July 2014

CONCEPTS
Risk Analysis Can Mitigate the Impact of Extreme Events

BY JOE ENGLOT, P.E.

Building codes haven’t caught up with the steady acceleration of extreme weather events that have devastated communities across the nation in recent decades. Massive tornado, fire, flood, and hurricane destruction has cost billions of dollars and left the development industry wondering whether existing building codes are adequate to protect America’s infrastructure.

Simultaneously, developers fear if codes are adjusted to require properties be constructed to withstand catastrophic events that may never occur, the costs will make new projects virtually impossible to build.

Fortunately, there’s another option: A risk-based analysis approach can dramatically lessen the risk of extreme event damage to a critical asset property, without threatening the project financially.

The Realities
Building codes are developed based on probabilities that an event will occur in a given area, based on location-specific historical data. Often, existing codes are sufficient. Increasingly, extreme climate-related events outside of what the historical record anticipates are wreaking widespread socioeconomic havoc in terms of injuries and loss of life; emergency response and recovery; asset downtime; and physical damage to the asset.

With the number and severity of extreme events increasing, the Federal Emergency Management Agency’s ability to respond with adequate recovery support is limited. Climate change and the pervasive threat of terrorism demand proactive approaches to cost-effectively evaluate and build, or retrofit, high-value infrastructure.

Beyond Code Requirements
A risk-based analysis approach looks beyond building codes to establish a risk assessment model, evaluate the risk for each of a structure’s individual components, and calculate a total risk based on how critical the asset is, the asset’s location, and the asset’s vulnerability.

While risk can never be eliminated, it can be reduced. Strategic, innovative mitigations can increase a structure’s ability to avoid or withstand an extreme event without adding significantly to the project’s cost. Some examples include:

• Mitigating against location risk. In a known tornado alley, rather than constructing a single, centralized hospital to serve a community, building two smaller hospitals on opposite ends of town cuts risk dramatically.
• Protecting against vulnerability. Explosives are terrorists’ weapon of choice. The larger the explosive they can bring next to an asset, the more damage they’re able to inflict. For a structure whose criticality makes it an attractive target, risks can be minimized by erecting barriers to traffic and nearby parking, limiting the number of entry points, screening people coming into the building, and creating distance between the structure and the parking lot. These actions require modest additional expense, but significantly reduce the asset’s exposure.
• Planning for the worst-case scenario. During Hurricane Katrina, air was trapped under Lake Pontchartrain’s twin I-10 bridges, permitting the storm surge to shift the bridge deck segments off their piers and rendering the bridge impassable. The risk analysis approach would have encouraged drilling air vent holes in the bridge deck and using strong tie-down bearings to ensure the bridge’s survival.
• Making infrastructure resilient. Current codes require building envelopes to be designed for hurricane-force winds but not for tornado-force winds. Under the risk analysis process, the strategy would be to allow the cladding to come off during a tornado to reduce pressures on the structure, and design a sound frame and foundation to survive the event and allow rebuilding rather than demolition and replacement, which costs more and takes longer.

Goal: Resiliency
Risk assessment looks not only at how to strengthen structures, but also how to address cataclysmic events when they occur. The approach evaluates potential consequences and establishes a relevant rapid recovery plan that focuses on:

• Reducing casualties by placing priority on evacuating people first or preventing collapse until occupants can evacuate;
• Reducing environmental impact by implementing sensors, monitoring crucial infrastructure and periodically inspecting safety systems and containment structures for signs of deterioration;
• Reducing property damage by maintaining redundant facilities and hardening essential facilities in advance of an extreme event; and
• Reducing recovery time with prioritized plans and procedures to quickly restore critical infrastructure to operability.

Instead of confining ourselves to codes, we need to think about how to address the challenges of extreme events with protective design in mind.

Every community should commission an assessment by a qualified engineering firm that can tell city leaders where their risks are and how those risks can be resolved before a disaster occurs. Similarly, owner/operators of critical infrastructure, such as power plants, hospitals, and manufacturing facilities, should also perform risk assessments.

Joe Englot, P.E., serves as the national director of infrastructure security at HNTB. He oversees projects that reduce the vulnerability of transportation facilities to malevolent acts through the use of physical hardening, surveillance, and incident management in addition to projects to rehabilitate and retrofit structures against the effects of natural hazards and general structural deterioration.

The views expressed in this article are those of the author and not necessarily those of NSPE.