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## CHAPTER 14

DAM SAFETY PERFORMANCE MONITORING PROGRAMChapter 14 Monitoring the Performance of Dams

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## 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 Analys is report as a support document to the conduct of the FERC Part 12D Dam Safety Inspection ...................................... 27 14.3.6 Updating the Potential Fa ilure 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 Interrela tionship 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 Identific ation 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 Understa ndings - Example Write Up Appendix F ..................................................................................................................... 14-F-1 Estimated Time Requirements Appendix G..................................................................................................................... 14-G-1 Dam Safety Performance M onitoring Program Process Appendix H..................................................................................................................... 14-H-1 Part 12D Safety Inspection Report Outline Appendix I ..... ............................................................................................................... .. 14-I-1 Guidelines for Supporting Technical InformationChapter 14 Monitoring the Performance of Dams

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## 14.1 INTRODUCTION

The guidelines presented in this chapter prov ide recommended procedures and criteria to develop a Dam Safety Performance Monitoring Program based upon "failure mode thinking" to assist in reviewing and evaluating the safe ty 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 th e 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 c onducted 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 SM P is developed. The SMP defines the appropriate monitoring for the water retain ing project works based upon the PFMA. An integral part of the SMP is the integration of the licen see’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 Consu ltant’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 Surv eillance 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 co rrects, clarifies, or supplements the understanding of potential fa ilure modes and scenarios;

• Archiving the key technical informati on 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 m odes that present the greatest risk to the safety of the dam; and

• Developing operating procedures to assure that there ar e no weak links that could lead to mis-operation failures. Although the traditional emphasis of Part 12D inspectio ns has been on project dams, 18CFR12.32 specifically states that all project works with the exception of transmission and transformation facilities and gene rating equipment are to be in cluded in the inspection by theChapter 14 Monitoring the Performance of Dams

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0 independent consultant. In addi tion, certain other water retaini ng 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 th e 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 commo nly 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 inform ation 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 unsatisf actory performance of the dam or a portion thereof. The dam does not have to complete ly 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 ga te failure, are also considered. Potential Failure Mode Analysis (PFMA) The process utilized to determine the Pote ntial Failure Modes pertinent to the dam under investigation. Major Findings and Understandings (MFU) The most significant items learned by the pa rticipants in the PFMA session regarding such items as the construction, perfor mance, 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 Ca tegory I and appropria te Category II and Category III failure modes and be designed to minimize the risk associated with these potential failure modes by providing early wa rning if the failure modes become active

or worsen.Chapter 14 Monitoring the Performance of Dams

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## 14.2 SUPPORTING TECHNICAL INFORMATION

14.2.1 Purpose The purpose of the Supporting Technical Info rmation document (STI) is to summarize those project elements and details that do not change signifi cantly between quinquennial FERC Part 12D Independent Consultant Safety Insp ection 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 inform ation 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 th e project and project works

• A summary of the constructi on history of the project

• Summaries of Standard Operating Procedures

• A description of geologic conditi ons affecting the project works

• A summary of hydrologic a nd hydraulic information

• Summaries of instrumentation and surveilla nce 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 ne w data or analyses become available they are appended to the initial STI and outdated mate rial 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 w ith the Part 12D inspection report outline to be sure the Independent Consultant will have al l 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 inse rt 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 re port, either a digital c opy of the most current STI in *.pdf, *.jpg, *.tif, or othe r acceptable formats (check w ith 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.Chapter 14 Monitoring the Performance of Dams

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0 Licensees should include complete copies of the reference documents referred to in the STI, or, in some instances, all documents review ed in the PFMA session, in CD or DVD format with the STI document. The complete STI should be reviewed and reprin ted at least every 15 years and hard copies submitted with the Part 12D report. The initial STI should be provided to the Indepe ndent 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 li censee 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.Chapter 14 Monitoring the Performance of Dams

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## 14.3 POTENTIAL FAILURE MODE ANALYSIS

14.3.1 Introduction
The FERC in association with Dam Owners a nd the Independent Consultants who perform the Part 12D Dam Safety Evaluations have de veloped 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 regul ated 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 Failu re Mode Analysis, as outlined below, will serve as the focal point and linking feat ure 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 a nd project works safety evaluation. Traditional dam and project works safety evaluations ha ve tended to focus on a limited number of “standards based” concerns such as hydraulic cap acity of spillways and st ability 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 An alysis 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, m onitoring 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 safe ty 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 dur ing subsequent Part 12D inspections. A supplementary PFMA should also be conducted after failure of a st ructure or prior to major modifications or remedial work on a st ructure. The purpose of the supplementary PFMA is to explore the reasons for the failure or evaluate the recommended modification/remediation plan prior to constr uction. 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 alternativ e 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 a nd supporting materials to enable a Potential Failure Mode Analysis to be carried out, as follows:

• A brief description of a Pote ntial Failure Mode Analysis;

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

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

o A brief statement of the expecta tions and requirements for a PFMAChapter 14 Monitoring the Performance of Dams

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0 o Detailed, step by step guidance for th e 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 Surveillan ce and Monitoring Plan for the project;

• A description of the process for “upda ting of the PFMA” by future Part 12D Independent Consultants, the licensee or the FERC; and

• Appendices containing supporting material s and example products from a PFMA.
14.3.2 Description A Potential Failure Mode Analysis is an info rmal 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 st ructure. It is base d on a review of existing data and information, first hand input from fi eld and operational personn el, 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 insi ght 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 in tentionally seeking input from the diverse team of individuals who have information on the pe rformance and operation of the dam. A PFMA includes and uses all of the available data and informati on from standard engineering analyses of an existing dam. A PFMA should be viewed as a supplem ent 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 ex amination 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 fa ilure 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 da ta, information or analyses necessary to evaluate dam safety and each potential failure mode;

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

• Document the results of the study for guidanc e on future dam safety inspections. By updating the documentation (as a living doc ument), the benefit of increased understanding and insight lives on.Chapter 14 Monitoring the Performance of Dams

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0 14.3.3 Key Goals and Typical Outcomes The primary product and the main focus of a Pote ntial 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. opera tions, 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 iden tify why this potential failure mode is being considered for this site. Also the significan ce of the potential failure modes for the site in terms of the need for awareness, monitoring a nd surveillance, analyses and investigation or for making operational changes, st ructural repairs or modifications is discussed. Example descriptions of potential failure modes that ha ve come from prior potential failure mode analyses are provided in Appendi x A for a potential operational type potential failure mode and for a potential piping type failure. The Potential Failure Mode Analysis (PFMA) pr ocess is not a substitu te for, but rather a guide to help focus, periodic, comprehensive, dam safety inspections. Both activities require and benefit from a comprehens ive review and discussion of all available information (historic records and photos, engi neering analyses, previous insp ection 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 part icipate 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 ca rrying out a PFMA in the manner described in this guidance document.

• The process of searching out all the info rmation about the dam for the specific purpose of identifying potential failure m odes (plus the involvement of a diverse group of people in the PFMA process), t ypically results in uncovering data and information that most personnel currently i nvolved in the dam’s safety evaluation had not been aware of. Frequently this informa tion 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 prev iously perceived from the standpoint of consequence, remoteness or physical possibility.Chapter 14 Monitoring the Performance of Dams

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0 • Enhancements to the monitoring and visu al 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 te nder to the owner’s dam safety program manager), become aware of the dam’s mo st significant vulnerabilities and the relationship of the surveilla nce 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 a nd Monitoring Plan, operations, structure response or emer gency 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, pe riodic reviewers, insp ectors, designers and others) about:

1. The potential failure modes for this dam;

2. How monitoring, including use of specific in strumentation and visual surveillance is used to look for specific symptoms, beha viors or evidence that might warn of a developing failure for the identi fied potential failure modes;
3. How “general health” monitoring (e.g., cres t 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, unusua l) 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” Pote ntial 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, fo r a PFMA to be comprehensive, consistent, and complete. However, in completing these sp ecific steps it is very important that the principles of the process be understood and follo wed 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 at titude toward identifying and understanding potential failure modes and failure scenarios;

• Dedication of the assigned persons to th e reviewing / reading of all the background information on the dam prior to the PFMA session;Chapter 14 Monitoring the Performance of Dams

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0 • Diversity in input to the process – field personnel, ope rations 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 thei r normal hats and focus on what the data, information, and experience / knowledge of i ndividuals can teach us about the dam.

Overall Guidance – Potential Failure Mode Analysis Expectations / Requirements

1. Collect all data, studies and information on th e investigation, design, construction, analysis, performance and operation of the project. All studie s and investigation reports existing that relate to the ongoing safety of the dam must be included and reviewed and evaluated. A listing should be ma de 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 fo r potential failure modes, structural and geologic conditions, review ope rations, 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 bac kground 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 mode s recognized and being appropriately monitored by visual surveillan ce 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 e nhancement and structural remediation

measures.
3. Brainstorm potential failure modes and fa ilure 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 a dverse / 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 failu re mode for consideration by the owner and the Independent Consultant in the Part 12D inspection and report.Chapter 14 Monitoring the Performance of Dams

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0 5. Document the analysis, including immedi ately recording the major findings and understandings from the brainstorming session.

Procedural Guidance – Potential Failure Mo de 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 licen see 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 Pote ntial Failure Modes - (Note that the Surveillance and Monitoring Plan for Id entified Potential Failure Modes is provided to the owner by the Independent Consultant in the Part 12D report) Step 7 Documentation of the PFMA and Su rveillance and Monitoring and/or Risk Reduction opportunities (I ndependent Consultant)

The time frame for completing the documenta tion of the PFMA session is provided in the Table below.Chapter 14 Monitoring the Performance of Dams

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0 Action Item Time Frame 1) Independent Consulta nt (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 draf t PFMA report and sends it to the Facilitator for peer review. Within 30 days of the PFMA session. 4) Facilitator complete s 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 PFM A, 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 Fa ilure Mode Analysis Team Participants The potential failure mode analysis participants (team members) consist of all those who will participate in the brainstorming session in wh ich potential failure modes are identified, defined, discussed and categorized. Fundame ntally these are persons who have past experience with the design, cons truction, analyses, performance and operation of the dam or who will obtain knowledge of th e 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 proce ss (and it is a very significant advantage ) is that more ideas and more questions are put fo rward; more knowledge and information is available; and a greater diversity of opinion is input to the process. Some of the team members have specific ro les and responsibilities a nd need to have the requisite experience and capability to fulfill thes e roles. The roles and requirements of the team members are given below:Chapter 14 Monitoring the Performance of Dams

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0 Team Leader - The dam owner would designate one of the participants as the team leader, responsible for coordination activiti es – including collecti on of the background information.

Core Team - At least four participants are de signated 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 Owner s 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 Poten tial 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 r eading 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 materi al”. 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 ow ner should be designated to pa rticipate 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 know ledge and experience related to dam safety evaluations. It is especially help ful to have persons who have interest and knowledge related to dam failures and w ho have an inquisitive / investigative personality (they think like coroners or detectives).

• The Facilitator should, in ge neral, 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 vigor ous look at the structure. Dam owner representatives who have the knowledge, skil l and interest and who gain the requisite experience to serve as F acilitators 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.Chapter 14 Monitoring the Performance of Dams

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0 • The Independent Consultant may or may not be new to the facility, but like the Facilitator must have extensive experien ce 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 Faci litator should not be from the same organization / firm.

• Persons who had experience with the orig inal design and/or construction of the project can provide invaluable insights and data. Wher ever 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 or ganization has sufficient resources, the dam safety inspector responsible for the s ubject 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, geotechni cal engineer or engineeri ng geologist with a broad background and experience in dam safety e ngineering and experi ence in performing a PFMA similar to that described in this gui dance. A recommended qualification for the Facilitator is that th e proposed Facilitator for a project should have been involved in an actual PFMA of the nature descri bed in these guidelines eith er 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 th e case. As an a lternative to actual experience participating or facilitating a PFMA, the propos ed 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 th at if the Facilita tor, working with the assembled PFMA team, does not accomplish the goals of the PFMA, which is identifying and obtaining a clear understanding of each da m’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 designate d Core Team member, a dam experienced engineering geologist should pa rticipate in the PFMA and should review all geological background material, make appropriate obs ervations during the field review and participate in discussions of foundation related PFMs.Chapter 14 Monitoring the Performance of Dams

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0 In formulating the team it is important to include those individuals with intimate knowledge of the project operations and structur es, especially the senior dam tenders and those responsible for collecting monitoring da ta. 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 incr easing the general awar eness of dam safety issues by sharing knowledge at a ll levels. Experience has shown th at 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 actual ly done or known in practice. The field personnel also can verify data and in formation discussed in the session.

Supplemental Resources - In addition to the team participants there are other people who have specific technical knowledge or expe rience 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-tectoni c specialists, hydrologists, stru ctural engineers, electrical engineers, mechanical engineers, geotechni cal engineers, field personnel, inspectors, instrumentation personnel, emergency prepared ness 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 e ngineer/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 conjuncti on with the Facilitator, FERC inspector, Independent Consultant, projec t staff, and geologist, collec ts 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 Se ssion. The general rule is: collect all information on the project. If there is a question about th e need to bring / collect certain material, the Facilitato r and owner should discuss this in advance. The types of material which should be coll ected (if available) include but are not limited to the items listed below.

• Any FERC or state agency construction in spection 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 engi neering analyses, including stability and stress analyses

• The most recent monitoring and instrume ntation 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 extr emely valuable and should be availableChapter 14 Monitoring the Performance of Dams

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0 at the PFMA session. The licensee or cons ultant should also provide verification that the instrumentati on is properly functioning.

• The most recent surveys for each of the project structures (i.e. horizontal and vertical survey data). This should prefer ably be the survey that was conducted as part of the current Part 12D inspection. A detailed survey of the crest of all structures including principa l and emergency spillway cr est elevations to confirm the freeboard assumed in the discussions . Elevations of natural grounds that could result in overflows ar ound the structures should be considered. Also, the datum of the project relative to surro unding grounds should be stated (i.e., conversion of project records to NGVD)

• Current hydrologic studies a nd the associated flood r outings and any hazard / consequence analyses

• The current Emergency Action Plan

• The most up-to-date aerial photograph s of the downstream areas that could potentially be impacted by failure of the project structures.

• Original and subsequent modification construction de sign reports, as-builts, photographs

• Boring logs

• The most recent underwater inspection report. This should preferably be the underwater inspection that was conducte d as part of the current Part 12D inspection.

• Recent and historic meteorological and pe rtinent river records from project or nearby dam or gage records ( http://waterdata.usgs.gov/nwis ).

• Operation records(particular ly historic) of primary and secondary (e.g. fuse plugs) spillway discharge rating curves, m echanism and response times for opening (i.e., stanchion gates, bulkheads, flashboard s, 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, meteor ological and/or stream flow data should be reviewed to ensure that previous fi ndings 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 se ssion 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 a nd 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.Chapter 14 Monitoring the Performance of Dams

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0 The owner should establish a means to retain / archive all the in formation 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 re view and to refresh knowledge of the dam and stimulate “potential failure m ode thinking” by all pa rticipants 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 a nd the Core Team (and any other proposed participants) for familiarization with the proj ect 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 w ould lead to uncontrolled release of the reservoir or other incidents, conditions or situations that would have an adverse impact. This review of materials is sche duled to occur followi ng the site visit and discussion with project personnel.

4. A questionnaire on potentia l failure mode identificat ion and surveillance and monitoring is to be sent by the Team L eader 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 informati on). Note that prior to the PFMA session, team participants, other than the Core Team members, are only required to complete this questionnaire, review thei r own files (re-acquaint them selves relative to the work within their area of expertise), and bring their hist oric 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, incl uding the geologist if present and the owner’s personnel) are first assembled at th e 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 a nd 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 operati ng staff probably is unfamiliar with the process. Therefore, a qui ck review of the process to make sure everyone is on board is a good id ea. Likewise when the Core Team gathers to do the reading, a quick discussion of the plan and objectives of the read ing 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 th e owner’s personnel andChapter 14 Monitoring the Performance of Dams

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0 the Core Team. The basic purposes of th is 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 employ ees that they plan to have participate in the PFMA also participate in the site review.

2. Typically the site review performed in a ssociation with the Potential Failure Mode Analysis should be scheduled just befo re the Core Team members review the background materials. Such a schedule take s greatest advantage of the interaction between potential failu re mode analysis and site visitation.
3. The site review should incl ude the opportunity to disc uss 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 b ackground materials after a physic al review of the site.

Step 4 – Comprehensive Review of the Background Material Prior to the Core Team beginning its review of the background mate rial, 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 revi ew 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. Th e 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 af ternoon/evening of the s ite review and evening before PFMA as necessary. This revi ew is essential to an effective PFMA. )
Step 5 - Conduct the Potential Fa ilure Mode Analysis Session A brief description of the Pote ntial Failure Mode Analysis Se ssion is given below – a more comprehensive example of a typical session is gi ven in Appendix C. It is important for the Facilitator to involve all partic ipants in the discussions and give everyone an opportunity to provide their knowledge, understanding and views on the potential failure modes, consequences and possible risk re duction actions / measures.
Just as discussed for the site review and the reading session, the Facilita tor, at the outset of the PFMA session, should give some introductory remarks about the PFMA session, (goals,Chapter 14 Monitoring the Performance of Dams

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0 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 potenti al failure mode is to be categorized), and should discus s with the entire team that the product of the exercise is not a decision document but rather an informati onal, 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 wo rks so efficiently and effectively)

1. Consider the possibilities for failure, load ing by loading condition (static reservoir, hydrologic, seismic, ice, debris impact and any other loading releva nt 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 sy stem operation aspects (communication and response [i.e., personnel, remote telemetr y], 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 se ssion vary and can take several paths. If a candidate potential failure mode is suggested, it is discussed until a clear characterization of the potent ial failure mode and failure scenario is developed. Once a candidate potential failure mode is fu lly 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 phas e” (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 likel y or not likely to develop and what other adverse or positive aspects exists relative to the potential failure mode. Sometimes this preliminary or developmenta l discussion of the initial suggestion may lead to two or more separate or relate d potential failure modes, which are then developed separately. Sometimes an item or issue brought up re lates to dam safet y, surveillance and monitoring or is of general concern but is recognized by all as something that does not or would not result in failu re of the dam or other wate r retaining structure at the project and is thus not a candi date 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 Disc ussed” 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 preliminar y 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 identifie d for discounting theChapter 14 Monitoring the Performance of Dams

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0 viability of the potential failure mode ( based on information currently available) and there is team consensus on this findi ng, then the candidate mode along with the fundamental reason(s) for its lack of vi ability or credibility is documented as “Category IV” (see Table 1 below) and sub-steps 3-5 below are skipped. The Facilitator should move to fu ll consideration of the Potential Failure Mode (sub-steps 3-5) if there is not clear consensus am ong the PFMA team on the candidate mode’s lack of credibility. One exception to the general rule of not carryin g 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 I ndependent Consultant’s Safety Inspection, Potential Failure Modes related to acts of terrorism are not considered. However, the PFMA process may be applicable in a ssisting a licensee in evaluating the vulnerability and risk associ ated with acts of terrorism.
3. Once a candidate potential failure mode has been characterized / described such that there is a common understanding of the pot ential failure mode, (See Appendix A – Part 1 for example potential failure mode de scriptions.) 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 br each (or other failure condition) is defined and the potential consequences of failure ar e discussed. The failure mode should be developed so that each step in the fail ure mechanism from the loading condition to the final failure condition is sufficiently defined so that the Surveillance and Monitoring Plan can be developed to dete ct a developing failure as soon in the process as possible. All the data, inform ation, factors and conditions that suggest the ways that the potential failure mode is more likely or less lik ely 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 faci litate documenting the suggestions. Although some PFMAs have su ccessfully utilized a computer with projector to record the PFM information, th e 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 efficientlyChapter 14 Monitoring the Performance of Dams

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0 complete the PFMA report. When a computer is used to record the session, a person other than a Core Team member should ta ke the notes to assure the Core Team members can actively participate in the di scussions. The note taker should be an experienced dam engineer. The consequences of failure and the ci rcumstances surrounding a failure (advance warning, detection possibilities, impact of the failure, et c.) should be discussed for each potential failure mode during the discus sion 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 poten tial failure mode conseque nce related factors (in the event they have been overlooked during th e technical discussi on 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 disc ussed and the range of failure scenarios and consequences that may result are id entified. The emergency action plan response to potential failure scenarios is ex amined and any concerns with the plan are identified.
5. After a potential failure mode has been id entified, described and discussed, each potential failure mode is classified / categor ized according to the classification system given in Table 1. After all potential failure modes have been discussed the classifications made are reviewed and disc ussed. Note that if team members do not reach consensus on the category, dual categoriz ation 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 discusse d, the classifications made are reviewed and discussed. The Part 12D Independe nt Consultant may later recommend resolution or modification of the classification as part of the Part 12D Report. It is important to note that the categorizati on of potential failure modes is not related to a possible need for additional surveillance, monitoring, maintenance or remediation. The categorization is intende d 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 th e Surveillance and Monitoring Plan, and to provide focus to inspections of the dam.Chapter 14 Monitoring the Performance of Dams

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0 Table 1 - Categories of Identified Potential Failure Modes

Category I - Highlighted Potential Failure Modes - Those potential failure modes of greatest significance consideri ng need for awareness, potential for occurrence, magnitude of cons equence and likelihood of adverse response (physical possibility is evident, fundamental flaw or weakness is identified and condi tions and events leading to failure seemed reasonable and cred ible) 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 mode s 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 A nalyses 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 recomme nded. 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 possi bility does not exist, information came to light which eliminated the concern that had generated the development of the potential failur e mode, or the potential failure mode is clearly so remote a possibil ity as to be non-credible or not reasonable to postulate.

Category I Potential Failure Modes are thos e considered most credible and most important to be brought to the attenti on of the dam owner, dam operators, and personnel performing the monitoring and rout ine and periodic inspections. Because of the importance of monitoring the performa nce of the dam, surv eillance, 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 fo r one or more reasons such as no direct or indirect evidence of any indication of problem developm ent, 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.Chapter 14 Monitoring the Performance of Dams

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0 Category III Potential Failure Modes are t hose 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 ha ve 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 Ca tegory II. However, there may be some Potential Failure Modes where the physical impossibility of the failure mode is only discovered after full developmen t 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 th e use of judgment by the team and to provide an easy differentiation of re lative importance for the owner. The differentiation between Categor y 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 Surveill ance 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, te ndons maintain sufficient prestre ss, 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 assu re that operating and technical staff are aware of the critical nature of these facili ties. The magnitude of consequences is a factor that should used to differe ntiate between Categories I and II. Category II should be reserved for those Po tential Failure Modes that are physically possible but do not need to be highlighted to the owner fo r 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 inst ance, failure of a gate where the water release would stay in bank and there is not a significant recrea tion use of the river downstream of the dam, could be classified Category II. Similarly, a dam that has high calculated factors of safe ty, i.e. the probability of fa ilure is remote, and or the downstream consequences are small, may al so 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 inform ation/analyses required to resolve a Category III PFMA are completed, that potential failure mode should be recategorized. Attention to monitoring and surveillance relates to Ca tegory II and III potential failure modes just as it does for Category I modes.Chapter 14 Monitoring the Performance of Dams

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0 As noted above, in some instances a ca ndidate potential fa ilure mode can be dismissed as a potential failure mode w ithout fully carrying out numbers 3 through 5 above. In such cases the PFM will be clas sified as Category IV. Category IV can also include PFMs with fully developed descri ptions if the physical impossibility of the PFM is only discovered after a full di scussion. 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 incl ude PFMs that have been dismissed as physically impossible. Low consequences an d/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 re lates to dam safet y, surveillance and monitoring or is of general concern but is recognized by all as something that does not or would not result in failu re of the dam or other wate r retaining structure at the project and is thus not a candi date 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 Disc ussed” and are to be included in the report in a section under that heading.

6. In the Part 12D report, all Potential Failu re 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 s upporting the recommendation.
It is important to note that the Potentia l Failure Modes are pl aced into categories by judgment. The basic purpose is to help the dam owner’s personnel and the current and future inspectors dealing with the da m to understand what the evaluation team considered were the most significant pot ential failure modes, so that they can consider / prioritize for action a smaller numbe r of items rather than the total array of potential failure modes considered. The br eakdown may also help with prioritization of actions to be taken. It is quite co mmon in the PFMA for a monitoring or visual inspection action to be identified for a Cate gory II potential failure mode that is easy to implement.

Step 6 – Evaluation of Surveillanc e and Monitoring Requirements As a part of the Part 12D report the Independe nt 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. Surveillan ce and Monitoring Plans will also be included for selected Category II and III Potential Failu re Modes which the Independent Consultant believes are warranted. In the Part 12D report the Independent Consulta nt 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 de fined. The plan presented should consider the items enumerated below. To facilitate deve lopment of Surveillance and Monitoring Plans,Chapter 14 Monitoring the Performance of Dams

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0 the PFMA team should include comment and di scussion on these items as appropriate for each potential failure mode identified.

1. The type and frequency of inspections (v isual surveillance requi rements) 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 owne r. The checklist should identif y specific visual clues that may indicate a suspected potential failu re 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 su rveillance program should be critiqued. It should be determined if the existing instru mentation is operating properly and that the readings can be relied upon. In some cas es, 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 su rveillance may be needed to monitor for a potential failure mode development
3. Reporting requirements should be review ed. Action limits may need to be established for some of the instruments and procedures developed for reporting variations in instrumentati on readings. As a minimum, annual engineering review, evaluation and reporting of the in strumentation data is required.

4. In some cases additional analyses or invest igations may be required to fully evaluate a potential failure mode pr ior to establishing a SMP for it. The PFMA team should identify what information is needed. Th e Part 12D Independent Consultant would recommend what information is needed and how to obtain this information.
5. If enhancements to the monitoring or vi sual surveillance are identified by the PFMA/Part 12D process then priorities for improvement in the SMP should be discussed, and appropriate recommendations and schedules provi ded, in the Findings and Recommendations Section of the Part 12D Report.

Step 7 - Documentation of the Po tential Failure Mode Analysis

1. For the knowledge gained, information obtai ned and results achieved in the Potential Failure Mode Analysis to be effectively us ed 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., surveillan ce and/or monitoring, investigations, remediation activities); andChapter 14 Monitoring the Performance of Dams

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0 • Clearly relay the major findings and unders tandings achieved as a result of the process. It was specifically noted dur ing 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 th e participants to reflect on what they learned during the PFMA proce ss. 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 sessi on. Typically this is done by going around the room and asking each participant to pr ovide a MFU and then starting again with the first person until all participants ha ve had the opportunity to express their findings. MFUs may relate directly to a Po tential 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 accurate ly reflect what the individu al participants stated as their major finding or understanding gain ed 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 Consu ltant and included with the MFU. The write up of the major findings and understandi ngs 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, identif ying 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 inqui ries, investigations, analyses or risk reduction opportunities). The fa ilure mode should be presen ted pictorially whenever possible. The write up should include a brie f 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 consulta nts 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.Chapter 14 Monitoring the Performance of Dams

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0 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 da ta 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 refere nce. Photos of past conditions or photos of current conditions, elucidating key information about a potential failure mode, are highly recommended for inclusi on in the body or appendix of the PFMA report. The PFMA appendix should be conc ise 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 serv e as a valuable tool for the reviewers to use to assure that they have seen all the materials collect ed and should be included in the PFMA report.

6. The PFMA report will then become S ection 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 in clude a statement that the PFMA report is bound separately and provide a copy of th e cover of the PFMA report showing the title and date of the report. It is not th e 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 th at 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. phot ographs may show planar joints, or gunite treatment of the founda tion, 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 counter s what has been stated in opinions / observations in construction reports; eros ion or the lack of it may have been documented following a flood). These specifi c pages, photos, quotati ons 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 whethe r the findings are a consensu s of the team. If not a consensus, the differences of opinion and reasons therefore shoul d be documented in the report findings. If no consensus is re ached, 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 A dditional Monitoring or Performance Related Items Discussed. Issues or it ems that are brought up during the PFMA session that relate to dam safety and pe rformance monitoring or are of general concern but are recognized by all as somethi ng that does not or would not result in failure of the dam or other wa ter retaining structure at the project are included here.Chapter 14 Monitoring the Performance of Dams

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0 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 fu rnished for the Potential Failure Mode Analysis, identify any discrepancies, inaccuraci es, 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 speci fic potential failure modes.
10. When a PFMA is being conducted not in a ssociation with a Part 12D report (for example, in support of a major remediati on or maintenance), the report preparation should follow the same time frame or schedule described above. Following Core Team review and coordination of the draf t 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 pro cess in a task by task table format for dam owners as a supplement to the above discussion form at for their conven ience if desired.

14.3.5 Use of the Potential Failure Mode Analys is 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 failu re modes identified in the PFMA. Appendix H includes the Part 12D Report outlin e and provides guidance on what is to be included in each section. The manner in which that is intende d 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 doc ument the actual condition of the project
structures.

2. Part 12D Inspection Report – The inspec tion 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 inspec tion and the recommended actions that could be taken with regard to informa tion inquiry, investigations, analyses, or structural or non-structural actions in terms of the id entified potential failure modes. Recommendations may pert ain to changes in operations orChapter 14 Monitoring the Performance of Dams

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0 maintenance required in order to maintain the status quo as well as recommendations to improve project safety.
b. Discussion of the Potential Failure M odes Analysis Report - The Independent Consultant’s commentary on the Poten tial Failure Modes identified in the Potential Failure Mode Analysis report. This section of the Part 12D report is provided to allow the Independent C onsultant 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 Consulta nt’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 contribut e to or “allow” development of the potential failure mode. Any relevant comments relating historic and current performance indicators to identified pot ential 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 fiel d observations relative to each of the identified potential failure modes as we ll as the Independent Consultant’s own assessment on the significance of the identified potential failure modes and on whether any other potential failure m odes exist, or conditions may have changed that would impact previous c onclusions regarding potential failure modes.

e. Operation and Maintenance Program – A discussion of the Independent Consultant’s observations of the Li censee’s O&M program relative to identified Potential Failure Modes.
14.3.6 Updating the Potential Failure Mode Analysis The comprehensive “initial” Potential Failure Mo de 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 cha nge or as new information is obtained at any time following the initial PFM A 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 th e Independent Consultant inspection in subsequent Part 12D inspections. (Availa bility of this document should make the Independent Consultant’s work easier, more focuse d and effective and less costly) If as a result of the detailed insp ection, the Independent Consu ltant 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 thenChapter 14 Monitoring the Performance of Dams

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0 provide copies to all holders of the STI documen t 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 pote ntial impact on Project safety. That “updated” PFMA would then be the foundation fo r the next Part 12D Independent Consultant inspection report 5 years later. It is also possible that new in formation 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 th e Licensee for distribution to the STI holders as described above. In this way, the Potential Failure Mode An alysis 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 / ap pended PFMA report findings. It is important to retain the original PFMA re port as prepared so that the findings, discussions and thought processes of the origin al Potential Failure Mode Anal ysis session are retained for future evaluations.
14.3.7 Conduct of a “Supplementary” Potential Failure Mode Analysis A supplementary Potential Failure Mode Analys is should be conducted for projects that fall under Part 12 Subpart D of the Commission’s regul ations when major modifications are to be constructed. The “Supplementary” PFMA is conduc ted using the same procedures outlined above for the “Initial” Potentia l Failure Mode Analysis. Sup porting documentation is needed for the proposed modification. The design for th e proposed modification should be at least to the 50% level to enable the PFMA team to cr itically 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 Bo ard 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.Chapter 14 Monitoring the Performance of Dams

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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 failure s is an essential part of a dam safety program. These guidelines:

• Provide a discussion of the various perfor mance monitoring principles and methods used to aid in evaluation of a structure; and

• Present performance monitoring procedures and principles fo r a number of common adverse responses or conditions that typi cally are indicators or contributors to potential failure modes. These basic pr incipals 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 Surv eillance and Monitoring Plan for the dam / project. The SMP must include each Category I Potential Failur e 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 instrumentati on required, their locati ons and frequency of measurements, and action limits for each instru ment. 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 st udies 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 in strumentation necessary for monitoring the general health of a dam. Recommendations ma de by the consultant with respect to the SMP are actionable items, similar to the other re commendations contained within the Part 12D report, and should be included in the final recommendations sect ion 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 combina tions of failure, and particularly operating conditions that may present more complex potentia l failure modes and failu re scenarios, must be developed and the appropriate means fo r monitoring these unique or complex modes established.

14.4.1 Principles and Methods of Performance Monitoring
This section describes fundament al 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 obs ervations and data based on design assumptions and the findings from the PFMA.Chapter 14 Monitoring the Performance of Dams

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0 1. Visual observation Visual observation is an important surveilla nce activity. Many dams were constructed without the benefit of instrumentation and thus visu al observation offers a first impression/opportunity to evalua te integrity, movement and lo ads. Visual observation at regular intervals by trained personnel will often detect unusual conditions, such as increased seepage, cloudy seepage, or m ovements and is the dam owner’s primary defense against serious problems. However, visual observations are judgmental rather than quantifiable. Instrumentation may be n eeded to provide information to enhance our ability to analyze the co ndition of the structures.
Inspections/observations of remote projec ts 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 de veloped 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 investiga ting 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 de sired 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 su fficient to assess the total structure. The critical sections of the struct ure should be defined and the location of instruments relative to the critical section reviewed. The fr equency/regularity of reading and timing of readings should be reviewed. The occurren ce of taking the reading should be logically related to the date, corresponding reservoir leve ls, climatic conditions (i.e., rain, winter) and operations (i.e., lag times of drawdown) as appropriate. The personnel taking the readi ngs 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 fo r 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 s hould 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 presenta tion 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 s how the locations of all instruments at the development site should. Sections through th e 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 levelsChapter 14 Monitoring the Performance of Dams

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0 Threshold and Action limits should be develope d and the criteria used to develop them should be documented. A Threshold value is th e value used in the analysis or design, or is established from the historic record. An Action Level is the instrument reading that triggers increased surveillanc e 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 analyt ical studies (e.g. uplift pre ssure readings above which stability guidelines are no longer met). In ot her 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, read ings 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 coll ect additional comp lementary data. All data should be compared with design a ssumptions. For example, measured phreatic levels and uplift pressures should be compared ag ainst those used in st ability 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 wh ere 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 stabili ty of the dam should be evaluated using the elevated phreatic surface. All data will follow trends, such as decreasi ng or increasing with ti me or depth, seasonal fluctuation, direct variation w ith reservoir or tailwater le vel, direct variation with temperature, or a combination of such tre nds. The trends are us ually evident in the plotted data. Statistical anal ysis of data may be useful in evaluating trends that are obscured by scatter. However, such analys es are no substitute for judgment based on experience and common sense. Data inconsis tent with establishe d trends should be investigated. Readings deviating from esta blished 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 depe nds 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 read ing devices are working properly;

• reevaluating stability using new data;

• changing frequency of measurements;

• installing additional instrumentation;Chapter 14 Monitoring the Performance of Dams

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0 • special investigations;

• designing and constructing remedial measures;

• operating the reservoir at a lower level; and

• emergency lowering of the reservoir.
Guidance on methods for estab lishing Threshold and Action pa rameters is presented for the various types of instrumentation desc ribed. The Independent Consultant in consultation with the licensee should estab lish 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 functioni ng properly should be fu rther investigated. For example, data should be checked against redundant data to determine whether or not trends and magnitudes are the same. Calibra tion of the instruments should be checked (this is paramount). Often, te sts can be devised to evalua te 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 lo ng 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 requ ire additional instrument ation are: to check design assumptions; to provide data to evalua te 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 progre ssive conditions may require immediate action rather than belated installation of extra instruments.
Instruments should be reviewed for their lif e expectancy. Readings from advanced age instruments should also be evaluated with resp ect to whether the instrument readings can be trusted. A failed instrument should be rem oved 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 provi de the means for helping to develop the understanding or verify th e performance of a dam. The purpose of instrumentation and monitoring is to help quantify behavior and provide data to evaluate whether the dam is performi ng 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.Chapter 14 Monitoring the Performance of Dams

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0 If there is a discrepancy between the measured and expected behavior of the dam, it may indicate that the dam is not performing satis factorily and that failu re is developing or occurring or it may be that the data or observations do not ade quately 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 fi eld 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 instrume nts just to see the dam fail or confirm failure of the dam.

14.4.2 Surveillance and Monitoring Pr ocedures and Guidelines From these guidelines, necessary surveillance and monitoring techni ques and devices and threshold parameters to be employed at a spec ific 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 syst ems agreed upon as appropriate. Additional information on the details of surveillance and monitoring in strumentation 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 monitori ng 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 struct ure. 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 da ms, 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 potentia l 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 FoundationsChapter 14 Monitoring the Performance of Dams

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0 • Deterioration of Concrete

• Operations Procedures

• Equipment (e.g. gates) testing and/or maintenance

1 . Surveillance and Monitoring Guidelines for Abu tment or Foundation Movement
a. Visual Observation The first line of defense for monitoring al most all potential failure modes is visual observation. While visual observation of gross movement of a dam or foundation would indicate that a very serious co ndition is occurring or developing, more subtle indications of movement can be observed. Cracking, new areas of leakage through the dam or foundation, and displa ced foundation material, are all visual clues of possible movement. Visual obs ervation is beneficial in that it may readily identify changed conditions and it has the advantage of complete coverage (as opposed to instruments that only monito r point locations). For concrete dams, pins can be established at the crest or in galleries along cont raction joints to determine whether differential movement is indicated or has taken place. These pins can readily be observed during routin e site visitations a nd 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. T ypically, movement monuments are placed at several points along the cr est of the dam where they ar e line-of-site visible from benchmarks established some distan ce 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 infl uences 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 emba nkment movement. These devices are used to take frequent readings, generally quarterly, monthly or weekly, to obtain information on specific small moveme nts, generally related to ongoing investigations or to estab lish movement history with re gard to changing reservoir or foundation water levels, changes in te mperature, or in regard to special concerns triggered by other observations. d. Establishing Threshold and Action Parameters for MovementsChapter 14 Monitoring the Performance of Dams

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0 Once a series of movements over some period of time has been developed, and confirmed by stress analysis as being a ppropriate, threshold and action parameters can be established that w ould require further investig ation or action. Before initiating action however, measurements fa lling 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 foundatio ns or abutments of dams is a normal condition. However, increases in historical ly observed amounts of seepage, in the elevation of the phreatic su rface 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 rela ted problems. The appearance of transported material in the seeping water of an embankment or soil foundation may indicate piping or seepage er osion 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 pr oblem 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 ta ken. Visual observati ons of depressions or sinkholes in an embankment or upstr eam abutments or fo undations are strong indications of piping occurrence. To accurately monitor any seep age, 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 se veral reasons. It pr ovides a continuous means for settling and trapping particles th at 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 meas ured and weighed. If weirs are used in an area where fines may be blown or erode d into the weir, a cover is necessary. Also the weir should be routinely cleane d after each periodic measurement so the amount of new material between coll ections can be accurately assessed. Flumes allow for accurate measurement of seepage rate but do not provide a means for collecting material. Regard less 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 set tle out, at least overnight, to check for the presence of any suspended material (fines) being tran sported (piping or seepage erosion). Drainage pipes wi thin a downstream embankment provide a convenient method for collecti ng and measuring seepage. Care must be taken thatChapter 14 Monitoring the Performance of Dams

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0 such pipes are properly filtered to prev ent piping and if not it is even more important that the flow from the drain pi pe(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 em bankment 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 la rge stakes so that any change with time / season can readily be assessed. M onitoring of vegetation (big roots can initiate piping) and rodent holes is critical. The determ ination of the nature of such seepage can usually onl y 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 ar e generally considered to be more of an indicator of a potential problem, decr eases in seepage (particu larly in a concrete dam foundation but also within embankment da m foundations or dr ainage 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 rain fall and this possibility should be reviewed at sites with significant seepage.
b. Piezometers and Observation Wells A great benefit to understanding the pote ntial for failure mode development related to seepage from a dam /foundati on 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 founda tion (below the core of an embankment dam) exceed those in the dam then the direction of fl ow indicated is from the foundation into the dam and the possibility of piping of mate rial from the dam to the foundation is remote. Conversely if the di rection of flow indicated is from the dam base into the foundation then the physical possibil ity of piping from the dam through the foundation is indicated. The best way to de termine this flow regime is to review the piezometric, observation well and seepage data. Whenever there is concern for stability that may be sensitiv e 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 measuremen t 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 st rata or zones. Th e phreatic surface in the abutments or foundation can be meas ured by observation wells, usually open tube pipes with long sensing zones and w ith only the top of the tube sealed to prevent surface water infiltr ation. If stratif ication exists in the abutment,Chapter 14 Monitoring the Performance of Dams

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0 consideration for different piezometers se aled in the various soil horizons should be given. One of the key and often overlooked step s 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 ma ny 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 emanati ng from / through the dam, foundation or abutments, periodic checks on movement of material should be made. A sample of the seepage water should be collecte d and allowed to se ttle out, at least overnight, to check for transported material (piping). Crest settlement surveys are an important source of early warning of pi ping failures, particul arly 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 pr essures in the foundation or abutments may also indicate that movement of material is occurring. Where the foundation materials may be sus ceptible to solution from water of certain chemical properties, frequent checks on groundwater and reservoir water chemistry and on the chemical compositi on of seepage water should be made. Evidence of solution of foundation material s or strata such as gypsum layers requires prompt intervention. d. Establishing Threshold Parameters for Seepage Seepage through a concrete dam is us ually monitored by observation and mapping (see Visual Observation). If seepage appears to be spreading or increasing in volume, then an investiga tion 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, th en an investigation and evaluation of the situation is necessary to determine if re medial action is required. Once a history of variation in seepage flow has been established with respect to season and reservoir level, then corresponding threshol d parameter levels can be established that will trigger the need for further investigation and remedial action. The location of the phreatic surface in th e embankment or the seepage pressures at specific strata can be determin ed by piezometers. Seepage through the abutments or foundation is similarly mon itored. A steadily rising phreatic surface or increasing seepage forces should tri gger a prompt review and, if necessary, remedial action. Periodically, the measured phreatic su rface or seepage pressures must be reviewed against those surfaces or pressu res that were used for the most recent stability analyses. If the actual phreatic surfaces or seepage pressures exceedChapter 14 Monitoring the Performance of Dams

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0 those used in the stability analyses, then a special engineerin g 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 meas urement devices. Once a history of variation in seepage flow has been es tablished with respect to season and reservoir level, then threshold paramete r data related to seasons and reservoir levels can be established that will tri gger 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 struct ure itself is suspected as a result of observation of cracking, new leakage, m ovement monument measurements, or updated stress analyses, more detailed meas urements 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 direc tly on an existing dam unl ess stress or strain meters or load cells were installed during the initial constructi on. Therefore, most performance monitoring is aimed at determ ining strains under varied loadings to calibrate stress analyses. a. Precise movement surveys (sur face) – horizontal and vertical. Additional surface monuments can be qui ckly 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 usef ul. Tiltmeters can be installed on existing concrete structures and read ings can be obtained quickly after installation. Tiltmeters are sometimes used instead of plumb-lines because they are easier to install and require little ma intenance. Tilt Meters can be used to calibrate FEM models and to back calcul ate foundation moduli if the reservoir can be raised or lowered a significant amount.
d. Load cells
For direct measurement of loads in the da m, load cells must be installed during construction. While they can provide mean ingful data, if they are not in the area of highest stress, they have limited useful ness. If post-tensioned anchors are used to improve stability, either in part of the dam (such as abutment blocks) or in theChapter 14 Monitoring the Performance of Dams

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0 foundation, some anchors should have load ce lls installed to m onitor their loss of tension so that rete nsioning can be performed as necessary. e. Strain Gages Stain gages can provide valuab le direct stress data if in stalled 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 stru cture or for deformation models of an embankment. However, they are not usef ul 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 th e case of embankment dams, the rule is to prevent overtopping, because it can l ead to catastrophic failure.
a. Observation and Measurement of De terioration 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 sp ecific data on large flows that would impact the foundation. The foundation, abutments, and spillway out fall areas should be surveyed and a profile of the foundation impact area of overflows, abutments and/or spillway outfall/energy dissipater areas made. Becau se survey markers in such situations will probably be lost in flow situations , the survey should be at precise station points along the abutments within th e flow zone and on the downstream foundation offset from the cr est of the dam. Such su rveys should be repeated after major flows have o ccurred and the changes in the profile plotted and reviewed and the erosion potential quanti tatively estimated. Utilizing the flow volume and frequency relationships, an a ssessment of potential failure due to washout can then be made. b. Periodic Assessment of Geologi c Conditions and DeteriorationChapter 14 Monitoring the Performance of Dams

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0 In addition to the survey and assessment above, close geologic inspection of the foundation, abutments and/or spillway outfa ll/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 Leak s/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 leak age 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. Partic ular 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 th e quantity of dam seepage is increasing, various devices are available to measur e flow. Unfortunately, they may be physically difficult to install on the vertical or overhanging face of an arch dam. They would generally only be utili zed 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 cons truction. On older dams, alkali aggregate reaction is not uncommon. For dams at high elevations and in nor thern areas, freezethaw deterioration is a concern.
Concrete deterioration is mo re critical in Ambersen slab and buttress type dams where design stresses in the water retaini ng slabs and reinforced concrete beams are about 50% of the ultimate capacity ut ilized under normal loading. Concrete deterioration not only reduces the cross- section properties but also exposes the reinforcing allowing it to corr ode and reduce cross-section. a. Periodic Visual Inspection and Mapping of Deteriorated Areas. Make a periodic map of all areas of de terioration whether caused by freeze thaw, alkali-aggregate reaction, or other mechan isms. 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 deteri orated 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 elevationChapter 14 Monitoring the Performance of Dams

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0 should be made to ascertain the amount of swelling of the concrete. Also, cores of the expanded concrete should be take n 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 de terioration mechanisms, the depth of deterioration should be periodically determ ined. 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 inst all reference markers set in the deeper undisturbed concrete and peri odically measure the dist ance from the end of the marker to the sound concrete.
7. Operations Procedures Common to all Dams Mis-operation of a dam, either through e quipment 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 scenario s 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 add itional specific training of personnel and emergency procedures exercises that are tailored to specific identified potential failure modes. b. Equipment malfunction Power failure - Anytime electrical equi pment such as gate hoists, sensors, communications, etc is required for the sa fe operation of the dam, power failure can lead to a dam failure. Defensive measures could include having st andby power availabl e 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 mi s-operation or failure to operate. Defensive measures may include perfor ming regular telemetry testing, having redundant sensors for critical inst rumentation, and having redundant communication systems.
c. Access failure If personnel must be dispatch ed 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 impassibl e and helicopter travel impossible. Defensive measures may include having iden tified alternative routes to access the site or stationing personnel at the si te prior to failure of access roads.Chapter 14 Monitoring the Performance of Dams

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## 14.5 INSPECTION PROCESS and COORDINATION

14.5.1 Scope and Purpose To define the roles, responsibil ities and coordination of the Li censee, Independent Consultant and FERC and to develop a process flowchart which links together all of the inspection, analysis, evaluation and emergency action pla nning 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 insp ections / observations – These inspections are typically performed by the licensee or a consultant retained by the license e. 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 pot ential failure mode. The licensee is responsible for performing these inspectio ns 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 a ny action such as an alysis, repairs or monitoring needs to be implemented. 2. Licensee operation and maintenan ce 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 operati on and maintenance of the project. The FERC inspector and Independent Consultant should review these programs during their inspections to assure they meet th e needs of the Surveillance and Monitoring Plan. 3. FERC operation inspection - FERC will schedule with th e licensee in advance and perform this inspection. After the inspec tion FERC will discuss with Licensee any concerns found during the inspection. The di scussion will also in clude 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 ne w 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 es tablished 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 th e request in its one year reminder letter to the licensee. FERC will document this inspection a nd provide a copy to the licensee.Chapter 14 Monitoring the Performance of Dams

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0 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.
The FERC Operation Inspection will be done at the same time that the Part 12D Inspection is done. The Consultant will be provi ded 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 insp ector to review the project history including any past or current defici encies, completed remediation, special investigations previously completed, instru mentation, 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 c onsultant’s Part 12D inspection, though conducted concurrently, will be documented i ndependently. It is intended that the inspections allow opportunities for discu ssions of any problem areas and other important items that might come up. Upon completion of the inspections, the gr oup will meet to discuss any additional thoughts concerning potentia l failure modes that need to be developed. Any newly identified potential failure modes will be described by the Independent Consultant and included in Sect ion 4 of the Part 12D report. 5. FERC Construction and Special Inspections - FERC will be responsible for performing and documentation of these insp ections on as needed bases with proper coordination with the Licensee.
6. Licensee Initiated and FERC Dir ected Analyses and Evaluations - If during the operation or inspection of the project a c oncern 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 furt her analyses and evaluation to determine if a deficiency exists.Chapter 14 Monitoring the Performance of Dams

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0 7. Recommended Action Surveillance and Monitoring - If during the operation or inspection of the project a concern or issue is raised that is determin ed 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 Consu ltant 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 ope ration or inspection of the pr oject a concern or issue is raised that is determined to require a dam safety modification, it will be the responsibility of the Licens ee to design and make the necessary modifications with the coordination of the Indepe ndent 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 EAPO&M and TrainingPeriodic RoutineInspectionsFERC Op Inspection

Team Support Part 12D InspectionJoint 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 / SupportChapter 14 Monitoring the Performance of Dams

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0 

## 14.6 EMERGENCY PREPAREDNESS

The Independent Consultant should consider th e various potential failu re modes determined and review pre-planned procedures for deali ng with potential emergencies. If any preplanned measures need to be put in place, the Independent Consultant will make the necessary recommendations. These measures incl ude necessary equipment, materials, etc.Chapter 14 Monitoring the Performance of Dams

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## APPENDICIESChapter 14 Monitoring the Performance of Dams

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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 th e hydrologic engineerin g 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 si zeable portion of the probable maximum flood using the Main Spillway gates and the emerge ncy spillways. Thus there was concern for the hydrologic deficiency but not great concern. Ho wever, 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. Disc ussions with the owner revealed that use of the emergency spillway in such a manne r was highly improbable. This was due to the potential liability from such an action (a si zeable 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 th ere 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 th is flow was not relied on in the routing, the early shut off would have exace rbated the overtopping situation.

• Drawings were located for the secondary emergency spillway, which was referred to as a “fuse plug” spillway but this fuse pl ug 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 th e concrete structures would be overtopped prior to the embankment structures. Howeve r, examination of survey data, settlement records and settlement projections (a long 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 highlight ed 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 mode s definable at this site. Fa ilure of the Dikes poses a high hazard, and diligence in monitoring for developm ent of this potential failure mode is warranted.Chapter 14 Monitoring the Performance of Dams

Revision 1 14-A-2 July 1, 2005 Potential Failure Mode 1 - Dikes 1 and 2 - Seepage Erosion and Piping During site investigation the foundation of th ese dikes was found to contain joints much more open than anticipated, based on pre-constr uction investigations. These joints provide a potential path for subsurface erosion of the Z one 1 material leading to an unprotected exit downstream of the dam. Although grouting wa s 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 ft 3 /s of seepage, which occurred during first filling, from a dike of moderate heig ht 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 po tential failure mode paths and the factors relative to the likelihood fo r the development of this potential failure mode are as follows: Potential failure mode paths - there ar e two primary potential paths for seepage erosion/piping to take place through the founda tion 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 erodi ng and being carried th rough the open joints to an unprotected exit downstream. (Failu re would result if backward erosion (piping) through the Zone 1 materials reached the reservoir source. An ever increasing flow potential could then pr ogressively enlarge the flow channel downstream of the point of er osion 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 mate rial 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 eros ion of the foundation alluvium exiting through the open joints in th e rock. These are considered to be of significantly lesser likelihood

Part 2 - Example Record of Likely and No t Likely Factors Identified for a Specific Potential Failure Mode After each potential failure mode is identifie d 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 po tential 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 likeli hood of this potential failu re 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 por tion of the dikes)Chapter 14 Monitoring the Performance of Dams

Revision 1 14-A-3 July 1, 2005 • grouting near the surface was likely not very effective, considering the method used

• large seepage flows are occu rring, 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, bu t 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 foundati on rock behaves as a drain ke eping water away from or at low pressures at the dam/foundation contact.

• Seepage flows started downstream of th e dikes prior to th e 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).Chapter 14 Monitoring the Performance of Dams

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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 Safe ty 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 reque sted. This memo tells you all about how it will work and what your role is.

*** Individual Input to Potent ial 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 st udies. 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 indivi dually 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 avai lable team members following completion

of 1 and 2 above.

The concentrated effort will allow efficiency in preparation and consistency in the product.Chapter 14 Monitoring the Performance of Dams

Revision 1 14-B-2 July 1, 2005 Please complete each portion of the attached questionnaire for which you feel you can make

a contribution. Feel free to revi ew 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.Chapter 14 Monitoring the Performance of Dams

Revision 1 14-B-3 July 1, 2005 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 whic h causes unsatisfactory performance of the dam (or a portion thereof). I. What potential failure modes do you think ar e of specific concern at this project? Please provide a specific desc ription of the potential fail ure mode, including location of the area of concern.

Potential failure mode 1.

Potential failure mode 2.

Potential failure mode 3.Chapter 14 Monitoring the Performance of Dams

Revision 1 14-B-4 July 1, 2005 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 oka y relative to the poten tial failure mode, or that conditions that are c onducive to initiation of the potential failure mode have become present or that "activation" of th e 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 inspec tion or a general site visit, please identify a ny conditions that are notewor thy 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 descri be what is done in a typical PFMA session so participants will know what to expect and so that all the right informati on 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 bac kground package (inspection report and / or standards based engineering dam safety repor t) to become familiar with or to recall the project elements and issues.
3. All participants have comp leted / considered questionna ire on identification of potential failure modes prior to the workshop.

4. Inspector or instrumentation group has inst rumentation and surv eillance data updated and ready for review by Core Team prior to meeting and are avai lable to demonstrate reading procedures during the site visit as appropriate.
5. Project leader has references availabl e in meeting room – this includes:

• all engineering reports and key f eature drawings (large scale);

• construction photos and construc tion / design history data;

• flood frequency data and routings and earthquake loading data;

• data on consequences and emergency preparedness; and

• inspection reports and instrume ntation and surveillance data.

Begin Session

I. Adequacy of Project Documentation - Discuss adequacy of documentation provided for the exercise and determine if any defici encies exist for specific potential failure modes. Determine if sufficient information exists to adequately perform the Potential Failure Modes Analysis for the project. Do cument your findings regarding adequacy or deficiencies in project documentation.Chapter 14 Monitoring the Performance of Dams

Revision 1 14-C-2 July 1, 2005 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 load ing since it is the easiest fo r all to understand and sets out the reservoir loading conditions. Flood loading:

• Go over all the key data; size and freque ncy 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 m odes 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 tabl e. Based on this discussion, the team classifies the potential failure mode (Category I, high lighted; Category II, considered but not highlighted; etc.).

• Breach formation character and rate of fa ilure are discussed. Consequences of a flood related failure and of operational spillway discharges are discussed.

• Failure scenarios (exposure c onditions and warning aspect s; detection, decision to warn, dissemination of warning, evacuation, etc) are discussed. The anticipated response is reviewed with field / site pers onnel. In reality, this exercise is looking for potential failure modes in the preparedness arena.

• Opportunities to achieve ri sk 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 a dditions 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 clue s 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.Chapter 14 Monitoring the Performance of Dams

Revision 1 14-C-3 July 1, 2005 • 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 / unders tanding. Plans and / or profiles are sometimes needed as well.

• Evaluate failure scenarios for each signi ficant potential failure mode. These scenarios do not have the same warni ng associated with flood or earthquake loadings.

• A list of the reasons why these potential fa ilure modes are more likely or less likely to occur are discussed and recorded. This discussion is very important in evaluating the significance / category of pot ential failure modes suggested.

• Based on this discussion the team classifies the potential failure mode (Category I, highlighted; Category II, consider ed but not highlighted; etc.)
Earthquake loading Repeat above process. Key changes or a dditions 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 sim ilar and the degree to which the additional seismic loading may impact static condition can be examined.

• Go over all key magnitude and frequency da ta for site (histo ric and tectonic study data) and site attenuation or amplifica tion 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 si te to case histories of earthquake related failure.
Consider any other loading relevant to site: Ice, avalanche, landslide, etc. – Repe at process used for other loadings

III. Make final team categorization

I. Significant Potential Failure Modes (Hi ghlighted) in each loading category and Summarize / Rank.
II. Potential Failure Modes cons idered but not highlighted.
III. Potential Failure Modes considered but l acking key data or information to allow categorization. Identify data needs.
IV. Potential Failure Modes ruled out.

IV. Review possible risk reduction / inst rumentation / surveillance opportunities identified for all potential failure modes considered Place the identified potential risk reducti on opportunities into two categories: 1. Possible alternative mitigation actions to investigate, andChapter 14 Monitoring the Performance of Dams

Revision 1 14-C-4 July 1, 2005 2. Actions to be considered by the Indepe ndent Consultant for implementation by the

owner.

V. Identify and Record Major Findings and Understandings The major findings and understandings achieve d 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 discusse d 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 Po tential Failure Mode Analysis in the main text.Chapter 14 Monitoring the Performance of Dams

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## 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 deve loped 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 Potentia l Failure Mode and potential adverse consequence (scenario developed by the team [ including a sketch where applicable ] and a discussion of the potentia l adverse consequences of the formulated scenario.) For some Categor y 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 i ndicate 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 se lecting that category (i.e. – the factors with the greatest weight
The Potential Risk Reduction actions identi fied during the discu ssion 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 actionsChapter 14 Monitoring the Performance of Dams

Revision 1 14-D-2 July 1, 2005 • Information needed to resolve Category III PFMs

V. Additional Monitoring or Perfor mance 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 th e number of potential fa ilure modes identified within each category, any st udy specific comments relate d 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 refe rences, Figures, Sketches, Photos made during field review showing key elements of dam and auxiliary features should be included along with any photos th at show conditions leading to potential failure modes.

Note 1: The report of the PFMA session, alth ough 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 presen t 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 importa nt to remember that the description of the potential failure mode must provide a comple te 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 descri ption in Section IV text to ensure that future reviewers obtain a full understanding of the teams meani ng and intent. Tables may be used as a means to summarize or supplement a more co mplete written desc ription of potential failure modes. A possible table format is provided below.

PFM Description Adverse Factors Po sitive Factors Risk Reduction Actions CatChapter 14 Monitoring the Performance of Dams

Revision 1 14-E-1 July 1, 2005 

## Appendix E Major Findings and Understa ndings - Example Write Up

Given below is an example write up of the Ma jor Findings and Understandings gained from a Potential Failure Mode Analysis for a pr oject consisting of a Main Concrete Dam incorporating a Power Station and Two Auxilia ry Embankment Dams. Although this was an actual study and presents the ac tual findings, the names of th e dams and the river in the example are not the real names.

• Currently in the event of a very large fl ood on the Blue River, approaching the PMF, overtopping failure of Auxili ary Dam 1 is the main point of vulnerability at the project. This is because the crest of Auxilia ry 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 n early triple (from about 1900 m 3 /s at failure to 5700

m 3 /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 elevati on than Auxiliary Dam 1 and thus allowed to fail from overtopping the effects and cons equences of overtopping failure would be significantly less. Auxiliary Da m 2 failure peak discharges downstream are estimated to only be slightly larger than flows resulting from the PMF (from about 2100 m 3 /s at PMF to 2400 m 3 /s at breach). Several measures to achieve overtopping failure risk reduction are identified in the report and th e best alternative shoul d be selected after an appropriate risk management evaluati on. 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 physica lly possibility at A uxiliary Dam 1 as the result of one or more potential flow path s. Although there is no unequivocal physical evidence that piping has occurred or w ill occur in the future, the nature and relationship of the materials in the dam and foundation, th e water level and piezometric observations, and the perform ance of the structur e (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 materi al could occur subsurface and thus not be amenable to observation. The consequen ces of a “sunny day” piping failure of Auxiliary Dam 1 would be high with a grea ter life loss potential due to the possible lack of advance warning. From the standpoi nt of the Potential Failure Mode Analysis Team, awareness of this potential piping c ondition is a key finding of the study as this potential failure mode is the most signifi cant 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 identif ied for the Main Dam was the only PFM of significance identified for this structure. Alth ough, this foundation potential failure mode is considered physically possi ble it is highly probab le 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 Po tential Failure Mode Analysis team considers that analysis rather than consideration of remedial work is the appropriate initial cour se 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 poten tial 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 eith er of the earthfill dams. This would occur for the PMF but also for floods si gnificantly 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 th e 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 sp ill directly on the power plant and likely knock that plan t out of service and cause c onsiderable damage. This flow could be directed away from the pl ant area. Thus, main dam overtopping, while not a potential failure mode, would be a si gnificant incident for the Owner and the Potential Failure Mode Analysis team cons iders that risk reduction measures to reduce the impact of the overtopping of th e 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 subse quent Part 12D activities)

The typical time requirements for the major act ivities 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 par ticipants / send out advance packet of material, setup facility and make arrangements - (The time required for this step can vary widely dependi ng on how well the ow ner’s files are organized. Most owners start this ta sk up to a year in advance of the PFMA session to assure they have ad equate 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 PF MA 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 daysChapter 14 Monitoring the Performance of Dams

Revision 1 14-G-1 July 1, 2005 

## Appendix G Dam Safety Performance Monitoring Program Process

Task Description Responsibility 1 Data Assembly: Assemble all availabl e background data for the dam and appurtenant works for the project. These data should include investigation, desi gn, and construction reports, construction photos (and all othe r 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 se ismic studies, the most recent flood studies, stability and/or stre ss analyses, lab test results on rock, soil and concrete, summaries of instrumentation monitoring data and visual in spection reports, periodic dam safety reports including all Pa rt 12D reports, Emergency Action Plans, photographs of key elements and features showing present condition and any remedial wor k. A summary of key project history by dates including or iginal planning, design and construction as well as all modi fications, studies relating to project safety from project ince ption 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 proj ect The STI should use tables, figures, and drawings in pref erence to text and should not include complete copies of the original documents except for the “Potential Failure Mode Anal ysis” study report. Only key paragraphs of the orig inal reports should be included in the text of the STI document for clarit y. 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 ICChapter 14 Monitoring the Performance of Dams

Revision 1 14-G-2 July 1, 2005 4 Send out Potential Failure Mo des Analysis Questionnaire: Prepare and send a questi onnaire to the PFMA session participants (not just the Co re Team) requesting their thoughts prior to the PFMA session and to get them all “thinking potential failure modes” and gathering rele vant 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 a nd dam experienced Engineering Geologist where applicable. Also determine who the individuals will be that will s upport / attend the PFMA, dam engineering geologist, mechanical and electri cal specialists (if needed for gate/valve issues), consulting e ngineering 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 re late to dam safety). Try to observe / discuss potential circum stances / 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 th ey can effectively carry out the PFMA. It is not a substitution for the Part 12D field inspection by the IC, which is to determin e 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 consideri ng location of site/data/PFMA. Assemble in a group setting for efficiency in sharing the collected data and to provide a “c aptive” 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 co re group. The team geologist should ensure that the relevant geologic data is available for Core Team review and the geol ogist 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 TeamChapter 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 poten tial 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 respons e to potential failure). After discussion of each PFM, cat egorize 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, i nvestigations, analyses, remediation (struc tural or non-structural) and operational procedures & mainte nance programs. Surveillance and Monitoring Plans (SMPs) can vary from periodic visual inspections, to continuous reco rding 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 Ac tions to be considered to immediately reduce significant risks identified for specific PFMs. After discussion of each PFM, cat egorize 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 l earned or more fully understood during the workshop). All the i nput should be on flip charts (hand written) and should also be fully recorded electronically (laptop) or by copious notes. En sure that all participants have their input/concerns listed. Phot ograph 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 distribu te to staff for further input). All review and comment /send email to IC. IC modifies IC and Core TeamChapter 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 dr aft PFMA report to Core Team and Geologist. All review and email comments to IC. IC modifies PFMA report to incl ude comments (some discussion between IC and others is usua lly needed to achieve final agreement) as appropriate. Th e 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 : F ollowing completion of the PFMA report, the STID should again be reviewed by the Owner and IC and any omissions or additional data rev ealed in the PFMA data review and sessions included as appropr iate. 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 Inspect or 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 di scussed 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 Pa rt 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. OwnerChapter 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 ini tial page numbers for each section. If any subsection is not applicable, include the subsec tion 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 Fa ilure Mode Analysis Report
4. Surveillance and Monitoring with Respect to Potential Failure Modes
5. Field Inspection
6. Operation and Maintenance Programs Re lative 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.Chapter 14 Monitoring the Performance of Dams

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 a nd 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 in cluded within the report, provide a list of the photographs and the correspondi ng page number in Appendix E. F. Inspection Checklists and/ or Field Notes (Optional) G. Operation and Maintenance Documentation (If required)Chapter 14 Monitoring the Performance of Dams

Revision 1 14-H-3 July 1, 2005 1.0 Findings and Recommendations This Section includes a summary of the Pa rt 12D Independent C onsultant’s findings and assessments and the Part 12D Inde pendent Consultant’s conclusions and recommendations.
1.1 Findings 1.1.1 Summary assessment of the PFMA report 1.1.2 Summary assessment of the Su rveillance 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 C onsultant regarding the condition and suitability for continued safe and relia ble operation of the project and specific conclusions regarding the information in each Section of this Part 12D report. 1.2.1 Conclusions regarding th e suitability of the Projec t for continued safe and reliable operation. 1.2.2 Conclusions regarding the Project Description 1.2.3 Conclusions regarding the Potent ial Failure Modes Analysis Report 1.2.4 Conclusions regarding the Su rveillance and Monitoring Plan 1.2.5 Conclusions regardi ng the Field Inspection 1.2.6 Conclusions regarding the Oper ations and Maintenance Programs 1.2.7 Conclusions regarding the S upporting Technical Information

1.3 Recommendations The recommendations of the Independent Consultant to improve or maintain the condition and suitability for continued sa fe 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 suit ability of the Project for continued safe and reliable operation. 1.2.2 Recommendations regardi ng the Project Description 1.3.3 Recommendations regarding the Poten tial Failure Modes Analysis Report 1.3.4 Recommendations regarding the Su rveillance and Monitoring PlanChapter 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 Op erations and Maintenance Programs 1.3.7 Recommendations rega rding the Supporting

1.4 Certification Note: By signing this document, the Part 12D Independent Consultant is stating that the entire report has been deve loped by and under the direction of the undersigned. The Part 12D Independent C onsultant shall make a clear statement that he/she generally concurs with th e 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 in spection participants
1.4.2 Reference to FERC Order 122 date d 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 struct ure, provide a brief description of the type of structure, general dimensions, et c. 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 br ief 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 Classi fication. 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 (inc lude seasonal reservoir level operating levels and restrictions of reservoir le vel 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 sa fety. (i.e.: spillway gates reinforced, seepage drain, berm added, crest rais ed, 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 updat ed “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 tr ansmission 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 capacityChapter 14 Monitoring the Performance of Dams

Revision 1 14-H-6 July 1, 2005 2.5.3 Peak spillway discharge dur ing last five year period 2.5.4 Peak reservoir elevation dur ing 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 Fa ilure Mode Analysis Report Do not include security issues in the Part 12D report. For li censed projects that include multiple independent dam and powerhouse deve lopments, 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 Anal ysis (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 importan ce. Each PFM assessment should include:

• A description that includes the sequ ence of conditions and events that would lead to the potential failure mode;

• An assessment of the risk reducti on 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. Intern al erosion, piping) 3.2.1.1 Description of PFM (may be taken from PFMA report) 3.2.1.2 Assessment of Risk Re duction 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 Re duction Opportunities 3.2.2.3 Assessment of Surveillance and Monitoring Plan

Etc.
3.3 Are there new potential failure modes that have been identifie d and addressed in this report or that should be assessed? If so, include the ap propriate 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 Surveillan ce and Monitoring Plans must always be done from the point of view of poten tial 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 Le vel 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 su rveillance or an emergency action.
4.1 Operator’s Surveillance Program Daily/weekly operator’s in spections and reports.

4.2 Active Instrumentation: Include a schematic figure showing location of instrumentation (not deta iled or cross section). This will vary by project. Discuss only th e instruments actually at the project. Is instrumentation in accordance with Ch apter IX of the FERC “Engineering Guideline for the Evaluation of Hydropower Projects”? Is th e 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 instrume nts 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 r eadings 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 Incl ude newly identified potential failure modesChapter 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 syst em, etc.), observe and report visual observations of the following issues as appropriate. Include photographs to document significant project feat ures 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 hi ghlight changed cond itions 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 el ement 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 th at 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 / fl umes / 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 Recommend ation(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 Resp ect 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, provid e 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 Re lative 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 / In strumentation / Telemetry – Do the systems provide adequate reliabil ity and redundancy? Can a specific spillway gate, valve or other projec t component be operated remotely on demand?)
6.2.2 Electrical/Mech anical 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 Emergenc y 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 Re lative to Potential Failure Modes

See Appendix G: Operation and Maintenance DocumentationChapter 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 c onclusions of the analyses of record supporting the assessment of the safety of the Project. In each section, where appropriate, the Inde pendent Consultant shall make a clear statement that they have reviewed the pert inent analyses and evaluations along with the underlying assumptions and that they have c oncluded 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 Stud y 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 Pr ocess and Outstanding Issues
7.12 References
7.13 ConclusionsChapter 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 fi gures as appropriate. All Figures should be consecutively numbered. Figures should be ge neral without excessive detail so as to be clearly legible. Figures should include documentati on 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 lo cated including conveyance systems and access routes from main roads and nearest town

• Plans of project facilities

• Typical sections and profiles of key projec t features (dams, spillways, powerhouses, intakes, emergency/fuse plug sp illways, 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 loca tions of each instrument, including design phreatic surface or uplift pressure profile, a nd tabulated data for each instrument are included in the “Supporting Technical Inform ation” document only. See Chapter IX, Instrumentation and Monitoring, of the FERC Engineering Guidelines for the Evaluation of Hydropower Projects for a dditional 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 pl ot. 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 pe ople are color blind - Note that yellow and blue do not reproduce on Xerox machines)

• Include headwater and tailwat er 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 s cale 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 a nd 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 th e 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 Wor ks 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 gene ral, this information will come directly from existing sources such as prior Part 12D Inspection Repo rts, licensing or relicensing documents or company brochures. The detailed descrip tions would include the following elements as appropriate:

• General project description incl uding 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 c ontrol, regulating, and pressu re 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 w ith project facilities located including conveyance system alignment

• Plan of licensed project faci lities and project boundaries

• Typical sections and profiles of key pr oject works (dams, spillways, powerhouses, intakes, canals, tunnels, pe nstocks, flumes, surge chambers, inverted siphons, etc.)

• Satellite or aerial photo of project and downstream area if availableChapter 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 histor y 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 geotechni cal investigations

• Construction reports and photographs

• Specification documents

• Reports of major modifications conducte d for dam safety since last Part 12D inspection

• Construction chronology that includes al l 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 requi rements, lead and follow gate sequence, reservoir level restrictions by season, etc. 4.1 Dam Operations

• Schedule of Inspections (include ro utine operations by operating staff, inspections by engineering staff, and special inspections as appropriate)

• Inspection checklist(s)

• Procedures for assuring satisfactory op erating 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 spi llway and low level outlets as applicable). Are gates operated such that all gates are opened a similar amount? Are some gates opened fully be fore 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 info rmation 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 pert inent project works. 5.1.3 Potential landslides, loose rock forma tions or adverse be dding 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 (geotherma l, 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 proj ect. Differentiate between those traces that have been confirmed by trenchi ng or other means and those that are inferred from other means. 5.2.2 Table of fault, distances, depths, ma gnitude at fault, PGA at site, etc. including local (flo ating 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 docum ent the development of the Probable Maximum Flood (PMF) and the routing of th e PMF through the reservoir and project spillways. In general, this information will co me directly from existing sources such as prior Part 12D Inspection Reports or compa ny reports. The following information that should be included as applicable: 6.1 HydrologyChapter 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 descripti on including drainage area 6.1.4 Antecedent conditions 6.1.5 Loss rates 6.1.6 Basin and sub-basin prec ipitation/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 fl ood flows and reservoir elevations 6.2 Hydraulics – Dams 6.2.1 Project discharge-rating curves (F or multiple gate spillways, outlet structures, powerhouse units, and emer gency/fuse plug spillways, include the contribution of each component as well as the total capacity. Include the equations used to develop the cu rves 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 br eak) The pertinent information from dam break analyses necessary to su pport the determination of the IDF should be included 6.2.6 Reservoir Probable Maximum a nd Inflow Design Flood outflow hydrographs and corresp onding 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 dr awings and/or sketches show ing the location of each active instrument. Include cross-sections of pr oject 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 Projec ts 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 activ e 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 ap propriate information for the record 7.2 Reading frequency for each instrume nt (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 (pne umatic/vibrating wire piezometer, Parshall flume, gape gage, inclinometer, etc) 7.6 Predicted value for each instrument (thresho ld 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 possi ble to list here all the various items that are required to adequate ly detail stability or stress assessments of the project water retaining stru ctures. It will be the res ponsibility of the Licensee to include all information necessary for the r eader 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 anal yzed (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-sec tion) of each structure showing:

• the assumed self weight of the cross section

• all applicable loads in cluding, as appropriate:

• assumed uplift pressure distribution

• silt loads

• headwater and tailwater loads

• point loadsChapter 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 splitti ng tensile strengt h 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, cu toff 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 diagramsChapter 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 overbur den foundations, the material strengths used in the stability analyses should be properly identified i.e. effective stress or total stress. The methods used to determin e/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 beari ng 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 lubrica tion procedures, schedule, etc. 9.4 Summary of gate hoist motor load tests to date (motor name plate rating, line-line voltage, amperage draw, reservoir leve l, 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 Opera tion Inspection Report. Include any major correspondence from FERC or St ate 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 Supp orting Technical Information Document 2) Example of Summary of Em bankment Stability Analysis 3) Example of Summary of Structural Stability Analysis 4) Example of Summary of Hydr ologic and Hydraulic Information 5) Example of Summary of Instrume ntation and Surveillance Information 6) Example of Document Control Log SheetsChapter 14 Monitoring the Performance of Dams

Revision 1 14-I-10 July 1, 2005 

## Attachment 1

Example of Detail Expected in Supporting Technical Information DocumentChapter 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 Probab le Floods for the Middle Fork of the Big River Project", dated October 1961 an d revised in August 1962 by ABC. The de sign flood developed by that flood study, wh en routed through the reservoir and spillway, resulted in a peak discharge of 58,800 cfs at reservoir water surface Eleva tion 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 di rected Big County Water Agency to provide additional information on flood hydrology for the Middle Fork American River Project. The Agency retained Hydr otech of Bigville to perform that study. Hydrotech's report "Probable Maximum Fl ood 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

HoursFlow - Cubic Feet per Second

4,630 4,635 4,640 4,645 4,650 4,655 4,660 4,665 4,670Reservoir Elevation - Feet

Spillway Crest Elevation - 4630 Peak Outflow 69,300 cfs

Peak Reservoir Elevation 4644.8 Peak Inflow 71,600 cfs Big Hole Dam



## Fi g ure 1Chapter 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 usingprocedures 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 appr opriate 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 SecondReservoir Elevation - Feet Big Hole Dam Spillway Rating CurveChapter 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, confi guration and material of Big Hole Dam bu t 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 Fi ve 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 dete rmine the factor of safety of a slope using noncircular failure surfaces selected by the investigator. The sliding mass is divide d 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 tocompute 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 mode l 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 prof ile 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 loca ted 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 soft ened at the failure surface until the average acceleration above the failure surface wa s approximately equal to the yield acceleration. This procedure was required to keep th e system in static equilibrium. The accel eration 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 moti on produced greater accelerations at the failure surfaces. The program DISPLMT, developed at Arizona State University by WilliamChapter 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 a nd 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, γ m (pcf) 127 124
Saturated Unit Weight, γ s (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 condi tions. An analysis of the permeability of the upstream shell with respect to maxi mum rate of rapid drawdown was made and presented in the 1986 Five Year Dam Safety Inspection report. The assumptio n that the upstream rockfill was free-drain ing with respect to rapid drawdown was affirmed. E. Stability Conditions, Minimum Criteria, and Calculated Factors of Safety The stability conditions, minimum criteria, and the calculat ed factors of safety are presented in the fo llowing 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 Fi gures D-3 and D-4 in this Appendix. A Summa ry of the results is presented in the table following. An SDA was performed on the downstream failure surf ace with the lowest yield acceleration (Figure D-3, Case 3, Surface G). The ma ximum expected displacement was calcula ted to be 0.01 feet. On the upstream slope, the failure surface with the lowe st 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 fo r 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 Comple x 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 Associ ates, 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 AmericaChapter 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 - Po ol Elev. 4640, 10 feet above Norm al 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

Revision 1 14-I-19 July 1, 2005 

## Attachment 2

Example of Summary of Embankment Stability AnalysisChapter 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 Y sat (pcf) Y dry (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

Y sat = saturated (total) unit weight (pcf) Y dry = dry unit weight (pcf) Φ ' = effective stress friction angle (degrees) c' = effective stress cohesion intercept (tsf)Chapter 14 Monitoring the Performance of Dams

Revision 1 14-I-21 July 1, 2005 TABLE 5.2.3 - FACTORS OF SAFETY Lower Reservoir Sta. 12+00 Sample Project

LOWER RESERVOIR DAM EMBANKMENT 1
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 2.44 2 1.5 1.95 2.13 2 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/earthquake 3 900.5 1.25 1.0 N/A N/A

IVb Rapid drawdown w/earthquake 3 860.0 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 earthqua ke coefficient, a h = 0.10g.Chapter 14 Monitoring the Performance of Dams

Revision 1 14-I-22 July 1, 2005Chapter 14 Monitoring the Performance of Dams

Revision 1 14-I-23 July 1, 2005 TABLE D.5.2.4 - Factors of Safety Upper Reservoir Sta. 21 + 50 Sample Project

UPPER RESERVOIR DIKE 1 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 2.00 2 1.5 2.97 1.24 2 1.5

III Rapid drawdown 1940 N/A N/A 1.84 1.1

IIIa Normal maximum pool w/earthquake 3 2003 1.56 1.0 N/A N/A

IIIb Rapid drawdown w/earthquake 3 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 earthqua ke coefficient, a h = 0.10g.Chapter 14 Monitoring the Performance of Dams

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## Attachment 3

Example of Summary of Structural Stability AnalysisChapter 14 Monitoring the Performance of Dams

Revision 1 14-I-26 July 1, 2005 VALUES AND ASSUMPTIONS STABILITY ANALYSIS CONCRETE SECTIONS

1. Nomenclature: Effective Length = Uncracked Portion of Base

Σ F H = Summation of Hori zontal Forces - Kips

Σ F V = Summation of Ve rtical Forces - Kips

Σ M R = Summation of Resisting Moments - Kip-Ft.

Σ M O = Summation of Overturning Moments - Kip-Ft.

M R = Factor of Safety Against Overturning M O F H = Coefficient of Sliding F V
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 linear ly 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 pressu res, 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. Th e 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 th e drain', the foundation drains were assumed of greater capacity than the cr ack. This will result in an uplift pressure distribution equal to that w ithout the crack (fu ll headwater at heel and TW + 0.5(HWTW) at drain).Chapter 14 Monitoring the Performance of Dams

Revision 1 14-I-27 July 1, 2005 5. Lateral Water Pressure: Headwater pressures were computed using the full heights of water to headwater elevations over the projecte d 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 become s completely submerged, in accordance with data from U.S. Bureau of Reclamati on 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 resist ance of the foundation to horizontal movement must be investig ated 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 intern al friction of foundation material (Tan Φ = 0.75)

Σ V = Summation of vertical forces c = Unit shearing strength at zero normal load on foundati on material (0.192 ksi) A = Area of potential failure pl ane (area of base in compression)

Σ H = Summation of horizontal forces
According to U.S. Army Corps of Engineer s, Engineering Technical Letter No. 1110-2-256, dated June 24, 1981, which is intended to s upersede portions of EM 1110-2-2200 "Gravity Dam Design" criteria, the minimum allowable S s-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 Wa ter Power Magazine, March, April & May, 1969.Chapter 14 Monitoring the Performance of Dams

Revision 1 14-I-28 July 1, 2005 9. Bearing Pressure: Maximum bearing stress = 20 tsf on bedrock (278 psi).Chapter 14 Monitoring the Performance of Dams

Revision 1 14-I-29 July 1, 2005 SAMPLE PROJECT CASES USED IN STABILITY ANAL YSIS 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 WA TER 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 = 157.0Chapter 14 Monitoring the Performance of Dams

Revision 1 14-I-30 July 1, 2005Chapter 14 Monitoring the Performance of Dams

Revision 1 14-I-31 July 1, 2005Chapter 14 Monitoring the Performance of Dams

Revision 1 14-I-32 July 1, 2005Chapter 14 Monitoring the Performance of Dams

Revision 1 14-I-33 July 1, 2005 SAMPLE PROJECT STABILITY SUMMARY

BASE BASE STRESS (psi) CONDITION TOT LEN CRK LEN EFF LEN FH (kips) FV (kips) FH FV S s-f Resultant from Downstream M R M O M R M O 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 17.0 101.1Chapter 14 Monitoring the Performance of Dams

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## Attachment 4

Example of Summary of Hydrologic and Hydraulic InformationChapter 14 Monitoring the Performance of Dams

Revision 1 14-I-35 July 1, 2005 SAMPLE PROJECTChapter 14 Monitoring the Performance of Dams

Revision 1 14-I-36 July 1, 2005 SAMPLE PROJECT SPILLWAY RATING CURVEChapter 14 Monitoring the Performance of Dams

Revision 1 14-I-37 July 1, 2005 SAMPLE PROJECT TAILWATER RATING CURVEChapter 14 Monitoring the Performance of Dams

Revision 1 14-I-38 July 1, 2005 

## Attachment 5

Example of Summary of Instrumentation and Surveillance InformationChapter 14 Monitoring the Performance of Dams

Revision 1 14-I-39 July 1, 2005Chapter 14 Monitoring the Performance of Dams

Revision 1 14-I-40 July 1, 2005Chapter 14 Monitoring the Performance of Dams

Revision 1 14-I-41 July 1, 2005 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 1765.9Chapter 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 2000Jan-92Feb-93Mar-94Apr-95May-96Jun-97Jul-98Sep-99Oct-00Nov-01Dec-02

DateElevation (FT)

P2-3 P4-4 RESRNDBT

PLOT of PIEZOMETER READINGSChapter 14 Monitoring the Performance of Dams

Revision 1 14-I-43 July 1, 2005Chapter 14 Monitoring the Performance of Dams

Revision 1 14-I-44 July 1, 2005 

## SAMPLE PROJECT
Summary of Vertical Movement s (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 0.125Chapter 14 Monitoring the Performance of Dams

Revision 1 14-I-45 July 1, 2005Chapter 14 Monitoring the Performance of Dams

Revision 1 14-I-46 July 1, 2005 

## SAMPLE PROJECT
Summary of Horizont al 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 1.498Chapter 14 Monitoring the Performance of Dams

Revision 1 14-I-47 July 1, 2005Chapter 14 Monitoring the Performance of Dams

Revision 1 14-I-48 July 1, 2005Chapter 14 Monitoring the Performance of Dams

Revision 1 14-I-49 July 1, 2005Chapter 14 Monitoring the Performance of Dams

Revision 1 14-I-50 July 1, 2005 

## Attachment 6

Example of Document Control Log SheetsChapter 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:

____________________ _______________

____________________ _______________

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 Info rmation Change No. ____

Section Instructions Summary of Changes

Table of Contents Rem ove 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 7Chapter 14 Monitoring the Performance of Dams

Revision 1 14-I-53 July 1, 2005 SUPPORTING TECHNICAL INFORMATION
REVISION LOG NOTICE

BIG POWER PROJECT

Revised Item Date Entered In itials Date Read Initials