EMERGENCY PREPAREDNESS PLAN - World Bank

S A F E T Y O F D A M S A N D D O W N S T R E A M C O M M U N I T I E S

EMERGENCY PREPAREDNESS PLAN

(SAMPLE FRAMEWORK)

APPENDIX 4

MARCH 2021

GOOD PRACTICE NOTE ON

DAM SAFETY

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About the Water Global PracticeLaunched in 2014, the World Bank Group’s Water Global Practice brings together financing, knowledge, and implementation in one platform. By combining the Bank’s global knowledge with country investments, this model generates more firepower for transformational solutions to help countries grow sustainably.

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EMERGENCY PREPAREDNESS PLAN

(SAMPLE FRAMEWORK)MARCH 2021

APPENDIX 4

© 2021 International Bank for Reconstruction and Development / The World Bank1818 H Street NW, Washington, DC 20433Telephone: 202-473-1000; Internet: www.worldbank.org

This work is a product of the staff of The World Bank with external contributions. The findings, interpre-tations, and conclusions expressed in this work do not necessarily reflect the views of The World Bank, its Board of Executive Directors, or the governments they represent.

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This Appendix 4: Emergency Preparedness Plan (Sample Framework) is a supplementary document to the Good Practice Note on Dam Safety. Please cite the work as follows: World Bank. 2021. “Good Practice Note on Dam Safety – Appendix 4: Emergency Preparedness Plan (Sample Framework).” World Bank, Washington, DC.

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3Appendix 4: Emergency Preparedness Plan

Appendix 4Emergency Preparedness Plan (Sample Framework)

Introduction

This sample framework outlines the key elements of the Emergency Preparedness Plan (EPP), such as roles & responsibilities of relevant entities, emergency response matrix, EPP response process, prepa-redness activities, dam break inundation mapping and consequence assessment, and so on.

The EPP is one of the four dam safety plans that the client is required to prepare for certain dams1 according to the Environmental and Social Framework/Environmental and Social Standard 4/Annex 1 on safety of dams. The other three plans include (a) Construction Supervision and Quality Assurance Plan (CSQAP), (b) Instrumentation Plan (IP), and (c) Operation and Maintenance Plan (O&MP).

This sample EPP framework is intended to provide general guidance for the development of the full-fledged EPP to be prepared based on topographic survey, dam break analyses, and downstream inundation simulation and mapping during the early phase project implementation. In the World Bank’s project cycle, the EPP Framework Plan is required at appraisal.

In the case of a new dam’s construction, the full-fledged EPP should be completed no later than 12 months before the first reservoir impoundment. In the case of an existing dam’s rehabilitation, the full-fledged EPP should be completed during project implementation but before World Bank–funded downstream investment works begin so that potential emergency situation of the dam will not affect the invested facilities. A sample table of contents for the EPP is provided in Annex A.

Purpose of the EPP

The purpose of the EPP is to provide a predetermined plan of actions that a dam owner should implement in coordination with the emergency management agency and other relevant offices should a dam safety emergency develop. The EPP should specify the identification procedure of potential emergency condi-tions at a dam and actions that the dam owner should undertake to moderate or alleviate any problems at the dam and to minimize downstream consequences. It contains procedures and information to assist the dam owner in issuing early warning and notification messages to responsible authorities in charge of emergency management. It also contains inundation maps to indicate the emergency managing authorities of the critical areas for action in case of an emergency. The EPP also defines the roles and responsibilities of all entities involved and their coordination mechanism in case of an emergency.

Potential dam safety emergencies can be initiated by a range of adverse conditions that include floods, earthquakes, landslides, slope failure, abnormal behavior of dam (significant seepage, piping, spillway blockage, inoperable gates, and so on), incorrect operation, accidental damage, sabotage, and so on and

1 As per ESS4 – Annex 1, para 2, these are “large dams” and “small dams” that could cause safety risks or are expected to become large dams during their operating life.

4 Appendix 4: Emergency Preparedness Plan

will vary depending on the characteristics of the dam and its reservoir. Thus, the EPP should reflect the site-specific hazards and risks of a particular dam with due consideration to its credible potential failure modes and potential downstream consequences.

During the implementation of projects involving construction of large dams, the transition between construction and operation is often a challenging phase. In many cases, the entity that takes over the operation of a project is different from the one which supervised construction activities. The handing over process entails the transfer of a significant amount of information including elements pertaining to risk management, as emerged during construction and first reservoir filling. A Potential Failure Modes Analysis workshop (See Technical Note 5 on PFMA) is useful in the transition between the construction and the operation phase of a dam project. The relevant outcomes provide essential elements for the fine tuning of the EPP.

It is also important to note that emergencies could be caused by sudden uncontrolled release or excessive controlled release of water due to sudden or rapid opening of spillway or bottom outlet gates; or increase in hydropower generation turbine discharge. The release may be caused by damage to or failure of the structure, flood conditions unrelated to failure, or any condition that may affect the safe operation of the dam, which could endanger human life and downstream property. Thus, proper downstream notification and warning procedures should be established for large water discharge in addition to emergencies that could lead to dam failure.

Proportionality Principle

The level of detail of the EPP should be commensurate with the risk of a dam in terms of potential dam failure or operational incident. Preparation of the EPP for a dam with high risk and consequences will require extensive planning, consultation, and evaluation. In addition, high- and substantial-risk dams tend to involve more entities that must coordinate responsibilities and efforts to effectively respond to dam incidents and failure than low-risk dams. The present guidelines provide details for the preparation of an EPP in such cases.

Low-risk dams still require provisions for emergency preparedness, but the level of detail of such provi-sions can be much lower. In those cases, emergency preparedness arrangements should contain, at minimum, the following essential items:

• Emergency response matrix (see a sample in Annex C)

• Emergency contact list

• Notification flowchart

• Surveillance protocol with a checklist of potential issues

• Inundation maps

• List of supply and resources


It is a good practice to prepare a concise file including these items that are essential for operators on the frontline in case of emergency. These items should also be put on the wall at the dam operator’s and other relevant offices in a visible and readily available manner.

It must be noted that the level of risk of a dam can vary with time (for example, increasing downstream communities and infrastructure development, change of dam ownership, upstream catchment and reservoir condition, and so on). It is important to periodically review, test, and update the EPP with due consideration to those changing factors.

Main Features of the Dam

A description of the dam, such as its location and key dimensional data, should be provided in this section. A dam vicinity map and key drawings showing the dam’s features should be attached, along with a list of any significant upstream or downstream dams and downstream communities that would be affected by a potential dam failure or by flooding from large operational water releases.

Roles and Responsibilities of Key Relevant Entities

The EPP should clearly specify the responsibilities of all involved entities to ensure that effective and timely action would be undertaken should an emergency at the dam occur. In particular, the EPP should specify the roles and responsibilities of the dam owner and other relevant organizations that are responsible for execution of the EPP, including surveillance, investigation, operation and maintenance of the dam, and other actions, such as notification, warning, evacuation, and so on, required for various stages of the EPP.

Although dam owners and operators are responsible for assessing dam safety conditions and notifying the emergency management authority of dam safety incidents, emergency management authorities are in general responsible for evacuation planning and implementation with the legal authority to perform these actions. However, in the case of residential or recreational areas located immediately downstream of dams that would be inundated within minutes of the dam failure, dam owners may need to notify the people in these areas directly. When developing the EPP, the dam owner and emergency management authorities should discuss and determine the most efficient notification protocol to follow.

In addition to dam owners, operators, and emergency management agencies, other relevant and coordi-nating entities may include local and regional governments, sectoral ministries, civil defense, police, medical offices, meteorological and seismic research agencies, contractors, and so forth, depending on the country’s governance system and potential hazard and scale of emergency conditions.

Emergency Contact List

The EPP should include an easy-to-find list that provides key emergency contact details for all techni-cians and staff working at the dam site, key officials of external agencies in charge of emergency mana-gement, and so on. The details should include names, roles, addresses, and contact information (landline and mobile telephone numbers), all of which should be checked and updated regularly. The list of peo-ple and authorities to contact in the event of an emergency should be displayed in a central place at the dam, preferably near to a telephone or radio transceiver.


Emergency Response Matrix

In emergency situations, dam owners or operators have no time to read a report, even if they have been sufficiently trained in emergency handling. Thus, the EPP should include the emergency response matrix (ERM). The existence of such a tool empowers operators to undertake required actions in an expeditious manner. The ERM represents a correlation between different emergency situations, with corresponding emergency/response levels, as explained in the next section. Each cell in the matrix should contain clear indications (instrument readings, visual observations, and so on) prompting the appropriate response level. A sample of the ERM is attached in Annex C and should be adapted to each specific situation. For example, the classification of emergency/response levels should be discussed and determined case by case, and if large discharge from dams could cause potential loss of life and property damage, the required warning and notification procedure should be established.

EPP Response Process

When an unusual or emergency incident is detected at a dam, the dam owner or operator should generally follow four steps: (a) emergency identification, evaluation, and classification procedures; (b) notification procedure; (c) preventive and emergency actions; and (d) emergency termination and documentation.

Early identification and evaluation of the conditions or triggering events that require an emergency response are crucial. Annex B provides some examples of anomalies that would require prompt inspection by dam operators. It is important to develop procedures for reliable and timely determina-tion of an emergency level to ensure that the appropriate response actions are taken based on the urgency of the situation. Procedures for prompt notification are required to allow all entities involved with EPP implementation to respond appropriately. Preventive or mitigating actions can be taken to attempt to address emergency conditions of the dam. Eventually, a determination will need to be made concerning termination of the incident. After the incident is over, proper documentation of the incident will be required.

Emergency Identification, Evaluation, and Classification Procedure

Potential threats that could endanger the safety of the dam and thus require immediate action should be highlighted in the EPP. If detected early enough, potential dam safety threats can be assessed, and preven-tive or remedial actions can be taken to avoid a dam failure or to mitigate the size and extent of a failure. The EPP should provide clear procedures for taking action when a potential dam safety threat is identified.

A dam safety inspection should be carried out as quickly as possible following the identification of a potential threat. Appropriate monitoring should take place during the assessment and continued until the threat has been resolved. A list of qualified dam inspectors and technical specialists should be inclu-ded in the key emergency contacts list of the EPP.

The EPP should provide clear guidance on the conditions that require a dam safety emergency to be declared, who is empowered to declare one, how the emergency declaration should be recorded, and what guidelines should be followed in classifying the emergency category as defined hereafter.


The dam owner, in coordination with emergency management authorities, should set up suitable emer-gency level classification on a case-by-case basis, but for a generic reference, four dam safety emergency level categories—large flood discharge (without failure), internal warning, potential emergency/failure, and imminent failure—are provided as follows:

• Large flood discharge. The large flood discharge warning indicates that flooding is occurring on the river system but there is no evident threat to the safety of the dam. The large flood emergency level is used by the dam owner to convey to external agencies that downstream areas may be affected by the releases from the dam. Although the amount of flooding may be beyond the control of the dam owner, information on the timing and amount of release may be helpful to authorities in making decisions regarding warnings and evacuations. Notifications should be pre-determined based on correlations between releases and the timing of impacts to downstream areas. Large flood emergency level notifications are typically made to local jurisdictions that would be affected, downstream dam owners, and other agencies, as necessary. Dam owners are advised to develop a table that correlates gate openings and/or reservoir levels to outflows, expected downstream impacts, and agencies that will be contacted. The specific return period of such “large” floods depends on the characteristics of the downstream river terrain, discharge capacity, and so on.

• Internal warning. The internal warning level is appropriate for an event at a dam that will not, by itself, lead to a failure but requires investigation and notification of internal and/or external personnel. Examples are: (a) new seepage or leakage on the downstream side of the dam, (b) presence of unau-thorized personnel at the dam, and (c) malfunction of a gate. Some incidents, such as new seepage, may require an internal response only from the dam owner. Others, such a gate malfunction, may lead to unexpected high releases that could pose a hazard to the downstream public and would require the notification of outside agencies.

• Potential emergency/failure. The potential failure emergency level indicates that conditions are developing at the dam that could lead to a dam failure. Examples are: (a) rising reservoir levels that are approaching the top of the non-overflow section of the dam, (b) transverse cracking of an embankment, and (c) a verified sabotage threat. Potential emergency/failure warning should convey that time is available for analyses, decisions, and actions before the dam could fail. A failure may occur, but predetermined response actions may moderate or alleviate failure.

• Imminent failure. The imminent failure emergency level indicates that time has run out and the dam is about to fail or is failing. Imminent failure typically involves a continuing and progressive loss of material from the dam. It is not usually possible to determine how long a complete breach of a dam will take. Therefore, once a decision is made that there is no time to prevent failure, the imminent failure warning must be issued. For purposes of evacuation, emergency management authorities should assume the worst-case condition that failure has already occurred.


Notification Procedure and Flowchart

The EPP should provide clear notification procedures with flowcharts based on this emergency level classification so that all relevant entities can take follow-up actions easily. The EPP should include a list of all persons to be notified in the event that a dam safety emergency is declared and clearly indicate who is to make the calls and in what priority. The installation of automatic emergency messages release system (by short message service [SMS], for example) should be considered. The procedure, which is often best presented in a notification flowchart, should include notification with brief key messages to the dam owner, ministry in charge, emergency management authority, regional and local governments, police, civil defense, technical advisors, and contractors, as appropriate.

As aforementioned, for the list of emergency contacts, the procedure should include a list of individual names and position titles, office and home telephone numbers, and alternative contacts and means of communication. Copies of the notification procedure or flowchart should be available for all individuals with responsibilities under the EPP and should be prominently posted at the dam and at the owner’s emergency operations center.

Preventive and Emergency Actions

The EPP should provide a list of detailed preventive and emergency actions that can be taken as per the emergency level category to remedy or mitigate the potential effects of a dam failure.

Preventive or remedial actions taken before the declaration of a dam safety emergency may include reservoir drawdown, limiting inflows and outflows, placing material to mitigate potential seepage erosion or piping discharges, placing material or sandbags at low spots on a dam crest, or controlled breaching.

Preventive actions taken following the declaration of a dam safety emergency may include initiating physical works to reduce the likelihood of dam failure, reservoir drawdown, or evacuating people from the likely inundation area.

The EPP should also provide a list of actions that can be taken before the identification of a potential dam safety deficiency, which may include

• Agreements with supporting third parties to respond at short notice with equipment, materials, or expertise;

• The stockpiling of materials;

• The installation of warning systems to alert the population at risk; and

• Establishing coordinated plans and procedures with emergency management authority, regional and local governments, police, civil defense, and so on.

Termination and Documentation

The EPP should include procedures for terminating a dam safety emergency and notifying the emergency services that the dam safety emergency has been resolved. The emergency services are responsible for declaring an end to any public emergency response process.


Following the termination of a dam safety emergency, as determined by the dam owner and its technical advisor, the dam owner should fully document the emergency response in a report, which may include the following:

• The event or condition that initiated the emergency

• The response actions taken by the dam owner and all emergency service agencies

• The extent of any damage to the dam

The extent and effect of any downstream inundation

• The justification for terminating the dam safety emergency

• The strengths and weaknesses of the existing EPP, including the emergency notification and manage-ment procedures, equipment, resources, and so on

• Corrective actions to address any identified weaknesses in the EPP

Preparedness Activities

The EPP should provide a list of activities and actions taken before the development of an incident. Such preparedness activities attempt to facilitate response to an incident and prevent, moderate, or alleviate the effects of the incident and should address the following subjects, though they are not limited to them:

• Access to site

• Communication and warning systems

• Alternative power supplies

• Emergency supplies, materials, and support

• EPP maintenance and training

Access to Site

The EPP should provide the description of primary and secondary access routes, the means for reaching the site under various conditions (for example, road, foot, boat, helicopter, bulldozer), and the expected travel times. Earthquakes and heavy rainstorms can result in landslides, tree falls, and bridge washouts that block road access for days or weeks. Poor weather can also prevent helicopter access. It is, therefore, important that the accessibility of the site following a large natural event, and the effects of possible access constraints on the availability of equipment needed to manage a dam safety emergency, are given early consideration and that EPPs incorporate a level of resilience to minimize the adverse effects of access constraints. If such constraints are likely following a large natural event, it may be appropriate to store essential equipment at the site.


The EPP should also include response procedures for any situation in which access to the dam may be impaired during the following occasions:

• Periods of darkness, including those caused by power failures. Appropriate responses may include establishing emergency power and lighting, limiting areas of access or inspection, or waiting until daylight.

• Adverse weather, including extreme storms, landslides, snowfall, snow melting, and so on. Appropriate responses may include temporary shelters, appropriate clothing and equipment, or video rather than manned surveillance.

• Road closures and transport disruptions, and so on.

Communication and Warning Systems

The EPP should provide full details of the internal and external communication systems to be used in case of emergencies. Commonly used communication systems (cellphone, landline telephone, and e-mail) are vulnerable to failure or overload in the adverse conditions that may lead to a dam safety emergency (for example, earthquake, storm, heavy rainfall, and so on). As such, the robustness of the available communication systems should be assessed and, as appropriate, enhanced by additional communication systems, such as trunked radios, satellite phones, Internet messaging, and so on.

For dams immediately upstream of residential areas, the EPP should provide information on downstream warning systems, such as emergency sirens, radios, social media, automated mobile phone messages, and so on, for people in the residential and recreational areas within possible flooding areas along the river courses. The EPP should provide full details of the warning systems and their activation procedure, including who would be responsible for any decision to activate the warning systems, and so on. Also, downstream warning, in case of large water discharge without dam failure, should be covered as required. Furthermore, the EPP should provide public awareness measures regarding how people would be informed of an emergency, as well as the actions people should take during an emergency.

Alternative Power Supplies

The EPP should provide details on the location and operation of emergency power supplies (for exam-ple, portable generators and fuel). Although the main power source for the dam should be supplied by its own hydropower function or by the electrical grid extended to the dam site, the failure of such sys-tem could result in loss of power for telephone communication, monitoring equipment, and data trans-mission system. The EPP should also analyze the implications of a dam failure or an emergency situation on power supply to the dam operations, emergency activities, rescue activities, and so on and develop a system with adequate redundancy.

Emergency Supplies, Materials, and Support

The EPP should indicate the location and availability of emergency supplies (for example, food for response teams) and materials (for example, rockfill, filter, and drainage materials) for emergency use.


The location and availability of equipment (for example, torches, cameras, emergency lighting, and earthmoving plant) should be accessible. A list of local contractors that could be mobilized in a dam safety emergency should be available.

The EPP should also include a list of technical and operational support personnel, together with their contact details. In a dam safety emergency, it may become necessary to obtain specialist technical support to consider dam performance trends and identify the need for any preventive actions or tempo-rary support works. It may also become necessary to obtain additional resources for operation of the facilities.

EPP Review, Updating, and Training

The EPP should include provisions for appropriate review of the document, its procedures, and communi-cations systems for currency, relevance, and operability on a regular basis, at least annually. The EPP should also be reviewed during the periodic detailed dam safety inspections or reviews to verify that it is current and that the information, guidance, and direction are consistent with the dam’s condition and perfor-mance. The names and contact details for all personnel with emergency management responsibilities should be updated as necessary, as well as the distribution list of the EPP for document control purposes.

Provisions should be included for the training of personnel involved in the activation and implementa-tion of the EPP, including its schedule and plan. This is to ensure that all personnel nominated in the EPP are familiar with the elements of the plan and their responsibilities and are able to fulfill their duties during a dam safety emergency. Training exercises can range from a limited tabletop exercise, seminar, workshop, and so on for a specific dam safety emergency to a full-scale simulation of a dam safety emergency and mock drill.

Adequate stakeholder assessment should also be undertaken to tailor the means of communication—such as brochures, social media, and outreach to local associations and others—and to engage local communities so that they would internalize notification procedures and required actions in case of emergency.

The frequency and type of training exercises should reflect the consequences of failure and be sufficient to maintain the dam owner’s readiness for a dam safety emergency. It should also reflect the level of turnover in personnel having emergency preparedness responsibilities. Periodic consultations should be conducted with other relevant entities, such as emergency management authorities, civil defense, and so on, to maintain the coordination mechanism and readiness for a dam safety emergency.

Dam Break Inundation Mapping and Consequence Assessment

The EPP should present the results of dam break analysis or downstream flooding simulation and deli-neate the areas that would be affected in case of the dam failure and/or discharge of a large amount of flood water. The inundation maps should show inundation areas at scales sufficient for the identification of critical areas, major infrastructure, and so on at risk and include inundation tables that show the arrival time of the flood water, peak flood elevation, velocity, and so on at key locations linked with the maps.


Topographic mapping should cover the entire downstream areas affected by dam failure, including a more detailed survey of any singularity or major infrastructure reducing the hydraulic capacity of the river, such as bridges, river crossing, and so on.

The required level of topographic survey (topographic maps, digital elevation model [DEM], or light detection and ranging [LiDAR] to delineate flooding area); dam break analysis (breaching models and parameters, dam breach outflow hydrograph, and so on); flooding simulation (simplified routing method, 1-D or 2-D hydraulic model, and so on); and flood mapping (arrival time, flood depth, velocity, and so on) should be specified in the framework plan considering the potential risk or consequence of dam failure for each case.

Detailed inundation maps indicating the flooding area, water depth and velocity, and peak flood arrival time that would be heavily affected by topography are critical for undertaking detailed consequence assessment, including the estimation of the number of people at risk (PAR), potential loss of life (PLL), affected houses, commercial buildings, main infrastructure and others, and defining the required emer-gency measures in coordination with relevant stakeholders.

To assist emergency management authorities with potential evacuations, the maps may show areas inundated from a dam failure during (a) a “sunny” day dam break flood—usually associated with an earthquake under fair weather condition and (b) a “rainy” day dam break flood under design or check flood involving overtopping failure of the dam. Moreover, downstream inundation maps—in case of large floods (for example, 200- to 1,000-year return period), which would not cause dam failure but discharge of a large amount of flood water, leading to inundation of downstream residential and commercial areas—should be prepared to enable timely issuance of warnings to the downstream local governments and communities.

Dam break inundation maps would also assist the emergency management authorities in coordination with regional and local governments, police, civil defense, and so on in developing and managing evacuation plans. At the request of emergency management authorities, additional features, such as recommended evacuation routes and emergency shelters, may be included on the maps.

Additional Information

Additional items that may be incorporated as appendixes in EPP include

• General site plans, access routes, drawings, and photographs;

• Details and operating instructions for gates and valves that fulfil dam safety functions along with rating curves;

• Information on emergency reservoir drawdown procedures and rates; and

• Procedures and templates for the recording of emergency situations (for example, flood inspection checklists, post-earthquake checklists, and an emergency action log).


Annex A: Table of Contents (Sample)

1. Introduction

2. Purpose and Scope of the EPP

3. Main Features of the Dam

3.1. General Information

3.2. Characteristics of Dam and Appurtenant Structures

4. Roles and Responsibilities of Key Relevant Entities

4.1. Owner

4.2. Operator

4.3. Government Agencies (Disaster Management, Ministries, and So on)

4.4. Others

5. Emergency Identification, Evaluation, and Classification Procedures

5.1. General Introduction

5.2. Emergency Identification and Evaluation Procedures

5.3. Emergency Classification

5.3.1. Large Flood Discharge (without Dam Failure)

5.3.2. Internal Warning

5.3.3. Potential Emergency/Failure

5.3.4. Imminent Failure or Failure Occurring

6. Notification Procedure and Contact List

6.1. Notification Flowcharts and Procedures

6.2. Contact List of Key Persons

7. Preventive and Emergency Actions

7.1. Preventive and Mitigatory Actions

7.2. Emergency Actions (Warning, Evacuation, and So on)

8. Preparedness Activities

8.1. Access to Site under Different Timing and Conditions


8.2. Communication and Warning Systems

8.3. Emergency Supplies, Material, and Support

9. Termination and Documentation

9.1. Termination Procedure

9.2. Documentation/Reporting

10. EPP Review, Updating, and Training

10.1. Periodic Review and Updating

10.2. Training and Awareness Raising

11. Dam Break and Flooding Simulation and Consequence Assessment

11.1. Dam Break Analysis and Modeling

11.2. Flooding Simulation and Mapping

11.3. Consequences Assessment

Appendixes

A. General Site Plans and Access Routes

B. Emergency Response Matrix

C. Emergency Contact List

D. Notification Flowcharts

E. Emergency Reservoir Drawdown Procedure

F. Emergency Action/Response Forms

G. Dam Break Analysis Report and Inundation Maps


Annex B: Early Identification of Possible Emergency Conditions (Sample for Embankment Dams)

The dam operation staff should be able to identify an emergency condition and should be aware of the principal types of failure and associated tell-tales to identify and put in place action plans to either avert or reduce the disastrous impacts of a dam failure. The table 1 gives some example signs of abnormal behavior of embankment dams.

TABLE 1. Potentially Observed Anomalies, Causes and Required Actions

Potentially observed anomalies Potential causes and required actions

New seepage area, increased flow from an existing seepage or wet area, or anomalous increases in a monitored drain flow

New or increased seepage emerging at the toe of the dam, on the abutments, on the downstream slope of the dam, or in areas downstream of the dam could be of great concern because it could relate to initiation and development of a seepage-related potential failure mode. Similarly, an increase in any of the monitored seepage or drain flows would indicate changed seepage conditions at the dam site that could possibly relate to initiation and development of a seepage-related failure mode. Close monitoring of the dam should be instituted, and the situation should be promptly investigated.

Evidence of material transport by seepage flow

This is a direct indication of possible seepage erosion or piping. Small amounts of sediment or small seepage rates that are constant could indicate the potential failure mode is just initiating and developing. Muddy seepage that is rapidly increasing is very serious, and dam failure could be imminent. Emergency actions including notification and remedies, such as emergency reservoir drawdown and so on, should be undertaken immediately.

Anomalous water pressure data Unusual piezometer water pressure readings (not consistent with historical performance) could indicate changed seepage conditions and performance of the dam and/or foundation and should be promptly investigated. Such data would be of most concern when occurring with other evidence of changed seepage conditions (new seepage or wet areas, changes at existing seepage or wet areas, anomalous increases in monitored drain flows, and so on).

Sinkholes or unusual embankment

settlements or deformations

Sinkholes could be a result of subsurface removal of embankment or foundation material by seepage flow. Similarly, unusual settlements or deformations could indicate subsurface material is being removed by seepage flow. Sinkholes or unusual settlements or deformations of the dam embankment should be taken seriously and investigated quickly.

Transverse crack (upstream-downstream

direction)

This does not mean that a seepage-related failure mode is necessarily under way, only that increased attentiveness to this possibility is warranted. Changes in the seepage performance of the dam (including monitoring of embankment and foundation water pressures) provide the best indication of whether a seepage-related failure mode may have initiated. Close monitoring of the dam should be performed during reservoir filling above the current reservoir level.

Longitudinal crack (parallel to the axis of the dam)

This could be a result of sliding instability of the dam, which would be of great concern, or embankment settlement, perhaps because of differing rates of consolidation for adjacent zones in the embankment. In any event, the dam should be closely monitored for at least a few days to ensure that no continuing sliding movements are occurring.


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le

vel ,

star

ting

disc

harg

e ov

er th

e sp

illw

ay, a

nd

dow

nstr

eam

mun

icip

aliti

es

shou

ld b

e in

form

ed.

In c

ase

of e

arth

quak

es

with

a p

eak

grou

nd

acce

lera

tion

smal

ler

than

that

of t

he d

esig

n ba

se e

arth

quak

e,

the

dam

mus

t be

exam

ined

by

dam

saf

ety

engi

neer

s.

If w

ater

leve

l rise

s in

ob

serv

atio

n w

ells

at t

he

dam

’s do

wns

trea

m s

lope

or

at t

he d

owns

trea

m to

e,

or a

leak

age

is vi

sual

ly

obse

rved

, exa

min

atio

ns

mus

t be

perf

orm

ed b

y da

m

safe

ty e

ngin

eers

.

Dam

-spe

cific

. Typ

ical

in

stru

men

ts p

rovi

ding

“e

arly

war

ning

s” a

re

piez

omet

ers,

flow

m

eter

s, a

nd jo

int

met

ers.

Dam

age

can

be re

paire

d in

less

than

one

to th

ree

days

. Dam

age

cont

rol

repo

rt re

quire

d. C

onsid

er

upda

ting

the

Oper

atio

n an

d M

aint

enan

ce P

lan.

In c

ase

of a

n in

cide

nt o

r th

reat

to th

e da

m a

nd it

s fa

cilit

ies,

the

dam

sec

urity

of

ficer

s w

ill re

spon

d fir

st,

and

the

gend

arm

erie

will

be

info

rmed

ther

eof.

Leve

l II

Cond

ition

s m

ay

lead

to d

owns

trea

m

flood

ing

If th

e re

serv

oir w

ater

le

vel e

xcee

ds a

cer

tain

cr

itica

l ele

vatio

n , a

nd

the

inco

min

g flo

w ra

tes

abov

e, s

ay, o

ne h

undr

ed-

year

flow

are

ant

icip

ated

, do

wns

trea

m m

unic

ipal

ities

an

d co

mm

uniti

es s

houl

d be

al

erte

d.

In c

ase

of e

arth

quak

es

grea

ter t

han

the

desig

n ba

se e

arth

quak

e,

requ

iring

rapi

d re

serv

oir d

raw

dow

n,

all d

owns

trea

m

mun

icip

aliti

es a

nd

com

mun

ities

sho

uld

be

aler

ted

appr

opria

tely

.

If th

e am

ount

of w

ater

le

akag

e ob

serv

ed

dow

nstr

eam

of t

he d

am

incr

ease

s, a

nd th

e le

akag

e ca

rrie

s m

ater

ials

, rap

id

rese

rvoi

r dra

wdo

wn

may

be

nec

essa

ry. D

owns

trea

m

mun

icip

aliti

es a

nd

com

mun

ities

sho

uld

be

aler

ted.

Inst

rum

ents

sig

nal t

he

pers

isten

ce o

f abn

orm

al

beha

vior

; res

ervo

ir dr

awdo

wn

may

be

nece

ssar

y. E

xter

nal

notif

icat

ion

requ

ired.

Dam

age

cont

rol r

equi

res

mor

e th

an th

ree

days

. Ex

tern

al n

otifi

catio

n re

quire

d.

If th

e da

m e

mba

nkm

ent

and

spill

way

are

dam

aged

as

an

acci

dent

or s

abot

age,

do

wns

trea

m m

unic

ipal

ities

an

d co

mm

uniti

es s

houl

d be

ale

rted

.

Leve

l III

Imm

inen

t thr

eat

and

prep

are

for

evac

uatio

n

If it

is an

ticip

ated

that

the

rese

rvoi

r will

exc

eed

the

desig

n flo

od e

leva

tion,

an

d th

e in

com

ing

flow

rate

is

expe

cted

to re

ach,

say

, on

e-th

ousa

nd y

ear f

low

an

d m

ore,

pre

para

tions

will

be

star

ted

to e

vacu

ate

the

dow

nstr

eam

com

mun

ities

.

If a

stab

ility

pro

blem

ha

s oc

curr

ed in

the

dam

slo

pes

afte

r an

ear

thqu

ake,

pr

epar

atio

ns w

ill b

e st

arte

d to

eva

cuat

e th

e do

wns

trea

m

com

mun

ities

.

In c

ase

of m

ajor

incr

ease

s in

the

wat

er le

akag

es

with

turb

idity

on

the

dow

nstr

eam

par

t of t

he

dam

, pre

para

tions

will

be

star

ted

to e

vacu

ate

the

dow

nstr

eam

com

mun

ities

.

Dam

beh

avio

r is

such

to

thre

aten

unc

ontr

olle

d re

leas

e of

wat

er.

Prep

are

for e

vacu

atio

n.

Dam

age

pers

ists

and

impa

irs th

e fu

nctio

n of

wat

er c

ontr

ol w

orks

du

ring

high

rese

rvoi

r pe

riod.

Pre

pare

for

evac

uatio

n.

Dam

age

impa

irs th

e fu

nctio

n of

wat

er c

ontr

ol

wor

ks d

urin

g hi

gh

rese

rvoi

r per

iod.

Pre

pare

fo

r eva

cuat

ion.

tabl

e co

ntin

ues o

n th

e ne

xt p

age


Resp

onse

leve

l

Type

of e

vent

Rese

rvoi

r wat

er e

leva

tion

and

inco

min

g fl

ood

volu

me

Eart

hqua

keEx

cess

ive

leak

age,

in

tern

al e

rosi

on, o

r pip

ing

Abno

rmal

inst

rum

ent

read

ings

Gate

failu

re, p

ower

lo

ss, e

quip

men

t fai

lure

, or

fire

Acci

dent

or s

abot

age

Leve

l IV

Emer

genc

y de

clar

atio

n an

d ev

acua

tion

orde

r

If w

ater

leve

l is

exce

edin

g th

e de

sign

flood

leve

l an

d ap

proa

chin

g to

the

dam

cre

st le

vel,

the

dow

nstr

eam

com

mun

ity’s

evac

uatio

n sh

ould

be

orde

red.

If th

e da

m h

as b

een

seve

rely

dam

aged

suc

h th

at it

can

no

long

er

reta

in w

ater

aft

er a

n ea

rthq

uake

, eva

cuat

ion

of d

owns

trea

m

com

mun

ities

sho

uld

be

orde

red.

If th

e da

m h

as b

een

seve

rely

dam

aged

by

eros

ion

such

that

it c

ould

no

long

er re

tain

wat

er

safe

ly, e

vacu

atio

n of

do

wns

trea

m c

omm

uniti

es

shou

ld b

e or

dere

d.

Rese

rvoi

r can

not b

e co

ntro

lled:

Eva

cuat

ion

shou

ld ta

ke p

lace

.

Rese

rvoi

r lev

el c

anno

t be

cont

rolle

d: E

vacu

atio

n sh

ould

take

pla

ce.

Rese

rvoi

r lev

el c

anno

t be

cont

rolle

d: E

vacu

atio

n sh

ould

take

pla

ce.

SKU W20096

Date post:	29-Dec-2021
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