Appendix B: Integrated Assessment of Natural Hazards B.1.0 Natural Hazards A risk analysis of any asset is not complete unless natural hazards are considered. Natural hazards include, at a minimum, the effects of earthquake, hurricane, tornado, and flood. Each of these events can be considered for any particular asset by determining the expected frequency of the event and estimating the consequences. The vulnerability of the asset is dependent upon the type of structure and how it will be affected by the initiating event. Additional natural hazards, such as ice storms, extreme cold weather, wildfire, avalanche, tsunami, landslide, mud slide, and others, should be included if the probability of occurrence and the consequences are higher than the four basic natural hazards. Sector Specific Guidance documents will discuss how to report hazards not included in the basic set. Unlike terrorism events, the ability to withstand natural hazards of a specified intensity are normally included in the design specifications required for buildings and structures. In almost all areas of the United States, the local, state, or national statutes require new construction to meet the structural requirements of the Uniform Building Code (UBC)1. Every municipality or county typically has a building department that performs a plan check for new construction and revisions to existing structures. Once the plan check is approved, a building permit will be issued. In cases not covered by local statutes, the financial institution providing the loan or the insurance carrier will require that the building be designed and constructed in accordance with the UBC or, more recently, the International Building Code (IBC)2. The analysis methods, described in this Appendix, are conceptual and require significant additional effort to be considered as a “standardized” or “acceptable practice” for estimating losses due to natural events. Work is ongoing to improve the methodology. The following areas are under development:

1) Inclusion of seismic event magnitudes and damage factors. 2) Improvement and automation of hurricane maps. 3) Inclusion of the effect of hurricane dissipation with distance from coming ashore. 4) Incorporation of the effect of storm surges accompanying hurricanes. 5) Tabulation and automation of tornado frequency data for all counties and parishes in the

United States. 6) Development of a computer program to help automate the calculations.

As these improvements become available, they will be incorporated into the RAMCAP Plus SM

approach. A multidisciplinary peer review to evaluate the natural hazards calculation methods and contribute additional expertise would be highly desirable. As a RAMCAP standards committee

1 International Conference of Building Officials, 5360 Workman Mill Road, Whittier, CA 90601-2298 2 International Code Council, 500 New Jersey Avenue, Sixth Floor, Washington, D.C 20001-2070

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is reconvened to consider the RAMCAP Plus SM approach, it is anticipated that a subset of the group would assume this task. The severity and frequency of natural hazards depends upon the geographical location of the facility or asset. Earthquakes are much more likely to occur on the West Coast and Alaska, whereas hurricane risk is greater along the Gulf Coast and Florida. When considering natural hazards, the magnitude and expected frequency of the event must be determined from historical data. The geographical distribution and frequency of occurrence data of these initiating events are obtained from various governmental agencies. Source information will be discussed in the following sections. B.1.1 General Approach to Natural Hazards Assessment The knowledge that the assets being evaluated were designed to the requirements of the UBC or IBC provides a baseline for damage calculations. Damage estimates are based upon the following logic: 1) Assume that only initiating events that exceed the design basis would cause damage. It is assumed that an initiating event that is lower than or equal in magnitude to the design basis event would result in little or no significant structural damage. This should be a reasonable assumption since building codes include a safety margin for all design loads. It is also assumed that the building or structure has been maintained. The occurrence of an event (e.g., earthquake or hurricane) that is greater in magnitude than the design basis event would be expected to cause damage to the structure but the structure would be expected to remain stable up to some point. If the magnitude is further increased, the structure may be totally destroyed. When the repair or replacement value equals the current asset value based on future net cash flow,3 the asset is assumed to be a total loss. For low-end events, damage might include cracks and broken windows, loss of content on shelves and broken awnings, parapets and other ancillary attachments, but the basic structure would be expected to remain intact and not collapse on the inhabitants. 2) Assume that, the greater the difference between the design basis event and the actual event, the greater the expected damage. The logic here is obvious. If a building is designed to withstand an earthquake of Richter 5.5 in magnitude, there would be little or no damage for seismic events lower than or equal to 5.5. A 6.0 earthquake would be expected to cause some damage but not as much as a 6.5. Further, since the Richter scale is logarithmic, the damage would not be expected to be linear with Richter magnitude. (An earthquake of magnitude 6.0 is ten times as powerful as a 5.0) Hurricane damage is estimated in a similar way. If a building or structure is designed for a Category 4 hurricane (wind speed in the range of 131–155 mph), the structure would be expected to survive, if the wind speed reached 160 mph, with some relatively minor damage. Experience indicates there is considerable resilience in infrastructure equipment. Refineries in the path of 3 Future net cash flow can be estimated as annual net profit after tax plus depreciation for the life of the facility, discounted at the organization’s cost of capital.

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Hurricane Katrina were back on line soon after the storm passed through and employees could return to the area to restart their work. Wind forces are proportional to the square of the wind speed; thus, if wind speed is increased by 50%, the forces on the structures are more than doubled (225%). Loss would be expected to increase rapidly as the wind velocity exceeds design values. 3) Estimate risk based on the extent to which the magnitude of the initiating event exceeds the

design basis of the asset. A “damage factor” is assigned based on the fact that the amount of damage expected for different types of structures depends on how susceptible that type of construction is to the event. For discussion purposes, consider earthquakes and hurricanes as initiating events. Earthquakes result in lateral loads on structures (other loads may be developed as well, but this discussion will be limited to equivalent static lateral forces on simple, semi-rigid, structures). In an earthquake, cantilevered structures, e.g., tall buildings and tall pressure vessels such as found in refineries and towers, are subjected to bending moments because of the lateral loading. If the loads are increased beyond the design basis load, the structure will eventually fail. Structures of this type are more susceptible to damage due to lateral force loads than equipment, such as buried pipe or pumps and valves that are bolted to heavy foundations. The difference in structural “susceptibility” is introduced by defining a “damage factor” applied to the owner’s loss consequences to account for the type of equipment. Consistent with RAMCAP Plus SM

notation, this coefficient is defined as “vulnerability.” This term defines how vulnerable the equipment is to the event on a scale of zero to one. Thus, the standard risk equation can be used to estimate the consequences of an initiating event. The risk to an asset is defined as:

Ri = Ci x Vi x Ti Where: Ri = risk (measured in dollar losses, deaths or severe injuries) of an initiating event i. Ci = consequences of initiating event i. This could be fatalities, severe injuries, losses to the facility’s owner or losses to the community. Losses to the owner would consist of either repair or replacement cost depending upon the severity of damage, lost net revenue due to down time, liability costs, etc., and other direct losses as a result of damage to the asset by the initiating event i. Fatalities, injuries and community losses are estimated in the same way they are for other hazards, as described in the main text. Estimating losses to the owner is described in this Appendix. Vi = vulnerability of the structure or equipment for the type of event considered. For example, the vulnerability of underground piping to a hurricane would be very low. Pumps mounted on concrete foundations and reinforced concrete or explosion resistant control rooms in refineries are more susceptible to hurricane force winds, but not as vulnerable as

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towers, such as radio transmission towers and tall stacks. The vulnerability of various types of equipment for various initiating events will be defined in tabular form. Ti = frequency of the initiating event. This frequency is determined from historical data. The frequency of an event correlates inversely to the magnitude of the event. The larger the hurricane, earthquake or flood, the less frequent their occurrence. The subscript i indicates that losses are a function of the initiating event. For example, assume an asset is designed to hurricane Category 2 wind speeds. A Category 3 hurricane acting on this asset would be expected to cause a 50% loss. Hurricanes larger than a Category 3 are assumed to result in 100% loss for equipment designed to Category 2 events. 4) Total the natural hazard risk by summing the risks across all initiating events. The total risk to a particular asset from all natural hazards is the sum of the risks from each initiating event. This is written as follows: RT = R1H + R2H + R3H +R4H + … +R1E + R2E + R3E + R4E + … +R1F + R2F + R3F + R4F + … +RTOR Where: RnH = Risk to the asset due to hurricane of Category n (n = 1 through N) Similarly, E = Earthquake, F = flood and TOR = tornado. Simply stated, the risk due to hurricane is the sum of the risk due to categories 1 through 5; the risk due to earthquake is the sum of the risks for each magnitude of earthquake, etc. The total risk is the sum of all levels of risk over all types of natural hazards. The incremental risk does not necessarily decline with event magnitude. While the frequency of the initiating event declines as the magnitude increases, the consequence will typically increase with magnitude. The product of frequency, vulnerability and consequence could increase or decrease. All credible levels of event magnitude must be included in the summation to obtain an accurate risk estimate. The next sections contain additional details concerning how to apply this conceptual approach to each type of natural hazard. B.1.2 Earthquake Figure B-1 presents a seismic zone map of the United States. The current UBC and IBC provide more detailed seismic maps and the requirements for seismic design in the current codes are more complex. The older seismic zone approach is used because most of the existing infrastructure was designed and built before the current method was adopted. The map was taken from the 1997 version of the UBC. The seismic zone method of design has been utilized extensively from the outset of seismic design. This method consists of determining an equivalent static lateral force that is applied to the structure. The seismic force is combined with

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dead weight and other loads. Even this equivalent static force coefficient method can become quite complex for multi-story buildings and non-building structures. It was decided this simpler method would be adequate to estimate first-order damages. The more complex method, found in the current IBC, has not yet been adopted by all of the building code officials. The design of buildings and structures, which comprise the vast majority of the existing infrastructure, is based upon the equivalent static acceleration method. The design procedure was initially developed in the second half of the twentieth century. The Structural Engineers Association of California has been the driving force behind the design rules. This procedure, which is contained in the UBC, calculates the expected lateral force on a structure or equipment as a result of a seismic event. The magnitude of the calculated lateral seismic force depends upon a number of site dependent factors and the configuration of the structure. The design loading naturally depends upon the location of the structure. Figure B-1 shows the different zones in the United States. As one would expect, for example, the design requirements for California are different from Florida. This difference is realized by using a higher coefficient for lateral force in California than for Florida. (The lateral force is calculated by taking a percentage of the weight of the structure, thus the higher the seismic coefficient; the greater percentage of the weight is applied to the structure in the horizontal direction). The design of the resisting members is based upon the lateral force requirement. The expected lateral force on a structure is calculated by first determining the weight of the structure (not including the foundation, which is assumed to be attached directly to ground), and contents. The lateral force is the product of this weight multiplied by the lateral force coefficient, which is tantamount to the lateral static acceleration. (This is a highly simplified explanation of how the design engineer would use the UBC to perform earthquake design. However, the underlying principle presented is fundamental to seismic design. Understanding the basic design is very useful in evaluating assets for most natural hazards.)

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Figure B-1. Seismic Hazard Map of United States

Once the lateral loading is determined, the load is applied to the structure at the center of gravity for one-story structures. For multi-story structures, the load is applied along the height. As a result of the seismic loading, there will be shear loads on the walls of the structure as well as an overturning moment. The designer must provide sufficient strength to withstand these forces and moments. The taller the structure requires a more complex design. High-rise buildings will be more flexible than a one-story structure. When a building or structure is flexible, it will exhibit a lower period of vibration. Flexible structures may be subjected to more or less acceleration than rigid structures, depending on the frequency of the earthquake motion. Thus, the natural frequency of the structure can affect the design of flexible structures. Additional complexities include soil properties, attachment details, joint construction, and other construction and design details. The UBC also provides for dynamic analysis of structures using computerized dynamic analysis techniques. The approach used here is based on the simplest principle (equivalent static load design) contained in the Code. It is not the purpose of this guidance document to explain the detailed earthquake design methodologies, but rather to provide enough understanding for the user to make a damage assessment.

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B.1.3 Hurricane and Tornado/Wind Loading Figure B-2 provides a wind velocity map for the United States that indicates the maximum expected wind velocity for a fifty-year recurrence interval. The requirements of the Uniform Building Code for wind design are based upon data of this type. The UBC has a rather complex procedure for wind design that includes factors for gust effects, nearby buildings, trees, and ground effects that could reduce the local wind velocity. Consideration is also given to uplift forces due to aerodynamic effects, the height of the structure, etc. Wind velocity is converted to a design pressure in pounds per square foot (psf) of a projected area. The wind pressure is then applied to the structure as a static load. The largest component of wind load is always lateral, i.e., perpendicular to the force of gravity. Therefore, the wind load is treated similar to the earthquake load, with the effect of the hazard converted to lateral and vertical forces – typically applied to the structure as static loading (as opposed to dynamic loading).

Table B-1. Saffir-Simpson Hurricane Scale

Category Wind speed Storm surge

mph (km/h)

ft(m)

5 ≥156 (≥250) >18 (>5.5)

4 131–155 (210–249)

13–18(4.0–5.5)

3 111–130 (178–209)

9–12(2.7–3.7)

2 96–110 (154–177)

6–8(1.8–2.4)

1 74–95 (119–153)

4–5(1.2–1.5)

Additional classifications

Tropical storm

39–73 (63–117)

0–3(0–0.9)

Tropical depression

0–38 (0–62)

0(0

Wind loads seldom exceed the design basis in the UBC except for hurricanes and tornadoes. For the purposes of the hazards loss estimate, it is assumed that structures and equipment designed in accordance with the UBC, which includes most, if not all, critical infrastructures, do not suffer damage unless there is a hurricane that exceeds the design basis for that region or a tornado. While there are different categories of tornadoes, it is conservatively assumed that any category tornado that occurs will result in a total loss of the buildings and equipment. The frequency of occurrence for tornadoes is low and the area affected is normally small, compared to a hurricane or windstorm, thus the probability of being affected by a tornado is small resulting in low risk.

To estimate tornado loss, assume the vulnerability of the asset is based upon the type of structure. For example, underground piping and hardened structures, such as blast resistant control rooms, are expected to survive intact. Most above ground structures would be vulnerable to a tornado. The vulnerability of asset types to tornado is provided in Table B-8. The loss or cost estimate would be the replacement or repair costs. Cascading effects are estimated based upon lost production for the time necessary to replace the asset. The frequency of occurrence is estimated based upon the number (N) of tornadoes in a given location (i.e. in a given county),

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multiplied by the ratio of the average affected area (AAA) for a single tornado, divided by the total area of the location under consideration. Typically, data are reported by the number of tornadoes in a given county per year. In that case, N would be the number of observed tornadoes, and Area would be the area of the county in which the asset resides. In equation form:

Frequency = N x (AAA)/(Total Area of Interest) Hurricane damage is somewhat more difficult to characterize. If a building or structure is designed for a Category 4 hurricane (wind speed in the range of 131–155 mph), the structure itself would be expected to survive if the wind speed reached 160 mph. Experience indicates there is considerable resilience in infrastructure equipment. Refineries in the path of Hurricane Katrina were back on line soon after the storm passed through. A 50% rule is proposed to estimate damage, which is defined as follows: If an asset is designed for a Category N hurricane and is struck by a Hurricane of Category N+1, the damage is estimated at 50% of the lesser of replacement or repair value. If the asset is struck by a hurricane of Category N+2, the asset is 100% lost. Thus, 50% damage is assumed for each Category in excess of the design level.

Figure B-2. Basic Wind Speed Fifty-Year Recurrence Interval

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Storm surge and wave data associated with tropical storms and hurricanes are not yet included in the RAMCAP Plus SM approach, but research is ongoing to add them. Many localities where hurricanes are likely to threaten have conducted storm surge and wave studies that estimate water levels associated with each hurricane category. If these are available, the analyst can use them to assess whether the asset is likely to be affected by the surge. If so, the analysis can proceed as with a flood. If no such storm surge study is available, the analyst is advised to consult a topographic map of the asset to determine if a reasonable surge from seaward would affect the asset in question and, if so, the depth of inundation. Consequences would be estimated for water damage using the same approach as for general flooding. Storm surge and wave damage would be added to wind damage in a hurricane. B.1.4 Flood Estimating flood loss is somewhat different from losses from either seismic events or wind events. Wind and seismic events have the potential for destroying or severely damaging the entire structure. Floods, on the other hand, normally cause water damage only. (Extreme disasters, such as the Johnstown Flood of 1889, are the exception to this generalization. In the Johnstown Flood, the failure of a dam released a wall of water that destroyed the entire town, carrying away many houses and commercial buildings. This risk assessment does not apply to disasters such as the Johnstown Flood or tsunami events. The probability of these rare events is extremely small compared to other naturally occurring events and will not be addressed.) Flood loss is assumed to consist primarily of severe electrical damage to wiring and motors, switch gear, telephone and communication equipment, residual mud and debris, mold, rot and damage to carpets, drapes, furniture, and equipment that is sensitive to oxidation (rusting). Thus, the flood results in water damage to the structure and its contents rather than forces acting on the structures causing structural damage to the integrity of the asset. Flood damage is estimated by using FEMA flood maps (available from http://www.fema.gov/), which show flooded land areas and water depth. The flood data are based upon recurrence interval. Thus, a fifty-year flood would result in a smaller flooded area and lower water levels than a hundred-year flood. Once flood inundation information is found for the asset location, an assessment of the water damage to the asset is performed. Loss of production and other first-order events are included in the damage assessment to determine the loss. The vulnerability of the asset to water damage must be determined on a case-by-case basis. If the asset contains electrical components that will be severely damaged by inundation, equipment repair and replacement will be greater and outage time will be longer. If the structure is fairly impervious to water damage, repair costs could be minimal but there still may be significant losses due to deprivation of the asset function during the time of flooding. B.1.5 Loads in Combination Infrastructure components typically are designed for both wind and seismic loadings. However, the lateral force component will normally be dominated by either one or the other. The UBC does not require simultaneous application of both wind and seismic loads. In addition to the lateral force components, load combinations include weight, live load (i.e. personnel) and other

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occasional loads such as snow, etc. As can be seen from Figures B-1 and B-2, most locations in the United States are subjected to either high seismic hazard and relatively low wind loading or the inverse. For example, the Gulf Coast has little seismic activity (Figure B-1) but is subjected to high wind loading since major hurricanes often strike this area. On the other hand, the West Coast is known for high risk due to earthquake but the Pacific Ocean does not tend to spawn hurricanes containing high wind velocity. A study of the figures indicates that Alaska and Hawaii are areas which are at or near the extremes for both hazards. Figure B-2 shows that the highest wind velocity occurs near the coastline, as hurricanes tend to lose energy once they come ashore. What is somewhat less intuitive is that earthquakes are more severe along the western coast of the U.S. and in Hawaii. This is the so-called Pacific Rim activity, which includes the U.S., Japan, and other parts of Asia. Some exceptions exist in areas in the western United States where high volcanic activity is present. The other notable exception is the New Madrid Seismic Zone, also known as the Reelfoot Rift or the New Madrid Fault Line. This is a major seismic zone in the Southern and Midwestern United States. The New Madrid fault system was responsible for the 1812 New Madrid Earthquake and has the potential to produce damaging earthquakes on an average of every 300 to 500 years. The 150-mile (240 km) long fault system, which extends into four states, stretches southward from Cairo, Illinois, through Hayti-Caruthersville and New Madrid, Missouri, through Blytheville, to Marked Tree, Arkansas. It also covers a part of Tennessee, near Reelfoot Lake, extending southeast into Dyersburg.

Credit: USGS

Figure B-3. Earthquakes in the New Madrid Seismic Zone since 1974

This zone has had four of the largest North American earthquakes in recorded history, with magnitude estimates greater than 7.0 on the Richter scale, all occurring within a 3-month period between 1811 and 1812. Many of the published accounts describe the cumulative effects of all

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the earthquakes, known as the New Madrid Sequence, thus, finding the individual effects of each quake can be difficult. This series of temblors caused permanent changes in the course of the Mississippi River, which flowed backward temporarily, and were felt as far away as New York City and Boston, Massachusetts, where church bells rang. Large areas sank into the earth, fissures opened, lakes permanently drained, new lakes were formed, and forests were destroyed over an area of 150,000 acres (600 km²). Many houses at New Madrid were destroyed. "Houses, gardens, and fields were swallowed up," one source notes. However, fatalities and damage were low, because the area was sparsely settled. Hundreds of aftershocks followed over a period of several years. B.2.0 Estimating Consequences from Natural Hazards The philosophy of RAMCAP Plus SM is to estimate damage to an asset using the most severe set of reasonable assumptions. This is usually expressed as the “worst reasonable case.” For example, it is assumed that terrorists will strike at a time when the most people would be affected or the maximum possible damage would be caused. An attack on a stadium would be expected to occur during a game. An attack on a rail car carrying toxic chemicals would occur when the train is passing through a city with high population density in proximity to the railroad tracks. However, one should not necessarily assume that the wind is blowing at the optimum speed and direction at the exact time of the attack unless this is the typical or expected condition most of the time. A similar rule is proposed for estimating consequences due to natural hazards. If a structure is designed to withstand an earthquake with a lateral g loading of 0.25 g’s, the structure is assumed standing and functional after an earthquake of that magnitude. Similarly, if a refinery on the Gulf Coast is designed to withstand winds of 120 miles/hour, then little or no damage would be expected for a hurricane or wind storm producing winds of that magnitude. In order to test the reasonableness of this hypothesis, it is instructive to review the effects of the most recent major hurricane to hit the Gulf Coast of the United States. Hurricane Katrina was the costliest and one of the deadliest hurricanes in the history of the United States. It was the sixth-strongest Atlantic hurricane ever recorded and the third-strongest hurricane on record that made landfall. Katrina formed on August 23 during the 2005 Atlantic hurricane season and caused devastation along much of the north-central Gulf Coast of the United States. It formed over the Bahamas, crossed southern Florida as a moderate Category 1 hurricane, causing some deaths and flooding there, before strengthening rapidly in the Gulf of Mexico and becoming one of the strongest hurricanes on record while at sea, reaching Category 5 status with 175 MPH winds. A day later, it made landfall as a larger but weaker Category 3 storm. This large diameter hurricane inflicted tremendous damage to structures along the coast and for several miles inland. The storm weakened before making its second and third landfalls as a Category 3 storm on the morning of August 29 in southeast Louisiana and at the Louisiana/Mississippi state line, respectively. The most severe loss of life and property damage occurred in New Orleans, which flooded as the levee system failed catastrophically, in many cases hours after the storm had moved inland. The hurricane caused severe destruction across the entire Mississippi coast and into Alabama, as far

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as 100 miles (160 km) from the storm's center. However, most refineries in the path of this hurricane were able to return to full operation within weeks of the storm because the major refinery components were designed to withstand high winds. The effects of flooding and lack of access to the site by construction crews were the major causes of loss to the refinery operators. Information obtained from Hurricane Katrina Situation Reports, issued by the U.S. Department of Energy, provides the following description of damage to critical energy infrastructure.

September 2, 2005 (five days after coming ashore):

Colonial Pipeline - Operating 66% normal capacity. Pumps not operating due to lack of electricity. Major mechanical components undamaged.

Plantation Pipeline - 95% capacity - Electricity restored

ConocoPhillips Alliance Refinery - No electrical power

Exxon Mobile Refinery - No electrical power

Chalmette Refinery - No electrical power

Murphy Oil Refinery - No electrical power

Most Gulf Coast refineries reported limited damage. Most were shut down because of lack of power and water damage due to flooding.

September 13, 2005 (Sixteen days after coming ashore):

Colonial Pipeline - Operating 100% normal capacity

Plantation Pipeline - 100% capacity

ConocoPhillips Alliance Refinery - No electrical power. Shut down waiting for workmen to arrive.

Exxon Mobile Refinery - No electrical power – water damage

Chalmette Refinery - No report. Assumed to be up and running

Murphy Oil Refinery - No electrical power - water receding

Only four refineries reported being shut down, with two more reporting reduced capacity.

November 21, 2005 (85 days after coming ashore):

ConocoPhillips Alliance Refinery - Remains shut down

Murphy Oil Refinery - Remains shut down Discussions with ConocoPhillips indicate there was no major damage to equipment due to hurricane winds. They experienced loss of insulation and wind damage to auxiliary structures, but the mechanical equipment was not damaged. Extensive flooding to the refinery resulted in loss of electrical equipment which required repair and replacement. Access to the refinery was prevented by the flooding and lack of facilities for workers. The September 13, 2005 DOE

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Situation Report noted that “…the 565 foot training ship Empire State VI will be used to berth up to 700 ConocoPhillips employees and contract workers as they begin repairs on strategic infrastructure and facilities at ConocoPhillips oil refinery in Belle Chasse, Louisiana. The ship should arrive in New Orleans on September 16th.” These situation reports and communications with owners of critical infrastructure installations indicate that facilities designed to meet building code (and company developed) engineering specification wind requirements will not suffer significant mechanical damage even if the wind exceeds the design basis winds by a reasonable amount. The damage factors proposed in this process are judged conservative and should overestimate the losses incurred. A common misconception by the public is that risk due to natural hazards is always much greater than the risk associated with terrorism. This misconception may be based upon the widespread damage that can result from a hurricane. It should be noted that the amount of damage shown in media coverage is typically the result of the large area affected by the storm and the relatively soft infrastructure affected. Critical infrastructure, such as chemical plants, refineries, power plants, hospitals and other facilities, is designed to withstand natural hazards. Terrorist attacks are typically infrequent, isolated events that affect a single infrastructure target. Widespread damage to literally thousands of targets, as is the case in large natural events, would not be anticipated unless there is an all-out war. Further, the terrorist agent must be considered intelligent, resourceful, and capable of causing the maximum possible damage in an attack. Thus, when calculated on an asset-by-asset basis, terrorism risk may well exceed risk due to natural hazards, even though the frequency of a terrorist attack is much lower than the frequency of experiencing naturally occurring events, which also cause greater total destruction to the area. B.2.1 Estimating Consequences from Earthquake Events The damage to structures and other assets should be estimated as follows. First, calculate the estimated seismic replacement/repair cost of the infrastructure target. Note that this cost is not the same as the replacement cost assuming complete destruction. The loss assumes the equipment can be repaired and reused in many cases, depending upon the damage and whether a fire follows the earthquake, which is often the case. The loss of production will be calculated separately. Loss Coefficient. The loss coefficients in Table B-2 should be used to calculate the basic repair/replacement costs. For example, experience has shown that piping systems are quite robust and will survive a seismic event, in most cases. The piping systems used in chemical plants and refineries are generally well-supported, welded systems constructed of ductile metals. A seismic event may cause large deflections, loss of hangers and snubbers, etc., but the basic piping, valves and pumps are not severely damaged. However, underground pipe may be severely damaged. It is assumed that large, heavy walled vessels will be reusable. The cost is primarily the repair and replacement of the plant equipment. Buildings will generally suffer more damage due to a seismic event than equipment and piping. Frame structures are normally flexible and will deform significantly. This causes damage to masonry, veneer and internal walls, etc. Normally, the damage can be repaired but the cost is a

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higher percent of the total replacement cost. Newer buildings, presumably built to modern standards, should fare better than older buildings. Structures with seismic upgrades should be considered recent for costing purposes. Buildings not designed to code and portable buildings are expected to incur the greatest damage. These effects are reflected in Table B-2.

Table B-2. Repair/Replacement Costs

Vulnerability

Equipment Types and Mountings

0.2 • Slab Mounted Equipment – pumps, valves, compressors, meters, electric motors, electrical controls, consoles, etc.

• Buried piping • Hot water heaters and similar equipment equipped with

seismic restraints • Automobiles and trucks, heavy equipment

0.3 • Above ground piping designed to accepted codes and standards such as ANSI B31.1, ANSI B31.3

• Pressure Vessels designed to ASME Codes and Standards 0.5 • Buildings designed to UBC Code or equivalent 0.75 • Buildings not designed to codes 1.0 • Portable buildings and trailers

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Table B-3. Earthquake Effects for Use in Estimating Damage to Assets

+Adapted from U.S. Geological Survey documents. *Worldwide

Damage Coefficient. The next step is to determine the damage coefficient for the asset. Table B-3 provides a list of damage coefficients. The damage coefficients are based upon the severity of the earthquake as would be expected (the larger the magnitude of the earthquake (M in the table), the larger the amount of damage). Damage coefficients (D in the table) are also dependent upon the age of the structure. It can be shown that the lateral static acceleration used for designing buildings and structures has increased over the past fifty years. The typical design value for most building structures in California was approximately 0.1 g from the inception of the seismic design criteria back in the 1940’s until the 1970’s. By 1988, the lateral force coefficients had increased by 50% or more, in most cases. The science of earthquake engineering had improved and better methods of designing structures had evolved. Structures built in later years are more earthquake resistant and the cost of repairing them after a seismic event will be much less. The result is fewer injuries and fewer lives lost due to the collapse of

Earthquake Description

Richter Magnitudes

Earthquake Effects & Damage Factors+

Frequency of Occurrence*

Micro Zone 0

Less than 2.0 Micro-earthquakes, not felt About 8,000 per day

Very minor Zone0

Range 2.0-2.9 Generally not felt, but recorded About 1,000 per day

Minor Zone 0

Range 3.0-3.9 Often felt, but rarely causes damage 49,000 per year (est.)

Light Zone 1

Range 4.0-4.9 Noticeable shaking of indoor items, rattling noises. Significant damage unlikely

6,200 per year (est.)

Moderate Zone 2A Zone 2B

Range 5.0-5.9 M > 5.0Zone2(A) M > 5.5Zone2(B)

Can cause major damage to poorly constructed buildings over small regions. At most slight damage to well-designed buildings. Before 1988 D = 20%, after 1988 D = no damage Before 1988 D = 40%, after 1988 D = 20%

800 per year

Strong Zone 3(A) Zone 3(B)

Range 6.0-6.9 M > 6.0 Zone 3 M > 6.5 Zone 3

Can be destructive in areas up to about 100 miles across in populated areas. Before 1988 D = 60%, after 1988 D = 30% Before 1988 D = 80%, after 1988 D = 60%

120 per year

Major Zone 4(A) Zone 4(B)

Range 7.0-7.9 M > 7.0 Zone 4 M > 7.5 Zone 4

Can cause serious damage over larger areas Before 1988 D = 100%, after 1988 D = 80% Before 1988 D = 100%, after 1988 D = 100%

18 per year

Great Zone 4(C)

Range 8.0-8.9 M > 8 Zone 4

Can cause serious damage in areas several hundred miles across Before 1988 D = 100%, after 1988 D = 100%

1 per year

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the newer buildings or structures for the same level of event. This effect is included in the damage coefficient, shown in Table B-3. The values in Table B-3 are based upon the experience of a structural/mechanical engineer working in this field for over 30 years. These values should be reviewed and comments are welcomed. The seismic zones, as indicated on Figure B-1, are 0, 2A, 2B, 3 and 4. In Table B-2, the damage factors are provided for zones 2A, 2B, 3(A), 3(B), 4(A), 4(B) and 4(C). The seismic zone map does not differentiate inside zones 3 and 4 but the damage factors are increased to account for the increased magnitude of the event. The Richter scale is logarithmic (base 10) and the difference between a magnitude 5.0 and 6.0 earthquake is a factor of 10, i.e., the 6.0 earthquake is ten times as strong as the 5.0 earthquake. For small earthquakes, in the 0 and 1 zones, this is not a significant difference since little or no damage is expected. However, when the magnitudes become greater and considerable damage is expected, it is prudent to subdivide the range to obtain a better loss estimate. The author arbitrarily subdivided zones 3 and 4. This is indicated in Table B-3 by the use of parenthetical designations for the subdivisions. The seismic zone map is used to obtain the correct zone (either 3 or 4) for use in Table B-3, but the calculations are performed using the subdivided properties provided in Table B-3. This procedure is illustrated in the example problem on page 18. Frequency Determination. The next step in determining the risk to an asset is to estimate the frequency of occurrence of an event of a particular size. The following web site, maintained by the United States Geographical Survey (USGS), is used to determine the probability of having a seismic event equal to or greater than a particular input value (see http://eqint.cr.usgs.gov/eqprob/2002/index.php). Within the website, the zip code of the asset or plant can provide the location or, alternatively, the latitude and longitude can be input. The USGS site returns a map of the area which contains color-coded contours of the probability of occurrence. Typically, the recurrence interval used as input is fifty years. The color of the contour, in which the asset is located, is used to determine the frequency. For example, if one enters the zip code 92708 into the site, 7.1 for the magnitude and 50 for the recurrence interval, the results produce the map shown in Figure B-4. The asset is located at the small triangle shown on the map in Figure B-4 (look just to the right of “Huntington Beach”). The probability of occurrence can be obtained from the map. In this case, the color-coding provided in the plot finds the probability in the range between 0.01 and 0.15. Using the higher value for conservatism, calculate the frequency as the recurrence interval divided by the probability the event will occur during that time period. For this case, find F = 50/.15 = 333.3 years. This is an approximate estimate of the recurrence period. Thus, the probability of occurrence in one year is the reciprocal of 333.3 or .003 events/year. This is the frequency (also known as the likelihood) associated with an earthquake of Richter magnitude 7.01 or greater occurring in this zip code location. Next, repeat the procedure for a magnitude of 7.5 or greater. This will result in a frequency of approximately .001. The frequency or likelihood of an earthquake having a magnitude greater that 7.01 and less than 7.5 is F(7.0-7.5) = F(7.0) – F(7.5) = .003 - .001 = .002 events/year. This method can be repeated to obtain the frequency of an earthquake between 7.5 and 8.0. Finally,

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the frequency of an earthquake having a magnitude of 8.0 or greater can be obtained directly from the USGS site. The frequency data will then be used along with the damage coefficients to determine the risk for the asset. The total risk is the sum of the risks for all seismic events over the full range of magnitude covered by the zone, as indicated in Table B-3. For example, for zone 3 events, consider the sum of risks for M = 5.0 to 6.0. The probability of an earthquake larger than 6.0 occurring in zone 2 is so small that the risk contribution is negligible. Thus, risk is summed for the magnitude ranges (5.0-5.5) plus (5.5-6.0). Having determined the frequency for various ranges of earthquake magnitude, the next step is to determine the damage associated with the earthquake. The damage coefficient, D in Table B-4, provides a measure of how much destruction to expect from an event of a particular size. It is assumed that a building in zone 4 would not be significantly damaged by an earthquake less than 7.0. If the earthquake has a magnitude of 7.5 there would be significant damage, but not total destruction. As the earthquake magnitude increases, the damage would be more severe until at some point complete loss of the asset value would be assumed. Note, however, the method of calculating replacement/repair costs, used in the asset value calculations, accounts for the survival of some components especially resilient. Thus, even if there were a total loss of an asset, there is significant “scrap” value. This effect is approximated by using the vulnerability of the asset in calculating the owner’s loss. As discussed previously, the risk associated with the individual losses (Ri) is calculated using the standard risk formula is:

Ri = Ci x V x Ti

And the total risk due to earthquake is: RT =R1E + R2E + R3E + R4E + …

The definitions of the terms have already been provided. In summary, the total risk, RT, due to an earthquake event, for a particular asset of interest, is the sum of the risks due to all possible earthquake magnitudes that has a finite probability of occurring in the zone where the asset is located. The range of magnitudes is divided into finite segments and the integration, i.e. the summation of risk, is performed numerically.

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Example Problem - Earthquake Risk Assessment The approach is best explained by example. Refer to Table B-3. Assume that the asset is located in Zone 3. It is assumed the UBC provides adequate design strength for structures and buildings to resist moderate size earthquakes. Figure B-3 defines a moderate size earthquake as one which “can cause major damage to poorly constructed buildings over small regions. At most, slight damage to well-designed buildings.” Thus, it is assumed that only strong earthquakes would result in significant damage for buildings designed for Zone 3. In Zone 3, strong earthquakes are events greater than 6.0 up to (but not including) 7.0 maximum. Since the magnitudes are logarithmic, break the range into two parts, 6.0 to 6.5 and 6.51 up to 7.0. The process yields risk R1 for the first range and R2 for the second range. The total risk in zone 3 is the sum of R1 + R2. As noted earlier, it has been shown that seismic events greater than 7.0 in Zone 3 are so infrequent that they do not add significantly to the total risk.

Figure B4. Seismic Probability Map

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Asset 1- Pump station- water delivery system - Located in 92708 zip code. Components: 1. One-story building constructed to 1960 UBC, reinforced for earthquake loadings in 1992. 2. Holding tank, horizontal 3. Slab mounted equipment:

• Diesel Motor and Generator • Piping (Underground) • Control System • Pump

Solution: 1. Calculate loss value of infrastructure for purposes of determining the consequences due to

earthquake. Assets: Horizontal Tank - total replacement cost $500,000. From Table B-2, find vulnerability = .3, thus, loss for horizontal tank is (.3) ($500,000) = $150,000. One-Story Building - built in 1975 to then current Building Code. Total replacement cost = $1.2M. From Table B-2, find vulnerability = .5 for buildings built to UBC. The loss for the building is (.5) ($1.2M) = $600,000. Slab Mounted Equipment - Total replacement cost of all components is $2.5M. From Table B-2, find vulnerability = .2 for slab-mounted equipment of this type. The loss for the slab mounted equipment is (.2) ($2.5M) = $500,000. Total Loss for Earthquake = $150,000. + $600,000. + $250,000. = $1,000,000. 2. Determine lost revenue/profitability for facility.

Assume loss of net revenue of $1,000,000 while replacement and repairs are being performed.

3. Determine Seismic Zone and Earthquake Magnitudes. Use location of asset, from risk map,

(Figure B-1) to determine earthquake zone. From Figure B-1: Find Z = 4 (Major Earthquake Zone)

From Table B-3 it can be seen that seismic Zone 4 is designed for major earthquakes. Thus, it is assumed that earthquakes less than magnitude 7.0 would not cause significant damage. Risk to the asset is calculated for seismic events of magnitude 7.0 or greater. a) Determine probability of exceeding a 7.0 earthquake

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From web site http://eqint.cr.usgs.gov/eqprob/2002/index.php, find: P = 0.15 in 50 years. Thus, the recurrence interval is = 50/.15 = 333 years. Since one event would be expected every 333 years, the probability of occurrence can be approximated as (1/333) = .003 events per year. b) Determine probability of exceeding a 7.5 earthquake From web site http://eqint.cr.usgs.gov/eqprob/2002/index.php, find: P = 0.05 in 50 years. Frequency = 50/.05 = 1000 years or .001 per year. c) Determine probability of exceeding an 8.0 earthquake

From web site http://eqint.cr.usgs.gov/eqprob/2002/index.php, find:

P = 0.00 in 50 years. Frequency = 0.0 d) Determine damage factors (D) from Table B-3 Assume current UBC codes are in effect because the asset underwent a seismic upgrade in 1995.

For M = 7.0 to 7.5 D = 80% For M > 7.5 D = 100%

4) Calculate Risk

RT =R1E + R2E + R3E + R4E + …

a) Find net threat frequency for R1 and the risk associated with R1 The net threat frequency for the range 7.0 to 7.5 is the frequency of exceeding a 7.0 earthquake less the frequency of exceeding a 7.5 earthquake, thus

NTF1 = TF1 – TF2 = .003 -.001 = .002 The risk associated with an earthquake between 7.0 and 7.5 is thus:

R1 = (Loss) x (Damage factor) x (Net threat frequency) ($1,000,000) x (.8) x (.002) = $1,600 per year

b) Find net threat frequency for R2 and the risk associated with R2 The net threat frequency is the frequency of exceeding a 7.5 earthquake less the frequency of exceeding an 8.0 earthquake, thus:

NTF1 = TF2 – TF3 = .001 – 0.00 = .001

R2 = (Loss basis) x (Damage factor ) x (Net threat frequency) ($1,000,000) x (1.00) x (.001) = $1,000 per year

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c) Find net threat frequency for R3 and the risk associated with R3 The net threat frequency is the frequency of exceeding an 8.0 earthquake.

NTF1 = TF3 = 0.0 R3 = (Loss basis) x (Damage factor) x (Net threat frequency) ($1,000,000) x (1.00) x (0.0) = $0.0 per year d) Find the total risk for the asset due to earthquake in seismic zone 4 RT = R1E + R2E + R3E

RT = $1,600 + $1,000 + 0 = $2,600 per year

B.2.2 Estimating Consequences from Wind Loading Events A general discussion of how wind loading is characterized is provided in Section B.1.3. The details of how to calculate risk due to wind loading is provided in this section. B.2.2.1 Hurricanes and Wind Loading Figure B-2 provides a wind velocity map for the United States that indicates the maximum expected wind velocity for a fifty-year recurrence interval. The requirements of the Uniform Building Code for wind design are based upon data of this type. The UBC has a rather complex procedure for wind design that includes factors for gust effects, nearby buildings, trees, and ground effects that could reduce the local wind velocity, uplift due to aerodynamic effects, the height of the structure, etc. Wind velocity is converted to a design pressure in pounds per square foot (psf) of projected area.

Wind loads seldom exceed the design basis in the UBC, except for hurricanes and tornadoes. For the purposes of the hazards loss estimate, it is assumed that structures and equipment, designed in accordance with the UBC, which includes most, if not all, critical infrastructure, do not suffer damage unless there is a hurricane or strong wind that exceeds the design basis for that region. (It will be assumed that damage due to tornado will cause complete destruction of the asset, buildings and equipment. Tornado loss is discussed in Section B.2.2.) Hurricane damage is somewhat more difficult to characterize than tornado loss. If a building or structure were designed for a Category 3 hurricane (wind speed in the range of 111–130 mph), the structure would be expected to survive even if the wind speed was 150 mph, which would be classified as a Category 4 hurricane. Experience indicates there is considerable resilience in infrastructure equipment. Refineries in the path of Hurricane Katrina were back on line soon after the storm passed through and workers could return to the area. Wind forces are proportional to the square of the wind speed, thus, if wind speed is increased by 50%, the forces on the structures are more than doubled (approximately 225%). Losses would be expected to increase rapidly as the wind velocity exceeds the design value of the UBC.

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It is assumed that hurricanes and tornadoes are the only significant risk events attributable to high velocity wind. The probability of exceeding the UBC design basis for windstorms, not associated with hurricanes or tornadoes, is considered small enough to be ignored in comparison with other natural hazards. Further, freak windstorms that cause significant local damage are often categorized as tornadoes. The risk assessment procedure for hurricanes and high winds is as follows: 1) Determine the design wind velocity used for the infrastructure asset in question. If this cannot be determined, use the minimum wind speed map, provided in Figure B-2, to estimate the most likely design wind speed. 2) Determine the hurricane category from the Saffir-Simpson Scale (see Table B-1). Assume the wind speed exceeds the design speed by one category. For example, if the design speed is 110 mph (Category 2 hurricane) assume a Category 3 hurricane.

3) Find the frequency of occurrence for the higher category hurricane velocity. To estimate the approximate frequency a hurricane can be expected within 75 nautical miles (86 miles) of a given location, shown on the frequency maps contained in this section.

4) Determine the consequences by selecting the appropriate vulnerability or damage coefficient (see Table B-2) and calculating the asset repair/replacement cost.

5) Select the magnitude multiplier to a given category hurricane. For hurricanes one category above design speed, use 0.50; for hurricanes two categories or more above design speed, use 1.0. 6) Calculate the risk associated with this hurricane using the risk equations described previously. Repeat as necessary for all category hurricanes above the design speed. 7) Calculate the total risk to hurricane damage as the sum of the risks calculated in steps 5 and 6. Thus, the risk for a given category hurricane is:

Ri = Ci x Vi x Ti The total risk is the sum of all Rn for all categories above the design speed.

RT = R1H + R2H + R3H +R4H + … Calculating Consequences. The loss coefficients in Table B-2 should be used to calculate the basic repair/replacement costs. The loss includes the repair and replacement of the plant equipment, plus the first-order cascading effects. The total consequences are:

Loss = (Repair and replacement costs) x (vulnerability) + Owners first-order operating losses

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Buildings will generally suffer more damage due to a hurricane than equipment and piping. Frame structures are normally flexible and will deform significantly. This causes damage to masonry, veneer, internal walls, etc. Normally, the damage can be repaired but the cost is a higher percent of the total replacement cost. Newer buildings, presumably built to modern standards, should fare better than older buildings. Structures with structural upgrades should be considered recent for costing purposes. Buildings not designed to code and portable buildings are expected to incur the greatest damage. These considerations are reflected in Table B-2. Frequency Maps. The National Hurricane Center Risk Analysis Program (HURISK) provided the return period used in the risk calculations. Using historical hurricane data, a mathematical function is used to smooth out the data, fill in holes, and approximate the time period over which to expect a hurricane of a given Saffir-Simpson category or greater. Thus, an area with a return value of 35 should expect a hurricane of that level once every 35 years. The maps are divided into three areas (South and South East, Mid-Atlantic and New England) for each category of hurricane. Figure B-5. Category 3 or Greater

South

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Southeast

Mid-Atlantic and New England

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Figure B-6. Category 4 or Greater South

Southeast

Mid-Atlantic and New England

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Figure B-7. Category 5

South

Southeast

Mid-Atlantic and New England

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Example Problem – Hurricane Risk Assessment Location: Miami, Florida Referencing Figure B-2, find the design basis wind that is 110 mph. From Table B-1 (Saffir-Simpson Hurricane Scale), find that a Category 2 hurricane would be expected to have wind speeds up to 110 mph. Therefore, Category 3 and greater hurricanes are of concern since they would exceed the design basis loading. Assume the asset in question is a slab-mounted pump. Therefore, from Table B-2., find that the damage coefficient is 0.2. The repair/replacement cost of the pump is $2.5M. The first-order production loss is determined to be $500,000. Hurricane Category 3 Risk From Figure B-5, find the return period for a Category 3 hurricane is once every 5 years, or 0.2/year Damage Factor = 0.5 (one category above design basis) Loss: the slab mounted pump is fairly impervious to hurricane winds. Flooding will be checked later. Since the pump is not highly vulnerable a factor of 0.2 is used to reduce the potential loss of the entire asset cost. Thus, Loss for C3 = (Equipment Cost) x (Damage Factor) x (vulnerability to initiating event) + production loss = $2.5M x (0.5) x (.2) + $500,000 = $0.25M + $0.5M = $.75 Million Ri = Ci x Vi x Ti R3 = Ci x Vi x Ti = $750,000. x Ti = $750,000. x (0.2) = $150,000 Hurricane Category 4 Risk From Figure B-6, find T = 1 every 11 years, or 0.091/year The damage factor for two categories above design basis is 100% of the asset. Loss basis for C4 = (Equipment value) x (Damage Factor) x (vulnerability to initiating event) + production loss = $2.5M x (1.0) x (.2) + $500,000. = $0.5M + $0.5M = $1.0 Million

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Ri = Ci x Vi x Ti R4 = C4 x V4 x T4 = $1M. x Ti = $1M. x (0.2) = $200,000. Hurricane Category 5 Risk F = 1 every 33 years, or 0.03/year The damage factor for two categories or more above design basis is 100% of the asset. C5 = C4 = = $1.0 Million R5 = C5 x V5 x T5 = $1M. x Ti = $1M. x (0.03) = $30,000 Total Risk Total Risk is the sum of R3, R4, and R5

RT = R3 + R4 + R5 = $150,000 + $200,000 + $30,000 = $110,000

B.2.2.2 Tornadoes Damage caused by a tornado is of a significantly different nature than the damage caused by hurricanes or strong winds. Tornadoes typically exhibit wind speeds much higher than hurricanes or even freak windstorms. Additionally, a tornado derives its destructive force from a combination of effects. Hurricanes, in the area affected, consist primarily of unidirectional winds. While a hurricane does rotate about the eye, in a counterclockwise direction in the northern hemisphere, the radius of the storm is so large that the barometric pressure is essentially constant over the local area affected by the wind. A tornado is a violently rotating column of air, which is in contact with both a cumulonimbus (or, in rare cases, cumulus) cloud base and the surface of the earth. Tornadoes can come in many sizes, but are typically in the form of a visible condensation funnel, with the narrow end touching the earth. Often, a cloud of debris encircles the lower portion of the funnel. Most tornadoes have winds of 110 mph or less, are approximately 250 feet across, and travel a few miles before dissipating. However, some tornadoes can have winds of more than 300 mph, are more than a mile across, and stay on the ground for dozens of miles. The damage caused by a tornado is due to two effects. The first is the direct result of the wind impinging upon an object. The velocity of the air is suddenly reduced significantly when it encounters the object and the stagnation pressure results in a force on the exposed surface.

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The second effect causing damage is due to the small rotation radius of the tornado. The funnel of the tornado is typically only 250 feet in diameter. Thus, the high velocity air that circles the center of the funnel will produce a partial vacuum inside the funnel. This effect is due to the so-called Bernoulli effect. Daniel Bernoulli derived the following equation that provides the relationship between velocity and pressure:

Where v = fluid velocity along the streamline g = acceleration due to gravity h = height of the fluid p = pressure along the streamline ρ = density of the fluid In the case of a tornado, this equation explains why the higher the velocity of the moving air, the lower the pressure inside the funnel. The local pressure inside the funnel is quite low compared to normal atmospheric pressure because of the extremely high winds in a tornado and the small diameter. The tornado is a local phenomenon and moves at a relatively high velocity along its path of destruction. Thus, the tornado can quickly reduce the external pressure around an object without allowing time for the internal pressure to equalize with the lowered external pressure. A closed structure, such as a house, will literally explode when the tornado passes over it. The higher internal pressure inside the house will cause the walls and roof to be exploded outward, destroying the integrity of the structure. The high velocity winds can then demolish the remaining structure. The previous discussion explains why certain types of structures are more likely to be demolished by a tornado than others. Open space-frame type structures, like piping and slab mounted equipment, pipe racks, beam and column frames, free standing pressure vessels and machinery will be affected by the high velocity winds, but the pressure differential does not typically cause damage. Closed structures are much more likely to be demolished. However, blast-resistant structures, such as control rooms for refineries, underground storage for water treatment facilities, bunkers used for storing explosives and military equipment, etc., have the capability to survive tornados. For the purposes of this analysis, it is assumed that damage due to any category or magnitude tornado will cause complete loss to buildings and equipment. However, the economic loss, explained above, will be used to estimate the maximum reasonable consequences, so there may be considerable residual “scrap” value. The vulnerability factor for tornados is provided in Table B-4. The frequency of tornadoes is low and the area affected by a tornado is normally small, compared to a hurricane or windstorm, so the probability of tornado damage is small resulting in low risk.

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For estimating tornado loss, the vulnerability of the asset, based upon the loss factor cost estimate, is assumed to be 1.0 and the frequency is based upon the number (N) of tornadoes in a given location multiplied by the ratio of the average affected area (AAA) for a single tornado divided by the total area of interest. In equation form:

Frequency = N x (AAA) / (Total Area of Interest).

For the United States, the average tornado has a 4.4 mile length (standard deviation of 9.38 miles), .073 mile width (standard deviation of .12 miles) and 1.04 square mile area (standard deviation of 4.32 square miles). These measurements must be positive and since the standard deviations are larger than the mean values, highly skewed distributions exist. Many more small tornadoes occur than large tornadoes. Thus, in many ways the median tornado is more representative than the average; this “typical” United States tornado is .994 miles long, 141 feet wide and devastates 0.06 square miles.4 The affected area due to one tornado was taken to be 0.10 km2 or 0.062 square miles. The area of all counties in the United States is provided for reference. The average number of tornadoes occurring each year has also been tabulated by county. The frequency is determined by the preceding equation, using the data described. This information has been incorporated into an Excel database used for making risk calculations. The database is available from the authors.

Table B-4. Tornado Vulnerability

Tornado Vulnerability

Equipment Types and Mountings

0.4

• Slab Mounted Equipment – pumps, valves, compressors, meters, electric motors, electrical controls, consoles, etc.

• Buried piping • Hot water heaters and similar equipment equipped with

seismic restraints • Automobiles and trucks, heavy equipment

0.5

• Above ground piping designed to accepted codes and standards such as ANSI B31.1, ANSI B31.3

• Pressure Vessels designed to ASME Codes and Standards 1.0 • Buildings designed to UBC Code or equivalent 1.0 • Buildings not designed to codes 1.0 • Portable buildings and trailers

4 Schaefer, Joseph T., Kelly, Donald L., and Abbey, Robert F. “A Minimum Assumption Tornado-Hazard Probability Model,” Journal of Climate and applied Meteorology, Vol. 25, pp 1934-1945.

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Example Problem: Wind and Tornado Risk The loss is calculated using the same method as described in the preceding example problems. The loss of production is estimated and included as part of the potential loss estimate. These loss estimates are based upon the following assumptions: 1) Total replacement cost = $2.5 million. 2) Loss of operating revenue is estimated to be $1,000,000. 3) For the purposes of this analysis, it is assumed that damage due to tornado will not result in complete loss to buildings and equipment. Table B-4 indicates that for slab mounted equipment, such as the pump and ancillary equipment considered in this example problem, the vulnerability of this asset is 0.4, or that the repair/replacement cost for this event would amount to 40% of the value of replacing the whole unit. 4) The estimate for frequency (F) is the expected number (N) of tornadoes per year in a given county multiplied by the Average Affected Area (AAA) for a single tornado and divided by the total area of the county (Ac). In equation form:

F = N x (AAA)/(Ac) Where AAA is estimated to be 0.0386 mi2.

Givens for this problem: Location: El Paso County, Colorado Asset: Slab mounted pump and controls Cost to replace: $2.5M Vulnerability: 0.4 (Table B-4) Average affected area: 0.0386 mi2

It was determined from the ASME-ITI tornado frequency database that the probability of a tornado hitting this asset is 0.0000243 events/year. Data: (From ASME-ITI database) El Paso County averages 1.34 tornados each year The area of the county is 2,126 Sq. Miles The average area affected by a tornado is .0386 Sq. Miles

Frequency = 1.34/year x (0.0386 mi2/ 2,126 mi2) = 0.0000243/year The risk is calculated as: R = C x V x F R = (($2.5M x 0.4) + 1.0M) x 0.0000243/year R = $48.60/year Thus, the risk due to tornado is very low.

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B.2.3 Estimating Consequences from Floods Estimating flood loss is somewhat different from losses from either seismic events or wind events. Wind and seismic events have the potential for destroying or severely damaging the entire structure. Floods, on the other hand, normally cause water damage only. Water loss consists primarily of severe electrical damage to wiring and motors, switch gear, telephone and communication equipment, residual mud and debris, mold, rot and damage to carpets, drapes, furniture, and equipment that is sensitive to oxidation (rusting). In order to assess the loss, the following information will be required:

• Is the building/asset constructed using flood-resistant materials (concrete, ceramic, pressure-treated lumber)?

• Is the building/asset sealed so that water cannot enter ("dry flood-proof")?

• Are electrical system components (circuit breakers, meters, outlets) raised from the floor?

• Are all gas storage tanks and gas cylinders anchored?

• Is all HVAC equipment located on an upper floor as opposed to a basement level?

• Are sewer backflow valves installed on drainage pipes?

• Does the building/asset have alternative power sources available if it loses power?

• Are spare parts or critical equipment inventory available for use in the event of an attack/hazard?

It is also necessary to know the risk of flood and expected flood depth. Flood zone information can be obtained from a Flood Insurance Rate Map (FIRM), which can be accessed online from: http://msc.fema.gov/webapp/wcs/stores/servlet/CategoryDisplay?catalogId=10001&storeId=10001&categoryId=12001&langId=-1&userType=G&type=1. . In general, all flood zones should consider a 1% annual chance of flooding. Use the descriptions below to determine the likely depth of floods and then calculate consequences. The vulnerability table provided will help determine your organization’s vulnerability. B.2.3.1 Flood Loss Estimation Procedure Flood loss or consequence is highly dependent upon the details of the buildings and equipment subjected to the floodwater. The questions in Section B.2.3, above, should be addressed to determine the vulnerability of the facility. For example, if the building is constructed of water tolerant materials, then much less damage is expected than for materials that are ruined when water soaked. Similarly, if electrical components are subjected to inundation, such as in underground conduit, manholes and trenches, and are not waterproof, then it must be assumed there will be extensive damage.

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Mechanical equipment, such as piping, pumps, valves, and tanks, may not be damaged but the controls, motors, and electrical and communication equipment, thermocouples, etc. may need replacement or repair. Tall buildings typically sustain a smaller damage fraction than one-story buildings for obvious reasons. It is clear that flood damage is not easily characterized or generalized. The loss estimation procedure is as follows: First, using the FEMA FIRM (see above), determine the flood level for the site. The water heights are estimated in increments of one foot, 1.5 feet, and three feet. It is noted that the FEMA data may be incomplete and not specifically cover all parts of the site. It is recommended to use common sense in estimating water height. Historical information for the site and ground elevation should be included in the loss estimate. Second, using the insight gained from answering the above questions, determine which components will be damaged or completely ruined by standing water and their replacement costs. This will provide the best possible basis for estimating the flood loss. Third, estimate the down time required to repair or replace the assets. Knowing the down time and considering contingency plans, resilience and redundancy, estimate the loss due to down time. The total loss will consist of the sum of the repair and replacement cost plus the loss due to lost production capability and other first-order effects, such as denial of service to other assets, loss of access to the building during flood and clean-up, etc. The flood risk will then be the product of the likelihood, normally 1/100 years or 0.01 events per year, times the total estimated loss. In equation form: Ri = Fi x (total loss from step three). FEMA nomenclature should be interpreted as follows to maintain consistency:. Moderate to Low Risk Areas Zones B, C, and X Assume average flood depths are less than 1 foot. High Risk Areas Zone A Assume flood depth of at least 1 foot. Zone AE and A1-A30 Assume flood depth of at least 1 foot. In most instances, base flood elevations derived from detailed analyses are shown at selected intervals within these zones. Zone AH Assume average flood depth ranging from 1 to 3 feet.

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Zone AO Assume average flood depth ranging from 1 to 3 feet. Zone AR Assume flood depth of at least 1 foot due to the building or restoration of a flood control system (such as a levee or a dam). Zone A99 Assume flood depth of at least 1 foot. High Risk - Coastal Areas and Zone V Assume flood depth of at least 1 foot with an additional hazard associated with storm waves. Zone VE and V1 – 30 Assume flood depth of at least 1 foot with an additional hazard associated with storm waves. Undetermined Risk Area Zone D Areas with possible but undetermined flood hazards. Use best judgment on case-by-case basis.

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References and Further Reading

ASME, 2004. Risk Analysis and Management for Critical Asset Protection: General Guidance, Washington, D.C., July 30, 2004. ASME Innovative Technologies Institute, 2005. Risk Analysis and Management for Critical Asset Protection (RAMCAP) Applied to Terrorism and Homeland Security, Washington, D.C., August 30, 2005. ASME Innovative Technologies Institute, 2006. RAMCAP: The Framework, Version 2.0, Washington, D.C., May 2006. Baker, Arnold, et al. 2002. A Scalable Systems Approach for Critical Infrastructure Security, Sandia National Laboratories, SAND 2002-0877, www.sandia.gov/scada/documents/020877.pdf. Brealey, R. and S. Myers, 2000. Principles of Corporate Finance, Sixth Edition, Boston, MA: Irwin McGraw-Hill. Brigham, E., Gapenski L., and Ehrhardt, M., 1999. Financial Management: Theory and Practice, Ninth Edition, Fort Worth, TX: The Dryden Press. Fishhoff, B. 2002, “Assessing and Communicating the Risks of Terrorism,” in Science and Technology in a Vulnerable World, Teich, A.H., Nelson, S.D., and Lita, S. J. (eds.), AAAS, Washington, D.C., pp. 51-64. Hutchinson, Harry, 2005. “Calculating Risks: Can the Science that Judges the Safety of Nuclear Plants Secure the Infrastructure of a Nation,” Mechanical Engineering, January 2005. Kirkwood, Craig W., 1997. Strategic Decision Making: Multiobjective Decision Analysis with Spreadsheets, Wadsworth Publishing Co., New York. Moteff, John, September 2, 2004. Risk Management and Critical Infrastructure Protection: Assessing, Integrating and Managing Threats, Vulnerabilities, and Consequences, Congressional Research Service, Library of Congress (order code RL32561). Multihazard Mitigation Council, December 2005. Natural Hazard Mitigation Saves: Independent Study to Assess the Future Benefits of Hazard Mitigation Activities, Volume 2 - Study Documentation. Prepared for the Federal Emergency Management Agency of the U.S. Department of Homeland Security by the Applied Technology Council under contract to the Multihazard Mitigation Council of the National Institute of Building Sciences, Washington, D.C. National Research Council, 2002. Making the Nation Safer: The Role of Science and Technology in Countering Terrorism, The National Academic Press, Washington, D.C. (esp. Chapter 10, with its extensive bibliography).

RAMCAP PlusSM 35 © 2008 ASME Innovative Technologies Institute, LLC

Rose, A., 2004. “Economic Principles, Issues, and Research Priorities in Natural Hazard Loss Estimation,” in Okuyama Y. and Chang S. (eds.), Modeling the Spatial Economic Impacts of Natural Hazards, Heidelberg: Springer, 2004, pp.13-36. Rose, A., 2006. “Economic Resilience to Disasters: Toward a Consistent and Comprehensive Formulation,” in Paton D. and Johnston D. (eds.), Disaster Resilience: An Integrated Approach, Springfield, IL: Charles C. Thomas, pp. 226-48. Rose, A., 2007. “Macroeconomic Modeling of Catastrophic Events,” in Quigley, J. and Jaffee, D. (eds.), Real Estate, Catastrophic Risk, and Public Policy, Berkeley, CA: University of California Press (in preparation). Rose, A. and Liao, S., 2005. “Modeling Regional Economic Resilience to Disasters: A Computable General Equilibrium Analysis of Water Service Disruptions,” Journal of Regional Science, Vol. 45, No. 1, pp. 75-112. Rose, A., Oladosu, G., and Liao, S., 2007. “Business Interruption Impacts of a Terrorist Attack on the Water System of Los Angeles: Customer Resilience to a Total Blackout,” in Richardson, H., Gordon, P., and Moore, J. (eds.), Economic Costs and Consequences of Terrorist Attacks, Cheltenham, UK, forthcoming. U.S. Department of Homeland Security, February 2004. DHS Interim Rule on Procedures Associated with Sharing and Handling of Information Designated as Critical Infrastructure Information. Federal Register, Vol. 69, No. 34, pp. 8074-8089. U.S. Government Accountability Office, October 12, 2001. Homeland Security: Key Elements of a Risk Management Approach, GAO-02-150T.

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