Overview

This action helps review the Risk Assessment results to summarize how risk is distributed across hazards and threats, critical loads, and risk scenarios, and record the key interpretations that will be used to guide development of resilience solutions. For risk scenarios with high-risk results, the user will consider which model inputs generated that level of risk, and also consider any implicit factors that may contribute to the risk of these scenarios. This analysis will highlight some key resilience gaps, which will be used in the Solution Development module.

In-Depth

The TRN risk screening tool provides a streamlined view of the risk to a site’s critical missions based on an analysis of risk scenarios. The model provides estimates of two types of risk: unweighted risk and weighted risk. Unweighted risk is measured in terms of outage hours per year, and sites will use this value to determine whether the risk is acceptable or unacceptable for each of their critical loads and/or functions. Weighted risk multiplies the unweighted risk by the criticality weight associated with the critical loads impacted in each risk scenario and provides a way to compare risk that accounts for their affected critical loads’ relative importance. This action provides guidance, broken down into three steps, on how to interpret the unweighted risk and weighted risk and identify the key hazards and threats, critical loads, and scenarios that drive these risks. The results of this analysis will be recorded in this action’s worksheet.

Step 1: Analyze Outage Risks for Critical Loads

First, evaluate the unweighted risk and its distribution among critical loads. Unweighted risk represents the expected annual outage duration (hours/year). For each critical load, determine whether the critical load annual outage risk is below a threshold of concern (de minimis). It is possible that your site has not formally established a threshold for the acceptable annual outage of a given mission/critical load, but inspection of the outage risk for each critical load may result in the conclusion that that risk is de minimis and does not need immediate remedial action. For example, the risk assessment may show that a critical load has an unweighted risk of 72 hours/year (3 days/year). If that level of average annual outage will not significantly impact the site’s mission, users may conclude that the risk is acceptable for that load. Even though there is no pre-established bright line for what level of risk is acceptable, the resilience planning team may believe that if such a limit did exist, it would be well-above 72 hours/year for that critical load. In this case, that load may not be an appropriate target for resilience enhancement and risk reduction. Realistically, it’s unlikely that there will be many occasions on which such circumstances would eliminate a critical load from further consideration.

Step 2: Identify Key Drivers of Risk

Next, identify areas where resilience solutions are most needed to reduce risk. Sites have finite resources for resilience enhancement, and insights about the key drivers of risk at a site can help to focus the development of resilience solutions and, ultimately, provide a basis for the prioritization of expenditures. To identify the key drivers of risk, use weighted risk, since this takes into account the relative importance of each critical load. Weighted risk does not have meaningful units, and you should use it as a tool to compare risk levels rather than evaluating the absolute numbers. In the online webtool, critical loads are automatically ordered based on total weighted risk. This analysis may give a sense of where efforts are best expended to improve the performance of redundant systems or establish a means of accelerating the restoration of functions associated with these critical loads. Because of the screening nature of the TRN risk methodology, care should be taken not to over-interpret relatively minor risk differentials between critical loads.

Step 3: Analyze Key Hazards and Threats Driving Risk

Finally, review the hazards and threats that are driving the critical load outage risk. Since each hazard and threat is associated with a specific offsite energy or water outage duration, this analysis helps determine which outage durations are the principal risk drivers for a given critical load. Identify which grouped hazards and threats or dual-impact hazards and threats are driving weighted risk and record this information in the “Review Risk Factors” table in the action worksheet. For example, the biggest risk driver for a critical load may be associated with a primary power supply outage duration of 1 week (that is, 1-month primary power supply outage durations are of lower risk, as are outage durations of 1 day). This would indicate that development of solutions should focus on redundant systems for that critical load intended to provide power for primary supply outages of about a week. The systems for providing longer-term power redundancy are then de-prioritized. In this instance, the resilience planning team could look at the inputs to the risk model for that risk scenario to determine whether there is power redundancy in place to meet the load’s needs for a week and if so, if it lacks the attributes necessary to be relied upon (e.g., appropriate design, preventive maintenance program, start-up automation, written start-up procedures, and so on).

Such considerations determine where resilience gaps that impact the risk modeled in the TRN exist. Note that when resilience solutions are identified later in the TRN process, it may be that certain solutions have benefits beyond the critical load or hazard or threat that originally prompted the solution, such as designing a redundant system to provide a month of backup.

Next, identify any dual-impact hazards and threats that could impact onsite redundant systems and are high risk contributors. If the risk assessment determines that one reason these types of hazards are risk-drivers for a critical load is that redundant systems are not designed to withstand the hazard, then this indicates a resilience gap to be addressed in the Solution Development module.