Revision 1 July 1, 2005 

CHAPTER 14 

DAM SAFETY 

PERFORMANCE MONITORING PROGRAM
Chapter 14 Monitoring the Performance of Dams 

Revision 1 i July 1, 2005 

TABLE OF CONTENTS 

14.1 INTRODUCTION ............................................................................................... 1

14.2 SUPPORTING TECHNICAL INFORMATION............................................. 3

14.3 POTENTIAL FAILURE MODE ANALYSIS.................................................. 5

14.3.1 Introduction........................................................................................................... 5

14.3.2 Description............................................................................................................ 6

14.3.3 Key Goals and Typical Outcomes ........................................................................ 7 

14.3.4 Conduct of the “Initial” Potential Failure Mode Analysis.................................... 8 

14.3.5 Use of the Potential Failure Mode Analysis report as a support document to the 

conduct of the FERC Part 12D Dam Safety Inspection ...................................... 27 

14.3.6 Updating the Potential Failure Mode Analysis................................................... 28 

14.3.7 Conduct of a “Supplementary” Potential Failure Mode Analysis .......................... 29 

14.4 SURVEILLANCE and MONITORING PLAN ............................................. 30

14.4.1 Principles and Methods of Performance Monitoring.......................................... 30 

14.4.2 Surveillance and Monitoring Procedures and Guidelines................................... 34 

14.5 INSPECTION PROCESS and COORDINATION........................................ 43

14.5.1 Scope and Purpose .............................................................................................. 43 

14.5.2 Description and Interrelationship of Dam Safety Program Elements Using a 

Potential Failure Mode Analysis Approach ........................................................ 43 

14.5.3 Process flowchart................................................................................................ 45 

14.6 EMERGENCY PREPAREDNESS.................................................................. 46

Appendix A.....................................................................................................................14-A-1

Example Potential Failure Mode Descriptions 

Appendix B .....................................................................................................................14-B-1

Example Potential Failure Mode Identification Cover Letter and Questionnaire 

Appendix C.....................................................................................................................14-C-1

A Typical Potential Failure Mode Analysis Session 

Appendix D.....................................................................................................................14-D-1

General Format for Potential Failure Mode Analysis Reports 

Appendix E .....................................................................................................................14-E-1

Major Findings and Understandings - Example Write Up 

Appendix F ..................................................................................................................... 14-F-1

Estimated Time Requirements 

Appendix G.....................................................................................................................14-G-1

Dam Safety Performance Monitoring Program Process 

Appendix H.....................................................................................................................14-H-1

Part 12D Safety Inspection Report Outline 

Appendix I ..... ................................................................................................................. 14-I-1

Guidelines for Supporting Technical Information 
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14.1 INTRODUCTION 

The guidelines presented in this chapter provide recommended procedures and criteria to 

develop a Dam Safety Performance Monitoring Program based upon "failure mode thinking" 

to assist in reviewing and evaluating the safety and performance of water retaining project 

works regulated by FERC. The procedure includes: 

• Development of a Supporting Technical Information Document (STI); 

• A Potential Failure Mode Analysis (PFMA); and 

• Development of a Surveillance and Monitoring Plan (SMP). 

The Supporting Technical Information is prepared by the licensee with assistance as required 

by the Independent Consultant. A draft of the STI should be prepared prior to the PFMA 

session and provided to the Core Team to assist them in becoming familiar with the dam. 

Guidance on preparing the STI is provided in Section 14.2. 

The Potential Failure Mode Analysis is conducted jointly by the licensee, Independent 

Consultant (IC) and FERC staff. Guidance on conducting a PFMA is provided in Section 

14.3. 

Based upon the results of the PFMA, the SMP is developed. The SMP defines the 

appropriate monitoring for the water retaining project works based upon the PFMA. An 

integral part of the SMP is the integration of the licensee’s operation, maintenance and 

inspection programs. Guidance on preparing a Surveillance and Monitoring Plan is provided 

in Section 14.4 

In addition, the Part 12D Independent Consultant’s inspection and report and the FERC’s 

inspection program will also be focused using the PFMA and the SMP. 

The integration of a Potential Failure Mode Analysis with a Surveillance and Monitoring 

Plan and the Supporting Technical Information document, results in a more efficient and 

effective dam safety program. The added value to dam safety includes: 

• Uncovering data and information that corrects, clarifies, or supplements the 

understanding of potential failure modes and scenarios;

• Archiving the key technical information supporting the evaluation of the dam; 

• Identifying the most significant potential failure modes;

• Identifying risk reduction opportunities; 

• Focusing surveillance, instrumentation, monitoring and inspection programs to 

provide information on the potential failure modes that present the greatest risk to the 

safety of the dam; and

• Developing operating procedures to assure that there are no weak links that could 

lead to mis-operation failures.

Although the traditional emphasis of Part 12D inspections has been on project dams, 

18CFR12.32 specifically states that all project works with the exception of transmission and 

transformation facilities and generating equipment are to be included in the inspection by the 
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independent consultant. In addition, certain other water retaining structures such as canals, 

flumes, tunnels and penstocks may impact public safety if they were to fail. Accordingly, 

these types of project works may also warrant consideration during the PFMA session. In 

this document dam and project works may be used interchangeably to designate those 

licensed project works that could impact public safety in the event of a failure. 

The following definitions are provided to assure that all readers have a common 

understanding of the terms commonly used in this Chapter. 

Dam Safety Performance Monitoring Program 

The Program developed under this Chapter of FERC’s "Engineering Guidelines for 

the Evaluation of Hydropower Projects” incorporating a Supporting Technical 

Information document, a Potential Failure Modes Analysis and a Surveillance and 

Monitoring Plan to improve the ability of Owners, Consultants and the FERC to 

manage the risk associated with Commission regulated hydro projects. 

Supporting Technical Information (STI) 

A document prepared to capture the information necessary to have a complete and 

thorough understanding of the dam and the analyses completed that support the 

findings regarding the safety of the structure(s). 

Potential Failure Mode (PFM) 

The chain of events leading to unsatisfactory performance of the dam or a portion 

thereof. The dam does not have to completely fail in the sense of a complete release 

of the impounded water. Failure Modes that result in unintended releases of water, 

such as the Folsom Dam radial gate failure, are also considered. 

Potential Failure Mode Analysis (PFMA) 

The process utilized to determine the Potential Failure Modes pertinent to the dam 

under investigation. 

Major Findings and Understandings (MFU) 

The most significant items learned by the participants in the PFMA session regarding 

such items as the construction, performance, and safety of the dam. 

PFMA Report 

The document prepared to capture the information developed during the PFMA. 

Surveillance and Monitoring Plan (SMP) 

The SMP is a written monitoring plan that is prepared following the completion of the 

PFMA that addresses the site-specific potential failure modes that are identified in the 

PFMA report. It should address all Category I and appropriate Category II and 

Category III failure modes and be designed to minimize the risk associated with these 

potential failure modes by providing early warning if the failure modes become active 

or worsen. 
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14.2 SUPPORTING TECHNICAL INFORMATION 

14.2.1 Purpose 

The purpose of the Supporting Technical Information document (STI) is to summarize those 

project elements and details that do not change significantly between quinquennial FERC 

Part 12D Independent Consultant Safety Inspection Reports. The Licensee is responsible for 

compiling the “Supporting Technical Information” (STI) document and will create and 

maintain this document for use by themselves, the Part 12D Consultant and the FERC. 

The STI should include sufficient information to understand the design and current

engineering analyses for the project such as: 

• A complete copy of the Potential Failure Mode Analysis report 

• A detailed description of the project and project works 

• A summary of the construction history of the project 

• Summaries of Standard Operating Procedures 

• A description of geologic conditions affecting the project works 

• A summary of hydrologic and hydraulic information 

• Summaries of instrumentation and surveillance for the project and collected data 

• Summaries of stability and stress analyses for the project works 

• Pertinent correspondence from the FERC and state dam safety organizations related 

to dam safety 

The STI should use tables, figures, and drawings in preference to text and should not include 

complete copies of the original documents except for the “Potential Failure Mode Analysis” 

study report. Only key paragraphs of the original reports should be included in this document 

for clarity. 

The STI is a “living” document, in that as new data or analyses become available they are 

appended to the initial STI and outdated material is removed. The document should be 

bound in a three ring binder to facilitate updating the STI as necessary. 

The Licensee should coordinate this document with the Part 12D inspection report outline to 

be sure the Independent Consultant will have all the information necessary for review of the 

project. The initial STI should be provided to the IC and three hard copies and two digital 

copies shall be submitted to the FERC. Updates to this document shall be provided to the 

current FERC Part 12D IC for review, to the FERC and to other document holders. 

Document holders should be requested to insert the updated pages in the STI, and add the 

revision to the revision notice log in the front of the STI. 

Except for the initial submittal of an STI document, if no significant changes have been made 

to the STI since the prior Part 12D Inspection report, either a digital copy of the most current 

STI in *.pdf, *.jpg, *.tif, or other acceptable formats (check with the FERC for acceptability 

of alternative formats prior to submittal) or a hard copy of the STI shall be included with the 

Part 12D report. 
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Licensees should include complete copies of the reference documents referred to in the STI, 

or, in some instances, all documents reviewed in the PFMA session, in CD or DVD format 

with the STI document. 

The complete STI should be reviewed and reprinted at least every 15 years and hard copies 

submitted with the Part 12D report. 

The initial STI should be provided to the Independent Consultant and three hard copies and 

two digital copies shall be submitted to the FERC. As new information is obtained, or 

modifications are made to the project, the licensee will update this document as required. 

Updates to this document shall be provided to the current FERC Part 12D Independent 

Consultant for review, to the FERC and to other document holders. Document holders 

should be requested to insert the updated pages in the STI, and add the revision to the 

revision notice log in the front of the STI. 
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14.3 POTENTIAL FAILURE MODE ANALYSIS 

14.3.1 Introduction 

The FERC in association with Dam Owners and the Independent Consultants who perform 

the Part 12D Dam Safety Evaluations have developed these procedures for use within the 

Part 12D examination process. Specifically, they combine plans to improve and focus the 

Surveillance and Monitoring Plans for FERC regulated dams, and also provide a fundamental 

enhancement to the inspection process by focusing on site-specific factors of greatest 

importance at each project. The Potential Failure Mode Analysis, as outlined below, will 

serve as the focal point and linking feature within the Part 12D Inspection. 

A Potential Failure Modes Analysis is a dam and project safety evaluation tool to be used in 

the context of the Part 12D program of dam and project works safety evaluation. Traditional 

dam and project works safety evaluations have tended to focus on a limited number of 

“standards based” concerns such as hydraulic capacity of spillways and stability of structures 

under a set of pre-defined load conditions. PFMAs are intended to broaden the scope of the 

safety evaluations to include potential failure scenarios that may have been overlooked in 

past investigations. A Potential Failure Mode Analysis is an exercise to identify all potential 

failure modes under static loading, normal operating water level, flood and earthquake 

conditions including all external loading conditions for water retaining structures and to 

assess those potential failure modes of enough significance to warrant continued awareness 

and attention to visual observation, monitoring and remediation as appropriate. 

 A Potential Failure Mode Analysis is to be conducted for all FERC regulated dams that are 

required to undergo Independent Consultant safety inspections as defined in 18 CFR Part 12, 

Subpart D unless granted an exemption. Once completed, this initial PFMA will only need 

to be reviewed and updated as necessary during subsequent Part 12D inspections. 

A supplementary PFMA should also be conducted after failure of a structure or prior to 

major modifications or remedial work on a structure. The purpose of the supplementary 

PFMA is to explore the reasons for the failure or evaluate the recommended 

modification/remediation plan prior to construction. Before a supplementary PFMA can be 

conducted for major modifications or remedial actions, the design must have progressed to 

the point of a recommended alternative. Relatively detailed plans and preliminary 

specifications for the recommended alternative should be available for the supplementary 

PFMA. A PFMA type analysis may be useful for the design team to evaluate alternatives, 

but such evaluation would not be part of a supplementary PFMA. 

This section provides guidance and examples and supporting materials to enable a Potential 

Failure Mode Analysis to be carried out, as follows: 

• A brief description of a Potential Failure Mode Analysis;

• A listing of the key goals and outcomes anticipated from a PFMA;

• Guidance for the conduct of a PFMA is given in two ways: 

o A brief statement of the expectations and requirements for a PFMA 
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o Detailed, step by step guidance for the conduct and documentation of a PFMA. 

• A description of the intended application of the results of the PFMA as a support 

document for conducting the FERC Part 12D Dam Safety Examination with specific 

emphasis on the development of the Surveillance and Monitoring Plan for the project; 

• A description of the process for “updating of the PFMA” by future Part 12D 

Independent Consultants, the licensee or the FERC; and

• Appendices containing supporting materials and example products from a PFMA.

14.3.2 Description 

A Potential Failure Mode Analysis is an informal examination of “potential” failure modes 

for an existing dam or other project work(s) by a team of persons who are qualified either by 

experience or education to evaluate a particular structure. It is based on a review of existing 

data and information, first hand input from field and operational personnel, a site inspection, 

completed engineering analyses, identification of potential failure modes, failure causes and 

failure development and an understanding of the consequences of failure. The PFMA is 

intended to provide enhanced understanding and insight on the risk exposure associated with 

the dam. This is accomplished by including and going beyond the traditional means for 

assessing the safety of project works and by intentionally seeking input from the diverse team 

of individuals who have information on the performance and operation of the dam. A PFMA 

includes and uses all of the available data and information from standard engineering 

analyses of an existing dam. A PFMA should be viewed as a supplement to the traditional 

process in which a dam’s safety is judged based on its ability to pass standards-based criteria 

for stability and other conditions. 

Utilizing an intensive team inquiry process beginning from a basis of no preconceived 

notions, the potential failure mode examination process has the ability to: 

• Enhance the dam safety inspection process by helping to focus on the most critical 

areas of concern unique to the dam under consideration; 

• Identify operational related potential failure modes; 

• Identify structural related potential failure modes (e.g. piping) not covered by the 

commonly used analytical methods (e.g. slope stability, seismic analysis); 

• Enhance and focus the visual surveillance and/or instrumented monitoring program 

• Identify shortcomings or oversights in data, information or analyses necessary to 

evaluate dam safety and each potential failure mode; 

• Help identify the most effective dam safety risk reduction measures; and 

• Document the results of the study for guidance on future dam safety inspections. By 

updating the documentation (as a living document), the benefit of increased 

understanding and insight lives on.
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14.3.3 Key Goals and Typical Outcomes 

The primary product and the main focus of a Potential Failure Mode Analysis is identifying 

and obtaining a clear understanding of each dam’s – site specific - potential failure modes. 

At the outset of the PFMA the Facilitator should discuss with the entire team that the product 

of the exercise is not a decision document but rather an informational, resource document, 

developed from the combined input of the team, that is intended for use and reference for 

many years. 

The potential failure mode “identification” is intended to go beyond a simple generic 

statement of the potential problem (e.g. operations, piping, slope instability, foundation, 

overtopping, liquefaction, etc.). The potential failure mode identification, examination and 

description provides background information on the loadings, structural conditions, 

circumstances and events at each site that identify why this potential failure mode is being 

considered for this site. Also the significance of the potential failure modes for the site in 

terms of the need for awareness, monitoring and surveillance, analyses and investigation or 

for making operational changes, structural repairs or modifications is discussed. Example 

descriptions of potential failure modes that have come from prior potential failure mode 

analyses are provided in Appendix A for a potential operational type potential failure mode 

and for a potential piping type failure. 

The Potential Failure Mode Analysis (PFMA) process is not a substitute for, but rather a 

guide to help focus, periodic, comprehensive, dam safety inspections. Both activities require 

and benefit from a comprehensive review and discussion of all available information 

(historic records and photos, engineering analyses, previous inspection reports, etc.). Hence, 

the detailed reviews commonly done prior to a periodic inspection, especially if an 

Independent Consultant is not familiar with a project, are still necessary. Linking the 

accomplishments of the PFMA and periodic inspections is efficient and effective because it 

allows others, not often in the direct safety evaluation loop, to participate and contribute 

importantly to the outcome. 

Although potential failure mode identification is the focus product from the PFMA process, 

there are other outcomes that result from carrying out a PFMA in the manner described in 

this guidance document. 

• The process of searching out all the information about the dam for the specific 

purpose of identifying potential failure modes (plus the involvement of a diverse 

group of people in the PFMA process), typically results in uncovering data and 

information that most personnel currently involved in the dam’s safety evaluation had 

not been aware of. Frequently this information plays an important role in identifying 

a potential failure mode. 

• The most significant potential failure modes and failure scenarios will be identified 

and documented for use and consideration by future Independent Consultants and 

inspection teams. 

• Certain problems, issues and concerns that have been associated with the dam may be 

found to be of lesser significance than previously perceived from the standpoint of 

consequence, remoteness or physical possibility. 
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• Enhancements to the monitoring and visual inspection programs are recognized and 

readily developed. Monitoring efforts can become more focused on the important 

issues. 

• A wide range of persons (from the dam tender to the owner’s dam safety program 

manager), become aware of the dam’s most significant vulnerabilities and the 

relationship of the surveillance and monitoring programs to these vulnerabilities. 

• Gaps in data, information or analyses that prevent characterizing the significance of a 

potential failure mode are recognized and identified for consideration / action by the 

owner. 

• Risk reduction opportunities applicable to the Surveillance and Monitoring Plan, 

operations, structure response or emergency preparedness are recognized and 

identified for consideration by the owner. 

• Provides the opportunity to easily and effectively educate all who are concerned with 

the dam (dam tender, owner, regulator, periodic reviewers, inspectors, designers and 

others) about: 

1. The potential failure modes for this dam; 

2. How monitoring, including use of specific instrumentation and visual surveillance 

is used to look for specific symptoms, behaviors or evidence that might warn of a 

developing failure for the identified potential failure modes; 

3. How “general health” monitoring (e.g., crest monitoring, piezometers) is used as 

basic data to help watch for conditions that were not identified as potential failure 

modes; 

4. How operations (i.e., regulated, normal, unusual) of this dam and others upstream 

may influence dam safety; and 

5. Emergency actions that may be more commonly encountered. 

14.3.4 Conduct of the “Initial” Potential Failure Mode Analysis 

Specific steps and actions for carrying out a PFMA for a dam are enumerated below and 

these steps are recommended, as a minimum, for a PFMA to be comprehensive, consistent, 

and complete. However, in completing these specific steps it is very important that the 

principles of the process be understood and followed in order for the full value of the process 

to be achieved. These principles include: 

• Diligence in searching for all the background information; 

• An open – investigative attitude toward identifying and understanding potential 

failure modes and failure scenarios; 

• Dedication of the assigned persons to the reviewing / reading of all the background 

information on the dam prior to the PFMA session; 
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• Diversity in input to the process – field personnel, operations personnel, technical 

personnel, management personnel and others all contribute to the pool of information. 

There is no monopoly on good ideas and key information; 

• Documentation is the key to capturing the insight and ideas resulting from the 

process; and 

• Willingness of all parties to set aside their normal hats and focus on what the data, 

information, and experience / knowledge of individuals can teach us about the dam. 

Overall Guidance – Potential Failure Mode Analysis Expectations / Requirements 

1. Collect all data, studies and information on the investigation, design, construction, 

analysis, performance and operation of the project. All studies and investigation 

reports existing that relate to the ongoing safety of the dam must be included and 

reviewed and evaluated. A listing should be made of the data available for review and 

considered in the Potential Failure Mode Analysis and the reference list included in 

the PFMA report documentation. 

2. Visit the project site with an eye out for potential failure modes, structural and 

geologic conditions, review operations, and interview owners/operators for their input 

on potential failure modes. 

A Core Team, experienced in dam safety evaluation (familiar with dam failure 

mechanisms), is to review all the background information for general understanding 

and with these specific questions in mind: 

• How could this dam fail? (Site-specific consideration of loadings, structure 

condition, and project operations ) 

• What happens if the dam fails? 

• Are the identified potential failure modes recognized and being appropriately 

monitored by visual surveillance or instrumental monitoring? 

• What actions (immediate or long term) can be taken to reduce dam failure 

likelihood or to mitigate failure consequences? These actions could include any 

of the following: data collection, analysis or investigations, operational changes, 

communication enhancement, monitoring enhancement and structural remediation 

measures. 

3. Brainstorm potential failure modes and failure scenarios with the group of persons 

most familiar with design, analysis, performance, and operation of the dam. Record 

the identified potential failure modes, the reasons why each potential failure mode is 

favorable / less likely and adverse / more likely to occur and identify any possible 

actions related to each that could help reduce risk (i.e. monitoring enhancement, 

investigation, analysis, and/or remediation). 

4. Specifically identify possible Surveillance and Monitoring enhancements and/or risk 

reduction measures for each potential failure mode for consideration by the owner 

and the Independent Consultant in the Part 12D inspection and report. 
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5. Document the analysis, including immediately recording the major findings and 

understandings from the brainstorming session. 

Procedural Guidance – Potential Failure Mode Analysis Step by Step Guidance 

Step 1 Designation of the Potential Failure Mode Analysis Participants 

 (Licensee with input from IC and FERC ) 

Step 2 Collection of Background Data on the Dam for Review by the Core Team 

 (Licensee with input from the Independent Consultant) 

Step 3 Site review including interviews with key owner personnel at the Project. 

 (Core Team) 

Step 4 Comprehensive review of all of the Background Data on the Dam by the Core 

Team 

Step 5 Conduct of the PFMA Session (The licensee is responsible for the facilities, 

the Facilitator for assuring the process is followed, and the Core Team for 

performing the PFMA) 

Step 6 Consideration of Surveillance and Monitoring opportunities and/or Risk 

Reduction measures for Identified Potential Failure Modes - (Note that the 

Surveillance and Monitoring Plan for Identified Potential Failure Modes is 

provided to the owner by the Independent Consultant in the Part 12D report) 

Step 7 Documentation of the PFMA and Surveillance and Monitoring and/or Risk 

Reduction opportunities (Independent Consultant) 

The time frame for completing the documentation of the PFMA session is provided in the 

Table below. 
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Action Item Time Frame 

1) Independent Consultant (IC) Transcribes the 

Major Findings and Understandings and sends 

them to the Facilitator and the core team for 

comments. 

Within 14 days of the PFMA 

Session

2) The Facilitator and core team send their 

comments on the MF&U to the IC. 

Within 21 days of the PFMA 

Session

3) IC prepares the draft PFMA report and sends it 

to the Facilitator for peer review. 

Within 30 days of the PFMA 

session.

4) Facilitator completes Peer Review of draft 

PFMA Report. 

Within 2 weeks of receipt of the 

draft report. 

5) IC considers Facilitator’s comments and 

suggestions, makes any necessary revisions to 

the draft PFMA report and sends the revised 

report to each participant of the PFMA. 

Within 60 days of the PFMA 

session.

6) Participants of the PFMA review the draft 

PFMA report and send comments to IC. 

Within 2 weeks of receipt of the 

draft report. 

7) IC considers all comments received from the 

participants of the PFMA, makes any necessary 

revisions to the PFMA report and finalizes the 

PFMA report. 

Within 90 days of the PFMA 

session

The following sections describe each step in detail: 

Step 1 – Designation of the Potential Failure Mode Analysis Team Participants 

The potential failure mode analysis participants (team members) consist of all those who will 

participate in the brainstorming session in which potential failure modes are identified, 

defined, discussed and categorized. Fundamentally these are persons who have past 

experience with the design, construction, analyses, performance and operation of the dam or 

who will obtain knowledge of the project through reading all the background material. A 

dam-experienced engineering geologist should be a part of the team and should be included 

in the site visit. The primary advantage of having a variety of people participate in the 

potential failure mode identification process (and it is a very significant advantage) is that 

more ideas and more questions are put forward; more knowledge and information is 

available; and a greater diversity of opinion is input to the process.

Some of the team members have specific roles and responsibilities and need to have the 

requisite experience and capability to fulfill these roles. The roles and requirements of the 

team members are given below: 
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Team Leader - The dam owner would designate one of the participants as the team 

leader, responsible for coordination activities – including collection of the background 

information. 

Core Team - At least four participants are designated as the “Core Team” members. 

They are called the Core Team because they are specifically assigned the responsibility to 

read / review all of the background material. 

The Core Team will generally consist (as a minimum) of the following four persons: 

• The Independent Consultant(s) who will do the current Part 12D inspection and 

prepare the Potential Failure Mode Analysis Report. 

• A Technical Representative(s) of the Owners Staff (i.e., engineer, field operations 

person) may or may not be the team leader – see note below. 

• The FERC inspector for the dam. 

• The Facilitator of the Potential Failure Mode Analysis session who will facilitate 

the session and Peer Review the Potential Failure Mode Analysis Report on 

behalf of the owner and all the participants. 

• It is strongly recommended that an engineering geologist and a geotechnical 

engineer be included in the Core Team. Experience has shown that this expertise 

has proven valuable during the PFMA sessions and the people filling these roles 

should have the benefit of reading the background material. 

Note: The Team Leader may or may not be assigned by the owner as one of the 

designated Core Team “readers of the material”. This is because the coordination / 

logistic activities may keep the Team Leader from being able to meet the reading and 

review requirements. If the owner and team leader consider that this may be the case 

another representative of the owner should be designated to participate in the Core Team 

review of all the background material. 

The following criteria should be considered when selecting the Core Team members: 

General Criteria - 

• The Core Team members should have knowledge and experience related to dam 

safety evaluations. It is especially helpful to have persons who have interest and 

knowledge related to dam failures and who have an inquisitive / investigative 

personality (they think like coroners or detectives). 

• The Facilitator should, in general, be new with respect to examining the dam’s 

operation and history. This is considered an advantageous situation with respect 

to providing a fresh and vigorous look at the structure.

Dam owner representatives who have the knowledge, skill and interest and who 

gain the requisite experience to serve as Facilitators are encouraged to do so via 

an exchange program with other dam owners. It is considered inappropriate for 

dam owners to facilitate the PFMA on their own structures. 
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• The Independent Consultant may or may not be new to the facility, but like the 

Facilitator must have extensive experience in dams and an open mind relative to 

identification of potential failure modes. In accordance with current regulations 

the Independent Consultant must still meet FERC requirements and be approved 

by FERC.

• The Independent Consultant and the Facilitator should not be from the same 

organization / firm.

• Persons who had experience with the original design and/or construction of the 

project can provide invaluable insights and data. Wherever possible, they should 

be recruited for the PFMA field and data review and the PFMA session. 

Alternatively, they can be available by phone to answer questions raised during 

the session. 

• In states where the State Dam Safety organization has sufficient resources, the 

dam safety inspector responsible for the subject project can provide valuable data, 

information and insights into the project and should be invited. 

Facilitator Requirements - The Potential Failure Mode Analysis (PFMA) Facilitator 

should be a civil, geotechnical engineer or engineering geologist with a broad 

background and experience in dam safety engineering and experience in performing a 

PFMA similar to that described in this guidance. A recommended qualification for the 

Facilitator is that the proposed Facilitator for a project should have been involved in an 

actual PFMA of the nature described in these guidelines either as a Core Team member 

of a PFMA or actually facilitating a PFMA. This ensures that the person leading the 

PFMA process knows not only how the process is carried out, but also is aware of what 

can be accomplished. This is especially critical if the other Core Team members have not 

been through a PFMA which may often be the case. As an alternative to actual 

experience participating or facilitating a PFMA, the proposed Facilitator should have 

attended an FERC sponsored Dam Safety Performance Monitoring Program Training 

Workshop. FERC will periodically provide training opportunities to help develop 

Facilitators. 

It is important to understand that if the Facilitator, working with the assembled PFMA 

team, does not accomplish the goals of the PFMA, which is identifying and obtaining a 

clear understanding of each dam’s site-specific potential failure modes, the PFMA may 

be required to be supplemented or redone entirely. 

Additional PFMA Participants – In addition to the Core Team members, the PFMA 

sessions should include the key operating staff of the project who will be able to clarify 

operating rules and procedures and also will learn about the failure modes developed in 

the process. Also, if not a designated Core Team member, a dam experienced 

engineering geologist should participate in the PFMA and should review all geological 

background material, make appropriate observations during the field review and 

participate in discussions of foundation related PFMs. 
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In formulating the team it is important to include those individuals with intimate 

knowledge of the project operations and structures, especially the senior dam tenders and 

those responsible for collecting monitoring data. The benefits from conducting this 

exercise include not only bringing focus to the most likely modes of failure based on 

engineering judgment but also includes increasing the general awareness of dam safety 

issues by sharing knowledge at all levels. Experience has shown that it is very helpful and 

valuable to include senior (experienced) field personnel in the actual PFMA session 

because all information has not been written down and in certain cases assumptions in 

written reports differ from what is actually done or known in practice. The field 

personnel also can verify data and information discussed in the session. 

Supplemental Resources - In addition to the team participants there are other people 

who have specific technical knowledge or experience that may be useful to the team. 

These people would be notified and asked to be available or on call on the day of the 

PFMA session. This would include such persons as those involved with the construction 

of the facility, seismo-tectonic specialists, hydrologists, structural engineers, electrical 

engineers, mechanical engineers, geotechnical engineers, field personnel, inspectors, 

instrumentation personnel, emergency preparedness personnel, etc. If there has been a 

major change to the project (anchoring program) or if there is a complex instrumentation 

program (unique instrument), it is useful to have the responsible engineer/operator make 

a short presentation during the workshop so that all participants have a common 

understanding of the issue. 

Step 2 - Collection of the Background Data on the Dam

1. Preparation / Input by the Dam Owner’s Team Leader and FERC 

The Team Leader, working in conjunction with the Facilitator, FERC inspector, 

Independent Consultant, project staff, and geologist, collects and gathers for review, 

all background information on the project. This data and information is collected in a 

centralized location for reading by the Core Team members and would also need to 

be available during the PFMA Session. The general rule is: collect all information 

on the project. If there is a question about the need to bring / collect certain 

material, the Facilitator and owner should discuss this in advance. 

The types of material which should be collected (if available) include but are not 

limited to the items listed below. 

• Any FERC or state agency construction inspection reports (these have been found 

to be extremely useful, particularly if the original construction predates the 

Federal Power Act) 

• Current or most recent dam safety engineering analyses, including stability and 

stress analyses 

• The most recent monitoring and instrumentation data along with the historic 

records of monitoring data. Large scale, easily readable, plots of monitoring data 

over the life of the dam have proven extremely valuable and should be available 
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at the PFMA session. The licensee or consultant should also provide verification 

that the instrumentation is properly functioning. 

• The most recent surveys for each of the project structures (i.e. horizontal and 

vertical survey data). This should preferably be the survey that was conducted as 

part of the current Part 12D inspection. A detailed survey of the crest of all 

structures including principal and emergency spillway crest elevations to confirm 

the freeboard assumed in the discussions. Elevations of natural grounds that 

could result in overflows around the structures should be considered. Also, the 

datum of the project relative to surrounding grounds should be stated (i.e., 

conversion of project records to NGVD) 

• Current hydrologic studies and the associated flood routings and any hazard / 

consequence analyses 

• The current Emergency Action Plan 

• The most up-to-date aerial photographs of the downstream areas that could 

potentially be impacted by failure of the project structures. 

• Original and subsequent modification construction design reports, as-builts, 

photographs 

• Boring logs 

• The most recent underwater inspection report. This should preferably be the 

underwater inspection that was conducted as part of the current Part 12D 

inspection. 

• Recent and historic meteorological and pertinent river records from project or 

nearby dam or gage records (http://waterdata.usgs.gov/nwis). 

• Operation records(particularly historic) of primary and secondary (e.g. fuse plugs) 

spillway discharge rating curves, mechanism and response times for opening 

(i.e., stanchion gates, bulkheads, flashboards, gates) and problems (i.e., ice, 

debris). 

• The most recent seismic loading parameters that have been prepared for the site 

and print records of recent seismic activity (http://neic.usgs.gov/). 

• Any incident reports 

(Note: Basic demographic, seismic, meteorological and/or stream flow data should 

be reviewed to ensure that previous findings or assumptions related to potential 

failure mode hazards or consequences are up to date. Hence, recent data and 

information should be brought to the session or generated at the session as necessary. 

This will ensure that the PFMA report is an accurate representation of the likely 

potential failure modes and consequences based on the best information that was 

available on the date the exercise was conducted.) 

A listing of the data available for review and considered in the Potential Failure Mode 

Analysis should be prepared for use by the Core Team in reviewing the materials and 

included in the PFMA report documentation. 
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The owner should establish a means to retain / archive all the information collected 

for the PFMA. 

2. An advance review package on the dam would be prepared for all participants – this 

package would consist of material already prepared that provides an overview of the 

dam and its performance. The purpose of an advance package is twofold: to give the 

Facilitator familiarity with the dam prior to the site review and to refresh knowledge 

of the dam and stimulate “potential failure mode thinking” by all participants prior to 

the PFMA session. The previous Part 12D Inspection report, the most recent FERC 

Operation Report and the draft STI would provide a good “advance package 

document” to give to the Facilitator and the Core Team (and any other proposed 

participants) for familiarization with the project prior to the site review. The advance 

review package should be sent to site review participants prior to their travel to the 

site. 

3. Core Team members are to review all of the above information searching for site 

specific conditions or situations that would lead to uncontrolled release of the 

reservoir or other incidents, conditions or situations that would have an adverse 

impact. This review of materials is scheduled to occur following the site visit and 

discussion with project personnel. 

4. A questionnaire on potential failure mode identification and surveillance and 

monitoring is to be sent by the Team Leader to all PFMA participants and support 

personnel (Appendix B provides an example questionnaire along with a draft note to 

be sent explaining the request for information). Note that prior to the PFMA session, 

team participants, other than the Core Team members, are only required to complete 

this questionnaire, review their own files (re-acquaint themselves relative to the work 

within their area of expertise), and bring their historic knowledge and documents of 

the project to the session. Only the Core Team members are responsible for reading 

all the historical and technical documents related to the project. 

Step 3 - Site Review of the Dam and Project 

Typically the PFMA team (Core Team, including the geologist if present and the 

owner’s personnel) are first assembled at the time of the site review. This is a good 

occasion for the Facilitator to review the basic concept of the PFMA process and the 

objectives of the site review and ask if there are any questions (on the order of 5 to 10 

minutes). These guidelines layout what is to be accomplished in the PFMA and 

although the Core Team has likely read them, the licensees operating staff probably is 

unfamiliar with the process. Therefore, a quick review of the process to make sure 

everyone is on board is a good idea. Likewise when the Core Team gathers to do the 

reading, a quick discussion of the plan and objectives of the reading by the Facilitator 

is appropriate.

1. The detailed Part 12D Inspection of the project will be performed and the 

accompanying report prepared by the Independent Consultant following the Potential 

Failure Mode Analysis. However prior to the initial PFMA session, a review of the 

site, “thinking” potential failure modes, is carried out with the owner’s personnel and 
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the Core Team. The basic purposes of this site review are (1) to let those 

participating on the PFMA team, who have not seen the site, see it; (2) to have the 

team “think / see” potential failure modes in the field; and (3) to discuss the site and 

operations with site personnel in their own environment. Owner’s may find it 

valuable to include all or most of the employees that they plan to have participate in 

the PFMA also participate in the site review. 

2. Typically the site review performed in association with the Potential Failure Mode 

Analysis should be scheduled just before the Core Team members review the 

background materials. Such a schedule takes greatest advantage of the interaction 

between potential failure mode analysis and site visitation. 

3. The site review should include the opportunity to discuss the Project with field 

maintenance personnel and plant operators, including but not limited to those who 

will be team participants. 

4. The comprehensive review of background data and information on the dam by the 

Core Team is scheduled to occur following the above site visit and discussion with 

project personnel. Experience has shown that it is much more efficient and effective 

to review the bulk of the background materials after a physical review of the site. 

Step 4 – Comprehensive Review of the Background Material 

Prior to the Core Team beginning its review of the background material, the Facilitator 

should review the basic concept of the PFMA process and the objectives of the material 

review and ask if there are any questions. 

The Core Team and the geologist gather and review the data on the dam. The review of the 

material should take place at a convenient location considering the location of the site, data, 

and where the PFMA session will take place. The background material should preferably be 

in the same as room as the PFMA session in order to facilitate finding reference material 

during the PFMA session. 

Assemble in a group setting for efficiency in sharing the collected data and to provide a 

“captive” condition to ensure that the material is reviewed by all the Core Team members. 

Also being together allows for collaboration on items that may need clarification by the 

entire core group. The team geologist should ensure that the relevant geologic data is 

available for Core Team review and the geologist should also review this material personally. 

(Note: Allow one day for the review plus afternoon/evening of the site review and evening 

before PFMA as necessary. This review is essential to an effective PFMA.) 

Step 5 - Conduct the Potential Failure Mode Analysis Session 

A brief description of the Potential Failure Mode Analysis Session is given below – a more 

comprehensive example of a typical session is given in Appendix C. It is important for the 

Facilitator to involve all participants in the discussions and give everyone an opportunity to 

provide their knowledge, understanding and views on the potential failure modes, 

consequences and possible risk reduction actions / measures. 

Just as discussed for the site review and the reading session, the Facilitator, at the outset of 

the PFMA session, should give some introductory remarks about the PFMA session, (goals, 
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objectives, process), should provide everyone a handout on the Potential Failure Mode 

Categories (it is best to discuss this however at the point the first potential failure mode is to 

be categorized), and should discuss with the entire team that the product of the exercise is not 

a decision document but rather an informational, resource document, developed from the 

combined input of the team, that is intended for use and reference for many years. (This is 

one important reason that the process works so efficiently and effectively) 

1. Consider the possibilities for failure, loading by loading condition (static reservoir, 

hydrologic, seismic, ice, debris impact and any other loading relevant to the site) for 

each component of the project (main dam, spillway, gates, dikes, outlet works, power 

plant, etc.). Consider how an uncontrolled release of the reservoir or a dam breach 

could occur. Also consider total system operation aspects (communication and 

response [i.e., personnel, remote telemetry], facility access, weather conditions, 

equipment) with respect to the possibility of their contribution to development of a 

potential failure mode/failure scenario. 

2. Team participants are asked to suggest or propose “candidate” potential failure modes 

that they have considered during the site visit, review of the background material or 

when completing the advance questionnaire. The ideas, suggestions and comments 

brought up during the potential failure mode discussion session vary and can take 

several paths. 

If a candidate potential failure mode is suggested, it is discussed until a clear 

characterization of the potential failure mode and failure scenario is developed. Once 

a candidate potential failure mode is fully developed by the team and the team 

decides that the failure mode is a reasonable and credible potential failure mode, it is 

carried forward to the “discovery phase” (see Step 3 below) which is the 

identification by the team of the factors that indicate how and why the potential 

failure mode is either likely or not likely to develop and what other adverse or 

positive aspects exists relative to the potential failure mode. 

Sometimes this preliminary or developmental discussion of the initial suggestion may 

lead to two or more separate or related potential failure modes, which are then 

developed separately. 

Sometimes an item or issue brought up relates to dam safety, surveillance and 

monitoring or is of general concern but is recognized by all as something that does 

not or would not result in failure of the dam or other water retaining structure at the 

project and is thus not a candidate potential failure mode. However, such items still 

need to be included in the documentation to illustrate that they were identified, 

considered and were left to be addressed (potential identification of action) by the 

Part 12D consultant and or the owner. Such items are referred to as “Additional 

Monitoring or Performance Related Items Discussed” and are to be included in the 

report in a section under that heading. 

In other cases, a PFMA team member may suggest a “candidate” potential failure 

mode which the PFMA team, after preliminary discussion, believes is not a credible 

or viable potential failure mode or is considered to not be physically possible. If as a 

result of this preliminary discussion clear reasons are identified for discounting the 
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viability of the potential failure mode (based on information currently available) 

and there is team consensus on this finding, then the candidate mode along with the 

fundamental reason(s) for its lack of viability or credibility is documented as 

“Category IV” (see Table 1 below) and sub-steps 3-5 below are skipped. The 

Facilitator should move to full consideration of the Potential Failure Mode (sub-steps 

3-5) if there is not clear consensus among the PFMA team on the candidate mode’s 

lack of credibility. 

One exception to the general rule of not carrying forward a candidate potential failure 

mode that has, by consensus been judged as not viable, is when the preliminary 

discussion establishes that the mode is not credible but the owner (or regulator or IC) 

wants the mode to be fully developed and presented (e.g. – it has been a topic of 

discussion for a long time and the fact that it is judged to not be a credible potential 

failure mode [Category IV] deserves more complete documentation. Of course it is 

possible that after full discussion it could move to a different category. 

In the context of the FERC’s Part 12D Independent Consultant’s Safety Inspection, 

Potential Failure Modes related to acts of terrorism are not considered. However, the 

PFMA process may be applicable in assisting a licensee in evaluating the 

vulnerability and risk associated with acts of terrorism. 

3. Once a candidate potential failure mode has been characterized / described such that 

there is a common understanding of the potential failure mode, (See Appendix A – 

Part 1 for example potential failure mode descriptions.) The potential failure mode 

description is noted on a flip chart by the Facilitator and should be recorded in detail 

by the Independent Consultant at that time; then the potential failure mode and failure 

sequence is discussed. The nature of the breach (or other failure condition) is defined 

and the potential consequences of failure are discussed. The failure mode should be 

developed so that each step in the failure mechanism from the loading condition to 

the final failure condition is sufficiently defined so that the Surveillance and 

Monitoring Plan can be developed to detect a developing failure as soon in the 

process as possible. All the data, information, factors and conditions that suggest the 

ways that the potential failure mode is more likely or less likely to occur (adverse 

factors and positive factors) are noted. (See Appendix A – Part 2 for an example) 

Also during this discussion possible risk reduction actions that may be taken are 

suggested: 

• Means for monitoring/inspecting for the development of potential failure 

modes. 

• Opportunities for risk reduction. 

• Possible investigations or analyses. 

All of this information is noted (in brief) on a flip chart to facilitate documenting the 

suggestions. Although some PFMAs have successfully utilized a computer with 

projector to record the PFM information, the computer should not be considered a 

complete substitute for the use of flip charts. The flip charts are essential for keeping 

track and summarizing the PFMA discussions. The use of a computer can assist in 

recording and organizing the details which makes it possible for the IC to efficiently 
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complete the PFMA report. When a computer is used to record the session, a person 

other than a Core Team member should take the notes to assure the Core Team 

members can actively participate in the discussions. The note taker should be an 

experienced dam engineer. 

The consequences of failure and the circumstances surrounding a failure (advance 

warning, detection possibilities, impact of the failure, etc.) should be discussed for 

each potential failure mode during the discussion of the potential failure mode since 

these factors play a role in assessing the significance of the potential failure mode. 

However, experience has shown that it is necessary, valuable and instructive to 

specifically raise the topic of “consequences” as part of the PFMA and brainstorm 

site-specific factors and potential failure mode consequence related factors (in the 

event they have been overlooked during the technical discussion of the potential 

failure mode) 

4. When each site-specific potential failure mode is identified, the nature of the breach / 

uncontrolled release that may occur is discussed and the range of failure scenarios 

and consequences that may result are identified. The emergency action plan 

response to potential failure scenarios is examined and any concerns with the plan are 

identified. 

5. After a potential failure mode has been identified, described and discussed, each 

potential failure mode is classified / categorized according to the classification system 

given in Table 1. After all potential failure modes have been discussed the 

classifications made are reviewed and discussed. Note that if team members do not 

reach consensus on the category, dual categorization is permissible (e.g. I/II or III/II), 

requiring only that the reasoning behind each category used be provided After all 

potential failure modes have been discussed, the classifications made are reviewed 

and discussed. The Part 12D Independent Consultant may later recommend 

resolution or modification of the classification as part of the Part 12D Report. 

It is important to note that the categorization of potential failure modes is not related 

to a possible need for additional surveillance, monitoring, maintenance or 

remediation. The categorization is intended to give the licensee, the Independent 

Consultant and the FERC inspector a relative sense of the importance of the Potential 

Failure Modes, to assist in designing the Surveillance and Monitoring Plan, and to 

provide focus to inspections of the dam. 
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Table 1 - Categories of Identified Potential Failure Modes 

Category I - Highlighted Potential Failure Modes - Those potential failure modes 

of greatest significance considering need for awareness, potential for 

occurrence, magnitude of consequence and likelihood of adverse 

response (physical possibility is evident, fundamental flaw or 

weakness is identified and conditions and events leading to failure 

seemed reasonable and credible) are highlighted. 

Category II - Potential Failure Modes Considered but not Highlighted - These are 

judged to be of lesser significance and likelihood. Note that even 

though these potential failure modes are considered less significant 

than Category I they are all also described and included with reasons 

for and against the occurrence of the potential failure mode. The 

reason for the lesser significance is noted and summarized in the 

documentation report or notes.

 Category III - More Information or Analyses are Needed in order to Classify These 

potential failure modes to some degree lacked information to allow a 

confident judgment of significance and thus a dam safety investigative 

action or analyses can be recommended. Because action is required 

before resolution the need for this action may also be highlighted. 

Category IV - Potential Failure Mode Ruled Out Potential failure modes may be 

ruled out because the physical possibility does not exist, information 

came to light which eliminated the concern that had generated the 

development of the potential failure mode, or the potential failure 

mode is clearly so remote a possibility as to be non-credible or not 

reasonable to postulate. 

Category I Potential Failure Modes are those considered most credible and most 

important to be brought to the attention of the dam owner, dam operators, and 

personnel performing the monitoring and routine and periodic inspections. Because 

of the importance of monitoring the performance of the dam, surveillance, monitoring 

or instrumentation enhancement or other risk mitigation measures should be 

considered (See Step 6 below). 

Category II Potential Failure Modes are also considered credible, in that they are 

physically possible, but are not highlighted for one or more reasons such as no direct 

or indirect evidence of any indication of problem development, the loading required 

to initiate the potential adverse response is not as likely as Category I, or the 

magnitude of consequences is not as significant as Category I. 
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Category III Potential Failure Modes are those where more information or analyses 

are needed in order to be classified. 

Category IV Potential Failure Modes are those that have been ruled out as a result of 

finding specific information that shows that the subject PFM is not physically 

possible or initial brief consideration by the Core Team shows that it is not a credible 

failure mode. 

In general, Potential Failure Modes that have been fully developed and agreed to as 

reasonable and credible PFMs, i.e. they constitute a physically possible mode of 

failure, should be categorized as either Category I or Category II. However, there 

may be some Potential Failure Modes where the physical impossibility of the failure 

mode is only discovered after full development of the PFM description and discussion 

of the likely/not likely factors. These PFMs may be assigned to Category IV. 

Categories I and II are provided to allow the use of judgment by the team and to 

provide an easy differentiation of relative importance for the owner. The 

differentiation between Category I and II should be based on the need to “Highlight” 

the PFM for the benefit of the licensee’s operating and technical staff and for 

development of the Monitoring and Surveillance Plan. Generally, Potential Failure 

Modes that, if activated, would result in high downstream consequences, should be 

classified Category I. Similarly, dams that require operation or maintenance actions 

to maintain adequate factors of safety (i.e. such as assuring that drains are functioning 

to relieve uplift, tendons maintain sufficient prestress, gates must be operated to 

prevent overtopping, etc.) should be classified as Category I to make sure that the 

licensee’s O&M program is designed to assure that operating and technical staff are 

aware of the critical nature of these facilities. The magnitude of consequences is a 

factor that should used to differentiate between Categories I and II. 

Category II should be reserved for those Potential Failure Modes that are physically 

possible but do not need to be highlighted to the owner for various reasons. Category 

II PFMs would not result in a downstream hazard; have a low probability of 

occurrence; or there is an existing monitoring or maintenance program that makes the 

probability of occurrence remote. For instance, failure of a gate where the water 

release would stay in bank and there is not a significant recreation use of the river 

downstream of the dam, could be classified Category II. Similarly, a dam that has 

high calculated factors of safety, i.e. the probability of failure is remote, and or the 

downstream consequences are small, may also be classified as Category II. 

Category III Potential Failure Modes are those where there is insufficient information 

to make a determination as to classification. Generally, a Category III PFM will 

require additional investigations and/or analyses in order to determine an appropriate 

classification. When the additional information/analyses required to resolve a 

Category III PFMA are completed, that potential failure mode should be recategorized. 

Attention to monitoring and surveillance relates to Category II and III potential 

failure modes just as it does for Category I modes. 
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As noted above, in some instances a candidate potential failure mode can be 

dismissed as a potential failure mode without fully carrying out numbers 3 through 5 

above. In such cases the PFM will be classified as Category IV. Category IV can 

also include PFMs with fully developed descriptions if the physical impossibility of 

the PFM is only discovered after a full discussion. The PFMA report will include a 

brief description of the postulated PFM and identify why the team did not discuss it in 

further detail. Category IV should only include PFMs that have been dismissed as 

physically impossible. Low consequences and/or low probability of occurrence alone 

are not sufficient reason to classify a Potential Failure Mode Category IV. 

Sometimes an item or issue brought up relates to dam safety, surveillance and 

monitoring or is of general concern but is recognized by all as something that does 

not or would not result in failure of the dam or other water retaining structure at the 

project and is thus not a candidate potential failure mode. However, such items still 

need to be included in the documentation to illustrate that they were identified, 

considered and were left to be addressed (potential identification of action) by the 

Part 12D consultant and or the owner. Such items are referred to as “Additional 

Monitoring or Performance Related Items Discussed” and are to be included in the 

report in a section under that heading. 

6. In the Part 12D report, all Potential Failure Modes, irrespective of Category, should 

be reviewed and assessed by the Independent Consultant. In the Part 12D report the 

IC may make recommendations to move a Potential Failure Mode from one Category 

to another. If such a recommendation is made, the IC should provide the proposed 

category and the reasoning supporting the recommendation. 

It is important to note that the Potential Failure Modes are placed into categories by 

judgment. The basic purpose is to help the dam owner’s personnel and the current 

and future inspectors dealing with the dam to understand what the evaluation team 

considered were the most significant potential failure modes, so that they can 

consider / prioritize for action a smaller number of items rather than the total array of 

potential failure modes considered. The breakdown may also help with prioritization 

of actions to be taken. It is quite common in the PFMA for a monitoring or visual 

inspection action to be identified for a Category II potential failure mode that is easy 

to implement. 

Step 6 – Evaluation of Surveillance and Monitoring Requirements 

As a part of the Part 12D report the Independent Consultant will be required to assess the 

Surveillance and Monitoring Plan for the dam / project. A SMP is required for each 

Category I Potential Failure Mode. Surveillance and Monitoring Plans will also be included 

for selected Category II and III Potential Failure Modes which the Independent Consultant 

believes are warranted. In the Part 12D report the Independent Consultant must explain why 

surveillance and/or monitoring is not warranted for any specific Category II or III potential 

failure modes. In addition any requirements for “General Health Monitoring” independent of 

an identified potential failure mode will be defined. The plan presented should consider the 

items enumerated below. To facilitate development of Surveillance and Monitoring Plans, 
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the PFMA team should include comment and discussion on these items as appropriate for 

each potential failure mode identified. 

1. The type and frequency of inspections (visual surveillance requirements) should be 

evaluated to address the identified potential failure modes. This item may include the 

recommendation of developing customized checklists for the dam. (The nature and 

content of the checklist, if recommended, is developed by the Independent Consultant 

in consultation with the owner. The checklist should identify specific visual clues that 

may indicate a suspected potential failure mode has activated, and the checklist 

should provide instructions as to what step(s) should be taken once a clue is 

observed). 

2. The current instrumentation and visual surveillance program should be critiqued. It 

should be determined if the existing instrumentation is operating properly and that the 

readings can be relied upon. In some cases, instruments may be obsolete and serve 

no purpose in monitoring for the development of a potential failure mode. In other 

cases additional instrumentation or visual surveillance may be needed to monitor for a 

potential failure mode development 

3. Reporting requirements should be reviewed. Action limits may need to be 

established for some of the instruments and procedures developed for reporting 

variations in instrumentation readings. As a minimum, annual engineering review, 

evaluation and reporting of the instrumentation data is required. 

4. In some cases additional analyses or investigations may be required to fully evaluate 

a potential failure mode prior to establishing a SMP for it. The PFMA team should 

identify what information is needed. The Part 12D Independent Consultant would 

recommend what information is needed and how to obtain this information. 

5. If enhancements to the monitoring or visual surveillance are identified by the 

PFMA/Part 12D process then priorities for improvement in the SMP should be 

discussed, and appropriate recommendations and schedules provided, in the Findings 

and Recommendations Section of the Part 12D Report. 

Step 7 - Documentation of the Potential Failure Mode Analysis 

1. For the knowledge gained, information obtained and results achieved in the Potential 

Failure Mode Analysis to be effectively used for the current Part 12D and for future 

dam safety Part12D inspections the documentation of the work must: 

• Be done promptly; 

• Be definitive in describing the identified potential failure modes; 

• Be complete in recording factors considered relative to the viability of each 

potential failure mode considered; 

• Discuss possible risk reduction actions identified relative to each credible 

potential failure mode (e.g., surveillance and/or monitoring, investigations, 

remediation activities); and 
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• Clearly relay the major findings and understandings achieved as a result of the 

process. 

It was specifically noted during the review of pilot study draft reports that greater 

attention needs to be paid to fully stating the sequence of conditions and events that 

constitute the potential failure mode and failure scenario. (See Appendix A for an 

example potential failure mode description) 

The time frame for completing each of the steps described below is provided in 

Section 14.3.4 “Procedural Guidance”. 

2. At the end of the PFMA session, the Facilitator should ask the participants to reflect 

on what they learned during the PFMA process. After a few minutes the Facilitator 

should ask the participants to state what were the Major Findings and Understandings 

(MFU) they gained during the PFMA session. Typically this is done by going around 

the room and asking each participant to provide a MFU and then starting again with 

the first person until all participants have had the opportunity to express their 

findings. MFUs may relate directly to a Potential Failure Mode or may reflect a more 

general understanding about the dam or the PFMA process. 

If any MFU describes a serious dam safety issue, this should be immediately brought 

to the attention of the FERC-D2SI Regional Office. 

The Independent Consultant writes up the “Major Findings and Understandings” 

immediately after the session. The items noted during the session are typically 

abbreviated and should accurately reflect what the individual participants stated as 

their major finding or understanding gained during the session. Where the MFU 

relates to a PFM, a brief discussion (3 to 5 sentences) relating the MFU to the PFM 

should be prepared by the Independent Consultant and included with the MFU. The 

write up of the major findings and understandings is then sent to the Facilitator and 

the other Core Team members for review. Appendix E provides an example of a 

write up of major findings and understandings resulting from a potential failure mode 

analysis. 

3. The Independent Consultant prepares the draft Potential Failure Mode Analysis 

Report, describing each potential failure mode considered and referencing key 

adverse/likely and positive/not likely factors, identifying any suggested visual 

surveillance or instrumental monitoring, describing consequences of potential failure 

and site-specific conditions or factors related to consequences and noting any 

potential actions identified (information inquiries, investigations, analyses or risk 

reduction opportunities). The failure mode should be presented pictorially whenever 

possible. The write up should include a brief statement as to the adequacy of the 

project documentation and overall quality of the data that formed the basis of the 

PFMA. If prepared technical presentations of new material, not contained in the 

record documents, were made by consultants during the course of the PFMA their 

presentation should be documented in, or appended to the PFMA report. 

The draft report is then sent by the Independent Consultant to each participant of the 

PFMA session for review and comment. 
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Appendix D provides an example outline for the documentation of the analysis. This 

outline is designed to take advantage of the information collected on flip charts 

during the potential failure mode analysis session in order to make the documentation 

process simple, fast and effective. 

4. All reference material available and used by the team in the Potential Failure Mode 

Analysis is recorded and key items of data and information (that led to important 

findings or conclusions – see discussion under point 5 below) are included in an 

appendix to the PFMA report for ready reference. Photos of past conditions or 

photos of current conditions, elucidating key information about a potential failure 

mode, are highly recommended for inclusion in the body or appendix of the PFMA 

report. The PFMA appendix should be concise and not duplicate parts of the STI or 

Part 12D report. 

5. Preparation of a listing of the documents gathered by the owner for review, in 

advance of the review, has been found to serve as a valuable tool for the reviewers to 

use to assure that they have seen all the materials collected and should be included in 

the PFMA report. 

6. The PFMA report will then become Section 1 in the Supporting Technical 

Information (STI) document and the findings of the PFMA report will be discussed 

and summarized in the Part 12D report. In some instances, due to the size of the 

PFMA report or the STI document, the PFMA may be bound as a separate volume in 

which case Section 1 of the STI should include a statement that the PFMA report is 

bound separately and provide a copy of the cover of the PFMA report showing the 

title and date of the report. It is not the intent of the PFMA appendix to include the 

reports and documents that comprise the “background material” that was read and 

used in the discussions. However, often a key paragraph, photograph, test results or 

other documentation is found in a document that elucidates whether or not a potential 

failure mode is more or less likely and it is valuable to include that specific 

information in the PFMA appendix. (e.g. photographs may show planar joints, or 

gunite treatment of the foundation, or shear keys; statements might be made by the 

consulting review board about the condition of the filter material, tests results might 

provide definitive information that counters what has been stated in opinions / 

observations in construction reports; erosion or the lack of it may have been 

documented following a flood). These specific pages, photos, quotations or data that 

provide direct support to the “likely” or “not likely” aspects of a potential failure 

mode should be reproduced and included in the appendix to the PFMA report. 

7. The report should state whether the findings are a consensus of the team. If not a 

consensus, the differences of opinion and reasons therefore should be documented in 

the report findings. If no consensus is reached, the Part 12D consultant is still 

required to make a definitive assignment of all identified failure modes. 

8. The Report should include a section on Additional Monitoring or Performance 

Related Items Discussed. Issues or items that are brought up during the PFMA 

session that relate to dam safety and performance monitoring or are of general 

concern but are recognized by all as something that does not or would not result in 

failure of the dam or other water retaining structure at the project are included here. 
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There are a variety of these types of items that get raised and for completeness they 

need to be included in the documentation to illustrate that they were identified, 

considered and were left to be addressed (potential identification of action) by the 

Part 12D consultant and or the owner. 

9. The report should include an assessment of the overall adequacy, completeness and 

relevance of background data that was furnished for the Potential Failure Mode 

Analysis, identify any discrepancies, inaccuracies, or deficiencies in the records, and 

determine if adequate information was provided to conduct the PFMA. The report 

should document any potential shortcomings in the PFMA due to lack of sufficient 

data for consideration of specific potential failure modes. 

10. When a PFMA is being conducted not in association with a Part 12D report (for 

example, in support of a major remediation or maintenance), the report preparation 

should follow the same time frame or schedule described above. Following Core 

Team review and coordination of the draft report, the final PFMA report should be 

submitted within 60 days of the PFMA session. At the next Part 12D inspection, the 

Independent Consultant should include a review of this supplemental PFMA report in 

Section 3.0 of the Part 12D Report (see Appendix H). 

Appendix G provides the PFMA process in a task by task table format for dam owners as 

a supplement to the above discussion format for their convenience if desired. 

14.3.5 Use of the Potential Failure Mode Analysis report as a support document to the 

conduct of the FERC Part 12D Dam Safety Inspection 

Appropriate sections of the Part 12D report should provide commentary and/or information 

that relates to and addresses the potential failure modes identified in the PFMA. Appendix H 

includes the Part 12D Report outline and provides guidance on what is to be included in each 

section. The manner in which that is intended to be accomplished is outlined in general 

terms below: 

1. Field Inspection – The Part 12, Subpart D Independent Consultant should make 

observations of project features independent of the PFMA. It is important that the 

consultant keeps an open mind during the Part 12D Dam Safety inspection and be 

alert for any unusual conditions that may not have been identified in the PFMA. The 

purpose of the Part 12D inspection is not to only inspect for those conditions that may 

develop as described in the PFMA but to document the actual condition of the project 

structures. 

2. Part 12D Inspection Report – The inspection report includes the following with 

respect to Potential Failure Modes: 

a. Findings and Recommendations – A brief summary of the Independent 

Consultant’s findings during the inspection and the recommended actions that 

could be taken with regard to information inquiry, investigations, analyses, or 

structural or non-structural actions in terms of the identified potential failure 

modes. Recommendations may pertain to changes in operations or 
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maintenance required in order to maintain the status quo as well as 

recommendations to improve project safety. 

b. Discussion of the Potential Failure Modes Analysis Report - The Independent 

Consultant’s commentary on the Potential Failure Modes identified in the 

Potential Failure Mode Analysis report. This section of the Part 12D report is 

provided to allow the Independent Consultant the discretion to increase 

emphasis on or to de-emphasize any of the “team findings” presented in the 

Potential Failure Mode Analysis report. It also allows for incorporation of 

any new information, results of analyses, or other findings that come to light 

during the Independent Consultant’s inspection and report. 

c. Surveillance and Monitoring Plan - Each potential failure mode identified 

shall be reviewed to determine whether visual surveillance or instrument 

monitoring is adequate to detect the onset of the potential failure mode or the 

onset of conditions which may contribute to or “allow” development of the 

potential failure mode. Any relevant comments relating historic and current 

performance indicators to identified potential failure modes are provided. The 

Independent Consultant should address whether the instrumentation at the 

dam is functioning properly. 

d. Field Inspection - A discussion of the field observations relative to each of the 

identified potential failure modes as well as the Independent Consultant’s own 

assessment on the significance of the identified potential failure modes and on 

whether any other potential failure modes exist, or conditions may have 

changed that would impact previous conclusions regarding potential failure 

modes. 

e. Operation and Maintenance Program – A discussion of the Independent 

Consultant’s observations of the Licensee’s O&M program relative to 

identified Potential Failure Modes. 

14.3.6 Updating the Potential Failure Mode Analysis 

The comprehensive “initial” Potential Failure Mode Analysis and the resulting section in the 

STI appended to the Part12D report described above is intended to be performed only once 

for each project (or at extended intervals (e.g. - 15-20 years), but it should be regarded as a 

living document to be appended as conditions at the site change or as new information is 

obtained at any time following the initial PFMA or discovered during subsequent Part 12, 

Subpart D inspections. 

If the initial Potential Failure Modes Analysis is successfully performed, then that report will 

serve as a key document and foundation for the Independent Consultant inspection in 

subsequent Part 12D inspections. (Availability of this document should make the 

Independent Consultant’s work easier, more focused and effective and less costly) If as a 

result of the detailed inspection, the Independent Consultant finds new or varying 

information or has a professional opinion that necessitates revision of the findings of the 

original PFMA, the Independent Consultant would provide the licensee with a fully 

developed PFMA description as a supplement to the PFMA report. The licensee would then 
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provide copies to all holders of the STI document with a request to append the supplement to 

the PFMA report as discussed in Appendix I. The licensee’s cover letter transmitting the 

revision to the PFMA report should discuss the reason for the revision including who 

developed the supplemental PFMA and its potential impact on Project safety. That 

“updated” PFMA would then be the foundation for the next Part 12D Independent Consultant 

inspection report 5 years later. 

It is also possible that new information would come to light in the interim between the Part 

12D inspections. In this case, the owner and FERC would prepare a supplemental PFMA 

description and provide it to the Licensee for distribution to the STI holders as described 

above. In this way, the Potential Failure Mode Analysis report as maintained in Section 1 of 

the STI is a living document that will document the progression and variety of analyses and 

professional opinions that went into the current updated / appended PFMA report findings. 

It is important to retain the original PFMA report as prepared so that the findings, discussions 

and thought processes of the original Potential Failure Mode Analysis session are retained for 

future evaluations. 

14.3.7 Conduct of a “Supplementary” Potential Failure Mode Analysis 

A supplementary Potential Failure Mode Analysis should be conducted for projects that fall 

under Part 12 Subpart D of the Commission’s regulations when major modifications are to be 

constructed. The “Supplementary” PFMA is conducted using the same procedures outlined 

above for the “Initial” Potential Failure Mode Analysis. Supporting documentation is needed 

for the proposed modification. The design for the proposed modification should be at least to 

the 50% level to enable the PFMA team to critically evaluate the modification for potential 

failure modes and to determine if construction of the recommended alternative may adversely 

impact other structures, resulting in new failure modes not considered in the “Initial” PFMA. 

Conceptual designs would not be adequate for this evaluation as they may undergo 

significant modifications during the design process, which might trigger the requirement for 

additional PFMAs. 

At a minimum, the supplementary PFMA session should include a Core Team similar to that 

described above for an initial PFMA. If a Board of Consultants has been convened for the 

project, the PFMA may be held as part of a Board meeting to obtain the insights and thoughts 

of the Board.
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14.4 SURVEILLANCE and MONITORING PLAN 

Monitoring the performance of the dam / project to assure that possible dam failures are 

avoided or adequate warning time of potential or impending failures is an essential part of a 

dam safety program. 

These guidelines: 

• Provide a discussion of the various performance monitoring principles and methods 

used to aid in evaluation of a structure; and

• Present performance monitoring procedures and principles for a number of common 

adverse responses or conditions that typically are indicators or contributors to 

potential failure modes. These basic principals and procedures provide general 

guidance that is then made specific for an individual dam for the potential failure 

modes identified as part of the PFMA process.

As part of the Part 12D report the Independent Consultant shall assess, or develop if a SMP 

does not already exist, the Surveillance and Monitoring Plan for the dam / project. The SMP 

must include each Category I Potential Failure Mode, unless the Category I Potential Failure 

Mode is recommended to be addressed through dam safety modifications. The Plan should 

show details of the types of instrumentation required, their locations and frequency of 

measurements, and action limits for each instrument. The SMP must also include each 

Category II Potential Failure Mode unless the Independent Consultant discusses the reasons 

that he/she considers a specific SMP to be not warranted for any such potential failure mode. 

The IC may recommend monitoring of the Category III failure modes as part of the SMP inlieu of further studies if in his judgment studies to further define the failure mode are 

unnecessary. In addition, any requirements for “General Health Monitoring” independent of 

an identified potential failure mode should be identified. Chapter IX of the Engineering 

Guidelines provides guidance on the level of instrumentation necessary for monitoring the 

general health of a dam. Recommendations made by the consultant with respect to the SMP 

are actionable items, similar to the other recommendations contained within the Part 12D 

report, and should be included in the final recommendations section of the Part 12D report. 

The adverse responses and conditions and the companion monitoring procedures and 

principles described in this guideline should not be considered as complete, as each dam will 

have its own characteristics. ALL combinations of failure, and particularly operating 

conditions that may present more complex potential failure modes and failure scenarios, must 

be developed and the appropriate means for monitoring these unique or complex modes 

established. 

14.4.1 Principles and Methods of Performance Monitoring 

This section describes fundamental principles and methods used to aid in the evaluation of 

the performance of a dam. Performance is assessed through evaluation of observations and 

instrument data relative to the expected observations and data based on design assumptions 

and the findings from the PFMA. 
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1. Visual observation 

Visual observation is an important surveillance activity. Many dams were constructed 

without the benefit of instrumentation and thus visual observation offers a first 

impression/opportunity to evaluate integrity, movement and loads. Visual observation at 

regular intervals by trained personnel will often detect unusual conditions, such as 

increased seepage, cloudy seepage, or movements and is the dam owner’s primary 

defense against serious problems. However, visual observations are judgmental rather 

than quantifiable. Instrumentation may be needed to provide information to enhance our 

ability to analyze the condition of the structures. 

Inspections/observations of remote projects which may not be accessible in winter 

conditions and may be covered by snow and ice must be specially programmed. The 

Surveillance and Monitoring Plan must be developed with consideration of such winter 

conditions and persons performing inspections / observations must be specially briefed 

on the requirements. The necessity for winter inspections/observations should consider 

the criticality of a particular potential failure mode. 

2. Instrumentation systems 

The types of instruments used for investigating a certain behavior are generally outlined 

in Chapter IX of the Engineering Guidelines. Each instrument should be reviewed for its 

location/depth, suitability to provide the desired information and confidence that the 

instrument is providing valid readings. The overall number and types of instrumentation 

should be reviewed to determine if they are sufficient to assess the total structure. The 

critical sections of the structure should be defined and the location of instruments relative 

to the critical section reviewed. The frequency/regularity of reading and timing of 

readings should be reviewed. The occurrence of taking the reading should be logically 

related to the date, corresponding reservoir levels, climatic conditions (i.e., rain, winter) 

and operations (i.e., lag times of drawdown) as appropriate. 

The personnel taking the readings should be queried for the procedures used to acquire 

the readings and their awareness of certain threshold/action levels. The procedure for 

processing the raw data should be reviewed for correctness and timeliness. If data are not 

being processed and evaluated in a timely and correct manner, personnel involved in the 

instrumentation and monitoring program should be reminded, and further trained if 

necessary, in the importance of each phase of the program and the potential impacts with 

respect to dam safety. The type of presentation graphs should be reviewed for the data 

included and the use of proper scales and format to improve the ability to interpret data 

(refer to Chapter IX). Often great clutter is apparent because graphs are presented 

monochromatically using only minute symbols to differentiate the lines. Project plan 

drawings should be prepared that clearly show the locations of all instruments at the 

development site should. Sections through the structure should be prepared to show 

information such as the sensing zone of piezometers. Details of the instrument 

installation should also be available. 

3. Comparison of instrument readings to predicted and required action levels 
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Threshold and Action limits should be developed and the criteria used to develop them 

should be documented. A Threshold value is the value used in the analysis or design, or 

is established from the historic record. An Action Level is the instrument reading that 

triggers increased surveillance or an emergency action. Threshold and Action limits 

should be established based on the specific circumstances. In some cases, they can be 

based on theoretical or analytical studies (e.g. uplift pressure readings above which 

stability guidelines are no longer met). In other cases, they may need to be developed 

based on measured behavior (e.g. seepage from an embankment dam). Sometimes they 

may be used to identify unusual readings, readings outside the limits of the instrument’s 

historic range, or readings which, in the judgment of the responsible engineer, demand 

evaluation. Both magnitude and rate of change limits may need to be established. If 

trends or inter-relationships between data are not clear, it may be appropriate to take 

more frequent measurements or collect additional complementary data. 

All data should be compared with design assumptions. For example, measured phreatic 

levels and uplift pressures should be compared against those used in stability analyses. If 

data are available for unusual load cases, such as rapid drawdown and floods, they should 

be compared with assumed pressures. 

More than one phreatic surface may exist where there are impervious strata in the 

foundation or embankment. Piezometric data should be evaluated with geologic and 

construction data to identify multiple phreatic surfaces. If the phreatic surface for any 

strata is above the ground surface, the stability of the dam should be evaluated using the 

elevated phreatic surface. 

All data will follow trends, such as decreasing or increasing with time or depth, seasonal 

fluctuation, direct variation with reservoir or tailwater level, direct variation with 

temperature, or a combination of such trends. The trends are usually evident in the 

plotted data. Statistical analysis of data may be useful in evaluating trends that are 

obscured by scatter. However, such analyses are no substitute for judgment based on 

experience and common sense. Data inconsistent with established trends should be 

investigated. Readings deviating from established trends should be verified by more 

frequent readings. Erroneous readings should be so noted on the original data sheets and 

should be removed from summary tables and plots. 

If no unusual behavior or evidence of problems is detected, the data should be filed for 

future reference. If data deviates from expected behavior or design assumptions, action 

should be taken. The action to be taken depends on the nature of the problem, and should 

be determined on a case-by-case basis. Possible actions include: 

• performing detailed visual inspection;

• repeating measurements to confirm behavior;

• verify that instruments and reading devices are working properly;

• reevaluating stability using new data;

• changing frequency of measurements;

• installing additional instrumentation;
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• special investigations;

• designing and constructing remedial measures;

• operating the reservoir at a lower level; and

• emergency lowering of the reservoir.

Guidance on methods for establishing Threshold and Action parameters is presented for 

the various types of instrumentation described. The Independent Consultant in 

consultation with the licensee should establish Threshold and Action parameters. 

4. Consider a way to flag instruments that are trending in an adverse manner and 

what additional focus should be placed on those instruments 

Instruments that do not appear to be functioning properly should be further investigated. 

For example, data should be checked against redundant data to determine whether or not 

trends and magnitudes are the same. Calibration of the instruments should be checked 

(this is paramount). Often, tests can be devised to evaluate proper functioning. It is 

important to plot all the data on record so as to be sure to detect slow trending data. 

5. Additions/deletions/duration (how long an instrument should be read) 

Instrumentation, in addition to the minimum recommended, should be required wherever 

there is a concern regarding a condition that may affect dam safety or other critical water 

retaining structures. Typical reasons to require additional instrumentation are: to check 

design assumptions; to provide data to evaluate specific problems such as continuing 

movement, excessive cracking, or increased seepage; to provide data to support design of 

remedial modifications; and to provide data to evaluate effectiveness of remedial work. 

Note that continually progressive conditions may require immediate action rather than 

belated installation of extra instruments. 

Instruments should be reviewed for their life expectancy. Readings from advanced age 

instruments should also be evaluated with respect to whether the instrument readings can 

be trusted. A failed instrument should be removed to avoid obtaining erroneous data later. 

6. Redundancy 

There is no such thing as a redundant instrument. All instruments should have real value, 

if not they should be eliminated. The only redundancy would be to use different 

instruments to measure the same feature. 

7. Summary 

Instrumentation and visual surveillance provide the means for helping to develop the 

understanding or verify the performance of a dam. 

The purpose of instrumentation and monitoring is to help quantify behavior and provide 

data to evaluate whether the dam is performing as expected and to provide a warning of 

developing or changing conditions that could endanger the safety of the dam. This 

information and data are used to maintain and improve dam safety. 
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If there is a discrepancy between the measured and expected behavior of the dam, it may 

indicate that the dam is not performing satisfactorily and that failure is developing or 

occurring or it may be that the data or observations do not adequately represent the 

behavior of the dam, or that conditions exist that were not accounted for in the expected 

behavior. In either case it is often useful to perform field investigations and install 

additional instrumentation to evaluate the behavior. Note again that rational judgment 

must be used to take action rather than do further investigation. If what is going on is 

serious enough you could put in more instruments just to see the dam fail or confirm 

failure of the dam. 

14.4.2 Surveillance and Monitoring Procedures and Guidelines 

From these guidelines, necessary surveillance and monitoring techniques and devices and 

threshold parameters to be employed at a specific dam can be developed. The existing 

surveillance and monitoring systems in place at that specific dam can then be reviewed by 

the licensee, the Independent Consultant and the FERC Inspector together and supplemental 

surveillance and monitoring systems agreed upon as appropriate. Additional information on 

the details of surveillance and monitoring instrumentation is presented in Chapter IX, 

Instrumentation, of the Engineering Guidelines. 

This section has been designed to acquaint you with some of the adverse responses of dams 

and the associated surveillance and monitoring systems and suggested methods to develop 

threshold parameters. Many dams will share the commonality of a potential failure mode but 

the SMP must be customized for each structure. Some of the types of dams are: 

• Concrete Arch Dams (including multiple arches)

• Concrete Gravity Dams (including cyclopean and RCC)

• Masonry Dams

• Earthfill Dams (homogenous dams, zoned dams, asphalt core or faced dams, and 

concrete or membrane faced dams.)

• Rockfill Dams (earth core dams, asphalt core or faced dams, and concrete or 

membrane faced dams.)

• Concrete Slab and Buttress Dams

• Timber Crib Dams

• Rubber Dams

Some typical adverse responses and conditions related to potential failure modes and 

scenarios are: 

• Abutment and/or Foundation Movement

• Abutment and/or Foundation Seepage

• Structure Movements and Stresses 

• Overtopping of Dam and Washout of Abutments or Foundations
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• Deterioration of Concrete

• Operations Procedures

• Equipment (e.g. gates) testing and/or maintenance

1. Surveillance and Monitoring Guidelines for Abutment or Foundation Movement 

a. Visual Observation 

The first line of defense for monitoring almost all potential failure modes is visual 

observation. While visual observation of gross movement of a dam or foundation 

would indicate that a very serious condition is occurring or developing, more 

subtle indications of movement can be observed. Cracking, new areas of leakage 

through the dam or foundation, and displaced foundation material, are all visual 

clues of possible movement. Visual observation is beneficial in that it may 

readily identify changed conditions and it has the advantage of complete coverage 

(as opposed to instruments that only monitor point locations). For concrete dams, 

pins can be established at the crest or in galleries along contraction joints to 

determine whether differential movement is indicated or has taken place. These 

pins can readily be observed during routine site visitations and after significant 

loading events as well as during regular inspections rather than depending only on 

annual surveys for an indication of movement. 

b. Precise Movement Surveys – Horizontal and Vertical 

Precision surveys of permanent monuments on the dam and adjacent foundation is 

a periodic monitoring requirement. Typically, movement monuments are placed 

at several points along the crest of the dam where they are line-of-site visible from 

benchmarks established some distance away from the dam abutments. 

Monuments may need to be located at foundation contact locations where 

abutment instability is a potential failure mode. Periodic measurements of the 

location of such monuments provide data for detecting movements of the dam or 

adjacent foundation. To avoid seasonal influences on the readings, it is helpful to 

take the readings at the same time each year. 

c. Movement Monitoring Devices (Inclinometers, Deformeters, Tiltmeters, 

Pendulums, Extensometers, optical surveys) 

Devices for more frequent monitoring of small movements of structures and 

foundations include inclinometers (generally used to define planes of movement 

in soil), extensometers (measure change in distance between two fixed points), 

tiltmeters (measures vertical or horizontal angular changes) and embedded crossarm settlement devices for internal embankment movement. These devices are 

used to take frequent readings, generally quarterly, monthly or weekly, to obtain 

information on specific small movements, generally related to ongoing 

investigations or to establish movement history with regard to changing reservoir 

or foundation water levels, changes in temperature, or in regard to special 

concerns triggered by other observations. 

d. Establishing Threshold and Action Parameters for Movements 
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Once a series of movements over some period of time has been developed, and 

confirmed by stress analysis as being appropriate, threshold and action parameters 

can be established that would require further investigation or action. Before 

initiating action however, measurements falling outside of a threshold parameter 

should be carefully checked and confirmed. 

Other threshold parameters can be defined relative to assumed parameters used in 

the stability analyses. 

2. Surveillance and Monitoring Guidelines for Dam Structure, Abutment and 

Foundation Seepage 

Seepage through a dam or through the foundations or abutments of dams is a normal 

condition. However, increases in historically observed amounts of seepage, in the 

elevation of the phreatic surface in the dam, or abutments, in the uplift/seepage 

pressures beneath the dam or the appearance of transported material in the seeping 

water may be symptoms of a developing potential seepage related problems. The 

appearance of transported material in the seeping water of an embankment or soil 

foundation may indicate piping or seepage erosion which could lead to a failure. 

a. Visual Observation and Leakage Weirs 

The visual observation of new seepage or an increase in volume of seepage 

requires action be taken to quantify the problem and to watch for the presence of 

material being transported in the seepage. For example, if a rapid increase in the 

seepage rate is observed, it may be a strong indication of a developing failure 

situation and emergency action must be taken. Visual observations of depressions 

or sinkholes in an embankment or upstream abutments or foundations are strong 

indications of piping occurrence. 

To accurately monitor any seepage, it must be collected and passed through a weir 

for periodic measurement. A weir is a superior way for monitoring for the 

possibility of material movement for several reasons. It provides a continuous 

means for settling and trapping particles that may be piping or eroding as a result 

of the seepage flow. Episodic material discharge has been observed in several 

instances, thus a periodic check of seepage flow for material may not reveal 

whether the seep is actually moving material. Weirs also allow the material 

collected over a period of time to be measured and weighed. If weirs are used in 

an area where fines may be blown or eroded into the weir, a cover is necessary. 

Also the weir should be routinely cleaned after each periodic measurement so the 

amount of new material between collections can be accurately assessed. 

Flumes allow for accurate measurement of seepage rate but do not provide a 

means for collecting material. Regardless of the method used to measure the 

seepage rate (weir, flume or bucket and stop watch), a sample of the seepage 

water should be collected and allowed to settle out, at least overnight, to check for 

the presence of any suspended material (fines) being transported (piping or 

seepage erosion). Drainage pipes within a downstream embankment provide a 

convenient method for collecting and measuring seepage. Care must be taken that 
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such pipes are properly filtered to prevent piping and if not it is even more 

important that the flow from the drain pipe(s) be routed through a weir to allow 

capture of any material being moved. 

When new wet areas are observed on the downstream face of an earthfill dam, a 

determination needs to be made as to whether this water is emanating from a 

perched, more pervious zone in the embankment lying above a less pervious 

layer, or is indicative of a high phreatic surface. Wet areas and points of seepage 

exit should be marked on the dam face by large stakes so that any change with 

time / season can readily be assessed. Monitoring of vegetation (big roots can 

initiate piping) and rodent holes is critical. The determination of the nature of 

such seepage can usually only be confirmed by the installation of piezometers. 

The flow rate of such seeps should be monitored by weirs and checks made on 

transported material in the flow. 

Although increases in seepage are generally considered to be more of an indicator 

of a potential problem, decreases in seepage (particularly in a concrete dam 

foundation but also within embankment dam foundations or drainage elements) 

may indicate that flow paths / drains are being blocked within or near their exit 

from the dam or foundation resulting in an increase in pressures. Thus when 

seepage decreases occur, checks should be made on piezometer or uplift gauges 

(if this instrumentation is present) and on the cleanliness of the drain elements. 

The onset of significant increases in seepage may correlate with reservoir 

elevation reaching particular levels or recent heavy rainfall and this possibility 

should be reviewed at sites with significant seepage. 

b. Piezometers and Observation Wells 

A great benefit to understanding the potential for failure mode development 

related to seepage from a dam /foundation system is to develop an understanding 

of the relative pore pressures and direction of flow within and through the dam. If 

the pressures in the foundation (below the core of an embankment dam) exceed 

those in the dam then the direction of flow indicated is from the foundation into 

the dam and the possibility of piping of material from the dam to the foundation is 

remote. Conversely if the direction of flow indicated is from the dam base into 

the foundation then the physical possibility of piping from the dam through the 

foundation is indicated. The best way to determine this flow regime is to review 

the piezometric, observation well and seepage data. 

Whenever there is concern for stability that may be sensitive to the phreatic 

surface or seepage forces in the abutment, foundation or embankment (such as in 

a rockfill dam with a wide central core), periodic measurement of water levels 

must be made. The measurement of seepage forces in abutments and foundations 

and particularly in a dam embankment is usually made by piezometers sealed to 

determine the water pressure in specific strata or zones. The phreatic surface in 

the abutments or foundation can be measured by observation wells, usually open 

tube pipes with long sensing zones and with only the top of the tube sealed to 

prevent surface water infiltration. If stratification exists in the abutment, 
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consideration for different piezometers sealed in the various soil horizons should 

be given. 

One of the key and often overlooked steps in interpretation of piezometer and 

open well instrumentation is failure to correlate the water level with the bottom 

elevation of the well/piezometer tip. In many cases, they turn out to be the same 

elevation and the unit is dry. 

c. Monitoring for Movement of Material (Piping) 

Whenever seepage is observed emanating from / through the dam, foundation or 

abutments, periodic checks on movement of material should be made. A sample 

of the seepage water should be collected and allowed to settle out, at least 

overnight, to check for transported material (piping). Crest settlement surveys are 

an important source of early warning of piping failures, particularly in earth and 

rock-fill dams. Specific inspections to look for depressions or sinkholes, 

particularly in upstream areas, should be made frequently. 

Increases in phreatic surface or seepage pressures in the foundation or abutments 

may also indicate that movement of material is occurring. 

Where the foundation materials may be susceptible to solution from water of 

certain chemical properties, frequent checks on groundwater and reservoir water 

chemistry and on the chemical composition of seepage water should be made. 

Evidence of solution of foundation materials or strata such as gypsum layers 

requires prompt intervention. 

d. Establishing Threshold Parameters for Seepage 

Seepage through a concrete dam is usually monitored by observation and 

mapping (see Visual Observation). If seepage appears to be spreading or 

increasing in volume, then an investigation and action to reduce the seepage may 

be necessary. It is generally difficult to accurately determine the effects of 

through seepage on concrete dams. 

Seepage through an embankment dam is usually monitored by observation, timed 

flows discharging from drainage pipes and weirs or other flow measurement 

devices. If seepage flow is increasing, then an investigation and evaluation of the 

situation is necessary to determine if remedial action is required. Once a history 

of variation in seepage flow has been established with respect to season and 

reservoir level, then corresponding threshold parameter levels can be established 

that will trigger the need for further investigation and remedial action. 

The location of the phreatic surface in the embankment or the seepage pressures 

at specific strata can be determined by piezometers. Seepage through the 

abutments or foundation is similarly monitored. A steadily rising phreatic surface 

or increasing seepage forces should trigger a prompt review and, if necessary, 

remedial action. 

Periodically, the measured phreatic surface or seepage pressures must be 

reviewed against those surfaces or pressures that were used for the most recent 

stability analyses. If the actual phreatic surfaces or seepage pressures exceed 
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those used in the stability analyses, then a special engineering review must be 

initiated and remedial action may be required. 

Seepage through abutments or foundation however can usually be collected and 

measured by weirs or other flow measurement devices. Once a history of 

variation in seepage flow has been established with respect to season and 

reservoir level, then threshold parameter data related to seasons and reservoir 

levels can be established that will trigger further investigation and remedial 

action. 

3. Surveillance and Monitoring Guidelines for Structure Movements and Stresses – 

Static and Seismic Loading 

When possible distress of the dam structure itself is suspected as a result of 

observation of cracking, new leakage, movement monument measurements, or 

updated stress analyses, more detailed measurements of dam structural performance 

are required. Slab and buttress dam designs have typically been designed for in plane 

loading only. They are often inadequately reinforced and are incapable of resisting 

cross canyon earthquake accelerations. 

It is difficult to determine stresses directly on an existing dam unless stress or strain 

meters or load cells were installed during the initial construction. Therefore, most 

performance monitoring is aimed at determining strains under varied loadings to 

calibrate stress analyses. 

a. Precise movement surveys (surface) – horizontal and vertical. 

Additional surface monuments can be quickly installed and more frequent 

measurements made to obtain additional data. 

b. Plumb lines 

Plumb-lines are very difficult to install on existing concrete structures. They also 

require vertical alignment that cannot be achieved in double-curvature arch dams 

unless galleries have been specifically placed to accommodate installation. 

c. Tilt meters 

Measurements by tilt-meter are also useful. Tiltmeters can be installed on 

existing concrete structures and readings can be obtained quickly after 

installation. Tiltmeters are sometimes used instead of plumb-lines because they 

are easier to install and require little maintenance. Tilt Meters can be used to 

calibrate FEM models and to back calculate foundation moduli if the reservoir can 

be raised or lowered a significant amount. 

d. Load cells 

For direct measurement of loads in the dam, load cells must be installed during 

construction. While they can provide meaningful data, if they are not in the area 

of highest stress, they have limited usefulness. If post-tensioned anchors are used 

to improve stability, either in part of the dam (such as abutment blocks) or in the 
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foundation, some anchors should have load cells installed to monitor their loss of 

tension so that retensioning can be performed as necessary. 

e. Strain Gages 

Stain gages can provide valuable direct stress data if installed during construction. 

However, they are subject to the same limitations as load cells. 

f. Seismographs 

Seismographs provide a valuable research tool when they are mounted on dams 

and triggered by significant earthquakes. They can provide response data for 

improving seismic stress models of the structure or for deformation models of an 

embankment. However, they are not useful for monitoring performance of dams 

but can confirm the response of the dam to an earthquake, e.g. crest amplification 

of shaking. 

g. Additional piezometers can be installed and more frequent measurement made to 

obtain additional data. 

4. Surveillance and Monitoring Guidelines for Erosion of Abutments or 

Foundations 

Surveillance and monitoring of embankment dams relative to washout is pertinent 

only with respect to ensuring the condition and levelness of the crest. Low spots, 

rutting or “built in” unevenness in the crest can exacerbate the potential for 

overtopping failure of an embankment dam. Spillway capacity must be adequate to 

prevent this potential failure mode. In the case of embankment dams, the rule is to 

prevent overtopping, because it can lead to catastrophic failure. 

a. Observation and Measurement of Deterioration of Abutments, Foundations, 

and/or Spillway Outfall/Energy Dissipater Areas 

In order to monitor the deterioration of dam abutments, foundations, and/or 

spillway outfall/energy dissipater areas to assess the potential for washout failure, 

it is necessary to have data on the potential for flow over the abutments, including 

volume and frequency relationships, and specific data on large flows that would 

impact the foundation. 

The foundation, abutments, and spillway outfall areas should be surveyed and a 

profile of the foundation impact area of overflows, abutments and/or spillway 

outfall/energy dissipater areas made. Because survey markers in such situations 

will probably be lost in flow situations, the survey should be at precise station 

points along the abutments within the flow zone and on the downstream 

foundation offset from the crest of the dam. Such surveys should be repeated 

after major flows have occurred and the changes in the profile plotted and 

reviewed and the erosion potential quantitatively estimated. Utilizing the flow 

volume and frequency relationships, an assessment of potential failure due to 

washout can then be made. 

b. Periodic Assessment of Geologic Conditions and Deterioration 
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In addition to the survey and assessment above, close geologic inspection of the 

foundation, abutments and/or spillway outfall/energy dissipater areas should be 

made including mapping of joints that could permit loss of foundation or 

abutment rock material. Such inspections should be repeated after major flows 

and the potential for washout failure made. 

5. Surveillance and Monitoring Guidelines for Leakage through Dam Joints or 

Cracks, Along Penetrations, Conduits and Structures

a. Periodic Visual Mapping of Leaks/Wet Areas on Downstream Dam Face 

Using a downstream profile map of the dam, showing any visible vertical joints 

and horizontal joint or lift lines, make a periodic map of all cracks, leakage 

locations and seepage areas. The mapping should be supplemented by detailed 

photographs. If there are significant leakage locations or areas, such maps and 

photographs should be made at least semi-annually, at coolest and warmest times 

of the year, and regularly compared. Particular care must be taken to note areas 

of increasing leakage flow or extension of cracks. 

b. Measurement of Seepage Quantity by Weirs, Flow Meters or Other Devices 

Where it is difficult to determine if the quantity of dam seepage is increasing, 

various devices are available to measure flow. Unfortunately, they may be 

physically difficult to install on the vertical or overhanging face of an arch dam. 

They would generally only be utilized in cases of significant concern. 

6. Surveillance and Monitoring Guidelines for Deterioration of Concrete 

Concrete in dams sometimes deteriorates. Usually such deterioration is due to poor 

quality concrete having been used for construction. On older dams, alkali aggregate 

reaction is not uncommon. For dams at high elevations and in northern areas, freezethaw deterioration is a concern. 

Concrete deterioration is more critical in Ambersen slab and buttress type dams 

where design stresses in the water retaining slabs and reinforced concrete beams are 

about 50% of the ultimate capacity utilized under normal loading. Concrete 

deterioration not only reduces the cross-section properties but also exposes the 

reinforcing allowing it to corrode and reduce cross-section. 

a. Periodic Visual Inspection and Mapping of Deteriorated Areas. 

Make a periodic map of all areas of deterioration whether caused by freeze thaw, 

alkali-aggregate reaction, or other mechanisms. The map should show any visible 

vertical joints, horizontal joints, lift lines, any loss of masonry elements or mortar 

from the joints. The mapping should be supplemented by detailed photographs. If 

there are significant deteriorated locations or areas, such maps and photographs 

should be made at least semi-annually. 

b. Periodic Measurement of Deteriorated Areas 

Measurements should be periodically made to assess the changes in the structure. 

In the case of alkali-aggregate reaction, periodic surveys of dam crest elevation 
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should be made to ascertain the amount of swelling of the concrete. Also, cores 

of the expanded concrete should be taken at intervals and tested for compression 

and tension (if subject to tensile stresses.) The strength data obtained from the 

tests should be compared with the results of a stress analysis, to determine the 

adequacy of the structure. 

In the case of freeze thaw or other deterioration mechanisms, the depth of 

deterioration should be periodically determined. If the area is quite localized, the 

depth can be determined by probing and measurements from the surface of 

unaffected areas. One technique is to install reference markers set in the deeper 

undisturbed concrete and periodically measure the distance from the end of the 

marker to the sound concrete. 

7. Operations Procedures Common to all Dams 

Mis-operation of a dam, either through equipment malfunction or human error, is 

often a viable potential failure mode. This section identifies some adverse conditions 

and associated defensive measures. 

a. Human error 

This includes all the site specific scenarios of mis-operation or failure to act. For 

example, if gate operation is required to pass a flood, but nobody raises the gates, 

the dam could fail. 

Defensive measures could include additional specific training of personnel and 

emergency procedures exercises that are tailored to specific identified potential 

failure modes. 

b. Equipment malfunction 

Power failure - Anytime electrical equipment such as gate hoists, sensors, 

communications, etc is required for the safe operation of the dam, power failure 

can lead to a dam failure. 

Defensive measures could include having standby power available at the site, and 

having manual overrides on critical equipment 

Sensor/Telemetry malfunction - If the site is remotely operated, a sensor error or 

telemetry failure can lead to mis-operation or failure to operate. 

Defensive measures may include performing regular telemetry testing, having 

redundant sensors for critical instrumentation, and having redundant 

communication systems. 

c. Access failure 

If personnel must be dispatched to a site to operate it in an emergency, they have 

to be able to get there. Large flood events are typically accompanied by severe 

weather that may make roads impassible and helicopter travel impossible. 

Defensive measures may include having identified alternative routes to access the 

site or stationing personnel at the site prior to failure of access roads. 
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14.5 INSPECTION PROCESS and COORDINATION 

14.5.1 Scope and Purpose 

To define the roles, responsibilities and coordination of the Licensee, Independent Consultant 

and FERC and to develop a process flowchart which links together all of the inspection, 

analysis, evaluation and emergency action planning elements of the FERC’s dam safety 

program using a potential failure mode analysis approach. 

14.5.2 Description and Interrelationship of Dam Safety Program Elements Using a 

Potential Failure Mode Analysis Approach 

1. Periodic routine inspections / observations – These inspections are typically 

performed by the licensee or a consultant retained by the licensee. People performing 

the routine inspections or observations should be provided with background 

information on the potential failure modes identified for the site along with a 

surveillance and monitoring plan for each potential failure mode. The licensee is 

responsible for performing these inspections and for coordinating with the FERC 

resolution of any issues discovered during the inspections. After a discussion with 

FERC, a decision will be made whether any action such as analysis, repairs or 

monitoring needs to be implemented. 

2. Licensee operation and maintenance inspection and training programs - Those 

persons performing the inspections or observations should be provided with 

background information on the potential failure modes identified for the site along 

with the surveillance and monitoring plan for each potential failure mode. The 

licensee is responsible for ensuring that its personnel are properly trained and remain 

current in the knowledge of proper operation and maintenance of the project. The 

FERC inspector and Independent Consultant should review these programs during 

their inspections to assure they meet the needs of the Surveillance and Monitoring 

Plan. 

3. FERC operation inspection - FERC will schedule with the licensee in advance and 

perform this inspection. After the inspection FERC will discuss with Licensee any 

concerns found during the inspection. The discussion will also include various items 

relating to the project, such as the operation and maintenance of the project, any 

instrumentation and monitoring currently at the project and the emergency action plan 

that is in place at the project site. 

 If during the FERC operation inspection a new potential failure mode is identified, 

the FERC will provide this information to the licensee in the Operation Inspection 

follow-up letter. If the potential failure mode needs to be evaluated prior to the next 

Part 12D inspection, a schedule will be established to accomplish this. If it is 

determined that evaluation of the potential failure mode may be delayed until the next 

Part 12D Inspection, the FERC will include the request in its one year reminder letter 

to the licensee. 

 FERC will document this inspection and provide a copy to the licensee. 
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4. Joint Part12D and FERC Operation Inspection - Every 5 years a joint inspection will 

be made by the Independent Consultant and FERC with proper coordination and 

support of the licensee. 

TheFERC Operation Inspection will be done at the same time that the Part 12D 

Inspection is done.

 The Consultant will be provided the current Potential Failure Mode Analysis (initial 

plus any updates) and the Surveillance and Monitoring Plan. The Part 12D inspection 

will begin with a meeting between the necessary licensee representatives, the 

Independent Consultant, and the FERC inspector to review the project history 

including any past or current deficiencies, completed remediation, special 

investigations previously completed, instrumentation, etc. The group will discuss the 

development of the potential failure modes and the surveillance and monitoring plan.

 The FERC’s operation inspection and the consultant’s Part 12D inspection, though 

conducted concurrently, will be documented independently. It is intended that the 

inspections allow opportunities for discussions of any problem areas and other 

important items that might come up.

 Upon completion of the inspections, the group will meet to discuss any additional 

thoughts concerning potential failure modes that need to be developed.

 Any newly identified potential failure modes will be described by the Independent 

Consultant and included in Section 4 of the Part 12D report.

5. FERC Construction and Special Inspections - FERC will be responsible for 

performing and documentation of these inspections on as needed bases with proper 

coordination with the Licensee. 

6. Licensee Initiated and FERC Directed Analyses and Evaluations - If during the 

operation or inspection of the project a concern or issue is raised that requires 

additional studies it is the responsibility of the party identifying the concern or issue 

to initiate a discussion with all parties involved. The Independent Consultant and 

should review/comment on the scope/results of the additional studies. The FERC will 

also review/comment on the scope and results of the studies. If policies change as to 

the design guidelines, FERC may direct further analyses and evaluation to determine 

if a deficiency exists. 
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7. Recommended Action

 Surveillance and Monitoring - If during the operation or inspection of the project a 

concern or issue is raised that is determined to require surveillance and/or monitoring 

to determine if the dam's performance is at risk, it will be the responsibility of the 

Licensee to install, monitor, and evaluate monitoring instrumentation with the 

coordination of the Independent Consultant and FERC. The Surveillance and 

Monitoring Plan should be updated when new instrumentation is installed or other 

changes are made to the existing SMP.

 Modification - If during the operation or inspection of the project a concern or issue is 

raised that is determined to require a dam safety modification, it will be the 

responsibility of the Licensee to design and make the necessary modifications with 

the coordination of the Independent Consultant and FERC. 

14.5.3 Process flowchart 

CONSULTANT LICENSEE FERC

Issues

Issues

Issues

Background Information Inspection Reports Instrumentation Data

Design Drawings Foundation Investigations

Construction Reports EAP

O&M and Training Periodic Routine Inspections FERC Op Inspection

Team Support

Part 12D 

Inspection

Joint Inspection - Part 12D 

& FERC 5-Yr Operation

Coordination if 

Required

Team Support

Operation 

Inspections

Coordination

Failure Modes 

Analysis

FERC 5-Yr 

Operation

Periodic Routine 

Inspections

Coordination if 

Required

Coordination if 

Required

Operation, 

Maintenance & 

Training

Coordination if 

Required

Coordination / 

Support

Coordination if 

Required

Coordination / 

Support
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14.6 EMERGENCY PREPAREDNESS 

The Independent Consultant should consider the various potential failure modes determined 

and review pre-planned procedures for dealing with potential emergencies. If any preplanned measures need to be put in place, the Independent Consultant will make the 

necessary recommendations. These measures include necessary equipment, materials, etc. 
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APPENDICIES
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Appendix A 

Example Potential Failure Mode Descriptions 

Operational Related Potential Failure Mode

The design flood was routed through Dam A by the hydrologic engineering consulting firm 

using the traditional means and assumptions and the capacities for the facilities provided by 

the owner. The dam was found to pass a sizeable portion of the probable maximum flood 

using the Main Spillway gates and the emergency spillways. Thus there was concern for the 

hydrologic deficiency but not great concern. However, examination at the site for potential 

failure modes revealed a significant potential for an Overtopping Failure mode due to the 

following factors: 

• The emergency spillway bays were fronted by arch rings designed to be blasted away 

if the emergency spillway was needed. Discussions with the owner revealed that use 

of the emergency spillway in such a manner was highly improbable. This was due to 

the potential liability from such an action (a sizeable town is located just a mile or so 

downstream) and also due to the physical arrangement of the dynamite ports on the 

top of the spillway bays (it was likely that these would be underwater by the time a 

decision to use them was made). Further there were no plans or procedures in place 

to do the blasting. 

• The first location for overtopping of the structure was immediately above the 

transformer yard. Overflow at this location would have resulted in loss of capability 

to pass flow through the turbines and while this flow was not relied on in the routing, 

the early shut off would have exacerbated the overtopping situation. 

• Drawings were located for the secondary emergency spillway, which was referred to 

as a “fuse plug” spillway but this fuse plug actually had to be excavated by a dozer 

before it was functional. Operators at the site did not know the location of the 

spillway limits and had no procedures or equipment to initiate this spillway. 

• Design crest elevations indicated that the concrete structures would be overtopped 

prior to the embankment structures. However, examination of survey data, settlement 

records and settlement projections (along with the physical location of the 

monuments relative to the crests) revealed that the low point for the project was 

currently an earthen saddle dam. 

Piping Related Potential Failure Mode

The following potential failure mode was highlighted because the specific conditions at Dike 

1 and 2 are such that this potential failure mode is physically possible and is one of the most 

significant potential failure modes definable at this site. Failure of the Dikes poses a high 

hazard, and diligence in monitoring for development of this potential failure mode is 

warranted. 
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Potential Failure Mode 1 - Dikes 1 and 2 - Seepage Erosion and Piping

During site investigation the foundation of these dikes was found to contain joints much 

more open than anticipated, based on pre-construction investigations. These joints provide a 

potential path for subsurface erosion of the Zone 1 material leading to an unprotected exit 

downstream of the dam. Although grouting was performed following construction (during 

the first filling of the reservoir) and the seepage levels were reduced, the fundamental 

potential failure mode remains). The presence of 4 to 5 ft3 /s of seepage, which occurred 

during first filling, from a dike of moderate height and length attests to the possibility of open 

joints in the foundation capable of carrying adequate flow to result in erosion, and transport 

of eroded material downstream. The specific potential failure mode paths and the factors 

relative to the likelihood for the development of this potential failure mode are as follows: 

Potential failure mode paths - there are two primary potential paths for seepage 

erosion/piping to take place through the foundation jointing and two of lesser likelihood. 

These are: 

• Flow through the dike embankment across the Zone 1/ foundation interface. This 

could result in the Zone 1 materials eroding and being carried through the open joints 

to an unprotected exit downstream. (Failure would result if backward erosion 

(piping) through the Zone 1 materials reached the reservoir source. An ever 

increasing flow potential could then progressively enlarge the flow channel 

downstream of the point of erosion initiation in the core to an extent large enough to 

carry continually increasing flows). 

• Flow under the foundation attacking the base of the Zone 1 material and removing it 

by seepage erosion through the foundation jointing 

The other two potential flow paths leading to a seepage erosion/piping failure are (1) piping 

of the Zone 1 through the foundation alluvium and (2) seepage erosion of the foundation 

alluvium exiting through the open joints in the rock. These are considered to be of 

significantly lesser likelihood 

Part 2 - Example Record of Likely and Not Likely Factors Identified for a Specific 

Potential Failure Mode 

After each potential failure mode is identified and clearly stated and recorded the team 

brainstorms and discusses what conditions make this potential failure mode more adverse / 

more likely and what conditions about this potential failure mode are positive making it less 

likely or less significant. An example of the factors identified for the potential failure mode 

previously described above is presented below. 

Factors increasing the likelihood of this potential failure mode developing include: 

• the observation of very open joints in the foundation (greater than 2" wide) 

• surface treatment was not provided to exposed bedrock 

• grouting procedures used likely resulted in some of the most open joints remaining 

open due to the presence of the reservoir produced seepage flows during the grouting 

(this is most likely in the higher head, lower elevation portion of the dikes) 
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• grouting near the surface was likely not very effective, considering the method used 

• large seepage flows are occurring, which can dilute and potentially mask observation 

of particles being carried by the flows. If an attack begins, large flows can erode 

large amounts of material relatively quietly. 

Factors indicating less likelihood of this potential failure mode developing include: 

• There has been no observation of any material being carried by seepage flows at these 

dikes. 

• The Zone 1 appears to be clayey, very impervious, and not easily erodible. 

• The placement of the Zone 1 cutoff-wall well upstream of the dike centerline creates 

a closer source for the reservoir’s water, but a large portion of the dike would remain 

if an erosion path developed at the base of the cutoff. 

• The lack of water in the toe drains is a likely indicator that the dikes have not 

saturated and that the foundation rock behaves as a drain keeping water away from or 

at low pressures at the dam/foundation contact. 

• Seepage flows started downstream of the dikes prior to the water reaching the 

upstream toe of the dikes. This indicates the pervious nature of the foundation and 

the likelihood that a large portion of the seepage water passes beneath the dikes 

(relatively independent of it). 
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Appendix B 

Example Potential Failure Mode Identification 

Cover Letter and Questionnaire 

POTENTIAL FAILURE MODE IDENTIFICATION 

__________ Dam will undergo a Potential Failure Mode Analysis (PFMA) as part of the 

FERC’s Part 12D Independent Consultant Safety Inspection. The PFMA process provides 

for the identification of potential failure modes along with the potential effects and 

consequences with input from all people with data and information relevant to the design and 

performance of the dam. Your input is requested. This memo tells you all about how it will 

work and what your role is. 

*** Individual Input to Potential Failure Mode Analysis *** 

How is this special effort going to work?

The idea is to produce the potential failure mode analysis efficiently without sacrificing the 

specific knowledge, information and opinions of people who have worked on the dams in the 

past or are working on them at present. The information and knowledge you have will be 

collected in three ways as enumerated below. Please note that the potential failure modes 

developed as part of this concentrated effort will be based on available data and information. 

We do not expect you to do any additional studies. However, you may suggest what 

additional study may be valuable as part of a PFMA for this dam. 

How will we get your input?

1. Through a questionnaire completed individually and designed specifically to obtain 

the information needed to help develop the potential failure mode analysis; 

2. Through Core Team review of all work that has been prepared for the dam; and 

3. Through a round table discussion with available team members following completion 

of 1 and 2 above. 

The concentrated effort will allow efficiency in preparation and consistency in the product. 
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Please complete each portion of the attached questionnaire for which you feel you can make 

a contribution. Feel free to review any relevant portion of your past work on the project to 

refresh your memory prior to completing the questionnaire. When you have completed the 

questionnaire send the completed document to ________________________. 

Thanks for your help. 
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POTENTIAL FAILURE MODE QUESTIONNAIRE 

for 

_______________________ Dam 

Name ___________________________________________ 

Team Members Experience / Role _____________________________________ 

Phone _________________ 

Date Due _______ 

Part 1 - Potential failure modes

"Failure" is considered to be something which causes unsatisfactory performance of the dam 

(or a portion thereof). 

I. What potential failure modes do you think are of specific concern at this project? 

Please provide a specific description of the potential failure mode, including location 

of the area of concern. 

Potential failure mode 1. 

 Potential failure mode 2. 

 Potential failure mode 3. 
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Part 2 – Surveillance and Monitoring 

For each potential failure mode identified in Part 1: 

II A. Please describe as specifically as possible what may be observed, monitored or 

measured to verify that performance is okay relative to the potential failure mode, or 

that conditions that are conducive to initiation of the potential failure mode have 

become present or that "activation" of the potential failure mode appears to be taking 

place. Please suggest how that may be observed or monitored. 

II B. Is the monitoring or observation you suggested currently in use at the dam? 

III. If you have visited the site either as part of an official inspection or a general site 

visit, please identify any conditions that are noteworthy from the standpoint of 

performance of the dam. 
Chapter 14 Monitoring the Performance of Dams 

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Appendix C 

A Typical Potential Failure Mode Analysis Session 

Step by Step Description of a Typical Work Session 

• Identifying Key Technical Back up Information Needed 

• Typical Sequence of Brainstorming Activities 

• Key information to document during the process

The intent of this appendix is to describe what is done in a typical PFMA session so 

participants will know what to expect and so that all the right information and data will be on 

hand and the people needed are there or on call. 

Owner / organization prerequisite work: - Gather all background materials for review 

prior to the session and have available at the session 

Required individual advanced preparation activities: 

1. Core Team members have read all background materials. 

2. All participants have read a general background package (inspection report and / or 

standards based engineering dam safety report) to become familiar with or to recall 

the project elements and issues. 

3. All participants have completed / considered questionnaire on identification of 

potential failure modes prior to the workshop. 

4. Inspector or instrumentation group has instrumentation and surveillance data updated 

and ready for review by Core Team prior to meeting and are available to demonstrate 

reading procedures during the site visit as appropriate. 

5. Project leader has references available in meeting room – this includes: 

• all engineering reports and key feature drawings (large scale); 

• construction photos and construction / design history data; 

• flood frequency data and routings and earthquake loading data; 

• data on consequences and emergency preparedness; and 

• inspection reports and instrumentation and surveillance data. 

Begin Session 

I. Adequacy of Project Documentation - Discuss adequacy of documentation provided 

for the exercise and determine if any deficiencies exist for specific potential failure 

modes. Determine if sufficient information exists to adequately perform the Potential 

Failure Modes Analysis for the project. Document your findings regarding adequacy or 

deficiencies in project documentation. 
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II. Potential Failure Mode Identification 

A. Go loading by loading and feature by feature. 

B. Have drawings or sketches of features. 

C. Typically start with flood loading since it is the easiest for all to understand and sets 

out the reservoir loading conditions. 

Flood loading:

• Go over all the key data; size and frequency of floods analyzed, routing data. 

• Show crest elevations of key features and amount of overtopping / freeboard for 

each flood routed. Discuss slope protection, crest condition, discharge locations. 

• Examine potential effects / potential failure modes / adverse conditions for dam 

structures and spillways / outlets. Note: go over each structure to see if any 

potential failure mode is evident. 

• Candidate (suggested) potential failure modes are called for and means / steps to 

failure are discussed. A decision is made whether or not to further consider the 

candidate potential failure mode. 

• If a suggested potential failure mode is considered, the potential failure mode is 

clearly described. Then, the reasons why the candidate potential failure mode is 

more or less likely to develop (adverse and positive factors) are listed on a flip chart 

and/or a computer based table. Based on this discussion, the team classifies the 

potential failure mode (Category I, highlighted; Category II, considered but not 

highlighted; etc.). 

• Breach formation character and rate of failure are discussed. Consequences of a 

flood related failure and of operational spillway discharges are discussed. 

• Failure scenarios (exposure conditions and warning aspects; detection, decision to 

warn, dissemination of warning, evacuation, etc) are discussed. The anticipated 

response is reviewed with field / site personnel. In reality, this exercise is looking 

for potential failure modes in the preparedness arena. 

• Opportunities to achieve risk reduction, structural or non–structural and ways to 

improve detection via instrumentation or surveillance are identified and listed. 

• Data / information needs are discussed and identified. 

Reservoir loading / Static load:

Repeat above process. Key changes or additions or points of emphasis in examining 

this loading are noted below: 

• Discuss annual and historic pattern of reservoir loading. 

• Discuss performance history of each feature. 

• Discuss any instrumentation clues to potential failure mode. 

• Discuss Geologic / foundation rock and soils relationship to structures. Examine 

for potential failure modes. For concrete dams, discern whether or not a foundation 

analysis based on adequate engineering geologic studies has been completed. 
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• Trace (from a projection) on a white board a sketch of the cross section of each 

structure to be evaluated in turn. Sketch each potential failure mode as suggested to 

enable brainstorming / developing / understanding. Plans and / or profiles are 

sometimes needed as well. 

• Evaluate failure scenarios for each significant potential failure mode. These 

scenarios do not have the same warning associated with flood or earthquake 

loadings. 

• A list of the reasons why these potential failure modes are more likely or less likely 

to occur are discussed and recorded. This discussion is very important in evaluating 

the significance / category of potential failure modes suggested. 

• Based on this discussion the team classifies the potential failure mode (Category I, 

highlighted; Category II, considered but not highlighted; etc.) 

Earthquake loading 

Repeat above process. Key changes or additions or points of emphasis in examining 

this loading are noted below: Note, dynamic loading follows static loading because 

some of the potential failure modes are similar and the degree to which the additional 

seismic loading may impact static condition can be examined. 

• Go over all key magnitude and frequency data for site (historic and tectonic study 

data) and site attenuation or amplification data to get sense of the loading 

likelihood. 

• Review any dynamic analyses. 

• Examine what it takes for failure to occur; i.e. does damage result in failure. 

• Compare structures at site to case histories of earthquake related failure. 

Consider any other loading relevant to site:

Ice, avalanche, landslide, etc. – Repeat process used for other loadings 

III. Make final team categorization 

I. Significant Potential Failure Modes (Highlighted) in each loading category and 

Summarize / Rank. 

II. Potential Failure Modes considered but not highlighted. 

III. Potential Failure Modes considered but lacking key data or information to allow 

categorization. Identify data needs. 

IV. Potential Failure Modes ruled out. 

IV. Review possible risk reduction / instrumentation / surveillance opportunities 

identified for all potential failure modes considered

Place the identified potential risk reduction opportunities into two categories: 

1. Possible alternative mitigation actions to investigate, and 
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Revision 1 14-C-4 July 1, 2005 

2. Actions to be considered by the Independent Consultant for implementation by the 

owner. 

V. Identify and Record Major Findings and Understandings

The major findings and understandings achieved as a result of the session (give team 

members a few minutes to think about these before listing) along with the description 

of each potential failure mode considered should be written up and distributed to 

participants of the PFMA session.

VI. Documentation of PFMA Session 

The Major Findings and Understandings achieved during the session and the PFMA 

report should be documented as discussed in Section 14.3.4 Step 6. The overall 

schedule for preparation of the MFU and PFMA reports is summarized in Section 

14.3.4 Conduct of the Initial Potential Failure Mode Analysis in the main text. 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-D-1 July 1, 2005 

Appendix D 

General Format for 

Potential Failure Mode Analysis Reports 

For further guidance and example see a typical report developed from this outline. An 

electronic copy of an example report was developed for the training classes and may be 

obtained from the FERC. 

I. Introduction and Background 

Purpose / description of study 

II. Brief Description of Dam and other Key features of project 

III. Major Findings and Understandings from study 

IV. Potential Failure Modes Identified 

The presentation of potential failure modes should be grouped by category. 

I Highlighted 

II Considered but not highlighted 

III Information needed to allow classification 

IV Ruled out / Not physically possible 

For each Category I, II, III or IV potential failure mode identified there needs to be: 

• A Detailed Description of the Potential Failure Mode and potential adverse 

consequence (scenario developed by the team [including a sketch where 

applicable] and a discussion of the potential adverse consequences of the 

formulated scenario.) For some Category IV PFMs there may not be a detailed 

description if the PFM was ruled out by the Team prior to fully developing the 

PFM. 

• A listing of factors that indicate the PFM is more likely or less likely to occur. 

• The PFM category selected by the team for each potential failure mode. 

• A description of the rationale used for selecting that category (i.e. – the factors 

with the greatest weight 

The Potential Risk Reduction actions identified during the discussion of each potential 

failure mode should also be documented in the report. These may include items such 

as: 

• Surveillance and monitoring enhancements 

• Risk Reduction measures to evaluate 

• Investigations / analyses needed 

• Data and information needed to collect / prepare for decisions on prioritization 

of dam safety actions 
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Revision 1 14-D-2 July 1, 2005 

• Information needed to resolve Category III PFMs 

V. Additional Monitoring or Performance Related Items Discussed 

This section should include issue or items that are brought up during the PFMA session 

that relate to dam safety and performance monitoring or are of general concern but are 

that do not or would not result in failure of the dam or other water retaining structure at 

the project. They need to be included in the documentation to illustrate that they were 

identified, considered and were left to be addressed (potential identification of action) 

by the Part 12D consultant and or the owner. 

VI. Summary and Conclusions 

This section should include a review of the number of potential failure modes identified 

within each category, any study specific comments related to the potential modes of 

failure, and a summary of potential actions identified in the PFMA with respect to 

Surveillance and Monitoring. 

Appendix to Report 

Key supporting data and information and references, Figures, Sketches, Photos made 

during field review showing key elements of dam and auxiliary features should be 

included along with any photos that show conditions leading to potential failure modes. 

Note 1: The report of the PFMA session, although it will reside and be appended in the 

STID, should be prepared as a stand alone document. 

Note 2: Use of tables to present Potential Failure Modes information 

Tables may be an effective way to present the information related to each potential 

failure mode identified. However, it may not be possible to fully describe the potential 

failure mode in a table format. It is important to remember that the description of the 

potential failure mode must provide a complete understanding of the intent of the team 

to reviewers 5 to 25 years in the future. Thus, if tables are to be used then extra care 

must be taken by complete description in Section IV text to ensure that future reviewers 

obtain a full understanding of the teams meaning and intent. Tables may be used as a 

means to summarize or supplement a more complete written description of potential 

failure modes. A possible table format is provided below. 

PFM Description Adverse Factors Positive Factors Risk Reduction 

Actions 

Cat 

 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-E-1 July 1, 2005 

Appendix E 

Major Findings and Understandings - Example Write Up 

Given below is an example write up of the Major Findings and Understandings gained from a 

Potential Failure Mode Analysis for a project consisting of a Main Concrete Dam 

incorporating a Power Station and Two Auxiliary Embankment Dams. Although this was an 

actual study and presents the actual findings, the names of the dams and the river in the 

example are not the real names. 

• Currently in the event of a very large flood on the Blue River, approaching the PMF, 

overtopping failure of Auxiliary Dam 1 is the main point of vulnerability at the 

project. This is because the crest of Auxiliary Dam 1 it is at a lower elevation than is 

the crest of Auxiliary Dam 2. In the event of Auxiliary Dam 1 failure, peak 

discharges downstream would nearly triple (from about 1900 m3

/s at failure to 5700 

m3/s at breach) and the consequences of failure of Auxiliary Dam 1 would be high 

(life loss potential and large economic losses). On the other hand if Auxiliary Dam 2 

were to be established at a lower elevation than Auxiliary Dam 1 and thus allowed to 

fail from overtopping the effects and consequences of overtopping failure would be 

significantly less. Auxiliary Dam 2 failure peak discharges downstream are estimated 

to only be slightly larger than flows resulting from the PMF (from about 2100 m3/s at 

PMF to 2400 m3/s at breach). Several measures to achieve overtopping failure risk 

reduction are identified in the report and the best alternative should be selected after 

an appropriate risk management evaluation. However, the Potential Failure Mode 

Analysis team emphatically concluded that it is essential that as long as the potential 

for overtopping failure of the earthfill dams exists, Auxiliary Dam 2 should be 

established at a lower elevation than Auxiliary Dam 1. 

• Dam failure as a result of piping is a physically possibility at Auxiliary Dam 1 as the 

result of one or more potential flow paths. Although there is no unequivocal physical 

evidence that piping has occurred or will occur in the future, the nature and 

relationship of the materials in the dam and foundation, the water level and 

piezometric observations, and the performance of the structure (observation of 

surface seepage and a depression at the toe) allow for this possibility. Further the 

surveillance and instrumentation have not been extensive enough to rule out the 

possibility that piping episodes (turbid water or particle transport) have occurred, and 

even if they had been transport of material could occur subsurface and thus not be 

amenable to observation. The consequences of a “sunny day” piping failure of 

Auxiliary Dam 1 would be high with a greater life loss potential due to the possible 

lack of advance warning. From the standpoint of the Potential Failure Mode Analysis 

Team, awareness of this potential piping condition is a key finding of the study as this 

potential failure mode is the most significant structural vulnerability found at the 

project. Several risk reduction measures, both structural and non-structural were 

identified and should be considered in the risk management evaluation of the project. 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-E-2 July 1, 2005 

• A potential foundation failure mode identified for the Main Dam was the only PFM 

of significance identified for this structure. Although, this foundation potential 

failure mode is considered physically possible it is highly probable that a foundation 

stability analysis would show that the factor of safety against failure is quite high and 

thus risk reduction measures would not be required. Thus, the Potential Failure Mode 

Analysis team considers that analysis rather than consideration of remedial work is 

the appropriate initial course of action relative to this potential failure mode. 

• The Potential Failure Mode Analysis team considered that failure of the Main Dam 

by overtopping was not a realistic potential failure mode and should not be 

highlighted. However, the main dam would be the first structure to be overtopped 

during a major flood condition, well before either of the earthfill dams. This would 

occur for the PMF but also for floods significantly less than the PMF. It was 

determined in the Potential Failure Mode Analysis that overtopping of the main dam 

would result in significant damage to the power facility and that much if not all of this 

damage is preventable. For example the cable trays are at crest level on the 

downstream side of the dam and would be destroyed with mild overtopping. Also 

water flowing over the top of the dam would currently spill directly on the power 

plant and likely knock that plant out of service and cause considerable damage. This 

flow could be directed away from the plant area. Thus, main dam overtopping, while 

not a potential failure mode, would be a significant incident for the Owner and the 

Potential Failure Mode Analysis team considers that risk reduction measures to 

reduce the impact of the overtopping of the main dam should be evaluated. 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-F-1 July 1, 2005 

Appendix F 

Estimated Time Requirements 

(PFMA items only – not subsequent Part 12D activities) 

The typical time requirements for the major activities in the set up and completion of an 

initial PFMA are as follows: 

Task 1 - Advance preparation 

Facilitator: Consult with and provide information/guidance to owner – 1⁄2 day 

Owner: Assemble materials, notify participants / send out advance packet of 

material, setup facility and make arrangements - (The time required for 

this step can vary widely depending on how well the owner’s files are 

organized. Most owners start this task up to a year in advance of the 

PFMA session to assure they have adequate time to discover all the 

pertinent information.) 

IC: Preparation – 2-3 days 

Task 2 ----Visit site, review materials, carry out PFMA session 

Owners Core Team representative: Travel to and visit site with Core Team – review 

materials and participate in session – 3 days 

IC, Facilitator, FERC representative: As above - 3 days each 

Task 3 – Documentation of study 

IC: Prepare draft of Major Findings and Understandings, distribute for review 

and comment. Prepare draft of PFMA report distribute for review and 

comment and finalize - 5 days 

Core Team Members: Review and comment on Major Findings and Understandings 

and PFMA reports - 1 1⁄2 days 
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Revision 1 14-G-1 July 1, 2005 

Appendix G 

Dam Safety Performance Monitoring Program 

Process 

Task Description Responsibility 

1 Data Assembly: Assemble all available background data for the 

dam and appurtenant works for the project. These data should 

include investigation, design, and construction reports, 

construction photos (and all other project photos), construction 

and as built drawings, geologic reports, construction inspection 

reports by the owner / designer and those by state and federal 

agencies for the original construction. Similar data for any 

project enlargements or modifications for enhanced operation or 

to improve project safety must also be assembled. Data 

assembled should also include seismic studies, the most recent 

flood studies, stability and/or stress analyses, lab test results on 

rock, soil and concrete, summaries of instrumentation 

monitoring data and visual inspection reports, periodic dam 

safety reports including all Part 12D reports, Emergency Action 

Plans, photographs of key elements and features showing present 

condition and any remedial work. A summary of key project 

history by dates including original planning, design and 

construction as well as all modifications, studies relating to 

project safety from project inception to the present should be 

developed. 

Owner with 

assistance from 

IC 

2 Prepare Draft STI Document: The STI should include 

sufficient information to understand the design and current

engineering analyses for the project The STI should use tables, 

figures, and drawings in preference to text and should not 

include complete copies of the original documents except for the 

“Potential Failure Mode Analysis” study report. Only key 

paragraphs of the original reports should be included in the text 

of the STI document for clarity. Licensees should include 

complete copies of the reference documents referred to in the 

STI, or, in some instances, all documents reviewed in the PFMA 

session, in CD or DVD format with the STI document 

Owner with 

assistance from 

IC 

3 Prepare summary informational packet: Send out a summary 

informational packet to the Core Team to familiarize them with 

the project before their site review and to familiarize all other 

participants before they come to the PFMA session. The 

summary information packet should included documents 

describing the dam / project (e.g. the most recent Part 12D 

Report, FERC operation report, Draft STI). 

Owner with 

assistance from 

IC 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-G-2 July 1, 2005 

4 Send out Potential Failure Modes Analysis Questionnaire: 

Prepare and send a questionnaire to the PFMA session 

participants (not just the Core Team) requesting their thoughts 

prior to the PFMA session and to get them all “thinking potential 

failure modes” and gathering relevant materials and information 

that may be helpful to the session. A suggested letter format is 

included in Appendix B.

Owner 

5 Determine PFMA Session Participants: Establish “Core 

Team” to carry out PFMA - Experienced PFMA Facilitator, 

Independent Consultant (IC), Owners representative/PFMA 

Coordinator, FERC Inspector and dam experienced Engineering 

Geologist where applicable. Also determine who the individuals 

will be that will support / attend the PFMA, dam engineering 

geologist, mechanical and electrical specialists (if needed for 

gate/valve issues), consulting engineering staff, operating staff 

responsible for surveillance and maintenance of each specific 

dam, project manager, etc. 

Owner, FERC, 

IC, Facilitator 

6 PFMA Field Review: Physically inspect all aspects of the dam 

structures and appurtenances (that relate to dam safety). Try to 

observe / discuss potential circumstances / conditions that could 

lead to a potential failure (structural or operational). Discuss 

operations with plant operators / site personnel. The PFMA field 

inspection is to familiarize the Core Team with the project 

features and conditions so that they can effectively carry out the 

PFMA. It is not a substitution for the Part 12D field inspection 

by the IC, which is to determine the condition of all safety 

aspects of the dam and power facilities. (Note: Allow 

approximately one-half day per dam. May be more depending on 

the complexity of the project.) 

Core Team 

Geologist, 

Operating 

Staff, 

Specialists 

7 PFMA Data Review: Review data on the dam. This should be 

at convenient location considering location of site/data/PFMA. 

Assemble in a group setting for efficiency in sharing the 

collected data and to provide a “captive” condition to ensure that 

the material is reviewed by all the Core Team members. Also 

being together allows for collaboration on items that may need 

clarification for the entire core group. The team geologist 

should ensure that the relevant geologic data is available for 

Core Team review and the geologist should also review this 

material personally. (Note: Allow one day for the review plus 

evening of site review and evening before PFMA as necessary. 

Large projects may require additional time. A thorough review 

is essential to an effective PFMA.) 

Core Team 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-G-3 July 1, 2005 

8 Facilitated Potential Failure Mode Analysis: Discussion led 

by Facilitator of candidate potential failure modes (PFMs) for 

Flood, Earthquake, Normal Operating and other pertinent 

conditions for each of the structures. Develop (describe events 

and conditions from initiation to breach or other adverse 

outcome) each Potential Failure Mode considered realistic and 

credible by the PFMA team then brainstorm and list all the 

adverse factors that make the potential failure mode more likely 

to occur and then all the positive factors that make the potential 

failure mode less likely to occur. 

Discuss consequences of each PFM (and / or at end of PFMA 

discuss consequences and response to potential failure). 

After discussion of each PFM, categorize the potential failure 

mode (see Table 1 PFMA Guidance Document). Review the 

categorizations at the conclusion of the PFMA. 

During each PFM discussion, identify possible risk reduction 

actions including; monitoring, surveillance, investigations, 

analyses, remediation (structural or non-structural) and 

operational procedures & maintenance programs. Surveillance 

and Monitoring Plans (SMPs) can vary from periodic visual 

inspections, to continuous recording instrumentation and may 

include monitoring of weather forecasts and monitoring of 

earthquake activity. 

List Action Items or steps to be taken to resolve difficulties with 

Classifications of PFMs or Actions to be considered to 

immediately reduce significant risks identified for specific 

PFMs. 

After discussion of each PFM, categorize the potential failure 

mode (see Table 1 PFMA Guidance Document). Review the 

categorizations at the conclusion of the PFMA. 

To complete the PFMA, solicit individual input on the Major 

Findings and Understandings (MFU) reached during the PFMA 

process (all the key things learned or more fully understood 

during the workshop). All the input should be on flip charts 

(hand written) and should also be fully recorded electronically 

(laptop) or by copious notes. Ensure that all participants have 

their input/concerns listed. Photograph hand written charts. End 

PFMA meeting. 

Core Team, 

Geologist, 

Operating 

Staff, 

Specialists as 

needed 

9 Draft MFU: IC prepares the Major Findings and 

Understandings (MFU) of the PFMA, sends MFU to Core Team 

and Geologist. (Note: Owner may distribute to staff for further 

input). All review and comment /send email to IC. IC modifies 

IC and Core 

Team 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-G-4 July 1, 2005 

MFU to include comments as appropriate. 

10 Draft PFMA Report: IC prepares draft PFMA report using 

FERC report outline and sends draft PFMA report to Core Team 

and Geologist. All review and email comments to IC. IC 

modifies PFMA report to include comments (some discussion 

between IC and others is usually needed to achieve final 

agreement) as appropriate. The final report must specify the 

SMP for all Category 1 and 2 PFMs. 

Core Team, 

Geologist 

11 Finalize PFMA Report: IC prepares final PFMA report. 

Owner forwards final report to FERC with copies to Core Team. 

Review and comments on the MFU and PMFA drafts typically 

average about one day for the Facilitator and 1⁄2 day or less for 

each Core Team member and the geologist. 

IC, Owner 

12 STID Review: Following completion of the PFMA report, the 

STID should again be reviewed by the Owner and IC and any 

omissions or additional data revealed in the PFMA data review 

and sessions included as appropriate. The IC will provide 

comment on the final STID as part of the Part 12 D report.

Owner, IC 

13 Part 12 D Field Inspection: Should be conducted by the IC in 

conjunction with the FERC Inspector and the Owner’s staff. 

The field inspection should be conducted as soon after 

completion of the PFMA session as reasonable, so that the field 

conditions relating to issues discussed in the PFMA session can 

be inspected meaningfully.

IC, Owner, 

FERC 

14 O&M Documentation: Summarize PFMA identified O&M 

issues and procedures and assess relative to highlighted failure 

modes. 

Document O&M for App E (if required as necessary). 

IC and Owner 

15 Draft Part 12 D report: To be prepared in accordance with 

FERC guidelines and outline. The Part 12 D report must 

specifically discuss and comment on or recommend SMPs for 

each Category 1 and 2 PFMs. Submit draft report to Owner for 

review/comment.

IC, Owner 

16 Finalize Part 12 D Report: Responding to Owners comments, 

IC prepares and certifies final Part 12 D report and delivers to 

Owner. 

IC, Owner 

17 Part 12 D Report Submission: Owner submits Part 12 D report 

to FERC along with STID, including STID.

Owner 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-H-1 July 1, 2005 

Appendix H 

Part 12D Safety Inspection Report Outline 

Table of Contents 

The Table of Contents must show the initial page numbers for each section. If any 

subsection is not applicable, include the subsection with a statement of “Not Applicable” and 

an explanation of the reason(s) why. 

For licensed projects that include multiple independent dam and powerhouse developments, 

separate Part 12D reports should be published for each development. 

1. Findings and Recommendations 

2. Project Description 

3. Discussion of Potential Failure Mode Analysis Report 

4. Surveillance and Monitoring with Respect to Potential Failure Modes 

5. Field Inspection 

6. Operation and Maintenance Programs Relative to Potential Failure Modes 

7. Assessment of Supporting Technical Information Document 

 

List of Tables (with location) 

List of Figures (with location) 

List of References 

Appendices for Part 12D Inspection Report

A. FERC Letter Requiring Part 12D Inspection 

B. FERC Letter Approving Part 12D Consultant - Include date of current report 

outline provided by FERC. Use report outline provided with FERC letter, not latest 

revision. 

C. Project Figures 

Only provide general overview drawings necessary to understand the project and 

items discussed in the report. If figures are placed in Section 2, provide a statement 

that figures may be found in Section 2. Optionally, if the STI is bound with the Part 

12D report provide a statement that figures may be found in the STI document; 

duplicate drawings from the STI do not need to be included in the Part 12D report 

proper. 

Detailed drawings should be included in the Supporting Technical Information 

document. 
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Revision 1 14-H-2 July 1, 2005 

D. Instrumentation Monitoring Data Plots 

 List each figure and drawing included in the report. Optionally, instrumentation plots 

may be placed in Section 4 of the report and a statement included in Appendix D that 

the plots may be found in Section 4. 

E. Inspection Photographs 

 Optionally, some or all of the photographs may be included in the appropriate 

sections of the report. If photographs are included within the report, provide a list of 

the photographs and the corresponding page number in Appendix E. 

F. Inspection Checklists and/or Field Notes (Optional) 

G. Operation and Maintenance Documentation (If required) 
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Revision 1 14-H-3 July 1, 2005 

1.0 Findings and Recommendations 

This Section includes a summary of the Part 12D Independent Consultant’s findings 

and assessments and the Part 12D Independent Consultant’s conclusions and 

recommendations. 

1.1 Findings 

 1.1.1 Summary assessment of the PFMA report 

 1.1.2 Summary assessment of the Surveillance and Monitoring Plan 

 1.1.3 Summary of Field Inspection Findings 

 1.1.4 Summary of O&M status 

 1.1.5 Summary Assessment of “Supporting Technical Information” document 

Note: Specifically identify any new calculations prepared subsequent to 

the previous Part 12D Report. 

1.2 Conclusions 

The conclusions of the Independent Consultant regarding the condition and 

suitability for continued safe and reliable operation of the project and specific 

conclusions regarding the information in each Section of this Part 12D report. 

1.2.1 Conclusions regarding the suitability of the Project for continued safe and 

reliable operation. 

1.2.2 Conclusions regarding the Project Description 

1.2.3 Conclusions regarding the Potential Failure Modes Analysis Report 

1.2.4 Conclusions regarding the Surveillance and Monitoring Plan 

1.2.5 Conclusions regarding the Field Inspection 

1.2.6 Conclusions regarding the Operations and Maintenance Programs 

1.2.7 Conclusions regarding the Supporting Technical Information 

1.3 Recommendations 

The recommendations of the Independent Consultant to improve or maintain the 

condition and suitability for continued safe and reliable operation of the project 

and specific recommendations regarding the information in each Section of this 

Part 12D report. 

1.3.1 Recommendations regarding the suitability of the Project for continued 

safe and reliable operation. 

1.2.2 Recommendations regarding the Project Description 

1.3.3 Recommendations regarding the Potential Failure Modes Analysis Report 

1.3.4 Recommendations regarding the Surveillance and Monitoring Plan 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-H-4 July 1, 2005 

1.3.5 Recommendations regarding the Field Inspection 

1.3.6 Recommendations regarding the Operations and Maintenance Programs 

1.3.7 Recommendations regarding the Supporting 

1.4 Certification 

Note: By signing this document, the Part 12D Independent Consultant is stating 

that the entire report has been developed by and under the direction of the 

undersigned. The Part 12D Independent Consultant shall make a clear statement 

that he/she generally concurs with the assumptions, methods of analyses, and 

results of all studies documented in the report. 

The Part 12D Independent Consultant is thus taking responsibility for the Part 

12D report contents as a Professional Engineer. 

1.4.1 List of all field inspection participants 

1.4.2 Reference to FERC Order 122 dated March 1, 1981 and paragraph 12.37 

(c) (7).

1.4.3 Signature(s) of Part 12D Independent Consultant(s) and PE Stamp

See Appendix A: FERC Letter Requiring Part 12D Inspection

See Appendix B: FERC Letter Approving Part 12D Consultant - (Include date of 

current report outline provided by FERC) 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-H-5 July 1, 2005 

2.0 Project Description 

2.1 Brief Project Description 

For each major element and ancillary structure, provide a brief description of the 

type of structure, general dimensions, etc. The detailed project description will be 

in the “Supporting Technical Information” document. 

For multi-project or development licenses, include a brief outline of how this site

fits with the other projects. 

Include a short paragraph with very brief project history. When constructed, 

when modified, any incidents. 

2.2 Hazard Potential Classification. 

Based on views from the dam, other project works inspected and discussion with 

the licensee, document any changes in upstream or downstream conditions that 

might affect the Hazard Potential Classification. Review with the licensee the 

methods and assumptions used to develop the IDF. If the IDF is less than the 

PMF, the IC should confirm that the IDF is still valid based on an assessment of 

the downstream conditions as noted above. 

2.3 Summary of Standard Operating Procedures 

2.3.1 Purpose of Project (Run of river, storage, flow augmentation, flood 

surcharge storage, control reserve, pumped storage, etc.) 

2.3.2 Reservoir rule curves by season (include seasonal reservoir level operating 

levels and restrictions of reservoir level due to safety concerns, if any) 

2.3.4 Standard gate operation procedures (lead and following gates, emergency 

power systems, etc.) 

2.4 Modifications Conducted for Project Safety 

Document any modifications to project works since the last Part 12D inspection 

that have been done to improve project safety. (i.e.: spillway gates reinforced, 

seepage drain, berm added, crest raised, post-tensioned anchors installed, 

foundation drains or relief wells cleaned, etc.). In the next Part 12D Safety 

Inspection Report, these items will become part of Section 2.1. This information 

should be fully described in the updated “Supporting Technical Information” 

document submitted with the Part 12D report. 

Do not include routine maintenance such as unit overhaul, gate painting, etc. 

Note, that generators, transformers, and transmission facilities are excluded from 

the Part 12D program under 18CFR subsection 12.35. 

2.5 Flood History 

2.5.1 Flood of Record, PMF, IDF 

2.5.2 Zero freeboard spillway capacity 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-H-6 July 1, 2005 

2.5.3 Peak spillway discharge during last five year period 

2.5.4 Peak reservoir elevation during last five year period 

See Appendix C: Project Figures (Note: If the STI is bound with this report, do not 

duplicate figures)
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-H-7 July 1, 2005 

3.0 Discussion of Potential Failure Mode Analysis Report 

Do not include security issues in the Part 12D report. For licensed projects that include 

multiple independent dam and powerhouse developments, separate PFMA studies and 

reports should be made for each development. 

3.1 General 

Identify the Core Team members, and their affiliations, who developed the 

comprehensive Potential Failure Modes Analysis (PFMA) or its update. Note that 

the process was in accordance with FERC “Engineering Guideline for the 

Evaluation of Hydropower Projects,” Chapter 14. 

3.2 Assessment of Potential Failure Mode Analysis Report 

Assess the viable potential failure modes identified in the PFMA report. These 

would generally be Category 1 through Category 3 PFMs. Provide an assessment 

of the reasonableness and completeness of the failure mode scenario and whether 

the PFMs identified have a real possibility of occurrence. Potential Failure modes 

should be listed in order of importance. Each PFM assessment should include: 

• A description that includes the sequence of conditions and events that 

would lead to the potential failure mode; 

• An assessment of the risk reduction opportunities for each PFM; and 

• An assessment of the Surveillance and Monitoring Plan for each PFM. 

For example, the report would be formatted as follows. 

3.2.1 PFM 1. (i.e. Internal erosion, piping) 

3.2.1.1 Description of PFM (may be taken from PFMA report) 

3.2.1.2 Assessment of Risk Reduction Opportunities 

3.2.1.3 Assessment of Surveillance and Monitoring Plan 

3.2.2 PFM 2. (i.e. Seismic induced deformation) 

3.2.2.1 Description of PFM (may be taken from PFMA report) 

3.2.2.2 Assessment of Risk Reduction Opportunities 

3.2.2.3 Assessment of Surveillance and Monitoring Plan 

Etc. 

3.3 Are there new potential failure modes that have been identified and addressed in 

this report or that should be assessed? If so, include the appropriate Description 

of the PFM, Assessment of mitigation actions and Assessment of the SMP as 

discussed above. 

See “Supporting Technical Information” document: Potential Failure Mode Analysis 

Study Report (Update as appropriate) 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-H-8 July 1, 2005 

4.0 Surveillance and Monitoring with Respect to Potential Failure Modes 

Note: Review and assessment of Surveillance and Monitoring Plans must always be 

done from the point of view of potential failure modes. Although the primary 

assessment is with respect to the potential failure modes identified in the PFMA study, 

the Independent Consultant must determine if there are potential failure modes not 

previously addressed or not adequately considered. 

For the purposes of this section, a Threshold Level is the value used in the analysis or 

design, or is established from the historic record. An Action Level is the instrument 

reading that triggers increased surveillance or an emergency action. 

4.1 Operator’s Surveillance Program 

Daily/weekly operator’s inspections and reports. 

4.2 Active Instrumentation: Include a schematic figure showing location of 

instrumentation (not detailed or cross section). 

This will vary by project. Discuss only the instruments actually at the project. Is 

instrumentation in accordance with Chapter IX of the FERC “Engineering 

Guideline for the Evaluation of Hydropower Projects”? Is the instrumentation 

functioning properly? Etc. 

• Piezometers 

• Weirs 

• Settlement/alignment monuments 

• Crack gages 

• Upstream river and/or rain gage stations 

• Headwater/tailwater (alarm systems) 

• etc. 

4.3 Threshold and Action levels 

For each instrument, or group of instruments as appropriate, provide a table of 

Threshold and Action levels as defined above. 

4.4 Reading procedures/frequency 

For each instrument, or group of instruments as appropriate, discuss: 

• Data acquisition procedures (manual/automated) 

• Data evaluation procedures (process; is data evaluated in a timely manner 

by a qualified engineer; are readings compared to Threshold and Action 

levels defined for each instrument) 

• Spurious readings (are spurious readings confirmed or explanations 

provided) 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-H-9 July 1, 2005 

4.5 Assessment of Instrumentation Data and Surveillance and Monitoring Plans 

Relative to Potential Failure Modes Include newly identified potential failure 

modes 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-H-10 July 1, 2005 

5.0 Field Inspection 

5.1 Field Inspection Observations 

For each element of the project (i.e.: spillway, earthfill embankment, gravity 

section, intake, powerhouse, conveyance system, etc.), observe and report visual 

observations of the following issues as appropriate. Include photographs to 

document significant project features and observations. If an inspection checklist 

is used, include a copy of the checklist Appendix F. A site specific inspection 

checklist should be formatted to include specific visual surveillance items 

identified in the PFMA. 

The intent of this section is to highlight changed conditions for the report 

reviewer, not to document unimportant or minor details. 

The report should be in text format by structure or element addressed 

individually. For each structure or element of the project, the Part 12D 

Independent Consultant should consider the following items as appropriate: 

• Settlement

• Movement – including abutments (cracks or other signs of distress or change)

• Erosion

• Seepage/Leakage

• Cracking

• Deterioration

• Spillway gate Operation/Standby Power (At a minimum, the Part 12D 

Independent Consultant needs to review the licensee’s annual certificates of 

spillway gate operation and interview project operating staff to assure that 

emergency backup systems work and that operating personnel know how to 

use them. At least one spillway gate should be operated at least one foot 

during the Part 12D inspection using the standby generator.)

• Outlet/Sluice Gate Operation

• Water conveyance systems (canals / flumes / penstocks / tunnels / surge 

chambers, emergency bypass or closure systems, etc.)

• Foundation Drain/Relief Well Operation

• Evidence of high artesian or uplift pressures (structures / foundations / 

abutments)

• Observations of sediment transport (piping evidence)

• Observations of seeps, wet areas, springs, green grass

• Other Pertinent Observations

5.2 Status of Response(s) to Recommendation(s) in Last Part 12D Report. 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-H-11 July 1, 2005 

5.3 Field Observations with Respect to Potential Failure Modes 

Document field observations pertinent to each potential failure mode noted in 

Section 3 

5.4 Adequacy/Operation of Public Alert Systems 

Note: Are upstream spillway warning buoys, and downstream sirens and lights 

operable? 

See Appendix E: Inspection Photographs (Optionally, some or all of the photographs 

may be included in the appropriate sections of the report. If photographs are included 

within the report, provide in Appendix E a list of the photographs and the 

corresponding page number) 

See Appendix F: Inspection Check List (optional) 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-H-12 July 1, 2005 

6.0 Operation and Maintenance Programs Relative to Potential Failure Modes 

Do not include security issues in the Part 12D inspection report. If observations of 

significant O&M issues are made, include in report for possible new potential failure 

mode analysis. 

6.1 Summary of PFMA identified O&M issues (from PFMA report) 

6.2 Operation and Maintenance Procedures 

6.2.1 Communication/Response 

Address adequacy and reliability of remote monitoring, communication 

and control systems (Operations / Instrumentation / Telemetry – Do the 

systems provide adequate reliability and redundancy? Can a specific 

spillway gate, valve or other project component be operated remotely on 

demand?) 

6.2.2 Electrical/Mechanical Systems 

• Spillway Gate Motors (line/line voltage, amperage draw, motor name 

plate rating information) 

• Standby and Redundant Power Sources 

• Manual/Remote/Automatic Operation of Gates and Valves 

• Gate Operation Sequence 

• Icing protection (heaters/bubblers/reservoir level restriction) 

6.2.3 Human Factors 

• Adequate Staff for Emergency Response (Multiple Sites) 

• Reliable Access Routes (winter/storm conditions) 

• Training 

• Electricians/Mechanics/Laborers 

• Adequate Time to Respond 

• Call Out Systems (time for crew to reach site after call out) 

6.3 Assessment of O&M Procedures Relative to Potential Failure Modes 

See Appendix G: Operation and Maintenance Documentation
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-H-13 July 1, 2005 

7.0 Assessment of Supporting Technical Information Document 

The purpose of this section is for the Part 12D Independent Consultant to assess the 

contents of the “Supporting Technical Information” document compiled by the 

licensee. The STI document should include information needed to understand and 

confirm the underlying assumptions and the conclusions of the analyses of record 

supporting the assessment of the safety of the Project. 

In each section, where appropriate, the Independent Consultant shall make a clear 

statement that they have reviewed the pertinent analyses and evaluations along with the 

underlying assumptions and that they have concluded that the assumptions and methods 

of analysis or evaluation were appropriate for the structure, were applied correctly and 

are appropriate given current guidelines and the state of dam safety practice. 

7.1 Potential Failure Mode Analysis Study Report (Include a statement referring to 

Section 3 for a discussion of the Potential Failure Mode Analysis) 

7.2 Description of Project 

7.3 Construction History 

7.4 Standard Operating Procedures 

7.5 Geology and Seismicity 

7.6 Hydrology and Hydraulics 

7.7 Surveillance and Monitoring Program 

7.8 Stability and Stress Analyses of Project Structures 

7.9 Spillway Gates 

7.10 Pertinent Correspondence Related to Safety of Project Works 

7.11 Status of Studies in Process and Outstanding Issues 

7.12 References 

7.13 Conclusions 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-H-14 July 1, 2005 

APPENDICES 

List of Tables (with location) 

List of Figures (with location) 

List of References 

A. FERC Letter Requiring Part 12D Inspection 

Note: May include specific FERC concerns to be addressed by Part 12D Independent 

Consultant.

B. FERC Letter Approving Consultant 

 Note: Include date of report outline provided by FERC.

C. Project Figures 

This Appendix should include the following figures as appropriate. All Figures should 

be consecutively numbered. Figures should be general without excessive detail so as to 

be clearly legible. Figures should include documentation of significant changes since 

last Part 12D report. If STI document to be directly bound in this report, do not 

duplicate the figures. FERC Exhibit and relicensing drawings can be used. 

• Location map with project facilities located including conveyance systems and 

access routes from main roads and nearest town 

• Plans of project facilities 

• Typical sections and profiles of key project features (dams, spillways, powerhouses, 

intakes, emergency/fuse plug spillways, chute profiles, etc.) 

• Profiles and typical sections of water conveyance systems (canals, tunnels, 

penstocks, flumes, surge chambers, etc) 

• Satellite or aerial photo of project and downstream area 

• Spillway and tailwater rating curves 

D. Instrumentation Monitoring Data Plots 

Note: Plans and cross-sections with locations of each instrument, including design 

phreatic surface or uplift pressure profile, and tabulated data for each instrument are 

included in the “Supporting Technical Information” document only. See Chapter IX, 

Instrumentation and Monitoring, of the FERC Engineering Guidelines for the 

Evaluation of Hydropower Projects for additional information. Only time versus 

reading graphs are included here as NEW information. Tables of data should be 

provided on a CD bound into the Part 12D report 

If data plots are included in Section 4 of the Part 12D report, a statement should be 

provided here directing the reader to Section 4 for the information. 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-H-15 July 1, 2005 

• Time versus Reading data plots 

• Plot all data to date, not just last five years (alternative is to plot last 15 years and 

note historic range for each unit) 

• Do not put too many instruments on one plot 

• Try to put all instruments from one section or profile on the same plot 

• Mark tip elevation, unscreened length, ground elevation and top of piezometer 

elevation for each piezometer on the data plot. This information can be provided in 

a Table to enhance legibility of the graph. 

• Use symbols and/or different line types for each unit, not just colors (colors do not 

reproduce in black and white and some people are color blind - Note that yellow 

and blue do not reproduce on Xerox machines) 

• Include headwater and tailwater levels on each plot 

• Force all time scales to show full year cycles from January through December 

• For multiple plots for the same project, force vertical and horizontal scales on all 

plots of the same type to have the same scale or total range so plots can be directly 

overlaid 

• Mark threshold values 

• Show monthly precipitation on one sheet 

• Mark action levels requiring emergency response 

E. Inspection Photographs 

F. Inspection Checklist (optional) 

G. Operation and Maintenance Documentation (if required) 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-I-1 July 1, 2005 

Appendix I 

Guidelines for Supporting Technical Information 

The “Supporting Technical Information” document must include a revision sheet and contain 

the following sections: 

Section Title 

 Table of Contents 

1. Potential Failure Mode Analysis Study Report 

2. Description of Project Structures 

3. Construction History 

4. Standard Operation Procedures 

5. Geology and Seismicity 

6. Hydrology / Hydraulics 

7. Surveillance and Monitoring Plan 

8. Stability / Stress Analysis of Project Structures 

9. Spillway Gates 

10. Pertinent Correspondence Related to Safety of Project Works 

11. References 

The information to be included in each section is described below. If an item is not pertinent 

to the Project, include the item in the report and state that the item is Not Applicable (i.e. 

Section 9 “Spillway Gates” if the dam has an uncontrolled spillway).
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-I-2 July 1, 2005 

SUPPORTING TECHNICAL INFORMATION 

Revision Log 

Table of Contents 

1.0 Potential Failure Mode Analysis Study Report 

Include a complete copy of the latest “Potential Failure Modes Analysis Report” with 

all attachments. All updates shall be included in this Section of the STI. 

2.0 Description of Project Works and Project Drawings 

This is a detailed description of the project and project works that is part of the Part 

12D Independent Consultant review. In general, this information will come directly 

from existing sources such as prior Part 12D Inspection Reports, licensing or 

relicensing documents or company brochures. The detailed descriptions would include 

the following elements as appropriate: 

• General project description including project name and owner 

• Project location including nearest town(s), river system, etc. 

• Purpose of Project 

• Main dam and any auxiliary dams 

• Spillway(s) including stilling basins 

• Non-overflow water retaining structures such as powerhouses 

• Intakes 

• Conveyance systems (penstocks, tunnels, surge chambers, flumes, canals, 

inverted siphons, including control, regulating, and pressure relief devices, etc.) 

• Powerhouse(s) 

• Low level outlets including minimum flow devices 

The following drawings shall be included 

• USGS Quad map or other location map with project facilities located including 

conveyance system alignment 

• Plan of licensed project facilities and project boundaries 

• Typical sections and profiles of key project works (dams, spillways, powerhouses, 

intakes, canals, tunnels, penstocks, flumes, surge chambers, inverted siphons, etc.) 

• Satellite or aerial photo of project and downstream area if available 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-I-3 July 1, 2005 

3.0 Construction History 

In general, this information will be copied directly from existing sources such as prior 

Part 12D reports, construction reports or company brochures. Include a summary of the 

project construction history based on the following sources of information: 

• Design reports and pertinent memoranda from licensing and permitting 

documents 

• Laboratory investigations and construction testing reports 

• Field and lab geotechnical investigations 

• Construction reports and photographs 

• Specification documents 

• Reports of major modifications conducted for dam safety since last Part 12D 

inspection 

• Construction chronology that includes all a summary of original construction and 

all significant work completed related to project safety. Do not include routine 

maintenance items such as gate painting, unit overhauls, etc. 

4.0 Standard Operation Procedures 

Include summaries of the standard operating procedures for the project. This section 

should include: seasonal minimum flow requirements, lead and follow gate sequence, 

reservoir level restrictions by season, etc. 

4.1 Dam Operations 

• Schedule of Inspections (include routine operations by operating staff, 

inspections by engineering staff, and special inspections as appropriate) 

• Inspection checklist(s) 

• Procedures for assuring satisfactory operating condition of critical systems 

including; SCADA systems, spillway gate operators, spillway gates, and low 

level outlet works 

4.2 Reservoir Operations 

4.2.1 Normal Operations 

• Typical filling schedule 

• Inflow forecasting procedure 

• Ramping rate requirements (reservoir and releases) 

• Downstream minimum flow requirement schedule 

4.2.2 Flood Operations 

• Criteria for starting gate operations 

• Method of gate operation (local or remote) 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-I-4 July 1, 2005 

• Gate operating sequence (both spillway and low level outlets as 

applicable). Are gates operated such that all gates are opened a similar 

amount? Are some gates opened fully before others are operated? etc. 

5.0 Geology and Seismicity 

In general, this section should be copied from existing reports and company brochures. 

Include summaries of applicable information in the following sections: 

5.1 Geology 

5.1.1 Regional geology 

5.1.2 Site geology and local foundation conditions including geologic maps, 

cross-sections and profiles under the dam(s) and pertinent project works. 

5.1.3 Potential landslides, loose rock formations or adverse bedding orientations 

that could affect project works 

5.1.4 Potential sinkhole, karst, solutioning, basalt flow issues, etc. that could 

impact project works 

5.1.5 Potential weak seams such as bentonite or soluble gypsum layers 

5.1.6 Geologic artesian sources (geothermal, high abutments, etc.). Do not 

include artesian pressures due to normal dam seepage. 

5.2 Seismicity 

5.2.1 Map of fault traces that effect project. Differentiate between those traces 

that have been confirmed by trenching or other means and those that are 

inferred from other means. 

5.2.2 Table of fault, distances, depths, magnitude at fault, PGA at site, etc. 

including local (floating or random crustal) earthquake. 

5.2.3 Site MCE and DBE development 

5.2.4 Time history of adopted earthquakes 

5.2.5 Response spectrum used in analyses 

5.2.6 Historic earthquake centers map 

The USGS website (http://neic.usgs.gov) includes information on seismicity and 

may be a useful reference. 

6.0 Hydrology and Hydraulics 

Provide supporting information to document the development of the Probable 

Maximum Flood (PMF) and the routing of the PMF through the reservoir and project 

spillways. In general, this information will come directly from existing sources such as 

prior Part 12D Inspection Reports or company reports. The following information that 

should be included as applicable: 

6.1 Hydrology 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-I-5 July 1, 2005 

6.1.1 Hydrometeorology report used 

6.1.2 Probable Maximum Precipitation for general and local storms 

6.1.3 Drainage basin description including drainage area 

6.1.4 Antecedent conditions 

6.1.5 Loss rates 

6.1.6 Basin and sub-basin precipitation/runoff models 

6.1.7 Unit Hydrograph 

6.1.8 Reservoir inflow and outflow hydrographs for the PMF event 

6.1.9 Floods of record including highest flood flows and reservoir elevations 

6.2 Hydraulics – Dams 

6.2.1 Project discharge-rating curves (For multiple gate spillways, outlet 

structures, powerhouse units, and emergency/fuse plug spillways, include 

the contribution of each component as well as the total capacity. Include 

the equations used to develop the curves including overtopping and orifice 

flow where appropriate). 

6.2.2 Tailwater rating curve (Compare to dam break studies) 

6.2.3 Normal and IDF freeboard without wave action 

6.2.4 Zero freeboard flood capacity (without wave allowance) 

6.2.5 Inflow Design Flood (based on dam break) The pertinent information from 

dam break analyses necessary to support the determination of the IDF 

should be included 

6.2.6 Reservoir Probable Maximum and Inflow Design Flood outflow 

hydrographs and corresponding reservoir levels 

6.2.7 Freeboard for general and thunderstorm events 

6.2.8 Stilling basin or plunge pool design flood flow 

6.2.9 Operating rule curve (if storage reservoir) including license restrictions on 

storage levels by season 

6.3 Hydraulics – Water Conveyance Systems 

6.3.1 Hydraulic capacity of water conveyance system(s) 

6.3.2 Normal operating freeboard 

6.3.3 Spillway discharge rating curve(s) 

6.3.4 Summary of transient analysis 

7.0 Surveillance and Monitoring Plan 

This section is to include drawings and/or sketches showing the location of each active 

instrument. Include cross-sections of project structures showing instrument tip 

elevation, ground elevation and readout point location. See Chapter IX, 

Instrumentation and Monitoring, of the FERC Engineering Guidelines for the 

Evaluation of Hydropower Projects for additional discussion. 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-I-6 July 1, 2005 

Note: time versus reading graphs for each instrument will be included only in the Part 

12D Inspection Report, not in the STI. 

7.1 Plans, sections, and details of active or useful reference instrumentation 

If a unit has been abandoned or replaced, but the historic data is still being used 

for safety evaluations, include the appropriate information for the record 

7.2 Reading frequency for each instrument (reading procedures should not be 

included in this document) 

7.3 Procedures for resolving spurious readings 

7.4 Tabulated Data for each instrument (may be included on CD in Excel format) 

7.5 Type of instrument (pneumatic/vibrating wire piezometer, Parshall flume, gape 

gage, inclinometer, etc) 

7.6 Predicted value for each instrument (threshold values are values used in design or 

analysis of project structures) 

7.7 Historic range of readings for each instrument 

7.8 Threshold and Action level for each instrument 

8.0 Stability and Stress Analyses of Project Structures 

Because every dam and hydroelectric project is unique, it is not possible to list here all 

the various items that are required to adequately detail stability or stress assessments of 

the project water retaining structures. It will be the responsibility of the Licensee to 

include all information necessary for the reader to understand the assumptions, methods 

of analysis, and load cases assessed for each project structure. Stability and stress 

analyses for each structure shall be summarized graphically for ease of understanding. 

The following types of information should be provided: 

8.1 General 

8.1.1 Listing of credible load cases analyzed (including water levels for dam, 

canal and flume analyses or pressure for penstock and flowline analyses) 

8.1.2 Statement of the method of analysis used and the computer program 

adopted. 

8.1.3 Properties of materials based on site specific tests or assumptions (state 

which). Include representative test data and summary sheets. 

8.2 For each gravity structure and load case: 

8.2.1 Graphic free body diagram (cross-section) of each structure showing: 

• the assumed self weight of the cross section 

• all applicable loads including, as appropriate: 

• assumed uplift pressure distribution 

• silt loads 

• headwater and tailwater loads 

• point loads 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-I-7 July 1, 2005 

• ice load 

8.2.2 Key elevations 

8.2.3 Key lateral dimensions 

8.2.4 Piezometer and drain locations 

8.2.5 Foundation shear strength parameters 

8.2.6 Minimum cohesion to meet stability criteria 

8.2.7 Negative crest pressures 

8.2.8 Concrete unconfined and splitting tensile strength test results 

8.2.9 AAR potential or evidence 

8.2.10 Failure planes investigated, etc. 

8.3 For each embankment structure and load case: 

8.3.1 Graphic cross-section showing 

• embankment zoning 

• phreatic surface by load case 

• critical failure surfaces 

• key elevations 

• key lateral dimensions 

• slopes 

• headwater and tailwater elevations 

• relief wells, drainage layers, cutoff trenches, slurry walls, etc 

8.3.2 Potential for uncontrolled seepage at toe 

8.3.3 Summary of liquefaction analyses 

8.3.4 Summary of deformation analyses 

8.3.5 Procedures used to determine soil types and properties, etc. 

• Soil Classification 

• Atterberg limits 

• etc. 

8.3.6 Procedures used to determine soil strengths 

• Triaxial Tests (type and loadings) 

• Standard Penetration Tests 

• Cone Penetration Tests 

• Becker Hammer Tests 

• etc. 

8.4 For each arch dam load case: 

8.4.1 Finite element mesh 

8.4.2 Stress contours 

8.4.3 Vector diagrams 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-I-8 July 1, 2005 

8.4.4 Thrust block stability and joint sterionets 

8.4.5 Pulsating load potential, etc. 

8.5 For each water conveyance system that has a highlighted PFM 

8.5.1 Stress and stability analyses 

8.6 Summary table of factors of safety for each structure and load case, with required 

value. 

For embankment structures and overburden foundations, the material strengths 

used in the stability analyses should be properly identified i.e. effective stress or 

total stress. The methods used to determine/estimate pore pressures, such as flow 

nets or field measurements, should also be described. 

For gravity structures, it is useful to provide a spreadsheet of the key numbers 

from the analysis. 

9.0 Spillway Gates 

For each spillway gate type, include the following information: 

9.1 Table of material properties (steel type, trunnion bearing type and friction 

properties, etc). 

9.2 A summary of the stress analysis computations 

9.2.1 Graphic of gate model used for stress analysis 

9.2.2 Table of critical stresses in each member for each load condition. 

9.3 Trunnion, wheel, or other lubrication procedures, schedule, etc. 

9.4 Summary of gate hoist motor load tests to date (motor name plate rating, line-line 

voltage, amperage draw, reservoir level, and initial draw if available) 

9.5 Spillway gate detailed inspection report 

10.0 Pertinent Correspondence Related to Safety of Project Works 

Include the most recent FERC Annual Operation Inspection Report. Include any major 

correspondence from FERC or State Dam Safety Agencies related to outstanding dam 

safety issues for the project. 

11.0 References 

List of references available for review of dam safety issues and that were used to 

assemble this document. 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-I-9 July 1, 2005 

Attachments 

1) Example of Detail Expected in Supporting Technical Information Document 

2) Example of Summary of Embankment Stability Analysis 

3) Example of Summary of Structural Stability Analysis 

4) Example of Summary of Hydrologic and Hydraulic Information 

5) Example of Summary of Instrumentation and Surveillance Information 

6) Example of Document Control Log Sheets 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-I-10 July 1, 2005 

Attachment 1 

Example of Detail Expected 

in 

Supporting Technical Information Document 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-I-11 July 1, 2005 

BASIC DATA AND ANALYSES 

Spillway Adequacy 

A. Previous Studies 

 The original design flood study for 

Big Hole Dam was presented in "A Study 

of the Maximum Probable Floods for the 

Middle Fork of the Big River Project", 

dated October 1961 and revised in August 

1962 by ABC. The design flood developed 

by that flood study, when routed through 

the reservoir and spillway, resulted in a 

peak discharge of 58,800 cfs at reservoir 

water surface Elevation 4,643.2, leaving a 

freeboard of 6.8 feet to the nominal dam 

crest. 

 In February 1965, ABC updated 

the flood study by deriving a probable 

maximum flood based on U.S. Weather 

Service Hydrometeorological Report No. 

36 and U.S. Corps 

of Engineers 

reductions. This 

1965 study resulted 

in a maximum water 

surface Elevation 

4,646.7, leaving a 

freeboard of 3.3 feet 

to the nominal dam 

crest elevation. 

 In 1973, T. J. 

Corwin reviewed the 

flood studies, made 

some independent 

evaluations, and 

concluded that the 

maximum inflow 

flood would be 

66,000 cfs. When 

routed through the 

reservoir and 

spillway, the peak 

discharge would be 55,000 cfs with a 

maximum reservoir water surface Elevation 

4,644, leaving 6.0 feet of freeboard. 

B. Methodology to Determine PMF 

 In 1982, FERC directed Big County 

Water Agency to provide additional 

information on flood hydrology for the 

Middle Fork American River Project. The 

Agency retained Hydrotech of Bigville to 

perform that study. Hydrotech's report 

"Probable Maximum Flood Study for Big 

Hole, Interbay, and Little Hole Afterbay 

Dams", dated October 1982, was reviewed 

and excerpts presented as part of the 1986 

Five Year Dam Safety Inspection report. 

Excerpts from that report describing the 

methodology used to determine the PMF 

for Big Hole Dam follow. 

 “The probable maximum floods 

HELL HOLE DAM 

 JANUARY - FEBRUARY GENERAL PMF HYDROGRAPHS

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

0 6 12 18 24 30 36 42 48 54 60 66 72 78 84

Hours

Flow - Cubic Feet per Second

4,630

4,635

4,640

4,645

4,650

4,655

4,660

4,665

4,670

Reservoir Elevation - Feet

Spillway Crest Elevation - 4630

Peak Outflow 69,300 cfs

Peak Reservoir 

Elevation 4644.8

Peak Inflow 71,600 cfs

Big Hole Dam

Figure 1
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-I-12 July 1, 2005 

are based upon a probable maximum 

storm that could occur during January or 

February. The storm is estimated using 

procedures presented in Hydrometeorological Report No. 36, entitled 

“Interim Report, Probable maximum 

Precipitation in California”, which was 

originally issued in October 1961, and was 

revised in October 1969.” 

 “The probable maximum storm 

was distributed into hourly precipitatio0n 

amounts, hourly melting of snowpack was 

calculated using probable maximum storm 

temperature and winds, immediate surface 

runoff losses were subtracted from the 

hourly precipitation and snowmelt, and the 

remaining excess amounts of precipitation 

and snowmelt along with spill from any 

upstream reservoirs were routed through 

the basin stream channels to the basin 

discharge point...” 

 The Hydrotech report is organized 

into three sections describing the basin 

characteristics, the flood analysis, and the 

probable 

maximum 

flood 

calculation. 

The Clark 

Unit Graph 

method (C. O. 

Clark, 

“Storage and 

the Unit 

Graph” ASCE 

Transactions, 

1945.) 

 “Proba

ble maximum 

flood inflows 

to Big Hole 

Reservoir ... 

have been calculated using estimated 

probable maximum precipitation, 

snowmelt associated with the probable 

maximum storm, applying losses based 

upon losses during historic storms, and 

routing the sub-basin runoff to the 

appropriate reservoir.” “Each reservoir 

was assumed to be full at the start of the 

probable maximum flood.” 

 The flood routing from the 

Hydrotech study is presented on Figure 1. 

Peak flood inflow was found to be 71,600 

cfs and peak outflow was 69,300 cfs at a 

maximum reservoir stage of 4,644.8. 

 It is considered that the Hydrotech 

flood study was carried out in accordance 

with previously appropriate standards and 

procedures. However, in May 1996 and 

January 1997, large rainfall floods 

occurred which could affect the unit 

hydrographs and loss rates used to develop 

the probable maximum flood (PMF) from 

the probable maximum precipitation 

(PMP). In 1999, the National Oceanic and 

Atmospheric Administration and the Army 

Corps of Engineers issued 

Hydrometeorological Report (HMR) No. 

Figure 2 

HELL HOLE DAM - SPILLWAY RATING CURVE

4,630

4,632

4,634

4,636

4,638

4,640

4,642

4,644

4,646

4,648

4,650

0 10,000 20,000 30,000 40,000 50,000 60,000 70,000 80,000

Discharge - Cubic Feet per Second

Reservoir Elevation - Feet

Big Hole Dam Spillway Rating Curve 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-I-13 July 1, 2005 

59, which superseded HMR No. 36 on 

which the precipitation developed in the 

Hydrotech 1982 study was based. While 

the precipitation, loss rates and unit 

hydrographs used in the Hydrotech study 

were appropriate and conservative for that 

time, the precipitation is no longer current 

data and the loss rates and unit 

hydrographs should be reviewed as a 

result of the 1996 and 1997 storms. 

 The maximum reservoir stage for 

the routed flood left 5.2 feet of freeboard to 

the nominal dam crest elevation. That 

freeboard is judged to be adequate for a 

dam the height, configuration and material 

of Big Hole Dam but a new flood study 

must be prepared for Big Hole Dam and the 

freeboard adequacy must be reviewed when 

the results of that study are available. 

C. Spillway Rating Curve 

 The spillway rating curve from the 

Hydrotech 1982 report is presented on 

Figure 2. That rating curve has again been 

reviewed and found to be conservative and 

appropriate for the spillway at Big Hole 

Dam. 

Structural Stability 

A. Previous Studies 

 The original design analysis was 

carried out by AB Engineers (ABE) as 

reported in their 1982 Engineering Data 

Report. Harlan Miller Tait Associates 

(HMTA) updated the Stability Analysis for 

the dam as a supplement, dated April 4, 

1984, to the fourth Five Year Dam Safety 

Inspection Report. In the fifth Five Year 

Dam Safety Inspection Report (HMTA, 

1986), the stability analysis was again 

updated using additional seismicity data 

and a more complete analysis. 

 To comply with FERC criteria, a 

Simplified Displacement Analysis (SDA) 

was performed as part of the 1991 Five 

Year Dam Safety Inspection by HTA. 

Data and analysis descriptions from those 

HTA reports are summarized in this 

Appendix. 

B. Method of Analysis 

 1. Static Analysis 

 To analyze the static loading 

conditions, the static stability analysis 

computer program TSLOPE (by TAGA 

Engineering Software Services of San 

Ramon, California) was used. 

 The Spencer's method program option 

was selected to determine the factor of 

safety of a slope using noncircular failure 

surfaces selected by the investigator. The 

sliding mass is divided into slices, and all 

interslice side forces are parallel to each 

other. Spencer's method satisfies 

equilibrium conditions for overall moment, 

individual slice moment, and vertical and 

horizontal forces. 

 2. Earthquake Deformation 

 Analysis 

 For the earthquake deformation 

analysis, a simplified displacement 

analysis (SDA) was carried out. The 

controlling causative fault for the Big Hole 

Dam site is the undefined “local 

earthquake” that is capable of an MCE of 

M=5 at a distance of 5 km that could result 

in a peak ground acceleration (PGA) at 

Big Hole Dam of up to 0.19g (Section IV, 

E. Seismicity) (Sadigh, et.al., 1997). A 

conservative seismicity of 0.2g was used 

in the 1991 analysis. 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-I-14 July 1, 2005 

 The SDA was performed in three 

steps: 

1. A yield acceleration was 

determined using static analysis for 

failure surfaces that would intersect the 

crest and adversely affect the freeboard. 

2. A time-history of accelerations in 

the dam caused by the controlling 

earthquake was calculated for the 

selected yield acceleration surface. 

3. The time-history accelerations that 

exceeded the yield acceleration were 

used to estimate incremental 

displacements, which were averaged to 

calculate the permanent displacement 

along the failure surface. 

 TSLOPE was used to determine the 

yield acceleration for the selected failure 

surfaces. The yield acceleration is defined 

as the pseudostatic seismic coefficient 

necessary to reduce the static factor of 

safety for the selected failure surface to 1.0, 

the point of incipient static failure. The 

Spencer's method program option was 

selected to determine the factor of safety of 

a slope using failure surfaces selected by 

the investigator, as described under Static 

Analysis, above. Various failure surfaces, 

which were selected to intersect the crest of 

the dam and to adversely affect the 

freeboard, were tried until several surfaces 

with lower yield accelerations were found. 

 The program SHAKE, developed at 

the University of California at Berkeley by 

Per Schnabel, John Lysmer, and H. Bolton 

Seed, was used to model the dam's dynamic 

response to site-modified earthquake 

records and to estimate the time-history of 

acceleration on the selected yield 

acceleration surfaces. SHAKE is used to 

compute the dynamic response of a onedimensional system of infinitely long, 

homogenous, visco-elastic layers subjected 

to vertically traveling shear waves. The 

program is based on the continuous 

solution to the wave-equation (Kanai, 

1951) adapted for use with transient 

motions through the use of the Fast Fourier 

Transform Algorithm (Cooley and Tukey, 

1965). The input to the program is discrete, 

consisting of acceleration values spaced at 

a constant time interval. The maximum 

absolute acceleration value and the time 

interval between the acceleration values are 

varied so that the acceleration and 

predominant period of the record matches 

those expected at the site. The earthquake 

records chosen to model the site were the 

1954 Taft earthquake and a synthetic 

motion created by H. B. Seed and I. M. 

Idriss, both scaled to a PGA of 0.20g. The 

output from SHAKE is also in discrete 

format, consisting of acceleration values at 

constant time intervals that represent the 

acceleration time-history curve of points 

within the soil profile chosen by the 

investigator. 

 The dynamic response of the dam 

embankment due to an earthquake with a 

PGA of 0.20g was computed on the 

maximum section at several vertical 

locations in profiles located near the axis of 

the dam, near mid-slope, and near the 

embankment toe (see Figures D-3 and D-4) 

using the program SHAKE. In a trial and 

error process, the material stiffness 

parameters were softened at the failure 

surface until the average acceleration above 

the failure surface was approximately equal 

to the yield acceleration. This procedure 

was required to keep the system in static 

equilibrium. The acceleration time history 

at the failure surfaces at the various profiles 

was then computed, and the maximum 

value is presented on the Figures. 

Typically, the Taft motion produced greater 

accelerations at the failure surfaces. 

 The program DISPLMT, developed 

at Arizona State University by William 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-I-15 July 1, 2005 

Houston and Sandra Houston, was used to 

compute expected permanent 

displacements in the dam embankment 

using the acceleration time-history on the 

selected yield failure surfaces. The 

program estimates permanent 

displacements by double integrating 

accelerations above the yield acceleration 

produced at the failure surface. The 

program utilizes the Newmark numerical 

method to perform the integration, 

determining the area under the portion of 

the acceleration time-history curve that 

exceeds the minimum yield acceleration. 

 The DISPLMT program calculates 

the movements along the failure surface 

using the acceleration time-history 

generated by SHAKE as the response or 

input motion. The yield acceleration is 

assumed constant with respect to time and 

displacement. The calculated displacement 

varies from the near-axis, middle, and toe 

profiles of the embankment slope. 

C. Material Properties

 ABE data (1962 and 1968) indicate 

that the foundation was to be on 

unweathered rock. As-built drawings show 

the foundation to be hard, massive granitic 

rock. For the purpose of the stability 

analysis, it is considered that the foundation 

is substantially stronger than the 

embankment. 

 Materials obtained from the borrow 

areas and used in the core of the 

embankment were tested by ABE for their 

strength characteristics. These tests are 

summarized in their report (ABE, 1962), 

and the design parameters adopted are 

given below. The material strength 

parameters discussed in that report were 

judged conservative and appropriate; 

therefore, those same parameters were used 

in the 1986 and 1991 analysis and are as 

follows: 

Material Properties Used in Analyses 

Parameter Zone 

1 

Zone 

2 - 7 

Moist Unit Weight, γm (pcf) 127 124 

Saturated Unit Weight, γs 

(pcf) 

130 140.4

Friction Angle, Ø (degrees) 33 40 

Cohesion, c (psf) 200 0 

D. Phreatic Surface Assumptions and 

Seepage Pressure Distribution

 The phreatic surfaces and 

hydrostatic forces are based on the water 

levels shown on the stability analysis 

drawings (Figures D-3 and D-4). Uniform 

head loss was used through the core, and it 

was considered that the transition, drain 

material, and rockfill are free draining with 

no head loss in the upstream rockfill and 

transition. In 1984, FERC questioned the 

assumption that the upstream rockfill 

would be free-draining with respect to rapid 

drawdown stability conditions. An analysis 

of the permeability of the upstream shell 

with respect to maximum rate of rapid 

drawdown was made and presented in the 

1986 Five Year Dam Safety Inspection 

report. The assumption that the upstream 

rockfill was free-draining with respect to 

rapid drawdown was affirmed. 

E. Stability Conditions, Minimum 

Criteria, and Calculated Factors of 

Safety 

 The stability conditions, minimum 

criteria, and the calculated factors of safety 

are presented in the following table. The 

minimum criteria factors of safety are from: 

“Engineering and Design Stability of Earth 

and Rockfill Dams,” EM1110-2-1902, by 

the Corps of Engineers, April 1, 1970. 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-I-16 July 1, 2005 

 For the earthquake deformation 

analysis, the criterion adopted is that the 

displacement must not be great enough to 

lower the crest of the dam below the 

maximum normal storage elevation in the 

case of occurrence of the MCE. 

 Stability analyses were performed 

for the maximum dam section with the 

crest at elevation 4660 to allow for the 

original camber. Pool elevations used in 

the analysis are elevation 4640, 10 feet 

above normal maximum operating level, 

PMF pool elevation 4646, and partial pool 

elevations 4340, 4465, and 4565. 

 Analyses were performed for full 

suites of possible failure surfaces for each 

of the loading conditions listed above. For 

each static loading case, we found a surface 

with a lowest factor of safety and bounded 

above and below with more stable slip 

surfaces. To determine the yield 

accelerations for the earthquake 

deformation analysis, the same procedure 

was used. Earthquake time-histories and 

displacement analyses were performed on 

only the most critical surfaces (based on the 

results of the yield acceleration analyses) 

that, based on their location relative to the 

crest, adversely affect the freeboard of the 

dam. 

F. Summary of Results - Embankment

 The detailed results of the analyses 

were presented on Figures VII-1 and VII-2 

in the HTA 1991 report, and those figures 

are reproduced as Figures D-3 and D-4 in 

this Appendix. A Summary of the results is 

presented in the table following. 

 An SDA was performed on the 

downstream failure surface with the lowest 

yield acceleration (Figure D-3, Case 3, 

Surface G). The maximum expected 

displacement was calculated to be 0.01 feet. 

 On the upstream slope, the failure 

surface with the lowest yield acceleration 

(Figure D-4, Case 8, Surface E) was judged 

to not adversely affect the freeboard of the 

dam if displacement occurred. Therefore, 

an SDA was performed on the failure 

surface with next lowest yield acceleration, 

Surface D with water at Elevation 4465. 

The maximum expected displacement was 

calculated to be 0.01 feet. 

 The results of these stability and 

displacement analyses were reviewed as 

part of this (2001) Inspection. The results 

indicate that the dam has satisfactory 

factors of safety for all static loading 

conditions and that the deformations under 

earthquake loading are expected to be small 

and will not reduce the freeboard. The 

seismicity used for the displacement 

analysis is judged to be conservative and 

appropriate.

References 

Cooley, J. W., and Tukey, J. W., 1965, 

“An Algorithm for the Machine 

Calculation of Complex Fourier Series,” 

Mathematics of Computation, Vol. 19, 

No. 90, pp. 297-301. 

Harlan Miller Tait Associates, 1984, 

Stability Investigation, Big Hole Dam. 

Harlan Miller Tait Associates, 1986, FiveYear Dam Safety Inspection Report, Big 

Hole Dam. 

Harlan Tait Associates, 1991, Five-Year 

Dam Safety Inspection Report, Big Hole 

Dam. 

McCreary Koretsky Engineers, 1962, “Big 

Hole Dam Engineering Data,” dated 

March, 1962. 

McCreary Koretsky Engineers, 1968, 

“Placer County Water Agency, Middle 

Fork American River Project, Big Hole 

Dam, Sections and Details,” dated January, 

1968. 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-I-17 July 1, 2005 

Sadigh, K.;Chang; Egan; Makdisi; Youngs 

(Geomatrix) Attenuation Relationships for 

Shallow Crustal Earthquakes Based on 

California Strong Motion Data. 

Seismological Research Letters, Volume 

68, Number 1; January/February 1997, 

Seismological Society of America 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-I-18 July 1, 2005 

Case Slope/Condition Min. Criteria F.S. Min. Computed F.S. 

1 Downstream - Pool Elev. 4640, 10 

feet above Normal Maximum 

Operating level 

1.5 1.47 

2 Downstream/PMF 

Pool Elev. 4646 

1.4 1.47 

3 Downstream - Pool Elev. 4640 with 

Seismic 

N. A. Displacement 0.01 ft. 

Yield Accel. 0.22 

4 Upstream - Pool Elev. 4640 1.5 2.33 

5 Upstream - PMF 

Pool Elev. 4646 

1.5 2.34 

6 Upstream Pool Elev. 4640 with 

Seismic 

N.A. Max. Displacement 0.01 ft.- 

Minimum Yield Accel. 0.30 

7 Upstream: Pool Elev. 4340 

Pool Elev. 4465 

Pool Elev. 4565 

1.5 1.98 

1.88 

2.10 

8 Upstream w/ Seismic: Pool El. 4340 

Pool Elev. 4465 

Pool Elev. 4565 

N. A. Min. Yield Accel's.0.34 

0.25 

0.24 

9* Upstream/Rapid Drawdown from 

Normal Maximum Operating Pool to 

Elev. 4340 

1.2 1.95 

 *Results of Analysis taken from 1986 Five Year Dam Safety Inspection Report 

(HMTA, 1986). 
Chapter 14 Monitoring the Performance of Dams 

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Attachment 2 

Example of Summary 

of 

Embankment Stability Analysis 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-I-20 July 1, 2005 

TABLE 5.2.1 - MATERIAL PROPERTIES

Stability Analysis of Embankments

SAMPLE Project

Material Description Ysat (pcf) Ydry (pcf) Φ' (deg.) c' (tsf) 

Lower Reservoir 

Random Fill 147 135 40 0 

Compacted Rockfill 144 130 45 0 

Filter 141 125 35 0 

Clay Core 134 113 25 0 

Silt Core 140 — 35 0 

Sand/Gravel Foundation 141 125 35 0 

Red Silt Foundation 140 — 40 0 

Berm Fill 132 110 30 0 

Upper Reservoir Dike 

Random Fill 147 135 40 0 

Core/Random Fill 147 135 40 0 

Filter 141 125 35 0 

Sand/Gravel Foundation 141 125 35 0 

Ysat = saturated (total) unit weight (pcf) 

Ydry = dry unit weight (pcf) 

Φ' = effective stress friction angle (degrees) 

c' = effective stress cohesion intercept (tsf) 
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TABLE 5.2.3 - FACTORS OF SAFETY

Lower Reservoir Sta. 12+00

Sample Project

LOWER RESERVOIR DAM EMBANKMENT1 

STA.12+00 

Factor of Safety 

Downstream Slope Upstream Slope Load 

Case 

Description Reservoir 

Elevation 

 (feet) Calc. Req'd Calc. Req'd 

I Normal maximum pool with 

steady seepage 

900.5 1.74 

2.442

1.5 1.95 

2.132

1.5 

II Flood surcharge (PMF) 908.5 1.66 1.4 N/A N/A 

III Rapid drawdown 860.0 N/A N/A 1.51 1.1 

IVa Normal maximum pool 

w/earthquake3

900.5 1.25 1.0 N/A N/A 

IVb Rapid drawdown 

w/earthquake3

860.0 N/A N/A 1.03 1.0 

1. From: Second Safety Inspection Report, Supplement 2, dated February 1988. 

2. Based on infinite slope. 

3. Pseudo-static earthquake coefficient, ah = 0.10g. 
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Chapter 14 Monitoring the Performance of Dams 

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TABLE D.5.2.4 - Factors of Safety

Upper Reservoir Sta. 21 + 50

Sample Project

UPPER RESERVOIR DIKE1 STA. 21+50 

Factor of Safety 

Downstream Slope Upstream Slope 

Load Case Description Reservoir 

Elevation 

(feet) 

Calc. Req'd Calc. Req'd 

I Normal maximum pool with 

steady seepage 

2003 2.31 

2.002

1.5 2.97 

1.242

1.5 

III Rapid drawdown 1940 N/A N/A 1.84 1.1 

IIIa Normal maximum pool 

w/earthquake3

2003 1.56 1.0 N/A N/A 

IIIb Rapid drawdown 

w/earthquake3

1940 N/A N/A 1.24 1.0 

1. From: Second Safety Inspection Report, Supplement 2, dated February 1988. 

2. Based on infinite slope. 

3. Pseudo-static earthquake coefficient, ah = 0.10g. 
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Chapter 14 Monitoring the Performance of Dams 

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Attachment 3 

Example of Summary 

of 

Structural Stability Analysis 
Chapter 14 Monitoring the Performance of Dams 

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VALUES AND ASSUMPTIONS 

STABILITY ANALYSIS 

CONCRETE SECTIONS 

1. Nomenclature: 

Effective Length = Uncracked Portion of Base 

Σ FH = Summation of Horizontal Forces - Kips 

Σ FV = Summation of Vertical Forces - Kips 

Σ MR = Summation of Resisting Moments - Kip-Ft. 

Σ MO = Summation of Overturning Moments - Kip-Ft. 

MR = Factor of Safety Against Overturning 

MO

FH = Coefficient of Sliding 

FV

2. Unit Weight of Concrete: 150 lbs./cu. ft. 

3. Unit Weight of Water: 62.4 lbs./cu. ft. 

4. Uplift Pressure: 

The base pressure was assumed to vary linearly from full head-water pressure at the 

upstream side to full tailwater pressure at the downstream side taken over 100% of the 

base area for each case analyzed. 

For analyses which included a reduction in uplift due to foundation drainage, the 

drains were assumed 50% effective. 

Uplift pressure at drain = TW = 0.5(HW - TW), where HW and TO are the headwater 

and tailwater pressures, respectively. 

Full headwater pressure over 100% of the area was assumed to extend into the concrete 

bedrock contact during any case where an assumed crack formed due to the existence of 

tension stresses in the section foundation. The pressure was assumed to vary linearly 

from full headwater pressure at the upstream end of the uncracked effective base length 

to full downstream tailwater pressure at the downstream face. 

Due to the transient or short-term nature of earthquake loading, the uplift is not changed 

from the pre-earthquake condition due to further propagation of a tensile crack. 

In the event of a tensile crack extending from the heel to the drain', the foundation drains 

were assumed of greater capacity than the crack. This will result in an uplift pressure 

distribution equal to that without the crack (full headwater at heel and TW + 0.5(HWTW) at drain). 
Chapter 14 Monitoring the Performance of Dams 

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5. Lateral Water Pressure: 

Headwater pressures were computed using the full heights of water to headwater 

elevations over the projected height of the structures. Tailwater pressures were 

computed using full heights of water Co tailwater elevations for nonoverflow 

sections and at 60% of full value for cases where deep flow occurs over the ogee 

spillway, in accordance with U.S. Army Corps of Engineers EM 1110-2-2200 

"Gravity Dam Design." 

Tailwater pressures were computed at 100% full value when deep flow occurs over the 

ogee spillway such that the structure becomes completely submerged, in accordance with 

data from U.S. Bureau of Reclamation presented in Open Channel Hydraulics by Chow, 

Ven Te (1959). Figures 14-17 and 14-18. 

6. Ice Load: 

5 kips per linear foot at normal water level. If the normal water level is 

maintained by pin flashboards, water level and ice load are assumed to be at the 

top of the concrete ogee. 

7. Earthquake: 

An acceleration of 0.10 g was applied in a horizontal direction. 

The hydrodynamic force was determined using a method presented in Design of 

Small Dams, USBR, pages 336-338. 

8. Resistance to Sliding: 

Where the ratio of FH/FV is greater than 0.75, the shearing resistance of the foundation 

to horizontal movement must be investigated using the Shear Friction Formula. 

The factor of safety against sliding is determined by the Shear Friction Formula 

as: 

Sg-f = f V + C A

 H 

where: 

f = Coefficient of the angle of internal friction of foundation material (Tan Φ = 0.75) 

ΣV = Summation of vertical forces 

c = Unit shearing strength at zero normal load on foundation material (0.192 ksi) 

A = Area of potential failure plane (area of base in compression) 

ΣH = Summation of horizontal forces 

According to U.S. Army Corps of Engineers, Engineering Technical Letter No. 1110-2-256, 

dated June 24, 1981, which is intended to supersede portions of EM 1110-2-2200 "Gravity 

Dam Design" criteria, the minimum allowable Ss-f for static loading conditions is 2.0, and for 

seismic loading conditions, 1.3. Typical values of "f" and "c" were taken from "The Sliding 

Stability of Dams" by Harald Link in Water Power Magazine, March, April & May, 1969. 
Chapter 14 Monitoring the Performance of Dams 

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9. Bearing Pressure: 

Maximum bearing stress = 20 tsf on bedrock (278 psi). 
Chapter 14 Monitoring the Performance of Dams 

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SAMPLE PROJECT 

CASES USED IN STABILITY ANALYSIS OF CONCRETE STRUCTURES 

CASE I NORMAL OPERATING WATER LEVELS 

H.W.L = 242.0 

T.W.L = 157.0 

CASE II NORMAL OPERATING LEVELS WITH ICE 

H.W.L = 242.0 

T.W.L = 157.0 

ICE LOADS 5 kips/ft 

CASE III NORMAL OPERATING WATER LEVELS WITH EARTHQUAKE 

Water Levels same as CASE I 

Horizontal acceleration due to earthquake is 0.10g 

CASE IV PROJECT DESIGN FLOOD 

H.W.L = 249.0 

T.W.L = 157.0 
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Chapter 14 Monitoring the Performance of Dams 

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Chapter 14 Monitoring the Performance of Dams 

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SAMPLE PROJECT 

STABILITY SUMMARY 

CONDITION BASE BASE STRESS (psi) 

TOT LEN CRK LEN EFF LEN 

FH 

(kips) 

FV 

(kips) 

FH

FV 

S s-f Resultant from 

Downstream 

MR MO MR

MO Upstream Downstream

Spillway 

CASE I 87.0 0.0 87.0 15170 30880 0.49 10.94 42.24 2112000 807300 2.62 37.5 44.7 

CASE II 87. 0 0.0 87.0 15170 30880 0.50 10.73 41. 38 2112000 834000 2.53 35.1 47.1 

CASE III 87.0 0.0 87.0 20440 30880 0.66 8.12 36.37 2112000 988600 2.14 20. 9 61.3 

CASE IV 87.o 0.0 87.0 17610 29870 0.59 9.38 38.12 2122000 987000 2.15 25.3 54.7 

North Bulkhead 

CASE I 95.0 0.0 95.0 18600 45210 0.41 10.21 37.86 3147000 1209000 2.60 38.9 71.2 

CASE II 95.0 0.0 95.0 18910 45210 0.42 10.04 42.20 3147000 1239000 2.54 36.6 73.5 

CASE III 95.0 0.0 95.0 26010 45210 0.58 7.3 36.33 3147000 1505000 2.09 16.2 94.0 

CASE IV 95.0 0.0 95.0 21320 43980 0.48 8.86 38.76 3147000 1430000 2.20 25.2 62.1 

Non-Overflow 

Section 

 

CASE I 75.6 0.0 75.6 18590 37710 0.49 8.20 32.36 2249000 1028000 2.19 32.8 82.6 

CASE II 75.6 0.0 75.6 18890 37710 0.50 8.07 31.55 2249000 1058000 2.12 29.1 86.3 

CASE III 75.6 1.2 74.4 25100 37710 0.67 5.99 24.80 2249000 1513000 1.71 0.0 117.3 

CASE IV 75.6 0.0 75.6 21310 38670 0.55 7.18 28.80 2263000 1147000 1.97 17.0 101.1 
Chapter 14 Monitoring the Performance of Dams 

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Attachment 4 

Example of Summary 

of 

Hydrologic and Hydraulic Information 
Chapter 14 Monitoring the Performance of Dams 

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SAMPLE PROJECT
Chapter 14 Monitoring the Performance of Dams 

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SAMPLE PROJECT 

SPILLWAY RATING CURVE

 
Chapter 14 Monitoring the Performance of Dams 

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SAMPLE PROJECT 

TAILWATER RATING CURVE 

 
Chapter 14 Monitoring the Performance of Dams 

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Attachment 5 

Example of Summary 

of 

Instrumentation and Surveillance Information 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-I-39 July 1, 2005 
Chapter 14 Monitoring the Performance of Dams 

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Chapter 14 Monitoring the Performance of Dams 

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TABLE 1 - PIEZOMETER READINGS 

PRESS 

PIEZO 

ELEV PRESS 

PIEZO 

ELEV 

PIEZO DATE (psi) (ft) PIEZO DATE (psi) (ft) 

P2-3 1/30/1997 0.0 1685.0 P4-4 8/30/1997 37.0 1770.5 

P2-3 2/28/1997 0.0 1685.0 P4-4 9/30/1997 38.0 1772.8 

P2-3 3/30/1997 0.0 1685.0 P4-4 10/30/1997 36.0 1768.2 

P2-3 4/30/1997 0.0 1685.0 P4-4 11/30/1997 36.0 1768.2 

P2-3 5/30/1997 0.0 1685.0 P4-4 12/30/1997 36.0 1768.2 

P2-3 6/30/1997 0.0 1685.0 P4-4 1/30/1998 36.0 1768.2 

P2-3 7/30/1997 0.0 1685.0 P4-4 2/28/1998 35.0 1765.9 

P2-3 8/30/1997 0.0 1685.0 P4-4 3/30/1998 35.0 1765.9 

P2-3 9/30/1997 0.0 1685.0 P4-4 4/30/1998 36.0 1768.2 

P2-3 10/30/1997 0.0 1685.0 P4-4 5/30/1998 36.0 1768.2 

P2-3 11/30/1997 0.0 1685.0 P4-4 6/30/1998 36.0 1768.2 

P2-3 12/30/1997 0.0 1685.0 P4-4 7/30/1998 36.0 1768.2 

P2-3 1/30/1998 0.0 1685.0 P4-4 8/30/1998 36.0 1768.2 

P2-3 2/28/1998 0.0 1685.0 P4-4 9/30/1998 36.0 1768.2 

P2-3 3/30/1998 0.0 1685.0 P4-4 10/30/1998 36.0 1768.2 

P2-3 4/30/1998 0.0 1685.0 P4-4 11/30/1998 36.0 1768.2 

P2-3 5/30/1998 0.0 1685.0 P4-4 12/30/1998 35.0 1765.9 

P2-3 6/30/1998 0.0 1685.0 P4-4 1/30/1999 35.0 1765.9 

P2-3 7/30/1998 0.0 1685.0 P4-4 2/28/1999 36.0 1768.2 

P2-3 8/30/1998 0.0 1685.0 P4-4 3/30/1999 35.0 1765.9 

P2-3 9/30/1998 0.0 1685.0 P4-4 4/30/1999 35.0 1765.9 

P2-3 10/30/1998 0.0 1685.0 P4-4 5/30/1999 35.0 1765.9 

P2-3 11/30/1998 0.0 1685.0 P4-4 6/30/1999 36.0 1768.2 

P2-3 12/30/1998 0.0 1685.0 P4-4 7/30/1999 36.0 1768.2 

P2-3 1/30/1999 0.0 1685.0 P4-4 8/30/1999 36.0 1768.2 

P2-3 2/28/1999 0.0 1685.0 P4-4 9/30/1999 36.0 1768.2 

P2-3 3/30/1999 0.0 1685.0 P4-4 10/30/1999 36.0 1768.2 

P2-3 4/30/1999 0.0 1685.0 P4-4 11/30/1999 36.0 1768.2 

P2-3 5/30/1999 0.0 1685.0 P4-4 12/30/1999 35.0 1765.9 

P2-3 6/30/1999 0.0 1685.0 P4-4 1/27/2000 36.0 1768.2 

P2-3 7/30/1999 0.0 1685.0 P4-4 2/29/2000 36.0 1768.2 

P2-3 8/30/1999 0.0 1685.0 P4-4 3/31/2000 36.0 1768.2 

P2-3 9/30/1999 0.0 1685.0 P4-4 4/27/2000 36.0 1768.2 

P2-3 10/30/1999 0.0 1685.0 P4-4 5/30/2000 36.0 1768.2 

P2-3 11/30/1999 0.0 1685.0 P4-4 6/27/2000 36.0 1768.2 

P2-3 12/30/1999 0.0 1685.0 P4-4 7/31/2000 36.0 1768.2 

P2-3 1/27/2000 0.0 1685.0 P4-4 8/30/2000 36.0 1768.2 

P2-3 2/29/2000 0.0 1685.0 P4-4 9/29/2000 37.0 1770.5 

P2-3 3/31/2000 0.0 1685.0 P4-4 10/30/2000 36.0 1768.2 

P2-3 4/27/2000 0.0 1685.0 P4-4 11/29/2000 36.0 1768.2 

P2-3 5/30/2000 0.0 1685.0 P4-4 12/27/2000 35.0 1765.9 

P2-3 6/27/2000 0.0 1685.0 P4-4 2/1/2001 35.0 1765.9 

P2-3 7/31/2000 0.0 1685.0 P4-4 2/28/2001 35.0 1765.9 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-I-42 July 1, 2005 

Plot B-5 - Dam Embankment Piezometers in Core

1600

1625

1650

1675

1700

1725

1750

1775

1800

1825

1850

1875

1900

1925

1950

1975

2000

Jan-92

Feb-93Mar-94

Apr-95

May-96

Jun-97

Jul-98

Sep-99

Oct-00Nov-01

Dec-02

Date

Elevation (FT)

P2-3 P4-4 RESRNDBT

PLOT of PIEZOMETER READINGS 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-I-43 July 1, 2005 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-I-44 July 1, 2005 

SAMPLE PROJECT 

Summary of Vertical Movements (Spring 1993 to Spring 1996) 

Point To 

 From

F93 95% 

 A=> Conf. Region 

 (mm) (mm)

S94 95% 

 A=> Conf. Region 

 (mm) (mm)

F94 95% 

 A=^ Conf. Region 

 (mm) (mm)

SM1 S93 

 Incremental

 -0.278 1.134 

 -0.278 1.134

 -0.426 1.159 

 -0.444 1.133

 -0.212 1.143 

 0.511 1.142

SM2 S93 

 Incremental

 -0.641 1.130 

 -0.641 1.130

 -0.502 1.157 

 -0.159 1.130

 -0.330 1.138 

 0.470 1.138

SM3 S93 

 Incremental

 -0.672 1.130 

 -0.672 1.130

 -0.609 1.158 

 -0.234 1.128

 -0.105 1.136 

 0.801 1.135

SM4 S93 

 Incremental

 -0.94 1.140 

 -0.94 1.140

 -0.946 1.185 

 -0.359 1.140

 -0.364 1.145 

 0.936 1.145

SM5 S93

 Incremental

 -1.388 1.138 

 -1.388 1.138

 -0.853 1.185 

 -0.183 1.138

 -0.399 1.143 

 0.807 1.143

SM6 S93 

 Incremental

 -0.887 1.136 

 -0.887 1.136

 -0.548 1.184 

 -0.014 1.137

 -0.278 1.140 

 0.623 1.141

SM7 S93 

 Incremental

 -0.893 1.135 

 -0.893 1.135

 -0.119 1.184 

 0.421 1.135

 -0.196 1.138 

 0.276 1.138

WP1 S93 

 Incremental

 0.210 0.843 

 0.210 0.843

 -0.209 0.750 

 -0.790 0.843

 -0.111 0.853 

 0.468 0.853

WP2 S93 

 Incremental

 0.057 0.845 

 0.057 0.845

 1.224 1.184 

 0.815 0.845

 0.390 0.848 

 -0.482 0.848

MM6 S93 

 Incremental

 -0.236 0.777 

 -0.236 0.777

 0.188 0.672 

 0.023 0.777

 -0.228 0.781 

 -0.015 0.782

MM7 S93 

 Incremental

 -0.031 0.124 

 -0.031 0.124

 0.022 0.078 

 -0.048 0.124

 -0.051 0.125 

 0.028 0.125
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-I-45 July 1, 2005 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-I-46 July 1, 2005 

SAMPLE PROJECT 

Summary of Horizontal Movements (Spring 1993 to Spring 1996) 

Point To 

 From

F93 95% 

 A=> Direction Conf. Region 

 (mm) (degrees) (mm)

S94 95% 

 A=> Direction Conf. Region 

 (mm) (degrees) (mm)

F94 95% 

 A=^ Direction Conf. Region 

 (mm) (degrees) (mm)

SM1 S93 

 Incremental

 1.955 76 1.85 

 1.955 76 1.85

 0.846 329 1.751 

 2.813 290 2.073

 0.935 352 1.582 

 0.752 149 1.746

SM2 S93 

 Incremental

 2.463 39 1.752 

 2.463 39 1.752

 1.227 356 1.742 

 1.933 268 2.182

 1.389 0 1.606 

 0.627 165 1.833

SM3 S93 

 Incremental

 2.277 35 1.793 

 2.277 35 1.793

 1.593 357 1.782 

 1.677 279 2.264

 0.981 13 1.658 

 1.353 165 1.922

SM4 S93 

 Incremental

 1.797 32 1.802 

 1.797 32 1.802

 1.286 12 1.749 

 0.943 280 2.157

 1.028 331 1.742 

 1.204 218 1.682

SM5 S93

 Incremental

 1.004 36 1.798 

 1.004 36 1.798

 0.739 96 1.982 

 0.555 187 2.071

 0.776 351 1.723 

 0.904 291 2.11

SM6 S93 

 Incremental

 1.487 84 1.447 

 1.487 84 1.447

 0.935 64 1.376 

 0.947 300 1.868

 1.776 356 1.705 

 1.361 314 1.719

SM7 S93 

 Incremental

 2.942 57 1.779 

 2.942 57 1.779

 0.288 124 1.875 

 2.896 235 1.867

 2.003 2 1.625 

 1.877 354 1.762

WP1 S93 

 Incremental

 2.355 56 1.821 

 2.355 56 1.821

 0.63 299 1.318 

 2.839 265 1.96

 1.089 33 1.197 

 1.268 102 1.375

WP2 S93 

 Incremental

 3.648 133 1.781 

 3.648 133 1.781

 1.946 214 1.645 

 3.953 282 1.848

 2.515 277 1.591 

 2.291 320 1.734

MM6 S93 

 Incremental

 0.557 215 1.308 

 0.557 215 1.308

 0.84 299 1.308 

 0.988 312 1.447

 0.236 231 1.204 

 0.906 131 1.337

MM7 S93 

 Incremental

 1.053 289 1.426 

 1.053 289 1.426

 0.997 158 1.374 

 1.152 147 1.73

 0.708 211 1.115 

 0.312 234 1.29

MM8 S93 

 Incremental

 0.346 249 0.961 

 0.346 249 0.961

 4.087 242 3.494 

 0.605 245 1.052

 0.395 262 0.916 

 0.732 52 0.907

MM9 S93 

 Incremental

 0.18 63 1.458 

 0.18 63 1.458

 -0.218 159 0.651 

 1.468 87 1.808

 0.357 107 1.511 

 1.315 255 1.498
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-I-47 July 1, 2005 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-I-48 July 1, 2005 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-I-49 July 1, 2005 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-I-50 July 1, 2005 

Attachment 6 

Example of Document Control Log Sheets 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-I-51 July 1, 2005 

THIS 

SUPPORTING TECHNICAL INFORMATION 

IS THE PROPERTY OF 

LITTLE POWER COMPANY 

111 MAIN STREET 

ANYTOWN, USA 

(If this STI is lost, 

finder please return to 

the above address) 

ISSUED TO: 

___________________________________ 

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STI NO. ______________________ 

The person or organization to whom this manual 

is issued, is responsible for its safekeeping and 

its being kept up to date. 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-I-52 July 1, 2005 

LITTLE POWER COMPANY 

Big Power Project: FERC No. XYZ 

Supporting Technical Information Change No. ____ 

Section Instructions Summary of Changes 

Table of Contents Remove previously issued 

Table of Contents (6/18/2002) 

and replace with 

Table of Contents dated 

1/22/2003 rev. 1 

Updates revision numbers 

and effective dates 

Section 1 

Failure Modes Analysis 

Insert Addenda 1, 

Failure Mode 7 

dated 1/2/2003 

Addends Failure Modes 

Analysis Report to include 

new Failure Mode 7 
Chapter 14 Monitoring the Performance of Dams 

Revision 1 14-I-53 July 1, 2005 

SUPPORTING TECHNICAL INFORMATION 

REVISION LOG NOTICE 

BIG POWER PROJECT 

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