Dam Safety ManagementGUIDELINES BY AUSTRALIAN NATIONAL COMMITTEE ON LARGE DAMS (ANCOLD)

Dam Safety ManagementObjective Element of

Dam Safety

ANCOLD vs Malaysia

Responsibility Owner Responsibility

Why Dam Safety

A dam can fail

Failure Statistics

Dam Safety Legislation

St Francis Dam Vaiont Dam Malpasset Dam

Why Dam Safety?

Major consequence

St Francis Dam Vaiont Dam Mt. Polley Why Dam Safety?Early Warning

Baldwin Dam

Fontenelle

Zeyzoun

What Should Dam Safety Program Do?

Who should be involved?

Who have interest?

What is knowledge required?

Dam Safety Objectives

• To protect life, property (e.g., community infrastructure, dam) and the environment from the failure of any dam.

• These objectives can be achieved by implementing and maintaining an appropriate dam safety program

Element of Dam Safety Program (ANCOLD)• Plan• Design• Investigate• Construct• Commission

• Public Awareness• Role of Owner• Role of Government• Regulator

Operation & Maintenance

SurveillanceSafety Review

Risk Assessment

ReportingEducation & Training

Emergency Preparedness

Information Management

Deficiency

Is Dam Still Required?

Remedial Action

Continue Dam Safety Program

Decommission

Yes

YesNo

No

Operation Maintenance

Operation and Maintenance

Guidelines for Operation, Maintenance and

Surveillance of Dams (1989)

Monitoring Inspection

Surveillance

Safety Review

Data Collection

Responsibility and Accountability

Owner

• Safe Operation & Maintenance

• Dam Hazard Categories

• Surveillance Program

• Dam Safety Emergency Plan

• Qualified & Experienced Personnel

• Dam Safety Reviews

• Dam Risk Profiles

Regulatory Authorities

• Maintain register of dams

• Ensure that dams are designed, operated and maintained to current standard

• Owners of “significant” or higher Hazard Category Dams and other dam with Population at Risk (PAR)

Dams Operators

• Damage Potential

• Able to recognize deficiencies /adverse trends

Dam Safety Management Program

Why have dam safety program?

• A dam can fail

ABSTRACT FROM UNICIV REPORT ON ANALYSIS OF

EMBANKMENT DAM FAILURE INCIDENTS

Overall statistics of failure occurring before and after 1950, large embankment dams

Mode of Failure % Total

Failures (where

mode of failure

known)

% Failures

pre 1950

% Failures

post

1950

Overtopping 34.2 % 36.2 % 32.2 %

Spillway/gate (appurtenant works) 12.8 % 17.2 % 8.5 %

Piping through embankment 32.5 % 29.3 % 35.5 %

Piping from embankment into

foundation 1.7 % 0 % 3.4 %

Piping through foundation 15.4 % 15.5 % 15.3 %

Downstream slide 3.4 % 6.9 % 0 %

Upstream slide 0.9 % 0 % 1.7 %

Earthquake 1.7 % 0 % 3.4 %

Totals (3) 102.6 % 105.1 % 100 %

Total overtopping and appurtenant

works

48.4 %

53.4 %

40.7 %

Total piping 46.9 % 43.1 % 54.2 %

Total slides 5.5 % 6.9 % 1.6 %

Total no. of embankment dam

failures (exc. During construction) 124 61 63

Total embankment dam years

operation (up to 1986) 300,400 71,000 229,400

Annual probability of failure 4.1 x 10-4 8.6 x 10-4 2.7 x 10-4

Notes: 1. Percentages based on the % of cases where the mode of failure is known.

2. Percentages are for failures of embankment dams in operation only, i.e. excluding failures during construction.

3. Percentages do not necessarily sum to 100% as some dams were classified as

multiple modes of failure.

Failure Incidents

UPPER TAUM SAUKPUMPED STORAGE

• Overtopping failure (Dec 2005)

• No Spillway

SWIFT 2 DAM

• Piping failure

Dam Safety ManagementINCIDENTS LED TO DAM SAFETY LEGISLATION

ST FRANCIS DAM

• Failed on March 1928

• “Sole judgement of one man”

• State of California enacted legislation in 1929

MALPASSET DAM

• Foundation defect (1959)

• 421 fatalities

VAIONT DAM (ITALY)

• H = 265 m

• Thin arch dam. 160 m long

• 115 m3 x 106 capacity

VAIONT SLOPE FAILURE UPSTREAM

• Landslide into reservoir, overtopping

Dam Safety Management Program

Why have dam safety program?

• Major consequence failure

ST FRANCIS DAM (USA)

• 450 fatalities, economic & major infrastructure damages

VAIONT DAM (ITALY)

• 2,600 fatalities, economic & major infrastructure damages

• Animals move out 3 days prior to failure

MOUNT POLLEY MINE (BC CANADA)

• Breached August 2014

• Copper & Gold Mine Tailings

• No fatalities, environmental damage, business impacts

UPPER TAUM SAUKPUMPED STORAGE

• No fatalities

• Environmental damage

• Business impact

Dam Safety Management Program

Why have dam safety program?

• Early Warnings

• Failed in 1963.

• 11.15am: Caretaker noticed high seepage flows

• 3.38pm: Dam failed, 1,600 people evacuated

• 5 fatalities

BALDWIN HILLS DAM(USA)

• H = 71 m, 198m long

• Homogenous Earthfill

• 0.95 m3 x 106 cap.

FONTENELLE DAM (USA)

• Nearly failed in May 1965 due to excessive seepage

• Operation personnel draw reservoir down

• Rockfill placement over seepage area

TSF DAM CONSTRUCTION STANDARD

REQUIREMENTS

1.) If seepage points are observed to have increased in flow by >50%, the following pre-emptiveaction is to be taken to prevent any further increase in flow which could lead to piping

Step 1: excavate a 2mx2m trench connecting the seepage point to the chimney drain.

Step 2: line the excavation with non-woven geo-fabric.

Step 3: backfill with TSF 150 coarse filter material. Place in 300mm lifts and bucket tamp.

2m

2m

TSF 150 CF

Cross-section Longitudinal Section

Seepage point

2m

Chimney drain

Dam Batter

Geo-fabric

Emergency Remediation of Excess

Dam Seepage

ZEYZOUN DAM(SYRIA)

• Embankment dam.

• Failed on June 2002

• Cracked appear several days before it collapse

• Thousand homeless and damage to cultivated land

What Should Safety Program Do?

Assurance that dams are safe

• Resources

• Prevailing Technology

• Sound Management

Who should be involved?

• Owner

• PAR

• Property’s Owner

• Those maintaining infrastructure facilities

• Those with interest in the environment

Who have interest in Dam Safety Management?

• Private owner

• Dam operators

• Dam safety professionals

• Emergency management agencies

• Governments

• Professional bodies (ANCOLD)

What is the knowledge required?Regulator

• Dam engineering & risk management

• Legislation & community expectation

Owner’s Manager• Significance of Hazard & Risk

• Risk Profile

What is the knowledge required?O&M Engineer

• O&M Procedure & Practice

• M&E Design Principle

• Dam Failure Modes

• Operating Risk

• Environmental & Water Quality Issue

What is the knowledge required?Inspector/Field Personnel

• Dam Failure Modes

• O&M Procedures

• ERP

• Surveillance i.e., Principles, Visual Sign

What is the knowledge required?Dams Engineer

• Design Principles (Structure, Geotechnical, Hydrology, Hydraulic)

• Construction

• O&M Procedures

• Dam Failure Modes, Consequence Assessment

• Surveillance process

• Audit, Review & Risk Management

• Emergency Planning

SurveillanceActivities

Monitoring, visual inspection, reporting

Monitoring

What do we monitor?

Loads parameter Response parameter

Available Instrument Example

Surveillance Activities

• Monitoring

• Visual field inspection

• Examination and reporting of the data and results of monitoring field inspections and routine or special reports on operation and maintenance

ICOLD Definition (Bulletin 118)

Objects of

Surveillance

• Dam

• Foundation

• Reservoir

• Appurtenant Structures (outlets, spillway)

• Structural Monitoring system

• Security Monitoring system

• Alert System

Surveillance

Monitoring VisualInspection

Checking &Testing

ReportsReportsData

Manual

Acquisition

Transmission

Processing

PreliminaryAnalysis

PreliminaryAnalysis

Automated

Acquisition

Transmission

Processing

PreliminaryAnalysis

Overall Assessment of Dam Safety

PreliminaryAnalysis

SurveillanceMONITORING

Monitoring Features (what do we monitor)1. Loads

• External and Internal

2. Structural Response/Performance/Behaviour

• Dam- wall, foundations & Appurtenant Structures

3. Structural Integrity/Condition/State

• Deterioration/ageing

EXTERNAL LOAD PARAMETERS▪ What are the loads being applied to the dam and associated structures

and what are their parameters?

▪ Reservoir and tailwater - metres depth & uplift (PWP)

▪ Sediment – Depth, Density grading & permeability

▪ Temperature (During and After Construction)

▪ Ice

▪ Climate (Sun - solar radiation; wind – speed & direction, rain – depth & duration )

▪ Earthquakes – acceleration

▪ Other dynamic loads (Blasting Ambient Vibration) – acceleration and Peak Particle Velocity

RESPONSE PARAMETERS• 1, 2, & 3D Deformation and Displacements

• Foundation• Concrete dam • Embankment dam • Reservoir Rim

• Seepage and Leakage quantity and quality

• Pore-water (interstitial) pressures and piezometric level

• Erosion

• Cavitation

• Sedimentation

• Unusual Animal Behaviour (Vaiont)

AVAILABLE INSTRUMENTS EXAMPLES Parameter Instrument

Foundation deformation Inclinometer, Trivec or Pendulum, Extensometer

Concrete Dam deformation Trivec or pendulum, Geodetic surveys, crack meters

Embankment Dam

deformation

Inclinometer, settlement gauges/plates, Geodetic

surveys

Seepage Pipes, or V notch weirs

Interstitial pressures and

piezometric level

Standpipes or piezometers (vibrating wire, pneumatic,

hydraulic)

Pore water pressure Piezometers (vibrating wire, pneumatic, hydraulic)

Stress and Strain Strain rosettes, Stress cells

Temperature Thermometer, Thermistor, Thermocouples

Pressure Barometer, Pressure Plate/Cell

Level Analogue/Digital - Gauge Plate, piezometer, Drum,

Sonar, bubbler

SurveillanceVISUAL INSPECTION

Dam Safety InspectionsANCOLD 2003

Type of

Inspection Personnel Purpose

Comprehensive Dams Engineer

and Specialists1

(where relevant)

The identification of deficiencies by a thorough onsite

inspection; by evaluating surveillance data; and by applying

current criteria and prevailing knowledge.

Equipment should be test operated to identify deficiencies.

For a Safety Review consider:

• Draining of outlet works for internal inspection.

• Diver inspection of submerged structures.

Intermediate Dams Engineer The identification of deficiencies by visual examination of

the dam and review of surveillance data against prevailing

knowledge with recommendations for corrective actions.

Equipment is inspected but not necessarily operated.

Routine Dam

Safety

Inspector The identification and reporting of deficiencies, by structured

observation of the dam and surrounds, by an inspector, other

than the operator, with recommendations for corrective

actions.

Routine Visual Operations

Personnel

The identification and reporting of deficiencies by visual

observation of the dam by operating personnel as part of their

duties at the dam.

Special /

Emergency

Dams Engineer

and Specialists1

The examination of a particular feature of a dam for some

special reason (eg. after earthquakes, heavy floods, rapid

drawdown, emergency situation) to determine the need for

pre-emptive or corrective actions.

Inspection Frequencies (ANCOLD)Inspection Type

Hazard

Category Comprehensive Intermediate Routine Dam

Safety Routine Visual Special

Extreme On first filling

then 5 yearly Annual Monthly Daily

1 As required

High A,B,C On first filling

then 5 yearly Annual Monthly

Daily to1

Tri-Weekly As required

Significant On first filling

then 5 yearly

Annual to

2-Yearly 3-Monthly

Twice Weekly

to Weekly 1

As required

Low On first filling,

then 5 yearly Monthly As required

Very Low Dam Owner’s

Responsibility2

Dam Owner’s

Responsibility2

As required

Arrangements before the inspection

• Determine the type of inspection – This defines• Who is required for the inspection – Operator, specialists,

owner representative;• Equipment needed and access requirements;• Testing requirements for operational and monitoring

equipment

• Job Safety Analysis• Risk identification

• Hazards

• Likelihood

• Mitigation

• Travel arrangements and contacts

A PHILOSOPHICAL POINT OF VIEW

In Dam Monitoring we work with x,y,z and t- coordinates.

In Dam Surveillance we have to add:• Common sense• Sound engineering judgement• Due Diligence

– Interest– Commitment– Dedication

(Some of these are forgotten human attributes)• Attending to detail• Putting things into perspective

Safety Condition

• Satisfactory – No deficiencies

• Fair – Maintenance, minor deficiencies

• Poor – Major repairs

• Unsatisfactory – Failure possible

Safety ReviewRequirements Reporting Scope Outcome

Safety Review Requirements• Existing Dams not subject to routine and surveillance

inspection Safety Review ASAP

• From the outcome of Surveillance Inspection Report

• Following unusual events – earthquakes, major floods etc

• ANCOLD = 10 to 20 years depending on hazard, condition of dam etc

Safety Review Reporting• Reporting on original design criteria.

• Evaluation of the dam against current criteria including investigation where required

• Statement on the safety of the dam, indicating whether or not the dam is in a satisfactory condition, and what and when remedial or emergency action should be carried out to rectify the deficiencies

• Review of older dams may be more extensive

Safety Review Scope (Indicative)• Geology

• Seismicity (where applicable)

• Hydrology and Design Flood

• Dam Structure, Spillway and Outlet

– Materials

– Foundation

– Analytical data

– Operation and Maintenance

Safety Review Outcome• Dam Satisfactory

• Repair or Remedial Work

• Removal or abandonment

• Emergency Action

• Change in O&M Procedures

• Routine Maintenance Work

Risk Assessment

Hazard Classification What is Hazard?

Assessment Process

Data and Level of assessment

Hazard categories

Application Example

What is Hazard?ANCOLD 2003

The threat or condition which may result from external cause (e.g., flood, earthquake) with potential to create adverse consequence

Assessment Process

• Inundation Maps

• Estimate Damage & PAR

• Assign Category

Data assembly and level of assessment (ANCOLD)

Hazard (Consequence) Categories ANCOLD 2003

Population at

Severity of Damage and Loss

Risk

Negligible

Minor

Medium

Major

0

Very Low

Very Low

Low

Significant

1 to 10

Low Notes 1 and 4

Low Notes 4 and 5

Significant Note 5

High C Note 6

11 to 100

Note 1

Significant Notes 2 and 5

High C Note 6

High B

Note 6

101 to 1000

Note 2

High A Note 6

High A Notes 6

>1000

Note 3

Extreme Note 6

Note 1: With a PAR of 5 or more people, it is unlikely that the severity of damage and loss

will be “Negligible”.

Note 2: “Minor” damage and loss would be unlikely when the PAR exceeds 10.

Note 3 “Medium” damage and loss would be unlikely when the PAR exceeds 1000.

Note 4: Change to Significant where the potential for one life being lost is recognised.

Note 5 Change to High where there is the potential for one or more lives being lost

Note 6 See Section 2.7 and 1.6 for explanation of the range of High Hazard Categories

Inspection Frequencies ANCOLDInspection Type

Hazard

Category Comprehensive Intermediate Routine Dam

Safety Routine Visual Special

Extreme On first filling

then 5 yearly Annual Monthly Daily

1 As required

High A,B,C On first filling

then 5 yearly Annual Monthly

Daily to1

Tri-Weekly As required

Significant On first filling

then 5 yearly

Annual to

2-Yearly 3-Monthly

Twice Weekly

to Weekly 1

As required

Low On first filling,

then 5 yearly Monthly As required

Very Low Dam Owner’s

Responsibility2

Dam Owner’s

Responsibility2

As required

Hazard Category in dam safety

• Cost of ownership and potential liability

• Resource and management efforts allocated according to risk of business

• Consequence of Failure vs Likelihood of Failure

LAWN LAKE DAM (USA)

• About 8m high, 0.8 x 106m3

• 3 fatalities, Estes Park

• Remote location

• Damage to residential, commercial and infrastructure

Failure Mode Analysis (FMA)What is Failure Mode

What you need to know

What to do after you identified potential failure mode?

Component Definition Example

Identify PFM

Example PFM Description

Identify PFM FMA for monitoring program

What is a Failure Mode?

ANCOLD 2003A way that failure can occur, described by the

means by which element or component failures must occur to cause loss of the sub-system or system function.

What do you need to know?

• To understand and identify the potential failure of or weakness in a dam, inspecting personnel must have extensive knowledge of the causes of failure

• Failure modes analysis✓ Identify the components of the dam✓ What can go wrong with them (failure mode)✓ How will this happen (loads, weaknesses, operating errors etc)✓ What will the result be (consequences)✓ What can be done about it (mitigating action)

What to do after you identified potential failure mode?

• Fix (Remedial Works)

• Reduce Risk (Surveillance)

• Ignore

Component Definition Example

Reservoir Spillway

Foundation Rip Rap Shell Core Chimney Filter Blanket Drain Toe Drain

Main Dam Saddle Dam

Embankments Downstream Areas OUtlet Works

A Dam

Identify PFM

• 1- Spillway/Wall Interface

• 2-Adjacent to Conduit

• 3-Crack in Abutment

Identify PFM

• 4- Dessication

• 5- Embankment to Foundation

• 6 - Foundation

• 7 - Embankment (e.g., poorly compacted layer)

Identify PFM

• Different Probability of Internal Erosion!

• Upper Berm and Lower Berm

3 1B 1A 1B 2

Flow path 1A

Flow path 1B

Photo 1: Freshly placed fill unsealed and

saturated by heavy rainfall

Photo 2: Fill placement over saturated,

unsealed fill

UNSEALED FILL = WRONG

Sealing fill prior to rainfall

PLACING FILL OVER WET

FILL = WRONG

Photo 3: Main Dam southern flank upstream -

Fill placed over waterlogged ground

Photo 4: Main Dam southern flank downstream

- Fill placed over waterlogged ground

PLACING DRY OVER WET FILL = WRONG

Placing fill over wet ground

FMA for monitoring programCENTRAL CORE EARTHFILL OR ROCKFILL EMBANKMENT (CC)

Failure Modes and Instrumentation Central Core DamFailure Mode Cause/Loading Indicator Instrument to monitor

CCE1 Foundation piping

Erodible material

Joints open during seismic event

No blanket filter/incompatible gradings

Hydraulic gradient

Seepage increasing, non-linear with reservoir level or turbid

Increase in groundwater pressure

V-notch weirs

Rain gauge

Piezometer

CCE2 Embankment piping

Erodible material

Inadequate filter

Transverse cracking of core (drying shrinkage, differential settlement or seismic loading)

Hydraulic gradient

Seepage increasing, non-linear with reservoir level or turbid

Increase in pore water pressure if piezometer in area of piping

V-notch weirs

Piezometer

Rain gauge

CCE3 Upstream slope failure

Rapid drawdown – inadequate pore pressure dissipation

Inadequate material strength under seismic or normal loading

Movement of wall survey points

Visual observation of wall alignment, shape

Increased seepage (indicates failure may have occurred)

Increase in pore water pressure (indicates failure may have occurred)

Survey monuments

V-notch weirs

Piezometers

Accelerograph

CCE4 Downstream slope failure

As for CCE4 except no rapid drawdown

CCE5 Overtopping

Extreme flood

Inadequate spillway capacity

Spillway gate failure (if present)

Gate operational alarms

Water over crest

Spillway gate alarms

Water level gauge

Visual observations

Conclusion

Element of Dam Safety Program• Plan• Design• Investigate• Construct• Commission

• Public Awareness• Role of Owner• Role of Government• Regulator

Operation & Maintenance

SurveillanceSafety Review

Risk Assessment

ReportingEducation & Training

Emergency Preparedness

Information Management

Deficiency

Is Dam Still Required?

Remedial Action

Continue Dam Safety Program

Decommission

Yes

YesNo

No

References

• ANCOLD Guidelines on Dam Safety Management, 2003

• ANCOLD Guidelines on Assessment of the Consequences of Dam Failure, 2000

• Malaysia Dam Safety Training Seminar, 2008

• Guidelines for Operation, Maintenance and Surveillance of Dams, 1989

• USBR Dam Safety Risk Analysis and Best Practice

• Geotechnical Engineering of Dams, Fell et al, 2014