HAZARD AND RISK ASSESSMENTS

FOR

SCHOOL DISTRICT

HAZARD MITIGATION PLANS

TECHNICAL GUIDANCE MANUAL

August 7, 2014

Kenneth A. GoettelGoettel & Associates Inc.

1732 Arena DriveDavis, CA 95618(530) 750-0440

DISCLAIMER

The information provided in this report is collected from various sources and may change over time without notice. The Office of Superintendent of Public Instruction (OSPI) and its officials, employees, and consultants take no responsibility or legal liability for the accuracy, completeness, reliability, timeliness, or usefulness of any of the information provided.

The information has been developed and presented for the sole purpose of developing school district mitigation plans and to assist in determining where to focus resources for additional evaluations of natural hazard risks. The reports are not intended to constitute in-depth analysis or advice, nor are they to be used as a substitute for specific advice obtained from a licensed professional regarding the particular facts and circumstances of the natural hazard risks to a particular campus or building.

EXECUTIVE SUMMARY

The purpose of this Technical Guidance Manual is to help districts evaluate the hazard and risk levels for the six major natural hazards considered in the Washington State K–12 Facilities Hazard Mitigation Plan: earthquakes, tsunamis, volcanic hazards, floods, wildland/urban interface fires, and landslides.

This manual also documents the hazard and risk assessment methodologies built into the ICOS Pre-Disaster Mitigation database. The ICOS Pre-Disaster Mitigation database automates as much of the hazard and risk assessments as possible, using available GIS data and other data, supplemented by district-provided, district-specific data on an as-needed basis. The ICOS Pre-Disaster Mitigation database also includes, to the extent practicable, automation of the interpretation of hazard and risk data to reach conclusions and generate recommendations.

The approach to hazard and risk assessments outlined in this manual is a three step process:

[1.] Preliminary screening to identify which hazards pose enough risk to one or more campuses in a district to warrant detailed evaluation and which hazards pose no of negligible levels of risk, and thus can be excluded entirely, or addressed only briefly, in a district’s mitigation plan.

1.[2.] Campus-level hazard and risk assessments.

2.[3.] Building-level hazard and risk assessments to provide more in-depth evaluation of hazards such as earthquakes and floods for which the level of risk may vary markedly from building to building.

This manual complements the mitigation planning information in three other reference documents for districts developing local mitigation plans:

1. The Washington State K–12 Facilities Hazard Mitigation Plan,

2. The Chapter Templates for District Mitigation Plans and

3. The Mitigation Planning Toolkit.

Together these documents provide a wealth of information for districts developing hazard mitigation plans and are designed to minimize the level of effort required for districts to complete robust, pragmatic, useful hazard mitigation plans.

TABLE OF CONTENTS

1.0 INTRODUCTION................................................................................................................1

1.1 Hazard and Risk Concepts..............................................................................................11.2 Hazards: Natural and Anthropogenic (Human-Caused).................................................2

1.3 Three-Step Hazard and Risk Assessment Approach......................................................52.0 EARTHQUAKES.................................................................................................................7

2.1 Earthquake Hazard Assessment.....................................................................................72.1.1 Methodology.............................................................................................................7

2.1.2 Earthquake Hazard Screening: ICOS Pre-Disaster Mitigation...............................102.2 Earthquake Risk Assessment: Campus Level.............................................................11

2.3 Earthquake Risk Assessment: Building Level..............................................................142.4 Seismic Retrofits: Commentary....................................................................................20

3.0 TSUNAMIS.......................................................................................................................233.1 Tsunami Hazard Assessment.......................................................................................23

3.2 Tsunami Risk Assessment: Campus Level..................................................................243.3 Tsunami Mitigation Guidance........................................................................................27

3.4 Tsunami Risk Assessment: Building Level..................................................................304.0 VOLCANIC HAZARDS.....................................................................................................32

4.1 Volcano Hazard Assessment........................................................................................324.2 Volcanic Hazards Risk Assessment: Campus-Level...................................................35

4.3 Volcanic Hazards Mitigation Guidance.........................................................................375.0 FLOODS...........................................................................................................................42

5.1 Flood Hazard Assessment............................................................................................425.3 Flood Risk Assessment: Building Level – With Quantitative Flood Data.....................47

5.3.1 Overview.................................................................................................................475.3.2 Technical Guidance................................................................................................49

5.4 Flood Risk Assessment: Building Level – Without Quantitative Flood Data................535.4.1 Documentation of Historical Flood Events..............................................................53

5.4.2 Estimating Flood Return Periods............................................................................566.0 WILDLAND/URBAN INTERFACE FIRES.........................................................................58

6.1 Wildland/Urban Interface Fire Hazard Assessment......................................................586.2 Wildland/Urban Interface Fire Hazard and Risk Assessment: Campus Level..............62

6.3 Wildland/Urban Interface Fire Risk Assessment: Building Level.................................646.4 Evacuation Planning for Wildland/Urban Interface Fires...............................................66

7.0 LANDSLIDES....................................................................................................................677.1 Landslide Hazard Assessment......................................................................................67

7.2 Landslide Hazard and Risk Assessment: Campus Level..............................................687.3 Landside Risk Assessment: Building Level...................................................................71

1.0 INTRODUCTION

1.1 Hazard and Risk Concepts

Chapter Six: Natural Hazards Risk of the Washington State K–12 Facilities Hazard Mitigation Plan provides an overview of the important concepts of hazard and risk. A brief summary of these concepts is given below. Careful reading of Chapter Six is recommended as the first step in developing a district mitigation plan.

Risk from natural hazards means the chance of death, injury, damage, or economic loss. Risk is best expressed quantitatively by estimates of the likely extent of damage and economic losses and the numbers of deaths and injuries in future disaster events that may affect a given K–12 facility.

Evaluation of natural hazards and estimates of risk have considerable uncertainties: it is not possible to predict where or when a given natural hazard event will occur or exactly how severe the damages, losses, or casualties may be for an affected facility. For any given natural hazard event, the damages, losses, and casualties may be higher or lower than pre-event estimates.

However, mitigation planning can identify which hazards pose the greatest threats to each K–12 facility. Mitigation planning can also help allocate financial resources efficiently by identifying which facilities would benefit most from pro-active mitigation measures to reduce casualties, damages, and economic losses in future disasters.

The level of risk from natural hazards for a given facility results from the combination of hazard and exposure, as shown in the figure below.

Figure 1.1Hazard and Exposure Combine to Produce Risk

HAZARD EXPOSURE RISK

Frequency Value and Threat to the and Severity + Vulnerability of = Community:

of Hazard Events Inventory People, Buildingsand Infrastructure

Hazard

Quantitative evaluation of natural hazards requires making estimates of the frequency of natural hazard events as a function of the severity or size of an event. All natural hazard events may occur over a wide range of severities. For example, a flood for a given campus may be several feet below the first floor of a building or several feet above the first floor. Similarly, the level of ground shaking from earthquakes affecting a campus may vary greatly, depending on the location and magnitude of future earthquake events. Thus, evaluation of each natural hazard must

consider events over the full range of hazard events severe enough to result in damages, losses, or casualties.

The type of data necessary to evaluate natural hazards varies from hazard to hazard. Detailed information for each hazard is provided in Chapters Six through Twelve of the Washington State K–12 Facilities Hazard Mitigation Plan, which address the six major hazards: earthquakes, tsunamis, volcanic hazards, floods, wildland/urban interface fires, and landslides.

Exposure

Exposure has two elements: value and vulnerability. Value means the importance of a K–12 facility. Measures of value include the replacement value, the occupancy, and the criticality of a facility for providing services. Vulnerability means the expected extent of damages as a function of the severity of a hazard event.

For example, two schools with the same level of earthquake hazard and enrollment may have the same value, but may differ markedly in their vulnerability to earthquake damage, depending on the details of their construction. In this case, the school with the higher vulnerability has the higher risk.

Risk

For any given hazard level, the greater the value and vulnerability, the greater the risk. Facilities with the highest level of risk are those that have both a high hazard level and a high value and a high vulnerability to the hazard.

However, it is important to recognize that a facility with a moderate or even relatively low hazard level, but very high exposure (value and vulnerability), may well have higher risk than a similar facility with a very high hazard level but with much lower exposure. For example, an unreinforced masonry school in a moderate earthquake hazard location may well have substantially higher risk than a school recently built to recent seismic design standards in a much higher earthquake hazard location.

1.2 Hazards: Natural and Anthropogenic (Human-Caused)

FEMA’s guidance for local hazard mitigation plans requires consideration of each natural hazard that poses significant risk to the local jurisdiction developing a plan. There are numerous natural hazards that may impact school district facilities in Washington State. The six major natural hazards for Washington are:

Earthquakes,

Tsunamis,

Volcanic Hazards,

Floods,

Wildland/Urban Interface Fires, and

Landslides.

These six major hazards are addressed in Chapters Seven to Twelve in the Washington State K–12 Facilities Hazard Mitigation Plan. Each of these chapters contains important information about these hazards, including “primers” that define terms and provide a basic understanding of each hazard. Careful reading of the chapter for each hazard that is known to or may pose significant risk to a district is recommended before beginning district-specific hazard and risk assessments.

The guidance and templates for hazard and risk assessments for school district hazard mitigation plans focus primarily on the six major hazards.

However, in addition to the major natural hazards listed above, there are other natural hazards that may impact a few K–12 facilities or that may affect many K–12 facilities but typically with significantly less severe consequences than those from the major hazards. These lesser natural hazards include:

Avalanches,

Climate Change,

Droughts,

Erosion,

Extreme Temperatures

Severe Weather Events, and

Subsidence

These hazards are briefly addressed in Chapter Thirteen of the Washington State K–12 Facilities Hazard Mitigation Plan. The guidance for hazard and risk assessments provides brief suggestions for districts that wish to consider one or more of these lesser hazards in their hazard mitigation planning.

In addition to the above natural hazards, there are many types of anthropogenic (human-caused) hazards that may affect school district facilities, including: terrorism or other deliberate malevolent actions, hazmat incidents, accidents (vehicle, rail, or aircraft), pipeline or utility line failures, pandemics, and many others. However, consideration of anthropogenic hazards in hazard mitigation plans is not required by FEMA for approval of mitigation plans.Anthropogenic hazards are not addressed in the Washington State K–12 Facilities Hazard Mitigation Plan because these types of hazards are more appropriately addressed by emergency planning rather than by hazard mitigation planning.School districts may include anthropogenic hazards in their hazard mitigation plans if they wish. However, given limited resources, it is suggested that district hazard mitigation plans focus on natural hazards and address anthropogenic hazards through separate emergency planning efforts.

1.3 Three-Step Hazard and Risk Assessment Approach

Detailed evaluation of every district facility for every natural hazard would be very expensive and is impractical and unnecessary. Rather, the objective is to focus most attention on the hazards that pose the greatest threats to districts’ facilities and people. The suggested approach for hazard and risk assessments includes three steps:

1. Preliminary screening to identify the hazards which pose significant risk to a district and to exclude hazards that pose negligible or very low risk to a district’s facilities,

2. Campus-level assessments, and

3. Building-level assessments.

To minimize the level of effort required from districts, all three steps in the hazard and risk assessment approach:

Use available hazard and risk data to the maximum possible extent,

Draw conclusions from available data to guide districts in the interpretation of the data, and

Minimize the district-specific and facility-specific data necessary to complete the hazard and risk assessments.

The three-step hazard and risk assessment approach has been incorporated into the ICOS Pre-Disaster Mitigation database software and automated to the extent practicable. The flow chart on the following page outlines the hazard and risk assessment approach in ICOS.

The stepwise approach explained in the following sections recognizes that districts have limited resources to evaluate risks from natural hazards and provides an efficient way to prioritize hazard and risk assessments on the hazards that pose the greatest threats to a district’s facilities and people.

The technical details of hazard and risk assessments necessarily vary from hazard to hazard, but the three-step approach outlined above applies to all natural hazards.

The following sections provide detailed documentation of the hazard and risk assessment approach for each of the six major natural hazards.

Figure 1.2Hazard and Risk Assessment Flowchart

District Criteria, Judgment and Inputs

Schematic Flow Chart for ICOS Hazard and Risk Assessment Approach

Campus Level Hazard and Risk Assessments

Automated Inputs from ICOS GIS Data and

Interpretations

District-Provided Data Inputs

Automated Inputs from ICOS from GIS Data and

Interpretations

Building Level Hazard and Risk Assessments

District-Provided Data Inputs

Automated Screening to Identify Hazards Clearly Posing

Significant Risk to the District

District-Provided Information to Identify Other Hazards that May

Pose Significant Risk to the District

Final List of Hazards For Which Hazard and Risk Assessments are Necessary

District's Prioritized Mitigation Measures

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2.0 EARTHQUAKES

2.1 Earthquake Hazard Assessment

2.1.1 Methodology

Every K–12 facility in Washington State has some level of earthquake hazard, although the level of earthquake hazard varies markedly with location. High earthquake hazard means a high probability of ground motions sufficient to cause damages and casualties in buildings without adequate seismic design. Conversely, low earthquake hazard means a lower probability of ground motions sufficient to result in damages and casualties in buildings without adequate seismic design.

See Chapter Seven: Earthquakes in the Washington State K–12 Facilities Hazard Mitigation Plan for a summary of earthquake hazards in Washington, including definitions of technical terms, maps, and other information about earthquakes.

Campus-level earthquake hazard levels are based on three factors:

1. Ground shaking data from the United States Geological Survey's 2008 National Seismic Hazard Data for the latitude-longitude of each campus,

2. Adjustments to ground shaking for the “site class” – the type of soil or rock at a given location – made by the Washington Department of Natural Resources (DNR), based on surface geology mapping and

3. Estimates of liquefaction potential made by DNR.

Earthquake ground shaking hazard levels are based on the ground motion with a 2% chance of being exceeded in 50 years, including adjustments for the site class. A map showing the variation in seismic hazard in Washington is on the following page

Table 2.1Earthquake Ground Shaking Hazard Levels

Very High 60% or higher

High 40% to 60%

Moderate to High 30% to 40%

Moderate 20% to 30%

Low Less Than 20%

Ground Shaking Hazard Level

2% in 50 Years Peak Ground Acceleration

(% g)

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Figure 2.12008 USGS Seismic Hazard Map: Washington State

Peak Ground Acceleration (percent g) with a Two Percent Chance of Exceedance in 50 years

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The following table shows the distribution of K–12 campuses between the earthquake ground shaking hazard levels defined above.

Table 2.2Earthquake Ground Shaking Hazard Levels: Distribution by Number of K-12 Campuses1

2% in 50 Years Peak Ground Acceleration

(% g)

Number of Campuses

Percent of Campuses

Percent of Campuses This Level or Higher

Ground Shaking Hazard Level

70% to 74% 26 1.07% 1.07%

60% to 70% 246 10.14% 11.21%

50% to 60% 913 37.63% 48.85%

40% to 50% 465 19.17% 68.01%

30% to 40% 136 5.61% 73.62% Moderate to High

25% to 30% 173 7.13% 80.75%

20% to 25% 215 8.86% 89.61%

15% to 20% 243 10.02% 99.63%

Less Than 15% 9 0.37% 100.00%

Totals 2,426 100.00%

Very High

High

Moderate

Low

1 United States Geological Survey 2008 National Seismic Hazard Data, with adjustments based on site class estimates by the Washington Department of Natural Resources.

As shown above, about 68% of the campuses are located in high or very high ground shaking hazard areas. About 22% are located in moderate or moderate to high ground shaking hazard areas and only about 10% are located in low ground shaking hazard areas.

Table 2.3 on the following page shows the qualitative hazard levels for liquefaction potential used by DNR. Liquefaction occurs when porous soils with high water content lose bearing strength during strong earthquake ground shaking and temporarily behave like a liquid. Liquefaction may cause settlement and lateral spreading (downslope movement), either of which may substantially increase the level of earthquake damage to buildings.

Table 2.4 shows the combined earthquake hazard levels used in ICOS. The combined hazard levels consider both ground shaking hazard and liquefaction potential. The ground shaking hazard level is increased by one step if the liquefaction potential is moderate or higher. For example, a site with a high ground shaking hazard would have a combined hazard level of very high if the liquefaction potential were moderate or higher.

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Table 2.3DNR Liquefaction Potential: Hazard Levels

HighModerate to High

ModerateLow to Moderate

LowVery Low to Low

Very LowNone

Unknown

Liquefaction Potential Hazard Levels

Table 2.4 Combined Earthquake Hazard Levels: Ground Shaking and Liquefaction Potential

Extremely HighVery High

HighModerate to High

ModerateLow

Combined Earthquake Hazard Levels

2.1.2 Earthquake Hazard Screening: ICOS Pre-Disaster Mitigation

The ICOS Pre-Disaster Mitigation methodology automatically includes earthquakes as a hazard to be considered by districts if one or more campuses have an earthquake ground shaking hazard level of “moderate” or higher. That is, the level of ground shaking with a 2% chance of being exceeded in 50 years is 20% g or higher.This level of ground shaking is high enough to result in significant damage to buildings without adequate seismic design and thus high enough to pose life safety risks to occupants.

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As shown previously in Table 2.2, about 10% of campuses have lower levels of earthquake ground shaking hazards. It is important to recognize that a relatively low level of earthquake hazard does not mean that earthquake risk is zero. Districts with all or some of their campuses in the “low” earthquake hazard level are strongly encouraged to include earthquakes in their mitigation plans – albeit with a lower level of detail than districts with higher earthquake hazards – and to consider more detailed earthquake risk assessments.

For campuses with a "low" earthquake hazard level, the level of earthquake risk is low for most buildings, but may be significant for a few buildings that are especially vulnerable to major damage or collapse in earthquakes. Districts are encouraged to "opt-in" to the earthquake section of ICOS for campuses that have one or more buildings of the following structural types:

Unreinforced masonry (all dates),

Concrete moment frame, more than one story (built before 1978),

Wood frame buildings with cripple wall foundations1 (built before 1978),

Tilt-up concrete buildings (built before 1999), and

Any other buildings for which an engineer has expressed substantial concern about the building’s seismic vulnerability.1 Cripple walls are short wood stud foundations that raise a building's first floor above the ground or foundation, typically by two or three feet.

2.2 Earthquake Risk Assessment: Campus Level

Every K–12 campus and every K–12 building in Washington State has some, non-zero level of earthquake risk, although the level of risk varies markedly with location and the seismic vulnerability of each building. Earthquake risk means the potential for damages, casualties, and economic losses.

Campus level earthquake risk is generally proportional to the combined earthquake hazard level. That is, the higher the earthquake hazard level, the more likely it is that the earthquake risk may also be high. However, there are many profound exceptions to this very rough rule of thumb: earthquake risk depends very strongly on the seismic vulnerability of each building. For example:

A campus with very high earthquake hazard level may have low earthquake risk if all of the buildings were designed and built to current or very recent seismic building codes.

On the other hand, a campus with moderate or even low earthquake hazard level may have significant or even high earthquake risk if several buildings are unusually vulnerable to earthquake – such as multistory unreinforced masonry buildings.

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Therefore, earthquake risk at the campus level cannot be defined meaningfully except by doing building-level evaluations and then aggregating building results to determine the campus-level risk.

Given the above considerations, the initial campus-level earthquake risk assessment emphasizes prioritizing buildings for more detailed, building-level risk assessments.

An example ICOS campus-level earthquake report is shown on the following page. This report summarizes the earthquake hazard level (ground shaking, liquefaction potential, and combined) for each campus and displays recommendations regarding building evaluations and geotechnical evaluations for each campus.

Building-Level Seismic Risk Evaluations

The recommended method for completing building-level seismic risk evaluations for buildings is the American Society of Civil Engineers Standard “Seismic Evaluation and Retrofit of Existing Buildings” which is known as ASCE 41-13. This publication provides a standard, widely-used, three-tier process for evaluating seismic vulnerability of buildings. Initial evaluations are done using the Tier 1 checklist, with more detailed Tier 2 and Tier 3 evaluations possibly done later for selected high risk buildings for which more detailed information is desired. ASCE 41-13 risk evaluations should be done by an engineer thoroughly familiar with seismic design issues.

For ASCE 41-13 evaluations of buildings, it is important to recognize that a single “building” may need to be evaluated in two or more parts if different parts of the building were built at different times or with different structural systems.

Geotechnical Evaluations

Geotechnical engineering deals with analyses of the stability of soils and foundations. For campuses with significant liquefaction potential, a geotechnical evaluation of the site is an important part of a seismic risk evaluation. Liquefaction of soils during earthquake ground shaking may result in settlement or lateral spreading of soils, either of which may substantially increase the level of earthquake damage. For sites with a substantial likelihood of major liquefaction, soil, or foundation remediation measures may be a necessary part of seismic retrofits. For sites with high liquefaction potential, replacing a building with high seismic risk with a new building on a different site may sometimes be the best choice.

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Table 2.5Example ICOS Campus-Level Earthquake Report

Yes/No Priority Yes/No Priority

Washington Elementary 63% Very High Low to Moderate

Very High Yes Very High Yes Moderate

Adams Middle School 62% Very High High Extremely High

Yes Extremely High

Yes High

Jefferson High School 25% Moderate Moderate Moderate to High

Yes Moderate to High

Yes Moderate

Madison Elementary 18% Low High Moderate Limited3 Moderate Yes Moderate

Monroe High School 18% Low Low Low Limited3 Moderate No N/A

2 Earthquake ground motion measured as peak ground acceleration (PGA) relative to "g", the acceleration of gravity.

Geotechnical Evaluation

Recommendations

Campus

Earthquake Ground

Shaking 2% in 50 Years2 (% g)

Earthquake Ground Shaking

Hazard Level

Liquefaction Potential

Combined Earthquake

Hazard Level

Building Level Risk Assessment

1Campus level risk is generally proportional to the combined earthquake hazard, but depends VERY strongly on the seismic vulnerability of buildings which MUST be evaluated at the building level. Thus, earthquake risk is cannot be defined meaningfully at the campus level, except by doing building-level evaluations and then aggregating building results to provide campus-level risk.

3 For campuses with "low" ground shaking hazard (2% in 50 year PGA less than 20%), building-level risk assessments are recommended only for the most vulnerable building types.

The above example has a wide range of levels of earthquake hazards to illustrate the range of recommendations. For a given district, the range in levels of earthquake hazards will be much smaller.

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Building-level risk assessments are recommended for all campuses where the combined earthquake hazard level is “moderate” or higher, as defined previously in Tables 2.2 and 2.4. For these campuses, the priority for building-level risk assessments shown in Table 2.5 is the same as the combined hazard level.

For campuses, with “low” earthquake ground shaking hazard (2% in 50 year peak ground acceleration less than 20% g) a more limited building-level evaluation is recommended–to evaluate only the buildings of the most vulnerable building types. Further details are provided in the building-level section which follows.

The recommendations for geotechnical evaluations depend on the earthquake ground shaking hazard and on the liquefaction potential, as shown in Table 2.6.

Table 2.6Logical Basis for Geotechnical Evaluations and Priorities

Moderate or higher YES High

Low YES Moderate

Moderate or higher YES Moderate

Low NO N/A

Moderate or higher NO N/A

Low NO N/A

Geotechnial Evaluation Priority

Moderate or higher

Low to moderate

Low or lower

Liquefaction Potential Ground Shaking Hazard Level

2.3 Earthquake Risk Assessment: Building Level

As discussed previously, the recommended methodology for building-level earthquake risk assessments is the American Society of Civil Engineers Standard “Seismic Evaluation and Retrofit of Existing Buildings” which is known as ASCE 41-13.

ASCE 41-13 includes the concept of “benchmark year” which means the year for which the seismic design provisions in building codes provides an adequate level of life safety as currently understood. For example, all buildings designed to the 2003 or later International Building Code (which was adopted by Washington State, effective July 1, 2004) are deemed post-benchmark year. This means that such buildings provide an acceptable, adequate level of life safety as long as the construction conforms to the building design. For buildings designed to the previous Uniform Building Code, benchmark years are defined for specific building structural types. The following table summarizes the ASCE 41-13 benchmark years.

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Table 2.7ASCE 41-13 Benchmark Years1

IBC Code Year

WA Adoption

Year

Year Built2

UBC Code Year

WA Adoption

Year

Year Built2

2003 2004 2005 N/A N/A N/A

W1 Wood Light Frame4 1976 1977 1978 or Later

W2Wood Commercial

and Industrial41976 1977 1978 or

Later

W1 Wood Light Frame4 1994 1995 1996 or Later

W2Wood Commercial

and Industrial41994 1995 1996 or

Later

C1Concrete Moment

Frame5 1994 1995 1996 or Later

C2 Concrete Shear Walls 1994 1995 1996 or

Later

PC1 Tilt-Up Concrete 1997 1998 1999 or Later

RM1Reinforced Masonry with Wood or Metal

Decks1997 1998 1999 or

Later

RM2Reinforced Masonry

with Precast Concrete Decks

1994 1995 1996 or Later

S1 Steel Moment Frame 1994 1995 1996 or

Later

S2 Steel Braced Frame 1997 1998 1999 or Later

S4Steel Frame with Concrete Shear

Walls1994 1995 1996 or

Later

Building Types

All Building Types in All Districts3

1ASCE 41-13 recommends that post-benchmark code buildings be evaluated by an engineer to verify that that the as-built seismic details conform to the design drawings. Most post-benchmark buildings will be compliant, unless poor construction quality degrades the expected seismic performance of the building.2Determination that a building is post-benchmark is best done using the building code to which the building was designed. Using the year built as a proxy for the building code to which a building was designed may not always be accurate.

3"All" buildings includes buildings of structural types listed in the table, as well as those building types not listed, including URM, Precast Concrete Frame, Light Steel Frame, Concrete Frame with Masonry Infill and Steel Frame with Masonry Infill

Wood Frame Buildings in 53 Districts that were in UBC

Seismic Zone 2/2B Before UBC Seismic Zone 3 in 1994.

See list on next page.

All Districts except those in the following category

All Districts

All Districts

All Districts

All Districts

All Districts

All Districts

All Districts

All Districts

5Flat slab concrete moment frame buildings shall not be considered post-benchmark buildings.

4There are very few K-12 buildings of Type W1. The vast majority of wood frame schools of all sizes are best characterized as W2.

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The blue shaded rows for building Types W1 and W2 are for locations that were in UBC Seismic Zone 2 or 2B until the 1994 UBC. Prior to the 1994 UBC, all buildings in these locations were designed to significantly lower seismic forces than later buildings. Therefore, the benchmark years are much later than for W1 and W2 buildings in other parts of Washington State. The districts for which the benchmark code year is the 1994 UBC and the benchmark year built is 1996 for W1 and W2 buildings are shown below.

Table 2.8Districts in UBC Seismic Zone 2 or 2B before 1994 UBC Seismic Zone 3

Aberdeen OakvilleAdna Ocean Beach

Battleground OcostaBoistfort OnalaskaCamus Pe Ell

Cape Flattery Queets-ClearwaterCastle Rock Quillayute ValleyCosmopolis RaymondCrescent1 Ridgefield

Elma SatsopEvaline Skamania

Evergreen (Clark) Skynomish1

Green Mountain South BendHockinson Stevenson-Carson

Hoquim TaholahKalama ToledoKelso Touttle Lake

La Center Trout Lake1

Lake Quinalt VancouverLongview Wahkiakum

Mary M. Knight WashougalMcCleary1 White Pass1

Montesano Willapa ValleyMount Pleasant Winlock

Naselle - Grays River Valley Wishkah ValleyNorth Beach WoodlandNorth River

1 These districts may have been in UBC Seismic Zone 3 starting with the 1988 UBC. W1 and W2 buildings in these districts may be considered post-benchmark year if confirmed that they were designed to the 1988 UBC or later codes.

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An example of the ICOS building-level earthquake report is shown below.

Table 2.8ICOS Building-Level Earthquake Report: Example

CAMPUS:

Year Built

UBC or

IBC

Code Year

Post-Benchmark1

(Yes/No)Yes/No

Risk Level and

Priority2,3Completed

ASCE 41-33 Compliant (Yes/No)

Further Evaluation

Desired (Yes/No)

2005 YES W1 High Code NO Low N/A YES NO

1955 NO PC1 Moderate Code

YES High YES NO YES

1995 YES C2 Moderate Code

NO Low YES YES NO

2 The priority for ASCE 41-13 evaluations is based on the building type, the combined earthquake hazard level (ground shaking and liquefaction potential), the seismic design basis, and whether a building has been identified has having substantial vertical or horizontal irregularities. These priorities recognize that many districts may have limited funding for ASCE 41-13 evaluations. Districts with adequate funding may wish to complete ASCE 41-13 evaluations on all pre-benchmark year buildings.

Building-Level Report: Earthquake

ASCE 41-13 Tier 1 Evaluation

Recommended1

Library

West Wing of Classroom Building

Gymnasium

Millard Fillmore Elementary School

Building NameSeismic Design Basis

Mitigation Desired (Yes/No)

Mitigation Type

Mitigation Completed (Yes/No)

Building Type

ASCE 41-13 Tier 1 Evaluation4Seismic Design Criteria

1 ASCE 41-13 seismic evaluations are recommended for buildings that were not designed to a "benchmark" seismic code deemed adequate to provide life safety. However, ASCE 41-13 recommends that post-benchmark code buildings be evaluated by an engineer to verify that the as-built seismic details conform to the design drawings. Most such buildings should be compliant, unless poor construction quality degrades the expected seismic performance of the building.

3 The earthquake risk level is low for all buildings for which an ASCE 41-13 evaluation is not recommended as necessary. For other buildings, the preliminary risk level risk level and the priority for ASCE 41-13 evaluation are based on the earthquake hazard level, the building structural type, the seismic design level and whether a building has vertical and horizontal irregularities.4 The final determination of priorities for retrofits for buildings that are not compliant with the 41-13 life safety criteria should be set in close consultation with the engineer who completed the ASCE 41-13 evaluations. The goal is to focus on the buildings with the greatest seismic vulnerabilities.

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The logical basis for the ICOS building-level risk evaluation methodology, as shown in the report example on the previous page, includes the following steps:

1. Whether a given building is ASCE 41-13 post benchmark is determined by the combination of building structure type and the code year (UBC or IBC) for the seismic design of the building, using the criteria in Table 2.8 on page 15. If the code year is unknown, the year built is used as a proxy for the code year. Buildings built two or more years after the code year are deemed post-benchmark. The two-year time period is used because Washington State adopts a given code effective in July of the year after the code is published, and buildings permitted before code adoption may be built later. Year built is less accurate than code year, because the allowable time period between permitting and construction varies between jurisdictions in Washington.

2. The seismic design basis, which is determined by the design year and location, is another measure of the likely seismic vulnerability of a building. This data entry is not used directly in the ICOS prioritization, but is helpful to an engineer completing a building-level risk assessment.

3. Completing ASCE 41-13 evaluations is recommended for all buildings that are not post benchmark year. However, there are several important caveats, especially if districts have limited financial resources for seismic risk evaluations:

a. For campuses with “low” seismic hazard level, as defined previously, districts may wish to evaluate only buildings of the most vulnerable building types as defined previously.

b. An engineer experienced with seismic risk evaluations may be able to prioritize evaluations based on a quick review of building drawings and quick building inspection to determine which buildings appear to have highest likelihood of major seismic deficiencies.

c. Districts may decide to exclude buildings which are scheduled to be replaced within a few years and/or which have very low occupancy.

4. The preliminary estimate of the risk level and the priority for completing 41-13 evaluations is based on the following criteria:

a. For buildings that are post benchmark year, the risk level and priority for completing ASCE 41-13 evaluation is low. ASCE 41-13 evaluations are not necessary unless a district has reason to believe that the building may have significant seismic deficiencies or that the as-built building does not conform to the design drawings.

b. For buildings that are not post benchmark year, the risk level and priority for completing ASCE 41-13 are based on the combined seismic hazard level, the building type, and whether the building has significant horizontal or vertical irregularities.

Once a Tier 1 ASCE 41-13 evaluation has been completed, the interpretation of the results is as follows:

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1. If the building is “compliant” with all of the questions in the ASCE 41-13 checklists, the building meets the criteria for adequate life safety. No further evaluations are necessary and a seismic retrofit is not necessary.

2. If the building is “non-compliant” with one or more of the questions in the ASCE 41-13 checklists, the “formal” next step per ASCE 41-13 is to complete a Tier 2 evaluation, which includes more calculations and much more detailed analyses than a Tier 1 evaluation.

3. However, especially districts with limited financial resources, completing Tier 2 evaluations for all non-compliant buildings may not be feasible or necessary. Rather, it often makes more sense to focus on a smaller subset of buildings that appear to have the most severe seismic deficiencies.

4. For example, a district may have 10 buildings that have been determined to be non-compliant. Rather than completed ASCE 41-13 evaluations for all 10 buildings a district may wish to:

a. Consult with the engineer who completed the Tier 1 evaluations to determine which buildings appear to have the most severe seismic deficiencies.

b. Complete Tier 2 evaluations for a subset of the 10 buildings, perhaps only one building if it is very important (functionally or historically), has a high occupancy and obvious seismic deficiencies or perhaps several buildings.

c. Determine priorities for seismic retrofits for the subset of buildings for which Tier 2 evaluations have been completed.

d. Later, if all of these further-evaluated buildings have been retrofitted or replaced with new buildings, the district may wish to re-examine other buildings lower on the original list of priorities.

In summary, there are four key steps in the approach suggested above:

Determine which buildings are post benchmark year per ASCE 41-13 and can be excluded from further study.

Complete ASCE 41-13 Tier 1 evaluations for all of the non-excluded buildings, or if financial resources are very limited, perhaps only a subset of buildings, based on an initial discussion with an engineer, also considering buildings’ importance occupancy and condition.

Review and interpret the ASCE 41-13 Tier 1 evaluations and determine the buildings for which further evaluation is desired (such as ASCE 41-13 Tier 2).

From the above evaluated buildings, determine the district’s priorities for seismic retrofits or replacements with new buildings.

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2.4 Seismic Retrofits: Commentary

Building codes are not retroactive and unless a given jurisdiction has a mandatory seismic retrofit ordinance for specified types of buildings or occupancies, seismic retrofits are voluntary. Thus, in many cases, seismic retrofits are voluntary and are undertaken when a building’s owner determines that the level of earthquake risk is unacceptable for a given building. However, seismic retrofits may be mandated when an existing building undergoes “substantial alterations” asa defined in the International Building Code (IBC) and the International Existing Building Code (IEBC).

For K–12 facilities, the primary factor governing seismic retrofits is most often life safety. That is, most seismic retrofits are undertaken when a district determines that the level of life safety risk is unacceptably high. Of course, other factors such as the importance of a building (function or historical), avoiding damages and other economic losses may also be important factors.

There are several circumstances when a seismic retrofit may not be justified, necessary, or appropriate even if a building has major seismic deficiencies, including:

A building is functionally obsolete and/or in generally poor condition.

A building is in a location subject to other natural hazards, such as tsunami, volcanic lahars, floods, or others.

A building has significant risks from anthropogenic hazards such as hazardous material releases.

Seismic retrofit costs are a high percentage of replacement costs.

A building is scheduled to be replaced in the near future.

A building or campus is scheduled to be abandoned in the near future because of declining enrollment, a new campus will be built, or any other reason.

In the above circumstances, either abandoning a building or replacing it with a new current seismic code building with modern amenities and functionalities may be preferable to retrofitting the existing building.

The ASCE 41-13 evaluation methodology summarized previously, focuses on life safety. Any building that is non-compliant in one or more of the ASCE 41-13 criteria does not meet the ASCE Standard definition of “life safety.”

The above notwithstanding, there are many possible levels of seismic retrofits, that include bringing an existing building to a lower standard of performance or a higher standard of performance than the ASCE 41-13 life safety criteria. The table below summarizes five possible levels of performance for seismic retrofit.

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Table 2.9Possible Seismic Retrofit Performance Objectives

Seismic Performance Objective Definition

Risk Reduction

Incremental measures such as better connections between floors and walls in an unreinforced masonry building, bracing parapets or chimneys or limited anchoring or bracing of building contents such as tall, heavy library shelves or non-structural building elements such as ceilings. Damage and life safety risk are reduced to some extent.

Collapse Prevention Structural retrofit to prevent collapse, although building may have major damage and may not be repairable.

Life SafetyStructural and nonstructural retrofit to provide life safety - collapse prevention and unimpeded post-earthquake egress and access - although building may have major damage and not be repairable.

Immediate Occupancy Structural and nonstructural retrofit to minimize damage so building is safe to occupy post-earthquake. Building is repairable.

Post-Earthquake OperabilityStructural and nonstructural retrofit to minimize damage so building is safe to occupy post-earthquake and on-site backups to ensure continuity of critical utilities. Building is repairable.

For schools, the most common seismic performance objective for retrofits is life safety. However, when resources are limited, implementing risk reduction measures or collapse prevention may significantly lower life safety risk, albeit without fully meeting the life safety criteria. When a building undergoes “substantial alteration” as defined in the IBC, the IEBC dictates the performance level based on the Occupancy Category of the building.

For schools, retrofitting to immediate occupancy or post-earthquake operability seismic performance level is not common. Retrofits to these levels might be appropriate for schools that are designated as emergency shelters or for K–12 facilities that are essential for district operability.

In evaluating the desired seismic performance objective of a given building, it is essential to consider the level of ground shaking to which a retrofit meets the seismic performance level. For example, in ASCE 31-03, to meet a typical performance objective, the ground motions for the Life Safety and Collapse Prevention Objectives were the 10% in 50 year ground motion and the 2% in 50 year ground motion, respectively. However, under ASCE 41-13, these ground motions were reduced to the 20% in 50 year ground motion for the Life Safety Objective and the 5% in 50 year ground motion for the Collapse Performance Objective. For high occupancy, high importance buildings such as schools, the ground motions per ASCE 31-03 may be more appropriate design targets than those in ASCE 41-13, to the extent practicable for a given building.

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Seismic retrofits are often completed at one time. However, in some circumstances, incremental seismic retrofits make sense. For example, a risk reduction measure to brace unreinforced masonry parapets above entrances to a building and to brace a tall chimney might be done right away with a more comprehensive retrofit done later when funding becomes available.

Incremental seismic retrofits may also be done during maintenance activities or during building modernization. In these cases, the marginal cost to add seismic retrofit measures to maintenance or modernization measures may be significantly lower than doing stand-alone seismic measures, because demolition and replacement of building elements is already included in the maintenance or modernization. Examples include:

Adding plywood to strengthen a roof diaphragm and improving the roof to wall connections when roof covering is being replaced.

Adding shear walls or improving floor to wall connections in a building undergoing major renovations.

Every K–12 facility in Washington State has some level of earthquake risk, even though the level of earthquake hazard varies markedly with location. Even in low seismic hazard areas of the state, there may be a few unusually vulnerable buildings with high enough risk to warrant more detailed evaluation. Therefore, all districts should include earthquakes in their mitigation plan.

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3.0 TSUNAMIS

3.1 Tsunami Hazard Assessment

Tsunami hazard areas in Washington State are limited to locations which are near the coasts of the Pacific Ocean or Puget Sound and which are located at low elevations above sea level. High tsunami hazard means a high probability of inundation by tsunamis, with the inundation depth sufficient to result in damages and casualties. Conversely, low tsunami hazard means a lower probability of inundation by tsunamis. For many locations in Washington, the tsunami hazard is negligible.

The most common source mechanism for tsunami generation is earthquakes within the oceanic floor. For Washington, the most important near-field earthquake sources are the Cascadia Subduction Zone and two faults crossing Puget Sound: the Seattle Fault Zone and the Tacoma Fault Zone.

Earthquake sources for tsunamis are commonly divided into two types:

Distant or far-field earthquake events within the Pacific Ocean that occur thousands of miles from Washington State. For far-field events, the warning time between an earthquake event that generates a tsunami and arrival of tsunami waves is several hours or more.

Local or near-field earthquake events that occur very close to the Washington coast. For near-field events, the warning time is generally an hour or less and may be as short as a few minutes.

See Chapter Eight: Tsunamis in the Washington State K–12 Facilities Hazard Mitigation Plan for a summary of tsunami hazards in Washington, including definitions of technical terms, maps, and other important information about tsunamis.

Campus-level tsunami hazards are based on:

1. Whether a campus is located within a tsunami inundation zone mapped by the Washington State Department of Natural Resources (DNR).

2. The elevation of each campus and the distance to the coast.

Tsunami hazard areas are not limited to only areas mapped by DNR. Tsunamis may affect locations outside of the mapped areas for several reasons:

1. DNR has mapped most, but not all, developed areas at risk for tsunamis.

2. Tsunami modeling is not an exact science and tsunamis much larger than anticipated may occur in the future, as occurred in Japan in 2011.

[3.] Tsunamis may be generated by earthquakes on faults not yet discovered.

3.[4.] Tsunamis may be generated by submarine landslides or terrestrial landslides into bodies of water; tsunamis from these sources are not included in the DNR tsunami maps.

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The ICOS Pre-Disaster Mitigation database includes six levels of tsunami hazard, as shown below.

Table 3.1Tsunami Hazard Levels

Tsunami Campus-Level Hazard Categories

Tsunami Hazard Zones Hazard Level

In mapped tsunami zone High or Very High

Not in mapped zone and:

Elevation <30 feet and <5 miles from coast Moderate

Elevation between 30 and 50 feet and <5 miles from coast Low

Tsunami Table 1

The ICOS Pre-Disaster Mitigation database automatically opens the tsunami hazard and risk screen for any campus within the tsunami hazard zones listed above, except for the “none” category. Districts may wish to “opt-in” to a tsunami risk assessment if they have reason to believe that a campus may be at risk, even though it does not fall in the categories above.

3.2 Tsunami Risk Assessment: Campus Level

For tsunamis, the predominant concern is life safety and the predominant mitigation measure is to prevent or minimize casualties in future tsunamis by immediate evacuation to designated safe locations at elevations well above the anticipated tsunami inundation level before the first arrival of tsunami waves.

Campus-level risk assessments have three main elements:

Tsunami hazard levels shown above in Table 3.1,

Travel distance to the nearest designated safe location, and

Travel time to the nearest designated safe location.

Designated safe locations for tsunami evacuations are determined locally by emergency management agencies or by districts. Ideal safe locations are at elevations above 100 feet, are as near as possible to campuses, and have travel routes that do not have possible impediments to rapid travel on foot. Travel distance is the path length for walking, not the straight-line distance.

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Travel times are estimated from the typical walking speeds for students in different age groups, with slower walking speeds for elementary students. Travel times also include 10 minutes for mobilization time–the time between the onset of strong earthquake ground shaking and the beginning of travel to a designated safe area. Estimated walking speeds for tsunami evacuation are shown in the following table.

Table 3.2Estimated Walking Speeds for Tsunami Evacuations

Tsunami Campus-Level Hazard Categories

Tsunami Hazard Zones

In mapped tsunami zone

Not in mapped zone and:

Tsunami Table 1The ICOS life safety risk levels for tsunamis are shown in the following table.

Table 3.3ICOS Tsunami Life Safety Risk Levels

Tsunami Campus-Level Hazard Categories

Tsunami Hazard Zones Hazard Level

In mapped tsunami zone High or Very High

Not in mapped zone and:

Elevation <30 feet and <5 miles from coas Moderate

Elevation between 30 and 50 feet and <5 m Low

Elevation between 50 and 100 feet and <5 Very Low

Tsunami Table 1

An example ICOS Campus-Level Tsunami Report is shown on the following page.

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Table 3.2Example ICOS Campus-Level Tsunami Hazard and Risk Report

Tsunami: Functionality Criteria and Guidance

Opt-In Text

ICOS Auto-In Criteria GIS Data ONLY:

District has at least 1 campus in mapped tsunami zones or within the blue shaded categories in Tsunami Table 1: all except NONE.

Districts may wish to opt-in to a tsunami risk assessment if they have reason to believe one or more campuses may be at risk, even though the campuses are outside of the criteria in ICOS for automatically considering tsunami risk.Districts may wish to include tsunamis in their mitigation plan even though no campuses are at risk, if parts of the district are within mapped tsunami inundation zones. In this case, including tsunamis may serve a valuable outreach/education purpose for the community to raise awareness of tsunami hazards and risk. One or more campuses may serve as designated evacuation centers for tsunami events. However, in this case, including tsunamis in the district's mitigation plan does not require making tsunami entries in ICOS.

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3.3 Tsunami Mitigation Guidance

1. Do we need to develop a tsunami evacuation plan?

Developing and practicing tsunami evacuation plans is:

An essential urgent priority for campuses within the mapped tsunami inundation zones.

Strongly recommended for campuses with elevations below 50 feet and within 5 miles of the coast.

Encouraged for all campuses near the coast at elevations below 100 feet and within 5 miles of the coast.

Developing and practicing tsunami evacuation plans for campuses at low elevations near the coast, but outside of mapped tsunami inundation zones is recommended or encouraged because prediction of the run-up heights of tsunamis is not an exact science: there are considerable uncertainties.

Tsunamis much larger than anticipated can and do occur. For example, in the March 2011 Tohoku earthquake and tsunami disaster in Japan, thousands of people died because the tsunami was much larger than anticipated with much higher inundation depths and many designated evacuation locations were inundated by the tsunami.

Given the potential for mass casualties from tsunamis, it is preferable to error on the side of caution to ensure being safe rather than sorry.

2. How do we determine appropriate evacuation assembly areas?

The ideal evacuation assembly area is located as near as possible to a campus, with an elevation of at least 50 feet above sea level (above 100 feet, if possible), with a direct travel route between the campus and the evacuation assembly area without any potential impediments to rapid evacuation.

For communities with mapped tsunami inundation zones, there are already-designated assembly areas for tsunami evacuation. These maps are included as part of the OSPI Mitigation Planning Toolkit For campuses within these communities, these designated evacuation assembly areas may be the best available evacuation locations. However, in some cases, the locations might be too far from some campuses or the elevations may not be high enough.

The following guidance re: selection of evacuation locations is provided for districts with at-risk campuses for which there are no already-designated evacuation locations and for districts who may wish to determine whether there may be a better evacuation location for a given campus then an already designated location.

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A campus-level assessment for tsunami evacuation planning includes the following steps:

1. Identify one or more nearest safe-haven evacuation locations with elevations greater than 100 feet when possible and at least 50 feet if higher elevation locations are not reachable within the estimated time between the end of earthquake ground shaking and the tsunami arrival time. The community-designated evacuation assembly areas noted above may be good candidates, but districts may want to consider other locations as well, especially if other suitable locations are nearer to an at-risk campus.

2. For initial planning purposes, designated evacuation locations should ideally be reachable in significantly less time than the estimated time period between the end of ground shaking and the arrival of the first tsunami wave. Longer travel distances result in longer travel times and increase the likelihood of casualties because people may not reach the safe haven in time. For planning purposes. Therefore, when an ideal site is not available, a nearby site without shelter may be preferable to a more distant site with shelter.

3. Evaluate prospective travel routes to evacuation locations for possible impediments to successful evacuations and avoid such routes when possible:

a. Low elevation areas that may be flooded from co-seismic subsidence of up to six feet from the earthquake, for Cascadia Subduction Zone interface earthquakes.

b. Routes that include bridges that may not survive earthquake ground shaking.

c. Routes where possible landslides, falling hazards such as overhead power lines, and highly vulnerable buildings such as unreinforced masonry buildings, or hazardous material sites with potential spills that may impede evacuation.

4. Designate at least one location as a tsunami evacuation assembly point.

3. Can our students, staff, and visitors reach designated evacuation assembly areas before the arrival of tsunamis?

For tsunamis generated by earthquakes on the Cascadia Subduction Zone or by earthquake faults within Puget Sound, the time period from the end of earthquake ground shaking is everywhere less than one hour and is less than 15 minutes for some locations. The ideal evacuation location is no more than 5 minutes walking time from a campus. However, many campuses do not have suitable evacuation locations within 5 minutes walking time.

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For evacuation planning and selection of evacuation assembly locations, considerations of travel times must recognize that evacuation cannot start until after strong earthquake ground shaking stops, which may be several minutes for Cascadia Subduction Zone earthquakes, and that mobilization for evacuation will likely take at least several additional minutes because of the nearly inevitable confusion and panic after a major earthquake. Given these considerations, mobilization before starting evacuation towards designated areas is likely to take at least 5 to 10 minutes, perhaps longer.

Practice drills for tsunami evacuations are essential to minimize the mobilization time after earthquakes and to maximize the likelihood that evacuees can reach safe havens before arrival of the first tsunami waves.

Travel times to safe havens depend on the mobilization time and on the travel distance and corresponding travel time. Tsunami evacuations are almost always by foot. There is not enough time to mobilize vehicular transport and travel by vehicles may be impeded by traffic congestion and/or by earthquake debris.

4. Do we need to consider vertical evacuation for tsunamis?

Whenever possible, evacuation to natural high ground is always the preferred evacuation alternative. However, for some locations, the minimum travel time to natural high ground evacuation locations are shorter than the expected first arrival of tsunami waves. The level of life safety risk for campuses with this situation is extreme. Given a major tsunami, mass casualties are almost inevitable, absent effective mitigation.

Facilities within mapped tsunami inundation zones for which there are no safe-haven evacuation locations reachable within the estimated arrival time of tsunamis have extreme risk. The level of life safety risk is higher for these campuses than for any other natural hazard events in Washington. Therefore, mitigation for such facilities is an urgent priority.

Vertical evacuation for tsunamis means an engineered structure on or very near a campus which is designed to withstand tsunami forces, has a capacity to hold all or as many as possible of people from the “collection” area around the structure, at an elevation well above the anticipated tsunami inundation elevation. Typical vertical evacuation structures include:

Heavily-reinforced concrete structures with deep foundations,

Earth berms with armoring to prevent scour during tsunamis, or

Multi-story buildings with capacity to withstand both earthquake and tsunami forces.

In some cases, an engineered structure such as a pedestrian bridge to shorten the travel distance and time to natural high ground may be a viable, cost-effective

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mitigation measure when access to the high ground is blocked by a body of water or the travel route includes a bridge with a high likelihood of not surviving the earthquake.

5. When should a District Include Tsunamis in their Mitigation Plan?

All districts with one or more campuses within the tsunami hazard zones listed previously in Table 3.1 should definitely include tsunamis in their mitigation plan.

However, there are two additional circumstances where districts may wish to include tsunamis because some communities within district boundaries have, or may have, significant tsunami risk, including:

Districts which have mapped tsunami inundation zones within their boundaries, and

Districts whose boundaries include the coasts of the Pacific Ocean or Puget Sound.

In these cases, including tsunamis in a district’s mitigation plan may serve a valuable public education purpose by raising awareness and knowledge about tsunami hazards. Figure 3.1 on the following page shows districts whose boundaries include mapped tsunami inundation zones and districts whose boundaries include the coasts of the Pacific Ocean or Puget Sound and thus may have significant tsunami risks. Districts on the coast may have substantial tsunami risks, even if tsunami inundation maps have not yet been completed.

3.4 Tsunami Risk Assessment: Building Level

Tsunami risk assessment is predominantly at the campus-level. The objective is to evacuate the entire campus population to a safe area before the first arrival of tsunami waves.

However, there is one circumstance where a building-level assessment may be appropriate. Some existing multi-story K–12 buildings may have adequate capacity to withstand both earthquake forces and tsunami forces, with enough confidence to consider vertical evacuation to an upper floor or the roof.

In this case, a thorough, rigorous evaluation of the building by a structural engineer is essential to evaluate a building’s possible suitability for vertical evacuation, either in the as-is condition or after retrofit to strengthen the building. An important caveat, as noted previously, is that vertical evacuation should be considered as a last resort, to be implemented if and only if there is no natural high ground at high enough elevation reachable in the anticipated time period between the end of earthquake ground shaking and the first arrival of tsunami waves.

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Figure 3.1Districts WithTsunami Hazards Within Their Boundaries

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4.0 VOLCANIC HAZARDS

4.1 Volcano Hazard Assessment

Washington State has five major active volcanoes: Mount Baker, Glacier Peak, Mount Rainier, Mount Adams, and Mount St. Helens. In addition, there is a broad area of volcanic activity around Mount Adams, and Mount Hood in Oregon is located very near Washington’s southern border.

There are several types of volcanic hazards that are classified as proximal hazards which affect only areas near a volcano, and distal hazards, which may affect areas tens or hundreds of miles from a volcano. Proximal hazards include lava flows, pyroclastic flows, blast effects, landsides, debris avalanches and debris flows. Distal hazards include lahars and ash falls.

For K--12 facilities in Washington, the predominant volcanic hazard is lahars – there are many campuses located within mapped lahar zones. The level of risk from proximal volcanic hazards such as blasts or lava flows is lower because there are only a few campuses located in such zones and the return periods of these events are much longer than the return periods for lahar events.

Volcanic ash falls may extend for hundreds of miles downwind from an erupting volcano and may thus affect any campus in Washington. However, the effects of ash fall events are generally much less severe than lahar events or the other volcanic hazard events listed above.

Many campuses not subject to lahars are subject to volcanic ash falls. In this case, volcanic hazards (ash falls) may be addressed briefly in a “lesser” hazards chapter or excluded from the mitigation plan entirely by noting that no campuses are subject to lahars and that volcanic ash events are addressed in the district’s emergency plan.

See Chapter Nine: Volcanic Hazards in the Washington State K–12 Facilities Hazard Mitigation Plan for further information about volcanic hazards and risks, including definitions of technical terms, volcanic hazard zone maps, and other important information about volcanic hazards.

Volcanic hazards are characterized by the type of event, the area affected, and the estimated return period of the event. Volcanic hazard assessments draw heavily on mapping of hazard zones by the United States Geological Survey (USGS). The USGS mapped volcanic hazard zones that include K–12 facilities are summarized in Table 4.1 on the following page.

For each volcano, events may occur over a wide range of severities and return periods. For example, larger lahars or blast events have longer return periods than smaller events.

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An important caveat is that the return periods for volcanic events are less well known than for most other natural hazards and there is considerable uncertainty in the estimates shown in Table 4.1. The return period estimates shown are estimates by Kenneth Goettel, drawing heavily on the available USGS information.

Table 4.1USGS Mapped Volcanic Hazard Zones

ICOS ICOS ICOS ICOS ICOSLAHAR CODING FOR Column References to Columns on Site List

Column 11 Column 12 Column 13 Not on Site list Not on Site List

Volcano Volcanic Hazard TypeVolcano ICOS Code Letter Code

Adams 1 A Adams Zone LA Lava Flows & Pyroclastic Deposits

Adams 1 A Adams Zone LB Lava Flows & Pyroclastic Deposits

Adams 1 A Adams Zone LC Lava Flows & Pyroclastic Deposits

Adams 1 A Adams Zone DL Lahars

Baker 2 B Baker Case 1 Lahars

Baker 2 B Baker Case M Lahars

Baker Blast Zone Blast Zone

Glacier 3 G Glacier Peak Lahars

Glacier Peak Lahars

Glacier 3 G Glacier Peak & Baker Case M & GP Lahar Lahars

Baker & Glaci 4 GB Hood Case DA Lahars/Flooding/Erosion

Hood 5 H Rainier Case M Lahars

USGS Mapped Hazard Zone

GP Lahar1

GP Lahar2

There are 25 campuses that are subject to lahars from both Mount Baker and Glacier Peak. For these campuses and for campuses subject to lahars of various sizes and return periods, the governing volcanic hazard event is the event with the shortest return period.

Mount St. Helens has 13 USGS-mapped lahar zones, which are not shown above because there are no campuses located within these zones.

The map on the following page shows mapped volcanic hazard zones. Chapter Nine: Volcanic Hazards in the Washington State K–12 Facilities Hazard Mitigation Plan has higher resolution maps for each volcano.

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Figure 4.1Mapped Volcanic Hazard Zones

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ICOS hazard levels for volcanic events of various return periods are shown below.

Table 4.2ICOS Volcanic Hazard Levels

VOLCANIC HAZARDS: Notes

Andrew and Robert: We need to make some edits to the text on the Lahar screen in ICOS.However, we don't need to change the district entries.

1. The label at the top of the screen says "lahar" it should say Volcanic

Volcanic hazard events with relatively long return periods – such as 500 years, 1,000 years, or even 5,000 years or more – pose significant risks to campuses because the consequences can be catastrophic. For example, the death rate for a campus buried by a lahar event before evacuation could approach 100%.

The ICOS Pre-Disaster Mitigation database automatically opens the volcanic hazards screen for districts with one or more campuses within USGS mapped volcanic hazard zones. However, volcanic hazard levels are not zero outside of the mapped zones because there is inevitable uncertainty in volcanic hazard mapping. Districts that have one or more campuses in the following circumstances are strongly encouraged to “opt-in” to the volcanic hazard screen and enter the district-specific data necessary to complete a volcanic hazards risk assessment for these campuses:

Campuses within one-mile of mapped volcanic hazard zones, and

Campuses within valleys with mapped volcanic hazard zones.

Districts with campuses in the above categories should include volcanic hazards in the mitigation plan, even without having campuses in mapped volcanic hazard zones.

4.2 Volcanic Hazards Risk Assessment: Campus-Level

Risk assessments for volcanic hazards focus almost entirely on life safety. There are few, if any, mitigation measures to reduce the likelihood of damage from volcanic events that are feasible from either an engineering perspective or a cost perspective.

Campus-level risk assessments for lahars have three main elements:

Volcanic hazard levels shown above in Table 4.1,

Travel distance to the nearest designated safe location, and

Travel time to the nearest designated safe location.

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Designated safe locations for lahar evacuations are determined locally by emergency management agencies or by districts. Ideal safe locations are at least 50 feet above the maximum mapped lahar boundary, are as near as possible to campuses, and have travel routes that do not have possible impediments to rapid travel on foot. Travel distance is the path length for walking, not the straight-line distance.

Travel times are estimated from the typical walking speeds for students in different age groups, with slower walking speeds for elementary students. Travel times also include 10 minutes for mobilization time – the time between awareness of an approaching lahar and the beginning of travel to a designated safe area. Estimated walking speeds for lahar evacuation are shown in the following table.

Table 4.3Estimated Walking Speeds for Lahar Evacuations

Tsunami Campus-Level Hazard Categories

Tsunami Hazard Zones

In mapped tsunami zone

Not in mapped zone and:

Tsunami Table 1

The ICOS life-safety risk levels for lahars are shown below.

Table 4.4ICOS Lahar Life Safety Risk Levels

Volcano Campus-Level Hazard Categories

Return Period (Years) Volcanic Hazard Level

500 or less Very High

501 to 1,000 High

1,001 to 5,000 Moderate

5,001 to 10,000 Low

10,001 to 30,000 Very low

Volcano Table 1

Andrew: near zones based on which zone the campus is near too (highest hazard zone within 1 mile)

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4.3 Volcanic Hazards Mitigation Guidance

Evacuation planning for lahars and other volcanic hazard events is significantly more complex than for tsunamis for which the only warning before the event is strong ground shaking from an earthquake. Volcanoes most often, but not always, show increasing signs of impending activity for days, weeks, or months before an eruption or other activity occurs.

Pro-active evacuations of campuses at risk could be made before an eruption, when the volcanic reaches a specified USGS Alert Level, such as the “Watch” level. This alternative provides the greatest safety, but may result in evacuations for weeks or months before an event happens or evacuations when an event doesn’t occur at all.

Figure 4.1USGS Volcanic Alert Levels for People on the Ground

Alert Term Description

NORMALVolcano is in typical background, noneruptive state or, after a change from a higher level, volcanic activity has ceased and volcano has returned to noneruptive background state.

ADVISORY

Volcano is exhibiting signs of elevated unrest above known background level or, after a change from a higher level, volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase.

WATCHVolcano is exhibited heightened or escalating unrest with increased potential of eruption, timeframe uncertain, or eruption is underway but poses limited hazards.

WARNING Hazardous eruption is imminent, underway or suspected.

For campuses subject to blast effects or pyroclastic flows, pro-active evacuation is the only viable choice. Once a blast or pyroclastic flow begins, there would not be enough time to evacuate a campus, so shelter in place would be the only option.

For lahar events, evacuation once a lahar is initiated may be a viable option in some – but not all – events. In many cases, the only notice of an approaching lahar would be a load rumbling sound similar to a locomotive or jet which would be audible for only a few minutes before the lahar arrived. In this, case evacuation is very problematic and evacuation may not be possible before lahar arrival, unless mobilization is very rapid and a safe area is very near a campus.

As of 2014, lahar warning systems are in place only for two valleys on Mount Rainier: the Puyallup and Carbon River valleys. Even with a warning system, it may be 30 minutes or more before a lahar is detected and the communication chain reaches an

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individual campus. For campuses near Mount Rainier, the warning system may or may not provide adequate time for evacuation. For campuses further way, the warning system is more likely to provide adequate time for evacuation.

1. Do we need to develop a lahar evacuation plan?

Developing and practicing lahar evacuation plans is:

Essential for campuses within the mapped lahar inundation zones.

Recommended for campuses near mapped lahar inundation zones or in the same valleys as mapped lahar zones.

Encouraged for all campuses in a valley downslope from an active volcano.

Developing and practicing lahar evacuation plans, including the categories listed above outside of mapped lahar inundation zones is recommended or encouraged because prediction of lahars is not an exact science: there are considerable uncertainties.

Lahars much larger than anticipated may occur. Also, there are circumstances such as a temporary debris dam or a debris dam created by a landslide that may temporarily impound a lahar flow, which subsequently ruptures, generating an extreme lahar flow downstream.

Given the potential for mass casualties from lahars, it is preferable to error on the side of caution to ensure being safe rather than sorry.

2. How do we determine appropriate evacuation assembly areas?

The ideal evacuation assembly area is located as near as possible to a campus, with an elevation of at least 50 feet above nearest boundary of the largest mapped lahar zone.

For communities with mapped lahar zones, there may be already-designated assembly areas for lahar evacuation. The following guidance re: selection of evacuation locations is provided for districts with at-risk campuses for which there are no already-designated evacuation locations, and for districts who may wish to determine whether there may be a better evacuation location for a given campus.

A campus-level assessment for lahar evacuation planning includes the following steps:

[1.] Identify one or more nearest safe-haven evacuation locations with elevations with elevations greater than at least 50 feet higher than the nearest boundary of the largest mapped lahar zone. The community-designated evacuation assembly areas noted above are likely good candidates, but districts may want to consider other locations as well, especially if other suitable locations are nearer to an at-risk campus.

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1.[2.] For initial planning purposes, designated evacuation locations should ideally be reachable in significantly less time than the estimated lahar arrival time. Longer travel distances result in longer travel times and increase the likelihood of casualties because people may not reach the safe haven in time. For planning purposes. Therefore, when an ideal site is not available, a nearby site without shelter may be preferable to a more distant site with shelter.

2.[3.] Designate at least one location as a lahar evacuation assembly point.

3. Can our students, staff, and visitors reach designated evacuation assembly areas before the arrival of lahars?

Table 9.4 in Chapter Nine: Volcanic Hazards in the Washington State K–12 Facilities Hazard Mitigation Plan identifies the campuses within mapped lahar zones. This table also includes rough, preliminary estimates of the travel time between the volcanic peak and each campus. The preliminary estimates of lahar travel times to campuses within mapped lahar zones range from about 45 minutes to180 minutes.

The actual warning time may be much less than these estimated lahar travel times, because a lahar may be initiated and travel a considerable distance before a given school is aware of the event and begins evacuation. For locations, where awareness of a lahar is due to hearing the roaring sound, the evacuation time may be less than 5 minutes.

For Mount Rainier, USGS estimates for lahar arrival times at various communities are shown on the vertical axis in Figure 4.2 on the following page. The communities with asterisks after their name are served by the Mount Rainier lahar warning system. Warning of lahars detected by the system would be communicated approximately 30 minutes after the initiation of a lahar. Therefore, the actual time available for evacuation for a given community is likely to be at least 30 minutes less than the times shown in Figure 4.2.

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Figure 4.2Mount Hood: Estimated Lahar Arrival Times1

1Nathan Wood and Christopher Soulard, Variations in Population Exposure and Sensitivity to Lahar Hazards from Mount Rainier, Washington (2009). Journal of Volcanology and Geothermal Research, Volume 188, pages 367-378.

4. When Should a District Include Volcanic Hazards in their Mitigation Plan?

All districts with one or more campuses within or near the volcanic hazard zones listed previously in Table 4.1 should definitely include volcanic hazards in their mitigation plan.

However, there are additional circumstances where districts may wish to include volcanic hazards because some communities within district boundaries have, or may have, significant volcanic hazards risk, including:

Districts with campuses in valleys with mapped volcanic hazard areas, and

Districts which have mapped volcanic hazard zones within their boundaries.

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In these cases, including volcanic hazards in a district’s mitigation plan may serve a valuable public education purpose by raising awareness and knowledge about volcanic hazards.

5. Is Vertical Evacuation Possible for Lahars?

Vertical evacuation for lahars would mean constructing an engineered structure on, or very near, a campus which is designed to withstand lahar forces, has a capacity to hold all, or as many as possible, people from the “collection” area around the structure, at an elevation well above the anticipated lahar inundation elevation. Such structures might be feasible from the engineering perspective and the cost effectiveness perspective in rare circumstances. However, no such structures have been built in the United States or perhaps anywhere in the world.

When natural high ground above anticipated lahar elevations is not reachable, a more practical alternative is pro-active evacuation before a lahar is initiated. However, in some cases, an engineered structure such as a pedestrian bridge to shorten the travel distance and time to natural high ground may be a viable, cost-effective mitigation measure when access to the high ground is blocked by a body of water or major impediment to rapid evacuation.

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5.0 FLOODS

5.1 Flood Hazard Assessment

Many K–12 facilities in Washington are subject to flooding from several different sources, including:

Overbank flooding from rivers and streams,

Coastal storm surge flooding,

Local stormwater drainage flooding,

Alluvial fan (sheet flow) flooding,

Flooding from migrating rivers and streams,

Flooding from failures of dams, reservoirs, or levees, and

Earthquake-related flood sources – subsidence, tsunamis, and seiches.

See Chapter Ten: Floods in the Washington State K–12 Facilities Hazard Mitigation Plan for further information about flood hazards and risks, including definitions of technical terms. The approaches for flood hazard assessments vary significantly depending on the type of flooding and the type of data available.

The most accurate flood hazard assessments are possible for overbank flooding and coastal storm surge flooding when quantitative flood hazard data are available. For riverine flooding, the necessary quantitative data include stream discharges for floods of several return periods, the corresponding flood elevations at a given location, and the stream bottom elevation. For coastal flooding, the necessary data are the flood elevations for floods of several return periods.

The quantitative flood hazard data summarized above are most commonly available from FEMA Flood Insurance Studies, but may also be available in similar flood studies by other agencies or by flood engineering firms. This quantitative data allows calculation of the probability of flooding of any depth in a building for which the building elevation is known. FEMA’s benefit-cost analysis software automates these calculations upon entry of the data noted above.

For locations where quantitative flood hazard data are not available, but there is history of repetitive flooding and documentation or estimates of the damage levels for a given building, good estimates of the level of flood hazards can be generated by mathematical interpretation of the flood history data. FEMA’s benefit-cost software also automates these calculations upon entry of the flood history data.

Flood hazard assessment for some types of flooding, including flooding from channel migration, failures of dams, reservoirs or levees, and earthquake-related flooding require site-specific analyses by engineers or other subject-matter experts familiar with such analyses.

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The ICOS Pre-Disaster Mitigation database automatically opens the flood hazard and risk screen for districts with one or more campuses within FEMA-mapped floodplains or within 0.5 mile of a FEMA-mapped floodplain. However, flood risks are not zero outside of the FEMA-mapped floodplains. Nationwide, and in Washington State, much flooding happens outside of mapped floodplains from rivers and streams not mapped by FEMA, from stormwater drainage and other types of flooding and because some FEMA floodplain mapped is outdated and flood hazards have increased over time.

Districts are strongly encouraged to “opt-in” to the flood hazard and risk analysis in ICOS for any campus with any of the following characteristics:

There is a history of floods from any source affecting or near a campus.

Local storm water drainage flooding is common on or near a campus,

Campus is near a river or stream not mapped by FEMA.

Campus is on an alluvial fan subject to sheet flows.

Campus is near a migrating river or stream.

Campus is behind a levee or downstream of a dam or reservoir.

A local flood hazard study is available for the campus and vicinity.

Whether a campus has a history of flooding or is subject to localized storm water drainage, flooding can be determined from district records, from the collective memory of district staff, and/or by consultation with local flood officials or flood engineers. Determining whether a campus is located behind a levee, or downstream, or downslope from a dam or reservoir, is readily determined from maps or from local data and observations. Alluvial fans are gently sloping deposits of sediments at the base of hills or mountains. Flooding may occur from overbank flooding of drainage channels or by what is known as sheet flows. Sheet flows are shallow flows over a broad area.

5.2 Flood Hazard and Risk Assessment: Campus Level

Flood risk assessment at the campus level is preliminary, for the primary purpose of identifying campuses which may have enough flood risk to warrant more accurate building-level flood risk assessments. The ICOS campus-level flood risk assessment is based on a combination of auto-populated data from GIS data and district-entered data. The auto-populated data include the at-grade elevation and whether the campus is within a FEMA-mapped floodplain or within 0.5 mile of a FEMA floodplain. The district entered data include elevations for the stream bottom and the 10-, 50-, 100- and 500-year floods, from the FEMA Flood Insurance Study (or a local flood study with similar information), along answers to questions listed previously in the context of districts opting-in to the flood hazard and risk screen in ICOS.

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Flood elevations, at-grade elevations, and building elevations are commonly expressed relative to two different reference datums, known as NGVD 1929 and NAVD 1988. In reporting elevations, it is essential to enter the reference datum which are shown in FEMA Flood Insurance Studies and noted on surveyed building elevations. In ICOS, elevations in NGVD 1929 are corrected to the more recent NAVD 1988 reference data.

The ICOS logic for campus-level flood risk assessment is shown below in Table 5.1.

Table 5.1ICOS Campus-Level Flood Risk Categories

Flood Hazard Level Criteria

Revised C

ategories

High In FEMA A or V flood zones or two or more historical flood events

Moderate

Low to Moderate Near FEMA-mapped flood zones

Low

Flood Table 1 In other FEMA flood zones or one historical flood event or

expressed concern about other types of flood events

Not in or near FEMA-mapped floodplains and NO answers for local flood study, historical flood events and other flood concerns.

If both the quantitative flood data and the other data exist, the flood risk category is the higher of the two criteria. If only the quantitative flood data or the other data exist, then the flood risk category is based on the available data. If neither data set is available, the flood risk level is unknown. The recommendations and priority for building-level flood risk assessments are based on the campus-level risk categories.

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Table 5.2Recommendations for Building-Level Flood Risk Assessments

3. There is a history of floods from any source affecting or near a campus.

4. Campus is near a river or stream not mapped by FEMA.

5. Campus is behind a levee or downstream of a dam or reservoir.

6. Campus is on an alluvial fan subject to sheet flows.

7. Campus is near a migrating river or stream.

NOTE: All districts should consider floods in their emergency plan, including: evacuation and temporary protective measures such as sand bagging and moving high value assets out of harm's way.

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An example ICOS campus-level flood hazard and risk report is shown below.

Table 5.3Example ICOS Campus-Level Flood Hazard and Risk Report

Flood: Functionality Criteria and Guidance

CampusOpt-In Text

ABC School Yes

DEF School Yes

1. A local flood hazard study has been completed for the area including a campus. GHI School No

2. Local storm water draining flooding is common on or near a campus. JKL High School Yes

3. There is a history of floods from any source affecting or near a campus. MNO Middle School Yes

4. Campus is near a river or stream not mapped by FEMA. PQR Elementary School No

5. Campus is behind a levee or downstream of a dam or reservoir. STV School No

6. Campus is on an alluvial fan subject to sheet flows.

ICOS Auto-In Criteria GIS Data ONLY:

Within FEMA-mapped floodplain or within 0.5 mile of FEMA-mapped floodplain???

Within FEMA

Floodplain

All districts are encouraged to opt-in to the flood PDM screens because a substantial fraction of total flood damage in Washington occurs outside of FEMA-mapped floodplains. Flood risk is significant for many campuses that are not within or near FEMA-mapped floodplains, especially in the following circumstances:

1 With quantitative flood hazard data, similar to FEMA Flood Insurance Study

7. Campus is near a migrating river or stream. 2 Applicable only if campus is not within a mapped flood zone.

NOTE: All districts should consider floods in their emergency plan, including: evacuation and temporary protective measures such as sand bagging and moving high value assets out of harm's way.

3 Severe enough to result in school closure and/or damage to at least one building.

4 Local storm water drainage flooding, campus near stream/river without FEMA flood mapping, campus behind levee or downstream from a dam, campus on alluvial fan subject to sheet flows, campus near a migrating stream/river, or local flood study completed.

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5.3 Flood Risk Assessment: Building Level – With Quantitative Flood Data

5.3.1 Overview

The ICOS Pre-Disaster Mitigation flood screens for building-level flood risk assessment are applicable only to locations where quantitative flood hazard data are available. Guidance on these building-level risk assessments is provided below.

Table 5.54 on the following page has an example ICOS Building-Level Flood Risk Assessment Report.

The key data for the building level assessment are the first floor elevation of each building being evaluated, the stream bottom elevation and the flood elevations for 10-, 50, 100- and 500-year floods. The building first floor elevation is the top of the lowest floor, excluding basements unless the basement is fully finished and furnished similar to the higher floors. Building first floor elevations may be surveyed elevations or, if surveyed elevations are not available, but estimating the elevation from nearby surveyed elevations. Stream bottom elevations and flood elevations are available in FEMA Flood Insurance Studies or local flood studies with similar information. As noted previously, the reference datum (NGVD 1929 or NAVD 1988) must be obtained for all elevation data.

Flood elevations vary along the reach of a river or stream, always higher upstream and lower downstream. For a campus with buildings spread along a significant distance along a river or stream, the flood elevations should be obtained for each building. For a campus with a small number of buildings closely grouped together, a single set of elevation data may suffice, especially if the gradient of the river or stream is low.

The flood return period shown in the ICOS Building-Level Flood Risk Assessment Report is for floods reaching the first floor elevation or higher. Basement flooding may occur in more frequent flood events. The flood risk level for each building is set by comparison of each building’s first floor elevation with the flood elevations.

Table 5.4Building Level Flood Risk Categories

Building-Level Risk Assessments: Flood

There are two approaches to building-level flood risk assessments:

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Table 5.5Example ICOS Building-Level Flood Risk Assessment Report

Building-Level Risk Assessments: Flood Building-Level Flood Report: With Quantitative Flood Hazard Data

CAMPUS: Bart Simpson Elementary School

There are two approaches to building-level flood risk assessments:

Building Name

Flood Elevations (Feet) (NAVD 1988)

Campus-Level Flood Data 93.99 101.23

Classroom/Library Building No 100.01 94.11 101.33

Cafeteria/Auditorium Building No 102.22 94.16 101.38

Basement (Yes/No)

First Floor Elevation

(Feet) (NAVD 1988)

1. A rigorous quantitative approach which is applicable when there are quantitative flood hazard data including flood discharges (the volume of water flowing per second in a river or stream) and flood elevation data for several flood return periods. These data are included in most of the FEMA Flood Insurance Studies and similar data may be included in local flood studies. With these data and the elevation of the first floor of a building, the probability (or return period) of flooding reaching the first floor or the probability of a flood of any depth (below or above the first floor) can be calculated. THIS METHOD IS IN ICOS.

Stream Bottom

10-Year Flood

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5.3.2 Technical Guidance

For campuses within FEMA-mapped floodplains, quantitative flood hazard data are readily available from FEMA Flood Insurance Studies (FIS) and FEMA Flood Insurance Rate Maps (FIRMs). Flood Insurance Rate Maps and Flood Insurance Studies may be available from city, county, or state flood agencies and all are available for a nominal charge from the Map Service Center on the FEMA website: http://fema.gov

Flood Insurance Studies and Flood Insurance Rate Maps for a given community are accessed and downloaded on the FEMA Map Service Center simply by entering the state, county, and community for which these materials are desired. Older FISs are typically for individual cities, while newer FISs are typically for entire counties. For a given community, the appropriate FIS and FIRMs are the most recent versions. FEMA updates these materials periodically to incorporate new flood data and new flood modeling results.

The materials below focus on FEMA data. However, for some communities there may be local flood studies that provide similar data to the FEMA data. If the local studies are more recent than FEMA studies or if there are no FEMA data for a given community, the local flood studies can be interpreted in the same ways as discussed below for FEMA studies.

The steps for obtaining and interpreting FEMA and/or local flood data and maps are summarized below.

1. How do we determine if a given campus is located within a FEMA-mapped floodplain and, if so, what is the FEMA flood zone designation?

See Chapter Ten: Floods in the Washington State K–12 Facilities Hazard Mitigation Plan for further information about flood hazards and risks. Table 10.1 in Chapter Ten lists the campuses within FEMA-mapped flood zones. This chapter also has definitions of the FEMA floodplain zones, which have changed over time.

There are three caveats on the lists of campuses within FEMA-mapped floodplains discussed above:

First, the determinations are based on statewide GIS latitude and longitude data for campuses. Small errors in latitude-longitude may exist. Thus, these lists may include some campuses that are near FEMA-mapped floodplains, but not within the floodplain boundaries. Conversely, these lists may miss some campuses that may be incorrectly identified as being near, but not within mapped floodplains.

Second, the FEMA floodplain zones are incompletely identified in the statewide lists because the available GIS data sources don’t distinguish between the many types of A-Zones (100-year floodplains).

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Third, FEMA has an ongoing map modernization effort. As older floodplain maps are updated, the floodplain boundaries may change significantly.

Districts can determine whether or not a given campus is located within a FEMA-mapped floodplain and also determine the FEMA flood zone designation by examining either the FEMA Flood Insurance Rate Maps or what are known as Firmettes. FIRMs cover large areas within a given community, while Firmettes are “zoom-ins” to a specified smaller area.

To obtain and use FEMA Flood Insurance Rate Maps:

Download the community Flood Insurance Rate Maps from the Map Service Center on the FEMA website: http://fema.gov

Use the FIRM Index map (included above) to identify which FIRM panel(s) covering the location of a given campus.

Look at the FIRM panel to see whether or not a given campus is within a mapped floodplain and, if so, determine the FEMA flood zone designation.

To obtain and use a FEMA Firmette:

Go to: http://msc.fema.gov

At this site, enter the campus address in the upper left corner of the screen and then click on the “search by street address” button.

Follow the instructions to generate a Firmette and save in either PDF orf JGP formats. The full instructions are given in How to Make a Firmette.pdf which is included in the Mitigation Planning Toolkit.

2. How do I find the quantitative flood hazard data in a FEMA Flood Insurance Study?

There are two types of quantitative flood hazard data in a FEMA FIS:

Stream discharges, which are the volume of water flowing in the stream in cubic feet per second, and

Flood profile graphs, which provide flood elevations for any mapped location along the reach of a river.

Together with elevation data for a campus or a building, these flood data facilitate quantitative understanding of the annual probabilities of flooding, or the return periods, of any specified depth of flooding. A given FIS will contain discharge and flood profile graphs for many rivers and streams. The name of the river or stream that is the potential flood source for a given campus can be determined from a Flood Insurance Rate Map or from other maps.

The stream discharge data are listed in a Table of Discharges in the FIS. There may be more than one set of values at different locations for a given river or stream. Use the data for the nearest location downstream from the campus location. These data

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are typically for the 10-, 50-, 100- and 500-year flood events. An example of discharge data is shown below from Table 13 on page 34 of the Flood Insurance Study for Lewis County (November 11, 2010):

Table 5.6Flood Insurance Study Data Example

Chehalis River at Confluence with Skookumchuck River

10 45,084

50 65,410

100 75,084

500 100,333

Flood Frequency (Years)

Discharge (cfs)a

Flood elevations vary along the reach of every river and are always higher upstream and lower downstream. Therefore, flood elevation data must be obtained for the specific location of a given campus or building along a river. The flood elevation data shown above in Table 5.6 are from the flood profile graph shown on the following page for the Chehalis River at the confluence with the Skookumchuck River in Centralia, Washington. The elevations shown on this flood profile graph are the 10-, 50-, 100- and 500-year flood elevations, along with the stream bottom elevation. For this location, the flood elevations for the 10-, 50-, 100- and 500-year floods are 179.5, 176.3, 175.0 and 172.8, respectively. The stream bottom elevation is 140.8.

When obtaining elevation data from flood profile graphs, it is essential to read the profile graph at the exact location corresponding to the campus or building being evaluated. Accurate reading may require using other maps to determine the distance downstream of a campus or building from reference locations noted on a flood profile graph. Elevations should be read as accurately as possible, usually to the nearest 0.1 foot. Small elevation differences may significantly affect flood risk levels.

For areas subject to coastal storm surge flooding, FEMA Flood Insurance Studies include elevation data similar to that shown in Table 5.6 without the stream bottom elevation. However, there are no discharge data, because discharges apply only to rivers and streams.

These quantitative flood data, along with elevation data for a given building can be entered into the FEMA Benefit-Cost Analysis software for floods to generate rigorous evaluations of flood risk.

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Figure 5.1Flood Profile Graph

Chehalis River

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Flood data as discussed above can also be used semi-quantitatively to evaluate the level of flood risk. For example, a building where the first floor elevation is one foot below the first floor elevation would have extremely high flood risk – with flooding above the first floor expected, on average, more often than once every 10 years. On the other hand, a building where the first floor elevation is at the 100-year flood elevation would have relatively low flood risk, with flooding above the first floor only once every 100 years, on average. A building whose first floor elevation is well above the 500-year flood would have extremely low flood risk.

Caveat: Some FEMA Flood Insurance Studies are several decades old and current flood risk may not be accurately reflected in the FIS. In some cases, flood elevations may be up to several feet higher than shown in an old FIS because increased development upstream has greatly increased runoff, or channel conditions have changed because of sedimentation, growth of vegetation in the channel or other changes. A history of significantly more flood events than indicated by an old FIS is an indication that flood conditions may have changed substantially since the FIS was published.

5.4 Flood Risk Assessment: Building Level – Without Quantitative Flood Data

For campuses where the flood hazard data used in the previous section don’t exist – either from a FEMA FIS or from a local flood study, the quantitative approach in the previous section cannot be used. Absent the quantitative flood hazard data, flood risk assessments can be made by documenting historical floods and/or by analyses by flood engineers of other subject matter experts.

5.4.1 Documentation of Historical Flood Events

Documentation of historical flood events affecting a campus provides one measure of the level of flood risk. Available data for past flood events should be collected as far back in time as documentation exists. Longer historical records provide more accurate pictures of the level of flood risk than shorter historical records.

A history of several flood events is an indication of significant risk. Conversely, an absence of historical flood events, especially over a considerable time period of several decades, is an indication that the level of flood risk is probably low.

However, there are important caveats on these conclusions. For example, flood risk may be lower than previously if flood control measures, such as levees or flood control dams have been constructed. On the other hand, a campus may have little or no history of flooding, but may be subject to severe flooding in larger events than have occurred over the period of record of past events. Flood risk may also increase over time. For example, increasing development upstream may increase runoff or changes in channel conditions, such as sedimentation or growth of vegetation may raise flood levels.

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Ideally, documentation of past flood events should include the following information for each event:

Dates.

Description of the spatial extent and duration of flooding.

Documentation of high water flood levels in each affected building.

Description of damages and impacts.

Quantitative data, including:

o Economic loss data or estimates in dollars for damage, clean-up costs, and any other flood-related costs.

o Duration of closure of the campus and of individual buildings.

o Flood depths relative to the campus at-grade elevation and relative to the first floor elevation of affected buildings.

o Estimates of the return period for the flood event (if available).

In most cases, complete data for historical flood events simply doesn’t exist. In this case, collection of available data, even if limited, is still useful.

The example building-level report on the following page provides a template to document basic information about historical flood events affecting campuses. This template is also included in the Mitigation Toolkit Risk Assessment Package as an editable Excel file. Districts that have additional data about the consequences of past flood events are encouraged to tabulate and keep this data, which may be helpful for future grant applications.

The flood return periods and flood risk levels estimated only from the historical record of floods are less accurate than those determined from quantitative flood hazard data, but are useful in the absence of the data necessary for more quantitative estimates. The risk level categories are as shown below.

Table 5.7Building-Level Flood Risk Levels

Building-Level Flood Report: With Quantitative Flood Hazard Data

CAMPUS: Bart Simpson Elementary School

Building Name

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Table 5.8Example Template for Documentation of Historical Flood Events

CAMPUS:

Flood Return Period

(Years)1

Flood Risk

Level2

7.0 Very High YES Replacement NO

Basement (Yes/No) YES 2010 42 $654,321

Year Built 1952 2003 6 $22,000

Year Flood Records Start 1972 1996 15 $40,000

1981 2 $6,500

1980 -6 $3,000

1972 23 $110,000

21.0 High YES Elevation NO

Basement (Yes/No) NO 2010 12 $90,000

Year Built 1972 1972 4 $7,000

Year Flood Records Start 1972

8.7 Very High YES Replacement NO

Basement (Yes/No) NO 2010 36 $888,888

Year Built 1988 2003 0 $20,000

Year Flood Records Start 1988 1996 8 $123,456

N/A N/A TBD Minor Flood Proofing?

NO

Basement (Yes/No) NO 2010 12 $222,222

Year Built 2005Year Flood Records Start 2005

3 Common mitigation measures include: Elevation, Replacement, Flood Barriers, or Minor Flood Proofing.

West Wing of Classroom Building

East Wing of Classroom Building

Library

Notes:

Notes:

Gymnasium

Notes:

1 Prelilminary estimate based only on the number of flood events reported in the time period since flood records started. The value is calculated only if there are at least two flood events.2 Flood risk level based on the estimated return period for flooding.

Notes:

Building Name

Building-Level Flood Report: Flood History - Without Quantitative Flood Data

Roosevelt Elementary School: EXAMPLE

Qualitative Estimates

Mitigation Desired (Yes/No)

Mitigation Type3

Mitigation Completed (Yes/No)

Flood Year or Date

Flood Depth

Above or Below

First Floor (Inches)

Damage Amount ($)

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5.4.2 Estimating Flood Return Periods

Estimating flood return periods for historical flood events is not required for a district mitigation plan. However, a brief synopsis of methods to estimate flood return periods is included below because it may be important for mitigation grant applications.

Estimates of the return period of past historical floods are very useful in evaluating the level of risk, if such estimates are available. Return periods for past flood events can be estimated in several ways, which require technical expertise. These methods are briefly described below. If district staff lack sufficient technical understanding to make these estimates, consultations with flood engineers or other flood experts may be necessary.

FEMA Method

FEMA has developed a simple methodology to estimate the return period of historical flood events directly from the time-history of past damages. This FEMA method provides estimates of the return periods from several historical events, based only on three parameters: the year of past flood events, the dollar amount of damages, and the period of record (number of years for which flood data exists).

These estimates can be made using one of the modules in FEMA’s benefit-cost analysis software: the Damage-Frequency Assessment module. This software is available for download at no cost from the FEMA website: http://fema.gov

Quantitative Methods

Return periods for historical flooding events can be calculated if the flood source is a river or stream with quantitative flood hazard data such as discussed previously for flood analyses for campuses within FEMA-mapped floodplains. Quantitative estimates of flood return periods can sometimes be made with only partial data. For example, the location of a campus may not be included in a FEMA Flood Insurance Study or local flood study. However, the river or stream may have stream gages operated by the USGS or state flood agencies. Such gage datae would include the measured stream discharges for flood events. From these data it is possible to calculate the return periods for historical flood events on the river.

For floods where quantitative flood hazard data are not available, return periods can also be estimated from rainfall data. Such estimates are based on comparing rainfall totals for the flood event with historical rainfall data. Such analyses require technical expertise. For example, flood events on small watersheds may be governed by rainfall over a short time period of a few hours or less, while flood events on larger watersheds may be governed by rainfalls over a day, several days, or a week or more. Such estimates are best made by flood engineers or other flood experts.

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More Complex Flood Situations

More complex flood situations include campuses subject to flooding from:

localized storm water drainage problems,

sheet flow flooding on alluvial fans,

migrating rivers or streams,

failures of levees, dams, or reservoirs,

earthquake-related flooding, including subsidence, tsunamis, and seiches.

The historical flood method discussed previously in Section 5.4.1 is applicable to some of these situations, including localized storm water drainage flooding and sheet flow flooding on alluvial fans. However, more detailed analyses of these situations may require evaluations by flood engineers or other flood experts.

For localized stormwater drainage flooding, local public works departments or local flood agencies may be able to provide estimates of the capacity of the existing stormwater system and estimates of the level of flood risk for events larger than the capacity of the stormwater system.

Analyses of the other types of flooding most likely require technical support from flood engineers or other subject matter experts.

Analyses of migrating rivers or streams are based upon extrapolation of historical migration rates into the future.

Analyses of flood risk for campuses protected by levees or downstream of dams or reservoirs require sophisticated probabilistic analyses of the likelihood of failures of levees or dams and analyses of the consequences of failure. Most levees, dams, and reservoirs operating by large agencies are well designed and maintained. In most cases, the probability of failure is low, but not zero. Levees, dams, and reservoirs owned and operated by private owners or small public entities like drainage or irrigation districts are typically somewhat more likely to fail because of lower design standards, inspections, and maintenance.

Analyses of earthquake-related flooding may require consultation with engineers or other subject matter experts knowledgeable about earthquake, tsunami, and flood risk assessments.

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6.0 WILDLAND/URBAN INTERFACE FIRES

6.1 Wildland/Urban Interface Fire Hazard Assessment

Many K–12 facilities in Washington are at risk from wildland/urban interface fires. The defining characteristic of the wildland/urban interface area is that structures are built in, adjacent to, or near areas with essentially continuous vegetative fuel loads, including forests, brushlands, and grasslands. Wildland/urban interface fires are those where the fuel is a mix of both structures and vegetation. In contrast, wildland and structure fires are those where the fuel is predominantly vegetation or structures, respectively. In wildland/urban interface fire areas, fires may spread quickly from wildland areas to developed areas or vice-versa.

The level of fire hazard for wildland/urban interface fires depends on:

Vegetative fuel load,

Topography,

Climate,

Ignition sources and frequency of fire ignitions, and

Fire suppression resources (fire agency response time and resources of crews and apparatus, access, and water supplies).

High vegetative fuel loads, especially brush and trees, increase the level of wildland/urban fire hazard. Steep topography increases the level of fire hazard by exacerbating fire spread and impeding fire suppression efforts by making access more difficult.

The level of fire hazard in areas prone to wildland/urban interface fires is also higher in areas where the climate includes long periods of hot, dry weather, especially on days with high temperatures, low humidity, and high winds which greatly accelerate the spread of wildland fires and may make containment of a fire difficult or impossible.

Fire suppression resources are typically much lower in wildland/urban interface fire areas than in more highly developed areas. Fire stations are more widely spaced, with fewer resources of crews and apparatus and longer response times because of distance and/or limited access routes. Water resources for fire suppression are typically lower in these areas, which are often predominantly residential and may be served by pumped pressure zones with limited water storage or by individual wells which provide no water for fire suppression. These reduced fire suppression resources make it more likely that a small wildland fire or a single structure fire in an urban/wildland interface area will spread before it can be extinguished.

See Chapter Eleven: Wildland/Urban Interface Fires in the Washington State K–12 Facilities Hazard Mitigation Plan for further information about wildland/urban interface fire hazards and risks.

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Preliminary screening for wildland/urban interface fire hazards is based on two fire hazard mapping efforts:

Wildland/urban interface communities as designated by the Washington State Department of Natural Resources (DNR), and

USGS Landfire wildland burn return period mapping.

These maps, which are shown on the following pages, especially the Landfire map, provide a general picture of which parts of the state have the highest fire hazards. However, more accurate assessment of the level of wildland/urban fire hazard and risk levels for a given campus requires more detailed site-specific evaluation.

The DNR rankings and the USGS Landfire Return Periods are based on analysis of fire regime characteristics – such as vegetative fuel loads, topography, climate, and fire suppression resources – may indicate higher levels of fire risk than suggested by historical fire data.

There are important caveats for the interpretation of the DNR and USGS Landfire maps shown above that must be understood before making wildland/urban interface fire mitigation decisions for K–12 facilities within mapped fire hazard areas:

The DNR rankings of Wildland/Urban Interface Communities as having extreme, high, moderate, or low risk should be interpreted only as qualitative or semi-quantitative indicators of the relative level of risk. Facilities identified as being located in communities with “extreme” or “high” levels of risk may not have extreme or high risk as generally understood for mitigation planning purposes. For example, some of the extreme or high risk interface communities have long burn return periods per the USGS Landfire map.

The USGS Landfire Return Period values should also be interpreted as semi-quantitative indicators of the relative level of risk. The numerical estimates of the burn return period and the corresponding probabilities over a 50-year time period should not be interpreted literally.

The ICOS Pre-Disaster Mitigation database automatically opens the wildland/urban interface fire hazard and risk screen for campuses that meet either of two criteria:

DNR designated wildland/urban interface community with fire hazard rating of moderate or higher, or

USGS Landfire burn return period of 200 years or less.

Districts are encouraged to “opt-in” to the wildland/urban interface fire hazard and risk analysis in ICOS for campuses with any of the following characteristics:

High vegetative fuel load areas adjacent to, or near, a campus,

History of wildland/urban interface fires affecting, or near, a campus, or

Local fire agencies or others have expressed concerns about wildland/urban interface fires.

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Figure 6.1Wildland/Urban Interface Communities Identified by Washington Department of Natural Resources

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Figure 6.2United States Geological Survey Landfire Fire Return Period Map

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6.2 Wildland/Urban Interface Fire Hazard and Risk Assessment: Campus Level

Wildland/urban interface fire hazard levels are characterized in ICOS by the following parameters:

Table 6.1Wildland/Urban Interface Fire Hazard Levels

WUI Campus-Level Hazard Categories

Extreme N/A

High 50 years or lessWUI Table1

DNR Fire Hazard Ratings For WUI Communities

USGS Landifire Burn Return Periods

The combined wildland/urban interface fire hazard level is the higher of the two criteria above, excluding “extreme” because making this designation requires more detailed campus- or building-level data. Hazard levels are raised one level if one or more of the “opt-in” criteria listed previously apply to a campus.

The ICOS wildland-urban interface campus-level fire hazard and risk report is shown in Table 6.2 on the following page. The recommendation to consult with local fire agencies about the level of fire hazard and risk is made for campuses with a combined hazard level of moderate or higher. Local fire agencies can also provide guidance and recommendations regarding possible mitigation measures to reduce fire risk.

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Table 6.2Example ICOS Campus-Level Wildland/Urban Interface Fire Hazard and Risk Report

WUI Campus-Level Hazard Categories WUI: Functionality Criteria and Guidance

N/A Opt-In Text:

50 years or less

51 to 200 years

201 years or more

N/A (No data)

USGS Landfire Burn Return Periods

ICOS Auto-In Criteria GIS Data ONLY:

DNR Fire Hazard Rating moderate or higher OR Landfire return period less than 201 years

District are encouraged to opt-in to the WUI PDM screens, if there are any concerns about WUI fires for one or more campuses. The WUI hazard assessment levels based on available GIS data only are preliminary and more accurate hazard assessments additional information about local conditions.

Opting into the WUI PDM screens is strongly recommended if any of the following conditions apply to one or more campuses

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6.3 Wildland/Urban Interface Fire Risk Assessment: Building Level

More detailed risk assessments at the building-level or refinement of campus-level hazard and risk assessments are best done with technical support from local fire agencies or other subject matter experts.

The key elements of more detailed wildland/urban interface fire risk assessments include evaluations of:

Vegetative fuel loads adjacent to are near a campus or building,

Defensible space around buildings, and

Ignition resistant construction details.

The current version of ICOS does not track building or campus level details such as those noted above. Districts who undertake building-level risk assessments are encouraged to carefully document the results of studies and the progress in implementing suggested mitigation measures. An example template for tracking the results studies is shown on the following page.

For existing buildings, mitigation measures address deficiencies in the above three categories, including:

Implement fuel reduction activities for high fuel load areas adjacent to a campus.

Improve defensible space around buildings by eliminating or minimizing flammable vegetation and creating non-flammable ground cover such as gravel or pavement or low-flammability vegetation such as irrigated, mowed grass.

Implement fire-resistance construction details such as;

o Non-flammable roofs,

o Non-flammable building exteriors,

o Covering vent openings, overhangs and other areas where embers might be trapped with wire mesh,

o Replacing windows with tempered fire-resistant glass.

In some cases, implementing fire-resistant construction details can be done during normal maintenance activities, such as installing a non-flammable roof when an existing roof is being replaced.

An effective mitigation measure for wildland/urban interface fires is to locate new facilities outside areas with high wildland/urban interface risk whenever possible.

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Table 6.3Example Template for Documenting Building-Level Risk Assessments and the Progress in

Implementing Recommendations

Building-Level Risk Assessments: WUI

Examples where a building-level assessment may be prudent include situations such as:

Buildings with high value, importance or significant historical importance

For most K-12 facilities, the predominant concern is life safety. Thus, developing and practicing an effective evacuation plan for wildland/urban interface fires is a very high priority for any campus at risk from wildland/urban interface fires. Shelter in place is NOT a viable option for wildland/urban interface fires.

Building-level risk assessments are necessary only if a district is considering physical mitigation measures to reduce the potential for future fire damages to buildings and contents.

Buildings on campuses with moderate or high WUI fire hazards, especially for campuses with high fuel load areas adjacent to or near the campus or a history of WUI fires near the campus.

Fire risk assessments are most often done by professionals from fire agencies or fire consultants with similar expertise. However, a preliminary evaluation may be done by a non-fire professional with familiarity with buildings. Key elements include:

1) Defensible space: evaluation of landscaping and natural vegetation around a building and campus with regard to flammability and fuel load.

2) Evaluation of building characteristics to determine the extent to which building elements are fire resistant.

The determination of the levels of hazard and risk for wildland/urban interface fires is more difficult for many other natural hazards.

Therefore, it is not possible to establish specific definitive criteria to determine whether or not mitigation measures to reduce the potential for damage from wildland/urban interface fires are necessary for desired by a district. Local fire agencies can help districts evaluate the local data parameters thatn govern the level of fire risk, including:

Interpretation of the DNR designations of wildland/urban interface fire communities and USGS estimates of burn return periods,

History of nearby wildland/urban interface fires,

Evaluation of vegetative fuel loads, defensible space, and the extent of ignition resistant construction details in campus buildings,

Level of concern, including other factors such as water supplies and fire suppression resources.

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6.4 Evacuation Planning for Wildland/Urban Interface Fires

1. Do we need to develop a wildland/urban interface fire evacuation plan?

Developing and practicing wildland/urban interface fire evacuation plans is strongly recommended for any campus which has a possibility of wildland/urban interface fires. Shelter in place is never a viable option for wildland/urban interface fires.

The size, location, and direction of fire spread for future wildland/urban interface fires near campus at risk are all unknown. Therefore, evacuation planning should include designation of more than one route and more than one location for evacuation sites. For wildland/urban interface fires, evacuations typically require transport by vehicles, because evacuation distances are often several miles or more. Therefore, the evacuation planning should include protocols for rapid mobilization of buses.

2. How do we determine appropriate evacuation assembly areas?

Determining appropriate evacuation assembly areas is best conducted in cooperation with local government agencies and local fire agencies. Rapid mobilization and evacuation may be necessary if a wildland/urban interface fire ignites suddenly near a campus.

Determining appropriate evacuation assembly areas for wildland/urban interface fires is easier than for evacuations for tsunamis or lahars, where immediate proximity to a campus is critical. Given transport by vehicles, assembly areas for wildland/urban fires can be located a considerable distance from an at-risk community or campus.

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7.0 Landslides

7.1 Landslide Hazard Assessment

Many K–12 facilities in Washington may be subject to landslides. The term “landslide” refers to a variety of slope instabilities that result in the downward and outward movement of slope-forming materials including rocks, soils, and vegetation. Many types of landslides are differentiated based on the types of materials involved and the mode of movement.

Debris flows and mudslides (mudflows) are often differentiated from the other types of landslides, for which the sliding material is predominantly soil and/or rock. Debris flows and mudslides typically have high water content and may behave similarly to floods. However, debris flows may be much more destructive than floods because of their higher densities, high debris loads, and high velocities.

There are three main factors that determine susceptibility (potential) for landslides: 1) slope, 2) soil/rock characteristics, and 3) water content.

Although slope is an important parameter for landslide hazards, the level of hazard also depends strongly on the soil/rock conditions and on whether or not a given slope is water saturated. Loose soils or weak rock is much more prone to landslides than are dense soils or competent rock.

Locations with heavy rainfall resulting in saturated soils/rocks are more prone to landslides than otherwise similar locations with lower rainfall and less frequently saturated soils. Landslides may occur at any time, with or without rainfall. However, landslides are most common during, or after, periods of heavy rain.

Landslide risk is also correlated with seismic hazard level. Major earthquakes may trigger numerous landslides. Therefore, all other factors being equal, higher earthquake hazard locations have greater landslide risk than lower earthquake hazard locations.

Proximity is also important for steep slopes near deeply incised streams or cut and fill slopes. A building 10 feet from a deeply incised stream with an eroding bank is much more likely to experience damage from undermining than a building located much further from the bank. Buildings that are located a horizontal distance comparable to the vertical elevation of a steep slope may be at high risk for damage in landslide events.

See Chapter Twelve: Landslides in the Washington State K–12 Facilities Hazard Mitigation Plan for further information about landslide hazards and risks, including definitions of technical terms.

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The ICOS Pre-Disaster Mitigation database automatically opens the landslide hazard and risk screen for campuses that meet either of two criteria:

Campus within 500 feet of DNR mapped landslide, or

Maximum slope near the campus is >30%.

There are undoubtedly other campuses that have landslide hazards.

Districts are encouraged to “opt-in” to the landslide PDM screen if any of the following conditions apply to one or more campuses:

There are channels, gullies, or swales upslope of a campus. Debris flows can travel long distances downslope (miles in some cases, even on gentle slopes).

There are steep ground slopes or historical landsides upslope.

A campus has buildings less than 50 feet from a deeply incised stream or other steep slopes including cut and fill slopes.

A geologist, engineer, or geotechnical engineer has expressed concerns about possible landslide hazards.

7.2 Landslide Hazard and Risk Assessment: Campus Level

Evaluation of the level of hazard and risk is more difficult for landslides than for any of the other major hazards. The hazard and risk assessments for landslides outlined in this section should be interpreted as preliminary. More accurate assessments usually require detailed site-specific evaluations by engineers, geotechnical engineers, or geologists with extensive landslide experience.

Landslide hazard and risk assessment at the campus level is predominantly for the purpose of determining which campuses or buildings need more detailed evaluation by a geologist, engineer, or geotechnical engineer.

In ICOS, a preliminary estimate of the level of landslide hazard is based on the maximum slope determined from GIS elevation data in the vicinity of a campus. Slopes are calculated from the elevation difference of grid points, 90, 180, 270 and 360 meters from the campus in the north, south, east and west directions. The at-grade elevation of the campus is determined from the GIS elevation datum at the latitude and longitude for the campus. A refined, but still preliminary estimate of the landslide hazard and risk level is based on the slope data and the answers to four questions dealing with site-specific characteristics that affect landslide potential.

The ICOS criteria for landslide hazard and risk level ranking are shown in Table 7.1 on the following page.

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Table 7.1Landslide Hazard and Risk Criteria

Landslide Campus-Level Hazard Categories

Landslide Hazard Levels: Logic Combined Risk Level: Logic

SlopeLandslide Table 1

Preliminary Landslide

Hazard Level

Landslide Hazard and Risk Level1

SlopeRisk

1 >40% High High High

2 30% to 40% Moderate Moderate to High Moderate

Landslide Table 1

Preliminary Landslide

Hazard Level

Landslide Hazard and Risk Level1

Answer "Yes" for One or More Landslide Questions2

Answer "No" for All Landslide Questions3

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An example of the ICOS campus-level landslide hazard and risk report is shown below.

Table 7.2Example ICOS Campus-Level Landslide Hazard and Risk Report

Landslide Campus-Level Hazard Categories Landslide Functionality Criteria and Guidance

Landslide Hazard Levels: Logic Combined Risk Level: Logic

Opt-in Text

High High

Moderate to High Moderate

Low to Moderate Low

<19.5% Low Very Low

2. There are ground slumps or historical landslides upslope of a campus.

Andrew: the landslide risk levels are based n the Hazard Level and on whether on not there is one of more yes answer:

ICOS Auto-In Criteria GIS Data ONLY:

Slope 30% or Higher (High or Moderate hazard based on slope only) OR within 500 feet of DNR mapped landslide.

Math Cut-0ffs for rounding to whole percents

Answer "Yes" for One or More Landslide Questions2

Answer "No" for All Landslide Questions3

>39.5%Note: Landslide hazard and risk are the most difficult to evaluate based on GIS data only, because both depend VERY strongly on local conditions that cannot be evaluated accurately from GIS data alone.

>29.5%, <39.5%

>19.5%, <29.5%

Districts are encouraged to opt-in to the Landslide PDM screens if any of the following conditions apply to one or more campuses

Andrew: note correction of mathematical logic, Low bounds for Risk Yes to one or more of the 4 questions in the Purple columns in the Campus Report

No to all 4 questions: blank answers don't count as No.

1. There are channels, gullies or swales upslope of a campus. Debris flows can travel long distances (miles in some cases), even on gentle slopes.

3. A campus has buildings <50 feet from a deeply incised stream or other steep slopes, including cut and fill slopes.

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7.3 Landside Risk Assessment: Building Level

As noted previously, landslide hazard and risk assessment at the campus level is predominantly for the purpose of determining which campuses or buildings need more detailed evaluation by a geologist, engineer, or geotechnical engineer. That is, it is often not possible to reach firm conclusions about the level of landslide risk without more detailed investigations.

More quantitative evaluation of landslide hazards and risks at either the campus level or building level almost always requires evaluations by an experienced geologist, engineer, or geotechnical engineer. A geotechnical evaluation of landslide potential typically starts with field observations to evaluate evidence for historical landslides and to evaluate landslide potential. More detailed evaluations generally require borings to evaluate subsurface conditions, along with analysis and calculations to determine the stability of slopes.

An important caveat for landslide hazard assessments is that even with detailed site-specific evaluations by a geotechnical engineer there is often considerable uncertainty because interpretation of geotechnical data is part science and part art, with a heavy contribution from professional judgment and experience. That is, it is very difficult to make quantitative predictions of the likelihood or the size of future landslide events. In some cases, landslide hazard assessments by more than one geotechnical engineer may reach conflicting opinions.

These limitations and uncertainties notwithstanding, a detailed site-specific landslide hazard assessment does provide the best available information about the likelihood of future landslides. For example, such studies can provide enough information to determine that the landslide risk is higher at one location than another location and thus provide meaningful guidance for siting future development.

Geotechnical engineers can also provide inputs into possible mitigation measures to reduce the threat of landslides. Common measures include:

Dewatering slopes by adding subsurface drainage and other methods of slope stabilization.

Construction of retaining walls.

Construction of berms or other structures to block or deflect shallow landslides such as debris flows.

For sites subject to major, high volume landslides, there may be no feasible mitigation option except to abandon the site and replace the facilities at another non-landslide prone site.

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Landslide Technical Appendix: Slope

Slope is an important parameter in determining the level of landslide risk: the greater the slope, the higher the potential for landslides. Mathematically, slope can be expressed as an angle from 0o to 90o or as a ratio (or percent) of the rise over the run of a plane. For example, a slope that rises 100 feet in elevation (y) for 100 feet of horizontal distance (x) has an angle of 45o which can also be expressed as a slope of 1 or 100%.

Similarly, for example, a slope of 35% means an elevation rise of 35 feet over a horizontal difference of 100 feet. The percent slopes for various angles of slopes are illustrated in the following figure.

In general terms, the risk of landslides increases with slope: the steeper the slope the greater the likelihood of landslides. Sites with slopes greater than about 30% have significantly more chance of being at risk from landslides than sites with more gentle slopes. However, nearby slopes are a less important factor for debris flows because once initiated, debris flows may extend for considerable distances down shallow slopes. In some cases, debris flows may extend for several miles down a channel or swale.

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