Committee on Dam Safety

Transcription

1 Committee on Dam Safety New bulletin on Dam Safety Management for all phases preceding operational phase M. Balissat D. Hartford M. Poupart

2 Structure of Bulletin (revised Feb. 2016) Introduction - Why this bulletin? - Importance of dam safety at all development stages - Overarching principles (from Bulletin 154) Dam development phases and actors - Dam as a prototype - Related (pre-operation) development phases - Typical activities at each of pre-operational phases - Definition and role of the different actors Key issues to be addressed - Risks involved in design and construction of dams - Development stages and need for investigation - Project development as a continuous process - Risk management 17 May

3 Structure of Bulletin (revised Feb. 2016) Overarching Safety Management System - Overarching management system concept - Form of management system activities - Delivering dam safety objectives through an integrated management system - Transformation of project objectives into implementable actions - Role of the Owner/Investor in securing the safety objectives - Owner Management System - Role of the other Actors in securing the safety objectives - Management of risk and uncertainty in a dam development - Importance of Management of Changes - Role of arbitration in disputes Engineering Principles - Fundamental defense in depth principles - General consideration on dam design - Safety design principles - Safety assessment principles Conclusion 17 May

4 Introduction Reference to existing ICOLD bulletins on: - structural safety (11) - functional safety (12) - operational safety (8) Why this new bulletin? - Identifying the risk factors and trying to minimize them is essential to structural safety and to (planned) operational safety - Large number of Actors (especially at construction and commissioning stages) > need to define an overarching management system 17 May

5 Dam development phases and actors (1) Dam as a prototype - Dam design is based on state of the art rules. Standards do apply only to materials and structural elements. - Guidelines by regulatory agency provide in some countries a procedure to be followed, but many issues are left over to appreciation of Designer. - Planning and design of a dam involve assessment of potential hazards such as flood and earthquake. Dam design features to be such that they can accommodate these hazards, but residual risk remains. - Design and construction of dams is not a standardized industrial process. - Safety requirements spread over at different project stages and concerning several stakeholders ( Actors ), therefore difficult to unify. - Uniqueness of every designed and constructed dam scheme. 17 May

6 Dam development phases and actors (2) Related development phases a) Phases preceding the operational phase > from the preliminary studies to commissioning > specificity of each phase > increased number of Actors as project is progressing b) Activities at each of the pre-operational phases entailing risks concern : planning and design (desk activities) site activities (site investigation / construction / commissioning) but also: economical aspects 17 May

7 Dam development phases and actors (3) Definition and role of the different Actors a) The Developer (Owner) - Bears full responsibility for the safe structural behavior of his dam and for its operation - Relies on the skill and experience of his Engineer (Designer) - Shall communicate with the public at large, the stakeholders and the Authorities - Is interested in getting a maximal return on his investment and that of his partners and/or shareholders b) The Designer - Is acting on all phases preceding operation and is bound to the Investor/Owner by several successive contracts - Has to apply the best technical knowledge (state of the art). Has to make sure that all technical and safety aspects of the design are properly interpreted. - Shall perform his design activities within a given budget - Is instrumental in proposing cost saving solutions to the Owner/Investor. 17 May

8 Dam development phases and actors (4) Definition and role of the different Actors (c td) c) The Site Supervisor - Site supervision is provided by the Owner or by the Designer or by a combination of both. - Reports directly to the Owner - Has to manage the construction works within given contractual prices and an overall budget - Has a decisive impact on the quality of the work performed by the Contractor. - Shall be informed by the Designer on why and how design solutions have been adopted - Is responsible for identifying and controlling required design changes on site 17 May

9 Dam development phases and actors (5) Definition and role of the different Actors (c td) d) The Contractor - Several forms of work contract (single work contract, general contractor agreement, EPC, etc.) - Is a key person in every project as he has to guarantee a good quality of workmanship - Is bound to provide services mainly paid on the basis of piecework prices and lump sums. Difference between offered unit prices and effective cost prices, if negative, will lead to sloppy work and/or attempts to renegotiate prices (claim management). 17 May

10 Dam development phases and actors (6) Definition and role of the different Actors (c td) e) The Supplier - Suppliers are usually providers of goods and systems in the electro- and hydromechanical fields. They can be also specialized firms performing a subsidiary task in a dam (drilling works, instrumentation, etc). - Supply is included in overall package of the general contractor agreement or is in a single contract with the Owner. - Installation of equipment is to be coordinated with the Contractor, therefore provisions shall be made in the Contractor s work contract for any service provided to the Supplier. - Responsibility of the Supplier is limited to his supply package. This can lead to interface problems. Thus often a larger E+M package is delimited under the lead of one major Supplier. 17 May

11 Dam development phases and actors (7) Definition and role of the different Actors (c td) f) The Licensing Agency - Is usually at the National/Federal level, but in case of a decentralized (federal) type of structure also at the State or Province level. - A hydro license concerns essentially the water use, but specifies also the major safety requirements. - Hydro licensing progress involves consultation between national and local agencies for reaching terms and conditions to protect and enhance water quality, fishery resources, public recreation, renewable energy production and other public interests g) The State Regulatory Agency - Is in charge of the high surveillance of dam safety - Issues rules or guidelines concerning the design and operation of dams. Regularly check whether Owners meet the safety requirements - New projects and major rehabilitation works have to be approved by the State Regulatory Agency. 17 May

12 Dam development phases and actors (8) Definition and role of the different Actors (c td) h) The public - Distinction to be made between public at large (power consumer, beneficiaries of water supply, etc) and population downstream of a dam, respectively around a reservoir. These two groups require different types of communication. - Opposition to a dam project by radical people (for societal or ecological reasons) can last during construction and commissioning of the scheme and have an impact on dam design and safety. - Safety aspects: public generally understand that any technical activity entails a residual risk (even extremely low), but is not always ready to accept it if directly concerned by a possible dam break. Acceptance is conditioned by the foreseen countermeasures (emergency plans) in such a case. 17 May

13 Dam development phases and actors (9) Timely involvement of the actors during a dam development project PHASE OF PROJECT PROJECT ENTITY DEGREE OF INVOLVEMENT PRE-OPERATIONAL PHASES (Conceptual over multiple years) AUTHORITY INVESTMENT LIFE-CYCLE INVESTOR/OWNER CONCEPT DEVELOPMENT INVESTOR/OWNER DESIGNER CONTRACTOR FEASIBILITY INVESTIGATION INVESTOR/OWNER DESIGNER CONTRACTOR DESIGN AND ENGINEERING OWNER/DEVELOPER DESIGNER CONTRACTOR PROCUREMENT INVESTOR/OWNER DESIGNER CONTRACTOR CONSTRUCTION INVESTOR/OWNER DESIGNER CONTRACTOR ENTRY TO SERVICE INVESTOR/OWNER DESIGNER CONTARCTOR 17 May

14 Key issues to be addressed (1) Risks involved in the design and construction of dams Non technical aspects > human aspects - unrealistic Qwner - lack of experience or qualification (Designer/Contractor) - overconfidence (Designer) - non cooperative attitude within design or supervision team -... see also R. Peck (1973) on nontechnical aspects > organizational aspects - lack of information/communication between site inspection and design staff - long construction interruption (lack of funds, political reasons) - change of material sources during course of works May

15 Key issues to be addressed (2) Risks involved in the design and construction of dams (c td) Technical aspects 17 May

16 Key issues to be addressed (3) Development stages and need for investigation Dam Design - drawing up alternatives > optimization process - criteria for evaluating alternatives: subjective > layout quality, operating easiness objective > safety requirements, constructions costs, operating expenses - uncertainty on > external actions (hazards) > foundation conditions (geology) > material properties - codes and standards only applicable to materials and structural elements (appurtenant structures), but reliability analysis on load and resistance parameters (see for instance Eurocodes) could be used for dams also. - not so usual combination of usual loads can lead to critical stage 17 May

17 Key issues to be addressed (4) Development stages and need for investigation (c td) 17 May

18 Key issues to be addressed (5) Development stages and need for investigation (c td) Construction phase - Highest number of Actors during dam lifetime! - Interdependence between Actors described and regulated in number of contracts (numerous forms of contracting) - Respective responsibilities for work quality, construction delays and costs - Liabilities towards third parties - Main critical issue: river diversion (selection of diversion flood) - Encountered conditions on site different from anticipated ones (management of changes) - Influence of non-technical factors > human factors > organizational or economical factors (interruption of construction over a long period, change in sources of material, etc) > political requirements 17 May

19 Key issues to addressed (6) Development stages and need for investigation (c td) First impounding / Commissioning - Major risk at impounding : hydrology - Optimum balance to be found between impounding program and requirements of E+M testing - On middle size and high dams impounding in stages (need for constant pressure and seepage conditions over several days or weeks) - Closure of diversion involves risks of imperfect sealing (defective sill or jamming bulkhead!) - First impounding can initiate landslides at the reservoir banks either immediate or differed at first reservoir drawdown - Induced seismicity caused by impounding - Defective functions of hydro- or electromechanical equipments at their first wet test. 17 May

20 Key issues to addressed (7) Project development as a continuous process At the design stage project developed at each step in terms of alternatives comparison > best suited solution reduction of uncertainties by additional investigation Set of principles: - continuity (designers involved and/or adequate documentation from phase to phase) - independent checking (internal / external: Board of Consultants) - traceability (design records) Principles apply also to construction stage (design adjustments approved by designers + construction records) 17 May

21 Risk management / Risk categories Key issues to addressed (7) Risk of the project Investment loss Societal risk Risk from the project Conception, planning and implementation Risk to the project Scope, budget and schedule Management of changes Owner / Investor Designer Site supervision Contractor > Categories of risk are not completely separable > Risk of one category can migrate to another category 17 May

22 Overarching Safety Management System (1) General form of a management system (ICOLD, Bulletin 154, 2011) Policies and Objectives Continuous Improvement Planning Audit, Review and Reporting Implementation Monitoring and Evaluation 17 May

23 Overarching Safety Management System (2) Continuous Improvement Policies and Objectives Planning Continuous Improvement Policies and Objectives Planning Continuous Improvement Policies and Objectives Planning DAM SAFETY OBJECTIVES ACHIEVED Audit, Review Reporting Monitoring and Evaluation Impelmenting Audit, Review Reporting Monitoring and Evaluation Implementing Audit, Review Reporting Monitoring and Evaluation Implementing 17 May

24 Overarching Safety Management System (3) INEVESTOR/OWNER DESIGNER CONTRACTOR Policies and Objectives Planning and organising Policies and Objectives Implementing Planning and organising Policies and Objectives Monitoring and Evaluation Implementing Planning and organising Audit, Review and Reporting Monitoring and Evaluation Implementing Continuous improvement Audit, Review and Reporting Monitoring and Evaluation Continuous improvement Audit, Review and Reporting Continuous improvement DAM SAFETY OBJECTIVES ACHIEVED 17 May

25 Overarching Safety Management System (4) OBJECTIVE KEY CAPABILITY REQUIREMENT CAPABILITY REQUIREMENT 1. Water Management KCR1.01 Maintain reservoir level control KCR1.02 Minimise impacts of floods KCR1.03 Maintain downstream flows CR1.1 Water Catchment CR1.2 Water Storage CR1.3 Water Discharge Key capability requirements and capability requirements 2.Power Generation KCR2.01 Capability to Generate Power CR2.1 Power Capacity CR2.2 Power Revenue CR2.3 Electrical Services CR2.3 Black Start 3. Extreme Events KCR3.01 Maintain control during floods CR3.1 Flooding KCR3.02 Maintain control post earthquake CR3.2 Earthquake CR3.3 Other hazards 4. Operations CR4.1 Operational control CR4.9 See Figure X.X 5. Environment KCR5.01 Avoid/minimise/offset impacts CR5.1 Fish CR5.2 Riparian habitat CR5.3 Land environment CR5.4 Water pollution CR5.5 Air pollution (GHG) CR5.6 Waste 6. Communities KCR6.01 Meet local and societal interests KCR6.02 Ensure local water use objectives CR6.1 People CR6.2 Property CR6.3 Recreation 17 May Meet Constraints CR6.4 Infrastructure CR7.1 See Figure X.Y

26 Overarching Safety Management System (5) Operational characteristics of capability requirements / Extreme events OBJECTIVE KEY CAPABILITY REQUIREMENT CAPABILITY REQUIREMENT OPERATIONAL CHARACTERISTICS 3. Extreme Events KCR3.01 Maintain control during floods KCR3.02 Maintain control post earthquake CR3.1 Flooding CR3.1.1 Store and spill floods with adequate dam safety CR3.1.2 Maintain discharge capability as required CR3.1.3 Limit random functional failure of flow controls CR3.1.4 Adhere to flood operating rules CR3.1.5 Pass floods without operational intervention CR3.1.6 Post extreme event operational integrity CR3.1.7 Capability to drawdown reservoirs CR3.2 Earthquake CR3.2.1 Integrity of water barriers during/after earthquakes CR3.2.2 Integrity of hydraulic structures during/after earthquakes CR3.2.3 Post earthquake restoration of generation CR3.2.4 Post earthquake restoration of environmental and social flows CR3.3 Other hazards CR3.3.1 Sustain operations during forest/other fires CR3.3.2 Withstand surges from landslide waves CR3.3.3 Protect workers from facility fire/explosions CR3.2.4 Sustain river system operations in severe freeze 17 May

27 Overarching Safety Management System (6) Operational characteristics of capability requirements / Operation OBJECTIVE KEY CAPABILITY REQUIREMENT CAPABILITY REQUIREMENT OPERATIONAL CHARACTERISTICS 4. Operations CR4.1 Operational control CR4.1.1 Implement local control capacity as required CR4.2 Access CR4.1.7 Enable automatic operation of hydraulic control CR4.2.1 Assets accessible under all conditions CR4.3 Operational reliability CR4.3.1 Capacity to rectify faults CR4.4 System integrity CR4.4.1 Sustain generation capability CR4.4.2 Provide asset security CR4.5 Hydraulic control CR4.6 Monitoring CR4.7 Communications CR4.5.1 Control flow at, through and around dam CR4.5.2 Balance flows along river CR4.6.1 Monitor state of river system CR4.6.2 Monitor condition of river system assets CR4.6.3 identification of incidents CR4.6.4 Manage changes under operation CR4.7.1 Sustain communications in support of operation CR4.8 Maintenance CR4.9 Equipment CR4.8.1 Maintain river system assets CR4.8.2 Ensure reliability is met CR4.8.3 Avoid outages during high inflow seasons CR4.9.1 Operate in correct modes CR4.9.2 Ensure equipment health CR4.9.3 Manage obsolescence 17 May

28 Overarching Safety Management System (7) Role of the Owner / Investor in securing the safety objectives Commitment of the Owner to dam safety Policies and objectives Implementation actions General responsibility of the Owner : ensuring - continuity - traceability - independent checking To be detailed according to project phase: - Preliminary studies - Feasibility studies / Detail design - Construction phase 17 May

29 Overarching Safety Management System (8) Owner Management System Policies and general organisation Project development entity sufficient staffing qualified personal Monitoring and evaluation means of checking that project is on good track (different aspects) Audit review and reporting independent Board of Consultants (Advisory Board) 17 May

30 Overarching Safety Management System (9) Role of the other Actors in securing the safety objectives Designer transformational role make sure that endeavour of Owner can be realized not only engineering competence, but also organisational capacity has to provide guidance to Owner on safety aspects Contractor financial strength organisational capacity appointment of qualified construction and construction monitoring staff 17 May

31 Overarching Safety Management System (10) Management of risk and uncertainty in a dam development - Assessing dam safety using risk based analytical techniques - But risk analyses cannot be used as a substitute for sound professional judgement Management of changes - Essential element of risk management - Impact on dam safety - Can cause delays in construction and has contractual implications Arbitration in disputes - Change management can lead to claims - Requires arbitration of the disputes between the parties - Contract(s) shall guarantee that safety of constructed works is not compromised during the dispute 17 May

32 Engineering principles (1) Background At the conceptual stage a design should present the following engineered features: - Redundancy: more than one way to achieve the system output - Diversity: different ways to achieve the same function - Segregation: output served from different directions - Defense in depth: large margins of capacity over demand (in all systems) - Fault tolerant: a single fault (incl. human fault) will not cause loss of system function - Fail to a safe condition: if the system does fail, it will be rendered to a harmless condition 17 May

33 Engineering principles (2) Fundamental Defense in depth principles Principle 1: Principle 2: Principle 3: Conservative design and high quality in construction Control of abnormal behaviour and detection of failures, through surveillance and monitoring Control of accidents within the design basis through engineered safety features and accident procedures (These principles are in line with the defence in depth principles used in the nuclear industry) 17 May

34 Siting and Layout Safety Design Principles PR1 : Facilities and structures shall be situated with due consideration to the risks posed to them by their environment PR2 : Selection of the dam type and spillway type shall be done in due consideration of their impact on the overall project safety PR3 : Dams and appurtenant structures shall be situated with due consideration to the added risks posed to adjacent and downstream communities and assets. Proven engineering practices Engineering principles (3) PR4 : Dam design is based on engineering practices that are proven by testing and experience. 17 May

35 Other principles Engineering principles (4) Safety Design Principles (c td) PR5: Design of structures, systems and components should adopt materials and methods which ease the works, minimize the risks of harm to workers during building and installation and minimize the likelihood of introducing defects. PR6 : Design of structures, systems and components should give due consideration to preservation of asset function through life time and to the means by which such functions can be safely preserved and verified. PR7 : Design of structures, systems and components should reliably meet, in a safe and predicable manner, the requires levels of in-service performance under the expected full range of operating conditions 17 May

36 Engineering principles (5) Safety Assessment Principles General Principle The safety assessment is made before construction and operation of a dam scheme begin. The assessment is well documented and independently reviewed. It is subsequently updated in the light of significant new safety information. Safety Classification and Standard PR1 : The functions of structures, systems and components shall be identified and classified according to their overall significance to safety. Dam as a system PR2 : Dam is a system, and dam safety assessment should therefore consider a systemic approach. Structural resistance - Loadings and Performance Demands PR3 : The design basis shall be thoroughly established and recorded, such that all credible loading and performance demands on the design are identified, assessed and quantified where appropriate and possible. 17 May

37 Safety Assessment Principles (c td) Safety assessment for serviceability Engineering principles (6) PR4 : Potential changes with time of dam sub system efficiency, evolution of external loadings, and reliability of mechanical and electronic equipment are addressed during the safety assessment process. Risk analysis PR5 : The potential safety risks arising from areas of complexity in the design and/or uncertainty in the design basis should be examined through a proportionate and appropriate use of risk analysis techniques. Human factors PR6 : A systematic approach should be taken to identifying, examining and optimizing the expected range of human interactions with the design, so that safety risks to workers and (indirectly) to the public are minimized. 17 May

38 Engineering principles (7) Engineering Principles : an overview Fundamental Principles Conservative design Detection of failure Control of accidents Accident prevention Accident mitigation Safety Design Principles Siting and general layout Proven engineering practices Manufacture Build and Installation Commissioning, Testing, Maintenance and Inspection Performance and Operation Decommissioning Safety Assessment Principles Safety Classification and Standard Systemic approach Structural resistance Serviceability assessment Risk Analysis Human factors 17 May