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<pubnumber>OSWERHCHAP</pubnumber>
<title>Handbook of Chemical Hazard Analysis Procedures (Includes Computer Disk)</title>
<pages>520</pages>
<pubyear>1989</pubyear>
<provider>NEPIS</provider>
<access>online</access>
<operator>BO</operator>
<scandate>01/14/97</scandate>
<origin>PDF</origin>
<type>single page tiff</type>
<keyword>liquid materials vapor hazardous accident model hazard tank discharge container gas emergency planning one material spill pressure accidents rate temperature</keyword>

                          OSWERHCHAP
          HANDBOOK
               OF
CHEMICAL HAZARD  ANALYSIS
         PROCEDURES
        FEDERAL EMERGENCY MANAGEMENT AGENCY
                 f         i,

        U.S. DEPARTMENT OF TRANSPORTATION



        U.S. ENVIRONMENTAL PROTECTION AGENCY
 image: 








document has ceen reviewed by the Federal Emergency Management
    tjiegepartment of* ansportaFion, and  the  Environmental
                                                     ~~
        £ReQiiteabs_necessiJ[y re£ lect the views ............ and ........ polices
         .—                                         "
       -_.
- an
                                 of tradenames
                                         ^
                            o"recommenaation for use
 image: 








                                  FOREWORD

Introduction

The Federal Government has a long record of concern about hazardous materials and their
potential impact on people and the environment Over the years, several Federal agencies
have provided training, technical assistance and guidance to State and local governments and
industry  in  planning and response to emergencies involving hazardous materials. For
example, the Federal Emergency Management Agency (FEMA) published the Planning
Guide and Checklist for Hazardous Materials Contingency Plans (FEMA-10) in 1981 to
assist communities developing emergency response plans The Department of Transporta-
tion (DOT) has published several editions of the Emergency Response Guidebook to serve as
guidance for initial action to be taken by fire fighters, police, and emergency services
personnel at the scene of transportation incidents involving hazardous materials In 1985, the
Environmental  Protection  Agency (EPA)  published Chemical Emergency Preparedness
Program (CEPP) Interim Guidance to provide technical assistance for a voluntary program
focusing on airborne  toxic chemicals under EPA's National  Strategy  for  Toxic Air
Pollutants

Government-wide guidance on emergency planning for hazardous material was introduced in
1987 after the passage of Title in of the Superfund Amendments and Reauthonzation Act
(SARA)  with the publication of  the National Response  Team's Hazardous Materials
Emergency Planning Guide (NRT-1). This effort to coordinate Federal planning processes
concerning specific hazardous materials addressed by SARA  was followed with the joint
publication by EPA, FEMA and DOT of Technical Guidance for Hazards Analysis

Handbook of Chemical Hazards Analysis Procedures

This Handbook of Chemical Hazard Analysis Procedures has several objectives one of which
is to expand NRT-1 and the Technical Guidance on Hazards Analysis document by including
information for explosive, flammable, reactive and otherwise dangerous  chemicals  Al-
though NRT-1 was aimed at addressing planning for all types of hazardous materials, SARA
Title m required local planners to focus on a specific initial list of acutely toxic chemicals
(referred to as Extremely Hazardous Substances) due to their high inhalation toxicity when
airborne, and this was  the primary focus  of the supplemental guidance document By
introducing  additional  methodologies  on  how  to plan  for  these and other dangerous
chemicals, this handbook serves as a stepping stone from NRT-1 and the Technical Guidance
on Hazards Analysis to  a more comprehensive approach for emergency planning  If deemed
necessary and appropriate by the National Response Team after distribution and field use of
this handbook by emergency planning personnel, a further enhanced hazard analysis guide
may be prepared in the future.

Because  this handbook provides methods to investigate local hazards in greater detail than
permitted by earlier guidance, results of calculations using air dispersion models may differ
The  Federal Government is continuing to evaluate these types of models and others to
determine the degree of impact on calculations concerning the consequences of a chemical
release  For  these  reasons and  because this handbook requires use of the accompanying
software for full utilization, users should carefully assess accident scenarios selected for
evaluation to ensure that computational procedures are appropnate for the  chemical being
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studied. Difficulties encountered and suggestions or comments (both positive and negative)
should be submitted to DOT, FEMA, and/or the EPA. Be advised that workshops are being
planned by these Agencies during 1989 to address comments, gather input on the handbook
and the related software, and explain their functions  Similarly, DOT, FEMA and EPA are
interested in receiving information on problems and expenences associated with use of the
Technical Guidance on Hazards Analysis document and NRT-1.

Beyond providing additional methodologies for assessing the potential impacts of hazardous
material releases, this handbook also expands the three-step hazards analysis approach
(hazard identification, vulnerability analysis, and risk analysis) presented in NRT-1 and its
supplement by introducing a four-step approach involving hazard identification, consequence
analysis, probability  analysis,  and risk  analysis  In addition, it provides  a tutorial  on
hazardous chemicals, suggestions for applying hazard analysis results to writing and updating
an emergency plan,  and an expanded discussion  of issues  relating  to sheltenng-in-place
(in-place protection) and evacuation. Because additional projects are underway concern-
ing these and other topics described in Chapter 14 and Appendix C of the handbook,
sponsoring agencies are especially interested  in comments on these  sections. The
•workshops mentioned above will provide an opportunity  for discussion and comment.
General  comments  on the  handbook,   its  associated  computer program  named
ARCHIE, and earlier planning aids are highly encouraged and may also be submitted
in writing to:

                       Federal Emergency Management Agency
                           Technological Hazards Division
                                Federal Center Plaza
                                 500 C Street, S.W
                               Washington, DC 20472

                          U.S. Department of Transportation
                     Research and Special Programs Administration
                      Office of Hazardous Materials Transportation
                            DHM-50,400 7th Street, S.W.
                               Washington, DC 20590

                        U.S Environmental Protection Agency
                 Chemical Emergency Preparedness and Prevention Office
                              401M Street, S.W., OS-120
                               Washington, DC 20460

 Alternatively, input to these agencies may be transmitted via use of the Hazardous Materials
 Information Exchange (HMIX) computerized bulletin board system operated  and maintained
 by FEMA and the DOT. HMIX includes a Conference dedicated to ARCHIE where users
 may leave messages, questions or comments relating to the program or handbook, exchange
 viewpoints, and receive responses to inquiries  HMIX  may be accessed by modem  and
 commercial phone line af

                                   (312) 972-3275
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An HMDC users manual and technical assistance can be obtained by calling-

                           1-800-PLAN-FOR Nationwide

                                       or

                             1-800-367-9592 in Illinois
If you are unable to access HMIX to submit comments or questions relating specifically to
the computer program, please send them in writing to*

                      ARCHIE Support (DHM-51/Room 8104)
                     Office of Hazardous Materials Transportation
                    Research and Special Programs Administration
                         US  Department of Transportation
                               400 7th Street, SW
                             Washington, D.C. 20590
Additional copies of this handbook maybe obtained by writing to

                       Federal Emergency Management Agency
                                Publications Office
                                500 C Street, SW.
                             Washington, D.C. 20472
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                               TABLE OF CONTENTS
1.0  Introduction                                                             1-1
     1.1   Background                                                         1-1
     1 2   Related Planning Guides and Documents                                1-2

2.0  Key Properties of Chemical Substances                                    2-1
     21   States of Matter                                                     2-1
     2.2   Definitions of Temperature and Heat                                   2-2
     23   Definition of Pressure                                                2-3
     2 4   Vapor Pressures of Liquids and Solids                                  2-4
     2 5   Boiling Points as a Function of Pressure                                 2-9
     2 6   Definitions of Specific Gravity and Density                              2-10
     27   Solubility in Water                                                   2-13
     2.8   Molecular Weights of Chemical Substances                              2-14

3.0  Actions Upon Release to the Environment                                  3-1
     31   Physical State Prior to Release                                        3-1
     3.2   Material States During and Initially After Release                        3-1
     3 3   Discharges Onto Land                                                3-5
     3 4   Discharges Into Water                                                3-7
     3 5   Fundamental Concepts Pertaining to Discharges into Air                  3-11
     3.6   Variables that Influence Atmospheric Vapor Dispersion                   3-17

4.0  Fire Hazards of Chemical Substances                                      4-1
     4.1   Introduction                                                        4-1
     4 2   Measures of Flammability Potential                                    4-1
     43   Measures of Flammability Effects                                      4-6
     44   Types of Fires                                                       4-6
     4 5   Products of Combustion                                              4-11

5.0  Explosion Hazards of Chemical Substances                                 5-1
     51   Definitions                                                         5-1
     5 2   Factors that Influence Explosion Potential                               5-2
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                           TABLE OF CONTENTS (Cont.)
                                                                           Page
   53   Measures of Explosion Effects                                       5-3
   5.4   Types of Explosions                                                5-7

6.0  Toxicity Hazards of Chemical Substances                                6-1
   6.1   Introduction                                                       6-1
   6.2   Routes of Entry                                                    6-1
   6.3   Types of Toxic Effects                                              6-3
   6.4   Acute Vs Chronic Hazards                                          6-6
   6.5   Importance of Exposure Level and Duration                           6-7
   6.6   Toxicity Vs. Toxic Hazard                                          6-8
   6.7   Recognized Exposure Limits for Airborne Contaminants                 6-9
   6.8   Advantages and Disadvantages of Various Limits                       6-16
   6.9   Relationship of Recommendations to EPA LOCs                       6-18
   6.10  Consideration of Mixtures of Harmful Gases and Vapors                 6-19
   6.11  Exposure Limits for Contaminated Water                             6-21
   6 12  Understanding Toxicological Data in the Literature                     6-22

7.0   Reactivity Hazards of Chemical Substances                             7-1
   7.1   Introduction                                                       7-1
   7.2   Exothermic Reactions                                              7-2
   7.3   Neutralization Reactions                                            7-4
   7.4   Corrosivity Hazards                                                7-5
   7.5   Other Hazardous Results or Products of Reactions                      7-6
   7.6   Sources of Chemical Reactivity Data                                 7-6

8.0   Hazardous Material Classification Systems                              8-1
   8.1   Introduction                                                       8-1
   8.2   U.S Department of Transportation Classifications                      8-1
   8 3   U.S. Environmental Protection Agency Classifications                  8-5
   8.4   National Fire Protection Association Hazard Rankings                  8-8
   8 5   International Maritime Organization Classifications                     8-8
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                          TABLE OF CONTENTS (Cont.)
                                                                           Page
9.0  Overview of the Hazard Analysis Process                                9-1
   9.1   Introduction                                                       9-1
   92   Step 1: Hazard Identification                                         9-3
   93   Step 2 Probability Analysis                                         9-4
   94   Step 3: Consequence Analysis                                       9-5
   95   Step 4- Risk Analysis                                               9-5
   96   Step 5 Use of Hazard Analysis Results in Emergency Planning           9-6
10.0  Hazard Identification Guidelines                                      10-1
   101   Introduction                                                      10-1
   10.2   Reason for the Desired Information                                  10-1
   10 3   Suggested Scope of the Effort                                       10-2
   10.4   Nature of Desired Information                                       10-4
   105   Available Methodologies to Compile Desired Information               10-12
   106   Sources of Additional Hazard Identification Guidance                   10-20
   10.7   Formulation of Credible Accident Scenarios for
         Planning Purposes                                                 10-20
   10 8   Organization of the Data                                           10-21
11.0  Probability Analysis Procedures                                      11-1
   11.1   Introduction                                                      11-1
   112   General Seventy of Accidents Considered                            11-3
   113   Bulk Transportation of Hazardous Matenals by Highway                11-3
   114   Bulk Transportation of Hazardous Matenals by Rail                    11-13
   115   Bulk Transportation of Hazardous Matenals by
         Marine Vessels                                                   11-20
   116   Transportation of Hazardous Matenals by Pipeline                     11-26
   117   Handling and Transfer of Hazardous Matenals at
         Fixed Facilities                                                   11-31
   118   Transportation of Packaged Hazardous Materials                      11-40
   119   Transportation of Hazardous Matenals by Air                         11-42
   11  10  Summary                                                        11-43
   1111  References                                                       11-43
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                          TABLE OF CONTENTS (Cont.)
                                                                           Page
12.0  Consequence Analysis Procedures                                      12-1
     12.1   Introduction to ARCHIE                                         12-1
     12.2   Installation of the ARCHIE Computer Program                      12-6
     12.3   General Notes on Responding to Questions from the Program          12-7
     12.4   Initialization of Program Configuration Settings                      12-9
     12 5   Display of the Program Title Screen                                12-10
     12.6   Introduction to Options on the Main Task Selection Menu             12-10
     12.7   Introduction to the Hazard Assessment Model Selection Menu         12-14
     12.8   Discharge Menu Option A- Non-Pressurized Rectangular
            Tank of Liquid                                                 12-20
     12.9   Discharge Menu Option B: Non-Pressurized Spherical Tank
            of Liquid                                                      12-23
     12.10  Discharge Menu Option C: Non-Pressurized Vertical
            Cylinder of Liquid                                               12-26
     12.11  Discharge Menu Option D: Non-Pressurized Horizontal
            Cylinder of Liquid                                               12-29
     12.12  Discharge Menu Option E- Pressurized Liquid when Discharge
            Location is 4 Inches or Less from the Tank Surface                   12-32
     12.13  Discharge Menu Option F  Pressurized Liquid when Discharge
            Location is More Than 4 Inches from the Tank Surface                12-36
     12 14  Discharge Menu Option Gf Pressurized Gas Release from
            any Container                                                   12-40
     12.15  Discharge Menu Option H Release from a Pressurized
            Liquid Pipeline                                                  12-44
     12 16  Discharge Menu Option I*  Release from a Pressurized
            Gas Pipeline                                                    12-49
     12.17  Hazard Model Menu Option B Pool Area Estimation Methods         12-52
     12.18  Hazard Model Menu Option C Pool Evaporation Rate
             and Duration Estimates                                           12-56
     12.19  Hazard Model Menu Option D  Toxic Vapor Dispersion Model         12-59
     1220  Hazard Model Menu Option E. Liquid Pool Fire Model               12-63
     12.21  Hazard Model Menu Option F Flame Jet Model                      12-64
     1222   Hazard Model Menu Option G  Fireball Thermal
             Radiation Model                                                12-67
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                          TABLE OF CONTENTS (Cont.)

     12.23  Hazard Model Menu Option H  Vapor Cloud or Plume
            Fire Model                                                     12-68
     12.24  Hazard Model Menu Option I: Unconfined Vapor Cloud
            Explosion Model                                                12-72
     1225  Hazard Model Menu Option J. Tank Overpressurization
            Explosion Model                                                12-75
     1226  Hazard Model Menu Option K. Condensed-Phase
            Explosion Model                                                12-78
     12.27  Remaining Options on the Hazard Assessment Model
            Selection Menu                                                  12-80
     12 28  Use of the Vapor Pressure Input Assistance Subprogram               12-81
     12 29  Use of the Tank and Container Contents
            Characterization Subprogram                                      12-84
     1230  Other Computer Programs                                         12-85
13.0  Formulation of a Planning Basis                                        13-1
     131   Introduction                                                    13-1
     13 2   Definition of Annual Accident Probability Categories                  13-1
     13 3   Definition of Accident Seventy Categones                          13-3
     13 4   Application of Screening Guidelines                                13-5
     135   Motivation for Continued Planning                                 13-7
14.0  Use of Hazard Analysis Results In Emergency Planning                   14-1
     141   Introduction                                                    14-1
     14 2   Organization of the Chapter                                       14-2
     14.3   Additional Sources of Planning Guidance and Information             14-2

Appendix A:   A Tutorial on Fundamental Mathematical Skills                     A-1
Appendix B    Technical Basis for Consequence Analysis Procedures               B-l
Appendix C    Overview of "Shelter-m-Place" Concepts                          C-l
Appendix D    Chemical Compatibility Chart                                    D-l
Appendix E    Guide to Installation of the ARCHIE Computer Program             E-l
Appendix F    Basis of Probability Analysis Procedures                           F-l
                                         V
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                                  LIST OF TABLES
Table                                                                        Page
2.1    Vapor Pressures as a Function of Temperature                             2-6
2 2    Atomic Weights of Common Elements                                    2-15
3.1    Typical States of Materials in Storage or Transportation
       Containers                                                            3-2
3 2    Expected Behavior of Spills Into Water                                   3-8
3.3    Atmospheric Stability Class Selection Table                               3-19
4.1    Example Flammability Characteristics                                    4-5
4.2    Thermal Radiation Burn Injury Catena                                   4-7
5.1    Explosion Overpressure Damage Estimates                                5-5
6.1    Effects of Oxygen Depletion                                            6-5
6.2    Four Stages of Asphyxiation                                            6-5
6 3    Summary of Emergency Exposure Guidance Levels from the
       National Research Council                                              6-14
8.1    NFPA Hazard Rankings                                                8-9
8 2    Basic IMO Material Classes and Divisions                                8-11
10.1   Spill Source Characterization Factors                                     10-5
10 2   Miscellaneous Potential Spill Sources                                    10-11
11.1    Chemical Accidents Requiring Evacuations                               11-4
11.2   Estimated Number of Transportation Accidents                            11-4
11.3    Major Hazardous Materials Accidents                                    11-5
11.4    Suggested Figures for Truck Transportation                               11-9
11.5    Suggested Figures for Rail Transportation                                11-17
11.6    Suggested Figures for Marine Transportation                              11-23
11.7    Suggested Figures for Pipeline Transportation                             11-29
11.8    Suggested Figures for Fixed Facilities                                    11-36
12.1    Special Index to Chapter                                               12-
12.2    Main Task Selection Menu                                             12-
12.3    System Description and Use Instructions                                  12-
12.4    Hazard Assessment Model Selection Menu                               12-
 12.5    Discharge Model Selection Menu                                       12-
                                          VI
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                              LIST OF TABLES (Cont.)
Table                                                                       Page
12 6   Assistance Display for Liquid Specific Heat                               12-39
12.7   Assistance Display for Vapor/Gas Specific Heat Ratio                      12-39
12 8   Atmospheric Stability Class Selection Table                               12-54
12 9   Assistance Display for Explosion Yield Factor                            12-74
12 10  Example Output from Explosion Models                                 12-76
13 1   Annual Individual Mortality Rates for Natural and Accidental
       Causes of Death                                                      13-8
14 1   Index to Planning Items                                                14-6
                                 LIST OF FIGURES

Figure                                                                       Page
2 1    Evaporation and Vapor-Liquid Equilibrium Phenomena                      2-7
3.1    Initial Stages of Vapor Cloud or Puff Dispersion                             3-13
3 2    Cross-Section of Puff Concentration Vs. Time                              3-14
3.3    Maximum Puff Concentration Vs. Time or Distance                          3-14
3 4    Puff or Cloud Isopleths at Increasing Tunes                                 3-15
3 5    Isopleths in a Continuous Plume                                          3-15
3 6    Behavior of Lighter Than Air Puffs or Clouds                               3-21
3 7    Some Effects of Elevated Emissions                                       3-23
3 8    Vapor Dispersion Hazard Zone Boundaries                                 3-27
8.1    US DOT Placards                                                     8-6
12 1   Overview of Acute Spill Hazards on Land                                  12-16
12 2   Model Selection Charts                                                  12-17
13.1   Accident Frequency/Seventy Screening Matrix                             13-6
                                          vii
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                             1.0  INTRODUCTION
1.1 BACKGROUND

     The fact that hazardous materials pose a threat to public safety and the environment is
of vital concern to industry and all levels of government, particularly in the aftermath of the
tragedy in Bhophal, India, that took over 2000 lives and injured tens of thousands of others in
the course of a few hours. Although the safety record of the oil and gas and chemical
manufacturing and transportation industries in the United States has been excellent in recent
years, and there has not been a similar catastrophic accident or incident with major loss of
life in the United States  in several decades, there is nevertheless a clear need for constant
vigilance on the part of government agencies and those responsible for the movement and
handling of hazardous materials to minimize the possibility of significant discharges to the
external  environment. Similarly,  there is a  clear and possibly even more urgent need to
ensure that both government and industry are prepared to respond quickly, efficiently, and
effectively in the event of an accident to reduce or prevent adverse impacts on public safety
and the environment  Tune is critical in the first moments of an accident. A  mismanaged
response due to a lack of preplanning can contribute to the causation of fatalities and injuries
as well as an increase in damage to property and the environment

     The primary purpose of this  handbook and its associated computer program is to
provide emergency planning personnel with the resources necessary to undertake comprehen-
sive evaluations of potentially hazardous facilities and activities  within their respective
jurisdictions and thereby formulate a basis for their planning efforts  Chapters 2 through 8 of
the handbook discuss fundamental definitions and concepts relating to hazardous material
properties and associated threats  to public  safety.  Chapter 9 provides an overview  of the
overall hazard analysis process required to identify, characterize, and  evaluate the  subject
threats  Chapter 10 follows with specific guidance relating to hazard identification while
Chapter  11  provides  assistance in  evaluating  the likelihood that any given  accident or
incident will actually occur in the foreseeable future  Chapter 12 describes and discusses the
Automated Resource for Chemical  Hazard Incident Evaluation (ARCHIE)  computer
program and how  it may be used to conduct consequence analysis for postulated accident
scenarios Chapter 13  next guides  the user through a simplified nsk analysis procedure
designed to provide a planning basis, while Chapter 14 provides guidance on how results of
the overall hazard analysis process may be utilized in development of  a comprehensive
emergency response plan

     Several appendices to the handbook provide additional guidance and details Appendix
A is a tutorial on fundamental  mathematical skills Appendix B presents an overview of the
technical basis for consequence analysis procedures, while Appendix C provides an overview
of "Shelter-m-Place" concepts. Appendix D follows with the presentation of a chemical
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compatibility chart for potentially reactive materials. Appendix E is a guide to installation of
the ARCHIE computer program, while Appendix F ends the handbook with the basis for
accident/Incident probability analysis procedures

12 RELATED PLANNING GUIDES AND DOCUMENTS

     Multi-Agency Publications of the Federal Government

     The National Response Team (NRT) is comprised of representatives of 14 federal
agencies having major responsibilities for issues involving the environment, transportation,
and public health and  safety. It is the primary  body in the United States charged  with
responsibility for planning, preparedness, and response actions related to spills or discharges
of oil and hazardous materials into the environment.

     The NRT published the Hazardous Materials Emergency Planning Guide in March
1987 as document NRT-1. This guide provides a fairly detailed overview of the efforts
required for:

     •    Selecting and organizing an emergency planning team
     •    Defining the tasks of the planning team
     •    Developing an emergency plan and individual plan elements
     •    Appraising, testing, and maintaining the plan

     The guide focuses on the needs and requirements of public authorities in local and state
governments but also contains useful information for industrial planning personnel in terms
of the basic elements of the planning process. Additionally, it provides insights into those
issues  of concern to public authorities and the importance of cooperation and coordination of
emergency planning  activities between the public and private sectors. Copies of the guide
are available by writing:

                    Hazardous Materials Emergency Planning Guide
                    OS-120
                    401 M Street, S.W.
                    Washington, D.C. 20460

     Subsequent to completion and distribution of NRT-1, the U.S. Environmental Protec-
tion Agency (EPA), in conjunction with the Federal Emergency Management  Agency
(FEMA) and the U.S. Department  of Transportation (DOT), published Technical Guidance
for Hazards Analysis  — Emergency Planning for Extremely Hazardous Substances to
fulfill obligations mandated by the  Superfund Amendments and Reauthonzation Act (SARA)
of 1986. Focusing primarily on the hazards associated with a specific list of highly  toxic
substances deemed to pose acute inhalation  hazards when discharged into the atmosphere,
                                        1-2
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the guide provides simplified guidance for hazard identification, vulnerability analysis, and
risk  analysis of facilities  subject to reporting requirements  under Title in  of SARA.
Additionally, the document contains a simplified screening procedure for ranking the threats
due to designated Extremely Hazardous Substances (EHS) in a community  Copies may be
obtained by writing the same address given above for NRT-1.

     Publications of the Federal Emergency Management Agency

     The  Federal Emergency  Management Agency (FEMA) publishes  the  Guide for
Development of State and Local Emergency Operations Plans (CPG 1-8) and the Guide for
Review  of State and Local Emergency Operations Plans (CPG  1-8A), which  provide
information to emergency management personnel and state and local government officials
about FEMA's concept of planning under the Integrated Emergency Management System
(IEMS). This system emphasizes integration of planning for all types of hazards that pose a
threat to a community and provides  extensive guidance in the coordination, development,
review, validation, and revision of emergency operations plans.

     The  concepts  if not the  specific  details of FEMA's guidance are applicable to
individual communities and chemical facilities in that many such sites may be subject to a
variety of natural and technological hazards. Under a wide variety of circumstances, a single
emergency plan that provides "umbrella coverage"  for a locality can ensure increased
efficiency and effectiveness of a planning effort by  reducing duplication of  common
activities.

      FEMA, in conjunction with DOT and the EPA, has also published a wide variety of
emergency planning guidance documents relating to emergencies involving nuclear power
plants,  the  transportation  of radioactive materials,  and natural disasters A sample of
planning aids that address hazardous materials include:

      •    Hazardous Materials Contingency Planning Course (student manuals)

      •    Disaster Planning Guidelines for Fire Chiefs

      •    Disaster Operations: A Handbook for Local Governments

      •     Objectives for Local Emergency Management

      Publications of the Federal Emergency Management Agency relating to a wide variety
of threats to public health and safety can be obtained by writing:
                                        1-3
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                  Federal Emergency Management Agency
                  Publications Office
                  500 C Street, S.W,
                  Washington, D C. 20472

     Publications of the U.S. Department of Transportation

     The U.S  Department of Transportation (DOT)  has sponsored a large  number of
research studies and demonstration projects related to planning for transportation emergen-
cies involving hazardous materials  over the years  Appendix E of NRT-1 contains a fairly
comprehensive list of resulting reports  A representative sample of current and past available
titles includes:

     •    Community Teamwork: Working Together to Promote Hazardous Mate-
          rials Transportation Safety -A Guide for Local Officials

     •    A Community Model for Handling Hazardous Materials Transportation
          Emergencies

     •    Risk Assessment Users Manual for Small Communities and Rural Areas

     •    Manual for Small  Towns  and Rural Areas to  Develop a Hazardous
          Materials Emergency Plan; with an Example Application of the Method-
          ology  in Developing a Generalized Emergency Plan for Riley County,
          Kansas

     •    Community Model for Handling Hazardous Material Transportation
          Emergencies: Executive Summaries

     •    Hazardous Materials Demonstration Project Report: Puget Sound Region

     •    Hazardous Materials Hazard Analysis: Portland, Oregon

     •    Hazardous Materials Management System: A Guide for Local Emergen-
          cy Managers

     •    Lessons Learned: A Report on  the  Lessons Learned from  State and
          Local Experiences  in Accident Prevention and Response Planning for
          Hazardous Materials Transportation

     The Community Teamwork document may be obtained by writing to*
                                       1-4
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                  Office of Hazardous Materials Transportation
                  Attention: DHM-50
                  Research and Special Programs Administration
                  Department of Transportation
                  400 7th Street, S.W
                  Washington, D C 20590

     Information on the availability of the Hazardous Materials Management System Guide
and other documents developed for the Portland, Oregon area can be obtained by writing.

                   Multmomah County Emergency Management
                   12240 NE Ghzan
                   Portland, Oregon 97230

Most of the other publications and documents of a similar nature  are available from the
National Technical Information Service, 5285 Port Royal Road, Springfield, Virginia 22161
(telephone 703-487-4650).

     Publications of the U.S. Environmental Protection Agency

     The EPA has published a series of documents to assist emergency planning personnel
Available titles include

     •    Introduction to Exercises in Chemical Emergency Preparedness  Pro-
          grams

     •    A Guide to Planning and Conducting Table-Top Exercises

          A Guide to Planning and Conducting Field Simulation Exercises

     •    Report of a Conference on Risk Communication and Environmental
          Management

     •    Identifying Environmental Computer Systems for Planning Purposes

     •    Chemicals in Your Community

These documents may be obtained by writing

                    Environmental Protection Agency
                    OS-120
                    401 M Street, S W.
                    Washington, DC 20460
                                       1-5
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     Publications of the Chemical Manufacturers Association

     Even before SARA required the assignment of individual facility emergency coordina-
tors  to Local Emergency Planning Committees (LEPC's), the Chemical  Manufacturers
Association (CMA) established a Community Awareness and Emergency Response (CAER)
program to encourage local chemical plant managers to take the initiative in cooperating with
local communities in the development of integrated emergency plans for response  to
hazardous material incidents. The NRT guidance document cited above notes that knowl-
edgeable chemical  industry representatives can be  especially helpful during the planning
process and advises community planners to seek out local CMA/CAER program participants
More specifically,  the document points out that many chemical plant officials are both
willing and able to share equipment and personnel during emergency response operations

     The CMA publishes three documents that could prove considerably useful during the
overall planning process, including.

     • Community Awareness and Emergency Response Program Handbook

     • Site Emergency Response Planning

     • Community Emergency Response Exercise Program

     These publications  are available at nominal cost from the CMA Information on
specific items can be obtained by calling (202) 887-1100 or writing.

                   Publications Fulfillment
                   Chemical Manufacturers Association
                   2501M Street, N.W.
                   Washington, D.C. 20037

     Publications oftheAIChE Center for Chemical Process Safety

     Established under  the auspices of the American Institute of Chemical  Engineers
(AIChE), this being the primary professional society of chemical engineers in the United
States, the Center for Chemical Process Safety has undertaken an ambitious program  to
promote  and ensure safety at chemical plants.  Initial efforts have involved the development
and  publication of a senes of safety guideline documents. The first four titles below are
complete and currently available to the public. The latter tides are expected to be published
during 1989 or shortly thereafter.
                                        1-6
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    •     Guidelines for Hazard Evaluation Procedures

          Guidelines for Safe Storage  and Handling of High  Toxic Hazard
          Materials

    •     Guidelines for Use of Vapor Cloud Dispersion Models

    •     Guidelines for Vapor Release Mitigation

    •     Guidelines for Chemical Process Quantitative Risk Assessment

    •     Guidelines for Technical Management of Chemical Process Safety

    •     Guidelines for Obtaining Process Equipment Reliability Data

    •     Guidelines for Human Reliability in Process Safety

    •     Guidelines for Process Control Safety

    •     Guidelines for Processing and Handling Reactive Chemicals

    Information on these and other AIChE publications is available from4

                   AIChE Publication Sales Department
                   345 East 47 Street
                   New York, NY 10017

     Other Pertinent Publications

     Besides the  above fairly recent and generalized planning guides published by the
federal government or industry trade associations, there are several other sources of general
information and data available that may be helpful during the overall emergency planning
process. Selected publications are listed and described in Chapter 14. Publications devoted
to specific topics of possible interest to readers are referenced at appropriate locations
throughout the chapters and appendices that follow.
                                        1-7
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         2.0 KEY PROPERTIES OF CHEMICAL SUBSTANCES
         SOLID
LIQUID
GAS
2.1 STATES OF MATTER

     Most materials can exist in more than one physical state, a common example being
ordinary water.  It is well known that liquid water will freeze and become a solid at 32
degrees Fahrenheit (°F) at normal atmospheric pressure The temperature of 32°F is known
as the freezing point for this substance Alternatively, this temperature can be referred to as
its melting point For water, both the freezing point and melting point are exactly the same
and well-defined  This is true for most other substances, but there are exceptions to this
general rule

     At 212°F, liquid water begins to boil at normal atmospheric pressure as it begins a
transition or phase change from a liquid state to a vapor or gas. The specific temperature at
which a liquid boils under a given set of environmental conditions is known as its boiling
point temperature or boiling point for short  If the boiling takes place at normal atmospheric
pressure, the more appropriate and accurate phrase to use is normal boiling point or boiling
point at one atmosphere. The importance of qualifying the term boiling point with the words
"normal" and "one atmosphere" will be discussed a bit later For now, it is simply adequate
to note that a great many materials in the environment have their own unique freezing/melt-
ing and normal boiling points which can be radically different than those of water For
example,  the petroleum product  known  as butane, the flammable  substance in most
disposable lighters, has a normal boiling point of 31°F and will boil and rapidly vaporize if
spilled as a liquid on a block of ice having a temperature of 32°F A temperature of -216°F
 image: 








would be required to  solidify  or freeze the butane to a solid, yet even  this very low
temperature would be insufficient to prevent boiling of such substances as liquid hydrogen,
helium, nitrogen, and several others.

     Not all substances, incidentally, can exist in all three states of matter in the natural
environment. Some solids undergo a piocess called sublimation upon heating whereby the
solid state directly transforms to a gaseous state without first becoming a liquid A good
example is solid carbon dioxide, also known as "dry ice "  Carbon dioxide can only become a
liquid in confinement under special conditions of storage.

2.2 DEFINITIONS OF TEMPERATURE AND HEAT

     The discussion so  far has  demonstrated that  the  temperature of  a  substance can
influence its  form and properties. There is a  great deal more to be said on the subject,
however, so there is value in formal definition of important terms before proceeding We
start with the concept  of temperature and the flow of heat and energy from one body to
another.

     The dictionary defines the temperature of a substance as its  "degree of hotness or
coldness measured on a definite scale " The key word here is scale. In the United States, the
scale with which we are most familiar is the Fahrenheit scale, and most of us are aware that
most of the world uses  the Celsius or Centigrade scale, this being a part of the metric system
Both of these temperature measurement systems are considered relative scales because key
numbers are essentially the freezing point and boiling point of water at normal atmospheric
pressure. These numbers are 32°F and 212°F respectively on the Fahrenheit scale and 0°C
and 100°C on the Celsius scale In order to convert from one scale  to another, one of two
common equations is used, these being:

                         degrees F  - (1.8 x degrees C) + 32

                            degrees C = (degrees F - 32)/1.8

It is also useful to know that a one degree change on  the Celsius scale is equal to a 1 8°
change on the Fahrenheit scale. Thus, a temperature rise of 18° on  the Fahrenheit scale is
equivalent to a rise of 10° on the Celsius scale

      Besides these two scales,  there are two others that are commonly used in the scientific
community and which are defined as absolute  scales  in the sense that zero degrees refers to
an absolute lack  of heat in the object being measured  Absolute zero is about 460° below
zero on the Fahrenheit scale and about 273° below zero on the Celsius scale
                                         2-2
 image: 








     One of these absolute scales is known as the Rankine scale and is related to the
Fahrenheit scale such that a temperature in degrees Rankine  equals the temperature in
degrees F plus 460. Thus, 100°F equals 560°R, where the R denotes use of the Rankine
scale.

     The second absolute scale is the Kelvin scale and is in very common use by today's
engineers and scientists on a worldwide basis  It is related to the Celsius scale such that a
temperature in degrees Kelvin equals the temperature expressed in degrees  Celsius plus
273.15. Thus, 100°C equals 373.15°K, where the K denotes use of the Kelvin scale

     As noted before, all temperature scales are used to measure and represent the degree of
hotness or coldness of a substance.  In actuality, however, this is a somewhat misleading
statement, because heat can be technically defined as  "energy whose interchange between a
system and its surroundings takes place only by virtue of a temperature difference "  Thus,
heat is a form of energy that increases the temperature of substances and  which can flow
from a warm body to one which is cooler Whenever a  cold body is placed in a warm
environment, there will be a temperature difference, and heat will flow from the wanner
environment to the colder body. Alternatively, if the body is warmer than its surroundings, it
will lose heat Thus, when  a cold liquid is  spilled into a warm environment,  it will
experience a heat gain. Depending on the temperatures involved, this temperature may be
sufficient to cause the liquid to boil (remember the  boiling butane on the block of ice'')
Alternatively, if the liquid was hot to begin with, it may lose sufficient heat to solidify or
freeze   The importance of these concepts will become apparent as the discussion turns to the
topic of how a chemical may behave when released into varying environmental conditions

2.3 DEFINITION OF PRESSURE

     The next concept to be discussed  is that of pressure, which can be defined as the
amount of force brought to bear on some unit area of an object. When we press our thumb
down on a table, we are applying force on the table. The harder we press, the greater the
force, and the greater the pressure we apply to the table surface.

     As we sit here, the air in the sky above us presses down on our bodies and all objects
around us  with the pressure of approximately 14.7 pounds per square inch of surface area,
commonly abbreviated as  14 7 psi. This pressure, essentially the average air pressure at sea
level, is also known as one standard atmosphere. When one speaks of a  pressure of two
atmospheres as might be found in a tank, pipeline, or other container of a hazardous material,
it generally means that 29 4 psi is present, or two times 14 7 psi
                                        2-3
 image: 








     The word generally is emphasized because pressure also has absolute and relative
scales of measurement  The 14 7 psi of atmospheric pressure  at sea level is an absolute
measurement and is more properly presented in units of pounds per square inch - absolute, or
psia for short. Zero psia in this case refers to a complete absence of pressure such as one
might find in the perfect vacuum  of outer space  The most common  relative scale of
measurement, this being one only used in the United States for the most part, presents
numerical values in terms of gauge pressure, where a reading of zero matches an absolute
pressure of one standard atmosphere.  In this system, an absolute pressure of 15.7 psia would
be expressed as 1 0 pound per square inch - gauge, or 1 0 psig for short Two atmospheres of
absolute pressure would be equivalent to one atmosphere gauge pressure

   There are several other systems of pressure  measurement that are of an absolute nature
The most common include:

     •     Millimeters of mercury (mm Hg) - in which 760 mm Hg are equivalent to
           one standard atmosphere

     •     Newtons per square meter (N/m2) - in which 101,325 N/m2 are equal to one
           standard atmosphere

     •     Pascals (Pa) - which are another name for N/m2, such that 101,325 Pa are
           equal to one standard atmosphere.

     •     Bars - in which 1 01325 bars are equal to one standard atmosphere

     •     Inches of water (in H^O) - in which  407 6 in Hp are equal to one standard
           atmosphere

     •     Inches of mercury (in Hg) - in which 29 9 in Hg are equal to one standard
           atmosphere

     The latter two sets of units are not in as common use in the scientific community as the
first four but it is well to know of their existence Those of you who pay attention to weather
forecasts will recognize that meteorologists have traditionally reported current atmospheric
pressures in units of inches of mercury

2.4 VAPOR PRESSURES OF LIQUIDS AND SOLIDS

      Liquids have a tendency to evaporate even at temperatures well below their boiling
points. The reason for this stems from the observation that molecules of a liquid (these being
 the smallest parts of the liquid which retain the identity of the substance at the atomic level)
 have a tendency to break away from the surface of a liquid and enter the vapor state The
                                         2-4
 image: 








speed of this process, in the absence of wind effects, is a function of temperature such that a
warm hquid will evaporate more quickly than the same liquid at a cooler temperature  Note,
however,  that different liquids at the same temperature  will evaporate at different rates
depending on their particular properties

     One primary measure of a liquid's tendency to vaponze is known as its vapor pressure,
this being the pressure exerted by its vapors on the walls of a container which is partially full
of the liquid and free of any other vapor or gas. Higher temperatures cause increases in the
vapor pressure Lower temperatures  cause a decrease, and there is a direct relationship
between the temperature of any given  substance and its vapor pressure Table 2 1 provides a
list of vapor pressures for variety of common substances  showing how they differ with
respect to temperature Note that the pressures are  expressed in units of millimeters of
mercury (mm Hg), this being the most common set  of units used for  this purpose  m the
United States, particularly for substances at temperatures below then- normal boiling points
Note also that there are wide variations in the temperatures associated  with specific vapor
pressures and that even iron  will have a measurable vapor pressures if heated to very high
temperatures.

     The substances listed in Table 2.1,  and all others, exert their specific vapor pressures
whether or not they are enclosed in a sealed container  When m a container, they reach a
state of equilibrium such that some molecules go from the liquid state to the vapor state
while others pass back from the vapor to the hquid at the same rate, and no material is lost to
the outside environment. When in the open, molecules entering the vapor state mix with air
and  move further and further away from the liquid surface with time. As they are replaced
above the surface with new molecules evaporating from the liquid, the volume of liquid is
depleted.  Eventually, all the  liquid evaporates (be it in minutes, hours,  days, or years) and
the surface becomes dry.

     Figure 2 1  illustrates these various phenomena.  In  the top  diagram, we  observe
molecules evaporating from a pool of hquid and entering the atmosphere  Note that any type
of wind or breeze blowing  across the surface of the hquid would help the individual
molecules in escaping and moving away from the liquid and thereby increase the overall rate
of evaporation. This rate is indeed a partial function of air velocity over the surface such that
higher velocities usually produce higher evaporation rates

     In the middle diagram of Figure 2.1, the liquid is confined within  a container and the
escaping vapor molecules are trapped Eventually, as illustrated m the  bottom diagram, a
state of equilibrium is attained.
                                         2-5
 image: 








                                             TABLE 2.1
                            VAPOR PRESSURES AS A FUNCTION OF TEMPERATURE


Chemical
Benzene
Butane
Ethyl alcohol
Ethylene glycol
Iron
Methyl alcohol
Propane
Water
Vapor Pressure (mm Hg)
1
10
40
100
400
760
Temperature (°F)
-382
-1507
-24.3
127.4
3249
-47.2
-2000
-18*
11.3
-1080
279
1978
3702
28
-163.3
523
45.7
-74.4
662
248.0
4035
41.0
-1343
93.3
79.0
-47.6
948
2872
4280
702
-1113
122.3
1411
27
1463
3533
4721
1218
-681
1765
176.2
31.1
173.1
3871
4955
1485
-43.8
2120
t-o
       *Approximate
 image: 








                             FIGURE 2.1
EVAPORATION AND VAPOR-LIQUID EQUILIBRIUM PHENOMENA
                     EVAPORATION  MOLECULES ESCAPING FROM
                                THE LIQUID TO BECOME VAPOR

\ x
f \
Vtf
\r========-)

                      EVAPORATION MOLECULES CONFINED
                    VAPOR-LIQUID EQUILIBRIUM
                           MOLECULES ESCAPE FROM AND
                           RETURN TO THE LIQUID
                                 2-7
 image: 








     It should be realized that there is a direct relationship between the vapor pressure of an
evaporating substance and the maximum concentration that its vapor or gas may achieve
when mixed with air in the open environment  This is true because higher vapor pressures
above the surface of a substance require that more molecules of the substance be physically
present Thus, if the vapor  pressure of the  substance  is known, one can compute the
approximate maximum airborne contaminant (i e, chemical) concentration it may attain.
Such concentrations are most commonly expressed in units of percent in air by volume, parts
per million parts of air (ppm) by volume, parts per billion parts of air (ppb) by volume, or
milligrams of chemical per  cubic meter (mg/m3) of air. The equations needed for these
computations are'

     ^          .     vapor pressure (mm Hg)  ,._
     % concentration =  F  F   ,„ v	— x 100
                               7oU

                        vapor pressure (mm Hg) ^, ^ nnn
     ppm concentration=—-—-—=77:	x 1,000,000

     ppb concentration = concentration in ppmxlOOO

     me              (ppm concentration) x (molecular weight)
     -concentrate	0 08205 x (273 15+* C)	

     A restriction to remember in using these equations is that the concentration of a gas or
 vapor cannot under any circumstances exceed 100% by volume or its equivalent of 1,000,000
 ppm regardless of the answer obtained An example should help the understanding of these
 relationships.

     From Table  2.1, we find that benzene has  a  vapor pressure of 100 mm Hg  at a
 temperature of 79 0°F. From earlier discussion, we  also know that 79.0°F is equal to 26 1°C
 Therefore:

      „          .    100x100  *~~M.    ,
      % concentration = —=77:— = 13 16% by volume
                         100x1,000,000  .„„„     .    ,
      ppm concentration=	—	= 131,600ppm by volume
                             760
      Computation of the equivalent concentration in mg/m3 requires not only knowledge of
 the temperature in degrees Celsius but of the molecular weight (m w) of the material, this
 being an atomic measure of the weight of the substance. This weight is  often (but  not
 always) listed in material safety data sheets (MSDS) and product bulletins that present data
                                        2-8
 image: 








on the physical and chemical properties of chemicals Section 2.8 of this chapter demon-
strates how to compute the molecular weight of a substance given knowledge of its chemical
formula  The molecular weight of benzene is 78. 1, so
2.5 BOILING POINTS AS A FUNCTION OF PRESSURE

     It was reported earlier that a pressure of 760 mm Hg is equal to  14 7 psia or one
standard atmosphere From Table 2 1 we see that water has a vapor pressure of 760 mm Hg
at a temperature of 212°F, a temperature we recognize as its normal boiling point. What is
significant about this observation is that it holds true for all liquids  Any liquid will begin to
boil at the temperature at which its vapor pressure equals the pressure being exerted by the
environment onto the surface of the liquid  In practical terms, this means that:

     •     Boiling points of materials are a function of pressure.

     •     Liquids in sealed  containers (with  an exception discussed below) will
           remain as liquids when heated above their normal boiling points although
           then: vapor pressures  may far exceed one standard atmosphere pressure
           within the container.

     •     If heating continues and the pressure is not adequately relieved by a safety
           device (such as a pressure relief valve), the pressure and temperature within
           the  tank may eventually nse to the point that some part or all of the
           container may burst or rupture, possibly in a violent fashion This may also
           occur if the capacity of the safety device is inadequate to  prevent an
           excessive buildup of pressure

     •     Materials exposed  to environmental pressures below one standard atmo-
           sphere will boil at  temperatures below then- normal boiling points. Thus,
           water will boil at a  temperature below 212°F when heated on top of a high
           mountain.  Water released into a vacuum at any temperature will almost
           instantly vaporize.

     It is well to realize that many substances with normal boiling points far below normal
ambient temperatures are shipped or  stored in commerce as liquids This is most often
achieved by placing the liquid  within a strong tank  and permitting it to remain in the liquid
state under its own vapor pressure at equilibrium conditions Examples of the most common
of these materials considered hazardous include  liquid  anhydrous  ammonia,  ethylene,
chlorine, ethylene oxide, vinyl chloride, and liquefied petroleum gas (LPG) or propane Such
                                        2-9
 image: 








substances, frequently referred to as compressed liquefied gases, are particularly hazardous
because: 1) leaks may result in rapid venting of gas to the atmosphere; 2) leaks may result
in discharge of liquids that rapidly flash vaporize and/or boil upon exiting their containers;
and 3) the flammable, toxic,  or otherwise hazardous  gases and vapors evolved may travel
considerable  distances  downwind  before  becoming diluted with air  below hazardous
concentrations.

     Less frequent in transportation but more common at storage and processing sites are
bulk quantities of substances  such as chlorine, anhydrous ammonia, or liquefied natural gas
(LNG) which have been liquefied by cooling to low temperatures via the use of refrigeration
systems. Although  the vapor pressure of gases liquefied by refrigeration may  be close to
ambient pressures within storage vessels, spills into the warmer external environment will
again result in boiling and the evolution of large quantities of potentially hazardous gases and
vapors

      The exception to the "rule" that liquids in sealed containers will remain as liquids when
heated above their normal boiling points involves the fact that this is true only so long as the
temperature of the liquid is below what is referred to as its critical temperature  The critical
temperature of a substance is  the temperature above which it cannot remain in the liquid state
regardless of any increase in  pressure. Thus, substances heated above then: critical tempera-
 tures are neither liquid nor gaseous, but rather, in a state somewhere in between.  Picture
 them as very thick vapors.

 2.6 DEFINITIONS OF SPECIFIC GRAVITY AND DENSITY

      Boiling points,  vapor pressures, and melting or freezing points can tell us much  about
 how a  material will initially  behave when released into the  environment, but  more
 information is needed to better define actions and behavior  This section discusses relative
 and absolute measures of the weights of materials, while the next discusses the degree to
 which one substance can mix with another

      Every solid or liquid in the environment occupies a specific volume of space and has a
 certain weight  Thus, we may express the weight density of a substance as its weight divided
 by its volume. It is well known, for example, that pure water weighs about 62 4 pounds per
 cubic foot (lb/ft3) of volume, which is equivalent to 1 0 gram per cubic centimeter (g/cm3) or
 1,000 kilograms per  cubic meter (kg/m3) in the metric system We also have observed that
 different substances  have different weights  for the same  volume. One cubic foot of oil
 weighs about 50 pounds.  A cubic foot of steel weighs about 487 pounds
                                         2-10
 image: 








      An alternative method of expressing the weight density of a solid or liquid involves use
 of a quantity known as the liquid or solid specific gravity Quite simply, this quantity is
 determined by dividing the density of a substance by the density of water. Since 62 4 divided
 by 62 4 has a value of 1.0, water has a specific gravity of 1 0 and serves as the reference
 point for all materials. The liquid specific gravity of a typical oil is 50 divided by 62.4,
 giving a value of 0 80  The solid specific gravity of steel is 487 divided by 62 4 and equals
 780

      As is the case with vapor pressures, both the density and  specific gravity of solids and
 liquids vary with temperature. Heat causes most (but not all) materials to expand in volume
 while cold causes them to shrink.  Since the volume changes while the weight remains the
 same, the density of a substance generally decreases with heating and increases with cooling.
 This explains why most sources of information on the density of chemicals will provide the
 temperature at which the value was measured   In the case of specific gravities, they may list
 both the temperatures of the water and chemical substance used to determine the specific
 gravity.

     Knowledge of liquid or solid specific gravities is most important when it is desired to
 determine how a substance will behave in the presence of water. For example, the fact that
 the specific gravity of a typical oil is 0 80 supports the observation that most oils are lighter
 than water and have an initial tendency to float The fact that steel's specific gravity is about
 7.80 explains why a block of steel will immediately sink in water.

     Discussion of vapor or gas specific gravities and densities is more complicated because
 these properties  are affected by changes in pressure as well as temperature. However, since
 we are primarily interested in chemical substances that escape into the natural environment,
 since the natural environment has a  nominal  atmospheric pressure of one atmosphere, and
 since any gas or vapor entenng the atmosphere will quickly adjust its volume to achieve a
 total pressure of one atmosphere, it is sufficient for the purposes of this text to only consider
 specific gravities and densities of gases or vapors at atmospheric pressure.

     The discussion begins with the observation that air has a density of 0 0763 lb/ft3 (about
 1.22 kg/m3) at a temperature of 60°F and a pressure of one atmosphere As in the case of
 other substances, higher temperatures cause a decrease in density  and lower temperatures
 cause an increase.  Similarly, there  is  a quantity known as the vapor specific gravity or vapor
 density which is a ratio of the density of a pure gas or vapor to the density of air. Found in
many data sources, this specific  gravity or  density  (the former term being used rather
interchangeably with the latter) is based on the assumption that  an- has a value of 1 0. Thus,
vapors or gases with vapor specific gravities less that 1 0 are presumably lighter than air in
the natural environment while those with values greater than 1.0  are presumably heavier.
                                          2-11
 image: 








     The word presumably is emphasized because the values for vapor specific gravities
found in all too many data sources are frequently misinterpreted by their users, particularly
and specifically in the case of substances below a temperature that permits them to exist as a
pure vapor or gas at a pressure of one atmosphere. This can lead to incorrect conclusions
about the actions of a vapor or gas upon its release to the environment.

     The problem has arisen because many sources compute the vapor density  of any
substance by a shortcut method involving division of the molecular weight of the substance
by the molecular weight of air, the latter being approximately 28 9 (as the weighted average
for the mixture of gases that comprise air)  Thus, since benzene has a molecular weight of
78.1, these sources will report  a vapor specific gravity  or density value of approximately
2.70, which to many people suggests that the vapors of benzene in the natural environment
are always 2.70 times heavier than  air, which is an absolutely untrue  assumption The
misinterpretation results in the belief that benzene vapors will always hug the ground over
considerable distances as they  spread  from the site  of  a release and may somehow
accumulate and persist in pits, hollows, basements, or other low lying areas

      It  was earlier explained  that benzene has a vapor pressure of 100  mm Hg at a
temperature  of  79 0°F and that this vapor pressure translates  into a  maximum  vapor
concentration directly over the  liquid surface  of  approximately 13 16%  by  volume  It
follows  that  benzene cannot exist  as  a pure vapor at this temperature in the natural
environment and that it is incorrect to assume that it is a pure vapor when estimating its
vapor density relative to air (which is what is being done when a molecular weight ratio is
 computed). Rather,  it is necessary to compare the benzene-air mixture density  with  the
 density of pure air to determine whether the vapors generated by the release will be heavier
 or lighter than  air. This  is accomplished  in  an approximate fashion via the following
 procedure:

       Step 1-   Compute the approximate density pv of pure chemical vapor in lb/ft3 at
                temperature T (in °F).

                      1 3691 x molecular weight
                 pV=        (T+460)

       Step 2:   Compute the approximate density pa of air in lb/ft3 at ambient
                temperature T (in °F).

                       39.566
                 pa=-
                      (T+460)

       Step 3:   Compute the relative vapor density of the chemical-air mixture
                                            2-12
 image: 








           r> i *.         j       {Cxpv} + {(100-C)xpa}
           Relative vapor density=	*-—*•——	-—*—i
                     v        y           lOOxpa

           Where C =  saturated concentration of the chemical vapor in air in percent
                       by volume.

      Benzene has a molecular weight of 78.1 and a maximum vapor concentration (more
precisely referred to as its saturated vapor concentration) of 13 16% in air at 79°F. Use of
these values in the above equation,  together with  the assumption of an air temperature of
79°F, provides a true relative vapor density  value of 1.22  What this means is that the
benzene-air mixture directly above a pool of  benzene at the specified temperature is only
1 22 times heavier than air and not the 2.7 times suggested by the vapor density frequently
reported in the literature for this substance  Since  this mixture will very quickly mix with
additional air as it drifts away from the pool, it will rapidly approach the density of pure air
and behave as if there were little or  no difference  in its density. In scientific terms, it will
behave as a neutrally buoyant vapor-air mixture.

     If the relative vapor density of a substance under prevailing discharge conditions
exceeds 1.5 (as a general rule of thumb),  then vapors or gases may  indeed behave as
heavier-than-air (or  negatively buoyant) mixtures for some distance from  the source of
discharge.  Conversely, a relative vapor density significantly less than one suggests that a
vapor-air mixture may be lighter than air (or positively buoyant).

     In determining or deciding whether any particular gas or vapor will be negatively,
neutrally, or positively buoyant in air, it is also often necessary to consider the circumstances
under which the substance may be  released to the atmosphere For example, in situations in
which a compressed liquefied gas  is discharged from a container, particularly when in the
liquid state, the resulting vapor cloud or plume may include a considerable amount of fine
liquid droplets. Although the gas or vapor mixture with air may normally be positively or
neutrally buoyant, the presence of  these relatively heavy droplets (also referred to  as
aerosols) may cause the cloud or plume to behave initially in a negatively buoyant fashion.

2.7 SOLUBILITY IN WATER

     All of us have observed that sugar and salt dissolve in water and seem to disappear, that
our favorite alcoholic beverage can be mixed freely with water-based mixers, and that the
"fizz" in containers of soda pop, tonic, or beer is due to carbon dioxide gas that has been
dissolved in the liquid In each case, the solid, liquid, or gas that has dissolved in water is
said to be soluble in water.
                                         2-13
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     An important concept to understand is that different materials have different degrees of
solubility. At one extreme, there are liquids which are soluble in all proportions with water
and which are also said to be miscible  This means that any amount of the substance can be
added to water and at no point in the process will the substance form a separate layer or
phase.  At the other extreme, there are substances which do not dissolve in water whatsoever
and which are considered to be insoluble or immiscible.  A somewhat extreme example of
the latter case involves stone pebbles in a glass of water. No matter how hard the pebbles are
shaken or stirred, they will not dissolve or form a solution with water, this being the term
used for a mixture of two liquid substances which are mutually soluble.

     In between the above extremes are substances which are partially  soluble in water. For
example, there is only a certain amount of ordinary table salt that can be dissolved in water
before any new salt added to the solution simply sinks to  the bottom and is unable to
dissolve. In the case of table salt,  35.7 grams of salt will dissolve in 100 grams of water at a
temperature of 32°F and this will nse to about 39.8 grams (there are about 454 grams in a
pound) at a temperature near 212°F. And yes, that means that solubility is also a function of
temperature.  Generally speaking,  hot liquids can dissolve more of a partially soluble liquid
or solid than cold liquids.  Alternatively, because of effects involving vapor pressures and
their increase with temperature, cold liquids can generally dissolve more gases and vapors
than hot liquids. Increases in pressure may also increase the solubility of gases in liquids.

2.8 MOLECULAR WEIGHTS OF CHEMICAL SUBSTANCES

     There are approximately 89  natural elements in the world that in  various combinations
make up all  matter that surrounds us.  In addition, a number of man-made elements have
been produced under laboratory conditions involving nuclear reactions and many more have
been theorized but never observed. The atoms of all elements have been assigned individual
atomic weights relative to oxygen by scientists. These  are listed in Table 2.2 for most
common elements likely to be encountered in normal commerce and use.

      Combinations of various atoms called molecules make up  the smallest part of any
 chemical compound that retains the  specific properties of the substance and have specific
 molecular weights that can be computed from the number of atoms of each element present
 in the compound, as determined by examination of the chemical formula of the substance.
 Such formulae are always found in material safety data sheets for pure substances and many
 other sources of chemical data. Examples include.

      •    Hp         for water
      •    CO         for carbon dioxide
               2
            NaCl        for sodium chlonde
                                         2-14
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                        TABLE 2.2
        ATOMIC WEIGHTS OF SOME COMMON ELEMENTS

Table gives chemical symbol, name, and atomic weight of each element.
Ag
Al
As
B
Ba
Be
Bi
Br
C
Ca
Cd
Ce
Cl
Co
Or
Cs
Silver
Aluminum
Arsenic
Boron
Barium
Beryllium
Bismuch
Bromine
Carbon
Calcium
Cadmium
Cerium
Chlorine
Cobalt
Chromium
Cesium
10787
2698
7492
1081
13734
901
208.98
7991
1201
4008
11240
14012
3545
5893
5200
13291
Cu
F
Fe
Ga
H
Hg
I
Li
K
Mg
Mn
Mo
N
Na
Ni
O
Copper
Fluorine
Iron
Gallium
Hydrogen
Mercury
Iodine
Lithium
Potassium
Magnesium
Manganese
Molybdenum
Nitrogen
Sodium
Nickel
Oxygen
6354
1900
5585
6972
100
20059
12690
694
3910
24.31
5494
9594
1401
22.99
5871
1600
P
Pb
Rb
S
Sb
Se
Si
Sn
Sr
Ta
Ti
U
V
W
Zn
Zr
Phosphorus
Lead
Rubidium
Sulfur
Antimony
Selenium
Silicon
Tin
Strontium
Tantalum
Titanium
Uranium
Vanadium
Tungsten
Zinc
Zirconium
3097
207.19
85.47
3206
12175
78.96
28.09
11869
87.62
18095
47.90
23803
5094
183.85
65.37
91.22
 image: 








          KOH       for potassium hydroxide
                      for methyl hydrazine
                      for benzene
     As noted earlier, knowledge of molecular weights is required for computation of vapor
concentrations in air in some cases, and indeed, knowledge of this weight is mandatory for a
wide variety of calculations involving hazardous materials. Since molecular weights are not
always found on materials safety data sheets, however, it is  worthwhile to understand how
they may be computed using the information provided in Table 2.2. This is best accom-
plished by an example.

     From  the  list  above we see that  methyl hydrazine has a  chemical formula of
CHjNHNHj (which may also be shown as CH6N2 in some references). What this means is
that each molecule of this chemical consists of:

     •     One (1) atom of carbon represented by the symbol "C"
     •     Two (2) atoms of nitrogen represented by the symbol "N", and
     •     Six (6) atoms of hydrogen represented by the symbol "H".

     From Table 2.2 we find that the atomic weights of carbon, nitrogen, and hydrogen are
respectively 12.01, 14.01, and 1.00. Thus, we  can compute the molecular weight of this
substance by multiplying the atomic weight of each of the three elements by the number of
its atoms in the molecule, and then summing the results  For methyl hydrazine, the result is:

     Molecular weight =  (1 x 12.01) + (2 x 14.01) + (6 x 1 00) = 46.03
                                        2-16
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        3.0 ACTIONS UPON RELEASE TO THE ENVIRONMENT
3.1 PHYSICAL STATE PRIOR TO RELEASE

     The first step  in  determining how a  substance will behave  upon release  to the
environment requires knowledge of the physical state of the material within its storage or
transportation  container  This in turn requires knowledge  of the relationship between the
temperature of the material, its boiling point, and its melting point  The possibilities are:

     •     The temperature of the material in its container is less than its melting
           point, in which case the material is a solid in its container. A good example
           would be dry table salt in a large drum

     •     The temperature is greater than the melting point of the material but less
           than its normal boiling point, in which case the material is a liquid and the
           container contents are approximately at normal atmospheric pressure. An
           example is water in a tank at temperatures above freezing. Such liquids,
           however, could also  consist of substances which are normally solids but
           which have been melted and maintained at relatively high temperatures to
           keep them liquid. They could also be substances which are normally gases
           in the natural environment but which have been liquefied via refrigeration.

     •     The temperature is greater than the boding point of the material, in which
           case the material is a compressed gas (gas under high pressure in a cylinder
           or  other container) or a liquefied compressed gas (a  substance that is
           normally a gas at normal ambient conditions but which has been turned into
           a liquid by subjecting it to and maintaining it at high pressures, thus raising
           its actual boiling point).

     Table 3 1 summarizes the various possibilities in greater detail  The table requires a bit
of study for complete understanding, but the effort is extremely worthwhile

32 MATERIAL STATES DURING AND INITIALLY AFTER RELEASE

     Once there is an understanding of the state of a hazardous material within a storage or
transportation  container, it is next necessary to consider how the substance will behave
initially when discharged into an environment of normal ambient temperatures and pressures
There are 10 scenarios to consider based on the last column of Table 3 1, all of which assume
that the spill or discharge does not take place during a fire or other abnormal event which
would change internal and/or external temperatures
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                                                           TABLE 3-1
                    TYPICAL STATES OF MATERIALS IN STORAGE OR TRANSPORTATION CONTAINERS
             Normal Melting or Boiling Points
      Container Conditions
     State of Material (Scenario #)
        Melting point less than ambient T
T less than melting point and less
than ambient T
Cold solid (1)
        Melting point greater than ambient T
T near ambient T
Solid near ambient T (2)
        Boiling point greater than ambient T
T greater than melting point, greater
than ambient T, but less than boiling
point
Warm or hot liquid
(molten solid) (3)
        Melting point less than ambient T
T greater than melting point but less
than ambient T and boiling point
Cold liquid (4,5)
N>
        Boiling point greater than ambient T
T near ambient T

T greater than ambient T but less
than boiling point

T greater than boiling point and
greater than ambient T
Liquid at ambient T (6)

Hot liquid (7)
                                                                                   Hot or warm compressed gas or vapor over
                                                                                   hot liquid (8)                	
         Boiling point less than ambient T
T near ambient T
                                                  T greater than boiling point and
                                                  greater than ambient T
Compressed gas or compressed liquefied
gas under pressure at ambient T (9,10)
                                  Hot or warm compressed gas or com-
                                  pressed liquefied gas under pressure at T
                                  greater than ambient (9,10)    	
        Notes: T = temperature within container, ambient T = temperature outdoors
 image: 








     Scenario #1: Cold or Refrigerated Solids

     Some materials that are normally liquids or gases at ordinary temperatures or pressures
are handled  as  solids  at temperatures below their  melting  points  and below ambient
temperatures to make them easier or safer to transport or use.  When exposed to a warmer
environment, they will melt to become liquids, or if they are substances that pass directly
from a solid to gaseous  phase  (ie., substances  that "sublime") they will vaporize. For
example, ice spilled on the ground in summer will melt to become liquid water. Solid carbon
dioxide (dry ice) will "sublime" as it warms to become carbon dioxide gas.

     Scenario #2: Normally Solid Materials

     Materials that are solids at ordinary ambient temperatures  and which are transported or
otherwise handled  at such  temperatures will remain as  solids upon release  from their
containers. Dry table salt and sugar are good examples.

     Scenario #3: Molten Solids

     Some substances which are normally solids are melted to become liquids, since liquids
are sometimes easier to handle. Indeed, for transportation, a solid may be melted and poured
into a  tank vehicle of some kind where  it will slowly cool with time,  and even possibly
resolidify. When it reaches  its destination, it will be pumped out if still a liquid, or first
remelted (possibly using heating coils  inside the tank) and then pumped  out.  Such
substances will either be discharged as solids or as liquids  that may solidify if exposed to
cooler  ambient temperatures during an accidental spill or discharge situation.

     Scenarios #4 and #5: Cold or Refrigerated Liquids

     Liquids that are handled  at cold temperatures and/or which are refrigerated may have
normal boiling points that  are either  below or  above ambient temperatures.  The  latter
substances will simply warm up when released to the environment (Scenario #4), much as
cold water will heat in  the  sun. Those with below ambient boiling points (Scenario #5),
which  are typically cooled  to reduce their vapor pressures  in equipment or  for use in
air-conditioning or refrigeration systems,  will warm to their normal boiling point tempera-
tures upon release and begin to boil Due to thermodynamic cooling effects associated with
liquid  evaporation or boiling,  these liquids will remain at their normal  boiling points. If
spilled onto a surface that is  a good heat insulator, the boiling may eventually slow down or
stop, but the quiescent pool that remains will continue to rapidly evaporate  This evaporation
process will maintain the remaining liquid near its boiling point as it picks up heat from its
surroundings
                                        3-3
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     Scenario #6: Normally Liquid Materials

     Materials that are normally liquids at ordinary temperatures and pressures and which
are transported or otherwise handled at such temperatures will remain as liquids upon release
to the environment. Good examples would be gasoline or fuel oils pouring from a hole in a
storage or transportation container.

     Scenarios #7 and #8: Hot Liquids

     There are many cases where a substance that is a liquid at normal ambient temperatures
and pressure might be heated for one purpose or another.  Such liquids, if below then- boiling
point (Scenario #7),  will cool upon release to the environment  and remain as liquids.
However, if they were heated above their boiling points (Scenario #8), then any space above
the liquid in a container will contain gas or vapor at a pressure in excess of one atmosphere.
What happens in the event of an accident or incident in this latter case will depend on what
part of the container is damaged.

      •     If the container is punctured or otherwise damaged in the space above the
           liquid, vapors of the liquid will blow out (i e, vent) from the resulting hole
           into the atmosphere and will continue to do so until the liquid cools below
           its boiling point  For example, picture steam blowing out the stack of an
           old-tome steam locomotive.

      •     If the container is punctured below its liquid surface, the liquid will pour
           out of the hole while some amount of its "flashes" to vapor upon release.
           The part that remains as liquid will boil briefly and then slowly cool to
           ambient temperature while evaporating. As an example, picture a leak on
           the  face of an automobile radiator with steam, a hot water mist, and hot
           water exiting the leak area.

     Scenario #P: Compressed Liquefied Gases

     Regardless of whether these liquids are at ambient or higher temperatures, they will
typically be in pressure vessels designed to maintain and withstand substantial pressures As
in the prior case, what happens during an accident or incident will depend on what part of the
container is damaged.

     •     If the container is punctured or otherwise damaged in the space above the
           liquid, the gas will typically vent at high velocity  from the resulting hole
           into the atmosphere, possibly creating some amount of liquid droplets
           during the process  The  velocity is likely to drop  with time as boiling
           within the  tank cools the mass of liquid (the tank  surface may  actually
                                         3-4
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          become  quite cold and  even frost over due to  thermodynamic cooling
          effects),  but such venting of gas may continue for considerable penods of
          time (possibly until no more liquid is left in the tank)

     •    If the container is punctured  below its liquid surface, the liquid may
          literally jet from the hole (remember the very high pressure apt to be in the
          vapor space over the  liquid) and potentially large amounts may flash into
          gas or vapor.  Indeed, depending on the material and the temperatures and
          pressures involved, the tank may blow out a large mass of vapor mixed
          with small liquid droplets (an aerosol)  to the extent that no liquid reaches
          the surface beneath the tank If liquid does reach the surface, it will have a
          tendency to form a boiling or rapidly evaporating pool.

     Scenario #10: Compressed Gases

     Gases which are compressed to high pressures in  a container or gas cylinder but which
have not been liquefied will vent from any opening in the container at high velocity. As the
gas vents, the pressure in the container will drop and the container and its contents will cool
At some point, when the pressure within the tank drops to standard atmospheric pressure,
venting will cease or drop  to a low rate consistent with the amount of heat that enters the
container from its surroundings

3.3 DISCHARGES ONTO LAND

     Up to this point, the discussion has essentially focussed on how the boiling point and
melting point of a substance may affect its  actions upon release to the environment It is now
time to consider how the density and solubility of the substance impacts on where it will go
once outside and how there are differences to be considered between discharges on land or
water or into the air. The discussion begins with discharges  onto land and again considers
the physical states in which spilled substances may reach a land surface

     Cold or refrigerated solids  with melting points below ambient temperature will either
melt to form a liquid or sublime when  spilled onto a land surface  Substances that are
normally solid will remain m the solid state, while molten solids may flow for a time as
liquids and eventually solidify as  they cool.

     Liquids with boiling points above ambient temperatures  will remain as liquids and will
generally cool down or heat up  as  necessary to approach the temperature of the ambient
environment  Those with boiling points below  ambient temperatures  may boil on a land
surface until most of the liquid has volatilized (i e , vaponzed)  Alternatively, as the ground
                                         3-5
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surface cools beneath a boiling pool that has been confined by natural or man-made barriers,
the boiling may cease and the remaining quiescent pool may simply evaporate at a fairly
steady rate

     Gases or vapors may contaminate a land surface if they are soluble in water and either:
1) it is raining;  or 2) water sprays are applied by  spill response personnel  to absorb,
"knockdown" or otherwise  accelerate  the dispersion of the gas or vapor in  air.  The
contamination occurs because the water droplets pick up some amounts of the gas  or vapor
and then fall to the ground.

      Solids of any kind can contaminate the land surface, and are particularly of concern if
they are soluble in water. In such cases, rain or other sources of water will dissolve the solids
and permit them to soak deeper into the ground in a process called percolation  Eventually,
the dissolved chemicals may reach the water table  (if any)  below the land's surface and
contaminate  groundwater supplies serving public, private, or industrial water wells  Such
contamination may pose a toxic hazard to the people, animals, and plant life that may be
exposed to the soil or which use the contaminated groundwater for drinking, cooking, or crop
irrigation.  Similarly, the dissolved chemicals may cause undesired reactions, contamination,
or corrosion of equipment upon entry to industrial  processing equipment relying on  well
water. The situation for spilled liquids is about the same except that it must be realized that a
liquid need not be soluble in water  to percolate into soil or to contaminate groundwater
supplies.  Additionally, it must be noted that liquids are more mobile than spilled solids and
do not necessarily require rain  or other sources of  water  to assist  in the spreading  of
contamination. The rate at which a liquid substance percolates or otherwise penetrates the
ground is, of course, influenced by many factors. Penetration  can be  rapid in areas  of
extremely high permeability including limesinks, caverns, highly fractured rocks, or fractures
widened by solution.

       Other concerns associated with discharges of  hazardous materials onto land surfaces
 are:

       •    Combustible substances may be ignited and pose a fire or explosion hazard
           (see Chapters 4 and 5).

       •    Hazardous vapors or gases  may be liberated into the  atmosphere from
           substances with  significant vapor  pressures  at prevailing  chemical or
           ambient temperatures (see Section 3 5 and Chapters 4 and 6).

       •    Solids, solids dissolved in or earned by land surface water runoff, or liquids
           may flow into drains or sewers leading to  bodies of water  or may directly
           contaminate such bodies (see Section 3.4).
                                          3-6
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3.4 DISCHARGES INTO WATER

     Discharges of a chemical substance into a body of water may occur directly from
damaged ships, barges, underwater pipelines, or railroad cars or trucks that have fallen into
the water, or indirectly, as outflows from sewer or drain outfalls, runoff from spills on land,
runoff of water used  to control fires, or entry of contaminated groundwater into the water
body.  Virtually all key physical and chemical properties of hazardous materials discussed in
this document play important roles in determining how a material will behave when spilled
into water.

     •    The boiling point and vapor pressure of the material will determine whether
           some part of the  material will boil off  or otherwise  vaporize  upon
           contacting the water.

     •    The liquid or solid specific gravity or density of the material will determine
           whether it has an initial tendency to float or sink in water.

     •    The solubility of the material will determine whether it will dissolve in the
           water and the rate at which this will occur.

     Table 3.2 describes the expected behavior of spills into water of materials with varying
combinations of boiling point, vapor pressure, specific gravity, and solubility attributes  To
be  stressed is that the table describes spill behavior only m the minutes and hours directly
after a release and that longer penods of time may result in different effects. For example,
although it is well appreciated  that oil will float on water, forming a surface slick that may
foul shorelines, it is not as  well known that waves, water, turbulence,  and time  may
eventually cause a floating petroleum oil slick to emulsify (i e., to become tiny droplets) that
distribute themselves through  the water column (i.e.,  throughout the depth of the water
body), to dissolve in water to some extent, and to eventually settle on the bottom of the water
body as a sludge. This sludge, in the case of petroleum oils, may mix with sand or dirt and
form the "tar balls" often observed on shorelines after an offshore spill.

     One  special point  to be  made about substances often described as insoluble  is that
many  of these may actually dissolve at such a slow rate  in water that they are considered
insoluble "for all practical purposes" Given enough time or agitation, a sufficient amount
may actually dissolve to cause  a toxic  hazard to  anybody or anything exposed  to the
contaminated water Always be wary of claims of complete insolubility when a  highly toxic
substance has spilled into water.
                                           3-7
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                                                             TABLE 3.2
                                         EXPECTED BEHAVIOR OF SPILLS INTO WATER
           Boiling Point
Vapor Pressure
Specific Gravity
  Solubility
          Expected Behavior in Water
          Below ambient
   Very high
      Any
  Insoluble
All of the liquid will rapidly boil from the surface of
the water.  Underwater spills will most often result in
the liquid boiling and bubbles rising to the surface.
          Below ambient
   Very high
Less than Water
Low or Partial
Most of the liquid will rapidly boil off but some
portion will dissolve in the water Some of the
dissolved material will evaporate with time from the
water. Underwater spills will result in more dissolu-
tion in water than surface spills.
          Below ambient
   Very high
      Any
    High
oo
As much as 50% or more of the liquid may rapidly
boil off the water while the rest dissolves in water
Some of the dissolved material will evaporate with
time from the water.  Underwater spills will result in
more dissolution in water than surface spills. Indeed,
little vapors may escape the surface if the discharge
is sufficiently deep
          Above ambient
     Any
Less than Water
  Insoluble
The liquid or solid will float on water. Liquids will
form surface slicks. Substances with significant
vapor pressures will evaporate with time.
          Above ambient
     Any
Less than Water
Low or Partial
The liquid or solid will float on water as above but
will dissolve over a period of time. Substances with
significant vapor pressures may simultaneously
evaporate with time
          Above ambient
     Any
Less than Water
    High
These materials will rapidly dissolve in water up to
the limit (if any) of their solubility Some evapora-
tion of the chemical may take place from the water
surface with time if its vapor pressure is significant.
 image: 








                                                       TABLE 3.2 (Continued)
                                          EXPECTED BEHAVIOR OF SPILLS INTO WATER
           Boiling Point
Vapor Pressure
 Specific Gravity
  Solubility
          Expected Behavior in Water
           Above ambient
     Any
   Near Water
  Insoluble
Difficult to assess Since they will not dissolve, and
since specific gravities are close to water, they may
float on or beneath the surface of the water or
disperse as blobs of liquid or solid particles through-
out the water column.  Some evaporation of the
chemical may take place from the water surface with
time if its vapor pressure is significant.
           Above ambient
     Any
   Near Water
Low or Partial
Although a material with these properties will be-
have at first like materials described directly above,
it will eventually dissolve in the water Some evapo-
ration of the chemical may take place from the water
surface with time if its vapor pressure is significant.
VO
           Above ambient
     Any
      Any
    High
These materials will rapidly dissolve in water up to
the limit (if any) of their solubility. Some evapora-
tion of the chemical may take place from the water
surface with time if its vapor pressure is significant.
           Above ambient
     Any
Greater than Water
  Insoluble
Heavier-than-water insoluble substances will sink to
the bottom and stay there. Liquids may collect in
deep water pockets.
           Above ambient
     Any
Greater than Water
Low or Partial
These materials will sink to the bottom and then
dissolve over a period of time.	
           Above ambient
     Any
Greater than Water
    High
These materials will rapidly dissolve in water up to
the limit (if any) of their solubility. Some evapora-
tion of the chemical may take place from the water
surface with time if its vapor pressure is significant
 image: 








     A second point to be made is that concentrations of water soluble contaminants in
water are typically measured or expressed in units of parts (of contaminant) per million parts
(ppm) of water on a weight basis or in units of milligrams (of contaminant) per liter (mg/l) of
water.  These units are essentially equivalent such that one ppm equals one mg/l When a
material is dissolved in water, the mixture is often referred to as an aqueous solution of the
material. Conversely, materials that do not contain water are considered to be anhydrous.

     Of interest with respect to the evaporation  of chemicals from water is that such
evaporation can take place not only from floating pools or slicks of chemicals but from the
surface of solutions.  It is important to realize, however, that the vapor pressure of a chemical
will drop when the chemical is added to water or water is added to the chemical,  and the less
chemical  there  is in the solution,  the lower its vapor  pressure  will be  at a specific
temperature. Thus, evaporation from a concentrated solution (i e, one containing consider-
able chemical) near a spill site might create a downwind vapor hazard, but the hazard might
be negligible some time later after the chemical has had a chance to mix with more water.
Similarly, a water-soluble chemical or solution that has a flammable vapor concentration
above its surface at a given temperature may often be rendered nonflammable by  the addition
of a sufficient quantity of water.

     Besides generating flammable or toxic vapors, chemicals spilled into water or sewers
can pose a variety of hazards to the public and the environment.

     •     Flammable chemicals or solutions can pose a fire or explosion hazard in
           sewers, water treatment facilities, or any other spaces they may enter when
           extracted from a body of contaminated water.

     •     Insoluble  materials, particularly  oils, may cause  drowning of waterfowl
           because of loss of buoyancy, exposure due to loss of the insulating capacity
           of feathers, and starvation  and vulnerability to predators due to lack of
           mobility.  Coating  of the gills of fish  may cause death due  to lack of
           oxygen.  Coating of any life forms on the bottom of a water body can kill
           by smothering.

      •    Any insoluble or  soluble toxic substance that contaminates water may
           poison animals (including humans) or plant life (aquatic plants or irrigated
           crops) exposed to the water.

      •    Organic substances can potentially kill fish and other aquatic life forms by
           lowering the oxygen content of the water via biological as well as chemical
           processes.
                                         3-10
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     •    Contaminated water  drawn  into  industrial processes may  corrode or
          otherwise  damage  or destroy equipment,  and possibly cause  fire or
          explosion hazards.

3.5 FUNDAMENTAL CONCEPTS PERTAINING TO DISCHARGES INTO AIR

     Hazardous vapors or gases, ie., those  that are flammable or toxic to man  or his
environment, may enter the atmosphere from several sources.

     •    They may be vented directly into the air from a pressure relief valve,
          "smokestack", ruptured reaction vessel,  broken pipe, or other item of
          equipment at a chemical plant or other fixed site facility.

     •    They may be vented directly from a pressure relief valve,  broken valve,
          loose fitting, or puncture in a transportation vehicle, container, or cylinder.

     •    They may evolve from volatile liquids or solids discharged onto the ground
          or into water.

     Evaluation of vapor or gas discharge hazards first requires that the duration over which
the discharge takes place be characterized  It then requires assessment of how the liberated
vapors or gases will mix with air over time in a process referred to as vapor dispersion, and
finally, requires knowledge of the specific hazards posed by exposure of people to resulting
concentrations of airborne contaminants at downwind locations.

     Instantaneous vs. Continuous vs. Finite Duration Discharges

     The most  common methods available for assessment of vapor dispersion hazards
require that  discharges of vapor or gases into the atmosphere be classified as either being
instantaneous or continuous in duration. Instantaneous discharges are those that take place
over the course of a few seconds or a minute or so and then stop for all intents and purposes
The result of such a discharge is typically a puff of vapor or gas or a distinct  cloud
Continuous discharges take place over longer periods of time and produce long stretched-out
plumes of  gas or  vapor such  as  those typically seen from  continuously  operating
smokestacks. These cases represent the two extremes by which contaminant emissions  may
be characterized  In  the real world, many discharges may be of too long a duration to be
characterized as truly instantaneous, yet too short in duration to establish a continuous plume
These latter discharges are commonly said to be of finite duration,

     In  the following, we concentrate upon describing the behavior  of gases  or  vapors
liberated from instantaneous or continuous discharges to the atmosphere, thus  providing the
reader an understanding of the two possible extreme cases   Realize, however, that the actual
                                         3-11
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behavior of a volume of contaminated air dispersing in the atmosphere,  particularly if
generated from a finite duration discharge, will behave in a manner somewhat between these
two extremes.

     Dispersion of Vapor Puffs or Clouds

     Picture if you will a large semi-spherical puff or cloud of a pure chemical vapor or gas
on the ground that has somehow entered the atmosphere over the period of a few seconds and
has a vapor specific gravity and vapor density similar to that of air. As the wind pushes on
the puff, the puff will begin to move  in the direction of the wind at a similar velocity
Simultaneously,  air will begin to mix  with the surface of the puff, thus diluting surface
vapors.  As more and more air mixes with the puff, the volume of the contaminated airspace
will become larger and larger. Dilution with air, however,  will cause vapor concentrations to
drop with time at any point in the puff, although the central core of the puff may remain pure
for a while.

      What happens over time and distance as a puff disperses in air is somewhat hard to
visualize with  words alone, so it is worthwhile to use various illustrations and graphs in this
endeavor. Figure 3.1 shows four initial stages as a puff moves downwind, each accompanied
below by a graph of vapor concentration in air on the ground along a cross-section of the
puff.  At time equals zero, the instant the puff is formed, the concentration within the puff is
close to 100%  pure vapor and the air surrounding the puff is uncontaminated  At time equals
20, the puff has grown hi size by mixing with air, and that portion which is still 100% pure
vapor has become smaller. The vapor  concentration in the remainder of the cloud ranges
from 100%  at the edge of the pure core of vapor to 0% at the edge of the cloud By time
equals 40, the core of 100% vapor has  become even smaller, and by time equals 80,  it has
just disappeared. From this point onward, the peak or maximum groundlevel concentration
will drop below 100% and continue to drop steadily.

      Figure 3.2 continues the above sequence for a variety of later times on a single graph.
What is happening is  that the cloud grows larger and larger but its peak concentration, the
point at its center along the ground, becomes lower and lower  At some point, this peak level
will drop below whatever concentration level of the  gas or vapor in an-  is considered
hazardous.  If one were to plot the groundlevel peak concentration at the center of the cloud
with time or distance, it would resemble the graph in Figure 3.3

      Yet another useful way to look at cloud or puff dispersion is to look at the ground area
covered by a particular preselected concentration (which could be a flammabihty or toxicity
limit of some kind). Figure 3.4 demonstrates how this ground area changes from the point at
which the puff is generated to the downwind location that every point in the puff is below the
selected concentration The view is looking down at the  puff from a point up above, with
                                          3-12
 image: 








                                           FIGURE 31
                      INITIAL  STAGES OF  VAPOR CLOUD  OR  PUFF  DISPERSION
              Wind direction
100% pure  vapor
            Time = 0
 100%—,
   100% air out  here
                                  Air-vapor mixture
Time  =  20
Time  = 40
                                                                               Time = 80
  0%
                                                 Downwind distance
 image: 








 100%
 O
 fl
 o
 0%
                          Time=80
                                   Figure 3.2
                              Cross—Section of Puff

                             Concentration vs  Time
                             Time=160
                                 Time=320
                                     Time=640
           Distance  Crosswind
100%
a>
o
a
o
o


S
0
s
•»s
X
CO
         Figure 3.3


Maximum Puff  Concentration

    vs.  Time  or Distance
 0%
            Time or  Distance —
                        3-14
 image: 








                                 FIGURE  3 4
            PUFF OR CLOUD ISOPLETHS  AT  INCREASING  TIMES
Wind  Direction
                                                             All circles  are
                                                             isopleths for  the
                                                             same  concentra-
                                                             tion  in  air at
                                                             different times
                                 FIGURE  35
                   ISOPLETHS  IN  A  CONTINUOUS  PLUME
Wind  Direction
                                                             Larger ovals
                                                             represent lower
                                                             concentration  iso—
                                                             pleths   All can
                                                             exist simultaneously
                                                             in  a continuous
                                                             plume
                                    3-15
 image: 








each circle representing a different point in time  The line around the set of circles encloses
the ground area that will be subjected at some time to airborne contaminant concentrations at
or above the preselected concentration. In somewhat technical terms, the individual circles,
these being lines  of constant concentration, are referred to as isopleths, as is  the line
enclosing the entire set of circles The latter is  also sometimes referred to as the cloud's
footprint on the ground for a particular hazardous concentration.

      The downwind distance that any point in puff, cloud, or plume will travel within any
elapsed period of time is related to the velocity of the wind in its direct vicinity by the
relationship:

                      Distance = Wind Velocity x Time

Although this expression seems rather simple and straightforward, there is a "catch" to its
general use. As observed above, the distance traveled is proportional to the wind velocity in
the  direct vicinity  of the puff  Meterologists  and  weather stations typically report the
velocity or speed  of the wind as it has been measured at a point 10 meters (about 33 feet)
 above the ground, where the velocity is usually greater than that very close  to a ground
 surface. Indeed, volumes of contaminated air released at groundlevel may  travel as little as
 50 percent of the distance given by the above relationship when the wind velocity used in the
 equation is measured at  a  10 meter  height.  Clouds, puffs, or plumes  liberated to  the
 atmosphere above this height may travel faster than the reported wind velocity

      Dispersion of Continuous Plumes

      As noted previously,  the  emission of gases or vapors to the  atmosphere over an
 extended period of time results in establishment of a vapor or gas plume. Points downwind
 of the source of  emissions  will be exposed to a relatively constant  airborne contaminant
 concentration for a penod of time approximately equal to the duration of the emission so
 long as the wind  direction holds steady. Note however, as is also the case in instantaneous
 discharges, that some amount of time will be necessary for the front edge of a cloud or plume
 to reach  downwind  locations after the initiation of a discharge  and  for  contaminant
 concentrations to rise to relatively constant levels at these locations  A similar amount of
 time will be necessary for the trailing edge to pass downwind points after cessation of vapor
 or gas liberation and for contaminant concentrations to drop below levels deemed to be safe.
 Thus,  there are different arrival and departure times associated with different downwind
 locations for both clouds and plumes

       Figure 3 5 shows an example of what various concentration isopleths look like through
 a horizontal cross-section of an established plume The innermost isopleth encloses the area
                                         3-16
 image: 








subjected  to the highest concentrations. Moving out from the innermost isopleth, each
isopleth in the outer direction represents a lower concentration than the previous isopleth  As
in the previous case, the view is looking down from above.

3.6 VARIABLES THAT INFLUENCE ATMOSPHERIC VAPOR DISPERSION

     There are numerous factors that influence the size and shape of downwind hazard
zones resulting from vapor or gas discharges into the atmosphere. The most important of
these variables are discussed individually  and sometimes  in  combination below  Since
several of them interact with each other, it may be a good idea to read this section more than
once to better understand various interrelationships  A solid understanding of vapor cloud
and  plume behavior under various conditions  is an  important prerequisite  to proper
emergency response as well as emergency planning

     Effect of Toxic or Flammable Limit Selection on Hazard Zone Size

     As  explained in prior  discussions, the  concentration of an airborne contaminant
decreases with increasing distance along the downwind centerline direction of the cloud or
plume path as well as in the crosswind direction What this means in practical terms is that
the choice of  a higher toxic or flammable  limit for definition  of hazard zone boundaries
during accident consequence analysis efforts will result in a smaller overall hazard zone than
if a lower limit had been chosen. Conversely, lower limits will lead to  larger hazard zones
than higher limits.

     The choice of an appropriate toxic limit, also referred to as a "level of concern" in
earlier guidance documents published by the federal government, is discussed in  Chapter 6
Flammable limits are discussed in Chapter 4.

     Effects of Discharge Rates and Amounts on Vapor Dispersion

     In the case of instantaneous discharges and others of relatively short duration,  the total
amount (i e., weight) of vapor or gas released to the atmosphere has an impact on the size and
shape of downwind hazard zones All other factors being equal, larger discharge amounts
will  result in  longer and larger downwind  hazard  zones. Smaller amounts will result in
shorter and smaller zones

     The case with continuous releases is  similar  All other factors  being equal, higher
discharge rates will produce  longer and larger hazard zones. Lower discharge rates  will
produce shorter and smaller zones
                                         3-17
 image: 








     The area from which  a vapor evolves is particularly  important when the vapor
originates from a boiling or evaporating pool of liquid  A smaller pool will usually evolve a
lesser amount of vapor per unit of time than a larger pool and  therefore pose less of a
downwind hazard. A larger pool, having a  greater surface area, will produce vapors at a
higher rate and pose a greater downwind hazard Thus, control of exposed pool surfaces can
provide some degree of control over adverse downwind impacts.

     Effects of Atmospheric Stability Conditions on Vapor Dispersion

     The time of day, the strength of sunlight (if any) in the area, the extent of cloud cover,
and the wind velocity all play major roles in determining the level of turbulence in the
atmosphere  and thereby the distances downwind over  which airborne contaminants  will
remain hazardous  Meteorologists  typically categorize  atmospheric  conditions  into  six
atmospheric stability  classes that range generally from  "A"  to  "F".  Class  A represents
unstable conditions under which there are strong sunlight, clear  skies,  and high levels of
turbulence in the atmosphere, conditions which promote rapid  mixing and dispersal of
airborne contaminants. At the other extreme, atmospheric stability Class F represents light
steady winds, nighttime skies, and low levels of turbulence Airborne contaminants mix and
disperse far less slowly with air under these conditions, which  also include atmospheric
inversions (when temperatures increase with altitude rather than decrease as usual), and may
travel much farther downwind at hazardous concentrations than  in other cases  Table 3 3
denotes the various criteria used for determination of these stability classes  Information on
the percentage of time that any particular locale expenences the conditions associated with
each class can be generally obtained from the nearest office of the National Weather Service,
which is listed under the heading of U.S. Department of Commerce in telephone directories
 of major cities. Meteorologists associated with local radio and television stations or airports
 will also be knowledgeable of these statistics.

      During  an actual emergency, it  will be  necessary to understand that atmospheric
 conditions may change with time and that these changes will influence the behavior of the
 dispersing cloud or plume. As inspection of Table 3.3 reveals, atmospheric stability vanes
 strongly with time of day, wind speed, extent of cloud cover, and strength of sunlight As we
 are aware, these are all highly variable factors, possibly changing on an hour by hour basis m
 some locations during certain seasons

      Gas or Vapor Buoyancy Effects on Vapor Dispersion

      The descriptions of vapor cloud  and plume behavior given earlier  started with the
 assumption that the vapor specific gravity or  density of the gas or vapor being released  is
 approximately equal to that of air.  However, as also discussed earlier, certain gases or vapors
 and their initial mixtures with air may actually  be heavier or lighter than air.
                                          3-18
 image: 








                                                        TABLE33
                                   ATMOSPHERIC STABILITY CLASS SELECTION TABLE
                         A ~ Extremely Unstable Conditions
                         B ~ Moderately Unstable Conditions
                         C - Slightly Unstable Conditions
D — Neutral Conditions*
E - Slightly Stable Conditions
F — Moderately Stable Conditions


Surface Wind
Speed, mph
Less than 4.5
45-67
6.7-11.2
11.2-134
Greater than 13.4
Daytime Conditions
Strength of sunlight
Strong
A
A-B
B
C
C
Moderate
A-B
B
B-C
C-D
D
Slight
B
C
C
D
D
Nighttime Conditions

Thin Overcast
greater than or =
4/8
Cloudiness**
-
E
D
D
D
less than or = 3/8
Cloudness
-
F
E
D
D
H
VO
         *Apphcable to heavy overcast conditions day or night
       **Degree of Cloudiness = Fraction of sky above horizon covered by clouds.
 image: 








     In general, lighter-than-air gases, vapors, or mixtures will mix with air in the same
fashion as those that are closer to the vapor specific gravity of air.  Groundlevel contaminant
concentrations are likely to be lower, however, because maximum concentrations along the
centerline of the cloud or plume will tend to be elevated The rate at which a cloud or plume
will rise as it moves downwind will primarily be a function of the difference in vapor specific
gravity between it and air and the prevailing wind speed. Lighter gases or vapors will rise
faster.  Strong winds will tend to keep the cloud or plume closer to the ground for longer
periods of time. Figure 3.6 for distinct clouds or puffs demonstrates these concepts and the
principles that also apply to plumes  In both cases, it is necessary to remember  that the
velocity of the wind will influence downwind travel distances within any given period of
time.

     Heavier-than-air gases, vapors, or mixtures tend to hug the ground for a  time when first
released  and may even follow terrain in  directions across or against wind directions  on
certain boundaries.  However, as these vapors and gases become more diluted with air, they
will at some point begin behaving like mixtures with vapor specific gravities  close to that of
air.  Thus, consideration of heavy gas or vapor dispersion phenomenon is more important for
higher concentrations near the source (such as those associated with lower flammable limits)
than for the lower concentrations typically associated with toxic limits.

     The overall behavior of a heavy (negatively  buoyant)  cloud or plume can  be very
different than that of a neutrally or positively buoyant cloud or  plume and the shape and
dimensions of the cloud or plume can be strongly influenced by the duration of the discharge,
prevailing atmospheric stability conditions, and prevailing wind velocities. For example, an
instantaneous discharge of a flammable liquefied gas can result m a flammable or potentially
explosive cloud that is 25 percent greater in maximum width than its length under neutral
atmospheric conditions (see Table 3.3) when winds are of moderate velocity  Under more
stable  atmospheric  conditions with lower wind speeds, the maximum width  of the cloud
could  drop to approximately 80 percent of its length. Under  specific combinations of
conditions, particularly for large releases, cloud widths could be as much as 150 percent of
length dimensions.

     Continuous or otherwise prolonged discharges of heavy gases or vapors can behave yet
differently from short-term releases  Under neutral  atmospheric stability conditions, maxi-
mum plume widths typically range from  30 to  60  percent of lengths when winds  are of
moderate velocity Under stable conditions, these widths can vary from 75 to 90 percent of
lengths.  In  contrast, the maximum widths  of  neutrally or positively buoyant clouds or
plumes are typically in the range of 40 to 50 percent of lengths.
                                          3-20
 image: 








                        Figure 3.6



    Behavior of Lighter than  Air Puffs  or Clouds
Wind Direction
                           Rise of cloud in low wind conditions
                            Rise of cloud in high wind conditions
                         Time or Distance
 image: 








     Effects of Source Elevation on Vapor Dispersion

     Although many discharges of  gases or vapors are  likely to  take place at or near
groundlevel, some may occur from the top of an elevated item of equipment or from a tall
smokestack, pressure relief valve, or  similar venting device. The principles set forth earlier
with respect to post-discharge behavior of gases and vapors remain applicable in such cases,
but it must be noted that groundlevel concentrations due to elevated sources may vary
significantly from groundlevel concentrations  due to groundlevel  sources. Figure 3.7
illustrates some of the reasons for such differences.

     The most important concept to  understand about elevated discharges is that maximum
concentrations will be along the centerline path of cloud or plume travel in the downwind
direction. In the  case of neutrally  buoyant clouds or plumes, groundlevel contaminant
concentrations may be essentially zero until the bottom of the cloud or plume first touches
ground.  These concentrations will then rise with increasing downwind  distance, reach  a
peak, and then  drop with further distance.  As  demonstrated by the graph in Figure 3.3
presented earlier, this differs markedly from the variation of concentration with distance seen
along the centerline path of such a cloud or plume.

      When vapors or gases are lighter than air and therefore positively buoyant, the presence
of harmful contaminant concentrations near groundlevel will strongly depend upon the wind
velocity. As  illustrated  in Figure 3.6, the cloud or plume may nse quickly, slowly,  and
possibly not all depending on the wind speed (and the velocity with which the vapors or
 gases are discharged upwards into the air). Groundlevel concentrations will vary according-
 ly.
      Effects on Dispersion Relating to Physical States of Contaminants

      Although the discussion to this point has focused on the dispersion of gases and vapors
 in air, it is also important to understand that fine mists, fumes, or aerosols of liquids as well
 as fine dusts or powders may also be transported by the wind to downwind  locations. Some
 discharges could involve mixtures of chemical vapors and aerosols and dusts.

      Larger and  heavier droplets of liquid or particles of solids may "settle out" of the cloud
 or plume and drop to ground surfaces fairly close to their point of origin  Somewhat smaller
 particles may settle out  a bit further downwind, while the smallest of all may travel as far as
 vapors  and gases at equivalent concentrations in air. Droplets of volatile liquids may
 vaporize as they  are earned by the wind or after they settle out of the main cloud or plume.
 They may also cause part or all of a cloud or plume to behave as if it is heavier than air even
 if the same substance in a purely gaseous state might be lighter than air or neutrally buoyant
 at prevailing temperatures. All of these phenomena can have an impact on groundlevel or
 close to groundlevel  contaminant concentrations, generally resulting in levels above those
                                          3-22
 image: 








          Wind  Direction
  1   Puff  dispersion  of  neutrally buoyant  vapors   Groundlevel
  concentrations may  be  zero  for  some  time  until the  puff  first
   hits" the  ground    Same  puff  shown at different  times above
 2   Continuous  plume dispersion of neutrally buoyant  vapors  in
 air   Note again that some  distance may  be  required before any
 contamination occurs near the  ground
3   Plume dispersion of heavy  vapor   Puffs may  follow a similar
path during dilution  with  air
                        Figure  3.7
     Some   Effects   of  Elevated  Emissions
                            3-23
 image: 








that would be expected in the absence  of mists, fumes,  aerosols, or dusts. Accurate
prediction  of cloud or plume behavior under these conditions is extremely complex and
prone to substantial errors.

     Effects of Discharge Velocities on Dispersion

     Vapors or gases may be released to the atmosphere at relatively low velocities or may
be vented under high pressure as a jet There are various "jet" momentum effects that alter
puff or plume behavior, particularly near the source of a discharge A strong jet of vapor or
gas will tend to entrain and mix with air rapidly at first, thus tending to reduce contaminant
concentrations These effects become less important, however, as the puff or plume moves
downwind.

      In the event that a high velocity high rate discharge of a heavies? than air mixture of gas
and liquid aerosols takes place in the downwind direction, there is a distinct possibility that
downwind hazard zone lengths will be greater than those predicted by most vapor dispersion
models in general use The behavior of such highly pressurized discharges of compressed
 liquefied gases is a subject receiving considerable attention in scientific cicles at present, but
 accurate  prediction  of  contaminant behavior  under these conditions  remains prone to
 substantial errors

      Effects of Local Terrain on Vapor Dispersion

      In virtually all that has been said about atmospheric vapor dispersion phenomena up to
 this point, it has been tacitly assumed that the vapors or gases being discussed are dispersing
 over flat terrain without obstacles of any kind  In the real world, however, large portions of
 the country are  by no means flat or devoid of hills, mountains, trees, or buildings  All of
 these topographical features and others influence the manner in which airborne contaminants
 disperse

       In most cases, a certain degree of "roughness" in  the terrain is beneficial  in the sense
 that it tends to speed up the rate at which contaminants mix with air and are thereby diluted
 This is understandable if one thinks about how the wind behaves as it swirls around and over
 trees,  hills, buildings, and other objects  There are two situations, however, in which terrain
 effects may cause increased hazards at or near groundlevel locations

       The first case involves situations in which contaminants are trapped within some sort of
 canyon, valley,  or bowl-like depression in the land surface Under these conditions, the walls
  or sides  of  these topographical features can  prevent spreading of clouds or  plumes and
  restrict dilution with air. The net result is that hazard zones might be of different size and
                                           3-24
 image: 








shape than otherwise expected  If an atmospheric inversion were to occur such that there was
essentially a "cap" placed over a bowl-like depression or valley, airborne contaminants could
be literally trapped for extended periods of time

     The second case involves the dispersion of gases or vapors from an elevated source
when there are buildings or similar shaped features on the land in the downwind direction.
As the wind passes over a building, some part of it may be drawn down into a swirling eddy
pattern in a space behind the structure commonly referred to as its "wake cavity".  The
practical significance of this phenomenon is that contaminants liberated from  elevated
sources could potentially be drawn down towards groundlevel much sooner and at much
shorter downwind distances than might otherwise be expected

     Readers should be advised that many of these phenomena are extremely difficult if not
impossible to address in any sort of generalized vapor dispersion hazard prediction model or
methodology regardless of its claimed level of sophistication or cost Those  who may be
tempted to purchase any expensive software package to evaluate downwind vapor dispersion
resulting from chemical accidents for planning purposes should first compare the results of
the package with the results obtained from the computer program provided with this guide
for several scenarios

     Effects of Wind Meandering on Evacuation or Protective Action Zones

     The main reason  that one would wish to determine or  predict the concentration
isopleths or footprints of gas or vapor clouds or plumes is to determine those  downwind areas
that may require public evacuation or other protective action in the event of a toxic and/or
flammable vapor or gas release. It is important to realize, however, that the direction of the
wind is rarely steady over any significant penod of time and that the wind direction tends to
shift back and forth between various directions. This shifting over time is often referred to as
meandering. The practical significance of wind meandering is that an area larger than that
predicted by strict application of dispersion estimation methods may require evacuation or
other means of public protection during an actual emergency.

     The probability and extent of wind meandering in any locale is a complex function of
several factors,  but one of the  most important  involves the atmospheric stability class
prevalent in the area at the time  The wind tends to meander less on average under stable
conditions than in unstable weather

     Based on data presented on page 28 of the Handbook of Atmospheric Diffusion (U S
Department  of Energy, DOE/TIC-11223) by Hanna, Bnggs, and  Hosker,  it has been
determined that there is a 90 percent probability on average that a cloud or plume will remain
within a downwind arc of 120 degrees from its point  of origin under atmosphenc stability
class conditions A, B, and C For more stable stability classes, the arc narrows to a 40 degree
                                        3-25
 image: 








angle.  Figure 3.8 illustrates these observations, the practical significance of which is the
finding that the area requiring evacuation  or  other protective  action (such as sheltenng
populations in place) in the first hour of a hazardous vapor or gas release should usually be
based on the above arcs and not the actual width of selected concentration isopleths  Where
an evacuation is to be attempted, it is often best to start from a point nearest the emission
source and work outwards towards downwind areas subject to lower concentrations  Be
advised, however, that there is an exception to the above findings When the velocity of the
wind is very low under special circumstances, the direction of the wind can become very
erratic. It is best to be prepared under low wind conditions for one or more sudden shifts in
wind directionW the possibility that a cloud or plume may literally "hop" from one position
or direction to another

      Indications of the specific areas that may require protective action in the event of
specific spill or discharge situations can be obtained by drawing hazard zone boundaries on a
map of the region in accordance with the "scale" shown on the map  These boundaries can
be drawn for various wind directions and atmospheric stability classes to illustrate potential
hazard zones under various conditions Local census data may then be used to estimate the
maximum number of people that may require protection  Note that the drawings will be most
easily drawn using a ruler and protractor, keeping in mind that a full circle has 360 degrees.

      If the discharge or release may be prolonged, the probability will increase that there
will be a  major shift in wind direction When and where possible, it  is best to consult a
meteorologist with detailed knowledge of current local conditions immediately for advice on
how to expand the evacuation area as time progresses For truly prolonged situations
involving  hazardous emissions, it may eventually become necessary to evacuate a full circle
 around the accident site out to the radial limits of the estimated hazard zone

      It is precisely because the direction of the wind during an accident cannot be predicted
 in advance and that the direction may shift during a hazardous event that the zone considered
 vulnerable around a potential  accident or incident site encompasses a full circle around the
 site (or a  "corridor"  of overlapping circles if the site is along a railroad, pipeline, barge, or
 truck route)  Although there may be many cases in which only a portion of the vulnerable
 zone will require protective action, public and industry officials must realize that the entire
 zone is at risk and will require attention during the emergency planning process, particularly
 with respect to populations at special risk or requiring special assistance

       The average probability of the wind being in any particular direction may be useful
 knowledge, particularly in locations where the wind is prone to flow in certain directions on a
 regular basis during various seasons  As in the case  of atmospheric  stability  classes, the
 planning  process can therefore benefit from consultation with a meteorologist at the nearest
 office of the National Weather Service 01 associated with a local radio or television station or
                                           3-26
 image: 








                              FIGURE  3.8
            VAPOR  DISPERSION  HAZARD  ZONE BOUNDARIES
Wind direction
     t
40 degree arc

Use for discharges less
than one  hour  in duration
under  atmospheric stability
conditions D,  E, and  F
	  \
                                   ,  \   \  \ X
                                 I—i—V—«- \	-N:	
                                    120\ degre^  a\c
                                    Uac \for—discharges
                                    less \than  one Sour
                                    undeb-  atmospher
                                    stability  conditio
                                    A, B,\or  C
            Emission source
     Arrows within boundaries of  estimated  hazard  zones
     indicate  length of  downwind  hazard  distance  in downwind
     centerline  direction  of wind

     Longer duration  discharges  may  require  up  to 360  degree
     evacuations or protective measures if the  wind direction
     may shift  during the discharge.   Consult  a qualified
     meteorologist  in  actual emergencies for  advice.
                                 3-27
 image: 








airport. It is common practice for these piofessionals to maintain or have access to detailed
historical data pertaining to the frequency of various wind directions in the locale of their
concern.
                                            3-28
 image: 








          4.0 FIRE HAZARDS OF CHEMICAL SUBSTANCES
4.1 INTRODUCTION

     When most of us think of an unwanted fire, we typically picture a burning building, a
burning transport vehicle of some kind, or a burning forest with flames and smoke rising into
the sky. These are clearly the most common types of fires and typically involve ordinary
combustible materials such as paper, wood, cloth, plastics, and rubber  Fire departments
across the nation face such fires on a daily basis and are well-equipped and trained to deal
with them. Hazardous materials, however, may pose additional types  of fire hazards with
unusual characteristics  In the following, we first discuss measures of flammability potential,
continue with a discussion of how the effects of fires may be evaluated, and finally, describe
a number of "special" types of fires associated with hazardous materials

4.2 MEASURES OF FLAMMABILITY POTENTIAL

     It hardly needs saying, but most of us realize that some matenals are much more easily
ignited than others Some require only a spark, such as the propane or LP-gas fuel in a gas
barbecue,  while others, such as a piece of granite, will not ignite even  if placed under a
welding torch  The most common measures of flammability potential for matenals which are
flammable or combustible are  1) flash points, 2) lower flammable or lower explosive limits;
3) upper flammable or upper explosive limits, and 4) autoigmtion temperatures  These data
are readily available in various handbooks and hazardous material data bases when known,
and are commonly listed in chemical company material safety data sheets (MSDS)  Fire
 image: 








safety and combustion experts may also consider ignition energy requirements, fire points,
flame spread rates, and heat and  smoke generation rates of materials in evaluating then*
flammability characteristics, but knowledge of these latter attributes is not truly needed for
the purposes of this document and sources of appropriate data are not readily available to the
general public for a large number of subtances.

     FlashPoints

     The flash point of a combustible substance, in simple terms, is the lowest temperature
of a material at which  the vapors over its liquid or solid surface will ignite and burn when
exposed to a specified ignition source without necessarily causing self-sustaining combustion
of the liquid or solid Flash points vary from temperatures far below zero degrees Fahrenheit
for flammable gases (such as natural gas, LP-gas, propane or butane), and volatile flammable
liquids (such as gasoline), to hundreds of degrees above zero for heavy fuel oils. (Note:  The
temperature at which the vapors over a liquid or solid will ignite and continue to bum due to
self-sustaining combustion of a liquid or solid is called its fire point.  These temperatures are
available in  the professional literature for only a relatively few materials.)

     Materials with low flash points relative to temperatures  in the ambient (i e., natural)
environment are usually ignited easily by a spark (be it from metal scraping metal or stone or
from static electricity)  or by a flame from any source. Most frequently, they are substances
that are normally gaseous at ambient temperatures or liquids that readily evaporate or boil
upon release. These vapors  or gases can sometimes be earned by the wind to a source of
ignition somewhat distant from the discharge site of the material and flashback to the spill
source causing one or more of the fire hazards described later

     Substances with flash point temperatures close to ambient temperatures are also easily
ignited by sparks or flames.  The main difference between such materials and those described
in the previous paragraph is that the ignition source must be closer to the fuel in order for
ignition to take place.  This follows  from the observation that such materials are  generally
liquids of lower volatility than materials with substantially lower flash points.

     The higher the flash point temperature is above ambient temperature, the more difficult
it becomes to ignite a substance  Under normal circumstances,  a fuel with a high flash point
cannot be ignited by a spark or even a nearby flame unless: 1) the  fuel is a liquid sprayed
into the air  as a fine mist, 2) the fuel is a finely divided solid, 3)  a portion of the fuel is
heated to its flash point by a nearby source of heat and then exposed to an ignition source; or
4) the fuel is heated  to a temperature  at  or above its flash point prior to release and
encounters an ignition  source before cooling
                                          4-2
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     The flash point temperatures of combustible materials are determined using testing
methods and equipment standardized by various organizations, with the American Society of
Testing and Materials (ASTM) being the primary standard-setting body in the United States.
There are two main classes of testing methods which respectively provide "open cup" or
"closed cup" flash points, and each class represents more than one specific testing method
Because of differences in equipment design and testing procedure, the numerical value of
closed-cup flash points is typically some 5-10° Fahrenheit lower than that of the open-cup
flash point for the same substance, but the difference may be greater or less in individual
cases  Due to other factors, most importantly the purity of the sample tested, it is not
surprising to find a number of different closed cup or open  cup flash points for any given
substance,  all of which differ to some extent. It is well, therefore, to consider flash point
values reported in the literature as approximate rather than exact values

     Flammability and Explosivity Limits

     It is rather well known that combustion cannot take place in the absence of a certain
minimum amount of oxygen, be it available in air mixed with gases or vapors evolved from a
combustible substance or from an internal component of the fuel  Conversely, there must be
sufficient fuel  vapors or  gases available in a fuel-air mixture to  support  and  sustain
combustion. Thus, there are both lower and upper limits associated with fuel concentrations
in air that  will ignite and permit flames to spread away from the source of ignition  (i e,
permit  flames  to propagate)  Fuel  concentrations below  the lower limit  will  contain
insufficient fuel to ignite and propagate flame  and are commonly referred to as  being too
lean to burn  Those above the upper limit are considered too rich to ignite, that is, they
contain too much fuel and/or too little oxygen, as in  the case of a  "flooded" automobile
engine

     The minimum concentration of a vapor or gas in air that will ignite and propagate
flame is known as its lower flammable limit (LFL) concentration or its lower explosive limit
(LEL) concentration and is usually expressed as a percentage by volume of fuel vapors in air.
The words flammable and explosive are used interchangeably such that LFL values typically
equal LEL values in the literature  The reasoning behind this is that the concentration of a
fuel that will burn in air can also be expected to explode under the appropriate conditions
This supposition is only approximately true for some fuels (where precise LEL values might
be slightly higher than LFL values), but it has become widely accepted over decades of use

      Similar to the above, the  maximum concentration of  a gas or  vapor in  air that will
ignite and propagate flame is known as the upper flammable limit (UFL) or upper explosive
limit (UEL) of the fuel. Again, the  words flammable and  explosive  are often used in an
interchangeable fashion.
                                         4-3
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      LFL or LEL values are related to flash points of combustible substances in that the
flash point is theoretically the temperature at atmospheric pressure to which a substance must
be raised to produce a vapor or gas concentration over its surface equivalent to its LFL or
LEL concentration  The relationship is not always observed in practice, however, because
flash point measurement equipment  and  procedures, as discussed above,  do not always
produce precise values.

      Flammable and explosive limits found in the literature are usually measurements made
at normal atmospheric temperatures and pressures unless indicated otherwise. Be advised
that there can be considerable variation in these limits at pressures or temperatures above or
below normal.  The general effect of an increase in temperature or pressure is to reduce the
lower limit and increase the upper  limit Decreases in temperature or pressure have the
opposite effect.

      As a final note, it is also important to appreciate that certain solids, when dispersed in
air as fine powders, may also be capable of burning or exploding upon  encountering a
suitable source of ignition. Some examples include coal dust produced in mining operations,
grain dust produced in silos during storage or transfer operations, and flour produced in
milling operations. Flammable or explosive limits for solid materials are usually expressed
in units of weight of solid present in a specified volume of air.

     Autoignition Temperatures

     The ignition or autoignition temperature  (ATT) of a substance, whether solid, liquid,
or gaseous, is the minimum temperature necessary to  initiate  or cause  self-sustaining
combustion in the absence of a flame or spark. Even more so than flash points or flammable
limits, these temperatures should be viewed as approximations due to the many factors that
can affect testing results.  Indeed, it must be noted that most values currently found in the
literature  were determined by testing methods that are now considered obsolete  Newer
testing methods adopted by the ASTM frequently demonstrate substantially lower tempera-
tures for the onset of combustion than older methods.

     Table 4.1 provides examples  of various  hazardous  materials and their associated
flammability data  Those at or near the top of the list are extremely flammable and volatile
and more likely to produce large  quantities of flammable vapors or  gases upon release,
vapors or gases that may travel a considerable distance from the spill site and still be within
flammable or explosive limit concentrations in an*. Those at or near the bottom of the list are
difficult to ignite without prior preheating and tend to have much lower vapor pressures (i.e.,
are generally of low volatility).
                                        4-4
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                                 TABLE 4.1
              EXAMPLE FLAMMABILITY CHARACTERISTICS
Substance
Propane
Gasoline
Acetone
Isopropyl alcohol
Turpentine
Fuel oil no. 2
Motor oil
Peanut oil
Closed-cup
Flash Point (°F)
Very low
-45 to -36
-4
53
95
126-204
275-600
540
LFL (%)
21
1.4-1.5
25
20
0.8
*
*
*
UFL (%)
9.5
7.4-7.6
13
12.7 at
200°F
*
*
*
*
AIT(0F)
842
536-853
869
750
488
494
325-625
833
*Note:      Flash points are often not recorded for substances that are gases
            at ambient temperatures because of the very low temperatures
            required to determine them. Similarly, flammable limits are not
            always available for substances with high flash points due to
            the high temperatures needed for ignition  Substances that are
            complex mixtures of a number of materials, (e g., fuel oils) may
            have a range of flash points.

Sources:     Fire Protection Guide  on Hazardous Materials, 8th  ed.,
            National Fire Protection Association, Quincy, MA, 1984.

            CHRIS Hazardous Chemical Data, U S  Coast Guard, U.S.
            Department of Transportation, Washington, D C, 1978.
                                     4-5
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43 MEASURES OF FLAMMABILITY EFFECTS

     Direct contact with a flame of any sort is obviously not a good idea for any prolonged
period of time since the extreme heat may ignite combustible materials or severely burn and
destroy living tissue  What may not be fully realized is that fires can also cause damage or
injury from a distance via transmission of thermal radiation, not unlike the manner in which
the sun warms the  earth. Such radiation, which  is completely different from  nuclear
radiation, will be strongest at the surface of a flame  and will become rapidly weaker as one
moves away in any direction.  Consequently, during a major hazardous  material release
involving fire, property damage and human injuries may occur not only in burning areas, but
also in a zone surrounding the fire.

     Thermal radiation levels (also referred to as thermal radiation fluxes) are measured and
expressed in units of power per unit area of the item receiving the energy.  However, since
the damage or injury sustained by a receiving object  is a function of the duration of exposure
as well as the level, thermal radiation dosages are also of concern  These dosages are
determined by combining radiation levels with exposure times and are expressed in units of
energy per unit time per unit area of receiving surface Table 4 2 lists some of the known
effects of thermal radiation on bare skin as a function of exposure level and time.

4.4 TYPES OF FIRES

      There are essentially six types of fires associated with hazardous material discharges,
with the type of fire a function not only of the characteristics and properties of the spilled
substance but the circumstances surrounding its release and/or ignition  The six types are'

      •     Flame jets

      •     Fireballs  resulting from  Boiling  Liquid Expanding  Vapor  Explosions
           (BLEVEs)

      •     Vapor or dust cloud fires

      •     Liquid pool fires

      •     Fires involving flammable  solids  (as defined by the U S Department of
           Transportation), and

      •     Fires involving ordinary combustibles
                                         4-6
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                               TABLE 4.2
            THERMAL RADIATION BURN INJURY CRITERIA
       Radiation Intensity
kW/m1
1
2
3
4
5
6
8
10
12
Btu/hr-ft2
300
600
1000
1300
1600
1900
2500
3200
3800
Time for Severe
Pain (sec)
115
45
27
18
13
11
7
5
4
Time for 2nd
Degree Burn (sec)
663
187
92
57
40
30
20
14
11
Data sources:
Buettner, K, "Effects of Extreme Heat and Cold on Human Skin, n
Surface Temperature, Pain and Heat Conductivity in Experiments with
Radiant Heat," J. Ap Phys., Vol. 3, p. 703,1951.

Mehta, A K., et al, "Measurement of Flammabihty and Burn Potential
of Fabrics," Summary report to the NSF under Grant #GI-31881, Fuels
Research Laboratory, Mass. Inst of Tech, Cambridge, Mass., 1973.
                                  4-7
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     Flame Jets

     Transportation or storage tanks or pipelines  containing gases under pressure (ie.,
compressed gases) or normally gaseous substances that have been pressurized to the point
they become liquids (i e., compressed liquefied gases) may discharge gases at a high speed if
somehow punctured or broken during an accident The gas discharging or venting from the
hole will form a gas jet that "blows" into the atmosphere in the direction the hole is facing,
all the while entraining and mixing with air. If the gas is flammable and encounters an
ignition source, a flame jet of considerable length may form (possibly hundreds of feet in
length) from a hole less than a foot in diameter  Such jets pose a thermal radiation hazard to
nearby people and property, and are particularly hazardous if they impinge upon the exterior
of a nearby intact tank containing  a flammable, volatile, and/or self-reactive hazardous
material. Such events sometimes occur during multi-car train derailments or in incidents  at
crowded chemical plants or oil/gas processing or storage facilities. In these cases, the heat of
the flame increases pressure in the intact tank while simultaneously weakening its outer wall.
This may eventually cause the tank to rupture violently or explode in an event referred to as a
BLEVE (see below), particularly if the flame impinges on the wall in the vapor space of the
container where there is no adjacent liquid to draw heat away from the wall surface. If the
contents of the intact tank are flammable, a large rising fireball may result  If the contents
are nonflammable but  toxic, a large amount of toxic vapors or gases may be suddenly
released to the atmosphere

     Fireballs Resulting from BLEVES

     Boiling Liquid Expanding Vapor Explosions (BLEVEs) are among the most feared
events when sealed tanks of liquid or gaseous hazardous materials are exposed to  fire.
Although they are called explosions, they are not associated with strong blast waves in many
cases.  Rather, they involve the violent rupture of a container of flammable material and the
rapid vaporization of the material  If the substance is flammable, a large rising fireball may
form, the size of which will vary with the amount of hazardous material present, and which
may be as much as 1,000 feet in diameter when involving a railroad tank car containing a
flammable liquefied compressed gas like liquid propane or LPG Although the fireball  is
generally of short duration, the intense thermal radiation generated can cause  severe and
possibly fatal burns to exposed people over relatively considerable distances m a matter of
seconds. In addition, if the tank is relatively long and cylindrical in shape, part of the tank
may literally "rocket" into the air,  all the while spewing forth burning  gases and liquids.
Pieces of such tanks have been known to travel up to 5,000 feet in BLEVEs involving
railroad tank cars.  Fires and various impact damages have occurred at the landing points of
larger pieces. (Note- Be advised that theie is potential for the tank to rocket upon rupturing
violently or exploding regardless of whether its contents are flammable or nonflammable)
                                         4-8
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     The phenomena leading to a BLEVE can occur with most hquids excessively heated in
a closed or inadequately vented container, whether they are flammable or not, or are pure
materials or mixtures,  unless other circumstantial factors are  considered. Two important
factors are the duration of the external exposure fire and the flow capacity of any pressure
relief valve if one is present  If the exposure fire is not of sufficiently long duration, or if the
relief valve can vent vapor as fast as it is generated, a BLEVE will not occur  An additional
factor is the availability of external cooling via fixed water  spray systems, fire monitors, hose
streams, etc. These can contribute to the prevention of a BLEVE either by suppressing the
external fire or by cooling the heated vessel  Finally, note that the possibility of a BLEVE
increases with the volatility of the  hazardous material Substances  with higher vapor
pressure at any given temperature are more at risk than those with lower vapor pressures

     Vapor or Dust Cloud Fires

     Vapors evolved from a pool of volatile liquid or gases venting from a punctured or
otherwise damaged container, if not ignited immediately, will form a plume or cloud of gas
or vapor that moves in the downwind direction. If this cloud or plume contacts an ignition
source  at a point at which its concentration is within the range of its  upper and lower
flammable limits, a wall of flame may flash back towards the source of  the  gas or vapor,
engulfing anything and everything in its path Similarly, fires may flash through airborne
clouds  of finely divided combustible dusts whether  or not they are formally classified as
hazardous materials. People or property caught within the cloud as the flame passes may be
severely injured or damaged if not protected

      Liquid Pool Fires

      A liquid pool fire is defined as a fire involving a quantity of liquid fuel such as gasoline
 spilled on the surface of the land or water. As in pnor cases, primary hazards to people and
property  include exposure to  thermal  radiation and/or toxic  or  corrosive products of
 combustion. An added complication is that the liquid fuel, depending on terrain, may flow
 downslope from the  accident  site and into sewers, drains, surface waters,  and other
 catchments. There have  been  cases where  such fires  have ignited other combustible
 materials in the  area  or have caused BLEVEs of containers  subjected to the flames On
 occasion, pools of burning liquids floating on water have entered water intakes of industrial
 facilities and caused internal fires or explosions.  Burning fuels entenng  sewers and drains
 not completely full of fluid have caused underground fires and/or threatened industrial or
 municipal treatment facilities at the receiving end of the sewer or drain.
                                         4-9
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     Flammable Solid Fires

     A flammable solid is defined by the U S  Department of Transportation as any solid
material, other than one classed as an explosive, which under conditions normally incident to
transportation is liable to cause fires through friction, retained heat from manufacturing or
processing,  or  which can be ignited readily and  when ignited burns so vigorously and
persistently  as to create a senous transportation hazard. Included in this class are sponta-
neously combustible and water-reactive materials

     As the above definitions suggests, the term  flammable solid encompasses materials
with a wide range of hazardous properties.

     •    Some of these solids are considered hazardous because they can be ignited by
          friction, much like the head of a match

     •    Some are organic materials such as charcoal, powdered coal, wet paper, and even
          fish scrap or fish meal which may at times internally generate heat to the point of
          self-ignition when improperly stored or transported.

     •    Some are metals in the form of powders or  other small pieces which can
          self-ignite in prolonged contact with moisture,  burn  at very high temperatures,
          and/or be difficult if not impossible  to extinguish without special techniques or
          materials, with aluminum and magnesium being good examples

     •    Some of these materials (i.e., pyrophonc substances) may ignite if exposed to air
          or burn vigorously in the fashion of highway flares. Phosphorus has both of these
          properties and also generates large quantities of toxic and irritating smoke.

     •    Some have several of these properties.

     Fires Involving Ordinary Combustibles

     Some hazardous materials, including some of the flammable solids described above,
burn with no special hazards beyond those associated with paper, wood, and other common
materials of everyday  life Wet paper waste, for  example, is only considered hazardous
because it may ignite spontaneously (i e, self-heat  and  self-ignite)  Once burning, it poses
no special or unusual  threat This is not meant to imply  that  such a fire would not be
significant or important to consider in planning for  emergencies, only that the nature  of the
threat is one encountered frequently by fire service personnel and well known to them.
                                       4-10
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4.5 PRODUCTS OF COMBUSTION

     Besides evolving heat and thermal radiation, fires involving certain hazardous materials
may generate smoke and gases that are  more toxic than those  evolved from ordinary
substances In most cases, the heat of a fire will cause these products of combustion to rise
into the sky  where they  will  become  diluted with  air below harmful  levels before
reapproaching the ground surface. On occasion, however, their toxicity level may be so high
as to necessitate public evacuations  until the fire has been extinguished  Indeed, a  1986
incident  in  Ohio involving the burning  of  phosphorus  in a railroad car required the
evacuation of at least 40,000 people  due to the toxic and  irritating smoke generated  This
was the largest evacuation associated with a train wreck in the history of the United States

     Material safety data sheets (MSDS)  and other data  bases and handbooks describing
individual substances will typically provide a general indication of expected  products of
combustion or thermal decomposition. The term "general" is used because far more often
than not the discussion will be rather imprecise and unlikely to highlight more than a few
rather common products of combustion or decomposition.

      In  the case of organic materials comprised solely of carbon, hydrogen, and oxygen,
products of combustion virtually always  include carbon dioxide and highly toxic carbon
monoxide together with water vapor and some amounts of unburned vapors of the hazardous
material Substances of low molecular weight (i e., simple hydrocarbons and alcohols), may
indeed  only  generate these products of  combustion when burning freely in the natural
environment  More complex and heavier substances, however, may generate a  complicated
mixture of substances,  some of which may be extremely toxic  A general  rule  of thumb to
follow is that most strictly  organic materials usually pose no more hazard when burning
(although the hazard may indeed be very significant) than a burning wooden home or other
building  The key exception involves fires involving organic materials of high toxicity in the
unburned state, with pesticides being primary examples. Fires involving such materials may
be particularly hazardous not only due to toxic combustion products but due to  the potential
dispersion of unburned pesticides.

      One can obtain a general idea of unusual products of combustion or decomposition by
looking at the chemical formula for any particular hazardous material of concern, this being
an item almost always  given  in MSDS  and other safety related  publications for  pure
materials. Some of the more common symbols used for various individual components (i.e.,
elements) of chemical molecules include:
                                         4-11
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Element
Bromine
Carbon
Chlorine
Fluorine
Hydrogen
Lead
Mercury
Nitrogen
Oxygen
Phosphorus
Sulfur
Chemical Symbol
Br
C
Cl
F
H
Pb
Hg
N
O
P
S
     Hazardous materials containing bromine, chlorine, or fluorine, if subject to combustion
or decomposition in a fire environment, may generate irritating and corrosive substances
such as hydrogen bromide or hydrobromic acid, hydrogen chloride or hydrochloric acid, or
hydrogen fluoride or hydrofluoric acid, and possibly gaseous bromine, chlorine or fluorine
themselves. The extremely toxic substance known as phosgene may be formed in some cases
when chlorine is present, particularly in combination with oxygen in the chemical molecule,
so it is important to check for this possibility in MSDS and other information sources

     Both lead and mercury are well-known toxic metals that can be found as components
of numerous chemical substances. Smoke or fumes from fires involving these toxic heavy
metals and others  (such as arsenic), must always be of concern.

     Although pure nitrogen gas is non-toxic and a major component of air, chemical
molecules containing nitrogen atoms may evolve toxic nitrogen oxides under fire conditions.
The combination of carbon with nitrogen in  a  -CN  group within a chemical molecule
suggests that highly toxic cyanides may be generated in fires

     Dry phosphorus may ignite upon contact with air and generate thick white smoke
containing phosphoric acid and  phosphorus pentoxide.  As noted earlier, this smoke is both
highly irritating and highly toxic.
                                       4-12
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      5.0 EXPLOSION HAZARDS OF CHEMICAL SUBSTANCES
5.1 DEFINITIONS

     The dictionary contains two definitions of the word explode relevant to hazardous
materials, these being

   •    To burn suddenly so that there  is violent expansion of hot gases with great
        disruptive force and a loud noise (in what is called a thermal explosion).

   •    To burst violently as a result of pressure from within (in  what is  called a
        non-thermal explosion).

     The first definition clearly involves ignition  and release of thermal energy from an
explosive material or mixture while the second does not  In the following, we first discuss
the conditions and  factors that define the potential for both  thermal and non-thermal
explosions, follow with a discussion of how the effects of explosions can be measured, and
then discuss the various types of explosions which meet the above criteria and which may be
encountered in accidents involving hazardous materials
 image: 








5.2 FACTORS THAT INFLUENCE EXPLOSION POTENTIAL

      Thermal Explosions

      The definitions of lower and upper flammability limits presented earlier explained that
these terms are used interchangeably with the terms lower and upper explosive limits in air.
The reason for this is that a flammable mixture of a gaseous fuel in air, i e, a mixture within
the range of lower and upper flammable limit concentrations, may explode if ignited under
appropriate conditions. Similarly,  a cloud  of  combustible dust may explode if airborne
concentrations are within these limits and the cloud is confined

      The set  of conditions under which explosions of gases or vapors are most common
involves ignition within the confined space of a building, sewer pipe, tunnel, partially empty
liquid storage tank (on land or on a marine vessel), or other container. Dust explosions have
frequently occurred in grain handling facilities and storage silos as well as other locations
where fine combustible dusts are handled or generated.

      It follows from the above that virtually all substances that are handled under conditions
in which fuel-air mixtures  are within explosive or flammable limits and  fill a significant
fraction of an enclosed space have a high probability of exploding rather than simply burning
upon  ignition.  However, it must also be leahzed that gaseous mixtures may also explode at
times when only partially confined or even if completely unconfined in an open environment
These latter explosions, referred to as unconfined vapor cloud explosions, often have far less
power than explosions in confinement, and it has been  observed that some substances have a
far greater probability of exploding when unconfined than others Nevertheless, past events
have  proven that unconfined explosions can occasionally cause devastating damage and
widespread injuries, especially when the weight of airborne gas or vapor exceeds 1000 Ibs
Below this weight, unconfined vapor cloud explosions are quite rare and typically involve a
relatively few specific materials.

      There also are many solids and liquids which  may explode or detonate if ignited,
shocked, or subjected to heat or  friction,  depending on  their individual properties and
characteristics. Some  of the  best known examples are TNT, dynamite,  gunpowder, and
nitroglycerine  which may be referred to at times as  condensed-phase  explosives or high
explosives Determination of whether any particular liquid or solid may be explosive, and
the conditions  under which it may  explode, requires investigation on a case-by-case basis,
since  there is  no specific property  or characteristic that sets explosives apart from other
materials Fortunately, manufacturers of these materials and hazardous  matenal data bases
and guidebooks will usually highlight the explosive properties of such materials

      The power or strength of a thermal explosion, however one wishes to express it, is a
function of three primary factors:
                                          5-2
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     •    The amount of fuel present that is capable of exploding

     •    The amount of energy available in this portion of the fuel

     •    The fraction of the available energy (known as the yield) expected to be
          released in the explosion process.

     In simpler terms, it is understandable that two sticks of dynamite produce a larger blast
than one stick, that fuel-air mixtures above or below explosive limit concentrations in air
may not give additional strength to an explosion, and  that some  substances contain more
energy per unit weight than others

     Non-thermal Explosions

     The most simple type  of  non-thermal  explosion to understand  is  that  due to
overpressunzation of a sealed or inadequately vented  container of some sort. Much  as a
balloon will burst if too much air is blown in, the walls of a sealed tank or other container
may rupture violently if too much gas or liquid is forced in, if an internal chemical reaction
produces excessive gases or vapors, or if a reaction or other source of heat increases the
internal vapor pressure of the contents to the point that the walls are "stretched" beyond their
breaking point. Since ignition and fire are not involved in the actual explosion process, these
events are considered non-thermal explosions, although the  contents of the container  may
ignite subsequent to its release if a suitable  ignition source is present and the substance is
flammable or combustible.

      The strength of a non-thermal tank overpressunzation explosion is a function of the
pressure at which the walls of the container burst and the nature of the walls (i e, whether
they are brittle and will break suddenly with a "snap" or are ductile  and more likely to stretch
and then split or tear along some line on the surface). If the tank contains gas under pressure,
the volume of the gas in the tank will also be important.

      A final note is that non-thermal explosions involving compressed gases or vapors are
far more likely to cause damage to distant objects than those involving liquids This follows
from the definition of shock and blast waves presented below and the relatively incompress-
ible nature of liquids.

5.3 MEASURES OF EXPLOSION EFFECTS

      When  a firecracker or a stick of dynamite explodes,  the violence and speed of the
reactions taking place produce what is either referred to  as  a shock wave or a blast wave.
Technically  speaking, there is a difference between these two terms, but we will treat  them
rather interchangeably here. Either type of wave can be thought of as a thin shell of highly
                                         5-3
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compressed air and/or hot gases that rapidly expands in all directions from the point at which
the explosion is initiated Such waves can move at velocities exceeding the speed of sound
in air, and, therefore, are capable of producing sonic "booms," much like  those associated
with supersonic aircraft. This is why significant explosions produce a loud "bang "

      The damage caused by a shock or blast wave striking an object or a person is a
complex function of many factors, and it is well beyond the scope of this document to
attempt to describe all the complex interactions involved.  Instead, we will simply refer to the
wave as a rapidly expanding shell of compressed gases  The strength of the wave can then be
measured in units of pressure (psi, e g), and the effects of peak overpressures within the
wave (i.e., the maximum pressure in the wave in excess of normal atmospheric pressure) can
be related to the level of property damage or personal injury likely to result

      Table 5.1 presents a list of peak overpressures and their expected effects on people and
property. It is important to note that peak overpressures in a shock or blast wave are highest
near the source of the explosion and decrease very rapidly with distance from the explosion
site. Additionally, it must be noted that the location of the blast relative to nearby "reflecting
surfaces" will influence the extent of damage incurred. For example, picture an explosion
that takes place well above the surface of the ground. In this type of elevated or "free-air"
event, the spherical shock wave has the opportunity to travel and dissipate in all directions
simultaneously. Conversely, if the same explosion were to take place directly on the ground
surface, the major portion of the energy released would only dissipate upwards and outwards
The ground surface would reflect most energy directed downward, and the  net result would
be  a blast  or shock wave  with approximately  twice  the strength  expanding from a
hemi-sphencal shaped volume of space situated on the ground Hazard analysis procedures
discussed in Chapter 12 and  Appendix B of this guide and incorporated into the ARCHIE
Computer Program therefore consider  the location of an explosion relative to the ground
surface. Not considered, however, are potential reflections from building  walls  and other
surfaces that may cause actual  damage patterns to be somewhat more erratic  than those
predicted by generalized hazard assessment methodologies for explosion events

      Beside  personal  injuries and property  damage caused by direct exposure to peak
overpressures, the blast or shock wave also has the potential to cause indirect impacts.  These
secondary effects of explosions include:

    •    Fatalities or injuries due to missiles, fragments, and environmental debns  set in
        motion by the explosion or by the heat generated.

    •    Fatalities  or injuries  due to forcible movement of exposed people  and their
        subsequent impact with ground surfaces, walls, or other stationary objects
                                         5-4
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                                            TABLE 5.1
                        EXPLOSION OVERPRESSURE DAMAGE ESTIMATES
Overpressure*
(psig)
003
004
010
015
030
040
050-10
07
10
10-20
10-80
13
20
20-30
23
24-122
25
30
30-40
40
50
50-70
70
70-80
90
100
14 5-29 0
Expected Damage
Occasional breaking of large windows already under stress
Loud noise (143 dB), sonic boom glass failure
Breakage of small windows under strain
Typical pressure for glass failure
Some damage to house ceilings, 10% window glass breakage
Limited minor structural damage
Windows usually shattered, some window frame damage
Minor damage to house structures
Partial demolition of houses, made unmihabitable
Corrugated metal panels fail and buckle Housing wood panels blown in
Range for slight to serious injuries due to skin lacerations from flying glass and other missiles
Steel frame of clad building slightly distorted
Partial collapse of walls and roofs of houses
Non-reinforced concrete or cinder block walls shattered
Lower limit of serious structural damage
Range for 1-90% eardrum rupture among exposed populations
50% destruction of home brickwork
Steel frame building distorted and pulled away from foundation
Frameless steel panel building ruined
Cladding of light industrial buildings ruptured
Wooded utility poles snapped
Nearly complete destruction of houses
Loaded tram cars overturned
8-12 in thick non-reinforced bnck fail by shearing of flexure
Loaded tram box cars demolished
Probable total building destruction
Range for 1-99% fatalities among exposed
populations due to direct blast effects
*These are the peak pressures formed in excess of normal atmospheric pressure by blast and shock waves

Source Lees J'P, Loss Prevention m the Process Industries. Vol 1, Butterworths, London and Boston, 1980
                                               5-5
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     The most common injuries due to missiles and the like are attributable to violent glass
breakage  and impact of  airborne shards of glass with people. Fragments  may  include
portions of any container  that explodes and pieces of structures or equipment that are torn
loose by the explosion and become airborne. Environmental debris essentially covers all else
that may be forced out of place The entire category can also be considered to encompass
situations in which people  are buried in the rubble of collapsed buildings or other structures.

     It is very important to realize that a tank that BLEVEs or otherwise ruptures violently
may break  up into various  fragments, one or more of which may  be projected  for
considerable distances  Portions of cylindrical tanks have been  known to literally "rocket"
into the air while spewing forth burning liquids and have caused fires and impact damages
upon falling back to the ground.

     Where railroad tankcars or highway tank vehicles  are at nsk, hazardous material
response guides have typically  suggested that  a radius of one-half mile be  evacuated to
prevent injuries from both fragment and thermal radiation  hazards  Recent incidents have
indicated, however, that individual fragments may occasionally travel as far as 4000-5000
feet from a tankcar BLEVE, and it is therefore prudent to evacuate to a radius of one mile in
such cases,  if this is practical  Since railroad tankcars carry 2-4 times  as much cargo as
typical highway tank vehicles, the one-half mile radius improbably sufficient for major truck
accidents, but this is not absolutely certain for all cases

     The  evacuation  distances required  for  smaller  or  larger  tanks than typically
3,000-12,000 gallon highway vehicles or 20,000-30,000 gallon capacity railroad tankcars
will vary somewhat with the quantity of hazardous material present, but not as much as one
might think. At the lower  end of the scale, one major authority suggests a 1500 ft evacuation
radius for situations in which an ordinary gas cylinder is involved in fire.  Limited data for
explosions or BLEVEs involving major  stationary storage  tanks  do not indicate fragment
hazards beyond one mile in the majority of known cases.

     Where a tank or container ruptures violently  due  to internal overpressunzation,
fragment hazards are to some degree a function of whether the wall materials are battle or
ductile. Brittle materials (such as glass) may shatter into many  smaller pieces  Tanks or
containers made of ductile materials (such as most metals at or above  relatively normal
temperatures) are more likely to split or tear into a few large pieces

     Fatalities or injuries  due to forcible movement of exposed people and then- subsequent
impact with objects quite literally involves situations in which the shock or blast wave pushes
or picks up and throws bodies against obstacles
                                          5-6
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5.4 TYPES OF EXPLOSIONS

     Many of the basic types of explosions have already been described, but there are
benefits in listing them again and providing more formal definitions of terms.

     Container or Tank Overpressurization Explosions

     As noted earlier, these events are a result of excessive pressure within a sealed tank or
other container and are deemed to be non-thermal explosions  They occur when excessive
pressure causes the walls of  a tank or container to rupture violently, much as a balloon
"pops" when too much air is blown in.

     Dust Explosions

     A cloud of combustible dust that is airborne and has concentrations within its upper
and lower explosive limits may explode when  ignited Explosions usually occur when the
dust fills most of an enclosed space of some kind.

     An earlier discussion of fire hazards described how non-exploding clouds of dust in air
may simply burn in a dust cloud fire that can also be referred to as a deflagration It is
important to realize that there is no fine line between a deflagration and an explosion, since
deflagrations are also capable of producing  shock waves with measurable peak overpres-
sures.  It is usually when these overpressures  become significant to  the point of causing
damage or injury that the event is called an  explosion It is when the shock or blast wave
moves at a velocity greater than the speed of sound under the conditions present, thus being
capable of causing maximum damage, that the event may be called a detonation

     Gas or Vapor Explosions

     As in the case of  airborne dusts, a  gas or vapor within flammable or explosive limit
concentrations may cause a  deflagration, explosion,  or detonation upon ignition. These
events can occur when  the fuel-air mixture is confined, partially confined, or completely
unconfined, but confinement  of the mixture most definitely  increases the probability  of
significant personal injury or property damage  Note  that the gas or vapor may be directly
released to the vulnerable environment or may evolve from evaporating or boiling liquids
that have entered the area
                                         5-7
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     Condensed-Phase Explosions or Detonations

     As noted above, when the substance that explodes or detonates is a liquid or a solid, the
event is often called a condensed-phase explosion or detonation  Those who use this term
may be prone to call events involving gases or vapors in air as diffuse-phase or gas-phase
explosions or detonations.

     Boiling Liquid Expanding Vapor Explosions (BLEVEs)

     BLEVEs were described in some detail in the prior section discussing fire hazards of
concern, where it was stated that they are not associated with strong shock or blast waves in
many cases. Obviously, this also means that shock or blast waves with sufficient power to
cause injury or damage may indeed occur at times.

     Although some experts may disagree with the fine points of what is being said,
BLEVEs can also be described as a combination of other types of fires  and explosions.
Indeed, bursting of a tank of liquid or compressed liquefied gas due to overheating is related
to tank or container overpressunzation explosions. Subsequent ignition of expanding gases,
which may result in a large fireball, can be thought of as resulting in one type of gas or vapor
cloud deflagration.
                                         5-8
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       6.0 TOXICITY HAZARDS OF CHEMICAL SUBSTANCES
6.1  INTRODUCTION

     Although hazardous materials  can pose both short-term  and possibly long-term
lexicological threats to terrestrial and aquatic wildlife and plants, the immediate concern
during significant discharges is protection of human life and health Consequently, this
section addresses the toxicity and toxic hazards posed to the public by chemical substances
It must be noted, however,  that much of what will be presented can also be applied to
understanding lexicological hazards to plants and animals

62  ROUTES OF ENTRY

     Toxic materials, be they solids, liquids, or gases/vapors, can affect living creatures via
three primary routes of entry.

     •    Inhalation -- the process by which irnlanls or loxins enter ihe body via the
          lungs as a resull of the respiratory process
          Ingestion — the process of consuming conlaminaled food  or water or
          olherwise permitting oral inlake of imlanls or loxins
 image: 








     •     Direct  contact  with skin or eyes  ~  the  process  by which hazardous
           materials cause injury to bodily tissues  via direct contact 01 cause poison-
           ing via absorption through the skin or other external  tissues Also included
           in this category is the passage of toxic materials into the body via puncture
           wounds or other breaks in the skin

     Inhalation exposures  may result from breathing gases vented from containers, vapors
generated from evaporating liquids  (on land or in  water), liquid aerosols generated dunng
venting of pressurized liquids, fumes generated from spilled acids, gases or fumes generated
by chemical reactions, dusts that become airborne due to an explosion or due to wind forces,
the products  of  combustion  of a  burning hazardous  material, or  a  variety  of other
mechanisms.

     Ingestion (i e., oral) exposures may follow from poor hygiene practices after handling
of contaminated materials or from ingestion of contaminated food or water.  Ingestion may
also occur following inhalation of insoluble  particles  that become  trapped  in  mucous
membranes and swallowed after being cleared from the respiratory tract

     Direct contact may result from exposures to  hazardous gases, liquids or solids in the
environment, either  on land,  in the  air, or  in water  Effects  may  be local and involve
irritation or burns  of the skin or eyes or involve poisoning via  absorption through external
bodily tissues.

     The fact that a toxic chemical can cause harm by inhalation, mgestion, or irritation or
burning of the skin or eyes is probably well appreciated by  most people  Poisoning due to
absorption through external bodily tissues, however,  is not as well known a  hazard and
benefits from further explanation.

     In  simple terms, there are various specific  gases, liquids,  and even solid materials
which have the capability of passing thiough the skin or tissues of the eyes at various rates
upon contact  Those that are highly toxic and which penetrate the body rapidly are the most
hazardous Those that penetrate slowly or which are of relatively low toxicity may require
long term contact  with large parts of the body to cause significant effects. Although some
materials may give some warning that contact has occurred by causing some sort of burning
sensation, others may give little or no warning to the victim.

     While on this topic, it is also worthwhile to consider the commonly accepted meaning
of phrases hke high toxicity and low toxicity  When one speaks of a material that is of high
toxicity, it generally means that relatively small  quantities may cause  significant health
effects upon inhalation, ingestion, and/or direct contact  Conversely, a low toxicity substance
generally requires larger amounts  to be inhaled, ingested, or contacted for  an equally
significant adverse health effect  It is therefore well to always remember that a large quantity
                                          6-2
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of a low toxicity material may present the same or greater toxic hazard to a community or
individual than a much smaller quantity of a highly toxic material. It is also necessary to
understand that the toxicity of a material is only one of several factors to be considered in
determining the toxic hazard posed  by the material. These concepts  are  reiterated and
discussed in further detail in a later section.

6.3 TYPES OF TOXIC EFFECTS

     Most  toxic substances can be  classified  as  irritants,  asphyxiants, anesthetics and
narcotics, systemic poisons, sensitizers, carcinogens, mutagens, and/or teratogenic  sub-
stances.  Systemic poisons may be further disaggregated into the categones  of hepatotoxic
agents, nephrotoxic agents, neurotoxic agents, agents which act on the blood or hematopoiet-
ic system, and agents which damage the lung.

     Many of these  terms  may be  unfamiliar because  they are mostly used  in  the
medical/public health community and among lexicologists. Fortunately, they need not all be
memonzed  because  most hazardous material data bases and guides, material safety  data
sheets,  and manufacturers'  product  bulletins generally "translate" the effects  of toxic
materials upon the body into more common language. There are, however, certain terms and
expressions that appear  frequently  and which can be helpful in understanding the most
common effects of toxic materials upon the body.

     Irritants

     Irritants are substances with the ability to cause inflammation or chemical burns of the
eyes, skin, nose,  throat,  lungs, and other tissues of the body in which they may come in
contact.  Some substances such  as strong acids  (eg, sulfunc acid, oleum,  chlorosulfonic
acid, hydrochloric acid, hydrofluoric acid, or nitric acid) may be irritating to the point of
being corrosive when concentrated, and may quickly cause second or third degree chemical
burns upon contact with the skin or eyes.  If inhaled as a gas, vapor, fume, mist, or dust, they
may cause  severe lung  injury,  and if ingested, can  senously damage the  mouth, throat,
stomach, and/or intestinal tract.  Yet other irritants may have milder effects and may  only
cause reddening of the skin or eyes after contact.

      Some of the most common irritants are organic solvents or hydrocarbon fuels which
can dissolve natural oils ui the skin and cause dermatitis. After repeated or  prolonged
contact, these will dry the  skin to the point that it may become cracked, inflamed and
possibly infected. These same materials often cause irritation of the eyes and possibly loss
upon contact of the cornea! epithelium, a clear thin membrane that covers the surface of the
cornea. Although the effect is temporary, since the epithelium will usually regrow in a few
days, some data sources may refer to the effect as a "cornea! burn."
                                         6-3
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     Entry into the lungs of many kquid hydrocarbons and some organic liquids that are
irritants may cause chemical pneumonia or pneumonitis together with pulmonary edema
(filling of the lungs with fluid), hemorrhage, and tissue necrosis (i e., death of living tissue)
Since entry of liquids into the lungs usually involves aspiration when a victim who has
accidentally ingested the substance vomits, the first aid instructions for such substances
typically recommend against intentional inducement of vomiting. They also are likely to
mention that the effects of aspiration into the lungs may not appear for several hours or even
days after the exposure has taken place

     Asphyxiants

     Simple asphyxiants are typically non-toxic gases that may cause injury by inhalation
only if they are present hi air in such high concentrations that they displace and exclude the
oxygen needed to maintain consciousness and life A good example is nitrogen, a gas that
makes up about 78% of the air we breathe and which is perfectly harmless at this level as a
component of  air. If additional nitrogen or another such simple asphyxiant were added to the
air to the point that the normal oxygen concentration of approximately 21 percent by volume
was significantly  reduced, however, the situation could become life-threatening Tables 6 1
and 6.2 illustrate the effects  of oxygen depletion  on the body and the  four  stages of
asphyxiation.

     Chemical asphyxiants are substances that in one way or another prevent the body from
using the oxygen it takes in and are often highly toxic substances. One classic example is
carbon monoxide which combines with and "ties up" the component of blood (hemoglobin)
that transports oxygen from our lungs to other organs If too much of the hemoglobin
becomes unavailable for carrying oxygen, a person may pass out and eventually die  Other
examples are among the family of cyanides (i e, substances which have a -CN, carbon-nitro-
gen, combination in their molecule and which somewhere in their names have the word
"cyanide" or the  letter combinations "cyan" or "nitrile"). These  act by interfering with the
action of the enzymes necessary for Irving tissues to use available oxygen, thus resulting in a
condition referred to as cyanosis.

     Anesthetics and Narcotics

      Numerous  hydrocarbon  and organic  compounds classified as hazardous  materials,
including some alcohols, act on the body by depressing the central nervous system (CNS)
Early symptoms  of exposure to these substances include dizziness, drowsiness, weakness,
 fatigue, and incoordination. Severe exposures may lead to unconsciousness, paralysis of the
 respiratory system, and possibly death
                                         6-4
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TABLE 6.1
EFFECTS OF OXYGEN DEPLETION
Percent of Oxygen
In Air
20
17
12 to 15
10 to 12
6 to 8
6 or below
Symptoms
Normal
Respiration volume increases, muscular coordination diminishes,
attention and clear-thinking requires more effort
Shortness of breath, headache, dizziness, quickened pulse, efforts
fatigue quickly, muscular coordination for skilled movements lost
Nausea and vomiting, exertion impossible, paralysis of motion
Collapse and unconsciousness occurs.
Death in 6 to 8 minutes
Source   Kimmerle, George, "Aspects and Methodology for the Evalution of Toxicological
         Parameters During Fire Exposure," JFF'/Combustion Toxicology, Vol. 1, February,
         1974
TABLE 6.2
FOUR STAGES OF ASPHYXIATION
1st Stage
2nd Stage
3rd Stage.
4th Stage:
21-14% oxygen by volume, increased pulse and breathing rate with
disturbed muscular coordination.
14-10% oxygen by volume, faulty judgment, rapid fatigue, and
insensitivity to pain
10-6% oxygen by volume,nausea and vomiting, collapse.and perma-
nent brain damage
Less than 6% by volume, convulsion, breathing stopped, and death
Source   Cryogenics Safety Manual, Bntish Cryogenics Council, London, 1970
                                           5-5
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     Sensitizers

     A few hazardous materials are sensitizers and cause sensitization. What this means is
that some people who are exposed to one of these materials may not be abnormally affected
the first time, but may expenence significant and possibly dangerous effects even in the
presence of very low levels of the contaminant if ever exposed again.  In simple terms,
victims become extremely allergic to the material and possibly others of a similar nature
     Other Types of Toxic Agents

     •     Hepatotoxic agents are materials that cause liver damage

     •     Nephrotoxic agents are materials that cause kidney damage

     •     Neurotoxic agents are substances that in one way or another impact the
           nervous system and possibly cause neurological damage.

     •     Carcinogens are substances that may incite or produce cancer within some
           part of the body.

     •     Mutagens can produce changes in the genetic material of cells.

     •     Teratogenic materials may have adverse effects on sperm, ova, and/or fetal
           tissue.

 Note: Besides the chemical asphyxiants described above, there are other  substances that in
 one way or  another  act on the blood or the hematopoietic system (i.e.,  bone marrow).
 Inhalation of free silica or asbestos  over a period of time can cause changes in lung tissue
 with serious  health consequences Yet other toxic substances also have unusual or unique
 effects on human health.

 6.4 ACUTE VS. CHRONIC HAZARDS

      The majority of industries and many common daily activities of life  utilize equipment,
 processes, and materials that continuously or intermittently discharge toxic materials into the
 occupational and/or natural environment  Some workers may be exposed to such materials 8
 hours per day, 5 days per week or so, over a large part of their careers.  Similarly, the general
 public  may  be  exposed to various contaminants continuously or  intermittently. Such
 exposures are said to be of a chronic nature  and usually but not  always  involve low
 concentrations of contaminants in air, food, water, and/or soil.
                                          6-6
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     When a major accident or other rare event causes a significant spill or discharge of a
toxic material into the environment, the general public or nearby workers may be exposed to
relatively high levels of one or more toxic contaminants until such time as they escape or are
rescued from contaminated locations or the contaminant becomes diluted below hazardous
levels. These short-term, rare exposures  (in the sense there will be long periods of time
between repeated exposures if they reoccur at all) are referred to as acute exposures Not all
acute exposures, of course, need involve high concentrations of toxic materials  A small spill
or discharge may produce low levels of contamination yet still be of an acute nature

     To be noted is that many chemicals will not persist for long periods of time in the
environment, or at least in those parts of the environment of concern, while others may
remain present for weeks, months, or even years. The former materials include substances
that may be digested by bacteria (i e, which are biodegradable), substances that will undergo
various reactions with materials in the environment that render them harmless, or those that
become so diluted in air or water that they no longer present a hazard  Examples are simple
alcohols that may be digested by bacteria in soil or water much as humans drink and digest
alcoholic beverages, as well as volatile materials which evaporate and are swept away into
the vast ocean of air above us. Such materials are unlikely to pose long-term  chronic hazards
in the event of a major spill or discharge in most cases Alternatively, toxic substances which
are relatively inert and which do not degrade, react, vaponze, or dissolve freely may pose
health hazards for extended periods of time within a localized environment and may require
additional planning to address long-term chronic exposure hazards to the public Examples
include heavy metals and various chlorinated hydrocarbons such as DDT, tnchloroethylene,
and PCBs

6.5 IMPORTANCE OF EXPOSURE LEVEL AND DURATION

     In considering the effects of toxic  exposures,  it is necessary to understand that  the
duration of an exposure can be as important as the level  of exposure in determining  the
outcome  This follows from the observations that:

     •     The body has a capacity to cope with the intake of many contaminants at a
           certain rate Below a certain threshold rate of intake or absorption which
           can be counterbalanced by the body's ability to excrete or somehow convert
           the contaminant to a harmless substance,  toxic effects may be minimal or
           non-existent  For example, note that arsenic is commonly found in  all
           human bodies at low levels. It is only when the level  exceeds the safe
           threshold due  to excessive  intake that symptoms  of  toxicity become
           apparent.
                                        6-7
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     •     The rate at which a contaminant enters the body by inhalation is a function
          of the concentration of the contaminant in the air being breathed, the rate of
          breathing, the  length of time the body  remains within a  volume  of
          contaminated air, and the specific properties of the contaminant. Higher
          concentrations in air obviously lead to higher rates of intake or absorption
          into bodily tissues.

     •     The potential  for toxic effects via skin absorption is  a function of the
          amount of toxic material that contacts the body, the properties of the
          material, and the length of time it is permitted to remain in contact

     •     Toxic effects via ingestion can also be a function of the amount or rate of
          intake over a period of time. Small doses of certain poisons ingested hours
          or days apart may not be harmful, but taking the total amount all at once
          may be deadly. Other poisons may accumulate in the body such that small
          doses taken over time may buildup to a fatal dose.

     The reason that chronic exposure to low levels of toxic materials commonly found in
the environment does not often cause widespread health problems is that the rate of intake is
below the threshold at which health effects become apparent  Conversely, major spills or
discharges of  toxic materials may pose a significant threat to public health because  the
resulting contaminant concentrations in the local area may be so high that only a moment or
two of exposure is  sufficient to produce severe health problems due to an excessive body
burden  of contamination. This is particularly true where large amounts of toxic gases or
vapors are released into  the  air. Relatively  few members of the general public are ever
harmed by direct contact with toxic materials, since most individuals have the common sense
not to touch or go walking through spilled chemicals and will cleanse themselves promptly if
such contact is made.  Similarly, few people are likely to drink potentially contaminated
water or eat contaminated food once warned of the possibility of contamination  Most at risk
in such situations are emergency response personnel who enter contaminated areas without
adequate personnel protective clothing  and  respiratory devices  in attempts to contain or
otherwise mitigate the impacts of the spill

6.6 TOXICITYVS. TOXIC HAZARD

     The observations above naturally lead to a further discussion of the difference between
the toxicity of a substance and the toxic hazard it poses to the public This is an extremely
important concept because materials of high toxicity are often assumed to pose a severe toxic
hazard regardless of the other properties of the material and the  circumstances surrounding
its spillage.
                                          6-8
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      Imagine a one ton discharge of two different materials. The first is an extremely toxic,
non-volatile solid material that has spilled in the middle of a street in a densely populated
metropolis. The material is so extremely toxic that only 10 pounds would be sufficient to kill
100,000 people by mgestion if somehow introduced into their food in equal portions. The
second discharge involves an overturned tank truck on the same street that has just released a
very common compressed liquefied gas that is considered to be of moderate toxicity. As it
boils and vaponzes upon release, the ton of liquid may become as much as 30,000 cubic feet
or more of pure gas  If it were to mix uniformly with air and happened to be deadly in very
short-term exposures at a concentration of 5,000 ppm in  air, the potentially lethal cloud
spreading over the city would conceivably have a total volume of 6 million cubic feet

      On a strictly weight basis, the solid material may be many thousands  of times more
toxic than the gas, but is unlikely to poison members of the public just a short distance away
because it lacks mobility Thus,  the solid must be carefully handled and removed from the
scene, but actually poses a relatively low toxic hazard to the public  Authorities may wish to
evacuate the  immediate spill area and cover the solid with plastic sheeting to prevent any
dust from becoming airborne until its careful recovery, but the risk of fatalities among the
general public will be low in most cases.

     The situation with the lower toxicity liquefied gas poses a greater toxic hazard because
the gas will quickly spread over downwind areas.  The gas may prove rapidly fatal to people
near the spill site and cause toxic effects among many  hundreds or thousands of others in the
downwind direction.

     The moral of this story  is that the toxic hazard posed by a material is not a sole
function of its toxicity.  One must always consider the amount of material present or spilled,
the properties of  the substance,  and the  opportunity  it has to affect the population in its
vicinity.

6.7 RECOGNIZED EXPOSURE LIMITS FOR AIRBORNE CONTAMINANTS

     It should be fairly clear by this point that discharges of  gases  and vapors  into  the
atmosphere generally pose greater toxic hazards  to people than  discharges of non-volatile
materials  As is widely appreciated, one of the key tasks in planning for hazardous materials
emergencies  involves  preparations  for identifying,   notifying,  evacuating,  sheltering, or
otherwise protecting populations that may be exposed to such gases and vapors

     Achievement of the above goal requires planning personnel to select the airborne
concentration in air that can be tolerated by exposed populations while toxic vapors or gases
remain in the immediate area, since it is this concentration that will determine the boundaries
of the hazard zone. This, in turn, requires knowledge of the source and nature of commonly
                                          6-9
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available and accepted exposure limits for airborne contaminants as well as their various
advantages and disadvantages for the intended use  Primary data sources to be considered
include:

          ACGIH Threshold Limit Values (TLVs)

     •    OSHA Permissible Exposure Limits (PELs)

     •    AIHA Workplace Environmental Exposure Limits (WEELs)

     •    NIOSH Immediately Dangerous to Life or Health Levels (IDLHs)

     •    AIHA Emergency Response Planning Guidelines (ERPGs)

     •    NAS/NRC Emergency Exposuie Guidance Levels (EEGLs) and Short-term
          Public Emergency Guidance Levels (SPEGLs)

     ACGIH TLVs

     The American Conference of Governmental Industrial Hygiemsts (ACGIH) formed a
committee in 1941 to review available data on toxic compounds and to establish exposure
limits for employees working  in the  presence of airborne toxic agents  The committee
continues to this  day to publish an annual  list  of several hundred  compounds  and
recommended exposure limits in a booklet titled Threshold Limit Values and Biological
Exposure Indices. Copies of the latest edition were available for $5 in late 1988 from the
ACGIH at 6500 Glenway Ave, Bldg D-7, Cincinnati, Ohio 45211 or (513) 661-7881.

     The primary purpose of the exposure limits adopted by the ACGIH is to protect healthy
male workers in chronic exposure situations and the ACGIH specifically notes that  "These
limits are not fine lines between safe and dangerous concentrations nor are they a relative
index oftoxicity, and should not be used by anyone untrained in the discipline of industrial
hygiene." Nevertheless,  the information provides valuable guideposts for identifying expo-
sure limits that will usually be decidedly safe for short-term acute exposures

      Exposure limits established and published by the ACGIH are of several different types
 and include:

           Threshold Limit Value - Time Weighted Average (TLV-TWA). The time
           weighted average concentration for a normal 8-hour workday and a 40-hour
           workweek, to  which nearly all workers may be repeatedly exposed, day
           after day, without adverse effect
                                         6-10
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          Threshold Limit Value-Short Term Exposure Limit (TLV-STEL)  A
          time-weighted average concentration to which workers should not be
          exposed for longer than 15 minutes and which should not be repeated more
          than four times per day, with at least  60 minutes between successive
          exposures  This limit supplements the TLV-TWA where there are recog-
          nized acute effects from a substance whose toxic effects are primarily of a
          chronic nature. STELs are recommended only where toxic  effects have
          been reported from high short-term exposures in either humans or animals

          Threshold Limit Value-Ceiling (TLV-C):  The concentration in air that
          should not be exceeded during any part of the working exposure Ceiling
          limits may supplement other limits or stand alone.

     In addition to the above limits, the ACGIH occasionally enters the notation "skin" after
listed substances. This notation indicates the potential for  absorption of the  substance
through the skin, eyes, or other membranes and the possibility that such absorption may
contribute to the overall exposure. An excessive amount of absorption may invalidate any
TLV limit, a high potential for direct contact with the substance may suggest the need for
special protective measures.

     For many of  the materials with an assigned TLV-TWA, the ACGIH  could not find
sufficient lexicological data to establish a TLV-STEL For these substances,  it recommends
"Short-term exposures should exceed three times the TLV-TWA for no more than a total of 30
minutes during a work day and under no circumstances should they exceed five times  the
TLV-TWA, provided  that the TLV-TWA is not exceeded" for the  8-hour  workday The
airborne concentrations denved from this recommendation are referred to as excursion
limits

     OSHAPELs

     The Occupational Safety and Health Administration (OSHA) within the U S  Depart-
ment of Labor is responsible for the adoption and enforcement of standards for safe and
healthful working conditions for men and women employed m any business engaged in
commerce m the United States.  When first established in the early 1970's, OSHA essentially
adopted the then current ACGIH TLV-TWAs and TLV-Cs as occupational exposure limits
and made them official federal standards  Instead of calling the limits Threshold Limit
Values, however, it referred to them as Permissible Exposure Limits (PELs)  As in the case
of TLVs, there are both time-weighted average (TWA) and ceiling (C) values for various
materials as well as  occasional peak values for shorter time penods While the ACGIH
reviews and frequently revises its TLVs on an annual basis, OSHA did not similarly update
                                        6-11
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its PELs except for a relatively small number of individual substances until early 1989 when
it lowered the PELs for 212 widely used chemicals, adopted new PELs for 164 substances
not previously regulated, and reaffirmed the PELs for 52 materials.

     PELs are formally listed in Title 29 of the Code of Federal Regulations (CFR), Part
1910, Subpart Z, General Industry Standards for Toxic  and Hazardous Substances An
inexpensive and valuable  source of current PELs and much other information on chemical
hazards is the NIOSH Pocket Guide to Chemical  Hazards published by the National
Institute for Occupational Safety and Health, a part of the U S Department of Health and
Human Services.  When in stock, single copies may be available at no cost from  NIOSH
Publications, 4676 Columbia Parkway, Cincinnati, Ohio 45226 (Telephone-  513-533-8287)
Copies are otherwise available at nominal cost as DHHS (NIOSH) Publication No  85-114
from the Superintendent of Documents, U.S Government Printing Office, Washington, D C
20402 or one of the many regional branches of the GPO. Be advised, however, that it may
take some time for NIOSH to update the currently available guide with the new PELs

      Besides PELs and  a wide variety  of other valuable  information, the pocket  guide
includes the IDLH values described below

   AIHA WEELs

      The American Industrial Hygiene Association (AIHA) has established a committee to
 develop  Workplace Environmental Exposure Levels (WEELs) for toxic  agents which have
 no current exposure guidelines established by other organizations Essentially, the commit-
 tee is attempting to establish occupational exposure limits for materials not addressed by the
 ACGffiL or OSHA but of interest to various segments of industry A separate guide providing
 documentation is being prepared for each substance

      There are two WEEL limits for most materials The first is an 8-hour TWA value
 similar in concept to ACGIH TLV-TWA values. The second, which is only available in a
 limited number of cases, is  a short-term TWA for exposures of either 1- or  15-minute
 duration. As of October of 1988, WEELs were available for 33 materials  Non-members
 prices were $5 for each individual guide  and $125  for the entire set (plus shipping and
 handling).

      The WEEL guides  are available fiom AIHA Publications, 475 Wolf Ledges Parkway,
 Akron,  Ohio, 44311-1087 (Telephone- 216-762-7294)  A  price list and order form are
 available at no charge
                                         6-12
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     NIOSHIDLHs

     NIOSH defines Immediately Dangerous  to Life or Health (IDLH) levels as  the
maximum airborne contaminant concentrations  "from which one could escape within 30
minutes without any escape-impairing symptoms or  any  irreversible health effects" Not
surprisingly, given that these limits are for 30-minute exposures under what are essentially
emergency conditions, IDLH values generally far exceed corresponding TLVs or PELs
They are  available  in the pocket guide referenced above for most substances currently
regulated by OSHA.

     NAS/NRC EEGLs and SPEGLs

     The Committee on Toxicology of the National Research Council (NRC), an operating
arm of the National Academy of Sciences (NAS),  has published a list of Emergency
Exposure Guidance Limits (EEGLs) and Short-term Public Emergency Guidance Levels
(SPEGLs) as guidance in advance planning for the management of emergencies. Although
the Committee has been adding toxic substances to the list on a periodic basis, the careful
attention to detail and thoroughness of its work has resulted in EEGLs being established for
relatively few materials to date. Table 6.3 lists those available as of late 1988.

      SPEGLs are concentrations whose occurrence is expected to be rare in the lifetime of
any one individual. These values, of which there are only four in the table, "reflect an
acceptance of the statistical likelihood of a nomncapacitating reversible effect in an exposed
population while avoiding significant decrements in performance".  They are concentrations
considered acceptable for public exposures during emergencies

      EEGLs differ from SPEGLs in that they are intended to apply to defined occupational
groups such as military or space personnel rather than the general public  Because these
groups are typically younger and healthier, the EEGL for any particular substance may differ
substantially from the SPEGL.

      Further information on these exposure limits and levels may be obtained by writing the
National  Academy  of Sciences, Committee on  Toxicology, 2101  Constitution  Avenue,
Washington, D.C, 20418 to the attention of Dr. Bakshi  Note that the  Committee plans to
have completed work on tnchloroethylene and lithium  chromate by early 1989 if not sooner.

     AIHA ERPGs

      Several major chemical companies formed a task force in 1986 to develop Emergency
Response Planning Guidelines (ERPG) values  for selected toxic materials  The results of
their joint efforts are being published by the AIHA and are available from the publication
office cited earlier As of late  1988, guidelines  had been completed for 10 substances
                                         6-13
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                                                 TABLE 63
                            SUMMARY OF EMERGENCY EXPOSURE GUIDANCE LEVELS
                                  FROM THE NATIONAL RESEARCH COUNCIL
Chemical
Acetone
Acrolein
Aluminum oxide
Ammonia
Arsine
Benzene
Bromotnfluoromethane
Carbon disulfide
Carbon monoxide
Chlorine
Chlorine tnfluonde
Chloroform
Dichlorodifluoromethane
(Freon-12)
60-MinuteEEGL
(ppm)
8,500
0.05
15 mg/m3
100
1.0
1000 (proposed)
25,000
50
400
3
1
100
10,000
Chemical
Dichlorofluoromethane
(Freon-21)
Dichlorotetrafluoromethane
(Freon-114)
1,1-Dimethylhydrazine
Ethanolamine
Ethylene oxide
Ethylene glycol
Fluonne
Hydrazine
Hydrogen chlonde
Hydrogen chlonde
Hydrogen sulfide
Isopropyl alcohol
Lithium bromide
60-MinuteEEGL
(ppm)
100
10,000
024*
50
20 (proposed)
40
7.5
012
20
1*
10(24hr)
400
15 mg/m3
ON

I-1
-P-
       Note'    Units in parts per million by volume in air unless otherwise stated.
       *SPEGL (Short-term Public Emergency Guidance Levels)
       11/88
 image: 








                                              TABLE 6.3 (Continued)
                             SUMMARY OF EMERGENCY EXPOSURE GUIDANCE LEVELS
                                    FROM THE NATIONAL RESEARCH COUNCIL
Chemical
Mercury vapor
Methane
Methanol
Monomethyl hydrazme
Nitrogen dioxide
Nitrous oxide
Ozone
Phosgene
60-Minute EEGL
(ppm)
02mg/m3(24hr)
5,000 (24k)
200
024*
1*
10,000
1
02
Chemical
Sodium Hydroxide
Sulfur dioxide
Sulfunc acid
Toluene
Tnchlorofluoromethane
(Freon-11)
Tnchlorotrifluoroethane
(Freon-113)
Vinyhdene chlonde
Xylene
60-Minute EEGL
(ppm)
2mg/m3
10
1 mg/m3
200
1,500
1,500
10(24hr)
200
H
Ul
        Note:    Units in parts per million by volume in air unless otherwise stated
        *SPEGL (Short-term Public Emergency Guidance Levels)
        11/88
 image: 








including ammonia, chlorine, chloroacetyl chloride, chloropicrm, crotonaldehyde, diketene,
formaldelhyde, hydrogen fluoride, perfluoroisobutylene, and phosphorous pentoxide.  Pub-
lished in two sets of five, the first set costs $7 while the second is pnced at $11.

     As in the case of NAS/NRC efforts,  the  task force is attempting to define  toxic
exposure limits suitable for use in advance planning for emergencies.  It ultimately wishes,
however, to address a much greater number of chemicals than those considered to date by the
NAS/NRC.

     The task force intends to establish thiee limits for each material, these being:

     •     ERPG-3: The maximum airborne  concentration below wjiich, it is be-
           lieved, nearly all individuals could be exposed for up to one hour without
           experiencing or developing life threatening health effects.

     •     ERPG-2: The maximum airborne  concentration below which, it is be-
           lieved, nearly all individuals could be exposed for up to one hour with out
           experiencing  or developing  irreversible adverse or  other senous health
           effects or symptoms which  could  impair an  individual's ability  to  take
           protective action. This particular limit is being developed using criteria
           similiar to those applied by the NAS/NRC.

      •     ERPG-1: The  maximum aiiborne concentration  to  which  nearly all
           individuals could be exposed for up to one hour without experiencing or
           developing health effects  more  severe than sensory perception or mild
           irritation, if relevant.

 6.8 ADVANTAGES AND DISADVANTAGES OF VARIOUS LIMITS

      A key problem of using TLV, PEL,  or WEEL values in the course of evacuation
 planning or hazard  assessment  is that they  are intended for use in the  occupational
 environment where  presumably healthy workers are exposed to concentrations near these
 limits day after day throughout their careers This, and the desire to prevent health effects
 associated with both acute and chronic exposures, means that these values are often (but not
 always) much lower than what they need be  to protect the public from exposures associated
 with rare or infrequent spills of brief duration.  Consequently, use of a TLV, PEL, or WEEL
 value, although decidedly safe in the vast majority of cases, could conceivably result in major
 overprediction of downwind evacuation or hazard zones in many situations  Key exceptions
 involve materials such as chlorine, acids, caustics, and other generally corrosive materials for
 which  limits  are based on irritant rathei than toxic effects and for  which applied safety
 factors may be minimal.
                                          6-16
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     NIOSH IDLH limits are considerably higher, are defined for an exposure duration
closer to what would be expected in many actual short-term spill emergencies, and are closer
to the borderline between levels that are barely tolerable and those that may cause significant
injury  The  problem is  that "barely  tolerable" contaminant concentrations may have the
potential to cause considerable irritation or other distress, possibly to the point of prompting
large numbers of people to seek medical assistance. Also, since NIOSH is again assuming
that healthy workers are being exposed, IDLH concentrations may have the potential to cause
significant injury to young  children, the  elderly,  or individuals  with preexisting health
problems. Consequently, it is apparent that a  safety factor must be applied if the IDLH is
used in any way for protection  of the general public, especially  if exposures exceed 30
minutes in duration

     The NAS/NRC SPEGLSs  and AfflA ERPG-2 values are possibly the  best choice
among currently available guidelines for protection of the public during relatively short-term
events given the objectives of their respective  developers. Unfortunately, only  a small
number of hazardous materials have been addressed to date.

     Overall, the above discussion  might seem to suggest there is no widely accepted
method available for selection of an appropriate  exposure limit  for  general populations
subjected to toxic vapors or gases, particularly where the exposure limit is to be used for
public emergency planning  purposes  That  is  indeed  (and  unfortunately)  an accurate
appraisal  of the  current situation. So what  should you  do?  Some options,  in order  of
decreasing preference, and by no means mandatory for use, are as follows:

           Use the NAS/NRC SPEGL or the AfflA ERPG-2 value for the material if
           one has been established

      •     Consult a lexicologist or similarly qualified individual for advice based on
           a formal review of the toxicity of the material of concern

      •     Use the highest value among the following:

                IDLH value divided by 10 (with " 10" being a safety factor)
                TLV-STEL
                TLV-TWA multiplied by 3 (if a TLV-STEL does not exist)
                TLV-C

      •     If the evacuation of additional areas is  not a problem,  or the exposure may be
           prolonged beyond one hour, use the TLV-TWA or the TLV-C value or apply an
           additional safety factor to other selections
                                         6-17
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     The above suggestions should not be considered more than rough guidelines that will
generally lead to an adequately "safe" answer for most members of a community. There is,
however, one more problem to consider.

     The chronic exposure limits for substances known or suspected to be carcinogens are
usually  set at  very low levels to protect workers from developing cancer during their
lifetimes. Such values are generally many times (possibly  several hundred times) lower than
the limits enforced for the same materials prior to the discovery of a potential cancer threat.
For example, the TLV-TWA for vinyl chloride is now 5  ppm whereas it was 200 ppm for
many years, yet even 200 ppm is well below any  concentration causing  observable health
effects in short-term acute exposures. Obviously, the size of the evacuation or hazard zone
for a 5 ppm limit would be many times larger than a zone  with boundaries of 200 ppm. The
difference in the numbers of people that may require  evacuation or other protective action
may differ by thousands if not tens of thousands in urban areas.

     There is no hard evidence that a single exposure to a substance such as vinyl chloride
will cause excess cancers in a population of exposed humans However, some scientists are
of the opinion that any exposure might lead to at least a minor increased nsk of such cancers,
and this belief poses a dilemma during planning for evacuations, especially given the public
fears that may naturally accompany the announcement that a cancer-causing agent has been
released into the atmosphere It is therefore necessary  for  government and industry to
consider cases involving carcinogens carefully and  on  a  case-by-case  basis,  giving full
attention to the  safety issues involving  large-scale evacuations  as well as the potential
long-term health, political, and legal implications of their decisions.

6.9 RELATIONSHIP OF RECOMMENDATIONS TO EPA LOCs

      Under the Superfund Amendments and Reauthonzation (SARA) Act of 1986, the U S
Environmental Protection  Agency (EPA) established a list of several hundred Extremely
Hazardous Substances  (EHS) subject  to emergency  planning, community right-to-know,
hazardous  emissions reporting,  and emergency  notification requirements. In providing
guidance to planning personnel for screening and prioritizing threats posed by EHS, the EPA
made a first attempt at specifying what it termed Levels of Concern  (LOCs) for these
substances, essentially adopting portions of the approach recommended above.

      For the 390 or so substances for which NIOSH  has established IDLH levels, the EPA
set LOCs  to  one-tenth of available IDLHs  until such  time as industry and government
develop more appropnate exposure limits  for protection of the public during episodic
short-term emergencies  For substances for which IDLHs had not been established, the EPA
developed a  highly approximate procedure to  estimate LOCs comparable  to  IDLHs
Essentially, IDLHs were  estimated for new substances via use of data  obtained from
                                        6-18
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laboratory experiments involving acute exposures of animals to toxic substances.  Inhalation
data were used in preference to data for other routes of exposure when available, but data for
other routes of exposure were indeed used when necessary The following equations were
then applied to convert available data to airborne concentrations presumably comparable to
IDLHs.

           1)    Estimated IDLH = LC^ x 0.1
           2)    Estimated IDLH = LCLo
           3)    Estimated IDLH = LD^x 0.01
           4)    Estimated IDLH = LDLo x 0.1

     The abbreviations used above for lethal concentrations  and dosages are defined and
described in Section 6.12 of this chapter. Please note that the above discussion only provides
a  general  overview  of the EPA's general approach  and should  not  be  applied in  an
indiscriminate fashion.

6.10 CONSIDERATION OF MIXTURES OF HARMFUL GASES AND VAPORS

     Preceding discussions have focused on relatively pure substances.  As is well appreciat-
ed, however, many materials handled by industry are multi-component mixtures. It is well
therefore to discuss how to determine appropriate toxic limits for mixtures via a review of
traditional guidance found in the literature.

     The ACGIH, in an appendix to its TLV booklet,  reports that one of the first tasks in
looking  at mixtures  is a determination of whether mixture components have additive or
independent effects on the human body. In other words, when two or more toxic agents in a
mixture  act upon the same organ system, it is their combined or additive effect rather than
their individual effects that should be given primary consideration,  and  indeed, this is the
preferred approach in the absence of specific information to the contrary.  Where toxicologi-
cal data  firmly support a finding that the chief effects of the different substances are not in
fact additive (in the sense that they produce purely local effects or affect  different organs of
the body), it is only then acceptable to assume that adverse effects are independent.

     Where effects are evaluated as being additive, the ACGIH suggests  that the sum of the
following fraction be computed:

            Ci  C2   Cn
      Sum=-+-...-
                                         6-19
 image: 








     where:    Cn indicates the measured or predicted atmospheric concentration, Tn
               indicates the corresponding  toxic limit in the  same units as Cn, and
               there are "n" number of toxic substances in the mixture.

     When the Sum of the fractions equals 1.0 or less, then the vapor mixture is considered
to be at or below the toxic limit In those  cases where all components of a  mixture are
deemed to produce independent effects, the toxic limit is considered to be exceeded only
when one or more of the individual CJ Tn fractions has a value greater than one.

     To be noted is that synergistic action or potentiation may occur with some combina-
tions of toxic agents: these being cases in which the combined effect of the mixture actually
exceeds the impact indicated by assumption  of additive effects  Such cases, which are
fortunately rather rare, must be considered on a case-by-case basis.

     When the source of airborne contamination is a liquid mixture, the ACGIH suggests (to
its typical audience of industrial hygiemsts and other occupational health personnel) that the
composition of the airborne mixture be  assumed similar to the composition of the original
liquid mixture. In effect,  this results  in the further assumption that all components of the
mixture will evaporate at a constant rate in direct proportion to then* concentration in the
liquid mixture. The assumption has ment when one in interested in evaluation of a relatively
long-term  time-weighted  average exposure  resulting from a mixture that  will eventually
evaporate in its entirety, but has severe limitations when applied to the assessment of acute
exposures resulting from accidental and episodic events.  It is well, nevertheless,  to present
the ACGIH's  general methodology  for estimating the toxic limit of a liquid mixture of this
type, this being:

     Toxic Limit (mixture)  = „—•=.—=-
                            £j_, £2   £»
                            Ci  <*'"<*

     where:   Fn indicates the weight fractions of individual components in  the liquid
               mixture, and Cn indicates the corresponding toxic limits in units of mg/m3.

     A more  formal approach to determining the airborne mixture toxic limit for evaporat-
ing or boiling pools of liquid requires  consideration of vapor-equihbnum factors beyond the
scope of this  text. Nevertheless, where needs for  a more precise limit are critical,  it is
desirable to apply more sophisticated analytical procedures to evaluate vapor compositions
above  liquid  mixtures  or to make direct measurements of representative samples  The
procedures for such efforts are well within the state of the art of engineering practice and
entail fundamental principles of thermodynamics
                                          6-20
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6.11 EXPOSURE LIMITS FOR CONTAMINATED WATER

     The U.S. Environmental Protection Agency (EPA) has established or recommended
water quality criteria for a variety of water uses and a relatively large number of chemicals.
Advice  from their personnel as to what concentrations of any  particular chemical are
tolerable in any given situation may be available with only a telephone call to one of the
EPA's 10 regional offices

     Among the various standards and guidelines developed by the EPA for protection of
water quality are:

     •    National Drinking Water  Standards   The  maximum contaminant  levels
          (MCLs) for selected heavy metals, pesticides, radioactive substances, and
          other water quality characteristics permitted by law in water destined for
          human consumption  Listed in Parts 141 and 143 of Title 40 of the Code of
          Federal Regulations (CFR).

     •    Drinking Water Health Advisones (HAs) -- previously called Suggested No
          Adverse Response Levels (SNARLS):  Human health effects advisories for
          unregulated drinking water contaminants commonly found in potable water
          supplies. HAs are somewhat unique  in that they  provide guidance for
          short-term exposure as well as the long-term chronic exposures typically of
          interest to the EPA.

     •    Maximum Contaminant Level Goals (MCLGs) — formerly known as
          Recommended Maximum  Contaminant Levels (RMCLs). Published in the
          Federal Register of June 12, 1984, the EPA proposed zero contamination
          limits for six halogenated hydrocarbons and  benzene.  Low levels of
          contamination were permitted for two other halogenated hydrocarbons (i e,
           1,1,1-tnchloroethane  and  1,4-dichlorobenzene)  MCLGs were recently
          proposed for several additional contaminants.

      •    Federal Water Quality Criteria  Criteria for acute and chronic exposure of
           freshwater and saltwater aquatic life and human health based on long-term
           consumption of drinking water and contaminated fish or shellfish.  Avail-
           able for a relatively long list of substances.

      Spills  of toxic materials into a  body of surface water differ from discharges of toxic
 vapors  or gases into the an* in that a large number of people are unlikely to suffer toxic
 effects  before authorities have a chance to restrict water use  Indeed, response planning for
 the spill of any hazardous material into water more typically involves preparations to:
                                         6-21
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     •    Alert proper state and federal authorities.

     •    Warn public, industrial, agricultural, and recreational users of the water on
          as prompt a basis as possible of the contamination

     •    Attempt to limit the  degree  of contamination or the amount of water
          affected.

     •    Attempt to remove as much of the contaminating substance as possible
          from the water (possibly employing a contractor with specialized expertise
          and equipment).

     •    Analyze the water to determine the extent of contamination.

     •    Consult with proper authorities  as to whether the water is fit for use or
          whether other remedial actions are first necessary; and

     •    Prepare for the  eventuality that a  particular water supply  may become
          unavailable for use for a time.

6.12 UNDERSTANDING TOXICOLOGICAL DATA IN THE LITERATURE

     Toxicologists have a number  of "short-hand" methods of expressing the toxicity of
hazardous materials by various routes of entry. An  understanding of some of the more
common abbreviations used can  lead to  a  greater understanding  of how the toxicities of
various materials can be assessed, particularly when these abbreviations are encountered in
hazardous material data bases or the safety related literature of chemical manufacturers that
address the effects of acute exposures.

     The easiest way to learn the abbreviations is to look at a few examples and then discuss
their meaning:

          The orl rat LDj,, for Chemical A is 200 mg/kg.

     •    The ihl LCj,, for the mus or gpg is 800 ppm/4 hrs  The TCLo is 100 ppm/4
          hrs.

     •    The rbt skn LDCT is 50 mg/kg.

     LD in the above examples is an abbreviation for lethal dose while LC stands for lethal
concentration. TC is short for toxic concentration while TD means toxic dose.  There are
other similar abbreviations but these  are by far the most common.
                                        6-22
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     Each of the LD or LC notations are followed by a number that is usually a subscript  A
"50" means that 50%  of the test population of animals were killed  under stated test
conditions, a "67" means 67% were killed and so forth. The letters "Lo" instead of a number
mean this is the lowest reported level having the stated effect

     In order for one of the above notations to have meaning, both the species of animal
tested and the route of entry must be specified. Typical abbreviations are:
Species of Animal
Rat = rat
Mouse = mus
Guinea pig = gpg
Rabbit = rbt
Human = hmn
Mammal = mam
Monkey = mky
Route of Entry
Oral = orl
Skin application = skn
Inhalation = ihl




      Both oral and skin application dosages are typically expressed in units of milligrams of
 chemical applied per kilogram of the animal's body weight, or mg/kg for short The actual
 total amount of a toxic material necessary to cause the stated effect is  determined by
 multiplying the dose in units of mg/kg by the weight of the animal species expressed in units
 of kilograms (1 kg = approximately 2 2 Ib).

      Inhalation data must include the concentration in air to which the animal species was
 subjected as well as the duration of exposure. Concentrations in air are typically expressed in
 units of ppm (by volume) or mg/m3 Times are typically given in  minutes  or hours  Be
 advised that any airborne concentration not accompanied by an indication of the duration
 of exposure should be considered a useless and thoroughly meaningless item of informa-
 tion

      One of the most comprehensive compilations of lexicological data is a  multi-volume
 set of documents tided Registry of Toxic Effects of Chemical Substances  The 1985-1986
 edition, published in April 1987, is available for a cost close to $100 from the Superintendent
 of Documents, U.S  Government Printing Office, Washington, D C, 20402,  or one of the
                                          6-23
 image: 








many regional offices of the GPO, as Stock No  17-33-00431-5. Developed jointly by the
U.S. Public Health Service, Centers for Disease Control and NIOSH, the set is also listed as
DHHS (NIOSH) Publication No. 87-114.
                                        6-24
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     7.0  REACTIVITY HAZARDS OF CHEMICAL SUBSTANCES
7.1 INTRODUCTION

     It has up to this point been assumed that the hazardous materials being discharged or
spilled do not in any way react with or chemically transform due to contact with water, an-,
other common materials in the environment, or other chemicals that may be present in the
vicinity  It has also assumed that these materials are not self-reactive under conditions that
may be encountered. Although the overall topic of chemical reactivity hazards is extremely
complex, it is necessary  to at least briefly outline some of  the more  common and/or
dangerous types of reactions and how they  may pose a threat to nearby populations With
due apologies to chemists, chemical engineers, and others with a knowledge of these topics,
it  is acknowledged that  some liberties are taken in this process to ensure that various
concepts are more easily understood by non-technical audiences.

73 EXOTHERMIC REACTIONS

     When one  substance is brought together or mixed with another and the resulting
interaction evolves or generates heat, the process is referred to as an exothermic reaction.
Alternatively, if  no reaction will take place unless  heat is  continuously added to the
combination of reactants, the interaction resulting from the provision of heat is called an
endothermic  reaction. However, it  is important to understand that some  exothermic
reactions may require heating just to get started, and will then proceed on their own
 image: 








     Exothermic reactions pose special hazards whether occurring in the open environment
or within a closed container.  In the open, the heat evolved will raise the temperature of the
reactants, of any products of the reaction, and of surrounding  materials.  Since several
properties of all substances are a function of temperature, the resulting higher temperatures
may affect how the materials involved may behave in the environment. Of key importance is
the realization that heat will increase the vapor pressures of hazardous materials and the rate
at  which they  vaporize.  If very high temperatures  are  achieved,  nearby combustible
materials may ignite. Explosive materials, be they the reactants or products of the reaction,
may explode upon ignition or excessive heating

      Similar hazards are associated with exothermic reactions taking place  in  closed
containers. In this case, however, increasing internal temperatures as well as the evolution of
gases from the reaction may increase internal pressures to the point that the tank or container
ruptures violently in an overpressunzation explosion, thus suddenly releasing large amounts
of possibly flammable and/or toxic  gases or vapors into the atmosphere  Such gases  or
vapors may also be released through ruptured pipes, opened pressure relief devices, or any
other paths to the external environment

      Reactions with Water or Air

      Some of the most basic types of exothermic reactions  (which are barely "reactions" in
the true sense of the  term)  occur when certain materials are dissolved in water Such
substances have what is called a positive  heat of solution.  They do not transform to a
different material, but simply  generate  heat while mixing  Some examples are sodium
hydroxide (also called caustic soda) and sulfunc acid, which generates considerable  heat to
the point of causing some degree of "violence" when concentrated or pure materials are
spilled into water. Yet other materials may ignite, evolve  flammable gases, or otherwise
react violently when in contact with water. Knowledge of the reactivity of any substance
with water is especially important when water is present in the spill area or a fire takes place
and firefighters do not wish to make the situation worse by  applying water to the flames or
chemicals.

      While discussing such substances, it is well to add that several of the strong acids and
related substances in this category of materials may evolve large amounts of fumes when in
contact with water or moisture  in the air. These fumes, which may consist of a mixture of
fine droplets of acid  in air and  acid vapors, are usually highly irritating,  corrosive, and
heavier than air.

      Many substances referred to as being pyrophoric will react violently or  exothermically
with air and are likely  to ignite  in a spontaneous  fashion. Such  substances (such  as
phosphorus) are commonly transported or stored in a manner that prevents exposure to air,
                                          7-2
 image: 








often submerged in water or some type of compatible oil. Note that the fact that a substance
can be safely stored under water in no way suggests that it may also be safely submerged in
oil. Nor may submersion in water be safe for a substance usually maintained under some
type of oil.

     Reactions with Combustible Organic Materials

     Certain chemicals are known as strong oxidizing agents or oxidizers.  They have the
common characteristic of being able to decompose or oxidize organic materials and react
with a variety of inorganic materials while generating heat, oxygen, flammable gases,  and
possibly toxic gases. If the heat generated is sufficient to ignite a combustible or flammable
material, a fire or explosion may occur.

     Another group of chemicals  are referred to  as strong reducing  agents. These
substances may evolve hydrogen upon reaction with many other chemicals, may evolve other
flammable or toxic  gases, and like oxidizing agents, may generate heat.  As above, a fire or
explosion may result if sufficient heat is  generated to ignite a  combustible or flammable
substance  Strong reducing agents and oxidizing agents should  never be allowed to make
contact without appropriate safeguards since they represent opposite extremes of chemical
reactivity.

     Exothermic Polymerization Reactions

     A few of the more common plastics in use on a widespread basis are polyethylene,
polypropylene, polystyrene, and polyvinyl chloride (PVC). Although all are manufactured
from liquids or gases, they are typically solids in then- final form

      The above plastics are respectively manufactured from ethylene,  propylene, styrene,
and vinyl chloride by means of a polymerization reaction in  which molecules of these
materials are linked together into long chains of molecules.  As the chains become longer and
begin  connecting to each other, thus greatly increasing the molecular weight of individual
molecules, a solid plastic is formed

      Some chemicals capable of being polymerized have a strong tendency to do so even
under normal ambient conditions and are especially prone to polymerize if heated above a
certain temperature or if contaminated by a catalyst or polymerization initiator, which in
some cases might be a rather common substance such as water or rust. Once polymerization
starts, an exothermic chain reaction may occur that develops high temperatures and pressures
within containers and which can lead to possible explosion or violent rupture of the container
and/or discharge of flammable and/or toxic gases if safety and control systems malfunction
or are lacking  The incident in Bhopal, India partially involved this type of reaction when a
container of methyl isocyanate contaminated with water and chloroform began polymerizing.
                                         7-3
 image: 








The heat of the runaway (i.e., out of control) reaction caused a large portion of the highly
toxic isocyanate to vaporize into the air through a pressure relief system before it had a
chance to polymerize.

     Quite often,  substances with the above tendency to self-polymerize or to undergo
autocatalytic polymerization are transported or stored only while containing an amount of a
substance called an  inhibitor. As  their name  implies, inhibitors act to inhibit,  slow, or
interfere with the chemical processes that can lead to a runaway uncontrolled polymerization
reaction under normal conditions of transportation or storage. Inadvertent contamination or
excessive heat, however, may  overpower the inhibitor and  allow the reaction to proceed
Thus, an inhibited cargo should not be considered safe if there is a possibility of it being
overheated or contaminated with those substances that may initiate polymerization. The very
fact that a substance needs an inhibitor for safe storage is in many cases (but by no means all)
a sign of potential hazardous instability.

     Exothermic Decomposition Reactions

     Much as  some chemical molecules can join together to form larger molecules via
exothermic polymerization, others are unstable and can break apart in a runaway exothermic
reaction once the process is initiated  Again, inhibitors may be used to slow the process
down or to prevent  its occurrence and various contaminants or heat may overcome the
inhibitors or otherwise start a reaction. Containers may explode, rupture, and/or vent various
flammable and/or toxic gases to the atmosphere

     Incidentally, the above decomposition and polymerization reactions are hazardous only
if they somehow become uncontrolled and start a chain reaction that cannot be stopped with
available equipment, materials, or safety systems. They are widely and safely conducted in
chemical and other manufacturing plants across the nation on a daily basis without incident
It is only when control or safety systems break down or people make mistakes that problems
begin.

73 NEUTRALIZATION REACTIONS

     Spill response guides often suggest consideration of neutralization as a way in which a
hazardous substance can be converted via a chemical reaction to one or more substances that
pose lesser threats to the public health or the environment It is therefore worthwhile to say a
few words on the topic

     In the traditional sense of the word, neutralization typically refers to the combination of
an acid and a base or alkaline material to form some sort of  salt A good example involves
the careful combination of sodium hydroxide (caustic soda — NaOH) with hydrochloric acid
(muriatic  acid -- HC1 in water). This reaction, which may proceed violently for a time,
                                        7-4
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generate heat and gases, and cause boiling and spattering of acid if not properly controlled,
results in the combination of sodium (Na) atoms with chlorine (Cl) atoms to form sodium
chloride (NaCl),  which is ordinary table  salt The remaining hydrogen (H) atoms and
hydroxide (OH) molecules  combine  to  form ordinary water (Hp). Thus, one strongly
corrosive and hazardous substance is used to convert another to a solution of ordinary salt
and water.

     When used in the spill response community, neutralization refers to the general use of
one or more chemicals or other substances to render another less harmful  The term need not
solely apply to acid-base reactions.

7.4 CORROSIVITY HAZARDS

     The process by which a chemical  gradually erodes or dissolves  another material is
often referred to as corrosion. The process represents yet another type of chemical reactivity
that must be  considered in assessing the  hazards of any given material, and is particularly
important when. 1) choosing materials of construction for container walls or linings, piping,
pumps, valves, seals, gaskets, and so forth; and 2) assuring that equipment and materials used
during response to emergencies will not be damaged or destroyed by contact with the spilled
material during their period of use. The word corrosive is also used descriptively to indicate
that a  substance may cause  chemical burns of the skin, eyes, or other bodily tissues upon
contact

     In evaluating whether one material is corrosive to another via reference to material
safety  data sheets, chemical company product bulletins, hazardous material data bases, or
other reference sources, it is often important to place the time frame and rate of corrosion
into the proper context For  example, certain reference sources may state that one substance
is unacceptably corrosive to a particular material of construction because long term (i.e., 10
to 20 years) exposure will result in failure of the material prior to the desired lifetime of the
equipment Yet other reference  sources may  discuss the  issue in terms  of short term
resistance of equipment or clothing construction materials to chemical attack, particularly if
addressing use under emergency conditions This distinction is not always clear in  the
literature

     Finally, note that some of the most corrosive substances to common metals include
strong acids  of one type or another  Not only may the "wrong" acid  in contact with the
"wrong" metal cause rapid corrosion of the metal, but the process may generate flammable
and potentially explosive hydrogen gas
                                         7-5
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73 OTHER HAZARDOUS RESULTS OR PRODUCTS OF REACTIONS

     The above discussions have really only scratched the surface of the overall topic of
hazardous chemical reactions. It is also necessary to point out that:

     •    The combination of various chemicals may produce new chemicals with
          hazards quite different and possibly more severe than those associated with
          the original materials.

     •    Some combinations may result in spontaneous fires; spontaneous explo-
          sions; formation of substances which will ignite or explode if shocked,
          heated or subjected to friction; generation of toxic gases, liquids or solids;
          or generation of flammable gases, liquids, or solids

     •    It is  necessary  to look at hazardous  materials  on a  fairly  specific
          case-by-case basis to determine their reactivity hazards.

7.6 SOURCES OF CHEMICAL REACTIVITY DATA

     There  are  numerous  sources  of  chemical reactivity data that  address  the  topic
somewhat superficially and several  that are highly technical and somewhat beyond the
perceived "needs" of the audience to which this document is directed. The following three
sources provide  an excellent balance between  completeness,  precision, specificity, and
common availability.

     •    Fire Protection Guide on Hazardous Materials, containing "Manual of
          Hazardous Chemical Reactions," NFPA 491M-1986, National Fire Protec-
          tion Association, Batterymarch Park, Qumcy,  MA  02269 (Telephone
           1-800-344-3555 for orders).

      •    Brethenck, L., Handbook of Reactive Chemical  Hazards, 3rd edition,
          Butterworths, London and Boston,  1985. Available through libraries and
          bookstores serving the scientific community

      •    Hatayama, H K., et al, A Method for Determining the Compatibility of
          Hazardous Wastes, EPA Report No. EPA-600/2-80-076, Municipal Envi-
           ronmental  Research  Laboratory, U.S. Environmental Protection Agency,
           Cincinnati, Ohio, Apnl 1980. Available as publication PB80-221005 from
           the National Technical Information Service, Springfield, Virginia 22161.
                                        7-6
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     The NFPA Fire Protection  Guide on  Hazardous Materials  contains the described
manual of chemical reactions as well as considerable additional information and data on
hazardous materials. Found in the libraries of numerous fire departments, it was available in
1988 at a cost of approximately $49 to non-members. Although the section on hazardous
chemical reactions has not truly been updated since 1975, and is not nearly as extensive as
the work by Brethenck, the guide remains an excellent source for a broad range of specific
information. Major sections of the guide can also be found in the NFPA National Fire Codes
as Sections 325M, 49,491M, and 704.

     The handbook by  Brethenck  covers  approximately 9000 compounds versus the
1600-1700 found in the NFPA guide. It is a major and somewhat unique  work in the field
which retails for $110.

     The report prepared by Hatayama and his co-workers under the sponsorship of the EPA
is an excellent supplement to either of the above sources of information. Those above mostly
list and  describe the  specific hazardous consequences  of combining  various  sets  of
chemicals, as reported in the general literature  Since there are many tens of thousands of
known chemicals, and since only  a small fraction of the possible combinations have been
reported upon, neither of these sources can even begin to claim that combinations not listed
are safe. The work by Hatayama et al. attempts to fill the gaps by providing a general
indication of the typical  effects of mixing a substance from one chemical family with a
substance from another family via a single chemical compatibility chart. The title of the
work suggests it only considers hazaidous waste materials, but that in no way affects the
validity of the information for hazardous materials in general  Appendix D to this guide
contains a copy of the chart as well as additional explanatory information.

     It is also necessary to note that many of the product  bulletins and safety-related
documents available free from most chemical manufacturers can be excellent sources of
information  when one is concerned with the reactivity hazards of a relatively small number
of materials. The problem is that collection of such publications for a  large number of
materials can be a burdensome and lengthy process.

     Chemical company literature, however, can be a great source of information on the
compatibility of  common materials  of equipment construction with specific chemicals.
Alternatives include some of the better hazardous materials data bases, books devoted to this
topic,  and more widely  available handbooks in the fields of chemical and mechanical
engineering. Many of these same sources address the compatibility of materials used for
chemical protective clothing, and substantial information is available from the manufacturers
of such clothing  One excellent source of information on protective clothing that deserves
special notice is:
                                        7-7
 image: 








Schwope, A D., et al, Guidelines for the Selection of Chemical Protective
Clothing, 3rd edition, 1987; sponsored  by the EPA and  USCG  and
available for approximately $35 from the ACGIH Publications Section,
6500  Glenway  Ave,  Bldg  D-7,  Cincinnati,  Ohio 45211   (Telephone
513-661-7881).
                             7-8
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      8.0  HAZARDOUS MATERIAL CLASSIFICATION SYSTEMS
                                             5
B-
\
 111
                00
                 NFPA
 J  INTRODUCTION

     Vanous organizations in the United States have established or defined classes or lists of
hazardous materials for regulatory purposes or for the purpose of providing rapid indication
of the hazards associated with individual substances. An awareness and knowledge of these
classification systems can assist emergency preparedness personnel in identifying those
materials that may pose a potential threat to their respective jurisdictions.

8.2  U.S. DEPARTMENT OF TRANSPORTATION CLASSIFICATIONS

     As the primary regulatory agency concerned with the safe transportation of hazardous
materials in  interstate  commerce, the US Department of Transportation  (DOT)  has
established definitions of various classes of hazardous materials, established placarding and
marking requirements  for containers and packages, and adopted an international cargo
commodity  numbering  system. Each  of these  topics is individually  discussed in the
following Further details are available in 49 CFR 171-179.

     Material Classification Definitions

     The DOT classifies hazardous materials in transportation into one or more of the
following categories.
 image: 








     An explosive is defined as "any chemical compound, mixture, or device, the primary or
common purpose of-which is to function by explosion, i e., with substantially instantaneous
release of gas and heat.  " within certain limitations noted in DOT regulations  The overall
category of explosives is further broken down into Class A, Class B, and Class C explosives
Class A materials  are among the most powerful and include bombs, mines, torpedoes, and
ammunition used by the military; various high explosives like nitroglycerm  and dynamite;
blasting caps, detonating fuzes, and powerful rocket propellants. Class B substances and
devices are generally less powerful and typically (not always) function by rapid combustion
rather than detonation. The class includes special fireworks, flash powders, some pyrotech-
nic signal devices, liquid or solid propellants, some smokeless powders, and certain types of
ammunition. Class C explosives are manufactured articles which contain  Class A or B
materials, or both, as components in strictly restricted quantities  The class also includes
certain types of fireworks

      A  blasting  agent is a material designed for blasting  which has been tested in
accordance with DOT regulations and "found  to be so insensitive  that there  is very little
probability of accidental  initiation to explosion  or of transition from deflagration to
detonation" In other words,  the material  is capable of exploding  under  very  special
conditions, but these conditions are unlikely to occur in transportation, even  in the event of
an accident involving fire or impact

      Flammable  liquid refers to any liquid, within certain limitations and exceptions, that
has a "closed-cup" flash point below 1GO°F (37 8°C) Similarly, combustible liquid refers to
any liquid that has a flash point of 100°F or more but no higher than 200°F A pyrophoric
liquid is any liquid that ignites spontaneously in dry or moist air at or below 130°F (54 5°C)

      Flammable solids are "any solid material, other than one classed as an explosive,
which, under conditions normally incident to transportation is liable to cause fires through
friction, retained  heat from manufacturing or processing, or which can be ignited readily
 and -when ignited burn so vigorously and persistently as to create a serious transportation
 hazard  Included in this class are spontaneously combustible and water-reactive materials "

       An oxidizer,  according to DOT regulations, "is  a substance such  as a chlorate,
permanganate, inorganic peroxide, or a nitrate, that yields oxygen readily to stimulate the
 combustion of organic matter"  The key hazard associated with oxidizing agents or materials
 is that contact with a combustible substance, particularly organic materials, may cause the
 substance to ignite and possibly even explode

       An organic peroxide is essentially a derivative of hydrogen peroxide (H/)^ where one
 or more of the hydrogen atoms have  been replaced by molecular chains containing carbon
                                          8-2
 image: 








and hydrogen atoms. The substances in this category do not meet the definitions of Class A
or B explosives but may be capable of exploding under certain conditions  They may also
have the hazards associated with oxidizers.

     DOT defines a corrosive material as "a liquid or solid that causes visible destruction or
irreversible alterations in human skin tissue at the site of contact, or in the case of leakage
from its packaging, a liquid that has a severe corrosion rate on steel" A liquid is considered
to have a severe corrosion rate if it "eats away" more than 0.25 inch of a certain type of steel
at 130°F over the course of one year.

     A compressed gas is defined as any material or mixture with an absolute pressure in a
container of

           More than 40 psia at 70°F

           More than 104 psia at 130°F

     •     If the substance is flammable and in the liquid state, more than 40 psia at
           100°F.

   A flammable compressed gas is a compressed gas that has a lower flammable limit (LFL)
concentration of 13% or less  by volume in air, or  which has a flammable range (i e, the
difference  between the  LFL and  UFL)  of greater than  12%,  or which behaves in  a
prespecified manner in a flammability testing apparatus. A liquefied compressed gas is a gas
which  is partially a liquid under the pressure  in the container at  70°F. A non-liquefied
compressed gas is a substance which is entirely gaseous at a temperature of 70°F.

     Poisonous materials are divided into three groups in DOT regulations according to their
degree of hazard in transportation. Poison A  substances are  "poisonous gases or liquids of
such a nature that a very small amount of the gas, or vapor  of the liquid, mixed with  air is
dangerous  to life "  Poison B materials are liquids or solids,  other than Class A poisons or
irritating materials, "which are known to be so toxic to man  as to afford a hazard to health
during transportation, or which, in the absence of adequate data on human toxicity,  are
presumed to be toxic to man" because they meet certain criteria for inhalation, ingestion, or
skin exposures when tested on laboratory animals  Irritating materials are liquid or solid
substances  "which  upon  contact with fire or when exposed to air give  off dangerous  or
intensely irritating fumes"

     In the aftermath of the Bhopal incident, DOT rules were  modified to require special
marking of packages or containers of  volatile toxic liquids  which had previously escaped
classification as poisons  After adopting a new  set of special criteria for inhalation toxicity
hazards, the DOT required that packages containing more than  one liter and no more than
                                         8-3
 image: 








110 gallons of these materials be marked Inhalation Hazard. Poison placards were required
in addition to other required placards for trucks, rail cars or containers carrying any amount
of these materials.  Shipping papers for containers holding more than one liter were required
to include the statement Poison - Inhalation Hazard.

     An etiologic agent is "a viable microorganism, or its toxin, which causes or may cause
human disease " For the most part, such agents include potentially infected living tissue and
bacteriological materials.

     Radioactive  materials  are  substances  that  give  off potentially  harmful nuclear
radiation, and are classed in  three gioups according to the controls needed  to provide
"nuclear criticality safety"  during transportation. Fissile Class I materials  are  among the
safest of these substances, do not require nuclear cnticahty safety controls dunng transporta-
tion, and may be shipped together in an unlimited number of packages Fissile Class II
substances are somewhat more dangerous and can only be shipped in limited amounts when
packages are shipped together.  Fissile Class HI do not meet the requirements of the other
classes  and must be controlled to provide nuclear criticality safety in  transportation by
special arrangement between the shipper and the earner

     Finally the DOT has a category called Other Regulated Material (ORM) for a wide
variety of hazardous materials shipped in limited quantities and in certain kinds of packaging
There are five classes of such cargos with the designations ORM-A, ORM-B, ORM-C,
ORM-D,andORM-E

     Identification Numbers

     The DOT has assigned a four-digit identification to  each of the hazardous materials
regulated in transportation. When appearing in documentation, these numbers are preceded
by the letters "UN" or "NA" The UN numbers, such as UN1203 for gasoline, were assigned
in cooperation with the United Nations and  are used on  an international  basis  The NA
numbers are not recognized in international transportation except to and from Canada.

      Most of the numbers and the material shipping names  to which  they are assigned
represent very specific materials. It is well to recognize, however, that the DOT also permits
 some cargos to be identified in a rather  genenc fashion. For example, the identification
 number UN1993 applies to flammable liquid, nos  The last three letters are an abbreviation
 for not otherwise specified, so the number does not permit identification of the specific
 material in the container.
                                         8-4
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     Placards and Labels

     The DOT has numerous regulations dealing with the placards and labels that must
appear respectively  on bulk containers and packages of hazardous materials.  Figure 8.1
illustrates the required placards, these being the fairly large signs that must appear on railroad
tankcars, highway tank trucks, and other large transport vehicles Labels are fairly similar
and any differences are rather self-explanatory.

     Special Notes

     Before continuing, it  is necessary  to make two important observations  about DOT
classification systems and  placarding and labeling requirements The first is that these
systems and requirements are modified on a frequent basis and there has been considerable
activity to improve  them in the aftermath of the Bhopal incident. Although the material
presented herein is of a fairly general nature, some items may become outdated with time.
Indeed, even as this document was being prepared, the DOT was  in the process of finalizing
new regulations in this area.

     Secondly, and most importantly, be intensely aware that the current  DOT material
classification system has weaknesses that prompted the above activities. Furthermore, the
current system is primarily designed to denote the perceived primary hazard of a material as
determined by application of rigorous classification criteria Do not under any circum-
stances assume that the  hazard indicated by a warning label or placard attached to a
container is the only hazard associated with the material found therein.

8.3 U.S. ENVIRONMENTAL PROTECTION AGENCY CLASSIFICATIONS

     The EPA has developed several lists  of chemicals  and chemical wastes that may be
broadly categorized as"hazardous substances." Besides the water pollutants discussed earlier
in Chapter 6, they include:

     •    A list of specific hazardous wastes and  criteria for designating other
          materials  as wastes under the Resource Conservation and Recovery Act
          (RCRA) of 1976 and subsequent amendments  See Title 40, Part 261 of the
          Code of Federal Regulations (40 CFR 261) for details.

     •    A list of hazardous substances developed under Section 311 (b) (2) (A) of
          the Clean Water  Act of 1977.  See 40 CFR 112-114 for details

     •    Chemicals listed as toxic pollutants under Sections 307(a) and 307(c) of
          the Clean Water  Act  See 40 CFR 116-117 for details.
                                        8-5
 image: 








                                          FIGURE 8.1

                                   U.S. D.O.T. PLACARDS

  The alternate display incorporating the  UN/NA 4-digit number appears to the right of the placard
   FLAMMABLE GAS

                 «
               FLAMMABLE SOLID

                 .*
                                                                          FLAMMABLE SOLID
NON-FLAMMABLE GAS
                    FLAMMABLE
                                                       COMBUSTIBLE

                                                                   *
     CORROSIVE
                    OXYGEN
                                                          CHLORINE
                                                                  «
      EXPLOSIVES

    *            *
                     POISON
                                                RADIOACTIVE
EXPLOSIVES


   POISON GAS
                                                          NOTE No alternate
                                                          display Is permitted
                                                          for EXPLOSIVES A,
                                                          POISON GAS,
                                                          and RADIOACTIVE
                                                          materials
      OXIDIZERS
   FLAMMABLE GAS
               ORGANIC PEROXIDES

              £•
             ORGAHIC
            .PEROXIDE
          PLACARDED EMPTY TANK CARS

NON-FLAMMABLE GAS                 FLAMMABLE
                                                                 NOTE

                                                          Hazard Class Numbers

                                                       1  Explosives
                                                       2  Compressed gases
                                                       3  Flammable/Combustible
                                                          Liquids
                                                       4  Flammable solids
                                                       51 Oxldlzers
                                                       5 2 Organic peroxides
                                                       6  Poisons
                                                       7  Radioactive materials
                                                       8  Corrosives
                                                                             FLAMMABLE SOLIDS
             When required on t«nk cars, portable tanks or cargo tanks, Identification numbers, as specified In §172101 or §172102, shall be dlsplayec

             An ldenmicatlon"mimber may not be displayed on a Poison Gas, Radioactive or Explosives placard §172 334(a), but If a tank car,
             p^rtabltunk or Mrgotank casing such a commodity requires an Identification number, It must be displayed on an orange panel §172
                                               8-6
 image: 








     •     A list of materials deemed to be Extremely Hazardous Substances (EHS)
           by virtue of their acute inhalation toxicity in air. Established under Title
           IE, section 302(a) of the Superfund Amendments and Reuthorization Act of
           1986, this list has been subject to frequent changes. It may be expanded in
           the future to include materials with other hazardous characteristics.

     •     A list of hazardous substances established under the 1980 Comprehensive
           Environmental  Response, Compensation, and Liability  Act (CERCLA),
           also known as Superfund The list is comprised of chemicals listed under
           RCRA, the Clean Air Act, and/or the Clean Water Act  See 40 CFR 302
           for details Extremely Hazardous Substances are also to be included in this
           list.

     •     A list of toxic chemicals established under section 313 of SARA Title  HI
           for emissions reporting  See 40 CFR 372 for details

     The hazardous  substances listed under CERCLA  have been  assigned  reportable
quantities by the EPA. These are the amounts that must be spilled within a specified penod
of time before the party responsible for the spill or discharge is required to report the spill to
federal, state, and local governments They  range from one pound for materials considered
to be extremely  harmful to the environment (plus some chemicals which are under review
and have not yet been assigned more appropriate reportable quantities) to 5000 Ibs for those
substances considered to pose significant but comparatively moderate environmental hazards.
It is well to recognize that.

     •     The  current EPA CERCLA  hazardous substance list mostly  includes
           substances that were identified as a result of then- long-term environmental
           and public health hazards There are many significant hazardous materials
           which do not appear in the list

           Reportable quantities (RQs) were generally derived from an evaluation of
           the long-term health and environmental hazards of the listed chemicals.
           RQ values represent a relative ranking of the chemicals vis-a-vis each other
           and are not absolute indicators of risk Due to the criteria by which they
           were derived, RQs should not be used to rank substances for planning or
           emergency  response activities involving episodic spills  or discharges  of
           hazardous materials posing acute  threats to the public.

     Each Extremely Hazardous Substance designated by the EPA has been  assigned a
Threshold Planning  Quantity  (TPQ)   which  triggers  various  reporting,  community
right-to-know, and emergency planning requirements. Please note that:
                                         8-7
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     •    The list of Extremely Hazardous Substances was prepared quickly after the
          Bhopal incident as an attempt to denote those materials which pose a high
          acute toxicity hazard to the public when discharged into the environment
          The list contains several substances that are highly toxic but lack mobility
          under ordinary spill conditions

     •    Although Threshold Planning Quantities have an important role in defining
          regulatory requirements, there is no guarantee that lesser quantities of a
          designated EHS will not pose threats to public health and safety under all
          accident conditions.

8.4 NATIONAL FIRE PROTECTION ASSOCIATION HAZARD RANKINGS

     In an attempt to provide fire service personnel a rapid means of assessing the dangers
of hazardous materials, the National Fire Protection Association  (NFPA) has developed a
ranking system that assigns separate values in the range of zero to  four to  the health,
flammability, and reactivity hazards of individual materials A fourth category for "special"
hazards uses the following symbols among occasional others:

      •    "W to denote unusual reactivity with water

      •    "OX" to denote that the material has oxidizing properties

      •    "COR" to denote that the material is corrosive to living tissue

      •    The standard radioactivity symbol to denote radioactivity hazards

      Table  8.1 defines  the rankings  specified by the NFPA for health, flammability, and
reactivity. Although the individual rankings are often simply listed by category  in NFPA
documents and many chemical company material safety data sheets, they may also be seen
within a  diamond-shaped sign with  blue, red, yellow, and white squares containing  the
respective rankings for health (blue), fire (red), reactivity (yellow) and other (white)

8.5 INTERNATIONAL MARITIME ORGANIZATION CLASSIFICATION

      Under the  auspices of the United Nations, the International Maritime Organization
 (IMO) has developed and continues to refine its International Maritime Dangerous Goods
 Code (1MDG) to facilitate and ensure the safety of international shipments of hazardous
 materials. The DOT has adopted and/or permits use of IMDG requirements under numerous
 circumstances, and it is very common to see references to these requirements in MSDS  and
                                         8-8
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                                            TABLE 8.1
                                      NFPA HAZARD RANKINGS
oo
Identification of Health Hazard
Color Code: BLUE
Signal
«
8
ft
a
®
Type of Possible Injury

Materials which on very
short exposure could cause
death or maior residual in-
jury even though prompt
medical treatment were
given
Materials which on short ex-
posure could cause serious
temporary or residual injury
even though prompt medical
treatment were given.
Materials which on intense
or continued exposure could
cause temporary incapacita-
tion or possible residual in-
jury unless prompt medical
treatment is given
Materials which on exposure
would cause irritation but
only minor residual injury
even if no treatment is given
Materials which on exposure
under fire conditions would
offer no hazard beyond that
of ordinary combustible ma-
terial
Identification of Flammabihty
Color Code- RED
Susceptibility of Materials to Burning
Signal
«
§
ft
Q
(D

Materials which will rapidly
or completely vaporize at
atmospheric pressure and
normal ambient tempera-
ture, or which are readily
dispersed in air and which
will burn readily.
Liquids and solids that can
be ignited under almost all
ambient temperature condi-
tions.
Materials that must be mod-
erately heated or exposed to
relatively high ambient tem-
peratures before ignition can
occur
Materials that must be pre-
heated before ignition can
occur
Materials that will not burn
Identification of Reactivity
(Stability) Color Code YELLOW
Susceptibility to Release of Energy
Signal
4
8
ft
Q
(D

Materials which in themselves are
readily capable of detonation or of
explosive decomposition or reaction at
normal temperatures and pressures
Materials which m themselves are
capable of detonation or explosive
reaction but require a strong initi-
ating source or which must be heated
under confinement before initiation
or which react explosively with water
Materials which in themselves are
normally unstable and readily under-
go violent chemical change but do
not detonate. Also materials which
may react violently with water or
which may form potentially explosive
mixtures with water
Materials which in themselves are
normally stable, but which can be-
come unstable at elevated tempera-
tures and pressures or which may re-
act with water with some release of
energy but not violently
Materials which in themselves are
normally stable, even under fire ex-
posure conditions, and which are not
reactive with water
 image: 








other hazardous material  publications. Indeed, the DOT  has proposed to adopt IMDG
performance oriented packaging requirements  in their entirety for implementation in the
United States.

     The IMO has categonzed its overall list of hazardous materials into nine major classes,
many of which are further broken down into  two or more divisions. Table 8 2 lists and
describes the basic definitions of IMO classes and divisions Detailed definitions, including
more specific breakdowns for explosives, are provided in the text of the IMDG code.
                                           8-10
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                                      TABLE 8.2
                 BASIC IMO MATERIAL CLASSES AND DIVISIONS
Class 1 -- Explosives
Division  1.1    Substances and articles which have a mass explosion hazard  Explosive A
Division  1.2    Substances and articles which have a projection hazard but not a mass explosion
               hazard.  Explosive A or B
Division  1.3    Substances and articles which have a fire hazard and either a minor blast hazard
               or a  minor projection  hazard or  both, but not  a  mass  explosion hazard.
               Explosive B
Division  1.4    Substances and articles which present no significant hazard. Explosive C
Division  1.5    Very insensitive substances. Blasting Agent
Class 2 -- Gases (compressed, liquelified or dissolved under pressure)
Division  2.1    Flammable gases. Flammable gas
Division  2.2    Nonflammable gases. Nonflammable gas
Division  2 3    Poison gases. Poison A and other poison gas
Class 3 - Flammable liquids
Division  3.1    Low flash point group (liquids with flash points below 0°F)  Flammable liquid
Division  3.2    Intermediate flash point group (liquids with flash points of 0°F or above but less
               than73°F). Flammable liquid
Division  3.2    High  flash point group (liquids with flash points of 73°F or above up to and
               including 141°F). Flammable liquid or Combustible liquid
Class 4 - Flammable solids or substances
Division  4.1    Flammable solids Flammable solid
Division  4.2    Substances liable to spontaneous combustion. Flammable solid or, for py-
               rophoric liquids, Flammable liquid
Division  4.3    Substances emitting flammable gases when wet. Flammable solid
Class 5 -- Oxidizing substances
Division  5.1    Oxidizing substances or agents.  Oxidizer
Division  5.2    Organic peroxides. Organic peroxide
Class 6 -- Poisonous substances and infectious substances
Division  6.1    Poisonous substances. Poison B
Division  6.2    Infectious substances. Etiologic agent
Class 7 — Radioactive  substances. Radioactive material
Class 8 — Corrosives.  Corrosive material
Class 9 — Miscellaneous dangerous substances. Other regulated material

Note:  Corresponding DOT classes are shown in italics following IMO classes and divisions.

                                           8-11
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        9.0  OVERVIEW OF THE HAZARD ANALYSIS PROCESS
          PROBABILITY
            ANALYSIS
     Likelihood of  Accidents
        Outcome of  Events
                                     HAZARD
                                IDENTIFICATION

                                Locations and Routes
                               Materials and Amounts
                                   Characteristics
                                  RISK  ANALYSIS

                                  Combination of
                                 Consequences and
                                    Probabilities
   CONSEQUENCE
      ANALYSIS
 Nature of  Hazards
Magnitude  of Impacts
                                     PLANNING
                                        FOR
                                     ACCIDENTS
9.1 INTRODUCTION

    Chapter 1 to this document reported that recent guidance manuals published by the federal
government have used  the  term hazard analysis  to  describe the overall  procedure  for
evaluating the hazards, consequences, vulnerabilities, probabilities, and nsks associated with
the presence of hazardous materials within any given locality or jurisdiction.  This term will
also be used herein for the  sake of consistency with earlier publications,  although it is
recognized that hazard  analysis is often applied in a somewhat different context within
government and industry.

    There are four basic steps presented in this guide for the conduct of a hazard analysis, and
a related fifth step that takes advantage of the knowledge gained during the effort to develop a
comprehensive emergency plan for hazardous  materials that focuses attention on the known
threats to a community or facility while maintaining sufficient flexibility to deal effectively and
efficiently with unforeseen events These steps include:

    •    Location, identification,  and characterization of potential spill sources and
        accident sites in  the jurisdiction or locality of concern in a process referred to as
        hazard identification.  This step  essentially concludes with the identification
                                        9-1
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        and/or postulation of fundamental accident scenarios requiring further considera-
        tion and analysis  Results from the probability analysis step which follows can
        often help in further refining these scenarios.

   •    Evaluation of the likelihood of individual accident scenarios in a process called
        probability  analysis. This step permits examination  and/or pnontization of
        potential accident scenarios in terms of their probability of occurrence.

   •    Evaluation of the  consequences and impacts associated with the occurrence of
        postulated accident scenarios in a process that is referred to as consequence
        analysis.  This step provides  an understanding of the nature and outcome of an
        accident and permits examination and/or pnontization of scenarios in terms of
        their potential impact on people and property.

   •    Combination of results from the accident probability and consequence analysis
        efforts to provide a measure of overall nsk associated with the specific activity
        or activities being studied in a process referred to as risk analysis. The effort
        permits examination and/or pnontization of scenarios in terms of overall "risk".

   •    Use of the results of the above activities (which in aggregate provide a planning
        basis for emergency preparedness  personnel)  during actual development  and
        preparation of an emergency plan.

    It is the express purpose of this chapter to introduce and describe these various steps
further  and  to  set the stage for accomplishment of necessary efforts  via  use of the data,
information, analysis procedures and computational methods presented in subsequent chapters
of this guide.

    Note that the various steps of  the overall  hazard analysis need  not  be performed m
precisely the order shown for all postulated accident scenarios. Indeed,  as descriptions of the
various steps are read, keep in mind that:

   •    Some users of this guide may wish to employ all steps outlined to one postulated
        accident sceneano at a time, starting with the scenano they perceive as posing
        the greatest threat to their jurisdiction and then working down their "list".

   •    Some users may wish to perform one step at a time for all postulated accident
        scenarios.

   •    Some users may wish  to ignore the probability analysis step for one or more
        postulated accident scenarios if they perceive or determine that the consequences
        of an accident would be major or catastrophic  and wish  to plan  for them
                                          9-2
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       regardless of  their likelihood of occurrence.  Such decisions  are  specifically
       supported by guidance provided below and in Chapter 13.  Although the most
       severe yet credible accidents that can be foreseen in any jurisdiction or locality
       are most likely to have low probabilities of occurrence,  the very fact that
       consequences  may be catastrophic or major is usually sufficient justification for
       consideration of the scenario during the emergency planning process.

   •   Some users may wish to skip the assessment of accident impacts and conse-
       quences for scenarios that are determined to  be highly unlikely and are also
       known to pose comparatively low threats to the public due to the quantity and/or
       characteristics of the materials involved.

   •   Some users may wish to perform a "quick and dirty" assessment  of potential
       accident probabilities and/or consequences using readily  available  information
       and assuming "worst case" conditions for unknown  data or parameters  The
       answers obtained could then be used to prioritize more  formal  analyses of
       important accident scenarios

92 STEP 1: HAZARD IDENTIFICATION

    Hazard  identification  involves  delineation  and  specification of those facilities and
transportation modes  that handle hazardous materials within the locality  or jurisdiction  of
concern  In other words, it requires that planning  personnel determine where and  how
hazardous materials are stored, handled, or processed in their locality, how and by what routes
they are transported to and from these facilities, and where  and how hazardous materials may
pass through the area  on their way to other destinations via rail, highway, marine, or pipeline
transportation routes.

    A directly related and important activity involves characterization of each potential spill or
accident  site in sufficient detail to formulate  potential accident  scenarios and to  permit
subsequent evaluation of accident probability, likely spill amount, and nature and magnitude of
resulting impacts  In other words, once detective work  has discovered  where  hazardous
materials are located, this step involves gathering the  data  and information necessary  to
eventually postulate the circumstances under which accidents  may occur and to evaluate the
approximate hazards and risks that these accidents may pose to surrounding populations

     Specific guidance and advice pertaining to the conduct of a hazard identification effort
follow in Chapter 10 of this guide.
                                          9-3
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93 STEP 2: PROBABILITY ANALYSIS

    With all the media attention given to the topic on a national as well as international basis
in recent times, one might easily come to believe that a major disastei involving hazardous
materials is bound to occur within the foreseeable future wherever such materials are handled,
stored, processed, or transported Indeed, a survey of public authorities a few years ago placed
such events at the top of a list of concerns for conceivable emergencies in their respective
jurisdictions  Fortunately, however, catastrophic spills or discharges, i e, those that actually
fall or significantly injure more than a few people at a time, are actually rare events in our large
and heavily industrialized nation, although accidents in general involving hazardous  materials
are very common The vastly increased attention given to chemical safety in recent times by
industry and government alike should serve to further improve overall safety performance in
the future. Better preparedness to respond to accidents should serve to reduce overall risks to
society by helping to reduce or limit adverse impacts once an accident has occurred

     The probability analysis step may be considered optional where  community leaders or
facility owners wish to prepare for every conceivable accident regardless of its probability of
occurrence and have the time, manpower, and resources to achieve their goals More often
than not, however, emergency planners will find that time and resources are limited, that other
threats to the  community  or public needs compete for attention, and that there is value in
conducting a  probability  analysis  Pnontization of chemical  related threats in  terms of
probability permits attention to these threats in an orderly fashion and reduces the chance that
time and resources will be  expended  on  scenarios  of exceedingly low credibility or
significance.

     The task of evaluating the potential for a hazardous material emergency in any locality or
jurisdiction involves use of historical accident data in conjunction with local factors (to the
extent possible) to predict the frequency of future accidents, and to some extent, the  general
consequences of these events. Prediction of the future, of course, is an inexact science, but
probabilistic accident assessment methods can provide approximate indications of the number
and nature of accidents expected on average in a given locale within a specified penod of time,
and can therefore provide valuable guideposts for decision-making purposes

     There are many localities where the total traffic and use of hazardous materials pose a
clear threat to public health  and safety  and which are  generally aware of the  need for
 comprehensive emergency  planning These  localities could  benefit from  a  probabilistic
 assessment of accident potential which permits the various threats to be ranked and prioritized,
 thus ensuring that the most important and serious threats receive the full attention they  deserve
 and that available resources are wisely allocated  (Note- At least one instance is known where
 a city purchased a  set of expensive  chemical protective clothing -- fully encapsulating suits
                                           9-4
 image: 








resembling space suits ~ and stored them away after allowing its hazmat response team
members to try them on once The suits eventually mildewed and rotted from lack of need and
attention.)

    At the opposite end of the spectrum are localities which face relatively few hazardous
material threats and which may be unsure whether the nsk of an accident warrants extensive
expenditures of time and resources for emergency preparedness  A probabilistic assessment of
accident potential, coupled with the results of a consequence analysis, can assist these localities
in deciding upon the appropriate level of planning and preparedness. Together with assess-
ments of other natural and man-made threats to the locality, priorities can be set for allocating
time and resources to threats with the highest  potential for harming the public. Efforts can be
initiated for sharing response capabilities and resources among neighboring jurisdictions where
the chances of a significant accident in a  region encompassing several jurisdictions are
considerable, but the chance that the accident will occur in any specific locale within the region
is comparatively low.

     Guidelines and methods for probabilistic assessment of hazardous materials emergencies
are presented in Chapter 11 of this guide

9.4 STEP 3: CONSEQUENCE ANALYSIS

     Probabilistic assessment of accident potential can provide a good idea of the likelihood
that a potential accident will actually take place It must be realized, however, that the most
frequent types of spills or discharges have  relatively minor  consequences, and that  more
 serious accidents will generally have lower probabilities of occurrence.  Thus, a full under-
 standing  of the risks faced  by any specific  locale requires  knowledge not only of  the
probabilities associated with different types of accidents, but also the expected impacts and
 consequences of these events

     Estimation of potential accident impacts and consequences can be  accomplished  via a
variety of consequence,  vulnerability, and hazard assessment methodologies described in
 Chapter 12 of this guide and incorporated within the computer program named ARCHIE that is
 an integral part of this document

 9.5  STEP 4: RISK ANALYSIS

     The nsk analysis step is also somewhat optional in the sense that it relies upon the results
 of the accident probability analysis for completion. It entails combination of the probability or
 likelihood of an accident occurring with a  measure of the predicted consequences of the
 accident to provide an overall measure of risk that can be used for threat pnontization and
 planning purposes.
                                          9-5
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    Readers should be aware that the term risk is often misused by society. Being usually
defined as a combined measure of the probability and seventy of potential threats, it is
possible for a threat with low probability of occurrence and relatively high potential seventy to
pose a comparable level of risk to a community (from a planning perspective) as a threat with a
higher probability of occurrence but lower seventy. Thus, the performance of a nsk analysis
permits all threats to be viewed from a perspective that is not biased by consideration of either
probabilities or consequences alone.

    Chapter 13 provides guidance on how the accident scenarios evaluated in Steps 2 and 3
may be evaluated in terms  of nsk It also contains a discussion of how the nsks associated
with hazardous materials compare with more common threats to life and property  The latter
topic  is considered important because the hazardous matenals accident problem has  several
emotional and political aspects that sometimes tend to distort the truth.

9.6 STEP 5: USE OF HAZARD ANALYSIS RESULTS IN EMERGENCY PLANNING

    The scenarios resulting from the overall hazard analysis process will hopefully represent
the full range of significant hazardous material emergencies that have a reasonable likelihood
of occurring in the foreseeable  future within any given locality. It remains to consider how
these scenarios and related analysis results may be used to focus an emergency response plan
on credible threats to the locality of concern and to ensure that the emergency plan provides for
efficient, rapid, and comprehensive mitigation of adverse impacts

    Chapter 14  of the guide discusses the planning ramifications associated with individual
accident scenarios in  some detail and serves as a guide for the use of these scenarios during
emergency planning.  Note that each scenario deemed credible and worthy of consideration
gives planning personnel the opportunity to sit back under non-emergency conditions, identify
steps that must be taken to protect the public, and ensure that response personnel will have the
necessary organization, communications systems, equipment, matenals, manpower, sources of
assistance, and training to cope with the situation and minimize casualties, property damage,
and environmental pollution.
                                         9-6
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             10.0 HAZARD mENTIFICATION GUIDELINES
                     ©xgr
10.1 INTRODUCTION

     The purpose of this  chapter is to assist planning personnel  in  identifying and
characterizing  potential sources and locations of hazardous material spills within  their
jurisdiction.  It is primarily directed to local and county governments, but broad application
of its guidance also permits use at the state level and within industry.

     The chapter outlines a variety of methods to obtain the desired information. It is left to
individual localities or jurisdictions to select the method or combination of methods best
suited to local conditions

10.2 REASON FOR THE DESIRED INFORMATION

     There are three fundamental and interrelated reasons why a town, city, county, or state
government should have knowledge of the identity, location, and characteristics of hazardous
materials and related processes within its boundaries.

   1.    For hazard assessment purposes:  The desired information, together with
        identified accident scenarios and the use of consequence analysis procedures
        presented in this guide, can provide  emergency command personnel with an
 image: 








        indication of the potential nature and magnitude of hazardous material threats
        facing a community. This knowledge in turn can facilitate decisions concern-
        ing protection of the public and on-scene response personnel in the event of
        an actual emergency.

   2.    For emergency  planning  purposes: It can be  difficult and extremely
        inefficient to plan and prepare for every conceivable emergency situation The
        desired information, together with the probability analysis and consequence
        analysis procedures presented in  this guide, permit emergency plans to be
        "tailored" to the specific threats facing a community

   3.    For actual response purposes: Hazardous material spills are often confus-
        ing and dangerous situations in their initial stages, especially if responding
        emergency personnel do not have a good idea of the nature and quantities of
        the substances that may be involved upon arriving at the accident scene. The
        hazard identification process permits compilation of a centralized data base
        that can be accessed upon first notification of an emergency to determine (or
        at least limit) the overall range of possibilities.

10.3 SUGGESTED SCOPE OF THE EFFORT

     The guidance that follows  may suggest to some readers that the collection and
compilation of the desired data will require a major effort on the part of planning personnel
This will be true to some degree in highly  industrialized communities, but the effort can be
made manageable by keeping certain thoughts and concepts in mind.

   •    Small amounts  of  hazardous materials (unless  they  have  unusual  and
        extremely dangerous properties)  are generally likely to cause problems in
        only a very localized area. Data collection efforts can be greatly minimized
        by concentrating  efforts on transportation routes and facilities that handle or
        store significant quantities of hazardous materials

   •    Industrial concerns  that  manufacture or use large amounts of hazardous
        materials are  likely to employ or have access  to  technical personnel with
        expertise in chemical safety and  will be well aware in  most cases of their
        Labilities for any deaths, injuries,  or property damages caused by an accident.
        Some facilities, particularly those  associated with major corporations, may be
        willing to compile the desired data and even perform the analyses described in
        Chapters 11,12, and 13 of this guide  if asked to do so at the appropriate level
        of management These firms have a clear and vested interest m ensuring that
        the local community is well prepared to protect the health and property of the
        public in the event of an accident. Many of them, especially since the Bhopal
                                        10-2
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tragedy and its attendant litigation, have already taken steps to assess and
reduce the nsks that their chemical-related activities may pose to nearby
populations  and the  continued viability of their business operations in the
event of a major accident.

Major accidents are fairly rare events, particularly when one focuses on any
relatively small part  of the nation, as is the case with the 4000 or so  local
emergency planning  committees (LEPCs) that have been established in
response to  federal laws and regulations relating to the Superfund Amend-
ments and Reauthonzanon Act (SARA) of 1986 The detailed and time-con-
suming work can be spread out over some reasonable period of time  once
minimum planning requirements mandated by SARA have been fulfilled.

Everyone has  a stake in hazardous materials safety.  Civic-minded citizens,
business organizations, and individual companies may be willing to volunteer
time and resources  to the overall effort.  The fact that LEPCs have  been
established across the nation has set the stage for, should facilitate, and should
indeed encourage planning efforts that transcend the limitations of mandatory
planning requirements.

Neighboring communities and jurisdictions will need much of the same data
and information, not only  on hazardous material transportation traffic, but
also with respect  to facilities that may pose a threat across junsdictional
boundaries  in the event of an  accident Cooperation  and integration of
activities on a regional basis may not only reduce the workload for all parties,
but result in cooperative agreements that may increase the effectiveness and
efficiency of  emergency response actions during  actual emergencies  Fire
departments across the nation, for example, have long appreciated the  value
of regional mutual aid systems. This concept can be extended in a variety of
ways for response to hazardous material related accidents, thus reducing the
burden on individual jurisdictions.

Many of the  efforts and tasks described in this and the  following chapters
appear more complex when first looked over than they really are.  The work
will go much  more smoothly and quickly as experience is gained in applying
suggested methods and interpreting their results

Most importantly, federal laws and regulations require many (though not all)
facilities that  utilize hazardous materials to provide LEPC's all information
needed (with  certain exemptions related to trade secrets) for preparation of
emergency  plans  Those facilities that store quantities  of Extremely Haz-
ardous  Substances  (EHSs)  in  excess of designated Threshold  Planning
                                10-3
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         Quantities (TPQs) are required to appoint a. facility emergency coordinator to
         assist the LEPC in its planning efforts Other facilities may also be required
         by SERCs to participate in the planning process under Tide HI of SARA

10.4 NATURE OF DESIRED INFORMATION

     Table 10.1 briefly summarizes the types of information generally needed for various
transportation modes and stationary facilities, while subsequent discussions provide further
descriptions of data requirements  Both the table and associated discussions are somewhat
general because the specific details needed are not only a function of the properties of the
hazardous materials being handled, but the circumstances under which they are transported,
stored, transferred, or processed, and the degree of detail that emergency planning personnel
wish to include in their overall effort. It is therefore strongly recommended that Chapters 11
and 12 of this guide be carefully studied and that examples  be worked  out so that  data
collection personnel will have (or can be given) specific guidance with respect to the detailed
information desired m any given situation or jurisdiction

     Rail Transportation

     If the locality of interest has one or more railroad nght-of-ways, it is first necessary to
determine whether these tracks are used for  shipments  of hazardous materials. Any track
segments used for this purpose should then be characterized in terms of specific location and
length. Special attention should be  given to identifying track segments that  pass over  or
along the side of bodies of water. For subsequent response planning purposes, particularly in
rural areas, some  thought should  be given to how various portions of the route may be
accessed or approached by emergency response personnel and vehicles  Any information
collected on these topics can best be shown on maps of the area, which may also be modified
to highlight population centers and special occupancies  such as schools, hospitals, prisons,
and nursing homes ~ not just for railroad accident purposes, but for all credible accident
scenarios.

     There are maj'or railroad corridors in the United States that provide passage for a wide
variety of hazardous materials, and there are numerous routes that only have limited traffic to
specific destinations.  Some part of this traffic may consist of regularly scheduled shipments
(e.g., weekly or monthly shipments from a particular shipper to a particular receiver), another
part may consist of non-regular but recurrent shipments, and a smaller part may consist of
unique, non-recurrent shipments Ideally, it is desired that planning and emergency response
personnel obtain as complete a picture as possible of the specific hazardous cargos handled
over the course of a recent 6-12 month penod, the types and capacities of their containers, the
general frequency of individual shipments, and the frequency of trains (called "consists" in
the railroad industry) which haul hazardous cargos  Such data are best obtained by initiating
direct  contact with personnel within the safety department(s) of the railroad(s) that use the
                                          10-4
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                                    TABLE 10.1
                 SPILL SOURCE CHARACTERIZATION FACTORS

Rail Transportation
   •   Route(s) and associated mileage through locality
   •   Classifications of track
   •   Location and layout of railroad yards
   •   Specific hazardous cargos
            Number of cars passing through and length of stay m yards
            Types and capacities of containers
Highway Transportation
         Route(s) through locality
    •    Nature and length of roads by segment
    •    Location and layout of local terminals
    •    Specific hazardous cargos
            Number of trucks passing through and length of stay
            Types and capacities of containers
Water Transportation
    •    Route(s) through locality
    •    Mileage of route(s)
    •    Nature and characteristics of waterway(s)
         Location and layout of moorings and anchorages
     •    Specific hazardous cargos
            Number of ships or barges passing through and length of stay
            Types and capacities of vessels and containers
 Pipeline Transportation
     •    Pipeline route(s)
         Mileage of route(s) through locality
     •    Contents of pipehne(s)
     •    Pressure and temperature of pipelme(s)
     •    Flowrate through pipelme(s)
         Overall length and diameter of hne(s)
     •   Characteristics of leak detection and shutdown system(s) (if any)
                                       10-5
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                                 TABLE 10.1 (Cont.)
                 SPILL SOURCE CHARACTERIZATION FACTORS

Chemical and Petroleum Bulk Processing Facilities
    •    Location and layout of overall facility
    •    Location, type, dimensions, capacity, venting systems, contents, pressure, and tempera-
         ture of chemical reactors, storage tanks, holding tanks, and other vessels
    •    Route, length, diameter,  flowrate, pressure, temperature,  and contents  of major
         intraplant pipelines, together with information on leak detection and shutdown systems
    •    Location and nature of bulk cargo  loading and unloading facilities and frequency of
         transfer operations
    •    Location, size, and layout of secondary containment systems such as sumps, trenches,
         dikes, or barriers around potential spill locations
    •    Location, layout, and destination of sewer and drainage systems
Chemical and Petroleum Bulk Storage Facilities
    •    Location and layout of overall facility.
    •    Location, type, dimensions, capacity, pressure, temperature, venting systems,  and
         contents of bulk storage tanks.
    •    Route, length, diameter, flowrate, pressure, temperature, contents, and frequency of use
         of major intrafacihty pipelines together with information  on  leak detection  and
         shutdown systems.
    •    Location and nature of bulk cargo  loading and unloading facilities and frequency of
         transfer operations.
    •    Location, size, and layout of secondary containment systems, as above
    •    Location, layout, and destination of sewer and drainage systems.
Pesticide and Other Packaged Chemical Warehouses
    •    Location and layout of overall facility.
    •    List of products stored in f acility together with data on storage locations
    •    Fire protection systems in the facility
    •    Location, layout, and destination of sewer and drainage systems in area.
    •    Location, size, nature, and  layout for secondary containment of spilled chemicals or
         contaminated water used for flrefighting
                                         10-6
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track(s) in question.  Although these individuals  may refer you elsewhere within their
organizations for the desired data, contact with them can also be beneficial because they will
have knowledge of the plans and preparations undertaken by  the railroad to respond to
emergencies involving hazardous commodities along their routes -- information which will
be highly useful during the community emergency planning process. (Note: Railroads are
common carriers,  as  are many trucking firms  and marine shipping operations.  Although
such earners do not own the cargos they transport, and very often do not own the vehicles in
which  the cargo is placed, they are legally and financially  responsible for the damages
resulting from any accidents that occur while a hazardous commodity is in their possession.
As common earners,  they in most cases have little choice but to  transport any commodity
placed in their custody in accordance with current federal regulations.)

     If the locality includes a railroad terminal or yard that  transfers cars with  hazardous
cargos between trains heading to  different destinations and/or which stores them  for a time
(which could be days or more) before they move on, a map should be obtained of the specific
location and  layout of the facility.  In addition, if hazardous  material cars are in any way
segregated or sorted into special  holding areas, these areas should be identified. As in the
case of moving traffic, as much information  as possible should be obtained  as to the
identities,  quantities, frequency, and length of residence of individual cargos  over  a
representative  period of  time. Employees  at the facility are  the best initial  source of
information  Be sure to ask if they have prepared an emergency plan for the facility and if
they are willing to integrate and/or coordinate this plan with the general community planning
effort.

     Highway Transportation

      Much of the information desired for railroad earners of hazardous matenals is  also
desired for over-the-road earners  Specific needs include identification of major traffic
corridors;  specification of the location, length,  and nature  of roads; characterization of
hazardous cargos, shipment frequencies, container types, and  container capacities,  and
characterization (as in the case of railroads) of any local terminals or other gathering areas
for hazardous material transport vehicles such as truck stops,  weigh stations, motels, and so
forth.  It may also be beneficial to compile data on any travel  and  route restrictions  in effect
in the region.

      Water Transportation

      Those localities on  the coastline of the United States, bordering inland waterways, or
 home to a port or harbor must be concerned with haulage of hazardous matenals by ship or
 barge. Although relating to the marine environment, the desired information is similar to that
 discussed above for railroad and highway transport.
                                        10-7
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     Pipeline Transportation

     Most major cross-country pipelines in the United States convey natural gas, crude oil,
LPG, refined petroleum products or  anhydrous ammonia,  but one  may occasionally
encounter more exotic commodities being transferred between specific sites (e.g., between
the manufacturer and a major user of a particular chemical)  Besides the specific route of a
pipeline and its length through the jurisdiction of  concern, it is desirable to  determine
pipeline contents, pressure,  temperature, typical and maximum flowrate,  diameter, and
overall  length, as well as characteristics of any leak  detection  and shutdown systems. The
effort should probably include high pressure natural gas  transmission lines  and larger
distribution lines, but not the smaller low pressure pipelines serving individual buildings and
neighborhoods.

     Bulk Chemical and Petroleum Processing Facilities

     This category includes a variety of chemical manufacturing plants, oil  refineries, and
facilities which use large quantities (i.e, bulk quantities) of hazardous materials during the
manufacture  of  their  products  In order to make the information gathering  task  more
manageable at large and complex facilities, it may be  necessary to screen chemical handling
areas and focus on those that utilize the largest quantities of the most hazardous materials,
keeping in mind the difference between the toxicity of a substance and the toxic hazard
presented to the public. Plant personnel, if cooperative, can be of invaluable assistance  in
this task. Screening can also be facilitated by asking  plant personnel for a list of hazardous
materials used at the facility together with typical quantities on hand.

     Of key importance is the need to obtain a plot plan of the facility showing the location
of hazardous  material stores (tanks, loading racks, pipelines, etc.) as well as the identity and
amount of chemicals present This information is useful for actual emergency response  as
well as planning purposes. Aerial photographs can also be valuable.

     It is next prudent to focus on any storage tanks of chemicals or large containers used
for mixing or reacting chemicals. Desired information includes type and location of the tank
or container, working capacity, dimensions, maximum potential pressure and temperature  of
contents, identity of contents, the  discharge orifice size of any emergency pressure relief
vents, and any systems installed to  capture, recover, or destroy flammable and/or toxic gases
that may be released under emergency conditions. While looking at such tanks, it is also
important to  determine if the contents  have the ability to undergo  any type of runaway
exothermic polymerization or decomposition reaction, or  if they are subject to any  other
hazardous reaction in the event of equipment failure, human operator error,  or inadvertent
contamination by materials available in the general area of the tank or container (particularly
                                         10-8
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those that are somehow linked to the tank by a pipeline system). Make note also of the
diameters of pipelines and various pipes that exit each tank and which could discharge the
contents of the tank or container in the event of a break or rupture.

      While on the subject of intraplant pipelines, note that such facilities may have literally
miles of relatively small pipes linking items of equipment together and possibly a limited
number of intraplant lines of large capacity. It is well to gather the list of information under
Pipeline Transportation above for the larger lines conveying hazardous materials.

      Facilities that handle large volumes of chemicals are also likely to ship and/or receive
hazardous materials by rail, highway or water transportation modes, thus necessitating cargo
loading and unloading facilities. Details of interest at these sites include identity, frequency,
and volume of individual shipments, diameter and type of loading/unloading hoses  or arms,
normal pumping rates of cargos through hoses or  arms,  time required to observe any tank
overflows and to shutdown pumps, type and capacity of transport vehicles, and the number,
contents, and duration of stay of railcars, trucks, or marine vessels serving the facility.

      Many facilities have installed secondary containment systems around storage tanks,
process  areas, and loading/unloading areas to collect  and contain  any spilled materials,
typically in the form of dikes, curbs, or other barriers surrounding items of equipment or pits
or sumps to which spilled cargo will flow and collect  Since the total rate at which vapors or
gases will evolve from a pool of boiling or evaporating liquid is a function of the surface area
of the pool, and since the size of a liquid pool fire is also a function of pool dimensions, the
dimensions of  diked  areas or sumps provide highly  useful  information For response
planning purposes, information  is desirable on plant fire protection systems and emergency
 spill response capabilities.

      Finally, it is also desirable to determine whether spilled materials have the opportunity
 to enter underground sewer or drain pipes and where these pipes lead. Flammable liquids in
 pipes that are not full and exposed to a source of air can evolve vapors that might explode
 violently if ignited. Either flammable or toxic substances might pose problems at the end of
 the pipe, be it a nver, lake, or water treatment facility.

      Chemical and Petroleum Bulk Storage Facilities

      There are various bulk storage  facilities across the United States that  receive bulk
 quantities of chemical and petroleum products, including liquefied energy gases such as LPG
 and LNG, by one or more modes of transportation, store them for a time, and then load them
 onto other transport vehicles for distribution to buyers and users of the products.
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     The information desired about such facilities is the same as that needed for the portions
of bulk chemical and petroleum processing facilities that store and transfer products. Refer
to the previous section for a discussion of specific items.

     Pesticide and Other Packaged Chemical Warehouses or Distribution Centers

     Numerous types of common businesses store hazardous materials in bottles, drums,
boxes, cylinders, and other packaging materials. Although the amount in any given package
might be relatively small, the facility may store a large number of such packages in some sort
of warehouse facility or even on the shelves of a store of some kind.  Some materials may be
in small containers simply because buyers do not need or want larger quantities at any given
time. Others may be hi such packages, particularly at laboratory supply companies, because
DOT regulations prohibit transportation of bulk quantities due to then: special hazards

     As in prior cases, it is desired to obtain information on the location and layout of the
overall facility, the products typically stoied therein, their usual storage locations, sewer and
drainage systems in the area, secondary containment systems, and fire protection systems.
The latter two topics are particularly important for this category, because one of the more
worrisome scenarios involves  fire.  Serious environmental impacts may  occur if large
amounts of water applied to burning chemicals cause contaminated runoff into sewers or
drains leading to bodies of water or  treatment plants  Indeed, some fire departments have
prefire plans, particularly for warehouses storing toxic pesticides, that call for allowing the
facility to burn while only protecting surrounding buildings with water until all chemicals are
consumed, thus avoiding a water contamination problem. Although the building may be a
total loss,  and populations subject to smoke  exposure may require evacuation or other
protective action, savings may actually be realized because  of the expenditures that would
otherwise be necessary to decontaminate land and water bodies polluted by  contaminated
runoff.

     Miscellaneous Facilities

     Besides the large number of facilities and transportation modes that are commonly
associated with the chemical and petroleum industries, there are many other common types
of businesses and facilities that are apt to use or store hazardous materials and which should
not be overlooked Some possibilities are listed in Table 10 2 but are only a sampling of the
many  types of facilities  likely to store and use hazardous materials  in some significant
quantity.
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                                         TABLE 10.2
                  MISCELLANEOUS POTENTIAL SPILL SOURCES

Airport and marine fuel depots - gasolines and fuel oils
Breweries and distilleries - alcohols
Compressed gas suppliers - medical and industrial gases
Construction firms and sites - explosives, compressed gases, fuels
Dry cleaners - cleaning solvents, perchloroethylene
Electronic circuit makers - acids
Embalming supply houses - formaldehyde
Farm/garden supply shops - pesticides, fertilizers, herbicides
Fireworks manufacturers - explosives, pyrotechnics
Food stores or warehouses - ammonia (in refrigeration systems), combustible dusts
Foundries - resins, other chemicals
Fuel oil companies - fuel oils
Furniture snipping operations - solvents
Gasoline stations - gasoline
Gun and ammo shops - ammunition, explosives
Hazardous waste disposal facilities - virtually anything
 Hospitals - compressed gases, medicines, radioactive materials, ebologic agents
 Laboratories, chemical and biological - various chemicals, etiologic agents
 Lawn fertilizer companies - pesticides, herbicides, fertilizers
 Leather tanners - various chemicals
 LP-gas or propane suppliers - liquefied flammable gases
 Paint, varnish, and lacquer makers and wholesalers - resins, solvents, chemical pigments and additives
 Pest control companies - pesticides, poisons
 Plastic and rubber makers - solvents, additives, bulk chemicals
 Plating shops - acids, cyanides
 Pulp and paper mills - bleaches, caustics, acids, sulfur compounds, and others
 School and university chemical laboratories - various chemicals
 Swimming pools (public) - liquefied chlorine
 Swimming pool supply houses - oxidizers (calcium hypochlonte), hydrochloric acid, algaecides
 Steel mills - acids, degreasers
 Textile and fiber manufacturers - solvents, dyes, resins, various other bulk chemicals
 Water treatment facilities - liquefied chlorine, acids
 Welding shops - compressed gases
 Welding supply shops - compressed gases
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10.5 AVAILABLE METHODOLOGIES TO COMPILE DESIRED INFORMATION

     Previous sections have discussed the primary reasons for identifying and characterizing
potential spill sources and accident sites, and briefly described the information and data
desired for hazard identification and analysis purposes. It is now time to briefly review some
of the  methods available for fulfilling these information needs.  In reviewing this material,
keep in mind that major potential spill sources outside the the community of interest may
also have the capability to impact residents and their property in  the event of an accident It
may not be enough to only study facilities that he within the precise boundaries of the
community or jurisdiction of concern

     Enforcement ofRight-to-Know Laws

     Right-to-Know laws  or regulations, be they of federal, state or local origin, typically
require that manufacturers and users of specified hazardous materials provide material safety
data sheets (MSDS) or lists of available MSDS for the substances handled on their respective
sites to employees, community leaders, fire departments, state emergency planning groups,
and/or members of  the general  public.  The various laws  and regulations enacted or
promulgated over the years  have differed in  several important aspects, but all,  in some
fashion or another, have had the potential to facilitate identification of facilities which handle
or otherwise utilize specified hazardous materials.

     Although Right-to-Know laws were enacted in more than 25 states in recent years,
recently  revised federal laws  and regulations have essentially preempted most  of these
legislative initiatives. The new laws and regulations are very  comprehensive and have the
net objective of ensuring that State Emergency Response Commissions (SERCs) and LEPCs
will be automatically informed of  the piesence of most hazardous materials present at
facilities within their respective jurisdictions. Indeed, enforcement of right-to-know  laws
and regulations is the most  direct and efficient method available to  LEPCs for the
identification of facilities  that manufacture, store, process,  or otherwise use hazardous
materials that may pose a threat to  community health  and safety. In most cases,
enforcement may require little more than informing these facilities, either individually or via
a general public relations  campaign, that they are subject  to these  laws  and regulations
Although progress is being made in this area, there remain many facilities and businesses,
particularly those that do not consider themselves part of the chemical industry, who have
been slow to realize or recognize that they are fully subject to the mandates of these laws and
regulations regardless of the nature of then: operations.

     The specific reporting  requirements originally mandated by SARA  are summarized
within  Appendix A of the Hazardous Materials Emergency Planning Guide (NRT-1) cited
in Chapter 1 of this document.  Stated quite briefly, SARA requires that facilities storing or
using EHSs in excess of TPQs must notify the local SERC and LEPC, appoint a facility
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emergency coordinator to assist the LEPC in emergency  planning and to  provide any
additional information and data required during the  planning process  In addition, any
facility subject to the the Hazard Communication Standard (29 GFR 1910  1200) of the
Occupational Safety and Health Administration (OSHA) must submit a list of the hazardous
chemicals on its site or a set of material safety data sheets for these materials to the state
emergency response commission (SERC), local emergency planning committee (LEPC), and
local  fire department  These organizations are  also to be provided annual reports  of
hazardous material mventones grouped by hazard category Because SARA Title III makes
planning for EHS's a mandatory effort, hazard identification should  begin with these
materials.

     A very significant  and somewhat recent development (late 1988) is that OSHA
succeeded, after a battle  in the courts, to  expand coverage of its hazard communication
standard from a very specific and somewhat limited set of industries to all  employers except
those in the construction industry Thus,  many loopholes  (though not all) that would
otherwise have complicated the hazard identification efforts of LEPCs have now been closed
by the federal government

     The various laws and regulations discussed above are being frequently modified and/or
expanded in coverage in a concerted attempt to further facilitate the work of local emergency
planning personnel.  Current information on federal initiatives under the Resource Conserva-
tion and Recovery Act and Superfund law may be obtained by calling the  RCRA/Superfund
Hotline at 800-424-9346 or 202-383-3000  Current information on the specific regulations
prompted by Title IH of  SARA can be obtained by calling the Emergency Planning and
Community Right-to-Know Hotline at 800-535-0202 or 202-479-2449  Both hotlines have
been established by the federal government and are operational from 8 30 am to 7 30 pm
EST during the normal work week.

     NOTE WELL: Although the above laws and regulations will greatly help community
emergency planning personnel  in identifying  fixed-site facilities that handle hazardous
materials, they are not necessarily all inclusive and encompassing There  will  still be many
cases in which hazardous materials are handled at a facility but insufficient  data will be made
automatically available to LEPCs to permit the performance of a comprehensive hazard
analysis. Additionally, the fact that reporting requirements  do not apply to transportation
modes conveying hazardous materials through individual jurisdictions is  highly significant
and important, as is the fact that many fities    and businesses are not yet aware of their
specific responsibilities Consequently, comprehensive planning for hazardous materials
emergencies, although not fully mandated by law, requires a concerted effort on the
part of LEPCs to identify and characterize  potential threats that have in one way or
another escaped mandatory reporting and planning assistance requirements.
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     Use of Fire Department and Building Inspection Records

     Over the years, local fire departments may have accumulated substantial data on the
businesses and facilities within their jurisdiction as a part of fire hazard surveys, inspections
associated with regulatory or insurance requirements, response to accidents, and preplanning
for fire emergencies. It follows  that fire department records and personnel can be a key
source of  desired information  hi many  communities and counties  Similarly,  building
inspection departments of local governmental entities may have useful records and knowl-
edgeable personnel And  last but not least, note that local police departments will have
considerable general knowledge  of the businesses that operate in their respective jurisdic-
tions. Law enforcement personnel patrol the streets on a 24-hour basis and will often have
first hand knowledge of many of the potentially hazardous activities of concern

     Use of Industry Questionnaires

     A reasonably detailed  questionnaire mailed to all businesses which may  handle
hazardous materials, particularly  if accompanied by a letter from the mayor, town  or city
council, or local fire chief, can provide valuable information on a significant fraction of the
facilities contacted. It is a good  idea to call first to determine to whom the questionnaire
should be  directed, and also, to determine who can be called  for  follow-up questions.
Alternatively,  a self-addressed,  stamped  postcard can be inserted  in the package  with a
request that the person given responsibility for completing  the document list his or her name
and telephone number  on the card and drop it in the mail A news release to local media
about the effort can alert the business community as to the arrival of the questionnaire and
alert the public about the planning effort being undertaken. In all cases, be sure to stress the
fact that the information is solely desired for emergency response planning purposes. As
discussed later, be sensitive to the possible need to maintain  the confidentiality of certain
data.

     Meetings with Business Organizations and Trade Groups

     Many businesses throughout the country are members of local Chambers of Commerce
or mutual aid groups (i e., groups of companies in the same industry that have agreed to help
each other as  best they can in time of emergency). Presentation of community emergency
response planning information needs during a general meeting  of such a group has the
potential to obtain publicity for the effort, to obtain assistance and cooperation from the local
business community, and most importantly, to obtain formal endorsement of the organization
for the effort, thus encouraging individual members to cooperate fully with public authorities.
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     Meetings with Individual Business Personnel

     Where the effort is within reason, planning personnel assigned this task may choose to
meet with key personnel within the individual companies  or organizations handling
hazardous materials, explain  the benefits of cooperation to both the community and the
business, and request a tour of facilities. Necessary details of operations can be obtained
during these meetings and tours, or questionnaire forms may  be left behind for  later
completion.

     It is well to keep in mind during such meetings or other contacts that many companies
have undertaken intensive efforts to determine the hazards and nsks faced by the community
and themselves due to the storage and use of hazardous materials, especially hi the aftermath
of the Bhopal incident. Requests for the results of such analyses might lead to the receipt of
much desired information.  Given  that the Chemical Manufacturers Association is actively
encouraging such efforts  among the entire chemical industry under its Community Aware-
ness and Emergency Response (CAER) Program (see Chapter 1), a request may even provide
impetus for initiating such work, which could ultimately save community planning personnel
considerable effort.

     It is also desirable to ask if the facility has a contingency plan for dealing with on-site
emergencies and whether any  attempt has been made to coordinate and integrate the plan
with community efforts. This can prompt some thought on preparing a facility plan where
none exists, lead to obtaining a copy of the  plan (which is bound to  contain useful
information), and/or initiate a useful  and continuing dialog between company and public
emergency preparedness personnel.

     As noted earlier, it is important during such meetings  to  stress that the ultimate
objective of the community is to ensure it is prepared to protect the public during potential
hazardous material emergencies and to lend appropriate assistance to the responsible party
(i.e., the company or firm  that owns  and/or has custody of the materials in question) in
mitigating damages resulting from an accident. It is also important, however, to be sensitive
to the fact  that the success and commercial viability of some  businesses may depend on
proprietary technology or  processes that cannot fully be protected with patents or copyrights
Indeed, one or more products of  any chemical-related business may be  based on  "secret
recipes" that would hurt the  company if disclosed to competitors. Do not be surprised,
therefore, if there is reluctance at times to discuss certain details of company operations

     The right-to-know  laws  and regulations discussed above have specific provisions
relating to claims of trade secrets by facilities and these provisions  should be followed when
applicable.  When not applicable, there are essentially two methods to approach the problem
when there is an acknowledged or known threat to the community and issues of confidentiali-
ty that hamper planning efforts The first involves a formal agreement between the company
                                       10-15
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and the community to use any information provided solely for emergency planning purposes
and not to disclose the information to any third parties. This places a substantial legal burden
on the community and requires active management of sensitive data, but potentially serves
the needs of both parties The other approach necessitates that the company itself undertake
the analysis procedures outlined in Chapters 11 and 12 and provide planning personnel with
only the final results and a promise to disclose the identity  of any discharged or spilled
materials immediately in the event of an accident. The effort may be facilitated on the part of
the company by the employment of independent consultants or contractors.

      Queries of Rail, Marine, and Pipeline Transportation Companies

      One of the more difficult tasks in some localities will involve compilation of sufficient
data on transportation of hazardous commodities in the area, particularly if these cargos do
not have a specific destination in the locality that can be identified and queried but are simply
passing through  The survey methods to be considered vary with the mode of transportation
being utilized.

      As note above, the best  source of railroad traffic data is the railroad company that
owns and operates any specific track segment of interest. Many  will have computerized
records of train movementss and the cargos earned. Others might be willing to compile the
desired data over a specific penod of time to assist the data collection effort  Companies that
receive or ship hazardous materials and which have facilities in the area can  provide data on
the portion and nature of the traffic for which they are responsible if cooperative. They can
also  act to inform emergency  planners of the  specific transportation companies that they
employ for potentially hazardous cargo movement.

      Pipeline routes, particularly those conveying hazardous commodities, are often clearly
marked and known to public authorities, particularly those who may have issued a permit for
 the route at some time in the past   Substantial information may be readily available  from
 "digsafe" program offices in many areas of the country that maintain records of buried
 pipelines and  cables. Local utilities  will know of  such  programs,  as will construction
 companies, and a hotline number for the local digsafe program is  likely to be prominently
 displayed in the local telephone directory Contact with the owner of any pipeline is likely to
 provide current  operating conditions, specific route of the  pipeline,  and  any emergency
 response preparations that have been undertaken in anticipation of a future accident

       Sources  of information in ports and harbors include the port or harbor master, the
 companies that offload, ship, or receive hazardous cargos, the public commission or council
 (if any)  that operates or has regulatory or oversight responsibility for the waterfront, the
 marine transportation companies that operate in the area, and any local or regional offices of
                                         10-16
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the U.S. Coast Guard or U.S Army Corps of Engineers. The best approach is to locate a
person who knows how the port or harbor operates and how records are kept, and ask his or
her advice on how best to proceed.

     Truck Traffic Surveys

     By their very nature, trains, pipelines, and marine vessels follow routes that are fixed in
location, readily identifiable, and utilized by a comparatively small number of transportation
companies.  This is not true in the case of truck traffic which may be found on a wide variety
of roads and highways and potentially involve a large number of different carriers. The task
of characterizing truck traffic and its routes will therefore be substantially more time-con-
suming in many jurisdictions but can be accomplished to a large extent using the following
methods and procedures.

     Almost all jurisdictions are served by firms that provide fuels such as gasoline, fuel oil,
and LP-gas (LPG)  or propane to industry and the public These should never be overlooked
Trucks conveying  gasoline are known to be involved in more serious accidents than those
transporting any other hazardous  material in the United States due to the flammable and
explosive properties  of the  substance and its extremely widespread  use  and distribution.
LP-gas and liquefied propane, which are also used in large  quantities in most parts of the
country, are highly flammable compressed liquefied gases that may  fuel pool fires, flame
jets, BLEVEs, vapor cloud deflagrations,  and  confined  and  unconfined  vapor cloud
explosions if discharged to the external environment  Fortunately, the vast majority of firms
that receive,  sell, and deliver these  commodities will be readily identifiable.  Those
companies that serve commercial accounts or the general public usually advertise frequently
to gain new customers and will be easily found in the "yellow paces'* of local or regional
telephone companies, as will product wholesalers or  distribution companies.  Discussions
with the operators of a sample of local gasoline stations can also be helpful.

     The shippers  and receivers of other hazardous materials in the locality of concern are
one good source of information about the nature and frequency of over-the-road shipments
Routing and additional shipment information can be obtained from the trucking firms that
deliver or pick-up cargos

     Most large tracking companies have established terminals at various locations  across
the country.  Although these terminals  may  be  located outside the locale of concern,
company management, safety or  dispatch personnel may be able to provide substantial
information on the cargos routed through the subject jurisdiction They may  also have a
good idea of the operations of other earners that function in the area, since  keeping track of
the activities and operations of competitors is often good business practice Similarly, smaller
companies in the region, particularly those that specialize in carnage of hazardous materials,
can be a useful source of information.
                                        10-17
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     Finally, when all else fails to provide a reasonably complete overview of hazardous
materials traffic by highway, there is always the possibility of conducting a roadside traffic
survey. One form of survey involves stationing observers along highways at key locations of
interest, such as major intersections or entrances into the jurisdiction for a period of time and
making counts of traffic.  The placards and other signs on individual vehicles  (see Chapter 8
for descriptions)  will provide a general if not  specific indication  of  the  nature of any
hazardous cargos being earned The names of transportation firms on vehicles can provide
leads to sources of more detailed information when needed

     The task can be somewhat facilitated for  major highway traffic  if there is a truck
weighing station  on the  route and observers  are positioned at these locations Similarly,
survey activities may be coordinated at times with roadside safety inspections conducted by
the highway patrol, state police and/or  department of motor vehicles  Police forces may also
be asked to make note of hazardous materials traffic at all  times during routine duties on a
periodic basis, as may collection personnel at toll booths.

     Although much of the information of interest for planning purposes has been provided
above, it is well to note that the U.S. Department of Transportation and the U S. Department
of Energy  jointly  sponsored a study to identify  and characterize methods by which
information may be obtained  on hazardous material shipments at the local level. The
resulting report is:

       •     Overcast,  T.D,  and Dively, D.D.,  Options for Gathering Information
            About Shipments of Radioactive and Other Hazardous Materials, DOT
            feeport DOT/RSPA/DHM-61-86-2,  1987, available from  the  National
            Technical Information Service, Springfield, VA 22161.

      Use of Permit Records

      Companies that handle hazardous materials typically require a variety  of permits and
 licenses to build their facilities, to handle or store flammable materials, chemicals or wastes,
 and to discharge  pollutants into the air or water.  These permits and licenses  are issued by a
 variety of local, state, and federal authorities and may provide a reasonably efficient means to
 identify these facilities in some jurisdictions. Organizations with possibly useful records
 include fire and police departments, building inspection agencies, zoning boards, public or
 occupational  health and safety departments,  state and federal environmental protection
 agencies, water and sewer commissions, the U.S Army Corps of Engineers,  and the U S
 Coast Guard, among others.
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      Use of the "Yellow Pages"

      The local telephone company "yellow pages" directory can be of major assistance in
identifying all types of firms that potentially store, handle, or transport significant quantities
of hazardous materials. Better yet, it can provide their addresses and telephone numbers

      Access to Detailed Chemical Property Data and Hazard Information

      As readers will realize, industry is generally required to provide  emergency planning
personnel with material safety data sheets (MSDS) or information similar to that found on
such  sheets It is important to note that this information and data, although of considerable
value in many respects, is not always adequate for a full and complete understanding of the
hazards and properties of individual hazardous materials. Indeed, it is not uncommon to
review several MSDS for the same material, each prepared by a different manufacturer, and
to find numerous subtle and sometimes major inconsistencies in then- contents

      Quite frankly,  MSDS  with  different origins and authors often vary greatly in both
accuracy and completeness, although the situation has improved vastly in recent years Even
the best available MSDS, however, provide but a simplified overview  of material hazards,
appropriate first aid measures, suggested emergency response actions, and so  forth. It is
often best, therefore, to use MSDS as a screening tool to identify those materials that clearly
pose the greatest hazards to a jurisdiction, and then to make an additional effort to compile
more complete information on these substances  Realize also, however, that some manufac-
turers have a tendency to exaggerate hazards  of then- products to avoid the possibility that
they will be found negligent in warning customers of possible dangers in the event of an
accident Conversely, though this is not nearly as common as it once was, and may simply
have been due to a lack of knowledge or expertise, some firms have been known to downplay
the hazards of their products in the past

      There are essentially three available methods to obtain more detailed information on a
specific hazardous material. The first involves access and study of the numerous hazardous
material data bases, handbooks, and guides available in the marketplace The best of these
contain considerable  useful and accurate data on the common and sometimes rare chemical
products and fuels used in industry. The worst,  however, can be a  considerable waste of
funds, so it is wise to purchase these documents or computer programs with care.  (Note.
Some computerized data bases, in particular, have absurdly high prices given the nature and
quality of the data they provide In many cases, the authors have simply copied data that is
available in hardcopy documents selling for a tiny fraction of the computer program price )

      The name and addresses of chemical manufacturers and distributors, together with
indexed lists of then- products, can  be  found  in several chemical buying guides. Potential
sources of  these guides include major public  and university libraries,  the  purchasing
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departments of companies that buy chemicals, and even individual chemists and chemical
engineers in the community. The second approach involves identification of the manufac-
turers of materials of special  concern and the mailing  of requests for  detailed product
information bulletins and safety handling guides  Most large corporations will honor such
requests at no cost.

     The third approach, which is best suited to identifying a source of detailed information
for an unusual  hazardous material, involves calling the Chemical Referral Center  in
Washington, D.C. This Center was established by the Chemical Manufacturers Association
(CMA) in late 1985  to assist callers in contacting sources of information on over 250,000
chemical products and basic chemicals on a non-emergency basis. The center operates from
8  a.m to 9 p.m. (EST) Monday through Fnday and may be reached toll-free from the
continental United States and Hawaii at 800-CMA-8200. Callers in the District of Columbia
and Alaska may telephone 202-887-1315 on a collect basis.

10.6  SOURCES OF ADDITIONAL HAZARD IDENTIFICATION GUIDANCE

      The U.S. Department of Transportation and  the Federal Emergency  Management
Agency have sponsored numerous demonstration projects associated with hazardous materi-
als safety and emergency response planning.  The experiences of the local, county, and state
authorities involved  in these projects, as documented in the reports they have prepared on
their activities, can provide additional ideas  and insights on how best to  conduct a hazard
identification survey in any given locale. Most of these reports are listed and referenced in
Appendix E of the Hazardous Materials Emergency Planning Guide (NRT-1).

10.7  FORMULATION  OF CREDIBLE  ACCIDENT SCENARIOS FOR  PLANNING
      PURPOSES

      As noted earlier, it is not sufficient to determine the locations and characteristics of the
sites  and hazardous  materials that may become involved in  a future accident; it  is also
necessary to gain an  understanding of the potential nature and outcome of potential accidents
for comprehensive planning purposes. An important step in this process is the formulation or
postulation of credible accident scenarios based on  the information obtained during hazard
identification  activities.  These scenarios  can then  be evaluated with respect to specific
probabilities of occurrence, consequences, and/or nsks to the community via the procedures
respectively described in Chapters 11,12, and 13 of this guide.

      Chapter 11, in particular, describes, discusses, and enables  probability analysis  for
credible accidents at fixed site facilities and in transportation. Although the probability
analysis step  itself is considered optional, planning personnel should nevertheless refer to
Chapter 11  for  assistance in the definition of accident  scenarios in then-  respective
jurisdictions based upon results of the hazard identification procedures They may choose to
                                       10-20
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select several scenarios for each hazardous activity (ranging from low to high seventy) for
further analysis, or to simplify matters by only selecting worst case scenarios (i e., those
posing the greatest threats to the community.)

10.8 ORGANIZATION OF THE DATA

     As noted previously, the information compiled during the hazard identification and
characterization task is not only useful for planning and hazard analysis purposes, but can
also be valuable during actual emergency response if readily accessible in a centralized data
base.  It is therefore a good idea to organize the information and data in a filing system of
your choosing, and/or to enter the most important facts into  a data management system
installed on a personal computer. If placed in a location that is manned on a 24-hour basis,
such as police or fire department dispatch offices or a designated emergency operations
center, response personnel can be briefed on potential hazards by radio while en route to an
accident site and be given answers to specific questions that may arise upon their arrival at
the scene.
                                         10-21
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              11.0  PROBABILITY ANALYSIS PROCEDURES
11.1  INTRODUCTION

     The transportation and use of hazardous materials poses threats that are of concern to
society, but which are not always fully understood in terms of their likelihood of occurrence
or viewed in perspective with regard to their relation to other threats  The purpose of this
chapter is to provide  emergency planning personnel with the basic information, data, and
procedures necessary to refine and evaluate individual hazardous material accident scenarios
in terms of their annual probability or frequency of occurrence on at least an order of
magnitude basis

     As noted earlier in Chapter 9, this probability analysis step may be considered optional
where  community leaders (or  individual facility  operators) wish  to prepare for every
conceivable accident regardless of its likelihood of occurrence and have the time, manpow-
er, and resources to achieve their goals.  More often than not, however, these individuals will
find that time and resources are limited and that other threats or needs compete for attention
Pnontization of potential accidents  in terms of annual probability as well as seventy will
permit attention to these threats (and it is eventually hoped all threats to public health and
safety) in a logical and orderly fashion and thereby reduce the chance that time and resources
will be expended on  emergency scenarios of exceedingly low credibility or significance
Note, however, that  assessment of hazardous material accidents  or any other threats on a
probabilmsttc basis does not guarantee that all such hazards will be identified or that less
likely events will not occur

     The chapter addresses seven primary activities associated  with hazardous materials,
each with the potential to result in public emergencies  These include

     •     Bulk transportation by truck
     •     Bulk transportation by rail
     •     Bulk transportation by barge or other marine vessel
     •     Transportation by pipeline
     •     Bulk storage, processing, or handling at fixed facilities
     •     Transportation of packages
     •     Transportation by air

     The  overall approach  presented in this  chapter involves use  of  average  national
accident rates determined from historical records and relevant exposure data  While such
rates  may overestimate  or underestimate average annual  accident  probabilities  for any
specific facility or transportation activity, they are not expected to  be vastly in error in
aggregate for any jurisdiction or facility The ultimate goal, after  all, is not exact estimation
of  accident probabilities, but their approximation at a level of accuracy  sufficient for
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emergency planning purposes. Appendix F to this guide presents the basis and rationale for
the recommendations and procedures that follow, and additionally, discusses the use of local
and other data and information (where available) to further refine estimates where this may
be desireable.

      The actual computation of the annual accident probability associated with any specific
activity involves using the frequency with which  such accidents  are known to occur in
combination with a measure of the "exposure" of the community or other jurisdiction to the
potentially  hazardous activity  For most transportation modes, for example,  historical
accident rates are presented in terms of the number of accidents expected per mile of travel
and exposures are expressed in terms of the number of trips made per year and the mileage of
routes within the locality. Simple multiplication of these values provides the  expected
number of accidents per year involving the activity being considered Further multiplication
of this result by such factors as the fraction  of accidents that result in loss of cargo to the
environment and the fraction of accidents that result in a prespecified amount  of cargo loss
permits greater specificity in predictions  Worksheets for each activity facilitate computa-
tions, and are provided  in lieu of tabulated or generalized categorizations of accident
probabilities to provide planning personnel with the  option of using local data for greater
accuracy. Planning personnel may use the predicted accident frequencies to determine an
appropriate "accident probability category" during the nsk analysis step described in Chapter
13 of this guide.

      An important point to be made is that  the analysis methods presented herein provide
their users with the annual accident probability expected for the entire area of concern  and
not for specific locations or subregions within the locality Should it be desired to determine
the probability of a release near a specific populated area, a specific body of water, or a
specific  environmentally sensitive habitat, it will be necessary for users  to determine  that
fraction  of the overall community or facility exposure associated with this special area and
to adjust overall accident frequency predictions in an appropriate fashion

      Special Notes

      Wherever the term "spill" is used in the discussions that follow, readers are advised to
interpret the term as referring to any release or discharge of a hazardous material in a manner
capable  of posing a threat to the public or the environment

      The procedures that follow permit the user  to estimate the  number of "spills/year"
expected on average from individual activities or operations involving hazardous materials.
The average reoccurrence interval for a specific spill scenario can be determined by dividing
the number "1.0" by the predicted frequency of spills per year Thus, a spill frequency of 2 x
 1O2 spills per year can be translated to mean  that a spill can be expected to occur once every
                                         11-2
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50 years on average. Where desired, readers may also sum the spill frequencies denved for
similar individual activities and then determine the reoccurrence interval associated with the
combination using the same methodology

     Throughout this chapter, historical accident rates  and other data are frequently
presented in "scientific notation"  Readers unfamilar with this method of representing very
small (or very large) numbers are referred to Appendix A for guidance

11J  GENERAL SEVERITY OF ACCIDENTS CONSIDERED

     The types of accident scenarios that could theoretically be covered in this chapter range
from minor spills of gasoline at service stations to  major catastrophes that occur once every
10 or 20 years on average on a worldwide basis.  The primary focus, however, is somewhere
between these extremes, and on the types of events which occur somewhere in the United
States every week or month, but for which the nsks to any one specific community might be
low but nevertheless significant  In  other words, we are not highly concerned  with routine
and common  spills and discharges of relatively  minor significance Nor are we  overly
concerned with extremely rare events.

     For a general perspective on  hazardous materials accidents, consider that there  are
many thousands of hazardous materials releases which occur each year in transportation and
at fixed facilities, yet the vast majority are of very limited consequence  Tables  11 1 to 11 3
give some idea of the total numbers of accidents reported each year and  the relative
contribution made by various activities. More specifically, Table 111 addresses the number
of evacuations in recent years that were of sufficient magnitude to warrant reporting. Table
11.2 provides an estimate of the total number of accidents over a ten year period  involving
hazardous material releases from transportation activities, while Table 11.3 focuses on major
events by type of activity  Although  the data presented in the  latter table are somewhat
dated, they are  nevertheless  sufficient to demonstrate that only  a  small  fraction  of all
accidents result in major consequences.

11.3  BULK TRANSPORTATION OF HAZARDOUS MATERIALS BY HIGHWAY

     Bulk transportation of hazardous materials by highway involves the use of tank trucks
or trailers and certain types of more  specialized bulk cargo vehicles  In all, trucks transport
more than sixty percent of the hazardous materials not earned by pipelines, with just under
fifty percent of this  material being gasoline (OTA, July 1986)  Average trip lengths are 28
miles for  gasoline trucks and 260 miles for chemical trucks, implying that most gasoline
shipments are very localized while chemical shipments may be regional or interstate Since
trucks carry hazardous materials the  greatest number of miles near populated areas, and are
also responsible for the largest number of shipments, it is not surprising that this mode of
transportation is also responsible for the greatest number of accidents.
                                         11-3
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                                 TABLE 11.1
             CHEMICAL ACCIDENTS REQUIRING EVACUATIONS
Type of Accident
Train derailment
Railcar spill/fire
Truck accident
Truck spill/fire
Chemical plant release
Industrial plant release
Pipeline
Ship incident
Waste site accident
Other*
TOTAL
1980-1984
55
23
35
32
43
78
4
4
7
14
295
1984
8
5
5
7
5
24
0
1
1
1
57
*Includes helicopter crash, plane crash, sewer gas episode, oil well explosion, swimming pool
 chlorine accident, pesticide spill hi retail store, mine fire, two military missile silo accidents,
 and two electrical transformer leaks.
Source:
Sorensen, 1986
                                 TABLE 11.2
           HAZARDOUS MATERIAL TRANSPORTATION ACCIDENTS
Mode
Highway
Rail
Air
Water
Number of Accidents
Per Year1
10,000-15,000
1,000
200
20
1973-1983 Average1
10,289
975
150
26
 Source:  Materials Transportation Bureau, 1983 and Check et al, 1985
         *OTA, March, 1986
                                     11-4
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                                 TABLE 11.3
               MAJOR HAZARDOUS MATERIALS ACCIDENTS*
Activity
Chemical plants
Oil refineries and storage
Gas storage tanks
Oil drilling ngs
Pipelines
Fireworks plants
Marine tankers, barges
Railroad tank cars
Trucks
TOTAL
1964-1973
6
10
1
2
1
0
8
5
3
36
1953-1973
12
13
2
2
1
2
15
8
8
63
*10 or more fatalities, 30 or more injuries, $3,000,000 or more
 in property damage

Source     Office of Radiation Programs, 1980
                                   11-5
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     Tank trucks are usually tractor-semitrailer vehicles or smaller bobtail-type units. The
tanks themselves are usually constructed of steel or an aluminum alloy, but may also be
stainless steel, nickel and other materials.  Capacities are usually in the range of 3000-10,000
gallons, although slightly smaller and larger units  are available.  Intermodal tanks which
consist of a tank within a protective rigid framework, one-ton tanks which are lifted on and
off the transporting vehicle, and large gas cylinder bundles are also commonly used for bulk
transport by highway.

      Commodity breakdowns for trucks,  as  described in various data sources are not
considered very accurate  and vary widely. However,  a one-month survey of cargoes in
Virginia found a fairly close match (by percentage) to the average distribution of commodi-
ties  involved in accidents. The  comparison  for commodities involved in accidents in
Virginia also matched national accident breakdowns fairly well (Urbanek and Barber, 1980).
National involvement in accidents by  type of commodity  for the  time  period  July
1973-December 1978 was:

                Flammable liquids                    60.5%
                Combustible liquids                   16.3%
                Corrosives                           11.6%
                Flammable compressed gases          3.2%
                Oxidizers                            2.1%
                Poisons (liquid or solid)                2.1%
                Nonflammable compressed gases       1.9%
                Explosives                           1.5%
                Radioactive materials                 0.5%
                Flammable solids                     0.3%

      Causes and Examples of Past Accidents

      Truck accidents on roadways, regardless of the cargo involved, are generally due to:

    •    Collisions with other vehicles
    •    Collisions with fixed objects such as bridges or overpass supports
    •    Running off the road
    •    Overturns due to excessive speed on curves

These four events are most likely to result in a release  of large quantities of hazardous
materials, and are predominantly the result of human error. Smaller releases may arise due to
defective or loose valves, fittings or couplings; weld failures; and various  other structural
defects. (Note: Loading or unloading spills  are considered separately in the category of fixed
facilities below and actually result in the majority of overall releases involving trucks)
                                         11-6
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     The severity and consequences of discharges resulting from truck accidents can vary
widely. Some examples include:

   •     A tank truck carrying 11,000 gallons of gasoline blew a tire, struck a cement
         barrier which ripped open the side of the tank, and then burst into flames on
         Interstate 95 near Peabody, Massachusetts. State troopers closed down the
         highway while an emergency crew from Logan International Airport spread
         foam on  the wreckage. The highway  remained partially closed for several
         days, since one section had melted and needed to be replaced. There were no
         injuries or deaths.  (December 3,1985)

   •     Littleton, New Hampshire, was spared  a potentially catastrophic  accident
         when a tank trailer loaded with 9,200 gallons of liquefied propane jack-knifed
         on an  icy hill and tipped on its side about 75 yards from a large storage tank
         of liquid propane  and less than  100 yards from large fuel oil storage  tanks.
         No propane leaked from the truck, but a diesel fuel tank  was ruptured, 1500
         people residing within a half mile radius were evacuated until the propane
         was safely transferred to another vehicle the next day.  (February 11,1982)

   •     A truck pulling two tank trailers loaded with molten sulphur collided with a
         highway barrier on a toll bridge and burst into flames taking two lives and
         injuring twenty-six Firemen encountered difficulty extinguishing the fire and
         rescuing victims.  Visibility at the time was poor due to  fog and the spilled
         sulfur had burned through water supply lines. (January 19,1986)

   •     In Houston, a tank truck carrying liquefied anhydrous ammonia collided with
         a car  and fell from  an  elevated highway to  a busy freeway. The truck
         exploded violently on impact releasing billowing clouds of ammonia Four
         persons  (including the truck driver) were killed, dozens of motorists were
         overcome by the fumes in a three-mile area, and at least 100 were treated at
         area hospitals. The vapors and  fumes were so thick that police helicopters
         were initially repelled. The city was forced to use all available  ambulances
         and pnvately-owned hearses to transport the injured. (May 12,1976)

   •     Although certain  details are unclear, a tank truck carrying liquid propylene
         sprang a leak in  the  vicinity of a crowded campsite in Spain  Flammable
         gases  spread from the truck, encountered a source of  ignition, flashed back to
         the vehicle, and caused a BLEVE with a large fireball The death toll from
         burns was approximately 170  Numerous other people suffered  moderate to
         severe burns but otherwise survived  (July 11,1978)
                                        11-7
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     Suggested Approach for Assessment of Accident Potential

     Since we are concerned with accidents with the potential to cause major problems for a
community or other jurisdiction and not those which are handled on a routine basis, it is best
to focus on vehicular accidents rather than relatively minor leaks from valves, fittings, or
open relief valves. Based on the information discussed in Appendix F, an average accident
rate of 2 x 106 accidents/mile is considered representative of the general expenence of trucks
carrying bulk quantities of hazardous materials  If adequate local/state data are available for
determination of individual accident rates for divided and undivided roadways, then* use is
recommended because the resulting rates will more accurately reflect accident probabilities
under local conditions.

     With respect to the fraction of truck accidents that result in a spill or discharge, the
available data suggest a consensus opinion on the order of 0.50 (50%) if all spills including
very minor valve and fitting leaks are considered Omitting these,  a spill appears to result
from an accident in about 0.15-0 20 (15% - 20%) of accidents. A value of 0.20 (20%) is
therefore adopted for use for the sake of conservatism.

     Based upon available spill size distributions, and considering the likely causes of
accidents, the following distribution is suggested for general use:

    •     10% cargo loss (thru 1" hole) or 1000 gal --60% of the time
         30% cargo loss (thru 2" hole) or 3000 gal — 20% of the time
    •     100% cargo loss (instantly) or 10,000 gal --20% of the time

These values  cover the  range of  significant releases If desired, a two-point distribution
assuming that 3000-gallon spills occur 80% of the time and 10,000-gallon spills occur 20%
of the time may be used to simplify consequence analysis procedures.

     The suggested accident rates and other factors for  truck accidents are summarized in
Table 11.4. Worksheet 11.1 presents a simplified format for computing the annual average
probabilities  of truck accidents resulting in  spills of  various amounts  A  copy of the
worksheet should be  completed for each hazardous material transported in bulk by  truck
within or through the community, or (if desired) groups of chemicals or materials posing
similar threats in the event of a release may be analyzed together  Local information needed
for the task includes:

    •     Matenal(s) of concern

    •     Annual number of shipments

    •     Total capacity per shipment
                                         11-8
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                                   TABLE 11.4
             SUGGESTED FIGURES FOR TRUCK TRANSPORTATION
Accident Rate:                          2 x 106 accidents/mile


Conditional Spill Probability              0 2 for significant spills


Spill Size Distribution                   0 60 for 10% loss of cargo through 1" hole, or 1,000
                                      gal

                                      0 20 for 30% of cargo through 2" hole, or 3,000 gal

                                      0.20 for 100% of cargo, or 10,000 gal
Note:   Worksheet 11.1 demonstrates how these figures can be used to estimate annual
        accident probabilities and associated spill volumes for truck transportation.
                                       11-9
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                                WORKSHEET 11.1

    ESTIMATING BULK TRUCK TRANSPORTATION RELEASE FREQUENCIES
Hazardous Material(s):
Total Number of Annual Shipments:
Length of Route of Concern:
Total Number of Miles Per Year*:
                                       A =	
                                       (loaded trucks only)
                                       Tj _ m
                                           (miles within jurisdiction)
                                         = AxB=-
Accident Frequency:
Spill Frequency:
                                = Cx2xlO« =
                                         = Dx0.2 =
_(accidents/year)
        _(spills/year)
Spills by Size*

     10% loss of cargo (1" hole) or 1,000 gal:


     30% loss of cargo (2" hole) or 3,000 gal
                                              Ex06 =
                                              E x 0.2 =
     100% loss of cargo or 10,000 gal-
                                              Ex02 =
Notes:
           _(spills/year)
           _(spills/year)
           _(spills/year)
     *If there are a number of different routes with varying numbers of shipments, multiply the
     number of shipments by the route length for each route individually and then sum For
     example,  100 shipments of 15 miles and 50 shipments of 7 miles would give (100 x 15) +
     (50 x 7) = 1850 total miles.

     + The user may consider  all three  scenarios for consequence  modelling and planning
     purposes or just the largest spill.
                                     11-10
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   •    Total length of route within community

   •    Type of roadways travelled (if specific rates by type of highway are available)

Note that it may be necessary in some cases to combine the number of shipments with the
length of route within the community to compute total mileage because there may be several
routes for the same material. A prune example is for gasoline which may be delivered to
several locations within any community or jurisdiction as well as driven through the locality.
Worksheet 11.1 provides further information on how this may be accomplished.

     Additional Data/Methodologies

      Should more precise methodologies be desired or should special circumstances warrant
attention, the reader can consider one of the techniques listed below. First efforts should be
directed at obtaining more precise data either on a local, county, state or regional basis. The
data specific to one carrier should not be broadly applied, however, as there can be major
differences between earners - even when they operate in the same area. This may occur due
to differences in truck design and upkeep, characteristics of the cargo, training of the drivers,
enforcement of speed restrictions, and other factors.

      More detailed methodologies  which take into  account specific accident situations
include:

    •     Separate models to predict accidents on interstates, rural highways or urban
         arterials as a function of several input variables (Urbanek and Barber, 1980).

    •     Analyses of rail/highway grade crossing accidents (National Transportation
         Safety  Board, 1981).  Note: There are only 60  or  so  of these each  year,
         nationwide,  on average. They usually involve  trucks carrying petroleum
         products and occur close to distribution/storage terminals, with very localized
         impacts.

    •     Breakdowns of rates by rural,  urban, suburban and number of lanes (Smith
         and Wilmot, 1982).

    •     Risk assessments of transportation through tunnels (Considine, 1986).

    •     Detailed considerations  of the  severities of various types of accidents for
         particular vehicle configurations (Clarke et al, 1976).
                                         11-11
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     Use of Results in Consequence Analysis

     Each of the three accident scenarios denoted and evaluated above actually provides the
user with two  options, the first being assumption of a certain percentage  of cargo  loss
through an orifice of a given size, and the  second being assumption of a specific total amount
of cargo loss. For example, in the first scenario considered, the user can assume that 10% of
the total cargo of the vehicle is discharged through a hole having a diameter of one inch, or
alternatively, simply assume that 1000 gallons of presumably liquid cargo are released before
the discharge is terminated for one reason or another under average accident conditions
These results are based on generalized historical records of past accidents and provide one
way in which  the ultimate consequences of an incident can  be evaluated by use of the
analysis procedures discussed in Chapter 12 of this guide  Conversely, depending upon the
type of hazardous material involved and the desires of the user, these scenarios can be further
refined for  consequence analysis  purposes, taking better  advantage of locally  available
information.

     Where the user  wishes  to assume a fixed percentage of cargo loss (this requiring
knowledge of total cargo amounts) or a fixed amount of spillage for liquid cargos, the  spill
can be assumed to take place instantaneously, thus obviating need for use of discharge rate
and duration estimation methods discussed in Chapter 12 and available in the  computer
program provided with this guide It is cautioned, however, that  the  assumption of an
instantaneous release in such situations may greatly  overestimate resulting hazard zones from
evolution of toxic or flammable vapors, fires, or explosions Spill amounts presented in units
of  gallons of liquid can be converted to the units of pounds required by the  computer
program by  use of the following expression:

     Amount in pounds =  8.34 x Amount in gallons x Liquid specific gravity

     Where a hole size is specified and cargo tank or compartment dimensions are known, it
is alternatively possible (and recommended) to utilize  available discharge rate and duration
estimation procedures  to obtain an ultimately more realistic indication of accident conse-
quences. This  is particularly  advisable when the  cargo is a compressed gas, a  liquefied
compressed gas, or  an  otherwise highly volatile material. The suggested percentage of cargo
loss, when less than 100%, can be ignored, if necessary, in deference to the results obtained
from the discharge  models. (This is due to the fact that the hazard zone will be primarily
determined  by the release rate and the first ten or so minutes of the release;  the ultimate
release quantity is less  significant)
                                        11-12
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11.4  BULK TRANSPORTATION HAZARDOUS MATERIALS BY RAIL

     According to recent statistics, about 80 million tons of hazardous materials are shipped
annually by rail in the U.S. (OTA, March 1986)  The majority of these shipments are in a
single tank permanently mounted on a rail car. Exceptions include multi-tank tank cars (the
units are usually ton containers), seamless steel cylinders (as for very high pressure service),
and compartmented tank cars in which each compartment is treated as a separate tank. The
sizes of these will range from a few hundred gallons in the case of a ton container to 45,000
gallons in so-called jumbo tank cars. Since 1970, however, the capacity of new tank cars has
been limited  to  34,500  gallons  There is also occasional  use of mtermodal tanks, as
mentioned under truck transportation.

      The design, construction, inspection, and use of tank cars are regulated by both the
American Association of Railroads (AAR) and the Federal Railroad Administration (FRA)
within the U.S. Department of Transportation (USDOT)  Carbon steel is used to construct
over 90% of the tanks, with aluminum for most but not all of the remainder Nickel or nickel
alloy is found in acid service, and there are a small number of stainless steel cars (Wright and
Student, 1985). Safety relief valves (and vents)  are required, unless otherwise  specified
Cars are usually classified into the categones of pressure  tank cars, non-pressure tank cars,
cryogenic liquid tank cars, and miscellaneous tank cars. Tanks may be lined, insulated, and
possibly fitted with heating coils Some may have  special  thermal  protection to prevent
BLEVEs or other explosions in the event of exposures to pool fires or flame jets Relatively
recent regulations have required shelf couplers - which limit potential for the puncturing
 adjacent cars in the event  of a derailment or collision - for all new and old cars  Cars
 carrying liquefied flammable gases or ammonia have been required to have head shields to
 further limit puncture potential, and new housings for bottom outlets have also been adopted

      It has been estimated that 35% of all freight trains carry hazardous materials, but that
 only 7 5% of railroad accidents involve trains carrying these materials (von Herberg, 1979)
 This figure corresponds  to the percentage of  all cars which carry  chemicals and allied
 products or petroleum products versus the total number of cars on an annual basis (AAR,
 1985).

      A fairly extensive  data base on commodity flows is available for railroads The July
 1986 OTA report provides the following breakdown on a tonnage basis*

            Flammable liquids                    26%
            Corrosive matenals                    25%
            Combustible liquids/
             nonflammable compressed gases       22% (less than 12% each)
            Flammable compressed gases           12%
                                         11-13
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           Poison B                              3%
           Poison A                             0.1%
           Radioactive materials                  0.03%

Detailed breakdowns by state, railroad company, and other divisions are also available from
various sources described in the OTA report.

     Data on rail yards shows that the number of hazardous materials cars handled by each
ranges from 1-15 percent of the total throughput (Chemical and Engineering News, July 29,
1985). In one study, based on data through 1977, it was found that 36% of derailments and
73% of collisions occurred in such yards (Nayak et al, 1983).

     Causes and Examples of Past Accidents

     For releases of hazardous materials from rail accidents, there are two types of events of
concern. The most  important for this  analysis is the accident that involves a collision or a
derailment, since these typically involve the largest spills  or discharges.  However, there is a
second class of releases which may arise from fitting or seal leaks, relief valve leaks, and
other releases  associated with improper tightening of  closures or defective equipment
Harvey et al (1987) estimate that  these account for 70%  of the roughly 1000 releases each
year.  Rail accidents, like those for trucks, can result in virtually no adverse consequences up
to very large losses  of life, depending on the materials involved and the circumstances of the
accident Many of the more severe accidents occur in yards and on sidings (Wolfe, 1984)
As for truck transportation, incidents arising during loading  or unloading operations are
addressed under fixed facilities.

     AAR data (Wolfe,  1984) showed that the materials most often involved in accidents
with more than $100,000 of damage in 1981 were:

        LPG
   •    Acrylonitrile
   •    Fuel oil
   •    Vinyl chloride
   •    Anhydrous ammonia

The same source found that there were less than 30 accidents each year with this level of
damage.

     Examples of past accidents involving the rail transportation of hazardous materials are
given below. These particular incidents include some of the most severe that have occurred
in recent times.
                                        11-14
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        In Waverly, Tennessee the derailment of two propane cars was treated rather
        casually as crews worked to clear the track and nght the cars. As this was
        being done, some 40 hours after the derailment, propane began leaking from
        one car, reached a source of ignition, flashed back to the car, and caused an
        explosion and fireball. The town center looked like a battle scene after the
        explosion with  16 dead,  54  requiring hospitalization for burns,  and  42
        requiring outpatient care  (February 24,1978)

        Over 240,000 people were evacuated for all or part of a week in Mississauga,
        Canada after a derailment involving 11 propane cars, 1 chlonne car and 10
        cars loaded with other chemicals. The  wreckage produced a series  of
        explosions, launched missiles more than half a mile, and prompted fears of a
        massive chlonne release. No fatalities or major injuries occurred partly due
        to the quick accident response of authorities, a well executed emergency
        evacuation plan, and various fortuitous circumstances. (November 10,1979)

        A white cloud of toxic smoke towered a thousand feet over the community of
        Miamisburg, Ohio and covered an area about a mile wide  and 10-15 miles
        long at one point after a derailment caused a car containing white phosphorus
        to fail and  ignite. The intense heat and difficulties in controlling the  fire
        forced authorities to wait four days for the blaze to burn itself out.  Eleven
        persons were hospitalized after exposure to the toxic smoke, with a total of
        273 being treated for skin, eye, and lung irritations. The 40,000 (or more)
        evacuees were the largest number ever resulting from a train accident in the
        U.S. (July 8,1986)

     Suggested Approach for Assessment of Accident Potential

     Based on the data presented in Appendix F, it is suggested that an accident rate of 3 x
    per train-mile be used for mainline track. To convert this  to a per car-mile basis, it is
assumed that 0.20 (20%) of the cars  will be damaged  in an accident (based upon data
presented in Nayak,  1979). The overall rate therefore becomes 0 2 x 3 x 10V train-miles or
about 6 x 10-7 per car-mile.

     The accident rate for rail yards is obtained by taking 1 3 x 10-s accidents per train-mile
and a 20% damage estimate to obtain about 3 x lO-Ycar-mile for the  track m yards. Sidings
also pose a risk, but these nsks are considered herein to be overshadowed by those associated
with mainline and yard track.

     It is suggested that 0.15  (15%) of accidents be assumed as resulting in a spill for both
mainline and yard accidents, as no data are available to permit distinctions  between these
events.
                                         11-15
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     With respect  to the distributions of spill amounts  m  accidents,  the  available data
suggest use of:

   •     3,000  gallons or 10% of cargo (thru 2" hole) -50% of the time
         10,000 gallons or 30% of cargo (thru 2" hole) - 20% of the time
   •     30,000 gallons or 100% loss of cargo - 30% of the time

The higher weighting of the last category partially accounts for the potential for more than
one car to release part of its contents in an accident.

     Table 11.5 summarizes the accident rates and other factors suggested for use, while
Worksheet 11.2 outlines the procedure for determining the annual average probability of an
accident involving spills of various amounts.  A copy of the worksheet should be completed
for each hazardous material transported in bulk by rail within or through the community  (As
for trucks, groups of chemicals posing similar hazards may be considered together) Local
information that will be required to accomplish the effort includes'

   •     Matenal(s) of concern
   •     Annual number of cars
   •     Total capacity per car
   •     Total miles of mainline track within community
   •     Total miles of yard track travelled by a typical car

Railcar trips and associated mileage involving loaded vehicles are of primary concern as
these pose the greatest risk  Nevertheless, it is important to realize that the residual materials
within tank vehicles considered "empty" can also pose a hazard under certain circumstances
If local  data on accident  rates or spill  frequencies are available, they can  be  directly
substituted for the rates and other factors listed in Table 115.

     Additional Data/Methodologies

     Should a more detailed evaluation be desired or required, readers can consider use one
of the  techniques listed below. However, any effort to improve the  specificity of accident
predictions  should probably first involve the determination and use of individual state or
railroad company accident rates for specific routes.

     More detailed evaluations of rail transportation can also include consideration of
several different factors (alone or in combination) in the analysis. Examples of these include:

    •     Detailed review of accident seventy to determine the overall  likelihood of
         puncture, crush, impact and fire scenarios (Clarke et al, 1976)
                                         11-16
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                                   TABLE 11.5
              SUGGESTED FIGURES FOR RAIL TRANSPORTATION
Mainline accident:                          6 x lO7/car-mile


Yard accident rate:                          3 x KWcar-mile
Spill size distribution:                       0.5 for 10% cargo loss through a 2" hole, or
                                          3,000 gallons

                                          0 2 for 30% cargo loss through a 2" hole, or
                                          10,000 gallons

                                          0 3 for complete loss of a cargo load, or about
                                          30,000 gallons on average
 Note:    Worksheet 11.2 demonstrates how these figures can be used to estimate annual
         accident probabilities and associated spill probabilities for rail transportation
                                        11-17
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                               WORKSHEET 11.2
     ESTIMATING BULK RAIL TRANSPORTATION RELEASE FREQUENCIES
Hazardous Material(s):
Number of Cars Per Year:
Number of Car-Miles in Yards:
Number of Car-Miles on Mainline:
 A=-
                                                (loaded cars only)
 B=-
                                                (miles per trip in jurisdiction)
 C=-
                                                (miles per top in jurisdiction)
Accident Frequency:   D = (AxBx3x 10«) + (A x C x 6 x 1O7) =
                         _(accidents/year)
Spill Frequency:
   = Dx015 =
      _(spills/year)
Spills by Size*
    10% loss of cargo (2" hole) or 3,000 gal:   E x 0 5 =
    30% loss of cargo (2" hole) or 10,000 gal:  E x 0.2 =
                     _(spills/year)
                     _(spills/year)
    100% loss of cargo or 30,000 gal:
Ex03 =
_(spills/year)
Notes:
     *The user may consider all three scenarios for consequence modelling and planning
     purposes or j'ust the largest spill
                                      11-18
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                                          "         WA*
   •     Detailed consideration of specific types of accidents and associated leak sizes.
        (Note  One  study  in Finland considered  14 types of accidents  and four
        categones of leaks, including valve leaks, broken valves, moderate breaks and
        punctures, and large breaks) (Lautkaski et al, 1979)

   •     Separate consideration  of different classes or quality of track (FRA, 1988,
        gives some the additional information needed for this type of evaluation)

   •     Separate consideration of mainline, yard, and sidings

     Use of Results in Consequence Analysis

     Each of the three accident  scenarios denoted and evaluated above actually provides the
user  with  two  options,  the first being assumption of a certain percentage of cargo loss
through an orifice of a given size, and the second being assumption of a specific total amount
of cargo loss  For example, in the first scenario considered, the user can assume that 10% of
the total cargo of the vehicle is discharged through a hole having a diameter of two inches, or
alternatively, simply assume that 3000 gallons of presumably liquid cargo are released before
the discharge is terminated for one reason or another under average accident conditions
These results are based  on generalized historical records of past accidents and provide one
way in which  the ultimate consequences of an incident can be evaluated by use of the
analysis procedures discussed in Chapter 12 of this guide. Conversely, depending upon the
type of hazardous material involved and the desires of the user, these scenarios can be further
refined for consequence analysis purposes, taking better  advantage of locally available
information.

      Where  the user wishes to assume a fixed percentage of cargo loss (this requiring
knowledge of total cargo amounts) or a fixed amount of spillage for liquid cargos, the spill
can be assumed to take place instantaneously,  thus obviating need for use of discharge rate
and  duration estimation methods discussed in Chapter 12 and available in the computer
program provided with this  guide.  It is cautioned,  however, that the  assumption of an
instantaneous release in such situations may greatly overestimate resulting hazard zones from
evolution of toxic or flammable vapors, fires, or explosions  Spill amounts presented in units
of gallons of  liquid can  be  converted to the units  of pounds required by the computer
program by use of the following expression.

      Amount in pounds = 8.34 x Amount in gallons x Liquid specific gravity

      Where a  hole size is specified and cargo tank or compartment dimensions are known, it
 is alternatively possible (and recommended) to utilize available discharge rate and duration
 estimation procedures to obtain an ultimately more realistic indication  of accident conse-
 quences  This is particularly advisable when the cargo is a compressed gas, a liquefied
                                         11-19
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compressed gas, or an otherwise highly volatile material. The suggested percentage of cargo
loss, when less than 100%, can be ignored, if necessary, in deference to the results obtained
from the discharge models.

113  BULK TRANSPORTATION OF HAZARDOUS MATERIALS BY MARINE VES-
      SELS

     A large portion  (about 550 million  tons in  1982 according  to  the  OTA) of the
hazardous materials shipped annually in the United States is transported by barge or other
marine vessel on coastal and inland waterways. Extensive regulations cover safety proce-
dures,  cargo  documentation, vessel  construction  and  certification, hazardous  material
transfers,  and the handling of explosives or  dangerous  cargos within or near waterfront
facilities.  Individual shipments can be vastly larger than those conveyed by rail or truck due
to the size differences among these conveyences.

     The primary types of marine vessels used for bulk  transportation of hazardous goods
are bulk liquefied gas earners, chemical tankers, oil tankers and tank barges, but bulk cargos
may also be found in smaller tanks placed on the decks of vessels or in standard intermodal
cargo containers. Some barges are self-propelled but most  are designed to be pushed by a
tugboat singly or in arrays called "tows".  Marine transportation generally involves volumes
of 300-600 thousand gallons in barges, though some such vessels are of far larger capacity.
Tank ships can have capacities that are ten times or more greater (OTA, July 1986).

     Commodity flow data are compiled  fairly rigorously for marine transportation Crude
petroleum, petroleum products, and chemicals  and liquefied gases constitute a large fraction
of all shipments in and out of most major  ports. Petroleum products include alcohols, crude
oil, refined fuels, solvents and residuals.  Typical chemicals include sulfunc acid, benzene,
toluene, sodium hydroxide, inorganic speciality products, and fertilizers. The most frequent-
ly transported liquefied gases are propane and butane, but anhydrous ammonia, chlorine,
propylene, butylene and butadiene are also frequently transported by water, as are many
other bulk commodities

     Causes and Examples of Past Accidents

     Marine transportation is generally at slow speeds and involves many precautions and
traffic controls  Hence, it has the lowest accident rate per ton-mile and the lowest number of
accidents. However, the large energies involved when these massive vessels  strike  each
other or other objects can result in severe consequences at times in terms of cargo loss  As
with other modes of transport, small releases can result from problems with gaskets, flanges,
valves or even the tanks themselves.  The separation from population limits the consequences
of small releases, however.
                                       11-20
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     A few examples of accidents involving marine transportation of hazardous materials
include:

   •     A total of 23,000 gallons of leaded and unleaded gasoline spilled into the
         southern approach to Cape Cod Canal when a barge ran aground. The Army
         Corps of Engineers  and the Coast Guard responded with divers and marine
         safety personnel to assess the damage after the tugboat called for assistance.
         The Coast Guard expected the sea current to dissipate the spill  Environmen-
         tal damage  was said to be minimal. There were  no deaths or injuries
         (August 18,1986)

   •     A collision in the Houston Ship Channel between a tug and barges and a grain
         ship resulted in an explosion and fire involving one 33,000 gallon tank of
         butadiene. Two burning barges were towed to sea where they burned for five
         days.  (August?, 1980)

   •     A 565-foot long tanker carrying two million gallons of gasoline rammed an
         unlighted oil drilling ng in  the Gulf of Mexico.  The tanker caught fire and
         had to be abandoned. (August 21,1980).

   •     A  barge carrying 400,000  gallons of acrylonitnle struck the  Galveston
         Causeway railroad bridge and ignited  Resultant explosion caused one end of
         the barge to  sink and release an unknown amount of chemical into  the water
         (January 3,1982)

    •     Up to 40,000  pounds of  hydrobromic  acid  spilled into the Mississippi
         waterway after a collision between two ships. Violent reactions between the
         acid and water required  evacuation of 3000 people  on the adjacent shore
         (July 22,1980)

      Suggested Approach for Assessment of Accident Potential

      Based  upon the information  and  data  presented  in Appendix  F,  and given  the
 understanding  that harbors and inland waterbodies  are  of greater  concern than shipping
 activities on the open ocean  and/or otherwise distant from coastlines (in terms  of the
 distances typically associated with spill effects that may pose a threat to  human life and
 health), accident rates and other spill characterization factors are presented below for.

    •     Collisions in lakes, nvers, and intercoastal waterways
    •     Groundings  in lakes, nvers,  and intercoastal waterways
    •     Collisions and groundings in harbors and bays
    •     Collisions/casualties while vessels are moored/docked
                                        11-21
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     An accident rate of lOVmile of travel is suggested for use for collisions in the first
category to cover both the lower expected accident rates on certain slow speed waterways
and  the  higher  ones for congested, highly utilized routes. Based on Gulf  Intercoastal
Waterway (ICWW) statistics, a grounding casualty rate of 5 x 1O6/ mile is suggested for the
serious type of grounding which could lead to a release. Note that this is also a "per mile"
rate. The harbor/bay area grounding and collision rate given below is "per transit", while the
moored collision rate is "per port call."  (There are two transits per port call) The suggested
rate for groundings and collisions m a harbor area is lOVtransit, while the suggested casualty
rate for moored or docked vessels is 2 x 104 per port call.

     If no distinction is being made with regard to vessel type and construction, it should be
assumed that 0.15 (15%) of accidents result in actual  loss of cargo to the environment
Alternatively, it can be assumed that accidents involving single-hulled vessels result in cargo
loss  0.25 (25%) of the time and that accidents  involving double-hulled and  bottomed
watercraft result in cargo loss 0.05 (5%) of the time.

The recommended distribution of spill amounts is:

   •     10% loss of cargo in one tank/compartment ~ 35% of the time
   •     30% loss of cargo in one tank/compartment — 35% of the time
   •     Full loss of cargo in one tank/compartment — 30% of the time

This distribution is weighted toward more severe events than the spill distributions presented
earlier, because the earlier distributions are heavily influenced by minor fitting leaks.

     Table 11.6 summarizes the accident rates and  other factors suggested for use,  while
Worksheet 11.3 outlines the procedure for determining the annual  average probability of an
accident involving spills of various amounts. A copy of the worksheet should be completed
for each hazardous material or group of similar materials transported hi bulk by waterborne
vessels through  the community or other jurisdiction of concern. Local information that will
be required to accomplish the effort includes:

   •     Material(s) of concern

   •     Maximum tank capacity of vessels carrying this material

   •     Total number of lake, river, or mtercoastal waterway miles in the area,

   •     Total ships traveling this route in a year,

   •     Total, cargo barges/tankers entenng and exiting the bay area or harbor,

   •     Total barge/tanker port calls,
                                        11-22
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                                    TABLE 11.6
             SUGGESTED FIGURES FOR MARINE TRANSPORTATION
Accident Rates*                            10-5/rmle for collision on lakes, rivers and inter-
                                          coastal waterways

                                          5 x IfrYmile for groundings on same

                                          lOVtransit for collisions and groundings in
                                          harbors/bays

                                          2 x lOVport call for collisions/casualties while
                                          moored

Conditional Spill Probabilities'               0 15 if using one rate regardless of vessel

                                          0 05 for double-hulled/double-bottomed vessels

                                          0.25 for single-hulled vessels

Spill Size Distribution:                      0.35 for 10% loss of one tank or compartment

                                          0.35 for 30% loss of one tank or compartment

                                          0.30 for 100% loss of one tank or compartment
Note:     Worksheet 11.3 demonstrates how these figures can be used to estimate annual
          accident probabilities and associated spill probabilities for marine transportation.
                                          11-23
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                                WORKSHEET 11.3

   ESTIMATING BULK MARINE TRANSPORTATION RELEASE FREQUENCIES
Hazardous Material(s):

Length of Lake, River, ICWW
Route*:

Annual Number of Trips on Route*:
Annual Number of Transits of Har-
bor/Bay*:

Annual Number of Dockings*:
                B=-


                C=-


                D=-
                     (miles within jurisdiction)
                                          (loaded trips only)
(loaded transits only)
                                          (loaded dockings only)
Accident Frequency:  E = (AxBxl.5x 1O5) + (C x 1O3) + (D x 2 x 1O»)=•
                                                                 (accidents/year)
Spill Frequency*:
F = Ex0.15=.
(all vessels)

OR

F = Ex0.25=.
(single hull)
     _(spills/year)
                                               _(spills/year)
                      F = Ex0.05 =
                      (double hull) '
                          _(spills/year)
Spills by Size°

     10% loss of one tank or compartment:

     30% loss of one tank or compartment:

     100% loss of one tank or compartment:
Fx035 =
Fx0.35 =
Fx03 =
(spills/year)
(spills/year)
(spills/year)
Notes:
    *If applicable
    *If it is known how many vessels are single-hulled and how many are double hulled, this
    worksheet can be completed twice; the first tome for single-hulled vessels and the second for
    double-hulled.
    0 The user may consider all three scenarios for consequence modelling and planning purposes
    or just the largest spill.
                                       11-24
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   •    Total river miles in the area,

   •    Number of barges/tankers traveling the river route in a year.

     When totaling barge/tanker port calls or harbor transits, remember to count only those
involving actual carnage of hazardous materials.  Empty vessels may pose some risk of fire
or explosion, but are not as important as loaded vessels. Also, note that all of the data listed
above may not be needed for every location. For example, a community located on a nver
and not having a harbor or bay area only needs  the total nver miles and number of ships
traveling the nver. In this  case, only moving collisions and nver groundings would be of
interest.

     Nonimpact casualties, such as fire/explosions, hull and machinery  damage or break-
downs, and structural failture have a very low likelihood of occurrence It is not considered
necessary to include them in the analysis

     Additional Data/Methodologies

     A more detailed and accurate analysis may  be performed  if one chooses to denve the
appropnate casualty rates and conditional probabilities for a specific harbor or water route
using local data. An  accident  rate may be derived by  combining  a measure of vessel
movements with the number of past accidents reported for the  type of movement being
looked at  The movement measure may consist of' 1) the total waterbody, nver, or waterway
miles traveled; 2) the total port calls made; or 3)  the total harbor transits  Counts should be
made only for loaded hazardous material tankers and barges   The number of accidents is
then divided by the total number of transits or  miles, as appropnate, for a similar penod of
time to determine the accident rate.

     Conditional spill probabilities and spill distnbutions are  denved in a similar fashion
The probability of a spill is obtained by dividing the number of spill accidents by the total
number of accidents that  occurred for  a specific type of  movement A spill amount
distnbution from local or national data can then be applied to determine the percentage of the
spills expected in vanous size ranges.

     Several other means exist for estimating the probability of marine casualties and spills
but they are generally highly technical, time-consuming, and occasionally quite expensive.
The reader is directed to the reference list at the end of the chapter for further information
                                        11-25
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     Use of Results in Consequence Analysis

     Due to  the special nature of the discharges from marine vessels, and difficulties in
estimating discharge rates and durations when there is water outside the cargo tank rather
than air, it is recommended (in the absence of more specific information or assumptions) that
all discharges be assumed to take place instantaneously for emergency planning purposes.
Spill amounts available in units of gallons of liquid can be converted to units of pounds by
use of the following expression-

     Amount in pounds = 8.34 x Amount in gallons x Liquid specific gravity

11.6  TRANSPORTATION OF HAZARDOUS MATERIALS BY PIPELINE

     Pipelines in the United States  primarily carry petroleum liquids, such as crude oil,
gasoline and natural gas liquids, and energy gases which include natural gas and liquefied
petroleum gas (LPG). To a much smaller extent, pipelines also transport ethane, ethylene,
liquefied natural gas (LNG), anhydrous ammonia, carbon monoxide, sour (hydrogen sulfide
containing) gas, and many other chemicals. The majority of these pipelines are between a
limited number of suppliers and users, as opposed to natural gas transmission lines. Low
pressure gas  distribution lines found  within many cities and towns are not the focus of this
section.

      Pipelines are generally constructed out of steel, although some cast iron is still in use
and plastic,  nickel  alloys, stainless  steel, carbon steel and other materials are also used.
Diameters also vary tremendously, from 2 to 4 inches  to 36 inches and over. The more
hazardous  materials tend to be conveyed  in lines at the smaller  end of the size range
Pressures also span a wide range,  and can be several thousands of pounds per square inch or
more in the highest pressure lines encountered.

      In order to reduce failures caused by corrosion, pipelines are frequently coated and/or
cathodically  protected. Lines may also be insulated, heated, double-piped for additional
protection and control, and protected with leak detection and shutdown systems.

      Causes and Examples of Past Accidents

      Pipeline failures may be a result of

    •    Internal corrosion -- especially on  two-phase flow lines  and those in sour
         service

    •    External corrosion ~ from defects in protective systems,  in cased crossings
         beneath roads and railway lines
                                         11-26
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   •    External impact ~ due to farm or construction machinery

   •    Structural failures or mechanical defects - as a result of defective seams or
        welds

   •    Natural hazards — from seismic events, subsidence, etc.

Operating errors  and construction defects are also potential causes of pipeline incidents.
Leaks may also occur at valves and pump stations.

     While there are over a thousand leaks reported each year, many of these are very small
and  have minor or no consequences to the public  For instance, 1984 data show the
following number of incidents and deaths resulting from pipeline failures (Transportation
Systems Center, 1985):

Gas pipelines
Liquid pipelines
No. of failures
967
188
No. of deaths
35
0
These rates are not particularly consistent from year to year. In 1983, there were 1575 gas
pipeline failures, but only 12 deaths resulted  There were also 6 deaths from liquid pipeline
failures.

     The following three examples illustrate typical accidents involving pipeline transport of
propane and  natural gas  No injuries occurred in  these accidents because of their remote
locations.

   •    In Port Hudson, Missouri, propane  escaped from a pipeline, flowed into a
        sparsely inhabited valley, ignited, and exploded with a blast equivalent to 50
        tons of  TNT.  No  fatalities or  injuries occurred  because  the  area was so
        sparsely inhabited.  (September 12,1977)

   •    In Prattville, Alabama, a natural gas  pipeline exploded into  two  fireballs, and
        shot flames 600 feet high. Two houses were  scorched;  200  people were
        evacuated, but no one was hurt. (My 12,1986)

   •    A natural gas pipeline explosion ignited  a 200-ft flame jet and left a huge
        crater: 60 ft across and 20 ft deep. No one was injured but an unmanned
        metering station at the accident site was destroyed.  (November 2,1985)
                                         11-27
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     Another typical pipeline accident did not have so fortunate an outcome as the above
three.

   •    In Jackson, Louisiana, a natural gas pipeline explosion resulted in 50-foot
        high flames.  The blaze was battled by firefighters for several hours. The five
        dead and twenty injured were gas company employees repairing the pipeline.
        (November 26,1984)

     Suggested Approach for Assessment of Accident Potential

     Based on the information presented in Appendix F, an accident rate of 1.5 x lOVmi-yr
is suggested for lines of unknown size or lines less than 20" in diameter For pipelines with
diameters greater than or equal to 20", a rate of 5 x 10Vmi-yr is proposed.

     The following spill size  distribution, incorporating the limited data available  , is
suggested for analyzing pipeline releases of hazardous materials*

    •     For liquid pipelines: discharge computed using consequence analysis proce-
         dures of Chapter 12 assuming a complete line break along the route of the
         pipeline — 20% of the time

    •     For gas pipelines: discharge computed using consequence analysis proce-
         dures of Chapter 12 assuming complete line break along the route of the
         pipeline — 20% of the time

    •     For either gas or liquid pipelines. 1 hour release through 1" hole	80% of
         the tune

Table 11.7 summarizes these rates, and Worksheet 11.4 demonstrates the procedures for their
use.

      The application of this material requires local information on:

    •     Material of concern
    •     Length  of pipeline within jurisdiction
    •     Pipeline diameter
    •     Flow rate (capacity) of pipeline
    •     Presence (or not) of a leak detection and emergency shutdown system

 Should a pipeline be a very short segment between two facilities, it is possible to include it
 with one of the facilities, rather than analyzing it separately.
                                          11-28
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                                   TABLE 11.7
            SUGGESTED FIGURES FOR PIPELINE TRANSPORTATION
Accident Rates:                              1.5 x 10 Vmi-yr with diameters less than 20"
                                           of if diameter is not known

                                           5 0 x lO-Vmi-yr lines with diameters greater
                                           than or equal to 20"


Spill Size Distribution:                        0.20 for 15 mm. (or 1 hour if no emergency
                                           shutdown) at the capacity flow rate through
                                           an orifice equal to the pipe size

                                           0.80 for 1 hour release through 1" hole
Note:      Worksheet 11.4 provides guidance on how to utilize these rates and probabilities
           for estimating releases of hazardous materials from pipelines.
                                      11-29
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                                 WORKSHEET 11.4

                ESTIMATING PIPELINE RELEASE FREQUENCIES
Hazardous Material(s):
Length of Pipeline of Unspecified       A =	•
Diameter:                                  (miles in jurisdiction)

Length of Pipeline < 20" in Diameter:   B =	
                                            (miles in jurisdiction)


Length of Pipeline ^ 20" in Diameter:   C =
                                            (miles in jurisdiction)



 Spill Frequency:  D = (A x 1.5 x 1O') + (B x 1.5 x 10*) + (C x 5 x 1(H) =	(spills/year)



 Spills by Size*

   1 hour release through 1" hole:             D x 0.8 =	(spills/year)


   Complete line break calculated according    D x 0.2 =	_(spills/year)
   to procedures given in Chapter 12:
 Note:
      *The user may consider both scenarios for consequence modelling and planning purposes
      or just the scenario posing the greatest threat to public safety. If several pipelines have
      been grouped by diameter, the line posing the greatest threat should not automatically be
      assumed to be the line with the largest diameter within any group. Rather, the various
      pipelines  should be individually  evaluated using the consequence  analysis procedures
      described in Chapter 12 to determine the actual worst case scenario, if this is desired.
                                          11-30
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     Additional Data/Methodologies

     The main alternative to  the appioach given above is the specific consideration of
pipeline design and the operating environment to more precisely determine the failure rate
associated with each potential cause of failure (Techmca, 1983).

     Use of Results in Consequence Analysis

     For pipelines conveying compressed (but not liquefied gas), the consequence analysis
procedures described in Chapter 12 and incorporated into its associated computer program
are fully capable of estimating the rate and duration of gas release from either full line breaks
or smaller leaks.

     Due  to  the  complexity  of the problem, the computer program's liquid pipeline
discharge model is only capable of addressing full line breaks It will be necessary to consult
with the pipeline owner or operator for assistance in estimating discharge rates and durations
for outflows from one inch diameter holes if  these scenarios are considered worthy of
analysis.

11.7  HANDLING AND  TRANSFER OF  HAZARDOUS  MATERIALS  AT FIXED
      FACILITIES

     A broad range of facilities may pose potential risks associated with the release of
hazardous  materials These can include,  large refineries, chemical plants,  and storage
terminals, more moderately sized industrial users, warehouses, and isolated storage tanks for
water treatment, small quantity users/storage as may be found in high school and college
laboratones, florists, greenhouses, hardware and automotive stores, paint stores, etc.

     As a result of this broad spectrum of potential spill sources, virtually no accurate data
exists to  determine the magnitude of this problem  Marine terminals and loading/unloading
activities for rail cars and trucks are somewhat more widely reported and are considered
within this overall category.

     FEMA has a database that identifies the number of chemical and petroleum facilities by
county.  These facilities are broken down into chemical and allied products, petroleum and
coal products, and rubber and miscellaneous plastic products  No  accident information is
maintained, however As of 1981, there were 16,000 chemical process industry plants with
20 or more employees and 6,000 plants with 100 or more employees  Los Angeles and Cook
(Illinois)  counties each have over 200 plants The number of counties with between 11 and
50 plants is 160, all the rest have ten or fewer plants About 50% of all the counties m the
U.S. have no chemical process industry plants (Check et al, 1985)  (This is not to say that
                                       11-31
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there are no facilities handling hazardous materials in these counties.) McGraw Hill has
published a map of the plant locations  and a booklet entitled  "Census of the Chemical
Process Industries."

      Causes and Examples of Past Accidents

      Releases from fixed facilities may arise from storage tank or container ruptures or
leaks, piping ruptures  or  leaks, releases through safety and relief valves, fire-induced
releases, other equipment failures, malicious or deliberate actions, overfills and overflows of
storage tanks, human errors, open valves, failed loading hoses, or improper hose connections
These may generally be grouped into three categories for large facilities:

      •     Transfer, loading and unloading activities
      •     Processing activities
      •     Storage tanks and their spill control systems

Smaller facilities may not have any processing activities

      Transfer areas include pipelines, pumps, valves, and control instrumentation needed to
 achieve the movement of material within a facility. The loading/unloading area involves the
 most handling operations and the largest potential for human error in most facilities. This is
 where  the raw  materials are brought in and products and by-products are removed, and
 temporary connections  are frequently used. The  storage area may be for raw materials,
 intermediates, products, or by-products. The greatest volumes are contained here, so spill
 sizes can be quite large. The processing area has equipment for raw material conversion into
 products.  This  is the area that will only be found in a plant, while handling and storage
 activities  may  take place at warehouses, water treatment facilities, greenhouses, and
 numerous other types of miscellaneous facilities.

      Examples of a broad spectrum of accidents are given below These cover events which
 start with a release of hazardous materials, as well as those where a fire propagates into a
 hazardous materials release.

       •    A natural  gas pipeline rupture at a  Texas refinery  caused  a series of
            explosions and fires  Two hundred firefighters worked nearly  six hours to
            control the blaze  fed by  three other propane pipelines  Two refinery
            workers were killed; a town of 1,200 people was evacuated. Damage to the
            complex was predicted "into the millions " At least three similar explo-
            sions had occurred in the area in the prior five years.
                                          11-32
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Lightning struck a power pole in a chemical plant, then jumped to a tank of
dilute hydrochloric acid, damaging a tank valve. A cloud of gas floated
across several nearby neighborhoods. Hundreds of residents were forced to
evacuate their homes; three plant workers were injured  (August 1,1980)

A refrigeration line at  an ice cream plant  in Burbank, California ruptured
spilling 300 gallons of anhydrous ammonia  Firefighters sprayed water to
control  the fumes until  the main valve could be shut off  and the leak
stopped. Eleven people were hospitalized  and 60 residents were forced to
leave the surrounding area.  (November 13,1984)

In Covington, Kentucky a chlorine gas cylinder ruptured  at a swimming
pool  jammed with about  300 swimmers More than 140  people were
hospitalized; no serious injuries were reported. (June 21,1981)

At least 11  people were injured  and 100 persons evacuated  from a
one-square mile  area  East Los Angeles  after  100 gallons of chlorine
overflowed from a storage tank. (March 1,1982)

A 25,000 ton storage  tank in Portland, Oregon, discharged 3-5 tons of
anhydrous  ammonia due to  a valve malfunction.  An  area three miles
downwind  was evacuated  while response personnel  used water fog to
knock down vapors and had the spill vacuumed. (February 5,1982)

Falling equipment sheared off a pipe leading to a tank of hydrofluoric acid.
There were 66 senous injuries and roughly 3000 people were evacuated
around the  Texas  City oil refinery  Water fog was used to help control the
vapor cloud and the tank contents were transferred to adjacent rail cars.
(October 31,1987)

More than 16,000 south Chicago residents were evacuated from the vicinity
of a bulk storage and  terminal when a silicon tetrachlonde  storage tank
sprang a leak.  The escaping liquid, on the order of 150,000 gallons, reacted
with the moisture  in the air to form hydrogen chlonde, resulting hi a dense,
corrosive, choking plume that stretched 5-10 miles downwind at times  It
required 8 days for authorities to stop the leak, neutralize the  spillage, and
transfer remaining tank contents to other  containers. Approximately 100
people were hospitalized during the incident.  (April 26,1974)
                              11-33
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     •    A  truck  driver  delivering  sodium  hydrosulfide  to  a Chicago  leather
          company was directed to the wrong valve and began unloading the sodium
          hydrosulfide cargo into a tank of chromic acid. The reaction of the two
          chemicals released a deadly gas, hydrogen sulfide. Over 170 persons
          working inside the four-story tannery were overcome by the gas; a total of
          eight died and twenty-nine were injured.  (February 14,1978)

     There  is one last type of accident that ments special  attention for fixed facilities,
whether they be small or large. This is the potential for external events to cause releases,
with earthquakes being of particular concern Any natural disaster can cause releases as well
as affect responses For instance, transportation and access to the facility may be restricted,
water lines for fire protection may be broken, and resources may not be adequate to cover all
situations simultaneously Within any one site,  an earthquake may impair the integrity of
containment (e.g., dikes)  and/or may cause multiple containers/tanks  to  fail,  thereby
exceeding the capacity of dikes,  curbs,  or other  types  of containment. Jurisdictions
particularly prone to such natural events as major earthquakes and floods should consider a
more formal analysis of facility nsks,  taking into  account the presence or lack thereof of
appropriate protective measures for these threats.

      Suggested Approach for Assessment of Accident Potential

      Based upon the information presented in Appendix F, the  approach suggested for
getting a handle on fixed facility accident scenarios is to consider three basic types of release
events for plants; one or two release scenarios for facilities such as water treatment plants,
laboratories and  industrial facilities;  and one release scenario for warehouses and other
facilities  storing hazardous materials. It has been  shown  that very little specific historical
information exists upon which to base accident rates. Hence,  the best general approach is  to
look at equipment failure rates. The increasing  use of  physical barriers to limit spills,
 drainage systems to channel spills, and venting and scrubbing systems to control releases all
 help to render this simplified accident estimation procedure more meaningful.

      For example, a large facility may be coarsely modelled as having storage operations,
 loading/unloading operations, and processing operations.  These  can respectively be repre-
 sented by  storage  tank failures and  leaks, hose  failures, and piping and process vessel
 failures.  The rates suggested for each of these are.

       Storage tank - double walled       lO^/tank-year
       Storage tank - single walled        KH/tank-year
       Pressure vessels                   lOYvessel-year
       Inplant piping                    1-5 x 10-«/ft-year
                                          11-34
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     Loading hoses                   lOVoperatton or
                                      lO2/hose-year

While these certainly do not cover all potential release scenarios, they do capture some of the
more likely ways to lose large volumes of material.  The only piping of prune concern is that
of relatively large diameter and long segments.  In other words, a 100-foot expanse of 8" pipe
should be counted during assessment of failure potential if it contains hazardous materials,
but not 10 or 20 foot sections between vessels.  As shown in Table 11.8, the spill size is
generally taken to be a function of the specific release scenario.

     For the middle category of industrial users, water treatment plants, laboratories, etc.,
the main focus should be on storage tank or container failures. Piping failures or loading
hose failures may be considered if there is a significant amount of piping (say over 100 feet)
or if there are frequent loading/unloading operations (say 10 or more per year). The rates to
be used are the same as those listed above and summarized in Table 11.8.

     Storage of hazardous materials, such as in warehouses or greenhouses, may also result
in failures of storage containers, but the greater threat here is probably from a fire which
spreads to the storage area and results in release, ignition, explosion, and/or combustion of
stored materials (with attendant evolution of potentially toxic smoke). The occurrence rate of
such fires is  suggested to be 10-Vyr resulting in a release of  10% to 100% of the stored
volume of hazardous materials -- as summarized in Table 118. This is one area in which
more specific local data and information would be particularly helpful for better definition of
scenarios  and estimation of their likelihood.   Worksheet 11.5  summarizes  the overall
recommended procedure recommended for analysis of fixed facilities.

     The data required for an analysis that generally focuses on the larger and/or more likely
(yet significant) events at fixed facilities are:

     •    Material(s) of concern

     •    Number, dimensions, capacities, and contents of storage containers or tanks

     •    Number, dimensions, capacities, and contents of other vessels with large
          inventories of hazardous  material (such as columns,  separators, reaction
          vessels)

     •     Size, length, and operating conditions of piping systems

     •     Number of unloading and loading operations per year, materials involved,
          and transfer flowrates
                                        11-35
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                                          TABLE 11.8
                     SUGGESTED FIGURES FOR FIXED FACILITIES
            ITEM
ACCIDENT RATE
              SPILL SIZE
Chemical Plants

Double-walled storage tank
Single-walled storage tank or
pressure vessel
Piping
Loading hose
   10 x 10«/tank-year


   10 x lOVtank-year
100% of tune ~ total amount of typical contents
released instantaneously

90% of tune - release of contents through 1" hole
until leak can be plugged or otherwise terminated

10% of time — total contents released
instantaneously
   15 x 10*/foot-year    90% of time - release through 1" hole in wall of
                       pipe until leak can be plugged or otherwise
                       terminated

                       10% of tune — complete rupture of pipe

lO'Vloading or unloading or 100% of time — release through full hose diameter
      10-Vhose-year      at loading/unloading rate until flow can be
                       terminated
 Industrial Users, Laboratories, Water Treatment Plants
 Storage tank/container
 Piping (if more than 100 ft)
 Loading hose (if used more than 10
 times/yr)
    lOxlOVtank-year
    15 x lOVfoot-year
     10^/operation or
      102/hose-year
 90% of time — as above for single-walled storage
 tank or vessel

 10% of time - as above for single-walled storage
 tank or vessel

 90% of time ~ release through 1" hole in wall of
 pipe until leak can be plugged or otherwise
 terminated

 10% of time — complete rupture of pipe

 100% of time - release through full hose diameter
 at loading/unloading rate until flow can be
 terminated
 Warehouses and Other Storage Facilities
 Storage containers (drams, cylinders,
 etc)
        10-3/year
 90% of time ~ release of 10% of total stored
 volume

 10% of time - 100% loss of total stored volume
 (i e, all containers combined)
                                              11-36
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                                 WORKSHEET 11.5
            ESTIMATING FIXED FACILITY RELEASE FREQUENCIES
Hazardous Materials):

Number of Process Vessels/Single-Wall
Storage Tanks:

Number of Double-Walled Storage Tanks:

Length of Pipe:

Annual Number of Loadings/Unloadings:

    (or number of hoses)

Spill Frequencies*

    Process Vessels/Storage Tanks:

    Double-Walled Storage Tanks:

    Piping:

    Loading/Unloading Hoses'



Spills by Size**

Process Vessels/Storage Tanks
     10% of contents (1" hole):

     100% of contents:

Piping
release through 1" hole:

    release through full pipe diameter for
    time needed for shutdown or until
    associated tank is emptied:

Loading/Unloading Hoses
    release through full hose diameter
    at transfer rate for time needed for
    shutdown:
 Notes:
A=-


B=-
f^ _
Dl=-

D2=-
  = Axl(H=
OR
H = D2xlO2 =
Ex 0.9=.

(ExO.lH


Gx0.9 =
 Gx0.1 =
                              (feet)
                         _(spills/year)

                         _(spills/year)

                         _(spills/year)
                          _(spills/year)

                          	(spills/year)
                      _(spills/year)

                      	(spills/year)
                      _(spills/year)
                      _(spills/year)
H =
                 _(spills/year)
      *Assumes that the consequences of releases will be based on the tanks, piping and loading
      hoses which give the worst consequences If desired, individual components or smaller
      groupings may be evaluated by completing the worksheet separately for each grouping.

      +The user may  consider all these scenarios for consequence modelling and  planning
      purposes, or just the largest spill in each category.
                                         11-37
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The more of this data available, the better. A first cut analysis could start with just the
storage tanks/containers and any other large vessels, adding loading activities and piping
only if the more information is desired or needed. Tanks of similar size and contents may be
grouped together for probability analysis purposes, as may pipelines.

     Additional Data/Methodologies

     In addition to the multi-tiered approach discussed above, there are a number of more
detailed analysis procedures that are appropriate for fixed facilities.  These generally require
more complete risk assessments which can be time consuming and expensive, and which
mandate the complete cooperation of plant/facility management in order to obtain accurate
and complete results. Numerous data sources discuss the merits and requirements of such
analyses. Some starting  points might  include CONCAWE:  1982, Atherton et  al:  1980,
Simmons: 1974, COVO: 1982, and literally dozens of other reports and hundreds of articles.

     Use of Results in Consequence Analysis

     The choice of consequence procedures to be utilized for any given potential source of
hazardous material discharge or spillage depends on the type of container or tank involved
and the nature of the particular hazardous material contained therein. Although Chapter 12
of this guide and its related computer program provide a wide variety of analysis tools to
assist  users in evaluating individual  accident scenarios, the large number of diverse
situations that may be encountered at many fixed facilities does not permit the provision of
detailed guidance for each and every case. Rather, emergency planning personnel need to
apply the following guidelines with some degree of flexibility and common sense.

     The first objective of a consequence analysis for a fixed facility should be evaluation of
threats posed by  storage  tanks  or process vessels that contain  significant amounts of
hazardous materials. Releases from short lengths (10-20 feet) of piping  attached to these
containers  are included in the vessel failure rates Each container of this type should be
evaluated individually. If a length of piping between containers can result in simultaneous
discharges from more than one container, this fact should be considered in the analysis.  To
the extent possible,  the  analysis should utilize available information on  the  operating
conditions of each  vessel in terms of typical and maximum amount of contents, operating
temperature, pressure, and so forth. Any container of a  substance with the potential  for
runaway polymerization, decomposition,  or other unusual reactivity hazard should be given
special consideration and attention. (However, the frequency of such events cannot be
estimated using general historical data)
                                         11-38
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     Most intraplant or facility piping systems will be attached to one or more storage or
process vessels and should consider the amount of contents of such vessels.  In addition,
larger  lines of significant diameter and length may require analysis via use of pipeline
discharge models to the extent that is feasible, or alternatively, the use of tank discharge
models Although the procedures of Chapter 12 permit evaluation of full line breaks and
leaks from small holes in compressed gas pipelines, only full line breaks can be considered
for liquid  pipelines  Consequently, assistance  will be  required from facility owners or
operators for analysis of smaller liquid leaks if this lower consequence but higher probability
scenario is to be  addressed. If shutdown  capability is not known, a reasonable release
duration may be assumed to be 15 minutes

     Loading hose failures commonly involve transfers to and from transportation vehicles.
It will  be necessary in many (but not all) such cases to assume a discharge rate equivalent to
the cargo transfer rate through the hose, though the actual rate of discharge may be somewhat
higher (especially initially). The potential duration of discharge should be determined by
investigation of the presence of emergency shutdown systems, available response forces, and
the likely time needed for them to terminate the release by various means at their disposal. In
no case, however, should the total amount of discharge exceed the total contents of the
storage tank and the transportation vehicle. While evaluating such situations, pay special
attention to situations in which manually activated emergency shutdown systems  may be
present but not approachable due to the hazardous properties of the material being released
Obviously, a  truck driver may be reluctant or unable to approach a vehicle to  pull an
emergency shutoff valve lever if his vehicle is venting large amounts of a highly toxic,
flammable, and/or explosive gas or liquid.  In the absence of such information, a recom-
mended release duration is 5 minutes.

     Evaluation of consequences from small containers or cylinders stored in  warehouses,
laboratories, and  a  wide  variety of  other commercial or public facilities  will require
consideration  on a case by case basis where greater specificity is desired  than that given in
Table  11.8 and Worksheet 11.5, giving due consideration to the nature of potential accidents
and their likely outcome.  Gas cylinder leaks can generally be  evaluated in  a direct  and
straightforward manner using the procedures of Chapter 12 and its related computer program
Note,  however, that one of the most common major problems in this general type of facility
is not leakage from  one or more containers but a fire in the facility  that  involves the
hazardous materials stored therein  and produces large quantities of toxic smoke that may
adversely impact downwind areas. Given the diversity of substances that may  be involved,
there is no simple manner in which the downwind area possibly requiring evacuation or other
protective action can be precisely estimated in such events. Rather the general emergency
plan must be  sufficiently flexible to permit on scene decisions during an actual emergency
and the rapid initiation of evacuation or protective action activities.
                                         11-39
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11.8  TRANSPORTATION OF PACKAGED HAZARDOUS MATERIALS

     It has been estimated that there are up to 700,000 vehicles and vessels used to carry
hazardous materials hi small packages in the United States  (OTA, March  1986). Such
packages may be cylinders, drums, barrels,  cans, boxes, casks, bottles, or other  similar
containers, and are defined as having a capacity of less than 110 gallons or 1000 pounds
They may be transported by air, water, rail (usually in box cars), truck or van  Non-bulk
transportation of hazardous goods is estimated to represent 50% of the total tons shipped by
truck and 80% of the  total truck spills  (OTA, July  1986)  Up to 8% of the  marine
transportation of hazardous materials involves dry cargo barges carrying portable tanks or
drums.

     Commodity flow information for such shipments is  very limited due  to the large
number and variety of shipments that take place and a lack of reporting requirements  Thus,
there is also a lack of accident rates or spill amount distributions which can be applied on a
general basis.  But the small amounts of materials involved usually (not always) imply
limited consequences in the event of a release.

     Causes and Examples of Past Accidents

     The causes of releases from small packages include:

     •    Improperly tightened or faulty fittings, valves, and closures

     •    Dropping packages (while loading/unloading or in transit)

     •    Puncturing packages (again while handling or in transit)

     •    Improper blocking and bracing which allows packages to move, fall or fail
          from impact or crushing while in a vehicle

     •    Fires

     •    Freezing, getting wet, or other severe environmental exposure

     Examples of some incidents involving small  packages  are  given below. These
particular examples cover transportion as well  as loading and unloading incidents

     •    Ten employees were treated and released when a container of  arsenic
          trichloride was found ruptured  as a truck was being unloaded  (July 19,
           1985)
                                      11-40
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     •     A drum loaded with pesticide began leaking its contents as it was being
          transported on a flatbed truck near  Cologne,  Germany. The small spill
          formed a large gas cloud which was toxic and corrosive.  Traffic had to be
          halted for a considerable time to allow clean-up  crews to neutralize the
          situation.  (May 15,1985)

     •     A container loaded with drums of phosphorous was being lifted by crane
          from a barge to the dock when it ignited after  an adjacent obstruction
          punctured a drum through the container walls. The crane driver submerged
          the entire container in the  water away from the barge.  The phosphorous
          reigmted when the container was placed on the dock; by then the fire
          department had  arrived and  extinguished the  fire with dry powder. No
          deaths or injuries resulted. (May 15,1986)

     •     In a Houston port, a freight container explosion from improperly packaged
          aluminum phosphide killed  a dock worker. When inspectors from the
          Marine Safety Office opened the container, boxes  of high explosives were
          found, even though the aluminum phosphide had warning labels marked,
          "Do not store with high explosives." (January 20,1986)

     •     Amid heavy tourist traffic, a truck driver noticed that water was leaking
          from his cargo, drums containing nuclear reactor sludge Further inspection
          at a busy truck stop showed that the hole in the drum had been patched with
          electrician's tape.  (November 14,1979)

     Suggested Approach for Assessment of Accident Potential

     The available accident data covers accidents per  unit of handling for a package
(without designation of spill or  nonspill events) (Kloeber  et al, 1979), and there are a few
data sources (ICF, 1984) which give  release fractions for transit as well as at associated
terminals. The methods needed to take advantage of these data,  however, require more
information than can be obtained by emergency planning personnel with a reasonable amount
of effort in the vast majority of cases

     The approach suggested is  to identify particular shipments of concern which were
discovered during initial data collection efforts  and to only analyze those selected materi-
als/shipments  which involve sufficient volumes of materials to pose major hazards  The
basic approach is to then utilize the basic accident rates for rail, marine, or highway transport
as dictated by the type of transportation taking  place, and to combine the resulting annual
accident rate with the fraction of accidents expected to result in a spill or discharge. As a first
pass on estimating the spill size distribution, consider using:
                                        11-41
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     •    Loss of one container (or group of containers, such as 12 bottles in a box)
          --90% of the time

     •    Full loss of cargo (all containers) — 10% of the time

     Additional Data/Methodologies

     Should more precise estimates be needed, one of the more detailed methodologies
should be utilized (for example, see ICF, 1984, and the references contained therein).

     Use of Results in Consequence Analysis

     Given the relatively small  amounts of hazardous materials transported in individual
packages and the manner in which most fail,  the best course  of action for  consequence
analysis purposes is to assume that the amount of cargo specified directly above is released
instantaneously to the environment

11.9  TRANSPORTATION OF HAZARDOUS MATERIALS BY AIR

     The transportation of hazardous materials by air is generally limited to small packages,
but this category of accidents also applies to crop dusters applying pesticides. The materials
transported by air are usually of high value or of high priority time-wise. The annual tonnage
shipped is between 200 and 300 thousand tons, but this involves a very large number of
shipments  One study (OTA, March 1986) reports that in an evaluation of the  air cargo
packages at 39 major airports, 5% involved hazardous materials.

     As demonstrated at the beginning of this chapter, there are relatively few hazardous
materials incidents each year involving this mode of transportation. One source (Hazardous
Materials Intelligence Report, May 31, 1985) found that there were only 6 incidents in 1984
which resulted in death, injury or more than $25,000 of property damage on a nationwide
basis. The accidents tend to concentrate in the vicinity of airports, as might be expected

     There are numerous regulations covering the transportation of hazardous goods by air,
including quantity restrictions and detailed regulations involving packaging. Many incidents
which occur have been shown upon investigation to involve violations of these regulations

     In terms of emergency response planning, there is little that can be done to accurately
determine a community's potential vulnerability to this type of accident, and admittedly,
there is a question of whether planning should go beyond the development of communica-
tions links with airport facilities that handle  hazardous materials,  and the identification of
                                        11-42
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those locations where hazardous materials may be found on airport property  This observa-
tion follows from both the very low  frequency of serious incidents and  the extremely
incomplete data available on commodity flows.

     Crop dusters present a special case. Although accident rates and specific consequences
cannot be predicted in advance due again to a ranty of senous incidents, it is a good idea for
jurisdictions in which these aircraft work to give some thought to how to respond to a crash.
Note that these planes usually carry pesticides and herbicides that may be highly toxic when
concentrated. The crash site and surrounding areas may be highly contaminated. Crashes in
or near bodies of water may threaten water supplies or cause environmental damage.

11.10  SUMMARY

     The preceding sections have presented  methodologies for estimating  the annual
probability of hazardous material releases from fixed facilities and transportation systems.
Individual worksheets have been provided for truck, rail, marine, pipeline and fixed facility
activities and operations. At the very least, a separate worksheet will need to be completed
for each material or group of materials of concern and/or each facility of concern. Even if
accident probabilities are not computed, the worksheets and related text can  be valuable for
the identification and refinement of individual accident scenarios.

      The most critical local information needed for completion of worksheets involves
exposure data - i.e., the number and length of shipments, the number and capacity  of storage
tanks  or process vessels, and  so forth.  When obtaining  this information, it is usually
 sufficient to obtain the correct order of magnitude - great expenditures of resources or very
precise counts are not warranted. Should information be unavailable, it may be necessary  to
make  a best estimate, with  advice from  other knowledgeable individuals. This is surely
 better than eliminating any potentially significant accident scenario from consideration.

      Another  important point is that no one event can result in all  possible potential
 consequences simultaneously. In  other words, if a rail car or tank  truck expenences a
 BLEVE, it cannot then also have major downwind  toxic vapor dispersion hazards as these
 require  non-ignition of the cloud. Also,  not all ignitions  of flammable vapors result  in
 explosions. The percentage of events which result in various consequences is very  dependent
 on the material involved, the quantity released, and the reason for the release. General
 percentage breakdowns cannot be given.

 11.11   REFERENCES

 Association of American Railroads.  "Railroad Facts, 1985 Edition," August 1985.
                                         11-43
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Atherton, J.G. et al "The Bulk Storage and Handling of Flammable Gases and Liquids,"
London: Oyez Publishing Limited, 1980

Chemical and Engineering News.  "Emergency plans urged for railyard chemicals," July 29,
1985, p. 6.

Cheok, M.C., G.D. Kaiser and G.W. Parry. "Development of a Methodology for Compren-
sive Hazard Analysis - A  Feasibility Study," prepared by NUS  Corp. for  the Federal
Emergency Management Agency, June 1985.

Clarke, R.K. et al. "Severities of Transportation  Accidents,"  Sandia Laboratories, NTIS
SLA-74-0001, July 1976

CONCAWE. "Methodologies for Hazard Analysis and Risk Assessment in the Petroleum
Refining and Storage Industry," CONCAWE Report No. 10/82, Den Haag, December 1982.

Considine, M. "Risk Assessment  of the Transportation of Hazardous Substances Through
Road Tunnels," Recent Advances in Hazardous  Materials Transportation Research, An
International Exchange, State-of-the-Art Report 3, Transportation Research Board, Washing-
ton, DC, 1986, pp  178-185.

Considine, M., G.C. Gnnt  and P L  Holden. "Bulk Storage of LPG - Factors  Affecting
Offsite Risk," Institution of Chemical Engineers Symposium Series No. 71, pp. 291-320.

COVO Steering Committee.  Risk Analysis of Six  Potentially Hazardous Industrial Objects
in the Rijnmond Area, a Pilot Study, Boston.  D Reidel Publishing Co., 1982.

Federal Railroad Administration. "Accident/Incident Bulletin, No 156, Calendar Year 1987,"
July 1988.

Harvey, A E, P.C. Cordon  and T S.  Ghckman.  "Statistical Trends  in Railroad Hazardous
Materials Transportation  Safety  - 1978 to 1986,"  Publication  R-640,  Association  of
American Railroads, Washington Systems Center, September 1987.

Hazardous Materials Intelligence Report, May 31,1985

ICF, Inc. "Assessing the Releases  and Costs Associated with Truck Transport of Hazardous
Wastes," prepared for the U S Environmental Protection Agency, NTIS PB84-224468,1984

Kloeber, G. et al.  "Risk Assessment of Air Versus  Other  Transportation  Modes for
Explosives and Flammable  Cryogenic Liquids, Volume  I:  Risk Assessment Method and
Results," prepared by ORI, Inc for Materials Transportation Bureau, NTIS PB80-138472,
December 1979.
                                       11-44
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Lautkaski, R., T. Mankamo and M. Karkkainen. "Chlorine Transportation Risk Assessment,"
Revised Edition, Nuclear Engineering Laboratory, Report 27, Technical Research Centre of
Finland, September 1979.

Materials Transportation Bureau "Annual Report on Hazardous Materials Transportation,
Calendar Year 1983."

National Transportation Safety Board. "Railroad/Highway Grade Crossing Accidents Involv-
ing Trucks Transporting Bulk Hazardous Materials," NTIS PB82-113432, September 1981.

Nayak, P.R., D.B. Rosenfield and JH Hagopian. "Event Probabilities and Impact Zones for
Hazardous Materials Accidents on Railroads," prepared by Arthur D. Little, Inc. for the
Federal Railroad Administration, DOT/FRA/ORD-83/20, November 1983.

Office of Radiation Programs. "The Consequences and Frequency of Selected Man-Originat-
ed Accident Events,"  U.S. Environmental Protection Agency, NTIS PB80-211303, June
1980.

Office of Technology Assessment. "Transportation of Hazardous Materials," OTA-SET-340,
Washington, DC: U.S.  Government Printing Office, July 1986

Office of Technology Assessment. "Transportation of Hazardous Materials' State and Local
Activities," OTA-SET-301, Washington, DC: U.S. Government Printing Office, March 1986.

Simmons, J.A. "Risk  Assessment of  Storage and Transport of Liquid Natural  Gas and
LP-Gas," prepared by Science Applications, Inc. for the U.S. Environmental Protection
Agency, NTIS PB-247 415, November 1974.

Smith,  R.N. and EL. Wilmot  "Truck Accident  and  Fatality Rates  Calculated from
California Highway Accident Statistics for 1980  and 1981," prepared by Sandia National
Laboratories for U.S. Department of Energy, SAND-82-7066, November 1982.

Sorensen, J.H. "Evacuations Due to Chemical Accidents: Expenence from 1980 to  1984,"
prepared by Oak Ridge National Laboratory, ORNL/TM-9882, January 1986.

Techmca. "Ethane and Ethylene Pipelines Between Mossmorran and Grangemouth, Assess-
ment of Residual Risk," Production No 9, London, January 1983

Transportation Systems Center. "Transportation Safety Information Report,  1984 Annual
 Summary," U.S.  Department of Transportation, DOT-TSC-RSPA-85-1, April 1985.

Urbanek, G.L. and E J. Barber  "Development of Catena to Designate Routes for Transport-
 ing Hazardous Materials," prepared by Peat,  Marwick, Mitchell and Co  for the Federal
Highway Administration, NTIS PB81-164725, September 1980.
                                       11-45
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von Herberg, P. "Prevention is the Best Cure," Chemical Purchasing, September 1979, pp
79-84.

Wolfe, K E  "An Examination of Risk Costs Associated with the Movement of Hazardous
Materials," submitted to the Transportation Research Forum's 26th Annual Proceedings,
October 22-24,1984.

Wright, CJ.  and PJ.  Student. "Understanding  Railroad Tank  Cars,"  Fire  Command,
November 1985, pp. 18-21 and December 1985, pp. 36-41.
                                      11-46
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            12.0  CONSEQUENCE ANALYSIS PROCEDURES
12.1 INTRODUCTION TO ARCHIE

     With the wide proliferation of personal computers throughout the United States in
recent years, particularly of IBM™ PC and fully compatible systems, it is now possible to
provide emergency preparedness personnel at all levels of government and industry with
relatively sophisticated computational tools to evaluate the nature and magnitude of threats
facing  individual jurisdictions  To  facilitate what would  otherwise be a difficult, time
consuming, and expensive (if not impossible) task in many cases, the majority of accident
hazard assessment and consequence analysis procedures required for a comprehensive hazard
analysis have been incorporated into a single software program titled Automated Resource
for Chemical Hazard Incident Evaluation (ARCHIE)  A copy of Version 1.0 of the program
has been provided together with this guide Future efforts being considered by the federal
government to further refine ARCHIE include installation of a data base of chemical and
physical properties for a  large number of hazardous  materials,  installation  of  more
sophisticated analysis procedures enabled by availability of a database, and development of a
version that will function on Apple™ Macintosh computers  Whether or not these enhance-
ments  are undertaken will depend  upon the  acceptance  of  ARCHIE by emergency
preparedness personnel and feedback received by the government on the usefulness of the
program to their individual planning efforts
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     Due to the length of this chapter and the likelihood that users will refer to it often,
Table 12.1 provides a special index to the following sections

     Purpose and Objectives of ARCHIE

     The primary purpose of ARCHIE is to provide emergency preparedness personnel with
several integrated estimation methods that may be used to assess the vapor dispersion, fire,
and explosion impacts associated with episodic discharges of hazardous materials into the
terrestial  (i.e.,  land)  environment The program is  also  intended to  facilitate a better
understanding of the nature and  sequence of events that may follow an accident and their
resulting consequences

     Be  advised that the detailed site-specific modeling  techniques incorporated  within
ARCHIE differ from the more  simplistic approaches in Technical Guidance for Hazard
Analysis and are likely to produce different results  In addition, ARCHIE permits assess-
ments for numerous types of hazards not addressed in the earlier guide

      General Features of the Program

      The core of the ARCHIE computer program is a set of hazard assessment procedures
and models that can be sequentially utilized to  evaluate consequences of potential discharges
of hazardous materials and thereby assist in the development of  a basis  for emergency
planning. In other words, ARCHIE can help emergency planning personnel understand 1)
the nature and magnitude of hazards posing a threat to their jurisdictions, 2) the sequence of
events that must take place for these threats to be realized, and ultimately 3) the nature of
response  actions that may be necessary in the event  of  an emergency to mitigate adverse
impacts upon the public and its property  Among the  models  or calculation procedures
incorporated into Version 1.0 of ARCHIE are

      •    Nine methods for estimating the discharge rate and duration of a gas or
           liquid release  from a tank or pipeline

      •    Seven methods to help the user estimate the  size of any liquid pools that
           may form on the ground

      •    Two methods to estimate the rate at which a liquid pool will evaporate or
           boil and the duration of these phenomena until the point in time that the
           pool is depleted.

      •    A method to estimate the size of the downwind hazard zone that  may
           require evacuation or other public  protective action due to the release of a
           toxic gas or vapor into the atmosphere
                                         12-2
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        TABLE 12.1
SPECIAL INDEX TO CHAPTER 12

121
122
123
12.4
125
126
127
128
129
1210
1211
1212
1213
1214
1215
12.16
1217
12.18
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
Section Title
ntroduction to ARCHIE
nstallation of the ARCHIE Computer Program
General Notes on Responding to Questions from the Program
Initialization of Program Configuration Settings
Display of the Program Title Screen
'ntroduction to Options on the Main Task Selection Menu
Introduction to the Hazard Assessment Model Selection Menu
Discharge Menu Option A' Non-Pressurized Rectangular Tank of Liquid
Discharge Menu Option B Non-Pressurized Spherical Tank of Liquid
Discharge Menu Option C Non-Pressurized Vertical Cylinder of Liquid
Discharge Menu Option D- Non-Pressurized Horizontal Cylinder of Liquid
Discharge Menu Option E. Pressurized Liquid When Discharge Location is 4
inches or Less from the Tank Surface
Discharge Menu Option F Pressurized Liquid When Discharge Location is
More Than 4 Inches from the Tank Surface
Discharge Menu Option G. Pressurized Gas Release from Any Container
Discharge Menu Option H. Release from a Pressurized Liquid Pipeline
Discharge Menu I* Release from a Pressurized Gas Pipeline
Hazard Model Menu Option B: Pool Area Estimation Methods
Hazard Model Menu Option C. Pool Evaporation Rate and Duration Esti-
mates
Hazard Model Menu Option D Toxic Vapor Dispersion Model
Hazard Model Menu Option E: Liquid Pool Fire Model
Hazard Model Menu Option F Flame Jet Model
Hazard Model Menu Option G Fireball Thermal Radiation Model
Hazard Model Menu Option H. Vapor Cloud or Plume Fire Model
Hazard Model Menu Option I Unconfined Vapor Cloud Explosion Model
Hazard Model Menu Option J Tank Overpressunzation Explosion Model
Hazard Model Menu Option K- Condensed-Phase Explosion Model
Remaining Options on the Hazard Assessment Model Selection Menu
Use of the Vapor Pressure Input Assistance Subprogram
Use of the Tank and Container Contents Characterization Subprogram
Other Computer Programs
Page
12-1
12-6
12-7
12-9
12-10
12-10
12-14
12-20
12-23
12-26
12-29
12-32
12-36
12-40
12-44
12-49
12-52
12-56
12-59
12-63
12-64
12-67
12-68
12-72
12-75
12-78
12-80
12-81
12-84
12-85
            12-3
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      •     A method  to  evaluate the thermal radiation hazards resulting from the
           ignition of a flammable or combustible pool of liquid

      •     Two methods to evaluate  the  size of the downwind area that may be
           subjected to flammable or explosive concentrations of gases or vapors in air
           due to the release of a flammable or explosive gas or vapor -- together with
           the maximum weight of potentially explosive gas or vapor in air that occurs
           during the incident.

      •     A method  to  evaluate the consequences  of an unconfined vapor cloud
           explosion if  the flammable  gas or vapor  in  air  should  explode upon
           ignition.

      •     A method to evaluate the consequences of an explosion arising from the
           internal overpressunzation of a sealed or inadequately vented tank due to
           external heating or internal reaction

      •     A method  to evaluate the consequences of an  explosion arising from
           ignition of a true explosive material in the solid or liquid state.

An overview of technical details for individual models and the assumptions applied during
their development are supplied in Appendix B for those who wish to review these aspects of
the models  This chapter provides generalized discussions more suitable to the average user

      Given a potential accident scenario defined during the  Hazard Identification and/or
Probability Analysis portions of the overall hazard analysis, the program user is expected to
select the appropriate sequence of calculation procedures to be utilized (generally starting
from the top of the above list and working down)  At the conclusion of the process, when the
user is satisfied that the scenario has been properly represented, the user may then ask for a
printed summary of the accident scenario evaluation results for future reference Subsequent
sections of this chapter will provide greater details on these topics

      To facilitate  conduct of  accident  scenario evaluations  and organization or results,
assessment of each new  scenario begins with the creation of what is  referred to  as an
Accident Scenario File (ASF). This is a computer data file that automatically stores both the
input data provided by the user and the results of all computations For convenience, the user
may assign any name to the fUe so long as the name is no longer than eight alphanumeric
characters. Files are automatically assigned the name extension " ASF" to differentiate them
from others on the computer  Each is intended to consider a single specific accident scenario
involving a specific hazardous material The files  are stored and retnved from the disk drive
and directory specified by the  user during the system initialization step described below
                                         12-4
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Please note that users should never rename an ASF file using DOS commands outside the
ARCHIE operating environment. Any such attempt  will result in  the file becoming
unusable until its original name is restored.

     Once an ASF file has been created,  it may be recalled, revised,  and placed back in
storage under its original name, or it may be copied to an ASF file with a new name  This
provides a great deal of flexibility to the ARCHIE program because.

     •     Users that are unsure of the validity of any particular input parameter value
           during initial evaluation of a scenario may provide an estimate, determine
           the  proper value at their convenience, recall and correct the value in the
           ASF file without having to start from scratch, and rerun the various models
           as necessary to finalize the overall evaluation

     •    Users who wish to evaluate a series of scenarios  that differ only slightly
           from one another may recall the first file created, rename  it, change the
           input values associated with scenario differences, and rerun the appropnate
           models  with the new values. This procedure automatically  creates a new
           ASF file with minimal effort while leaving the original file unchanged

     Accuracy and Limitations of Hazard Evaluation Methodologies

      Several comments are in order with  respect to the accuracy and other  features of the
 consequence modelling and  hazard assessment  procedures found  in ARCHIE These
 procedures are in many cases simplified versions of more sophisticated methods developed
 by and/or available to professionals in the field. ARCHIE is intended to provide approximate
 answers for general emergency planning purposes   It will in most cases produce results that
 overestimate rather than underestimate threats to a community, but occasional exceptions are
 both possible  and likely  Application of  safety factors by users is both encouraged and
 recommended.

      Although ARCHIE has the ability  to address a  wide variety of common accident
 scenarios in  a fairly  comprehensive manner, it  is not capable of addressing several
 potentially hazardous phenomena that may result from  accidents and which may therefore
 require  special consideration by emergency planning personnel. These  limitations  are
 common to most if not all programs of this type and include inabilities to address:

       •    Downwind public exposures to toxic combustion products from fires.

       •    Damages to people or property from impact by  high velocity fragments
           produced in explosions.
                                         12-5
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     •    Damages and  injuries  resulting from liquid  superheat  explosions  or
          significant explosions taking place inside a building or other structure

     •    Damages to property caused by exposure to thermal radiation or corrosive
          substances.

     •    Unusual threats or phenomena associated with hazardous chemical reac-
          tions

     Be sure to carefully evaluate the accident scenario you select and ensure that it applies
to the hazardous material being studied

     Use of ARCHIE for Mixtures of Hazardous Materials

     The hazard evaluation methodologies in ARCHIE are primarily designed to address
spills or discharges of relatively  pure  substances Mixtures  can only  be handled by
knowledgeable  users in certain special cases by provision  of the physical  and chemical
properties of the mixture where and when such properties are requested by the program

     Inconsistent or Inappropriate Use of Models

     A great deal of effort was devoted during development of ARCHIE to ensure that users
do  not apply hazard evaluation methodologies in  an inconsistent and/or inappropriate
fashion. Although  anyone who  attempts to use  the program in such a fashion will find a
large number of checks and balances in the system to prevent misuse, the complexity of the
processes and phenomena being considered did not permit development of a fully foolproof
program It is  therefore necessary  for users to  apply  common sense at each stage of an
analysis to ensure that the input data and information provided to the program are reasonable
For example, it is obviously inappropriate to attempt to force the program  to utilize one of
the fire or explosion models for a substance that is not inherently flammable, combustible, or
explosive. Postulation  of accident  scenarios that are beyond the realm of reasonable
credibility should be avoided to prevent unreasonable assessment results

122 INSTALLATION OF THE ARCHIE COMPUTER PROGRAM

     Detailed instructions for installation of the computer program on a variety of IBM™ PC
and fully compatible personal computer systems are presented in Appendix E to this guide
Please refer to  Appendix E and follow its instructions exactly prior to any attempt to run
the program. Although you are unlikely to harm the program diskette, it is also unlikely that
the program will operate as desired without reference to these instructions
                                        12-6
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12.3 GENERAL NOTES ON RESPONDING TO QUESTIONS FROM THE PROGRAM

     Throughout program use, the user will be required to answer numerous questions of
various types  These typically involve

     •    Input of yes or no in response to simple questions
     •    Input of letters or numbers for selection of menu options
          Input of numbers for measurable quantities

     Response to Yes or No Questions

     Whenever a question requires a simple yes or no answer, the query will generally end
with one of the following  three phrases in parentheses Note that the key that must  be
pressed after any entry to the program is variously referred to as the CARRIAGE RETURN,
RETURN, or ENTER key  Although the program uses the abbreviation "<cr>" to represent
this key on screen displays, the following text will refer to this key as the ENTER key

     •    (Y or <cr>/N) ~ means that the program will accept either a "F1 or "y"
          followed  by a press of the ENTER key, or simply a press of the ENTER
          key alone, to indicate a yes answer A "N" or "n" followed by a press of the
          ENTER key is required to indicate a no answer
                                                                        !*,„II
     •    (Y/N or <cr>) — means that the program will only accept "Y" or "y
          followed by a press of the ENTER key as meaning yes. A "N" or "n"
          followed by a press of the ENTER key, or simply a press of the ENTER
          key alone, indicates a no answer

     •    (Y/N) -- means that entry of an upper or lower case "y" or "n" followed by
          a press of the ENTER key are the only acceptable responses

     The choice of which of these options appears at the end of every question was made on
the basis of which answer is most likely to be provided by the user in any given situation
Thus, although the program asks the user numerous questions during an accident scenario
evaluation, a great many of them can be quickly answered by  simply keeping the  "little"
finger of the tight hand close to the ENTER key on the keyboard

     Selection of Menu Options

     All primary menus in ARCHIE present a list of options with each line item preceded by
a  lower case  letter.  Selection  of any  specific  option is accomplished by  typing the
appropnate letter (either lower or upper case letters are acceptable) and following the entry
with a press of the ENTER key
                                        12-7
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     Several shorter menus displayed during use of various  hazard  assessment  models
typically denote available options with a number instead of a letter. As in the pnor case,
selection of an option is accomplished by entry of the appropriate number followed by a
press of the ENTER key.

     Entry of Required Input Parameter Data

     During the course of an accident scenario evaluation, the user will be asked to  provide
a variety of numerical input data about the hazardous material involved and the  circum-
stances under which it may pose a hazard to the public. Each time that the computer program
requires a particular data item not previously provided by the program user, it will display a
custom tailored parameter input screen. These screens define and describe the data item, the
units in which the value is desired, and the range of values considered reasonable  Each
screen also provides an opportunity for the user to confirm that the proper value has been
entered, and several will ask if the user desires assistance in estimating an appropriate value
A yes  answer to one of these questions will activate one of several help sections of the
program. These ranges  from one or two screens of text that  provide guidance to major
subprograms that provide assistance in estimating the vapor pressures of hazardous materials
at various temperatures from minimal input data or which assist the user in characterizing the
tank or container in which the hazardous material resides and the  physical states, weights,
and volumes of container contents.

     Once a user provides an input value to a model at the request of the program, that value
is immediately stored in the ASF file.  If the same value is required by a subsequent hazard
assessment model, the value is shown in a list of previously stored data (applicable to the
model being used) together with a query as to whether the user wishes to change any value
before continuing. It is VITALLY important to realize that  changing  one of these values
AFTER earlier use may invalidate results of a pnor model  Consequently, if a parameter
value is changed, it may become necessary to return to and rerun any pnor models that used
this value to ensure that the entire sequence of computations is based upon a consistent set of
input data.

      Of particular interest is that ARCHIE generally requires no  more  data  about  a
hazardous material than can usually be found on a well written and complete material
safety data sheet (MSDS). Nevertheless, users with access to more detailed  knowledge of
material characteristics and properties are in several cases given the opportunity to  improve
the overall accuracy of scenario evaluation results by providing more exact input data  This
is especially true in those cases where ARCHIE suggests use of typical values for needed
data not found on a MSDS.
                                         12-8
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12.4 INITIALIZATION OF PROGRAM CONFIGURATION SETTINGS

     Once the program is properly installed, it can be started by simply typing ARCHIE
followed by a press of the ENTER key at the appropnate system prompt A few seconds will
be required while the computer reads the program into memory from its storage location.
Indeed, such waits of a several seconds in duration for the reading and writing of program
and data files from disk storage locations are common during use of the computer program
and are no cause for concern

     The first time that the program is executed, it will begin with a series of two to four
questions   The answers to these questions will tell the program  about  the video display
attached to the system and the locations  where you wish to store and retrieve  data from
Accident Scenario Files (ASF)

     The first question is straightforward and simply asks if a color computer video monitor
is attached to the system Although there are programming techniques available to determine
whether the computer contains a video adapter card capable of displaying color, no  such
method exists to determine if the card is actually attached to a color monitor  (Note  Some
of you with monochrome  monitors may wish to experiment with telling the program you
have a color monitor, simply to learn if you prefer the screen displays generated to the more
simple screens that will otherwise appear)

     The second question only appears if you answered yes to the first question and may be
a bit difficult to answer if you have limited knowledge of the computer system you are using
The question itself is "Is an EGA card installed and operating in the EGA mode?" EGA is
an  abbreviation for Enhanced Graphics Adapter, a video display board option for computers
that permits higher resolution graphics than the more typical boards found in older and/or
less expensive systems The presence of an operational EGA  requires special program
instructions to set the colors of screen borders  Do not be concerned whatsoever if you do
not know the answer to the question  Just answer no and continue  The absolute worst that
can happen is that some screens will have a black border in place of the more colorful border
that would otherwise appear Indeed, the very fact that black borders appear consistently is a
 good clue that you should change your answer at some point m the future  (Note We tell
 you below how  to  change your answers to any of these questions once the program is
 running Nothing is  cast in stone1)

      The third question (which could be the second at times) requests the letter of the disk
 drive  on  which you wish to store and retrieve Accident Scenario File  data Most of you
 should not have any  problem deciding where you wish these files to be stored  For the rest of
 you, until you can obtain assistance for  a more expenenced computer  user, here is  some
 simple advice that will keep you out of trouble
                                         12-9
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     •    If you are running the program from two floppy diskettes and there are two
          floppy drive slots in the front of the computer, place a blank or semi-blank
          but formatted diskette in the drive on the nght (if the drives are side by
          side) or lower nght (if one drive is on top of the other), close the door of the
          drive by twisting the lever, and then answer B to the question

      •    If you are running the program from two diskettes, but there is only one
          floppy drive in the system, answer C for the time being. This will result in
          storage of ASF files in the root directory of the hard drive or card installed
          in your system.

      •    If the entire program fits on one diskette and you are using a floppy, just
          answer A to the question for now

      •    If the program is installed on a fixed or hard drive within the computer, just
          press ENTER

     The last question only appears when you have installed the program on a fixed or hard
drive within the computer. If you do not understand the question, simply press ENTER to
continue and all will be well

     The program will save the answers to these questions and use them automatically next
time you use the system  As  noted above, however,  you can change your answers quite
easily. If you are within the program, choose Option E from the Mam Task Selection Menu
(see below)  to restart the initialization procedure  If you are outside the program, you can
force an automatic initialization the next time the program is used by erasing  the file named
ARCHIE.INI on your program disk

12.5 DISPLAY OF THE PROGRAM TITLE SCREEN

     The title screen for the program is  simply that  Give it a look and press ENTER to
continue. This screen will be the first to appear in systems that were initialized during prior
use of the program. Otherwise, it will follow the questions described above

12.6 INTRODUCTION TO OPTIONS ON THE MAIN TASK SELECTION MENU

     The title screen is followed by the Main Task Selection Menu leproduced in Table
12 2, this being the place where you decide which major task you wish to accomplish There
are six options available lettered "a" to "f'  These are discussed m the following, but  not
quite in the order that you might expect, primarily because your needs the first time or two
you use the program will be different than your needs at later times.
                                       12-10
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                          TABLE 12.2
                MAIN TASK SELECTION MENU
                               MAIN
                     TASK SELECTION MENU
a   Start assessment procedure for a new hazardous material accident scenario
b   Recall and modify data for previously considered accident scenario
c   Print summary of accident scenario hazard evaluation after completion
d   Proceed to system descnption menu
e   Reset system configuration settings
f   Terminate session
              ENTER LETTER OF SELECTED OPTION (a-f)
                          TABLE 12.3
        SYSTEM DESCRIPTION AND USE INSTRUCTIONS
                   TASK SELECTION MENU

          SYSTEM DESCRIPTION AND USE INSTRUCTIONS
	TASK SELECTION MENU	
 a  Program purpose and objectives
 b  Suggested sequence of model use
 c  Creation and use of accident scenario files
 d  Recall and modification of previously created accident scenario files
 e  Printout of accident scenario hazard evaluation summaries
 f  Sources of assistance
 g  Return to main menu
              ENTER LETTER OF SELECTED OPTION (a-g)
                                  12-11
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     Option D: Proceed to System Description Menu

     Selection of Option D results in the appearance of the System Description and Use
Instruction Task  Selection Menu which is reproduced in Table 12 3 and which has seven
options lettered "a" to "g" This part of the program provides bnef descriptions of various
program features and objectives as well as other general information about the program It is
included primarily for users who ignore pnnted manuals or program instructions or who may
receive the program without a pnnted copy of this guide It can also help users who may not
have used the program for a time and simply need their memory to be refreshed Selection of
any option but the last will display one or more screens of information about the program and
then return you to this menu Selection of the last option will return you to the Main Task
Selection Menu.

     Option E: Reset System Configuration Settings

     Remember the questions discussed concerning  initialization of the  program7 This
option on the Main Task Selection Menu permits you to change any of your previous
answers by restarting the initialization process

     Option F: Terminate Session

     Simply stated, selection  of this  option from the Mam Task  Selection  Menu says
"goodbye" and ends the program.

     Option A: Start Assessment for a New Hazardous Material Accident
             Scenario

     When  Option A is chosen from the Mam Task Selection Menu, the program begins the
process of creating a new Accident Scenario File (ASF). As reported earlier, this is a data
file that automatically  stores both the input data provided by the user as well as results of all
computations.  Initial file  creation steps entail answers by the user to several questions, these
involving:

     •    The name to be assigned to the ASF file (mandatory)

     •    The name of the hazardous material of concern (optional).

     •    The name, location, or address of the facility or transportation route where
          the postulated accident may occur (optional).

     •    The geographical latitude of the potential accident location (optional).

     •    The geographical longitude of the potential accident location (optional)
                                        12-12
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     •    The date on which the scenario was evaluated (optional).

     •    A one to three line textual  description of the accident scenario being
          evaluated (optional).

     •    An indication of whether or not the hazardous material of interest  is
          flammable or combustible (mandatory).

     The program will prompt the user for necessary information at each step of the ASF
file initialization process and provide opportunities to change or modify user responses to the
above quenes. When this process is complete, the program will proceed to the Hazard
Assessment Model Selection Menu described further below.

Option B:  Recall and Modify Data for Previously Considered Accident Scenario

     Once an Accident Scenario File has been created via use of Option A on the menu, it
may be recalled, copied and renamed (this is optional), modified, and eventually placed back
into storage by selection of Option B on the menu

     Prior to display  of the Hazard Assessment  Model  Selection Menu, the program
provides opportunities to:

     •    View the names of all ASF  files stored  at the location  specified during
          program initialization.

     •    Specify the name of the file that is  to be retrieved

     •    Indicate whether he or she wishes to copy the data in the named file to a
          new file with a different name, and

     •    Review and revise the file initialization data provided when Option A was
          used to create the file.

Option C:   Print Summary of Accident Scenario Hazard Evaluation After Completion

     Option C of the Main Task Selection Menu  permits the user to  obtain a  printed
summary of the overall results of the accident  scenario evaluation for any scenario previously
analyzed using ARCHIE. This printout will be two to seven pages in length depending on
which evaluation procedures were used and the number of tables that were generated.

     The printouts are formatted using standard commands of the BASIC program language
and should therefore print without problem on a wide variety of computer printers. It cannot
be guaranteed, however, that all output devices will behave as desired, particularly in the
                                        12-13
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case of laser printers. Many brands of these devices require individual special software
"drivers" that are normally only provided with specific types of commercial word processing
and graphics generation programs. In some cases,  the presence of a "print spooler" may
cause problems during printing.

     While on the topic of printed output, it is also well to note that a printout of most
individual program screens can often be obtained by pressing the PrtSc, Print Scrn, or similar
key on the keyboard. Some earlier keyboards, particularly those provided with  the first
generation of personal computers, may require simultaneous pressing of the Shift and PrtSc
keys. As in the case of scenario evaluation summaries, be advised of the possibility that this
method may not work with some laser printers.

12.7 INTRODUCTION TO THE  HAZARD ASSESSMENT MODEL  SELECTION
     MENU

     The hazard assessment models incorporated into the computer program are made
available to the user as options on the Hazard Assessment Model Selection Menu reproduced
in Table 12.4. The menu has 14 options lettered "a" to "n"

     The first major step in use of the computer program to evaluate a specific accident
scenario requires selection of  appropriate models from the model selection menu  To
facilitate this task, Figure 12 1 provides a logic diagram pertaining to the most common spill
hazards associated with  episodic discharges of hazardous materials Figure 12 2 is a related
directory of the models available in ARCHIE to evaluate these hazards As noted on  the
diagrams in this figure, letters in  parentheses within individual blocks refer to options
available on the Hazard Assessment Model Selection Menu  In all cases, it is best to start at
the  top  of one of the charts  shown in the figure and work downwards towards  the
conclusion of each threat scenario. Note that the model selection charts can be viewed from
within the computer program by selection of Option M from the subject menu

      The second step  in  most accident scenario  evaluations  in  which  fairly  detailed
information is available with regards to  the tank, pipeline, or  other container that may
discharge its contents will usually involve use of a discharge rate and duration estimation
model. Table 12 5 reproduces  the  separate menu for these models  that will appear when
 Option A is chosen from the Hazard Assessment Model Selection Menu

      The first four options (a through d) on the Discharge  Model Selection  Menu  are
intended for use when the temperature of a liquid chemical within a tank or other container is
 at or below its boiling point temperature, with the choice of any particular option depending
 on the general shape of the container  Containers are assumed to be non-pressunzed because
 the vapor pressure of their liquid contents will be at or below ambient atmospheric pressure
                                        12-14
 image: 








               TABLE 12.4
HAZARD ASSESSMENT MODEL SELECTION MENU
HAZARD ASSESSMENT MODEL SELECTION MENU
a
b
c
d
e
f
g
h
i
J
k
1
m
n

Estimate discharge rate of liquid or gas
Estimate area of liquid pool
Estimate vaporization rate of liquid pool
Evaluate toxic vapor dispersion hazards
Evaluate pool fire radiation hazards
Evaluate fireball radiation hazards
Evaluate flame jet hazards.
Evaluate vapor cloud/plume fire hazards
Evaluate vapor cloud explosion hazards
Evaluate tank overpressunzanon rupture hazard
Evaluate solid/liquid explosion hazard
Review model descnptions
Review model selection charts
Return to mam menu
ENTER LETTER OF SELECTED OPTION














(a-n)
                     12-15
 image: 








N5
                                                         HAZARDOUS MATERIAL
                                                              ACCIDENT
                                          CLOSED
                                        CONTAINER
                                                 IN
                                           FIRE
                                                                                EXPLOSIVE
                                                                                MATERIALS
                                                                                 AT RISK
                      RELEASE
                   ON LAND
                 FORMS POOL
PRESSURIZED
GAS
   TO MR
                               ABE
                           LIQtJID VSPORS
                              TOXIC?
                  SEE IIQDID CR &S
                 EEIEflSE CF OCN3EHTS
                   AS AHEBOEKBIE
                          IS Gas
                        FLSMMSBIE?
     IS
  GftS TCKIC>
EXPLOSICN
 HAZAFD
                                            ABE
                                          CONTESTS
                                         FTAMfiPIE
                                                      CONTAINER
                                                   CVEBEEESSQRIZKnCN
                                                    EXPLOSION HAZfiRD
                                  IGNmCNOF
                                    LIQUID
       DOWNWIND
      TOXIC GAS
        HAZARD
                                                                                                 DOWNWIND
                                                                                                TOXIC VAPOR
                                                                                                  HAZARD
FIREBALL OR
BLEVE HAZARD
                             VAPOR CLOUD
                             FIRE HAZARD
                              IF IGNITED
                   JET
             HAZARD IF
              IGNITED
VAPOR CLOUD FIRE
HAZARD IF IGNITED
                 D06«NWIND TOXEC
                  VRPCRCRGAS
                     HAZARD
                                                                           POOL FIRE HAZARD
                                                                             UPON IGNITION
                                                                               CF LIQUID
                                                                                  EXPLOSION HAZARD
                                                                                    IN SEWERS AND
                                                                                   CONFINED SPACES
                  VAPOR CLOUD EXPLOSION
                    HAZARD IF IGNITED
                                                                                                 VAPOR CLOUD EXPLOSICN
                                                                                                   HAZARD IF IGNITED
                                                               FIGURE 12.1
                                                          HP AfTTTV QPTT.T. HA7ARm
 image: 








                                 FIGURE 12.2
                         MODEL SELECTION CHARTS
 FIRE/EXPLOSION  MODELS
 ONLY APPLY TO FLAMMABLE
 OR COMBUSTIBLE  MATERIALS
 UPON THEIR IGNITION.
   TANK OR PIPELINE
      DISCHARGES
(A)COMPUTE DISCHARGE
   RATE AND DURATION
LETTERS IN () REFER
TO OPTIONS IN MAIN
MODEL SELECTION
MENU.
                 J_
         (B)COMPUTE  POOL AREA
           FOR  LIQUID  SPILLS
                               1
                    FOR VAPOR/GAS DISCHARGE
                    DIRECT TO ATMOSPHERE
(E)EVALUATE  POOL
   FIRE HAZARDS
                                      1
  (c)COMPUTE POOL
   EVAPORATION RATE
     (G)EVALUATE
        FLAME JET
        HAZARDS
(H)EVALUATE  VAPOR  CLOUD  FIRE HAZARD
(i)EVALUATE  VAPOR  CLOUD  EXPLOSIONS
                                                           1
               (D)EVALUATE DOWNWIND TOXIC GAS
                  OR VAPOR DISPERSION HAZARDS
                             CLOSED TANK ENGULFED
                                   IN FIRE
                  J_
         (F) EVALUATE FIREBALL
            RADIATION HAZARD
            UPON TANK RUPTURE
                             1
                    (j)  EVALUATE TANK
                      OVERPRESSURIZATION
                      EXPLOSION HAZARD
 FIRE/EXPLOSION MODELS
 ONLY APPLY TO FLAMMABLE
 OR  COMBUSTIBLE MATERIALS
 UPON THEIR IGNITION.
                               SOLID OR LIQUID
                                 EXPLOSIVES
                                      _L
                            (K) EVALUATE EXPLOSION/
                               DETONATION EFFECTS
EXPLOSION MODELS ABOVE
DO NOT CONSIDER HAZARD
OF AIRBORNE FRAGMENTS!
  *** SEE GUIDE ***
LETTERS IN () REFER
TO OPTIONS IN MAIN
MODEL SELECTION
MENU.
                                   12-17
 image: 








                          TABLE 12.5
             DISCHARGE MODEL SELECTION MENU
               DISCHARGE MODEL SELECTION MENU
NON-PRESSURIZED TANKS CONTAINING LIQUID

  a   Rectangular tank

  b   Spherical tank

  c   Vertl cylindrical tank

  d   Horzl cylindrical tank

PRESSURIZED TANKS CONTAINING GAS AND/OR LIQUID

  e   Liquid discharge from tank when hole/pipe end 4 inches or less from tank.

  f   Liquid discharge from tank when hole/pipe end more than 4 inches from tank.

  g   Gas discharge from any tank.


RELEASE FROM A LONG PIPELINE

  h   Pipeline containing liquid under pressure.

  i   Pipeline containing gas under pressure

  j   Return to main model selection
               ENTER LETTER OF SELECTED OPTION (a-j):
                              12-18
 image: 








     Options "e" and "f' pertain to tanks or other containers of compressed liquefied gases,
and are generally applicable to situations in which the temperature of the liquid is above its
normal boiling point  Option "e" should be used when the location from which the liquid is
expected to exit is four inches or less from the internal wall surface of the tank Option "f" is
more appropriate when the discharge outlet may be more than four inches from the internal
wall, as may occur when a pipe directly connected to a container breaks or ruptures some
distance from the vessel  Option "g" on the menu is intended for use when the tank or
container (excluding long pipelines) only stores a compressed gas

     Options "h" or  "i" on the menu should be used to evaluate discharges from  long
pipelines. The first applies to  lines solely  containing some type of liquid  The  second
applies to lines solely containing compressed gases

     The next nine sections of this chapter provide information on use of the nine discharge
models listed under Options A to I on the  Discharge  Model Selection Menu The tenth
option of this particular menu (this being Option J)  will return the user to the Hazard
Assessment Model Selection Menu  The nine sections pertaining to discharge models  each
have titles that begin with the prefix "12 JfX Discharge Menu Option X "

     The discharge model descriptions are followed by descriptions of the remaining model
options available from the Hazard Assessment Selection Menu Each of these sections has a
title that begins with the prefix "12 XX Hazard Model Menu Option X "  Subsequent sections
discuss and describe non-model related options available from this menu,  special subpro-
grams, and utilities available to assist the user in describing and defining input parameter
values necessary for model use. A final section of the  chapter provides information about
related computer programs that have been developed under sponsorship  of the  federal
government

     Be advised that each of the model descriptions was intentionally written to stand alone
to the maximum extent possible, thus facilitating future reference to these discussions. It is
for this reason that there is a considerable degree of redundancy within the sections that
follow

     As a final note before individual model selection options are introduced and discussed,
emergency planning personnel should realize that the most common hazardous material
likely to be encountered is automative gasoline, yet specific  properties of this material are
generally difficult to  locate in the literature.  Based upon an evaluation of the 24  most
common components  of a typical fresh unleaded gasoline blend, key properties that should
be provided to ARCHIE in the absence of more precise data, include
                                        12-19
 image: 








     •    Molecular weight = 90.9
     •    Normal boiling point =114 9°F
     •    Specific Gravity = 0.64 at 68°F
     •    Vapor pressure = 82 mm Hg at 0°F
     •    Vapor pressure = 343 mm Hg at 68°F
          Vapor pressure = 595 mm Hg at 100°F
     •    Lower flammable limit =  1 4%
     •    Heat of combustion = 18,570 Btu/lb

12.8  DISCHARGE MENU OPTION A: NON-PRESSURIZED RECTANGULAR TANK
      OF LIQUID

     Purpose of Model

     Intended for use with liquids having temperatures at or below their respective normal
boiling points, this model is used to estimate the duration and average rate of liquid discharge
from a punctured or otherwise leaking rectangular tank or container  A container should be
classified as rectangular if it resembles a box of tissues or a shoebox in general shape

     Required Input Data

     The following input parameter  values and information may be requested during use of
this model.

      •     Normal boiling point of the liquid (°F)
      •     Temperature of the liquid in the tank or container (°F)
      •     Ambient environmental temperature (°F)
      •     Weight of liquid in the container (Ibs)
      •     Indication of whether or not an instantaneous spill is to assumed
      •     Length of the rectangular tank or container (ft)
      •     Width of the rectangular tank or container (ft)
      •     Height of liquid in the container as measured from its bottom (ft)
      •     Diameter of the hole from which liquid will discharge (inches)
      •     Discharge coefficient of the hole
      •     Specific gravity of the liquid

      As discussed in Chapter 2 of this guide, many properties of hazardous matenals are a
 function of temperature, with one of the most  important being the vapor pressure  of the
 substance (since this property will ultimately have a major effect on the magnitude of toxic
 or flammable vapor dispersion threats)  Consequently, for planning purposes, it is desireable
 to select both tank and ambient environmental temperatures among the highest that may be
 experienced during a typical year. In selecting these temperatures, note that the temperature
                                        12-20
 image: 








of the contents inside a metal tank can often (not always) be 20°F or more higher than the
ambient  air temperature on a sunny  day.  Even when  not higher in  the container, the
temperature of the liquid may increase upon spillage onto a hot surface or when exposed to
the sun (particularly when the vapor pressure of the material is relatively low and evaporative
cooling does not play a major role)

     Prior to asking the user to provide the weight of liquid in the tank,  an input parameter
value that would otherwise require several manual computations, the program asks if the user
desires assistance in characterizing the volume of the container and the weights, volumes,
and physical states of its contents  Further details on the  Tank and Container Contents
Characterization  Subprogram and its  general data requirements are provided in Section
12 29 of this chapter  Use of the subprogram may result in requests for a few informational
items not listed above but is nevertheless highly recommended

     Hazard evaluations for emergency planning purposes should strive to assume the worse
credible conditions under which an accident may take place. In  the case of the  amount of
liquid m the tank or container, guidance should be obtained from the owner or operator of the
vessel with respect to the largest amounts that may be expected to be present. In the case of
transportation vehicles, it is usually sufficient to assume that the container is at least 90% full
unless other information is available.

     There may be situations envisioned in which the tank or container of interest may be
expected to fail in a very quick and catastrophic fashion; for  example,  in  the event of its
exposure to a major explosion or collapse due to severe structural failure  Consequently,
after the user  has supplied the weight of liquid in the tank, the program asks if the user
wishes to  assume that the  spill  or discharge should  be  assumed as  being essentially
instantaneous  A yes answer to this question  will halt use of the  model and result in the
assumption that the entire contents of the container will be released to the environment in one
minute and that the average rate of discharge will be the weight of tank contents per minute.
A no answer will result in normal continuation of model use.

     The program inherently assumes that the  discharge outlet is circular in shape In those
instances where the expected shape is not expected to be  circular it will be necessary to: 1)
determine  or estimate the  area of the expected outlet in units  of square inches, and 2)
compute the diameter of the equivalent circle having this area Appendix  A to  this guide
provides assistance in this task for those who require further guidance.

     The discharge coefficient of the hole is a measure of its edge  characteristics that has a
major and direct influence on the rate of discharge The input parameter screen for the data
item will provide guidance in selection of an appropnate value
                                         12-21
 image: 








     The specific gravity of the liquid should ideally be the value associated with the liquid
at its temperature in the container or tank of concern  Note, however, that this value vanes
very little with changes in temperature for the vast majority of liquids for which this model is
applicable. The specific gravity given at a temperature of 68°F (20°C) on a typical material
safety data sheet (MSDS) will be of more than acceptable accuracy in most cases

     Model Results and Usage

     Results of the model include the average rate of liquid discharge in pounds/minute, the
duration of discharge in minutes,  the total weight of contents discharged in pounds,  and the
physical state of the discharged material (which will always be liquid when this particular
discharge model is used)

      Results of the model are typically utilized by the program  as input parameters to the
pool area estimation  methods (Hazard Model Menu Option B) available from the Hazard
Assessment Model Selection Menu

      Major Assumptions of the Methodology

      The model assumes that the  hole or other discharge outlet from which  the liquid is
 being released is at  or near the bottom  of the tank for  initial  calculation  purposes, thus
 resulting in a further assumption of complete loss of liquid contents Note, however, that an
 opportunity is given at the  end of  the procedure, prior to the point in time that results are
 stored in the ASF file, to replace the computed duration  of discharge with  a  shorter time
 This is one way in which users can  adjust discharge model results to account for situations in
 which the discharge outlet being  considered is actually above the bottom portion of the tank
 or container.  An alternative approach would be  to  specify a height of liquid measured
 upward from the location of the expected discharge outlet and not from the bottom of the
 tank or container

       Another major assumption  is that there is an opening somewhere m the top portion of
 the tank or container that permits entry of air to fill the volume previously taken by liquid
 discharged to the enviroment This assumption will be valid for any container that has some
 sort of pressure equalization system to maintain  standard atmospheric pressure above the
 liquid surface while liquid is being pumped m or drawn out of the container  In cases where
 no such system exists or is  operational, it is well to recognize that the model will estimate a
 much shorter discharge time duration and much higher average discharge rate than would be
 expected in the real world  The reason for this is that the flow of liquid will be periodically
 interrupted as air enters through the discharge outlet to fill the new vapor space created above
  the liquid surface. The situation will m  many respects resemble that which occurs when a
  bottle or can  of a soft drink is turned upside down and the liquid exits in a senes  of spurts
  rather than in a continuous  and smooth flow pattern
                                          12-22
 image: 








     A final and relatively minor assumption is that the discharge outlet, be it a hole in the
side of the tank or a broken pipe attached to the container, is relatively close to the container
This assumption can lead to underprediction of discharge durations and overprediction of
discharge rates in cases when the discharge outlet is at the end of a complicated and/or
lengthy piping system attached to the container since such piping systems produce friction
that can slightly slow the flow of liquid and hence reduce the discharge rate

12.9  DISCHARGE MENU OPTION B: NON-PRESSURIZED SPHERICAL TANK OF
      LIQUID

     Purpose of Model

     Intended for use with liquids stored at temperatures at or below their respective normal
boiling points, this model is used to estimate the duration and average rate of liquid discharge
from a punctured or otherwise leaking spherical tank or container resembling a ball of some
kind in general shape.

     Required Input Data

     The following input parameter values and information may be requested during use of
this model

     •  Normal boiling point of the liquid (°F)
     •  Temperature of the liquid in the tank or container (°F)
     •  Ambient environmental temperature (°F)
     •  Weight of liquid in the tank or container (Ibs)
     •  Indication of whether or not an instantaneous spill is to assumed
     •  Diameter of the spherical tank or container (ft)
     •  Height of liquid in the container as measured from its bottom (ft)
     •  Diameter of the hole from which liquid will discharge (inches)
     •  Discharge coefficient of the hole
     •  Specific gravity of the liquid

     As discussed in Chapter 2 of this  guide, many properties of hazardous materials are a
function of temperature, with one of the most important being the vapor pressure of the
substance (since this property will ultimately have a major effect on the magnitude of toxic
or flammable vapor dispersion threats)  Consequently, for planning purposes, it is desireable
to select both tank and ambient environmental temperatures among the highest that may be
experienced during a typical year In selecting these temperatures, note that the temperature
of the  contents inside a metal tank can  often (not always) be 20°F or more higher than the
ambient  air temperature on  a  sunny day  Even  when  not higher in the container, the
                                        12-23
 image: 








temperature of the liquid may increase upon spillage onto a hot surface or when exposed to
the sun (particularly when the vapor pressure of the material is relatively low and evaporative
cooling does not play a major role).

     Prior to asking the user to provide the weight of liquid in the tank, an input parameter
value that would otherwise require several manual computations, the program asks if the user
desires assistance in characterizing the volume of the container and the weights, volumes,
and physical states of its contents.  Further details on  the  Tank and Container Contents
Characterization Subprogram and its general  data requirements are provided in  Section
12.29 of this chapter.  Use of the subprogram may result in requests for a few informational
items not listed above but is nevertheless highly recommended.

     Hazard evaluations for emergency planning purposes  should strive to assume the worse
credible conditions under which an accident may take place In the case of the amount of
liquid in the tank or container, guidance should be obtained from the owner or operator of the
vessel with respect to the largest amounts that may be expected to be present  In the case of
transportation vehicles, it is usually sufficient to assume that the container is at least 90% full
unless other information is available.

     There may be situations envisioned in which the tank or container of interest may be
expected  to fail in a  very quick and catastrophic fashion, for example, in the event of its
exposure  to a major  explosion or collapse  due to  severe structural failure  Consequently,
after the  user has supplied  the weight of liquid in the  tank, the program asks if the user
wishes  to assume that  the spill or discharge should be assumed as being essentially
instantaneous. A yes answer to this question will halt  use of the model  and result in the
assumption that the entire contents of the container will be released to the environment in one
minute and that the average rate of discharge will be the weight of tank contents per minute.
A no answer will result in normal continuation of model use

      The program inherently assumes that the discharge outlet is circular in shape  In those
instances where the expected shape is not expected to be circular it will be necessary to* 1)
determine or estimate the area of the expected outlet in units  of  square inches,  and 2)
compute  the diameter of the equivalent circle  having this area  Appendix A  to this guide
provides assistance in this task for those who may require guidance

      The discharge coefficient of the hole is a measure  of its edge characteristics that has a
major and direct influence on the rate of discharge  The input parameter screen for the data
item will provide guidance in selection of an appropriate  value.
                                         12-24
 image: 








     The specific gravity of the liquid should ideally be the value associated with the liquid
at its temperature in the container or tank of concern  Note, however, that this value vanes
very little with changes in temperature for the vast majority of liquids for which this model is
applicable  The specific gravity given at a temperature of 68°F (20°C) on a typical material
safety data sheet (MSDS) will be of more than acceptable accuracy in most cases

     Model Results and Usage

     Results of the model include the average rate of liquid discharge in pounds/minute, the
duration of discharge in minutes, the total weight of contents discharged in pounds, and the
physical state of the discharged material (which will always be  liquid when this particular
discharge model is used).

     Results of the model are typically utilized by the program as input parameters to the
pool area estimation methods (Hazard  Model Menu Option B)  available  from the Hazard
Assessment Model Selection Menu.

     Major Assumptions of the Methodology

     The model assumes  that the hole or other discharge outlet from which the liquid is
being released is at or near the bottom of the tank for initial calculation purposes, thus
resulting in a further assumption of complete loss of liquid contents Note, however, that an
opportunity is given at the end of the procedure, prior to the point in time that results are
stored in the ASF file, to replace the computed duration of discharge with a shorter time
This is one way in which users can adjust discharge model results to account for situations in
which the discharge outlet being considered is actually above the bottom portion of the tank
or container  An alternative approach would be to specify  a  height of liquid measured
upward from the location of the expected discharge outlet and not from the bottom of the
tank or container

      Another major assumption is that there is an opening somewhere in the top portion of
the tank or container that  permits entry of air to fill the volume previously taken by liquid
discharged to the enviroment.  This assumption will be valid for any container that has some
sort of pressure equalization system to maintain  standard atmospheric pressure above the
liquid surface while liquid is being pumped in or drawn out of the container. In cases where
no such system exists or is operational, it is well to recognize that the model will estimate  a
much shorter discharge time duration and much higher average discharge rate than would be
expected in the real world The reason for this is that the flow of liquid will be periodically
interrupted as air enters through the discharge outlet to fill the new vapor space created above
the liquid surface The situation will in many respects resemble that which occurs when  a
bottle or can of a soft drink is turned upside down and the liquid exits m a senes of spurts
rather than in a continuous and smooth flow pattern
                                        12-25
 image: 








     A final and relatively minor assumption is that the discharge outlet, be it a hole in the
side of the tank or a broken pipe attached to the container, is relatively close to the container.
This assumption can lead to underproduction of discharge durations and overprediction of
discharge rates in  cases when the discharge outlet  is at  the end of a complicated and/or
lengthy piping system attached to the container since such piping systems produce friction
that can slightly slow the flow of liquid and hence reduce the discharge rate

12.10 DISCHARGE MENU OPTION C: NON-PRESSURIZED VERTICAL CYLINDER
      OF LIQUID

     Purpose of Model

     Intended for use with liquids stored at temperatures at or below their respective normal
boiling pouits, this model is used to estimate the duration and average rate of liquid discharge
from a punctured  or otherwise leaking vertical cylindrical tank or container  A tank or
container that would be classified as a vertical cylinder would resemble (in general shape) a
can of tuna fish or a can of soft drink sitting  upright on  a  table Such tanks are the most
typical containers  seen at facilities that  store gasoline and/or fuel oils  in above ground
vessels.

     Required Input Data

     The following input parameter values and information  may be requested during use of
this model.

     •     Normal boiling point of the liquid (°F)
     •     Temperature of the liquid in the tank or container (°F)
     •     Ambient environmental temperature (°F)
     •     Weight of liquid  in the tank or container (Ibs)
     •     Indication of whether or not an instantaneous spill is to assumed
     •     Diameter of the vertical cylindrical tank or container (ft)
     •     Height of liquid in the container as measured from its bottom (ft)
     •     Diameter of the hole from which liquid will discharge (inches)
     •     Discharge coefficient of the hole
     •     Specific gravity of the liquid

     As discussed in Chapter 2 of this guide,  many properties of hazardous materials are a
function of temperature, with one of the most important being the vapor pressure of the
substance (since this property will ultimately have a major effect on the magnitude of toxic
or flammable vapor dispersion threats) Consequently, for planning purposes, it is desireable
to select both tank and ambient environmental temperatures among the highest that may be
experienced during a typical year  In  selecting these temperatures, note that the temperature
                                        12-26
 image: 








of the contents inside a metal tank can often (not always) be 20°F or more higher than the
ambient  air temperature on a sunny  day  Even when  not higher in the container, the
temperature of the liquid may increase upon spillage onto a hot surface or when exposed to
the sun (particularly when the vapor pressure of the material is relatively low and evaporative
cooling does not play a major role)

     Prior to asking the user to provide the weight of liquid in the tank, an input parameter
value that would otherwise require several manual computations, the program asks if the user
desires assistance in characterizing the volume of the container and the weights, volumes,
and physical states of  its contents  Further details on the  Tank  and Container Contents
Characterization Subprogram  and its general data requirements  are provided in Section
12 29 of this chapter  Use of the subprogram may result in requests for a few informational
items not listed above but is nevertheless highly recommended

      Hazard evaluations for emergency planning purposes should strive to assume the worse
credible  conditions under which  an accident may take place In the case of the amount of
liquid in the tank or container, guidance should be obtained from the owner or operator of the
vessel with respect to the largest amounts that may be expected to be present  In the case of
transportation vehicles,  it is usually sufficient to assume that the container is at least 90% full
unless other information is available.

      There may be situations envisioned m which the tank  or container of interest may be
expected to fail in a very quick and catastrophic fashion; for example, in the event of its
exposure to a major explosion or collapse due to severe structural failure Consequently,
after the user has supplied  the weight of  liquid m the tank, the program asks if the user
wishes  to  assume that the spill or discharge should  be  assumed as being  essentially
instantaneous  A yes answer to this question will halt use  of the model and result in the
assumption that the entire contents of the container will be released to the environment m one
minute and that the average rate of discharge will be the weight of tank contents per minute
A no answer will result m normal continuation of model use

      The program inherently assumes that the discharge  outlet is circular in shape In those
instances where the expected shape is not expected to be circular it will be necessary to  1)
determine or estimate  the area  of the expected outlet  in units of square inches, and  2)
compute the diameter of the equivalent circle having this area. Appendix A to  this guide
provides assistance in this task  for those who may require guidance

      The discharge coefficient of the hole is a measure of its edge characteristics that has a
 major and direct influence on the rate of discharge  The input parameter screen for the data
 item will provide guidance in selection of an appropriate value
                                         12-27
 image: 








     The specific gravity of the liquid should ideally be the value associated with the liquid
at its temperature in the container or tank of concern. Note, however, that this value vanes
very little with changes in temperature for the vast majority of liquids for which this model is
applicable. The specific gravity given at a temperature of 68°F (20°C) on a typical material
safety data sheet (MSDS) will be of more than acceptable accuracy in most cases

     Model Results and Usage

     Results of the model include the average rate of liquid discharge in pounds/minute, the
duration of discharge in minutes, the total weight of contents discharged in pounds, and the
physical state of the discharged material (which will always be liquid when this particular
discharge model is used).

     Results of the model are typically utilized by the program as input parameters to the
pool area estimation methods (Hazard Model Menu Option B) available from the  Hazard
Assessment Model Selection Menu

     Major Assumptions of the Methodology

     The model assumes that the hole or other discharge outlet from which the liquid is
being released is at or near the bottom of the tank for initial calculation purposes, thus
resulting in a further assumption of complete loss of liquid contents  Note, however, that an
opportunity is given at the end of the procedure, prior to the point in time that results are
stored in the ASF file, to replace the computed duration of discharge with a shorter time
This is one way in which users can adjust discharge model results to account for situations in
which the discharge outlet being considered is actually above the bottom portion of the tank
or container. An alternative approach would be to  specify  a  height of liquid measured
upward from the location of the expected discharge outlet and not from the bottom of the
tank or container.

     Another major assumption is that there is  an opening somewhere in the top portion of
the tank or container that permits entry of an- to fill the volume previously taken by liquid
discharged to the environment This assumption will be valid for any container that has some
sort of pressure equalization system to maintain standard atmospheric pressure above the
liquid surface while liquid is being pumped in or drawn out of the container  In cases where
no such system exists or is operational, it is well to recognize that the model will estimate a
much shorter discharge time duration and much higher average discharge rate than would be
expected in the real world  The reason for this is that the flow of liquid will be periodically
interrupted as air enters through the discharge outlet to fill the new vapor space created above
the liquid surface   The situation will in many respects resemble that which occurs  when a
bottle or can of a soft drink is turned upside down and the liquid exits in a senes of spurts
rather than in a continuous and smooth flow pattern
                                         12-28
 image: 








     A final and relatively minor assumption is that the discharge outlet, be it a hole in the
side of the tank or a broken pipe attached to the container, is relatively close to the container.
This assumption can lead to underprediction of discharge durations and overproduction of
discharge rates in  cases when the discharge outlet is  at the end of a complicated and/or
lengthy piping system attached to the container since such piping systems produce friction
that can slightly slow the flow of liquid and hence reduce the discharge rate

12.11    DISCHARGE  MENU OPTION  D:  NON-PRESSURIZED  HORIZONTAL
         CYLINDER OF LIQUID

     Purpose of Model

     Intended for use with liquids stored at temperatures at or below then: respective normal
boiling points, this model is used to estimate the duration and  average rate of liquid discharge
from a punctured or otherwise leaking horizontal cylindrical tank or container. A container
classified as being a horizontal cylinder would resemble the tank seen on the back of a
typical gasoline truck in general shape.

     Required Input Data

     The following input parameter values and information may be requested during use of
this model.

      •    Normal boiling point of the liquid (°F)
      •    Temperature of the liquid in the tank or container  (°F)
      •    Ambient environmental temperature (°F)
      •    Weight of liquid in the tank or container (Ibs)
      •    Indication of whether or not an instantaneous spill is to assumed
      •    Diameter of the horizontal cylindrical tank or container (ft)
      •    Length of the horizontal cylindrical tank or container (ft)
      •    Height of liquid in the container measured from its bottom (ft)
      •    Diameter of the hole from which liquid will  discharge (inches)
      •    Discharge coefficient of the hole
      •    Specific gravity of the liquid

      As discussed in Chapter 2 of this guide, many properties of hazardous materials are a
function of temperature, with one of the most important being the vapor pressure of the
 substance (since this property will ultimately have a major effect on the magnitude of toxic
 or flammable vapor dispersion threats). Consequently,  for planning purposes, it is desireable
 to select both tank and ambient environmental temperatures among the highest that may be
 expenenced during a typical year. In selecting these temperatures, note that the temperature
 of the contents inside a metal tank can often (not always) be 20°F or more higher than the
                                        12-29
 image: 








ambient  air temperature on a sunny  day  Even when  not higher in  the container, the
temperature of the liquid may increase upon spillage onto a hot surface or when exposed to
the sun (particularly when the vapor pressure of the material is relatively low and evaporative
cooling does not play a major role)

     Prior to asking the user to provide the weight of liquid in the tank,  an input parameter
value that would otherwise require several manual computations, the program asks if the user
desires assistance in characterizing the volume of the container and the weights, volumes,
and physical states of its contents  Further details on the  Tank and Container Contents
Characterization  Subprogram and its general data requirements are provided in Section
12.29 of this chapter  Use of the subprogram may result in requests  for a few informational
items not listed above but is nevertheless highly recommended

     Hazard evaluations for emergency planning purposes should strive to assume the worse
credible  conditions under which an accident may take place In the case of the amount of
liquid in the tank or container, guidance should be obtained from the owner or operator of the
vessel  with respect to the largest amounts that may be expected to be present  In the case of
transportation vehicles, it is usually sufficient to assume that the container is at least 90% full
unless other information is available

     There may be  situations envisioned in which the tank  or container of interest may be
expected to fail in a very quick and catastrophic fashion, for example, in the event of its
exposure to a major explosion or collapse due to severe structural failure Consequently,
after the user has supplied  the weight of liquid in the tank, the program  asks if the user
wishes to  assume that the spill or  discharge should  be  assumed as being  essentially
instantaneous.  A yes answer to this question  will halt use  of the model and result in the
assumption that the entire contents of the container will be released to the environment in one
minute and that the average rate of discharge will be the weight of tank contents per minute
A no answer will result in normal continuation  of model use

     It  should be  recognized that  not  all   horizontal cylindrical tanks  have circular
cross-sections or flat ends as inherently assumed by the model  Where the tank cross-section
is more of an oval, set the requested diameter equal to either the widest part of the tank (or to
the average of the narrowest and widest sections if somewhat greater accuracy is desired)  It
is always safe to set the length of the tank to its longest dimension regardless whether its
ends are hemispherical, dished, or flat  The errors introduced will be  relatively minor.

     The program inherently assumes that the discharge outlet is circular in shape  In  those
instances where the expected shape is not expected to be circular it  will be necessary to 1)
                                         12-30
 image: 








determine or estimate  the area of the expected outlet in units  of square inches; and 2)
compute the diameter of the equivalent circle having this area  Appendix A to this guide
provides assistance in this task for those who may require guidance

     The discharge coefficient of the hole is a measure of its edge characteristics that has a
major and direct influence on the rate of discharge  The input parameter screen for the data
item will provide guidance in selection of an appropriate value

     The specific gravity of the liquid should ideally be the value associated with the liquid
at its temperature in the container or tank of concern Note, however, that this value vanes
very little with changes in temperature for the vast majority of liquids for which this model is
applicable The specific gravity given at a temperature of 68°F (20°C) on a typical material
safety data sheet (MSDS) will be of more than acceptable accuracy in most cases

     Model Results and Usage

     Results of the model include the average rate of liquid discharge in pounds/minute, the
duration of discharge in minutes, the total weight of contents discharged in pounds, and the
physical state of the discharged material (which will always be liquid when this particular
discharge model is used)

     Results of the model are typically utilized by the program  as input parameters to the
pool area estimation methods  (Hazard Model Menu Option B) available from the Hazard
Assessment Model Selection Menu

     Major Assumptions of the Methodology

      The model assumes that the hole or other discharge outlet from which  the liquid is
being  released is at or near the bottom of the tank for initial  calculation purposes, thus
resulting in a further assumption of complete loss of liquid contents Note, however, that an
opportunity is  given at the end of the procedure, pnor to the point in time that results are
stored in the ASF file, to replace the computed duration of discharge with a shorter time
This is one way in which users can adjust discharge model results to account for situations in
which the discharge outlet being considered is actually  above the bottom portion of the tank
or container. An alternative approach would be to specify a height of liquid measured
 upward from the location of the expected discharge outlet and not from the bottom of the
 tank or container.

      Another major assumption is  that there is an opening somewhere in the top portion of
 the tank or container that permits entry of air to fill the  volume previously taken by liquid
 discharged to the enviroment.  This assumption will be valid for any container that has some
 sort of pressure equalization system to maintain standard atmospheric pressure above the
                                        12-31
 image: 








liquid surface while liquid is being pumped in or drawn out of the container In cases where
no such system exists or is operational, it is well to recognize that the model will estimate a
much shorter discharge time duration and much higher average discharge rate than would be
expected in the real world. The reason for this is that the flow of liquid will be periodically
interrupted as air enters through the discharge outlet to fill the new vapor space created above
the liquid surface.  The situation will in many respects resemble  that which occurs when a
bottle or can of a soft dnnk is turned upside down and the liquid exits in a senes of spurts
rather than in a continuous and smooth flow pattern.

     A final and relatively minor assumption is that the  discharge outlet, be it a hole in the
side of the tank or a broken pipe attached to the container, is relatively close to the container
This assumption can lead to underprediction of discharge durations and overprediction of
discharge rates in  cases when the discharge outlet is at the end of a complicated and/or
lengthy piping system attached to  the container since such piping systems produce faction
that can slightly slow the flow of liquid and hence reduce  the discharge rate

12.12  DISCHARGE  MENU OPTION  E:  PRESSURIZED LIQUID  WHEN DIS-
        CHARGE LOCATION IS 4 INCHES OR LESS FROM THE TANK SURFACE

     Purpose of Model

     Intended for use with liquids stored at temperatures above their  respective normal
boiling points, this model estimates \h&peak rate of discharge and  duration of discharge from
a punctured or otherwise leaking tank or container of what must be considered a compressed
liquefied gas under the specified conditions of storage. A special qualification  is that the
model is only appropriate for use when the discharge outlet or hole is four inches or less from
the inner wall surface of the tank or container  The discharge model described under Option
F below should be used if the discharge location is more than four  inches distant

     Required Input Data

      Primary data requirements for use of the model include:

      •     Normal boiling point of the liquid (°F)
      •     Temperature of the liquid in the tank or container (°F)
      •     Ambient environmental temperature (°F)
      •     Weight of liquid in the tank or container (Ibs)
      •     Indication of whether or not an instantaneous  spill is to assumed
      •     Diameter of the horizontal cylindrical tank or container (ft)
      •     Length of the horizontal cylindrical tank or container (ft)
      •     Height of liquid in the container measured from its bottom (ft)
                                        12-32
 image: 








          Diameter of the hole from which liquid will discharge (inches)
     •    Discharge coefficient of the hole
     •    Specific gravity of the liquid

     As discussed in Chapter 2 of this guide, many properties of hazardous materials are a
function of temperature, with  one of the most important being the vapor pressure of the
substance (since this property will ultimately have a major effect on the magnitude of toxic
or flammable vapor dispersion threats). Consequently, for planning purposes, it is desireable
to select both tank and ambient environmental temperatures among the highest that may be
experienced during a typical year In selecting these temperatures, note that the temperature
of the contents inside a metal tank can often (not always) be 20°F or more higher than the
ambient air temperature on a sunny day

      Prior to asking the user to provide the weight of liquid in the tank, an input parameter
value that would otherwise require several manual computations, the program asks if the user
desires  assistance in characterizing the volume of the container and the weights, volumes,
and physical states of  its contents  Further details on the  Tank and Container Contents
Characterization Subprogram  and  its general data requirements are provided m Section
12 29 of this chapter. Use of the subprogram may result in requests for a few informational
items not listed above but is nevertheless highly recommended.

      Hazard evaluations for emergency planning purposes should strive to assume the worse
credible conditions under which an  accident may take place  In the case of the amount of
liquid in the tank or container, guidance should be obtained from the owner or operator of the
vessel with respect to the largest amounts that may be expected to be present  In the case of
transportation vehicles, it is usually sufficient to assume that the container is at least 90% full
unless other information is available

      The user may request assistance in determining the vapor pressure of the liquid at the
point in time that the program asks for this parameter value  See Section 12 28 below for a
description of the Vapor Pressure Input Assistance Subprogram

      There may be situations  envisioned in which the tank or container of interest may be
 expected to fail in a very quick and catastrophic fashion, for example, m the event of its
 exposure to a major explosion or collapse due to severe structural failure  Consequently,
 after the user has  supplied the weight of liquid in the tank, the program asks if the user
 wishes  to  assume that  the spill  or discharge  should be  assumed as being  essentially
 instantaneous   A yes  answer to  this question will halt use of the  model and result m the
 assumption that the entire contents of the container will be released to the environment in one
 minute and that the average rate of discharge will be the weight of tank contents per minute
 A no answer will result in normal continuation of model use
                                         12-33
 image: 








     The program inherently assumes that the discharge outlet is circular in shape In those
instances where the expected shape is not expected to be circular it will be necessary to* 1)
determine or estimate the  area of the expected outlet in units of square inches;  and 2)
compute the diameter of the equivalent circle having this area  Appendix A to this guide
provides assistance in this task for those who may require guidance

     The discharge coefficient of the hole is a measure of its edge characteristics that has a
major and direct influence on the rate of discharge. The input parameter screen for the data
item will provide guidance in selection of an appropnate value

     The specific  gravity of the liquid should ideally be the value associated with the liquid
at its temperature in the container or tank of concern Note, however, that this value vanes
little with changes in temperature for many liquids for which this model is applicable The
specific gravity given at a temperature of 68°F (20°C) on a typical material safety data sheet
will be of acceptable accuracy in most cases.

     Model Results and Usage

     Results of the  model include the peak rate of liquid discharge in pounds/minute, the
duration of discharge in  minutes  based on the  peak rate, the total weight  of contents
discharged in pounds, and an indication of the expected physical state of the discharged
material Depending upon  the material, environmental, and normal boiling point tempera-
tures involved, the model  may indicate that either an airborne mixture of gas and liquid
droplets (i.e, aerosols) or liquid is being discharged

     In the case of liquid discharges from the container,  results of the model are normally
utilized by the program as input parameters to the pool  area estimation  methods (Hazard
Model Menu Option B) available from the Hazard Assessment Model Selection Menu. In
the case of airborne gas and aerosol mixture discharges from the container, the results  may be
utilized as necessary for input to the toxic vapor dispersion model (Hazard Model Menu
Option D) and/or the vapor cloud or plume fire hazard model (Hazard Model Menu Option
H)  on the menu In addition, the duration of gaseous discharge may be utilized by the flame
jet model (Hazard Model Menu Option F)

     Major Assumptions of the Methodology

     The model assumes that the hole or other discharge outlet from which the liquid is
being released in  at or near the bottom of the tank for initial calculation purposes, thus
resulting in a further assumption of complete loss of liquid contents Note, however, that an
opportunity is given to the user at the  end of the procedure, prior to  the point in time that
results  are stored  in the ASF file, to  replace the computed duration of discharge with a
shorter  time. This is one way in which users can adjust discharge model results to account
                                       12-34
 image: 








for situations in which the discharge outlet being considered is actually above the bottom
portion of the tank or container. An alternative approach would be to specify a height of
liquid measured upward from the location of the expected discharge outlet and not from the
bottom of the  tank or container. It is necessary to stress,  however, that either of these
modifications to normal program use will result in a situation in which any gas exiting the
discharge outlet after completion of liquid discharge will not be accounted for in model
results  This discharge of gas, which will quickly drop from a high to low rate when the tank
or  container is not being  heated  or somehow  internally  generating  heat, will  pose a
downwind toxic or flammable gas hazard for a period of time that may be greater than that
estimated for the liquid discharge. If the remaining liquid in the tank or container is indeed
being heated, the flow of gas could be of considerable rate and duration yet incapable of
being estimated via use of ARCHIE It is for this reason that the model inherently assumes
that the entire tank will empty quickly and at a high rate to provide a conservative basis for
emergency planning purposes

      A second assumption is that vaporization of liquid m the tank or container to generate
vapor or gas to fill the void left by escaping liquid will not result in a major thermodynamic
cooling  effect. A  significant cooling effect  would tend to lower  the estimated rate  of
discharge and  increase its duration, but this phenomena usually plays only a minor role in
influencing discharge rate and duration  estimates The rate is  primarily controlled by the
height of the liquid in the tank above the discharge outlet location and the specific gravity of
the substance

      The decision as to whether  the discharged material  will be  a mixture of  gas and
 aerosols or a liquid depends upon the temperature of the hazardous material in its container
 and the normal boiling point of the substance. An airborne mixture of gas and  aerosols is
 assumed whenever the container content temperature exceeds the normal boiling point by
 10 8°F (6°C) as a general rule of thumb The assumption is conservative in that it may at
 times indicate that no liquid will reach the ground although this may indeed occur to some
 degree  More  precise assessment of the physical characteristics of  the discharged material
 requires  knowledge of physical property data not expected to be readily  available to the
 average user of Version  1.0 of ARCHIE and must therefore await installation of a database in
 this program.
                                         12-35
 image: 








12.13    DISCHARGE  MENU OPTION F: PRESSURIZED LIQUID  WHEN  DIS-
         CHARGE LOCATION IS MORE THAN 4  INCHES FROM THE TANK
         SURFACE

     Purpose of Model

     Intended for use with liquids stored at temperatures above their respective normal
boiling points, this model estimates the peak rate of discharge and duration of discharge at
this rate from a punctured or otherwise leaking tank or container of a compressed liquefied
gas.  A special qualification is that the model is only appropriate for use when the discharge
outlet or hole is more than four inches from the intarnal wall surface of the tank or container
The discharge model described under Option E should be used if the discharge location is
four inches or less distant from the wall

     Required Input Data

     Primary data requirements for use of the model include

     •     Normal boiling point of the liquid (°F)
     •     Temperature of the liquid in the tank or container (°F)
     •     Ambient environmental temperature (°F)
     •     Weight of liquid in the tank or container (Ibs)
     •     Indication of whether or not an instantaneous spill is to assumed
     •     Diameter of the horizontal cylindrical tank or container (ft)
     •     Length of the horizontal cylindrical tank or container (ft)
     •     Height of liquid in the container measured from its bottom (ft)
     •     Diameter of the hole from which liquid will discharge (inches)
     •     Discharge coefficient of the hole
     •     Specific gravity of the liquid

     As discussed in Chapter 2 of this guide,  many properties of hazardous materials are a
function  of temperature,  with one of the most important being the vapor pressure of the
substance (since this property will ultimately have a major effect on the magnitude of toxic
or flammable vapor dispersion threats). Consequently, for planning purposes,  it is desireable
to select  both tank and ambient environmental temperatures among the  highest that may be
experienced during a typical year. In selecting these temperatures, note  that the temperature
of the contents  inside a metal tank can often (not always) be  20°F or more higher than the
ambient air temperature on a sunny day.

     The user may request assistance in determining the vapor pressure of the liquid at the
point in time that the program asks for this parameter value  See Section 12 28 below for a
description of the Vapor Pressure Input Assistance Subprogram
                                       12-36
 image: 








     Prior to asking the user to provide the weight of hquid in the tank, an input parameter
value that would otherwise require several manual computations, the program asks if the user
desires assistance in characterizing  the volume of the container and the weights, volumes,
and physical states of its contents. Further details on the Tank and Container Contents
Characterization Subprogram and  its general data requirements are provided in Section
12 29 of this chapter. Use of the subprogram may result in requests for a few informational
items not listed above but is nevertheless highly recommended

     Hazard evaluations for emergency planning purposes should strive to assume the worse
credible  conditions under which an accident may take place In the case of the amount of
liquid in the tank or container, guidance should be obtained from the owner or operator of the
vessel with respect to the largest amounts that may be expected to be present. In the case of
transportation vehicles, it is usually sufficient to assume that the container is at least 90% full
unless other information is available

     There may be situations envisioned in which the tank or container of interest may be
expected to fail in a very quick and catastrophic fashion; for example, in the event  of its
exposure to a major explosion or collapse due to severe  structural failure. Consequently,
after the user has supplied  the weight of liquid in the tank, the program asks if the user
wishes  to assume that the spill or discharge should  be assumed as being essentially
instantaneous.  A yes answer to this question  will halt use of the model  and result in the
assumption that the entire contents of the container will be released to the environment in one
minute and that the average rate of discharge will be the weight of tank contents per minute.
A no answer will result in normal continuation of model use

      The program inherently assumes that the discharge outlet is circular in shape. In those
instances where the expected shape is not expected to be circular it will be necessary to. 1)
determine or estimate  the  area of the expected outlet  in units of square inches, and  2)
compute the diameter of the equivalent circle having this area. Appendix A to this guide
provides assistance in this task for those who may require guidance.

      The discharge coefficient of the hole is a measure of its edge characteristics that has a
major and direct influence on the rate of discharge. The input parameter screen for the data
item will provide guidance in selection of an appropriate value.

      The specific gravity of the liquid should ideally be the value associated with the liquid
at its temperature in  the container or tank of concern  Note, however, that this value vanes
very little with changes in temperature for many liquids for which this model is applicable.
The specific gravity  given at a temperature of 68°F (20°C) on a typical material safety data
 sheet will be of acceptable accuracy in most cases.
                                          12-37
 image: 








     The specific heat capacity of the hquid is a measure of the heat necessary to raise the
temperature of a unit weight of the material by one degree  Prior to request of this value, the
program will provide the user an opportunity to request  assistance in selection of an
appropriate heat capacity value using several  generalized rules-of-thumb  (reproduced in
Table 12.6) that require user knowledge of the chemical formula of the hazardous material
being evaluated.  Although the accuracy of model answers  would be unproved by provision
of a more precise value for the substance at or near the temperature in its container, errors
introduced by use of an estimation method presented by the program should not be highly
significant in most (but not all) cases Note that liquid heat capacity values provided in units
of calories/gram-°C in various data bases and technical handbooks are numerically equiv-
alent to values expressed in units of Btu/lb-0F

     Model Results and Usage

     Results of the model include the peak rate of liquid discharge in pounds/minute, the
duration of discharge in minutes, the total weight of contents discharged in  pounds, and an
indication of the expected physical state of the discharged material Depending upon the
material, environmental, and normal boiling  point temperatures  involved,  the model  may
indicate that either an airborne mixture of gas and liquid droplets (i e, aerosols) or a liquid is
being discharged.

     In the case of liquid discharges from the container, results of the model are normally
utilized by the program as input parameters  to the pool area  estimation methods  (Hazard
Model Menu Option B) available from the Hazard Assessment Model Selection Menu In
the case of airborne gas and aerosol discharges from the container, the results may be utilized
as necessary for input to the toxic vapor  dispersion model (Hazard Model Menu Option D)
and/or the vapor cloud or plume fire hazard model (Hazard Model Menu Option H) on the
menu. In addition, the duration of gaseous discharge may be utilized by the  flame jet model
(Hazard Model Menu Option F).

      Major Assumptions of the Methodology

      The model assumes that the hole or other discharge outlet from which the liquid is
being released is at or near the bottom of the tank  for  initial  calculation purposes, thus
resulting in a further assumption of complete  loss of liquid contents  Note, however, that an
opportunity is given at the end of the procedure, pnor to the  point m time that results are
stored in the ASF file, to replace the computed duration  of discharge with a shorter  time
This is one way in which users can adjust discharge model  results to account for situations in
which the discharge outlet being considered is actually above the bottom portion of the tank
or container. An alternative  approach would be  to  specify  a height of liquid measured
upward from the location of the expected discharge outlet and not from the bottom of the
                                         12-38
 image: 








                          TABLE 12.6
      ASSISTANCE DISPLAY FOR LIQUID SPECIFIC HEAT
         LIQUID SPECIFIC HEAT SELECTION ASSISTANCE
  For organic materials predominantly consisting of carbon (C), hydrogen (H),
  oxygen (O), nitrogen (N), and/or sulfur (S), values range from 0.30 to 0.80  A
  value of 0.30 will usually give a conservative result and is suggested for use in the
  absence of better data.
   For materials containing chlonne (Cl), fluorine (F), or silicon (Si), values typically
   range from 0 20 to 0.40  A value of 0 20 will usually give a conservative result
   and is suggested for use in the absence of better data.
   For materials containing bromine (Br) or iodine (I), or organic  compounds
   containing one or more metals such as  nickel (Ni), iron (Fe), magnesium (Mg),
   cadmium (Cd), tin  (Sn), zinc  (Zn), vanadium (Vd), or titanium (Ti), values
   typically range from 0 10 to 0 20. A value of 0.10 will usually give an acceptable
   result and is suggested for use in the absence of better data
                           TABLE 12.7
ASSISTANCE DISPLAY FOR VAPOR/GAS SPECD7IC HEAT RATIO
    SPECIFIC HEAT RATIO SELECTION ASSISTANCE FOR GASES
   Monatomic gases are substances such as argon, neon, xenon, krypton, or helium
   Such gases have only one atom in each molecule when in the gaseous state. An
   approximate specific heat ratio of 1.67 may be used for such gases when more
   precise values are not readily available.
   Diatomic gases are substances with two atoms in each molecule when in the
   gaseous state. Examples include  oxygen (0^, nitrogen (N^, hydrogen  (Hj),
   chlonne (Cy, and carbon monoxide (CO). An approximate specific heat ratio of
   1.40 may be used when more precise values are not readily available for such
   gases.
   Polyatomic gases have more than two atoms in each molecule when in the gaseous
   state Examples include ammonia (NlrQ, propane (CjjHg), and methyl bromide
   (CHjBr)  An approximate specific heat ratio of 1 30 may be used for such gases if
   more precise values are not readily available
                                 12-39
 image: 








tank or container. It is necessary to stress, however, that either of these modifications to
normal program use will result in a situation in which any gas exiting the discharge outlet
after completion of liquid discharge  will not be  accounted for  in  model results  This
discharge of gas, which will quickly drop from a high to low rate when the tank or container
is not being heated or somehow internally generating heat, will pose a downwind toxic or
flammable gas hazard for a period of time that may be greater than that estimated for the
liquid discharge. If the remaining liquid in the tank  or container is indeed being heated, the
flow of gas could be of considerable rate and duration yet incapable of being estimated via
this first version of ARCHIE  It is for this reason that the model inherently assumes that the
entire  tank will empty quickly and at a high  rate to provide a conservative basis for
emergency planning purposes.

     A second assumption is that vaporization of liquid in the tank or container to  generate
vapor or gas to fill the void left by escaping liquid will not result in a major thermodynamic
cooling effect  A  significant cooling  effect would tend to lower the  estimated rate of
discharge and increase its duration, but this phenomena usually plays only a minor role in
influencing discharge rate and duration estimates  The  rate is primarily controlled by the
height of the liquid in the tank above the discharge outlet location and the specific gravity of
the substance.

     The decision  as  to whether  the  discharged material will be a  mixture  of  gas and
aerosols or a liquid depends upon the temperature of the hazardous material in its container
and the normal boiling point of the substance. An  airborne  mixture of gas and aerosols is
assumed whenever the container content temperature exceeds the normal boiling  point by
10.8°F (6°C) as a general rule of thumb. The assumption is conservative in that it may at
times indicate that no liquid will reach the ground although this may indeed occur to  some
degree. More precise assessment of the physical characteristics of the discharged material
requires knowledge of physical property data not expected to be readily available to the
average user of Version 10 of ARCHIE and must therefore await installation of a database in
this program.

12.14   DISCHARGE MENU OPTION G: PRESSURIZED GAS RELEASE FROM ANY
        CONTAINER

     Purpose of Model

      The  primary purpose  of this model is to estimate the peak rate of  discharge and
duration of discharge at this rate when a compressed gas is being released to the atmosphere
from a tank or other container that is not a long distance pipeline
                                         12-40
 image: 








     The model  may  be used in a very approximate fashion to evaluate  gas or vapor
discharge rates and durations when a runaway exothermic chemical reaction of some kind
takes place in the container Use of the model for the latter purpose requires that the user
provide the program with suitably high values for the pressure and temperature in the tank
(accuracy in providing these values is not extremely important) and an appropriate molecular
weight and  ratio  of specific heats for the gas actually being discharged If the reaction
involves polymerization of one  or more substances, some  thought  should be given to
reducing the weight of hazardous matenal(s) presumed to be in the tank by at least 10 to 33%
since the portion that polymerizes during the reaction is unlikely to be discharged to the
atmosphere as a gas or vapor.

     Required Input Data

     Primary data requirements for use of the model include

      •     Normal boiling point of the liquid (°F)
      •     Temperature of the gas and/or liquid in the container (°F)
      •     Ambient environmental temperature (°F)
      •     Pressure of the gas in the container (psia)
      •     Weight of hazardous material in the container (Ibs)
      •     Indication of whether or not an instantaneous spill is to assumed
      •     Diameter of the hole from which gas will discharge (inches)
     *     Discharge coefficient of the hole
      •     Ratio  of specific heats (Cj/Cv) for the gas
      •     Height of liquid in the container measured from its bottom (ft)
      •     Molecular weight of the gas and/or liquid

      As discussed in Chapter 2 of this guide, many properties of hazardous materials are a
function of temperature, with one of the most important being  the vapor pressure of the
substance (since this property will ultimately have a major effect on the magnitude of toxic
or flammable vapor dispersion threats). Consequently, for planning purposes, it is desireable
to select both tank and ambient environmental temperatures among the highest that may be
experienced during a typical year. In selecting these temperatures, note that the temperature
of the contents inside a metal tank can often (not always) be  20°F or more higher than the
ambient air temperature on a sunny day

      The user may request assistance in determining the  pressure of the gas  at the point in
time that the program asks for this parameter value  See Section 1228  below for a
description of the Vapor Pressure Input Assistance Subprogram  Note, however, that some
compressed  gas  containers may normally  be at temperatures  in excess  of the critical
temperature of the gas.  This is a temperature above which the substance cannot exist in a
                                         12-41
 image: 








hquid state regardless of the pressure applied  Consequently, the term vapor pressure no
longer has meaning when a material is at a temperature above its critical temperature, the
vapor pressure input assistance subprogram is no longer applicable, and it is necessary for the
user to specify any required pressures.

     Prior to asking  the user to provide the weight of hazardous material in the tank, an
input parameter  value that would  otherwise  require  several manual computations, the
program asks if the user desires assistance in characterizing the volume of the container and
the weights,  volumes, and physical states of its contents Further details on the Tank and
Container Contents  Characterization  Subprogram and  its general data requirements are
provided in Section 12.29 of this chapter. Use of the subprogram may result in requests for a
few informational items not listed above but is nevertheless highly recommended

     Hazard evaluations for emergency planning purposes should strive to assume the worse
reasonable and credible conditions under which an accident may take place  In the case of
the amount of liquid in the tank or container, guidance should be obtained from the owner or
operator of the vessel with respect to the largest amounts that may be expected to be present
In the case of transportation vehicles, it is usually sufficient to assume that the container is at
least 90% full unless other information is available

      There may be situations envisioned in which the tank or container of interest may be
expected to  fail in a very quick and catastrophic  fashion, for example, m the event of its
exposure to  a major explosion  or collapse  due to severe  structural failure  Consequently,
after the user has supplied the  weight of liquid in the tank,  the program asks if the user
wishes to assume that the spill or  discharge should be assumed as being essentially
instantaneous.  A yes answer to this question will halt use of the model and result m the
assumption that the entire contents of the container will be released to the environment in one
minute and that the average rate of discharge will be the weight of tank contents per minute.
A no answer will result in normal continuation of model use.

      The program inherently assumes that the discharge outlet is circular m shape.  In those
instances where the expected shape is not expected to be circular it will be necessary to* 1)
determine or estimate the area of the expected outlet  m units  of square  inches, and 2)
compute the diameter of the equivalent circle  having this area Appendix A to this guide
provides assistance in this task for those who may require guidance

      The discharge coefficient of the hole is a measure of its edge characteristics that has  a
major and direct influence on the rate of discharge. The input parameter screen for the data
item will provide guidance in selection of an appropriate value
                                         12-42
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     The ratio of specific heats  for the compressed gas or vapor is  a thermodynamic
property related to the amount of heat necessary to increase the temperature of a unit weight
of gas or vapor by one degree under specified conditions  Prior to request of this value, the
program  will provide the user an  opportunity to request assistance in  selection of  an
appropnate specific heat ratio using several generalized rules-of-thumb (reproduced in Table
12 7) that require user knowledge  of the chemical formula of the hazardous material being
evaluated Although the accuracy  of model  answers would be improved by provision of a
more precise value for the  substance at  or near  the temperature in its container, errors
introduced by use of the property estimation methods provided by the program should not be
highly significant in most (but not all) cases

     The program provides assistance (upon request of the user) in computing the molecular
weight of the discharged substance from its chemical formula via a procedure similar to that
described in Section 2 8 of the guide.

     Model Results and Usage

     Results of the  model  include the peak dicharge rate  of compressed gas or vapor
discharge in pounds/minute,  the duration of discharge in minutes at this peak rate, the total
weight of contents discharged in pounds,  and the physical state of the discharged material
(which will always be gas when this particular discharge model is used)   It is vital that the
user read and understand the  assumptions made during formulation and use of this model

     Results may be utilized as  necessary  for input to  the toxic vapor dispersion model
(Hazard Model Menu Option D) and/or the vapor cloud or plume fire hazard model (Hazard
Model Menu Option H) on  the menu  In addition, the duration of gas discharge may be
utilized by the flame jet model (Hazard Model Menu Option F).

     Major Assumptions of the Methodology

     As  a  compressed gas  or vapor is  discharged from a  tank  or other container only
containing the material in its gaseous state,  the loss of gas to the atmosphere together with
thermodynamic cooling effects associated with gas expansion will typically result m a rapid
decrease  of the discharge rate with time. Since this model bases its results solely on the
initial peak discharge rate of the gas or vapor, it will consistently overestimate the discharge
rate and underestimate the duration of discharge The overestimation of discharge rate may
result in overestimation of downwind toxic or flammable gas hazard zones (which is  not bad
for emergency planning purposes) and underestimation of hazard durations (which must be
kept clearly in mind) when Options D and H are respectively  chosen from the  Hazard
Assessment Model Selection Menu  Similarly, the flame jet model available as Option G on
the menu may underestimate the time duration of the flame jet on occasion.
                                        12-43
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     When the tank contains a liquefied compressed gas and the gas discharge model is
being used to evaluate a discharge of gas or vapor from the head space of the tank (i.e., the
volume above the liquid surface),  there is a excellent chance  that the computed peak
discharge rate will vary even more significantly from  the actual average discharge rate,
primarily because the model assumes that all of the tank or container contents, including the
liquid portion, will discharge at the computed peak gas discharge rate  In actuality, there
may be  cases  when thermodynamic cooling effects will rapidly  cool  the  liquid to a
temperature near its boiling point, at which tune flow from the tank will greatly decrease and
even possibly stop while the tank still contains a considerable amount of hazardous material

      The assumptions described above can be restated in a different  fashion by noting that
the model formulation inherently assumes that sufficient heat is entenng the tank or container
from  the external environment, or is being internally generated due to an internal chemical
reaction of some kind, to offset any thermodynamic cooling effects and to maintain the gas
discharge rate near  its  peak value. Since  this model may be used at times to evaluate
discharge rates and  durations under  these "worst case" conditions, and any number of
accident scenarios may involve the potential for exposure of the tank or container to an
external  fire or an  internal exothermic chemical  reaction, the assumptions clearly have
advantages as well as disadvantages.

      The  primary reason  why it was necessary  to provide a  model that  may  provide
inaccurate results at times (but results that tend more  often than not to  overestimate the
hazards  of the  release) is that a  more ngorous  and  formal analysis procedure would
necessitate a substantially larger program and chemical  physical property data not readily
available to the expected average user of Version 1.0 of ARCHIE.

12.15    DISCHARGE MENU OPTION H: RELEASE FROM A PRESSURIZED
          LIQUID PIPELINE

      Purpose of Model

      This highly simplified model is intended to provide an estimate of the discharge rate
and duration expected when a long distance pipeline totally filled with liquid completely
ruptures at some point along its route.  No distinction is made between liquids that are below
or above their respective normal boiling points  Since the topography of the  land surface
over the pipeline route will greatly influence model results, and since the topography is likely
to vary over the  route,  it may be necessary to use this model several times for any given
pipeline, each time assuming a different pipeline break location near sensitive environmental
areas or population zones
                                         12-44
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     Required Input Data

     Data requirements of the model include the following input parameter values, some of
which are unusual  The program makes a special attempt to assist the user in selecting a
value wherever an unusual item of information is required, but does expect the user to have a
rather complete understanding of pipeline, pipeline contents, and pipeline route characteris-
tics  Note, however, that the relatively uninformed user should not hesitate to use the model
Input parameter values not known can be  guessed at and modified at a later time.  An
opportunity is always provided to discard the results of any analysis when it is completed
      •     Normal boiling point of the liquid (°F)
      •     Temperature of the liquid in the pipeline (°F)
      •     Ambient environmental temperature (°F)
      •     Molecular weight of the liquid
      •     Specific gravity of the liquid
      •     Vapor pressure of the liquid in the pipeline (psia)
      •     Length of pipeline that will empty m the event of a rupture (ft)
      •     Diameter of the pipeline (inches or feet)
      •     Maximum height of the liquid column in the line that will empty (ft)
      •     Total pressure of the liquid in the pipeline (psia)
      •     Pipeline shutdown time if a discharge is detected (minutes)
      •     Indication of whether line breaks at one end or along route
      •     Pumping rate of liquid through the pipeline (Ibs/mmute)
      •     Discharge coefficient of the hole

      As discussed in Chapter 2 of this guide, many properties of hazardous materials are a
 function of temperature, with one  of the most important being the vapor pressure of the
 substance (since this property will ultimately have a major effect on the magnitude of toxic
 or flammable vapor dispersion threats). Consequently, for planning purposes, it is desireable
 to select both pipeline and ambient environmental temperatures among the highest that may
 be experienced during a typical year

      The program provides assistance (upon request of the user) in computing the molecular
 weight of the discharged substance from its chemical formula via a procedure similar to that
 described in Section 2 8 of the guide.

      The specific gravity of the liquid should ideally be the value associated with the liquid
 at its temperature in the container or tank of concern.  Note, however, that this value vanes
 very little with changes in temperature for the vast majority of liquids for which this model is
 applicable  The specific gravity given on a typical material safety data sheet (MSDS) will be
 acceptable in most cases
                                        12-45
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     The user may request assistance in determining the vapor pressure of the liquid at the
point in tune that the program asks for this parameter value. See Section 12.28 below for a
description of the Vapor Pressure Input Assistance Subprogram

     The question regarding the length of the pipeline that will empty in the event of a
rupture can be rather tricky when the line travels up and down various hills and valleys  The
length that empties will not necessarily be the total length of the pipeline from its beginning
to its end.

     Picture a pipeline that starts at the top of one hill, travels down to the floor of a valley,
and then travels up the side of another hill to its top If the pipeline breaks at the top of either
hill, and we assume there is no pressure in the line for the moment, then it can be understood
that little if any of the pipeline  contents will escape  to  the environment   Alternatively,
picture what would happen if the  pipeline were to break on the floor of the valley  In this
case, all contents of both resulting pipeline sections from the top of one hill to the top of the
second will  empty onto the valley  floor  Thus,  it is important to  carefully consider the
topography of the land and specific potential accident sites when dealing with long pipelines.
A tracing of the route on a topographical map of the area can be invaluable in estimating
appropriate pipeline lengths.  It is prudent,  however, to first  ask the pipeline owner or
operator if a discharge volume analysis of any kind was conducted prior to installation of the
line since these analyses are sometimes necessary  for compliance with environmental impact
reporting requirements associated with the obtainment of permits from regulatory authorities

      A question related to the desired length of pipeline asks  the user for  the maximum
height of the liquid column in the pipeline that will empty upon pipeline rupture  This is the
maximum vertical height between the assumed  point of  discharge and the highest  point
within the pipeline from which liquid is expected to empty  In the second example presented
 above, it would be the vertical height fiom the top of the highest hill to the floor of valley
 where the pipeline rupture is expected  A highly accurate estimate is not necessary

      The next question essentially requests the user to provide the total pressure of the liquid
 in the pipeline. Provision of an answer requires the user to realize that the force that moves
 the liquid from one end of the pipeline to the other is the pressure mechanically provided by
 various pumping stations along the route. This pressure can be considerable and far above
 the simple vapor pressure of the liquid as it is pushed up various hills Although the program
 uses this pressure in units of psia, the user is given five sets of units to choose among while
 providing an answer to the question

       Many pipeline systems have sensors and alarms that  alert operators to the fact that the
 pipeline has developed  a major leak and permit  them  to shutdown pumping  stations
 manually, while others have systems that act automatically to shutdown pumps   Quicker
                                          12-46
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shutdowns obviously result in less loss of pipeline contents since the pumps will cease to
push the liquid through the line. Thus, even a rough estimate of how long it will require the
owner or operator of the line to detect and act upon a major pipeline break will help improve
the accuracy of analysis results. This information should be readily available from pipeline
owners or operators.

     If a pipeline breaks or ruptures at one  end, then the liquid will be released from one
open  end of the line  Conversely, if the line breaks along its  travel path, there could
conceivably be two open ends of the line from which liquid will flow, thus increasing the
discharge rate and reducing the duration of discharge  It follows that the program requires
some indication of whether the discharge will involve one or two ends of the pipeline.

     During the elapsed time between the instant that the pipeline breaks or ruptures and the
pumps are shut down, there will be some penod of time in which liquid continues to spill
from the line due to continued pumping. Consequently, the program asks the user for the
normal flowrate of liquid through the line under normal operating conditions  This also is an
item of information that should be readily available from the owner or operator of the line
Although the program will use this rate internally in units of pounds  per minute, the user is
given a choice of five sets of units in which to provide an answer

     The discharge coefficient of the hole is a measure of its edge characteristics that has a
major and direct influence on the rate of discharge  The input parameter screen for the data
item will provide guidance in selection of an appropriate value  The proper value for
pipeline breaks will usually be 0.62.

     Model Results and Usage

     In  cases where the pumping  shutdown time is  specified as zero, the program will
provide the average discharge rate  in pounds per minute, the duration of discharge in
minutes, the total weight of discharged material in pounds,  and an indication of whether the
pipeline contents will be discharged as an airborne mixture of gas and small liquid droplets
(i e., aerosols) or as a liquid. When the pumping shutdown time is  greater than zero, a brief
paragraph will describe  the discharge rates and times associated with various time periods
and provide an overall average rate and duration of discharge for use by subsequent models

     In the case of liquid discharges from the pipeline, results of the model are normally
utilized by the program as input parameters to the pool area estimation methods (Hazard
Model Menu Option B) available from the Hazard Assessment Model Selection Menu  In
the case of gas and airborne aerosol discharges from the container, the results may be utilized
as necessary for input to the toxic vapor dispersion model (Hazard Model Menu Option D)
                                       12-47
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and/or the vapor cloud or plume fire hazard model (Hazard Model Menu Option H) on the
menu. In addition, the duration of gaseous discharge may be utilized by the flame jet model
(Hazard Model Menu Option F).

      Major Assumptions of the Methodology

      As noted earlier, this is a highly simplified model for estimating discharge rates and
durations from liquid pipelines

      The first simplifying assumption made, one that is not highly consequential, is that the
liquid experiences no friction as it flows through the pipeline. In reality, the walls of the line
will produce friction that will tend to slow the outward flow of liquid when a break occurs.
Inclusion of friction into the model, however,  would not produce significantly decreased
discharge rates except under very unusual circumstances for the types  of full line  break
scenarios being considered

      A major assumption that can indeed adversely affect the accuracy of results involves
the inherent assumption that the liquid in the pipeline does not contain a dissolved gas under
high  pressure and is  not itself a liquefied compressed gas  Liquids with dissolved gases
under pressure (such as a crude oil pipeline containing  significant amounts of dissolved
natural  gas) will experience what is sometimes referred to as a "champagne" effect upon
rupture.  In other words, expansion of the dissolved gases when the pressure is relieved may
cause a gushing forth  of pipeline contents to  the extent that the total amount of  liquid
discharged will be greater than that normally predicted by  the model  Similarly, liquefied
compressed gases may erupt from the pipeline in a manner not fully considered by the model.

      The decision as to whether the discharged  material will  be a  mixture  of gas and
 aerosols or a  liquid depends upon the temperature of the hazardous material in its container
 and the normal boiling point of the substance.  An airborne mixture of gas and aerosols is
 assumed whenever the container content temperature exceeds the normal boiling point by
 10 8°F (6°C) as a general rule of thumb. The assumption is conservative in that it may at
 times indicate that no liquid will reach the ground although this may indeed  occur to some
 degree.  More precise assessment of the physical characteristics of the discharged material
 requires knowledge of physical property data  not expected to be readily available to  the
 average user of Version 10 of ARCHIE and must therefore await installation of a database in
 this program.
                                         12-48
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12.16  DISCHARGE MENU OPTION I: RELEASE FROM A PRESSURIZED GAS
       PIPELINE

     Purpose of Model

     This model is intended to provide an estimate of the discharge rate and duration
expected when  a pressurized long distance pipeline totally filled with a gaseous substance
develops a leak or completely ruptures at some point along its route.  The model cannot be
used for pipelines containing both liquid and gas.

     Required Input Data

     Data requirements of the model include the following input parameter values:

     •    Normal boiling point of the substance (°F)
     •    Temperature of the gas in the pipeline (°F)
     •    Ambient environmental temperature (°F)
          Vapor pressure of the gas in the pipeline (psia)
     •    Molecular weight of the gas
     •    Length of the pipeline from beginning to end (ft)
     •    Diameter of the pipeline (niches or feet)
     •    Actual pressure of the gas in the pipeline where applicable (psia)
     •    Indication of whether small hole or full rupture occurs in line
     •    Diameter of the hole from which gas will discharge (inches)
     •    Discharge coefficient of the hole
          Ratio of specific heats (Cj/Cv) for the gas

     As discussed m Chapter 2 of this guide, many properties of hazardous materials are a
function of temperature, with one of the most important being the vapor pressure  of the
substance (since this property will ultimately have a major effect on the magnitude of toxic
or flammable vapor dispersion threats)  Consequently, for planning purposes, it is desireable
to select both pipeline and ambient environmental temperatures among the highest that may
be experienced during a typical year

     The user may request assistance in determining the vapor pressure of the gas at the
point in time that the program asks for this parameter value  See Section 12 28 below for a
description of the Vapor Pressure Input Assistance Subprogram Note, however, that many
gas pipelines, especially those conveying fuel gases with low normal boiling points, typically
operate at temperatures in excess of the critical temperature of the gas. This is a temperature
at or above  which  the substance  canno^ exist in a liquid state regardless of the pressure
applied and permits pipeline operators to compress the gas to high pressures without causing
hquefication  Consequently, the term vapor pressure no longer has meaning when a material
                                       12-49
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is at a temperature above its critical temperature,  the  vapor pressure input assistance
subprogram is no longer applicable, and it is necessary for the user to specify the pressure in
the pipeline using information obtained from the pipeline owner or operator  For purposes of
checking whether or not the temperature of the gas in the pipeline is above or below the
critical temperature, without actually asking for this value, the program estimates the critical
temperature of the gas as being  1.8  times the normal boiling point temperature of the
substance expressed in degrees Kelvin. (Technically oriented users may remember that the
rather common rule-of-thumb being applied typically uses  a multiplication factor of 1 65
instead of 1.8. The higher factor was chosen to prevent the program from  erroneously
assuming the critical temperature  has been exceeded when the actual  temperature  is
somewhat greater than the value estimated when a factor of 1 65 is applied)

      In those cases in which the critical temperature of the gas has not been exceeded, there
is a possibility that the pipeline might be operated at a pressure below the vapor pressure of
the material being transported  Although this is not likely, the user is given the opportunity
to specify the actual pressure in the pipeline. Be advised that input of a pressure  that exceeds
the vapor pressure of the pipeline gas at its specified temperature will result in a warning
message to the user to the effect that the pipeline contains liquid   Since the model is only
applicable when  there is no liquid in the line, it will be necessary for the user to  either revise
the  pipeline pressure to  an acceptable value (i.e., one  at  or below the specified vapor
pressure) or to choose the liquid pipeline model for use (Discharge Menu Option H)  As
noted above, neither of the available pipeline models can cope with a situation in which the
pipeline contains both gas and liquid

      The program provides assistance (upon request of the user) in computing the molecular
weight of the discharged substance from its chemical formula via a procedure similar to that
described in Section 2.8 of the guide.

      The program gives the user the option of specifying that.  1) a relatively small hole
 should be  assumed  to occur in the pipeline, 2) the line should be  assumed  to break
completely at one end; or 3) the line should be assumed to break  completely at some point
 along its route of travel. The diameter of the discharge outlet hole will only be requested if
 the first option is chosen.

       The program inherently assumes that the discharge outlet is circular in shape In those
 instances where  the expected shape is not expected to be circular  it will  be necessary to. 1)
 determine  or estimate the area  of the expected  outlet m  units  of square inches,  and 2)
 compute the diameter of the equivalent circle having this area Appendix A to this guide
 provides assistance in this task for those who may require guidance
                                         12-50
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     The discharge coefficient of the hole is a measure of its edge characteristics that has a
major and direct influence on the rate of discharge. The input parameter screen for the data
item will provide guidance in selection of an appropriate value  The proper value will
usually be 0 62 for a leaking or ruptured pipeline

     The ratio of specific heats for the compressed gas  or vapor is a  thermodynamic
property related to the amount of heat necessary to increase the temperature of a unit weight
of gas or vapor by one degree under specified conditions  Prior to request of this value, the
program will  provide  the user an opportunity  to request assistance in selection of  an
appropriate specific heat ratio using several generalized rules-of-thumb (reproduced in Table
12 7) that require user  knowledge of the chemical formula of the hazardous material being
evaluated Although the accuracy of model answers would  be improved by provision of a
more precise value for the substance at or near the temperature  in its container, errors
introduced by use of the property estimation methods provided by the program should not be
highly significant in most (but not all) cases

     Model Results and Usage

     Results of the model include the peak rate of gas discharge in pounds/minute (adjusted
in the case of full line break scenarios), the duration of discharge in minutes at the computed
rate of discharge, the total weight of contents discharged m pounds, and the physical state of
the discharged material (which will always be gas when this particular discharge model is
used).

     To be realized is that the initial peak rate of gas discharge will drop  in magnitude
extremely rapidly in any scenario involving a full break or rupture of the pipeline  In order to
avoid gross overestimation of the discharge rate and  underestimation of the discharge
duration in such cases, the model provides a rate of discharge that is 75% of the initial peak
discharge rate  The impact of  the adjustment should not be cause for concern  since the
model will in all likelihood continue to overestimate the  discharge rate  and this is not
undesireable for emergency planning purposes

     Results of  the model  may be  utilized  as  necessary for input to  the toxic vapor
dispersion model (Hazard Model Menu Option D) and/or  the vapor cloud or plume fire
hazard model (Hazard Model Menu Option H) on the menu  In addition, the duration of gas
discharge may be utilized by the flame jet model (Hazard Model Menu Option F)

     Major Assumptions of the Methodology

     The first simplifying assumption made, one that  is not highly consequential, is that the
flow of gas is not hindered by friction  In reality, the walls of the pipeline will produce some
degree of friction that will tend to slow the discharge rate.
                                        12-51
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     A second assumption is that the model assumes that thermodynamic cooling effects
will also not reduce the discharge rate of gas

22.17 HAZARD MODEL MENU OPTION B: POOL AREA ESTIMATION METHODS

     Purpose of Methods

     In the event of a discharge that results in formation of a pool of liquid on the ground, it
is necessary to  obtain an estimate of the area of the pool  This estimate is required by the
pool evaporation (Hazard Model Menu Option C) that estimates the rate of vapor evolution
to the  atmosphere and by the liquid pool fire model (Hazard Model Menu Option E) that
estimates the height of the flame and surrounding hazard zones

     Required Input Data

     Use of the model requires the following information

     • Molecular weight of the liquid
     • Specific gravity of the liquid
     • Discharge rate of the liquid from its container (Ibs/minute)
     • Duration of liquid discharge (minutes)
     • Normal boiling point of the liquid (°F)
     • Temperature of the liquid in its container (°F)
     • Ambient environmental temperature (°F)
     • Wind velocity (mph)
      • Vapor pressure of the liquid at ambient temperature (mm Hg)
      • Area to which the liquid may be restricted if a secondary
        containment system is present (ft2)
      • Other input parameter values discussed below

      The program provides assistance (upon request of the user) in computing the molecular
 weight of the discharged substance from its chemical formula via a procedure similar to that
 described hi  Section 2 8 of the guide

      The specific gravity of the liquid should ideally be the value associated with the liquid
 at its temperature in the container or tank of concern Note, however, that this value vanes
 very little with changes in temperature for the vast majority of liquids for which this model is
 applicable. The specific gravity given on a typical material safety data sheet (MSDS) will be
 acceptable in most cases.
                                        12-52
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     The hquid discharge rate and duration of discharge are usually computed via use of an
appropnate model from the Discharge Model Selection Menu. Any attempt to estimate pool
areas before these input parameters have been computed will result in a warning to the user
and a question as to whether he or she wishes to continue the analysis.

     As discussed in Chapter 2 of this guide, many properties of hazardous materials are a
function of temperature,  with one of the most important being the vapor pressure of  the
substance (since this property will ultimately have a major effect on the magnitude of toxic
or flammable vapor dispersion threats)  Consequently, for planning purposes, it is desireable
to select both tank and ambient environmental temperatures among the highest that may be
experienced during a typical year  In selecting these temperatures, note that the temperature
of the contents inside a metal tank can often (not always) be 20°F or more higher than  the
ambient air temperature on  a sunny  day. Even when  not higher in the container,  the
temperature of the liquid may increase upon spillage onto a hot surface or when  exposed to
the sun (particularly when the vapor pressure of the material is relatively low and evaporative
cooling does not play a major role).

     Assistance in selection of a wind velocity that  is consistent with the atmospheric
stability class specification that will be required  by one or more subsequent models is
provided during model use (upon request of the user) by display of the class selection chart
(reproduced here in Table  12.8). The  longest downwind hazard  distances  along  the
centerhne of the wind direction are usually obtained when stability class F is specified, and
this is usually a good choice for general emergency planning purposes ~ as is a wind velocity
specification of 4.5 mph. However, be advised that there  may be exceptions to this general
rule  when an evaporating liquid pool is the source of  hazardous  vapor emissions  Higher
wind velocities typically  produce greater evaporation rates, yet are usually associated with
atmospheric stability classes other than F Thus,  the  actual worse case for toxic vapor
dispersion hazard assessments may involve a different combination than suggested above  for
some materials. In the absence of more precise historical meterological  data for the region of
concern, an atmospheric stability class of D together with a wind velocity of about 10 mph
can be assumed to evaluate threats under more typical atmospheric conditions. (Note. The
wind velocity  and atmospheric stability class are not always used by these  models but  are
always requested. They will definitely be needed  by subsequent  models so this poses  no
additional burden  on the user.)

     The user may request assistance in determining the vapor pressure of the liquid at  the
point m time that the program asks for this parameter value.  See Section 12 28 below for a
description of the  Vapor Pressure Input Assistance Subprogram.
                                        12-53
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                                                        TABLE 12.8
                                   ATMOSPHERIC STABILITY CLASS SELECTION TABLE
                         A — Extremely Unstable Conditions
                         B - Moderately Unstable Conditions
                         C - Slightly Unstable Conditions
D - Neutral Conditions*
E -- Slightly Stable Conditions
F ~ Moderately Stable Conditions


Surface Wind
Speed, mph
Less than 4 5
45-67
67-112
134
Greater than 134
Daytime Conditions
Strength of sunlight
Strong
A
A-B
B
C
C
Moderate
A-B
B
B-C
C-D
D
Slight
B
C
C
D
D
Nighttime Conditions

Thin Overcast
> or = 4/8
Cloudiness**
-
E
D
D
D
< or = 3/8
Cloudness
-
F
E
D
D
S3

(J1
f*
         *Apphcable to heavy overcast conditions day or night

         **Degree of Cloudiness = Fraction of sky above horizon covered by clouds
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     Many facilities install secondary containment systems in the form of dikes, curbs,
sumps, or pits designed to restrict and contain the spreading of discharged liquids in the event
of an accidental spill The program will ask if such a system is present  If the answer is yes,
the  program will next ask the user to provide an estimate of the area to  which liquid
spreading will be restricted.

     In the event that the program decides it best to assume that the liquid will boil upon its
release to the environment, it will directly compute the area of the boiling pool In all other
cases, the program will first estimate the maximum credible pool area for non-boiling but
potentially volatile liquid pools based on the information provided. It will then proceed to a
menu that provides the user with a variety of options for specifying  or estimating the
expected pool area

     Once the area of the evaporating or potentially boiling pool has been determined,  it
next becomes necessary (only in the case of combustible or flammable liquids) to estimate
the area of the burning pool that will occur if the  liquid is ignited  This first involves a
question to  the user as to whether  he or she wishes  to  assume the liquid  is ignited
immediately upon release or after  the pool has attained its maximum size, with the latter
choice resulting in the larger and more hazardous fire. The  program will then proceed to
estimate the area of the resulting burning pool.

     Model Results and Usage

     Use of the model provides  two results  The first is  the approximate area of the
expected boiling  or evaporating liquid pool  The  second, only provided in the  case of
combustible or flammable liquids, is the estimated area of the burning pool

     The boiling or evaporating pool area is typically utilized as an input parameter to the
liquid pool evaporation rate and duration estimation model (Hazard Model Menu Option C).
In addition, this area is used to adjust estimated initial evacuation zone widths resulting from
use of the toxic vapor dispersion model (Hazard Model Menu Option D). The estimated area
of the burning pool is normally utilized as an input parameter to" the liquid pool fire model
(Hazard Model Menu Option E)

     Major Assumptions of the Methodologies

     Estimation of pool areas resulting from liquid spills is one of the most difficult  and
error prone aspects of accident scenario evaluations for hazardous materials, except in those
cases m which the discharge source is confined by a secondary containment system of known
dimensions and the liquid will cover the the bottom of the confinement area Unconfined
spills rarely occur in a location where the ground surface is flat and impermeable to liquids
Rather, in the real world, and particularly in transportation accidents, the spilled liquid will
                                       12-55
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usually follow rainwater drainage paths while simultaneously vaporizing, burning,  and/or
soaking into the ground. Thus, this model is actually comprised of a number of different
estimation procedures,  all designed to ease the task of the program user in obtaining a
reasonable though not always highly accurate answer.

     In the case of liquids that are expected to boil upon release to the environment, the
program uses a relatively simple and crude methodology to estimate the rate at which the
liquid will vaporize.  It then uses this rate in conjunction with a liquid spreading model to
estimate the desired pool area. Various assumptions made are described in Appendix B.

     For non-boiling liquids, the program first uses an evaporation rate model in conjunction
with a pool spreading model to estimate the pool area that would be necessary in order for
the total vaporization rate of the spilled liquid to approximate the discharge rate of the liquid
from its tank or other container. The result is a maximum credible pool area that provides an
upper bound that cannot be exceeded. The program then provides the user various options
for estimation of a more accurate pool area. Assumptions of these procedures are again of a
rather technical nature and require reference to Appendix B of this guide.

     Burning pool areas are determined in a fashion similar to that used for boiling pools
with the exception that the vaporization rate of the pool is replaced with an estimate of the
rate at which the liquid will burn.

12.18   HAZARD MODEL MENU  OPTION C: POOL EVAPORATION RATE AND
        DURATION ESTIMATES

     Purpose of Methods

      Once the area of a boiling or evaporating pool of liquid has been estimated by the
 above model or provided by the user, it next becomes necessary to obtain an estimate of the
 total rate at which at which potentially hazardous vapors will evolve from the pool and the
 duration of vapor evolution.

     Required Input Data

      Input parameter values that are most commonly requested by the program are listed
 below.  If the liquid is among a small group of substances with an extremely  low  normal
 boiling point, only the boiling point,  the discharge rate of the liquid m pounds per minute,
 and the duration of discharge in minutes will be requested.

      •     Normal boiling point of the liquid (°F)
      •     Molecular weight of the liquid
      •     Specific gravity of the liquid
                                        12-56
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     •    Temperature of the liquid in its container (°F)
     •    Ambient environmental temperature (°F)
     •    Vapor pressure of the liquid at ambient temperature (mm Hg)
     •    Area of the evaporating or boiling pool of liquid (ft2)
     •    Total weight of discharged liquid (Ibs)
     •    Atmospheric stability class (A to F)
     •    Wind velocity (mph)

     The program provides assistance (upon request of the user) in computing the molecular
weight of the discharged substance from its chemical formula via a procedure similar to that
described in Section 2 8 of the guide

     The specific gravity of the liquid should ideally be the value associated with the liquid
at its temperature in the container or tank of concern Note, however, that this value vanes
very little with changes in temperature for the vast majority of liquids for which this model is
applicable. The specific gravity given on a typical material safety data sheet (MSDS) will be
acceptable in most cases

     As discussed in Chapter 2  of this guide, many properties of hazardous materials are a
function of temperature, with one of the most important being the vapor pressure of the
substance (since this property will ultimately have a major effect on the magnitude of toxic
or flammable vapor dispersion threats) Consequently, for planning purposes, it is desireable
to select both tank and ambient environmental temperatures among the highest that may be
experienced during a typical year.  In selecting these temperatures, note that the temperature
of the contents inside a metal tank can often (not always) be 20°F or more higher than the
ambient air temperature  on a  sunny day  Even when  not higher m the  container, the
temperature of the liquid may increase upon spillage onto a hot surface or when exposed to
the sun (particularly when the vapor pressure of the material is relatively low and evaporative
cooling does not play a major role)

      The user may request assistance in determining the vapor pressure of the liquid at the
point in time that the program asks for this parameter value  See Section 12 28 below for a
description of the Vapor Pressure Input Assistance Subprogram

      The area of the evaporating or boiling pool is usually computed via use of the pool area
estimation method listed  as Option B on the Hazard  Assessment Model Selection Menu
The total weight of spilled liquid is usually determined via use of one of the models available
from the Discharge Model Selection Menu Any attempt to use this model before these
parameters have  been estimated by a prior model will result  in a warning to the user and a
question as to whether he or she wishes to continue the analysis
                                        12-57
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     Assistance in selection of the appropriate atmospheric  stability class and a wind
velocity consistent with this class is provided (upon request of the user) by reproduction of
the class selection chart  (reproduced here in Table 12.8). The longest downwind hazard
distances along the centerhne of the wind direction are usually obtained when stability class
F is specified, and this is usually a good choice for general emergency planning purposes ~
as is a wind velocity specification of 4 5 mph  However, be advised that there may be
exceptions to this general rule when an evaporating liquid pool is the source of hazardous
vapor emissions. Higher wind velocities typically produce greater evaporation rates, yet are
usually associated with atmospheric stability classes  other than F  Thus, the actual worst
case for toxic vapor dispersion hazard assessments may involve a different combination than
suggested above for some materials. In the absence of more precise historical meterological
data for the region of concern, an  atmospheric stability class  of D together with a wind
velocity of about 10 mph can be assumed to evaluate threats under more typical atmospheric
conditions. (Note: The wind velocity and atmospheric stability class are not always used by
this model but are always requested  They will definitely be needed by subsequent models so
this poses no additional burden on the user)

     Model Results and Usage

     Results of the model include the rate of vapor evolution into the atmosphere in pounds
per minute  and the duration of vapor evolution in minutes  These results are  typically
utilized as necessary as input parameter values to the toxic vapor dispersion model (Hazard
Model Menu Option D) and/or the vapor cloud or plume fire hazard model (Hazard Model
Menu Option H).

     Major Assumptions of the Methodologies

     As in the case of pool area estimation, estimation of pool vaporization  rates and
durations from liquid spills is one of the most difficult and error prone aspects of accident
scenario evaluations for hazardous materials  Although relatively sophisticated and accurate
estimation methods have been developed and validated in recent years, they unfortunately
require knowledge of chemical property data  that are not always readily available and/or
entail  complex algorithms that demand excessive computation times on typical personal
computers.  Appendix B describes the rather unusual  and relatively simple and crude
methodology  employed by ARCHIE  Be advised that answers will not be highly accurate
but will be in the correct "ballpark" for most cases  Only occasionally should vaporization
rates be underestimated
                                       12-58
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12.19 HAZARD MODEL MENU OPTION D: TOXIC VAPOR DISPERSION MODEL

     Purpose of Model

     The discharge, emission, or release of a toxic gas or vapor to the atmosphere has the
potential to pose an inhalation hazard to downwind populations under a wide variety of
circumstances The purpose of this model is to provide an estimate of the dimensions and
characteristics of the initial downwind zone that may require protective action in the event of
a hazardous material discharge.

     Although primarily designed for gas or vapor releases, the model can be used in a very
approximate fashion for discharges  of fine dusts  or powders to the atmosphere. In such
cases, the user will be required to estimate and provide the program with the rate at which
these materials are emitted to the atmosphere and the duration of this emission

     Required Input Data

     The model requires eight input parameter values, these being.

     •     Molecular weight of the toxic substance
     •     Toxic vapor limit selected by the user (ppm, mg/m3, or gm/m3)
     •     Discharge height of the vapor or gas above groundlevel (ft)
     •     Atmospheric stability class (A to F)
     •     Wind velocity (mph)
     •     Temperature of the toxic substance in its container (°F)
     •     Ambient environmental temperature (°F)
     •     Vapor/gas emission rate (Ibs/rmnute)
     •     Duration of vapor/gas emission (minutes)

     The program provides assistance (upon request of the user) in computing the molecular
weight of the discharged substance from its chemical formula via a procedure similar to that
described in Section 2 8 of the guide.

     Selection of an appropriate toxic vapor limit is discussed in Chapter 6. Note that the
program will provide you with a choice of units in which this toxic limit may be expressed
All subsequent presentations of results, however, will utilize units of parts per million (ppm)
by volume in air.

      Assistance in  selection of  the  appropriate  atmospheric  stability class and a wind
velocity consistent with this class is provided (upon request of the user) by reproduction of
the class selection chart (reproduced here in Table 12 8)  The longest downwind hazard
distances along the centerline of the wind direction are usually obtained when stability class
                                         12-59
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F is specified, and this is usually a good choice for general emergency planning purposes --
as is  a wind velocity specification  of 4.5 mph  However,  be advised that there may be
exceptions to this general rule when an evaporating liquid pool is the source of hazardous
vapor emissions Higher wind velocities typically produce greater evaporation rates, yet are
usually associated with  atmospheric stability classes other than F  Thus, the  actual worst
case for toxic vapor dispersion hazard assessments may involve a different combination than
suggested above for some materials.  In the absence of more precise historical meterological
data for the region of concern, an  atmospheric stability class of D together with a wind
velocity of about 10 mph can be assumed to evaluate threats under more typical atmospheric
conditions

      As discussed in Chapter 2 of this guide, many properties of hazardous materials are a
function of temperature, with  one of  the most important being the vapor pressure of the
substance (since this property will ultimately have a major effect on the magnitude of toxic
or flammable vapor dispersion  threats). Consequently, for planning purposes, it is desireable
to select both tank and ambient environmental temperatures  among the highest that may be
experienced during a typical year. In selecting these temperatures, note that the temperature
of the contents inside a  metal tank can often (not  always) be 20°F or more higher than the
ambient air temperature on a sunny day.

      The vapor or gas emission rate to the atmosphere and the duration of the emission are
usually computed by one or more of the preceding models on the Hazard Assessment Model
Selection  Menu. Any attempt to  use the  toxic vapor dispersion model  before  these
parameters have been computed will result in a warning to the user and a question as to
whether he or she wishes to continue the analysis

      Model Results and Usage

      Estimation of hazard zone dimensions and characteristics requires  a complex iterative
procedure that literally searches in the downwind direction for distances associated with the
user specified toxic limit concentration The program displays the results of this search as it
proceeds to find the downwind length of the hazard zone at the discharge height of the vapor
or gas, the peak concentration expected at groundlevel together with the location of this peak
for elevated sources, and the downwind length of the hazard zone at groundlevel. It then
provides a summary report of distances appropnate for the scenario being evaluated.

      Two tables provide groundlevel concentrations, source height concentrations, recom-
mended initial evacuation zone widths, contaminant arrival times, and contaminant departure
times as a function of downwind distance.
                                       12-60
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     Due to the numerous uncertainties associated with even the most sophisticated vapor
dispersion modeling procedures, emergency planners should use the results of this model
only as guideposts in decisions regarding necessary protective action in the event of an actual
emergency. The pnme value of the model is hi its ability to provide a rough estimate of the
magnitude of downwind areas that will be at nsk, and in no way should model results be
expected to be either highly accurate or precise. Indeed, be advised that many professionals
consider the answers produced by a vapor dispersion model to be of acceptable accuracy if
they are correct within a factor of two in 50% or more of trials.

     A special note is necessary with respect to the procedures used to estimate contaminant
arrival and departure times at downwind locations. Since the velocity of the wind generally
increases with height, and since the wind velocity reported by meteorologists is usually the
velocity measured  at a height of  10  meters (about  33  feet) above  the  ground surface,
estimation of these times is at best highly approximate, particularly if the source of toxic gas
or vapor emissions is elevated above the ground   The model will generally underestimate
rather than overestimate contaminant arrival  times, but exceptions to this  general rule are
distinctly possible.  Similarly, the model will generally overestimate rather than underesti-
mate contaminant departure times, but exceptions to this general rule are again possible
under certain circumstances. See Appendix B  for details of the computation procedures

     Yet another special note is necessary  with respect to the evacuation zone widths
predicted by the model when the wind velocities in the hazard zone are very low Under
such conditions, the direction of the wind can become very erratic, and it may not always be
wise to fully trust the results of the analysis in terms of its high probability that the wind will
not change direction within the first hour of the release. Be prepared at any time under low
wind conditions for one or more sudden shifts in wind direction and the possibility that the
cloud or plume of vapor or gas may literally "hop" from one position or direction to another.
Also,  always remember  that the evacuation zone widths  are  based on a  probabilistic
evaluation of wind direction shifts  Many a favorite race horse at the track has lost its event
by a wide margin. Longshots actually win at times.

     Use of model  results are rather self-evident. They provide emergency planning
personnel with an  indication of the land area and thus populations subject  to inhalation
exposures at or above the specified toxic limit concentration in the event of an accident In
addition, they provide an estimate of the duration of the toxic vapor or gas hazard  These
items of information, in tarn, permit estimation of the number of people in the jurisdiction of
concern that may require notification, protective action, transportation, shelter, medical care,
and so forth.
                                         12-61
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     Mty'or Assumptions of the Methodology

     The particular vapor dispersion  model  being utilized for  toxic vapors  primarily
assumes:

     •    The discharge is of finite duration.
     •    All vapors or gases are discharged from a single point
     •    The vapors or gases are neutrally buoyant.
     •    The ground surface is flat and generally free of obstacles.
     •    Atmospheric conditions remain constant during the discharge.
     •    The emission rate to the atmosphere is a constant during the release
     •    The gas or vapor enters the atmosphere at a low velocity
     •    Only gases or vapors are being released to the atmosphere

     Because of the importance of this topic, Sections 3 5 and 3 6 of the guide are devoted
to a description and discussion of fundamental vapor dispersion phenomena and the factors
that influence the size and characteristics of downwind hazard zones  Please refer to these
sections  for  an  understanding of the  significance of these assumptions.  Also note that
Appendix B of the guide provides additional discussion of model assumptions, albeit m more
technical terms.

     Be advised and stay aware that there is at least one special case in which the type of
dispersion model(s) being employed by ARCHIE may underestimate downwind hazard zone
lengths.  This involves scenarios  in  which a compressed liquefied gas under very high
pressure in its container vents a high velocity jet of gas and liquid aerosols at a high rate m
the downwind direction. When the jet is forceful  and  the gas  and aerosol mixture is
heavier-than-air, actual downwind travel distances to given concentrations m air may at times
exceed those predicted by ARCHIE

     Due to the possibility  that airborne contaminants released well  above the ground
surface may  be forced by local terrain  effects to drop to groundlevel locations sooner than
would be expected, it is worthy to highlight the fact that evacuation zone width estimates are
based on the assumption that all discharges occur at groudlevel  In other words, populations
residing  under a cloud or plume of airborne contaminants are always assumed to be at risk
regardless of the fact that there may be times when the cloud or plume may harmlessly pass
over them.
                                       12-62
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12.20  HAZARD MODEL MENU OPTION E: LIQUID POOL FIRE MODEL

     Purpose of Model

     The purpose of the hquid pool fire model is to compute the radius of the circular zone
around a fire in which unprotected and/or unsheltered people may expenence lethal burns
due to thermal radiation exposures. Additionally, the model computes the radius of the zone
in which second degree burns and/or severe pain may be experienced by exposed individuals

     Required Input Data

     The model requires four input parameter values, these being

      •     Molecular weight of the liquid
      •     Specific gravity of the liquid
      •     Normal boiling point temperature of the liquid (degrees F)
      •     Area of the burning pool (ft2)

      The program provides assistance (upon request of the user) in computing the molecular
weight of the discharged substance from its chemical formula via a procedure similar to that
described in Section 2 8 of the guide.

      The specific gravity of the liquid should ideally be the value associated with the liquid
at its temperature in  the container or tank of concern  Note, however, that this value vanes
little with  changes m temperature for the vast majority of liquids for which this model  is
applicable  The specific gravity given on a typical material safety data sheet (MSDS) will be
acceptable in most cases.

      The  area of the burning  pool is typically estimated using  one of the pool area
estimation procedures available when Option B  is selected from the Hazard Assessment
Model Selection Menu  An attempt to use this model before this area has been computed
will result  in a warning to the user and a question  as to whether he or she wishes to continue
the analysis.

      Model Results and Usage

      The  model provides the  radius  of the burning pool, the height of the expected flame,
 the radius  from the center of the pool in which exposed people may be fatality burned, and
 the  radius from the center of the pool in which exposed people may expenence second
 degree burns or severe pain
                                        12-63
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     These results are useful to emergency planning personnel for estimating the number of
people that may require rescue and medical  care, and for giving fire departments an
indication of the size and nature of the fire they must be prepared to confront. They are also
potentially useful for identifying other containers or stores of hazardous materials in the area
that may  be subject to fire or thermal radiation exposures, possibly resulting in a tank
overpressurization explosion, a massive discharge of toxic gas, formation of a fireball, and/or
the high velocity  dissemination of container fragments that may  damage  more distant
containers or populations.

     Major Assumptions of the Methodology

     The model assumes that the wind velocity in the burning pool area will be insufficient
to tilt the flame in the direction of the wind to a significant degree, thus resulting in circular
hazard zone estimates  In the event the wind does indeed cause tilting of the flame, hazard
zones will be more of an oval shape and have a somewhat greater radius from the flame in
the downwind direction The radii of the respective zones will be somewhat smaller in the
upwind direction.

     The model assumes that people in direct view of the flame and m the open will have
exposed skin.  In other words, their skin will not be protected completely from the effects of
thermal radiation by any clothing being worn

     Hazard zone estimates are based on the assumption that the base of the flame will be
fairly circular in shape. Any major deviation  from such a shape  may invalidate  model
results, but these results are likely to remain conservative

      The model assumes that neither carbon dioxide or water vapor in the air will absorb
any of the thermal radiation impinging on exposed people

      Based on experimental data, a radiation intensity  of 5 kW/m2 ( 1600 Btu/hr-ft2) was
selected for the purpose of defining injury zones since this incident flux will cause second
degree burn inj'unes on bare skin within  45 seconds  An incident flux level of 10 kW/m2
(3200 Btu/hr-ft2) was chosen as the level capable of causing fatalities among exposed people
since it can be expected to quickly cause third degree burns leading to potential fatalities.

1221  HAZARD MODEL MENU OPTION F: FLAME JET MODEL

      Purpose of Model

      The flame jet model has the purpose of estimating the length of the flame and the zone
around it that may be subjected to harmful levels of thermal radiation when a flammable gas
discharges from its container at high speed and is ignited Due to special properties of the
                                        12-64
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material, be advised that the model may greatly overpredict flame jet lengths associated with
discharges of hydrogen but is expected to produce relatively accurate estimates for other
substances.

     Required Input Data

     The model requires eight input parameter values, these being

     •     Normal boiling point of the material (°F)
     •     Temperature of the material in its container (°F)
     •     Ambient environmental temperature (°F)
     •     Pressure of the flammable gas in the container (psia)
     •     Ratio of specific heats (C,/CV) for the gas
     •     Molecular weight of the gas
     •     Lower flammable limit of the gas (volume %)
     •     Diameter of the hole from which the gas is venting (inches)

     As discussed in Chapter 2 of this guide, many properties of hazardous materials are a
function of temperature, with one of the most important being the vapor pressure of the
substance (since this property will ultimately  have a major effect on the magnitude of toxic
or flammable vapor dispersion threats)   Consequently, for planning purposes, it is desireable
to select both tank and ambient environmental temperatures among the highest that may be
experienced during a typical year. In selecting these temperatures, note that the temperature
of the contents inside a metal tank can  often (not always) be  20°F or  more higher than the
ambient air temperature on a sunny day.

      The user may request assistance in determining the pressure of the gas or vapor in the
container at the point in time that the program asks for this  parameter value  See Section
 12 28 below for a description of the Vapor Pressure Input Assistance Subprogram

      The ratio of specific heats for the compressed  gas or  vapor  is  a  thermodynamic
property related to the amount of heat necessary to increase the temperature of a unit weight
 of gas or vapor by one degree under specified conditions. Prior to request of this value, the
 program will provide  the user  an opportunity to request  assistance in selection of an
 appropriate specific heat ratio using several generalized rules-of-thumb (reproduced in Table
 12.7) that require user knowledge of the chemical formula of the hazardous material being
 evaluated. Although the accuracy of model  answers would be  improved by provision of a
 more  precise value for the substance  at or near the temperature  in its container,  errors
 introduced by use of the property estimation methods provided by the program should not be
 highly significant in most (but not all) cases
                                         12-65
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     The program provides assistance (upon request of the user) in computing the molecular
weight of the discharged substance from its chemical formula via a procedure similar to that
described in Section 2 8 of the guide

     The lower flammable limit (LFL) of a gas or vapor was defined in Chapter 4 of this
guide.  Values are always listed on material safety data sheets (MSDS) when appropriate and
available for the material of concern

     The program inherently assumes that the discharge outlet is circular m shape In those
instances where the expected shape is not expected to be circular it will be necessary to  1)
determine or estimate the area of the expected outlet in units  of  square inches, and  2)
compute the diameter of the equivalent circle having this  area  Appendix A to this guide
provides assistance in this task for those who may require guidance

     Model Results and Usage

     The model estimates the length of the expected flame jet and a safe separation distance
from the flame, both in  units of feet  If a gas discharge model providing a duration  of
discharge has been used previously, the model will also display the expected duration of the
flame jet in minutes.

     The length of the flame jet and its  surrounding  hazard  zone radius are useful  to
emergency planning personnel  not only in estimating the number of people that may subject
to injury from the fire, but perhaps more importantly, the number and  characteristics of other
containers or stores of hazardous materials at industrial sites that may be adversely impacted
by the fire.  Of special concern is that a flame jet involving one storage  or transportation
container may impinge on another container, thus possibly causing a tank overpressunzation
explosion, a massive discharge of toxic gas, formation of a fireball, and/or  the high velocity
dissemination of container fragments that may damage more distant containers or popula-
tions

     Major Assumptions of Methodology

     The model assumes that the pressurized gas or vapor will  discharge  at sufficient
velocity to form a lengthy flame jet resembling a large torch In the event that this condition
is not satisfied, the flame exiting from the discharge outlet is likely to  be shorter and to curve
upwards. In technical terms,  this  model  is  said to address  turbulent  or  momemtum
dominated flame jets. If flow velocity criteria are not fulfilled, the flame will be buoyancy
dominated.
                                        12-66
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     Due to the complexities involved in estimating safe separation distances from flame
jets that may have a wide variety of orientations with respect to the person or persons at risk
of receiving burn injuries, the safe separation distance provided by the model is simply twice
the length of the flame  This is considered to be a conservative estimate based on evaluations
conducted with more sophisticated models of flame jet phenomena

12 22  HAZARD  MODEL MENU OPTION G: FIREBALL  THERMAL RADIATION
       MODEL

     Purpose of Model

     This model characterizes  the fireball and  associated thermal radiation hazard zones
resulting from exposure of a sealed or inadequately vented container of a flammable liquid or
liquefied compressed gas to an  external fire or other source of excessive heat sufficient to
cause explosion or violent rupture of the container. The model may also be used in an
approximate fashion for containers of flammable compressed gas

     Required Input Data

     The model only requires the  user to provide the  weight in pounds of the flammable
material in the container  at the point in  time that  it explodes or  ruptures.  The most
conservative course of action  is to simply assume that the container will explode or rupture
when it is full. Realize, however, that many Boiling Liquid Expanding Vapor Explosions
(BLEVES) occur when flame weakens the wall of the vapor or head space of the container.
If the tank is fairly full to begin  with and is fitted with a pressure relief device, it may vent a
considerable portion of its contents before occurrence of a BLEVE

     Model Results and Usage

     The fireball that results from rupture of a tank or  container and subsequent ignition of
its contents will quickly nse while growing in size and then burn out. Results of the model
include estimates of the:

      •     Maximum diameter of the fireball (ft)

      •     Maximum expected height of the fireball (ft)

      •     Estimated duration of the fireball (seconds)

      •     Distance (radius) from  the container hi which fatalities may be expected
           due to thermal radiation burns (ft)
                                        12-67
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     •    Distance (radius) from the container in which significant burn injuries may
          be expected due to thermal radiation (ft)

     Output of the model during  the accident scenario evaluation session always stresses
that "Boiling Liquid Expanding Vapor Explosions (BLEVES) may cause high velocity tank
fragments to travel considerable distances  Some  tanks,  especially  horizontal cylindrical
types,  may  rocket  while  spewing forth flames"  See Chapter 5 for a more  complete
description and discussion of potential fragment hazards.

     Results of the model are useful to emergency planning personnel in defining safe
separation zones in situations where there is a potential for fireball formation and fragment
impact hazards. Additionally, where the event may occur without time for protective actions
to be taken, the results can help planners estimate the number of people that may be killed or
injured. Although specific characteristics and potential damages cannot be predetermined,
the fact that container fragments may disperse at high  velocity  can help identify other
containers or stores of hazardous materials that may be impacted by the  accident and pose
additional threats to the public.

     Major Assumptions of the Methodology

     Key assumptions of the model include:

      •    No thermal radiation will be absorbed by water vapor or carbon dioxide gas
           present in the atmosphere

      •    All flammable materials of interest are similar in characteristics to lique-
           fied compressed propane.

      •    Both the container and exposed people are on or near the ground

      •    The burn seventy depends upon the amout of energy absorbed by the skin
           after a surface temperature of 55°C is achieved  See  Appendix B  for
           additional information.

1233   HAZARD MODEL MENU OPTION H: VAPOR CLOUD  OR PLUME FIRE
        MODEL

      Purpose of Model

      A plume or cloud of flammable vapor or gas has the potential to either burn or burn and
 then explode upon encountering a suitable source of ignition. The purpose of this model is to
 estimate the dimensions of the downwind area that may be subjected  to flammable  and
                                         12-68
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potentially explosive vapors or gases in the event of an accidental discharge In addition, the
model estimates the maximum weight of flammable of explosive gas that may be airborne at
any time during dispersion of the cloud or plume.

     Required Input Data

     The model requires the following input parameter values'

     •    Molecular weight of the substance
     •    Normal boiling point of the discharged material (°F)
     •    Temperature of the substance in its container (°F)
     •    Ambient environmental temperature (°F)
     •    Vapor pressure of the substance after spill (mm Hg)
      •    Lower flammable limit of the gas or vapor (volume %)
      •    Atmospheric stability class (A to F)
      •    Wind velocity (mph)
      •    Vapor/gas emission rate (Ibs/minute)
      •    Duration of vapor/gas emission (minutes)

      The program provides assistance (upon request of the user) in computing the molecular
weight of the discharged substance from its chemical formula via a procedure similar to that
descnbed in Section 2 8  of the guide

      As discussed in Chapter 2 of this guide, many properties of hazardous materials are a
function of temperature, with one of the most  important being the vapor pressure of the
substance (since this property will ultimately have a major effect on the magnitude of toxic
or flammable vapor dispersion threats)  Consequently, for planning purposes, it is desireable
to select both tank and ambient environmental temperatures among the highest that may be
expenenced during a typical year. In selecting these temperatures, note that the temperature
of the contents inside a metal tank can often (not always) be 20°F or more higher than the
ambient air temperature on a sunny day.

      The user may request assistance in determining the vapor pressure of the discharged
substance at the point m time that the  program asks  for this parameter value  See Section
 12.28 below for a description of the Vapor Pressure Input Assistance Subprogram. The
model uses the vapor pressure in this case simply to confirm that flammable vapors can be
generated at specified temperatures in the external environment Thus, if the vapor pressure
of the gas or vapor is above one atmosphere (equivalent to 760 mm Hg), the value displayed
will be limited to a maximum vapor pressure of 760 mm Hg
                                         12-69
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     The lower flammable limit (LFL) of a gas or vapor was defined in Chapter 4 of this
guide.  Values are always listed on material safety data sheets (MSDS) when appropriate and
available for the material of concern.

     Assistance in selection of the appropriate atmospheric stability  class and  a  wind
velocity consistent with this class is provided (upon request of the user) by reproduction of
the class selection chart  (reproduced here in Table 12.8)  The  longest downwind hazard
distances along the centerlme of the wind direction are usually obtained when stability class
F is specified, and this is  usually a good choice for general emergency planning purposes ~
as is a wind velocity specification of  4 5 mph  However, be advised that there  may be
exceptions to this general rule when an evaporating liquid pool is the source of hazardous
vapor emissions. Higher wind velocities typically produce greater evaporation rates, yet are
usually associated with atmospheric stability classes other than  F Thus, the actual worst
case for toxic vapor dispersion hazard assessments may involve a different combination than
suggested above for some materials In the absence of more precise historical meterological
data for  the region of concern, an atmospheric stability class of D together with a wind
velocity of about 10 mph can be assumed to evaluate threats under more typical atmospheric
conditions

     The vapor or gas emission  rate  to  the atmosphere as well as the duration of the
emission is usually computed by one or more of the preceding models on the Hazard
Assessment Model Selection Menu Any attempt to use the toxic vapor dispersion model
before these parameters  have been computed will result in a warning to the  user and a
question as to whether he or she wishes to continue the analysis

     Model Results and Usage

     Output of the model includes:

     • Downwind hazard distance (feet)
     • Maximum downwind hazard zone width (feet)
     • Maximum weight of airborne gas (Ibs)
     • Initial relative vapor/air density
     • Type of model used for analysis

     Two sets of results are provided for the first four items in the above list  The first set is
based  on a concentration that is 50% of the specified lower flammable limit  (LFL) for the
gas or vapor in air. The second is based on the full value of the LFL
                                       12-70
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     The concentration of a gas or vapor at any specific point downwind will fluctuate about
an average value due to atmospheric turbulence even if all other factors  that can influence
vapor dispersion phenomena remain unchanged  Vapor dispersion models,  including the
models in ARCHIE, are usually formulated to provide this average value as a function of
downwind  location, which is perfectly acceptable for consideration of toxic gas or vapor
dispersion hazards.  In the case of flammable gases or vapors, however, it is necessary to
make a distinction between that portion of a cloud or plume that can burn and that portion
that may explode,  and  this requires consideration of peak to average concentrations at
downwind  locations. Without getting  into more technical details, suffice it to say  that a
cloud or plume has the potential to burn out to the boundaries of the area  encompassed by a
gas or vapor concentration that is approximately one-half the LFL. The area subject to
explosion, however, is better estimated via use of the actual LFL value.

     This procedure in ARCHIE actually consists of two separate and distinct models. If the
program  decides that the gases or vapors released to the atmosphere are best treated as being
neutrally buoyant, it uses elements of the toxic vapor dispersion model  to provide desired
results. Conversely, if the vapors are deemed to be best treated as being negatively buoyant
in air, it uses a specially formulated and simplified heavy gas model

     Results of  the  model  primarily provide emergency planning personnel  with an
indication of the size of the hazard zone that may be subject to a vapor or gas cloud or plume
deflagration, and  thus, indications of the  number of people that may be killed or severely
injured, and the number and characteristics of buildings and other resources that may be
exposed  to the flame  The maximum weight of potentially explosive airborne gas  or vapor
estimated by the model is typically utilized as an input parameter to the unconfined vapor
cloud or plume explosion model (Hazard Model Menu Option I).

      Major Assumptions of the Methodology

      Assumptions  associated with use of the vapor dispersion model for neutrally buoyant
vapors or gases are discussed in Section 12 19 above  Technical details and assumptions of
the heavy gas model are provided in Appendix B to this guide.

      The decision  as to which of the two models is to be used is based on a computation of
 the ratio of the  vapor-air mixture density to the density  of pure air The  computation
 procedure leading to this relative vapor density is presented in Section 2 6 of the guide. The
 concentration of gas or vapor in air is taken to be 100% by volume in the event of pressurized
 gas releases
                                       12-71
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     The program assumes that the vapor or gas is best treated as being neutrally buoyant if
its initial relative vapor density has a value of 1 5 or below. Values above 1.5 lead to use of
the heavy gas model for negatively buoyant  gases or vapors. Note that this version of
ARCHIE is incapable of taking the presence of airborne liquid aerosols into account and may
therefore occasionally err during this process.

     Be advised and stay aware that there is at least one special case in which the type of
dispersion model(s) being employed by ARCHIE may underestimate downwind hazard zone
lengths. This involves scenarios in which a  compressed liquefied  gas under very  high
pressure in its container vents a high velocity jet of gas and liquid aerosols at a high rate m
the downwind direction When the jet is forceful and  the gas and aerosol mixture is
heavier-than-air, actual downwind travel distances to given concentrations in air may at times
exceed those predicted by ARCHIE.

1224    HAZARD  MODEL MENU  OPTION I: UNCONFINED VAPOR  CLOUD
         EXPLOSION MODEL

     Purpose of Model

     Although some flammable and therefore potentially explosive gases and vapors have a
greater propensity to explode than others upon ignition when at or above their respective
lower flammable limit (LFL) concentrations in the open environment, the threat of such an
explosion exists with a large number of hazardous materials. This threat increases for most
materials as the degree of confinement is increased.

     The purpose of this particular model in ARCHIE is to evaluate the  impacts of an
explosion involving an unconfined (or even partially confined) gas or vapor cloud or plume
in air.

     Required Input Data

     Input data and information required by the model include.

     •  Lower heat of combustion of the gas or vapor (Btu/lb)
     •  Yield factor for the explosion
     •  Weight of airborne flammable gas or vapor (Ibs)
     •  Location of the explosion relative to the ground surface

     The heat of combustion of a material is the amount of heat generated when a unit
weight of the substance is burned under specified conditions  The lower heat of combustion
ideally desired for model use is the amount of heat liberated when the material is burned m
oxygen at a temperature of 25°C (77°F) and the products of combustion, including any water
                                       12-72
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that may form, remain as gases  The input screen for the parameter provides guidance for
selecting a value when more precise data are unavailable. For informational purposes, it is
noted that the CHRIS Hazardous Chemical Data manual available at a cost of $41 in late
1988 from branches of the Government Printing Office contains the desired value for over
1200 hazardous materials  This manual is widely used by fire service and other emergency
response personnel across the country and  is  very  likely to be locally available No
hazardous materials library would be complete without the document

     When a volume of gas or vapor in air burns and explodes, only a small fraction of the
energy in the cloud or plume actually contributes to the formation of shock or blast waves
that can damage people and property. This fraction is referred to as the yield factor and
vanes for different materials Upon request of the user, the program will provide guidance for
selection of an appropriate yield factor for the substance of concern when it is completely
unconfmed in the environment  This guidance is reproduced  in Table 129. Pay special
attention to the fact that the guidance only applies to situations in which the gas or vapor
cloud or plume is completely unconfined Yield factors can increase substantially when there
is a significant degree of confinement

     The weight of flammable gas or vapor in air is usually computed by the vapor cloud or
plume fire model described above (Hazard Model Menu Option H) Any attempt to use the
unconfined vapor cloud explosion model before this weight has been computed will result m
a warning to  the user and a question as to whether he or she wishes to continue the analysis
In addition, the user will be warned if the weight provided is less than 1000 pounds, since the
probability of a completely unconfined vapor cloud  explosion (based on historical data) is
very low in such cases, except for a very few reactive substances and for situations in which
there is some degree of confinement pnor to ignition

      As discussed in Chapter 5 of this guide, an explosion centered near  the ground can
behave quite differently than an explosion at some point well above the ground surface (a so
called free air blast).  Thus, the program asks the user whether a ground or elevated location
should be assumed Be advised that the damages caused by a groundlevel explosion will be
greater than those caused by a free air blast when all other factors are equal.

      Model Results and Usage

      The model produces a table which lists distances from the explosion center associated
with various degrees of injury and damage to people and property. It is important to realize
in the case of unconfined vapor  cloud explosions that the center of the explosion could be
anywhere within the area subjected to gas or vapor concentrations at or above the LFLfor
the material  of concern  This area is usually defined by use of the vapor cloud or plume fire
model described in Section 12 23 (Hazard Model Menu Option H)
                                        12-73
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                  TABLE 12.9
ASSISTANCE DISPLAY FOR EXPLOSION YIELD FACTOR
YIELD FACTOR SELECTION ASSISTANCE FOR COMPLETELY UNCONFINED
CLOUDS
EXAMPLES OF SUBSTANCES WITH YF = 0.03
Acetaldehyde
Acetone
Acrylonitrile
Amyl acetate
Amyl alcohol
Benzene
Butadiene
Butane
Butene
Butyl acetate
Carbon monoxide
Cyanogen
Cymene
Decane
Dichlorobenzene
Dichloroethane
Dimethyl ether
Dimenthyl sulfide
Ethane
Ethanol
Ethyl acetate
Ethyl amine
Ethyl benzene
Ethyl chloride
Ethyl formate
Ethyl propnonate
Furfural alcohol
Heptane
Hexane
Hydrocyanic acid
Hydrogen
Hydrogen sulfide
Isobutyl alcohol
Isobutylene
Isopropyl alcohol
Methane
Methanol
Methyl acetate
Methyl amine
Methyl butyl ketone
Methyl chloride
Methyl ethyl ketone
Methyl formate
Methyl mercaptan
Methyl propyl ketone
Naphthalene
iso - Octane
Pentane
Petroleum ether
Phthalic anhydride
Propane
Propanol
Propnonaldehyde
Propyl acetate
Propylene
Propylene dichlonde
Styrene
Tetrafluoroethylene
Toluene
Vinyl acetate
Vinyl chloride
Vmyhdene chlonde
Water gas
Xylene




EXAMPLES OF SUBSTANCES WITH YF = 0.06
Acrolein
Carbon disulfide
Cyclohexane
Diethyl ether
Divinyl ether
Ethylene
Ethyl nitrite
Methyl vinyl ether
Propylene oxide

EXAMPLES OF SUBSTANCES WITH YF = 0.19
Acetylene
Ethylene oxide
Ethyl nitrate
Hydrazine
Isopropyl nitrate
Methyl acetylene
Nitromethane
Vinyl acetylene
                      12-74
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     Each of the hazard zone  distances estimated by the program is associated with a
specific peak overpressure in the shock or blast wave and these in turn are related to specific
levels of expected damage using the information tabulated in Table 5 1 of this guide  Table
12 10 illustrates the format of the general results obtained from ARCHIE but shows the peak
overpressures associated with each level of damage or injury instead of a specific distance

     Results of the model provide emergency planning personnel with an indication of the
radii of the circular zones around the  center of the explosion that may be subject to
explosion impacts of various levels of seventy, thus additionally providing indications of the
number of people that may be killed or severly injured, and the number, characteristics, and
level of damage that may be sustained by buildings, homes, and other resources that may be
exposed to the shock or blast wave

     Major Assumptions of the Methodology

      Be advised that model results assume the surrounding area  is essentially flat and
without obstacles In actuality, potential reflections of the blast or shock wave from building
walls or the sides of other obstacles and surfaces may cause actual damage patterns to be
somewhat more erratic than those predicted by this generalized hazard assessment methodol-
ogy

12.25     HAZARD MODEL  MENU  OPTION J:  TANK OVERPRESSURIZATION
          EXPLOSION MODEL

      Purpose of Model

      The tank overpressunzation explosion model is used to evaluate the hazards resulting
from cases in which a sealed or inadequately  vented tank or container may be internally
overpressunzed by a gas or vapor to the point of violent rupture This type of explosion is
descnbed and discussed more fully in Chapter 5

      Required Input Data

      The model requires knowledge of

      •    The shape of the tank or container
      •    Pressure at which the tank or container will rupture (psia)
      •    Gas or vapor volume in the tank (ft3)
      •    Ratio of specific heats (Cj/Cv) for the gas or vapor
      •    Ambient environmental temperature (°F)
      •    Temperature of the gas or vapor in the tank (°F)
                                        12-75
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                                TABLE 12.10
               EXAMPLE OUTPUT FROM EXPLOSION MODELS
Peak Overpressure
(psia)
0.03
0.30
1.00 - 0.50
1.00
8.00 - 1.00
2.00
3.00 - 2.00
12.2-2.40
2.50
4.00 - 3.00
5.00
7.00 - 5.00
10.0
29.0 - 14.5
EXPECTED DAMAGE
Occasional breakage of large windows under stress.
Some damage to home ceilings; 10% window breakage.
Windows usually shattered; some frame damage.
Partial demolition of homes, made uninhabitable.
Range serious/slight injuries from flying glass/objects.
Partial collapse of home walls/roofs.
Non-reinforced concrete/cinder block walls shattered.
Range 90-1% eardrum rupture among exposed population.
50% destruction of home brickwork.
Frameless steel panel buildings ruined.
Wooden utility poles snapped.
Nearly complete destruction of houses.
Probable total building destruction.
Range for 99-1% fatalities among exposed populations due to direct
blast effects.
Note:   Output from the computer program shows Distance from Explosion in feet in place of
       Peak Overpressures shown here for reference purposes. See Table 5.1 of guide for
       additional information
                                       12-76
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     The first question asked by the program in cases where  the answer has not been
previously specified is the shape of the tank or other container  Valid choices are rectangular
tank, horizontal cylindrical tank, vertical cylindrical tank, and spherical tank  This particular
model cannot be used for pipelines

     Knowledge of the pressure  at which the tank will rupture when overpressunzed will
require some detective work since tank construction standards vary widely for different types
of hazardous materials. The best bet is to query the owner or operator of the tank, and if
necessary, the company that initially constructed the vessel for this information

     Prior to asking the user to provide the volume of the tank or other container that
contains compressed gas or vapor, an input parameter value that would otherwise require
several manual computations, the program asks if the user desires assistance in characterizing
the volume of the container and  the weights, volumes,  and  physical states of its contents
Further details on the Tank and Container Contents Characterization Subprogram and its
general  data  requirements are provided in Section 1229  of  this chapter. Use of the
subprogram may result in requests for a few informational items not listed above

      The ratio of specific heats for  the compressed gas or vapor is a  thermodynamic
property related to the amount of  heat necessary to increase the temperature of a unit weight
of gas or vapor by one degree under specified conditions Prior to request of this value, the
program  will provide the user  an opportunity to request  assistance in selection of an
appropriate specific heat ratio using several generalized rules-of-thumb (reproduced in Table
12 7) that require user knowledge of the chemical formula of the hazardous material being
evaluated. Be advised that the results of this particular model  are sensitive to the value
provided by the user. Accuracy of model results can and will be improved by provision of a
more precise value for the substance at or near the temperature in its container, but this is by
no means mandatory.

      As discussed in Chapter 2 of this guide, many properties of hazardous materials  are a
function of temperature, with one of the most important being the vapor pressure of the
substance (since this property will ultimately have a major effect on the magnitude of toxic
or flammable vapor dispersion threats). Consequently, for planning purposes, it is desireable
to select both tank and ambient environmental temperatures among the highest that may be
experienced during a typical year. In selecting these temperatures, note that the temperature
of the contents inside a metal tank can easily be 20°F or more higher than the ambient air
temperature on a sunny day

      Model Results and Usage
                                        12-77
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     The tank overpressurization explosion model produces a table which lists distances
from the explosion center associated with various degrees of injury and damage to people
and property. Each of the hazard zone distances estimated by the model is associated with a
specific peak overpressure in the shock or blast wave and these in turn are related to specific
levels of expected damage using the information tabulated in Table 5 1 of this guide  Table
12.10 illustrates the format of the general results obtained from ARCHIE, but shows the peak
overpressures associated with each level of damage or injury instead of a specific distance
Note that the model does not fully address the potential dispersion of high velocity tank or
container fragments that may result from the explosion and pose a threat to other containers
or stores  of hazardous materials or other vulnerable resources

     Results of the model provide emergency planning personnel with an indication of the
radii of  the circular zones  around the center of the explosion that may be subject to
explosion impacts of various levels of seventy, thus additionally providing indications of the
number of people that may be killed or severely injured, and the number, characteristics, and
level of damage that may be sustained by buildings, homes, and other resources that may be
exposed to the shock or blast wave.

     Major Assumptions of the Methodology

      Be advised that model results assume the surrounding area is essentially flat and
without obstacles In actuality, potential reflections of the blast or shock wave from building
walls or  the sides of other obstacles and surfaces may cause actual damage patterns to be
somewhat more erratic than those predicted by this generalized hazard assessment methodol-
ogy.

      Since most tanks or containers subject to this type of violent explosion or rupture are
likely to be on or near the ground, the  model assumes this location for the explosion in all
cases. See Chapter 5 for a discussion  of the difference between groundlevel and free air
explosions.  The latter type of event will typically produce specified damages over lesser
distances than those predicted for groundlevel explosions

1226 HAZARD MODEL MENU OPTION K: CONDENSED-PHASE EXPLOSION
       MODEL

      Purpose of Model

      This model is used to evaluate the hazards of solid or liquid explosive materials such as
nitroglycerine, TNT, dynamite, and a  wide  variety of lesser known substances with true
explosive properties. This type of detonation or  explosion is  more  fully described  and
discussed in Chapter 5.
                                        12-78
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     Substances most likely capable of detonation will be classified as explosives by the
DOT Explosives for which the model is applicable may also be formed at times during the
reaction of two or more substances which are not individually considered to have explosive
characteristics (see Chapter 7).

     Be advised that substances classified as blasting agents by the DOT, despite then-
name, are  considered to have a much lower  likelihood of exploding, even in accidents
involving fire or impact  See Chapter 8 for formal DOT definitions of blasting agents and
designated explosive materials

     Required Input Data

     The model requires only two input values, these being.

     •  Heat of combustion of the explosive material (Btu/lb)
     •  Weight of material at risk of exploding (Ibs)

     The heat of combustion  of a material is the amount of heat generated when a unit
weight of the substance is burned under specified conditions  The lower heat of combustion
ideally desired for model use is the amount of heat liberated when the material is burned m
oxygen at a temperature of 25°C (77°F) and the products of combustion, including any water
that may form, remain as gases The input screen for the parameter provides guidance for
selecting a  value when more precise data are unavailable. For informational purposes, it is
noted that the CHRIS Hazardous Chemical Data manual available at a cost of $41 from
branches of  the Government  Printing Office contains the desired  value for over 1200
hazardous  materials. This manual is widely  used by fire  service and other emergency
response personnel across the country and  is very  likely  to be  locally available  No
hazardous materials library would be complete without the document

     Model Results and Usage

     The model produces a table which lists distances from the explosion center associated
with various degrees of injury and damage to people and property  Each of the hazard zone
distances estimated by the program is associated  with a specific peak overpressure in the
shock or blast wave and these in turn are related to specific levels of expected damage using
the information tabulated in Table 5 1 of this guide Table 12 10 illustrates the format of the
general results  obtained from ARCHIE but shows the peak overpressures associated with
each level of damage or injury instead of a specific  distance.

     Results of the model provide emergency planning personnel with an indication of the
radii of the  circular zones  around the  potential explosion  site that may  be subject to
explosion impacts of various levels of seventy, thus additionally providing indications of the
                                        12-79
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number of people that may be killed or severly injured, and the numbei, characteristics, and
level of damage that may be sustained by buildings, homes, and other resources that may be
exposed to the shock wave

     Major Assumptions of the Methodology

     The model is the traditional TNT-equivalent procedure widely used for many years for
evaluation of high explosive detonation hazards A primary assumption, which is usually
quite valid for the types of explosives being considered, is that the blast or shock wave
produced by the explosion will dissipate in the same fashion as the explosion that would
occur if a weight of TNT having the same total energy of combustion were detonated.

     Since the explosive material is most likely to be on or near the ground surface when the
explosion occurs, the procedure assumes this location for the explosion in all cases See
Chapter 5 for a  discussion of the difference between groundlevel  and free air explosions
The latter type of event will typically pioduce specified damages over lesser distances than
those predicted for groundlevel explosions

     As in the case of the other types of explosions, be advised that model results assume
the surrounding area  is essentially flat  and  without obstacles  In  actuality, potential
reflections of the blast or shock wave from building walls or the sides of other obstacles and
surfaces may cause actual damage patterns to be somewhat more erratic than those predicted
by this generalized hazard assessment methodology.

12.27    REMAINING OPTIONS ON THE HAZARD ASSESSMENT MODEL SELEC-
          TION MENU

     Option L:  Review of Model Descriptions

     Selection of this option permits the user to view several screens of text containing bnef
descriptions of the models available from the Hazard Assessment Model Selection Menu

     Option M: Review of Model Selection Charts

     This option permits the user to view the model selection charts that were previously
presented in Figure 12 2

      Option N: Return to Main Menu

      As the title suggests, selection of this option returns the user to the Mam Task Selection
 Menu  Be advised that a return to this menu will "close" the Accident Scenario File (ASF)
                                       12-80
 image: 








being worked on while the Hazard Assessment Model Selection Menu is in use  In order to
make this ASF file active again, it will be necessary to select Option B from the Main Task
Selection Menu and recall the file into active service

12 28   USE OF THE VAPOR PRESSURE INPUT ASSISTANCE SUBPROGRAM

      Knowledge of the vapor pressure of a hazardous substance as a function of temperature
is an important prerequisite to an adequate evaluation of accident scenario results in most
cases There are likely to be many situations, even when some vapor pressure data points are
available for specific temperatures, however, when these data will be for temperatures other
that those needed by the program. Thus, the vapor pressure input assistance subprogram is
designed to facilitate characterization of the vapor pressure versus temperature relationship
for a hazardous substance regardless of whether detailed data are available or whether only
the data on a material safety data sheet are at hand  Upon a request of assistance from the
user at  one of the points  in the program that vapor pressures  are requested for specific
temperatures, the program will respond with a  short menu offering three options, these
being
     1
The user provides the vapor pressures at these temperatures
     2.   The user can provide whatever vapor pressure and other data are available
          and permit the program to estimate  the vapor pressures at the desired
          temperatures

     3    If available, the user can provide the coefficients for the Antome equation
          for the substance. Further information is given when this option is selected

     The first option is simply an escape mechanism for the user who arrives at this menu
unintentionally, and also, for the user who chooses one of the two following options, is not
satisfied with the results of the vapor pressure input assistance procedures, and desires to exit
the assistance subprogram

     The second option  takes advantage of any and all available  vapor pressure data sets
(where a set is defined to be a specific vapor pressure and  related temperature) for the
substance of interest  Selection of this option results in a series of questions  to the user
alternated with information screens The general order of events is

     1.   The user is asked if he or she has the vapor pressure for the material at a
          temperature of 68°F (20°C), this  being a  vapor  pressure  available on
          material safety data sheets for most volatile substances  If the user answers
          yes, he or she is next asked to choose the units in which the vapor pressure
          will be provided  Choices include pounds per square inch - absolute (psia),
                                        12-81
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     atmospheres  (atm) , millimeters  of mercury (mm  Hg), Pascals  (Pa),
     Newtons per square meter (N/m2), and Bars  (Note Definitions of these
     units appear in Chapter 2 of this guide ) Once the value has been input in
     the specified set of units, the program lists the vapor pressure provided in
     all sets of available units and asks the user to confirm that the value was
     entered properly.

2.   The vapor pressure of any substance, as noted in Chapter 2, is always 760
     mm Hg or the equivalent at its normal boiling point temperature  at one
     standard atmosphere  The program will report this fact to the user simply
     for informational purposes.

3.   The subprogram will now  have a least  one data  set and possibly two
     Although the subprogram can generate a curve of vapor pressure  versus
     temperature from two points, the curve would not be very accurate  Thus,
     the  subprogram continues with a  question asking if the user has a vapor
     pressure at another temperature  A yes answer from the user will result in a
     choice of units for the  vapor pressure, a request for input of the vapor
     pressure value, a choice of units for the related temperature, a request for
     input of this temperature, and a screen seeking confirmation that the data
     has been entered properly If three data  sets  are now  available,  the
     subprogram will skip to item 5 below Otherwise, it will repeat this step
     until it receives a no answer to its initial query.

4   If only one or two data sets are available  at this point, the subprogram will
      ask the user if the substance is flammable or combustible  A  yes  answer
     will result in requests for the lower flammable limit (LFL) of the substance
      in volume  percent and its flash  point (closed cup preferred) in  degrees
      Fahrenheit if they are available. These data will be used to generate a data
      set based  on the  assumption that the flash point of  a substance  is
      theoretically  equivalent to the temperature at which  its vapor pressure
      provides a vapor concentration equivalent to its LFL

 5.   If only one data set is available after all of the above steps, the  subprogram
      will inform the user that available data are insufficient and return him or her
      to the opening menu of the subprogram  If two data sets are available, the
      user will be warned  of the potential inaccuracy of vapor pressure estimates
      and will be shown vapor pressure predictions for the normal boiling point
      temperature of the hazardous material, the temperature of the material in its
      tank  or other container, and the ambient environmental temperature  A
      final question will ask if the predictions  appear  to be  of acceptable
                                    12-82
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           accuracy. If three data sets are  available, the subprogram will directly
           proceed to a display of the above predictions and  ask if  results  are
           acceptable  If they are, it will then display the Antoine equation coeffi-
           cients derived from the input data and the temperature bounds in which the
           equation should produce fairly accurate results.

     Several excellent reference sources  of chemical property data contain tables of vapor
pressure versus temperature for literally hundreds of substances, as  well as  a wide variety of
other data useful for hazard assessment purposes  Among the more  readily available of these
references m libraries and often in the possession of local chemical engineers and chemists
(including possibly the local high school chemistry teacher) are

           Perry's Chemical Engineers' Handbook, McGraw-Hill Book Company,
           New York, NY  (various editions have different editors and  publication
           dates).

           Weast, R C, et al, ed 's, CRC Handbook of Chemistry and Physics, CRC
           Press, Boca Raton, FL (various editions have different publication dates)

     The third option on the opening menu to the  subprogram, as noted above, asks if the
user has access to the Antoine equation coefficients for the hazardous material of interest
For those who may not be familiar with this equation, be advised that it is a commonly used
equation with  three coefficients  When provided a  temperature within the range  of
temperatures for which it is applicable, it predicts  the vapor pressure associated with this
temperature  Each hazardous material has its own relatively unique set of coefficients that
can be found in various data sources.  Two excellent sources of Antoine coefficients and
considerable other data for a large number of chemicals include.

           Reid, R C, et al, The Properties of Gases & Liquids, McGraw-Hill Book
           Company, New York, NY

           Dean, J A,  ed.,  Lange's Handbook of Chemistry, McGraw-Hill Book
           Company, New York, NY.

Various editions of both of these books  have  differents publication dates, but all contain
valuable data and information  The first book lists Antoine coefficients for almost 600
materials in its 4th edition. The second has coefficients listed for over 900 substances in its
most recent editions

     The general form of the Antoine equation is

                      log(P) or In(P) = A - (B / (T + C))
                                      12-83
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where A, B, and C are the three coefficients, T is the temperature at which the vapor pressure
is desired, and P is the vapor pressure (shown on the left side of the equal sign as the log or
natural log of the pressure).

     Different reference sources use different units for the various coefficients and other
parameters associated with the equation, so the subprogram begins with a series of question
designed to determine the specific units for which the coefficients on hand are valid These
initial questions request*

     •     An indication of whether the left side of the equation provides the log or
           natural log of the vapor pressure (P)

     •     An indication of whether the equation uses temperatures  (T) in units of
           degrees Celsius or Kelvin

     •     An indication of whether the vapor  pressure predicted  is in  units of
           millimeters of mercury  (mm Hg), Pascals (Pa), Newtons per square meter
           (N/m?), or Bars

      •     An optional specification of the temperature range over which the equation
           is valid

      Once the program has confirmed that the user has entered this information as he or she
 intended, it proceeds  to request the three equation coefficients  It then predicts vapor
 pressures for the normal boiling point temperature of the hazardous material, the temperature
 of the material in its tank or other container, and the ambient environmental temperature  A
 final question asks if the predictions appear to be of acceptable accuracy.

 12.29  USE  OF THE TANK AND CONTAINER CONTENTS CHARACTERIZATION
        SUBPROGRAM

      A user of ARCHIE will very often have knowledge of the dimensions of a tank or other
 container of the hazardous material of concern, the temperature and pressure of its contents,
 and some idea of how full  it might be on average or when m peak use  The tank and
 container contents characterization subprogram helps the user in  translating this information
 into the weights,  volumes, and other characteristics of the container and its contents that are
 required  by ARCHIE, thus reducing or eliminating the need for  a variety of manual
 calculations. The subprogram is available from any input parameter screen in ARCHIE that
 requests the weight of the hazardous material in the tank or the volume of the tank that
 contains a compressed gas. Be advised that use of the subprogram is highly recommended
 since denial of this offer of assistance creates a situation in which  ARCHIE must accept input
 data from the user without being able to ensure that all data are consistent
                                       12-84
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     Use of the subprogram is very  straightforward  First, it asks for several but not
necessarily all of the following input parameter values if these have not previously been
provided, including the:

     •     Shape of the tank or other container
     •     Length, width, height, and/or diameter of the tank as needed
           Molecular weight of the contents
     •     Normal boiling point temperature of the contents (°F)
     •     Vapor pressure of the material in the container (psia)
     •     Temperature of the material in the container (°F)
     •     Ambient environmental temperature (°F)
     •     An indication of whether or not the tank contains any liquid
     •     Specific gravity of the liquid, if applicable

     Once the above list of information has been obtained, the subprogram follows with
what might be the most important question of all (presuming the user has earlier indicated
there is liquid in the tank), this being "Which of the following do you know about the tank
contents?".

     1     Amount of liquid in the container in gallons
     2     Amount of liquid in the container in pounds
     3     Amount of liquid in the container in cubic feet
     4.    Height of liquid in the container as measured from its bottom
     5     Percentage of container filled with liquid
     6     None of the above

     Selection of one of these options and input of the appropriate answer leads to a screen
in which the dimensions of the tank and the characteristics of its contents are listed  A final
question asks if the user wishes to repeat the procedure (in case some item or another looks
in error). A yes answer leads to a screen summarizing user input values and asking which
ones should be changed A  no answer takes the user back to where he or  she was in
ARCHIE prior to  entering this subprogram

12.30   OTHER COMPUTER PROGRAMS

     There are a number of other computer programs that may be of interest to emergency
planning and response personnel  The EPA document entitled Identifying Environmental
Computer Systems for Planning Purposes (Preparedness and Prevention Technical Assis-
tance Bulletin #5) provides a checklist of computer system needs related to hazard analysis
and  information  on other  available systems applicable to local  planning efforts. The
checklist addresses a variety of systems for  air dispersion and other environmental modeling,
for access  to chemical properties data, and for emergency response  planning. Note that
                                       12-85
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different systems,  particularly those associated with consequence analysis, may provide
differring results due to varying assumptions made during model formulation by system
developers.
                                         12-86
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              13.0 FORMULATION OF A PLANNING BASIS
13.1  INTRODUCTION

     Chapter  10 of this  guide provides guidance  pertaining to the identification and
characterization of those activities or operations within a specific community or jurisdiction
that involve the use, storage, or transportation of hazardous materials and which therefore
pose some degree of hazard or risk to the public. Chapter 11 of the guide provides the data,
methods, and procedures necessary to estimate the probability of an accident associated with
each of these  activities or operations. In addition, the chapter provides an  opportunity in
many cases to  assess the probabilities associated with different levels of accident seventy and
discusses  how to analyze  scenarios with consequence analysis  procedures. Chapter  12
continues with a discussion of the ARCHIE program and its individual models that may be
used to evaluate many of the specific consequences of a spill, discharge, fire, or explosion
involving hazardous materials

     Planning personnel who apply the procedures presented in the referenced chapters will
obtain a great  deal of knowledge and insight into the specific threats facing their jurisdiction
from hazardous materials. Some may wish to use this knowledge  directly in an  attempt to
plan for all possible scenarios, and are not discouraged from .doing so if the time  and
resources available  are sufficient for this endeavor. For all intents and purposes, the entire
set of accident scenarios identified and considered during  the  hazard  analysis will m
aggregate become the basis for their planning effort and they may proceed to Chapter 14

     Those who do not have the resources available to plan for every possible contingency,
or who have other threats competing for attention, may wish to limit then- planning efforts for
hazardous materials by focusing on the most important situations This can be accomplished
by screening  accident scenarios  to identify those that have a reasonable likelihood of
occurrence in  the foreseeable future and/or which may have significant consequences in the
absence of an  organized, rapid,  and effective response effort It is the purpose of Chapter 13
to assist these  latter personnel in such a screening effort via a simplified risk analysis process.
The set of scenarios that remain after this process will then provide a planning basis for their
jurisdiction

13.2   DEFINITION OF ANNUAL ACCIDENT PROBABILITY CATEGORIES

     Each of the accident scenarios identified during prior efforts should first be classified
into five  categories based on the annual probability  determined for  the scenario using the
methods described in Chapter 11 of this guide The categories of interest include-
 image: 








     •     Common accidents,
     •     Likely accidents,
     •     Reasonably likely accidents,
     •     Unlikely accidents, and
     •     Very unlikely accidents

     Common accidents are defined heiein as events expected to occur one or more tunes
each year on average. Such incidents have occurred in the locality of concern in the past and
are likely to reoccur with some regularity.

     Likely accidents are defined herein as events expected to occur at least once every 10
years on average according to available statistics. Given the rapid increase in production and
usage of hazardous materials in the last 10 to 20 years, this type of accident is not one that
has necessarily occurred in the past in any given community, yet there is a 10% or greater
chance that it can occur in any given future year based on current levels of activity.

     Reasonably likely accidents are events predicted to occur between once every 10 years
and once every 100 years on average. There is somewhere between a 1% and 10% chance of
such an event occurring  in  the locality of concern in any given  year for the identified
scenario. In that  similar scenarios involving different materials may also occur, the overall
likelihood of an event requiring a certain type of emergency response could  be much higher.
(Note: This is equally true for the other categones.)

     Ujilikely accidents are events predicted to occur between once every 100 years and
once every 1000 years on average in a  specific locale. They are unlikely to  occur within the
foreseeable future or during the lifetime of current inhabitants. Chances of their occurring in
any given  future year are less  than  1% and possibly as low as  0.1% for each specific
scenario.

     Very unlikely accidents are events predicted to occur less than once in  1000 years  The
odds are at least  100  to 1 against such an event occurring in the next 10 years in a specific
locale.  The chances of one occurring in any particular future  year are less than one  m a
thousand.

     If one is only evaluating releases qualitatively, common and likely accidents may be
equated to "high", reasonably likely and unlikely accidents to "medium", and very unlikely
accidents to "low" probability categones.
                                         13-2
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13.3  DEFINITION OF ACCIDENT SEVERITY CATEGORIES

     It is also necessary to classify accident scenarios according to their seventy as defined
via application of  consequence analysis  procedures. To assist in this  effort,  accident
consequences are classified into the four categones defined below, these being*
           Minor accidents,
           Accidents of moderate seventy,
           Major accidents, and
           Catastrophic accidents
     Minor accidents are specified herein as those with the potential to have one or more of
the following features.

     •     Low potential for senous human injuries.

     •     No potential for human fatalities.

     •     No need for a formal evacuation, although the public may be cleared from
           the immediate area of the spill or discharge.

     •     Localized, non-severe contamination of the environment which does not
           require costly cleanup and recovery efforts

     •     No  need  for resources beyond those normally and currently available to
           local response forces

     Accidents are specified herein  as of moderate seventy when they have the potential to
have one or more of the following features:

     •     Up to 10 potential human fatalities.

     •     Up to 100 potential human injuries requinng medical treatment or observa-
           tion.

     •     Evacuation of up to 2000 people

     •     Localized contamination of the environment requinng a formal but quickly
           accomplished cleanup effort

      •     Possible assistance needed from county and state authorities.
                                         13-3
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      •     Only limited need for specialized equipment, services, or materials for a
           rapid and effective response.

      Major accidents are specified herein as those with the potential to have one or more the
following features:

      •     Up to 100 potential human fatalities

      •     Up to several hundred potential human injuries requiring medical treatment
           or observation.

      •     Evacuation of up to 20,000 people

      •     Significant contamination of the  environment requiring  a formal and
           somewhat prolonged cleanup effort.

      •     Assistance needed from county, state, and possibly federal authorities

      •     Significant need for specialized  equipment, services, or materials for a
           rapid and effective response.

      Catastrophic accidents are defined as those having the potential to have one or more of
the following features:

      •     More than 100 potential human fatalities

      •     More than 300 potential human injuries requiring formal medical treatment

      •     Evacuation of more than 20,000 people.

      •     Significant contamination of  the environment requiring a formal, pro-
           longed, and  expensive  cleanup effort to protect human health and the
           environment.

      •     Assistance needed from county, state, and federal authorities

      •     Significant need for specialized  equipment, services, or materials for a
           rapid and effective response.

      Which  category  a given scenario falls into  can be  determined by  considering
consequence analysis results along with local maps and population data
                                        13-4
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     There are two points to be made about the accident seventy categones defined above.
The first is that they do not represent hard and fast rules  What some people may perceive as
a minor or routine incident may seem to be a major event  to others  Do not hesitate,
therefore, to  make any changes to the procedure if some point  or another  makes you
uncomfortable  After all, the authorities in a major city are likely to deal with loss of life and
senous injuries due to various "non-natural" causes on almost a daily basis. It is understand-
able that they may have a different perspective on such events than the authorities of a small
and quiet town in a rural part of the country.

     The second point to be made is that the accident seventy categones above are partially
defined in terms of potential deaths  and injuries. It must be realized that consequence
analysis procedures essentially provide estimates of the area or zone that may be subjected to
harmful levels  of airborne contaminants, thermal radiation, and/or  explosion overpressure
Although people within such an area will have a definite potential to be killed or injured, a
large fraction may actually escape unharmed  Reasons for this are varied and complex, but
think about how many times the evening news has  shown a community devastated by a
tornado, with dozens of buildings and homes knocked flat, and only reported a death or two
(if any) and a handful of injuries

13.4  APPLICATION OF SCREENING GUIDELINES

     Figure 13.1 presents a matrix of accident probability categones versus accident seventy
classes  Each block of the matrix  suggests a planning approach to be taken for accident
groups that meet cntena associated with the block. These approaches are only suggestions
and should be treated as such.  Special circumstances may require special consideration on a
case by case basis. Specific guidelines should be worked out by each locale to best represent
the resources and relationships between organizations applicable to that community.

     The matrix should be applied only at the level of government or industry that identified
and analyzed the planning basis scenanos for a particular locale or jurisdiction  The reason
for this stems from  the fact that levels of authonty above the local  level typically have
responsibility for several individual junsdictions Since there is a higher probability that a
particular type of accident will take place within a large junsdiction than in a specific smaller
one within its borders  (e g,  a county  vs. a town), a  higher level of authonty may find it
necessary to plan for accidents that are too rare to worry about at a lower level This does not
mean, however, that all junsdictions should not work together in coordinating their response
to rare  events  Rather, it means that the higher level authority should  probably  take  a
leadership role in such instances
                                        13-5
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                              FIGURE 131
       ACCIDENT  FREQUENCY/SEVERITY  SCREENING  MATRIX
o
a
0)
CD
     I-T-)
                                   Severity
            Reasonably
               Likely
              Comprehensive planning and preparedness are essentially
              mandatory at the appropriate levels of government or industry
              Comprehensive planning is optional and does not necessarily
              warrant any major efforts or costs  Give consideration to
              sharing any necessary special response resources on a regional
              basis
              Comprehensive planning may be unwarranted and unnecessary
                                      13-6
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     The frequency (annual probability) has been reduced to three categories to reflect the
fact that the treatment of individual scenarios may produce low annual probabilities, yet the
chance of a similar accident involving one of a number of different hazardous materials may
be much higher. The original five categones may be used to prioritize accident scenarios
more precisely within the broader categones.

13.5  MOTIVATION FOR CONTINUED PLANNING

     The EPA recently sponsored an intensive effort to determine the number and severity
of accidents involving hazardous material releases in the six-year period of 1980-1985. The
total number of deaths  recorded was 138, for an average of 23.0 per year, for the  entire
United  States.  The annual average  expected for any jurisdiction of 100,000 people can
therefore be computed as being on the order of 0.01 per year.  Given that the identification of
deaths due to all episodic hazardous material accidents is difficult due to current reporting
requirements, it is  likely that the EPA underestimated the true  extent  of the problem.
Nevertheless, the fatality rate would still be relatively minor even if multiplied by 10 or even
100.

     These figures  can be compared to annual mortality statistics in the United States  to put
the overall problem of hazardous materials into the proper perspective. To help do this,
Table 13.1 presents annual mortality rates for a variety of natural and accidental causes of
death using statistics for recent years.  The actual number of deaths that may be expected
each year on average due to any specific cause in any particular jurisdiction can be obtained
by multiplying the annual mortality rate for that cause by the population of concern.

     Given the above findings one might wonder why there is such widespread concern
about the dangers  of hazardous materials. The answer to this question is actually quite
complex.  Part  of it involves the fact that recent major accidents  in other countries have
demonstrated the potential for a single accident to cause hundreds if not thousands of deaths
and injuries. Although the safety record of the U S. chemical industry has generally been
excellent, in terms of loss of life, people here (including government agencies) have naturally
felt a need to reassess safety standards and ensure our country is prepared to deal with  future
emergencies. Yet another part of the answer involves the realization that hazardous material
accidents differ greatly from more typical accidents and require special preparations  for an
effective response   Indeed, it is precisely a lack of knowledge about chemical threats  facing
a community, and a lack of specific preparations to counter these threats, that can lead to a
disaster that may otherwise have been prevented

     Finally, it must be appreciated that the general public has a greater fear of threats that
can cause multiple fatalities, threats they may not fully understand or have any control over,
and threats due to activities that do not provide a direct benefit  on an individual basis. The
                                         13-7
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                        TABLE 13.1

         ANNUAL INDIVIDUAL MORTALITY RATES FOR
         NATURAL AND ACCIDENTAL CAUSES OF DEATH
Cause of Fatality
All Diseases
Heart Disease
Cancer
Cercbrovascular Disease
Pneumonia
Diabetes
All Accidents
Motor Vehicles
Falls
Drowning
Fires, Burns
Natural Hazards and Environmental Factors
Cataclysm (tornado, flood, earthquake, etc.)
Excessive Heat
Excessive Cold
Lightning
Risk of Fatality
(per 100,000 people)
830
320
190
64
28.3
15.5
39
19
5.0
2.2
2.1
0.8
0.09
0.09
0.40
0.04
Source:   Accident Facts. 1988 Edition, National Safety Council
                            13-8
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reasons why tens of thousands of highway deaths are tolerated each year partially stem from
the facts that they usually occur one or two at time, individuals have control over whether
they drive or nde in automobiles, and because automobiles are perceived to provide a
substantial benefit to each individual.
                                         13-9
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               14.0  USE OF HAZARD ANALYSIS RESULTS
                        IN EMERGENCY PLANNING
14.1 INTRODUCTION

     Planning personnel who have followed the preceding guidance of this document should
have gained considerable insight into the true problems and nsks associated with hazardous
materials in their respective jurisdictions  Additionally, they should have an understanding
of the probability, nature, and likely consequences of potential  accidents. It remains to
discuss how this knowledge  can be best utilized during plan preparation to ensure prompt,
efficient, and effective response to actual emergencies

     The discussions that follow are intended to  supplement guidance provided by the
National Response Team in the Hazardous Materials Emergency Planning Guide (NRT-1)
That particular publication discusses how to organize the overall emergency planning process
and provides a suggested outline for the resulting plan, an outline that contains numerous
important topics not directly associated with hazard analysis  results but vital to the
completion of a comprehensive emergency plan  In contrast, this chapter mostly limits itself
to planning issues directly related to findings of a hazard analysis and has the objectives of 1)
providing more detailed guidance in this topical area than found in NRT-1; and 2) bridging
the gap between this guide to hazard analysis and other  more comprehensive publications
devoted to emergency planning and/or emergency response to emergencies.

     Readers are  advised that this  chapter focuses on planning for significant incidents
involving spillage or discharge of a hazardous material and not the minor types of spills or
leaks that are relatively common and of a routine nature. In addition, it should be noted that
chapter contents are only intended  to  give readers a strong push  in the right  direction.
Decisions will be necessary  on a case by case basis as to whether any particular planning
activity is desired  or considered warranted by local conditions Special  or unique circum-
stances may require planning efforts and activities not addressed by this chapter.

     Finally, be advised that the chapter is directed to planning personnel in state and local
governmental  agencies. Although much of the guidance and discussion presented in the
chapter is also applicable to  emergency planning for specific industrial sites, such sites are
likely to have additional planning needs not addressed herein  For the benefit of industrial
planning personnel, a later section of the chapter references specific publications better suited
to the needs of industry for development of m-plant emergency response plans.
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143 ORGANIZATION OF THE CHAPTER

     Chapter 14 addresses 43 separate topics associated with emergency response planning
in 12 subject areas, with Table 14.1 serving as an overall index. These topics are assigned
unique "item" numbers for reference and organization purposes

     Each topic is presented and discussed in an individual section of the chapter  using a
standardized format Each  of these sections denotes the circumstances under which the
planning item is applicable, states the planning goal to be achieved, suggests one or more
action items for accomplishment of this goal, and ends with a brief discussion of the overall
topic. Planning personnel should refer  to the Hazardous Material Emergency Planning
Guide for advice on how to organize results of their planning activities into their final written
plan.

14.3 ADDITIONAL SOURCES OF PLANNING GUIDANCE AND INFORMATION

     Additional details on what to plan for, how to plan, and how to manage response to an
overall incident involving spillage  or discharge  of a hazardous material can be found in
numerous other publications.

     Publications of the Federal Emergency Management Agency

     Given that FEMA is the primary agency of the federal government having responsibili-
ty for planning for all types of emergencies with the potential to threaten public health and
safety in the United States, and that the agency employs numerous personnel who are experts
in this field, it is not surprising to find that FEMA has published several documents that can
be extremely useful to state and local  planning agencies as well as industrial facilities.
Indeed, it is strongly recommended that planning personnel obtain, review, and make use of
at least the following three documents  while planning for emergencies related to  non-ra-
dioactive hazardous materials.  Chapter 1 provides information on how these documents may
be obtained, though it is highly likely that  most  governmental emergency preparedness
organizations (particularly civil defense agencies) will already have copies of the first two
publications on hand.

     •     Guide for Development of State and Local Emergency Operations Plans

     •     Guide for the Review of State and Local Emergency Operations Plans

     •     Hazardous Materials Contingency Planning Course (student manuals)
                                       14-2
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     The planning course is designed to be presented by a trained instructor and involves the
viewing of several video tapes in the classroom. Nevertheless, several of the nine separate
student  reference manuals  contain  truly excellent and highly detailed information and
guidance on important topics that could only be allocated a few paragraphs of general
discussion in this chapter.

     Publications of the Disaster Research Center

     Individuals wishing to obtain a more formal and indepth "education" with respect to
problems and issues associated with emergency planning and response are advised to request
a publication list from the Disaster Research Center, University of Delaware, Newark,
Delaware,  19716 (telephone  302-451-6618).  A representative sample  of some excellent
books, reports, and articles of potential value to both public and industrial planning personnel
includes.

     •     Tierney, K.J., A Primer for Preparedness for Acute Chemical Emergen-
           cies, Book and Monograph #14,1980.

     •     Quarantelh, E L, Organizational Behavior in Disasters and Implications
           for Disaster Planning, Report Senes #18,1985.

           Quarantelh,  E.L, and Gray,  J.,  First  Responders  and  Their  Initial
           Behavior in Hazardous Chemical Transportation Accidents, Preliminary
           Paper #96,1985

     •     Gray, J,  Three Case Studies of Organized Responses  to  Chemical
           Disasters, Misc  Report #29,1981.

     •     Quarantelli, EL,  People's Reactions to Emergency Warnings,  Article
           #170,1983.

     •     Quarantelli, EX.,  et al, Evacuation Behavior and Problems: Findings
           and Implications from the Research Literature, Book and Monograph
           Senes #18,1984

     •     Quarantelh, E.L,  et al, Evacuation Behavior: Case Study of the Taft,
           Louisiana Chemical Tank Explosion Incident, Misc Report #34,1983

     Publications Oriented Towards Industrial Emergency Planning

     Guidance documents  particularly suited to the task of emergency  planning for the
protection of employees and property within the boundaries of individual industrial facilities
include:
                                        14-3
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     •    Site Emergency Response Planning, Chemical Manufacturers Association,
          1986. See Chapter 1 for  information on obtaining publications of this
          organization.

     •    Newton,  JE.,  A Practical Guide to Emergency Response  Planning,
          Pudvan Publishing Co,  1935 Shermer Road, Northbrook, Illinois, 60062,
          1987 (telephone 312-498-9840)

     Other Books and Reports

     Dozens of books and manuals pertaining to planning or management of hazardous
material emergencies have been written over the years, with literally a flood  of  such
publications (some  good,  some not so good) appearing in the  aftermath of  the Bhopal
tragedy. A sample of publications worthy of special mention (who due apologies to authors
whose works were not identified or reviewed) includes

     •    American Petroleum  Institute, Developing a Highway Emergency Re-
          sponse Plan for Incidents Involving Hazardous Materials, API Recom-
          mended Practice 1112, available from the API,  1220 L Street Northwest,
          Washington, D.C., 20005, November 1984

     •    Bennett, G R, et al, Hazardous Materials Spills Handbook, McGraw-Hill
          Book Company, New York, 1982.

     •    Cashman, J.R, Hazardous Materials Emergencies Response and Control,
          TECHNOMIC Publishing Company, 851 New Holland Avenue, Box 3535,
          Lancaster, Pennsylvania 17604,1983

     •    International Association of Fire Chiefs, Fire Service Emergency Manage-
          ment Handbook, available from IAFC Foundation, 101 E Holly Ave -
          Unit 10B, Sterling, VA 22170, January 1985

          Omohundro, J.T,  Oil Spills: A Public Official's Handbook, Report No
          PB80-184351, prepared for the National Oceanic and Atmospheric Admin-
          istration, available from  the  National  Technical Information  Service,
          Springfield, VA 22151, March 1980.

     •    Shaver,  D K.,  and Berkowitz, R L, Guidelines Manual: Post Accident
          Procedures for  Chemicals  and  Propellants,  Report  No  AFRPL
          TR-82-077, prepared for the Air Force Rocket Propulsion Laboratory and
          the U.S.  Department of Transportation,  available  from the National
          Technical Information Service, Springfield, VA 22151, January 1983
                                      14-4
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Shaver, D K., Berkowitz, R.L., and Washburne, P.V., Accident Manage-
ment Orientation Guide, Report No. AFRPL TR-82-075, prepared for the
Air Force Rocket Propulsion  Laboratory and  the U.S. Department  of
Transportation, available from the National Technical Information Service,
Springfield, VA 22151, October 1983.

Smith, A J., Jr, Managing Hazardous Substance Accidents, McGraw-Hill
Book Company, New York, 1981.
                             14-5
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                                   TABLE 14.1
                          INDEX TO PLANNING ITEMS
      Item No.                              Subject                          Page
Notification
    Nl     Initial Notification of Spills                                        14-8
    N2     Notification of Response Organizations and Public Authorities           14-9
    N3     Facilities Requiring Special Notification                             14-11
    N4     Notification of Water Users                                        14-12
    N5     Notification of Water Treatment Plants                              14-13
    N6     Notification and Shutdown of Electric and Gas Utilities                 14-14
    N7     Notification and Control of Air, Rail, and Waterborne traffic            14-15
Command and Communications
    CC1    Establishment and Staffing of Command Posts                        14-16
    CC2    Establishment of Emergency Communications Systems                 14-19
    CCS    Formulation of Response Objectives and Strategy                     14-21
    CC4    Ensuring Health and Safety at Incident Sites                          14-23

Evacuation
    EV1    Designation of Decision Responsibility for Public Protective Actions      14-26
    EV2    Criteria for Evacuation and Shelter-in-Place Decisions                  14-27
    EV3    Public Alert/Notification/Lnstruction Procedures                       14-29
    EV4    Transportation Functions                                          14-31
    EV5    Care and Shelter of Evacuees                                      14-33
    EV6    Security of Evacuated Hazard Zones                                14-35
    EV7    Movement and Care of Domestic Livestock and Pets                   14-36

Fire Response
    FF1     Special Firefighttng Equipment and Materials                         14-38
    FF2     Identification of Water Sources in Rural Areas                        14-39

Health Care
    HC1     Establishment of Special Rescue Squads                              14-40
    HC2    Provision of Ambulance Services                                   14-42
    HC3     Establishment of a Mass Casualty Plan                               14-43

Personal Protection
    PP1     Availability of Respiratory Protective Devices                         14-46
                                       14-6
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                             TABLE 14.1 (Continued)
                          INDEX TO PLANNING ITEMS

      Item No.                               Subject                          Page

Personal Protection
    PP2     Availability of Special Protective Clothing                           14-48
    PP3     Decontamination of Exposed Protective Clothing and Other Response    14-50
            Equipment

Public Relations
    PR1     Public Relations in Emergency Situations                            14-51

Spill Containment and Cleanup
    SCI     Plugging/Stopping of Leaks                                       14-54
    SC2     Suppression of Hazardous Gas or Vapor Releases                     14-56
    SC3     Containment of Spills of Liquids or Solids on Land                    14-59
    SC4     Cleanup of Spills of Liquids or Solids on Land                        14-61
    SC5     Containment of Spills into Water Bodies                             14-63
    SC6     Cleanup of Spills into Water Bodies                                 14-65
    SC7     Support Services for Field Response Forces                          14-66
    SC8     Maintenance of Apparatus and Equipment                           14-67

Spill Documentation
    SD1     Documentation of Response Activities and Costs                      14-68

Spill Monitoring
    SMI    Momtonng of Atmospheric Conditions                              14-69
    SM2    Momtonng of Contaminant Concentrations                          14-70

Post-Spill Recovery
    SRI     Provision of Alternate Water Supplies                               14-71
    SR2    Cleanup of Dead or Contaminated Livestock or Wildlife                14-72
    SR3     Post-Incident Testing for Contamination                             14-73
    SR4    Structural Inspections after Fires or Explosions                       14-74
    SR5    Provision of Post-Incident Recovery Services                         14-75

Training
    TR1    Training of Response Personnel                                    14-76

Waste Disposal
    WD1    Disposal of Hazardous Wastes                                     14-77
                                        14-7
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ITEM#N1

Topic:   Initial Notification of Spills

When/Where Applicable.     Any locale with hazardous material spill or discharge poten-
                            tial
               I
Planning Goal:              Establishment of central contact pomt(s) for initial notification
                            of spills to facilitate response plan activation

Action Items:

      •     Identify the 24-hour telephone number(s) that is  (are) to be called by
           members of the public, industry personnel, and government employees to
           report a spill or discharge or any situation that could result in such an event
           in the near future.

      •     Identify and list the information that should be requested from the caller to
           facilitate initial assessment of the gravity of the situation

      •     Ensure that all parties have been advised of reporting procedures

Discussion:

      Ordinary citizens are likely to call local police or fire departments if they observe an
accident, and it is reasonable to  assume that most jurisdictions will not discourage the
practice. This does not mean, however, that one of these organizations must always serve as
the central point of contact for coordinating communications during hazardous material
emergencies. A better choice in  some jurisdictions may be  a predesignated emergency
command post or emergency operations center at either the local or county level that has
regular telephone, "hot" line, and/or radio communications links with response forces, public
authorities, and major industrial complexes

      Li localities with major fixed-site potential spill  sources, it is vital that all facility
operators know exactly when and where to call to report an incident to local government
authorities, and that all public officials in the area are in agreement as to required notification
procedures. Bluntly  stated,  the planning group should  make every effort to resolve "turf
battles" and interagency squabbles as well  as the real  (yet sometimes  political) needs of
elected officials.
                                         14-8
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ITEM#N2

Topic.   Notification of Response Organizations and Public Authorities

When/Where Applicable     Any locale with hazardous material spill or discharge poten-
                            tial

Planning Goal.              Rapid activation of emergency response  forces at a level
                            consistent with the known gravity of the situation
Action Items
      •     Provide the central contact point(s) with  instructions  and  procedures
           relating to alert or call-out of response forces, including the individual or
           his/her alternates with command responsibility for spill response in the
           jurisdiction of concern

Discussion:

      The watch-stander or dispatcher who first receives notification of an accident involving
hazardous materials should have fairly detailed instructions with respect to who should be
notified of the event and/or who should be asked to respond  Minor incidents may simply
require dispatch of a fire department to the scene.  More significant events may necessitate
call-out of additional forces and notification of county, state, and federal authorities  In any
case, it should be clear to all as to who will be alerted under varying circumstances and who
will be in charge of response actions during various phases of an emergency situation.

      Communities that frequently experience hazardous material emergencies of a minor
nature but are only rarely faced with more significant events may wish to consider a staged
response  For example, depending on the seventy of the situation as described by the initial
caller, various levels of response might  be established, thus avoiding the immediate need to
call out forces in strength for all incidents  Personnel amvmg at the scene could, of course,
request additional  assistance  and thereby raise the level or stage  of response, much as
additional alarms might be sounded during major fires or the threat thereof

      One strategy to be considered for establishing levels of response classifies responses
into three levels as follows*

      Level 1  An incident which can be controlled by the first response agencies and
      does not require evacuation of other than the involved structure or the immediate
      outdoor area The incident is confined to a  small area and  does not pose an
      immediate threat to life or property

      Level 2 An incident involving a greater hazard or larger area  which poses a
      potential threat to life or property  and which may require a limited evacuation of
      the surrounding area
                                         14-9
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     Level 3: An incident involving a severe hazard or a large area which poses an
     extreme threat to life and  property and  will probably require a large scale
     evacuation; or an incident requiring the expertise or resources of county, state,
     federal, or private agencies/organizations

     If military explosives can be found in the region of concern at times, the plan should
identify the nearest military base that can provide assistance with these materials  Similarly,
where radioactive  materials may  pose a threat, it should identify the nearest radiological
emergency assistance team established by the Department of Energy or the state (see NRT-1
for DOE regional contacts).  Where etiologic materials (those posing biological or biomedi-
cal hazards)  may be encountered, it is  well to list the emergency information telephone
number for the Director of the Center of Disease Control in Atlanta, Georgia,  this being
404-633-5313. Other important telephone numbers at the national level include'

          National Response Center-  800-424-8802 (202-426-2675 or 202-267-2675
          in Washington,  DC area),  for  notification, information,  and  assistance
          involving agencies of the federal government

     •    Chemical    Transportation    Emergency   Center    (CHEMTREC):
          800-424-9300, for information and assistance from industry as coordinated
          by the Chemical Manufacturers Association
                                        14-10
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ITEM#N3

Topic-   Facilities Requiring Special Notification

When/Where Applicable:     Where a major incident may occur in a location that threatens
                            schools, day care centers, hospitals, nursing homes, universi-
                            ties, prisons,  and similar facilities serving large groups of
                            people with needs for special transportation, protection, or
                            handling.

Planning Goal:              To ensure that the above facilities receive the earliest possible
                            notification of the need to  shelter-in-place or evacuate their
                            inhabitants
Action Items:
     •     Identify and obtain the telephone numbers and names of key supervisory
           personnel in facilities that meet the above criteria.

     •     Ensure that the emergency response plan provides for direct notification of
           these facilities on a prompt basis

     •     Ensure that the emergency response plan contains a procedure for notifica-
           tion of these facilities during penods of interrupted telephone service

     •     Encourage  facility operators to establish  emergency  evacuation  plans
           coordinated with those of the community.

     •     Ensure that the person(s) responsible for notification of these facilities
           document then* actions during an emergency.

Discussion:

     Time can be critical during some hazardous material emergencies  The above action
items ensure that facilities requiring special attention are notified at the earliest possible
indication  of a threat, thus  permitting them an  early start to evacuating or  otherwise
protecting their inhabitants.
                                        14-11
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ITEM#N4

Topic:    Notification of Water Users

When/Where Applicable:    Any locale that may experience a spill of a hazardous material
                            into a body of water.

Planning Goal:              To ensure that industrial, agricultural, public water supply, and
                            other users of water resources are quickly notified of potential
                            water contamination in the aftermath of a spill
Action Items*
      •     Compile a list of those companies or facilities that extract water from water
           bodies in the area of concern, together with a list of appropriate contacts
           and telephone numbers at these facilities

      •     Establish a mechanism by which these facilities may be quickly informed
           of potential water contamination in  the event of an upstream hazardous
           material spill.

Discussion*

      Numerous facilities intake water from nearby water bodies for industrial or food
processing purposes, farm irrigation,  drinking  supplies,  and so forth Entry of a toxic,
flammable, or corrosive material into their water intakes can contaminate food or drinking
water, damage equipment, ruin products, and possibly even cause a fire or explosion

      These facilities may be identified during the survey process discussed in Chapter 10, by
a special survey of facilities along the "waterfront", or possibly, by a search of local, state, or
federal permit records (presuming some sort of permit was required for them to intake water
from the water bodies in question)

      Note that it may not be necessary for public authorities to call a long list of facilities
themselves It is entirely feasible to establish a "waterway warning  network" in which each
person receiving a call on behalf of a facility is given responsibility to call two or more other
facilities in the downstream direction  This would mean that  public  officials would only
have to make one or two telephone calls to start the process

      In undertaking this planning task, realize that spills with the potential to adversely
impact water quality, particularly spills into rivers, need not actually occur in the jurisdiction
of concern Indeed, they could occur  at locations many miles upstream from junsdictional
boundaries.
                                         14-12
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ITEM#N5

Topic.   Notification of Water Treatment Plants

When/Where Applicable:    Where spillage of a hazardous material may enter a sewage or
                           drainage system leading to a municipal treatment plant

Planning Goal.              To  ensure  that the treatment  plant is warned as soon as
                           possible of the event
Action Items
     •     Identify the  24-hour telephone numbers and  names of key  supervisory
           personnel in the subject facilities.

     •     Plan to have these personnel notified immediately if hazardous materials
           enter the waste streams to their plant

     •     Identify sewer shut-off points for the containment of hazardous materials
           that may leak or flow into sanitary and storm sewers

Discussion:

     The sudden appearance of a toxic or flammable substance can cause many problems
and senous hazards at a treatment plant Early notification may help prevent or mitigate
adverse impacts.

     A study sponsored by the EPA may be of use to biological wastewater treatment plants
in assessing the effects  of potential hazardous materials spills and developing emergency
plans. The reference is:

     Bnnsko, G.A., et al, Hazardous Material Spills and Responses for Municipali-
     ties, Report No PB 80214141, available from the National Technical Information
     Service, Springfield, VA 22161, July 1980.

Note that this report is solely devoted to wastewater treatment plant problems. Its title is
somewhat misleading in that it suggests broader coverage of spills and related response
actions.

See Item #SC3 for additional information and discussion of problems associated with entry
of flammable liquids into storm drains
                                       14-13
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TTEM#N6

Topic:   Notification and Shutdown of Electric and Gas Utilities

When/Where Applicable:     Wherever  a large  explosion  or potential explosion may
                           necessitate shutdown of electric power or natural gas distribu-
                           tion systems in an area.

Planning Goal:              To identify who and where to call to have the above utilities
                           shutdown on a rapid basis.

Action Items:

      •    Contact local utility companies and  establish a mechanism to accomplish
          the planning goal.

Discussion:

      Major explosions may be caused by or may  themselves cause leaks or ruptures of
natural gas distribution systems.  Additionally, they can cause breaking of power lines and an
electrocution hazard to those who might make  contact with any "downed" lines. In either
case, there may be circumstances in which it is desired to shutdown natural gas or electric
power systems rapidly in an area.
                                        14-14
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ITEM#N7

Topic:    Notification and Control of Air, Rail and Waterborne Traffic

When/Where  Applicable:     Any  locale  in  which  a hazardous material accident may
                            threaten airplanes, helicopters, trains, barges, ships, recreation-
                            al boaters, and other non-highway traffic not normally aware
                            of local conditions.

Planning Goal:              To identify the means to warn aircraft, trains, and waterborne
                            traffic of a hazard and  to keep them away from the hazard
                            zone.
Action Items*
     •     Identify air traffic control facilities, railroad dispatchers, and Coast Guard
           or harbor master facilities that have the ability to  warn and control the
           movement of the subject traffic in the area or jurisdiction of concern

Discussion:

     The planning goal and action items are mostly self-explanatory. It is only necessary to
add that a  train accident on a heavily travelled segment of track may require immediate
dispatch of personnel to locations where they can attempt to flag down and stop other trains
approaching the accident site. Overflight  of any incident site should be prohibited except
with permission from the Federal Aviation Administration (FAA) and on-scene authorities.
Where available, helicopters having public address systems can facilitate warning of traffic
and even the general public.
                                        14-15
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ITEMtfCCl

Topic:   Establishment and Staffing of Command Posts

When/Where Applicable:     Wherever a coordinated, large-scale response may become
                           necessary due  to  a major spill or discharge of hazardous
                           materials.

Planning Goal:             To quickly establish one or more command posts from which
                           the emergency response may be directed and coordinated.

Action Items:

      •    Select an appropriate location (and possible alternate) for rapid establish-
           ment of a primary command post or emergency operations center.

      •    Plan for a field command post near the site of the emergency from which
           spill containment and countermeasure operations may be conducted when
           necessary.

      •    Designate the individuals who should immediately report to each site in the
           event of a major emergency.

      •    Establish a "check-in" location where key officials can be "logged in" and
           their movements tracked once they appear on the scene

      •    Establish an ID system to control and track entry and movement of public
           authorities and emergency crews.

      •    Equip sites with the office equipment, maps, data sources, communication
           systems, and other supplies and resources necessary for command and
           control of response activities.

      •    Provide security and access control  at vital sites such as the emergency
           operations center, communications center, media center, emergency supply
           center or depot, and the incident site itself.

 Discussion:

      A complex emergency requires coordination of numerous activities beyond spill
 containment and countermeasure efforts  There can therefore be benefits to establishment of
 both central and field command posts. The  former, while  in close communication with the
 field site, can handle relations with the press, evacuation operations, contacts with the public
 and outside government agencies, procurement of necessary supplies and resources, and a
 variety of other details The field  site can then concentrate  on its own key mission of
 directing hazard containment and control operations.
                                         14-16
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      The central command post should ideally be assigned representatives of all agencies
and organizations with a role in emergency response, as well as support personnel including
secretaries, clerks, radio operators, messengers, and so forth. This will facilitate communica-
tions, decision-making, and conduct of necessary efforts.

      Senous consideration  should be  given to establishing a "check-in" location at each
command post, for requiring all individuals to "sign in" and "sign out" (particularly at the
incident site), and to issuing ID cards and/or badges to personnel authorized to pass through
roadblocks and enter controlled areas. Color-coded badges or items of clothing may be used
to designate different levels of access and/or on-scene authority

      Note that the establishment of a local  command  organization for management of
emergencies is a related prerequisite  more fully discussed in the Hazardous Materials
Emergency Planning Guide and the Hazardous Materials Contingency Planning Course
manuals referenced earlier in this document  Emergency plans should contain a clear and
concise summary  of primary  and  support responsibilities for  Command and  Control,
Alerting and  Notification,  Communications,  Public Information,  Accident Assessment,
Public Health and Sanitation, Social  Services, Fire and Rescue, Traffic Control, Emergency
Medical Services, Law Enforcement, Transportation, Public Protective Actions, Exposure
Control, and Public Works  functions, among others. Block diagrams should illustrate the
relationships among the various response groups, each of which may require assignment of a
specific manager under the overall direction of an individual assigned overall responsibility
and authority for command of emergency operations  The command and control team and
its written plan must provide a capability for 24  hour protracted operations (requiring the
establishment of work shifts), definition of decision-making processes in at  least general
terms, availability  of  sources  of  assistance (including specialized  experts)  to  aid deci-
sion-making, and establishment of a means to determine operational readiness.  Possible
staging areas should be identified for gathering and dispatch of response forces as necessary.
One or means must be available to obtain detailed and accurate information on the hazards
and properties of any and all chemicals involved in an accident on a rapid basis

     Keep in mind during planning for the above activities that  areas outside established
hazard zones will continue to require some degree of police,  fire,  rescue, ambulance, health
care, and public works services.

     Give consideration to identifying sources of video and telephoto equipment that can be
used to view particularly hazardous accident sites from a safe distance on a continuous basis
at command, control, and media centers.  A closeup view of the site on a television screen
can be extremely helpful to all parties to the response action in evaluating and choosing the
appropriate course of action, as well as  satisfy media requests for photo coverage and many
of the information needs of government officials on scene  It also enables experts to provide
guidance to response personnel approaching the site to undertake fire control, leak plugging,
spill containment, and/or spill cleanup efforts.
                                       14-17
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     One of the first steps of a response action must be restriction of access to the spill site
and other hazardous areas. There is a not-so-old saying that states "if you want to draw a
very large crowd instantly, in the middle of nowhere, dump something lethal on the ground
and set it on fire." Experienced emergency coordinators will attest to the validity of this
observation
                                          14-18
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 ITEM#CC2

 Topic-    Establishment of Emergency Communication Systems

 When/Where Applicable.     Wherever a coordinated, large-scale response  may become
                           necessary due to a major spill or discharge of a hazardous
                           material

 Planning Goal.             To quickly establish secure communication links between all
                           major parties to a response action

 Action Items.

           Designate the primary and alternate individuals responsible for communica-
           tion links at important locations.

      •     Survey the kinds and types  of communication systems used by  various
           agencies  and organizations with a major role  in  emergency response,
           particularly with respect to radio-communications equipment

           Work out (at the very least) a system whereby the central command post
           can  communicate with all key  parties to an incident and relay messages
           between them regardless of the possible overloading of normal communica-
           tion channels.

      •     Where necessary, have telephones with "unlisted" numbers installed at key
           locations.

           Where necessary, determine the procedure necessary to request the installa-
           tion of new or additional telephone lines by the local telephone company at
           various locations on an emergency basis.

Discussion-

      Good communications are  critical to  a successfully  orchestrated response  action,
particularly if a number of different agencies or organizations at the local, county, state, and
even federal level have important roles  Unfortunately, however, radio systems are unlikely
to be compatible among all parties,  thus  complicating overall coordination  of activities.
Field personnel may  not have ready access to telephones at all times.  Incoming calls from
members of the public, news reporters, and a wide variety of others seeking information, can
tie up or slow available telephone service  to emergency operations centers, police depart-
ments, fire departments,  and  offices of  public officials, if not  throughout the  entire
community
                                       14-19
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     Where  current radio systems are incompatible and there is limited opportunity to
replace or supplement existing units with compatible devices, the problem can be solved in a
fashion by planning to have each key  responding agency  or organization  dispatch a
radio-equipped vehicle and driver to the central command post parking lot  If the command
post itself has radios compatible with one or more of the mobile units, messages can be
relayed between various systems by drivers of the vehicles.

     Incidents that are  obviously going to require long-term response  activities  and/or
evacuations (i.e., more than a day or two) may necessitate the installation of temporary
telephone lines at various centers of activity (including the field command post)   It is well to
know beforehand how to request such emergency service from the local telephone company
Alternatively, vehicles with cellular telephones may be stationed at the site

     There are definite benefits for all emergency operation centers (including those at
major  industrial  facilities) to have  several phone lines  with  unlisted  and  confidential
telephone numbers  These can provide open lines of communications when all others are
tied up.

     With respect to the overall use of telephones, take special precautions where an
explosion or fire at some critical location may destroy vital communication links or services

      Give serious thought to organizing and taking advantage of the capabilities of local
ham radio operators in the area where and when their services may be necessary  Many of
these individuals take their hobby very senously, are likely to have fixed station and portable
equipment that not only equals but exceeds the capabilities of local authorities (since most
ham radio operators truly enjoy  attempting to contact distant states, countries,  and even
continents with high power equipment), and will be more than willing to lend a helping hand
during an actual emergency.

      It can also be prudent to establish a system for tracking, documenting, and prioritizing
 messages, to test all vital communication links on a periodic basis, to inventory equipment
 every so often, and to  ensure vital equipment  is properly maintained  (and replaced with
 alternate systems while undergoing repair).
                                         14-20
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  TTEM#CC3

  Topic    Formulation of Response Objectives and Strategy

  When/Where Applicable-     Wherever a  spill, leak, fire, or potential explosion incident
                             involving hazardous materials may occur.

  Planning Goal.              To Establish procedures for formulating response objectives
                             and strategies, and to identify emergency situations in which
                             response personnel  should limit  their  activities until  the
                             situation has "stabilized" or until further information or expert
                             assistance has been obtained.
  Action Items:
       •    Use the results of the hazard analysis to identify situations in which
            response personnel should not intervene or should limit or restrict their
            response actions.

       •    Establish procedures for evaluating hazards, risks, and site conditions so
            that response objectives and strategy can be properly formulated at the
            scene of an incident or accident.

  Discussion:

       Spill response guides published by industry and government alike often contain phrases
  like "do not extinguish burning cargo unless the flow can be stopped safely."  Additionally,
  they almost universally advise response personnel to withdraw in the event of any sign that a
  tank may explode (such as discoloration of the tank or rising sound from a venting pressure
  relief device) or if the fire cannot be controlled by unmanned devices.  More than one fire
  department has planned to allow certain buildings (such as pesticide warehouses)  to burn
  while only protecting adjacent structures with water, thus preventing senous pollution
  problems from chemically-contaminated runoff.

       It follows from the above that there are potential accident scenarios in which the risks
  associated with certain types of response activities may exceed any benefits to be realized,
  thus providing ample reason to only undertake protective and containment actions from a
  safe distance until the situation has stabilized or expert assistance has been obtained  General
-Examples of situations in which the best course of action may be to hold back from a direct
  "attack" include

       •    When a major release takes place that poses unknown hazards or hazards
            for which response personnel are not equipped or prepared

       •    When a flammable gas or liquid is on fire and extinguishment could lead to    l
            release of  toxic or flammable vapors  or  gases, and possibly, explosive
            reigmtion                                                            /
                                         14-21
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     •    When there are no  endangered persons  or structures nearby  and the
          container(s)  and/or hazardous materials present significant  hazards to
          response personnel.

          When the addition of water to a fire may serve to spread highly  toxic
          contaminants into the enviionment, thus causing a pollution problem that
          may cost much more to resolve than the value of the burning materials,
          vehicles, or buildings

     Due to the possibility of such  situations, response personnel  should assess each
particular incident before taking action  and formulate realistic response objectives. The
assessment should be based on:

     •    Pre-mcident plans and/or standard operating procedures

     •    Information that has been obtained regarding-

                Matenal(s) involved
                Container(s) involved
                Vehicle(s) and/or structures involved
                Atmospheric conditions affecting the incident

     •    Environmental monitoring and sampling data, if available

     •    Public protective actions that have or have not been initiated

     •     Resource requirements (i.e., trained personnel, specialized protective gear,
           other equipment, etc.)

      •     Hazards and nsks posed to humans, animals, property, and the environ-
           ment.

      Upon completion of the incident assessment, command personnel will be in a better
 position to  determine whether their response  strategy should be defensive or offensive in
 nature. A defensive posture is best taken when intervention may  not favorably affect the
 outcome of the incident,  will likely  place emergency  response  personnel in  significant
 danger,  and/or may possibly cause more harm than good  An offensive posture (i e, one
 requiring response personnel to work well within the boundaries  of hazard zones) is best
 taken when intervention is likely to result in a favorable outcome without exposing personnel
 to undue danger and without causing new and potentially more severe problems  In all cases,
 of course,  actions to protect the public  and environment outside the immediate spill or
 discharge area and/or to contain the hazard from a safe distance can be initiated regardless of
 whether a defensive or offensive response strategy is chosen at the actual incident site
                                         14-22
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ITEM#CC4

Topic:   Ensuring Health and Safety at Incident Scenes

When/Where Applicable:     Wherever a coordinated response may be necessary due to a
                            significant spill or discharge of hazardous materials

Planning Goal:              To establish procedures for assuring the health and safety of
                            response personnel operating at hazardous material incidents
Action Items:
      •     Use  the results  of the hazard analysis to identify  situations in  which
           response personnel may be exposed to chemical or physical hazards at an
           incident scene.

      •     Establish standard operating procedures for a site safety and health program
           that addresses:

                Establishment of hazard control zones
                Positioning of personnel, apparatus, and equipment
                Selection and use of personal protective gear
                Safe operating practices
                Medical surveillance and care
                Decontamination of protective gear and equipment
                Decontamination of response personnel
                Maintenance of field personnel

      •     Identify equipment  and materials that may be needed to support the site
           safety and health program.

      •     Establish procedures for obtaining any equipment and materials that may be
           needed to support the site safety and health program

Discussion:

      A system must be established to ensure the health and safety of emergency response
personnel  The responsibility of establishing and managing the safety and health program
should be  assigned to a predesignated  Safety Officer and an alternate, who may  also be
assigned one or more assistants

      An important component of  the safety program will involve establishment of hazard
control zones at the incident scene to limit the number of people in the most hazardous areas.
The exact size and configuration  of  these hazard control zones must be determined and
visually  differentiated at each particular  incident based  on  incident-specific  factors and
situations and may include the following:
                                        14-23
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     •    "Hot Zone" - Area of maximum hazard surrounding the damaged contain-
          er(s) or fire area which may only be entered by specially equipped and
          trained response personnel.

     •    "Warm Zone" - Area of moderate hazard outside the Hot Zone in which
          properly equipped and trained backup crews standby and decontamination
          takes place.

     •    "Cold  Zone" - Area outside  the Warm Zone that  poses  minimal or
          negligible hazards to emergency personnel. The command post, most of
          the deployed apparatus, and the resource staging area should be located in
          the Cold Zone.

     Safe operating procedures to be established and enforced by the Site Safety and Health
Officer include but are not limited to:

     •    The use of appropriate protective gear and equipment (see Items #PP1 and
          #PP2 that follow).

     •    Limiting the number of personnel in the "Hot" and "Warm" hazard control
          zones.

     •    Utilizing the most experienced personnel for the most hazardous tasks.

     •    Positioning a backup team in the "Warm Zone" in case it is needed to assist
          or rescue personnel in the "Hot Zone".

     •    Providing medical surveillance for personnel before and after "Hot" and
          "Warm" Zone operations.

     •    Monitoring (visually and  through communications contact) the welfare of
          personnel operating within the "Hot" and "Warm" Zones.

     •    Ensuring that all personnel understand their assignments.

     •    Ensuring  that responders do  not ingest contaminants through eating,
          drinking, or smoking.

     •    Enforcing a "No Smoking" policy at incidents involving flammable or
          combustible materials.

     •    Decontamination of protective gear and response equipment (see Item #PP3
          that follows).

     •    Replacing fatigued personnel with "fresh" personnel.

     •    Adjusting hazard control zones to reflect changing conditions.
                                       14-24
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     Where deemed necessary,  properly equipped  medical personnel  and one or more
ambulances should be available to check and (if necessary) treat injured or contaminated
response personnel as necessary.  These personnel should check the vital signs and general
health of all personnel who will don specialized protective gear and enter "Hot" or "Warm"
Zones,  particularly where fully  encapsulating protective  suits  are  being used, since
non-cooled suits can be very stressful to the wearer. The  health of potentially exposed
response workers should be rechecked as appropriate and deemed necessary upon completion
of their duties

     Readers should be advised that the Occupational Safety and Health  Administration
(OSHA) has developed interim regulations for protection of workers at hazardous waste and
emergency spill sites. Covering all hazmat teams, local fire and police departments, and
emergency medical services, these regulations provide far more details  than that provided
herein on how to go about meeting site safety and health requirements.  Planning personnel
should therefore obtain the latest version of these requirements (see 29 CFR 1910.120) and
ensure they are prepared to  comply with then* provisions  Final rules on this  topic are
expected during 1989.

     The mtenm regulations currently  in force reference several publications that provide
guidance on establishing safe operating procedures.  A  sample of these and others of
potential interest include:

          Standard Operating Safety Guidelines, U.S  EPA Office of Emergency
          and Remedial Response, Hazardous Response Support Division, December
           1984.

     •    The Decontamination of Response Personnel, Field Standard Operating
          Procedures #7, available from same EPA  office cited above, December
           1984

     •    Preparation of a Site Safety Plan, Field Standard  Operating Procedures #9,
          available from same EPA office cited above, April 1985.

     •    Work Zones, Field Standard Operating Procedures #6, available from same
          EPA office cited above.

     •    Personal Protective Equipment for Hazardous Materials  Incidents^ A
          Selection Guide, U S  Department of Health and Human Services, Public
          Health Service, Centers for Disease Control, National Institute for Occupa-
          tional Safety and Health, October 1984 (see Items #PP1 and #PP2 also).
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ITEM#EV1

Topic:   Designation of Decision Responsibility for Public Protective Actions

When/Where Applicable:    Wherever public evacuations or other protective actions may
                            become necessary  due to hazardous  material spills or dis-
                            charges.

Planning Goal:              To ensure the emergency plan denotes the specific mdividu-
                            al(s) with authority to initiate and later terminate an evacuation
                            or other protective action under varying circumstances.
Action Items:
     •     Check local and state laws and regulations to determine who has responsi-
           bility for evacuation or "shelter-in-place" decisions.

     •     Ensure that this individual is aware of the responsibility and prepared to act
           in a timely fashion

Discussion:

     Laws  designating  authority  for public evacuations,  activation of the Emergency
Broadcast System (EBS), or activation of other means to alert or notify the public of an
emergency vary from state to state and even possibly at the local level  Since time is critical
during the initial stages of a real or potential emergency, it  is necessary to know who has
authority to make evacuation and similar decisions. In addition, it is necessary to ensure that
this (these) individual(s) will be contacted promptly, will be given the information needed to
make proper decisions, and will be capable of acting quickly and decisively

     Where these decisions  are the responsibility of elected officials such as the governor of
the state  or local mayors,  it may  be prudent to ask these individuals to delegate the
responsibility to the person(s) given overall command of response activities, particularly if
these latter personnel are better qualified to assess the nature and magnitude of the threat

     Once the emergency is over, a person in authority must  give approval to permit reentry
of evacuated areas or to give an "all clear" signal The response plan should also identify this
individual.
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ITEM#EV2

Topic:    Criteria for Evacuation and Shelter-in-Place Decisions

When/Where Applicable*     Wherever public evacuations or other protective actions may
                            become  necessary  due to hazardous material spills  or  dis-
                            charges.

Planning Goal.              To give command personnel guidelines with respect to* 1) the
                            circumstances under which the public should be evacuated or
                            instructed to shelter-in-place; and 2) the size and shape of the
                            areas that should  be  considered vulnerable  during  various
                            types of emergency situations

Action Items.

           Make policy decisions with  respect to levels  of toxic  agents, thermal
           radiation, and explosion overpressures  which may be tolerable by the
           public.

      •     Compile data on the size and shape of potential hazard zones.

      •     Develop criteria for evacuation and shelter-in-place decisions.

Discussion*

      This is not a topic commonly suggested for inclusion in hazardous materials emergency
response plans but is one that definitely warrants attention Time can be critical in situations
that may require public evacuations or related protective actions and may not permit lengthy
discussions or deliberations as to whether an evacuation is  warranted or how large an area
should  be considered  at risk. Predetermined criteria for  decision-making can therefore
greatly facilitate the process

      The accident scenarios developed via use of this guide, as well as the computational
methods described in Chapter 12, can be a key source of information for evacuation planning
where specific facilities or hazardous material shipments are known to pose a threat These
threats can be quantified via use of this guide and tabulated within the emergency response
plan. Separate tabulations can be prepared for toxic  vapor clouds or plumes,  liquid  pool
fires, flame jets, potential BLEVEs, and the other specific hazards addressed by Chapter 12
Where alternative  guidance  is lacking,  and  the incident  scenario is  not one that was
considered during the planning process, some thought may be given to the suggestion that the
methods of Chapter 12 be applied on a real-time basis during emergencies to evaluate hazard
zones
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     The 1987 Emergency Response Guidebook (DOT P 5800 4) contains guidance from
the U.S. Department of Transportation (DOT) with respect to recommended evacuation
distances for potential BLEVEs and vapor or gas hazards involving rail or highway vehicle
accidents. The list of hazardous materials considered for gas or vapor hazard purposes (in an
appendix to the DOT guide) is relatively short but includes those highly volatile substances
most commonly transported in commerce.

     This same section of the emergency plan should also give some guidance as to whether
the public should be evacuated from a toxic vapor hazard zone or told to shelter-m-place ~ or
whether both protective measures should be considered for use m different portions of the
zone  (i.e.,  evacuation  close  in to  the vapor source where  concentrations  are higher,
shelter-in-place at further distances)  See Appendix C to this document for further informa-
tion on evaluation and implementation of the shelter-m-place option

     In all cases, remember that hazardous material spills can be "dynamic" events in the
sense that incident conditions, the weather, and the wind direction can change with time.
Guidance obtained from consequence analysis procedures provided in this document or other
sources should  only be considered a starting point for the decision process  In an actual
emergency, evacuation area and/or hazard zone assessment must be a continuous activity.
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TTEM#EV3

Topic:   Public Alert/Notification/Instruction Procedures

When/Where Applicable-     Wherever public evacuations or shelter-in-place decisions may
                            become necessary  due to hazardous materials spills or dis-
                            charges.

Planning Goal:              To plan for and specify the methods and procedures by which
                            the public will be alerted of an emergency situation and given
                            instructions on what to do.

Action Items:

      •    Identify available alert and notification methods and practices.

      •    Specify which are to be used, who will use them, and when and how they
           are to be activated.

      •    Have lists of suitable shelter facilities available and procedures specified
           for assigning different groups of people to these various locations.

      •    Specify evacuation routes for all areas at risk based on results of the hazard
           analysis.

      •    Prepare sample messages for various situations.

      •    Establish  a procedure  to obtain and  distribute appropriate protective
           equipment to personnel  who may  experience prolonged or excessive
           exposures to toxic contaminants while performing notification or evacua-
           tion operations. Provide training in use of this equipment as necessary.

Discussion:

      Public authorities require the means to alert the public of an emergency situation and to
give instructions to those individuals within a hazard zone or approaching such a zone.

      Options for alerting the public include  community or industrial facility horns or sirens,
use of the Emergency Broadcast System (BBS), broadcasts by individual radio and television
 stations (including cable TV), use of police or fire department vehicles with public address
 systems, door-to-door coverage of neighborhoods by knocking on doors, use of an "all-call"
 system which rings  all telephones in the  area and repeats a recorded  message,  use of
 helicopters with public address systems, and various combinations of the above. Be advised
 that the public must be instructed before an actual emergency as to the meaning of warnings
 provided by horns or sirens via a public education program.  Emergency planning requires
 knowledge of the specific procedures and access codes for utilization of the EBS and radio
 and television station resources. As an  evacuation progresses, police, fire, public works,
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and/or other government employees (depending on who might be the most readily available
and tree of other important duties at the time) may have to go door-to-door to ensure that all
residents have been alerted and to provide assistance to the elderly, physically handicapped
or hearing unpaired  It is a good idea for these personnel to be equipped with appropriate
personal protective equipment when necessary and a supply of chalk or colorful tags that can
be used respectively to mark  doorsteps or place on door knobs to indicate that the building
has indeed been evacuated. Note that  evacuation of people in individual residences who
require special notification or assistance can be facilitated if public officials have compiled a
list of those homes requiring special attention

      In designating evacuation routes, keep in mind that major roads are most desirable, but
may not always be available.  Since the direction of the wind at the time of a hazardous gas
or vapor release cannot be predetermined, and since the direction may change with time,
emergency personnel may require more than one option for any given hazard zone. As soon
as an evacuation has been declared, police and auxiliary personnel should be prepared to
control traffic on evacuation  routes, to keep non-evacuation related traffic off these roads,
and to remove any vehicles  that breakdown and cause a slowdown of movement. These
activities may in turn require the ready availability of tow trucks and portable roadblock
materials (barricades, cones, signs, etc)  Additionally, thought should be given to removing
impediments to traffic flow caused by excessive precipitation (rain or snow), fallen trees,
crossing trains, and so forth.

      Standard message formats for use in radio and television broadcasts can facilitate and
reduce the time necessary to alert the public of a problem and inform them of the protective
actions to be taken.  The overall planning process must consider designation of evacuation
routes and these routes should  be  identified in public warning messages, as should the
location of shelters to  which  people with automobiles should proceed, the  locations where
people without  automobiles should gather for pick up by buses or vans (see item #EV4), and
what actions should be taken by people with children  at school in a potential hazard zone
These messages should instruct people to bring  any prescription medicines and  special
personal care items with them  See item #EV7 for a discussion of what to do about pets.
The Hazardous Materials Contingency Planning Course manuals referenced in Chapter 1
provide several sample messages for consideration in accomplishing this objective. Keep m
mind that messages may have to be  broadcast  in languages  other than English  in
communities with concentrations of ethnic minorities

     Incidentally, be advised  that there are likely to be people who for one reason or another
may resist instructions to evacuate, even when confronted face-to-face with  a police officer
Officers sent to persuade the  last few families  or individuals who  refused to evacuate in a
major 1986 evacuation in Miamisburg, Ohio, achieved considerable success by asking these
people to provide information on their "next of km" for use in the event of their demise. The
holdouts, to the last person, got the message and cooperated with the evacuation order
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ITEM#EV4

Topic.    Transportation Functions

When/Where Applicable*     Wherever public evacuations may become necessary due to
                            hazardous material spills or discharges and public authorities
                            find it necessary to provide transportation for evacuees

Planning Goal(s):            To plan for the availability of buses, vans, ambulances, and
                            other vehicles to transport general members  of the  public
                            without automobiles, school children, residents  of hospitals
                            and nursing homes, and possibly even pnson populations to
                            safe shelters
Action Items*
           Assign one or more persons responsibility for coordination of transporta-
           tion activities during an emergency.

           Establish agreements with public and private bus companies and ambulance
           services for provision of vehicles and drivers under emergency conditions

           Develop evacuation plans for special occupancies such as schools, day care
           centers, hospitals,  nursing  homes, and prisons and the  like,  possibly
           coordinating  efforts with similar  facilities in  some sort of mutual aid
           program

           Develop communications, dispatch, and command/coordination systems for
           control of the vehicle fleet.

           Bnef drivers on procedures periodically.

           Establish  a procedure  to obtain  and distribute  appropriate protective
           equipment to personnel  who  may expenence prolonged or excessive
           exposures to  toxic contaminants while performing notification or evacua-
           tion operations.

           Consider giving training to  at least a portion of the drivers in the use of
           self-contained breathing apparatus  (SCBA) if entry might be necessary or
           may unexpectedly occur (due to wind direction  shifts or other factors) to
           zones with toxic air contamination

           Select safe locations (to the extent possible) at which the public  should
           assemble  in  then: respective  neighborhoods for pick-up by  transport
           vehicles
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     •     Where large areas may be  at nsk (based upon results of the hazard
           analysis), plan for a staged evacuation with zones at highest nsk being first
           evacuated, followed by zones with lesser nsks.

Discussion:

     The action items are self-explanatory. Note  that a good evacuation plan is not only
useful for hazardous material emergencies but any other emergency  situation that may
require relocation of the public The presence of  hospitals, large schools,  nursing homes,
and/or prison facilities can require detailed planning and preparedness to facilitate what will
be a monumental task under the best of circumstances

     The individual given responsibility for transportation operations might also be given
responsibility for ensuring that any needed response equipment, materials, and personnel are
delivered promptly to the scene  of an accident  and for ensuring  an adequate  state of
operational readiness, thus consolidating the management of  all transportation  related
activities.
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ITEM#EV5

Topic:    Care and Shelter of Evacuees

When/Where Applicable:    Where public authorities may find it necessary  to provide
                            shelter for large numbers of evacuees

Planning  Goal(s)'           To  provide  safe and  comfortable  shelters  for relocated
                            populations.
Action Items.
     •     Use hazard analysis results to estimate the maximum number of people for
           which shelter might need to be provided and the possible duration of a
           major evacuation, taking into account those families and individuals that
           might stay with friends  or  relatives or prefer to check into hotels and
           motels.

     •     Coordinate shelter planning efforts with the American Red  Cross and
           ensure that the local  chapter can cope with the  number of potential
           evacuees.

     •     Have lists of shelters and route maps readily available  for use in giving
           instructions to evacuees and vehicle drivers.

     •     Where necessary, ensure plans are in place for populations needing special
           care.

Discussion.

     High schools with showers and cafeteria facilities are probably the best choices for use
as temporary shelters, with large churches having function halls a viable alternative in most
communities  During vacation seasons,  universities or other schools with dormitory facilities
should  be considered Not to be forgotten  are any nearby military bases with excess or
temporary housing facilities and overnight summer camps for youngsters in the off-season

      The American Red Cross has long established methods and procedures for sheltering
evacuees  Determine its capabilities in the locale or jurisdiction of concern, consider its
needs in overall emergency planning, and plan to provide any assistance required to achieve
the stated planning goal  Helpful hint Work with the local chapter in developing evacuation
instructions to be broadcast to the public, particularly with respect to the clothing, bedding,
medicines, and other supplies the Red Cross may wish the public to bring with them

      Once evacuees reach a shelter, people will want to report "missing"  persons or to
determine if their friends,  family members, relatives, or neighbors  are "lost" or at another
shelter Response to these quenes, as well as identification of persons legitimately missing,
will require registration of people upon entry and communications between shelters  Where
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the evacuation may be prolonged, and vehicles are available for use after  the primary
evacuation has been completed, a mechanism should be established for reunion of separated
families, relatives, and close friends that can provide a mutual support system under adverse
circumstances.

      Shelters should be assigned medical teams to care for people who become ill during the
evacuation or at later  times. These medical personnel should be alerted to the signs and
symptoms of exposure to the hazardous matenal(s) involved in the incident so that they may
identify  victims and  provide necessary care. Contaminated  individuals (those having
contaminant residues on their persons or clothing) should be segregated from unexposed
people until decontaminated. (Note:  Significant contamination is unlikely to be of concern
except where highly toxic aerosols, mists, or dusts have entered the atmosphere or where
individuals were in the immediate vicinity of the spill or discharge)  Facilities should also be
available for care of the handicapped or elderly.

      Thought should be given as to how best to manage any pets brought along by evacuees
Human services personnel may be necessary to fulfill counseling, recreational, and other
needs of confined populations. Quite obviously, shelters will require  initial and periodic
supplies of food, water, and all other personal need items of inhabitants
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ITEM#EV6

Topic     Security of Evacuated Hazard Zones

When/Where Applicable:     Wherever large areas may require evacuation due to hazardous
                            material spills or discharges.

Planning  Goal:              To ensure that  private and public property is safe-guarded
                            during evacuations and that unauthorized individuals do not
                            enter hazard zones
Action Items:
      •     Plan to provide police and/or other forces to man roadblocks on routes to
           potential hazard zones.

      •     Plan for ground and possibly aerial patrols of evacuated areas.

      •     Establish  procedures to  provide  personnel with  appropriate  personal
           protective devices and training hi their use where  changing accident or
           environmental conditions  may suddenly change  the  boundaries  of haz-
           ardous areas.

Discussion

      Personnel and vehicles should be available to establish and maintain roadblocks on the
boundaries of  hazardous areas.  One  reason for this is to prevent uninformed or curious
members of the public from entering hazardous locations  Another involves  prevention of
entry by those who may wish to take unlawful advantage of the fact that  some part of the
community has been temporarily abandoned

      Where and when it is safe to do so and deemed necessary, patrols of evacuated areas
can enhance  security while double-checking  that all members of the  public  have  left
designated areas Aenal patrols during daylight hours can provide a better  "picture" of what
is happening on the ground, while helicopters can help ferry critical personnel and supplies
Helpful hint: Helicopters may be available from the state police, local charter  services, local
radio and television stations, and nearby military posts.
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ITEM#EV7

Topic:   Movement and Care of Livestock and Pets

When/Where Applicable:     Wherever evacuations may become necessary due to haz-
                           ardous material spills or discharges

Planning Goal:              To plan for and specify the methods and procedures by which
                           domestic or other captive livestock may be moved to a safe
                           location and properly cared for when the potential arises for a
                           major toxic gas or vapor release to the environment and tome
                           permits this action. Also, to give some thought to tending pets
                           left behind in an evacuation or brought to shelters by evacuees

Action Items'

      •     Use the results of the planning basis development process to determine if a
           large number of valuable livestock might be threatened by a major spill or
           discharge.

      •     Decide whether resources and time might be available for this activity or
           whether it is only practical to protect human populations

      •     If desired and necessary, plan for the movement and care of livestock with
           local resources

      •     Establish procedures for handling household pets during evacuations

Discussion:

      Movement and care of domestic livestock is likely to be most applicable in rural areas
with large populations of valuable animals and relatively few people  It may  not be worthy
of consideration in other circumstances unless a zoo containing extremely valuable or rare
animals may be at risk.

      The subject of household pets may seem rather trivial at first, but it is well to remember
that many  people care deeply for their animal friends, and the issue of pets has caused
problems in past accidents Planning personnel will  have to decide  whether to permit
evacuees to bring their pets with them to shelters or to mandate that they be left behind, with
the knowledge that both options are surely to cause difficulties of one kind or another

      As time passes during an evacuation in which  pets have  been left  behind, and the
evacuation was ordered because of the threat of a release rather than an actual discharge,
people will ask  questions about what is being done to feed then: animals and/or may attempt
to enter evacuated areas to care for them  One way to handle the problem for pets left
outdoors is to assign someone the responsibility of leaving supplies of water and pet foods at
various locations on a daily basis when and where it is safe to do  so People who are forced
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to leave pets indoors can be told to set out several days of food and water before leaving
home  Keep in mind that pets exposed to toxic agents may  be injured or killed and that
hazard zone reentry activities after the threat has abated should include procedures to collect,
care for, and possibly dispose of these animals as necessary and appropriate.

     Even if evacuees are told to leave pets behind and not bring them to shelters,
emergency preparedness personnel should expect and plan for the fact that some people will
indeed bring then: pets with them and should have procedures worked out on how to handle
these situations.
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ITEMtfFFl

Topic:   Special Firefighting Equipment and Materials

When/Where Applicable:     Any locale in which a fire involving hazardous materials may
                            require special  equipment or extinguishing agents for control
                            and/or extinguishment

Planning Goal:              To ensure that  the fire service has rapid access to any special
                            equipment and materials it may need in the event of an unusual
                            fire situation
Action Items:
      •     Use the results  of the  hazard analysis to identify those  sites  or spill
           scenarios that appear to present unusual fire  hazards  in the sense that
           specialized equipment and/or supplies may be required for response

      •     Identify sources of needed firefighting equipment or supplies that may be
           called upon in an emergency.

Discussion:

      Public fire departments primarily rely upon water for fire control and extinguishment,
but are well aware that water can be ineffective on some types of fires and may actually be
counterproductive or dangerous for  use in other cases   Nevertheless, since water is  usually
adequate for most large fires encountered, these departments rarely stock more than a limited
number of portable dry chemical or carbon dioxide extinguishers and possibly a small
amount of foam concentrate These supplies of auxiliary  agents may not be adequate for
major chemical or petroleum product fires or fires involving combustible  metals  Thus,
where the  hazard analysis has identified scenarios requiring unavailable resources, the fire
department should be assisted in identifying sources of additional supplies and equipment for
use in emergencies.

      Airports comprise one potential source of assistance Military  airports  are likely to
have  crash/rescue vehicles  with  significant foam generation  and  dispensing capabilities
They are also likely to have large capacity units for discharging carbon dioxide, halons, and
possibly dry chemicals  Civilian  airports  are likely to have large foam trucks and/or dry
chemical trucks, and wheeled-portable dry chemical units  Both types of airports may have
supplies of special agents for combustible metal fires

      Chemical and petroleum processing facilities with internal fire brigades are another
potential source of supplies  They may also have special  portable equipment for fighting
storage tank fires.
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ITEM#FF2

Topic*   Identification of Water Sources in Rural Areas

When/Where Applicable.     Where an  accident requiring large amounts of water for
                           response takes place in an area distant from hydrant or other
                           water supply systems

Planning Goal'             To identify sources of water in areas not served by a central
                           water supply system

Action Items:

      •     Use hazard analysis results to identify potential incident locations distant
           from water systems

      •     Compile  a list of rivers,  streams, lakes, ponds, reservoirs, wells, farm
           holding tanks,  other water tanks, and swi