Pre‐operational Safety Principles are provided as follows:5

Responsibility for Integrity and Safety in the Pre‐Operational Phases:The prime responsibility for the overall integrity and safety of a dam should rest with the Dam Owner. The Owneris responsible for the third party liabilities. Responsibility for meeting safety objectives of the design should restwith the Designer, but the Owner has to make sure that he is fully understanding and accepting the design of theproject. He further carries full responsibility for implementing an adequate quality control system during designand construction. Responsibility for safety of the works during construction and commissioning should rest withthe Construction Supervising Engineer as determined by the contractual arrangements established by theInvestor/Owner.Role of Government:The legal and governmental framework for all industrial activities, including licensing, development, operation, andalteration of dams, provides the overarching structures for pre‐operational and operational integrity and safetyassurance, and for safety during renewal or retirement from service. The Government through its regulatoryagency requires a number of policies and design criteria to be satisfied. But the Owner has to be even moreconservative for reducing potential risks to a level satisfactory for the protection of the public and its own assets.Leadership and Management for Safety in the Pre‐Op

implementation of the modern safety management approach to other phases of the dam life cycle should be considered as a priority task for the CODS in the future. This document extends the general approach and concepts presented in Bulletin 154 to all phases of dam life