Module: Risk Assessment
In this action, characterize the vulnerability of energy and water systems that support critical loads. This is the final input into the TRN risk model. Vulnerability analysis in the TRN is specifically focused on the capability of onsite redundant energy and water systems to meet critical load requirements during a disruption, and the expected reliability of those systems. Condition of the primary energy and water supply infrastructure itself is considered to be implicit in the frequencies and outage durations selected in the hazard analysis.
Data Inputs Needed
- Redundant system data from Action 1 in the Baseline Development Module for up to two energy or water redundant systems per critical load (referred to as a first and second redundant system)
- Redundant systems conditions from Action 3 in the Baseline Development Module
- Critical load characterization from Action 1 in the Risk Assessment Module
Outputs of This Action
- Input to risk screening tool:
- For those working offline, input into Tab 4 of the TRN Risk Assessment Excel workbook
A key input for the TRN risk assessment is the vulnerability of onsite redundant energy and water systems that support critical loads. Use the following questions as a guide and refer back to previous data collected in the Baseline Development module to identify vulnerabilities:
- Which systems qualify as redundant in that they have the capability to actuate before the tolerable outage duration is reached AND function throughout the primary supply outage duration?*
- How reliable and well-maintained are your redundant systems?
- Are the redundant systems designed to withstand the hazards that could directly impact the performance of those systems?
- How are the redundant systems brought online—manually or automatically?
- Is there a procedure for start-up and operation of the redundant systems fully and are staff members trained on this procedure?
Many hazards and threats resulting in loss of the primary service will not directly affect the capability or reliability of the redundant systems supporting critical loads. For example, loss of primary power supply due to a random power line fault would not affect the efficacy or reliability of redundant systems. In other circumstances, the realized hazard or threat that causes loss of the primary service may also impact the capability and reliability of redundant systems (i.e., dual-impact hazard or threat). For example, loss of primary power supply due to a seismic event may also directly affect the first redundant system or a second redundant system and its ability to perform. Therefore, when considering the vulnerability of redundant systems, it is important to take into account the specific circumstances associated with the realized hazard or threat.
Complete the Risk Assessment Action 3 Worksheet: Critical Load Vulnerability
In the Risk Assessment Action 3 Worksheet: Critical Load Vulnerability, answer the vulnerability questions for each first redundant system and second redundant system being evaluated. The answers to these vulnerability questions will generate an estimated probability that the redundant system could fail to be used in the risk assessment. If there is insufficient information to answer the vulnerability questions, use the professional judgement of relevant staff (e.g., energy and water managers) to assign a vulnerability probability category to the redundant systems. This is an estimate of the likelihood of failure based on the experience of these personnel.
Instructions for Data Entry
For those working offline, the information collected in the Risk Assessment Action 3 Worksheet: Critical Load Vulnerability can be copied into Tab 4 the TRN Risk Assessment Excel workbook. Online users can enter information directly into the online form.