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Water Security, dam building and dam safety do priorities need to clash?

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This presentation

Why and how often do dams fail?

What does this mean in the Indonesian Context

Reducing the risks - dam safety guidelines and their impact

The next 10 years in Indonesia

Further tools to reduce risk - Risk based assessment methods

Case Study The use of Risk Based Tools

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Dam Safety A Historical Concern

Section 53 If somebody is too lazy to maintain his dam in adequateconditions and does not do it, if the dam fails and the fields are flooded, then that who caused the failure shall be sold for money, and the collectedmoney shall replace the wheat that was ruined because of him.

King Hammurabi Code, 1800 BC

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Why do dams fail?

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1. Overtopping Gate Failure to Open Inadequate Spill capacity

2. Foundation Concrete Dam Stability (Sliding) Embankment Dam Slope Stability

3. Internal Stability (Piping) Foundation Embankment Abutment

4. Other Gate Structural Failure Debris Human error Sabotage

23%

38%

33%

6% Foundation

Overtopping

Piping

Other

Source: ASCE/USCOLD, 1975

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Overtopping

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Swift 2 Failure - USA

Foundation (piping) Failure

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Sliding Failure - China

Sliding Failure - Taiwan

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Gate Failure

Structural/Mechanical Equipment Failures

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Risk of Gates Not Opening

Many non-structural possibilities why a gate may fail to operate Reservoir Debris Access issues Lack of redundancy

Overtopping risk not generally assessed in traditional dam safety assessments

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Failure Frequency Which are the most Vulnerable Dams

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Assessment of the Most Vulnerable dams Contd

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Probability of Dam Failure The Impact of Improving Dam Safety Practices In the United States, the probability of dam failure can be expressed as equivalent to a probability that, on average, every dam has an annual chance of 1:2500

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Similar frequencies are reported throughout the world

Area Reference No. ofFailures

Total DamYears(x10-3)

FailureRate

USA Gruner (1963, 1967) 33 71 5 x 10-4

Babb & Mermel (1968) 12 43 3 x 10-4

USCOLD (1975) 74 113 7 x 10-4

Mark & Stuart-Alexander (1977) 1 4.5 2 x 10-4

World Mark & Stuart-Alexander (1977) 125 300 4 x 10-4

Middlebrooks (1953) andMark & Stuart-Alexander (1977)

9 47 2 x 10-4

Japan Takase (1967) 1 046 30 000 4 x 10-5

Spain Gruner (1967) 150 235 6 x 10-4

World Foster and Fells 11,192 27,300 4 x 10-4

Overall Average Dam Failure Rate 4 x 10-4

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Major dam construction programs brings with it risks

Indonesia has both risks Defects arising from design and construction result in most failures being

during first filling or in first five years Indonesia also has a considerable stock of older dams which given the

challenging physical conditions (seismic, intense rainfall, volcanic soils) and economic conditions may put them in doubt

FF to 5 years > 5 years > 20 years

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Water and security in Indonesia a vital concern

Law No. 17 of 2007 regarding the National Long Term Development Plan 2005-2025 targets 100 percent access to safe water and sanitation by 2019

Raw water security is a vital ingredient but Indonesia faces a major challenge to raise stored water from the current very low 53m3/capita

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Reported Number of Large Dams in Indonesia Today

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000

USA India Japan Brazil N. Korea Canada South Africa

Spain Turkey Indonesia

9265

5102

3116

1392 1305 1166 1114 1082 976

132

Num

ber o

f Lar

ge D

ams

(ICO

LD, 2

014)

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Planned Dam Construction Program in Indonesia

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000

USA India Japan Brazil N. Korea Canada South Africa

Spain Turkey Indonesia

9,265

5,102

3,116

1,392 1,305 1,166 1,114 1,082 976

3,132

Num

ber o

f Lar

ge D

ams

(ICO

LD, 2

014)

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Reducing the Risk - Modern Dam Safety Programs

The failure of the Teton dam in in the United States (mid 1970s) was a catalyst for new approaches for ensuring the safety of dams Previously dam design based on precedent and

the experience of the designer Designs did not account implicitly for the risk the

dam presented Design criteria varied

This resulted in the growth of dam safety regulations world wide

June 5, 1976 Consequences

11 people died Millions in damages

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Dam Safety Globally

Argentina (Federal regulations for privatized dams only) Australia (Dam safety governed by the individual provinces) Austria (Federal Law governing large (>30m) dams only Canada (Provincial regulations since the mid 1970s) China (Federal Regulation) Finland (Federal regulation, 1984 governing all dams >3m in height) France (Federal regulation dating to 1960 for dams greater than 20m high or dams that

present a hazard) Germany (State Regulations) Ireland (Federal Regulation) Italy (Federal, dams >15m in height, smaller dams covered by regional legislation) Latvia (Federal Regulation) Mexico (Federal Regulation) Netherlands (Flood defenses act, 1996) New Zealand (Federal Regulation) Norway (Federal Regulation, dams > 4m) Portugal(Federal, amended in 1994 to cover dams < 15m in height) Romania (Federal Regulation, National Commission for Safety of Dams) Russia (Federal Regulation) Spain (Federal Regulation dating to 1967) South Africa (Federal Regulation, since 1998) Sweden (Federal Regulation) Switzerland (Federal Regulation dating from 1998) United Kingdom (Federal Regulation, the Reservoir Act, dating from 1975) USA (Federal Regulations (FEMA, FERC) and state laws)

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Dams In Canada

There are over 14,000 registered dams in Canada large and small and many more that are not registered

The Rideau Canal was Canadas first engineered system of dams constructed in the 1830s

The Rideau Canal 1830s The Jones Falls Dam on the Canal System

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A Short History of Dam Safety in Canada 1978 - Alberta Dam Safety Act 1979 - B.C. Hydro - EPPs mandatory 1985 - Canadian dam owners begin meeting 1985 - Quebec Hydros Dam Safety Program established 1986 - Ontario Hydro - Dam Safety Assessment Program 1987 - Manitoba Hydro - Began Dam Safety Inspections 1989 - Inaugural Meeting of the Canadian Association of Dam Safety Officials;

changed to CDA in 1995 1996 Saguenay Dam Failures 1999 - CDA Dam Safety Guidelines published 2007 Update to the CDA Dam Safety Guidelines published 2011 - Ontario Ministry of Natural Resources (MNR) tabled the Ontario Dam Safety

Guidelines 2012 MNR commissions task force (hatch, MNR, OPG to develop risk

assessment tool 2013 CDA issues update of dam safety guidelines to better incorporate risk

concepts

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The Saguenay Flood, Canada

July 20, 1996 20 collapsed dams $800 million in damages 2,600 houses destroyed 16,000 people displaced 7 killed

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The Dam Safety Management Approach A Common Theme

Dam safety programs have evolved to deal with the major dam failure risks through the use of standards based assessments with Factors of Safety used as a proxy for risk

How then is modern dam safety practiced?

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Typical Objectives

Typically the objectives of a dam safety program are two-fold To ensure the long-term safe operation of a dam To protect the public from unacceptable losses in case of a dam break

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Assessing Dam Safety Based on Consequence

The fundamental assumption in any dam safety plan is that a dam can fail, regardless of whether or not the dam is welldesigned. Statistics back this up:

Failure rates of 10-4 per dam year are seen world-wide, Foster and Fell, 2000 note the impact of modern dam safety

practices.

Failure rates before 1950 8.6 x 10-4 Failure rates after 1950 2.7 x 10-4

The ongoing evolution of dam safety programs will reduce thisnumber further.

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Dam Classification- How is it usedThe standard of care to be exercised by the dam designer and owner should be commensurate with the consequences of dam failure(Principle 1.2): Canadian dam association Guidelines (2005 update)

The dam classification determines: Frequency of periodic reviews Frequency of maintenance activities Level of details of an emergency preparedness plan Design standards for flood Design standards for earthquake Maintenance/upgrade prioritization

Overview of Dam Classification

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A Typical Classification Scheme

Dam Hazard Categories1) or Consequence Categories2)

1) ANCOLD Guidelines on Dam Safety Management, August 20032) New South Wales (NSW) Dam Safety Committee DSC 13, March 2002

Very Low 1 Population at Risk (PAR)

Severity of Damage and Loss

Low 2 Negligible Minor Medium Major

Significant 3 0 Very Low Very Low Low Significant

High C 4 1 to 10 Low Low Significant High C

High B 5 11 to 100 Significant High C High B

High A 6 101 to 1000 High A High A

Extreme 7 >1000 Extreme

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The Indonesian Context Statistical Potential for Dam Failure Incidents Associated with the Planned 5 Year program

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 2 4 6 8 10 12

Sta

tistic

al N

umbe

r of D

am

Failu

res

Statistical # of Failures per year

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However, dams can last a very long time

0

200

400

600

800

1000

1200

1400

1600

Spain Canada India Afghanistan Czech Republic Japan

Rep

orte

d Ag

e of

Old

est D

am (I

CO

LD, 2

014)

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The Use of Risk Assessment Methodologies to Reduce the Probability of Failure further

The use of risk assessment is gaining popularity in North America and Australia to better understand and reduce the risk

Reasons are associated with an increasing awareness that failures can and do occur as a result of issues that cannot be readily analyzed human error Debris blockage gate operation problems instrumentation in the wrong location

For example, BC Hydro demonstrated that the probability of overtopping at one of their dams changed from; about 1:100,000,000 if everything works about 1:1000 if random gate failures occurred at realistic, historical failure rates 1: a few thousand if there was one gate outage for 12 hours at the same time as

adverse weather conditions

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Quantitative Risk Assessment

Dam safety analysis has traditionally been standards based; deterministic. Many failure modes cannot be readily assessed;

Dam safety risk assessment is gaining international support as the next step in Dam safety, but detailed risk analysis can be very expensive

In Canada Hatch, OPG and the Ontario regulator developed a Risk Screening Tool to overcome this problem can assess the risk for a portfolio of dams from existing standards based data

in an inexpensive, consistent, repeatable manner The calculated risk can be systematically and easily compared to acceptability

thresholds to determine whether remediation is required These measures can be checked for cost effectiveness using an appropriate

and agreed ALARP test.

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RISK MODEL OVERVIEW PRELIMINARY STEPS

Select Dam Components

Tool Generates Risk Table and Failure Modes

AssessProbabilities

AssessConsequences

Graph Results

Input Data From DSR

Data Input By User

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RISK MODEL OVERVIEW REMEDIATION STEPS

AssessProbabilities

AssessConsequences

Graph ResultsALARP Test

RemediationMeasures

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BASIS OF PROBABILITY OF FAILURE ESTIMATES

Module Basis of Estimate

Remarks

Probability of Gates Not Opening

Expert judgement Feeds into Overtopping module

Overtopping Statistical Analysis 38% of all failures

Embankment Dam Internal Stability

Empirical Analysis 33% of all failures

Concrete Gravity Dam Stability

Mathematical Analysis

23% of all failuresEmbankment Dam Slope Stability

Empirical Analysis

Gate Structural Failure

Mathematical Analysis

Part of 8% of all failures

23%

38%

33%

6% Foundation

Overtopping

Piping

Other

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APPLICATION OF THE RISK ASSESSMENT TOOL A Canadian Example

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PROBABILITY ASSESSMENT

Number Name Type Sliding Embankment Gate Penstock1 Main Dam Concrete - Spillway Structure Yes Yes No Yes No No No2 Left Embankment Embankment - Homogeneous Earthfill - Sheetpile face Yes Yes Yes No Yes No No3 Right Embankment Embankment - Homogeneous Earthfill - Sheetpile face Yes Yes Yes No Yes No No

Number Name Type Sliding Embankment Gate Penstock1 Main Dam Concrete - Spillway Structure 1.42E-05 1.10E-07 7.64E-04 7.78E-042 Left Embankment Embankment - Homogeneous Earthfill - Sheetpile face 2.80E-08 6.09E-05 5.00E-04 8.60E-06 5.70E-04 Total3 Right Embankment Embankment - Homogeneous Earthfill - Sheetpile face 2.80E-08 6.09E-05 5.00E-04 8.60E-06 5.70E-04 1.92E-03

Number Name Type ILOL Economic (Million $) Environmental ILOL Economic (Million $) Environmental1 Main Dam Concrete - Buttress Dam 0.32 0.6 6.6 122 Left Embankment Embankment - Homogeneous Earthfill - Concrete Face 0.32 0.6 6.6 123 Right Embankment Embankment - Central Core and Rockfill 0.32 0.6 6.6 12

Number Name Type Sliding Embankment Gate Penstock1 Main Dam Concrete - Buttress Dam 9.35E-05 3.52E-08 5.04E-03 5.14E-032 Left Embankment Embankment - Homogeneous Earthfill - Concrete Face 1.85E-07 1.95E-05 3.30E-03 5.68E-05 3.38E-03 Total ILOL3 Right Embankment Embankment - Central Core and Rockfill 1.85E-07 1.95E-05 3.30E-03 5.68E-05 3.38E-03 1.19E-02 6.20

Number Name Type Sliding Embankment Gate Penstock1 Main Dam Concrete - Buttress Dam 1.70E-04 6.60E-08 9.17E-03 9.34E-032 Left Embankment Embankment - Homogeneous Earthfill - Concrete Face 3.36E-07 3.65E-05 6.00E-03 1.03E-04 6.14E-03 Total IEcon3 Right Embankment Embankment - Central Core and Rockfill 3.36E-07 3.65E-05 6.00E-03 1.03E-04 6.14E-03 3.35E-02 17.48

Table 2: Probability of FailureStability Mechanical

Stability MechanicalHydrologic Piping

Component Seismic Hydrologic

Table 1: Failure ModesComponent Seismic Hydrologic MechanicalPiping Stability

Piping

Note: These cells are calculated by multiplying the probability of failure by the appropriate consequence. 'Flood' consequences apply to 'Hydrologic' failures only.

Table 5: Economic Risk

Table 3: Consequence of FailureComponent Flood Normal

Table 4: Loss of Life RiskComponent Seismic

Note: Manually enter the consequences in this table

Note: Manually enter names for the station components

Note: Manually transfer the probabilities to this table from workbooks completed for each component

Note: These cells are calculated by multiplying the probability of failure by the appropriate consequence. 'Flood' consequences apply to 'Hydrologic' failures only.

Component Seismic Hydrologic Piping Stability Mechanical

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Risk Summary Table Failure Modes

Yes denotes that probability of failure was considered

Overtopping

Piping Sliding

Slope Failure

Sliding Embankment Gate Penstock Yes Yes No Yes No No No

hfill - Sheetpile face Yes Yes Yes No Yes No No hfill - Sheetpile face Yes Yes Yes No Yes No No

Table 1: Failure ModesSeismic Hydrologic MechanicalPiping Stability

Mixed1. Sliding2. Slope Failure3. Slope Failure

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Risk Summary Table Probability of Failure

PoF Values entered for each failure mechanism considered

Sliding Embankment Gate Penstock 1.42E-05 1.10E-07 7.64E-04 7.78E-0

- Sheetpile face 2.80E-08 6.09E-05 5.00E-04 8.60E-06 5.70E-0 - Sheetpile face 2.80E-08 6.09E-05 5.00E-04 8.60E-06 5.70E-0

Table 2: Probability of FailureStability MechanicalSeismic Hydrologic

Piping

kbooks completed for each component

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The Advantage of Risk Assessment The Risk Assessment methodology demonstrated that risks

could be reduced to tolerable levels by the following methods

Traditional Standards Based assessments would have not have identified these same issues

Remedial Measure CostStability Enhancement 760,000Piping Monitoring 173,000Total 933,000

Remedial Measure CostStability Enhancement 760,000

Spillway Enhancement 5,000,000

Total 5,760,000

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The Advantage of Risk Assessment

Rectifying the deficiencies identified as a result of the Standards Based review would cost five time more and the risk would remain intolerable

The risk assessment process better reduced the risk at a fraction of the cost

Methodology Cost Residual risk Description

Risk Assessment < 1 million 2 x 10-5 Tolerable

Standards Based Review > 5 million 4 x 10-4 Intolerable

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The Potential Benefit of Risk Informed Assessments

0

1

2

3

4

5

1 3 5 7 9 11

Stat

istic

al C

umul

ativ

e N

umbe

r of D

am

Failu

res

Risk Informed Dam Safety AssessmentsTraditional Dam Safety Assessments

Assume an order of magnitude reduction in the probability of failure

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Final Thoughts

Water security is dependent on dams functioning as intended The planned program carries with it risks

even if dams are designed and constructed in accordance with average modern standards

Well constructed Dam Safety Management programs have been shown to reduce the risk However, the potential for failures, statistically, still exists

Evolving concepts of risk informed dam safety can further enhance safety

Keys to ensuring success Ensure consistent design and construction standards are developed and

adhered to Ensure there is adequate capacity and experience to apply these standards Use the available modern dam safety tools

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For more information, please visit www.hatch.ca

Water Security, dam building and dam safety do priorities need to clash?This presentationSlide Number 3Why do dams fail?Slide Number 5Slide Number 6Slide Number 7Sliding Failure - ChinaGate FailureRisk of Gates Not Opening Failure Frequency Which are the most Vulnerable DamsAssessment of the Most Vulnerable dams ContdProbability of Dam Failure The Impact of Improving Dam Safety Practices Similar frequencies are reported throughout the worldMajor dam construction programs brings with it risksWater and security in Indonesia a vital concernReported Number of Large Dams in Indonesia TodayPlanned Dam Construction Program in IndonesiaReducing the Risk - Modern Dam Safety ProgramsDam Safety GloballySlide Number 21A Short History of Dam Safety in CanadaThe Saguenay Flood, CanadaSlide Number 24The Dam Safety Management Approach A Common ThemeTypical ObjectivesAssessing Dam Safety Based on ConsequenceDam Classification- How is it usedSlide Number 29The Indonesian Context Statistical Potential for Dam Failure Incidents Associated with the Planned 5 Year programHowever, dams can last a very long timeThe Use of Risk Assessment Methodologies to Reduce the Probability of Failure furtherQuantitative Risk AssessmentRISK MODEL OVERVIEW PRELIMINARY STEPSRISK MODEL OVERVIEW REMEDIATION STEPSBASIS OF PROBABILITY OF FAILURE ESTIMATESAPPLICATION OF THE RISK ASSESSMENT TOOL A Canadian ExamplePROBABILITY ASSESSMENTRisk Summary Table Failure ModesRisk Summary Table Probability of FailureThe Advantage of Risk Assessment The Advantage of Risk Assessment The Potential Benefit of Risk Informed AssessmentsFinal ThoughtsSlide Number 45