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Glossary
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Term Definition
Consequence The impact of a disruption to a site’s critical function(s)—and therefore critical mission(s). The severity of impact associated with a scenario in which a threat or hazard is realized and protective safeguards fail. Used interchangeably with impact in the TRN Lite.
Continuous Supply An energy or water resource that is delivered without interruption to the site, usually by a utility company, via distribution lines. For example, electricity and natural gas typically qualify as continuous supplies.
Continuity of Operations (COOP) An effort taken to ensure critical mission-essential functions continue to be performed during a wide range of emergencies, including localized acts of nature, accidents, and technological or attack-related incidents.
Critical Function An operation required to enable a critical mission. Usually starting with a verb, critical functions are activities rather than objects, departments, buildings, or facilities. Examples include “maintain lab ventilation system” and “analyze groundwater samples.”
Critical Load A load—usually defined as an asset, piece of equipment, or a system—required to enable a critical function. Critical loads typically depend on the supply of energy or water and can be negatively impacted by disruptions to these systems. They may also be impacted by failures inherent to their characteristics (e.g., a component of the critical load’s equipment breaks).
Critical Mission A mission of such high importance that its incapacitation or destruction would have a severely degrading effort on the ability of the site to execute the tasks or mission-essential tasks it supports in all operating environments. A critical mission is supported by critical functions, which are enabled by critical loads (e.g., facilities, systems, equipment, and assets).
Criticality Weighting A numeric value that assigns a relative importance of a critical function to the accomplishment of a site’s critical mission(s).
Dependencies Systems, processes, or people that rely on another entity or system to perform a specific function. For example, water systems typically rely on energy systems for treatment and distribution. When power is disrupted, impacts may cascade to cause disruptions in those non-energy specific, but still reliant, processes.
Dual-Impact Hazard or Threat A hazard or threat that may impact the operation of both offsite energy or water supplies and onsite systems, such as supply redundancies. May be natural, technological, or human-caused.
Energy and Water Resilience Planning

Key elements and outcomes include:

  • Optimized operations to reduce energy and water use, as well as peak demand, that enable the site to meet energy and water requirements.
  • Trained personnel and capabilities to anticipate, prepare for, adapt, withstand, respond to, and rapidly recover from energy and water disruption due to planned or unplanned events.
  • Actionable strategies for diverse solutions that address resource and infrastructure needs to minimize the consequence of interruptions of energy and water services to critical missions and functions during both normal and disrupted operations.
FEMA National Risk Index An open-source dataset created and maintained by the U.S. Federal Emergency Management Agency that provides estimated frequencies and risk-related metrics for 18 natural hazards across all U.S. states and territories.
Frequency The recurrence of a potential disruptor, such as a hazard or threat or load failure. In the TRN Lite, (annual) frequency refers to the number of times a disruptor is expected to occur each year and is analogous to likelihood.
Function Restoration The ability of a site to maintain operation of a critical function without support from the usual associated critical load(s). For example, a site may be able to temporarily move the function offsite.
Grouped Hazard or Threat A hazard or threat that impacts only offsite energy or water supplies. May be natural, technological, or human-caused. The TRN Lite allows users to group hazards that cause the same outage duration and analyze them together when they have equivalent consequences. This is also known as an all-hazards approach.
Hardening The act of instituting or installing mitigations.
Hazard A natural or accident-based driver with the potential to disrupt a site’s critical mission(s). Examples of natural hazards include earthquakes, storms, and wildfires. Examples of accident-based hazards include dam failures, train derailments, and industrial incidents. May also refer to the likelihood that such an event will occur, quantified as the probability of the hazard being realized. In the TRN Lite, hazards and threats are considered together and may refer to either dual-impact or grouped hazards.
Interdependency A mutual reliance between two systems.
Intermittent Supply An energy or water resource that is periodically delivered to the site rather than connected via distribution lines. Fuel oil and propane typically qualify as intermittent supplies.
Likelihood Synonymous with probability, likelihood generally refers to the chance that a hazard or threat (or other risk scenario-initiating event, such as a load failure) will occur or that a safeguard will fail or succeed (often quantified as vulnerability). It commonly represents an expected event frequency.
Load Redundancy An onsite asset, system, or piece of equipment that can sustain operation of a critical load in the event the primary asset/system/equipment fails. The load redundancy must not already be in use for other purposes and must be pre-installed and/or pre-configured to take over for the critical load for an indefinite length of time. It must be capable of fully replacing at least one unit of the critical load, if the critical load is defined as a group of units of the same piece of equipment (e.g., one server redundancy for five servers, or the n+1 redundancy policy).
Mutual Aid Agreement Establishes the terms under which one party provides resources (e.g., personnel, teams, facilities, equipment, and/or supplies) to another party.
Natural Hazard A hazard associated with an act of nature such as severe weather (e.g., winter storms, floods, hurricanes, and storm surges).
Resilience Broadly refers to the ability to anticipate, prepare for, and adapt to changing conditions and to withstand, respond to, and recover rapidly from disruptions through adaptable, holistic planning and technical solutions.
Resilience Gap Exists where risk—as a function of frequency, vulnerability, and consequence—exceeds a defined acceptable threshold or where conditions do not meet specific established resilience goals, standards, or best practices.
Resilience Planning Seeks to reduce potential impacts to operations from planned and unplanned disruptions via integrated and diverse solution sets. It is an iterative process that needs to be regularly revisited as part of an organization’s operations.
Risk The potential for an unwanted outcome resulting from an event, or sequence of events. Quantified in terms of the likelihood the event occurs and the consequences associated with the event. The TRN Lite assesses risk from energy and water outages and critical load failures.
Site Any collection of facilities (e.g., a campus) or a single location (e.g., an individual building).
Supply Redundancy An onsite asset, system, or piece of equipment that can supply energy or water in the event of a disruption to the primary supply of that resource. It may be operational for a limited or an indefinite length of time.
Technological Hazard Hazards associated with the potential for adverse impacts resulting from accidents or the failures of systems and structures to meet their design or operational intent. Examples include bridge collapses and grid outages. May be caused by random system failures or external influences, such as a vehicle impact with a piece of equipment. Outcomes of technological hazards may overlap with those from threats, but technological hazards do not involve malicious intent.
Threat An adverse event associated with malicious intent to create negative impacts. May also refer to the likelihood that such an event will occur, quantified as the probability of the threat being realized. In the TRN Lite, hazards and threats are considered together and may refer to either dual-impact or grouped hazards.
Tolerable Outage Duration The amount of time a critical load can be lost without unacceptable interruption to its associated critical function. Comprised of a) the amount of time the function can persist without access to the load and b) the site’s tolerance for loss of the function itself.
Vulnerability The probability that safeguards or protections intended to mitigate the hazard or threat fail. Equivalently, this is the conditional probability of a consequence occurring given that the hazard or threat has been realized. Estimated via characterization of supply redundancies in the TRN Lite.
Vulnerability Assessment Evaluates the potential vulnerability of the critical loads against a broad range of identified threats and hazards. Determines the sensitivity of a system’s infrastructure to the realization of specific threats or hazards and the potential disruption or loss of that system. Estimated through characterization of supply redundancies in the TRN Lite.