Dams Sector Consequence-Based Top Screen Methodology

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Dams Sector Consequence-Based Top Screen Methodology

Dams Sector

Consequence-Based Top Screen (CTS)

Methodology

April 2010


Table of Contents

Table of Contents ........................................................................................................................... i

Acknowledgements ......................................................................................................................iii

Foreword....................................................................................................................................... iv

Acronyms....................................................................................................................................... v

Introduction................................................................................................................................... 1

Purpose..................................................................................................................................... 1

Scope........................................................................................................................................ 3

Methodology Development ..................................................................................................... 4

Consequence-Based Top Screen Process .................................................................................... 6

Overview.................................................................................................................................. 6

Worst Reasonable Case Scenario ............................................................................................ 6

Assembling Relevant Information ........................................................................................... 7

Accessing the Web-Based Application.................................................................................... 8

Completing the Consequence-Based Top Screen.................................................................... 8

General Facility Information ................................................................................................... 9

Contact Information................................................................................................................. 9

Consequence Information ........................................................................................................ 9

Description of Consequence-Based Top Screen Parameters................................................. 10

Criticality Thresholds ............................................................................................................ 16

Prioritization Scheme............................................................................................................. 17

Appendix A: N% Exceedance Duration Pool Elevation ......................................................... 18

Appendix B: Consequence-Based Top Screen Worksheets .................................................... 21

Appendix C: Consequence-Based Top Screen Portfolio Prioritization................................ 37

Table of Contents

i


List of Figures

Figure 1: Consequence-Based Top Screen process.................................................................... 2

Figure 2: Types of Storage and Reservoir Levels. ..................................................................... 7

Figure 3: Portfolio Prioritization............................................................................................... 17

Figure A.1: Recorded pool elevations as a function of time over the period of record........ 20

Figure A.2: Pool elevations as a function of the percent time equaled or exceeded. ............ 20

Figure C.1: Parameter Damage Index Function...................................................................... 38

Figure C.2: Determination of relative weights......................................................................... 39

List of Tables

Table 1: Total population at risk (number of people) ............................................................ 11

Table 2: Close-range population at risk (number of people).................................................. 11

Table 3: Direct Economic Impacts (millions of dollars)......................................................... 12

Table 4: Total population served for water supply (number of people)............................... 14

Table 5a: Annual water deliveries (millions of dollars) ......................................................... 14

Table 5b: Annual water deliveries (acre-feet)......................................................................... 14

Table 6: Installed generating capacity (MW).......................................................................... 14

Table 7: Annual flood damages prevented (millions of dollars)............................................ 14

Table 8: Annual navigation tonnage (kilotons/year) .............................................................. 14

Table 9: Annual recreational visitors (number of people)..................................................... 15

Table 10: Loss of life (number of people) ................................................................................ 15

Table 11: Total economic impacts (millions of dollars).......................................................... 15

Table A.1: Determination of 1% Exceedance Duration Pool elevation................................. 19

Table C.1: Consequence severity levels ................................................................................... 37

Table of Contents

ii


Acknowledgements

The Office of Infrastructure Protection within the U.S. Department of Homeland Security had

the main responsibility for this project. The Sector-Specific Agency Executive Management

Office provided overall technical guidance and coordination for this project as the designated

Sector-Specific Agency (SSA) under the National Infrastructure Protection Plan.

The Dams Government Coordinating Council (GCC) and Sector Coordinating Council (SCC)

formed a Joint GCC/SCC Top Screen Workgroup to monitor, review, and provide input into the

development of the Consequence-Based Top Screen methodology. This team - comprised of

experts from private industry, State governments, and Federal agencies - served a key role in the

development of this document.

With the assistance of the Top Screen Workgroup, opportunities were arranged to conduct

several pilot tests in the field. These tests included both privately- and publicly-owned projects

of diverse sizes and geographic locations.

Sincere gratitude is extended to all contributors for participating in a true partnership of the

public and private sectors to advance the security and protection of the Dams Sector.

Acknowledgements

iii


Foreword

Homeland Security Presidential Directive 7, Critical Infrastructure Identification, Prioritization,

and Protection (December 17, 2003) gives the U.S. Department of Homeland Security (DHS)

authority to coordinate the overall national effort to enhance the protection of the critical

infrastructure and key resources of the United States (Sec 12). DHS was also given explicit

responsibility to coordinate protection activities for the Dams Sector (Sec. 18.d), which

encompasses water retention and water control structures that impound, divert, or control water

for a variety of purposes including water supply, irrigation, hydropower generation, navigation,

flood control, storm surge protection, recreation, environmental preservation, sediment control,

and hazardous material impoundment. In most cases, Dams Sector assets are part of multicomponent

systems (dam projects, navigation projects, flood damage reduction projects) that

may perform several functions.

A clear and consistent screening strategy is needed to conduct a systematic preliminary

prioritization of the assets included in the Dams Sector. Considering the large number of assets

within the sector, it is appropriate to initially identify and characterize the subset of those highconsequence

facilities whose failure or disruption could potentially lead to the most severe

impacts. This screening methodology should be scalable and able to be implemented at different

portfolio levels (national, regional, and State) by adopting consequence thresholds that

appropriately represent the corresponding scope under consideration. There is a clear need to

establish a sector-wide approach to measure and quantify the consequence elements included in

these prioritization analyses.

In addition, conducting a screening of high-consequence projects provides a great opportunity to

consolidate other data that may be extremely relevant in providing a full description of the

relative importance of a given project and its primary functions. This information is valuable not

necessarily for the prioritization purposes indicated above, but as part of the overall situational

awareness that is critically necessary to support and sustain the regional impact assessments that

need to be developed by the Dams Sector-Specific Agency during incidents related to natural

hazards or manmade events.

Foreword

iv


Acronyms

CTS

DHS

EAP

GCC

GIS

Consequence-Based Top Screen

U.S. Department of Homeland Security

Emergency Action Plan

Government Coordinating Council

Geographic Information System

HSPD-7 Homeland Security Presidential Directive -7

IP

NID

NIPP

PAR

SCC

SSA

PCI

LOL

Office of Infrastructure Protection

National Inventory of Dams

National Infrastructure Protection Plan

Population at Risk

Sector Coordinating Council

Sector-Specific Agency

Potential Consequence Index

Loss of Life

Acronyms

v


Introduction

Purpose

Homeland Security Presidential Directive 7 (HSPD-7), Critical Infrastructure Identification,

Prioritization, and Protection (December 17, 2003), directs the U.S. Department of Homeland

Security (DHS) to develop a National Infrastructure Protection Plan (NIPP) to identify,

prioritize, and coordinate the protection of the Nation’s critical infrastructure and key resources.

In the case of the Dams Sector, as the initial step towards developing a systematic prioritization

process and considering the large number of sector assets, it is clearly necessary to establish a

sound top screening methodology to quickly identify those projects whose failure or disruption

could potentially lead to the most severe consequences. The development of the Consequence-

Based Top Screen (CTS) methodology fulfills this need.

By focusing on consequences and decoupling the analysis from the threat and vulnerability

components of the risk process, the CTS approach can serve as an effective all-hazards

preliminary prioritization scheme for both dam security and dam safety purposes. The purpose of

the CTS methodology is to identify critical facilities within the Dams Sector (i.e., those highconsequence

facilities whose failure or disruption could be potentially associated with the

highest possible impact among Dams Sector assets). The methodology also provides a systematic

tool that can be used for updates of this corresponding information whenever necessary.

As a prioritization tool, the purpose of the CTS process is to inform and support decisions

regarding additional analyses and detailed studies. For example, in the case of an owner

responsible for a large portfolio of dams, those sites identified as high-consequence facilities

through the CTS process could be assigned higher priority for conducting detailed flood

inundation studies or detailed risk assessments. Another example would be the case of a natural

hazard such as an incoming hurricane threatening a large coastal region. The results from the

CTS process could effectively inform decision-makers about those facilities within the area that

should receive particular attention from the emergency management community because of their

potential for significant impacts at the local and regional levels.

In addition, conducting a screening of high-consequence projects provides a great opportunity

not only to update project contact information but also consolidate other data that may be

extremely relevant in providing a full description of the relative importance of a given project

and its primary functions. This information is valuable not necessarily for the prioritization

purposes indicated above, but as part of overall situational awareness that is critically necessary

to support and sustain the regional impact assessments that need to be developed by the Dams

Sector-Specific Agency (SSA) during incidents related to natural hazards or manmade events.

Introduction 1


Effective implementation of the CTS methodology allows the Dams Sector to achieve a

systematic baseline to:

• Establish common methods, assumptions, and measures to consistently quantify different

types of consequence elements (human health, economic, and mission disruption) leading

to a sector-wide prioritization framework to facilitate comparison of consequence

information within the sector.

• Consolidate asset consequence information that can assist dam owners in identifying the

most significant facilities within their corresponding portfolios in alignment with sectorwide

criteria.

• Identify updated contact information that would facilitate effective and direct

communication with asset owners potentially affected by imminent natural hazards

incidents, threat stream data, or other intelligence information.

• Support the development of accurate estimates for potential national and regional impacts

associated with high-consequence projects affected by natural hazards or manmade

incidents.

• Support DHS national critical infrastructure prioritization efforts which focus on

establishing a cross-sector set of assets with nationally significant consequences.

Figure 1: Consequence-Based Top Screen process.

Data Collection

General

Information

Contact

Information

Consequence

Information

Consequence-Based

Top Screen

Sector-Wide

Consequence-Based

Prioritization

Facility

Considered

Critical

Yes

Identification of

High-Consequence

Facilities

Relative Prioritization of

High-Consequence

Facilities

Figure 1 depicts the CTS process as the tool that enables a systematic sector-wide prioritization

that identifies those facilities, either individual assets or systems of multiple assets, that reach

critical importance based on the potential consequences resulting from severe damage or

disruption. A system of multiple assets is defined as a set of individual or structurally

independent assets that are not necessarily located in spatial proximity of each other or within a

single project, but work together to perform one or more primary functions (i.e., water supply,

flood damage reduction, etc.) within an integrated system. For example, an integrated flood

Introduction 2


damage reduction system may include a number of structures and components (spillways, pump

stations, etc.) that are essential to the function of the system but are not located within the same

local area. In general, a system of multiple assets is spatially distributed across the same

watershed or within the same floodplain.

The potential consequences associated with failure, significant damage, or prolonged disruption

of Dams Sector facilities could be quite severe, and could reach different levels of significance.

By using metrics that cover a range or spectrum of potential values, the CTS screening

methodology is completely scalable and could be effectively implemented at different portfolio

levels (owner, State, regional, and national). Therefore, the CTS process could assist in

identifying assets that may be of regional or State significance by adopting consequence

thresholds that are appropriate for each case.

The information collected through the effective implementation of the CTS methodology is

critical for sector-wide impact analyses and prioritizations. Whenever possible, the information

collected through this screening process must be:

Scope

• Generated by the appropriate technical personnel in active collaboration with emergency

responders and other relevant stakeholders such as the corresponding State dam safety

offices, using a reasonable and practical level of resources, and taking full advantage of

previous studies or evaluations.

• Consistent, comparable, and collected using similar assumptions.

• Sufficiently detailed to allow for consequence-based prioritization.

• Updated through periodic self-reviews voluntarily conducted by owners/operators.

• Collected in conformance with the appropriate information safeguarding procedures

available to owners/operators.

The CTS methodology has been developed for voluntary use by Dams Sector stakeholders. This

methodology is available to all those who own, operate, or regulate sector assets, or have

responsibility for security and protection of those assets. Dams Sector assets include the

following types of facilities:

• Dam Projects

• Flood Damage Reduction Systems

• Hurricane and Storm Surge Protection Systems

• Mine Tailings Projects

The CTS methodology presented in this document covers dam projects including some or all of

the following components: water retention structures (i.e., impounding structure - the structural

sections that hold back the water); impoundments (i.e., reservoir - the body of water impounded

Introduction 3


y the dam); water control structures (i.e., spillway - the structure that passes normal and/or

flood flows in a manner that protects the structural integrity of the dam, or outlet works - the

combination of structures and equipment required for safe operation and control of water

released from a reservoir); hydropower generation facilities (i.e., hydropower plant (conventional

plant, run-of-the river plant, or pumped-storage plant) - the structure that houses turbines,

generators, and associated control equipment for the production of hydroelectricity); navigation

structures (i.e., navigation locks - walled sections of a river or canal, closed by gates at both

ends, in which the water level can be raised or lowered by means of valves or sluiceways to

match the level in the upper or lower reach, as desired); water conveyance structures (i.e., canal

or aqueduct - a constructed channel, usually open, that conveys water by gravity or is used for

navigation); and remote operations and control facilities (i.e., remote operation center - off site

facility that performs monitoring and control operations). For the purposes of this document, the

term “dam” will be used to denote the entire facility (i.e., dam project, which may include some

or all of the functional components mentioned above).

Due to their special characteristics and functions, other Dams Sector assets such as mine tailings

projects, hurricane and storm surge protection systems, and flood damage reduction systems are

not addressed by this version of the CTS methodology.

Methodology Development

The Dams Sector established a Top Screen Workgroup consisting of members of the Dams

Sector Coordinating Council and the Dams Government Coordinating Council to oversee the

development of the CTS methodology. This workgroup - comprised of experts from private

industry, State governments, and Federal agencies - served a key role in the development of the

screening methodology.

The initial draft of the CTS methodology was tested in 2007 at Bonneville Lock and Dam,

Melvin Price Lock and Dam (both projects owned by the U.S. Army Corps of Engineers), and

Rocky Reach Dam (owned by Chelan County Public Utility District No. 1). The main purpose of

these initial tests was to evaluate the practicality and onsite resource requirements of the

proposed approach. On the basis of experiences and lessons learned during these tests, the CTS

methodology was slightly modified and piloted in 2008.

A first pilot was conducted in April 2008 as a way to validate the ranges used to assess

consequences, as well as to support the validation of the thresholds used to identify facilities

potentially associated with nationally significant consequences. This effort involved 26 projects in

the following States: Idaho, Montana, Nevada, Oregon, and Washington. The set included 20

hydropower projects. Participation in this effort required each project to complete a CTS

questionnaire with basic questions regarding project characteristics, infrastructure

interdependencies, and potential consequences associated with severe disruption or failure.

Participating projects completed this questionnaire using a Web-based password-protected portal.

Each respondent’s questionnaire was pre-populated with available National Inventory of Dams

(NID) facility-specific information. The portal also provided access to geographic information

system (GIS)-based maps to aid in identifying potentially impacted populations and infrastructure.

Introduction 4


The questionnaire included a number of tables from which participants selected, from preestablished

ranges, those consequence estimates applicable to their facility. Different

consequence parameters were used to obtain information on population at risk (PAR), asset

replacement cost, remediation cost, business interruption costs, population served for drinking

water supply, annual value of water deliveries, generating capacity, average annual damages

prevented, annual navigation tonnage, and annual number of recreational visits. The tables

contained follow-on questions for several of the consequence categories, requesting information

such as population centers served by the facility as a potable water supply source, percentage of

market share, names of affected water treatment facilities, and other additional information.

In addition to the tables and related follow-on questions, respondents were asked to provide

information on which, if any, military installations or Federal facilities could be impacted by

failure or disruption of the project. Respondents were also provided with a specific list of

infrastructure categories (e.g., fossil fuel electric power generation facilities, nuclear electric

power generation facilities, major airports, chemical manufacturing plants) and asked to identify

which, if any, facilities in those categories would be within the dam failure inundation area. A

review of collected data revealed that many of these questions related to interdependencies and

cascading impacts were not fully completed by many of the respondents or resulted in

inconsistent answers. By comparison, the direct consequence tables were completed and did not

appear to be sources of confusion or excessive complexity.

A second pilot was conducted later in September 2008 to expand the data set by including

additional projects with different characteristics. This effort included 22 projects in the following

States: California, Colorado, Montana, New Jersey, Ohio, and Pennsylvania. This second set

included only 2 hydropower projects. A streamlined version of the CTS questionnaire was

employed for this second pilot, consisting only of the consequence-related questions involving

numerical parameters. Participants provided the corresponding information by simply

completing a spreadsheet sent to the State dam safety officers of the participating States. Since

the process was significantly simplified, data collection was simpler and the spreadsheets were

easier to complete and disseminate. However, key information elements such as how the PAR

estimates were made or the economic estimates were calculated were not asked. Because of this,

it was very difficult to validate the answers and explain any inconsistencies.

A representative data set was generated by these pilot efforts as they were based on a balanced

mix of 48 dams with different ownership characteristics, since they include Federal (13 sites),

State (9 sites), local (11 sites), public utility (7 sites), and private (8 sites) owners. In addition, 22

of the participating projects are regulated by the Federal Energy Regulatory Commission. These

pilot efforts provided a substantial amount of information that was critical for the refinement of

the CTS methodology.

Introduction 5


Consequence-Based Top Screen Process

Overview

Consequence-based prioritization constitutes an important first step towards the implementation

of a risk management framework that can deal with a very large number of facilities. In addition,

a consequence-focused approach can fully support all-hazards considerations involving natural

hazards or manmade incidents, and therefore provide relevant information useful for both dam

security and dam safety purposes. In the case of human threats represented by an intelligent and

adaptive adversary, it would be practically impossible to conduct in-depth vulnerability

evaluations of all assets in a target-rich environment such as the Dams Sector. In this case, the

CTS process can effectively reduce the size of the problem by identifying those assets that could

potentially attract higher adversarial interest.

Worst Reasonable Case Scenario

For the purpose of identifying assets associated with high potential consequences, the screening

procedure is based on consideration of the worst reasonable case scenario, and its resulting

impacts on human health and safety caused by inundation of downstream populated areas;

economic impacts; and impacts associated with loss of critical functions.

The worst reasonable case scenario represents a condition of total or extremely severe damage to

the facility, but considering that the situation is not simultaneously compounded or exacerbated

by concurrent extreme events, freak acts of nature, or human error. It is important to note that the

screening criteria do not consider the structural condition or vulnerability of the facility nor do

they address the likelihood of the natural hazard or manmade incident triggering the worst

reasonable case scenario. Therefore, the resulting consequence estimates should constitute a

reasonable upper bound to the potential impacts associated with severe damage or disruption to

the facility, regardless of the triggering event.

Defining a reasonable scenario for consequence assessment of Dams Sector assets requires

determining an appropriate pool elevation. The objective is to establish the appropriate hydraulic

condition that can be reasonably assumed at the site. In spite of the fact that this consequence

assessment is conducted without any specific reference to a particular threat or hazard, it must be

assumed that the severe damage or disruption will take place under worst reasonable conditions

at the site.

Therefore, a reasonably conservative representation of the pool elevation must be selected within

the normal operating range between the minimum operating level and the level corresponding to

the top of the active storage. The minimum operating level is defined as the lowest level to which

Consequence-Based Top Screen Process 6


the reservoir is drawn down under normal operating conditions and the active storage is the

volume of the reservoir that is available for some use such as power generation, irrigation, flood

control, water supply, etc. The active storage does not include flood surcharge which is the

storage volume between the top of the active storage and the design water level.

Figure 2: Types of Storage and Reservoir Levels.

Design

Water Elevation

Top of Active Storage

Pool Elevation

Surcharge Storage

Surcharge Storage

Normal

Pool Elevation

Flood Storage

Minimum Operating

Pool Elevation

Maximum

Storage

Active Storage

Normal

Storage

Conservation Storage

(M&I Water Supply,

Irrigation, Hydropower,

Navigation, etc.)

Inactive Storage

Inactive Storage

Dead Storage

Dead Storage

The pool elevation corresponding to the top of active storage provides, in most cases, a

convenient and reasonable worst case scenario. For dams with uncontrolled spillways, this

elevation would typically correspond to the spillway crest. For dams with controlled or gated

spillways, this elevation would typically correspond to an elevation at or near the top of the

spillway gates. However, it must be highlighted that for some projects with unique

characteristics, an alternate pool elevation within the normal operating range may be more

appropriate for this type of all-hazards screening analysis. In some cases, it may be more

appropriate to define the screening scenario based on historical information, selecting a reservoir

condition that corresponds to a given exceedance duration (pool elevation that is equaled or

exceeded a given percentage of the time on an annual basis; see Appendix A for additional

details). Careful engineering judgment must be used in establishing pool elevations for allhazards

consequence-based screening.

Assembling Relevant Information

Prior to completing the CTS, it is beneficial to identify and collect the relevant technical

information in advance so there is an opportunity to verify the accuracy and completeness of

the data. This phase should include discussions with local emergency responders, as this

interaction could lead to additional information regarding potential impacts on local and

regional communities.

Consequence-Based Top Screen Process 7


The use of the following information and material is encouraged for application of the

CTS methodology:

• Information characterizing the worst reasonable case consequences resulting from severe

damage or disruption to the facility. Any available dam safety studies, previous

assessments and inspection reports may play a crucial role since they may contain much

of the consequence information required for the CTS process.

• Inundation maps that include sufficient detail to be able to identify and locate

downstream population centers, industrial facilities, and other critical infrastructure that

could be impacted by the worst reasonable case dam break scenario.

• Information related to the benefits arising from the project mission and operation, as

typically collected on an annual basis.

• Emergency action plans, mutual support agreements, incident response plans, recovery

plans, continuity of operations plans, community hazard mitigation plans, and any other

documents that may further contain information on the project and its potential impact on

the well-being of local and regional communities.

• Insurance information for capital replacement and business interruption expenses.

Collecting this information requires involvement of multi-disciplinary project personnel to

estimate the potential impacts associated with failure or disruption of the project. It is important

to highlight that a significant amount of the required consequence information may be readily

available in dam safety assessments and periodic inspection reports. Technical personnel

knowledgeable on dam safety, operations and maintenance, and any other relevant project

functional areas should be involved in the application of the CTS to a given facility.

Accessing the Web-Based Application

The CTS User Management Tool allows selected personnel to generate and manage accounts for

the different users participating in the process. The user management tool allows a hierarchical

user structure that can include up to four user levels. At levels 1-3, the user has the option of

completing the CTS questionnaire for a specific set of dam(s) or assigning its completion to

other users at the next level. A dam can only be assigned to one user of a given level to avoid

data conflicts. Level 4 users are restricted from assigning dams to other participants. Once the

CTS questionnaire is completed for a given facility, the information is progressively sent up the

user structure for review and concurrence. This process continues up to level 1. Once it reaches

the level 1 user, the completed CTS can be submitted to DHS. A report of the completed CTS

questionnaire may be printed by the user prior to submitting the document.

Completing the Consequence-Based Top Screen

The CTS methodology is implemented through an interactive questionnaire, which addresses

general facility information, contact information, and consequence information, as portrayed in

the top box in Figure 1. The proceeding paragraphs describe the content of these sections.

Consequence-Based Top Screen Process 8


General Facility Information

The first section of the CTS questionnaire includes general facility information such as data

fields associated with the NID and basic project characteristics. Many fields in this section are

pre-populated with the NID data.

Contact Information

The second section of the CTS questionnaire includes contact information for the facility point of

contact (owner/operator representative(s) designated as the point of contact and qualified to

answer technical questions about project characteristics and its different operations).

Consequence Information

The third section of the CTS questionnaire focuses on the different parameters used as part of the

screening and prioritization process, which are consistent with general consequence categories

established by the NIPP. The potential consequences are considered through a number of

parameters that quantify impacts or effects associated with failure or disruption of the project.

These parameters provide a characterization of human impacts, economic impacts, and impacts

on critical functions. The CTS questionnaire includes a number of tables that allow users to

select the appropriate parameter values applicable to the facility based on pre-established ranges.

It must be highlighted that some of the parameters provide only a measure of the project

“capacity” to perform a given function, and do not necessarily constitute a direct measure of

consequences. However, it is assumed that they effectively provide an indirect representation of

the total potential consequences associated with the failure or disruption of the project.

The CTS approach focuses on the following potential impacts associated with severe damage

or disruption:

• Human Impacts - Impacts on human health and safety caused by inundation of

downstream populated areas, industrial areas, and other critical infrastructure assets.

• Economic Impacts - Impacts associated with damages to the facility, direct damage to

downstream inundated areas, and direct monetary impacts associated with lost project

benefits.

• Impacts on Critical Functions - Secondary effects associated with the disruption or loss

of the critical functions provided by the facility.

• National Level Impacts - Standard set of cross-sector impacts used to identify facilities

of national significance in terms of potential consequences.

Consequence-Based Top Screen Process 9


The CTS questionnaire includes a series of questions linked to these different categories. The

following table contains a summary of the corresponding consequence parameters.

1. Human Impacts

Consequence Parameters

a. Total Population at Risk (PAR T ) within Flood Scenario Inundation Zone

b. Close Range Population at Risk

(i) Population at Risk within 0 and 3 Miles from the Dam (PAR 1 )

(ii) Population at Risk within 3 and 7 Miles from the Dam (PAR 2 )

(iii) Population at Risk within 7 and 15 Miles from the Dam (PAR 3 )

(iv) Population at Risk within 15 and 60 Miles from the Dam (PAR 4 )

2. Economic Impacts

a. Asset Repair/Replacement Cost (E 1 )

b. Remediation Cost (E 2 )

c. Business Interruption Costs (Lost Project Benefits) (E 3 )

3. Impacts on Critical Functions

a. Water Supply (M 1 )

b. Irrigation (M 2 )

c. Hydropower Generation (M 3 )

d. Flood Damage Reduction (M 4 )

e. Navigation (M 5 )

f. Recreation (M 6 )

4. National Level Impacts

a. Loss of Life (LOL)

b. Total Economic Costs (E T )

c. Mass Evacuation

d. National Security

Description of Consequence-Based Top Screen Parameters

1. Human Impacts

a. Total Population at Risk:

The CTS methodology requires an estimated value for the Total Population at Risk (PAR T )

within the flood inundation zone. For purposes of this methodology, the population at risk is the

total estimated number of humans occupying a permanent residence, commercial building, or

recreational area in the potential zone of inundation represented by the dam-break 1 flood

scenario. The (PAR T ) can be determined by use of the site-specific inundation map prepared for

the dam. This map provides an estimation of the boundary of the zone, and must be of a scale

sufficient to locate all permanent structures and population within the inundation zone. Recent

census data can be used to estimate the number of persons located within the entire inundation

zone. Since the approach is based on a worst reasonable case scenario, any persons using

1 A dam break means that the capability of the dam to impound water has been partially or totally lost, resulting in an uncontrolled

release of water.

Consequence-Based Top Screen Process 10


ecreational facilities (day-use or over-night) within the

zone should also be considered, including times of high

use such as on holidays or during special sporting or

other types of events that attract large crowds. Table 1

shows the different ranges considered for this

consequence parameter.

b. Close Range Population at Risk:

The CTS methodology requires estimated values for the

population within different downstream distance ranges

from the toe of the dam:

• 0 and 3 miles (PAR 1 )

• 3 and 7 miles (PAR 2 )

Table 1: Total population at risk

(number of people)

Total

Level PAR (PAR T )

1 PAR T > 800,000

2 400,000 < PAR T ≤ 800,000

3 200,000 < PAR T ≤ 400,000

4 100,000 < PAR T ≤ 200,000

5 50,000 < PAR T ≤ 100,000

6 25,000 < PAR T ≤ 50,000

7 0 < PAR T ≤ 25,000

8 PAR T = 0

• 7 and 15 miles (PAR 3 )

• 15 and 60 miles (PAR 4 )

For unusual cases, such as facilities that are not fed by a river or other natural means, the toe of

the dam is considered to be the most critical location around the walled peripheral of the

reservoir with the highest population at risk in the event of a breach. It is strongly emphasized

that this approach is not meant to capture expected loss of life. The focus of the methodology is

to approximately capture a reasonable estimate of the population that could be most severely

affected by the flood scenario arising from the dam failure. This involves not only the possibility

of fatalities, but also the disruption associated with emergency response activities, evacuation,

and relocation. Table 2 shows the different ranges considered for these consequence parameters.

Table 2: Close-range population at risk (number of people)

PAR PAR PAR PAR

Level 0-3 miles (PAR 1 ) 3-7 miles (PAR 2 ) 7-15 miles (PAR 3 ) 15-60 miles (PAR 4 )

1 PAR 1 > 4,000 PAR 2 > 8,000 PAR 3 > 16,000 PAR 4 > 64,000

2 2,0000 < PAR 1 ≤ 4,000 4,000 < PAR 2 ≤ 8,000 8,000 < PAR 3 ≤ 16,000 32,000 < PAR 4 ≤ 64,000

3 1,000 < PAR 1 ≤ 2,000 2,000 < PAR 2 ≤ 4,000 4,000 < PAR 3 ≤ 8,000 16,000 < PAR 4 ≤ 32,000

4 500 < PAR 1 ≤ 1,000 1,000 < PAR 2 ≤ 2,000 2,000 < PAR 3 ≤ 4,000 8,000 < PAR 4 ≤ 16,000

5 250 < PAR 1 ≤ 500 500 < PAR 2 ≤ 1,000 1,000 < PAR 3 ≤ 2,000 4,000 < PAR 4 ≤ 8,000

6 125 < PAR 1 ≤ 250 250 < PAR 2 ≤ 500 500 < PAR 3 ≤ 1,000 2,000 < PAR 4 ≤ 4,000

7 0 < PAR 1 ≤ 125 0 < PAR 2 ≤ 250 0 < PAR 3 ≤ 500 0 < PAR 4 ≤ 2,000

8 PAR 1 = 0 PAR 2 = 0 PAR 3 = 0 PAR 4 = 0

Consequence-Based Top Screen Process 11


It is clear that the number of expected fatalities resulting from a dam-break inundation may be

significantly less than the population at risk, and depends on many factors (e.g., time of warning,

depth of flooding, velocity of flood wave, etc). People residing immediately downstream of the

dam may be at greater risk than those further downstream because the dam-break flood wave

will reach them sooner. However, in some cases, people located at longer distances could be at

greater risk than those closer to the dam, depending on when and how the dam-break warnings

are issued. Therefore, distance downstream of a dam is not necessarily a reliable indicator of

potential life loss.

2. Economic Impacts

The economic consequences and impacts are estimated based on the worst reasonable case

scenario, which will often, but not always, represent some form of catastrophic failure. This

section refers only to economic losses as measured in US Dollars. For purposes of this

estimation, the dam-break flood condition is likely to be the initiating case, although site-specific

studies may show variations. The scenario resulting in maximum economic losses should be

used, which may differ from the scenario that can cause the greatest human impact. All pertinent

structures of value located within the downstream inundation zone must be considered. The

estimation must be made as to whether they would be damaged or destroyed based on expert

judgment and prior case histories of

dam failure incidents. If in doubt, total

destruction of affected structures

should be used. The highest value

property losses may not necessarily

correspond to the maximum number of

buildings and equipment. For example,

a central control building or switch

gear room at a dam is likely to have a

much higher replacement cost value

than a maintenance shop or

warehouse. Table 3 shows the

different ranges considered for the

consequence parameters representing

direct economic impacts, which are

described next.

a. Asset Repair/Replacement Costs:

Level

Table 3: Direct Economic Impacts

(millions of dollars)

Asset

Replacement

Cost (E 1 )

Remediation

Cost (E 2 )

1 E 1 > 3,200 E 2 > 16,000 E 3 > 800

Business

Interruption

Cost (E 3 )

2 1,600 < E 1 ≤ 3,200 8,000 < E 2 ≤ 16,000 400 < E 3 ≤ 800

3 800 < E 1 ≤ 1,600 4,000 < E 2 ≤ 8,000 200 < E 3 ≤ 400

4 400 < E 1 ≤ 800 2,000 < E 2 ≤ 4,000 100 < E 3 ≤ 200

5 200 < E 1 ≤ 400 1,000 < E 2 ≤ 2,000 50 < E 3 ≤ 100

6 100 < E 1 ≤ 200 500 < E 2 ≤ 1,000 25 < E 3 ≤ 50

7 0 < E 1 ≤ 100 0 < E 2 ≤ 500 0 < E 3 ≤ 25

8

E 1 = 0 E 2 = 0 E 3 = 0

Asset repair/replacement costs (E 1 ) include those costs associated with structures, equipment,

units, or other onsite property that would need to be repaired or replaced to restore the original

functionality of the facility to the design level. Asset repair/replacement costs represent a direct

loss caused by the damage or destruction of the facility and are estimated whether or not the

owner chooses to rebuild.

The economic value to repair or replace the damaged or destroyed facility is estimated in US

Dollars. For the purposes of this estimation, replacement values are used. Market values, which

Consequence-Based Top Screen Process 12


are volatile, should not be used for this estimate. Similarly to human impact, the worst

reasonable case scenario which yields the highest costs is used as the basis for the estimate.

b. Remediation Costs:

Remediation costs (E 2 ) include offsite costs related to property damage and environmental

restoration, as well as costs associated with temporary structures and emergency response efforts.

For the purpose of this estimation, remediation costs should not include indirect costs such as

lawsuits, increased insurance costs, higher financing/borrowing costs, fines imposed by

regulators, or liability costs associated with damage to other property or the environment.

Therefore, this estimate may include the following items:

• Costs to repair or replace downstream property directly damaged by the inundation or

any potential cascading failures (e.g., residential, commercial, and industrial property,

and critical infrastructure in general).

• Costs to remediate and restore any direct environmental effects caused by the failure

scenario, including release of hazardous materials or contaminants.

• Costs associated with temporary remediation measures such as temporary construction as

well as rented/leased facilities or equipment.

• Costs associated with emergency response efforts, search and rescue activities, and any

safety/security measures required for public protection within the affected area.

c. Business Interruption Costs (Lost Project Benefits):

Business interruption costs (E 3 ) represent the total estimated value of the benefits not being

produced over a standard time period during which the facility is considered out of service.

These lost benefits are estimated for the first 12 months after the incident or event. This estimate

represents only the value of the benefits not provided by the facility during the first year after the

incident, and does not include indirect impacts associated with business interruption, lost market

share, etc.

For the purpose of this estimation, all project purposes associated with quantifiable direct

benefits must be considered. This includes water deliveries for municipal and industrial

purposes, water deliveries for agricultural irrigation purposes, treaty water supply, hydropower

generation, flood damage reduction, fish and wildlife, inland navigation, recreation, etc. For

example, to approximate the lost benefits associated with costs of hydropower generation, the

facility could estimate an “average annual generation figure” and multiply it by a generic unit

value of $60 per mega-watt hour. 2 This product would represent an estimate of the value of the

hydropower generation benefits associated with the facility.

2 The estimated value is in 2010 US Dollars.

Consequence-Based Top Screen Process 13


3. Impacts on Critical Functions

The failure or disruption of the facility may severely impact essential services or critical

functions that affect populated centers, industrial areas, agricultural regions, flood protected

areas, or inland navigation systems. The CTS questionnaire requires an estimation of the relative

importance (in terms of “size” or “capacity”) of the critical

functions provided by the project. This provides an indirect

measure of the potential indirect impacts and secondary

effects that could be caused by the long-term interruption of

those functions. The CTS questionnaire considers the

following critical functions:

a. Water Supply:

The relative importance of this function is quantified

through the total population served by the facility as the

main water supply source for municipal and industrial use

(M 1 ). Table 4 shows the different ranges considered for this

parameter.

Table 5b: Annual water

b. Irrigation:

deliveries (acre-feet)

The relative importance of this

function is quantified by the value of

annual water deliveries quantified in

dollars or annual volume (M 2 ).

Tables 5a and 5b show the different

ranges considered for this parameter.

c. Hydropower Generation:

The relative importance of this

function is quantified in terms of

total installed capacity (M 3 ). Table

6 shows the different ranges

considered for this parameter.

d. Flood Damage Reduction:

The relative importance of this

function is quantified by the value

of annual flood damages prevented

(M 4 ). Table 7 shows the different

ranges considered for this

parameter.

Annual Water

Level Deliveries (M 2 )

1 M 2 > 6,400,000

2 3,200,000 < M 2 ≤ 6,400,000

3 1,600,000 < M 2 ≤ 3,200,000

4 800,000 < M 2 ≤ 1,600,000

5 400,000 < M 2 ≤ 800,000

6 200,000 < M 2 ≤ 400,000

7 0 < M 2 ≤ 200,000

8 M 2 = 0

Table 6: Installed generating

capacity (MW)

Installed

Level Capacity (M 3 )

1 M 3 > 8,000

2 4,000 < M 3 ≤ 8,000

3 2,000 < M 3 ≤ 4,000

4 1,000 < M 3 ≤ 2,000

5 500 < M 3 ≤ 1,000

6 250 < M 3 ≤ 500

7 0 < M 3 ≤ 250

8 M 3 = 0

Table 4: Total population served

for water supply (number of people)

Total

Level Population Served (M 1 )

1 M 1 > 4,000,000

2 2,000,000 < M 1 ≤ 4,000,000

3 1,000,000 < M 1 ≤ 2,000,000

4 500,000 < M 1 ≤ 1,000,000

5 250,000 < M 1 ≤ 500,000

6 125,000 < M 1 ≤ 250,000

7 0 < M 1 ≤ 125,000

8 M 1 = 0

Table 5a: Annual water

deliveries (millions of dollars)

Annual Water

Level Deliveries (M 2 )

1 M 2 > 800

2 400 < M 2 ≤ 800

3 200 < M 2 ≤ 400

4 100 < M 2 ≤ 200

5 50 < M 2 ≤ 100

6 25 < M 2 ≤ 50

7 0 < M 2 ≤ 25

8 M 2 = 0

Table 7: Annual flood damages

prevented (millions of dollars)

Flood Damages

Level Prevented (M 4 )

1 M 4 > 800

2 400 < M 4 ≤ 800

3 200 < M 4 ≤ 400

4 100 < M 4 ≤ 200

5 50 < M 4 ≤ 100

6 25 < M 4 ≤ 50

7 0 < M 4 ≤ 25

8 M 4 = 0

Consequence-Based Top Screen Process 14


e. Navigation:

The relative importance of this

function is quantified in terms of

the estimated annual navigation

tonnage in both directions (M 5 ).

Table 8 shows the different ranges

considered for this parameter.

f. Recreation:

Table 8: Annual navigation

tonnage (kilotons/year)

Navigation

Level Tonnage (M 5 )

1 M 5 > 100,000

2 50,000 < M 5 ≤ 100,000

3 25,000 < M 5 ≤ 50,000

4 12,500 < M 5 ≤ 25,000

5 6,250 < M 5 ≤ 12,500

6 3,125 < M 5 ≤ 6,250

7 0 < M 5 ≤ 3,125

8 M 5 = 0

Table 9: Annual recreational

visitors (number of people)

Annual

Level Visitors (M 6 )

1 M 6 > 4,000,000

2 2,000,000 < M 6 ≤ 4,000,000

3 1,000,000 < M 6 ≤ 2,000,000

4 500,000 < M 6 ≤ 1,000,000

5 250,000 < M 6 ≤ 500,000

6 125,000 < M 6 ≤ 250,000

7 0 < M 6 ≤ 125,000

8 M 6 = 0

The relative importance of this

function is quantified by the number of visitors to the project recreational area (M 6 ). Table 9

shows the different ranges considered for this parameter.

4. National Level Impacts Table 10: Loss of life

(number of people)

The CTS questionnaire also supports the identification of

infrastructure whose failure or disruption could cause nationally

or regionally catastrophic effects. This is conducted by

estimating the magnitude of the potential impacts that could be

associated with the severe damage or disruption of the facility in

terms of loss of lives, total economic consequences, mass

evacuations of urban areas, and degradation of national security.

a. Loss of Life:

This consequence category is quantified by the estimated range

of potential fatalities (LOL). Table 10 shows the different ranges

considered for this parameter.

b. Total Economic Costs:

This consequence category is quantified by the estimated range

of first-year total economic consequences (E T ). This estimate

may include not only direct impacts (e.g., asset

repair/replacement, remediation, and business interruption costs)

but also indirect impacts. Table 11 shows the different ranges

considered for this parameter.

c. Mass Evacuation:

Total

Level PAR (LOL)

1 LOL > 1,600

2 800 < LOL ≤ 1,600

3 400 < LOL ≤ 800

4 200 < LOL ≤ 400

5 100 < LOL ≤ 200

6 50 < LOL ≤ 100

7 0 < LOL ≤ 50

8 LOL = 0

Table 11: Total economic

impacts (millions of dollars)

Total Economic

Level Impacts (E T )

1 ET > 20,000

2 10,000 < ET ≤ 20,000

3 5,000 < ET ≤ 10,000

4 2,500 < ET ≤ 5,000

5 1,250 < ET ≤ 2,500

6 625 < ET ≤ 1,250

7 0 < ET ≤ 625

8 ET = 0

This consequence category focuses on potential mass evacuations caused by damage or

disruption to the facility and is quantified by the estimated duration.

Consequence-Based Top Screen Process 15


d. National Security:

This consequence category qualitatively focuses on any potential degradation of national security

capabilities that could be caused by damage or disruption to the facility.

It is important to highlight that these four consequence categories, in conjunction with a crosssector

set of consequence level thresholds, are used by DHS to identify facilities considered

critical from a national perspective.

Criticality Thresholds

A set of thresholds is defined for some of the consequence parameters to identify those facilities

that are considered critical from a sector perspective (i.e., those high-consequence facilities whose

failure or disruption could be potentially associated with the highest possible impacts compared to

other assets across the Dams Sector). The set of critical thresholds has the following form:

1. Total population at risk PAR T > PAR T_CRIT , or

2. Population at risk 0 and 3 miles PAR 1 > PAR 1_CRIT , or

3. Population at risk 3 and 7 miles PAR 2 > PAR 2_CRIT , or

4. Population at risk 7 and 15 miles PAR 3 > PAR 3_CRIT , or

5. Population at risk 15 and 60 miles PAR 4 > PAR 4_CRIT , or

6. Total first-year total direct economic impacts E TD = E 1 + E 2 + E 3 > E TD_CRIT , or

7. Total population served M 1 > M 1_CRIT , or

8. Annual water deliveries M 2 > M 2_CRIT , or

9. Installed generating capacity M 3 > M 3_CRIT , or

10. Annual flood damages prevented M 4 > M 4_CRIT , or

11. Annual navigation tonnage M 5 > M 5_CRIT , or

12. Annual recreational visitors M 6 > M 6_CRIT

Any facility that reaches any of these conditions is considered part of the sector list of high

consequence assets. Note that the direct economic consequences are consolidated into a single

value representing total first-year direct impacts. This facilitates the implementation of the

screening approach to include those cases where only a global estimate of direct economic

impacts is available. In addition, the screening approach considers potential human impacts in

terms of total and close-range population at risk, without explicitly using a given loss of life

threshold as part of the screening.

This type of screening is scalable because it can be done not only at the sector level, but also at

the State or regional levels by defining appropriate values for the thresholds corresponding to the

different consequence parameters.

Consequence-Based Top Screen Process 16


Prioritization Scheme

The identification of critical assets results in a number of high-consequence facilities whose

failure or disruption could potentially lead to severe impacts compared to other sector assets.

However, it is possible to establish different subsets within the set of critical facilities by

implementing an appropriate prioritization scheme. An overall potential consequence index

(PCI) for the facility can be calculated as a weighted combination of parameter severity indices

representing the severity levels achieved by the different consequence parameters (14

consequence parameters given by PAR T , PAR 1 , PAR 2 , PAR 3 , PAR 4 , E 1 , E 2 , E 3 , M 1 , M 2 , M 3 , M 4 ,

M 5 , and M 6 ). This index can be used to identify those facilities within the critical set that are

associated with the highest potential for severe consequences.

Figure 3 shows an application of the CTS portfolio prioritization approach to an example set of

35 facilities. The figure shows the computed values of the potential consequence index for each

project, arranged in decreasing order. The CTS portfolio prioritization scheme highlights those

projects potentially associated with the most significant combined impacts, and can effectively

assist in systematically identifying different priority groups within a given portfolio.

Figure 3: Portfolio Prioritization.

Potential Consequence Index

60

50

40

30

20

10

Highest Relative Priority

35 Projects

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

Facility

Consequence-Based Top Screen Process 17


Appendix A: N% Exceedance Duration Pool

Elevation

Definition

The N% exceedance duration pool elevation is defined as the resulting hydraulic condition (pool

elevation) that is equaled or exceeded N % of the time on an annual basis.

Calculation of N% Exceedance Duration Pool Elevation

It can be calculated in the following manner:

1. Gather daily average stage for the facility for an entire period of record.

2. Sort data according to stage in descending order (highest to lowest stage).

3. Rank entries in ascending order (1 through X, with X being the total number of entries).

4. The percent of time exceeded is the stage ranking divided by the total number of data entries

plus 1.

5. By utilizing the percent of time exceeded column, the N% exceedance duration pool

elevation can be obtained. The N% exceedance duration pool elevation is the stage that

corresponds to the percent of time exceeded closest to N% without exceeding.

Example

An example is included in this Appendix as reference. A calculation of the 1% exceedance

duration pool elevation is illustrated using a set of recorded pool elevations (daily average

stages) over a thirty year period of record (1978-2007) corresponding to the site selected for this

example. Table A.1 shows a partial summary of the ranking of daily average stages based on the

corresponding percent of time exceeded (calculated as described in the previous section). Table

A.1 also shows the resulting 1% exceedance duration pool elevation. Note that the table does not

show the entire data set. Figure A.1 shows a plot of the recorded pool elevations as a function of

time over the period of record. This figure also shows the pool elevation corresponding to the 1%

exceedance duration. Figure A.2 shows the pool elevations as a function of the percent time or

exceeded with the 1% exceedance duration elevation highlighted.

Appendix A: N% Exceedance Duration Pool Elevation 18


Rank

Date

Daily

Average

Stage

Table A.1: Determination of 1% Exceedance Duration Pool elevation

Percent of

Time

Exceeded Rank Date

Daily

Average

Stage

Percent of

Time

Exceeded Rank Date

Daily

Average

Stage

Percent of

Time

Exceeded

1 22-Jun-89 1680 0.01% 31 22-Jun-84 1674.6 0.28% 121 9-May-02 1672.3 1.10%

2 23-Jun-89 1679.9 0.02% 32 4-May-81 1674.5 0.29% 122 12-May-81 1672.2 1.11%

3 21-Jun-89 1679 0.03% 33 8-Apr-94 1674.5 0.30% 123 15-May-81 1672.2 1.12%

4 24-Jun-89 1679 0.04% 34 9-Apr-94 1674.4 0.31% 124 13-May-84 1672.2 1.13%

5 25-Jun-89 1677.9 0.05% 35 29-Apr-81 1674.3 0.32% 125 3-Jun-84 1672.2 1.14%

6 26-Jun-89 1676.6 0.05%

7 15-May-02 1676.3 0.06%

8 20-Jun-89 1676.2 0.07%

9 16-May-02 1676 0.08%

10 14-May-02 1675.7 0.09%

11 25-Jun-84 1675.5 0.10% 101 13-May-81 1672.4 0.92% 10938 19-Nov-91 1607.7 99.82%

12 13-Apr-94 1675.5 0.11% 102 14-May-81 1672.4 0.93% 10939 8-Dec-91 1607.6 99.83%

13 17-May-02 1675.5 0.12% 103 29-Jun-84 1672.4 0.94% 10940 20-Nov-91 1607.4 99.84%

14 24-Jun-84 1675.4 0.13% 104 15-Jun-89 1672.4 0.95% 10941 7-Dec-91 1607.2 99.84%

15 19-Jun-84 1675.3 0.14% 105 30-Jun-89 110 1672.4 0.96% 10942 21-Nov-91 1607.1 99.85%

16 20-Jun-84 1675.3 0.15% 106 19-May-90 1672.4 = 1.00% 0.97% 10943 6-Dec-91 1607 99.86%

10957 + 1

17 27-Jun-89 1675.3 0.16% 107 18-Apr-93 1672.4 0.98% 10944 22-Nov-91 1606.9 99.87%

18 18-May-02 1675.3 0.16% 108 17-May-96 1672.4 0.99% 10945 5-Dec-91 1606.8 99.88%

19 30-Apr-81 1675.2 0.17% 109 22-Apr-00 1672.4 0.99% 10946 23-Nov-91 1606.7 99.89%

20 1-May-81 1675.2 0.18% 110 23-May-00 1672.4 1.00% 10947 4-Dec-91 1606.5 99.90%

21 2-May-81 1675.2 0.19% 111 21-May-02 1672.4 1.01% 10948 24-Nov-91 1606.4 99.91%

22 11-Apr-94 1675.2 0.20% 112 19-Jun-02 1672.4 1.02% 10949 25-Nov-91 1606.2 99.92%

23 12-Apr-94 1675.2 0.21% 113 14-May-84 1672.3 1.03% 10950 26-Nov-91 1605.9 99.93%

24 14-Apr-94 1675.1 0.22% 114 7-Jul-87 1672.3 1.04% 10951 3-Dec-91 1605.9 99.94%

25 21-Jun-84 1675 0.23% 115 8-Jul-87 1672.3 1.05% 10952 27-Nov-91 1605.6 99.95%

26 10-Apr-94 1675 0.24% 116 20-May-89 1672.3 1.06% 10953 28-Nov-91 1605.3 99.95%

27 3-May-81 1674.8 0.25% 117 20-Apr-93 1672.3 1.07% 10954 29-Nov-91 1605.1 99.96%

28 26-Jun-84 1674.8 0.26% 118 4-May-96 1672.3 1.08% 10955 30-Nov-91 1604.9 99.97%

29 19-May-02 1674.7 0.26% 119 25-Apr-00 1672.3 1.09% 10956 1-Dec-91 1604.7 99.98%

30 18-Jun-84 1674.6 0.27% 120 25-May-00 1672.3 1.10% 10957 2-Dec-91 1604.6 99.99%

Appendix A: N% Exceedance Duration Pool Elevation 19


Figure A.1: Recorded pool elevations as a function of time over the period of record.

1700

1680

Reservoir Stage (feet)

1660

1640

1620

1600

1978 1983 1988 1993 1998 2003 2008

Date

Figure A.2: Pool elevations as a function of the percent time equaled or exceeded.

1700

1680

Reservoir Stage (feet)

1660

1640

1620

1600

0 10 20 30 40 50 60 70 80 90 100

Percent of Time Exceeded (%)

Appendix A: N% Exceedance Duration Pool Elevation 20


Appendix B: Consequence-Based Top Screen

Worksheets

Completion of CTS Worksheets

For individual assets or facilities, the potential consequences are considered through a number of

parameters that quantify impacts or effects associated with failure or disruption of the project.

All questions are answered based on the consequences for a specific facility.

In the case of a system of multiple assets, the loss, failure, or disruption of any one individual

asset may trigger consequences affecting the ability of the entire system to meet the critical

function. Therefore, when estimating consequences, the impact of losing the entire system

should be considered rather than the consequences of each individual component. Each asset of

the system that could result in human impact will be evaluated individually however, the

economic consequences and impacts on critical functions represents a reasonable worst case for

the entire system

1. General Facility Information

Project Identification Information

• Dam Name: Official name of the dam.

• Other Dam Names: Other names (i.e., reservoir name) of the dam in common use.

• Dam Former Name: Any previous reservoir or dam name(s), if changed.

• State or Federal Agency ID: Official State or Agency identification number for the

dam.

• NID ID Number: Official NID identification number for the dam.

• Number of Separate Structures: Number of secondary impounding structures

associated with this project (saddle dams or dikes).

• Other Structure ID: NID identification number(s) for secondary impounding

structure(s) associated with this project (saddle dams or dikes).

Appendix B: Consequence-Based Top Screen Worksheets 21


• Owner Name: Name of the dam owner.

• Owner Type: Type of owner (F: Federal, S: State, L: Local Government, U: Public

Utility, P: Private).

Project Location

• Longitude: Longitude at dam centerline as a single value in decimal degrees.

• Latitude: Latitude at dam centerline as a single value in decimal degrees.

• Section, Township, Range Location: Section, Township, and Range Location on the

state database.

• County and State Information: If the main features of the project (impounding

structure, navigation locks, etc.) are located across State lines, please provide all relevant

county/State information:

• County: Name of the county in which the dam is located.

• State: Name of the county in which the dam is located.

• River or Stream: Official name of the river or stream on which the dam is built.

• Nearest City/Town: Name of nearest downstream city, town, or village that is most

likely to be affected by the failure or disruption of the dam.

• Distance to Nearest Downstream City/Town (Miles): Distance from the dam to nearest

affected downstream city/town/village to the nearest mile (and tenth if appropriate).

Project Characteristics

General Characteristics

• Dam Type: Type of dam, list all applicable codes (RE: Earth, ER: Rockfill, PG: Gravity,

CB: Buttress, VA: Arch, MV: Multi-Arch, CN: Concrete, MS: Masonry, ST: Stone, TC:

Timber Crib, RC: Roller-Compacted Concrete, OT: Other).

• Core: Position, type of watertight member, and certainty (Position – F: Upstream Facing,

H: Homogeneous Dam, I: Core, X: Unlisted/Unknown; Type – A: Bituminous Concrete,

C: Concrete, E: Earth, M: Metal, P: Plastic, X: Unlisted/Unknown; Certainty – K:

Known, Z: Estimated).

• Foundation: Material upon which dam is founded, and certainty (Foundation – R: Rock,

RS: Rock and Soil, S: Soil, U: Unlisted/Unknown: Certainty – K: Known, Z: Estimated).

• Purposes: Project purposes for which the reservoir is used, list all applicable codes (I:

Irrigation, H: Hydroelectric, C: Flood Control and Storm Water Management, N:

Navigation, S: Water Supply, R: Recreation, P: Fire Protection, Stock, Or Small Farm

Pond, F: Fish and Wildlife Pond, D: Debris Control, T: Tailings, O: Other)

Appendix B: Consequence-Based Top Screen Worksheets 22


• Year Completed: Year when the original main dam structure was completed.

• Year Modified: Year when major modifications or rehabilitation of dam or major control

structures were completed, and type of modification (S: Structural, F: Foundation, M:

Mechanical, E: Seismic, H: Hydraulic, O: Other).

• Downstream Hazard Potential: Potential hazard to the downstream area resulting from

failure or misoperation of the dam (L: Low, S: Significant, H: High, U: Undetermined). 3

• Emergency Action Plan: Code indicating whether this dam has an Emergency Action

Plan (EAP) (Y/N).

• Inspection Date: Date of the most recent inspection of the dam.

• Inspection Frequency (Years): Scheduled frequency interval for periodic inspections.

• Condition Assessment: Assessment that best describes the condition of the dam based

on available information: Satisfactory; Fair; Poor; Unsatisfactory; Not Rated.

• Condition Assessment Detail: Specific detail that best describes the reason for condition

assessment. This field only applies to dams that were assigned the condition Satisfactory,

Poor, or Not Rated. Satisfactory: (hydrologic and seismic regulatory criteria / tolerable

risk criteria), Poor: (deficiency recognized / more analysis needed), Not Rated: (dam has

not been inspected / not under state jurisdiction / other).

• Condition Assessment Date: Date of the most recent assessment of the dam prior to the

transmittal of the data by the submitting agency.

Dam Dimensions

• Vertical Datum: A reference point, surface, or axis on an object against which

measurements are made.

• Dam Length (Feet): Length of the dam, defined as the length along the top of the dam.

This also includes the spillway, powerplant, navigation lock, fish pass, etc., where these

form part of the length of the dam. If detached from the dam, these structures should not

be included.

3 See Federal Guidelines for Dam Safety: Hazard Potential Classification System for Dams (FEMA 333) (Interagency Committee

on Dam Safety, January 2004). p. 5-6.

Low Hazard Potential

Dams assigned the low hazard potential classification are those where failure or misoperation results in no probable loss of

human life and low economic and/or environmental losses. Losses are principally limited to the owner’s property.

Significant Hazard Potential

Dams assigned the significant hazard potential classification are those dams where failure or misoperation results in no probable

loss of human life but can cause economic loss, environmental damage, disruption of lifeline facilities, or can impact

other concerns. Significant hazard potential classification dams are often located in predominantly rural or agricultural areas

but could be located in areas with population and significant infrastructure.

High Hazard Potential

Dams assigned the high hazard potential classification are those where failure or misoperation results will probably cause loss

of human life.

Appendix B: Consequence-Based Top Screen Worksheets 23


• Dam Height (Feet): Height of the dam, defined as the vertical distance between the

lowest point on the crest of the dam and the lowest point in the original streambed at the

downstream toe of the dam.

• Structural Height (Feet): Structural height of the dam, defined as the vertical distance

from the lowest point of the excavated foundation to the top of the dam.

• Hydraulic Height (Feet): Hydraulic height of the dam, defined as the vertical difference

between the maximum controllable water level and the lowest point at the downstream

end of the low-level outlet.

• Crest Width (Feet): The thickness or width of a dam at the level of the top of dam

(excluding corbels or parapets).

• Crest Elevation (Feet): The lowest elevation at which water can flow over the top of

dam not including flow through the spillway.

Spillway Characteristics

• Spillway Type: Type of spillway (C: Controlled, U: Uncontrolled, N: None).

• Spillway Width (Feet): Length of the spillway control section available for discharge

when the reservoir is at its maximum designed water surface elevation.

• Outlet Gates: Codes describing the type of spillway and controlled outlet gates, if any

(X: None, U: Uncontrolled, T: Tainter/Radial, L: Vertical Lift, R: Roller, B: Bascule, D:

Drum, N: Needle, F: Flap, S: Slide/Sluice Gate, V: Valve, O: Other).

• Maximum Discharge (Cubic Feet per Second): Spillway discharge capacity when the

reservoir is at its maximum designed water surface elevation.

• Spillway Crest Elevation (Feet): The lowest elevation at which water can flow over or

through the spillway.

Reservoir Characteristics

• Maximum Storage (Acre-Feet): Maximum storage, defined as the total storage space in

a reservoir below the maximum attainable water surface elevation, including any

surcharge storage.

• Normal Storage (Acre-Feet): Normal storage, defined as the total storage space in a

reservoir below the normal retention level, excluding any flood or surcharge storage. It

includes inactive storage and conservation storage.

• Flood Storage (Acre-Feet): Storage space available in a reservoir between the normal

pool elevation and the maximum operating pool elevation (top of active storage).

• Surface Area (Acres): Surface area of the impoundment at its normal retention level

(normal storage conditions).

Appendix B: Consequence-Based Top Screen Worksheets 24


• Drainage Area (Square Miles): Area that drains to a particular point (in this case, the

dam) on a river or stream.

• Streambed Elevation (Feet): The elevation at the dam corresponding to the lowest point

in the original streambed.

• Design Water Elevation (Feet): Maximum attainable water surface elevation, including

flood surcharge.

• Maximum Operating Pool Elevation (Feet): The upper limit or top of active storage.

The reservoir elevation that would be attained when the reservoir is fully utilized for all

purposes, including flood control. It represents the highest elevation achieved in the

reservoir under normal operating conditions.

• Normal Pool Elevation (Feet): The reservoir elevation at the normal or conservation

storage level (excluding flood and surcharge storage).

• Minimum Operating Pool Elevation (Feet): The lower limit or bottom of active

storage. It represents the lowest elevation to which the reservoir is drawn down under

normal operating conditions.

• 1% Duration Exceedance Elevation (Feet): The reservoir elevation that is exceeded on

average 1% of the time on an annual basis (approximately 3-4 days per year). Note: This

is not the same as the 1% probability exceedance elevation which is commonly referred

to as the 100 year flood.

• Historical Maximum Pool Elevation (Feet): The highest elevation attained in the

reservoir since construction.

• Date of Maximum Pool Elevation (MM/DD/YYYY): The date on which the highest

maximum pool elevation occurred.

Navigation Locks

• Number of Locks: Number of existing navigation locks for the dam.

• Length of Locks (Feet): Length of the main lock chamber.

• Lock Width (Feet): Width of the main lock chamber.

State and Federal Agency(ies)

• State Regulatory Agency: Name of the primary state agency with regulatory or approval

authority over the dam.

• Permitting Authority: State regulatory organization has the authority to review and

approve plans and construction specifications to construct, enlarge, remove, and abandon

dams (from the Dam Safety Act of 2006). (Y/N)

• Inspection Authority: State regulatory organization has the authority to require or

perform the inspection, at least once every five years, of all dams and reservoirs that

Appendix B: Consequence-Based Top Screen Worksheets 25


would pose a significant threat to human life and property in case of failure to determine

the continued safety of the dams and reservoirs (from the Dam Safety Act of 2006). (Y/N)

• Enforcement Authority: State regulatory organization has the authority to issue notices,

when applicable, to require owners of dams to perform necessary maintenance or

remedial work, revise operating procedures, or take other actions, including breaching

dams when necessary (from the Dam Safety Act of 2006). (Y/N)

• State Jurisdictional Dam: Dam meets the state regulatory organization’s definition of a

jurisdictional dam. (Y/N)

• Federal Agency Owner: Federal agency who partly or wholly owns the dam.

• Federal Regulatory Agency: Name of the primary Federal agency with regulatory or

approval authority over the dam.

• Federal Agency Involvement in Funding: Federal agency involved in funding of the

dam.

• Federal Agency Involvement in Design: Federal agency involved in the design of the

dam.

• Federal Agency Involvement in Construction: Federal agency involved in the

construction of the dam.

• Federal Agency Involvement in Regulatory: Federal agency involved in the regulation

of the dam.

• Federal Agency Involvement in Inspection: Federal agency is involved in the

inspection of the dam.

• Federal Agency Involvement in Operation: Federal agency is involved in the operation

of the dam.

2. Contact Information

Facility Point of Contact

Facility Contact(s) – Owner/operator representative(s) designated as facility point of contact

(e.g., project manager) and qualified to answer technical questions regarding project

characteristics and its different operations:

• Name: Name(s) plus title(s) or job classification(s) of the person(s) designated as facility

point of contact(s).

• Address: Address(es) for the person(s) designated as facility point of contact(s). This

should be the address at which they regularly receive business mail. (Include street, city,

Appendix B: Consequence-Based Top Screen Worksheets 26


state, and zip code information, including the 4-digit extension if applicable. Use local

road and street designations, not post office or rural box numbers, if possible.).

• Phone Number: Phone number(s) for the person(s) designated as facility point of

contact(s), including area code information (include office and mobile numbers, if

possible).

• Email: Email address(es) for the person(s) designated as facility point of contact(s).

3. Consequence Information

Human Impacts

The CTS requires an approximate estimate for the “Population at Risk” (PAR), which represents

the population occupying permanent residences, commercial buildings, and recreational areas

within the inundation zone at the time of failure associated with the worst reasonable case

scenario. The total population within the entire inundation zone, or Total PAR, is denoted PAR T .

The PAR in the inundation zone within 0 and 3 miles of the facility is denoted PAR 1 , within 3

and 7 miles is denoted PAR 2 , 7 and 15 miles is denoted PAR 3 , and within 15 and 60 miles is

denoted PAR 4 .

For PAR T select the appropriate range from the table below.

Total PAR in Inundation Zone, PAR T

Level

PAR T

1 PAR T > 800,000

2 400,000 < PAR T ≤ 800,000

3 200,000 < PAR T ≤ 400,000

4 100,000 < PAR T ≤ 200,000

5 50,000 < PAR T ≤ 100,000

6 25,000 < PAR T ≤ 50,000

7 0 < PAR T ≤ 25,000

8 PAR T = 0

• If available, provide the estimated value of Total PAR (PAR T ): _______

• Please provide the name(s) of any towns/cities/counties located TOTALLY or

PARTIALLY within the potential inundation zone.

- City/Town: ____ County: ____ State/Province: ____

• Please describe the process and any additional data sources used to develop the estimated

range or value of PAR T :

- Inundation maps: (Yes/No)

Appendix B: Consequence-Based Top Screen Worksheets 27


- Date of inundation study: (MM/DD/YYYY)

- Model used (including dates or version): (Name)

- Pool elevation used for breach analysis in the inundation study: (feet)

- Description of conditions/assumptions used for inundation study:

- Data sources and reference materials (if applicable, include title, author, date, and/or

version of any report, study and/or data source used as reference)

For PAR 1 select the appropriate range from the table below.

PAR within 0 and 3 miles, PAR 1

Level PAR 1

1 PAR 1 > 4,000

2 2,000 < PAR 1 ≤ 4,000

3 1,000 < PAR 1 ≤ 2,000

4 500 < PAR 1 ≤ 1,000

5 250 < PAR 1 ≤ 500

6 125 < PAR 1 ≤ 250

7 0 < PAR 1 ≤ 125

8 PAR 1 = 0

• If available, provide the estimated value of PAR 1 .

• Please provide any additional information that may be required to describe the process

and additional data sources used to develop the estimated range or value of PAR 1 .

For PAR 2 select the appropriate range from the table below.

PAR within 3 and 7 miles, PAR 2

Level PAR 2

1 PAR 2 > 8,000

2 4,000 < PAR 2 ≤ 8,000

3 2,000 < PAR 2 ≤ 4,000

4 1,000 < PAR 2 ≤ 2,000

5 500 < PAR 2 ≤ 1,000

6 250 < PAR 2 ≤ 500

7 0 < PAR 2 ≤ 250

8 PAR 2 = 0

Appendix B: Consequence-Based Top Screen Worksheets 28


• If available, provide the estimated value of PAR 2 .

• Please provide any additional information that may be required to describe the process

and additional data sources used to develop the estimated range or value of PAR 2 .

For PAR 3 select the appropriate range from the table below.

PAR within 7 and 15 miles, PAR 3

Level PAR 3

1 PAR 3 > 16,000

2 8,000 < PAR 3 ≤ 16,000

3 4,000 < PAR 3 ≤ 8,000

4 2,000 < PAR 3 ≤ 4,000

5 1,000 < PAR 3 ≤ 2,000

6 500 < PAR 3 ≤ 1,000

7 0 < PAR 3 ≤ 500

8 PAR 3 = 0

• If available, provide the estimated value of PAR 3 .

• Please provide any additional information that may be required to describe the process

and additional data sources used to develop the estimated range or value of PAR 3 .

For PAR 4 select the appropriate range from the table below.

PAR within 15 and 60 miles, PAR 4

Level PAR 4

1 PAR 4 > 64,000

2 32,000 < PAR 4 ≤ 64,000

3 16,000 < PAR 4 ≤ 32,000

4 8,000 < PAR 4 ≤ 16,000

5 4,000 < PAR 4 ≤ 8,000

6 2,000 < PAR 4 ≤ 4,000

7 0 < PAR 4 ≤ 2,000

8 PAR 4 = 0

• If available, provide the estimated value of PAR 4 .

• Please provide any additional information that may be required to describe the process

and additional data sources used to develop the estimated range or value of PAR 4 .

Appendix B: Consequence-Based Top Screen Worksheets 29


Economic Impacts

Assuming a reasonable worst case scenario, provide an approximated estimate for the

corresponding total “Asset Repair/Replacement Costs” (E 1 ) by selecting the appropriate range

from the table below.

Asset Repair/Replacement Costs, E1

Level

E 1 (Millions of Dollars)

1 E 1 > 3,200

2 1,600 < E 1 ≤ 3,200

3 800 < E 1 ≤ 1,600

4 400 < E 1 ≤ 800

5 200 < E 1 ≤ 400

6 100 < E 1 ≤ 200

7 0 < E 1 ≤ 100

8 E 1 = 0

• If available, provide the estimated value of E 1 .

• Provide a short description of how the total asset repair/replacement costs (E 1 ) were

estimated. Please identify relevant data sources and reference materials (if applicable,

include title, author, date, and/or version of any report, study and/or data source used as

reference).

Assuming a reasonable worst case scenario, provide an approximated estimate for the

corresponding “Total Remediation Costs” (E 2 ) by selecting the appropriate range from the

table below.

Total Remediation Costs, E 2

Level

E 2 (Millions of Dollars)

1 E 2 > 16,000

2 8,000 < E 2 ≤ 16,000

3 4,000 < E 2 ≤ 8,000

4 2,000 < E 2 ≤ 4,000

5 1,000 < E 2 ≤ 2,000

6 500 < E 2 ≤ 1,000

7 0 < E 2 ≤ 500

8 E 2 = 0

Appendix B: Consequence-Based Top Screen Worksheets 30


• If available, provide the estimated value of E 2 .

• Provide a short description of how the total remediation costs (E 2 ) were estimated. Please

identify relevant data sources and reference materials (if applicable, include title, author,

date, and/or version of any report, study and/or data source used as reference).

- Does the estimate include downstream property damages (Yes/No)

- Does the estimate include environmental damages (Yes/No)

- Does the estimate include temporary remediation measures (Yes/No)

- Does the estimate include emergency response costs (Yes/No)

Assuming a reasonable worst case scenario, provide an approximated estimate for the

corresponding “Business Interruption Costs” over a period of 12 months after the incident or

event by selecting the appropriate range from the table below.

First-Year Business Interruption Costs, E 3

Level

E 3 (Millions of Dollars/Year)

1 E 3 > 800

2 400 < E 3 ≤ 800

3 200 < E 3 ≤ 400

4 100 < E 3 ≤ 200

5 50 < E 3 ≤ 100

6 25 < E 3 ≤ 50

7 0 < E 3 ≤ 25

8 E 3 = 0

• If available, provide the estimated value of E 3 .

• Provide a short description of how the business interruption costs (E 3 ) were estimated.

Please identify relevant data sources and reference materials (if applicable, include title,

author, date, and/or version of any report, study and/or data source used as reference).

- Does the estimate include water deliveries for municipal and industrial use (Yes/No)

- Does the estimate include water deliveries for agricultural use (Yes/No)

- Does the estimate include treaty water deliveries (Yes/No)

- Does the estimate include hydropower generation benefits (Yes/No)

- Does the estimate include flood damage reduction benefits (Yes/No)

- Does the estimate include inland navigation benefits (Yes/No)

- Does the estimate include recreation benefits (Yes/No)

- Does the estimate include fish and wildlife benefits (Yes/No)

Appendix B: Consequence-Based Top Screen Worksheets 31


Impact on Critical Functions

Water Supply: Provide an approximated estimate for the population served by the facility as a

main water supply source by selecting the appropriate range from the table below.

Total Population Served, M 1

Level

M 1 (People)

1 M 1 > 4,000,000

2 2,000,000 < M 1 ≤ 4,000,000

3 1,000,000 < M 1 ≤ 2,000,000

4 500,000 < M 1 ≤ 1,000,000

5 250,000 < M 1 ≤ 500,000

6 125,000 < M 1 ≤ 250,000

7 0 < M 1 ≤ 125,000

8 M 1 = 0

• If available, provide the estimated value of M 1 .

• Provide the name(s) of the population center(s) for which the facility represents the main

water supply source:

- Population Center: ____ State: ____

• For each population center, indicate if there are any other water supply sources serving

the same population:

- Name other water supply sources: ____ State: ____

Irrigation: Provide an approximated estimate for the annual water deliveries provided by the

facility by selecting the appropriate range from the tables below. Pick the most severe case to

characterize the project.

Annual Water Deliveries, M 2

Annual Water Deliveries, M 2

Level

M 2 (Millions of Dollars)

Level

M 2 (Acre-feet)

1 M 2 > 800

2 400 < M 2 ≤ 800

3 200 < M 2 ≤ 400

4 100 < M 2 ≤ 200

5 50 < M 2 ≤ 100

6 25 < M 2 ≤ 50

7 0 < M 2 ≤ 25

8 M 2 = 0

1 M 2 > 6,400,000

2 3,200,000 < M 2 ≤ 6,400,000

3 1,600,000 < M 2 ≤ 3,200,000

4 800,000< M 2 ≤ 1,600,000

5 400,000 < M 2 ≤ 800,000

6 200,000 < M 2 ≤ 400,000

7 0 < M 2 ≤ 200,000

8 M 2 = 0

Appendix B: Consequence-Based Top Screen Worksheets 32


• If available, provide the estimated value of M 2 .

• Describe the agricultural markets or regions served by the facility.

• Indicate how the values selected above for annual water deliveries were obtained. Please

identify relevant data sources and reference materials (if applicable, include title, author,

date, and/or version of any report, study and/or data source used as reference).

Hydropower Generation: Provide an approximated estimate for the hydropower generation

capacity of the facility by selecting the appropriate range from the table below.

Installed Generating Capacity, M 3

Level

M 3 (MW)

1 M 3 > 8,000

2 4,000 < M 3 ≤ 8,000

3 2,000 < M 3 ≤ 4,000

4 1,000 < M 3 ≤ 2,000

5 500 < M 3 ≤ 1,000

6 250 < M 3 ≤ 500

7 0 < M 3 ≤ 250

8 M 3 = 0

• If available, provide the estimated value of M 3 .

• Number of generating units:

Flood Damage Reduction: Provide an approximated estimate of the value of average annual

flood damages prevented (damages resulting from seasonal flooding) by selecting the

appropriate range from the table below.

Average Annual Flood Damages Prevented, (M 4 )

Level

M 4 (Millions of Dollars /Year)

1 M 4 > 800

2 400 < M 4 ≤ 800

3 200 < M 4 ≤ 400

4 100 < M 4 ≤ 200

5 50 < M 4 ≤ 100

6 25 < M 4 ≤ 50

7 0 < M 4 ≤ 25

8 M 4 = 0

Appendix B: Consequence-Based Top Screen Worksheets 33


• If available, provide the estimated value of M 4 .

• Provide the name(s) of the population center(s) and/or local area(s) protected by the facility:

- Population Center: ____ State: ____

• Indicate how the value selected above for average annual damages prevented was obtained.

Please identify relevant data sources and reference materials (if applicable, include title,

author, date, and/or version of any report, study and/or data source used as reference).

Navigation: Provide an approximated estimate for the annual navigation tonnage through the

facility by selecting the appropriate range from the table below.

Annual Navigation Tonnage, M 5

Level

M 5 (kTons/Year)

1 M 5 > 100,000

2 50,000 < M 5 ≤ 100,000

3 25,000 < M 5 ≤ 50,000

4 12,500 < M 5 ≤ 25,000

5 6,250 < M 5 ≤ 12,500

6 3,125 < M 5 ≤ 6,250

7 0 < M 5 ≤ 3,125

8 M 5 = 0

• If available, provide the estimated value of M 5 .

• Indicate how the value selected above for annual navigation tonnage was obtained. Please

identify relevant data sources and reference materials (if applicable, include title, author,

date, and/or version of any report, study and/or data source used as reference).

Recreation: Provide an approximated estimate for the number of recreational visits to the

project area by selecting the appropriate range from the table below.

Annual Recreation Visits, M 6

Level

M 6 (Visitors/Year)

1 M 6 > 4,000,000

2 2,000,000 < M 6 ≤ 4,000,000

3 1,000,000 < M 6 ≤ 2,000,000

4 500,000 < M 6 ≤ 1,000,000

5 250,000 < M 6 ≤ 500,000

6 125,000 < M 6 ≤ 250,000

7 0 < M 6 ≤ 125,000

8 M 6 = 0

Appendix B: Consequence-Based Top Screen Worksheets 34


• If available, provide the estimated value of M 6 .

• Indicate how the value selected above for the number of annual recreational visits was

obtained. Please identify relevant data sources and reference materials (if applicable,

include title, author, date, and/or version of any report, study and/or data source used as

reference).

National Level Impact

Loss of Life: Assuming a reasonable worst case scenario, estimate the potential loss of life that

could be associated with the failure of the facility by selecting the appropriate range from the

table below. Please note, that loss of life estimates are different from population at risk estimates.

Potential Loss of Life, LOL

Level

LOL

1

2

3

LOL > 1,600

800 < LOL ≤ 1,600

400 < LOL ≤ 800

4 200 < LOL ≤ 400

5 100 < LOL ≤ 200

6 50 < LOL ≤ 100

7 0 < LOL ≤ 50

8 LOL = 0

• If Level = 1, please indicate if estimated value of potential loss of life could be:

- 2,500 or higher (Yes/No/Unknown)

- 5,000 or higher (Yes/No/Unknown)

• If available, please provide the estimated value for LOL.

• Please provide information on the methodology or approach used to determine loss of

life. Please identify relevant data sources and reference materials (if applicable, include

title, author, date, and/or version of any report, study and/or data source used as

reference).

Total Economic Impacts: Assuming a reasonable worst case scenario, provide an approximated

estimate for first-year total economic impacts ET, which include but are not limited to asset

replacement, remediation, business interruption, and any other relevant elements such as indirect

economic impacts.

Appendix B: Consequence-Based Top Screen Worksheets 35


Please select the appropriate range for E T from the table below.

Total Economic Impacts, E T

Level

E T (Millions of Dollars)

1 E T > 20,000

2 10,000 < E T ≤ 20,000

3 5,000 < E T ≤ 10,000

4 2,500 < E T ≤ 5,000

5 1,250 < E T ≤ 2,500

6 625 < E T ≤ 1,250

7 0 < E T ≤ 625

8 E 1 = 0

• If Level = 1, please indicate if the first-year total economic consequences could be:

- $25,000 Million or higher (Yes/No/Unknown)

- $75,000 Million or higher (Yes/No/Unknown)

• If available, please provide the estimated value for E T .

• Does the estimate include indirect economic impacts (Yes/No)

Mass Evacuation: Could the failure or severe disruption of the facility result in mass

evacuations with a prolonged absence:

• 1 month or longer (Yes/No/Unknown)

• 3 months or longer (Yes/No/Unknown)

• Please describe the geographic extent, population affected, and duration of evacuations

resulting from dam failure or disruption. Please identify the model, study, or prior event

that was used to calculate the evacuation estimates.

National Security: Could the failure or severe disruption of the facility result in severe

degradation of the country’s national security capabilities (including intelligence and defense

functions, but excluding military facilities) (Yes/No/Unknown)

• Please describe the nature and likely impact of the severe degradation of the country’s

national security capabilities resulting from dam failure or disruption.

Impacts to Other Critical Infrastructure: Could this facility’s partial or total failure or

disruption directly cause severe damage to other infrastructure assets of national or sector

significance (Yes/No/Unknown)

• Please elaborate by specifying the name of any asset(s) and associated impacts resulting

from this facility’s partial or total failure, or disruption.

Appendix B: Consequence-Based Top Screen Worksheets 36


Appendix C: Consequence-Based

Top Screen Portfolio Prioritization

Consequence Severity Levels

As previously shown, each consequence parameter can be

characterized by eight possible severity levels, ranging from

8 (least severe) to 1 (most severe). As indicated by Table

C.1, each severity level represents standard ranges for the

corresponding consequence parameter. As a general rule,

each consequence range is bounded by values that are a

factor of two greater than those corresponding to the

previous range:

3 8Δi < P i ≤ 16Δi

In this table,

P i

represents the i th consequence parameter. In 4 4Δi < P i ≤ 8Δi

addition, Δ

denotes the characteristic interval selected to

i

define the corresponding consequence ranges. For example,

in the case of total population at risk, and as represented by

Table 1, a characteristic interval equal to 25,000 was

selected to define the ranges of values associated with

different severity levels for PAR T . Note, however, that the

5

6

7

8

2Δi < P i ≤ 4Δi

Δi < P i ≤ 2Δi

0 < P i ≤ Δi

P i = 0

consequence range for the highest severity level does not have an upper bound, and that the

lower bound for the next-to-last severity level is arbitrarily adopted as Pi > 0

(instead of

P Δ

, which would have been the corresponding lower bound for this interval). In

i

> 0.5 i

addition, a zero consequence level is introduced for completeness.

Parameter Severity Index Function

Table C.1: Consequence

severity levels

Level Consequence Parameter (P i )

1 P i > 32Δi

2 16Δi < P i ≤ 32Δi

The relative importance of the standard severity levels can be quantified through a parameter

severity index function

f

. This function, which is assumed the same for all 14 consequence

C

parameters, maps the corresponding severity level (ranging from 1 to 8) to a parameter severity

index value between 0 and 100. This function can be defined as a linear or nonlinear function of

the severity level. In the linear case, each unit change in the severity level of a given

consequence parameter leads to a fixed change in the resulting index, whereas in the nonlinear

case, the index changes exponentially with the severity index. Figure C.1 shows an example of a

nonlinear definition for this function.

Appendix C: Consequence-Based Top Screen Portfolio Prioritization 37


Figure C.1: Parameter Damage Index Function.

100

90

Parameter Damage Index

80

70

60

50

40

30

20

10

0

8

7

6

5

4

3

2

1

Severity Level

Therefore, the relative severity of the individual consequence parameters can be quantified as

follows:

• For each consequence parameter , estimate the corresponding range and identify the

P i

associated severity level .

l i

• Adopt a parameter severity index function and determine the value corresponding to

f C

the severity level . This value can be expressed as .

l i

c i

= f C

( l i

)

Determination of Relative Weights

The determination of relative weights provides the flexibility of assigning different relative

importance to each one of the consequence parameters. This can be effectively determined based

on subject-matter expert opinion. Figure C.2 shows an example of the type of input collected for

this purpose.

For each consequence category (Human Impacts, Economic Impacts, or Impacts on Critical

Functions), the relative “importance” of the consequence parameters within that category is

quantified using a value between 0 and 100. For example, Figure C.2 shows that the population

at risk within the first 3 miles is assigned the highest relative importance (100) with respect to

the other population at risk metrics. Similarly, the relative importance of the three categories is

also established by assigning a value between 0 and 100. The example shown in Figure C.2

indicates “Human Impacts” are given the highest relative importance (100) with respect to

“Impacts on Critical Functions” (75) and “Economic Impacts” (45).

The relative weight for each consequence parameter can be obtained by normalizing the product

of the intra-category and inter-category values in such a way that the sum of the relative weights

Appendix C: Consequence-Based Top Screen Portfolio Prioritization 38


is equal to one. The normalized relative weight corresponding to the i th consequence parameter is

denoted as .

w i

Figure C.2: Determination of relative weights.

Human Impacts

Weight

(0-100)

Category Weight

(0-100)

Normalized

Weight

Total PAR 80 0.107

PAR 0 - 3 Miles 100 0.134

PAR 3 - 7 Miles 70 100

0.094

PAR 7 - 15 Miles 50 0.067

PAR 15 - 60 Miles 40 0.054

Economic Impacts

Weight

(0-100)

Category Weight

(0-100)

Normalized

Weight

Asset Repair/ Replacement Cost 60 0.036

Total Remediation Cost 100 45

0.060

First-Year Business Interruption Cost 80 0.048

Impacts on Critical Functions

Weight

(0-100)

Category Weight

(0-100)

Normalized

Weight

Water Supply -Total Population Served 60 0.060

Annual Value of Water Deliveries 100 0.101

Installed Generating Capacity 85 0.086

75

Average Annual Flood Damages Prevented 70 0.071

Annual Navigation Tonnage 50 0.050

Annual Recreational Visits 30 0.030

Facility Potential Consequence Index

An overall potential consequence index (PCI) for the facility can be calculated as a weighted

combination of the parameter severity index values associated with the 14 consequence

parameters. This potential consequence index can be obtained as the product of each parameter

severity index value

c

multiplied by its corresponding relative weight , as follows:

i

w i

PCI = w 1

c 1

+ w 2

c 2

+ w 3

c 3

+ w 4

c 4

+ w 5

c 5

+ w 6

c 6

+ w 7

c 7

+

+ w 8

c 8

+ w 9

c 9

+ w 10

c 10

+ w 11

c 11

+ w 12

c 12

+ w 13

c 13

+ w 14

c 14

For a given set of relative weights and once a parameter severity index function is selected, the

potential consequence index depends on the individual levels reached by each of the

consequence parameters.

Appendix C: Consequence-Based Top Screen Portfolio Prioritization 39

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