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Risk Based Regulation Seminar – June 2010

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RISK BASED REGULATION SEMINAR – POWERPOINT PRESENTATIONS

Table of Contents Item Page

1. Seminar Agenda ...................................................................................................... 1

2. Welcome, Summary and Closure by Brian Cooper.................................................. 3

3. DSC’s New Risk Based Approach by Len McDonald .............................................. 9

4. DSC Legislation and Legal issues by Dermot Armstrong ...................................... 29

5. Mining near/under Dams by David Hilyard ............................................................. 34

6. Safety Reviews/Peer Reviews by Jeff Gleeson ..................................................... 47

7. DSC’s Design issues by Pau Heinrichs ................................................................. 53

8. Emergency and Management by Norman Himsley ................................................ 64

9. Hydrology issues with regard to Dams by Assoc. Prof. Ian Cordery ...................... 71

10. DSC’s requirements for Surveillance Reports by Michael Karp ............................. 77

11. DSC’s requirements for Tailings Dam reports by Engin Hizbas ............................. 83

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Special points of interest:

● Briefly highlight your point of interest here.




1

1 10 100 1000 10000

N, number of fatalities due to dam failure

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loss

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10-4

10-5

10-6

10-7

10-3

Full SBA required as a minimum - final

DSC decision based on critical review of benefits and risks

Risks are negligible

Risks are to be as low as reasonably

practicable (ALARP)

Risks are intolerable

Limit of tolerability

Important Note: Where fatalities are expected in the event of dam failure, consultation with the affected public is recommended as part of the final decision process

Figure 1 – Proposed DSC Societal Risk Requirements: Existing Dams

Risk Based Regulation Seminar 10 June 2010

The Menzies Sydney Hotel

14 Carrington Street Sydney, NSW 2000

Australia

PROGRAMME

NSW Dams Safety Committee presents ‐

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RISK BASED REGULATION SEMINAR - PROGRAMME

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Assignment Name Time Assignment Timing

Assignment Presenter

Registration 8.15 – 8.45 am 30 mins DSC

Welcome 8.45 – 8.55 am 10 mins Brian Cooper, Chairman, DSC

Introduction 8.55 - 9.25 am 30 mins Brian Cooper, Chairman, DSC

DSC’s New Risk Based Approach

9.25 – 10.00 am 35 mins Len McDonald, Ex-Chairman, DSC

Welcome Minister 10.00 -10.05 am 05 mins Brian Cooper, Chairman, DSC

10.05 –10.20 am 15 mins

The Hon. Phillip John COSTA, DipEd MP

Minister for Water, and Minister for Corrective Services

Questions and Answers

10.20 – 10.30 am 10 mins

MORNING TEA 10.30 – 10.50 am 20 mins

DSC Legislation and Legal issues

10.50 – 11.10 am 20 mins Dermot Armstrong, Legal Services (Water) Manager, State Water Corporation

Mining near/under Dams

11.10 – 11.30 am 20 mins David Hilyard, Manager, Mining Impacts, DSC

Safety Reviews/Peer Reviews

11.30 – 11.50 am 20 mins Jeff Gleeson, Manager Engineering, Hunter Water Australia Pty. Ltd


11.50 – 12.00 am 10 mins

LUNCH 12.00 – 1.00 pm 60 mins

OPENING ADDRESS

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RISK BASED REGULATION SEMINAR - PROGRAMME—

Assignment Name Time Assignment Timing

Assignment Presenter

DSC’s Design Issues

1.00 – 1.20 pm Paul Heinrichs, Executive Engineer, DSC

Emergency and Management

1.20 – 1.40 pm 20 mins Norm Himsley, Member, DSC

Hydrology Issues w.r.t Dams

1.40 – 2.00 pm 20 mins

Assoc. Prof. Ian Cordery, Member, Hydrology Sub-Committee


2.00 – 2.15 pm 15 mins

AFTERNOON TEA 2.15 – 2.35 pm 20 mins

DSC’s requirements for Surveillance Reports

2.35 – 2.55 pm 20 mins Michael Karp, Secretary, Surveillance Sub-Committee, DSC

DSC’s requirements for Tailings Dam reports

2.55 – 3.05 pm 10 mins Engin Hizbas, Dams Engineer, DSC


3.05 – 3.15 pm 10 mins

Summary and Closure

3.15 – 3.30 pm 15 mins Brian Cooper, Chairman, DSC

Further Questions and Answers if necessary

3.30 – 3.45 pm? All DSC

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Brian Cooper – Welcome, Introduction, Summary and Closure

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Welcome, Introduction Summary and Closure by Brian Cooper Chairman, DSC

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RISK BASED REGULATION SEMINAR

10 June 2010 – The Menzies Sydney Hotel

30 March 2010

30 March 2010

10 June 2010NSW Dams Safety Committee��

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NSW Dams Safety Committee


• Welcome Dam Owners and Consultants• Background to New Guidance Sheets &

Ai f th D

WELCOME

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Aim of the Day• Housekeeping• Welcome to Minister & Invitation for him to

Open the Seminar


• The 2009 Seminar• New Guidance Sheets now finalised

BACKGROUND TO NEW GUIDANCE SHEETS& AIM OF THE DAY

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• Aim of the day is to explain all the new Guidance Sheets

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• Minister for Water and Corrective Services– Primary school principal– Local Government involvement since 1985 –

Mayor of Wollondilly Shire Council 2005 to 2007– Wollondilly Citizen of the Year 1984

f f f

Introduction of Minister Costa

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– Resident of Wollondilly for 35 years – therefore great interest in Illawarra mining and dams in the region

– Knowledge and interest in water supply issues and understanding of the long lead times involved in dam projects

– Great interest in the work of the DSC

INTRODUCTION• DSC Generational Change• DSC Strategic Plan• October 2008 Seminar introducing new,

draft, risk based Guidance Sheets

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• The Dams Safety Act 1978• DSC functions described in the Act• Goals based regulation• Accountability of Owners• Introduction of Speakers

INTRODUCTION• DSC generational change

– Len McDonald (past Chairman) now retired– Brian Cooper now the Chairman with Jeff

Gleeson the Deputy Chairman– Norm Himsley retired as Executive Engineer

CHANGES WITH THE DSC

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and is now a Committee Member– Paul Heinrichs is now the Executive Engineer

• POLICY CHANGE– Risk Based Policy approved by Parliament

in 2006 now being implemented

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INTRODUCTION• Strategic Plan developed for 2009 to 2014

(includes a Business Plan for 2009/2010)• Mission Statement: To ensure the safety of

dams• Vision:

DSC STRATEGIC PLAN

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– All dams meet a level of safety that is acceptable to the community; and– We inspire confidence in our stakeholders and are recognized for our technical

excellence.

• To implement this vision, the DSC has adopted the following key goals:– Formulation of measures to ensure the safety of dams;– Promotion of the progressive reduction of risk across all prescribed dams;– Ongoing review of the safety management of prescribed dams;– Maintenance of a relevant and current knowledge of the safety status of NSW dams;– Promotion of dam safety awareness through the direction, education and training of

stakeholders; and– Effective management of its resources (eg staffing and budgets).

INTRODUCTION• Strategic Plan Goal relevant to this Seminar: “Promote dam

safety awareness”

DSC STRATEGIC PLAN

Forge close DSC links with MinisterMinister/DSC Exec meetings 4 per year

Minister attend DSC meeting Annually

Operator training 3 per year

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Education and liaison with dam owners and consultants

Website update Annually

Guidance sheets Update every 3 years

Interactive DSC/SES/owner DSEP exercises

2 per year

Education and liaison with community Guidance sheets and website Regularly update

Forge close links with other risk regulators Organize regular forums Interstate regulator meeting at ANCOLD; Quarterly DSC/DWE meetings; NSW regulator workshop every 3 years; Emergency S/C meetings every six months

INTRODUCTION• Presented drafts on new Guidance

Sheets DSC1A, DSC1B, DSC2A, DSC2C, DSC2D and DSC2I – umbrella Guidance SheetsIncluded a workshop by attendees on

OCTOBER 2008 SEMINAR

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• Included a workshop by attendees on how to improve the draft Guidance Sheets

• Invitation to comment on the draft Guidance Sheets

• Led to final Guidance Sheets

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INTRODUCTION• DSC to oversight safety of dams and oversight and

regulate mining that could affect dams or their storages

• DSC has 9 part-time members and around 11 staff• Sections 14 and 15 of the Act prescribe certain

functions to the DSC relating to inter alia:

THE DAMS SAFETY ACT 1978

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functions to the DSC relating to, inter alia:– surveillance of prescribed dams– design, construction, modification, O & M of prescribed

dams– Information & records regarding the safety of dams– formulating measures to ensure the safety of dams– reporting to the Minister in relation to the safety of

dams

INTRODUCTION• Goals based regulation sets goals that allow

alternative ways of achieving compliance - does not specify the means of achieving that compliance

• In prescriptive regulation, the specific means of achieving compliance is mandated

GOALS BASED REGULATION

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achieving compliance is mandated• Goals based regulation a good fit with a risk

framework for dam safety• Greater flexibility coupled with increased

accountability• Accountability to be ensured by implementation of

Sections 15 and 18 of the Act if necessary

INTRODUCTION

• Described in Guidance Sheet DSC1ABACKGROUND, FUNCTIONS & OPERATION OF DSC

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INTRODUCTION• Len McDonald (Immediate Past Chairman): DSC’s

New Risk Based Approach• Dermot Armstrong (State Water Corporation – Legal

Adviser to DSC): DSC Legislation & Legal Issues• David Hilyard (Aurecom, previously Mgr. Mining

I t DSC) Mi i & d d

PRESENTERS & THEIR TOPICS

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Impacts, DSC):Mining near & under dams• Jeff Gleeson (Deputy Chairman): Safety Reviews &

Peer Reviews• Paul Heinrichs (Executive Engineer): Design Issues• Norm Himsley (Committee Member): Operational

Matters (Emergency Management, O&M, Security)

INTRODUCTION

• Associate Professor Ian Cordery(Hydrology Sub-committee): Hydrology issues with respect to dams

PRESENTERS & THEIR TOPICS (continued)

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• Michael Karp (Dams Manager, DSC): Requirements for Surveillance Reports

• Engin Hizbas (Dams Engineer, DSC): Requirements for Tailings Dams

• Handling of Questions

SUMMARY & CLOSURE• Recap of presentations• Thank you for interest & attention• Reminder that Guidance Sheets together with

Powerpoint Presentations are on the DSC web site

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www.damsafety.nsw.gov.au• Invitation to Dam Owners & their consultants

to discuss their dam(s) with the DSC• DSC looks forward to ongoing cooperation

with Dam Owners and their consultants to ensure the safety of dams in NSW

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DSC's New Risk Based Approach by Len McDonald Ex-Chairman, DSC

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DSC’s New Risk Based Approach

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byLen McDonald

Immediate Past Chairman of DSC and Convenor for the ANCOLD Guidelines on

Risk Assessment October 2003

OVERVIEW1. AIM OF THE PRESENTATION2. DSC GOALS3. KEY DEFINITIONS4. TRADITIONAL APPROACH TO DAM SAFETY

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5. ELEMENTS THE DSC EXPECTS TO SEE IN THE RISK BASED APPROACH

6. THE DSC PUBLIC SAFETY RISK GUIDELINES7. THE DEMONSTRATION OF SAFETY BY OWNERS8. SOME RECENT DEVELOPMENTS9. CHALLENGES FOR THE FUTURE

1. AIM OF THE PRESENTATION

• To explain DSC expectations for the new approach

• To outline the continued role for the traditional standards based approach

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pp• To show how the risk based approach

better discharges the duty of care, given the serious responsibility of owning a dam

• To indicate some challenges to be overcome

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2. DSC GOALS• risks to community interests are identified, assessed,

properly managed, reduced when necessary and kept under review for the life of a dam;

• risks to public safety meet the DSC public safety risk guidelines [Risk Management Policy Framework for Dam Safety, DSC1B - Section 6, under Principle D.3];

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• other risks with a potential for an adverse effect on community interests meet criteria set by the owner and agreed with the DSC;

• needed safety improvements are undertaken as soon as reasonably practicable, in a way that best serves community interests;

• the DSC approach will facilitate a whole of Government approach to public safety.

3. KEY DEFINITIONS

From ANCOLD risk guidelines 2003:• Standards based approach• Risk

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• Risk analysis• Risk evaluation• Risk assessment

WHAT IS THE STANDARDS BASED APPROACH?

• The traditional approach to damsengineering, in which risks arecontrolled by following established

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y grules as to design events andloads, structural capacity, safetycoefficients and defensive designmeasures.

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WHAT IS RISK?• Risk - Measure of the probability and severity of an

adverse effect to life, health, property, or theenvironment. In the general case, risk is estimatedby the combined impact of all triplets of scenario,probability of occurrence and the associated

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p yconsequence. In the special case, risk is estimatedby the mathematical expectation of theconsequences of an adverse event occurring (thatis, the product of the probability of occurrence andthe consequence, combined over all scenarios).

WHAT IS RISK ANALYSIS?The use of available information to estimate the riskto individuals or populations, property or theenvironment, from hazards. Risk analysesgenerally contain the following steps: scopedefinition, hazard identification, and risk estimation.

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, ,Consistent with the common dictionary definition ofanalysis, viz. “A detailed examination of anythingcomplex made in order to understand its nature orto determine its essential features” , risk analysisinvolves the disaggregation or decomposition of thedam system and sources of risk into theirfundamental parts.

WHAT IS RISK EVALUATION?The process of examining and judging thesignificance of risk. The risk evaluationstage is the point at which values(societal, regulatory, legal and owner’s)and judgements enter the decision

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process, explicitly or implicitly, byincluding consideration of the importanceof the estimated risks and the associatedsocial, environmental, economic, andother consequences, in order to evaluatea range of alternatives for managing therisks.

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WHAT IS RISK ASSESSMENT?

Risk assessment - The process ofdeciding whether existing risks aretolerable and present risk controlmeasures are adequate and if not

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measures are adequate and if not,whether alternative risk controlmeasures are justified or will beimplemented. Risk assessmentincorporates the risk analysis and riskevaluation phases.

4. TRADITIONAL APPROACH TO DAM SAFETY

• Is the standards based approach

• Has been adapted from design of new dams – philosophicdifference, die has been cast for existing dams

• Is a form of risk assessment – aims to assess and control risk

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• The focus is on the dam structure – does not addressaspects such as human factors, dam safety managementprocedures

• There are some key limitations

• But is valid and useful – is part of the new DSC approach

KEY LIMITATIONS OF TRADITIONAL APPROACH [A]

• Difficult to compare risks over failuremodes, elements of a dam and acrossdams

• Not easily understood by lay managers,

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y y y gstakeholders – they do not know what asliding stability factor of 2.23 means

• Uncertainties are hidden – not transparent• Consequences confined to a few “big

boxes” – not case specific - economicallyinefficient

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KEY LIMITATIONS OF TRADITIONAL APPROACH [B]

• Considers only extreme loads – not necessarilythe greatest risks

• No recognized standard for some failure modes• Does not address human factors - intervention,

training communication errors

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training, communication, errors• Does not account for such aspects as inspection,

surveillance and emergency response procedures• No “common currency” across dams for risk

reduction pathway planning

5. ELEMENTS THE DSC EXPECTS TO SEE IN THE RISK BASED APPROACH

• Communication and consultation• Context definition• System definition• Tolerable risk criteria• Hazard analysis

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• Hazard analysis• Failure modes analysis• Estimation of failure probabilities• Estimation of consequences• Risk evaluation• If needed, risk reduction commitment

RISK BASED PROCESS

• The process expected by DSCfollows the ANCOLD Guidelines onRisk Assessment October 2003

• The process is compatible with that

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• The process is compatible with thatset out in Clause 5 of theAustralia/New Zealand Standard RiskManagement – Principles andGuidelines AS/NZS ISO 31000:2009

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COMMUNICATION AND CONSULTATION

• Required by clause 5.2 of AS/NZS ISO31000:2009 throughout the riskmanagement process

• Encouraged by DSC

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g y• Required by DSC for demonstration that

risks are as low as reasonably practicable(ALARP)

• Community Consultation andCommunication DSC2I gives guidance

CONTEXT DEFINITION – WHAT IS THE STUDY CONTEXT?

• Purpose• Constraints• Organizational context

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• Regulatory context• Risks of interest – dam failure risks

to community required by DSC, business risks a matter for the owner

SYSTEM DEFINITION – WHAT IS TO BE STUDIED?

• Dams and dam elements• Storages• River basins and reaches

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• Inundation areas• Operating rules• Communication network• Dam safety procedures• Personnel

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TOLERABLE RISK CRITERIA – WHAT RISKS CAN WE LIVE WITH?

• Owner to define the criteria• Public safety – the DSC public safety risk guidelines

[DSC1B] are to be met• Economic loss – owner decide in consultation with

communityFi i l l d id

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• Financial loss – owner decide• Environmental impact – owner decide by legislation,

community views• Public health – owner decide with local authorities,

community – system specific• Owner credibility – owner decide• DSC to agree with criteria affecting the interests of the

community

HAZARD ANALYSIS – WHAT ARE THE SOURCES OF HARM?

• Identify hazards – flood, earthquake,stored water, inherent flaws, wind,fire, human error, mining movements

• Analyse hazards extreme rainfalls

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• Analyse hazards – extreme rainfalls,flood frequency curves, earthquakeshaking frequencies

• Stretch the mind – recall the peathazard for Wingecarribee Dam

ANCOLD BULLETIN NO. 113 DECEMBER 1999

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FAILURE MODES ANALYSIS – HOW COULD THE DAM FAIL?

• Identify all conceivable failure modes – what elements of the dam could fail to function as intended? How could failures occur?

• Classify modes as credible or not credible and document reasons

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• For credible modes, identify the failure mechanisms – what are the steps in the failure process? Best to represent by logic diagrams, such as event trees and fault trees

• DSC requires failure modes analysis for all High and Extreme Consequence dams

ESTIMATION OF PROBABILITIES – HOW LIKELY IS FAILURE?

• Assign probabilities to failuremechanisms – reliability analysis, MonteCarlo simulation, failure frequencydatabases, human factors analysis, damspecific tools, expert judgment of

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p , p j gexperienced panel, Barneich et al.

• Dam specific tools – internal erosion andpiping toolbox, overtopping systemresponse curve based on failure data,Monte Carlo analysis of gravity damsliding

ESTIMATION OF CONSEQUENCES – IF FAILURE OCCURS, WHAT HAPPENS?

• Selection of failure scenarios• Dam breach and dam break flood modelling• Inundation mapping• Persons, assets and environment at risk

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• Estimation of consequences according towarning time, flood severity

• Rate the severity of the losses – such asestimated loss of life, estimated dollar loss,estimated habitat destruction, estimated impacton public health

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RISK EVALUATION – ARE THE RISKS TOLERABLE?

• Comparison of the risks with thetolerable risk criteria

• Risks to public safety have specialrequirements addressed in next

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requirements – addressed in nextsection

• Required answer – is risk reductionneeded?

COMMITMENT TO RISK REDUCTION – WHAT MEASURES WOULD ACHIEVE TOLERABLE

RISKS?

• If risks to community interests arenot tolerable, the DSC requires theowner’s commitment to takemeasures that will achieve tolerable

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measures that will achieve tolerablerisk

• Timing of implementation is to be asagreed with the DSC – but as soonas reasonably practicable

6. THE DSC PUBLIC SAFETY RISK GUIDELINES

• Primary source – Risk Management Policy Framework for Dam Safety DSC1B [under Principle D.3] –endorsed by Government

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endorsed by Government• Secondary source – Demonstration

of Dam Safety for Dams DSC2D –clarifies the requirements

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IMPORTANCE OF PUBLIC SAFETY

• Public safety is a right• It applies uniformly across the state

– independently of thecircumstances of dam owners or

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circumstances of dam owners orcommunities

• It is the main determinant of safetylevels for the majority of dams with apopulation at risk

THE UK HEALTH AND SAFETY EXECUTIVE CONCEPT OF TOLERABLE RISK

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THE DSC ADAPTATION

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POINTS TO NOTE

• Terminology – the HSE unacceptable is the DSC intolerable and HSE broadly acceptable is DSC negligible

• That DSC terminology aligns with Department of Planning

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Planning• Region of Tolerability Review – a risk is not

tolerable by being within the region – there are other tests

• Therefore there is a gap between the intolerableand tolerable risk levels

RISK TO THE INDIVIDUAL• The term risk to the individual is less prone to

misunderstanding than the old individual risk• The limit of tolerability is 1 in 10,000 per annum• The negligible level is 1 in 1,000,000 per annum• The limit value would double the background risk of the

t l ld i l bj ti bl t

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average twelve year old girl – an objectionable outcome• DSC expects owners to aim for the negligible level for long

term safety• Risks in the intolerable zone must be reduced as soon as

reasonably practicable – a tough test on timing• See Demonstration of Safety for Dams DSC2D for the

detailed requirements

AUSTRALIAN MORTALITY DATA 1998

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SOCIETAL RISK

• Risks in the intolerable zone must bereduced as soon as reasonablypracticable – a tough test on timing.

• Risks in the negligible zone will be

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g gaccepted as safe enough for the longterm

• In between, risks would only be acceptedin the long term if ALARP is demonstrated

• See Demonstration of Safety for DamsDSC2D for the detailed requirements

F-N CHART - EXISTING DAMS

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ALARP• Applies only in the zone of tolerability review• Tests are:

Gross disproportion – Tables 8.6 and 8.7 of ANCOLDrisk guides 2003Level of risk – determines threshold values for

i t t

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previous testCost effectiveness – sorts improvement optionsGood practice – what owners around Australia aredoingSocietal concerns – requires consultation withcommunity

• Prevention, control and mitigation are all to be addressed• Demonstration of ALARP is meant to be a tough call

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PROGRESSIVE IMPROVEMENT

• For risks starting in the intolerable zone:Short term improvement – arrange animmediate reduction of riskMedium term improvement – get risks belowthe limit of tolerability

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the limit of tolerabilityLong term improvement – get risks into thenegligible zone or demonstrate ALARP

• An owner can accelerate improvement, providedthat does not delay the reduction of intolerablerisks on other dams

• Agree the risk reduction program with DSC

7. THE DEMONSTRATION OF SAFETY BY OWNERS

• It is the role of the owner to demonstratethat a dam is safe

• The DSC may request more information orchallenge – but it is not the job of the DSC

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g jto show that the dam is safe

• The approach is goals based – the DSCsets or agrees with global goals but it isfor the owner to work out how the goalswill be met

DSC EXPECTATIONS• These are set out in Demonstration of Safety for

Dams DSC2D• The DSC is concerned with scenarios with

potential for a significant adverse effect oncommunity interests

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• Owners are to employ suitably qualified, skilledand experienced persons

• Peer review is required – with a separate report• Reasoning underlying risk values is to be

documented – no plucking figures out of the air –need evidence and reasoning in support of riskvalues

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STANDARDS BASED ANALYSIS

• Is required under the new DSC approach• Initially at least, may be accepted as an

adequate demonstration of safety wherethere are standards for all failure modes

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• DSC encourages owners to makestandards based analysis just one part ofa wider risk based approach – expect thisto be a firmer position over time

FAILURE MODES ANALYSIS

• Is required for all High and ExtremeConsequence Category dams – whetheror not a risk assessment is required

• Is regarded as great value for money

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g g yinternationally – for example, by USFederal Energy Regulatory Commission

• Owners are encouraged by DSC toundertake failure modes analysis for alldams

PUBLIC SAFETY CONSEQUENCES

• For dam failure, estimation of loss oflife by Graham 1999 is acceptable

• For natural flood, estimation of lossof life by Hill et al 2007

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of life by Hill et al. 2007[ANCOLD/NZSOLD Conference] isacceptable

• Owners should keep abreast ofdevelopments because improvedmethods are likely to emerge

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GRAHAM METHOD

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HILL ET AL. (2007)

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SPILLWAY GATES

• There is no recognized standard ofreliability – only motherhoodstatements

• Risk analysis and assessment will

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• Risk analysis and assessment willnormally be required by DSC

• Experience has shown that riskanalysis is extremely valuable, evenwhen the probability values remainquite uncertain

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INTERNAL EROSION AND PIPING

• There is no recognized standard short of fully intercepting filters designed by contemporary methods

• Unless such filters will be provided

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• Unless such filters will be provided, risk analysis and assessment will normally be required by DSC

• Analysis by the “piping toolbox” will be accepted

PIPING TOOLBOX METHOD

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PIPING SUPPORTING INFORMATION

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PIPING - CATASTROPHIC

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8. SOME RECENT DEVELOPMENTS

• Publication of the Australia/New Zealand StandardRisk Management – Principles and GuidelinesAS/NZS ISO 31000:2009

• UK Health and Safety Executive development ofsocietal risk criteria

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societal risk criteria• US Army Corps of Engineers work on tolerability

of risk• The Netherlands move to a full risk based

approach• Further development of the risk based approach

by NSW Department of Planning

NEW NATIONAL STANDARD

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HSE WORK ON SOCIETAL RISK

• Reducing Risks, Protecting People (2001) – N of50 or more is intolerable if F exceeds 1 in 5,000per annum [para 136];

• Now two HSE tools – ARICOMAH and QuickFN –both complex - latter for screening

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both complex latter for screening• Cross – government task group on societal risk• Public consultation 2007• Independent review by Institution of Chemical

Engineers published 2009 – favoured F-N curvesto portray risk

WORK BY USACE• Work is for USACE, USBR and FERC• One driver – national Levee Safety

Act 2007 and National Committee on Levee Safety

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y• Two seminars in Alexandria, Virginia

– March 2008 and March 2010• Paper to USSD in April 2009• Propose to follow both ANCOLD and

USBR criteria

THE NETHERLANDS• Currently each dike ring area has safety standard

based on critical high water level – 1 in 1,250 to 1in 10,000 per annum

• New twin track approach - FLORIS and Water inthe 21st Century

• FLORIS all failure mechanisms fully

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30 March 2010


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54

• FLORIS – all failure mechanisms, fullyprobabilistic

• May 2010 – formulate tolerable risk criteria• Late 2010 – consultation with stakeholders• 2011 to 2017 – proposed tolerable risk criteria,

assess risks• 2017 – adopt new tolerable risk criteria

19

DEPARTMENT OF PLANNING

• In July 2008 an updated version of theHIPAP series of guidance sheets wasreleased for public comment

• HIPAP No 4 on risk criteria now has an F-

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55

N criterion chart for societal risk• It should be emphasised that the criteria

in Figure 3 are indicative and provisionalonly and do not represent a firmrequirement in NSW

DOP SOCIETAL RISK

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56

9. CHALLENGES FOR THE FUTURE

• Development of skills in risk basedanalysis – both owners and the regulator

• Learning to account for uncertainty in riskvalues

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57

• Learning to understand societal concernsthrough community consultation

• Better definition of good practice for dams• Acquiring better data on dam failures• Developing better tools for risk analysis

umaheswari

Text Box

DSC's Legislation and Legal issues by Dermot Armstrong Legal Services (Water) Manager State Water Corporation

umaheswari

Typewritten Text

1

NSW Dams Safety Committee– 2nd Seminar on Risk Based Regulation

Dams Safety Act 1978 and Legal Issues

Dermot Armstrong, Legal Services (Water) Manager, State Water Corporation

June, 2010

Review of the Dams Safety Act 1978

• The Act creates the Dams Safety Committee and gives it functions.

• The concern is expressly dam safety - rather than, for example, security of water supply

• The Committee is unique among the Australian States.

• The Act creates a single, discrete entity with the focused expertise of government and private experts. This preserves the gathered expertise and information and ensures a level of surveillance which benefits from the passing of time, the gathering of data and the increasing knowledge in a single place not distracted by other of data and the increasing knowledge in a single place, not distracted by other interests.

• The Committee is free to determine an appropriate standard of safety for dams in NSW to recommend to the Minister

• The Committee supervises dam safety without exercising the role of a regulator i.e. it does not licence dams and impose conditions but relies upon published Guidelines –albeit, backed up by the threat of exercise of statutory regulatory powers.

Backdrop to the Dams Safety Act

• Most significant dam building used to be by government - State and Local - and dam safety was an internal, governmental issue.

• In the 1970s there was an evident concern to develop the safety standards, in particular in relation to Council owned dams. This led in 1974 to the Local Government (Safety of Dams) Act 1974 which allowed the Minister for Public Works to supervise Council dams.

But, why limit government supervision to Council dams? And so, the Dams Safety Act 1978 was born.

On 8 March, 1978 – Laurie Ferguson – Minister for Public Works in the Second Reading Speech in the Legislative Assembly stated:

“The basic objective of the bill is to ensure the safety of dams against the possible loss of life or property which could take place in the event of a dam failure.”

He also said:

“In essence, the measure that the government is now proposing involves a co-operative of the State constructing authorities, and the engineering profession generally, to ensure that the works which either they or some other person operate or undertake have been subject to expert and independent review.”

2

Key Aspects of the Dams Safety Act

The DSC:• is a “legal person” – it is a corporation, not merely a group of engineers

who might prepare papers for the Minister

• includes representatives from the major dam owners including both public, quasi public and private (Institution of Engineers)

• is subject to the control and direction of the Minister – except when exercising their specialist, professional role in advising the Minister

• advises the Minister concerning acceptable safety standards and monitors dam safety

• is not ordinarily a regulatory body. It does not licence dams.

• if necessary, can exercise the powers of a regulator and demand information or that actions be taken by the dam owner or can take over a dam and act itself.

The Functions of the DSC

The DSC is given functions to:

• maintain surveillance of prescribed dams and environs, over and surrounding dams and waters or other materials – to ensure the safety of the dams

• examine and investigate location, design, construction, reconstruction, maintenance, operation etc of dams and environs and waters or materials impounded

• obtain information and keep records on safety of dams

• formulate measures to ensure safety of dams

• make reports and recommendations to the Minister - or other person

• make reports re prescription of dams

• such other functions as conferred by the Act, any other Act (e.g. Mining Act) or regulations

• such incidental and supplemental acts necessary or expedient

(see s.14)

Powers of the DSC

The DSC can

• direct an owner to make observations etc and supply the information to the DSC – or else the DSC can go and gather the data etc itself.

• enter land or authorise someone else to enter and carry out an inspection

• issue directions to a dam owner (or other person) when it appears to the DSC that a dam is unsafe or in danger of becoming unsafe – requiring the owner to do specified things things.

• conduct an enquiry and require a person to produce information and/or attend and give evidence under oath

3

Powers of the DSC (continued)

The Minister can declare a State of Emergency if a dam has failed or liableto failure.

• the DSC with the Minister’s approval, may take control of a dam, release water/material, carry out work, demolish the dam or take other action upon the declaration of a State of Emergency. (The costs of the action can be recovered against the owner.)

• enter into contracts, make arrangements with public authorities, enter arrangements for research and can delegate

• The Act permits the Governor to amend the schedule to the Act to omit or insert the names of prescribed dams.

• A person who contravenes or fails to comply with any provision of the Act commits and offence – proceedings in the Local Court

(see ss.15-26)

Comparison with Other States

The same common law duty of care (as now defined through Civil Liability Acts)applies throughout Australia. But:• there is a spectrum of approaches taken across the states of Australia

• the eastern seaboard States have a greater concern for dam safety regulation.

• where standards are defined, they are ANCOLD standards – except NSW where the DSC defines standards, which often reflect ANCOLD

Structure

The means of pursuing dam safety varies:• NSW - there is a discreet statutory corporation whose sole purpose is dam

safety, supported by express dam safety legislation.

• Tasmania - manages dam safety through a Department assisted by an Assessment Committee, which assesses the safety of new dams and considers applications for permits to build dams. An express dam safety regulation supports the model.

• Queensland - dam safety is managed through a Department. There is dam safety specific legislation, but in the context of securing the water supply. Guidelines are, however, published defining minimum dam safety standards.

• Victoria - dam safety is managed through a Department. There is no dam safety specific legislation.

4

Approach

The approach taken to pursuing dam safety varies:

• NSW dams are not licensed by the DSC. The DSC identifies dams which pose a sufficient risk to warrant supervision. These dams are “prescribed”. But a person does not have to obtain permission from the DSC in order to own or build a dam. The DSC recommends a safety standard to the Minister.

• Tasmania, requires existing dams to be registered and new dams are the subject of assessment and the issue of a permit with conditions. The Tasmanian model also requires a person proposing to undertake work on a dam to be competent to do so.dam to be competent to do so.The regulations require compliance with ANCOLD guidelines, where appropriate (and DSC 15 and industry practice).

Approach (continued)

• Queensland requires a risk assessment for dams, provided by the owner. When assessed as a certain level of risk, these “referable” dams are subject to conditions which will operate through an actual or deemed development permit. Conditions may require compliance with the Queensland Dam Safety Management Guidelines. These Guidelines are based on ANCOLD standards.

• Victoria imposes dam safety conditions through the licensing of the dams through the Water Act – which manages access to the water resource. The Minister must consider a range of issues when considering an application for a licence and may impose conditions concerning design safety and maintenance of a dam Further the Minister or Governor may issue directions concerning dam a dam. Further, the Minister or Governor may issue directions concerning dam safety in certain circumstances of deficiency or threat under this Act.

(Under the Water Industry Act 1994 the Minister imposes dam safety obligations on the Water Authorities through their Statements of Obligations. These obligations require regard to be paid to ANCOLD guidelines.)

Mining near/under Dams

David HilyardDavid Hilyard

Manager, Mining Impacts, DSCg , g p ,

1

Impact of mining on damsImpact of mining on dams

A talk for the DSC seminarA talk for the DSC seminarDavid HilyardDavid Hilyard

AureconAurecon10 June 201010 June 2010

Gypsum tailings dam failure, FloridaGypsum tailings dam failure, Florida

C:\Documents and Settings\David.DSCLOCALNW\My Documents\David's work\Mining\UofW talk\20100322 Tailings dam course talk - final.ppt

What happens when dams …

… have mining near them?

2

Mine subsidence impacts

Mine subsidence impacts

(Non-mining) subsidence impacts

Civil engineering inducedCivil engineering induced

NaturalNatural

3

PipingPiping--induced subsidence (noninduced subsidence (non--mine)mine)

•• Piping sink hole, June 2010, Guatemala CityPiping sink hole, June 2010, Guatemala City•• Piping is a Bad ThingPiping is a Bad Thing

•• 20 m diameter, 30 m deep, 0 casualties20 m diameter, 30 m deep, 0 casualties

Coal

•• Coal occurs as Coal occurs as seamsseams —— generally horizontal, generally horizontal, planar, laterally continuous sheetsplanar, laterally continuous sheets

Longwall mining 1011. Development of roadways2. Longwall extraction3. Goaf collapse & subsidence

4

Subsidence over extraction

Forster (1995)

Subsidence monitoringSubsidence monitoring

Subsidence monitoring

-0.40

-0.20

0.00

0.20

RR

0

RR

1

RR

2 (s

trai

n pe

g)

RR

3 (s

trai

n pe

g)

RR

4 (s

trai

n pe

g)

RR

5 (s

trai

n pe

g)

RR

6 (s

trai

n pe

g)

RR

7 (s

trai

n pe

g)

RR

8 (s

trai

n pe

g)

RR

9 (s

trai

n pe

g)

RR

10 (

stra

in p

eg)

RR

11 (

stra

in p

eg)

RR

12

RR

13

RR

14

RR

15

RR

16 (

stra

in p

eg)

RR

17 (

stra

in p

eg)

RR

18 (

stra

in p

eg)

RR

19 (

stra

in p

eg)

RR

20 (

stra

in p

eg)

RR

21 (

stra

in p

eg)

RR

22 (

stra

in p

eg)

RR

23 (

stra

in p

eg)

RR

24

RR

25

RR

26

RR

27

RR

28

(m)

Conventional surveys

Airborne l

Tailings dam wall undermined by LW

-1.40

-1.20

-1.00

-0.80

-0.60

SU

BS

IDE

NC

E

LW3 MAINGATE BLOCK EDGE

LW3 TAILGATE BLOCK EDGE

laser scanning

1.25 m

LW3

Satellite radar

5

Surface cracking over a longwallSurface cracking over a longwall

•• Extent of cracking depends on:Extent of cracking depends on:–– Depth of coverDepth of cover–– Working seam thicknessWorking seam thickness–– Longwall geometryLongwall geometry–– GeologyGeology

Far-field horizontal movements• Subsidence-induced movements remote from LWs

— may be 1 km +• May have significant impacts on infrastructure

MSEC data

1900 m

Mine blastsMine blasts

•• Blast vibration Blast vibration →→

Tailings embankment

–– Cracking of damCracking of dam•• InstabilityInstability•• PipingPiping

•• Managed by keeping PPVs lowManaged by keeping PPVs low Blast monitor

6

Effect of dam wall on vibration

20

25

30

blas

ts

Comparison of blast vibration at crest and

abutment

open cutopen cut

0

5

10

15

20

0.5 1 1.5 2 2.5 3 More

num

ber o

f

crest ppv / abutment ppv (n = 60)

open cutopen cut

Hunter Valley, NSWHunter Valley, NSW

Open cut downstream of damOpen cut downstream of dam

•• Consequence can be high Consequence can be high –– miners in pitminers in pit

•• Short distances Short distances →→ no warning timeno warning time•• Pit wall failure may undermine damPit wall failure may undermine dam•• Consequence can change quickly Consequence can change quickly —— developing pitdeveloping pit

Loss of storageLoss of storage

•• Major state assets Major state assets ——water supply for water supply for large populationslarge populations

•• Risk is loss of Risk is loss of st f st f storage from storage from reservoir, into mine / reservoir, into mine / out of catchmentout of catchment

•• Understanding Understanding groundwater system groundwater system criticalcritical

7

Mine subsidence — permeability impacts

vertically tight zone

surface cracks

Forster (1995)

free-draining zone

Centralia, PA

Permeability/depth — before and after mining0

50

100

150

200

250

No miningMiningD

epth

, m

Hawkesbury Ss

Bulgo Ss

Bald Hill Cs

Typical stratigraphic column.

No mining

Mining

10001000 10-09 10-08 10-07 10-06 10-05

250

300

350

Permeability, m/s (from Lugeon test)

Coal Measures

Wombarra Sh

Scarborough Ss

Stanwell Park Cs

Reid (1996)NSW Southern Coalfield

• Range of results decreases after mining• No “zero” results after mining

Implications for mining near storages

• Some mining under surface waters is possible• “Seals” are most vulnerable and may be damaged• In many cases the system is controlled by the

seals, so mining may result in changes, possibly significant, to these systemsg , y

8

Case study Case study —— LWs under tailings damLWs under tailings dam

TailingsTailings

← Open cut downstreamOpen cut downstream

Mining engineerMining engineer

LWs under embankment & storage

Tailings Dam

Tailings

Active pit

LW5

LW6

LW 7

LW 8

LWs

Barrier

1000 m

Observed subsidence LW 6

-0.50

-0.30

-0.10

0.10

NE

CC

1

NE

CC

3

NE

CC

5

NE

CC

7

NE

CC

9

NE

CC

11

NE

CC

13

NE

CD

1

NE

CD

3

NE

CD

5

NE

CD

7

NE

CD

9

NE

CD

11

NE

CD

13

NE

CD

15

NE

CD

17

NE

CD

19

NE

CD

21

NE

CD

23

NE

CD

25

NE

CD

27

NE

CD

29

NE

CD

31

NE

CD

33

NE

CD

35

NE

CD

37

NE

CD

39

NE

CD

41

NE

CD

43

NE

CE

5

NE

CE

3

NE

CE

1

NE

CD

45

NE

CD

47

NE

CD

49

NE

CD

51

NE

CD

53

NE

CD

55

NE

CD

57

NE

CD

59

18/7/2007

-1.90

-1.70

-1.50

-1.30

-1.10

-0.90

-0.70

SUB

SID

ENC

E (m

) 23/7/2007

30/07/2007

6/08/2007

14/08/2007

21/08/2007

27/08/2007

4/09/2007

11/09/2007

17/09/2007

23/10/2007

20/11/2007

Max PredictedPredicted subsidence ~ 1.85 m

9

Cracking of tailings dam by LW subsidenceCracking of tailings dam by LW subsidence

•• Subsidence c. 1.5 m in progress due to LWSubsidence c. 1.5 m in progress due to LW•• Compression ridge c. Compression ridge c. ┴┴ faceface

•• Tension cracks c. Tension cracks c. ║║ face face —— some en echelonsome en echelonS b id l i ibl i dS b id l i ibl i d•• Subsidence swale visible in roadSubsidence swale visible in road

Case study Case study —— piezo array adjacent piezo array adjacent to LWs and water supply damto LWs and water supply dam

•• Risk is loss of storageRisk is loss of storage•• Groundwater behavior near mining?Groundwater behavior near mining?

Seepage through rock barrierSeepage through rock barrierA model for hydrogeological response to LW miningA model for hydrogeological response to LW mining

As LW passed under pit wall:As LW passed under pit wall:

•• Subsidence Subsidence →→ extension extension →→ joints opened joints opened →→ seepage, seepage, thenthen

•• As subsidence wave moved on As subsidence wave moved on →→ compression compression →→ joints joints closed closed →→ seepage stoppedseepage stopped

10

DAM WALL PIEZZOMETERS

65.000

70.000

75.000

TER

LEV

ELR

L's Peizzo #1

Peizzo #2

As LW passed under pit wall:

50.000

55.000

60.000

20/0

4/20

06

20/0

5/20

06

20/0

6/20

06

20/0

7/20

06

20/0

8/20

06

20/0

9/20

06

20/1

0/20

06

20/1

1/20

06

20/1

2/20

06

20/0

1/20

07

20/0

2/20

07

DATE

WA

T

750

m →

420

m →

220

m →

0 m

→

-270

m →

-650

m →

-106

0m

→

-130

0m

→

Decompression & recovery

Piezo data — well-behaved & problem children

DDH42: Pressure (kPa) v Time

200

300

400

500

600

re (k

Pa)

or D

ista

nce

(m)

-1000

-800

-600

-400

-200

0

200

400

Piezo 1, 42.9 m CCS

Piezo 2, 50.2 m CCS

Piezo 3, 59.9 mWBCPiezo 4, 64.7 mWBCPiezo 5, 75.6 m SBS

Piezo 6, 82.5 m SBS

Piezo 7, 89.8 m SBS

Piezo 8, 93.0 m SBS

-100

0

100

17.0

2.05

00:

00

08.0

4.05

00:

00

28.0

5.05

00:

00

17.0

7.05

00:

00

05.0

9.05

00:

00

25.1

0.05

00:

00

14.1

2.05

00:

00

02.0

2.06

00:

00

24.0

3.06

00:

00

Date

Pre

ssur

-1800

-1600

-1400

-1200Piezo 9, 100.3 mSBSDistance from LW1face

Site 3 DDH46B: Total Head v Time

250

270

290

310

330

350

:00

:00

:00

:00

:00

:00

:00

:00

:00

:00

:00

-800

-600

-400

-200

0

200

400

600

800

1000

Fits our model

Doesn’t fit our model ??

900 m

500

DDH50

DDH37

(projected down dip to section)

DDH49

DDH48

Aquifer

Seal

Seam mined

Fracture zone over LWs

A’A

Possible flow path through aquifer from lake to workings

Possible flow from reservoir into mine

LW5 LW4 LW3

0

500

Base Scarborough Sandstone pick in DDH37 projected down dip to plane of section = 276 m RLSo head = 28 mHorizontal distance, lake to lip of sink = c. 920mHydraulic gradient (in plane of section)= 0.03

FSL 304 m RL

DSC concept; validated by mining company's numerical modelling; assessed by DSC quantitative risk assessment of flow

Lip of sink

11

Risk assessment

• Because life isn’t certain — especially when dealing with natural systems

• Focus is on consequences• Leads to rational evidence-based decision making

Dams Safety Act 1978

• NSW government statutory authority

• Regulates activities which can impact on safety of dams or stored waters (including mining)

Legislative framework

s 239(2) Mining Act s63, s64 s369s80

Min ist er f or Miner al Resour ces Dams Saf et y Commit t ee

Dams Safety Act s18(3)b

Pr emier

Mining Lease ConditionsNotification

Areas

• 3 Mechanisms• Mining act most

common: formal “approval” required

• DSC Act for certain situations

s18(3) notice "Cease Work"

s18(2) notice "Do

things"Mining Approval

Subsidence Management

Plan

Minister, via Manager

Titles

DMR DG, via SMPIAC

• SMP rarely

12

Important bits

• DSC has broad powers re dam safety• Notification Areas can be added or amended• Mining Lease conditions can be added or amended• Risks judged from dam safety perspective• All workings within a NA (development and • All workings within a NA (development and

extraction) require approval

umaheswari

Text Box

Safety Reviews/ Peer Reviews by Jeff Gleeson Manager Engineering Hunter Water Australia Pty. Ltd

1

Safety Reviews Peer Reviews

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Jeffrey GleesonMember DSC

Sheet 2D‘Demonstration of Safety’

Safety Review / Peer Review

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• How does it work now?• How will it work in the future?• Why?

Safety Review

Safety status of one or all aspects of the dam

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Peer Review

Independent assessment of that status

2

Safety Reviews

How do they work now?

• They develop out of the

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• They develop out of the recommendations of a Surveillance Report.

• They develop on ‘ad hoc’ basis.

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Safety Reviews

How will they work in the future ?

• From Surveillance Reports

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From Surveillance Reports• New developments• More than 15 years since last review• A more structured approach

3

Safety Reviews

Why?

Increase our awareness of change:

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Increase our awareness of change:

• Ageing structures• Changing methodologies• Changing hazards

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Grahamstown Dam

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4

How do they work now ?

• All work is to be undertaken by:

Peer Reviews

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y

“.... A professionally qualified engineer who is widely recognised by his peers as suitably

experienced in the engineering of dams.....”

How will they work in the future?

Peer reviewer(s)for all safety reviews

Peer Reviews

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( ) yEXTREME & HIGH C.C.’s

• They must be independent• The owner carries the responsibility

Why ?

• A ‘second opinion’ is best practice

Peer Reviews

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• Avoids the reinforcement of opinions• The owner is in charge

5

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umaheswari

Text Box

DSC's Design Issues by Paul Heinrichs Executive Engineer NSW Dams Safety Committee

NSW Dams Safety Committee 1

DESIGN ISSUESPaul Heinrichs

Executive Engineer, DSC

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Consequence Category governs Design standards

Sunny Day No Flooding

• Seismic• All others

Flood• Incremental• Total

Flood capacity

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• Total capacity

BASED ONProbable Loss of Life P.L.L. Priority 1

orPopulation At Risk P.A.R. Priority 2Some consideration of damages

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3

eg Environment, Infrastructure etc


REQUIRES

Dambreak study• Inundation maps• Flood depth, velocity

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• Flood arrival time• Dwelling flood levels

P.L.L. TableIncremental P.L.L.

Probable Loss of Life (PLL) (Note 4)

Severity of Damage and Loss

Negligible Minor Medium Major

0 Very Low Very Low Low Significant

<1 High C High C High C High B

1 to 10 (Note 1) High B (Note 2) High B High A

10 to 100 High A (Note 3) High A

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>100 Extreme

P.A.R. TABLE• TOTAL P.A.R.

Population at Risk (PAR)

(Note 7) Severity of Damage and Loss

Negligible Minor Medium Major

<1 Very Low Very Low Low Significant

1 to 10 Low (Notes 1, 4 & 5) Low (Notes 4 & 5) Significant (Note 5) High C (Note 6)

10 to 100 (Note 1) Significant (Notes 2 & 5) High C (Note 6) High B (Note 6)

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100 to 1000 (Note 2) High A (Note 6) High A (Note 6)

>1000 (Note 3) Extreme


ACCEPTABLE FLOOD CAPACITY (AFC)

• Starting position• Deterministic – Must check

FCC RATING (i) FLOOD OR AEP (ii) Extreme PMF (reservoir full)

High A PMPDF (reservoir full)

M f AEP f PMPDF 10-6 (iii)

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Also, called FALLBACKAlso, called FALLBACK

High B Max of AEP of PMPDF, or 10-6 (iii) not necessary to use PMP Design Flood, as PMPDF was used in the previous row for HIGH A)

High C Max of AEP of PMPDF, or 10-5) (iii)

Significant 10-4

Low 10-2 to 10-3

Very Low No requirements (iv)

PMP

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Risk Assessment

If outcome shows a higher risk AFC of dam than previous table: THEN

Submit to DSC for consideration

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Submit to DSC for consideration ie possibly smaller flood acceptable


Gated SpillwaysGate reliability analysis

Required with AFC determination

Must safely pass same flood without gates

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Dam Failures Due To Gate Failures

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Upgrade priorityTo be based on comparison between AEP of DCF c.f. AEP from table above

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AFC Summary• Check dam’s flood capacity c.f. Starting

point. If OK inform DSC and STOP• Does not comply..Inform DSC• Undertake Risk Assessment...If OK inform

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DSC....If NBG.............• Investigate risk reduction options• Submit Proposed remedial measures and

PROGRAM to DSC for endorsement

ACCEPTABLE EARTHQUAKE CAPACITY

• All extreme, high, significant dams to withstand Maximum Design Earthquake (M.D.E.)

• DSC 3C Table 5.3Earthquake Annual Exceedance

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• Seismic loading from seismologist

Consequence Category Earthquake Annual Exceedance Probability (AEP)

Extreme <1 in 10,000

High A

High B

High C

1 in 10,000

1 in 5,000

1 in 1,000

Significant 1 in 500

Design for Earthquake• Based on dynamic analysis• Determine potential liquefaction• Staged stability analysis• Employ defensive measures

L d lid i t d

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• Landslides into dams


Earthquake Dam Failure

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GENERAL DESIGN CONSIDERATIONS

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GEOLOGY/GEOTECH

• Comprehensive investigation– Regional geology– Site geology

Sectional geology

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– Sectional geology– Strength, compressibility, erodability,

permeability– Construction material sources– Reservoir rim


Geotech Reports• Mapping• Borehole and core logs & photos• Foundation/borrow area test results• Trench logs

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• Lab test results• Rock strength

Embankments• Basis for selecting design strength• Stability methodology• Pore pressure assumptions• Factor of Safety• Settlement predictions

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Settlement predictions• Piping safety assessment

Foundations/Abutments• correct keying• Battered abutment slopes to 1 in 1.5• Core trench walls (max 1 in 1) • No sharp profile changes• Grouting by experts

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• Exposed foundations logged• Concrete interfaces


Filters/drains• Not given adequate consideration• Slotted pipes not favoured• Seepage collection and monitoring• Finger drains NOT acceptable (use blanket)• Discharge capacity to cater for cracks

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• Discharge capacity to cater for cracks• Foundation under blanket to allow flow in• Geotextile not acceptable alternative• Concrete spillways to have drains• Extreme and High dams MUST have filters

CONDUITS• No unencased metal• Pressure pipes – welded, encased• No rubber ring joints• Conduits to be in natural foundationNOT in embankment

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• Use downstream filter collars NOT cutoffs

CONCRETE• Mix design for durability• AAR?• Water stops• USBR guidelines for new dams• FERC Chapter III guidelines

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p g• Uplift, Sliding, Overturning, Cracking


POST TENSIONING• Only re-stressable, monitorable• Fully grout encapsulated• Tendon anchors, bursting stress• Proof test anchors• Test some every 5 years

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Test some every 5 years

HYDRAULICS• Erosion resistance ---top and bottom

Depth and velocitiesDepth and velocitiesStanding wavesStanding wavesPhysical models as well as mathsPhysical models as well as mathsCorrect layoutCorrect layout separate from toeseparate from toe

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Correct layout Correct layout –– separate from toeseparate from toe

Mechanical/Electrical

• Adequate backup

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GATES AND VALVES

• Adequate capacity• Risk assessment• Emergency operation

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• dewatering

QUESTIONS?

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Emergency and Management by Norman Himsley Member NSW Dams Safety Committee

1

DSC Guidance Sheet Seminar10 June 2010

Main Points of Dam Operational

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pGuidance Sheets

DSC2F, DSC2G, DSC2H, DSC2I

DSC2F-1Operation and Maintenance for Dams

• Significant and Higher Consequence Category dams, and all tailings dams, are to have an effective O&M Manual (see ANCOLD etc)

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( )• Manuals are to be prepared by

qualified and experienced personnel• Manuals are to be updated every 5

years

DSC2F-2Operation and Maintenance for Dams

• Manuals shall incorporate a formal incident reporting scheme (internal and to DSC)

• Owners must have an effective archiving system to maintain appropriate dam

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records • Owners must ensure staff are appropriately

trained and kept up to date• Owners must have training plans in place

for their staff

2

DSC2G-1Emergency Management for Dams• Dambreak studies required where

loss of life or significant threat to community interests could result from dam failure

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from dam failure• A quality controlled Dam Safety

Emergency Plan (DSEP) is required for dams where persons may be at risk if the dam failed

DSC2G-2Emergency Management for Dams

• Dam owners must consult SES State Headquarters during DSEP preparation (see Appendix B for

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helpful checklist) and provide SES with relevant dambreak information

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3

Key Steps in DSEP Formulation and Review(Figure1 in DSC2G)

1. Owner initiates DSEP formulation or review2. Owner consults with SES3. Owner drafts DSEP and forwards to DSC for

review/audit


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review/audit4. DSC reviews and sends comments to owner for revision5. Owner revises DSEP and sends to SES to review

emergency contact arrangements6. SES reviews draft DSEP and sends comments to owner7. Owner revises DSEP and sends to DSC for

endorsement8. Owner distributes DSEP after DSC endorsement


• A Summary Information Sheet for Emergency Agencies is to be in each DSEP

• An emergency Notification Flowchart is to be in each DSEP

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be in each DSEP• DSEP distribution arrangements are set

out in DSC2G • DSEP are to provide prompt notification to

the DSC’s Executive Engineer of any actual or potential dam safety emergency

DSC2G-5Emergency Management for Dams• Dam failure alerts (white, amber and red) are

used to trigger emergency response actions.• White-defect noted or heavy rain-preliminary

alert-SES notified and check readiness

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• Amber-failure possible if continues-SES warns PAR to prepare to evacuate-SES Evacuation Warning

• Red-failure imminent-PAR evacuated by SES-SES Evacuation Order

4


• High and Extreme Consequence dams are to have telemetered storage level monitoring (and preferably rainfall and seepage as well)

• High and Extreme Consequence basins are t h t l t d it i f i f ll

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to have telemetered monitoring of rainfall nearby

• New High and Extreme Consequence dams are to have telemetered seepage/tailwater monitoring to warn of piping incidents


• SES, SEOC and DSC have an agreed emergency protocol-see Appendix A flow chartTh SES 24 h t t b i t

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• The SES 24-hour contact number is to be stressed for use-

1300 737 326

DSC2H-1 Dam Security• Owners must give an updated qualitative opinion

of the security risk status of their dams (including reviews) in each Surveillance Report

• DSC considers that each dam’s security information sho ld be categorised as STAFF or

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information should be categorised as STAFF or SECURITY-IN-CONFIDENCE at a minimum

• Owners must define in a security strategy how security information is protected and who can access

5

DSC2H-2 Dam Security• Owners must have and maintain for each

dam:– A risk-based security plan that addresses security

arrangements– Current security threat, vulnerability and risk

assessments

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– Procedures for reporting and responding to security incidents

– Record of outcomes of security surveys and reviews

– An O&M Manual section referring to security responsibilities and identifies location of security documentation

DSC2I-1Community Consultation & Communication (CC&C)

• Owners and advisers have full responsibility for ensuring appropriate CC&C of their dam safety management programs

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• DSC recommends owners engage in CC&C from an early stage when safety concerns identified at a dam and improvement strategies are being developed

DSC2I-2Community Consultation & Communication

• DSC2I identifies trends and issues in CC&C and provides guidance to owners in managing and responding to the key related questions:

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y q– Why?– Who?– What?– How? And– When?

6

DSC2I-3Community Consultation & Communication

• Why-reasons outlined in Section 6.1-required, DSC policy, good practice, due diligence

• Who-see 6 2-dam owner responsible

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Who see 6.2 dam owner responsible, Planning & DSC has requirements / recs

• What, How & When-outlined in Section 6.3-Table 6.1 summarises aspects to be considered by dam owners

DSC2I-3 Community Consultation & Communication

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Hydrology Issues with regard to Dams by Assoc. Prof. Ian Cordery Member Hydrology Sub- Committee

1

Hydrology Issues for Dams

Ian Cordery

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School of Civil and Environmental Engineering, University of New South Wales

Member, DSC Hydrology Sub Committee

Hydrology provides two major inputs for dams

1. Estimate of long term water supplyVolumes of flow and their fluctuation over time - affects supply

and operating rules

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and operating rules

2. Safety of dam from floodsSize and arrangement of spillway and dam crest

Here we are considering SAFETY

Risk Management is now approach adopted by NSW Govt

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General approach for flood safety is to make two steps

2

1. Estimate PMP - standardised for NSW - Meteorological expertise may be beneficial for some catchments

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2. Estimate design (extreme?) flood from PMP and other data

- Requires several data items

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- Several steps involved, usually using flood modelling techniques and/or software

• Flood modelling - necessary because we are going beyond our experience

• Extreme rains have occurred in a few places, usually undocumented

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• Formerly simple extrapolation used

• Practice now is to employ physical principles

3

Models developed in AustraliaRORB, RAFTS, WBNM also some

imported

- Well respected, but far from perfect

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- Little changed in 35 years mainly due to scarcity of data, but as good as anything routinely used elsewhere

- Overdue for improvement but suitable data not available

• Models need local calibration

• Can only be confident of model output for local area if data on large floods available for verification

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• For many sites - no data, or- few years of data

-dry years? years of no floods?

Data not available for many existing dams

Most will need capacity increase or safety upgrade

Data collection is essential – now!

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Data collection needs some expertiseNot difficult but some data collected has turned out to

be worthless due to naivety of collectors

4

Risk Management is now Govt Policy

What is Acceptable Risk?- Has NSW been excessively safe?

- First estimate, prescriptive requirements

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- Risk management - Explore possible risk reduction with small changes

in expectations, physical layout, land zoning, flood warning & protection arrangements etc.

Hydrologists wish to give range estimate for flood with which dam must cope

- this because modelling not reliable enough to produce definitive estimate - uncertainty involved

Owner needs “BEST ESTIMATE”

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Owner needs BEST ESTIMATE

Hydrologists need to provide solidly reasoned case for advice provided - for Owner, for DSC, for Public, later for Court (hopefully never needed)

But, still owners need a best estimate of the design flood

Debate continues over- Definitions of PMF- Frequency to assign to PMF

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These have large effects on risk assessment and therefore large safety and cost implications

5

Public must be kept informed of hydrological risks

- those residing downstream

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- those “itinerants” likely (possibly) in path of failure consequent flood

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DSC's requirements for Surveillance Reports by Michael Karp Dams Surveillance Engineer NSW Dams Safety Committee

1

DSC’s requirements for Surveillance Reports

(Guidance Sheet DSC2C)

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Michael Karp Dams Surveillance Engineer,NSW Dams Safety Committee

Failure of Briesis Dam, Tasmania, 1929

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Aim of presentation:• An overview of DSC’s new Guidance

Sheet DSC2C• Replaces DSC15 (first edition 1992)• Highlight new requirements in DSC2C

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• Highlight new requirements in DSC2C compared to DSC15

2

Surveillance Reports• Corresponds with “Comprehensive Reports” as

described in ANCOLD Guidelines on Dam Safety Management, 2003

• DSC’s Guidance Sheet DSC2C explains DSC’s

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requirements• Dam owner’s responsibility to arrange

preparation & submission at 5 yearly intervals

Types of Surveillance Reports:

• Type 1 – Req. for all Extreme, High A & High B Consequence Category dams

• Type 2 – Req. for all High C Consequence Cat. dams, & for

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q ,Significant Consequence Cat. dams > 15m high

• Type 3 – Req. for Significant Consequence Cat. dams up to 15m high & all Low Consequence Cat. prescribed dams

Who can prepare Surveillance Reports?

• Type 1 – A team comprising an experienced dams engineer & a dams surveillance engineer, as a minimum

• Type 2 An experienced dams engineer

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• Type 2 - An experienced dams engineer as a minimum

• Type 3 – D5 form to be completed by a dam owner or his consultant

3

Highlight 5 important issues:

• Conclusions & Recommendations (Sect. 2)• Consequence Categories (within Sect. 3)

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• Surveillance Inspection (Sect. 4)• Review of Dam Safety Status (Sect. 8)• Appendices (Sect. 9)

Conclusions & Recommendations(Sect. 2) - re Failure Mode

Analyses• For dam where potential for non-

itinerant loss of life, require conclusion re the continued adequacy of existing

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y gFMA

• If no FMA, require recommendation that a FMA be undertaken

Conclusions & Recommendations(Sect. 2 ) - Re Safety Reviews

• Require conclusion on whether changed circumstances (guidelines, extent of D/S development, signs of vulnerability of dam) warrant a safety review

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warrant a safety review• Where safety review is warranted, require

a recommendation that a safety review be undertaken, to include the required rigour & timing

4

Consequence Categories (from DSC3A)

• The higher of the Sunny Day Consequence Cat. (SDCC) & Flood Consequence Cat. (FCC) determine whether a dam is prescribed by DSC, & the Type of S/Rpt required

• The SDCC determines the freq of routine

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• The SDCC determines the freq. of routine inspections & instrumentation monitoring using ANCOLD guidelines

• The SDCC determines the req. earthquake load

• The FCC determines the req. flood capacity

Consequence Categories (in General Information (Sect. 3) of S/Reports)

• The PAR & potential loss of life (PLL) values from the latest dambreak study/risk assessment are to be

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yprovided for the Sunny Day, Total Flood & Incremental Flood failure cases

• If not available, S/Rpt to include as a recommendation

Surveillance Inspection (Sect. 4)

• Section 4 of DSC2C provides a very useful checklist on items to be included in the Surv. Inspection section of the S/Rpt

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S/Rpt• Include an inspection of the dambreak

affected zone to identify env. & development changes D/S of the dam that could affect the Consequence Categories

5

Review of Dam Safety Status (Sect. 8)

• Review/comment on likelihood of dam failure, & adequacy of dam re current criteria (flood cap., earthquake cap., seepage piping structural stability etc)

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seepage, piping, structural stability, etc)• Comment on changed circumstances

that warrant a safety review

Appendices (Sect. 9)

• Photos, particularly of issues raised as a result of surveillance inspection. Label photos

• Completed D15 Form (S/Rpt checklist)

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p ( p )• Completed D12 Form (Status of Dam Safety

Management System)• A Microsoft Word format file of the S/Rpt’s

text• D6 Form (Flood Security) now not required in

S/Rpts

Owner’s responsibility

• Complete D12 Form (Status of Dam Safety Management System – see DSC2A Appendix A) – include in S/Rpt Appendix

• Program of actions in response to the S/Rpts

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g p precommendations

• Submit S/Rpt & cover letter with program of actions to DSC as soon as reasonably practicable after receipt of S/Rpt from consultant

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DSC's requirements for Tailings Dam Reports by Engin Hizbas Dams Engineer NSW Dams Safety Committee

1

RISK BASED REGULATION SEMINAR10 JUNE 2010

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Engin HIZBASTailings Dam Engineer

NSW Dams Safety Committee

DSC3F GUIDANCE SHEET TAILINGS DAMS

Sunny Day Consequence Category Low Significant High C High B High A / Extreme

TABLE 4 - TAILINGS DAM SURVEILLANCE CRITERIA

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Extreme

Comprehensive Inspections 5yr 5yr 5yr 5yr 5yr

Intermediate Inspections 2yr Annual Annual Annual Annual

TYPES OF SURVEILLANCE REPORTS

REPORT TYPE CONSEQUENCE CATEGORYType 1 All Extreme, High A & High B DamsType 2 High C Dams, and

Significant Dams (>15m in height)Type 3 Significant Dams, up to 15m in height and

Low Dams

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Low DamsIntermediate Dams of All Categories

2

SURVEILLANCE TEAM

REPORT TYPE SURVEILLANCE TEAMType 1 A team comprising qualified engineers, experienced in dams

engineering, supported by other technical specialists asnecessary. The team could be as small as two people, provided itincludes and experienced dams engineer and a damssurveillance engineer; with further appropriate assistance in largedams from various specialists as required (e.g. geologist).

Type 2 A qualified, experienced dams engineer as a minimum. A

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yp A qualified, experienced dams engineer as a minimum. Asuitably experienced hydrologist should review flood estimates.Similarly a suitably experienced seismologist should advise onthe validity of any seismic loading estimates.

Type 3 Dam owners or their representatives or agents acting on theauthority of the owner.

Intermediate For dams requiring Type 1 and 2 Surveillance Reports, theseIntermediate Reports should be prepared by a suitably qualifiedengineer. Owners of other prescribed tailings dams are to submittheir Intermediate Reports in the format of Type 3 SurveillanceReports.

SURVEILLANCE REPORT FORMATFOR TYPE 1 & TYPE 2 REPORTS

• Executive Summary• Conclusions & Recommendations• General Information• Surveillance Inspection• Review of Surveillance Procedures

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• Operation & Maintenance and Emergency Management• Mining Activities• Review of Dam Safety Status• Forms

SURVEILLANCE REPORT FORMATFOR TYPE 1 & TYPE 2 REPORTS

• Executive Summary• Conclusions & Recommendations• General Information• Surveillance Inspection• Review of Surveillance Procedures

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• Operation & Maintenance and Emergency Management• Mining Activities• Review of Dam Safety Status• Forms

– D1 Basic Data– D8 Dam Owners Address– D15 or D19 Checklist

3

SURVEILLANCE REPORT FORMATFOR TYPE 3 REPORTS

• Standard D5 Form

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SURVEILLANCE REPORT FORMATFOR INTERMEDIATE REPORTS

Should cover the same surveillance issues addressed in fiveyearly Surveillance Reports, and include updates onoperations and programming, but need not as detailed asComprehensive Reports.

Th h ld l i l d F

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They should also include Forms:



Th h ld l i l d F

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They should also include Forms:• D1-Basic Data• D8-Owners Address• D19 Checklist

4



Th h ld l i l d F

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They should also include Forms:• D1-Basic Data• D8-Owners Address• D19 Checklist

An electronic copy of the entire report including drawings andphotos.