United States
Environmental Protection
Agency
Office of Solid Waste
and Emergency Response
(5104)
EPA 550-B-99-009
April 1999
www.epa.gov/ceppo/
RISK MANAGEMENT
PROGRAM GUIDANCE
FOR OFFSITE
CONSEQUENCE
ANALYSIS
Chemical Emergency Preparedness and Prevention Office
Pnnied on recycled paper
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This document provides guidance to the owner or operator of processes covered by the Chemical Accident
Prevention Program rule in the analysis of offsite consequences of accidental releases of substances regulated
under section 112(r) of the Clean Air Act. This document does not substitute for EPA's regulations, nor is it
a regulation itself. Thus, it cannot impose legally binding requirements on EPA, States, or the regulated
community, and may not apply to a particular situation based upon the circumstances. This guidance does
not constitute final agency action, and EPA may change it in the future, as appropriate.
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TABLE OF CONTENTS
Chapter Page
Table of Potentially Regulated Entities viii
Roadmap to Offsite Consequence Analysis Guidance by Type of Chemical x
1 Introduction 1-1
1.1 Purpose of this Guidance
1.2 This Guidance Compared to Other Models
1.3 Number of Scenarios to Analyze
1.4 Modeling Issues
1.5 Steps for Performing the Analysis
1.5.1 Worst-Case Analysis for Toxic Gases
1.5.2 Worst-Case Analysis for Toxic Liquids
1.5.3 Worst-Case Analysis for Flammable Substances
1.5.4 Alternative Scenario Analysis for Toxic Gases
1.5.5 Alternative Scenario Analysis for Toxic Liquids
1.5.6 Alternative Scenario Analysis for Flammable Substances
1.6 Additional Sources of Information 1-10
2 Determining Worst-Case Scenario 2-1
2.1 Definition of Worst-Case Scenario 2-1
2.2 Determination of Quantity for the Worst-Case Scenario 2-3
2.3 Selecting Worst-Case Scenarios 2-3
3 Release Rates for Toxic Substances 3-1
3.1 Release Rates for Toxic Gases 3-1
3.1.1 Unmitigated Releases of Toxic Gas 3-2
3.1.2 Releases of Toxic Gas in Enclosed Space 3-2
3.1.3 Releases of Liquefied Refrigerated Toxic Gas in Diked Area 3-3
3.2 Release Rates for Toxic Liquids 3-4
3.2.1 Releases of Toxic Liquids from Pipes 3-5
3.2.2 Unmitigated Releases of Toxic Liquids 3-5
3.2.3 Releases of Toxic Liquids with Passive Mitigation 3-7
3.2.4 Mixtures Containing Toxic Liquids 3-11
3.2.5 Release Rate Correction for Toxic Liquids Released at Temperatures
Between 25 °C and 50 °C 3-12
3.3 Release Rates for Common Water Solutions of Toxic Substances and for Oleum 3-14
4 Estimation of Worst-Case Distance to Toxic Endpoint 4-1
April 15, 1999 \
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TABLE OF CONTENTS
(Continued)
Chapter Page
5 Estimation of Distance to Overpressure Endpoint for Flammable Substances 5-1
5.1 Flammable Substances Not in Mixtures 5-1
5.2 Flammable Mixtures 5-2
Reference Tables of Distances for Worst-Case Scenarios 5-4
Table
Neutrally Buoyant Plume Distances to Toxic Endpoint for Release Rate Divided by
Endpoint, F Stability, Wind Speed 1.5 Meters per Second:
1 10-Minute Release, Rural Conditions 5-4
2 60-Minute Release, Rural Conditions 5-5
3 10-Minute Release, Urban Conditions 5-6
4 60-Minute Release, Urban Conditions 5-7
Dense Gas Distances to Toxic Endpoint, F Stability, Wind Speed 1.5 Meters per Second:
5 10-Minute Release, Rural Conditions 5-8
6 60-Minute Release, Rural Conditions 5-9
7 10-Minute Release, Urban Conditions 5-10
8 60-Minute Release, Urban Conditions 5-11
Chemical-Specific Distances to Toxic Endpoint, Rural and Urban Conditions, F Stability,
Wind Speed 1.5 Meters per Second:
9 Anhydrous Ammonia Liquefied Under Pressure 5-12
10 Non-liquefied Ammonia, Ammonia Liquefied by Refrigeration, or Aqueous
Ammonia 5-13
11 Chlorine 5-14
12 Sulfur Dioxide (Anhydrous) 5-15
Vapor Cloud Explosion Distances for Flammable Substances:
13 Distance to Overpressure of 1.0 psi for Vapor Cloud Explosions
of 500 - 2,000,000 Pounds of Regulated Flammable Substances 5-16
6 Determining Alternative Release Scenarios 6-1
7 Estimation of Release Rates for Alternative Scenarios for Toxic Substances 7-1
7.1 Release Rates for Toxic Gases 7-1
7.1.1 Unmitigated Releases of Toxic Gases 7-1
7.1.2 Mitigated Releases of Toxic Gases 7-4
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TABLE OF CONTENTS
(Continued)
Chapter Page
7.2 Release Rates for Toxic Liquids 7-6
7.2.1 Liquid Release Rate and Quantity Released for Unmitigated Releases 7-7
7.2.2 Liquid Release Rate and Quantity Released for Mitigated Releases 7-10
7.2.3 Evaporation Rate from Liquid Pool 7-10
7.2.4 Common Water Solutions and Oleum 7-14
8 Estimation of Distance to the Endpoint for Alternative Scenarios for Toxic Substances 8-1
9 Estimation of Release Rates for Alternative Scenarios for Flammable Substances 9-1
9.1 Flammable Gases 9-1
9.2 Flammable Liquids 9-2
10 Estimation of Distance to the Endpoint for Alternative Scenarios for Flammable
Substances 10-1
10.1 Vapor Cloud Fires 10-1
10.2 Pool Fires 10-5
10.3 BLEVEs 10-6
10.4 Vapor Cloud Explosion 10-6
Reference Tables of Distances for Alternative Scenarios 10-9
Table
Neutrally Buoyant Plume Distances to Toxic Endpoint for Release Rate Divided by
Endpoint, D Stability, Wind Speed 3.0 Meters per Second:
14 10-Minute Release, Rural Conditions 10-9
15 60-Minute Release, Rural Conditions 10-10
16 10-Minute Release, Urban Conditions 10-11
17 60-Minute Release, Urban Conditions 10-12
Dense Gas Distances to Toxic Endpoint, D Stability, Wind Speed 3.0 Meters per Second:
18 10-Minute Release, Rural Conditions 10-13
19 60-Minute Release, Rural Conditions 10-14
20 10-Minute Release, Urban Conditions 10-15
21 60-Minute Release, Urban Conditions 10-16
April 15, 1999 111
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TABLE OF CONTENTS
(Continued)
Chapter Page
Table
Chemical-Specific Distances to Toxic Endpoint, D Stability, Wind Speed 3.0 Meters per
Second:
22 Anhydrous Ammonia Liquefied Under Pressure 10-17
23 Non-liquefied Ammonia, Ammonia Liquefied by Refrigeration, or Aqueous
Ammonia 10-18
24 Chlorine 10-19
25 Sulfur Dioxide (Anhydrous) 10-20
Neutrally Buoyant Plume Distances to Lower Flammability Limit (LFL) for Release Rate
Divided by LFL:
26 Rural Conditions, D Stability, Wind Speed 3.0 Meters per Second 10-21
27 Urban Conditions, D Stability, Wind Speed 3.0 Meters per Second 10-21
Dense Gas Distances to Lower Flammability Limit:
28 Rural Conditions, D Stability, Wind Speed 3.0 Meters per Second 10-22
29 Urban Conditions, D Stability, Wind Speed 3.0 Meters per Second 10-23
BLEVE Distances for Flammable Substances:
30 Distance to Radiant Heat Dose at Potential Second Degree Burn Threshold Assuming
Exposure for Duration of Fireball from BLEVE 10-24
11 Estimating Offsite Receptors 11-1
12 Submitting Offsite Consequence Analysis Information for Risk Management Plan 12-1
12.1 RMP Data Required for Worst-Case Scenarios for Toxic Substances 12-1
12.2 RMP Data Required for Alternative Scenarios for Toxic Substances 12-2
12.3 RMP Data Required for Worst-Case Scenarios for Flammable Substances 12-3
12.4 RMP Data Required for Alternative Scenarios for Flammable Substances 12-3
12.5 Submitting RMPs 12-4
12.6 Other Required Documentation 12-4
APPENDICES
Appendix A: References for Consequence Analysis Methods A-l
Appendix B: Toxic Substances B-l
B. 1 Data for Toxic Substances B-l
B.2 Mixtures Containing Toxic Liquids B-10
April 15, 1999 iv
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TABLE OF CONTENTS
(Continued)
APPENDICES Page
Appendix C: Flammable Substances C-l
C. 1 Equation for Estimation of Distance to 1 psi Overpressure for Vapor Cloud
Explosions C-l
C.2 Mixtures of Flammable Substances C-l
C.3 Data for Flammable Substances C-2
Appendix D: Technical Background D-l
D. 1 Worst-Case Release Rate for Gases D-l
D. 1.1 Unmitigated Release D-l
D. 1.2 Gaseous Release Inside Building D-l
D.2 Worst-Case Release Rate for Liquids D-l
D.2.1 Evaporation Rate Equation D-l
D.2.2 Factors for Evaporation Rate Estimates D-2
D.2.3 Common Water Solutions and Oleum D-4
D.2.4 Releases Inside Buildings D-5
D.3 Toxic Endpoints D-7
D.4 Reference Tables for Distances to Toxic and Flammable Endpoints D-8
D.4.1 Neutrally Buoyant Gases D-8
D.4.2 Dense Gases D-9
D.4.3 Chemical-Specific Reference Tables D-10
D.4.4 Choice of Reference Table for Dispersion Distances D-10
D.4.5 Additional Modeling for Comparison D-12
D.5 Worst-Case Consequence Analysis for Flammable Substances D-12
D.6 Alternative Scenario Analysis for Gases D-13
D.7 Alternative Scenario Analysis for Liquids D-15
D.7.1 Releases from Holes in Tanks D-15
D.7.2 Releases from Pipes D-17
D.8 Vapor Cloud Fires D-18
D.9 Pool Fires D-18
D.10 BLEVEs D-21
April 15, 1999 V
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TABLE OF CONTENTS
(Continued)
APPENDICES Page
D. 11 Alternative Scenario Analysis for Vapor Cloud Explosions D-23
Appendix E: Worksheets for Offsite Consequence Analysis E-l
Worksheet 1. Worst-case Analysis for Toxic Gas E-l
Worksheet 2. Worst-case Analysis for Toxic Liquid E-2
Worksheet 3. Worst-case Analysis for Flammable Substance E-5
Worksheet 4. Alternative Scenario Analysis for Toxic Gas E-6
Worksheet 5. Alternative Scenario Analysis for Toxic Liquid E-9
Worksheet 6. Alternative Scenario Analysis for Flammable Substance E-l3
Appendix F: Chemical Accident Prevention Provisions F-l
April 15, 1999 VI
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LIST OF EXHIBITS
Exhibit Page
1 Required Parameters for Modeling 1-3
2 Generic Reference Tables of Distances for Worst-case Scenarios 4-3
3 Chemical-Specific Reference Tables of Distances for Worst-case Scenarios 4-3
4 Generic Reference Tables of Distances for Alternative Scenarios 8-2
5 Chemical-Specific Reference Tables of Distances for Alternative Scenarios 8-2
6 Reference Tables of Distances for Vapor Cloud Fires as Alternative Scenario for Flammable
Substances 10-2
A-1 Selected References for Information on Consequence Analysis Methods A-2
B-l Data for Toxic Gases B-2
B-2 Data for Toxic Liquids B-4
B-3 Data for Water Solutions of Toxic Substances and for Oleum B-7
B-4 Temperature Correction Factors for Liquids Evaporating from Pools at Temperatures
Between 25 °C and 50 °C (77 °F and 122 °F) B-8
C-l Heats of Combustion for Flammable Substances C-3
C-2 Data for Flammable Gases C-6
C-3 Data for Flammable Liquids C-9
April 15, 1999 vii
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TABLE OF POTENTIALLY REGULATED ENTITIES
This table is not intended to be exhaustive, but rather provides a guide for
readers regarding entities likely to be regulated under 40 CFRpart 68. This
table lists the types of entities that EPA is now aware could potentially be
regulated by this rule (see Appendix B of the "General Guidance for Risk
Management Programs "for a more detailed list of potentially affected NA1CS
codes). Other types of entities not listed in this table could also be affected. To
determine whether your facility is covered by the risk management program rules
in part 68, you should carefully examine the applicability criteria discussed in
Chapter 1 of the General Guidance and in 40 CFR 68.10. If you have questions
regarding the applicability of this rule to a particular entity, call the
EPCRA/CAA Hotline at (800) 424-9346 (TDD: (800) 553-7672).
Category
Chemical
manufacturers
Petroleum refineries
Pulp and paper
Food processors
Polyurethane foam
Non-metallic mineral
products
Metal products
NAICS
Codes
325
32411
322
311
32615
327
331
332
SIC
Codes
28
2911
26
20
3086
32
33
34
Examples of Potentially Regulated
Entities
Petrochemicals
Industrial gas
Alkalies and chlorine
Industrial inorganics
Industrial organics
Plastics and resins
Agricultural chemicals
Soap, cleaning compounds
Explosives
Miscellaneous chemical manufacturing
Petroleum refineries
Paper mills
Pulp mills
Paper products
Dairy products
Fruits and vegetables
Meat products
Seafood products
Plastic foam products
Glass and glass products
Other non-metallic mineral products
Primary metal manufacturing
Fabricated metal products
April 15, 1999
Vlll
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Category
Machinery
manufacturing
Computer and
electronic equipment
Electric equipment
Transportation
equipment
Food distributors
Chemical distributors
Farm supplies
Propane dealers
Warehouses
Water treatment
Wastewater treatment
Electric utilities
Propane users
Federal facilities
NAICS
Codes
333
334
335
336
4224
4228
42269
42291
454312
4931
22131
22132
56221
22111
SIC
Codes
35
36
36
37
514
518
5169
5191
5171
5984
422
4941
4952
4933
4911
Examples of Potentially Regulated
Entities
Industrial machinery
Farm machinery
Other machinery
Electronic equipment
Semiconductors
Lighting
Appliance manufacturing
Battery manufacturing
Motor vehicles and parts
Aircraft
Frozen and refrigerated foods
Beer and wines
Chemical wholesalers
Agricultural retailers and wholesalers
Propane retailers and wholesalers
Refrigerated warehouses
Warehouse storing chemicals
Drinking water treatment systems
Sewerage systems
Wastewater treatment
Waste treatment
Electric power generation
Manufacturing facilities
Large institutions
Commercial facilities
Military installations
Department of Energy installations
April 15, 1999
IX
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Roadmap to Offsite Consequence Analysis Guidance by Type of Chemical
Type of Chemical and Release Scenario
Applicable Sections and Appendices
Toxic Gas
Worst-Case Scenario
1) Define Worst Case
2) Select Scenario
3) Calculate Release Rates
Unmitigated
Passive Mitigation
Refrigerated
4) Find Toxic Endpoint
5) Determine Reference Table and Distance
Dense or Neutrally Buoyant Plume
Chemical-Specific Tables (ammonia, chlorine, sulfur dioxide)
Urban or Rural
Release Duration
Section 2.1
Sections 2.2 and 2.3
Section 3.1.1
Section 3.1.2
Section 3.1.3
Appendix B (Exhibit B-1)
Section 3.1.3, 3.2.3
Chapter 4 and Appendix B (Exhibit B-l)
Chapter 4
Section 2.1 and Chapter 4
Section 2.1
Alternative Scenario
1) Define Alternative Scenario
2) Select Scenario
3) Calculate Release Rates
Unmitigated (from tanks and pipes)
Active or Passive Mitigation
4) Find Toxic Endpoint
5) Determine Reference Table and Distance
Dense or Neutrally Buoyant Plume
Chemical-Specific Tables (ammonia, chlorine, sulfur dioxide)
Urban or Rural
Release Duration
Chapter 6
Chapter 6
Section 7.1.1
Section 7.1.2
Appendix B (Exhibit B-1)
Chapter 8 and Appendix B (Exhibit B-l)
Chapter 8
Section 2.1 and Chapter 8
Section 7.1
April 15, 1999
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Roadmap to Offsite Consequence Analysis Guidance by Type of Chemical (continued)
Type of Chemical and Release Scenario
Applicable Sections and Appendices
Toxic Liquid
Worst-Case Scenario
1) Define Worst Case
2) Select Scenario
3) Calculate Release Rates
Releases from Pipes
Unmitigated Pool Evaporation
Passive Mitigation (dikes, buildings)
Release at Ambient Temperature
Release at Elevated Temperature
Releases of Mixtures
Temperature Corrections for Liquids at 25-50 °C
Releases of Solutions
4) Find Toxic Endpoint
For Liquids/Mixtures
For Solutions
5) Determine Reference Table and Distance
Dense or Neutrally Buoyant Plume (liquids)
Dense or Neutrally Buoyant Plume (solutions)
Chemical Specific Table (aqueous ammonia)
Urban or Rural
Release Duration (liquids)
Release Duration (solutions)
Section 2.1
Sections 2.2 and 2.3
Section 3.2.1
Section 3.2.2
Section 3.2.3
Section 3.2.2, 3.2.3
Section 3.2.2, 3.2.3
Section 3.2.4 and Appendix B (Section B.2)
Section 3.2.5 and Appendix B (Exhibit B-4)
Section 3.3 and Appendix B (Exhibit B-3)
Appendix B (Exhibit B-2)
Appendix B (Exhibit B-3)
Chapter 4 and Appendix B (Exhibit B-2)
Chapter 4 and Appendix B (Exhibit B-3)
Chapter 4
Section 2.1 and Chapter 4
Section 3.2.2
Chapter 4
April 15, 1999
XI
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Roadmap to Offsite Consequence Analysis Guidance by Type of Chemical (continued)
Type of Chemical and Release Scenario
Applicable Sections and Appendices
Toxic Liquid
Alternative Scenario
1) Define Alternative Scenario
2) Select Scenario
3) Calculate Release Rates
Unmitigated (from tanks and pipes)
Active or Passive Mitigation
Release at Ambient Temperature
Release at Elevated Temperature
Release of Solution
4) Find Toxic Endpoint
For Liquids/Mixtures
For Solutions
5) Determine Reference Table and Distance
Dense or Neutrally Buoyant Plume (liquids/mixtures)
Dense or Neutrally Buoyant Plume (solutions)
Chemical-Specific Table (aqueous ammonia)
Urban or Rural
Release Duration (liquids/mixtures)
Release Duration (solutions)
Chapter 6
Chapter 6
Section 7.2
Section 7.2.1
Section 7.2.2
Section 7.2.3
Section 7.2.3
Sections 7.2.4 and 3.3 and Appendix B (Exhibit B-3)
Appendix B (Exhibit B-2)
Appendix B (Exhibit B-3)
Chapter 8 and Appendix B (Exhibit B-2)
Chapter 8 and Appendix B (Exhibit B-3)
Chapter 8
Section 2.1 and Chapter 8
Section 7.2
Chapter 8
April 15, 1999
Xll
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Roadmap to Offsite Consequence Analysis Guidance by Type of Chemical (continued)
Type of Chemical and Release Scenario
Applicable Sections and Appendices
Flammable Substance
Worst-Case Scenario
1) Define Worst Case
2) Select Scenario
3) Determine Distance to Overpressure Endpoint
For Pure Flammable Substances
For Flammable Mixtures
Sections 5.1 and 2.1
Sections 5.1, 2.2, and 2.3
Section 5.1
Section 5.2
Alternative Scenario
1) Define Alternative Scenario
2) Select Scenario
3) For Vapor Cloud Fires
Calculate Release Rates (gases)
Calculate Release Rates (liquids)
Find Lower Flammability Limit (gases)
Find Lower Flammability Limit (liquids)
Dense or Neutrally Buoyant (gases)
Dense or Neutrally Buoyant (liquids)
Urban or Rural
Release Duration
Determine Distance
4) For Pool Fires
5)ForBLEVEs
6) For Vapor Cloud Explosions
Chapter 6
Chapter 6
Section 9.1 and Appendix C (Exhibit C-2)
Section 9.2 and Appendix C (Exhibit C-3)
Appendix C (Exhibit C-2)
Appendix C (Exhibit C-3)
Appendix C (Exhibit C-2)
Appendix C (Exhibit C-3)
Section 10.1
Section 10.1
Section 10.1
Section 10.2 and Appendix C (Exhibit C-3)
Section 10.3
Section 10.4
April 15, 1999
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April 15, 1999 xiv
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1 INTRODUCTION
1.1 Purpose of this Guidance
This document provides guidance on how to conduct the offsite consequence analyses for Risk
Management Programs required under the Clean Air Act (CAA). Section 112(r)(7) of the CAA directed the
U. S. Environmental Protection Agency (EPA) to issue regulations requiring facilities with large quantities of
very hazardous chemicals to prepare and implement programs to prevent the accidental release of those
chemicals and to mitigate the consequences of any releases that do occur. EPA issued that rule,"Chemical
Accident Prevention Provisions" on June 20, 1996. The rule is codified at part 68 of Title 40 of the Code of
Federal Regulations (CFR). If you handle, manufacture, use, or store any of the toxic or flammable
substances listed in 40 CFR 68.130 above the specified threshold quantities in a process, you are required to
develop and implement a risk management program under part 68 of 40 CFR. The rule applies to a wide
variety of facilities that handle, manufacture, store, or use toxic substances, including chlorine and ammonia,
and highly flammable substances, such as propane. If you are not sure whether you are subject to the rule,
you should review the rule and Chapters 1 and 2 of EPA's General Guidance for Risk Management
Programs (40 CFR part 68), available from EPA at http://www.epa.gov/ceppo/.
If you are subject to the rule, you are required to conduct an offsite consequence analysis to provide
information to the state, local, and federal governments and the public about the potential consequences of an
accidental chemical release. The offsite consequence analysis consists of two elements:
+ A worst-case release scenario, and
+ Alternative release scenarios.
To simplify the analysis and ensure comparability, EPA has defined the worst-case scenario as the
release of the largest quantity of a regulated substance from a single vessel or process line failure that results
in the greatest distance to an endpoint. In broad terms, the distance to the endpoint is the distance a toxic
vapor cloud, heat from a fire, or blast waves from an explosion will travel before dissipating to the point that
serious injuries from short-term exposures will no longer occur. Endpoints for regulated substances are
specified in 40 CFR 68.22(a) and Appendix A of part 68 and are presented in Appendices B and C of this
guidance.
Alternative release scenarios are scenarios that are more likely to occur than the worst-case scenario
and that will reach an endpoint offsite, unless no such scenario exists. Within these two parameters, you
have flexibility to choose alternative release scenarios that are appropriate for your site. The rule, in 40 CFR
68.28 (b)(2), and the General Guidance for Risk Management Programs (40 CFR part 68), Chapter 4,
provide examples of alternative release scenarios that you should consider when conducting the offsite
consequence analysis.
April 15, 1999
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Chapter 1
Introduction
TM
RMP*Comp
To assist those using this guidance, the National Oceanic and Atmospheric Administration (NOAA) and
EPA have developed a software program, RMP*Comp™, that performs the calculations described in
this document. This software can be downloaded from the EPA/CEPPO Internet website at
http://www.epa.gov/ceppo/ds-epds.htnrfcomp.
This guidance document provides a simple methodology for conducting offsite consequence analyses.
You may use simple equations to estimate release rates and reference tables to determine distances to the
endpoint of concern. This guidance provides generic reference tables of distances, applicable to most of the
regulated toxic substances, and chemical-specific tables for ammonia, chlorine, and sulfur dioxide. This
guidance also provides reference tables of distances for consequences of fires and explosions of flammable
substances. In some cases, the rule allows users of this document to adopt generic assumptions rather than the
site-specific data required if another model is employed (see Exhibit 1).
The methodology and reference tables of distances presented here are optional. You are not
required to use this guidance. You may use publicly available or proprietary air dispersion models to do
your offsite consequence analysis, subject to certain conditions. If you choose to use models instead of this
guidance, you should review the rule and Chapter 4 of the General Guidance for Risk Management
Programs, which outline required conditions for use of models. In selected example analyses, this document
presents the results of some models to provide a basis for comparison. It also indicates certain conditions of a
release that may warrant more sophisticated modeling than is represented here. However, this guidance does
not discuss the procedures to follow when using models; if you choose to use models, you should consult the
appropriate references or instructions for those models.
This guidance provides distances to endpoints for toxic substances that range from 0.1 miles to 25
miles. Other models may not project distances this far (and some may project even longer distances). One
commonly used model, ALOHA, has an artificial distance cutoff of 6 miles (i.e., any scenario which would
result in an endpoint distance beyond 6 miles is reported as "greater than 6 miles"). Although you may use
ALOHA if it is appropriate for the substance and scenario, you should consider choosing a different model if
the scenario would normally result in an endpoint distance significantly greater than 6 miles. Otherwise, you
should be prepared to explain the difference between your results and those in this guidance or other
commonly used models. Also, you should be aware that the RMP*Submit system accepts only numerical
entries (i.e., it will not accept a "greater than" distance). If you do enter a distance in RMP*Submit that is the
result of a particular model's maximum distance cutoff (including the maximum distance cutoff in this
guidance), you can explain this in the executive summary of your RMP.
April 15, 1999
1 -2
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Exhibit 1
Required Parameters for Modeling (40 CFR 68.22)
WORST CASE
ALTERNATIVE SCENARIO
Endpoints (§68.22(a))
Endpoints for toxic substances are specified in part 68 Appendix A.
For flammable substances, endpoint is overpressure of 1 pound per square
inch (psi) for vapor cloud explosions.
Endpoints for toxic substances are specified in part 68 Appendix A.
For flammable substances, endpoint is:
4-Overpressure of 1 psi for vapor cloud explosions, or
4-Radiant heat level of 5 kilowatts per square meter (kW/m2) for 40
seconds for heat from fires (or equivalent dose), or
4-Lower flammability limit (LFL) as specified in NFPA documents or
other generally recognized sources.
Wind speed/stability (§68.22(b))
This guidance assumes 1 .5 meters per second and F stability. For other
models, use wind speed of 1 .5 meters per second and F stability class
unless you can demonstrate that local meteorological data applicable to
the site show a higher minimum wind speed or less stable atmosphere at
all times during the previous three years. If you can so demonstrate, these
minimums may be used for site-specific modeling.
This guidance assumes wind speed of 3 meters per second and D
stability. For other models, you must use typical meteorological
conditions for your site.
Ambient temperature/humidity (§68.22(c))
This guidance assumes 25°C (77°F) and 50 percent humidity. For other
models for toxic substances, you must use the highest daily maximum
temperature and average humidity for the site during the past three years.
This guidance assumes 25 °C and 50 percent humidity. For other
models, you may use average temperature/humidity data gathered at the
site or at a local meteorological station.
Height of release (§68.22(d))
For toxic substances, you must assume a ground level release.
This guidance assumes a ground-level release. For other models, release
height may be determined by the release scenario.
Surface roughness (§68.22(e))
Use urban (obstructed terrain) or rural (flat terrain) topography, as
appropriate.
Use urban (obstructed terrain) or rural (flat terrain) topography, as
appropriate.
Dense or neutrally buoyant gases (§68.22(1))
Tables or models used for dispersion of regulated toxic substances must
appropriately account for gas density. If you use this guidance, see Tables
1-4 for neutrally buoyant gases and Tables 5-8 for dense gases, or Tables
9-12 for specific chemicals.
Tables or models used for dispersion must appropriately account for gas
density. If you use this guidance, see Tables 14-17 for neutrally
buoyant gases and Tables 18-21 for dense gases, or Tables 22-25 for
specific chemicals.
Temperature of released substance (§68.22(g))
You must consider liquids (other than gases liquefied by refrigeration) to
be released at the highest daily maximum temperature, from data for the
previous three years, or at process temperature, whichever is higher.
Assume gases liquefied by refrigeration at atmospheric pressure to be
released at their boiling points. This guidance provides factors for
estimation of release rates at25°C or the boiling point of the released
substance, and also provides temperature correction factors.
Substances may be considered to be released at a process or ambient
temperature that is appropriate for the scenario. This guidance
provides factors for estimation of release rates at 25 °C or the boiling
point of the released substance, and also provides temperature
correction factors.
April 15, 1999
1 -3
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Chapter 1
Introduction
1.2 This Guidance Compared to Other Models
Results obtained using the methods in this document are expected to be conservative (i.e., they will
generally, but not always, overestimate the distance to endpoints). The chemical-specific reference tables in
this guidance provide less conservative results than the generic reference tables, because the chemical-specific
tables were derived using more realistic assumptions and considering more factors.
Complex models that can account for many site-specific factors may give less conservative estimates
of offsite consequences than the simple methods in this guidance. This is particularly true for alternative
scenarios, for which EPA has not specified many assumptions. However, complex models may be expensive
and require considerable expertise to use; this guidance is designed to be simple and straightforward. You
will need to consider these tradeoffs in deciding how to carry out your required consequence analyses.
Appendix A provides information on references for some other methods of analysis; these references do not
include all models that you may use for these analyses. You will find that modeling results will sometimes
vary considerably from model to model.
1.3 Number of Scenarios to Analyze
The number and type of analyses you must perform depend on the "Program" level of each of your
processes. The rule defines three Program levels. Processes are eligible for Program 1 if, among other
criteria, there are no public receptors within the distance to the endpoint for the worst-case scenario. Because
no public receptors would be affected by the worst-case release, no further modeling is required for these
processes. For processes subject to Program 2 or Program 3, both worst-case release scenarios and
alternative release scenarios are required. To determine the Program level of your processes, consult 40 CFR
68.10(b), (c), and (d), or Chapter 2 of EPA's General Guidance for Risk Management Programs (40 CFR
part 68).
Once you have determined the Program level of your processes, you are required to conduct the
following offsite consequence analyses:
• One worst-case release scenario for each Program 1 process;
• One worst-case release scenario to represent all regulated toxic substances in Program 2 and
Program 3 processes;
• One worst-case release scenario to represent all regulated flammable substances in Program
2 and Program 3 processes;
• One alternative release scenario for each regulated toxic substance in Program 2 and
Program 3 processes; and
• One alternative release scenario to represent all regulated flammable substances in Program
2 and Program 3 processes.
NOTE: You may need to analyze additional worst-case scenarios if release scenarios for regulated
flammable or toxic substances from other covered processes at your facility would affect different public
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Chapter 1
Introduction
receptors. For example, worst-case release scenarios for storage tanks at opposite ends of your facility may
potentially reach different areas where people could be affected. In that case, you will have to conduct
analyses of and report on both releases.
GUIDANCE FOR INDUSTRY-SPECIFIC RISK MANAGEMENT PROGRAMS
EPA developed guidance for industry-specific risk management programs for the following industries:
•f Propane storage facilities + Warehouses
+ Chemical distributors + Ammonia refrigeration
•f Waste water treatment plants + Small propane retailers & users
The industry-specific guidances are available from EPA at http://www.epa.gov/ceppo/.
Industry-specific guidances developed by EPA take the place of this guidance document and the General
Guidance for Risk Management Programs for the industries addressed. If an industry-specific program
exists for your process(es), you should use it as your basic guidance because it will provide more
information that is specific to your process, including dispersion modeling.
1.4 Modeling Issues
The consequences of an accidental chemical release depend on the conditions of the release and the
conditions at the site at the time of the release. This guidance provides reference tables of distances, based on
results of modeling, for estimation of worst-case and alternative scenario consequence distances. Worst-case
consequence distances obtained using these tables are not intended to be precise predictions of the exact
distances that might be reached in the event of an actual accidental release. For this guidance, worst-case
distances are based on modeling results assuming the combination of worst-case conditions required by the
rule. This combination of conditions occurs rarely and is unlikely to persist for very long. To derive the
alternative scenario distances, less conservative assumptions were used for modeling; these assumptions were
chosen to represent more likely conditions than the worst-case assumptions. Nevertheless, in an actual
accidental release, the conditions may be very different. Users of this guidance should remember that the
results derived from the methods presented here are rough estimates of potential consequence distances.
Other models may give different results; the same model also may give different results if different
assumptions about release conditions and/or site conditions are used.
The reference tables of distances in this guidance provide results to a maximum distance of 25 miles.
EPA recognizes that modeling results at such large distances are highly uncertain. Almost no experimental
data or data from accidents are available at such large distances to compare to modeling results. Most data
are reported for distances well under 10 miles. Modeling uncertainties are likely to increase as distances
increase because conditions (e.g., atmospheric stability, wind speed, surface roughness) are not likely to
remain constant over large distances. Thus, at large distances (e.g., greater than about 6 to 10 miles), the
modeling results should be viewed as very coarse estimates of consequence distances. EPA believes,
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Introduction
however, that the results, even at large distances, can provide useful information for comparison purposes.
For example, Local Emergency Planning Committees (LEPCs) and other local agencies can use relative
differences in distance to aid in establishing chemical accident prevention and preparedness priorities among
facilities in a community. Since worst-case scenario distances are based on modeling conditions that are
unlikely to occur, and since modeling of any scenario that results in large distances is very uncertain, EPA
strongly urges communities and industry not to rely on the results of worst-case modeling or any modeling
that results in very large toxic endpoint distances in emergency planning and response activities. Results of
alternative scenario models are apt to provide a more reasonable basis for planning and response.
1.5 Steps for Performing the Analysis
This Chapter presents the steps you should follow in using this guidance to carry out an offsite
consequence analysis. Before carrying out one or more worst-case and/or alternative release analyses, you
will need to obtain several pieces of information about the regulated substances you have, the area
surrounding your site, and typical meteorological conditions:
• Determine whether each regulated substance is toxic or flammable, as indicated in the rule or
Appendices B and C of this guidance.
• For the worst-case analysis, determine the quantity of each substance held in the largest
single vessel or pipe.
• Collect information about any passive or active (alternative scenarios only) release
mitigation measures that are in place for each substance.
• For toxic substances, determine whether the substance is stored as a gas, as a liquid, as a gas
liquefied by refrigeration, or as a gas liquefied under pressure. For alternative scenarios
involving a vapor cloud fire, you may also need this information for flammable substances.
• For toxic liquids, determine the highest daily maximum temperature of the liquid, based on
data for the previous three years, or process temperature, whichever is higher.
• For toxic substances, determine whether the substance behaves as a dense or neutrally
buoyant gas or vapor (see Appendix B, Exhibits B-l and B-2). For alternative scenarios
involving a vapor cloud fire, you will also need this information for flammable substances
(see Appendix C, Exhibits C-2 and C-3).
• For toxic substances, determine whether the topography (surface roughness) of your site is
either urban or rural as thse terms are defined by the rule (see 40 CFR 68.22(e)). For
alternative scenarios involving a vapor cloud fire, you will also need this information for
flammable substances.
After you have gathered the above information, you will need to take three steps (except for
flammable worst-case releases):
(1) Select a scenario;
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Chapter 1
Introduction
(2) Determine the release or volatilization rate; and
(3) Determine the distance to the endpoint.
For flammable worst-case scenarios, only steps one and three are needed. Sections 1.5.1 through 1.5.6
outline the procedures to perform the analyses. In addition to basic procedures, these sections provide
references to sections of this guidance where you will find detailed instructions on carrying out the applicable
portion of the analysis. Sections 1.5.1 through 1.5.3 below provide basic steps to analyze worst-case
scenarios for toxic gases, toxic liquids, and flammable substances. Sections 1.5.4 through 1.5.6 provide
basic steps for alternative scenario analysis. Appendix E of this document provides worksheets that may help
you to perform the analyses.
1.5.1 Worst-Case Analysis for Toxic Gases
To conduct worst-case analyses for toxic gases, including toxic gases liquefied by pressurization (see
Appendix E, Worksheet 1, for a worksheet that can be used in carrying out this analysis):
Step 1: Determine worst-case scenario. Identify the toxic gas, quantity, and worst-case release scenario, as
defined by the rule (Chapter 2).
Step 2: Determine release rate. Estimate the release rate for the toxic gas, using the parameters required by
the rule. This guidance provides methods for estimating the release rate for:
• Unmitigated releases (Section 3.1.1).
• Releases with passive mitigation (Section 3.1.2).
Step 3: Determine distance to endpoint. Estimate the worst-case consequence distance based on the release
rate and toxic endpoint (defined by the rule) (Chapter 4). This guidance provides reference tables of
distances (Reference Tables 1-12). Select the appropriate reference table based on the density of the
released substance, the topography of your site, and the duration of the release (always 10 minutes
for gas releases). Estimate distance to the endpoint from the appropriate table.
1.5.2 Worst-Case Analysis for Toxic Liquids
To conduct worst-case analyses for toxic substances that are liquids at ambient conditions or for
toxic gases that are liquefied by refrigeration alone (see Appendix E, Worksheet 2, for a worksheet for this
analysis):
Step 1: Determine worst-case scenario. Identify the toxic liquid, quantity, and worst-case release scenario, as
defined by the rule (Chapter 2). To estimate the quantity of liquid released from piping, see Section
3.2.1.
Step 2: Determine release rate. Estimate the volatilization rate for the toxic liquid and the duration of the
release, using the parameters required by the rule. This guidance provides methods for estimating the
pool evaporation rate for:
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Chapter 1
Introduction
• Gases liquefied by refrigeration alone (Sections 3.1.3 and 3.2.3).
• Unmitigated releases (Section 3.2.2).
• Releases with passive mitigation (Section 3.2.3).
• Releases at ambient or elevated temperature (Sections 3.2.2, 3.2.3, and 3.2.5).
• Releases of mixtures of toxic liquids (Section 3.2.4).
• Releases of common water solutions of regulated substances and of oleum (Section 3.3).
Step 3: Determine distance to endpoint. Estimate the worst-case consequence distance based on the release
rate and toxic endpoint (defined by the rule) (Chapter 4). This guidance provides reference tables of
distances (Reference Tables 1-12). Select the appropriate reference table based on the density of the
released substance, the topography of your site, and the duration of the release. Estimate distance to
the endpoint from the appropriate table.
1.5.3 Worst-Case Analysis for Flammable Substances
To conduct worst-case analyses for all regulated flammable substances (i.e., gases and liquids) (see
Appendix E, Worksheet 3, for a worksheet for this analysis):
Step 1: Determine worst-case scenario. Identify the appropriate flammable substance, quantity, and worst-
case scenario, as defined by the rule (Chapter 2).
Step 2: Determine distance to endpoint. Estimate the distance to the required overpressure endpoint of 1 psi
for a vapor cloud explosion of the flammable substance, using the assumptions required by the rule
(Chapter 5). This guidance provides a reference table of distances (Reference Table 13) for worst-
case vapor cloud explosions. Estimate the distance to the endpoint from the quantity released and the
table.
1.5.4 Alternative Scenario Analysis for Toxic Gases
To conduct alternative release scenario analyses for toxic gases, including toxic gases liquefied by
pressurization (see Appendix E, Worksheet 4, for a worksheet for this analysis):
Step 1: Select alternative scenario. Choose an appropriate alternative release scenario for the toxic gas. This
scenario should have the potential for offsite impacts unless no such scenario exists. (Chapter 6).
Step 2: Determine release rate. Estimate the release rate and duration of the release of the toxic gas, based
on your scenario and site-specific conditions. This guidance provides methods for:
• Unmitigated releases (Section 7.1.1).
• Releases with active or passive mitigation (Section 7.1.2).
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Chapter 1
Introduction
Step 3: Determine distance to endpoint. Estimate the alternative scenario distance based on the release rate
and toxic endpoint (Chapter 8). This guidance provides reference tables of distances (Reference
Tables 14-25) for alternative scenarios for toxic substances. Select the appropriate reference table
based on the density of the released substance, the topography of your site, and the duration of the
release. Estimate distance to the endpoint from the appropriate table.
1.5.5 Alternative Scenario Analysis for Toxic Liquids
To conduct alternative release scenario analyses for toxic substances that are liquids at ambient
conditions or for toxic gases that are liquefied by refrigeration alone (see Appendix E, Worksheet 5, for a
worksheet for this analysis):
Step 1: Select alternative scenario. Choose an appropriate alternative release scenario and release quantity
for the toxic liquid. This scenario should have the potential for offsite impacts (Chapter 6), unless no
such scenario exists.
Step 2: Determine release rate. Estimate the release rate and duration of the release of the toxic liquid, based
on your scenario and site-specific conditions. This guidance provides methods to estimate the liquid
release rate and quantity of liquid released for:
• Unmitigated liquid releases (Section 7.2.1).
• Mitigated liquid releases (Section 7.2.2).
The released liquid is assumed to form a pool. This guidance provides methods to estimate the pool
evaporation rate and release duration for:
• Unmitigated releases (Section 7.2.3).
• Releases with passive or active mitigation (Section 7.2.3).
• Releases at ambient or elevated temperature (Sections 7.2.3).
• Releases of common water solutions of regulated substances and of oleum (Section 7.2.4).
Step 3: Determine distance to endpoint. Estimate the alternative scenario distance based on the release rate
and toxic endpoint (Chapter 8). This guidance provides reference tables of distances (Reference
Tables 14-25) for alternative scenarios for toxic substances. Select the appropriate reference table
based on the density of the released substance, the topography of your site, and the duration of the
release. Estimate distance to the endpoint from the appropriate table.
1.5.6 Alternative Scenario Analysis for Flammable Substances
To conduct alternative release scenario analyses for all regulated flammable substances (i.e., gases
and liquids) (see Appendix E, Worksheet 6, for a worksheet for this analysis):
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Chapter 1
Introduction
Step 1: Select alternative scenario. Identify the flammable substance, and choose the quantity and type of
event for the alternative scenario consequence analysis (Chapter 6).
Step 2: Determine release rate. Estimate the release rate to air of the flammable gas or liquid, if the scenario
involves a vapor cloud fire (Section 9.1 for flammable gases, Section 9.2 for flammable liquids).
Step 3: Determine distance to endpoint. Estimate the distance to the appropriate endpoint (defined by the
rule). This guidance provides methods for:
• Vapor cloud fires (Section 10.1 and Reference Tables 26-29); select the appropriate
reference table based on the density of the released substance and the topography of your
site, and estimate distance to the endpoint from the appropriate table.
• Pool fires (Section 10.2); estimate distance from the equation and chemical-specific factors
provided.
• BLEVEs (Section 10.3 and Reference Table 30); estimate distance from the quantity of
flammable substance and the table.
• Vapor cloud explosions (Section 10.4 and Reference Table 13); estimate quantity in the
cloud from the equation and chemical-specific factors provided, and estimate distance from
the quantity, the table, and a factor provided for alternative scenarios.
1.6 Additional Sources of Information
EPA's risk management program requirements may be found at 40 CFR part 68. The relevant
sections were published in the Federal Register on January 31, 1994 (59 FR4478) and June 20, 1996 (61
FR 31667). Final rules amending the list of substances and thresholds were published on August 25, 1997
(62 FR 45130) and January 6, 1998 (63 FR 640). A consolidated copy of these regulations is available in
Appendix F.
EPA is working with industry and local, state, and federal government agencies to assist sources in
complying with these requirements. For more information, refer to the General Guidance for Risk
Management Programs Appendix E (Technical Assistance). Appendices C and D of the General Guidance
also provide points of contact for EPA and Occupational Safety and Health Administration (OSHA) at the
state and federal levels for your questions. Your LEPC also can be a valuable resource.
Finally, if you have access to the Internet, EPA has made copies of the rules, fact sheets, and other
related materials available at the home page of EPA's Chemical Emergency Preparedness and Prevention
Office (http://www.epa.gov/ceppo/). Please check the site regularly, as additional materials are posted when
they become available. If you do not have access to the Internet, you can call EPA's hotline at (800) 424-
9346.
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DETERMINING WORST-CASE SCENARIOS
In Chapter 2
2.1 EPA's definition of a worst-case scenario.
2.2 How to determine the quantity released.
2.3 How to identify the appropriate worst-case scenario.
2.1 Definition of Worst-Case Scenario
A worst-case release is defined as:
• The release of the largest quantity of a regulated substance from a vessel or process line
failure, and
• The release that results in the greatest distance to the endpoint for the regulated toxic or
flammable substance.
You may take administrative controls into account when determining the largest quantity.
Administrative controls are written procedures that limit the quantity of a substance that can be stored or
processed in a vessel or pipe at any one time or, alternatively, procedures that allow the vessel or pipe to
occasionally store larger than usual quantities (e.g., during shutdown or turnaround). Endpoints for regulated
substances are specified in the rule (40 CFR 68.22(a), and Appendix A to part 68 for toxic substances). For
the worst-case analysis, you do not need to consider the possible causes of the worst-case release or the
probability that such a release might occur; the release is simply assumed to take place. You must assume all
releases take place at ground level for the worst-case analysis.
This guidance assumes meteorological conditions for the worst-case scenario of atmospheric stability
class F (stable atmosphere) and wind speed 1.5 meters per second (3.4 miles per hour). Ambient air
temperature for this guidance is 25 °C (77 °F). If you use this guidance, you may assume this ambient
temperature for the worst case, even if the maximum temperature at your site in the last three years is higher.
The rule provides two choices for topography, urban and rural. EPA (40 CFR 68.22(e)) has defined
urban as many obstacles in the immediate area, where obstacles include buildings or trees. Rural, by EPA's
definition, means there are no buildings in the immediate area, and the terrain is generally flat and
unobstructed. Thus, if your site is located in an area with few buildings or other obstructions (e.g., hills,
trees), you should assume open (rural) conditions. If your site is in an area with many obstructions, even if it
is in a remote location that would not usually be considered urban, you should assume urban conditions.
Toxic Gases
Toxic gases include all regulated toxic substances that are gases at ambient temperature (25 °C, 77
°F), with the exception of gases liquefied by refrigeration under atmospheric pressure and released into diked
areas. For the worst-case consequence analysis, you must assume that a gaseous release of the total quantity
occurs in 10 minutes. You may take passive mitigation measures (e.g., enclosure) into account in the analysis
of the worst-case scenario.
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Chapter 2
Determining Worst-Case Scenarios
Gases liquefied by refrigeration alone and released into diked areas may be modeled as liquids at
their boiling points and assumed to be released from a pool by evaporation (40 CFR 68.25(c)(2)). Gases
liquefied by refrigeration alone that would form a pool one centimeter or less in depth upon release must be
modeled as gases. (Modeling indicates that pools one centimeter or less deep formed by gases liquefied by
refrigeration would completely evaporate in 10 minutes or less, giving a release rate that is equal to or greater
than the worst-case release rate for a gaseous release. In this case, therefore, it is appropriate to treat these
substances as gases for the worst-case analysis.)
Endpoints for consequence analysis for regulated toxic substances are specified in the rule (40 CFR
part 68, Appendix A). Exhibit B-l of Appendix B lists the endpoint for each toxic gas. These endpoints are
used for air dispersion modeling to estimate the consequence distance.
Toxic Liquids
For toxic liquids, you must assume that the total quantity in a vessel is spilled. This guidance
assumes the spill takes place onto a flat, non-absorbing surface. For toxic liquids carried in pipelines, the
quantity that might be released from the pipeline is assumed to form a pool. You may take passive mitigation
systems (e.g., dikes) into account in consequence analysis. The total quantity spilled is assumed to spread
instantaneously to a depth of one centimeter (0.033 foot or 0.39 inch) in an undiked area or to cover a diked
area instantaneously. The temperature of the released liquid must be the highest daily maximum temperature
occurring in the past three years or the temperature of the substance in the vessel, whichever is higher (40
CFR 68.25(d)(2)). The release rate to air is estimated as the rate of evaporation from the pool. If liquids at
your site might be spilled onto a surface that could rapidly absorb the spilled liquid (e.g., porous soil), the
methods presented in this guidance may greatly overestimate the consequences of a release. Consider using
another method in such a case.
Exhibit B-2 of Appendix B presents the endpoint for air dispersion modeling for each regulated toxic
liquid (the endpoints are specified in 40 CFR part 68, Appendix A).
Flammable Substances
For all regulated flammable substances, you must assume that the worst-case release results in a
vapor cloud containing the total quantity of the substance that could be released from a vessel or pipeline.
For the worst-case consequence analysis, you must assume the vapor cloud detonates. If you use a TNT-
equivalent method for your analysis, you must assume a 10 percent yield factor.
The rule specifies the endpoint for the consequence analysis of a vapor cloud explosion of a regulated
flammable substance as an overpressure of 1 pound per square inch (psi). This endpoint was chosen as the
threshold for potential serious injuries to people as a result of property damage caused by an explosion (e.g.,
injuries from flying glass from shattered windows or falling debris from damaged houses). (See Appendix D,
Section D.5 for additional information on this endpoint.)
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Chapter 2
Determining Worst-Case Scenarios
Effect of Required Assumptions
The assumptions required for the worst-case analysis are intended to provide conservative worst-case
consequence distances, rather than accurate predictions of the potential consequences of a release; that is, in
most cases your results will overestimate the effects of a release. In certain cases, actual conditions could be
even more severe than these worst-case assumptions (e.g., very high process temperature, high process
pressure, or unusual weather conditions, such as temperature inversions); in such cases, your results might
underestimate the effects. However, the required assumptions generally are expected to give conservative
results.
2.2 Determination of Quantity for the Worst-Case Scenario
EPA has defined a worst-case release as the release of the largest quantity of a regulated substance
from a vessel or process line failure that results in the greatest distance to a specified endpoint. For
substances in vessels, you must assume release of the largest amount in a single vessel. For substances in
pipes, you must assume release of the largest amount in a pipe. The largest quantity should be determined
taking into account administrative controls rather than absolute capacity of the vessel or pipe. Administrative
controls are written procedures that limit the quantity of a substance that can be stored or processed in a
vessel or pipe at any one time, or, alternatively, occasionally allow a vessel or pipe to store larger than usual
quantities (e.g., during turnaround).
2.3 Selecting Worst-Case Scenarios
Under part 68, a worst-case release scenario analysis must be completed for all covered processes,
regardless of program level. The number of worst-case scenarios you must analyze depends on several
factors. You need to consider only the hazard (toxicity or flammability) for which a substance is regulated
(i.e., even if a regulated toxic substance is also flammable, you only need to consider toxicity in your analysis;
even if a regulated flammable substance is also toxic, you only need to consider flammability).
For every Program 1 process, you must report the worst-case scenario with the greatest distance to an
endpoint. If a Program 1 process has more than one regulated substance held above its threshold, you must
determine which substance produces the greatest distance to its endpoint and report on that substance. If a
Program 1 process has both regulated toxics and flammables above their thresholds, you still report only the
one scenario that produces the greatest distance to the endpoint. The process is eligible for Program 1 if there
are no public receptors within the distance to an endpoint of the worst-case scenario for the process and the
other Program 1 criteria are met. For Program 2 or Program 3 processes, you must analyze and report on one
worst-case analysis representing all toxic regulated substances present above the threshold quantity and one
worst-case analysis representing all flammable regulated substances present above the threshold quantity.
You may need to submit an additional worst-case analysis if a worst-case release from elsewhere at the source
would potentially affect public receptors different from those affected by the initial worst-case scenario(s).
If you have more than one regulated substance in a class, the substance chosen for the consequence
analysis for each hazard for Program 2 and 3 processes should be the substance that has the potential to cause
the greatest offsite consequences. Choosing the toxic regulated substance that might lead to the greatest
offsite consequences may require a screening analysis of the toxic regulated substances on site, because the
potential consequences are dependent on a number of factors, including quantity, toxicity, and volatility.
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Chapter 2
Determining Worst-Case Scenarios
Location (distance to the fenceline) and conditions of processing or storage (e.g., a high temperature process)
also should be considered. In selecting the worst-case scenario, you may want to consider the following
points:
• Toxic gases with low toxic endpoints are likely to give the greatest distances to the endpoint
for a given release quantity; a toxic gas would be a likely choice for the worst-case analysis
required for Program 2 and 3 processes (processes containing toxic gases are unlikely to be
eligible for Program 1).
• Volatile, highly toxic liquids (i.e., liquids with high ambient vapor pressure and low toxic
endpoints) also are likely to give large distances to the endpoint (processes containing this
type of substance are unlikely to be eligible for Program 1).
• Toxic liquids with relatively low volatility (low vapor pressure) and low toxicity (large toxic
endpoint) in ambient temperature processes may give fairly small distances to the endpoint;
you probably would not choose such substances for the worst-case analysis for Program 2 or
3 if you have other regulated toxics, but you may want to consider carrying out a worst-case
analysis to demonstrate potential Program 1 eligibility.
For flammable substances, you must consider the consequences of a vapor cloud explosion in the
analysis. The severity of the consequences of a vapor cloud explosion depends on the quantity of the released
substance in the vapor cloud, its heat of combustion, and other factors that are assumed to be the same for all
flammable substances. In most cases, the analysis probably should be based on the regulated flammable
substance present in the greatest quantity; however, a substance with a high heat of combustion may have a
greater potential offsite impact than a larger quantity of a substance with a lower heat of combustion. In
some cases, a regulated flammable substance that is close to the fenceline might have a greater potential
offsite impact than a larger quantity farther from the fenceline.
You are likely to estimate smaller worst-case distances for flammable substances than for similar
quantities of most toxic substances. Because the distance to the endpoint may be relatively small, you may
find it worthwhile to carry out a worst-case analysis for each process containing flammable substances to
demonstrate potential eligibility for Program 1, unless there are public receptors close to the process.
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RELEASE RATES FOR TOXIC SUBSTANCES
In Chapter 3
3.1 Estimation of worst-case release rates for toxic gases.
3.2 Estimation of release rates for toxic liquids evaporating from pools.
3.3 Estimation of release rates for common water solutions of toxic substances
and for oleum.
This chapter describes simple methods for estimating release rates for regulated toxic substances for
the worst-case scenario. Simple release rate equations are provided, and factors to be used in these equations
are provided (in Appendix B) for each regulated substance. The estimated release rates may be used to
estimate dispersion distances to the toxic endpoint for regulated toxic gases and liquids, as discussed in
Chapter 4.
3.1 Release Rates for Toxic Gases
In Section 3.1
3.1.1 Method to estimate worst-case release rates for unmitigated releases
(releases directly to the air) of toxic gas.
3.1.2 Method to estimate worst-case release rates for toxic gas in enclosures
(passive mitigation).
3.1.3 Method to estimate worst-case release rates for liquefied refrigerated
toxic gases in diked areas (as toxic liquid - see Section 3.2.3), including
consideration of the duration of the release.
Regulated substances that are gases at ambient temperature (25 °C, 77 °F) should be considered
gases for consequence analysis, with the exception of gases liquefied by refrigeration at atmospheric pressure.
Gases liquefied under pressure should be treated as gases. Gases liquefied by refrigeration alone and released
into diked areas may be treated as liquids at their boiling points if they would form a pool upon release that is
more than one centimeter (0.033 foot) in depth. Gases liquefied by refrigeration alone that would form a pool
one centimeter (0.033 foot) or less in depth should be treated as gases. Modeling shows that the evaporation
rate from such a pool would be equal to or greater than the rate for a toxic gas, which is assumed to be
released over 10 minutes; therefore, treating liquefied refrigerated gases as gases rather than liquids in such
cases is reasonable. You may consider passive mitigation for gaseous releases and releases of gases liquefied
by refrigeration.
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Chapter 3
Release Rates for Toxic Substances
3.1.1 Unmitigated Releases of Toxic Gas
If no passive mitigation system is in place, estimate the release rate for the release over a 10-minute
period of the largest quantity resulting from a pipe or vessel failure, as required by the rule (40 CFR
68.25(c)). For a release from a vessel, calculate the release rate as follows:
(3-1)
10
where:
QR
QS
Release rate (pounds per minute)
Quantity released (pounds)
Example 1. Gas Release (Diborane)
You have a tank containing 2,500 pounds of diborane gas. Assuming the total quantity in the tank is released
over a 10-minute period, the release rate (QR), from Equation 3-1, is:
QR = 2,500 pounds/10 minutes = 250 pounds per minute
3.1.2 Releases of Toxic Gas in Enclosed Space
If a gas is released in an enclosure such as a building or shed, the release rate to the outside air may
be lessened considerably. The dynamics of this type of release are complex; however, you may use the
simplified method presented here to estimate an approximate release rate to the outside air from a release in
an enclosed space. The mitigation factor (i.e., 55 percent) presented in this method assumes that the release
occurs in a fully enclosed, non-airtight space that is directly adjacent to the outside air. If you are modeling a
release in an interior room that is enclosed within a building, a smaller factor (i.e., more mitigation) may be
appropriate. On the other hand, a larger factor (i.e., less mitigation) should be used for a space that has doors
or windows that could be open during a release. If any of these special circumstances apply to your site, you
may want to consider performing site-specific modeling to determine the appropriate amount of passive
mitigation. In addition, you should not incorporate the passive mitigation effect of building enclosures into
your modeling if you have reason to believe the enclosure would not withstand the force of the release or if
the chemical is handled outside the building (e.g., moved from one building to another building).
For the worst case, assume as before that the largest quantity resulting from a pipe or vessel failure is
released over a 10-minute period. Determine the unmitigated worst-case scenario release rate of the gas as
the quantity released divided by 10 (Equation 3-1). The release rate from the building will be approximately
55 percent of the worst-case scenario release rate (see Appendix D, Section D. 1.2 for the derivation of this
factor). Estimate the mitigated release rate as follows:
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OR = . x 0.55
10
where: QR = Release rate (pounds per minute)
QS = Quantity released (pounds)
0.55 = Mitigation factor (discussed in Appendix D, Section D. 1.2)
Example 2. Gas Release in Enclosure (Diborane)
Suppose the diborane gas from Example 1 is released inside a building at the rate of 250 pounds per minute.
The mitigated release to the outside air from the building would be:
QR = 250 pounds/minute x 0.55 = 138 pounds per minute
3.1.3 Releases of Liquefied Refrigerated Toxic Gas in Diked Area
If you have a toxic gas that is liquefied by refrigeration alone, and it will be released into an area
where it will be contained by dikes to form a pool more than one centimeter (0.033 foot) in depth, you may
carry out the worst-case analysis assuming evaporation from a liquid pool at the boiling point of the liquid. If
your gas liquefied by refrigeration would form a pool one centimeter (0.033 foot) or less in depth, use the
methods described in Section 3.1.1 or 3.1.2 above for the analysis. For a release in a diked area, first
compare the diked area to the maximum area of the pool that could be formed. You can use Equation 3-6 in
Section 3.2.3 to estimate the maximum size of the pool. Density factors (DF), needed for Equation 3-6, for
toxic gases at their boiling points are listed in Exhibit B-l of Appendix B. If the pool formed by the released
liquid would be smaller than the diked area, assume a 10-minute gaseous release, and estimate the release rate
as described in Section 3.1.1. If the dikes prevent the liquid from spreading out to form a pool of maximum
size (one centimeter in depth), you may use the method described in Section 3.2.3 for mitigated liquid
releases to estimate a release rate from a pool at the boiling point of the released substance. Use Equation 3-
8 in Section 3.2.3 for the release rate. The Liquid Factor Boiling (LFB) for each toxic gas, needed to use
Equation 3-8, is listed in Exhibit B-l of Appendix B. See the example release rate estimation on the next
page.
After you have estimated the release rate, estimate the duration of the vapor release from the pool
(the time it will take for the pool to evaporate completely) by dividing the total quantity spilled by the release
rate. You need to know the duration of release to choose the appropriate reference table of distances to
estimate the consequence distance, as discussed in Section 4. (You do not need to consider the duration of the
release for chlorine or sulfur dioxide, liquefied by refrigeration alone. Only one reference table of distances is
provided for worst-case releases of each of these substances, and these tables may be used regardless of the
release duration. The principal reason for making no distinction between 10-minute and longer releases for
the chemical-specific tables is that the differences between the two are small relative to the uncertainties that
have been identified.)
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Example 3. Mitigated Release of Gases Liquefied by Refrigeration (Chlorine)
You have a refrigerated tank containing 50,000 pounds of liquid chlorine at ambient pressure. A diked area
around the chlorine tank of 275 square feet is sufficient to hold all of the spilled liquid chlorine. Once the
liquid spills into the dike, it is then assumed to evaporate at its boiling point (-29 °F). The evaporation rate at
the boiling point is determined from Equation 3-8. For the calculation, wind speed is assumed to be 1.5 meters
per second and the wind speed factor is 1.4, LFB for chlorine (from Exhibit B-1) is 0.19, and A is 275 square
feet. The release rate is:
QR = 1.4 x 0.19 x 275 = 73 pounds per minute
The duration of the release does not need to be considered for chlorine.
3.2 Release Rates for Toxic Liquids
In Section 3.2
3.2.1 Method to estimate the quantity of toxic liquid that could be released from
a broken pipe.
3.2.2 Method to estimate the release rate of a toxic liquid evaporating from a
pool with no mitigation (no dikes or enclosures), including:
Releases at ambient temperature (25 °C),
Releases at elevated temperature, and
Estimation of the duration of the release.
3.2.3 Method to estimate the release rate of a toxic liquid evaporating from a
pool with passive mitigation, including:
Releases in diked areas,
Releases into other types of containment, and
Releases into buildings.
3.2.4 Estimation of release rates for mixtures containing toxic liquids.
3.2.5 Method to correct the estimated release rate for liquids released at
temperatures between 25 °C and 50 °C.
For the worst-case analysis, the release rate to air for toxic liquids is assumed to be the rate of
evaporation from the pool formed by the released liquid. This section provides methods to estimate the
evaporation rate. Assume the total quantity in a vessel or the maximum quantity from pipes is released into
the pool. Passive mitigation measures (e.g., dikes) may be considered in determining the area of the pool and
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the release rate. To estimate the consequence distance using this guidance, you must estimate how long it will
take for the pool to evaporate (the duration of the release), as well as the release rate, as discussed below.
The rule (40 CFR 68.22(g)) requires you to assume that liquids (other than gases liquefied by
refrigeration) are released at the highest maximum daily temperature for the previous three years or at process
temperature, whichever is higher. This chapter provides methods to estimate the release rate at 25 °C (77 °F)
or at the boiling point, and also provides a method to correct the release rate at 25 °C for releases at
temperatures between 25 °C and 50 °C.
The calculation methods provided in this section apply to substances that are liquids under ambient
conditions or gases liquefied by refrigeration alone that are released to form pools deeper than one centimeter
(see Section 3.1.3 above). You must treat gases liquefied under other conditions (under pressure or a
combination of pressure and refrigeration) or gases liquefied by refrigeration alone that would form pools one
centimeter or less in depth upon release as gas rather than liquid releases (see Sections 3.1.1 and 3.1.2
above).
3.2.1 Releases of Toxic Liquids from Pipes
To consider a liquid release from a broken pipe, estimate the maximum quantity that could be
released assuming that the pipe is full of liquid. To estimate the quantity in the pipe, you need to know the
length of the pipe (in feet) and cross-sectional area of the pipe (in square feet). Note also that liquid may be
released from both directions at a pipe shear (both in the direction of operational flow and the reverse
direction, depending on the location of the shear). Therefore, the length would be the full length of pipe
carrying the liquid on the facility grounds. Then, the volume of the liquid in the pipe (in cubic feet) is the
length of the pipe times the cross-sectional area. The quantity in the pipe (in pounds) is the volume divided
by the Density Factor (DF) times 0.033. (DF values are listed in Appendix B, Exhibit B-2. Density in
pounds per cubic foot is equal to 1/(DF times 0.033).) Assume the estimated quantity (in pounds) is released
into a pool and use the method and equations described below in Section 3.2.2 (unmitigated releases) or 3.2.3
(releases with passive mitigation) to determine the evaporation rate of the liquid from the pool.
3.2.2 Unmitigated Releases of Toxic Liquids
If no passive mitigation measures are in place, the liquid is assumed to form a pool one centimeter
(0.39 inch or 0.033 foot) deep instantaneously. You may calculate the release rate to air from the pool (the
evaporation rate) as discussed below for releases at ambient or elevated temperature.
Ambient Temperature
If the liquid is always at ambient temperature, find the Liquid Factor Ambient (LFA) and the Density
Factor (DF) in Exhibit B-2 of Appendix B. The LFA and DF apply to liquids at 25 °C; if your ambient
temperature is between 25 °C and 50 °C, you may use the method described here and then apply a
Temperature Correction Factor (TCP), as discussed in Section 3.2.5 below, to correct the calculated release
rate. Calculate the release rate of the liquid at 25 °C from the following equation:
QR = QS x 1.4 x LFA x DF (3-3)
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where:
QR
QS
1.4
LFA
DF
Release rate (pounds per minute)
Quantity released (pounds)
Wind speed factor = 1.5078, where 1.5 meters per second (3.4 miles per
hour) is the wind speed for the worst case
Liquid Factor Ambient
Density Factor
Example 4. Unmitigated Liquid Release at Ambient Temperature (Acrylonitrile)
You have a tank containing 20,000 pounds of acrylonitrile at ambient temperature. The total quantity in the
tank is spilled onto the ground in an undiked area, forming a pool. Assume the pool spreads out to a depth of
one centimeter. The release rate from the pool (QR) is calculated from Equation 3-3. For the calculation, the
wind speed is assumed to be 1.5 meters per second and the wind speed factor is 1.4. From Exhibit B-2,
Appendix B, LFA for acrylonitrile is 0.018 and DF is 0.61. Then:
QR = 20,000 x 1.4x0.018x0.61 = 307 pounds per minute
The duration of the release (from Equation 3-5) would be:
t = 20,000 pounds/307 pounds per minute = 65 minutes
Elevated Temperature
If the liquid is at an elevated temperature (above 50 °C or at or close to the boiling point), find the
Liquid Factor Boiling (LFB) and the Density Factor (DF) in Exhibit B-2 of Appendix B (see Appendix D,
Section D.2.2, for the derivation of these factors). For temperatures up to 50 °C, you may use the method
above for ambient temperature and apply the Temperature Correction Factors, as discussed in Section 3.2.5.
If the temperature is above 50 °C, or the liquid is at or close to its boiling point, or no Temperature Correction
Factors are available for your liquid, calculate the release rate of the liquid from the following equation:
QR = QS x 1.4 x LFB x DF
(3-4)
where:
QR
QS
1.4
LFB
DF
Release rate (pounds per minute)
Quantity released (pounds)
Wind speed factor = 1.5078, where 1.5 meters per second (3.4 miles per
hour) is the wind speed for the worst case
Liquid Factor Boiling
Density Factor
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Example 5. Unmitigated Release at Elevated Temperature (Acrylonitrile)
You have a tank containing 20,000 pounds of acrylonitrile at an elevated temperature. The total quantity in the
tank is spilled onto the ground in an undiked area, forming a pool. Assume the pool spreads out to a depth of
one centimeter. The release rate from the pool is calculated from Equation 3-4. For the calculation, the wind
speed factor for 1.5 meters per second is 1.4. From Exhibit B-2, Appendix B, LFB for acrylonitrile is 0.11 and
DF is 0.61. Then:
QR = 20,000 x 1.4x0.11 x 0.61 = 1,880 pounds per minute
The duration of the release (from Equation 3-5) would be:
t = 20,000 pounds/1880 pounds per minute =11 minutes
Duration of Release
After you have estimated a release rate as described above, determine the duration of the vapor
release from the pool (the time it will take for the liquid pool to evaporate completely). If you calculate a
corrected release rate for liquids above 25 °C, use the corrected release rate, estimated as discussed in Section
3.2.5 below, to estimate the release duration. To estimate the time in minutes, divide the total quantity
released (in pounds) by the release rate (in pounds per minute) as follows:
where: t = Duration of the release (minutes)
QR = Release rate (pounds per minute) (use release rate corrected for
temperature, QRc, if appropriate)
QS = Quantity released (pounds)
You will use the duration of the vapor release from the pool to decide which table is appropriate for
estimating distance, as discussed in Chapter 4 below.
3.2.3 Releases of Toxic Liquids with Passive Mitigation
Diked Areas
If the toxic liquid will be released into an area where it will be contained by dikes, compare the diked
area to the maximum area of the pool that could be formed; the smaller of the two areas should be used in
determination of the evaporation rate. The maximum area of the pool (assuming a depth of one centimeter)
is:
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A = QS x DF (3-6)
where: A = Maximum area of pool (square feet) for depth of one centimeter
QS = Quantity released (pounds)
DF = Density Factor (listed in Exhibit B-2, Appendix B)
Maximum Area Smaller than Diked Area. If the maximum area of the pool is smaller than the diked
area, calculate the release rate as described for "no mitigation" above.
Diked Area Smaller than Maximum Area. If the diked area is smaller than the maximum pool area,
go to Exhibit B-2 in Appendix B to find the Liquid Factor Ambient (LFA), if the liquid is at ambient
temperature, or the Liquid Factor Boiling (LFB), if the liquid is at an elevated temperature. For liquids at
temperatures between 25 °C and 50 °C, you may use the method described here and then apply a
Temperature Correction Factor (TCP), as discussed in Section 3.2.5 below, to correct the calculated release
rate. For gases liquefied by refrigeration alone, use LFB from Exhibit B-1. Calculate the release rate from
the diked area as follows for liquids at ambient temperature:
QR = 1.4 x LFA x A (3-7)
or, for liquids at elevated temperature or for gases liquefied by refrigeration alone:
QR = 1.4 x LFB x A (3-8)
where: QR = Release rate (pounds per minute)
1.4 = Wind speed factor = 1.5078, where 1.5 meters per second (3.4 miles per
hour) is the wind speed for the worst case
LFA = Liquid Factor Ambient (listed in Exhibit B-2, Appendix B)
LFB = Liquid Factor Boiling (listed in Exhibit B-1 (for liquefied gases) or B-2 (for
liquids), Appendix B)
A = Diked area (square feet)
Potential Overflow of Diked Area. In case of a large liquid spill, you also need to consider whether
the liquid could overflow the diked area. Follow these steps:
• Determine the volume of the diked area in cubic feet from surface area times depth or length
times width times depth (in feet).
• Determine the volume of liquid spilled in cubic feet from QS x DF x 0.033 (DF x 0.033 is
equal to I/density in pounds per cubic foot).
• Compare the volume of the diked area to the volume of liquid spilled. If the volume of
liquid is greater than the volume of the diked area:
Subtract the volume of the diked area from the total volume spilled to determine the
volume that might overflow the diked area.
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Estimate the maximum size of the pool formed by the overflowing liquid (in square
feet) by dividing the overflow volume (in cubic feet) by 0.033 (the depth of the pool
in feet).
Add the surface area of the diked area and the area of the pool formed by the
overflow to estimate the total pool area (A).
Estimate the evaporation rate from Equation 3-7 or 3-8 above.
After you have estimated the release rate, estimate the duration of the vapor release from the pool by
dividing the total quantity spilled by the release rate (Equation 3-5 above).
Example 6. Mitigated Liquid Release at Ambient Temperature (Bromine)
You have a tank containing 20,000 pounds of bromine at an ambient temperature of 25 °C. Assume that the
total quantity in the tank is spilled into a square diked area 10 feet by 10 feet (area 100 square feet). The dike
walls are four feet high. The area (A) that would be covered to a depth of 0.033 feet (one centimeter) by the
spilled liquid is given by Equation 3-6 as the quantity released (QS) times the Density Factor (DF). From
Exhibit B-2, Appendix B, DF for bromine is 0.16. Then:
A = 20,000 x 0.16, or 3,200 square feet
The diked area is smaller than the maximum pool area. The volume of bromine spilled is 20,000 x 0.16 x
0.033, or 106 cubic feet. The spilled liquid would fill the diked area to a depth of a little more than one foot,
well below the top of the wall. You use the diked area to determine the evaporation rate from Equation 3-7.
For the calculation, wind speed is 1.5 meters per second, the wind speed factor is 1.4, LFA for bromine (from
Exhibit B-2) is 0.073, and A is 100 square feet. The release rate is:
QR = 1.4 x 0.073 x 100 = 10 pounds per minute
The maximum duration of the release would be:
t = 20,000 pounds/10 pounds per minute = 2,000 minutes
Other Containment
If the toxic liquid will be contained by other means (e.g., enclosed catch basins or trenches), consider
the total quantity that could be spilled and estimate the surface area of the released liquid that potentially
would be exposed to the air. Look at the dimensions of trenches or other areas where spilled liquids would be
exposed to the air to determine the surface area of pools that could be formed. Use the instructions above to
estimate a release rate from the total surface area.
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Releases into Buildings
If the toxic liquid is released inside a building, compare the area of the pool that would be formed
(depending upon floor space or passive mitigation) to the maximum area of the pool that could be formed (if
the liquid is not contained); the smaller of the two areas should be used in determining the evaporation rate.
The maximum area of the pool is determined as described above for releases into diked areas, using Equation
3-6. If the toxic liquid would spread to cover the building floor, you determine the area of the building floor
as:
A = L x W (3-9)
where: A = Area (square feet)
L = Length (feet)
W = Width (feet)
If there are obstacles such as dikes inside the building, determine the size of the pool that would be formed
based on the area defined by the dikes or other obstacles.
The evaporation rate is then determined for a worst-case scenario (i.e., wind speed is 1.5 meters per
second (3.4 miles per hour)), using Equation 3-3 or 3-4, if the liquid spreads to its maximum area, or
Equation 3-7 or 3-8, if the pool area is smaller than the maximum. The maximum rate of evaporated liquid
exiting the building is taken to be 10 percent of the calculated worst-case scenario evaporation rate (see
Appendix D, Section D.2.4 for the derivation of this factor), as follows:
QRB = 0.1 x QR (3.10)
where: QRB = Release rate from building
QR = Release rate from pool, estimated as discussed above
0.1 = Mitigation factor, discussed in Appendix D, Section D.2.4
Note that the mitigation factor (i.e., 0.1) presented in this method assumes that the release occurs in a
fully enclosed, non-airtight space that is directly adjacent to the outside air. It may not apply to a release in
an interior room that is enclosed within a building, or to a space that has doors or windows that could be open
during a release. In such cases, you may want to consider performing site-specific modeling to determine the
appropriate amount of passive mitigation.
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Example 7. Liquid Release Inside Building (Bromine)
Suppose that your tank of bromine from Example 6 is contained inside a storage shed 10 feet by 10 feet (area
100 square feet). There are no dikes inside the shed. From Example 6, you see that the area covered by the
bromine in an unenclosed space would be 3,200 square feet. The building area is smaller than the maximum
pool area; therefore, the building floor area should be used to determine the evaporation rate from Equation 3-
7. For the calculation, first determine the worst-case scenario evaporation rate:
QR = 1.4 x 0.073 x 100 = 10 pounds per minute
The release rate to the outside air of the evaporated liquid leaving the building would then be:
QRB = 0.1 x 10 pounds per minute = 1 pound per minute
3.2.4 Mixtures Containing Toxic Liquids
Mixtures containing regulated toxic substances do not have to be considered if the concentration of
the regulated substance in the mixture is below one percent by weight or if you can demonstrate that the
partial vapor pressure of the regulated substances in the mixture is below 10 millimeters of mercury (mm
Hg). Regulated substances present as by-products or impurities would need to be considered if they are
present in concentrations of one percent or greater in quantities above their thresholds, and their partial vapor
pressures are 10 mm Hg or higher. In case of a spill of a liquid mixture containing a regulated toxic
substance with partial vapor pressure of 10 mm Hg or higher (with the exception of common water solutions,
discussed in the next section), you have several options for estimating a release rate:
• Carry out the analysis as described above in Sections 3.2.2 or 3.2.3 using the quantity of the
regulated substance in the mixture and the liquid factor (LFA or LFB) and density factor for
the regulated substance in pure form. This is a simple approach that likely will give
conservative results.
• If you know the partial pressure of the regulated substance in the mixture, you may estimate
a more realistic evaporation rate. An equation for the evaporation rate is given at the end of
Section B.2 in Appendix B.
In this case, estimate a pool size for the entire quantity of the mixture, for an
unmitigated release. If you know the density of the mixture, you may use it in
estimating the pool size; otherwise, you may assume the density is the same as the
pure regulated substance (in most cases, this assumption is unlikely to have a large
effect on the results).
• You may estimate the partial pressure of the regulated substance in the mixture by the
method described in Section B.2 in Appendix B and use the equation presented there to
estimate an evaporation rate. This equation is appropriate to mixtures and solutions in
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which the components do not interact with each other. It is probably inappropriate for most
water solutions. It is likely to overestimate the partial vapor pressure of regulated
substances in water solutions in which hydrogen bonding may occur (e.g., solutions of acids
or alcohols). As discussed above, use the pool size for the entire quantity of the mixture for
an unmitigated release.
OR= 0.0035 x l.Q x (53.06r/a x 30.500 x 51.
298
QR = 262 pounds per minute
Example 8. Mixture Containing Toxic Liquid (Acrylonitrile)
You have a tank containing 50,000 pounds of a mixture of acrylonitrile (a regulated substance) and N,N-
dimethylformamide (not regulated). The weight of each of the components of the mixture is known
(acrylonitrile = 20,000 pounds; N,N-dimethylformamide = 30,000 pounds.) The molecular weight of
acrylonitrile, from Exhibit B-2, is 53.06, and the molecular weight of N,N-dimethylformamide is 73.09. Using
Equation B-3, Appendix B, calculate the mole fraction of acrylonitrile in the solution as follows:
X,= (20.000/53.061
(20,000/53.06) + (30,000/73.09)
Xr= 377
377+410
>^ = 0.48
Estimate the partial vapor pressure of acrylonitrile using Equation B-4 as follows (using the vapor pressure of
acrylonitrile in pure form at 25°C, 108 mm Hg, from Exhibit B-2, Appendix B):
VPm = 0.48x 108 = 51.8 mmHg
Before calculating evaporation rate for acrylonitrile in the mixture, you must determine the surface area of the
pool formed by the entire quantity of the mixture, using Equation 3-6. The quantity released is 50,000 pounds
and the Density Factor for acrylonitrile is 0.61 in Exhibit B-2; therefore:
A = 50,000 x 0.61 = 30,500 square feet
Now calculate the evaporation rate for acrylonitrile in the mixture from Equation B-5 using the VPm and A
calculated above:
3.2.5 Release Rate Correction for Toxic Liquids Released at Temperatures
Between 25 °C and 50 °C
If your liquid is at a temperature between 25 °C (77 °F) and 50 °C (122 °F), you must use the higher
temperature for the offsite consequence analysis. You may correct the release rate calculated for a pool at 25
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°C to estimate from a pool at the higher temperature using Temperature Correction Factors (TCP) provided in
Appendix B, Exhibit B-4. Calculate a corrected release rate as follows:
• Calculate the release rate (QR) of the liquid at 25 °C (77 °F) as described in Section 3.2.2
(for unmitigated releases) or 3.2.3 (for releases with passive mitigation).
• From Exhibit B-4 in Appendix B:
Find your liquid in the left-hand column of the table.
Find the temperature closest to your temperature at the top of the table. If your
temperature is at the midpoint between two temperatures, go to the higher
temperature; otherwise go to the closest temperature (higher or lower than your
temperature).
Find the TCP for your liquid in the column for the appropriate temperature.
• Estimate a corrected release rate (QRc) by multiplying the estimated release rate by the TCP;
i.e.,
QRC = QR x TCP (3.11)
where: QRC = Corrected release rate
QR = Release rate calculated for 25 °C
TCP = Temperature Correction Factor (from Exhibit B-4, Appendix B)
The derivation of the Temperature Correction Factors is discussed in Appendix D, Section D.2.2. If
you have vapor pressure-temperature data for a liquid not covered in Exhibit B-4, you may correct the
evaporation rate using the method presented in Section D.2.2.
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Example 9. Liquid Release at Ambient Temperature Between 25 °C and 50 °C (Bromine)
Assume the tank containing 20,000 pounds of bromine, from Example 6, is at an ambient temperature of 35 °C
(95 °F). As in Example 6, the total quantity in the tank is spilled into a diked enclosure that completely contains
the spill. The surface area is 100 square feet. In Example 6, the release rate (QR) at 25 °C was calculated from
Equation 3-7 to be 10 pounds per minute. To adjust the release rate for the temperature of 35 °C, you find the
Temperature Correction Factor (TCP) for bromine at 35 °C from Exhibit B-4 in Appendix B. The TCP at this
temperature is 1.5; the corrected release rate (QRC) at 3 5 °C, from Equation 3 -11, is
QRC =10x1.5 = 15 pounds per minute
The duration of the release (from Equation 3-5) would be:
t = 20,000 pounds/15 pounds per minute = 1,300 minutes
3.3 Release Rates for Common Water Solutions of Toxic Substances and for
Oleum
In Section 3.3
Methods to estimate the release rates for several common water solutions and
for oleum, including:
Evaporation from pools with no mitigation (see 3.2.2),
Evaporation from pools with dikes (see 3.2.3),
Releases at elevated temperatures of solutions of gases, and
Releases at elevated temperatures of solutions of liquids.
This section presents a simple method of estimating the release rate from spills of water solutions of
several substances. Oleum (a solution of sulfur trioxide in sulfuric acid) also is discussed in this section.
The vapor pressure and evaporation rate of a substance in solution depends on its concentration in
the solution. If a concentrated water solution containing a volatile toxic substance is spilled, the toxic
substance initially will evaporate more quickly than water from the spilled solution, and the vapor pressure
and evaporation rate will decrease as the concentration of the toxic substance in the solution decreases. At
much lower concentrations, water may evaporate more quickly than the toxic substance. There is one
concentration at which the composition of the solution does not change as evaporation occurs. For most
situations of interest, the concentration exceeds this concentration, and the toxic substance evaporates more
quickly than water.
For estimating release rates from solutions, this guidance lists liquid factors (ambient) for several
common water solutions at several concentrations that take into account the decrease in evaporation rate with
decreasing concentration. Exhibit B-3 in Appendix B provides LFA and DF values for several concentrations
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of ammonia, formaldehyde, hydrochloric acid, hydrofluoric acid, and nitric acid in water solution. Factors for
oleum are also included in the exhibit. Chlorine dioxide also may be found in water solutions; however,
solutions of chlorine dioxide commonly are below one percent concentration. Solutions below one percent
concentration do not have to be considered. Chlorine dioxide, therefore, is not included in Exhibit B-3. These
factors may be used to estimate an average release rate for the listed substances from a pool formed by a spill
of solution. Liquid factors are provided for two different wind speeds, because the wind speed affects the rate
of evaporation.
For the worst case, use the factor for a wind speed of 1.5 meters per second (3.4 miles per hour).
You need to consider only the first 10 minutes of the release for solutions under ambient conditions in
estimating the consequence distance, because the toxic component in a solution evaporates fastest during the
first few minutes of a spill, when its concentration is highest. Modeling indicates that analysis considering
the first 10 minutes of the release gives a good approximation of the overall consequences of the release.
Although the toxic substance will continue to evaporate from the pool after 10 minutes, the rate of
evaporation is so much lower that it can safely be ignored in estimating the consequence distance. (See
Appendix D, Section D.2.3, for more information.) Estimate release rates as follows:
Ambient Temperature
• Unmitigated. If no passive mitigation measures are in place, and the solution is at ambient
temperature, find the LFA at 1.5 meters per second (3.4 miles per hour) and DF for the
solution in Appendix B, Exhibit B-3. Follow the instructions for liquids presented in
Section 3.2.2 above to estimate the release rate of the listed substance in solution. Use the
total quantity of the solution as the quantity released (QS) in carrying out the calculation of
release rate.
• Mitigated. If passive mitigation is in place, and the solution is at ambient temperature, find
the LFA at 1.5 meters per second (3.4 miles per hour) in Appendix B, Exhibit B-3, and
follow the instructions for liquids in Section 3.2.3 above. Use the total quantity of the
solution to estimate the maximum pool area for comparison with the diked area.
April 15, 1999 3-15
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Chapter 3
Release Rates for Toxic Substances
Example 10. Evaporation Rate for Water Solution at Ambient Temperature (Hydrochloric Acid)
You have a tank containing 50,000 pounds of 37 percent hydrochloric acid solution, at ambient temperature.
For the worst-case analysis, you assume the entire contents of the tank is released, forming a pool. The release
occurs in a diked area of 9,000 square feet.
From Exhibit B-3, Appendix B, the Density Factor (DF) for 37 percent hydrochloric acid is 0.42. From
Equation 3-6, the maximum area of the pool would be 50,000 times 0.42, or 21,000 square feet. The diked
area is smaller; therefore, the diked area should be used in the evaporation rate (release rate) calculation, using
Equation 3-7.
For the calculation using Equation 3-7, you need the pool area (9,000 square feet) and the Liquid Factor
Ambient (LFA) for 37 percent hydrochloric acid; you assume a wind speed of 1.5 meters per second, so the
wind speed factor is 1.4. From Exhibit B-3, Appendix B, the LFA is 0.0085. From Equation 3-7, the release
rate (QR) of hydrogen chloride from the pool is:
QR = 1.4 x 9,000 x 0.0085 = 107 pounds per minute
You do not need to consider the duration of the release, because only the first ten minutes are considered.
Elevated Temperature
• Known Vapor Pressure. If the solution is at an elevated temperature, the vapor pressure of
the regulated substance and its release rate from the solution will be much higher. This
guidance does not include temperature correction factors for evaporation rates of regulated
substances from solutions. If you know the partial vapor pressure of the toxic substance in
solution at the relevant temperature, you can carry out the calculation of the release rate
using the equations in Appendix D, Sections D.2.1 and D.2.2. As for releases of solutions at
ambient temperature, you only need to consider the first 10 minutes of the release, because
the evaporation rate of the toxic substance from the solution will decrease rapidly as its
concentration decreases.
• Unknown Vapor Pressure. If you do not know the vapor pressure of the substance in
solution, as a conservative approach for the worst-case analysis, use the appropriate
instructions, as follows:
Solutions containing substances that are gases under ambient conditions. The
list of regulated substances includes several substances that, in their pure form, are
gases under ambient conditions, but that may commonly be found in water
solutions. These substances include ammonia, formaldehyde, hydrogen chloride,
and hydrogen fluoride. For a release of a solution of ammonia, formaldehyde,
hydrochloric acid, or hydrofluoric acid above ambient temperature, if you do not
have vapor pressure data for the temperature of interest or prefer a simpler method,
assume the quantity of the pure substance in the solution is released as a gas over 10
April 15, 1999 3-16
-------
Chapter 3
Release Rates for Toxic Substances
minutes, as discussed in Section 3.1 above. You may determine the amount of pure
substance in the solution from the concentration (e.g., a solution of 37 percent
hydrochloric acid by weight would contain a quantity of hydrogen chloride equal to
0.37 times the total weight of the solution).
Example 11. Evaporation Rate for Gas in Water Solution at Elevated Temperature (Hydrochloric
Acid)
You have 50,000 pounds of 37 percent hydrochloric acid solution in a high-temperature process. For the
worst-case analysis, you assume the entire contents of the process vessel is released. In this case, because the
solution is at an elevated temperature, you consider the release of gaseous hydrogen chloride from the hot
solution.
The solution would contain 50,000 x 0.37 pounds of hydrogen chloride, or 18,500 pounds. You assume the
entire 18,500 pounds is released over 10 minutes. From Equation 3-1, the release rate is 18,500 divided by 10,
or 1,850 pounds per minute.
Liquids in solution. If you have vapor pressure data for the liquid in solution
(including nitric acid in water solution and sulfur trioxide in oleum) at the
temperature of interest, you may use that data to estimate the release rate, as
discussed above. You only need to consider the first 10 minutes of the evaporation.
For a release of nitric acid solution at a temperature above ambient, if you do not
have vapor pressure data or prefer to use this simpler method, determine the
quantity of pure nitric acid in the solution from the concentration. Assume the
quantity of pure nitric acid is released at an elevated temperature and estimate a
release rate as discussed in Section 3.2 above, using the LFB. For temperatures
between 25 °C and 50 °C, you may use the LFA and the temperature correction
factors for the pure substance, as described in Section 3.2.5. You do not need to
estimate the duration of the release, because you only consider the first 10 minutes.
Similarly, for a release of oleum at an elevated temperature, determine the quantity
of free sulfur trioxide in the oleum from the concentration and assume the sulfur
trioxide is released at an elevated temperature. Use the LFB or the LFA and
temperature correction factors for sulfur trioxide to estimate a release rate as
discussed in Section 3.2. You only need to consider the first 10 minutes of the
release in your analysis.
For a spill of liquid in solution into a diked area, you would need to consider the
total quantity of solution in determining whether the liquid could overflow the diked
area (see the steps in Section 3.2.3). If you find that the liquid could overflow the
dikes, you would need to consider both the quantity of pure substance remaining
inside the diked area and the quantity of pure substance spilled outside the diked
area in carrying out the release rate analysis as discussed in Section 3.2.3.
April 15, 1999 3-17
-------
Chapter 3
Release Rates for Toxic Substances
Example 12. Evaporation Rate for Liquid in Water Solution at Elevated Temperature (Nitric Acid)
You have 18,000 pounds of 90 percent nitric acid solution in a high temperature process. The solution would
contain 18,000 x 0.90 pounds of nitric acid, or 16,200 pounds. You assume 16,200 pounds of pure nitric acid
is released at an elevated temperature.
For the calculation using Equation 3-4, you need the quantity released (16,200); the Liquid Factor Boiling
(LFB) for nitric acid (0.12 from Exhibit B-2); the Density Factor (DF) for nitric acid (0.32 from Exhibit B-2);
and you assume a wind speed of 1.5 meter per second, so the wind speed factor is 1.4. From Equation 3-4, the
release rate (QR) of hot nitric acid is:
QR = 16,200 x 1.4 x 0.12 x 0.32 = 870 pounds per minute
You do not need to estimate the duration of release, because you only consider the first 10 minutes.
April 15, 1999
3- 18
-------
ESTIMATION OF WORST-CASE DISTANCE TO TOXIC
ENDPOINT
In Chapter 4
Reference tables of distances for worst-case releases, including:
Generic reference tables (Exhibit 2), and
Chemical-specific reference tables (Exhibit 3).
Considerations include:
Gas density (neutrally buoyant or dense),
Duration of release (10 minutes or 60 minutes),
Topography (rural or urban).
This guidance provides reference tables giving worst-case distances for neutrally buoyant gases and
vapors and for dense gases and vapors for both rural (open) and urban (obstructed) areas. This chapter
describes these reference tables and gives instructions to help you choose the appropriate table to estimate
consequence distances for the worst-case analysis.
Neutrally buoyant gases and vapors have approximately the same density as air, and dense gases and
vapors are heavier than air. Neutrally buoyant and dense gases are dispersed in different ways when they are
released; therefore, modeling was carried out to develop separate reference tables. These generic reference
tables can be used to estimate distances using the specified toxic endpoint for each substance and the
estimated release rate to air. In addition to the generic tables, chemical-specific reference tables are provided
for ammonia, chlorine, and sulfur dioxide. These chemical-specific tables were developed based on modeling
carried out for industry-specific guidance documents. All the tables were developed assuming a wind speed
of 1.5 meters per second (3.4 miles per hour) and F stability. To use the reference tables, you need the worst-
case release rates estimated as described in the previous sections. For liquid pool evaporation, you also need
the duration of the release. In addition, to use the generic tables, you will need to determine the appropriate
toxic endpoint and whether the gas or vapor is neutrally buoyant or dense, using the exhibits in Appendix B.
You may interpolate between entries in the reference tables.
Generic reference tables are provided for both 10-minute releases and 60-minute releases. You
should use the tables for 10-minute releases if the duration of your release is 10 minutes or less; use the tables
for 60-minute releases if the duration of your release is more than 10 minutes. For the worst-case analysis, all
releases of toxic gases are assumed to last for 10 minutes. You need to consider the estimated duration of the
release (from Equation 3-5) for evaporation of pools of toxic liquids. For evaporation of water solutions of
toxic liquids or of oleum, you should always use the tables for 10-minute releases.
The generic reference tables of distances (Reference Tables 1-8), which should be used for
substances other than ammonia, chlorine, and sulfur dioxide, are found at the end of Chapter 5. The generic
tables and the conditions for which each table are applicable are described in Exhibit 2. Chemical-specific
reference tables of distances (Reference Tables 9-12) follow the generic reference tables at the end of Chapter
5. Each of these chemical-specific tables includes distances for both rural and urban topography. These
tables are described in Exhibit 3.
April 15, 1999
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Chapter 4
Estimation of Worst-Case Distance to Toxic Endpoint
Remember that these reference tables provide only rough estimates, not accurate predictions, of the
distances that might be reached under worst-case conditions. In particular, although the distances in the
tables are as great as 25 miles, you should bear in mind that the larger distances (more than six to ten miles)
are very uncertain.
To use the reference tables of distances, follow these steps:
For Regulated Toxic Substances Other than Ammonia, Chlorine, and Sulfur Dioxide
• Find the toxic endpoint for the substance in Appendix B (Exhibit B-1 for toxic gases or
Exhibit B-2 for toxic liquids).
• Determine whether the table for neutrally buoyant or dense gases and vapors is appropriate
from Appendix B (Exhibit B-l for toxic gases or Exhibit B-2 for toxic liquids). A toxic gas
that is lighter than air may behave as a dense gas upon release if it is liquefied under
pressure, because the released gas may be mixed with liquid droplets, or if it is cold.
Consider the state of the released gas when you decide which table is appropriate.
• Determine whether the table for rural or urban conditions is appropriate.
Use the rural table if your site is in an open area with few obstructions.
Use the urban table if your site is in an urban or obstructed area. The urban tables
are appropriate if there are many obstructions in the area, even if it is in a remote
location, not in a city.
• Determine whether the 10-minute table or the 60-minute table is appropriate.
Always use the 10-minute table for worst-case releases of toxic gases.
Always use the 10-minute table for worst-case releases of common water solutions
and oleum from evaporating pools, for both ambient and elevated temperatures.
If you estimated the release duration for an evaporating toxic liquid pool to be 10
minutes or less, use the 10-minute table.
If you estimated the release duration for an evaporating toxic liquid pool to be more
than 10 minutes, use the 60-minute table.
April 15, 1999 4-2
-------
Chapter 4
Estimation of Worst-Case Distance to Toxic Endpoint
Exhibit 2
Generic Reference Tables of Distances for Worst-case Scenarios
Applicable Conditions
Gas or Vapor Density
Neutrally buoyant
Dense
Topography
Rural
Urban
Rural
Urban
Release Duration
(minutes)
10
60
10
60
10
60
10
60
Reference Table
Number
1
2
3
4
5
6
7
8
Exhibit 3
Chemical-Specific Reference Tables of Distances for Worst-case Scenarios
Substance
Anhydrous ammonia
liquefied under pressure
Non-liquefied ammonia,
ammonia liquefied by
refrigeration, or aqueous
ammonia
Chlorine
Sulfur dioxide (anhydrous)
Applicable Conditions
Gas or Vapor
Density
Dense
Neutrally buoyant
Dense
Dense
Topography
Rural, Urban
Rural, Urban
Rural, Urban
Rural, Urban
Release Duration
(minutes)
10
10
10
10
Reference
Table
Number
9
10
11
12
April 15, 1999
4-:
-------
Chapter 4
Estimation of Worst-Case Distance to Toxic Endpoint
Neutrally Buoyant Gases or Vapors
• If Exhibit B-1 or B-2 indicates the gas or vapor should be considered neutrally buoyant, and
other factors would not cause the gas or vapor to behave as a dense gas, divide the estimated
release rate (pounds per minute) by the toxic endpoint (milligrams per liter).
• Find the range of release rate/toxic endpoint values that includes your calculated release
rate/toxic endpoint in the first column of the appropriate table (Reference Table 1, 2, 3, or
4), then find the corresponding distance to the right (see Example 13 below).
Dense Gases or Vapors
• If Exhibit B-1 or B-2 or consideration of other relevant factors indicates the substance
should be considered a dense gas or vapor (heavier than air), find the distance in the
appropriate table (Reference Table 5, 6, 7, or 8) as follows;
Find the toxic endpoint closest to that of the substance by reading across the top of
the table. If the endpoint of the substance is halfway between two values on the
table, choose the value on the table that is smaller (to the left). Otherwise, choose
the closest value to the right or the left.
Find the release rate closest to the release rate estimated for the substance at the left
of the table. If the calculated release rate is halfway between two values on the
table, choose the release rate that is larger (farther down on the table). Otherwise,
choose the closest value (up or down on the table).
Read across from the release rate and down from the endpoint to find the distance
corresponding to the toxic endpoint and release rate for your substance.
For Ammonia, Chlorine, or Sulfur Dioxide
• Find the appropriate chemical-specific table for your substance (see the descriptions of
Reference Tables 9-12 in Exhibit 3).
If you have ammonia liquefied by refrigeration alone, you may use Reference Table
10, even if the duration of the release is greater than 10 minutes.
If you have chlorine or sulfur dioxide liquefied by refrigeration alone, you may use
the chemical-specific reference tables, even if the duration of the release is greater
than 10 minutes.
• Determine whether rural or urban topography is applicable to your site.
Use the rural column in the reference table if your site is in an open area with few
obstructions.
April 15, 1999 4-4
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Chapter 4
Estimation of Worst-Case Distance to Toxic Endpoint
Use the urban column if your site is in an urban or obstructed area. The urban
column is appropriate if there are many obstructions in the area, even if it is in a
remote location, not in a city.
• Estimate the consequence distance as follows:
In the left-hand column of the table, find the release rate closest to your calculated
release rate.
Read the corresponding distance from the appropriate column (urban or rural) to the
right.
The development of Reference Tables 1-8 is discussed in Appendix D, Sections D.4.1 and DA.2.
The development of Reference Tables 9-12 is discussed in industry-specific risk management program
guidance documents and a backup information document that are cited in Section DAS. If you think the
results of the method presented here overstate the potential consequences of a worst-case release at your site,
you may choose to use other methods or models that take additional site-specific factors into account.
Examples 14 and 15 below include the results of modeling using two other models, the Areal
Locations of Hazardous Atmospheres (ALOHA) and the World Bank Hazards Analysis (WHAZAN)
systems. These additional results are provided for comparison with the results of the methods presented in
this guidance. The same modeling parameters were used as in the modeling carried out for development of
the reference tables of distances. Appendix D, Section DAS, provides information on the modeling carried
out with ALOHA and WHAZAN.
Example 13. Gas Release (Diborane)
In Example 1, you estimated a release rate for diborane gas of 250 pounds per minute. From Exhibit B-1, the
toxic endpoint for diborane is 0.0011 mg/L, and the appropriate reference table for diborane is a neutrally
buoyant gas table. Your facility and the surrounding area have many buildings, pieces of equipment, and other
obstructions; therefore, you assume urban conditions. The appropriate reference table is Reference Table 3, for
a 10-minute release of a neutrally buoyant gas in an urban area.
The release rate divided by toxic endpoint for this example is 250/0.0011 = 230,000.
From Reference Table 3, release rate divided by toxic endpoint falls between 221,000 and 264,000,
corresponding to about 8.1 miles.
April 15, 1999 4-5
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Chapter 4
Estimation of Worst-Case Distance to Toxic Endpoint
Example 14. Gas Release (Ethylene Oxide)
You have a tank containing 10,000 pounds of ethylene oxide, which is a gas under ambient conditions.
Assuming the total quantity in the tank is released over a 10-minute period, the release rate (QR) from Equation
3-1 is:
QR = 10,000 pounds/10 minutes = 1,000 pounds per minute
From Exhibit B-l, the toxic endpoint for ethylene oxide is 0.09 mg/L, and the appropriate reference table is the
dense gas table. Your facility is in an open, rural area with few obstructions; therefore, you use the table for
rural areas.
Using Reference Table 5 for 10-minute releases of dense gases in rural areas, the toxic endpoint of 0.09 mg/L
is closer to 0.1 than 0.075 mg/L. For a release rate of 1,000 pounds per minute, the distance to 0.1 mg/L is 3.6
miles.
Additional Modeling for Comparison
The ALOHA model gave a distance of 2.2 miles to the endpoint, using the same assumptions.
The WHAZAN model gave a distance of 2.7 miles to the endpoint, using the same assumptions and the dense
cloud dispersion model.
Example 15. Liquid Evaporation from Pool (Acrylonitrile)
You estimated an evaporation rate of 307 pounds per minute for acrylonitrile from a pool formed by the release
of 20,000 pounds into an undiked area (Example 4). You estimated the time for evaporation of the pool as 65
minutes. From Exhibit B-2, the toxic endpoint for acrylonitrile is 0.076 mg/L, and the appropriate reference
table for a worst-case release of acrylonitrile is the dense gas table. Your facility is in an urban area. You use
Reference Table 8 for 60-minute releases of dense gases in urban areas.
From Reference Table 8, the toxic endpoint closest to 0.076 mg/L is 0.075 mg/L, and the closest release rate to
307 pounds per minute is 250 pounds per minute. Using these values, the table gives a worst-case
consequence distance of 2.9 miles.
Additional Modeling for Comparison
The ALOHA model gave a distance of 1.3 miles to the endpoint for a release rate of 307 pounds per minute,
using the same assumptions.
The WHAZAN model gave a distance of 1.0 mile to the endpoint for a release rate of 307 pounds per minute,
using the same assumptions and the dense cloud dispersion model.
April 15, 1999
4-6
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5 ESTIMATION OF DISTANCE TO OVERPRESSURE ENDPOINT
FOR FLAMMABLE SUBSTANCES
In Chapter 5
Methods to estimate the worst-case consequence distances for releases of
flammable substances.
5.1 Vapor cloud explosions of flammable substances that are not
mixed with other substances, and
5.2 Vapor cloud explosions of flammable substances in mixtures.
For the worst-case scenario involving a release of flammable gases and volatile flammable liquids,
you must assume that the total quantity of the flammable substance forms a vapor cloud within the upper and
lower flammability limits and the cloud detonates. As a conservative worst-case assumption, if you use the
method presented here, you must assume that 10 percent of the flammable vapor in the cloud participates in
the explosion. You need to estimate the consequence distance to an overpressure level of 1 pound per square
inch (psi) from the explosion of the vapor cloud. An overpressure of 1 psi may cause partial demolition of
houses, which can result in serious injuries to people, and shattering of glass windows, which may cause skin
laceration from flying glass.
This chapter presents a simple method for estimating the distance to the endpoint for a vapor cloud
explosion of a regulated substance. The method presented here for analysis of vapor cloud explosions is
based on a TNT-equivalent model. Other methods are available for analysis of vapor cloud explosions,
including methods that consider site-specific conditions. You may use other methods for your worst-case
analysis if you so choose, provided you assume the total quantity of flammable substance is in the cloud and
use an endpoint of 1 psi. If you use a TNT-equivalent model, you must assume a yield factor of 10 percent.
Appendix A includes references to documents and journal articles on vapor cloud explosions that may
provide useful information on methods of analysis.
5.1 Flammable Substances Not in Mixtures
For the worst-case analysis of a regulated flammable substance that is not in a mixture with other
substances, you may estimate the consequence distance for a given quantity of a regulated flammable
substance using Reference Table 13. This table provides distances to 1 psi overpressure for vapor cloud
explosions of quantities from 500 to 2,000,000 pounds. These distances were estimated by a TNT-
equivalent model, Equation C-l in Appendix C, Section C. 1, using the worst-case assumptions described
above and data provided in Exhibit C-l, Appendix C. If you prefer, you may calculate your worst-case
consequence distance for flammable substances from the heat of combustion of the flammable substance and
Equation C-l or C-2.
April 15, 1999
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Chapter 5
Estimation of Distance to Overpressure Endpoint for Flammable Substances
Example 16. Vapor Cloud Explosion (Propane)
You have a tank containing 50,000 pounds of propane. From Reference Table 13, the distance to 1 psi
overpressure is 0.3 miles for 50,000 pounds of propane.
Alternatively, you can calculate the distance to 1 psi using Equation C-2 from Appendix C:
D = 0.0081 x [ 0.1 x 50,000 x (46,333/4,680) ]1/3
D = 0.3 miles
5.2 Flammable Mixtures
If you have more than 10,000 pounds of a mixture of flammable substances that meets the criteria
for listing under CAA section 112(r) (flash point below 22.8 °C (73 °F), boiling point below 37.8 °C (100
°F), National Fire Protection Association (NFPA) flammability hazard rating of 4), you may need to carry out
a worst-case consequence analysis for the mixture. (If the mixture itself does not meet these criteria, it is not
covered, and no analysis is required, even if the mixture contains one or more regulated substances.) You
should carry out the analysis using the total quantity of all regulated flammable substance or substances in the
mixture. Non-flammable components should not be included. However, if additional (non-regulated)
flammable substances are present in the mixture, you should include them in the quantity used in the analysis.
For simplicity, you may carry out the worst-case analysis based on the predominant regulated
flammable component of the mixture or a major component of the mixture with the highest heat of
combustion if the whole vapor cloud consists of flammable substances (see Exhibit C-l, Appendix C for data
on heat of combustion). Estimate the consequence distance from Reference Table 13 for the major
component with the highest heat of combustion, assuming that the quantity in the cloud is the total quantity
of the mixture. If you have a mixture in which the heats of combustion of the components do not differ
significantly (e.g., a mixture of hydrocarbons), this method is likely to give reasonable results.
Alternatively, you may estimate the heat of combustion of the mixture from the heats of combustion
of the components of the mixture using the method described in Appendix C, Section C.2, and then use
Equation C-l or C-2 in Appendix C to determine the vapor cloud explosion distance. This method may be
appropriate if you have a mixture that includes components with significantly different heats of combustion
(e.g., a mixture of hydrogen and hydrocarbons) that make up a significant portion of the mixture.
Examples 17 and 18 illustrate the two methods of analysis. In Example 17, the heat of combustion
of the mixture is estimated, and the distance to the endpoint is calculated from Equation C-2. In Example 18,
the component of the mixture with the highest heat of combustion is assumed to represent the entire mixture,
and the distance to the endpoint is read from Reference Table 13. For the mixture of two hydrocarbons used
in the example, the methods give very similar results.
April 15, 1999 5 -'.
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Chapter 5
Estimation of Distance to Overpressure Endpoint for Flammable Substances
Example 17. Estimating Heat of Combustion of Mixture for Vapor Cloud Explosion Analysis
You have a mixture of 8,000 pounds of ethylene (the reactant) and 2,000 pounds of isobutane (a catalyst
carrier). To carry out the worst-case analysis, estimate the heat of combustion of the mixture from the heats of
combustion of the components of the mixture. (Ethylene heat of combustion = 47,145 kilojoules per kilogram;
isobutane heat of combustion = 45,576). Using Equation C-3, Appendix C:
HCm = [ (8,000/2.2) x 47,145 1 + [ (2,000/2.2) x 45,576]
(10,000/2.2) (10,000/2.2)
HCm = (37,716) + (9,115)
HCm = 46,831 kilojoules per kilogram
Now use the calculated heat of combustion for the mixture in Equation C-2 to calculate the distance to 1 psi
overpressure for vapor cloud explosion.
D = 0.0081 x [ 0.1 x 10,000 x (46,831/4,680) ]1/'
D = 0.2 miles
Example 18. Vapor Cloud Explosion of Flammable Mixture (Ethylene and Isobutane)
You have 10,000 pounds of a mixture of ethylene (the reactant) and isobutane (a catalyst carrier). To carry out
the worst-case analysis, assume the quantity in the cloud is the total quantity of the mixture. Use data for
ethylene because it is the component with the highest heat of combustion. (Ethylene heat of combustion =
47,145 kilojoules per kilogram; isobutane heat of combustion = 45,576, from Exhibit C-l, Appendix C). From
Reference Table 13, the distance to 1 psi overpressure is 0.2 miles for 10,000 pounds of ethylene; this distance
would also apply to the 10,000-pound mixture of ethylene and isobutane.
April 15, 1999
-------
Reference Table 1
Neutrally Buoyant Plume Distances to Toxic Endpoint for Release Rate Divided by Endpoint
10-Minute Release, Rural Conditions, F Stability, Wind Speed 1.5 Meters per Second
Release Rate/Endpoint
[(lbs/min)/(mg/L)]
0-4.4
4.4-37
37-97
97- 180
180-340
340 - 530
530 - 760
760- 1,000
1,000-1,500
1,500- 1,900
1,900-2,400
2,400 - 2,900
2,900 - 3,500
3,500 - 4,400
4,400 - 5,100
5,100 - 5,900
5,900 - 6,800
6,800 - 7,700
7,700 - 9,000
9,000 - 10,000
10,000-11,000
11,000- 12,000
12,000 - 14,000
14,000- 15,000
15,000-16,000
Distance to
Endpoint
(miles)
0.1
0.2
0.3
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
4.0
4.2
4.4
4.6
Release Rate/Endpoint
[(lbs/min)/(mg/L)]
16,000-18,000
18,000- 19,000
19,000-21,000
21,000-23,000
23,000 - 24,000
24,000 - 26,000
26,000 - 28,000
28,000 - 29,600
29,600 - 35,600
35,600 - 42,000
42,000 - 48,800
48,800 - 56,000
56,000 - 63,600
63,600-71,500
71,500-88,500
88,500 - 107,000
107,000 - 126,000
126,000 - 147,000
147,000 - 169,000
169,000- 191,000
191,000-215,000
215,000-279,000
279,000 - 347,000
>347,000
Distance to
Endpoint
(miles)
4.8
5.0
5.2
5.4
5.6
5.8
6.0
6.2
6.8
7.5
8.1
8.7
9.3
9.9
11
12
14
15
16
17
19
22
25
>25*
*Report distance as 25 miles
April 15, 1999
5-4
-------
Reference Table 2
Neutrally Buoyant Plume Distances to Toxic Endpoint for Release Rate Divided by Endpoint
60-Minute Release, Rural Conditions, F Stability, Wind Speed 1.5 Meters per Second
Release Rate/Endpoint
[(lbs/min)/(mg/L)]
0-5.5
5.5-46
46 - 120
120-220
220 - 420
420 - 650
650-910
910-1,200
1,200- 1,600
1,600-1,900
1,900-2,300
2,300 - 2,600
2,600 - 2,900
2,900 - 3,400
3,400 - 3,700
3,700-4,100
4,100-4,400
4,400 - 4,800
4,800 - 5,200
5,200 - 5,600
5,600 - 5,900
5,900 - 6,200
6,200 - 6,700
6,700 - 7,000
7,000 - 7,400
Distance to
Endpoint
(miles)
0.1
0.2
0.3
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
4.0
4.2
4.4
4.6
Release Rate/Endpoint
[(lbs/min)/(mg/L)]
7,400 - 7,700
7,700 - 8,100
8,100 - 8,500
8,500 - 8,900
8,900 - 9,200
9,200 - 9,600
9,600 - 10,000
10,000 - 10,400
10,400- 11,700
11,700-13,100
13,100- 14,500
14,500-15,900
15,900- 17,500
17,500-19,100
19,100-22,600
22,600 - 26,300
26,300 - 30,300
30,300 - 34,500
34,500 - 38,900
38,900 - 43,600
43,600 - 48,400
48,400-61,500
61,500-75,600
>75,600
Distance to
Endpoint
(miles)
4.8
5.0
5.2
5.4
5.6
5.8
6.0
6.2
6.8
7.5
8.1
8.7
9.3
9.9
11
12
14
15
16
17
19
22
25
>25*
*Report distance as 25 miles
April 15, 1999
5 - 5
-------
Reference Table 3
Neutrally Buoyant Plume Distances to Toxic Endpoint for Release Rate Divided by Endpoint
10-minute Release, Urban Conditions, F Stability, Wind Speed 1.5 Meters per Second
Release Rate/Endpoint
[(lbs/min)/(mg/L)]
0-21
21 - 170
170-420
420 - 760
760-1,400
1,400-2,100
2,100-3,100
3,100-4,200
4,200-6,100
6,100-7,800
7,800 - 9,700
9,700 - 12,000
12,000 - 14,000
14,000- 18,000
18,000-22,000
22,000 - 25,000
25,000 - 29,000
29,000 - 33,000
33,000 - 39,000
39,000 - 44,000
44,000 - 49,000
49,000 - 55,000
55,000 - 63,000
63,000 - 69,000
69,000 - 76,000
Distance to
Endpoint
(miles)
0.1
0.2
0.3
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
4.0
4.2
4.4
4.6
Release Rate/Endpoint
[(lbs/min)/(mg/L)]
76,000 - 83,000
83,000 - 90,000
90,000-100,000
100,000- 110,000
110,000-120,000
120,000- 130,000
130,000-140,000
140,000 - 148,000
148,000-183,000
183,000-221,000
221,000-264,000
264,000-310,000
310,000-361,000
361,000-415,000
415,000-535,000
535,000-671,000
671,000-822,000
822,000 - 990,000
990,000-1,170,000
1,170,000- 1,370,000
1,370,000-1,590,000
1,590,000-2,190,000
2,190,000-2,890,000
>2,890,000
Distance to
Endpoint
(miles)
4.8
5.0
5.2
5.4
5.6
5.8
6.0
6.2
6.8
7.5
8.1
8.7
9.3
9.9
11
12
14
15
16
17
19
22
25
>25*
*Report distance as 25 miles
April 15, 1999
5-6
-------
Reference Table 4
Neutrally Buoyant Plume Distances to Toxic Endpoint for Release Rate Divided by Endpoint
60-Minute Release, Urban Conditions, F Stability, Wind Speed 1.5 Meters per Second
Release Rate/Endpoint
[(lbs/min)/(mg/L)]
0-26
26-210
210-530
530 - 940
940-1,700
1,700-2,600
2,600 - 3,700
3,700 - 4,800
4,800 - 6,400
6,400 - 7,700
7,700 - 9,100
9,100- 11,000
11,000-12,000
12,000 - 14,000
14,000 - 16,000
16,000 - 17,000
17,000-19,000
19,000-21,000
21,000-23,000
23,000 - 24,000
24,000 - 26,000
26,000 - 28,000
28,000 - 30,000
30,000 - 32,000
32,000 - 34,000
Distance to
Endpoint
(miles)
0.1
0.2
0.3
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
4.0
4.2
4.4
4.6
Release Rate/Endpoint
[(lbs/min)/(mg/L)]
34,000 - 36,000
36,000 - 38,000
38,000-41,000
41,000-43,000
43,000 - 45,000
45,000 - 47,000
47,000 - 50,000
50,000 - 52,200
52,200 - 60,200
60,200 - 68,900
68,900 - 78,300
78,300 - 88,400
88,400 - 99,300
99,300- 111,000
111,000-137,000
137,000- 165,000
165,000-197,000
197,000-232,000
232,000-271,000
271,000-312,000
312,000-357,000
357,000 - 483,000
483,000 - 629,000
>629,000
Distance to
Endpoint
(miles)
4.8
5.0
5.2
5.4
5.6
5.8
6.0
6.2
6.8
7.5
8.1
8.7
9.3
9.9
11
12
14
15
16
17
19
22
25
>25*
*Report distance as 25 miles
April 15, 1999
5-7
-------
Reference Table 5
Dense Gas Distances to Toxic Endpoint
10-minute Release, Rural Conditions, F Stability, Wind Speed 1.5 Meters per Second
Release
Rate
(Ibs/mln)
1
2
5
10
30
50
100
150
250
500
750
1,000
1,500
2,000
2,500
3,000
4,000
5,000
7,500
10,000
15,000
20,000
50,000
75,000
100,000
150,000
200,000
Toxic Endpoint (mg/L)
0.0004
0.0007
0.001
0.002
0.0035
0.005
0.0075
0.01
0.02
0.035
0.05
0.075
0.1
0.25
0.5
0.75
Distance (Miles)
2.2
3.0
4.8
6.8
11
14
19
24
>25
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
1.7
2.4
3.7
5.0
8.7
11
15
18
22
>25
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
1.5
2.1
3.0
4.2
6.8
9.3
12
15
19
>25
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
1.1
1.5
2.2
3.0
5.2
6.8
8.7
11
14
19
23
>25
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
0.8
1.1
1.7
2.4
3.9
5.0
6.8
8.1
11
14
17
20
24
>25
*
*
*
*
*
*
*
*
*
*
*
*
*
0.7
0.9
1.5
2.1
3.4
4.2
5.8
6.8
8.7
12
15
17
20
23
>25
*
*
*
*
*
*
*
*
*
*
*
*
0.5
0.7
1.2
1.7
2.8
3.5
4.8
5.7
7.4
9.9
12
14
16
19
20
23
>25
*
*
*
*
*
*
*
*
*
*
0.5
0.7
1.0
1.4
2.4
3.0
4.2
5.0
6.2
8.7
11
12
14
16
18
20
22
25
>25
*
*
*
*
*
*
*
*
0.3
0.4
0.7
1.0
1.7
2.2
2.9
3.6
4.5
6.2
7.4
8.1
9.9
11
12
14
16
17
20
24
>25
*
*
*
*
*
*
0.2
0.3
0.5
0.7
1.3
1.7
2.2
2.7
3.4
4.7
5.5
6.2
7.4
8.7
9.3
9.9
11
13
15
17
20
23
>25
*
*
*
*
0.2
0.3
0.4
0.6
1.1
1.4
1.9
2.3
2.8
3.8
4.5
5.2
6.2
6.8
8.1
8.7
9.3
11
12
14
17
19
>25
*
*
*
*
0.2
0.2
0.3
0.5
0.9
1.1
1.6
1.9
2.3
3.1
3.7
4.2
5.0
5.6
6.2
6.8
7.4
8.7
9.9
11
13
15
21
>25
*
*
*
0.1
0.2
0.3
0.4
0.7
0.9
1.3
1.6
2.0
2.7
3.2
3.6
4.3
4.8
5.3
5.6
6.2
6.8
8.7
9.3
11
12
18
21
24
>25
*
0.1
0.1
0.2
0.2
0.4
0.6
0.8
0.9
1.2
1.6
1.9
2.2
2.5
2.9
3.2
3.4
3.8
4.2
4.9
5.5
6.2
7.4
10
12
13
15
17
#
<0.1
0.1
0.2
0.3
0.4
0.5
0.6
0.8
1.1
1.3
1.4
1.7
1.9
2.1
2.2
2.5
2.7
3.2
3.6
4.2
4.7
6.6
7.6
8.5
9.8
11
#
<0.1
0.1
0.1
0.2
0.3
0.4
0.5
0.6
0.9
1.0
1.1
1.3
1.5
1.6
1.7
2.0
2.1
2.5
2.8
3.2
3.7
5.0
5.8
6.4
7.4
8.2
* > 25 miles (report distance as 25 miles)
# <0.1 mile (report distance as 0.1 mile)
5-:
-------
Reference Table 6
Dense Gas Distances to Toxic Endpoint
60-minute Release, Rural Conditions, F Stability, Wind Speed 1.5 Meters per Second
Release
Rate
(Ibs/mln)
1
2
5
10
30
50
100
150
250
500
750
1,000
1,500
2,000
2,500
3,000
4,000
5,000
7,500
10,000
15,000
20,000
50,000
75,000
100,000
150,000
200,000
Toxic Endpoint (mg/L)
0.0004
0.0007
0.001
0.002
0.0035
0.005
0.0075
0.01
0.02
0.035
0.05
0.075
0.1
0.25
0.5
0.75
Distance (Miles)
3.7
5.3
8.7
12
22
>25
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
2.7
4.0
6.8
9.3
16
21
>25
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
2.2
3.2
5.3
8.1
14
18
>25
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
1.4
2.2
3.7
5.3
9.9
12
18
22
>25
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
1.0
1.6
2.7
4.0
7.4
9.3
13
17
22
>25
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
0.8
1.2
2.2
3.3
6.1
8.1
11
14
18
25
>25
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
0.6
1.0
1.7
2.7
4.9
6.2
9.3
11
14
20
25
>25
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
0.5
0.8
1.4
2.2
4.1
5.4
7.4
9.9
12
17
22
25
>25
*
*
*
*
*
*
*
*
*
*
*
*
*
*
0.3
0.5
0.9
1.4
2.9
3.8
5.5
6.8
8.7
12
15
17
20
24
>25
*
*
*
*
*
*
*
*
*
*
*
*
0.2
0.4
0.6
1.0
2.1
2.7
4.0
4.9
6.2
9.3
11
12
16
17
20
21
24
>25
*
*
*
*
*
*
*
*
*
0.2
0.3
0.5
0.8
1.6
2.2
3.2
4.0
5.2
7.4
9.3
11
12
14
16
17
20
22
>25
*
*
*
*
*
*
*
*
0.1
0.2
0.4
0.6
1.2
1.7
2.5
3.1
4.1
5.8
7.4
8.1
9.9
11
13
14
16
17
21
24
>25
*
*
*
*
*
*
0.1
0.2
0.3
0.5
1.0
1.4
2.1
2.7
3.5
5.0
6.1
6.8
8.7
9.9
11
12
14
15
18
20
24
>25
*
*
*
*
*
<0.1
0.1
0.2
0.3
0.5
0.7
1.1
1.4
1.9
2.9
3.5
4.0
5.0
5.7
6.2
6.8
8.1
8.7
11
12
14
16
22
>25
*
*
*
#
<0.1
0.1
0.2
0.3
0.4
0.7
0.9
1.2
1.8
2.2
2.6
3.2
3.7
4.2
4.5
5.2
5.7
6.8
7.4
9.3
9.9
14
17
18
21
23
#
<0.1
0.1
0.1
0.2
0.3
0.5
0.6
0.9
1.3
1.7
2.0
2.5
2.9
3.2
3.5
4.0
4.4
5.2
6.0
6.8
8.1
11
13
14
16
18
* > 25 miles (report distance as 25 miles)
# <0.1 mile (report distance as 0.1 mile)
5-9
-------
Reference Table 7
Dense Gas Distances to Toxic Endpoint
10-minute Release, Urban Conditions, F Stability, Wind Speed 1.5 Meters per Second
Release
Rate
(Ibs/mln)
1
2
5
10
30
50
100
150
250
500
750
1,000
1,500
2,000
2,500
3,000
4,000
5,000
7,500
10,000
15,000
20,000
50,000
75,000
100,000
150,000
200,000
Toxic Endpoint (mg/L)
0.0004
0.0007
0.001
0.002
0.0035
0.005
0.0075
0.01
0.02
0.035
0.05
0.075
0.1
0.25
0.5
0.75
Distance (Miles)
1.6
2.2
3.5
4.9
8.1
11
15
19
24
>25
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
1.2
1.7
2.7
3.8
6.2
8.1
11
14
18
>25
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
1.1
1.4
2.2
3.1
5.3
6.8
9.3
12
15
21
>25
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
0.7
1.1
1.6
2.2
3.7
4.8
6.8
8.1
11
15
18
21
>25
*
*
*
*
*
*
*
*
*
*
*
*
*
*
0.6
0.8
1.2
1.7
2.9
3.7
5.2
6.1
8.1
11
14
16
19
22
24
>25
*
*
*
*
*
*
*
*
*
*
*
0.4
0.6
1.0
1.4
2.4
3.1
4.2
5.2
6.8
9.3
11
13
16
18
20
22
25
>25
*
*
*
*
*
*
*
*
*
0.4
0.5
0.8
1.2
2.0
2.5
3.5
4.3
5.4
7.4
9.3
11
12
15
16
18
20
23
>25
*
*
*
*
*
*
*
*
0.3
0.4
0.7
1.0
1.7
2.1
3.0
3.6
4.6
6.2
8.1
9.3
11
12
14
16
17
20
24
>25
*
*
*
*
*
*
*
0.2
0.3
0.5
0.7
1.2
1.5
2.1
2.5
3.3
4.5
5.5
6.2
7.4
8.7
9.9
11
12
14
16
19
22
>25
*
*
*
*
*
0.2
0.2
0.4
0.5
0.9
1.1
1.6
1.9
2.4
3.4
4.1
4.6
5.6
6.2
6.8
7.4
8.7
9.9
12
14
16
19
>25
*
*
*
*
0.1
0.2
0.3
0.4
0.7
0.9
1.3
1.6
2.0
2.8
3.3
3.8
4.6
5.2
5.8
6.2
6.8
8.1
9.9
11
13
15
23
>25
*
*
*
0.1
0.1
0.2
0.3
0.6
0.7
1.0
1.2
1.6
2.2
2.6
3.0
3.7
4.1
4.7
5.0
5.6
6.2
7.4
8.7
11
12
17
21
24
>25
*
0.1
0.1
0.2
0.2
0.4
0.6
0.9
1.1
1.4
1.9
2.2
2.5
3.0
3.5
3.8
4.2
4.8
5.3
6.2
7.4
8.7
9.9
15
17
20
23
>25
#
<0.1
0.1
0.1
0.2
0.3
0.5
0.6
0.7
1.1
1.3
1.5
1.7
2.0
2.2
2.4
2.7
3.0
3.6
4.1
4.9
5.5
8.1
9.6
11
13
14
#
#
<0.1
0.1
0.1
0.2
0.3
0.4
0.5
0.7
0.8
0.9
1.1
1.3
1.4
1.6
1.7
1.9
2.3
2.6
3.1
3.5
5.1
6.0
6.8
8.1
8.9
#
#
#
<0.1
0.1
0.1
0.2
0.2
0.3
0.5
0.6
0.7
0.8
0.9
1.1
1.2
1.3
1.4
1.7
2.0
2.3
2.7
3.8
4.5
5.1
6.1
6.7
* > 25 miles (report distance as 25 miles)
# <0.1 mile (report distance as 0.1 mile)
5- 10
-------
Reference Table 8
Dense Gas Distances to Toxic Endpoint
60-minute Release, Urban Conditions, F Stability, Wind Speed 1.5 Meters per Second
Release
Rate
(Ibs/mln)
1
2
5
10
30
50
100
150
250
500
750
1,000
1,500
2,000
2,500
3,000
4,000
5,000
7,500
10,000
15,000
20,000
50,000
75,000
100,000
150,000
200,000
Toxic Endpoint (mg/L)
0.0004
0.0007
0.001
0.002
0.0035
0.005
0.0075
0.01
0.02
0.035
0.05
0.075
0.1
0.25
0.5
0.75
Distance (Miles)
2.6
3.8
6.2
9.3
16
22
>25
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
1.9
2.9
4.7
6.8
12
16
24
>25
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
1.5
2.3
3.9
5.6
9.9
14
20
24
>25
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
1.1
1.5
2.6
3.9
7.4
9.3
14
17
22
>25
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
0.7
1.1
1.9
2.9
5.3
6.8
9.9
12
16
24
>25
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
0.6
0.9
1.5
2.3
4.3
5.7
8.1
11
14
19
24
>25
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
0.4
0.7
1.2
1.8
3.4
4.5
6.8
8.1
11
16
19
22
>25
*
*
*
*
*
*
*
*
*
*
*
*
*
*
0.4
0.6
0.9
1.5
2.9
3.8
5.7
6.8
9.3
13
16
19
24
>25
*
*
*
*
*
*
*
*
*
*
*
*
*
0.2
0.4
0.6
0.9
1.9
2.6
3.8
4.8
6.2
9.3
11
13
16
19
20
22
>25
*
*
*
*
*
*
*
*
*
*
0.2
0.2
0.4
0.7
1.3
1.8
2.7
3.5
4.5
6.8
8.1
9.3
12
13
15
16
19
21
>25
*
*
*
*
*
*
*
*
0.1
0.2
0.3
0.5
1.0
1.4
2.2
2.8
3.7
5.4
6.8
7.4
9.3
11
12
13
16
17
20
24
>25
*
*
*
*
*
*
0.1
0.1
0.2
0.4
0.7
1.1
1.7
2.2
2.9
4.2
5.2
6.0
7.4
8.7
9.3
11
12
14
16
19
22
>25
*
*
*
*
*
0.1
0.1
0.2
0.3
0.6
0.9
1.4
1.8
2.4
3.5
4.3
5.0
6.2
7.4
8.1
8.7
9.9
11
14
16
19
21
>25
*
*
*
*
#
<0.1
0.1
0.2
0.3
0.4
0.7
0.9
1.2
1.9
2.4
2.8
3.4
4.0
4.5
4.9
5.6
6.2
7.4
8.7
11
12
18
21
24
>25
*
#
#
<0.1
0.1
0.2
0.2
0.4
0.5
0.7
1.1
1.4
1.6
2.1
2.5
2.8
3.0
3.5
4.0
4.8
5.5
6.8
7.4
11
13
15
18
20
#
#
#
<0.1
0.1
0.2
0.3
0.3
0.5
0.7
1.0
1.2
1.5
1.8
2.1
2.2
2.6
3.0
3.6
4.2
5.1
5.8
8.7
10
11
14
15
* > 25 miles (report distance as 25 miles)
# <0.1 mile (report distance as 0.1 mile)
5- 11
-------
Reference Table 9
Distances to Toxic Endpoint for Anhydrous Ammonia Liquefied Under Pressure
F Stability, Wind Speed 1.5 Meters per Second
Release Rate
(Ibs/min)
1
2
5
10
15
20
30
40
50
60
70
80
90
100
150
200
250
300
400
500
600
700
750
800
900
Distance to Endpoint (miles)
Rural
0.1
0.1
0.1
0.2
0.2
0.3
0.3
0.4
0.4
0.5
0.5
0.5
0.6
0.6
0.7
0.8
0.9
1.0
1.2
1.3
1.4
1.5
1.6
1.6
1.7
Urban
0.1*
0.1
0.1
0.1
0.2
0.2
0.2
0.3
0.3
0.3
0.3
0.4
0.4
0.4
0.5
0.6
0.6
0.7
0.8
0.9
0.9
1.0
1.0
1.1
1.2
Release Rate
(Ibs/min)
1,000
1,500
2,000
2,500
3,000
4,000
5,000
6,000
7,000
7,500
8,000
9,000
10,000
15,000
20,000
25,000
30,000
40,000
50,000
75,000
100,000
150,000
200,000
250,000
750,000
Distance to Endpoint (miles)
Rural
1.8
2.2
2.6
2.9
3.1
3.6
4.0
4.4
4.7
4.9
5.1
5.4
5.6
6.9
8.0
8.9
9.7
11
12
15
18
22
**
**
**
Urban
1.2
1.5
1.7
1.9
2.0
2.3
2.6
2.8
3.1
3.2
3.3
3.4
3.6
4.4
5.0
5.6
6.1
7.0
7.8
9.5
10
13
15
17
**
*Report distance as 0.1 mile
** More than 25 miles (report distance as 25 miles)
April 15, 1999
5-12
-------
Reference Table 10
Distances to Toxic Endpoint for Non-liquefied Ammonia, Ammonia Liquefied by Refrigeration, or
Aqueous Ammonia
F Stability, Wind Speed 1.5 Meters per Second
Release Rate
(Ibs/min)
1
2
5
10
15
20
30
40
50
60
70
80
90
100
150
200
250
300
400
500
600
700
750
800
900
Distance to Endpoint (miles)
Rural
0.1
0.1
0.1
0.2
0.2
0.3
0.3
0.4
0.4
0.4
0.5
0.5
0.5
0.6
0.7
0.8
0.8
0.9
1.1
1.2
1.3
1.4
1.4
1.5
1.5
Urban
0.1*
0.1
0.1
0.1
0.1
0.1
0.1
0.2
0.2
0.2
0.2
0.2
0.2
0.3
0.3
0.3
0.4
0.4
0.4
0.5
0.5
0.5
0.6
Release Rate
(Ibs/min)
1,000
1,500
2,000
2,500
3,000
4,000
5,000
6,000
7,000
7,500
8,000
9,000
10,000
15,000
20,000
25,000
30,000
40,000
50,000
75,000
100,000
150,000
200,000
250,000
750,000
Distance to Endpoint (miles)
Rural
1.6
2.0
2.2
2.5
2.7
3.1
3.4
3.7
4.0
4.1
4.2
4.5
4.7
5.6
6.5
7.2
7.8
8.9
9.8
12
14
16
19
21
**
Urban
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.5
1.6
1.7
2.0
2.4
2.6
2.8
3.3
3.6
4.4
5.0
6.1
7.0
7.8
13
*Report distance as 0.1 mile
** More than 25 miles (report distance as 25 miles)
April 15, 1999
5-13
-------
Reference Table 11
Distances to Toxic Endpoint for Chlorine
F Stability, Wind Speed 1.5 Meters per Second
Release Rate
(Ibs/min)
1
2
5
10
15
20
30
40
50
60
70
80
90
100
150
200
250
300
400
500
600
700
Distance to Endpoint (miles)
Rural
0.2
0.3
0.5
0.7
0.8
1.0
1.2
1.4
1.5
1.7
1.8
1.9
2.0
2.2
2.6
3.0
3.4
3.7
4.2
4.7
5.2
5.6
Urban
0.1
0.1
0.2
0.3
0.4
0.4
0.5
0.6
0.6
0.7
0.8
0.8
0.9
0.9
1.2
1.3
1.5
1.6
1.9
2.1
2.3
2.5
Release Rate
(Ibs/min)
750
800
900
1,000
1,500
2,000
2,500
3,000
4,000
5,000
6,000
7,000
7,500
8,000
9,000
10,000
15,000
20,000
25,000
30,000
40,000
50,000
Distance to Endpoint (miles)
Rural
5.8
5.9
6.3
6.6
8.1
9.3
10
11
13
14
16
17
18
18
19
20
25
*
*
*
*
*
Urban
2.6
2.7
2.9
3.0
3.8
4.4
4.9
5.4
6.2
7.0
7.6
8.3
8.6
8.9
9.4
9.9
12
14
16
18
20
*
: More than 25 miles (report distance as 25 miles)
April 15, 1999
5-14
-------
Reference Table 12
Distances to Toxic Endpoint for Anhydrous Sulfur Dioxide
F Stability, Wind Speed 1.5 Meters per Second
Release Rate
(Ibs/min)
1
2
5
10
15
20
30
40
50
60
70
80
90
100
150
200
250
300
400
500
600
700
Distance to Endpoint (miles)
Rural
0.2
0.2
0.4
0.6
0.7
0.9
1.1
1.3
1.4
1.6
1.8
1.9
2.0
2.1
2.7
3.1
3.6
3.9
4.6
5.2
5.8
6.3
Urban
0.1
0.1
0.2
0.2
0.3
0.4
0.5
0.5
0.6
0.7
0.7
0.8
0.8
0.9
1.1
1.3
1.4
1.6
1.9
2.1
2.3
2.5
Release Rate
(Ibs/min)
750
800
900
1,000
1,500
2,000
2,500
3,000
4,000
5,000
6,000
7,000
7,500
8,000
9,000
10,000
15,000
20,000
25,000
30,000
40,000
50,000
Distance to Endpoint (miles)
Rural
6.6
6.8
7.2
7.7
9.6
11
13
14
17
19
21
23
24
25
*
*
*
*
*
*
*
*
Urban
2.6
2.7
2.9
3.1
3.8
4.5
5.0
5.6
6.5
7.3
8.1
8.8
9.1
9.5
10
11
13
16
18
19
23
*
: More than 25 miles (report distance as 25 miles)
April 15, 1999
5-15
-------
Reference Table 13
Distance to Overpressure of 1.0 psi for Vapor Cloud Explosions of 500 - 2,000,000 Pounds of Regulated Flammable Substances
Based on TNT Equivalent Method, 10 Percent Yield Factor
Quantity in Cloud (pounds)
CAS No.
75-07-0
74-86-2
598-73-2
106-99-0
106-97-8
25167-67-3
590-18-1
624-64-6
106-98-9
107-01-7
463-58-1
7791-21-1
590-21-6
557-98-2
460-19-5
75-19-4
4109-96-0
75-37-6
124-40-3
463-82-1
74-84-0
107-00-6
75-04-7
Chemical Name
Acetaldehyde
Acetylene
Bromotrifluoroethylene
1,3-Butadiene
Butane
Butene
2-Butene-cis
2-Butene-trans
1 -Butene
2-Butene
Carbon oxysulfide
Chlorine monoxide
1 -Chloropropylene
2-Chloropropylene
Cyanogen
Cyclopropane
Dichlorosilane
Difluoroethane
Dimethylamine
2,2-Dimethylpropane
Ethane
Ethyl acetylene
Ethvlamine
500
2,000
5,000
10,000
20,000
50,000
100,000
200,000
500,000
1,000,000
2,000,000
Distance (Miles) to 1 psi Overpressure
0.05
0.07
0.02
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.04
0.02
0.05
0.05
0.05
0.06
0.04
0.04
0.06
0.06
0.06
0.06
0.06
0.08
0.1
0.04
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.06
0.03
0.08
0.08
0.08
0.1
0.06
0.06
0.09
0.1
0.1
0.1
0.09
0.1
0.1
0.05
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.08
0.04
0.1
0.1
0.1
0.1
0.08
0.09
0.1
0.1
0.1
0.1
0.1
0.1
0.2
0.06
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.1
0.05
0.1
0.1
0.1
0.2
0.1
0.1
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.08
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.1
0.06
0.2
0.2
0.2
0.2
0.1
0.1
0.2
0.2
0.2
0.2
0.2
0.2
0.3
0.1
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.2
0.08
0.2
0.2
0.2
0.3
0.2
0.2
0.3
0.3
0.3
0.3
0.3
0.3
0.4
0.1
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.2
0.1
0.3
0.3
0.3
0.4
0.2
0.2
0.3
0.4
0.4
0.4
0.3
0.4
0.5
0.2
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.3
0.1
0.4
0.4
0.4
0.5
0.3
0.3
0.4
0.5
0.5
0.5
0.4
0.5
0.7
0.2
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.4
0.2
0.5
0.5
0.5
0.6
0.4
0.4
0.6
0.6
0.6
0.6
0.6
0.7
0.8
0.3
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.5
0.2
0.6
0.6
0.6
0.8
0.5
0.5
0.7
0.8
0.8
0.8
0.7
0.8
1.0
0.4
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.6
0.3
0.8
0.8
0.8
1.0
0.6
0.6
0.9
1.0
1.0
1.0
0.9
April 15, 1999
5-16
-------
Reference Table 13 (continued)
Quantity in Cloud (pounds)
CAS No.
75-00-3
74-85-1
60-29-7
75-08-1
109-95-5
1333-74-0
75-28-5
78-78-4
78-79-5
75-31-0
75-29-6
74-82-8
74-89-5
563-45-1
563-46-2
115-10-6
107-31-3
115-11-7
504-60-9
109-66-0
109-67-1
646-04-8
627-20-3
463-49-0
Chemical Name
Ethyl chloride
Ethylene
Ethyl ether
Ethyl mercaptan
Ethyl nitrite
Hydrogen
Isobutane
Isopentane
Isoprene
Isopropylamine
Isopropyl chloride
Methane
Methylamine
3 -Methyl- 1-butene
2-Methyl-l-butene
Methyl ether
Methyl formate
2-Methylpropene
1,3-Pentadiene
Pentane
1-Pentene
2-Pentene, (E)-
2-Pentene, (Z)-
Propadiene
500
2,000
5,000
10,000
20,000
50,000
100,000
200,000
500,000
1,000,000
2,000,000
Distance (Miles) to 1 psi Overpressure
0.05
0.06
0.06
0.05
0.05
0.09
0.06
0.06
0.06
0.06
0.05
0.07
0.06
0.06
0.06
0.05
0.04
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.08
0.1
0.09
0.09
0.07
0.1
0.1
0.1
0.1
0.09
0.08
0.1
0.09
0.1
0.1
0.09
0.07
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.2
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.2
0.2
0.2
0.1
0.2
0.2
0.2
0.2
0.2
0.1
0.2
0.2
0.2
0.2
0.1
0.1
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.3
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.3
0.3
0.2
0.2
0.4
0.3
0.3
0.3
0.3
0.2
0.3
0.3
0.3
0.3
0.3
0.2
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.4
0.3
0.3
0.3
0.5
0.4
0.4
0.4
0.3
0.3
0.4
0.3
0.4
0.4
0.3
0.3
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.5
0.4
0.4
0.3
0.6
0.5
0.5
0.5
0.4
0.4
0.5
0.4
0.5
0.5
0.4
0.3
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.7
0.6
0.5
0.5
0.9
0.6
0.6
0.6
0.6
0.5
0.7
0.6
0.6
0.6
0.5
0.4
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.8
0.7
0.7
0.6
1.1
0.8
0.8
0.8
0.7
0.6
0.8
0.7
0.8
0.8
0.7
0.6
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
1.0
0.9
0.9
0.7
1.4
1.0
1.0
1.0
0.9
0.8
1.0
0.9
1.0
1.0
0.9
0.7
1.0
1.0
1.0
1.0
1.0
1.0
1.0
April 15, 1999
5-17
-------
Reference Table 13 (continued)
Quantity in Cloud (pounds)
CAS No.
74-98-6
115-07-1
74-99-7
7803-62-5
116-14-3
75-76-3
10025-78-2
79-38-9
75-50-3
689-97-4
75-01-4
109-92-2
75-02-5
75-35-4
75-38-7
107-25-5
Chemical Name
Propane
Propylene
Propyne
Silane
Tetrafluoroethylene
Tetramethylsilane
Trichlorosilane
Trifluorochloroethylene
Trimethylamine
Vinyl acetylene
Vinyl chloride
Vinyl ethyl ether
Vinyl fluoride
Vinylidene chloride
Vinylidene fluoride
Vinyl methyl ether
500
2,000
5,000
10,000
20,000
50,000
100,000
200,000
500,000
1,000,000
2,000,000
Distance (Miles) to 1 psi Overpressure
0.06
0.06
0.06
0.06
0.02
0.06
0.03
0.02
0.06
0.06
0.05
0.06
0.02
0.04
0.04
0.06
0.1
0.1
0.1
0.1
0.03
0.1
0.04
0.03
0.1
0.1
0.08
0.09
0.04
0.06
0.06
0.09
0.1
0.1
0.1
0.1
0.04
0.1
0.06
0.05
0.1
0.1
0.1
0.1
0.05
0.08
0.09
0.1
0.2
0.2
0.2
0.2
0.05
0.2
0.08
0.06
0.2
0.2
0.1
0.2
0.06
0.1
0.1
0.2
0.2
0.2
0.2
0.2
0.07
0.2
0.1
0.07
0.2
0.2
0.2
0.2
0.08
0.1
0.1
0.2
0.3
0.3
0.3
0.3
0.09
0.3
0.1
0.1
0.3
0.3
0.2
0.3
0.1
0.2
0.2
0.3
0.4
0.4
0.4
0.4
0.1
0.4
0.2
0.1
0.4
0.4
0.3
0.3
0.1
0.2
0.2
0.3
0.5
0.5
0.5
0.5
0.1
0.5
0.2
0.2
0.4
0.5
0.4
0.4
0.2
0.3
0.3
0.4
0.6
0.6
0.6
0.6
0.2
0.6
0.3
0.2
0.6
0.6
0.5
0.6
0.2
0.4
0.4
0.6
0.8
0.8
0.8
0.8
0.2
0.8
0.4
0.3
0.8
0.8
0.6
0.7
0.3
0.5
0.5
0.7
1.0
1.0
1.0
1.0
0.3
1.0
0.4
0.3
1.0
1.0
0.8
0.9
0.4
0.6
0.6
0.9
April 15, 1999
5-18
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DETERMINING ALTERNATIVE RELEASE SCENARIOS
In Chapter 6
Considerations for alternative release scenarios for regulated substances in
Program 2 or Program 3 processes.
Potential alternative scenarios for releases of flammable substances.
You are required to analyze at least one alternative release scenario for each listed toxic substance
you have in a Program 2 or Program 3 process above its threshold quantity. You also are required to analyze
one alternative release scenario for flammable substances in Program 2 or 3 processes as a class (i.e., you
analyze one scenario involving a flammable substance as a representative scenario for all the regulated
flammable substances you have on site in Program 2 or Program 3 processes). You do not need to analyze an
alternative scenario for each flammable substance. For example, if you have five listed substances - chlorine,
ammonia, hydrogen chloride, propane, and acetylene - above the threshold in Program 2 or 3 processes, you
will need to analyze one alternative scenario each for chlorine, ammonia, and hydrogen chloride and a single
alternative scenario to cover propane and acetylene (listed flammable substances). Even if you have a
substance above the threshold in several processes or locations, you need only analyze one alternative
scenario for it.
According to the rule (40 CFR 68.28), alternative scenarios should be more likely to occur than the
worst-case scenario and should reach an endpoint offsite, unless no such scenario exists. Release scenarios
considered should include, but are not limited to, the following:
• Transfer hose releases due to splits or sudden hose uncoupling;
• Process piping releases from failures at flanges, joints, welds, valves and valve seals, and
drains or bleeds;
• Process vessel or pump releases due to cracks, seal failure, or drain, bleed, or plug failure;
• Vessel overfilling and spill, or overpressurization and venting through relief valves or
rupture disks; and
• Shipping container mishandling or puncturing leading to a spill.
Alternative release scenarios for toxic substances should be those that lead to concentrations above
the toxic endpoint beyond your fenceline. Scenarios for flammable substances should have the potential to
cause substantial damage, including on-site damage. Those releases that have the potential to reach the
public are of the greatest concern. You should consider unusual situations, such as start-up and shut-down, in
selecting an appropriate alternative scenario.
For alternative release scenarios, you are allowed to consider active mitigation systems, such as
interlocks, shutdown systems, pressure relieving devices, flares, emergency isolation systems, and fire water
and deluge systems, as well as passive mitigation systems, as described in Sections 3.1.2 and 3.2.3.
For alternative release scenarios for regulated substances used in ammonia refrigeration, chemical
distribution, propane distribution, warehouses, or POTWs, consult EPA's risk management program guidance
April 15, 1999
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Chapter 6
Determining Alternative Release Scenarios
documents for these industry sectors.
You have a number of options for selecting release scenarios for toxic or flammable substances.
• You may use your worst-case release scenario and apply your active mitigation system to
limit the quantity released and the duration of the release.
• You may use information from your process hazards analysis, if you have conducted one, to
select a scenario.
• You may review your accident history and choose an actual event as the basis of your
scenario.
• If you have not conducted a process hazards analysis, you may review your operations and
identify possible events and failures.
Whichever approach you select, the key information you need to define is the quantity to be released
and the time over which it will be released; together, these allow you to estimate the release rate and use
essentially the same methods you used for the worst-case analysis.
For flammable substances , the choice of alternative release scenarios is somewhat more complicated
than for toxic substances, because the consequences of a release and the endpoint of concern may vary. For
the flammable worst case, the consequence of concern is a vapor cloud explosion, with an overpressure
endpoint. For alternative scenarios (e.g., fires), other endpoints (e.g., heat radiation) may need to be
considered.
Possible scenarios involving flammable substances include:
• Vapor cloud fires (flash fires) may result from dispersion of a cloud of flammable vapor and
ignition of the cloud following dispersion. Such a fire could flash back and could represent a
severe heat radiation hazard to anyone in the area of the cloud. This guidance provides
methods to estimate distances to a concentration equal to the lower flammability limit (LFL)
for this type of fire. (See Sections 9.1, 9.2, and 10.1.)
• A pool fire, with potential radiant heat effects, may result from a spill of a flammable liquid.
This guidance provides a simple method for estimating the distance from a pool fire to a
radiant heat level that could cause second degree burns from a 40-second exposure. (See
Section 10.2).
• A boiling liquid, expanding vapor explosion (BLEVE), leading to a fireball that may
produce intense heat, may occur if a vessel containing flammable material ruptures
explosively as a result of exposure to fire. Heat radiation from the fireball is the primary
hazard; vessel fragments and overpressure from the explosion also can result. BLEVEs are
generally considered unlikely events; however, if you think a BLEVE is possible at your site,
this guidance provides a method to estimate the distance at which radiant heat effects might
lead to second degree burns. (See Section 10.3.) You also may want to consider models or
April 15, 1999 6-2
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Chapter 6
Determining Alternative Release Scenarios
calculation methods to estimate effects of vessel fragmentation. (See Appendix A for
references that may provide useful information for estimating such effects.)
• For a vapor cloud explosion to occur, rapid release of a large quantity, turbulent conditions
(caused by a turbulent release or congested conditions in the area of the release, or both), and
other factors are generally necessary. Vapor cloud explosions generally are considered
unlikely events; however, if conditions at your site are conducive to vapor cloud explosions,
you may want to consider a vapor cloud explosion as an alternative scenario. This guidance
provides methods you may use to estimate the distance to 1 psi overpressure for a vapor
cloud detonation, based on less conservative assumptions than the worst-case analysis. (See
Section 10.4.) A vapor cloud deflagration, involving lower flame speeds than a detonation
and resulting in less damaging blast effects, is more likely than a detonation. This guidance
does not provide methods for estimating the effects of a deflagration, but you may use other
methods of analysis if you want to consider such events. (See Appendix A for references
that may provide useful information.)
• A jet fire may result from the puncture or rupture of a tank or pipeline containing a
compressed or liquefied gas under pressure. The gas discharging from the hole can form a
jet that "blows" into the air in the direction of the hole; the jet then may ignite. Jet fires
could contribute to BLEVEs and fireballs if they impinge on tanks of flammable substances.
A large horizontal jet fire may have the potential to pose an offsite hazard. This guidance
does not include a method for estimating consequence distances for jet fires. If you want to
consider a jet fire as an alternative scenario, you should consider other models or methods
for the consequence analysis. (See Appendix A for references that may provide useful
information.)
If you carry out an alternative scenario analysis for a flammable mixture (i.e., a mixture that meets
the criteria for NFPA 4), you need to consider all flammable components of the mixture, not just the regulated
flammable substance or substances in the mixture (see Section 5.2 on flammable mixtures). If the mixture
contains both flammable and non-flammable components, the analysis should be carried out considering only
the flammable components.
Chapter 7 provides detailed information on calculating release rates for alternative release scenarios
for toxic substances. If you can estimate release rates for the toxic gases and liquids you have on site based
on readily available information, you may skip Chapter 7 and go to Chapter 8. Chapter 8 describes how to
estimate distances to the toxic endpoint for alternative scenarios for toxic substances. Chapters 9 provides
information on calculation release rates for flammable substances. Chapter 10 describes how to estimate
distances to flammable endpoints.
April 15, 1999
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Chapter 6
Determining Alternative Release Scenarios
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April 15, 1999 6-4
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7 ESTIMATION OF RELEASE RATES FOR ALTERNATIVE
SCENARIOS FOR TOXIC SUBSTANCES
For the alternative scenario analysis, you may use typical meteorological conditions and typical
ambient temperature and humidity for your site. This guidance assumes D atmospheric stability and wind
speed of 3.0 meters per second (6.7 miles per hour) as conditions likely to be applicable to many sites.
7.1 Release Rates for Toxic Gases
In Section 7.1
7.1.1 Methods for unmitigated releases of toxic gases, including:
Release of toxic gas from a hole in a tank or pipe (for choked flow
conditions, or maximum flow rate),
Release of toxic gas from a pipe, based on the flow rate through the
pipe, or based on a hole in the pipe (using the same method as for a
hole in a tank),
Puff releases (no method is provided; users are directed to use other
methods),
Gases liquefied under pressure, including gaseous releases from holes
above the liquid level in the tank and releases from holes in the liquid
space, and
Consideration of duration of releases of toxic gas.
7.1.2 Methods for adjusting the estimated release rate to account for active or
passive mitigation, including:
Active mitigation to reduce the release duration (e.g., automatic
shutoff valves),
Active mitigation to reduce the release rate to air, and
Passive mitigation (using the same method as for worst-case
scenarios).
7.1.1 Unmitigated Releases of Toxic Gases
Gaseous Releases
Gaseous Release from Tank. Instead of assuming release of the entire contents of a vessel containing
a toxic gas, you may decide to consider a more likely scenario as developed by the process hazards analysis,
such as release from a hole in a vessel or pipe. To estimate a hole size you might assume, for example, the
hole size that would result from shearing off a valve or pipe from a vessel containing a regulated substance.
If you have a gas leak from a tank, you may use the following simplified equation to estimate a release rate
based on hole size, tank pressure, and the properties of the gas. This equation applies to choked flow, or
maximum gas flow rate. Choked flow generally would be expected for gases under pressure. (See Appendix
D, Section D.6 for the derivation of this equation.)
April 15, 1999
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Chapter 7
Estimation of Release Rates for Alternative Scenarios for Toxic Substances
QR = HA x pf
x GF
(7-1)
where:
QR
HA
Tt
GF
Release rate (pounds per minute)
Hole or puncture area (square inches) (from hazard evaluation or best
estimate)
Tank pressure (pounds per square inch absolute (psia)) (from process
information; for liquefied gases, equilibrium vapor pressure at 25 °C is
included in Exhibit B-l, Appendix B)
Tank temperature (K), where K is absolute temperature in kelvins; 25 °C
(77 °F) is 298 K
Gas Factor, incorporating discharge coefficient, ratio of specific heats,
molecular weight, and conversion factors (listed for each regulated toxic gas
in Exhibit B-l, Appendix B)
You can estimate the hole area from the size and shape of the hole. For a circular hole, you would
use the formula for the area of a circle (area = Tir2, where n is 3.14 and r is the radius of the circle; the radius
is half the diameter).
This equation will give an estimate of the initial release rate. It will overestimate the overall release
rate, because it does not take into account the decrease in the release rate as the pressure in the tank decreases.
You may use a computer model or another calculation method if you want a more realistic estimate of the
release rate. As discussed below, you may use this equation for releases of gases liquefied under pressure if
the release would be primarily gas (e.g., if the hole is in the head space of the tank, well above the liquid
level).
Example 19. Release of Toxic Gas from Tank (Diborane)
You have a tank that contains diborane gas at a pressure of 30 psia. The temperature of the tank and its
contents is 298 K (25 °C). A valve on the side of the tank shears off, leaving a circular hole 2 1A inches in
diameter in the tank wall. You estimate the area from the formula for area of a circle (itr2, where r is the
radius). The radius of the hole is 1 1/4 inches, so the area is it x (1 1/4)2, or 5 square inches. From Exhibit
B-l, the Gas Factor for diborane is 17. Therefore, the release rate, from Equation 7-1, is:
QR = 5 x 30 x l/(298)'/2 x 17 = 148 pounds per minute
Gaseous Release from Pipe. If shearing of a pipe may be an alternative scenario for a toxic gas at
your site, you could use the usual flow rate through the pipe as the release rate and carry out the estimation of
distance as discussed in Chapter 8.
April 15, 1999
7-2
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Chapter 7
Estimation of Release Rates for Alternative Scenarios for Toxic Substances
If you want to consider a release of toxic gas through a hole in a pipe as an alternative scenario, you
may use the method described above for a gas release from a hole in a tank. This method neglects the effects
of friction along the pipe and, therefore, provides a conservative estimate of the release rate.
Puff Releases. If a gaseous release from a hole in a tank or pipe is likely to be stopped very quickly
(e.g., by a block valve), resulting in a puff of toxic gas that forms a vapor cloud rather than a plume, you may
want to consider other methods for determining a consequence distance. A cloud of toxic gas resulting from a
puff release will not exhibit the same behavior as a plume resulting from a longer release (e.g., a release over
10 minutes).
Liquefied Gases
Gases Liquefied Under Pressure. Gases liquefied under pressure may be released as gases, liquids,
or a combination (two-phase), depending on a number of factors, including liquid level and the location of the
hole relative to the liquid level. The resulting impact distances can vary greatly.
For releases from holes above the liquid level in a tank of gas liquefied under pressure, the release
could be primarily gas, or the release may involve rapid vaporization of a fraction of the liquefied gas and
possibly aerosolization (two-phase release). It is complex to determine which type of release (i.e., gas, two-
phase) will occur and the likely mix of gases and liquids in a two-phase release. The methods presented in
this guidance do not definitively address this situation. As a rule of thumb, if the head space is large and the
distance between the hole and the liquid level is relatively large given the height of the tank or vessel, you
could assume the release is gaseous and, therefore, use Equation 7-1 above. (Exhibit B-l, Appendix B,
includes the equilibrium vapor pressure in psia for listed toxic gases liquefied under pressure at 25 °C; this
pressure can be used in Equation 7-1.) However, use of this equation will not be conservative if the head
space is small and the release from the hole is two-phased. In situations where you are unsure of whether the
release would be gaseous or two-phase, you may want to consider other models or methods to carry out a
consequence analysis.
For a hole in the liquid space of a tank, you may use Equation 7-2 below to estimate the release rate.
Exhibit B-l in Appendix B gives the equilibrium vapor pressure in psia for listed toxic gases at 25 °C; this
is the pressure required to liquefy the gas at this temperature. You can estimate the gauge pressure in the
tank from the equilibrium vapor pressure by subtracting the pressure of the ambient atmosphere (14.7 psi).
Exhibit B-1 also gives the Density Factor (DF) for each toxic gas at its boiling point. This factor can be used
to estimate the density of the liquefied gas (the density at 25 °C would not be significantly different from the
density at the boiling point for most of the listed gases). The equation to estimate the release rate is (see
Appendix D, Section D.7.1, for more information):
QR = HA x 6.82
LH + x Pg (7.2)
g ^ '
DF2 DF
April 15, 1999 1 -'.
-------
Chapter 7
Estimation of Release Rates for Alternative Scenarios for Toxic Substances
where: QR = Release rate (pounds per minute)
HA = Hole or puncture area (square inches) (from hazard evaluation or best
estimate)
DF = Density Factor (listed for each regulated toxic gas in Exhibit B-1, Appendix
B; 1/(DF x 0.033) is density in pounds per cubic foot)
LH = Height of liquid column above hole (inches) (from hazard evaluation or best
estimate)
Pg = Gauge pressure of the tank pressure (pounds per square inch gauge (psig),
from vapor pressure of gas (listed in Exhibit B-l, Appendix B) minus
atmospheric pressure (14.7 psi)
This equation gives the rate of release of liquid through the hole. For a gas liquefied under pressure, assume
that the released liquid will immediately flash into vapor (or a vapor/aerosol mixture) and the release rate to
air is the same as the liquid release rate. This equation gives an estimate of the initial release rate. It will
overestimate the overall release rate, because it does not take into account the decrease in the release rate as
the pressure in the tank and the height of the liquid in the tank decrease. You may use a computer model or
another calculation method if you want a more realistic estimate of the release rate.
For a release from a broken pipe of a gas liquefied under pressure, see equations 7-4 to 7-6 below for
liquid releases from pipes. Assume the released liquid flashes into vapor upon release and use the calculated
release rate as the release rate to air.
Gases Liquefied by Refrigeration. Gases liquefied by refrigeration alone may be treated as liquids.
You may use the methods described in Section 7.2 for estimation of release rates.
Duration of Release
The duration of the release is used in choosing the appropriate generic reference table of distances, as
discussed in Chapter 8. (You do not need to consider the duration of the release to use the chemical-specific
reference tables.) You may calculate the maximum duration by dividing the quantity in the tank or the
quantity that may be released from pipes by your calculated release rate. You may use 60 minutes as a
default value for maximum release duration. If you know, and can substantiate, how long it is likely to take
to stop the release, you may use that time as the release duration.
7.1.2 Mitigated Releases of Toxic Gases
For gases, passive mitigation may include enclosed spaces, as discussed in Section 3.1.2. Active
mitigation for gases, which may be considered in analyzing alternative release scenarios, may include an
assortment of techniques including automatic shutoff valves, rapid transfer systems (emergency deinventory),
and water/chemical sprays. These mitigation techniques have the effect of reducing either the release rate or
the duration of the release, or both.
April 15, 1999 7-4
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Chapter 7
Estimation of Release Rates for Alternative Scenarios for Toxic Substances
Active Mitigation
Active Mitigation to Reduce Release Duration. An example of a mitigation technique to reduce the
release duration is automatic shutoff valves. If you have an estimate of the rate at which the gas will be
released and the time it will take to shut off the release, you may estimate the quantity potentially released
(release rate times time). You must be able to substantiate the time it will take to shut off the release. If the
release will take place over a period of 10 minutes or more, you may use the release rate to estimate the
distance to the toxic endpoint, as discussed in Chapter 8. For releases stopped in less than 10 minutes,
multiply the initial release rate by the duration of release to estimate the quantity released, then divide the new
quantity by 10 minutes to estimate a mitigated release rate that you may apply to the reference tables
described in Chapter 8 to estimate the consequence distance. If the release would be stopped very quickly,
you might want to consider other methods that will estimate consequence distances for a puff release.
Active Mitigation to Directly Reduce Release Rate to Air. Examples of mitigation techniques to
directly reduce the release rate include scrubbers and flares. Use test data, manufacturer design
specifications, or past experience to determine the fractional reduction of the release rate by the mitigation
technique. Apply this fraction to the release rate that would have occurred without the mitigation technique.
The initial release rate, without mitigation, may be the release rate for the alternative scenario (e.g., a release
rate estimated from the equations presented earlier in this section) or the worst-case release rate. The
mitigated release rate is:
QRR = (1 - FK) x QR
(7-3)
where:
QRR
FR
QR
Reduced release rate (pounds per minute)
Fractional reduction resulting from mitigation
Release rate without mitigation (pounds per minute)
Example 20. Water Spray Mitigation (Hydrogen Fluoride)
A bleeder valve on a hydrogen fluoride (HF) tank opens, releasing 660 pounds per minute of HF. Water sprays
are applied almost immediately. Experimental field and laboratory test data indicate that HF vapors could be
reduced by 90 percent. The reduced release rate is:
QRR = (1 - 0.9) x (660 pounds per minute)
= 66 pounds per minute
In estimating the consequence distance for this release scenario, you would need to consider the release both
before and after application of the water spray and determine which gives the greatest distance to the endpoint.
You need to be able to substantiate the time needed to begin the water spray mitigation.
April 15, 1999
7-5
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Chapter 7
Estimation of Release Rates for Alternative Scenarios for Toxic Substances
Passive Mitigation
The same simplified method used for worst-case releases may be used for alternative release
scenarios to estimate the release rate to the outside air from a release in an enclosed space. For alternative
scenarios, you may use a modified release quantity, if appropriate. You may also adjust the mitigation factor
to account for the effects of ventilation, if appropriate for the alternative scenario you have chosen. Use the
equations presented in Section 3.1.2 to estimate the release rate to the outside air.
Duration of Release
You should estimate the duration of the release either from your knowledge of the length of time it
may take to stop the release (be prepared to substantiate your time estimate) or by dividing the quantity that
may be released by your estimated release rate. (You do not need to consider the release duration to use the
chemical-specific reference tables of distances.)
7.2 Release Rates for Toxic Liquids
In Section 7.2
7.2.1 Methods for estimating the liquid release rate and quantity released for
toxic liquids released without mitigation, including:
Release of toxic liquid from a hole in a tank under atmospheric
pressure (including toxic gases liquefied by refrigeration alone),
Release of toxic liquid from a hole in the liquid space of a pressurized
tank (the user is referred to equations provided in the section on toxic
gases or in the technical appendix), and
Release of toxic liquid from a broken pipe.
7.2.2 Methods for estimating the liquid release rate and quantity released for
toxic liquids released with mitigation measures that reduce the duration of the
liquid release or the quantity of liquid released (e.g., automatic shutoff valves),
7.2.3 Methods for estimating the evaporation rate of toxic liquids from pools,
accounting for:
Ambient temperature,
Elevated temperature,
Diked areas,
Releases into buildings,
Active mitigation to reduce the evaporation rate of the liquid,
Temperatures between 25 °C and 50 °C, and
Duration of the release.
7.2.4 Methods for estimating the evaporation rate for common water solutions
of regulated toxic substances and for oleum.
April 15, 1999
7-6
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Chapter 7
Estimation of Release Rates for Alternative Scenarios for Toxic Substances
This section describes methods for estimating liquid release rates from tanks and pipes. The released
liquid is assumed to form a pool, and the evaporation rate from the pool is estimated as for the worst-case
scenario. For the alternative scenario, you may assume the average wind speed in your area in the calculation
of evaporation rate, instead of the worst-case wind speed of 1.5 meters per second (3.4 miles per hour). For
the reference tables in this guidance, the wind speed for alternative scenarios is assumed to be 3.0 meters per
second (6.7 miles per hour).
If you have sufficient information to estimate the quantity of liquid that might be released to an
undiked area under an alternative scenario, you may go directly to Section 7.2.3 to estimate the evaporation
rate from the pool and the release duration. After you have estimated the evaporation rate and release
duration, go to Chapter 8 for instructions on estimating distance to the toxic endpoint.
7.2.1 Liquid Release Rate and Quantity Released for Unmitigated Releases
Release from Tank
Tank under Atmospheric Pressure. If you have a liquid stored in a tank at atmospheric pressure
(including gases liquefied by refrigeration alone), you may use the following simple equation to estimate the
liquid release rate from a hole in the tank below the liquid level. (See Appendix D, Section D.7.1, for the
derivation of this equation.)
QRL = HA x lH x LLF (7-4)
where: QRL = Liquid release rate (pounds per minute)
HA = Hole or puncture area (square inches) (from hazard evaluation or best
estimate)
LH = Height of liquid column above hole (inches) (from hazard evaluation or best
estimate)
LLF = Liquid Leak Factor incorporating discharge coefficient and liquid density
(listed for each toxic liquid in Exhibit B-2, Appendix B).
Remember that this equation only applies to liquids in tanks under atmospheric pressure. This
equation will give an overestimate of the release rate, because it does not take into account the decrease in the
release rate as the height of the liquid above the hole decreases. You may use a computer model or another
calculation method if you want a more realistic estimate of the liquid release rate.
You may estimate the quantity that might be released by multiplying the liquid release rate from the
above equation by the time (in minutes) that likely would be needed to stop the release. You should be able
to substantiate the time needed to stop the release. Alternatively, you may assume the release would stop
when the level of liquid in the tank drops to the level of the hole. You may estimate the quantity of liquid
above that level in the tank from the dimensions of the tank, the liquid level at the start of the leak, and the
level of the hole. Assume the estimated quantity is released into a pool and use the method and equations in
Section 7.2.3 below to determine the evaporation rate of the liquid from the pool and the duration of the
release. As discussed in Section 7.2.3, if you find that your estimated evaporation rate is greater than
estimated liquid release rate, you should use the liquid release rate as the release rate to air.
April 15, 1999 7-7
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Chapter 7
Estimation of Release Rates for Alternative Scenarios for Toxic Substances
Example 21. Liquid Release from Atmospheric Tank (Allyl Alcohol)
You have a tank that contains 20,000 pounds of allyl alcohol at ambient temperature and pressure. A valve on
the side of the tank shears, leaving a hole in the tank wall 5 square inches in area. The liquid column is 23
inches above the hole in the tank. From Exhibit B-2, the Liquid Leak Factor for allyl alcohol is 41. Therefore,
from Equation 7-4, the liquid release rate is:
QRL = 5 x (23)'/2 x 41 = 983 pounds per minute
It takes 10 minutes to stop the release, so 10 minutes x 983 pounds per minute = 9,830 pounds of allyl alcohol
released.
Pressurized Tank. If you have a liquid stored in a tank under pressure, you may estimate a release
rate for liquid from a hole in the liquid space of the tank using the equation presented above for gases
liquefied under pressure (Equation 7-2 in Section 7.1.1) or the equations in Appendix D, Section D.7.1.
Release from Pipe
If you have a liquid flowing through a pipe at approximately atmospheric pressure, and the pipeline
remains at about the same height between the pipe inlet and the pipe break, you can estimate the quantity of
liquid released from the flow rate in the pipe and the time it would take to stop the release by multiplying the
flow rate by the time. For liquids at atmospheric pressure, assume the liquid is spilled into a pool and use the
methods in Section 7.2.3 below to estimate the release rate to air.
For the release of a liquid under pressure from a long pipeline, you may use the equations below (see
Appendix D, Section D.7.2 for more information on these equations). These equations apply both to
substances that are liquid at ambient conditions and to gases liquefied under pressure. This method does not
consider the effects of friction in the pipe. First estimate the initial operational flow velocity of the substance
through the pipe using the initial operational flow rate as follows:
„ FR x DF x 0.033
•= <7-5)
where: Va = Initial operational flow velocity (feet per minute)
FR = Initial operational flow rate (pounds per minute)
DF = Density Factor (from Exhibit B-2, Appendix B)
Ap = Cross-sectional area of pipe (square feet)
You can estimate the cross-sectional area of the pipe from the diameter or radius (half the diameter
of the pipe) using the formula for the area of a circle (area = Tir2, where r is the radius).
The release velocity is then calculated based on the initial operational flow, any gravitational
April 15, 1999 7-8
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Chapter 7
Estimation of Release Rates for Alternative Scenarios for Toxic Substances
acceleration or deceleration effects resulting from changes in the height of the pipeline, and the pressure
difference between the pressure in the pipe and atmospheric pressure, using a form of the Bernoulli equation:
Vb =197 x ^[28.4 x (PT - 14.7) x DF\ + [5.97 x (Zfl - Z6)] + [2.58xlQ-5 x F/] (?_6)
where: Vb = Release velocity (feet per minute)
PT = Total pressure on liquid in pipe (psia)
DF = Density factor, see Exhibit B-1 or Exhibit B-2
Za = Height of pipeline at inlet (feet)
Zb = Height of pipeline at break (feet)
Va = Operational velocity (feet per minute), calculated from Equation 7-5
Please note that if the height of the pipe at the release point is higher than the initial pipe height, then Za-Zb is
negative, and the height term will cause the estimated release velocity to decrease.
The release velocity can then be used to calculate a release rate as follows:
V x A
QRL = * P— (7-7)
L DF x 0.033 v '
where: QRL = Release rate (pounds per minute)
Vb = Release velocity (feet per minute)
DF = Density Factor
Ap = Cross-sectional area of pipe (square feet)
You may estimate the quantity released into a pool from the broken pipe by multiplying the liquid
release rate (QRL) from the equation above by the time (in minutes) that likely would be needed to stop the
release (or to empty the pipeline). Assume the estimated quantity is released into a pool and use the method
and equations described in Section 7.2.3 below to determine the evaporation rate of the liquid from the pool.
You must be able to substantiate the time needed to stop the release.
As noted above in Section 7.1.1, for a release from a pipe of gas liquefied under pressure, assume
that the released liquid is immediately vaporized, and use the calculated liquid release rate as the release rate
to air. If the release duration would be very short (e.g., because of active mitigation measures), determine the
total quantity of the release as the release rate times the duration, then estimate a new release rate as the
quantity divided by 10. This will give you a release rate that you can use with the 10-minute reference tables
of distances in this guidance to estimate a distance to the endpoint.
In the case of very long pipes, release rates from a shear or hole will be lower than the estimates from
this method because of pipe roughness and frictional head loss. If friction effects are deemed considerable, an
established method for calculating frictional head loss such as the Darcy formula may be used.
April 15, 1999 7-9
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Chapter 7
Estimation of Release Rates for Alternative Scenarios for Toxic Substances
7.2.2 Liquid Release Rate and Quantity Released for Mitigated Releases
For alternative release scenarios, you are permitted to take credit for both passive and active
mitigation systems, or a combination if both are in place. Active mitigation techniques that reduce the rate of
liquid release or the quantity released into the pool are discussed in this section. Active and passive
mitigation to reduce the evaporation rate of liquid from a pool are discussed in the next section.
Active Mitigation to Reduce Quantity Released
Examples of mitigation techniques to reduce the quantity released into the pool include automatic
shutoff valves and emergency deinventory. You may use the equations in Section 7.2.1 above for calculating
liquid release rate, if applicable. Estimate the approximate time needed to stop the release by the mitigation
technique (you must be able to justify your estimate). Multiply the release rate times the duration of release
to estimate quantity released. Assume the estimated quantity is released into a pool and use the method and
equations described in Section 7.2.3 below to determine the evaporation rate of the liquid from the pool. You
should also consider mitigation (active or passive) of evaporation from the pool, if applicable, as discussed in
Section 7.2.3 below.
Example 22. Mitigated Liquid Release
A bromine injection system suffers a hose failure; the greatly lowered system pressure triggers an automatic
shutoff valve within 30 seconds of the release. The flow rate out of the ruptured hose is approximately 330
pounds per minute. Because the release occurred for only 30 seconds (0.5 minutes), the total quantity spilled
was 330 x 0.5, or 165 pounds.
7.2.3 Evaporation Rate from Liquid Pool
After you have estimated the quantity of liquid released, assume that the liquid forms a pool and
calculate the evaporation rate from the pool as described below. You may account for both passive and active
mitigation in estimating the release rate. Passive mitigation may include techniques already discussed in
Section 3.2.3 such as dikes and trenches. Active mitigation to reduce the release rate of liquid in pools to the
air may include an assortment of techniques including foam or tarp coverings and water or chemical sprays.
Some methods of accounting for passive and active mitigation are discussed below.
If the calculated evaporation rate from the pool is greater than the liquid release rate you have
estimated from the container, no pool would be formed, and calculating the release rate as the evaporation
rate from a pool would not be appropriate. If the pool evaporation rate is greater than the liquid release rate,
use the liquid release rate as the release rate to air. Consider this possibility particularly for relatively volatile
liquids, gases liquefied by refrigeration, or liquids at elevated temperature that form pools with no mitigation.
April 15, 1999 7-10
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Chapter 7
Estimation of Release Rates for Alternative Scenarios for Toxic Substances
Unmitigated
Ambient temperature. For pools with no mitigation, if the liquid is always at ambient temperature,
find the Liquid Factor Ambient (LFA) and the Density Factor (DF) in Exhibit B-2 of Appendix B (see
Appendix D, Section D.2.2 for the derivation of these factors). If your ambient temperature is between 25 °C
and 50 °C, you may use this method to calculate the release rate, and then use the appropriate Temperature
Correction Factor from Exhibit B-4, Appendix B, to adjust the release rate, as described below. For gases
liquefied by refrigeration, use the Liquid Factor Boiling (LFB) and DF from Exhibit B-l. Calculate the
release rate from the following equation for liquids at ambient temperature with no mitigation:
QR = QS x 2.4 x LFA x DF (7-8)
where: QR = Release rate (pounds per minute)
QS = Quantity released (pounds)
2.4 = Wind speed factor = 3.0078, where 3.0 meters per second (6.7 miles per
hour) is the wind speed for the alternative scenario for purposes of this
guidance
LFA = Liquid Factor Ambient
DF = Density Factor
This method assumes that the total quantity of liquid released spreads out to form a pool one
centimeter in depth; it does not take into account evaporation as the liquid is released.
Example 23. Evaporation from Pool Formed by Liquid Released from Hole in Tank (Allyl Alcohol)
In Example 21, 9,830 pounds of allyl alcohol were estimated to be released from a hole in a tank. From Exhibit
B-2, the Density Factor for allyl alcohol is 0.58, and the Liquid Factor Ambient is 0.0046. Assuming that the
liquid is not released into a diked area or inside a building, the evaporation rate from the pool of allyl alcohol,
from Equation 7-8, is:
QR = 9,830 x 2.4 x 0.0046 x 0.58 = 63 pounds per minute
Elevated temperature. For pools with no mitigation, if the liquid is at an elevated temperature (above
50 °C or at or close to its boiling point), find the Liquid Factor Boiling (LFB) and the Density Factor (DF) in
Exhibit B-2 of Appendix B (see Appendix D, Section D.2.2, for the derivation of these factors). For liquids
at temperatures between 25 °C and 50 °C, you may use the method above for ambient temperature and apply
the appropriate Temperature Correction Factor from Appendix B, Exhibit B-4, to the result, as discussed
below. For liquids above 50 °C, or close to their boiling points, or with no Temperature Correction Factors
available, calculate the release rate of the liquid from the following equation:
QR = QS x 2.4 x LFB x DF (7-9)
April 15, 1999 7-11
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Chapter 7
Estimation of Release Rates for Alternative Scenarios for Toxic Substances
where: QR = Release rate (pounds per minute)
QS = Quantity released (pounds)
2.4 = Wind speed factor = 3.0078, where 3.0 meters per second (6.7 miles per
hour) is the wind speed for the alternative scenario for purposes of this
guidance
LFB = Liquid Factor Boiling
DF = Density Factor
Mitigated
Diked Areas. If the toxic liquid will be released into an area where it will be contained by dikes,
compare the diked area to the maximum area of the pool that could be formed, as described in Section 3.2.3
(see Equation 3-6). Also verify that the quantity spilled will be totally contained by the dikes. The smaller of
the two areas should be used in determination of the evaporation rate. If the maximum area of the pool is
smaller than the diked area, calculate the release rate as described for pools with no mitigation (above). If the
diked area is smaller, and the spill will be totally contained, go to Exhibit B-2 in Appendix B to find the
Liquid Factor Ambient (LFA), if the liquid is at ambient temperature, or the Liquid Factor Boiling (LFB), if
the liquid is at an elevated temperature. For temperatures between 25 °C and 50 °C, you may use the
appropriate Temperature Correction Factor from Exhibit B-4, Appendix B, to adjust the release rate, as
described below. For gases liquefied by refrigeration, use the LFB. Calculate the release rate from the diked
area as follows for liquids at ambient temperature:
QR = 2.4 x LFA x A (7-10)
or, for liquids at elevated temperatures or gases liquefied by refrigeration alone:
QR = 2.4 x LFB x A (7-11)
where: QR = Release rate (pounds per minute)
2.4 = Wind speed factor = 3.0078, where 3.0 meters per second (6.7 miles per
hour) is the wind speed for the alternative scenario for purposes of this
guidance
LFA = Liquid Factor Ambient (listed in Exhibit B-2, Appendix B)
LFB = Liquid Factor Boiling (listed in Exhibit B-1 or B-2, Appendix B)
A = Diked area (square feet)
Releases Into Buildings. If a toxic liquid is released inside a building, compare the area of the
building floor or any diked area that would contain the spill to the maximum area of the pool that could be
formed; the smaller of the two areas should be used in determining the evaporation rate, as for the worst-case
scenario. The maximum area of the pool is determined from Equation 3-6 in Section 3.2.3 for releases into
diked areas. The area of the building floor is the length times width of the floor (in feet) (Equation 3-9).
If the floor area or diked area is smaller than the maximum pool size, estimate the outdoor
evaporation rate from a pool the size of the floor area or diked area from Equation 7-10. If the maximum
pool area is smaller, estimate the outdoor evaporation rate from a pool of maximum size from Equation 7-8.
April 15, 1999 7-12
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Chapter 7
Estimation of Release Rates for Alternative Scenarios for Toxic Substances
Estimate the rate of release of the toxic vapor from the building as five percent of the calculated outdoor
evaporation rate (multiply your evaporation rate by 0.05). See Appendix D, Section D.2.4 for more
information on releases into buildings.
Active Mitigation to Reduce Evaporation Rate. Examples of active mitigation techniques to reduce
the evaporation rate from the pool include water sprays and foam or tarp covering. Use test data,
manufacturer design specifications, or past experience to determine the fractional reduction of the release rate
by the mitigation technique. Apply this fraction to the release rate (evaporation rate from the pool) that
would have occurred without the mitigation technique, as follows:
QRRV= (l-FR) x QR (7.12)
where: Q^RV = Reduced evaporation rate (release rate to air) from pool (pounds per
minute)
FR = Fractional reduction resulting from mitigation
QR = Evaporation rate from pool without mitigation (pounds per minute)
Temperature Corrections for Liquids at Temperatures between 25 and 50 °C
If your liquid is at a temperature between 25 °C (77 °F) and 50 °C (122 °F), you may use the
appropriate Temperature Correction Factor (TCP) from Exhibit B-4, Appendix B, to calculate a corrected
release rate. Calculate the release rate (QR) of the liquid at 25 °C (77 °F) as described above for unmitigated
releases or releases in diked areas and multiply the release rate by the appropriate TCP as described in
Section 3.2.5.
Evaporation Rate Compared to Liquid Release Rate
If you estimated the quantity of liquid in the pool based on an estimated liquid release rate from a
hole in a container or pipe, as discussed in Sections 7.2.1 and 7.2.2, compare the evaporation rate with the
liquid release rate. If the evaporation rate from the pool is greater than the liquid release rate, use the liquid
release rate as the release rate to air.
Duration of Release
After you have estimated a release rate as described above, determine the duration of the vapor
release from the pool (the time it will take for the liquid pool to evaporate completely). To estimate the time
in minutes, divide the total quantity released (in pounds) by the release rate (in pounds per minute) (see
Equation 3-5 in Section 3.2.2). If you are using the liquid release rate as the release rate to air, as discussed
in the preceding paragraph, estimate a liquid release duration as discussed in Section 7.2.1 or 7.2.2. The
duration could be the time it would take to stop the release or the time it would take to empty the tank or to
release all the liquid above the level of the leak. If you have corrected the release rate for a temperatures
above 25 °C, use the corrected release rate to estimate the duration.
April 15, 1999 7-13
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Chapter 7
Estimation of Release Rates for Alternative Scenarios for Toxic Substances
7.2.4 Common Water Solutions and Oleum
You may use the methods described above in Sections 7.2.1, 7.2.2, and 7.2.3 for pure liquids to
estimate the quantity of a solution of a toxic substance or oleum that may be spilled into a pool. LFA, DF,
and LLF values for several concentrations of ammonia, formaldehyde, hydrochloric acid, hydrofluoric acid,
and nitric acid in water solution and for oleum are listed in Appendix B, Exhibit B-3. The LFA for a wind
speed of 3.0 meters per second (6.7 miles per hour) should be used in the release rate calculations for
alternative scenarios for pools of solutions at ambient temperature.
For unmitigated releases or releases with passive mitigation, follow the instructions in Section 7.2.3.
If active mitigation measures are in place, you may estimate a reduced release rate from the instructions on
active mitigation in Section 7.2.2. Use the total quantity of the solution as the quantity released from the
vessel or pipeline (QS) in carrying out the calculation of the release rate to the atmosphere.
If the solution is at an elevated temperature, see Section 3.3. As discussed in Section 3.3, you may
treat the release of the substance in solution as a release of the pure substance. Alternatively, if you have
vapor pressure data for the solution at the release temperature, you may estimate the release rate from the
equations in Appendix D, Sections D.2.1 and D.2.2.
If you estimated the quantity of solution in the pool based on an estimated liquid release rate from a
hole in a container or pipe, as discussed in Sections 7.2.1 and 7.2.2, compare the evaporation rate with the
liquid release rate. If the evaporation rate from the pool is greater than the liquid release rate, use the liquid
release rate as the release rate to air.
April 15, 1999 7-14
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8 ESTIMATION OF DISTANCE TO THE ENDPOINT FOR
ALTERNATIVE SCENARIOS FOR TOXIC SUBSTANCES
In Chapter 8
Reference tables of distances for alternative releases, including:
Generic reference tables (Exhibit 4), and
Chemical-specific reference tables (Exhibit 5).
Considerations include:
Gas density (neutrally buoyant or dense),
Duration of release (10 minutes or 60 minutes),
Topography (rural or urban).
For estimating consequence distances for alternative scenarios for toxic substances, this guidance
provides four generic reference tables for neutrally buoyant gases and vapors and four for dense gases. The
generic reference tables of distances (Reference Tables 14-21) are found at the end of Chapter 10. The
generic tables and the conditions for which each table is applicable are described in Exhibit 4. Four chemical-
specific tables also are provided for ammonia, chlorine, and sulfur dioxide. The chemical-specific reference
tables follow the generic reference tables at the end of Chapter 10. These tables, and the applicable
conditions, are described in Exhibit 5.
All the reference tables of distances for alternative scenarios were developed assuming D stability
and a wind speed of 3.0 meters per second (6.7 miles per hour) as representative of likely conditions for many
sites. Many wind speed and atmospheric stability combinations may be possible at different times in
different parts of the country. If D stability and 3.0 meters per second are not reasonable conditions for your
site, you may want to use other methods to estimate distances.
For simplicity, this guidance assumes ground level releases. This guidance, therefore, may
overestimate the consequence distance if your alternative scenario involves a release above ground level,
particularly for neutrally buoyant gases and vapors. If you want to assume an elevated release, you may want
to consider other methods to determine the consequence distance.
The generic reference tables should be used for all toxic substances other than ammonia, chlorine,
and sulfur dioxide. To use the generic reference tables, you need to consider the release rates estimated for
gases and evaporation from liquid pools and the duration of the release. For the alternative scenarios, the
duration of toxic gas releases may be longer than the 10 minutes assumed for the worst-case analysis for
gases. You need to determine the appropriate toxic endpoint and whether the gas or vapor is neutrally
buoyant or dense, using the tables in Appendix B and considering the conditions of the release. You may
interpolate between entries in the reference tables.
April 15, 1999
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Chapter 8
Estimation of Distance to the Endpoint for Alternative Scenarios for Toxic Substances
Exhibit 4
Generic Reference Tables of Distances for Alternative Scenarios
Applicable Conditions
Gas or Vapor Density
Neutrally buoyant
Dense
Topography
Rural
Urban
Rural
Urban
Release Duration
(minutes)
10
60
10
60
10
60
10
60
Reference Table
Number
14
15
16
17
18
19
20
21
Exhibit 5
Chemical-Specific Reference Tables of Distances for Alternative Scenarios
Substance
Anhydrous ammonia
liquefied under pressure
Non-liquefied ammonia,
ammonia liquefied by
refrigeration, or aqueous
ammonia
Chlorine
Sulfur dioxide (anhydrous)
Conditions of Release
Gas or Vapor
Density
Dense
Neutrally buoyant
Dense
Dense
Release Duration
(minutes)
10-60
10-60
10-60
10-60
Topography
Rural, urban
Rural, urban
Rural, urban
Rural, urban
Reference
Table
Number
22
23
24
25
April 15, 1999
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Chapter 8
Estimation of Distance to the Endpoint for Alternative Scenarios for Toxic Substances
Note the following concerning the use of the chemical-specific reference tables for ammonia,
chlorine, and sulfur dioxide:
• The table for anhydrous ammonia (Reference Table 22) applies only to flashing releases of
ammonia liquefied under pressure. Use Table 23 for release of ammonia as a gas (e.g.,
evaporation from a pool or release from the vapor space of a tank).
• You may use these tables for releases of any duration.
To use the reference tables of distances, follow these steps:
For Regulated Toxic Substances Other than Ammonia, Chlorine, and Sulfur Dioxide
• Find the toxic endpoint for the substance in Appendix B (Exhibit B-1 for toxic gases or
Exhibit B-2 for toxic liquids).
• Determine whether the table for neutrally buoyant or dense gases and vapors is appropriate
from Appendix B (Exhibit B-1 for toxic gases or Exhibit B-2, column for alternative case,
for toxic liquids). A toxic gas that is lighter than air may behave as a dense gas upon release
if it is liquefied under pressure, because the released gas may be mixed with liquid droplets,
or if it is cold. Consider the state of the released gas when you decide which table is
appropriate.
• Determine whether the table for rural or urban conditions is appropriate.
Use the rural table if your site is in an open area with few obstructions.
Use the urban table if your site is in an urban or obstructed area.
• Determine whether the 10-minute table or the 60-minute table is appropriate.
Use the 10-minute table for releases from evaporating pools of common water
solutions and of oleum.
If you estimated the release duration for gas release or pool evaporation to be 10
minutes or less, use the 10-minute table.
If you estimated the release duration for gas release or pool evaporation to be more
than 10 minutes, use the 60-minute table.
Neutrally Buoyant Gases or Vapors
• If Exhibit B-1 or B-2 indicates the gas or vapor should be considered neutrally buoyant, and
other factors would not cause the gas or vapor to behave as a dense gas, divide the estimated
release rate (pounds per minute) by the toxic endpoint (milligrams per liter).
April 15, 1999
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Chapter 8
Estimation of Distance to the Endpoint for Alternative Scenarios for Toxic Substances
• Find the range of release rate/toxic endpoint values that includes your calculated release
rate/toxic endpoint in the first column of the appropriate table (Reference Table 14, 15, 16,
or 17), then find the corresponding distance to the right.
Dense Gases or Vapors
• If Exhibit B-1 or B-2 or consideration of other relevant factors indicates the substance
should be considered a dense gas or vapor (heavier than air), find the distance in the
appropriate table (Reference Table 18, 19, 20, or 21) as follows;
Find the toxic endpoint closest to that of the substance by reading across the top of
the table. If the endpoint of the substance is halfway between two values on the
table, choose the value on the table that is smaller (to the left). Otherwise, choose
the closest value to the right or the left.
Find the release rate closest to the release rate estimated for the substance at the left
of the table. If the calculated release rate is halfway between two values on the
table, choose the release rate that is larger (farther down on the table). Otherwise,
choose the closest value (up or down on the table).
Read across from the release rate and down from the endpoint to find the distance
corresponding to the toxic endpoint and release rate for your substance.
For Ammonia, Chlorine, or Sulfur Dioxide
• Find the appropriate chemical-specific table for your substance (see the descriptions of
Reference Tables 22-25 in Exhibit 5).
If you have ammonia liquefied by refrigeration alone, you may use Reference Table
23, even if the duration of the release is greater than 10 minutes.
If you have chlorine or sulfur dioxide liquefied by refrigeration alone, you may use
the chemical-specific reference tables, even if the duration of the release is greater
than 10 minutes.
• Determine whether rural or urban topography is applicable to your site.
Use the rural column in the reference table if your site is in an open area with few
obstructions.
Use the urban column if your site is in an urban or obstructed area.
• Estimate the consequence distance as follows:
In the left-hand column of the table, find the release rate closest to your calculated
release rate.
April 15, 1999 8-4
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Chapter 8
Estimation of Distance to the Endpoint for Alternative Scenarios for Toxic Substances
Read the corresponding distance from the appropriate column (urban or rural) to the
right.
The development of the generic reference tables is discussed in Appendix D, Sections D.4.1 and
DA.2. The development of the chemical-specific reference tables is discussed in industry-specific risk
management program guidance documents and a backup information document that are cited in Section
DAS. If you think the results of the method presented here overstate the potential consequences of a your
alternative release scenario, you may choose to use other methods or models that take additional site-specific
factors into account.
Examples 24 and 25 below include the results of modeling using two other models, ALOHA and
WHAZAN, for comparison with the results of the methods presented in this guidance. Appendix D, Section
D.4.5 provides additional information on this modeling.
Example 24. Gas Release of Chlorine
Assume that you calculated a release rate of 500 pounds per minute of chlorine from a tank. A chemical-
specific table is provided for chlorine, so you do not need to consult Appendix B for information on chlorine.
The topography of your site is urban. For a release of chlorine under average meteorology (D stability and 3
meters per second wind speed), go to Reference Table 24. The estimated release rate of 500 pounds per
minute, with urban topography, corresponds to a consequence distance of 0.4 miles.
Additional Modeling for Comparison
The ALOHA model gave a distance of 3.0 miles to the endpoint, using the same assumptions.
The WHAZAN model gave a distance of 3.2 miles to the endpoint, using the same assumptions and the dense
cloud dispersion model.
April 15, 1999
i - 5
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Chapter 8
Estimation of Distance to the Endpoint for Alternative Scenarios for Toxic Substances
Example 25. Allyl Alcohol Evaporating from Pool
In Example 23, the evaporation rate of allyl alcohol from a pool was calculated as 63 pounds per minute. The total
quantity in the pool was estimated as 9,830 pounds; therefore, the pool would evaporate in 9,830/63 or 156
minutes. You would use a 60-minute reference table to estimate the distance to the endpoint. From Exhibit B-2 in
Appendix B, the toxic endpoint for allyl alcohol is 0.036 mg/L, and the appropriate reference table for the
alternative scenario analysis is a neutrally buoyant plume table. To find the distance from the neutrally buoyant
plume tables, you need the release rate divided by the endpoint. In this case, it is 63/0.036, or 1,750. Assuming
the release takes place in a rural location, you use Reference Table 15, applicable to neutrally buoyant plumes, 60-
minute releases, and rural conditions. From this table, you estimate the distance as 0.4 mile.
Additional Modeling for Comparison
The ALOHA model gave a distance of 0.7 mile to the endpoint for a release rate of 63 pounds per minute, using
the same assumptions and the dense gas model.
The WHAZAN model gave a distance of 0.5 mile to the endpoint for a release rate of 63 pounds per minute, using
the same assumptions and the buoyant plume dispersion model.
April 15, 1999
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ESTIMATION OF RELEASE RATES FOR ALTERNATIVE
SCENARIOS FOR FLAMMABLE SUBSTANCES
In Chapter 9
Methods to estimate a release rate to air for a flammable gas (9.1) or liquid
(9.2).
9.1 Flammable Gases
Gaseous Release from Tank or Pipe
An alternative scenario for a release of a flammable gas may involve a leak from a vessel or piping.
To estimate a release rate for flammable gases from hole size and storage conditions, you may use the method
described above in Section 7.1.1 for toxic gases. This release rate may be used to determine the dispersion
distance to the lower flammability limit (LFL), as described in Section 10.1. Exhibit C-2 in Appendix C
includes Gas Factors (GF) that may be used in carrying out the calculations for each of the regulated
flammable gases.
Example 26. Release Rate of Flammable Gas from Hole in Tank (Ethylene)
A pipe tears off a tank containing ethylene. The pipe is in the vapor space of the tank. The release rate from
the hole can be estimated from Equation 7-1 in Section 7.1. You estimate that the pipe would leave a hole with
an area (HA) of 5 square inches. The temperature inside the tank (Tt, absolute temperature, Kelvin) is 282 K,
9°C, and the square root of the temperature is 16.8. The pressure in the tank (Pt) is approximately 728 pounds
per square inch absolute (psia). From Exhibit C-2, Appendix C, the gas factor (GF) for ethylene is 18. From
Equation 7-1, the release rate (QR) is:
QR = 5 x 728 x (1/16.8) x 18 = 3,900 pounds per minute
Gases Liquefied Under Pressure
A vapor cloud fire is a possible result of a release of a gas liquefied under pressure. You may use the
methods described in Section 7.1.1 for toxic gases liquefied under pressure to estimate the release rate from a
hole in a tank for a flammable gas liquefied under pressure. The estimated release rate may be used to
estimate the dispersion distance to the LFL for a vapor cloud fire.
Flammable gases that are liquefied under pressure may be released very rapidly, with partial
vaporization of the liquefied gas and possible aerosol formation. Section 10.4 presents a method for
estimating the consequences of a vapor cloud explosion from such a release of a gas liquefied under pressure.
April 15, 1999
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Chapter 9
Estimation of Release Rates for Alternative Scenarios for Flammable Substances
Gases Liquefied by Refrigeration
Flammable gases liquefied by refrigeration alone can be treated as liquids for the alternative scenario
analysis, as discussed in Section 9.2 and Section 10.2, below.
9.2 Flammable Liquids
You may estimate a release rate for flammable liquids by estimating the evaporation rate from a
pool. Release rates also can be estimated for flammable gases liquefied by refrigeration alone by this method,
if the liquefied gas is likely to form a pool upon release. You first need to estimate the quantity in the pool.
You may use the method discussed in Section 7.2.1 to estimate a rate of liquid release for flammable
liquids into a pool from a hole in a tank or from a pipe shear. Exhibit C-3 in Appendix C includes liquid leak
factors (LLF) for calculating release rate from a hole. Note that the LLF is appropriate only for atmospheric
tanks. LLF values are not provided for liquefied flammable gases; you will need to estimate the quantity in
the pool from other information for liquefied flammable gases.
Once you have an estimate of the quantity of flammable liquid in a pool, you may use the methods
presented in Section 7.2.3 to estimate the evaporation rate from the pool. Liquid factors at ambient and
boiling temperature (LFA and LFB) for liquids for the calculation are listed in Exhibit C-3 in Appendix C,
and LFBs for liquefied gases are listed in Exhibit C-2. Both passive and active mitigation measures
(discussed in Sections 7.2.2 and 7.2.3) may be taken into account. You do not need to estimate the duration
of the release, because this information is not used to estimate distance to the LFL, as discussed in the next
chapter.
As for toxic liquids, if the rate of evaporation of the liquid from the pool is greater than the rate of
release of the liquid from the container, you should use the liquid release rate, not the pool evaporation rate,
as the rate of release to the air. You should expect rapid evaporation rates for liquefied flammable gases
from a pool. All of the regulated flammable liquids are volatile, so the evaporation rate from a pool may be
expected to be relatively high, particularly without mitigation.
April 15, 1999 9-2
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10 ESTIMATION OF DISTANCE TO THE ENDPOINT FOR
ALTERNATIVE SCENARIOS FOR FLAMMABLE SUBSTANCES
In Chapter 10
10.1 Method to estimate the dispersion distance to the LFL for vapor cloud
fires.
10.2 Method to estimate the distance to the heat radiation endpoint for a pool
fire involving a flammable liquid, based on the pool area and factors provided
in the appendix.
10.3 Method to estimate the distance to the heat radiation endpoint for a
fireball from a BLEVE, using a reference table of distances.
10.4 Alternative scenario analysis for vapor cloud explosions, using less
conservative assumptions than for worst-case vapor cloud explosions.
10.1 Vapor Cloud Fires
The distance to the LFL represents the maximum distance at which the radiant heat effects of a vapor
cloud fire might have serious consequences. Exhibit C-2, Appendix C, provides LCL data (in volume percent
and milligrams per liter) for listed flammable gases; Exhibit C-3 provides these data for flammable liquids.
This guidance provides reference tables for the alternative scenario conditions assumed in this guidance (D
stability and wind speed 3.0 meters per second, ground level releases) for estimating the distance to the LCL.
Release rate is the primary factor for determining distance to the flammable endpoint. Because the methods
used in this guidance assumes that the vapor cloud release is in a steady state and that vapor cloud fires are
nearly instantaneous events, release duration is not a critical factor for estimating vapor cloud fire distances.
Thus, the reference tables for flammable substances are not broken out separately by release duration (e.g.,
10 minutes, 60 minutes). The development of these tables is discussed further in Appendix D, Section D.4.
The reference tables for flammable substances (Reference Tables 26-29 at the end of Chapter 10) are listed in
Exhibit 6.
To use the reference tables of distances to find the distance to the LFL from the release rate, follow
these steps:
• Find the LFL endpoint for the substance in Appendix C (Exhibit C-2 for flammable gases or
Exhibit C-3 for flammable liquids).
• Determine from Appendix C whether the table for neutrally buoyant or dense gases and
vapors is appropriate (Exhibit C-2 for flammable gases or Exhibit C-3 for flammable
liquids). A gas that is lighter than air may behave as a dense gas upon release if it is
liquefied under pressure, because the released gas may be mixed with liquid droplets, or if it
is cold. Consider the state of the released gas when you decide which table is appropriate.
April 15, 1999
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Chapter 10
Estimation of Distance to the Endpoint for Alternative Scenarios for Flammable Substances
• Determine whether the table for rural or urban conditions is appropriate.
Use the rural table if your site is in an open area with few obstructions.
Use the urban table if your site is in an urban or obstructed area.
Exhibit 6
Reference Tables of Distances for Vapor Cloud Fires of Flammable Substances
Applicable Conditions
Gas or Vapor Density
Neutrally buoyant
Dense
Topography
Rural
Urban
Rural
Urban
Release Duration
(minutes)
10-60
10-60
10-60
10-60
Reference Table
Number
26
27
28
29
Neutrally Buoyant Gases or Vapors
If Exhibit C-2 or C-3 indicates the gas or vapor should be considered neutrally buoyant, and
other factors would not cause the gas or vapor to behave as a dense gas, divide the estimated
release rate (pounds per minute) by the LFL endpoint (milligrams per liter).
Find the range of release rate/LFL values that includes your calculated release rate/LFL in
the first column of the appropriate table (Reference Table 26 or 27), then find the
corresponding distance to the right.
Dense Gases or Vapors
If Exhibit C-2 or C-3 or consideration of other relevant factors indicates the substance
should be considered a dense gas or vapor (heavier than air), find the distance in the
appropriate table (Reference Table 28 or 29) as follows:
Find the LFL closest to that of the substance by reading across the top of the table.
If the LFL of the substance is halfway between two values on the table, choose the
value on the table that is smaller (to the left). Otherwise, choose the closest value to
the right or the left.
Find the release rate closest to the release rate estimated for the substance at the left
of the table. If the calculated release rate is halfway between two values on the
April 15, 1999
10-2
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Chapter 10
Estimation of Distance to the Endpoint for Alternative Scenarios for Flammable Substances
table, choose the release rate that is larger (farther down on the table). Otherwise,
choose the closest value (up or down on the table).
Read across from the release rate and down from the LFL to find the distance
corresponding to the LFL and release rate for your substance.
Example 27. Flammable Gas Release (Ethylene)
In Example 26, you estimated a release rate for ethylene from a hole in a tank of 3,900 pounds per minute. You
want to estimate the distance to the LFL for a vapor cloud fire resulting from this release.
From Exhibit C-2, Appendix C, the LFL for ethylene is 31 mg/L, and the appropriate table for distance
estimation is a neutrally buoyant gas table for flammable substances. Your site is in a rural area, so you would
use Reference Table 26.
To use the neutrally buoyant gas tables, you need to calculate release rate/endpoint. In this case, release
rate/LFL = 3,900/31 or 126. On Reference Table 26, 126 falls in the range of release rate/LFL values
corresponding to 0.2 miles.
April 15, 1999
10-3
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Chapter 10
Estimation of Distance to the Endpoint for Alternative Scenarios for Flammable Substances
Example 28. Vapor Cloud Fire from Evaporating Pool of Flammable Liquid
You have a tank containing 20,000 pounds of ethyl ether. A likely scenario for a release might be shearing of a
pipe from the tank, with the released liquid forming a pool. You want to estimate the consequences of a vapor
cloud fire that might result from evaporation of the pool and ignition of the vapor.
You first need to estimate the rate of release of the liquid from the tank. You can do this using Equation 7-4,
Section 7.2.1. For this calculation, you need the area of the hole that would result from shearing the pipe (HA),
the height of the liquid in the tank above the hole (LH), and the liquid leak factor (LLF) for ethyl ether, from
Exhibit C-3 in Appendix C. The pipe diameter is 2 inches, so the cross sectional area of the hole would be 3.1
square inches. You estimate that the pipe is 2 feet, or 24 inches, below the level of the liquid when the tank is
full. The square root of LH (24 inches) is 4.9. LLF for ethyl ether is 34. From Equation 7-4, the rate of release
of the liquid from the hole is calculated as:
QRL = 3.1x4.9x34
= 520 pounds per minute
You estimate that the release of the liquid could be stopped in about 10 minutes. In 10 minutes, 10 x 520, or
5,200 pounds, would be released.
The liquid would be released into an area without dikes. To estimate the evaporation rate from the pool formed
by the released liquid, you use Equation 7-8 from Section 7.2.3. To carry out the calculation, you need the
Liquid Factor Ambient (LFA) and the Density Factor (DF) for ethyl ether. From Exhibit C-3, Appendix C,
LFA for ethyl ether is 0.11 and DF is 0.69. The release rate to air is:
QR = 5,200x2.4x0.11x0.69
= 950 pounds per minute
The evaporation rate from the pool is greater than the estimated liquid release rate; therefore, you use the liquid
release rate of 520 pounds per minute as the release rate to air. To estimate the maximum distance at which
people in the area of the vapor cloud could suffer serious injury, estimate the distance to the lower flammability
limit (LFL) (in milligrams per liter) for ethyl ether, from the appropriate reference table. From Exhibit C-3,
Appendix C, LFL for ethyl ether is 57 mg/L, and the appropriate reference table is a dense gas table. Your site
is in a rural area with few obstructions, so you use Reference Table 28.
From Reference Table 28, the closest LFL is 60 mg/L. The lowest release rate on the table is 1,500 pounds per
minute, which is higher than the evaporation rate estimated for the pool of ethyl ether. For a release rate less
than 1,500 pounds per minute, the distance to the LFL is less than 0.1 miles.
April 15, 1999 10-4
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Chapter 10
Estimation of Distance to the Endpoint for Alternative Scenarios for Flammable Substances
10.2 Pool Fires
Pool fires may be considered as potential alternative scenarios for flammable liquids, including gases
liquefied by refrigeration alone. You may find, however, that other scenarios will give a greater distance to
the endpoint and, therefore, may be more appropriate as alternative scenarios. A "Pool Fire Factor" (PFF)
has been derived for each of the regulated flammable liquids and most of the flammable gases to aid in the
consequence analysis. The derivation of these factors is discussed in Appendix D, Section D.9. The PFF,
listed in Appendix C, Exhibit C-2 for flammable gases and C-3 for flammable liquids, may be used to
estimate a distance from the center of a pool fire where people could potentially receive second degree burns
from a 40-second exposure. The heat radiation endpoint for this analysis is 5 kilowatts per square meter
(kW/m2). Ambient temperature is assumed to be 25 °C (77 °F) for calculation of the PFF for flammable
liquids.
To estimate a distance using the PFF, you first need to estimate the size of the pool, in square feet,
that might be formed by the release of a flammable substance. You may use the methods described above for
toxic liquids to estimate pool size. Density factors (DF) for the estimation of pool size in undiked areas may
be found for flammable gases and flammable liquids in Exhibits C-2 and C-3 of Appendix C. For flammable
gases, the DF is based on the density at the boiling point. You may want to consider whether the released
substance may evaporate too quickly to form a pool of the maximum size, particularly for liquefied gases.
Distances may be estimated from the PFF and the pool area as follows:
d = PFF x JA (10-1)
where: d = Distance (feet)
PFF = Pool Fire Factor (listed for each flammable substance in Appendix C,
Exhibits C-2 and C-3)
A = Pool area (square feet)
April 15, 1999 10-5
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Chapter 10
Estimation of Distance to the Endpoint for Alternative Scenarios for Flammable Substances
Example 29. Pool Fire of Flammable Liquid
For a tank containing 20,000 pounds of ethyl ether, you want to estimate the consequences of a pool fire. You
estimate that 15,000 pounds would be released into an area without dikes, forming a pool. Assuming the liquid
spreads to a depth of 1 centimeter (0.39 inches), you estimate the area of the pool formed from Equation 3-6,
Section 3.2.3. For this calculation, you need the density factor (DF) for ethyl ether; from Exhibit C-3,
Appendix C, DF for ethyl ether is 0.69. From Equation 3-6, the area of the pool is:
A = 15,000 x 0.69 = 10,400 square feet
You can use Equation 10-1 to estimate the distance from the center of the burning pool where the heat radiation
level would reach 5 kW/m2. For the calculation, you need the square root of the pool area (A) and the pool fire
factor (PFF) for ethyl ether. The square root of A, 10,400 square feet, is 102 feet. From Exhibit C-3,
Appendix C, PFF for ethyl ether is 4.3. From Equation 10-1, the distance (d) to 5 kW/m2 is:
d = 4.3 x 102 = 440 feet (about 0.08 miles)
If you have a gas that is liquefied under pressure or under a combination of pressure and
refrigeration, a pool fire is probably not an appropriate alternative scenario. A fire or explosion involving the
flammable gas that is released to the air by a sudden release of pressure is likely to have the potential for
serious effects at a greater distance than a pool fire (e.g., see the methods for analysis of BLEVEs and vapor
cloud explosions in Sections 10.3 and 10.4 below, or see Appendix A for references that provide more
information on consequence analysis for fires and explosions).
10.3 BLEVEs
If a fireball from a BLEVE is a potential release scenario at your site, you may use Reference Table
30 to estimate the distance to a potentially harmful radiant heat level. The table shows distances for a range
of quantities to the radiant heat level that potentially could cause second degree burns to a person exposed for
the duration of the fire. The quantity you use should be the total quantity in a tank that might be involved in a
BLEVE. The equations used to derive this table of distances are presented in Appendix D, Section D. 10. If
you prefer, you may use the equations to estimate a distance for BLEVEs, or you may use a different
calculation method or model.
10.4 Vapor Cloud Explosion
If you have the potential at your site for the rapid release of a large quantity of a flammable vapor,
particularly into a congested area, a vapor cloud explosion may be an appropriate alternative release scenario.
For the consequence analysis, you may use the same methods as for the worst case to estimate consequence
distances to an overpressure endpoint of 1 psi (see Section 5.1 and the equation in Appendix C). Instead of
assuming the total quantity of flammable substance released is in the vapor cloud, you may estimate a smaller
April 15, 1999 10-1
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Chapter 10
Estimation of Distance to the Endpoint for Alternative Scenarios for Flammable Substances
quantity in the cloud. You could base your estimate of the quantity in the cloud on the release rate estimated
as described above for gases and liquids multiplied by the time required to stop the release.
To estimate the quantity in the cloud for a gas liquefied under pressure (not refrigerated), you may
use the equation below. This equation incorporates a "flash fraction factor" (FFF), listed in Appendix C,
Exhibit C-2 for regulated flammable gases, to estimate the quantity that could be immediately flashed into
vapor upon release. A factor of two is included to estimate the quantity that might be carried along as spray
or aerosol. See Appendix D, Section D. 11 for the derivation of this equation. The equation is:
QF = FFF x QS x 2 (10-2)
where: QF = Quantity flashed into vapor plus aerosol (pounds) (cannot be larger than
QS)
FFF = Flash fraction factor (unitless) (listed in Appendix C, Exhibit C-2) (must be
less than 1)
QS = Quantity spilled (pounds)
2 = Factor to account for spray and aerosol
For derivation of the FFF, the temperature of the stored gas was assumed to be 25 °C (77 °F) (except
as noted in Exhibit C-2). You may estimate the flash fraction under other conditions using the equation
presented in Appendix D, Section D. 11.
You may estimate the distance to 1 psi for a vapor cloud explosion from the quantity in the cloud
using Reference Table 13 (at the end of the worst-case analysis discussion) or from Equation C-l in
Appendix C. For the alternative scenario analysis, you may use a yield factor of 3 percent, instead of the
yield factor of 10 percent used in the worst-case analysis. As discussed in Appendix D, Section D. 11, the
yield factor of 3 percent is representative of more likely events, based on data from past vapor cloud
explosions. If you use the equation in Appendix C, use 0.03 instead of 0.1 in the calculation. If you use
Reference Table 13, you can incorporate the lower yield factor by multiplying the distance you read from
Reference Table 13 by 0.67.
April 15, 1999 10-7
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Chapter 10
Estimation of Distance to the Endpoint for Alternative Scenarios for Flammable Substances
Example 30. Vapor Cloud Explosion (Propane)
You have a tank containing 50,000 pounds of propane liquefied under pressure at ambient temperature. You
want to estimate the consequence distance for a vapor cloud explosion resulting from rupture of the tank.
You use Equation 10-2 to estimate the quantity that might be released to form a cloud. You base the
calculation on the entire contents of the tank (QS = 50,000 pounds). From Exhibit C-2 of Appendix C, the
Flash Fraction Factor (FFF) for propane is 0.38. From Equation 10-2, the quantity flashed into vapor, plus the
quantity that might be carried along as aerosol, (QF) is:
QF = 0.38 x 50,000 x 2 = 38,000 pounds
You assume 38,000 pounds of propane is in the flammable part of the vapor cloud. This quantity falls between
20,000 pounds and 50,000 pounds in Reference Table 13; 50,000 pounds is the quantity closest to your
quantity. From the table, the distance to 1 psi overpressure is 0.3 mile for 50,000 pounds of propane for a 10
percent yield factor. To change the yield factor to 3 percent, you multiply this distance by 0.67; then the
distance becomes 0.2 mile.
April 15, 1999
-------
Reference Table 14
Neutrally Buoyant Plume Distances to Toxic Endpoint for Release Rate Divided by Endpoint
10-Minute Release, Rural Conditions, D Stability, Wind Speed 3.0 Meters per Second
Release Rate/Endpoint
[(lbs/min)/(mg/L)]
0-64
64-510
510-1,300
1,300-2,300
2,300-4,100
4,100-6,300
6,300 - 8,800
8,800 - 12,000
12,000 - 16,000
16,000- 19,000
19,000-22,000
22,000 - 26,000
26,000 - 30,000
30,000 - 36,000
36,000 - 42,000
42,000 - 47,000
47,000 - 54,000
54,000 - 60,000
60,000 - 70,000
70,000 - 78,000
78,000 - 87,000
87,000 - 97,000
97,000-110,000
110,000- 120,000
120,000-130,000
Distance to
Endpoint
(miles)
0.1
0.2
0.3
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
4.0
4.2
4.4
4.6
Release Rate/Endpoint
[(lbs/min)/(mg/L)]
130,000-140,000
140,000 - 160,000
160,000-180,000
180,000- 190,000
190,000-210,000
210,000-220,000
220,000 - 240,000
240,000-261,000
261,000-325,000
325,000 - 397,000
397,000 - 477,000
477,000 - 566,000
566,000 - 663,000
663,000 - 769,000
769,000-1,010,000
1,010,000- 1,280,000
1,280,000-1,600,000
1,600,000- 1,950,000
1,950,000-2,340,000
2,340,000 - 2,770,000
2,770,000 - 3,240,000
3,240,000 - 4,590,000
4,590,000-6,190,000
>6, 190,000
Distance to
Endpoint
(miles)
4.8
5.0
5.2
5.4
5.6
5.8
6.0
6.2
6.8
7.5
8.1
8.7
9.3
9.9
11
12
14
15
16
17
19
22
25
>25*
*Report distance as 25 miles
April 15, 1999
10-9
-------
Reference Table 15
Neutrally Buoyant Plume Distances to Toxic Endpoint for Release Rate Divided by Endpoint
60-Minute Release, Rural Conditions, D Stability, Wind Speed 3.0 Meters per Second
Release Rate/Endpoint
[(lbs/min)/(mg/L)]
0-79
79-630
630-1,600
1,600-2,800
2,800 - 5,200
5,200 - 7,900
7,900-11,000
11,000- 14,000
14,000-19,000
19,000-23,000
23,000 - 27,000
27,000 - 32,000
32,000 - 36,000
36,000 - 42,000
42,000 - 47,000
47,000 - 52,000
52,000 - 57,000
57,000-61,000
61,000-68,000
68,000 - 73,000
73,000 - 79,000
79,000 - 84,000
84,000-91,000
91,000-97,000
97,000 - 100,000
Distance to
Endpoint
(miles)
0.1
0.2
0.3
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
4.0
4.2
4.4
4.6
Release Rate/Endpoint
[(lbs/min)/(mg/L)]
100,000 - 108,000
108,000- 113,000
113,000-120,000
120,000 - 126,000
126,000-132,000
132,000- 140,000
140,000-150,000
150,000- 151,000
151,000-171,000
171,000- 191,000
191,000-212,000
212,000-233,000
233,000 - 256,000
256,000 - 280,000
280,000 - 332,000
332,000 - 390,000
390,000 - 456,000
456,000 - 529,000
529,000-610,000
610,000-699,000
699,000 - 796,000
796,000- 1,080,000
1,080,000-1,410,000
>1,410,000
Distance to
Endpoint
(miles)
4.8
5.0
5.2
5.4
5.6
5.8
6.0
6.2
6.8
7.5
8.1
8.7
9.3
9.9
11
12
14
15
16
17
19
22
25
>25*
*Report distance as 25 miles
April 15, 1999
10- 10
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Reference Table 16
Neutrally Buoyant Plume Distances to Toxic Endpoint for Release Rate Divided by Endpoint
10-Minute Release, Urban Conditions, D Stability, Wind Speed 3.0 Meters per Second
Release Rate/Endpoint
[(lbs/min)/(mg/L)]
0-160
160- 1,400
1,400-3,600
3,600 - 6,900
6,900-13,000
13,000-22,000
22,000-31,000
31,000-42,000
42,000 - 59,000
59,000 - 73,000
73,000 - 88,000
88,000 - 100,000
100,000 - 120,000
120,000- 150,000
150,000-170,000
170,000-200,000
200,000 - 230,000
230,000 - 260,000
260,000-310,000
310,000-340,000
340,000 - 390,000
390,000 - 430,000
430,000 - 490,000
490,000 - 540,000
540,000 - 600,000
Distance to Endpoint
(miles)
0.1
0.2
0.3
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
4.0
4.2
4.4
4.6
Release Rate/Endpoint
[(lbs/min)/(mg/L)]
600,000 - 660,000
660,000 - 720,000
720,000 - 810,000
810,000 - 880,000
880,000 - 950,000
950,000- 1,000,000
1,000,000-1,100,000
1,100,000- 1,220,000
1,220,000-1,530,000
1,530,000- 1,880,000
1,880,000-2,280,000
2,280,000-2,710,000
2,710,000-3,200,000
3,200,000 - 3,730,000
3,730,000 - 4,920,000
4,920,000-6,310,000
6,310,000-7,890,000
7,890,000 - 9,660,000
9,660,000-11,600,000
11,600,000- 13,800,000
13,800,000-16,200,000
16,200,000-23,100,000
23,100,000-31,300,000
>3 1,300,000
Distance to
Endpoint
(miles)
4.8
5.0
5.2
5.4
5.6
5.8
6.0
6.2
6.8
7.5
8.1
8.7
9.3
9.9
11
12
14
15
16
17
19
22
25
>25*
*Report distance as 25 miles
April 15, 1999
10- 11
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Reference Table 17
Neutrally Buoyant Plume Distances to Toxic Endpoint for Release Rate Divided by Endpoint
60-Minute Release, Urban Conditions, D Stability, Wind Speed 3.0 Meters per Second
Release Rate/Endpoint
[(lbs/min)/(mg/L)]
0-200
200- 1,700
1,700-4,500
4,500 - 8,600
8,600 - 17,000
17,000-27,000
27,000 - 39,000
39,000 - 53,000
53,000 - 73,000
73,000 - 90,000
90,000-110,000
110,000- 130,000
130,000-150,000
150,000- 170,000
170,000-200,000
200,000 - 220,000
220,000 - 240,000
240,000 - 270,000
270,000 - 300,000
300,000 - 320,000
320,000 - 350,000
350,000 - 370,000
370,000-410,000
410,000-430,000
430,000 - 460,000
Distance to
Endpoint
(miles)
0.1
0.2
0.3
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
4.0
4.2
4.4
4.6
Release Rate/Endpoint
[(lbs/min)/(mg/L)]
460,000 - 490,000
490,000 - 520,000
520,000 - 550,000
550,000 - 580,000
580,000-610,000
610,000-640,000
640,000 - 680,000
680,000 - 705,000
705,000 - 804,000
804,000 - 905,000
905,000-1,010,000
1,010,000- 1,120,000
1,120,000-1,230,000
1,230,000- 1,350,000
1,350,000-1,620,000
1,620,000- 1,920,000
1,920,000-2,250,000
2,250,000 - 2,620,000
2,620,000 - 3,030,000
3,030,000 - 3,490,000
3,490,000 - 3,980,000
3,980,000 - 5,410,000
5,410,000-7,120,000
>7, 120,000
Distance to
Endpoint
(miles)
4.8
5.0
5.2
5.4
5.6
5.8
6.0
6.2
6.8
7.5
8.1
8.7
9.3
9.9
11
12
14
15
16
17
19
22
25
>25*
*Report distance as 25 miles
April 15, 1999
10- 12
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Reference Table 18
Dense Gas Distances to Toxic Endpoint
10-minute Release, Rural Conditions, D Stability, Wind Speed 3.0 Meters per Second
Release
Rate
(Ibs/mln)
1
2
5
10
30
50
100
150
250
500
750
1,000
1,500
2,000
2,500
3,000
4,000
5,000
7,500
10,000
15,000
20,000
50,000
75,000
100,000
150,000
200,000
Toxic Endpoint (mg/L)
0.0004
0.0007
0.001
0.002
0.0035
0.005
0.0075
0.01
0.02
0.035
0.05
0.075
0.1
0.25
0.5
0.75
Distance (Miles)
0.6
0.9
1.4
2.0
3.7
5.0
7.4
8.7
12
17
22
>25
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
0.4
0.6
1.1
1.5
2.7
3.7
5.3
6.8
8.7
13
16
19
23
>25
*
*
*
*
*
*
*
*
*
*
*
*
*
0.4
0.5
0.9
1.2
2.2
3.0
4.3
5.5
7.4
11
13
16
19
22
25
>25
*
*
*
*
*
*
*
*
*
*
*
0.2
0.4
0.6
0.9
1.5
2.1
3.0
3.8
5.0
7.4
9.3
11
13
15
17
19
22
>25
*
*
*
*
*
*
*
*
*
0.2
0.3
0.4
0.6
1.1
1.9
2.3
2.8
3.7
5.3
6.8
8.1
9.9
12
13
14
17
19
24
>25
*
*
*
*
*
*
*
0.1
0.2
0.4
0.5
0.9
1.2
1.7
2.3
3.0
4.5
5.6
6.8
8.1
9.3
11
12
14
16
19
22
>25
*
*
*
*
*
*
0.1
0.2
0.3
0.4
0.7
1.0
1.4
1.9
2.4
3.6
4.5
5.2
6.8
7.4
8.7
9.3
11
12
16
18
22
>25
*
*
*
*
*
0.1
0.1
0.2
0.4
0.7
0.9
1.2
1.6
2.1
3.0
3.8
4.5
5.6
6.8
7.4
8.1
9.3
11
13
16
19
22
>25
*
*
*
*
<0.1
0.1
0.2
0.2
0.5
0.6
0.9
1.1
1.4
2.1
2.7
3.1
3.9
4.5
5.2
5.7
6.8
7.4
9.3
11
13
16
24
>25
*
*
*
<0.1
0.1
0.1
0.2
0.3
0.4
0.6
0.8
1.1
1.6
1.9
2.3
2.9
3.4
3.8
4.2
4.9
5.6
6.8
8.1
9.9
11
18
22
>25
*
*
#
<0.1
0.1
0.1
0.3
0.4
0.6
0.7
0.9
1.3
1.6
2.2
2.4
2.7
3.2
3.5
4.1
4.7
5.8
6.8
8.1
9.3
15
18
21
>25
*
#
<0.1
0.1
0.1
0.2
0.3
0.4
0.6
0.7
1.1
1.3
1.5
1.9
2.2
2.5
2.8
3.3
3.7
4.7
5.3
6.8
7.4
12
15
17
20
23
#
#
<0.1
0.1
0.2
0.2
0.4
0.5
0.5
0.9
1.1
1.3
1.6
1.9
2.1
2.4
2.8
3.1
4.0
4.6
5.7
6.8
10
13
14
17
19
#
#
#
<0.1
0.1
0.2
0.2
0.3
0.4
0.6
0.7
0.8
1.0
1.2
1.3
1.4
1.7
2.1
2.4
2.8
3.5
4.0
6.5
7.8
8.9
11
12
#
#
#
<0.1
0.1
0.1
0.2
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.3
1.6
1.9
2.4
2.8
4.5
5.4
6.3
7.4
8.5
#
#
#
#
<0.1
0.1
0.1
0.2
0.2
0.3
0.4
0.4
0.6
0.6
0.7
0.8
0.9
1.1
1.3
1.5
1.9
2.2
3.6
4.4
5.0
6.0
6.8
> 25 miles (report distance as 25 miles)
# <0.1 mile (report distance as 0.1 mile)
10- 13
-------
Reference Table 19
Dense Gas Distances to Toxic Endpoint
60-minute Release, Rural Conditions, D Stability, Wind Speed 3.0 Meters per Second
Release
Rate
(Ibs/mln)
1
2
5
10
30
50
100
150
250
500
750
1,000
1,500
2,000
2,500
3,000
4,000
5,000
7,500
10,000
15,000
20,000
50,000
75,000
100,000
150,000
200,000
Toxic Endpoint (nig/L)
0.0004
0.0007
0.001
0.002
0.0035
0.005
0.0075
0.01
0.02
0.035
0.05
0.075
0.1
0.25
0.5
0.75
Distance (Miles)
0.5
0.8
1.6
2.0
4.0
5.5
8.7
12
17
>25
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
0.4
0.6
1.0
1.4
2.8
3.9
6.1
8.1
11
19
25
>25
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
0.3
0.5
0.8
1.2
2.2
3.1
4.8
6.2
8.7
14
19
24
>25
*
*
*
*
*
*
*
*
*
*
*
*
*
*
0.2
0.3
0.5
0.8
1.5
2.1
3.2
4.1
5.6
9.3
12
15
20
24
>25
*
*
*
*
*
*
*
*
*
*
*
*
0.2
0.2
0.4
0.6
1.1
1.5
2.2
2.9
4.0
6.2
8.7
11
14
17
19
22
>25
*
*
*
*
*
*
*
*
*
*
0.1
0.2
0.3
0.5
0.9
1.2
1.8
2.3
3.2
5.0
6.8
8.1
11
13
15
17
21
25
>25
*
*
*
*
*
*
*
*
0.1
0.2
0.2
0.4
0.7
1.0
1.4
1.8
2.5
3.9
5.1
6.1
8.1
9.9
12
13
16
19
25
>25
*
*
*
*
*
*
*
0.1
0.1
0.2
0.3
0.6
0.8
1.2
1.6
2.1
3.3
4.2
5.2
6.8
8.1
9.3
11
14
16
20
25
>25
*
*
*
*
*
*
<0.1
0.1
0.2
0.2
0.4
0.6
0.8
1.1
1.4
2.2
2.8
3.4
4.3
5.2
6.0
6.8
8.7
9.9
13
16
21
25
>25
*
*
*
*
#
<0.1
0.1
0.2
0.3
0.4
0.6
0.7
1.1
1.6
2.0
2.4
3.0
3.7
4.3
4.8
5.8
6.8
9.3
11
14
17
>25
*
*
*
*
#
<0.1
0.1
0.1
0.2
0.3
0.5
0.6
0.9
1.3
1.6
1.9
2.5
2.9
3.4
3.8
4.7
5.3
6.8
8.7
11
14
25
>25
*
*
*
#
<0.1
0.1
0.1
0.2
0.3
0.4
0.5
0.7
1.0
1.3
1.5
1.9
2.3
2.7
3.0
3.6
4.1
5.4
6.8
8.7
11
19
25
>25
*
*
#
#
<0.1
0.1
0.2
0.2
0.3
0.4
0.6
0.9
1.1
1.3
1.7
1.9
2.2
2.5
3.0
3.5
4.5
5.4
7.4
8.7
16
20
24
>25
*
#
#
#
<0.1
0.1
0.1
0.2
0.3
0.4
0.5
0.6
0.7
1.0
1.2
1.3
1.5
1.7
2.0
2.6
3.1
4.0
4.8
8.8
11
14
17
20
#
#
#
<0.1
0.1
0.1
0.1
0.2
0.2
0.4
0.4
0.5
0.7
0.7
0.9
1.0
1.2
1.4
1.7
2.1
2.6
3.1
5.6
7.3
9.4
11
13
#
#
#
#
<0.1
0.1
0.1
0.1
0.2
0.3
0.4
0.4
0.5
0.6
0.7
0.8
0.9
1.1
1.4
1.6
2.1
2.5
4.3
5.6
6.8
8.7
10
> 25 miles (report distance as 25 miles)
# <0.1 mile (report distance as 0.1 mile)
10- 14
-------
Reference Table 20
Dense Gas Distances to Toxic Endpoint
10-minute Release, Urban Conditions, D Stability, Wind Speed 3.0 Meters per Second
Release
Rate
(Ibs/mln)
1
2
5
10
30
50
100
150
250
500
750
1,000
1,500
2,000
2,500
3,000
4,000
5,000
7,500
10,000
15,000
20,000
50,000
75,000
100,000
150,000
200,000
Toxic Endpoint (nig/L)
0.0004
0.0007
0.001
0.002
0.0035
0.005
0.0075
0.01
0.02
0.035
0.05
0.075
0.1
0.25
0.5
0.75
Distance (Miles)
0.5
0.7
1.1
2.1
3.0
4.1
5.8
7.4
9.9
14
17
20
>25
*
*
*
*
*
*
*
*
*
*
*
*
*
*
0.3
0.5
0.8
1.2
2.2
3.0
4.3
5.5
7.4
11
13
15
19
22
24
>25
*
*
*
*
*
*
*
*
*
*
*
0.2
0.4
0.6
1.0
1.9
2.5
3.5
4.5
5.8
8.7
11
12
16
18
20
22
>25
*
*
*
*
*
*
*
*
*
*
0.2
0.3
0.5
0.7
1.2
1.6
2.7
3.1
4.1
5.9
7.4
8.7
11
12
14
16
18
20
>25
*
*
*
*
*
*
*
*
0.1
0.2
0.3
0.5
0.9
1.2
1.8
2.2
3.0
4.3
5.5
6.2
8.1
9.3
11
11
14
15
19
22
>25
*
*
*
*
*
*
0.1
0.2
0.3
0.4
0.8
1.0
1.4
1.9
2.5
3.6
4.5
5.3
6.2
7.4
8.7
9.3
11
12
16
18
22
>25
*
*
*
*
*
0.1
0.1
0.2
0.3
0.6
0.8
1.2
1.4
2.0
2.9
3.6
4.3
5.2
6.2
6.8
7.4
8.7
9.9
12
14
18
20
>25
*
*
*
*
0.1
0.1
0.2
0.3
0.6
0.7
1.0
1.2
1.7
2.5
3.1
3.5
4.5
5.2
6.0
6.8
7.4
8.7
11
12
16
18
>25
*
*
*
*
<0.1
0.1
0.1
0.2
0.4
0.5
0.7
0.9
1.1
1.7
2.1
2.5
3.0
3.7
3.8
4.5
5.3
5.8
7.4
8.7
11
12
20
25
>25
*
*
#
<0.1
0.1
0.1
0.3
0.3
0.6
0.7
0.9
1.2
1.6
1.8
2.2
2.7
3.0
3.3
4.0
4.4
5.5
6.2
8.1
9.3
15
18
21
>25
*
#
<0.1
0.1
0.1
0.2
0.3
0.4
0.6
0.7
1.0
1.2
1.5
1.8
2.2
2.2
2.7
3.2
3.6
4.5
5.2
6.8
7.4
12
15
17
21
24
#
#
<0.1
0.1
0.2
0.2
0.4
0.4
0.6
0.8
1.0
1.2
1.5
1.7
1.9
2.1
2.6
2.9
3.6
4.2
5.2
6.0
9.7
12
14
17
19
#
#
<0.1
0.1
0.1
0.2
0.3
0.4
0.5
0.7
0.9
1.0
1.2
1.4
1.7
1.9
2.1
2.4
3.0
3.6
4.4
5.2
8.3
10
12
14
16
#
#
#
<0.1
0.1
0.1
0.2
0.2
0.3
0.4
0.5
0.6
0.7
0.9
1.0
1.1
1.2
1.4
1.8
2.1
2.6
3.0
5.0
6.1
7.0
8.5
9.7
#
#
#
#
<0.1
0.1
0.1
0.2
0.2
0.3
0.4
0.4
0.5
0.6
0.7
0.7
0.9
0.9
1.2
1.4
1.7
2.0
3.3
4.1
4.7
5.7
6.5
#
#
#
#
#
<0.1
0.1
0.1
0.1
0.2
0.3
0.3
0.4
0.5
0.6
0.6
0.7
0.7
0.9
1.1
1.3
1.6
2.6
3.1
3.7
4.5
5.1
> 25 miles (report distance as 25 miles)
# <0.1 mile (report distance as 0.1 mile)
10- 15
-------
Reference Table 21
Dense Gas Distances to Toxic Endpoint
60-minute Release, Urban Conditions, D Stability, Wind Speed 3.0 Meters per Second
Release
Rate
(Ibs/mln)
1
2
5
10
30
50
100
150
250
500
750
1,000
1,500
2,000
2,500
3,000
4,000
5,000
7,500
10,000
15,000
20,000
50,000
75,000
100,000
150,000
200,000
Toxic Endpoint (nig/L)
0.0004
0.0007
0.001
0.002
0.0035
0.005
0.0075
0.01
0.02
0.035
0.05
0.075
0.1
0.25
0.5
0.75
Distance (Miles)
0.4
0.7
1.1
1.7
3.3
4.7
7.4
9.9
14
22
>25
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
0.3
0.5
0.8
1.2
2.4
3.3
5.2
6.8
9.3
16
20
24
>25
*
*
*
*
*
*
*
*
*
*
*
*
*
*
0.2
0.4
0.7
1.0
1.9
2.6
4.1
5.3
7.4
12
16
19
>25
*
*
*
*
*
*
*
*
*
*
*
*
*
*
0.2
0.2
0.4
0.7
1.3
1.7
2.7
3.4
4.7
7.4
9.9
12
16
19
23
>25
*
*
*
*
*
*
*
*
*
*
*
0.1
0.2
0.3
0.5
0.9
1.2
1.9
2.4
3.4
5.2
6.8
8.1
11
14
16
18
22
>25
*
*
*
*
*
*
*
*
*
0.1
0.2
0.2
0.4
0.7
1.0
1.5
1.9
2.7
4.2
5.4
6.8
8.7
11
12
14
17
20
25
>25
*
*
*
*
*
*
*
0.1
0.1
0.2
0.3
0.6
0.8
1.2
1.5
2.1
3.2
4.2
5.0
6.8
8.1
9.3
11
13
16
20
24
>25
*
*
*
*
*
*
<0.1
0.1
0.2
0.3
0.5
0.7
1.0
1.3
1.7
2.7
3.5
4.2
5.5
6.8
7.4
8.7
11
12
17
20
>25
*
*
*
*
*
*
#
<0.1
0.1
0.2
0.3
0.4
0.7
0.9
1.1
1.7
2.2
2.7
3.5
4.2
4.9
5.5
6.8
8.1
11
13
17
20
>25
*
*
*
*
#
<0.1
0.1
0.1
0.2
0.3
0.5
0.6
0.8
1.2
1.6
1.8
1.9
3.0
3.4
3.8
4.7
5.3
6.8
8.7
11
14
>25
*
*
*
*
#
#
<0.1
0.1
0.2
0.3
0.4
0.5
0.7
1.0
1.3
1.6
2.0
2.2
2.7
3.0
3.1
4.3
5.6
6.8
8.7
11
20
>25
*
*
*
#
#
<0.1
0.1
0.2
0.2
0.3
0.4
0.5
0.8
1.0
1.2
1.6
1.9
2.1
2.4
2.8
3.3
4.3
5.2
6.8
8.1
15
20
24
>25
*
#
#
<0.1
0.1
0.1
0.2
0.3
0.3
0.4
0.7
0.9
1.0
1.3
1.6
1.7
2.0
2.4
2.7
3.5
4.3
5.6
6.8
13
16
20
>25
*
#
#
#
<0.1
0.1
0.1
0.2
0.2
0.3
0.4
0.5
0.6
0.7
0.9
1.0
1.1
1.3
1.5
2.0
2.4
3.0
3.6
6.6
8.7
10
14
16
#
#
#
#
<0.1
0.1
0.1
0.1
0.2
0.2
0.3
0.4
0.5
0.6
0.6
0.7
0.9
1.0
1.2
1.5
1.9
2.3
4.0
5.3
6.3
8.2
9.9
#
#
#
#
#
<0.1
0.1
0.1
0.1
0.2
0.3
0.3
0.4
0.4
0.5
0.6
0.7
0.7
0.9
1.1
1.5
1.7
3.1
3.9
4.7
6.1
7.3
> 25 miles (report distance as 25 miles)
# <0.1 mile (report distance as 0.1 mile)
10- 16
-------
Reference Table 22
Distances to Toxic Endpoint for Anhydrous Ammonia Liquefied Under Pressure
D Stability, Wind Speed 3.0 Meters per Second
Release Rate
(Ibs/min)
<10
10
15
20
30
40
50
60
70
80
90
100
150
200
250
300
400
500
600
700
750
800
Distance to Endpoint (miles)
Rural
<0.1*
0.1
0.1
0.1
0.1
0.1
0.1
0.2
0.2
0.2
0.2
0.2
0.2
0.3
0.3
0.3
0.4
0.4
0.5
0.5
0.5
0.5
Urban
0.1*
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.2
0.2
0.2
0.2
0.2
0.2
Release Rate
(Ibs/min)
900
1,000
1,500
2,000
2,500
3,000
4,000
5,000
7,500
10,000
15,000
20,000
25,000
30,000
40,000
50,000
75,000
100,000
150,000
200,000
250,000
Distance to Endpoint (miles)
Rural
0.6
0.6
0.7
0.8
0.9
1.0
1.2
1.3
1.6
1.8
2.2
2.5
2.8
3.1
3.5
3.9
4.8
5.4
6.6
7.6
8.4
Urban
0.2
0.2
0.3
0.3
0.3
0.4
0.4
0.5
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.4
1.6
1.9
2.1
2.3
* Report distance as 0.1 mile
April 15, 1999
10-17
-------
Reference Table 23
Distances to Toxic Endpoint for Non-liquefied Ammonia, Ammonia Liquefied by Refrigeration, or
Aqueous Ammonia
D Stability, Wind Speed 3.0 Meters per Second
Release Rate
(Ibs/min)
<8
8
10
15
20
30
40
50
60
70
80
90
100
150
200
250
300
400
500
600
700
750
Distance to Endpoint (miles)
Rural
0.1*
0.1
0.1
0.1
0.1
0.1
0.1
0.2
0.2
0.2
0.2
0.2
0.2
0.3
0.3
0.4
0.4
0.4
0.5
0.6
0.6
0.6
Urban
O.I*
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.2
0.2
0.2
0.2
0.2
0.2
0.2
Release Rate
(Ibs/min)
800
900
1,000
1,500
2,000
2,500
3,000
4,000
5,000
7,500
10,000
15,000
20,000
25,000
30,000
40,000
50,000
75,000
100,000
150,000
200,000
Distance to Endpoint (miles)
Rural
0.7
0.7
0.8
1.0
1.2
1.2
1.5
1.8
2.0
2.2
2.5
3.1
3.6
4.1
4.4
5.1
5.8
7.1
8.2
10
12
Urban
0.2
0.3
0.3
0.4
0.4
0.4
0.5
0.6
0.7
0.7
0.8
1.0
1.2
1.3
1.4
1.6
1.8
2.2
2.5
3.1
3.5
* Report distance as 0.1 mile
April 15, 1999
10-18
-------
Reference Table 24
Distances to Toxic Endpoint for Chlorine
D Stability, Wind Speed 3.0 Meters per Second
Release Rate
(Ibs/min)
1
2
5
10
15
20
30
40
50
60
70
80
90
100
150
200
250
300
400
500
600
700
Distance to Endpoint (miles)
Rural
<0.1*
0.1
0.1
0.2
0.2
0.2
0.3
0.3
0.3
0.4
0.4
0.4
0.4
0.5
0.6
0.6
0.7
0.8
0.8
1.0
1.0
1.1
Urban
0.1*
0.1
0.1
0.1
0.1
0.1
0.1
0.2
0.2
0.2
0.2
0.2
0.2
0.3
0.3
0.3
0.4
0.4
0.4
0.4
Release Rate
(Ibs/min)
750
800
900
1,000
1,500
2,000
2,500
3,000
4,000
5,000
7,500
10,000
15,000
20,000
25,000
30,000
40,000
50,000
75,000
100,000
150,000
200,000
Distance to Endpoint (miles)
Rural
1.2
1.2
1.2
1.3
1.6
1.8
2.0
2.2
2.5
2.8
3.4
3.9
4.6
5.3
5.9
6.4
7.3
8.1
9.8
11
13
15
Urban
0.4
0.5
0.5
0.5
0.6
0.6
0.7
0.8
0.8
0.9
1.2
1.3
1.6
1.8
2.0
2.1
2.4
2.7
3.2
3.6
4.2
4.8
* Report distance as 0.1 mile
April 15, 1999
10-19
-------
Reference Table 25
Distances to Toxic Endpoint for Sulfur Dioxide
D Stability, Wind Speed 3.0 Meters per Second
Release Rate
(Ibs/min)
1
2
5
10
15
20
30
40
50
60
70
80
90
100
150
200
250
300
400
500
600
700
Distance to Endpoint (miles)
Rural
0.1*
0.1
0.1
0.2
0.2
0.2
0.2
0.3
0.3
0.4
0.4
0.4
0.4
0.5
0.6
0.6
0.7
0.8
0.9
1.0
1.1
1.2
Urban
0.1*
0.1
0.1
0.1
0.1
0.1
0.1
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.3
0.3
0.4
0.4
0.4
0.4
Release Rate
(Ibs/min)
750
800
900
1,000
1,500
2,000
2,500
3,000
4,000
5,000
7,500
10,000
15,000
20,000
25,000
30,000
40,000
50,000
75,000
100,000
150,000
200,000
Distance to Endpoint (miles)
Rural
1.3
1.3
1.4
1.5
1.9
2.2
2.3
2.7
3.1
3.3
4.0
4.6
5.6
6.5
7.3
8.0
9.2
10
13
14
18
20
Urban
0.5
0.5
0.5
0.5
0.6
0.7
0.8
0.8
1.0
1.1
1.3
1.4
1.7
1.9
2.1
2.3
2.6
2.9
3.5
4.0
4.7
5.4
: Report distance as 0.1 mile
April 15, 1999
10-20
-------
Reference Table 26
Neutrally Buoyant Plume Distances to Lower Flammability Limit (LFL)
For Release Rate Divided by LFL
Rural Conditions, D Stability, Wind Speed 3.0 Meters per Second
Release Rate/Endpoint
[(lbs/min)/(mg/L)]
0-28
28-40
40-60
60 - 220
220 - 530
530-860
860 - 1,300
1,300 - 1,700
1,700 - 2,200
2,200 - 2,700
Distance to
Endpoint
(miles)
0.1
0.1
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Release Rate/Endpoint
[(lbs/min)/(mg/L)]
2,700 - 3,300
3,300 - 3,900
3,900 - 4,500
4,500 - 5,200
5,200 - 5,800
5,800 - 6,800
6,800 - 8,200
8,200 - 9,700
9,700- 11,000
11,000- 13,000
Distance to
Endpoint
(miles)
0.9
1.0
1.1
1.2
1.3
1.4
1.6
1.8
2.0
2.2
Reference Table 27
Neutrally Buoyant Plume Distances to Lower Flammability Limit (LFL)
For Release Rate Divided by LFL
Urban Conditions, D Stability, Wind Speed 3.0 Meters per Second
Release Rate/Endpoint
[(lbs/min)/(mg/L)]
0-68
68 - 100
100- 150
150-710
710- 1,500
1,500 - 2,600
2,600 - 4,000
4,000 - 5,500
Distance to
Endpoint
(miles)
0.1
0.1
0.1
0.2
0.3
0.4
0.5
0.6
Release Rate/Endpoint
[(lbs/min)/(mg/L)]
5,500 - 7,300
7,300 - 9,200
9,200- 11,000
11,000- 14,000
14,000- 18,000
18,000-26,000
26,000-31,000
31,000-38,000
Distance to
Endpoint
(miles)
0.7
0.8
0.9
1.0
1.2
1.4
1.6
1.8
April 15, 1999
10-21
-------
Reference Table 28
Dense Gas Distances to Lower Flammability Limit
Rural Conditions, D Stability, Wind Speed 3.0 Meters per Second
Release
Rate
(Ibs/min)
<1,500
1,500
2,000
2,500
3,000
4,000
5,000
7,500
10,000
Lower Flammability Limit (mg/L)
27
30
35
40
45
50
60
70
100
>100
Distance (Miles)
#
<0.1
0.1
0.1
0.1
0.1
0.1
0.2
0.2
#
<0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.2
#
#
<0.1
0.1
0.1
0.1
0.1
0.1
0.1
#
#
#
<0.1
0.1
0.1
0.1
0.1
0.1
#
#
#
#
<0.1
0.1
0.1
0.1
0.1
#
#
#
#
<0.1
0.1
0.1
0.1
0.1
#
#
#
#
#
<0.1
0.1
0.1
0.1
#
#
#
#
#
#
<0.1
0.1
0.1
#
#
#
#
#
#
#
<0.1
0.1
#
#
#
#
#
#
#
#
<0.1
# < 0.1 mile (report distance as 0.1 mile)
April 15, 1999
10-22
-------
Reference Table 29
Dense Gas Distances to Lower Flammability Limit
Urban Conditions, D Stability, Wind Speed 3.0 Meters per Second
Release
Rate
(Ibs/min)
<5,000
5,000
7,500
10,000
Lower Flammability Limit (mg/L)
27
30
35
40
>40
Distance (Miles)
#
<0.1
0.1
0.1
#
<0.1
0.1
0.1
#
#
<0.1
0.1
#
#
#
<0.1
#
#
#
#
# < 0.1 mile (report distance as 0.1 mile)
April 15, 1999
10-23
-------
Reference Table 30
Distance to Radiant Heat Dose at Potential Second Degree Burn Threshold Assuming Exposure for Duration of Fireball from BLEVE
(Dose = [5 kW/rn2]4'3 x Exposure Time)
Quantity in Fireball (pounds)
Duration of Fireball (seconds)
CAS No.
75-07-0
74-86-2
598-73-2
106-99-0
106-97-8
106-98-9
107-01-7
25167-67-3
590-18-1
624-64-6
463-58-1
7791-21-1
557-98-2
590-21-6
460-19-5
75-19-4
4109-96-0
75-37-6
124-40-3
463-82-1
74-84-0
107-00-6
Chemical Name
Acetaldehyde
Acetylene
Bromotrifluoroethylene
1,3-Butadiene
Butane
1-Butene
2-Butene
Butene
2-Butene-cis
2-Butene-trans
Carbon oxysulfide
Chlorine monoxide
2-Chloropropylene
1 -Chloropropylene
Cyanogen
Cyclopropane
Dichlorosilane
Difluoroethane
Dimethylamine
2,2-Dimethylpropane
Ethane
Ethyl acetylene
1,000
3.5
5,000
5.9
10,000
7.5
20,000
9.4
30,000
10.8
50,000
12.7
75,000
14.8
100,000
15.5
200,000
17.4
300,000
18.7
500,000
20.3
Distance (miles) at which Exposure for Duration of Fireball May Cause Second Degree Burns
0.04
0.05
0.01
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.02
0.01
0.03
0.03
0.03
0.05
0.02
0.02
0.04
0.05
0.05
0.05
0.08
0.1
0.02
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.05
0.02
0.07
0.07
0.07
0.1
0.04
0.05
0.09
0.1
0.1
0.1
0.1
0.1
0.03
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.06
0.02
0.1
0.1
0.1
0.1
0.06
0.07
0.1
0.1
0.1
0.1
0.1
0.2
0.04
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.09
0.03
0.1
0.1
0.1
0.2
0.08
0.1
0.2
0.2
0.2
0.2
0.2
0.2
0.05
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.1
0.03
0.2
0.2
0.2
0.2
0.1
0.1
0.2
0.2
0.2
0.2
0.2
0.3
0.06
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.1
0.04
0.2
0.2
0.2
0.3
0.1
0.1
0.3
0.3
0.3
0.3
0.3
0.4
0.07
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.2
0.05
0.2
0.2
0.2
0.4
0.2
0.2
0.3
0.4
0.4
0.4
0.3
0.4
0.08
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.2
0.06
0.3
0.3
0.3
0.4
0.2
0.2
0.4
0.4
0.4
0.4
0.4
0.5
0.1
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.2
0.08
0.4
0.4
0.4
0.5
0.2
0.3
0.5
0.5
0.5
0.5
0.5
0.6
0.1
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.3
0.09
0.4
0.4
0.4
0.6
0.3
0.3
0.5
0.6
0.6
0.6
0.6
0.8
0.2
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.3
0.1
0.5
0.5
0.5
0.8
0.3
0.4
0.7
0.8
0.8
0.8
April 15, 1999
10-24
-------
Reference Table 30 (continued)
Quantity in Fireball (pounds)
Duration of Fireball (seconds)
CAS No.
75-04-7
75-00-3
74-85-1
60-29-7
75-08-1
109-95-5
1333-74-0
75-28-5
78-78-4
78-79-5
75-31-0
75-29-6
74-82-8
74-89-5
563-45-1
563-46-2
115-10-6
107-31-3
115-11-7
504-60-9
109-66-0
109-67-1
646-04-8
Chemical Name
Ethylamine
Ethyl chloride
Ethylene
Ethyl ether
Ethyl mercaptan
Ethyl nitrite
Hydrogen
Isobutane
Isopentane
Isoprene
Isopropylamine
Isopropyl chloride
Methane
Methylamine
3 -Methyl- 1-butene
2-Methyl-l-butene
Methyl ether
Methyl formate
2-Methylpropene
1,3-Pentadiene
Pentane
1-Pentene
2-Pentene, (EV
1,000
3.5
5,000
5.9
10,000
7.5
20,000
9.4
30,000
10.8
50,000
12.7
75,000
14.8
100,000
15.5
200,000
17.4
300,000
18.7
500,000
20.3
Distance (miles) at which Exposure for Duration of Fireball May Cause Second Degree Burns
0.04
0.03
0.05
0.04
0.04
0.03
0.08
0.05
0.05
0.05
0.04
0.04
0.05
0.04
0.05
0.05
0.04
0.03
0.05
0.05
0.05
0.05
0.05
0.09
0.07
0.1
0.09
0.08
0.06
0.2
0.1
0.1
0.1
0.09
0.07
0.1
0.08
0.1
0.1
0.08
0.06
0.1
0.1
0.1
0.1
0.1
0.1
0.09
0.1
0.1
0.1
0.09
0.2
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.08
0.1
0.1
0.1
0.1
0.1
0.2
0.1
0.2
0.2
0.2
0.1
0.3
0.2
0.2
0.2
0.2
0.1
0.2
0.2
0.2
0.2
0.2
0.1
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.1
0.4
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.1
0.2
0.2
0.2
0.2
0.2
0.3
0.2
0.3
0.2
0.2
0.2
0.5
0.3
0.3
0.3
0.3
0.2
0.3
0.2
0.3
0.3
0.2
0.2
0.3
0.3
0.3
0.3
0.3
0.3
0.2
0.4
0.3
0.3
0.2
0.6
0.4
0.4
0.4
0.3
0.3
0.4
0.3
0.4
0.4
0.3
0.2
0.4
0.3
0.4
0.4
0.4
0.4
0.3
0.4
0.3
0.3
0.3
0.6
0.4
0.4
0.4
0.4
0.3
0.4
0.3
0.4
0.4
0.3
0.2
0.4
0.4
0.4
0.4
0.4
0.5
0.3
0.5
0.5
0.4
0.3
0.9
0.5
0.5
0.5
0.5
0.4
0.6
0.4
0.5
0.5
0.4
0.3
0.5
0.5
0.5
0.5
0.5
0.5
0.4
0.6
0.5
0.5
0.4
1.0
0.6
0.6
0.6
0.6
0.4
0.6
0.5
0.6
0.6
0.5
0.4
0.6
0.6
0.6
0.6
0.6
0.7
0.5
0.8
0.7
0.6
0.5
1.2
0.8
0.8
0.7
0.7
0.5
0.8
0.6
0.8
0.7
0.6
0.4
0.8
0.7
0.8
0.8
0.8
April 15, 1999
10-25
-------
Reference Table 30 (continued)
Quantity in Fireball (pounds)
Duration of Fireball (seconds)
CAS No.
627-20-3
463-49-0
74-98-6
115-07-1
74-99-7
7803-62-5
116-14-3
75-76-3
10025-78-2
79-38-9
75-50-3
689-97-4
75-01-4
109-92-2
75-02-5
75-35-4
75-38-7
107-25-5
Chemical Name
2-Pentene, (Z)-
Propadiene
Propane
Propylene
Propyne
Silane
Tetrafluoroethylene
Tetramethylsilane
Trichlorosilane
Trifluorochloroethylene
Trimethylamine
Vinyl acetylene
Vinyl chloride
Vinyl ethyl ether
Vinyl fluoride
Vinylidene chloride
Vinylidene fluoride
Vinyl methyl ether
1,000
3.5
5,000
5.9
10,000
7.5
20,000
9.4
30,000
10.8
50,000
12.7
75,000
14.8
100,000
15.5
200,000
17.4
300,000
18.7
500,000
20.3
Distance (miles) at which Exposure for Duration of Fireball May Cause Second Degree Burns
0.05
0.05
0.05
0.05
0.05
0.05
0.01
0.05
0.01
0.01
0.04
0.05
0.03
0.04
0.01
0.02
0.02
0.04
0.1
0.1
0.1
0.1
0.1
0.1
0.02
0.1
0.03
0.02
0.09
0.1
0.07
0.09
0.02
0.05
0.05
0.08
0.1
0.1
0.1
0.1
0.1
0.1
0.02
0.1
0.04
0.03
0.1
0.1
0.09
0.1
0.03
0.07
0.07
0.1
0.2
0.2
0.2
0.2
0.2
0.2
0.03
0.2
0.06
0.04
0.2
0.2
0.1
0.2
0.04
0.09
0.09
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.04
0.2
0.07
0.05
0.2
0.2
0.2
0.2
0.05
0.1
0.1
0.2
0.3
0.3
0.3
0.3
0.3
0.3
0.05
0.3
0.08
0.06
0.3
0.3
0.2
0.2
0.06
0.1
0.1
0.2
0.4
0.4
0.4
0.4
0.4
0.4
0.06
0.3
0.1
0.07
0.3
0.4
0.2
0.3
0.08
0.2
0.2
0.3
0.4
0.4
0.4
0.4
0.4
0.4
0.07
0.4
0.1
0.08
0.4
0.4
0.3
0.3
0.09
0.2
0.2
0.3
0.5
0.5
0.5
0.5
0.5
0.5
0.09
0.5
0.2
0.1
0.5
0.5
0.3
0.4
0.1
0.3
0.3
0.4
0.6
0.6
0.6
0.6
0.6
0.6
0.1
0.6
0.2
0.1
0.6
0.6
0.4
0.5
0.1
0.3
0.3
0.5
0.8
0.8
0.8
0.8
0.8
0.7
0.1
0.7
0.2
0.2
0.7
0.8
0.5
0.6
0.2
0.4
0.4
0.6
April 15, 1999
10-26
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11 ESTIMATING OFFSITE RECEPTORS
In Chapter 11
How to estimate the number of offsite receptors potentially affected by your
worst-case and alternative scenarios.
Where to find the data you need.
The rule requires that you estimate residential populations within the circle defined by the endpoint
for your worst-case and alternative release scenarios. In addition, you must report in the RMP whether
certain types of public receptors and environmental receptors are within the circles.
To estimate residential populations, you may use the most recent Census data or any other source of
data that you believe is more accurate. Local authorities may be able to provide information on offsite
receptors. You are not required to update Census data or conduct any surveys to develop your estimates.
Census data are available in public libraries and in the LandView system, which is available on CD-ROM
(see box below). The rule requires that you estimate populations to two significant digits. For example, if
there are 1,260 people within the circle, you may report 1,300 people. If the number of people is between 10
and 100, estimate to the nearest 10. If the number of people is less than 10, provide the actual number.
How to obtain Census data and LandView
Census data can be found in publications of the Bureau of the Census, available in public libraries, including
County and City Data Book.
LandView ®III is a desktop mapping system that includes database extracts from EPA, the Bureau of the Census,
the U.S. Geological Survey, the Nuclear Regulatory Commission, the Department of Transportation, and the
Federal Emergency Management Agency. These databases are presented in a geographic context on maps that
show jurisdictional boundaries, detailed networks of roads, rivers, and railroads, census block group and tract
polygons, schools, hospitals, churches, cemeteries, airports, dams, and other landmark features.
CD-ROM for IBM-compatible PCS
CD-TGR95-LV3-KIT $99 per disc (by region) or $549 for 11 disc set
U.S. Department of Commerce
Bureau of the Census
P.O. Box 277943
Atlanta, GA 30384-7943
Phone: 301-457-4100 (Customer Services - orders)
Fax: (888) 249-7295 (toll-free)
Fax: (301) 457-3842 (local)
Phone: (301) 457-1128 (Geography Staff- content)
http://www.census.gov/ftp/pub/geo/www/tiger/
Further information on LandView and other sources of Census data is available at the Bureau of the Census web
site at www.census.gov.
April 15, 1999
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Chapter 11
Estimating Offsite Receptors
Census data are presented by Census tract. If your circle covers only a portion of the tract, you
should develop an estimate for that portion. The easiest way to do this is to determine the population density
per square mile (total population of the Census tract divided by the number of square miles in the tract) and
apply that density figure to the number of square miles within your circle. Because there is likely to be
considerable variation in actual densities within a Census tract, this number will be approximate. The rule,
however, does not require you to correct the number.
Other public receptors must be noted in the RMP. If there are any schools, residences, hospitals,
prisons, public recreational areas, or commercial, office, or industrial areas within the circle, you must report
that. Any of these locations inhabited or occupied by the public at any time without restriction by the source
is a public receptor. You are not required to develop a list of all institutions and areas; you must simply
check off which types of receptors are within the circle. Most of these institutions or areas can be identified
from local street maps. Recreational areas include public swimming pools, public parks, and other areas that
are used for recreational activities (e.g., baseball fields). Commercial and industrial areas include shopping
malls, strip malls, downtown business areas, industrial parks, etc. See EPA's General Guidance for Risk
Management Programs (40 CFRpart 68) for further information on identifying public receptors.
Environmental receptors are defined as national or state parks, forests, or monuments; officially
designated wildlife sanctuaries, preserves, or refuges; and Federal wilderness areas. All of these can be
identified on local U.S. Geological Survey (USGS) maps (see box below). You are not required to locate
each of these specifically. You are only required to check off in the RMP that these specific types of areas are
within the circle. If any part of one of these receptors is within your circles, you must note that in the RMP.
Important: The rule does not require you to assess the likelihood, type, or severity of potential
impacts on either public or environmental receptors. Identifying them as within the circle simply indicates
that they could be adversely affected by the release.
April 15, 1999 11-2
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Chapter 11
Estimating Offsite Receptors
How to obtain TJSGS maps
The production of digital cartographic data and graphic maps comprises the largest component of the USGS
National Mapping Program. The USGS's most familiar product is the 1:24,000-scale Topographic Quadrangle
Map. This is the primary scale of data produced, and depicts greater detail for a smaller area than
intermediate-scale (1:50,000 and 1:100,000) and small-scale (1:250,000, 1:2,000,000 or smaller) products, which
show selectively less detail for larger areas.
U.S. Geological Survey
508 National Center
12201 Sunrise Valley Drive
Reston, VA 20192
Phone: (703) 648-4000
http://mapping.usgs.gov
To order USGS maps by fax, select, print, and complete one of the online forms and fax to 303-202-4693.
A list of the nearest commercial dealers is available at: http://mapping.usgs.gov/esic/usimage/dealers.html
For more information or ordering assistance, call 1 -800-HELP-MAP, or write:
USGS Information Services
Box 25286
Denver, CO 80225
For additional information, contact any USGS Earth Science Information Center or call 1-800-USA-MAPS.
April 15, 1999 11-3
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Chapter 11
Estimating Offsite Receptors
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April 15, 1999 11-4
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12 SUBMITTING OFFSITE CONSEQUENCE ANALYSIS
INFORMATION FOR RISK MANAGEMENT PLAN
In Chapter 12
12.1 Information you are required to submit for worst-case scenarios for toxic
substances.
12.2 Information you are required to submit for alternative scenarios for toxic
substances.
12.3 Information you are required to submit for worst-case scenarios for
flammable substances.
12.4 Information you are required to submit for alternative scenarios for
flammable substances.
For the offsite consequence analysis (OCA) component of the RMP you must provide information on
your worst-case and alternative release scenario(s) for toxic and flammable regulated chemicals held above
the threshold quantity. The requirements for what information you must submit differ if your source has
Program 1, Program 2, or Program 3 processes.
If your source has Program 1 processes, you must submit information on a worst-case release
scenario for each Program 1 process. If your source has Program 2 or Program 3 processes, you must
provide information on one worst-case release for all toxic regulated substances present above the threshold
quantity and one worst-case release scenario for all flammable regulated substances present above the
threshold quantity. You may need to submit an additional worst-case scenario if a worst-case release from
another part of the source would potentially affect public receptors different from those potentially affected
by the initial worst-case scenario(s) for flammable and toxic regulated substances.
In addition to a worst-case release scenario, sources with Program 2 and Program 3 processes must
also provide information on alternative release scenarios. Alternative releases are releases that could occur,
other than the worst-case, that may result in concentrations, overpressures, or radiant heat that reach
endpoints offsite. You must present information on one alternative release scenario for each regulated toxic
substance, including the substance used for the worst-case release, held above the threshold quantity and one
alternative release scenario to represent all flammable substances held above the threshold quantity. The
types of documentation to submit are presented below for worst-case scenarios involving toxic substances,
alternative scenarios involving toxic substances, worst-case scenarios involving flammable substances, and
alternative scenarios involving flammable substances.
12.1 RMP Data Required for Worst-Case Scenarios for Toxic Substances
For worst-case scenarios involving toxic substances, you will have to submit the following
information. See the RMP*Submit User Manual for complete instructions.
• Chemical name;
• Percentage weight of the regulated liquid toxic substance (if present in a mixture);
April 12, 1999
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Chapter 12
Submitting Offsite Consequence Analysis Information for Risk Management Plan
• Physical state of the chemical released (gas, liquid, refrigerated gas, gas liquefied by
pressure);
• Model used (OCA or industry-specific guidance reference tables or modeling; name of other
model used);
• Scenario (gas release or liquid spill and vaporization);
• Quantity released (pounds);
• Release rate (pounds per minute);
• Duration of release (minutes) (10 minutes for gases; if you used OCA guidance for liquids,
indicate either 10 or 60 minutes);
• Wind speed (meters per second) and stability class (1.5 meters per second and F stability
unless you can show higher minimum wind speed or less stable atmosphere at all times
during the last three years);
• Topography (rural or urban);
• Distance to endpoint (miles, rounded to two significant digits);
• Population within distance to endpoint (residential population rounded to two significant
digits);
• Public receptors within the distance to endpoint (schools, residences, hospitals, prisons,
recreation areas, commercial, office or industrial areas);
• Environmental receptors within the distance to endpoint (national or state parks, forests, or
monuments; officially designated wildlife sanctuaries, preserves, or refuges; Federal
wilderness areas); and
• Passive mitigation measures considered (dikes, enclosures, berms, drains, sumps, other).
12.2 RMP Data Required for Alternative Scenarios for Toxic Substances
For alternative scenarios involving toxic substances held above the threshold quantity in a Program 2
or Program 3 process, you will have to submit the following information. See the Risk Management Plan
Data Elements Guide for complete instructions.
• Chemical name;
• Percentage weight of the regulated liquid toxic substance (if present in a mixture);
• Physical state of the chemical released (gas, liquid, refrigerated gas, gas liquefied by
pressure);
• Model used (OCA or industry-specific guidance reference tables or modeling; name of other
model used);
• Scenario (transfer hose failure, pipe leak, vessel leak, overfilling, rupture disk/relief valve,
excess flow valve, other);
• Quantity released (pounds);
• Release rate (pounds per minute);
• Duration of release (minutes) (if you used OCA guidance, indicate either 10 or 60 minutes);
• Wind speed (meters per second) and stability class (3.0 meters per second and D stability if
you use OCA guidance, otherwise use typical meteorological conditions at your site);
• Topography (rural or urban);
• Distance to endpoint (miles, rounded to two significant digits);
• Population within distance to endpoint (residential population rounded to two significant
digits);
April 12, 1999 12-2
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Chapter 12
Submitting Offsite Consequence Analysis Information for Risk Management Plan
• Public receptors within the distance to endpoint (schools, residences, hospitals, prisons,
recreation areas, commercial, office, or industrial areas);
• Environmental receptors within the distance to endpoint (national or state parks, forests, or
monuments; officially designated wildlife sanctuaries, preserves, or refuges; Federal
wilderness areas);
• Passive mitigation measures considered (dikes, enclosures, berms, drains, sumps, other); and
• Active mitigation measures considered (sprinkler system, deluge system, water curtain,
neutralization, excess flow valve, flares, scrubbers, emergency shutdown system, other).
12.3 RMP Data Required for Worst-Case Scenarios for Flammable Substances
For worst-case scenarios involving flammable substances, you will have to submit the following
information. See the Risk Management Plan Data Elements Guide for complete instructions.
• Chemical name;
• Model used (OCA or industry-specific guidance reference tables or modeling; name of other
model used);
• Scenario (vapor cloud explosion);
• Quantity released (pounds);
• Endpoint used (for vapor cloud explosions use 1 psi);
• Distance to endpoint (miles, rounded to two significant digits);
• Population within distance to endpoint (residential population rounded to two significant
digits);
• Public receptors within the distance to endpoint (schools, residences, hospitals, prisons,
recreation areas, commercial, office, or industrial areas);
• Environmental receptors within the distance to endpoint (national or state parks, forests, or
monuments, officially designated wildlife sanctuaries, preserves, or refuges, Federal
wilderness areas); and
• Passive mitigation measures considered (blast walls, other).
12.4 RMP Data Required for Alternative Scenarios for Flammable Substances
For alternative scenarios involving flammable substances held above the threshold quantity in a
Program 2 or Program 3 process, you will have to submit the following information. See the Risk
Management Plan Data Elements Guide for complete instructions.
• Chemical name;
• Model used (OCA or industry-specific guidance reference tables or modeling; name of other
model used);
• Scenario (vapor cloud explosion, fireball, BLEVE, pool fire, jet fire, vapor cloud fire, other);
• Quantity released (pounds);
• Endpoint used (for vapor cloud explosions, the endpoint is 1 psi overpressure; for a fireball
the endpoint is 5 kw/m2 for 40 seconds. A lower flammability limit (expressed as a
percentage) may be listed as specified in NFPA documents or other generally recognized
sources; these are listed in the OCA Guidance);
• Distance to endpoint (miles, rounded to two significant digits);
April 12, 1999 12-3
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Chapter 12
Submitting Offsite Consequence Analysis Information for Risk Management Plan
• Population within distance to endpoint (residential population rounded to two significant
digits);
• Public receptors within the distance to endpoint (schools, residences, hospitals, prisons,
recreation areas, commercial, office, or industrial areas);
• Environmental receptors within the distance to endpoint (national or state parks, forests, or
monuments, officially designated wildlife sanctuaries, preserves, or refuges, Federal
wilderness areas);
• Passive mitigation measures considered (e.g., dikes, fire walls, blast walls, enclosures,
other); and
• Active mitigation measures considered (e.g., sprinkler system, deluge system, water curtain,
excess flow valve, other).
12.5 Submitting RMPs
EPA's automated tool for submitting RMPs, RMP*Submit is available free from the EPCRA hotline
(on disk) or can be downloaded from www.epa.gov/ceppo/. The RMP*Submit User's Manual provides
detailed instructions for each data element. RMP*Submit does the following:
• Provides a user-friendly, PC-based RMP Submission System available on diskettes and via
the Internet;
• Uses a standards-based, open systems architecture so private companies can create
compatible software; and
• Performs data quality checks, accept limited graphics, and provide on-line help including
defining data elements and providing instructions.
The software runs on Windows 3.1 and above. There will not be a DOS or MAC version.
If you are unable to submit electronically for any reason, just fill out the Electronic Waiver form
available in the RMP*Submit User's Manual and send it in with your RMP. See the RMP*Submit User's
Manual for more information on the Electronic Waiver.
12.6 Other Required Documentation
Besides the information you are required to submit in your RMP, you must maintain other records of
your offsite consequence analysis on site. Under 40 CFR 68.39, you must maintain the following records:
• For worst-case scenarios, a description of the vessel or pipeline and substance selected as the
worst case, the assumptions and parameters used, and the rationale for selection.
Assumptions include any administrative controls and any passive mitigation systems that
were used to limit the quantity that could be released. You must document that anticipated
effects of these controls and systems on the release quantity and rate.
• For alternative release scenarios, a description of the scenarios identified, the assumptions
and parameters used, and the rationale for selection of the specific scenarios. Assumptions
include any administrative controls and any passive mitigation systems that were used to
April 12, 1999 12-4
-------
Chapter 12
Submitting Offsite Consequence Analysis Information for Risk Management Plan
limit the quantity that could be released. You must document that anticipated effects of
these controls and systems on the release quantity and rate.
• Documentation of estimated quantity released, release rate, and duration of the release.
• Methodology used to determine distance to an endpoint.
• Data used to estimate populations and environmental receptors potentially affected.
You are required to maintain these records for five years.
April 12, 1999 12-5
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Chapter 12
Submitting Offsite Consequence Analysis Information for Risk Management Plan
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April 12, 1999 12-1
-------
APPENDIX A
REFERENCES FOR CONSEQUENCE ANALYSIS METHODS
April 15, 1999
-------
APPENDIX A REFERENCES FOR CONSEQUENCE ANALYSIS
METHODS
Exhibit A-1 lists references that may provide useful information for modeling or calculation methods
that could be used in the offsite consequence analyses. This exhibit is not intended to be a complete listing of
references that may be used in the consequence analysis; any appropriate model or method may be used.
April 15, 1999
-------
Appendix A
References for Consequence Analysis Methods
Exhibit A-l
Selected References for Information on Consequence Analysis Methods
Center for Process Safety of the American Institute of Chemical Engineers (AIChE). Guidelines for
Evaluating the Characteristics of Vapor Cloud Explosions, Flash Fires, andBLEVEs. New York:
AIChE, 1994.
Center for Process Safety of the American Institute of Chemical Engineers (AIChE). Guidelines for Use of
Vapor Cloud Dispersion Models, Second Ed. New York: AIChE, 1996.
Center for Process Safety of the American Institute of Chemical Engineers (AIChE). International
Conference and Workshop on Modeling and Mitigating the Consequences of Accidental Releases
of Hazardous Materials, September 26-29, 1995. New York: AIChE, 1995.
Federal Emergency Management Agency, U.S. Department of Transportation, U.S. Environmental Protection
Agency. Handbook oj'Chemical Hazard Analysis Procedures. 1989.
Madsen, Warren W. and Robert C. Wagner. "An Accurate Methodology for Modeling the Characteristics of
Explosion Effects." Process Safety Progress, 13 (July 1994), 171-175.
Mercx, W.P.M., D.M. Johnson, and J. Puttock. "Validation of Scaling Techniques for Experimental Vapor
Cloud Explosion Investigations." Process Safety Progress, 14 (April 1995), 120.
Mercx, W.P.M., R.M.M. van Wees, and G. Opschoor. "Current Research at TNO on Vapor Cloud Explosion
Modelling." Process Safety Progress, 12 (October 1993), 222.
Prugh, Richard W. "Quantitative Evaluation of Fireball Hazards." Process Safety Progress, 13 (April
1994), 83-91.
Scheuermann, Klaus P. "Studies About the Influence of Turbulence on the Course of Explosions." Process
Safety Progress, 13 (October 1994), 219.
TNO Bureau for Industrial Safety, Netherlands Organization for Applied Scientific Research. Methods for
the Calculation of the Physical Effects. The Hague, the Netherlands: Committee for the Prevention
of Disasters, 1997.
TNO Bureau for Industrial Safety, Netherlands Organization for Applied Scientific Research. Methods for
the Calculation of the Physical Effects of the Escape of Dangerous Material (Liquids and Gases).
Voorburg, the Netherlands: TNO (Commissioned by Directorate-General of Labour), 1980.
TNO Bureau for Industrial Safety, Netherlands Organization for Applied Scientific Research. Methods for
the Calculation of the Physical Effects Resulting from Releases of Hazardous Materials. Rijswijk,
the Netherlands: TNO (Commissioned by Directorate-General of Labour), 1992.
TNO Bureau for Industrial Safety, Netherlands Organization for Applied Scientific Research. Methods for
the Determination of Possible Damage to People and Objects Resulting from Releases of
April 15, 1999 A - 2
-------
Appendix A
References for Consequence Analysis Methods
Hazardous Materials. Rijswijk, the Netherlands: TNO (Commissioned by Directorate-General of
Labour), 1992.
Touma, Jawad S., et al. "Performance Evaluation of Dense Gas Dispersion Models." Journal of Applied
Meteorology, 34 (March 1995), 603-615.
U.S. Environmental Protection Agency, Federal Emergency Management Agency, U.S. Department of
Transportation. Technical Guidance for Hazards Analysis, Emergency Planning for Extremely
Hazardous Substances. December 1987.
U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards. Workbook of
Screening Techniques for Assessing Impacts of Toxic Air Pollutants. EPA-450/4-88-009.
September 1988.
U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards. Guidance on the
Application of Refined Dispersion Models for Hazardous/Toxic Air Release. EPA-454/R-93-002.
May 1993.
U.S. Environmental Protection Agency, Office of Pollution Prevention and Toxic Substances. Flammable
Gases and Liquids and Their Hazards. EPA 744-R-94-002. February 1994.
April 15, 1999 A - 3
-------
APPENDIX B
TOXIC SUBSTANCES
April 15, 1999
-------
APPENDIX B TOXIC SUBSTANCES
B.I Data for Toxic Substances
The exhibits in this section of Appendix B provide the data needed to carry out the calculations for
regulated toxic substances using the methods presented in the text of this guidance. Exhibit B-l presents
data for toxic gases, Exhibit B-2 presents data for toxic liquids, and Exhibit B-3 presents data for several
toxic substances commonly found in water solution and for oleum. Exhibit B-4 provides temperature
correction factors that can be used to correct the release rates estimated for pool evaporation of toxic liquids
that are released at temperatures between 25 °C to 50 °C.
The derivation of the factors presented in Exhibits B-l - B-4 is discussed in Appendix D. The data
used to develop the factors in Exhibits B-l and B-2 are primarily from Design Institute for Physical Property
Data (DIPPR), American Institute of Chemical Engineers, Physical and Thermodynamic Properties of Pure
Chemicals, Data Compilation. Other sources, including the National Library of Medicine's Hazardous
Substances Databank (HSDB) and the Kirk-Othmer Encyclopedia of Chemical Technology, were used for
Exhibits B-1 and B-2 if data were not available from the DIPPR compilation. The factors in Exhibit B-3
were developed using data primarily from Perry's Chemical Engineers' Handbook and the Kirk-Othmer
Encyclopedia of Chemical Technology. The temperature correction factors in Exhibit B-4 were developed
using vapor pressure data derived from the vapor pressure coefficients in the DIPPR compilation.
April 15, 1999
-------
Exhibit B-l
Data for Toxic Gases
CAS
Number
7664-41-7
7784-42-1
10294-34-5
7637-07-2
7782-50-5
10049-04-4
506-77-4
19287-45-7
75-21-8
7782-41-4
50-00-0
74-90-8
7647-01-0
7664-39-3
7783-07-5
7783-06-4
74-87-3
74-93-1
10102-43-9
75-44-5
Chemical Name
Ammonia (anhydrous)0
Arsine
Boron trichloride
Boron trifluoride
Chlorine
Chlorine dioxide
Cyanogen chloride
Diborane
Ethylene oxide
Fluorine
Formaldehyde (anhydrous)0
Hydrocyanic acid
Hydrogen chloride
(anhydrous)0
Hydrogen fluoride
(anhydrous)0
Hydrogen selenide
Hydrogen sulfide
Methyl chloride
Methyl mercaptan
Nitric oxide
Phosgene
Molecular
Weight
17.03
77.95
117.17
67.81
70.91
67.45
61.47
27.67
44.05
38.00
30.03
27.03
36.46
20.01
80.98
34.08
50.49
48.11
30.01
98.92
Ratio of
Specific
Heats
1.31
1.28
1.15
1.20
1.32
1.25
1.22
1.17
1.21
1.36
1.31
1.30
1.40
1.40
1.32
1.32
1.26
1.20
1.38
1.17
Toxic Endpoint3
mg/L
0.14
0.0019
0.010
0.028
0.0087
0.0028
0.030
0.0011
0.090
0.0039
0.012
0.011
0.030
0.016
0.00066
0.042
0.82
0.049
0.031
0.00081
ppm
200
0.6
2
10
3
1
12
1
50
2.5
10
10
20
20
0.2
30
400
25
25
0.2
Basis
ERPG-2
EHS-LOC (IDLH)
EHS-LOC (Toxe)
EHS-LOC (IDLH)
ERPG-2
EHS-LOC
equivalent (IDLH)8
EHS-LOC
equivalent (Tox)
ERPG-2
ERPG-2
EHS-LOC (IDLH)
ERPG-2
ERPG-2
ERPG-2
ERPG-2
EHS-LOC (IDLH)
ERPG-2
ERPG-2
ERPG-2
EHS-LOC (TLVj)
ERPG-2
Liquid Factor
Boiling
(LFB)
0.073
0.23
0.22
0.25
0.19
0.15
0.14
0.13
0.12
0.35
0.10
0.079
0.15
0.066
0.21
0.13
0.14
0.12
0.21
0.20
Density
Factor (DF)
(Boiling)
0.71
0.30
0.36
0.31
0.31
0.30
0.41
1.13
0.55
0.32
0.59
0.72
0.41
0.51
0.25
0.51
0.48
0.55
0.38
0.35
Gas
Factor
(GF)k
14
30
36
28
29
28
26
17
22
22
19
18
21
16
31
20
24
23
19
33
Vapor
Pressure
@25 °C (psia)
145
239
22.7
f
113
24.3
23.7
f
25.4
f
75.2
14.8
684
17.7
151
302
83.2
29.2
f
27.4
Reference
Table"
Buoyant4
Dense
Dense
Dense
Dense
Dense
Dense
Buoyant4
Dense
Dense
Dense
Buoyant4
Dense
Buoyant1
Dense
Dense
Dense
Dense
Dense
Dense
April 15, 1999
B-2
-------
Exhibit B-l (continued)
CAS
Number
7803-51-2
7446-09-5
7783-60-0
Chemical Name
Phosphine
Sulfur dioxide (anhydrous)
Sulfur tetrafluoride
Molecular
Weight
34.00
64.07
108.06
Ratio of
Specific
Heats
1.29
1.26
1.30
Toxic Endpoint3
mg/L
0.0035
0.0078
0.0092
ppm
2.5
3
2
Basis
ERPG-2
ERPG-2
EHS-LOC (Toxe)
Liquid Factor
Boiling
(LFB)
0.15
0.16
0.25
Density
Factor (DF)
(Boiling)
0.66
0.33
0.25
(at -73 °C)
Gas
Factor
(GF)k
20
27
36
Vapor
Pressure
@25 °C (psia)
567
58.0
293
Reference
Table"
Dense
Dense
Dense
Notes:
a Toxic endpoints are specified in Appendix A to 40 CFR part 68 in units of mg/L. To convert from units of mg/L to mg/m3, multiply by 1,000. To convert mg/L to
ppm, use the following equation:
Endpoint
ppm
EndpointmgjL x 1,000 x 24.5
Molecular Weight
b "Buoyant" in the Reference Table column refers to the tables for neutrally buoyant gases and vapors; "Dense" refers to the tables for dense gases and vapors. See
Appendix D, Section D.4.4, for more information on the choice of reference tables.
0 See Exhibit B-3 of this appendix for data on water solutions.
Gases that are lighter than air may behave as dense gases upon release if liquefied under pressure or cold; consider the conditions of release when choosing the
appropriate table.
e LOG is based on the IDLH-equivalent level estimated from toxicity data.
f Cannot be liquefied at 25 °C.
8 Not an EHS; LOC-equivalent value was estimated from one-tenth of the IDLH.
h Not an EHS; LOC-equivalent value was estimated from one-tenth of the IDLH-equivalent level estimated from toxicity data.
1 Hydrogen fluoride is lighter than air, but may behave as a dense gas upon release under some circumstances (e.g., release under pressure, high concentration in the
released cloud) because of hydrogen bonding; consider the conditions of release when choosing the appropriate table.
J LOG based on Threshold Limit Value (TLV) - Time-weighted average (TWA) developed by the American Conference of Governmental Industrial Hygienists
(ACGIH).
Use GF for gas leaks under choked (maximum) flow conditions.
April 15, 1999
B-3
-------
Exhibit B-2
Data for Toxic Liquids
CAS
Number
107-02-8
107-13-1
814-68-6
107-18-6
107-11-9
7784-34-1
353-42-4
7726-95-6
75-15-0
67-66-3
542-88-1
107-30-2
4170-30-3
123-73-9
108-91-8
75-78-5
57-14-7
106-89-8
107-15-3
151-56-4
110-00-9
302-01-2
Chemical Name
Acrolein
Acrylonitrile
Acrylyl chloride
Allyl alcohol
Allylamine
Arsenous trichloride
Boron trifluoride compound
with methyl ether (1:1)
Bromine
Carbon disulfide
Chloroform
Chloromethyl ether
Chloromethyl methyl ether
Crotonaldehyde
Crotonaldehyde, (E)-
Cyclohexylamine
Dimethyldichlorosilane
1 , 1 -Dimethylhydrazine
Epichlorohydrin
Ethylenediamine
Ethyleneimine
Furan
Hvdrazine
Molecular
Weight
56.06
53.06
90.51
58.08
57.10
181.28
113.89
159.81
76.14
119.38
114.96
80.51
70.09
70.09
99.18
129.06
60.10
92.53
60.10
43.07
68.08
32.05
Vapor
Pressure
at 25 °C
(mmHg)
274
108
110
26.1
242
10
11
212
359
196
29.4
199
33.1
33.1
10.1
141
157
17.0
12.2
211
600
14.4
Toxic Endpoint3
mg/L
0.0011
0.076
0.00090
0.036
0.0032
0.01
0.023
0.0065
0.16
0.49
0.00025
0.0018
0.029
0.029
0.16
0.026
0.012
0.076
0.49
0.018
0.0012
0.011
ppm
0.5
35
0.2
15
1
1
5
1
50
100
0.05
0.6
10
10
39
5
5
20
200
10
0.4
8
Basis
ERPG-2
ERPG-2
EHS-LOC (Toxc)
EHS-LOC (IDLH)
EHS-LOC (Toxc)
EHS-LOC (Toxc)
EHS-LOC (Toxc)
ERPG-2
ERPG-2
EHS-LOC (IDLH)
EHS-LOC (Toxc)
EHS-LOC (Toxc)
ERPG-2
ERPG-2
EHS-LOC (Toxc)
ERPG-2
EHS-LOC (IDLH)
ERPG-2
EHS-LOC (IDLH)
EHS-LOC (IDLH)
EHS-LOC (Toxc)
EHS-LOC (IDLH)
Liquid Factors
Ambient
(LFA)
0.047
0.018
0.026
0.0046
0.042
0.0037
0.0030
0.073
0.075
0.055
0.0080
0.043
0.0066
0.0066
0.0025
0.042
0.028
0.0040
0.0022
0.030
0.12
0.0017
Boiling
(LFB)
0.12
0.11
0.15
0.11
0.12
0.21
0.16
0.23
0.15
0.19
0.17
0.15
0.12
0.12
0.14
0.20
0.12
0.14
0.13
0.10
0.14
0.069
Density
Factor
(DF)
0.58
0.61
0.44
0.58
0.64
0.23
0.49
0.16
0.39
0.33
0.37
0.46
0.58
0.58
0.56
0.46
0.62
0.42
0.54
0.58
0.52
0.48
Liquid
Leak
Factor
(LLF)1
40
39
54
41
36
100
48
150
60
71
63
51
41
41
41
51
38
57
43
40
45
48
Reference Tableb
Worst
Case
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Buoyant
Alternative
Case
Dense
Dense
Dense
Buoyant
Dense
Buoyant
Buoyant
Dense
Dense
Dense
Dense
Dense
Buoyant
Buoyant
Buoyant
Dense
Dense
Buoyant
Buoyant
Dense
Dense
Buoyant
April 15, 1999
B-4
-------
Exhibit B-2 (continued)
CAS
Number
13463-40-6
78-82-0
108-23-6
126-98-7
79-22-1
60-34-4
624-83-9
556-64-9
75-79-6
13463-39-3
7697-37-2
79-21-0
594-42-3
10025-87-3
7719-12-2
110-89-4
107-12-0
109-61-5
75-55-8
75-56-9
7446-11-9
75-74-1
509-14-8
Chemical Name
Iron, pentacarbonyl-
Isobutyronitrile
Isopropyl chloroformate
Methacrylonitrile
Methyl chloroformate
Methyl hydrazine
Methyl isocyanate
Methyl thiocyanate
Methyltrichlorosilane
Nickel carbonyl
Nitric acid (100%)f
Peracetic acid
Perchloromethylmercaptan
Phosphorus oxychloride
Phosphorus trichloride
Piperidine
Propionitrile
Propyl chloroformate
Propyleneimine
Propylene oxide
Sulfur trioxide
Tetramethyllead
Tetranitromethane
Molecular
Weight
195.90
69.11
122.55
67.09
94.50
46.07
57.05
73.12
149.48
170.73
63.01
76.05
185.87
153.33
137.33
85.15
55.08
122.56
57.10
58.08
80.06
267.33
196.04
Vapor
Pressure
at 25 °C
(mmHg)
40
32.7
28
71.2
108
49.6
457
10
173
400
63.0
13.9
6
35.8
120
32.1
47.3
20.0
187
533
263
22.5
11.4
Toxic Endpoint3
mg/L
0.00044
0.14
0.10
0.0027
0.0019
0.0094
0.0012
0.085
0.018
0.00067
0.026
0.0045
0.0076
0.0030
0.028
0.022
0.0037
0.010
0.12
0.59
0.010
0.0040
0.0040
ppm
0.05
50
20
1
0.5
5
0.5
29
3
0.1
10
1.5
1
0.5
5
6
1.6
2
50
250
3
0.4
0.5
Basis
EHS-LOC (Toxc)
ERPG-2
EHS-LOC (Toxc)
EHS-LOC (TLVe)
EHS-LOC (Toxc)
EHS-LOC (IDLH)
ERPG-2
EHS-LOC (Toxc)
ERPG-2
EHS-LOC (Toxc)
EHS-LOC (Toxc)
EHS-LOC (Toxc)
EHS-LOC (IDLH)
EHS-LOC (Toxc)
EHS-LOC (IDLH)
EHS-LOC (Toxc)
EHS-LOC (Toxc)
EHS-LOC (Toxc)
EHS-LOC (IDLH)
ERPG-2
ERPG-2
EHS-LOC (IDLH)
EHS-LOC (IDLH)
Liquid Factors
Ambient
(LFA)
0.016
0.0064
0.0080
0.014
0.026
0.0074
0.079
0.0020
0.057
0.14
0.012
0.0029
0.0023
0.012
0.037
0.0072
0.0080
0.0058
0.032
0.093
0.057
0.011
0.0045
Boiling
(LFB)
0.24
0.12
0.17
0.12
0.16
0.094
0.13
0.11
0.22
0.26
0.12
0.12
0.20
0.20
0.20
0.13
0.10
0.17
0.12
0.13
0.15
0.29
0.22
Density
Factor
(DF)
0.33
0.63
0.45
0.61
0.40
0.56
0.52
0.45
0.38
0.37
0.32
0.40
0.29
0.29
0.31
0.57
0.63
0.45
0.61
0.59
0.26
0.24
0.30
Liquid
Leak
Factor
(LLF)1
70
37
52
38
58
42
45
51
61
63
73
58
81
80
75
41
37
52
39
40
91
96
78
Reference Tableb
Worst
Case
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Alternative
Case
Dense
Buoyant
Dense
Dense
Dense
Buoyant
Dense
Buoyant
Dense
Dense
Dense
Buoyant
Buoyant
Dense
Dense
Buoyant
Buoyant
Buoyant
Dense
Dense
Dense
Dense
Buoyant
April 15, 1999
B-5
-------
Exhibit B-2 (continued)
CAS
Number
7550-45-0
584-84-9
91-08-7
26471-62-5
75-77-4
108-05-4
Chemical Name
Titanium tetrachloride
Toluene 2,4-diisocyanate
Toluene 2,6-diisocyanate
Toluene diisocyanate
(unspecified isomer)
Trimethylchlorosilane
Vinyl acetate monomer
Molecular
Weight
189.69
174.16
174.16
174.16
108.64
86.09
Vapor
Pressure
at 25 °C
(mmHg)
12.4
0.017
0.05
0.017
231
113
Toxic Endpoint3
mg/L
0.020
0.0070
0.0070
0.0070
0.050
0.26
ppm
2.6
1
1
1
11
75
Basis
ERPG-2
EHS-LOC (IDLH)
EHS-LOC (IDLH8)
EHS-LOC equivalent
(IDLH11)
EHS-LOC (Toxc)
ERPG-2
Liquid Factors
Ambient
(LFA)
0.0048
0.000006
0.000018
0.000006
0.061
0.026
Boiling
(LFB)
0.21
0.16
0.16
0.16
0.18
0.15
Density
Factor
(DF)
0.28
0.40
0.40
0.40
0.57
0.53
Liquid
Leak
Factor
(LLF)1
82
59
59
59
41
45
Reference Tableb
Worst
Case
Dense
Buoyant
Buoyant
Buoyant
Dense
Dense
Alternative
Case
Buoyant
Buoyant
Buoyant
Buoyant
Dense
Dense
Notes:
a Toxic endpoints are specified in the Appendix A to 40 CFR part 68 in units of mg/L. To convert from units of mg/L to mg/m3, multiply by 1,000. To convert mg/L
to ppm, use the following equation:
Endpoint
Endpoint
'mg/L
1,000 x 24.5
ppm
Molecular Weight
b "Buoyant" in the Reference Table column refers to the tables for neutrally buoyant gases and vapors; "Dense" refers to the tables for dense gases and vapors. See
Appendix D, Section D.4.4, for more information on the choice of reference tables.
0 LOG is based on IDLH-equivalent level estimated from toxicity data.
Use dense gas table if substance is at an elevated temperature.
e LOG based on Threshold Limit Value (TLV) - Time-weighted average (TWA) developed by the American Conference of Governmental Industrial Hygienists
(ACGIH).
f See Exhibit B-3 of this appendix for data on water solutions.
8 LOG for this isomer is based on IDLH for toluene 2,4-diisocyanate.
h Not an EHS; LOC-equivalent value is based on IDLH for toluene 2,4-diisocyanate.
1 Use the LLF only for leaks from tanks at atmospheric pressure.
April 15, 1999
B-6
-------
Exhibit B-3
Data for Water Solutions of Toxic Substances and for Oleum
For Wind Speeds of 1.5 and 3.0 Meters per Second (m/s)
CAS
Number
7664-41-7
50-00-0
7647-01-0
7664-39-3
7697-37-2
8014-95-7
Regulated
Substance
in Solution
Ammonia
Formaldehyde
Hydrochloric
acid
Hydrofluoric
acid
Nitric acid
Oleum - based
onSO3
Molecular
Weight
17.03
30.027
36.46
20.01
63.01
80.06
(S03)
Toxic Endpoint3
mg/L
0.14
0.012
0.030
0.016
0.026
0.010
ppm
200
10
20
20
10
3
Basis
ERPG-2
ERPG-2
ERPG-2
ERPG-2
EHS-
LOC
(IDLH)
ERPG-2
Initial
Concen-
tration
(Wt %)
30
24
20
37
38
37
36C
34C
30C
70
50
90
85
80
30 (SO3)
10-min. Average Vapor
Pressure (nun Hg)
1.5 m/s
332
241
190
1.5
78
67
56
38
13
124
16
25
17
10.2
3.5 (S03)
3.0 m/s
248
184
148
1.4
55
48
42
29
12
107
15
22
16
10
3.4 (S03)
Liquid Factor at 25° C
(LFA)
1.5 m/s
0.026
0.019
0.015
0.0002
0.010
0.0085
0.0072
0.0048
0.0016
0.011
0.0014
0.0046
0.0032
0.0019
0.0008
3.0 m/s
0.019
0.014
0.011
0.0002
0.0070
0.0062
0.0053
0.0037
0.0015
0.010
0.0013
0.0040
0.0029
0.0018
0.0007
Density
Factor
(DF)
0.55
0.54
0.53
0.44
0.41
0.42
0.42
0.42
0.42
0.39
0.41
0.33
0.33
0.33
0.25
Liquid
Leak
Factor
(LLF)
43
44
44
53
57
57
57
56
55
61
58
71
70
70
93
Reference Tableb
Worst
Buoyant
Buoyant
Buoyant
Buoyant
Dense
Dense
Dense
Dense
Buoyant
Buoyant
Buoyant
Dense
Dense
Dense
Buoyant
Alternative
Buoyant
Buoyant
Buoyant
Buoyant
Buoyant d
Buoyant d
Buoyant d
Buoyant d
Buoyant d
Buoyant
Buoyant
Buoyant d
Buoyant d
Buoyant d
Buoyant d
Notes:
a Toxic endpoints are specified in the Appendix A to 40 CFR part 68 in units of mg/L. See Notes to Exhibit B-l or B-2 for converting to other units.
b "Buoyant" in the Reference Table column refers to the tables for neutrally buoyant gases and vapors; "Dense" refers to the tables for dense gases and vapors. See
Appendix D, Section D.4.4, for more information on the choice of reference tables.
0 Hydrochloric acid in concentrations below 37 percent is not regulated.
d Use dense gas table if substance is at an elevated temperature.
April 15, 1999
B-7
-------
Exhibit B-4
Temperature Correction Factors for Liquids Evaporating from Pools at Temperatures
Between 25 °C and 50 °C (77 °F and 122 °F)
CAS
Number
107-02-8
107-13-1
814-68-6
107-18-6
107-11-9
7784-34-1
353-42-4
7726-95-6
75-15-0
67-66-3
542-88-1
107-30-2
4170-30-3
123-73-9
108-91-8
75-78-5
57-14-7
106-89-8
107-15-3
151-56-4
110-00-9
302-01-2
13463-40-6
78-82-0
108-23-6
126-98-7
79-22-1
60-34-4
624-83-9
556-64-9
75-79-6
Chemical Name
Acrolein
Acrylonitrile
Acrylyl chloride
Allyl alcohol
Allylamine
Arsenous trichloride
Boron trifluoride compound with
methyl ether (1:1)
Bromine
Carbon disulfide
Chloroform
Chloromethyl ether
Chloromethyl methyl ether
Crotonaldehyde
Crotonaldehyde, (E)-
Cyclohexylamine
Dimethyldichlorosilane
1 , 1 -Dimethylhydrazine
Epichlorohydrin
Ethylenediamine
Ethyleneimine
Fur an
Hydrazine
Iron, pentacarbonyl-
Isobutyronitrile
Isopropyl chloroformate
Methacrylonitrile
Methyl chloroformate
Methyl hydrazine
Methyl isocyanate
Methyl thiocyanate
Methyltrichlorosilane
Boiling
Point
(°C)
52.69
77.35
75.00
97.08
53.30
130.06
126.85
58.75
46.22
61.18
104.85
59.50
104.10
102.22
134.50
70.20
63.90
118.50
36.26
55.85
31.35
113.50
102.65
103.61
104.60
90.30
70.85
87.50
38.85
130.00
66.40
Temperature Correction Factor (TCP)
30 °C
(86 °F)
1.2
1.2
ND
1.3
1.2
ND
ND
1.2
1.2
1.2
1.3
1.2
1.3
1.3
1.3
1.2
ND
1.3
1.3
1.2
1.2
1.3
ND
1.3
ND
1.2
1.3
ND
1.2
ND
1.2
35 °C
(95 °F)
1.4
1.5
ND
1.7
1.5
ND
ND
1.5
1.4
1.5
1.6
1.5
1.6
1.6
1.7
1.5
ND
1.7
1.8
1.5
LFB
1.7
ND
1.6
ND
1.5
1.6
ND
1.4
ND
1.4
40 °C
(104 °F)
1.7
1.8
ND
2.2
1.8
ND
ND
1.7
1.6
1.8
2.0
1.8
2.0
2.0
2.1
1.8
ND
2.1
LFB
1.8
LFB
2.2
ND
2.0
ND
1.8
1.9
ND
LFB
ND
1.7
45 °C
(113°F)
2.0
2.1
ND
2.9
2.1
ND
ND
2.1
1.9
2.1
2.5
2.1
2.5
2.5
2.7
2.1
ND
2.7
LFB
2.2
LFB
2.9
ND
2.5
ND
2.2
2.4
ND
LFB
ND
2.0
50 °C
(122 °F)
2.3
2.5
ND
3.6
2.5
ND
ND
2.5
LFB
2.5
3.1
2.5
3.1
3.1
3.4
2.5
ND
3.4
LFB
2.7
LFB
3.6
ND
3.1
ND
2.6
2.9
ND
LFB
ND
2.4
April 15, 1999
B-8
-------
Exhibit B-4 (continued)
CAS
Number
13463-39-3
7697-37-2
79-21-0
594-42-3
10025-87-3
7719-12-2
110-89-4
107-12-0
109-61-5
75-55-8
75-56-9
7446-11-9
75-74-1
509-14-8
7550-45-0
584-84-9
91-08-7
26471-62-5
75-77-4
108-05-4
Chemical Name
Nickel carbonyl
Nitric acid
Peracetic acid
Perchloromethylmercaptan
Phosphorus oxychloride
Phosphorus trichloride
Piperidine
Propionitrile
Propyl chloroformate
Propyleneimine
Propylene oxide
Sulfur trioxide
Tetramethyllead
Tetranitromethane
Titanium tetrachloride
Toluene 2,4-diisocyanate
Toluene 2,6-diisocyanate
Toluene diisocyanate (unspecified
isomer)
Trimethylchlorosilane
Vinyl acetate monomer
Boiling
Point
(°C)
42.85
83.00
109.85
147.00
105.50
76.10
106.40
97.35
112.40
60.85
33.90
44.75
110.00
125.70
135.85
251.00
244.85
250.00
57.60
72.50
Temperature Correction Factor (TCP)
30 °C
(86 °F)
ND
1.3
1.3
ND
1.3
1.2
1.3
1.3
ND
1.2
1.2
1.3
ND
1.3
1.3
1.6
ND
1.6
1.2
1.2
35 °C
(95 °F)
ND
1.6
1.8
ND
1.6
1.5
1.6
1.6
ND
1.5
LFB
1.7
ND
1.7
1.6
2.4
ND
2.4
1.4
1.5
40 °C
(104 °F)
ND
2.0
2.3
ND
1.9
1.8
2.0
1.9
ND
1.8
LFB
LFB
ND
2.2
2.0
3.6
ND
3.6
1.7
1.9
45 °C
(113°F)
ND
2.5
3.0
ND
2.4
2.1
2.4
2.3
ND
2.1
LFB
LFB
ND
2.8
2.6
5.3
ND
5.3
2.0
2.3
50 °C
(122 °F)
ND
3.1
3.8
ND
2.9
2.5
3.0
2.8
ND
2.5
LFB
LFB
ND
3.5
3.2
7.7
ND
7.7
2.3
2.7
Notes:
ND:
LFB:
No data available.
Chemical above boiling point at this temperature; use LFB for analysis.
April 15, 1999
B-9
-------
Appendix B
Toxic Substances _
B.2 Mixtures Containing Toxic Liquids
In case of a spill of a liquid mixture containing a regulated toxic substance (with the exception of
common water solutions, discussed in Section 3.3 in the text), the area of the pool formed by the entire liquid
spill is determined as described in Section 3.2.2 or 3.2.3. For the area determination, if the density of the
mixture is unknown, the density of the regulated substance in the mixture may be assumed as the density of
the entire mixture.
If the partial vapor pressure of the regulated substance in the mixture is known, that vapor pressure
may be used to derive a release rate using the equations in Section 3.2. If the partial vapor pressure of the
regulated toxic substance in the mixture is unknown, it may be estimated from the vapor pressure of the pure
substance (listed in Exhibit B-2, Appendix B) and the concentration in the mixture, if you assume the mixture
is an ideal solution, where an ideal solution is one in which there is complete uniformity of cohesive forces.
This method may overestimate or underestimate the partial pressure for a regulated substance that interacts
with the other components of a mixture or solution. For example, water solutions are generally not ideal.
This method is likely to overestimate the partial pressure of regulated substances in water solution if there is
hydrogen bonding in the solution (e.g., solutions of acids or alcohols in water).
To estimate partial pressure for a regulated substance in a mixture or solution, use the following
steps, based on Raoult's Law for ideal solutions:
• Determine the mole fraction of the regulated substance in the mixture.
The mole fraction of the regulated substance in the mixture is the number of moles
of the regulated substance in the mixture divided by the total number of moles of all
substances in the mixture.
If the molar concentration (moles per liter) of each component of the mixture is
known, the mole fraction may be determined as follows:
Mr x v
xr = — : -
(B-l)
or (canceling out Vt):
Mr
(B-2)
April 15, 1999 B - 10
-------
Appendix B
Toxic Substances
where: X,. = Mole fraction of regulated substance in mixture (unitless)
Mr = Molar concentration of regulated substance in mixture (moles per liter)
Vt = Total volume of mixture (liters)
n = Number of components of mixture
M; = Molar concentration of each component of mixture (moles per liter)
For a mixture with three components, this would correspond to:
M
r
M2
(B-3)
where: X,. = Mole fraction of regulated substance in mixture (unitless)
Mr = Molar concentration of regulated substance (first component) in mixture
(moles per liter)
M2 = Molar concentration of second component of mixture (moles per liter)
M3 = Molar concentration of any other components of mixture (moles per liter)
If the weight of each of the components of the mixture is known, the mole fraction
of the regulated substance in the mixture may be calculated as follows:
wr
X. =
MW
r i
r
T
7~t(MWi
where: X,. = Mole fraction of the regulated substance
Wr = Weight of the regulated substance
MWr = Molecular weight of the regulated substance
n = Number of components of the mixture
W; = Weight of each component of the mixture
MWj = Molecular weight of each component of the mixture
(Note: Weights can be in any consistent units.)
For a mixture with three components, this corresponds to:
(B-4)
MW
r
_»?,
MW
(B-5)
MW
2
April 15, 1999 B - 11
-------
Appendix B
Toxic Substances
where:
Xr
Wr
MWr
W2
MW2
W3
MW
Mole fraction of the regulated substance
Weight of the regulated substance (first component of the mixture)
Molecular weight of the regulated substance
Weight of the second component of the mixture
Molecular weight of the second component of the mixture
Weight of the third component of the mixture
Molecular weight of the third component of the mixture
(Note: Weights can be in any consistent units.)
Estimate the partial vapor pressure of the regulated substance in the mixture as follows:
VP
(B-6)
where: VP
VP
Partial vapor pressure of the regulated substance in the mixture (millimeters
of mercury (mm Hg))
Mole fraction of the regulated substance (unitless)
Vapor pressure of the regulated substance in pure form at the same
temperature as the mixture (mm Hg) (vapor pressure at 25 °C is given in
Exhibit B-l, Appendix B)
The evaporation rate for the regulated substance in the mixture is determined as for pure substances,
with VPm as the vapor pressure. If the mixture contains more than one regulated toxic substance, carry out
the analysis individually for each of the regulated components. The release rate equation is:
0.0035
A x VP
where: QR
U
MW
A
VP
T
Evaporation rate (pounds per minute)
Wind speed (meters per second)
Molecular weight (given in Exhibit B-2, Appendix B)
Surface area of pool formed by the entire quantity of the mixture (square
feet) (determined as described in 3.2.2)
Vapor pressure (mm Hg) (VPm from Equation B-4 above)
Temperature (Kelvin (K); temperature in °C plus 273, or 298 for 25 °C)
See Appendix D, Section D.2. 1 for more discussion of the evaporation rate equation. Equation B-7
is derived from Equation D- 1 .
Worst-case consequence distances to the toxic endpoint may be estimated from the release rate using
the tables and instructions presented in Chapter 4.
April 15, 1999
B - 12
-------
APPENDIX C
FLAMMABLE SUBSTANCES
April 15, 1999
-------
APPENDIX C FLAMMABLE SUBSTANCES
C.I Equation for Estimation of Distance to 1 psi Overpressure for Vapor Cloud
Explosions
For a worst-case release of flammable gases and volatile flammable liquids, the release rate is not
considered. The total quantity of the flammable substance is assumed to form a vapor cloud. The entire
contents of the cloud is assumed to be within the flammability limits, and the cloud is assumed to explode.
For the worst-case, analysis, 10 percent of the flammable vapor in the cloud is assumed to participate in the
explosion (i.e., the yield factor is 0. 10). Consequence distances to an overpressure level of 1 pound per
square inch (psi) may be determined using the following equation, which is based on the TNT-equivalency
method:
( HCf } 1/3
D = 17 x o.l x Wfx -—J-\ (C-l)
^ NLTNT)
where: D = Distance to overpressure of 1 psi (meters)
Wf = Weight of flammable substance (kilograms or pounds/2.2)
Hcf = Heat of combustion of flammable substance (kilojoules per kilogram)
(listed in Exhibit C-l)
HCTNT = Heat of explosion of trinitrotoluene (TNT) (4,680 kilojoules per kilogram)
The factor 17 is a constant for damages associated with 1.0 psi overpressures. The factor 0. 1
represents an explosion efficiency of 10 percent. To convert distances from meters to miles, multiply
by 0.00062.
Alternatively, use the following equation for quantity in pounds and distance in miles:
HCf
D = 0.0081 x o.l x w,, x - f—
mi Ib
where: Dmi = Distance to overpressure of 1 psi (miles)
Wlb = Weight of flammable substance (pounds)
These equations were used to derive Reference Table 13 for worst-case distances to the overpressure
endpoint (1 psi) for vapor cloud explosions.
C.2 Mixtures of Flammable Substances
For a mixture of flammable substances, you may estimate the heat of combustion of the mixture from
the heats of combustion of the components of the mixture using the equation below and then use the equation
given in the previous section of this appendix to determine the vapor cloud explosion distance. The heat of
combustion of the mixture may be estimated as follows:
April 15, 1999
-------
Appendix C
Flammable Substances
w
HCm = -^
m W,
^
HC + -
x W,
HC,,
(C-3)
where:
HCm
Wx
wm
HCX
wy
HCy
Heat of combustion of mixture (kilojoules per kilogram)
Weight of component "X" in mixture (kilograms or pounds/2.2)
Total weight of mixture (kilograms or pounds/2.2)
Heat of combustion of component "X" (kilojoules per kilogram)
Weight of component "Y" in mixture (kilograms or pounds/2.2)
Heat of combustion of component "Y" (kilojoules per kilogram)
Heats of combustion for regulated flammable substances are listed in Exhibit C-1 in the next section
(Section C.3) of this appendix.
C.3 Data for Flammable Substances
The exhibits in this section of Appendix C provide the data needed to carry out the calculations for
regulated flammable substances using the methods presented in the text of this guidance. Exhibit C-l
presents heat of combustion data for all regulated flammable substances, Exhibit C-2 presents additional data
for flammable gases, and Exhibit C-3 presents additional data for flammable liquids. The heats of
combustion in Exhibit C-l and the data used to develop the factors in Exhibits C-2 and C-3 are primarily
from Design Institute for Physical Property Data, American Institute of Chemical Engineers, Physical and
Thermodynamic Properties of Pure Chemicals, Data Compilation. The derivation of the factors presented
in Exhibits C-2 and C-3 is discussed in Appendix D.
April 15, 1999
C-2
-------
Exhibit C-l
Heats of Combustion for Flammable Substances
CAS No.
75-07-0
74-86-2
598-73-2
106-99-0
106-97-8
25167-67-3
590-18-1
624-64-6
106-98-9
107-01-7
463-58-1
7791-21-1
590-21-6
557-98-2
460-19-5
75-19-4
4109-96-0
75-37-6
124-40-3
463-82-1
74-84-0
107-00-6
75-04-7
75-00-3
74-85-1
Chemical Name
Acetaldehyde
Acetylene [Ethyne]
Bromotrifluoroethylene [Ethene, bromotrifluoro-]
1,3 -Butadiene
Butane
Butene
2-Butene-cis
2-Butene-trans [2-Butene, (E)]
1 -Butene
2-Butene
Carbon oxysulfide [Carbon oxide sulfide (COS)]
Chlorine monoxide [Chlorine oxide]
1-Chloropropylene [1-Propene, 1-chloro-]
2-Chloropropylene [1-Propene, 2-chloro-]
Cyanogen [Ethanedinitrile]
Cyclopropane
Dichlorosilane [Silane, dichloro-]
Difluoroethane [Ethane, 1,1-difluoro-]
Dimethylamine [Methanamine, N-methyl-]
2,2-Dimethylpropane [Propane, 2,2-dimethyl-]
Ethane
Ethyl acetylene [1-Butyne]
Ethylamine [Ethanamine]
Ethyl chloride [Ethane, chloro-]
Ethylene [Ethene]
Physical
State
at 25° C
Gas
Gas
Gas
Gas
Gas
Gas
Gas
Gas
Gas
Gas
Gas
Gas
Liquid
Gas
Gas
Gas
Gas
Gas
Gas
Gas
Gas
Gas
Gas
Gas
Gas
Heat of
Combustion
(kjoule/kg)
25,072
48,222
1,967
44,548
45,719
45,200*
45,171
45,069
45,292
45,100*
9,126
1,011*
23,000*
22,999
21,064
46,560
8,225
11,484
35,813
45,051
47,509
45,565
35,210
19,917
47,145
April 15, 1999
C-3
-------
Exhibit C-l (continued)
CAS No.
60-29-7
75-08-1
109-95-5
1333-74-0
75-28-5
78-78-4
78-79-5
75-31-0
75-29-6
74-82-8
74-89-5
563-45-1
563-46-2
115-10-6
107-31-3
115-11-7
504-60-9
109-66-0
109-67-1
646-04-8
627-20-3
463-49-0
74-98-6
115-07-1
74-99-7
7803-62-5
Chemical Name
Ethyl ether [Ethane, l,l'-oxybis-]
Ethyl mercaptan [Ethanethiol]
Ethyl nitrite [Nitrous acid, ethyl ester]
Hydrogen
Isobutane [Propane, 2-methyl]
Isopentane [Butane, 2-methyl-]
Isoprene [1,3 -Butadiene, 2-methyl-]
Isopropylamine [2-Propanamine]
Isopropyl chloride [Propane, 2-chloro-]
Methane
Methylamine [Methanamine]
3 -Methyl- 1 -butene
2-Methyl- 1 -butene
Methyl ether [Methane, oxybis-]
Methyl formate [Formic acid, methyl ester]
2-Methylpropene [1-Propene, 2-methyl-]
1,3-Pentadiene
Pentane
1-Pentene
2-Pentene, (E)-
2-Pentene, (Z)-
Propadiene [1,2-Propadiene]
Propane
Propylene [1-Propene]
Propyne [1-Propyne]
Silane
Physical
State
at 25° C
Liquid
Liquid
Gas
Gas
Gas
Liquid
Liquid
Liquid
Liquid
Gas
Gas
Gas
Liquid
Gas
Liquid
Gas
Liquid
Liquid
Liquid
Liquid
Liquid
Gas
Gas
Gas
Gas
Gas
Heat of
Combustion
(kjoule/kg)
33,775
27,948
18,000
119,950
45,576
44,911
43,809
36,484
23,720
50,029
31,396
44,559
44,414
28,835
15,335
44,985
43,834
44,697
44,625
44,458
44,520
46,332
46,333
45,762
46,165
44,307
April 15, 1999
C-4
-------
Exhibit C-l (continued)
CAS No.
116-14-3
75-76-3
10025-78-2
79-38-9
75-50-3
689-97-4
75-01-4
109-92-2
75-02-5
75-35-4
75-38-7
107-25-5
Chemical Name
Tetrafluoroethylene [Ethene, tetrafluoro-]
Tetramethylsilane [Silane, tetramethyl-]
Trichlorosilane [Silane, trichloro-]
Trifluorochloroethylene [Ethene, chlorotrifluoro-]
Trimethylamine [Methanamine, N,N-dimethyl-]
Vinyl acetylene [l-Buten-3-yne]
Vinyl chloride [Ethene, chloro-]
Vinyl ethyl ether [Ethene, ethoxy-]
Vinyl fluoride [Ethene, fluoro-]
Vinylidene chloride [Ethene, 1,1-dichloro-]
Vinylidene fluoride [Ethene, 1,1-difluoro-]
Vinyl methyl ether [Ethene, methoxy-]
Physical
State
at 25° C
Gas
Liquid
Liquid
Gas
Gas
Gas
Gas
Liquid
Gas
Liquid
Gas
Gas
Heat of
Combustion
(kjoule/kg)
1,284
41,712
3,754
1,837
37,978
45,357
18,848
32,909
2,195
10,354
10,807
30,549
' Estimated heat of combustion
April 15, 1999
C-5
-------
Exhibit C-2
Data for Flammable Gases
CAS
Number
75-07-0
74-86-2
598-73-2
106-99-0
106-97-8
25167-67-3
590-18-1
624-64-6
106-98-9
107-01-7
463-58-1
7791-21-1
557-98-2
460-19-5
75-19-4
4109-96-0
75-37-6
124-40-3
463-82-1
74-84-0
107-00-6
75-04-7
Chemical Name
Acetaldehyde
Acetylene
Bromotrifluoroethylene
1,3-Butadiene
Butane
Butene
2-Butene-cis
2-Butene-trans
1 -Butene
2-Butene
Carbon oxysulfide
Chlorine monoxide
2-Chloropropylene
Cyanogen
Cyclopropane
Dichlorosilane
Difluoroethane
Dimethylamine
2,2-Dimethylpropane
Ethane
Ethyl acetylene
Ethvlamine
Molecular
Weight
44.05
26.04
160.92
54.09
58.12
56.11
56.11
56.11
56.11
56.11
60.08
86.91
76.53
52.04
42.08
101.01
66.05
45.08
72.15
30.07
54.09
45.08
Ratio of
Specific
Heats
1.18
1.23
1.11
1.12
1.09
1.10
1.12
1.11
1.11
1.10
1.25
1.21
1.12
1.17
1.18
1.16
1.14
1.14
1.07
1.19
1.11
1.13
Flammability
Limits (Vol %)
Lower
(LFL)
4.0
2.5
C
2.0
1.5
1.7
1.6
1.8
1.6
1.7
12.0
23.5
4.5
6.0
2.4
4.0
3.7
2.8
1.4
2.9
2.0
3.5
Upper
UFL
60.0
80.0
37.0
11.5
9.0
9.5
9.7
9.7
9.3
9.7
29.0
NA
16.0
32.0
10.4
96.0
18.0
14.4
7.5
13.0
32.9
14.0
LFL
(mg/L)
72
27
C
44
36
39
37
41
37
39
290
830
140
130
41
160
100
52
41
36
44
64
Gas
Factor
(GF)S
22
17
41C
24
25
24
24
24
24
24
26
31
29
24
22
33
27
22
27
18
24
22
Liquid
Factor
Boiling
(LFB)
0.11
0.12
0.25C
0.14
0.14
0.14
0.14
0.14
0.14
0.14
0.18
0.19
0.16
0.15
0.13
0.20
0.17
0.12
0.16
0.14
0.13
0.12
Density
Factor
(Boiling)
(DF)
0.62
0.78
0.29C
0.75
0.81
0.77
0.76
0.77
0.78
0.77
0.41
NA
0.54
0.51
0.72
0.40
0.48
0.73
0.80
0.89
0.73
0.71
Reference
Table3
Dense
Buoyant
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Pool Fire
Factor
(PFF)
2.7
4.8
0.42C
5.5
5.9
5.6
5.6
5.6
5.7
5.6
1.3
0.15
3.3
2.5
5.4
1.3
1.6
3.7
6.4
5.4
5.4
3.6
Flash
Fraction
Factor
(FFF/
0.018
0.23f
0.15C
0.15
0.15
0.14
0.11
0.12
0.17
0.12
0.29
NA
0.011
0.40
0.23
0.084
0.23
0.090
0.11
0.75
0.091
0.040
April 15, 1999
C-6
-------
Exhibit C-2 (continued)
CAS
Number
75-00-3
74-85-1
109-95-5
1333-74-0
75-28-5
74-82-8
74-89-5
563-45-1
115-10-6
115-11-7
463-49-0
74-98-6
115-07-1
74-99-7
7803-62-5
116-14-3
79-38-9
75-50-3
689-97-4
75-01-4
75-02-5
75-38-7
Chemical Name
Ethyl chloride
Ethylene
Ethyl nitrite
Hydrogen
Isobutane
Methane
Methylamine
3 -Methyl- 1-butene
Methyl ether
2-Methylpropene
Propadiene
Propane
Propylene
Propyne
Silane
Tetrafluoroethylene
Trifluorochloroethylene
Trimethylamine
Vinyl acetylene
Vinyl chloride
Vinyl fluoride
Vinvlidene fluoride
Molecular
Weight
64.51
28.05
75.07
2.02
58.12
16.04
31.06
70.13
46.07
56.11
40.07
44.10
42.08
40.07
32.12
100.02
116.47
59.11
52.08
62.50
46.04
64.04
Ratio of
Specific
Heats
1.15
1.24
1.30
1.41
1.09
1.30
1.19
1.08
1.15
1.10
1.16
1.13
1.15
1.16
1.24
1.12
1.11
1.10
1.13
1.18
1.20
1.16
Flammability
Limits (Vol %)
Lower
(LFL)
3.8
2.7
4.0
4.0
1.8
5.0
4.9
1.5
3.3
1.8
2.1
2.0
2.0
1.7
C
11.0
8.4
2.0
2.2
3.6
2.6
5.5
Upper
UFL
15.4
36.0
50.0
75.0
8.4
15.0
20.7
9.1
27.3
8.8
2.1
9.5
11.0
39.9
C
60.0
38.7
11.6
31.7
33.0
21.7
21.3
LFL
(mg/L)
100
31
120
3.3
43
33
62
43
64
41
34
36
34
28
C
450
400
48
47
92
49
140
Gas
Factor
(GF)S
27
18
30
5.0
25
14
19
26
22
24
21
22
21
21
19 c
33
35
25
24
26
23
27
Liquid
Factor
Boiling
(LFB)
0.15
0.14
0.16
e
0.15
0.15
0.10
0.15
0.14
0.14
0.13
0.14
0.14
0.12
e
0.29
0.26
0.14
0.13
0.16
0.17
0.22
Density
Factor
(Boiling)
(DF)
0.53
0.85
0.54
e
0.82
1.1
0.70
0.77
0.66
0.77
0.73
0.83
0.79
0.72
e
0.32
0.33
0.74
0.69
0.50
0.57
0.42
Reference
Table3
Dense
Buoyant
Dense
d
Dense
Buoyant
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Pool Fire
Factor
(PFF)
2.6
5.4
2.0
e
6.0
5.6
2.7
6.0
3.4
5.7
5.2
5.7
5.5
4.9
e
0.25
0.34
4.8
5.4
2.4
0.28
1.8
Flash
Fraction
Factor
(FFF/
0.053
0.63f
NA
NA
0.23
0.87f
0.12
0.030
0.22
0.18
0.20
0.38
0.35
0.18
0.41f
0.69
0.27
0.12
0.086
0.14
0.37
0.50
April 15, 1999
C-7
-------
Exhibit C-2 (continued)
CAS
Number
107-25-5
Chemical Name
Vinyl methyl ether
Molecular
Weight
58.08
Ratio of
Specific
Heats
1.12
Flammability
Limits (Vol %)
Lower
(LFL)
2.6
Upper
UFL
39.0
LFL
(mg/L)
62
Gas
Factor
(GF)S
25
Liquid
Factor
Boiling
(LFB)
0.17
Density
Factor
(Boiling)
(DF)
0.57
Reference
Table3
Dense
Pool Fire
Factor
(PFF)
3.7
Flash
Fraction
Factor
(FFF/
0.093
Notes:
NA: Data not available
a "Buoyant" in the Reference Table column refers to the tables for neutrally buoyant gases and vapors; "Dense" refers to the tables for dense gases and vapors. See
Appendix D, Section D.4.4, for more information on the choice of reference tables.
Gases that are lighter than air may behave as dense gases upon release if liquefied under pressure or cold; consider the conditions of release when choosing the
appropriate table.
0 Reported to be spontaneously combustible.
Much lighter than air; table of distances for neutrally buoyant gases not appropriate.
e Pool formation unlikely.
f Calculated at 298 K (25 °C) with the following exceptions:
Acetylene factor at 250 K as reported in TNO, Methods for the Calculation of the Physical Effects of the Escape of Dangerous Material (1980).
Ethylene factor calculated at critical temperature, 282 K.
Methane factor calculated at critical temperature, 191 K.
Silane factor calculated at critical temperature, 270 K.
8 Use GF for gas leaks under choked (maximum) flow conditions.
April 15, 1999
-------
Exhibit C-3
Data for Flammable Liquids
CAS
Number
590-21-6
60-29-7
75-08-1
78-78-4
78-79-5
75-31-0
75-29-6
563-46-2
107-31-3
504-60-9
109-66-0
109-67-1
646-04-8
627-20-3
75-76-3
10025-78-2
109-92-2
75-35-4
Chemical Name
1 -Chloropropylene
Ethyl ether
Ethyl mercaptan
Isopentane
Isoprene
Isopropylamine
Isopropyl chloride
2-Methyl-l-butene
Methyl formate
1,3-Pentadiene
Pentane
1-Pentene
2-Pentene, (E)-
2-Pentene, (Z)-
Tetramethylsilane
Trichlorosilane
Vinyl ethyl ether
Vinylidene chloride
Molecular
Weight
76.53
74.12
62.14
72.15
68.12
59.11
78.54
70.13
60.05
68.12
72.15
70.13
70.13
70.13
88.23
135.45
72.11
96.94
Flammabiliry Limit
(Vol%)
Lower
(LFL)
4.5
1.9
2.8
1.4
2.0
2.0
2.8
1.4
5.9
1.6
1.3
1.5
1.4
1.4
1.5
1.2
1.7
7.3
Upper
(UFL)
16.0
48.0
18.0
7.6
9.0
10.4
10.7
9.6
20.0
13.1
8.0
8.7
10.6
10.6
NA
90.5
28.0
NA
LFL
(mg/L)
140
57
71
41
56
48
90
40
140
44
38
43
40
40
54
66
50
290
Liquid Factors
Ambient
(LFA)
0.11
0.11
0.10
0.14
0.11
0.10
0.11
0.12
0.10
0.077
0.10
0.13
0.10
0.10
0.17
0.18
0.10
0.15
Boiling
(LFB)
0.15
0.15
0.13
0.15
0.14
0.13
0.16
0.15
0.13
0.14
0.15
0.15
0.15
0.15
0.17
0.23
0.15
0.18
Density
Factor
0.52
0.69
0.58
0.79
0.72
0.71
0.57
0.75
0.50
0.72
0.78
0.77
0.76
0.75
0.59
0.37
0.65
0.44
Liquid Leak
Factor
(LLF)a
45
34
40
30
32
33
41
31
46
33
30
31
31
31
40
64
36
54
Reference
Table"
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Dense
Pool Fire
Factor
(PFF)
3.2
4.3
3.3
6.1
5.5
4.1
3.1
5.8
1.8
5.3
5.8
5.8
5.6
5.6
6.3
0.68
4.2
1.6
Notes:
NA: Data not available.
a Use the LLF only for leaks from tanks at atmospheric pressure.
b "Dense" in the Reference Table column refers to the tables for dense gases and vapors.
reference tables.
See Appendix D, Section D.4.4, for more information on the choice of
April 15, 1999
C-9
-------
APPENDIX D
TECHNICAL BACKGROUND
April 15, 1999
-------
APPENDIX D TECHNICAL BACKGROUND
D.I Worst-Case Release Rate for Gases
D.I.I Unmitigated Release
The assumption that the total quantity of toxic gas is released in 10 minutes is the same assumption
used in EPA's Technical Guidance for Hazards Analysis (1987).
D.I.2 Gaseous Release Inside Building
The mitigation factor for gaseous release inside a building is based on a document entitled, Risk
Mitigation in Land Use Planning: Indoor Releases of Toxic Gases, by S.R. Porter. This paper presented
three release scenarios and discussed the mitigating effects that would occur in a building with a volume of
1,000 cubic meters at three different building air exchange rates. There is a concern that a building may not
be able to withstand the pressures of a very large release. However, this paper indicated that release rates of
at least 2,000 pounds per minute could be withstood by a building.
Analyzing the data in this paper several ways, the value of 55 percent emerged as representing the
mitigation that could occur for a release scenario into a building. Data are provided on the maximum release
rate in a building and the maximum release rate from a building. Making this direct comparison at the lower
maximum release rate (3.36 kg/s) gave a release rate from the building of 55 percent of the release rate into
the building. Using information provided on another maximum release rate (10.9 kg/min) and accounting for
the time for the release to accumulate in the building, approximately 55 percent emerged again.
The choice of building ventilation rates affects the results. The paper presented mitigation for three
different ventilation rates, 0.5, 3, and 10 air changes per hour. A ventilation rate of 0.5 changes per hour is
representative of specially designed, "gas-tight" buildings, based on the Porter reference. EPA decided that
this ventilation rate was appropriate for this analysis. A mitigation factor of 55 percent may be used in the
event of a gaseous release which does not destroy the building into which it is released. This factor may
overstate the mitigation provided by a building with a higher ventilation rate.
For releases of ammonia, chlorine, and sulfur dioxide, factors specific to the chemicals, the
conditions of the release, and building ventilation rates have been developed to estimate mitigation of releases
in buildings. For information on these factors and estimation of mitigated release rates, see Backup
Information for the Hazard Assessments in the RMP Offsite Consequence Analysis Guidance, the
Guidance for Wastewater Treatment Facilities and the Guidance for Ammonia Refrigeration -Anhydrous
Ammonia, Aqueous Ammonia, Chlorine and Sulfur Dioxide. See also the industry-specific guidance
documents for ammonia refrigeration and POTWs.
D.2 Worst-Case Release Rate for Liquids
D.2.1 Evaporation Rate Equation
The equation for estimating the evaporation rate of a liquid from a pool is from the Technical
Guidance for Hazards Analysis, Appendix G. The same assumptions are made for determination of
April 15, 1999
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Appendix D
Technical Background _
maximum pool area (i.e., the pool is assumed to be 1 centimeter (0.033 feet) deep). The evaporation rate
equation has been modified to include a different mass transfer coefficient for water, the reference compound.
For this document, a value of 0.67 centimeters per second is used as the mass transfer coefficient, instead of
the value of 0.24 cited in the Technical Guidance for Hazards Analysis. The value of 0.67 is based on
Donald MacKay and Ronald S. Matsugu, "Evaporation Rates of Liquid Hydrocarbon Spills on Land and
Water," Canadian Journal of Chemical Engineering, August 1973, p. 434. The evaporation equation
becomes:
0.284 x U°™ x MW x A x VP
82.05 x T *D~1*
where: QR = Evaporation rate (pounds per minute)
U = Wind speed (meters per second)
MW = Molecular weight (given in Exhibits B- 1 and B-2, Appendix B, for toxic
substances and Exhibits C-2 and C-3, Appendix C, for flammable
substances)
A = Surface area of pool formed by the entire quantity of the mixture (square
feet) (determined as described in Section 3.2.2 of the text)
VP = Vapor pressure (mm Hg)
T = Temperature of released substance (Kelvin (K); temperature in °C plus 273,
or 298 for 25 °C)
D.2.2 Factors for Evaporation Rate Estimates
Liquid Factors. The liquid factors, Liquid Factor Ambient (LFA) and Liquid Factor Boiling (LFB),
used to estimate the evaporation rate from a liquid pool (see Section 3.2 of this guidance document), are
derived as described in the Technical Guidance for Hazards Analysis, Appendix G, with the following
differences:
• The mass transfer coefficient of water is assumed to be 0.67, as discussed above; the value
of the factor that includes conversion factors, the mass transfer coefficient for water, and the
molecular weight of water to the one-third power, given as 0. 106 in the Technical Guidance
is 0.284 in this guidance.
• Density of all substances was assumed to be the density of water in the Technical Guidance;
the density was included in the liquid factors. For this guidance document, density is not
included in the LFA and LFB values presented in the tables; instead, a separate Density
Factor (DF) (discussed below) is provided to be used in the evaporation rate estimation.
With these modifications, the LFA is:
TE,A 0.284 x MW2'3 x VP
LFA = - (D-2)
82.05 x 298 v '
where: MW = Molecular weight
April 15, 1999 D-2
-------
Appendix D
Technical Background
LFB is:
VP = Vapor pressure at ambient temperature (mm Hg)
298 K (25 °C) = Ambient temperature and temperature of released substance
LFB - 0.284 x MW» x 760
82.05 x BP ^ '
where: MW = Molecular weight
760 = Vapor pressure at boiling temperature (mm Hg)
BP = Boiling point (K)
LFA and LFB values were developed for all toxic and flammable regulated liquids, and LFB values,
to be used for analysis of gases liquefied by refrigeration, were developed for toxic and flammable gases.
Density Factor. Because some of the regulated liquids have densities very different from that of
water, the density of each substance was used to develop a Density Factor (DF) for the determination of
maximum pool area for the evaporation rate estimation. DF values were developed for toxic and flammable
liquids at ambient temperature and for toxic and flammable gases at their boiling points. The density factor
is:
DF = - (D-4)
d x 0.033 l '
where: DF = Density factor (l/(lbs/ft2))
d = Density of the substance in pounds per cubic foot
0.033 = Depth of pool for maximum area (feet)
Temperature Correction Factors. Temperature correction factors were developed for toxic liquids
released at temperatures above 25 °C, the temperature used for development of the LFAs. The temperature
correction factors are based on vapor pressures calculated from the coefficients provided in Physical and
Thermodynamic Properties of Pure Chemicals, Data Compilation, developed by the Design Institute for
Physical Property Data (DIPPR), American Institute of Chemical Engineers. The factors are calculated as
follows:
VPT x 298
TCFT = - fD-51
where: TCFT = Temperature Correction Factor at temperature T
VPT = Vapor pressure at temperature T
^298 = Vapor pressure at 298 K
T = Temperature (K) of released substance
Factors were developed at intervals of 5 °C for temperatures up to 50 °C.
April 15, 1999 D - 3
-------
Appendix D
Technical Background
No correction factor was deemed necessary for changes in the density of the regulated toxic liquids
with changes in temperature, although the density could affect the pool area and release rate estimates.
Analysis of the temperature dependence of the density of these liquids indicated that the changes in density
with temperature were very small compared to the changes in vapor pressure with temperature.
D.2.3 Common Water Solutions and Oleum
Water solutions of regulated toxic substances must be analyzed somewhat differently from pure toxic
liquids. Except for solutions of relatively low concentration, the evaporation rate varies with the
concentration of the solution. At one specific concentration, the composition of the liquid does not change as
evaporation occurs. For concentrated solutions of volatile substances, the evaporation rate from a pool may
decrease, very rapidly in some cases, as the toxic substance volatilizes and its concentration in the pool
decreases. To analyze these changes, EPA used spreadsheets to estimate the vapor pressure, concentration,
and release rate at various time intervals for regulated toxic substances in water solution evaporating from
pools. In addition to the spreadsheet analysis, EPA used the ALOHA model with an additional step-function
feature (not available in the public version). With this step-function feature, changes in the release rate could
be incorporated and the effects of these changes on the consequence distance analyzed. The results of the
spreadsheet calculations and the model were found to be in good agreement. The distance results obtained
from the spreadsheet analysis and the model for various solutions were compared with the results from
various time averages to examine the sensitivity of the results. An averaging time of 10 minutes was found to
give reasonable agreement with the step-function model for most substances at various concentrations. The
spreadsheet analysis also indicated that the first 10 minutes of evaporation was the most important, and the
evaporation rate in the first 10 minutes likely could be used to estimate the distance to the endpoint.
Oleum is a solution of sulfur trioxide in sulfuric acid. Sulfur trioxide evaporating from oleum
exhibits release characteristics similar to those of toxic substances evaporating from water solutions.
Analysis of oleum releases, therefore, was carried out in the same way as for water solutions.
NOAA developed a computerized calculation method to estimate partial vapor pressures and release
rates for regulated toxic substance in solution as a function of concentration, based on vapor pressure data
from Perry's Chemical Engineers' Handbook and other sources. Using this method and spreadsheet
calculations, EPA estimated partial vapor pressures and evaporation rates at one-minute intervals over 10
minutes for solutions of various concentrations. The 10-minute time period was chosen based on the
ALOHA results and other calculations. For each one-minute interval, EPA estimated the concentration of the
solution based on the quantity evaporated in the previous interval and estimated the partial vapor pressure
based on the concentration. These estimated vapor pressures were used to calculate an average vapor
pressure over the 10-minute period; this average vapor pressure was used to derive Liquid Factor Ambient
(LFA) values, as described above for liquids. Use of these factors is intended to give an evaporation rate that
accounts for the decrease in evaporation rate expected to take place as the solution evaporates.
Density Factors (DF) were developed for solutions of various concentrations from data m Perry's
Chemical Engineers' Handbook and other sources, as discussed above for liquids.
Because solutions do not have defined boiling points, EPA did not develop Liquid Factor Boiling
(LFB) values for solutions. As a simple and conservative approach, the quantity of a regulated substance in a
solution at an elevated temperatures is treated as a pure substance. The LFB for the pure substance, or the
April 15, 1999 D - 4
-------
Appendix D
Technical Background
LFA and a temperature correction factor, is used to estimate the initial evaporation rate of the regulated
substance from the solution. Only the first 10 minutes of evaporation are considered, as for solutions at
ambient temperatures, because the release rate would decrease rapidly as the substance evaporates and the
concentration in the solution decreases. This approach will likely give an overestimate of the release rate and
of the consequence distance.
D.2.4 Releases Inside Buildings
If a liquid is released inside a building, its release to the outside air will be mitigated in two ways.
First, the evaporation rate of the liquid may be much lower inside a building than outside. This is due to wind
speed, which directly affects the evaporation rate. The second mitigating factor is that the building provides
resistance to discharge of contaminated air to the outdoors.
In this method, a conservative wind speed, U, of 0.1 meter per second (m/s) was assumed in the
building. (See end of text for a justification of this wind speed.) For a release outdoors in a worst-case
scenario, U is set to 1.5 m/s, and for an alternative scenario, U is set to 3 m/s. The evaporation rate equation
is:
QR = f/°'78 x (LFA, LFB} x A (D-6)
where: QR = Release rate (pounds per minute (Ibs/min))
U = Wind speed (meters per second (m/s))
LFA = Liquid Factor Ambient
LFB = Liquid Factor Boiling
A = Area of pool (square feet (ft2))
As can be seen, if U inside a building is only 0.1, then the evaporation rate inside a building will be much
lower than a corresponding evaporation rate outside (assuming the temperature is the same). The rate will
only be (0.1/1.5)078, about 12 percent of the rate for a worst case, and (0.1/3)078, about seven percent of the
rate for an alternative case.
The evaporated liquid mixes with and contaminates the air in the building. What EPA is ultimately
interested in is the rate at which this contaminated air exits the building. In order to calculate the release of
contaminated air outside the building, EPA adapted a method from an UK Health and Safety Executive paper
entitled, Risk Mitigation in Land Use Planning: Indoor Releases of Toxic Gases, by S.R. Porter. EPA
assumed that the time for complete evaporation of the liquid pool was one hour. The rate at which
contaminated air was released from the building during liquid evaporation (based on the paper) was assumed
to be equal to the evaporation rate plus the building ventilation rate (no pressure buildup in building). The
building ventilation rate was set equal to 0.5 air changes per hour. This ventilation rate is representative of a
specially designed, "gas-tight" building. (The mitigation factor developed based on this type of building
would overstate the mitigation provided by a building with higher ventilation rates.) EPA used a building
with a volume of 1,000 cubic meters (m3) and a floor area of 200 m2 (2,152 ft2) as an example for this
analysis. EPA assumed that the liquid pool would cover the entire building floor, representing a conservative
scenario.
April 15, 1999 D - 5
-------
Appendix D
Technical Background
To provide a conservative estimate, EPA calculated the evaporation rate for a spill of a volatile
liquid, carbon disulfide (CS2), under ambient conditions inside the building:
QR = 0.1078 x 0.075 x 2,152 = 26.8 pounds per minute (Ibs/min)
Next, this evaporation rate was converted to cubic meters per minute (mVmin) using the ideal gas
law (the molecular weight of CS2 is 76.1):
26.8 Ibs/min x 454 grams per pound (g/lb) x 1 mole CS/76.1 g x 0.0224 mVmole = 3.58 mVmin.
The ventilation rate of the building is 0.5 changes per hour, which equals 500 m3 per hour, or 8.33
mVmin. Therefore, during evaporation, contaminated air is leaving the building at a rate of 8.33 + 3.58, or
11.9m3/min.
EPA used an iterative calculation for carbon disulfide leaving a building using the above calculated
parameters. During the first minute of evaporation, 26.8 Ibs of pure carbon disulfide evaporates, and EPA
assumed this evenly disperses through the building so that the concentration of CS2 in the building air is
0.0268 lbs/m3 (assuming 1000 m3 volume in the building). Contaminated air is exiting the building at a rate
of 11.9 mVmin, so EPA deduced that 11.9 x 0.0268 = 0.319 Ibs of carbon disulfide exit the building in the
first minute, leaving 26.5 Ibs still evenly dispersed inside. Since this release occurs over one minute, the
release rate of the carbon disulfide to the outside is 0.319 Ibs/min. During the second minute, another 26.8
Ibs of pure carbon disulfide evaporates and disperses, so that the building now contains 26.8 + 26.5 = 53.3
Ibs of carbon disulfide, or 0.0533 lbs/m3. Contaminated air is still exiting the building at a rate of 11.9
m3/min, so 11.9 x 0.05328 = 0.634 Ibs of carbon disulfide are released, leaving 52.6 Ibs inside. Again, this
release occurs over one minute so that the rate of carbon disulfide exiting the building in terms of
contaminated air is 0.634 Ibs/min. EPA continued to perform this estimation over a period of one hour. The
rate of release of carbon disulfide exiting the building in the contaminated air at the sixty minute mark is 13.7
Ibs/min. This represents the maximum rate of carbon disulfide leaving the building. After all of the carbon
disulfide is evaporated, there is a drop in the concentration of carbon disulfide in the contaminated air leaving
the building because the evaporation of carbon disulfide no longer contributes to the overall contamination of
the air.
Note that if the same size pool of carbon disulfide formed outside, the release rate for a worst-case
scenario would be:
QR= 1.5078 x 0.075 x 2,152 = 221 Ibs/min.
and for an alternative case:
QR = 3078 x 0.075 x 2,152 = 380 Ibs/min.
The maximum release rate of carbon disulfide in the contaminated building air, assuming a 1,000 m3
building with a building exchange rate of 0.5 air changes per hour, was only about 6 percent (13.7^-221
Ibs/min x 100) of the worst-case scenario rate, and only about 3.6 percent (13.7 + 380 Ibs/min x 100) of the
alternative scenario rate. EPA set an overall building mitigation factor equal to 10 percent and five percent,
respectively, in order to be conservative. Please note that (at a constant ventilation rate of 0.5 changes per
April 15, 1999 D - 6
-------
Appendix D
Technical Background
hour) as the size of the building increases, the maximum rate of contaminated air leaving the building will
decrease, although only slightly, because of the balancing effect of building volume and ventilation rate.
Obviously, a higher ventilation rate will yield a higher maximum release rate of contaminated air from the
building.
For a release inside a building, EPA assumed a building air velocity of 0.1 m/s. This conservative
value was derived by setting the size of the ventilation fan equal to 1.0m2. This fan is exchanging air from
the building with the outside at a rate of 0.5 changes per hour. For a 1,000 m3 building, this value becomes
500 m3/hour, or 0.14 m3/s. Dividing 0.14 m3/s by the area of the fan yields a velocity of 0.14 m/s, which was
rounded down to 0.1 m/s.
D.3 Toxic Endpoints
The toxic endpoints for regulated toxic substances, which are specified in the RMP Rule, are
presented in Appendix B, Exhibits B-l, B-2, and B-3. The endpoints were chosen as follows, in order of
preference:
(1) Emergency Response Planning Guideline 2 (ERPG-2), developed by the American Industrial
Hygiene Association, if available;
(2) Level of Concern (LOG) derived for extremely hazardous substances (EHSs) regulated
under section 302 of the Emergency Planning and Community Right-to-Know Act (EPCRA)
(see the Technical Guidance for Hazards Analysis for more information on LOCs); the
LOG for EHSs is based on:
One-tenth of the Immediately Dangerous to Life and Health (IDLH) level,
developed by the National Institute of Occupational Safety and Health (NIOSH),
using IDLH values developed before 1994,
or, if no IDLH value is available,
One-tenth of an estimated IDLH derived from toxicity data; the IDLH is estimated
as described in Appendix D of the Technical Guidance for Hazards Analysis.
Note that the LOCs were not updated using IDLHs published in 1994 and later,
because NIOSH revised its methodology for the IDLHs. The EHS LOCs based on
earlier IDLHs were reviewed by EPA's Science Advisory Board, and EPA decided
to retain the methodology that was reviewed.
ERPG-2 is defined as the maximum airborne concentration below which it is believed nearly all
individuals could be exposed for up to one hour without experiencing or developing irreversible or other
serious health effects or symptoms that could impair an individual's ability to take protective action.
IDLH (pre-1994) concentrations were defined in the NIOSH Pocket Guide to Chemical Hazards as
representing the maximum concentration from which, in the event of respirator failure, one could escape
within 30 minutes without a respirator and without experiencing any escape-impairing (e.g., severe eye
April 15, 1999 D - 7
-------
Appendix D
Technical Background
irritation) or irreversible health effects. (As noted above, LOCs for EHSs were not updated to reflect 1994
and later IDLHs.)
The estimated IDLH is derived from animal toxicity data, in order of preferred data, as follows:
• From median lethal concentration (LC50) (inhalation): 0.1 x LC50
• From lowest lethal concentration (LCLO) (inhalation): 1 x LCLO
• From median lethal dose (LD50) (oral): 0.01xLD50
• From lowest lethal dose (LDLO) (oral): 0.1 x LDLO
The toxic endpoints based on LOCs for EHSs presented in the tables in Appendix B are, in some
cases, different from the LOCs listed in the Technical Guidance for Hazards Analysis, because some of the
LOCs were updated based on IDLHs that were published after the development of the LOCs (and before
1994) or on new or revised toxicity data.
D.4 Reference Tables for Distances to Toxic and Flammable Endpoints
D.4.1 Neutrally Buoyant Gases
Toxic Substances. Reference tables for distances to toxic endpoints for neutrally buoyant gases and
vapors were derived from the Gaussian model using the longitudinal dispersion coefficients based on work by
Beals (Guide to Local Diffusion of Air Pollutants, Technical Report 214. Scott Air Force Base, Illinois:
U.S. Air Force, Air Weather Service, 1971). The reasons for using the Beals dispersion coefficients are
discussed below.
Longitudinal dispersion (dispersion in the along-wind direction) is generated mostly by vertical wind
shear. Wind shear results from the tendency of the wind speed to assume a wind profile—the speed is lowest
next to the ground and increases with height until it reaches an asymptotic value at approximately a few
hundred feet above the surface. To account for shear-driven dispersion, any air dispersion model intended for
modeling short-duration releases must include either (a) a formulation that accounts, either implicitly or
explicitly, for the height-dependence of wind speed or (b) some type of parameterization that converts shear
effect into ox, the standard deviation function in the along-wind direction.
Because the standard Gaussian formula does not incorporate ox (it includes only oy and oz, the
crosswind and horizontal functions), very few alternate ways to formulate ox have been proposed. The
simplest method was proposed by Turner (Workbook of Atmospheric Dispersion Estimates, Report PB-191
482. Research Triangle Park, North Carolina: Office of Air Programs, U.S. Environmental Protection
Agency, 1970), who suggested simply setting ox equal to oy. Textbooks such as that by Pasquill and Smith
(Atmospheric Diffusion, 3rd ed. New York: Halstead Press, 1983) describe a well-known analytic model.
However, this model is more complex than a Gaussian model because according to it, dispersion depends on
wind shear and the vertical variation of the vertical diffusion coefficient. Wilson (Along-wind Diffusion of
Source Transients, Atmospheric Environment 15:489-495, 1981) proposed another method in which oxis
April 15, 1999 D - 8
-------
Appendix D
Technical Background
determined as a function of wind shear, but in a form that can then be used in a Gaussian model. However, it
is now believed that Wilson's formulation gives ox values that are too large.
To avoid the problems of the analytic method and Wilson's formulation, we chose to include a
formulation for ox derived from work by Beals (1971). We had three reasons for doing so. First, in terms of
magnitude, Beals' ox fell in the midrange of the alternative formulations that we reviewed. Second, Beals' ox
indirectly accounts for wind shear by using (unpublished) experimental data. Third, both the ALOHA and
DEGADIS models incorporate the Beals methodology.
When a substance is dispersed downwind, the concentration in the air changes over time. To assess
the health effects of potential exposure to the substance, the average concentration of the substance over
some time period is determined. Averaging time is the time interval over which the instantaneous
concentration of the hazardous material in the vapor cloud is averaged. Averaging time should generally be
equal to or shorter than either the release duration or cloud duration and, if possible, should reflect the
exposure time associated with the toxic exposure guideline of interest. The exposure time associated with the
toxic endpoints specified under the RMP Rule include 30 minutes for the Immediately Dangerous to Life and
Health (IDLH) level and 60 minutes for the Emergency Response Planning Guideline (ERPG). For the
neutrally buoyant tables, the 10-minute release scenario was modeled using a 10-minute averaging time. The
60-minute release scenario was modeled using a 30-minute averaging time to be consistent with the 30-
minute exposure time associated with the IDLH. A 60-minute averaging time may have underpredicted
consequence distances and, therefore, was not used for development of the distance tables for this guidance.
Cloud dispersion from a release of finite duration (10 and 60-minute releases) is calculated using an
equation specified in the NOAA publication ALOHA™ 5.0 Theoretical Description, Technical Memorandum
NOS ORCA 65, August 1992.
Flammable Substances. The reference tables of distances for vapor cloud fires of neutrally buoyant
flammable substances were derived using the same model as for toxic substances, as described above. The
endpoint for modeling was the lower flammability limit (LFL). For flammable substances, an averaging time
of 0.1 minute (six seconds) was used, because fires are considered to be nearly instantaneous events.
Distances of interest for flammable substances are generally much shorter than for toxic substance,
because the LFL concentrations are much larger than the toxic endpoints. For the short distances found in
modeling the flammable substances, modeling results were found to be the same for 10-minute and longer
releases; therefore, one table of distances for rural conditions and one table for urban conditions, applicable
for both 10-minute and longer releases, were developed for flammable substances.
D.4.2 Dense Gases
Toxic Substances. The reference tables for dense gases were developed using the widely accepted
SLAB model, developed by Lawrence Livermore National Laboratory. SLAB solves conservation equations
of mass, momentum, energy, and species for continuous, finite duration, and instantaneous releases. The
reference tables were based on the evaporating pool algorithm.
For the reference tables were developed based on modeling releases of hydrogen chloride (HC1). HC1
was chosen based on a SLAB modeling analysis of a range of dispersion behavior for releases of regulated
April 15, 1999 D - 9
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Appendix D
Technical Background
dense gases or vapors with different molecular weights. This analysis showed that releases of HC1 generally
provided conservative results under a variety of stability/wind speed combinations, release rates, and toxic
endpoints.
Similar to the modeling of neutrally buoyant plumes, the 10-minute release scenario of toxic
chemicals was modeled using a 10-minute averaging time. The 60-minute release scenario was modeled
using a 30-minute averaging time to be consistent with the 30-minute exposure time associated with the
IDLH.
For all dense gas tables, the reference height for the wind speed was 10 meters. Relative humidity
was assumed to be 50 percent, and the ambient temperature was 25 °C. The source area was the smallest
value that still enabled the model to run for all release rates. The surface roughness factor was one meter for
urban scenarios and three centimeters for rural scenarios.
Flammable Substances. For the reference tables for dispersion of dense flammable gases and vapors,
for analysis of vapor cloud fires, the same model was used as for toxic substances, as described above, and
the same assumptions were made. For the dispersion of flammable chemicals, averaging time should be very
small (i.e., no more than a few seconds), because flammable vapors need only be exposed to an ignition
source for a short period of time to initiate the combustion process. Thus, both the 10-minute and 60-minute
reference tables for flammable substances use an averaging time of 10 seconds. The 10-minute and 60-
minute tables were combined for flammable substances because the modeling results were found to be the
same.
DAS Chemical-Specific Reference Tables
The chemical-specific reference tables of distances for ammonia, chlorine, and sulfur dioxide were
developed for EPA's risk management program guidance for ammonia refrigeration and for POTWs. For
information on the chemical-specific modeling and development of the chemical-specific reference tables, see
Backup Information for the Hazard Assessments in the RMP Offsite Consequence Analysis Guidance, the
Guidance for Wastewater Treatment Facilities and the Guidance for Ammonia Refrigeration -Anhydrous
Ammonia, Aqueous Ammonia, Chlorine and Sulfur Dioxide. See also the industry-specific guidance
documents for ammonia refrigeration and POTWs.
The modeling carried out for aqueous ammonia also is applied in this guidance to ammonia released
as a neutrally buoyant plume in other situations. The tables of distances derived from this modeling would
apply to evaporation of ammonia from a water solution, evaporation of ammonia liquefied by refrigeration, or
ammonia releases from the vapor space of a vessel, because the ammonia would behave as a neutrally
buoyant plume (or possibly buoyant in some cases).
D.4.4 Choice of Reference Table for Dispersion Distances
Gases. Exhibit B-l of Appendix B indicates whether the reference tables for neutrally buoyant or
dense gases should be used for each of the regulated toxic gases. Exhibit C-2, Appendix C, provides this
information for flammable gases. The choice of reference table presented in these exhibits is based on the
molecular weight of the regulated substance compared to air; however, a number of factors that may cause a
substance with a molecular weight similar to or smaller than the molecular weight of air to behave as a dense
April 15, 1999 D - 10
-------
Appendix D
Technical Background
gas should be considered in selecting the appropriate table. For example, a cold gas may behave as a dense
gas, even if it is lighter than air at ambient temperature. Gases liquefied under pressure may be released as a
mixture of vapor and liquid droplets; because of presence of liquid mixed with the vapor, a gas that is lighter
than air may behave as a dense gas in such a release. A gas that polymerizes or forms hydrogen bonds (e.g.,
hydrogen fluoride) also may behave as a dense gas.
Liquids and Solutions. Exhibits B-2 and B-3, Appendix B, and Exhibit C-3, Appendix C, indicate
the reference table of distances to be used for each regulated liquid. The methodology presented in this
guidance for consequence analysis for liquids and solutions assumes evaporation from a pool. All of the
liquids regulated under CAA section 112(r) have molecular weights greater than the molecular weight of air;
therefore, their vapor would be heavier than air. However, because the vapor from a pool will mix with air as
it evaporates, the initial density of the vapor with respect to air may not in all cases indicate whether the vapor
released from a pool should be modeled as a dense gas or a neutrally buoyant gas. If the rate of release from
the pool is relatively low, the vapor-air mixture that is generated may be neutrally buoyant even if the vapor is
denser than air, because the mixture may contain a relatively small fraction of the denser-than-air vapor; i.e.,
it may be mostly air. This may be the case particularly for some of the regulated toxic liquids with relatively
low volatility. All of the regulated flammable substances have relatively high volatility; the reference tables
for dense gases are assumed to be appropriate for analyzing dispersion of these flammable liquids.
To identify toxic liquids with molecular weight greater than air that might behave as neutrally
buoyant gases when evaporating from a pool, EPA used the ALOHA model for pool evaporation of a number
of substances with a range of molecular weights and vapor pressures. Modeling was carried out for F
stability and wind speed 1.5 meters per second (worst-case conditions) and for D stability and wind speed 3.0
meters per second (alternative-case conditions). Pool spread to a depth of one centimeter was assumed.
Additional modeling was carried out for comparison assuming different pool areas and depths. The
molecular weight-vapor pressure combinations at which ALOHA used the neutrally buoyant gas model were
used to develop the reference table choices given in Exhibit B-2 (for liquids) and B-3 (for solutions) in
Appendix B. The neutrally buoyant tables should generally give reasonable results for pool evaporation
under ambient conditions when indicated for liquids. At elevated temperatures, however, evaporation rates
will be greater, and the dense gas tables should be used.
The liquids for which the neutrally buoyant table is identified for the worst case probably can be
expected to behave as neutrally buoyant vapors when evaporating from pools under ambient conditions in
most situations, but there may be cases when they exhibit dense gas behavior. Other liquids, for which the
neutrally buoyant tables are not indicated for the worst case, might release neutrally buoyant vapors under
some conditions (e.g., relatively small pools, temperature not much above 25 °C). Similarly, the liquids for
which the neutrally buoyant tables are indicated as appropriate for alternative scenario analysis probably can
be considered to behave as neutrally buoyant vapors under the alternative scenario conditions in most cases;
however, there may be cases where they will behave as dense gases, and there may be other liquids that in
some cases would exhibit neutrally buoyant behavior when evaporating. The reference table choices shown
in Exhibit B-2 are intended to reflect the most likely behavior of the substances; they will not predict
behavior of the listed substances evaporating under all conditions.
April 15, 1999 D - 11
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Appendix D
Technical Background
DAS Additional Modeling for Comparison
Modeling was carried out for two worst-case examples and two alternative-case examples, using two
different models, for comparison with the results obtained from the methods and distance tables in this
guidance. This modeling is discussed below.
ALOHA Model. The Areal Locations of Hazardous Atmospheres (ALOHA) system was developed
jointly by NOAA and EPA. ALOHA Version 5.2.1 was used for the comparison modeling. The parameters
for ALOHA modeling were the same as specified in this guidance document for worst-case and alternative
scenarios. The substances modeled are included in ALOHA's chemical database, so no chemical data were
entered for modeling. For consistency with the methodology used to develop the reference tables of distances,
a wind speed height of 10 meters was selected for ALOHA modeling.
For all of the substances modeled, the direct source model was chosen for ALOHA modeling, and the
release rate estimated using the guidance methodology was entered as the release rate for ALOHA. ALOHA
selected the dense gas model to estimate the distances to the endpoints in all cases.
WHAZAN Model. The World Bank Hazard Analysis (WHAZAN) system was developed by
Technica International in collaboration with the World Bank. The 1988 version of WHAZAN was used for
the comparison modeling. The parameters for atmospheric stability, wind speed, and ambient temperature
and humidity were the same as specified in this guidance document. For surface roughness, WHAZAN
requires entry of a "roughness parameter," rather than a height. Based on the discussion of this parameter in
the WHAZAN Theory Manual, a roughness parameter of 0.07 (corresponding to flat land, few trees) was
chosen as equivalent to the surface roughness of 3 centimeters used to represent rural topography in modeling
to develop the distance tables for this guidance. A roughness parameter of 0.17 (for woods or rural area or
industrial site) was chosen as equivalent to 1 meter, which was used to develop the urban distance tables.
Data were added to the WHAZAN chemical database for acrylonitrile and allyl alcohol; ethylene oxide and
chlorine were already included in the database.
For WHAZAN modeling of the gases ethylene oxide and chlorine and the liquid acrylonitrile, the
WHAZAN dense cloud dispersion model was used. For the alternative-case release of allyl alcohol, the
buoyant plume dispersion model was used for consistency with the guidance methodology. The release rates
estimated using the guidance methodology were entered as the release rates for all of the WHAZAN
modeling.
The WHAZAN dense cloud dispersion requires a "volume dilution factor" as one of its inputs. This
factor was not explained; it was presumed to account for dilution of pressurized gases with air upon release.
For the gases modeled, the default dilution factor of 60 was used; for acrylonitrile, a dilution factor of 0 was
entered. This factor appears to have little effect on the distance results.
D.5 Worst-Case Consequence Analysis for Flammable Substances
The equation used for the vapor cloud explosion analysis for the worst case involving flammable
substances is given in Appendix C. This equation is based on the TNT-equivalency method of the UK Health
and Safety Executive, as presented in the publication of the Center for Chemical Process Safety of the
American Institute of Chemical Engineers (AIChE), Guidelines for Evaluating the Characteristics of Vapor
April 15, 1999 D - 12
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Appendix D
Technical Background
Cloud Explosions, Flash Fires, and BLEVEs (1994). The assumption was made for the worst case that the
total quantity of the released substance is in the flammable part of the cloud. The AIChE document lists this
assumption as one of a number that have been used for vapor cloud explosion blast prediction; it was chosen
as a conservative assumption for the worst-case analysis. The yield factor of 10 percent was a conservative
worst-case assumption, based on information presented in the AIChE document. According to the AIChE
document, reported values for TNT equivalency for vapor cloud explosions range from a fraction of one
percent to tens of percent; for most major vapor cloud explosions, the range is one to ten percent.
The endpoint for the vapor cloud explosion analysis, 1 psi, is reported to cause damage such as
shattering of glass windows and partial demolition of houses. Skin laceration from flying glass also is
reported. This endpoint was chosen for the consequence analysis because of the potential for serious injuries
to people from the property damage that might result from an explosion.
The TNT equivalent model was chosen as the basis for the consequence analysis because of its
simplicity and wide use. This model does not take into account site-specific factors and many chemical-
specific factors that may affect the results of a vapor cloud explosion. Other methods are available for vapor
cloud explosion modeling; see the list of references in Appendix A for some publications that include
information on other vapor cloud explosion modeling methods.
D.6 Alternative Scenario Analysis for Gases
The equation for estimating release rate of a gas from a hole in a tank is based on the equations for
gas discharge rate presented in the Handbook of Chemical Hazard Analysis Procedures by the Federal
Emergency Management Agency (FEMA), DOT, and EPA, and equations in EPA's Workbook of Screening
Techniques for Assessing Impacts of Toxic Air Pollutants. The equation for an instantaneous discharge
under non-choked flow conditions is:
m = CdAh
\
(D-7)
where:
m
Cd
Ah
Y
Po
Pi
Po
Discharge rate (kg/s)
Discharge coefficient
Opening area (m2)
Ratio of specific heats
Tank pressure (Pascals)
Ambient pressure (Pascals)
Density (kg/m3)
Under choked flow conditions (maximum flow rate), the equation becomes:
April 15, 1999
D-13
-------
Appendix D
Technical Background
m urf Ah A
( 2 } —
2* y-l
v/7 Q i
'^U+iJ
(D-8)
For development of the equation and gas factors presented in this guidance, density (p) was rewritten
as a function of pressure and molecular weight, based on the ideal gas law:
P =
pQ MW
R Tt
(D-9)
where:
MJF = Molecular weight (kilograms per kilomole)
R = Gas constant (8,314 Joules per degree-kilomole)
Tt = Tank temperature (K)
The choked flow equation can be rewritten:
m =
'"
MW
8314
(D-10)
To derive the equation presented in the guidance, all the chemical-specific properties, constants, and
appropriate conversion factors were combined into the "Gas Factor" (GF). The discharge coefficient was
assumed to have a value of 0.8, based on the screening value recommended in EPA's Workbook of Screening
Techniques for Assessing Impacts of Toxic Air Pollutants. The GF was derived as follows:
GF = 132.2 x 6,895 x 6.4516xlO
~4
°\
'(
2
Y + ly
YH
I7"
N
7WF
8314
(D-ll)
where:
132.2
6,895
6.4516xlO-4
Conversion factor for Ibs/min to kg/s
Conversion factor for psi to Pascals (p0)
Conversion factor for square inches to square meters (Ah)
GF values were calculated for all gases regulated under CAA section 112(r) and are listed in
Appendix B, Exhibit B-l, for toxic gases and Appendix C, Exhibit C-2, for flammable gases.
April 15, 1999
D-14
-------
Appendix D
Technical Background
From the equation for choked flow above and the equation for the GF above, the initial release rate
for a gas from a hole in a tank can be written as:
QR = HA x Pt x — x GF
(D-12)
where: QR = Release rate (pounds per minute)
HA = Hole area (square inches)
Pt = Tank pressure (psia)
Tt = Tank temperature (K)
D.7 Alternative Scenario Analysis for Liquids
D.7.1 Releases from Holes in Tanks
The equation for estimating release rate of a liquid from a hole in a tank is based on the equations for
liquid release rate presented in the Handbook of Chemical Hazard Analysis Procedures by FEMA, DOT,
and EPA and EPA's Workbook of Screening Techniques for Assessing Impacts of Toxic Air Pollutants.
The equation for the instantaneous release rate is:
- Pa
where: m = Discharge rate (kilograms per second)
Ah = Opening area (square meters)
Cd = Discharge coefficient (unitless)
g = Gravitational constant (9.8 meters per second squared)
P! = Liquid density (kilograms per cubic meter)
P0 = Storage pressure (Pascals)
Pa = Ambient pressure (Pascals)
HL = Liquid height above bottom of container (meters)
Hh = Height of opening (meters)
A version of this equation is presented in the guidance for use with data found in Appendix B, for
gases liquefied under pressure. The equation in the text was derived using the conversion factors listed below
and density factors and equilibrium vapor pressure or tank pressure values listed in Appendix B, Exhibit B-l.
Equation D-13 becomes:
QR = 132.2x6.4516xl(T4x0.8x,ffi4 ^16.018xrfx[2x9.8xl6.018xrfxZ^x0.0254+2P x6895] (D-14)
April 15, 1999 D - 15
-------
Appendix D
Technical Background
where: QR = Release rate (pounds per minute)
HA = Hole area (square inches)
132.2 = Conversion factor for kilograms per second to pounds per minute
6.4516 x 10"4 = Conversion factor for square inches to square meters (HA)
0.8 = Discharge coefficient (0.8)
d = Liquid density (pounds per cubic foot); can derived by using the
density factor: l/(DFx0.033)
16.018 = Conversion factor for pounds per cubic feet to kilograms per cubic
meters (D)
9.8 = Gravitational constant (meters per second squared)
LH = Height of liquid above hole (inches)
2.54 x 10"2 = Conversion factor for inches to meters (LH)
Pg = Gauge pressure in tank (psi)
6,895 = Conversion factor for psi to Pascals (Pg)
After combining the conversion factors and incorporating the density factor (DF), this equation becomes:
QR = HA x 6.82
DF2 DF
For liquids stored at ambient pressure, Equation D-13 becomes:
07 - « *% « '. (D-15)
PL ~ Hk) (»-!«)
To derive the equation presented in the guidance for liquids under ambient pressure, all the chemical-
specific properties, constants, and conversion factors were combined into the "Liquid Leak Factor" (LLF).
The discharge coefficient was assumed to have a value of 0.8, based on the screening value recommended in
EPA's Workbook of Screening Techniques for Assessing Impacts of Toxic Air Pollutants. The LLF was
derived as follows:
LLF = 132.2 x 6.4516 x i(r4 x 0.1594 x 0.8 x ^/2 x 9.8 x p/ (D-17)
where: LLF = Liquid Leak Factor (pounds per minute-inches2 5)
132.2 = Conversion factor for kilograms per second to pounds per minute
(m)
6.4516 x 10"4 = Conversion factor for square inches to square meters (Ah)
0.1594 = Conversion factor for square root of inches to square root of meters
(HL-Hh)
0.8 = Discharge coefficient (0.8)
9.8 = Gravitational constant (meters per second squared)
P! = Liquid density (kilograms per cubic meter)
April 15, 1999 D-16
-------
Appendix D
Technical Background
LLF values were calculated for all liquids regulated under CAA section 112(r) and are listed in
Appendix B, Exhibit B-2, for toxic liquids and Appendix C, Exhibit C-3, for flammable liquids.
From the equation for liquid release rate from a hole in a tank at ambient pressure and the equation
for the LLF, the initial release rate for a liquid from a tank under atmospheric pressure can be written as:
QRL = HA
LLF
(D-18)
where:
QRL
HA
LH
Liquid release rate (pounds per minute)
Hole area (square inches)
Height of liquid above hole (inches)
D.7.2 Releases from Pipes
The equation used to estimate releases of liquids from pipes is the Bernoulli equation. It assumes
that the density of the liquid is constant and does not account for losses in velocity due to wall friction. The
equation follows:
(Pa ~
D
(D-19)
where:
P
va
vb
D
Isolating Vb yields:
Pressure at pipe inlet (Pascals)
Pressure at pipe outlet (Pascals)
Height above datum plane at pipe inlet (meters)
Height above datum plane at pipe release (meters)
Gravitational acceleration (9.8 meters per second squared)
Newton's law proportionality factor (1.0)
Operational velocity (meters per second)
Release velocity (meters per second)
Density of liquid (kilograms per cubic meter)
b ~ ^
D
2g(Za- Zh) + Fa2
(D-20)
To develop the equation presented in the text, conversion factors for English units and constants
were incorporated as follows:
April 15, 1999
D-17
-------
Appendix D
Technical Background
2x6895x(P7,-14.7)xJDFx0.033
16.08
(2x9.8xQ.3048x(Za-Zfe) + 0.005082xFa2
(D-21)
where: Vb = Release velocity (feet per minute)
197 = Conversion factor for meters per second to feet per minute
6895 = Conversion factor for psi to Pascals
PT = Total pipe pressure (psi)
14.7 = Atmospheric pressure (psi)
16.08 = Conversion factor for pounds per cubic foot to kilograms per cubic meter
DF = Density factor (1/(0.033 DF)= density in pounds per cubic foot)
9.8 = Gravitational acceleration (meters per second2)
0.3048 = Conversion factor for feet to meters
Za-Zb = Change in pipe elevation, inlet to outlet (feet)
0.00508= Conversion factor for feet per minute to meters per second
Va = Operational velocity (feet per minute)
D.8 Vapor Cloud Fires
Factors for leaks from tanks for flammable substances (GF and LLF) were derived as described for
toxic substances (see above).
The endpoint for estimating impact distances for vapor cloud fires of flammable substances is the
lower flammability limit (LFL). The LFL is one of the endpoints for releases of flammable substances
specified in the RMP Rule. It was chosen to provide a reasonable, but not overly conservative, estimation of
the possible extent of a vapor cloud fire.
D.9 Pool Fires
A factor used for estimating the distance to a heat radiation level from a pool fire that could cause
second degree burns from a 40-second exposure was developed based on equations presented in the AIChE
document, Guidelines for Evaluating the Characteristics of Vapor Cloud Explosions, Flash Fires, and
BLEVEs and in the Netherlands TNO document, Methods for the Determination of Possible Damage to
People and Objects Resulting from Releases of Hazardous Materials (1992). The AIChE and TNO
documents present a point-source model that assumes that a selected fraction of the heat of combustion is
emitted as radiation in all directions. The radiation per unit area received by a target at some distance from
the point source is given by:
471 x:
(D-22)
April 15, 1999
D-18
-------
Appendix D
Technical Background
where: q = Radiation per unit area received by the receptor (Watts per square meter)
m = Rate of combustion (kilograms per second)
ua = Atmospheric transmissivity
Hc = Heat of combustion (Joules per kilogram)
/ = Fraction of heat of combustion radiated
x = Distance from point source to receptor (meters)
The fraction of combustion energy dissipated as thermal radiation (f in the equation above) is
reported to range from 0.1 to 0.4. To develop factors for estimating distances for pool fires, this fraction was
assumed to be 0.4 for all the regulated flammable substances. The heat radiation level (q) was assumed to be
5 kilowatts (5,000 Watts) per square meter. This level is reported to cause second degree burns from a 40-
second exposure. One of the endpoints for releases of flammable substances specified in the RMP Rule is 5
kilowatts per square meter for 40 seconds. It was assumed that people would be able to escape from the heat
in 40 seconds. The atmospheric transmissivity (ua) was assumed equal to one.
For a pool fire of a flammable substance with a boiling point above the ambient temperature, the
combustion rate can be estimated by the following empirical equation:
0.0010 H A
m = c
(D-23)
+ Cp (Tb - Ta}
where: m = Rate of combustion (kilograms per second)
Hc = Heat of combustion (Joules per kilogram)
Hv = Heat of vaporization (Joules per kilogram)
Cp = Liquid heat capacity (Joules per kilogram-degree K)
A = Pool area (square meters)
Tb = Boiling temperature (K)
Ta = Ambient temperature (K)
0.0010 = Constant
Combining Equations D-22 and D-23 (above), and assuming a heat radiation level of 5,000 Watts
per square meter, gives the following equation for liquid pools of substances with boiling points above
ambient temperature:
\
0.0010 A
471
-------
Appendix D
Technical Background
x =
\
0.0001 A
5,00071 (Hv + C(Tb
(D-25)
where: x = Distance from point source to receptor (meters)
q = Radiation per unit area received by the receptor = 5,000 Watts per square
meter
Hc = Heat of combustion (Joules per kilogram)
/ = Fraction of heat of combustion radiated = 0.4
Hv = Heat of vaporization (Joules per kilogram)
Cp = Liquid heat capacity (Joules per kilogram-degree Kelvin)
A = Pool area (square meters)
Tb = Boiling temperature (K)
Ta = Ambient temperature (K)
0.0010 = Constant
For a pool fire of a flammable substance with a boiling point below the ambient temperature (i.e.,
liquefied gases) the combustion rate can be estimated by the following equation, based on the TNO
document:
m =
0.0010 Hc A
If..
(D-26)
where: m = Rate of combustion (kilograms per second)
Hv = Heat of vaporization (Joules per kilogram)
Hc = Heat of combustion (Joules per kilogram)
A = Pool area (square meters)
0.0010 = Constant
Then the equation for distance at which the radiation received equals 5,000 Watts per square meter becomes:
(D-27)
x =
\
0.0001 A
5,00071 H
where:
x = Distance from point source to receptor (meters)
5,000 = Radiation per unit area received by the receptor (Watts per square meter)
Hc = Heat of combustion (Joules per kilogram)
Hv = Heat of vaporization (Joules per kilogram)
A = Pool area (square meters)
0.0001 = Derived constant (see equations D-20 and D-21)
April 15, 1999
D-20
-------
Appendix D
Technical Background
A "Pool Fire Factor" (PFF) was calculated for each regulated flammable liquid and gas (to be applied
to gases liquefied by refrigeration) to allow estimation of the distance to the heat radiation level that would
lead to second degree burns. For the derivation of this factor, ambient temperature was assumed to be 298 K
(25 °C). Other factors are discussed above. The PFF for liquids with boiling points above ambient
temperature was derived as follows:
PFF =
c
\
0.0001
(D-28)
5,00071 [Hv + C(Tb - 298)]
where: 5,000 = Radiation per unit area received by the receptor (Watts per square meter)
Hc = Heat of combustion (Joules per kilogram)
Hv = Heat of vaporization (Joules per kilogram)
Cp = Liquid heat capacity (Joules per kilogram-degree K)
Tb = Boiling temperature (K)
298 = Assumed ambient temperature (K)
0.0001 = Derived constant (see above)
For liquids with boiling points below ambient temperature, the PFF is derived as follows:
PFF = H
\
0.0001
(D-29)
5,00071 H
where: 5,000 = Radiation per unit area received by the receptor (Watts per square meter)
Hc = Heat of combustion (Joules per kilogram)
Hv = Heat of vaporization (Joules per kilogram)
0.0001 = Derived constant (see above)
Distances where exposed people could potentially suffer second degree burns can be estimated as the
PFF multiplied by the square root of the pool area (in square feet), as discussed in the text.
D.10 BLEVEs
Reference Table 30, the table of distances for BLEVEs, was developed based on equations presented
in the AIChE document, Guidelines for Evaluating the Characteristics of Vapor Cloud Explosions, Flash
Fires, and BLEVEs. The Hymes point-source model for a fireball, as cited in the AIChE document, uses the
following equation for the radiation received by a receptor:
2.2 Ta R Hc mf°'67
q = a- — (D-30)
where: q = Radiation received by the receptor (Watts per square meter)
mf = Mass of fuel in the fireball (kg)
April 15, 1999 D - 21
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Appendix D
Technical Background
ua = Atmospheric transmissivity
Hc = Heat of combustion (Joules per kilogram)
R = Radiative fraction of heat of combustion
L = Distance from fireball center to receptor (meters)
TI = 3.14
Hymes (as cited by AIChE) suggests the following values for R:
R = 0.3 for vessels bursting below relief valve pressure
R = 0.4 for vessels bursting at or above relief valve pressure
For development of Reference Table 30, the following conservative assumptions were made:
R = 0.4
The effects of radiant heat on an exposed person depend on both the intensity of the radiation and the
duration of the exposure. For development of the table of distances for BLEVEs, it was assumed that the
time of exposure would equal the duration of the fireball. The AIChE document gives the following
equations for duration of a fireball:
tc = 0.45 mfv3 for mf < 30,000 kg (D-31)
and
tc = 2.6 mfv6 for mf > 30,000 kg (D-32)
where: mf = Mass of fuel (kg)
tc = Combustion duration (seconds)
According to several sources (e.g., Eisenberg, et al., Vulnerability Model, A Simulation System for
Assessing Damage Resulting from Marine Spills; Mudan, Thermal Radiation Hazards from Hydrocarbon
Pool Fires (citing K. Buettner)), the effects of thermal radiation are generally proportional to radiation
intensity to the four-thirds power times time of exposure. Thus, a thermal "dose" can be estimated using the
following equation:
Dose = t q4'3 (D-33)
where: t = Duration of exposure (seconds)
q = Radiation intensity (Watts/m2)
The thermal "dose" that could cause second-degree burns was estimated assuming 40 seconds as the
duration of exposure and 5,000 Watts/m2 as the radiation intensity. The corresponding dose is 3,420,000
(Watts/m2)4/3-second.
April 15, 1999 D - 22
-------
Appendix D
Technical Background
For estimating the distance from a fireball at which a receptor might receive enough thermal radiation
to cause second degree burns, the dose estimated above was substituted into the equation for radiation
received from a fireball:
,420,000
t
(D-34)
3,420,000
3/4
t
2.2
R Hc mf°'67
(D-35)
where:
L
m
R
t
L =
\
2.2 Ta R Hc m°'67
471
3,420,000
t
3/4
(D-36)
Distance from fireball center to receptor (meters)
Radiation received by the receptor (Watts per square meter)
Mass of fuel in the fireball (kg)
Atmospheric transmissivity (assumed to be 1)
Heat of combustion (Joules per kilogram)
Radiative fraction of heat of combustion (assumed to be 0.4)
Duration of the fireball (seconds) (estimated from the equations above);
assumed to be duration of exposure
Equation D-36 was used to develop the reference table for BLEVEs presented in the text (Reference
Table 30).
D.ll Alternative Scenario Analysis for Vapor Cloud Explosions
According to T.A. Kletz, in "Unconfmed Vapor Cloud Explosions" (Eleventh Loss Prevention
Symposium, sponsored by AIChE, 1977), unconfmed vapor cloud explosions almost always result from the
release of flashing liquids. For this reason, the quantity in the cloud for the alternative scenario vapor cloud
explosion in this guidance is based on the fraction flashed from the release of a flammable gas liquefied under
pressure. The guidance provides a method to estimate the quantity in the cloud from the fraction flashed into
vapor plus the quantity that might be carried along as aerosol. The recommendation to use twice the quantity
flashed as the mass in the cloud (so long as it does not exceed the total amount of flammable substance
available) is based on the method recommended by the UK Health and Safety Executive (HSE), as cited in the
AIChE document, Guidelines for Evaluating the Characteristics of Vapor Cloud Explosions, Flash Fires,
and BLEVEs. The factor of two is intended to allow for spray and aerosol formation.
April 15, 1999
D-23
-------
Appendix D
Technical Background
The equation for the flash fraction, for possible use in for the alternative scenario analysis, is based
on the Netherlands TNO document, Methods for the Calculation of the Physical Effects of the Escape of
Dangerous Material (1980), Chapter 4, "Spray Release." The following equation is provided:
T C T
where: Xvapa = Weight fraction of vapor after expansion
Xvap b = Weight fraction of vapor before expansion (assumed to be 0 for calculation
of the flash fraction)
Tb = Boiling temperature of gas compressed to liquid (K)
T, = Temperature of stored gas compressed to liquid (K)
C, = Specific heat of gas compressed to liquid (Joules/kilogram-K)
hv = Heat of evaporation of gas compressed to liquid (Joules/kilogram)
To develop a Flash Fraction Factor (FFF) for use in consequence analysis, compressed gases were
assumed to be stored at 25 °C (298 K) (except in cases where the gas could not be liquefied at that
temperature). The equation for FFF is:
777777 I TbCi , 298
= ~~ ~ (D"38)
where: Tb = Boiling temperature of gas compressed to liquid (K)
C, = Specific heat of gas compressed to liquid (Joules/kilogram-K)
hv = Heat of evaporation of gas compressed to liquid (Joules/kilogram)
298 = Temperature of stored gas compressed to liquid (K)
The recommendation to use a yield factor of 0.03 for the alternative scenario analysis for vapor cloud
explosions also is based on the UK HSE method cited by AIChE. According to the AIChE document, this
recommendation is based on surveys showing than most major vapor cloud explosions have developed
between 1 percent and 3 percent of available energy.
April 15, 1999 D - 24
-------
APPENDIX E
WORKSHEETS FOR OFFSITE CONSEQUENCE ANALYSIS
Using the Methods in this Guidance
April 15, 1999
-------
WORKSHEET 1
WORST-CASE ANALYSIS FOR TOXIC GAS
1. Select Scenario (defined by rule for worst case as release of largest quantity
over 10 minutes)
• Identify toxic gas
• Identify largest quantity in
largest vessel or pipeline
• Identify worst-case
meteorological conditions
Name:
CAS number:
Quantity (pounds}:
Atmospheric stability class: F
Wind speed: 1.5 m/s
Ambient temperature: 25 °C
Relative humidity: 50%
Guidance
Reference
Chapter 2
Section 3.1
2. Determine Release Rate
• Estimate release rate
Quantity/10 min, except
gases liquefied by
refrigeration in some cases
• Revise release rate to
account for passive mitigation
(enclosure)
Release rate dbs/min):
Will release always take place in enclosure?
(If yes, go to next step)
Can release cause failure of enclosure?
(If yes, use unmitigated release rate)
Factor to account for enclosure: 0.55
Mitisated release rate dbs/min):
Section 3.1.1
Section 3. 1.2
3. Determine Distance to the Endpoint Specified by Rule
• Identify endpoint
• Determine gas density
Consider conditions (e.g.,
liquefied under pressure)
• Determine site topography
Rural and urban defined by
rule
• Determine appropriate
reference table of distances
Use 10-minute tables
• Find distance on reference
table
Endpoint (mg/L):
Dense:
Neutrallv buovant:
Rural:
Urban:
Reference table used (number):
Release rate/endpoint (neutrallv buovant):
Distance to endpoint (mi):
Exhibit B-l
Exhibit B-l
Section 2.1
Chapter 4
Reference
Tables 1-12
Chapter 4
Reference
Tables 1-12
April 15, 1999
E- 1
-------
WORKSHEET 2
WORST-CASE ANALYSIS FOR TOXIC LIQUID
1. Select Scenario (defined by rule for worst case as release of largest quantity to
form an evaporating pool)
• Identify toxic liquid
• Identify concentration for
solutions or mixtures
• Identify largest quantity in
largest vessel or pipeline
• Identify worst-case
meteorological conditions
Name:
CAS number:
Concentration in solution or mixture fwt %):
•
Quantitv (pounds}:
Quantitv of regulated substance in mixture:
* •
Atmospheric stability class: F
Wind speed: 1.5 m/s
Ambient temperature: 25 °C
Relative humidity: 50%
Guidance
Reference
Chapter 2
Section 3. 2
Section 3. 2. 4
for mixtures
2. Determine Release Rate
• Determine temperature of
spilled liquid
Must be highest maximum
daily temperature or process
temperature, or boiling point
for gases liquefied by
refrigeration
• Determine appropriate
liquid factors for release rate
estimation
Temperature of liquid (°C):
LFA:
LFB:
DF:
TCP:
Section 3. 2
Section 3.1.3
Section 3. 2,
Exhibits B-2,
B-4
Section 3.3,
Exhibit B-3
for water
solutions
Estimate Maximum Pool Area
• Estimate maximum pool
area
Spilled liquid forms pool 1
cm deep
Maximum pool area (ft2):
Section 3. 2. 3
Equation 3-6
April 15, 1999
E-2
-------
WORKSHEET 2 (continued)
Estimate Pool Area for Spill into Diked Area
• Estimate diked area
Consider failure of dikes or
overflow of diked area
Diked area (ft2):
Is diked area smaller than maximum area?
(If no, use maximum area to estimate release rate)
Diked volume (ft3):
Spilled volume (ft3):
Is spilled volume smaller than diked volume?
(If no, estimate overflow)
Overflow volume (ft3):
Overflow area (ft2):
Section 3.2.3
• Choose pool area for release
rate estimation
Maximum area, diked area,
or sum of diked area and
overflow area
Pool area (ft2):
Section 3.2.3
Estimate Release Rate from Pool
• Estimate release rate for
undiked pool (maximum pool
area)
Based on quantity spilled,
LFAorLFB, andDF
Release rate (Ibs/min):
Section 3.2.2
Section 3.2.4
(mixtures)
Equation 3-3
or 3-4
• Estimate release rate for
diked pool (use pool area
from previous section)
Based on pool area and LFA
orLFB
Release rate (Ibs/min):
Section 3.2.2
Section 3.2.4
(mixtures)
Equation 3-7
or 3-8
• Revise release rate for
release in building
Apply factor to release rate
Release rate if outside (Ibs/min)
(Use release rate for undiked or diked pool)
Factor to account for enclosure: 0.1
Revised release rate (Ibs/min):
Section 3.2.3
Equations 3-9,
3-10
• Revise release rate for
temperature
Apply appropriate TCP to
release rate
Revised release rate (Ibs/min):
Section 3.2.5
Equation 3-11
Estimate duration of release
Release duration (min):
Section 3.2.2
Equation 3-5
April 15, 1999
E-:
-------
WORKSHEET 2 (continued)
3. Determine Distance to the Endpoint
• Identify endpoint
Specified by rule
• Determine vapor density
• Determine site topography
Rural and urban defined by
rule
• Determine appropriate
reference table of distances
Based on release duration,
vapor density, topography
• Find distance on reference
table
Endpoint (mg/L):
Dense:
Neutrally buovant:
~
Rural:
Urban:
Reference table used (number}:
Release rate/endpoint (neutrallv buovant):
Distance to endpoint (mi):
Exhibit B-2
Exhibit B-2
Section 2.1
Chapter 4
Reference
Tables 1-12
Chapter 4
Reference
Tables 1-12
April 15, 1999
E-4
-------
WORKSHEET 3
WORST-CASE ANALYSIS FOR FLAMMABLE SUBSTANCE
1. Select Scenario (defined by rule for worst case as vapor cloud explosion of
largest quantity)
Guidance
Reference
• Identify flammable
substance
• Identify largest quantity in
largest vessel or pipeline
Consider total quantity of
flammable substance,
including non-regulated
substances inflammable
mixtures
Name:
CAS number:
Chapter 2
Section 3.1
Quantity (pounds):
2. Determine Distance to the Endpoint (endpoint specified by the rule as 1 psi overpressure;
yield factor assumed to be 10% for TNT-equivalent model)
• Estimate distance to 1 psi
using Reference Table
Find quantity, read distance
from table
Distance to 1 psi (mi):
Chapter 5
Reference
Table 13
• Alternatively, estimate
distance to 1 psi using
equation
For pure substance:
Heat of combustion (kJ/kg):
For mixture:
Heat of combustion of major component
(kJ/kg):
Heats of combustion of other components
(kJ/kg): , ,
Distance to 1 psi (mi).
Chapter 5
Appendix C.I
Appendix C.2
Exhibit C-l
April 15, 1999
E-5
-------
WORKSHEET 4
ALTERNATIVE SCENARIO ANALYSIS FOR TOXIC GAS
1. Select Scenario
Guidance
Reference
Identify toxic gas
• Identify conditions of
storage or processing of toxic
gas
Treat gases liquefied by
refrigeration as liquids
• Develop alternative
scenario
> More likely than worst
case
> Should reach endpoint
off site
• Identify average
meteorological conditions
Name:
CAS number:
Non-liquefied pressurized gas:
Gas liquefied under pressure:
In tank:
In pipeline:
Other (describe):
Chapter 6
Chapter 7
Section 7.1
Describe scenario:
Atmospheric stability class: D
Wind speed: 3.0 m/s
Ambient temperature: 25 °C
Relative humidity: 50%
2. Determine Release Rate
• Estimate gas release rate
from hole in tank (choked/
maximum flow) for
> Pressurized gas
> Gas liquefied under
pressure released from vapor
space
Hole area (in2):
Tank pressure (psia):
Tank temperature (K):
GF:
Release rate (Ibs/min):
Section 7.1.1
Equation 7-1
Exhibit B-l
• Estimate flashing liquid
release rate from hole in tank
> Gas liquefied under
pressure released from liquid
space
Hole area (in2):
Tank pressure (psig):
DF:
Liquid height above hole (in):
Release rate (Ibs/min):
Section 7.1.2
Equation 7-2
Exhibit B-l
April 15, 1999
E-6
-------
WORKSHEET 4 (continued)
• Estimate flashing liquid
release rate from break in
long pipeline
> Gas liquefied under
pressure completely filling
pipeline
• Estimate release duration
• Revise release rate for
passive mitigation (enclosure)
• Revise release rate for
active mitigation
• Estimate release duration
(mitigated release)
• Other release rate
estimation
Initial flow rate (Ibs/min):
DF:
Initial flow velocity (ft/min):
Pipe pressure (psi):
Change in pipe elevation (ft):
Cross-sectional pipe area (ft2):
Release rate (Ibs/min):
~
Time to stop release (min):
Time to emptv tank or pipe (min):
Default release duration: 60 min
Release rate if outside (Ibs/min):
Factor to account for enclosure: 0.55
Revised release rate (Ibs/min):
~
Active mitigation technique used:
Time to stop release using active technique
(min):
Fractional release rate reduction by active
technique:
Revised release rate (Ib/min):
~
Release duration (min):
Release rate (Ib/min):
Method of release rate estimation (describe):
Release duration (min):
~
Sections 7.1.1
and 7.2.1
Exhibit B-l
Section 7.1.1
Section 7. 1.2
Section 3. 1.2
Section 7. 1.2
3. Determine Distance to the Endpoint
• Identify endpoint
Specified by rule
• Determine gas density
Consider conditions (e.g.,
liquefied under pressure,
refrigeration)
• Determine site topography
Rural and urban defined by
rule
Endpoint (mg/L):
Dense:
Neutrallv buovant:
Rural:
Urban:
Exhibit B-l
Exhibit B-l
Section 2.1
April 15, 1999
E-7
-------
WORKSHEET 4 (continued)
• Determine appropriate
reference table of distances
Based on release duration,
vapor density, and
topography
• Find distance on reference
table
Reference table used (number):
Release rate/endpoint (neutrallv buovant):
Distance to endpoint (mi):
Chapter 8
Reference
Tables 14-25
Chapter 8
Reference
Tables 14-25
April 15, 1999
-------
WORKSHEET 5
ALTERNATIVE SCENARIO ANALYSIS FOR TOXIC LIQUID
1. Select Scenario
• Identify toxic liquid Include
gases liquefied by
refrigeration
• Identify concentration for
solutions or mixtures
• Identify conditions of
storage or processing of toxic
liquid
• Develop alternative
scenario
> More likely than worst
case
> Should reach endpoint
off site
• Identify meteorological
conditions
Name:
CAS number:
Concentration in solution or mixture (wt %):
Atmospheric tank:
Pressurized tank:
Pipeline:
Other (describe}:
Describe scenario:
Atmospheric stability class: F
Wind speed: 3.0 m/s
Ambient temperature: 25 °C
Relative humidity: 50%
Guidance
Reference
Chapter 6
Chapter 7
Section 7.2
2. Determine Release Rate
Determine Liquid Release Rate and Quantity Released into Pool
• Estimate liquid release rate
from hole in atmospheric tank
• Estimate liquid release rate
from break in long pipeline
• Estimate liquid release
duration
Hole area (in2}:
LLF:
Liquid height above hole (in}:
Liquid release rate dbs/min}:
±
Initial flow rate dbs/min}:
DF:
Initial flow velocitv (ft/min):
Pipe pressure (psi):
Change in pipe elevation (ft}:
Cross-sectional pipe area (ft2}:
Liquid release rate dbs/min}:
Time to stop release (min):
Time to emvtv tank to level of hole (min}:
Section 7. 2.1
Equation 7-4
Exhibit B-2
Section 7. 2.1
Equations 7-5
-7-7
Exhibit B-2
Section 7. 2.1
April 15, 1999
E-9
-------
WORKSHEET 5 (continued)
• Revise liquid release
duration for active mitigation
• Estimate quantity of liquid
released into pool
Liquid release rate times
duration
Active mitigation technique (describe}:
Time to stop release (min):
Quantity of liquid released (Ibs):
Section 7.2.2
Sections 7. 2.1,
7.2.2, 7.2.3
Determine Pool Area and Evaporation Rate from Pool
• Determine temperature of
spilled liquid
• Determine appropriate
liquid factors for release rate
estimation
Temperature of liquid (°C):
LFA:
LFB:
DF:
TCP:
Section 7.2.3
Sections 7.2.3,
3.2, and
Exhibits B-2,
B-4
Section 3. 3
and Exhibit B-
3 for water
solutions
Estimate Maximum Pool Area
• Estimate maximum pool
area
Spilled liquid forms pool 1
cm deep
Maximum pool area (ft2):
Section 7.2.3,
3.2.3 Equation
3-6
Estimate Pool Area for Spill into Diked Area
• Estimate diked area
Consider possibility of failure
of dikes or overflow of diked
area
• Choose pool area for
evaporation rate estimation
Maximum area, diked area,
or sum of diked area and
overflow area
Diked area (ft2):
Is diked area smaller than maximum area?
(If no, use maximum area to estimate release rate)
Diked volume (ft3):
Spilled volume (ft3):
Is spilled volume smaller than diked volume?
(If no, estimate overflow)
Overflow volume (ft3):
Overflow area (ft2):
Pool area (ft2):
Section 7.2.3,
3.2.3
Section 7.2.3,
3.2.3
April 15, 1999
E- 10
-------
WORKSHEET 5 (continued)
Estimate Release Rate from Pool
• Estimate release rate for
undiked pool
Based on quantity spilled,
LFAorLFB, andDF
• Estimate release rate for
diked pool (use pool area
from previous section)
Based on pool area and LFA
orLFB
• Revise release rate for
temperature
Apply appropriate TCP to
release rate
• Revise release rate for
release in building
Apply factor to release rate
• Revise release rate for
active mitigation technique
• Compare liquid release rate
and pool evaporation rate
• Choose smaller release rate
as release rate for analysis
Release rate (Ibs/min):
Release rate (Ibs/min):
Revised release rate (Ibs/min):
Release rate if outside (Ibs/min):
Factor to account for enclosure: 0.05
Revised release rate (Ibs/min):
~
Active mitigation technique used:
Fractional release rate reduction by active
technique:
Revised release rate (Ib/min):
'
Release rate (Ib/min) :
Section 7.2 3
Section 3. 2. 4
(mixtures)
Equation 7-8
or 7-9
Sections 7.2.3,
3.2.2
Section 3. 2. 4
(mixtures)
Equation 7- 10
or 7-11
Sections 7.2.3,
3.2.5
Equation 3-11
Sections 7.2.3,
3.2.3
Section 7.2.3
Section 7.2.3
3. Determine Distance to the Endpoint
• Identify endpoint
Specified by rule
• Determine vapor density
• Determine site topography
Rural and urban defined by
rule
Endpoint (mg/L):
Dense:
Neutrallv buovant:
~
Rural:
Urban:
Exhibit B-2
Exhibit B-2
Section 2.1
April 15, 1999
E- 11
-------
WORKSHEET 5 (continued)
• Determine appropriate
reference table of distances
Based on release duration,
vapor density, and
topography
• Find distance on reference
table
Reference table used (number):
Release rate/endpoint (neutrallv buovant):
Distance to endpoint (mi):
Chapter 8
Reference
Tables 14-25
Chapter 8
Reference
Tables 14-25
April 15, 1999
E- 12
-------
WORKSHEET 6
ALTERNATIVE SCENARIO ANALYSIS FOR FLAMMABLE SUBSTANCE
1. Select Scenario
• Identify flammable
substance
• Identify conditions of
storage or processing of
flammable substance
Treat gases liquefied by
refrigeration as liquids
• Identify appropriate
scenario
> Vapor cloud fire
> Pool fire
> BLEVE/fireball
> Vapor cloud explosion
> Other (not covered by
OCA Guidance)
Name:
CAS number:
Non-liquefied pressurized gas:
Gas liquefied under pressure:
Gas liquefied bv refrigeration:
Liquid under atmospheric pressure:
Liquid underpressure greater than atmospheric :_
Other (describe):
Alternative scenario/type of fire or explosion
(describe):
Guidance
Reference
Chapter 6
2. Determine Release Rate
Determine Release Rate for Vapor Cloud Fire
• For gas releases and
flashing liquid releases, see
Worksheet 4
• For liquid releases (non-
flashing), see Worksheet 5
Release rate (Ibs/min):
Liquid release rate (Ibs/min):
Liquid release duration (min):
Ouantitv in pool (Ibs):
Release rate to air (Ibs/min):
Section 9.1
Section 7.1
Equations 7-1,
7-2, 7-3
Exhibit C-2
Section 9.2
Section 7.2
Equations 7-4-
7-12
Exhibit C-3
Determine Pool Area for Pool Fire
Estimate pool area: See
Worksheet 5
Ouantitv in pool (Ibs):
Pool area (ft2):
Sections 10.2
Section 7.2
Exhibits C-2,
C-3
April 15, 1999
E- 13
-------
WORKSHEET 6 (continued)
Determine Quantity for BLEVE
Determine quantity in tank
Ouantitv fibs):
'
Section 10.3
Determine Quantity for Vapor Cloud Explosion
Determine quantity in tank
Ouantitv fibs):
'
Section 10.4
3. Determine Distance to the Endpoint
• Identify endpoint suitable
for scenario
> LFL
> 5kW/m2for40
seconds
> 1 psi overpressure
Endpoint:
Chapter 6
Exhibits C-2,
C-3
Determine Distance to LFL for Vapor Cloud Fire
• Determine vapor density
• Determine site topography
Rural and urban defined by
rule
• Determine appropriate
reference table of distances
Based on vapor density and
topography
• Find distance on reference
table
Dense:
Neutrallv buovant:
~
Rural:
Urban:
Reference table used (number):
Release rate/endpoint (neutrallv buovant):
Distance to LFL (mi):
Exhibit B-2
Section 2.1
Section 10.1
Reference
Tables 26-29
Section 10.1
Reference
Tables 26-29
Determine Distance to Heat Radiation Endpoint for Pool Fire
• Calculate distance to 5
kW/m2
PFF:
Pool area (ft2):
Distance (ft):
Section 10.2
Equation 10-1
April 15, 1999
E- 14
-------
WORKSHEET 6 (continued)
Determine Distance to Heat Radiation Endpointfor BLEVE
Determine distance for
radiation from fireball
equivalent to 5 kW/m2 for 40
seconds
Quantitv (Ibs):
Distance (mi):
Section 10.3
Reference
Table 30
Determine Distance to Overpressure Endpoint For Vapor Cloud Explosion
Determine distance to 1 psi
Quantity in cloud can be
less than total quantity
Yield factor can be less
than 10%
FFF:
Quantitv flashed:
Yieldfactor:
Distance to 1 psi (mi):
Section 10.4
Exhibit C-2
Reference
Table 13
April 15, 1999
E- 15
-------
APPENDIX F
CHEMICAL ACCIDENT PREVENTION PROVISIONS
As codified at 40 CFR part 68 as of July 1, 1998
-------
Pt. 67, App. A
40 CFR Ch. I (7-1-98 Edition)
local agent, any noncompliance pen-
alties owed by the source owner or op-
erator shall be paid to the State or
local agent.
APPENDIX A TO PART 67—TECHNICAL
SUPPORT DOCUMENT
NOTE: EPA will make copies of appendix A
available from: Director, Stationary Source
Compliance Division, EN-341, 401 M Street,
SW., Washington, DC 20460.
[54 FR 25259, June 20, 1989]
APPENDIX B TO PART 67— INSTRUCTION
MANUAL
NOTE: EPA will make copies of appendix B
available from: Director, Stationary Source
Compliance Division, EN-341, 401 M Street,
SW., Washington, DC 20460.
[54 FR 25259, June 20, 1989]
APPENDIX C TO PART 67—COMPUTER
PROGRAM
NOTE: EPA will make copies of appendix C
available from: Director, Stationary Source
Compliance Division, EN-341, 401 M Street,
SW., Washington, DC 20460.
[54 FR 25259, June 20, 1989]
PART 68—CHEMICAL ACCIDENT
PREVENTION PROVISIONS
Subpart A—General
Sec.
68.1 Scope.
68.2 Stayed provisions.
68.3 Definitions.
68.10 Applicability.
68.12 General requirements.
68.15 Management.
Subpart B—Hazard Assessment
68.20 Applicability.
68.22 Offsite consequence analysis param-
eters.
68.25 Worst-case release scenario analysis.
68.28 Alternative release scenario analysis.
68.30 Defining offsite impacts—population.
68.33 Defining offsite impacts—environ-
ment.
68.36 Review and update.
68.39 Documentation.
68.42 Five-year accident history.
Subpart C—Program 2 Prevention Program
68.48 Safety information.
68.50 Hazard review.
68.52 Operating procedures.
68.54 Training.
68.56 Maintenance.
68.58 Compliance audits.
68.60 Incident investigation.
Subpart D—Program 3 Prevention Program
68.65 Process safety information.
68.67 Process hazard analysis.
68.69 Operating procedures.
68.71 Training.
68.73 Mechanical integrity.
68.75 Management of change.
68.77 Pre-startup review.
68.79 Compliance audits.
68.81 Incident investigation.
68.83 Employee participation.
68.85 Hot work permit.
68.87 Contractors.
Subpart E—Emergency Response
68.90 Applicability.
68.95 Emergency response program.
Subpart F—Regulated Substances for
Accidental Release Prevention
68.100 Purpose.
68.115 Threshold determination.
68.120 Petition process.
68.125 Exemptions.
68.130 List of substances.
Subpart G—Risk Management Plan
68.150 Submission.
68.155 Executive summary.
68.160 Registration.
68.165 Offsite consequence analysis.
68.168 Five-year accident history.
68.170 Prevention program/Program 2.
68.175 Prevention program/Program 3.
68.180 Emergency response program.
68.185 Certification.
68.190 Updates.
Subpart H—Other Requirements
68.200 Recordkeeping.
68.210 Availability of information to the
public.
68.215 Permit content and air permitting
authority or designated agency require-
ments.
68.220 Audits.
APPENDIX A TO PART 68—TABLE OF Toxic
ENDPOINTS
AUTHORITY: 42 U.S.C. 7412(r), 7601 (a) (1),
7661-7661f.
SOURCE: 59 FR 4493, Jan. 31, 1994, unless
otherwise noted.
36
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Environmental Protection Agency
§68.2
Subpart A—General
§68.1 Scope.
This part sets forth the list of regu-
lated substances and thresholds, the
petition process for adding or deleting
substances to the list of regulated sub-
stances, the requirements for owners or
operators of stationary sources con-
cerning the prevention of accidental
releases, and the State accidental re-
lease prevention programs approved
under section 112(r). The list of sub-
stances, threshold quantities, and acci-
dent prevention regulations promul-
gated under this part do not limit in
any way the general duty provisions
under section 112(r)(l).
§68.2 Stayed provisions.
(a) Notwithstanding any other provi-
sion of this part, the effectiveness of
the following provisions is stayed from
March 2, 1994 to December 22, 1997.
(1) In Sec. 68.3, the definition of "sta-
tionary source," to the extent that
such definition includes naturally oc-
curring hydrocarbon reservoirs or
transportation subject to oversight or
regulation under a state natural gas or
hazardous liquid program for which the
state has in effect a certification to
DOT under 49 U.S.C. 60105;
(2) Section 68.115(b)(2) of this part, to
the extent that such provision requires
an owner or operator to treat as a regu-
lated flammable substance:
(i) Gasoline, when in distribution or
related storage for use as fuel for inter-
nal combustion engines;
(ii) Naturally occurring hydrocarbon
mixtures prior to entry into a petro-
leum refining process unit or a natural
gas processing plant. Naturally occur-
ring hydrocarbon mixtures include any
of the following: condensate, crude oil,
field gas, and produced water, each as
defined in paragraph (b) of this section;
(iii) Other mixtures that contain a
regulated flammable substance and
that do not have a National Fire Pro-
tection Association flammability haz-
ard rating of 4, the definition of which
is in the NFPA 704, Standard System
for the Identification of the Fire Haz-
ards of Materials, National Fire Pro-
tection Association, Quincy, MA, 1990,
available from the National Fire Pro-
tection Association, 1 Batterymarch
Park, Quincy, MA 02269-9101; and
(3) Section 68.130(a).
(b) From March 2, 1994 to December
22, 1997, the following definitions shall
apply to the stayed provisions de-
scribed in paragraph (a) of this section:
Condensate means hydrocarbon liquid
separated from natural gas that con-
denses because of changes in tempera-
ture, pressure, or both, and remains
liquid at standard conditions.
Crude oil means any naturally occur-
ring, unrefined petroleum liquid.
Field gas means gas extracted from a
production well before the gas enters a
natural gas processing plant.
Natural gas processing plant means
any processing site engaged in the ex-
traction of natural gas liquids from
field gas, fractionation of natural gas
liquids to natural gas products, or
both. A separator, dehydration unit,
heater treater, sweetening unit, com-
pressor, or similar equipment shall not
be considered a "processing site" un-
less such equipment is physically lo-
cated within a natural gas processing
plant (gas plant) site.
Petroleum refining process unit means
a process unit used in an establishment
primarily engaged in petroleum refin-
ing as defined in the Standard Indus-
trial Classification code for petroleum
refining (2911) and used for the follow-
ing: Producing transportation fuels
(such as gasoline, diesel fuels, and jet
fuels), heating fuels (such as kerosene,
fuel gas distillate, and fuel oils), or lu-
bricants; separating petroleum; or sep-
arating, cracking, reacting, or reform-
ing intermediate petroleum streams.
Examples of such units include, but are
not limited to, petroleum based solvent
units, alkylation units, catalytic
hydrotreating, catalytic hydrorefining,
catalytic hydrocracking, catalytic re-
forming, catalytic cracking, crude dis-
tillation, lube oil processing, hydrogen
production, isomerization, polymeriza-
tion, thermal processes, and blending,
sweetening, and treating processes. Pe-
troleum refining process units include
sulfur plants.
Produced water means water ex-
tracted from the earth from an oil or
natural gas production well, or that is
37
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§68.3
40 CFR Ch. I (7-1-98 Edition)
separated from oil or natural gas after
extraction.
[59 FR 4493, Jan. 31, 1994, as amended at 61
FR 31731, June 20, 1996]
§ 68.3 Definitions.
For the purposes of this part:
Accidental release means an unantici-
pated emission of a regulated sub-
stance or other extremely hazardous
substance into the ambient air from a
stationary source.
Act means the Clean Air Act as
amended (42 U.S.C. 7401 et seq.)
Administrative controls mean written
procedural mechanisms used for hazard
control.
Administrator means the adminis-
trator of the U.S. Environmental Pro-
tection Agency.
AIChE/CCPS means the American In-
stitute of Chemical Engineers/Center
for Chemical Process Safety.
API means the American Petroleum
Institute.
Article means a manufactured item,
as defined under 29 CFR 1910.1200(b),
that is formed to a specific shape or de-
sign during manufacture, that has end
use functions dependent in whole or in
part upon the shape or design during
end use, and that does not release or
otherwise result in exposure to a regu-
lated substance under normal condi-
tions of processing and use.
ASME means the American Society
of Mechanical Engineers.
CAS means the Chemical Abstracts
Service.
Catastrophic release means a major
uncontrolled emission, fire, or explo-
sion, involving one or more regulated
substances that presents imminent and
substantial endangerment to public
health and the environment.
Classified information means "classi-
fied information" as defined in the
Classified Information Procedures Act,
18 U.S.C. App. 3, section l(a) as "any
information or material that has been
determined by the United States Gov-
ernment pursuant to an executive
order, statute, or regulation, to require
protection against unauthorized disclo-
sure for reasons of national security."
Condensate means hydrocarbon liquid
separated from natural gas that con-
denses due to changes in temperature,
pressure, or both, and remains liquid at
standard conditions.
Covered process means a process that
has a regulated substance present in
more than a threshold quantity as de-
termined under §68.115.
Crude oil means any naturally occur-
ring, unrefined petroleum liquid.
Designated agency means the state,
local, or Federal agency designated by
the state under the provisions of
§68.215(d) .
DOT means the United States De-
partment of Transportation.
Environmental receptor means natural
areas such as national or state parks,
forests, or monuments; officially des-
ignated wildlife sanctuaries, preserves,
refuges, or areas; and Federal wilder-
ness areas, that could be exposed at
any time to toxic concentrations, radi-
ant heat, or overpressure greater than
or equal to the endpoints provided in
§68.22(a) , as a result of an accidental
release and that can be identified on
local U. S. Geological Survey maps.
Field gas means gas extracted from a
production well before the gas enters a
natural gas processing plant.
Hot work means work involving elec-
tric or gas welding, cutting, brazing, or
similar flame or spark-producing oper-
ations.
Implementing agency means the state
or local agency that obtains delegation
for an accidental release prevention
program under subpart E, 40 CFR part
63. The implementing agency may, but
is not required to, be the state or local
air permitting agency. If no state or
local agency is granted delegation,
EPA will be the implementing agency
for that state.
Injury means any effect on a human
that results either from direct expo-
sure to toxic concentrations; radiant
heat; or overpressures from accidental
releases or from the direct con-
sequences of a vapor cloud explosion
(such as flying glass, debris, and other
projectiles) from an accidental release
and that requires medical treatment or
hospitalization.
Major change means introduction of a
new process, process equipment, or reg-
ulated substance, an alteration of proc-
ess chemistry that results in any
change to safe operating limits, or
38
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Environmental Protection Agency
§68.3
other alteration that introduces a new
hazard.
Mechanical integrity means the proc-
ess of ensuring that process equipment
is fabricated from the proper materials
of construction and is properly in-
stalled, maintained, and replaced to
prevent failures and accidental re-
leases.
Medical treatment means treatment,
other than first aid, administered by a
physician or registered professional
personnel under standing orders from a
physician.
Mitigation or mitigation system means
specific activities, technologies, or
equipment designed or deployed to cap-
ture or control substances upon loss of
containment to minimize exposure of
the public or the environment. Passive
mitigation means equipment, devices,
or technologies that function without
human, mechanical, or other energy
input. Active mitigation means equip-
ment, devices, or technologies that
need human, mechanical, or other en-
ergy input to function.
NFPA means the National Fire Pro-
tection Association.
Natural gas processing plant (gas plant)
means any processing site engaged in
the extraction of natural gas liquids
from field gas, fractionation of mixed
natural gas liquids to natural gas prod-
ucts, or both, classified as North Amer-
ican Industrial Classification System
(NAICS) code 211112 (previously Stand-
ard Industrial Classification (SIC) code
1321).
Offsite means areas beyond the prop-
erty boundary of the stationary source,
and areas within the property bound-
ary to which the public has routine and
unrestricted access during or outside
business hours.
OSHA means the U.S. Occupational
Safety and Health Administration.
Owner or operator means any person
who owns, leases, operates, controls, or
supervises a stationary source.
Petroleum refining process unit means
a process unit used in an establishment
primarily engaged in petroleum refin-
ing as defined in NAICS code 32411 for
petroleum refining (formerly SIC code
2911) and used for the following: Pro-
ducing transportation fuels (such as
gasoline, diesel fuels, and jet fuels),
heating fuels (such as kerosene, fuel
gas distillate, and fuel oils), or lubri-
cants; Separating petroleum; or Sepa-
rating, cracking, reacting, or reform-
ing intermediate petroleum streams.
Examples of such units include, but are
not limited to, petroleum based solvent
units, alkylation units, catalytic
hydrotreating, catalytic hydrorefining,
catalytic hydrocracking, catalytic re-
forming, catalytic cracking, crude dis-
tillation, lube oil processing, hydrogen
production, isomerization, polymeriza-
tion, thermal processes, and blending,
sweetening, and treating processes. Pe-
troleum refining process units include
sulfur plants.
Population means the public.
Process means any activity involving
a regulated substance including any
use, storage, manufacturing, handling,
or on-site movement of such sub-
stances, or combination of these activi-
ties. For the purposes of this defini-
tion, any group of vessels that are
interconnected, or separate vessels
that are located such that a regulated
substance could be involved in a poten-
tial release, shall be considered a sin-
gle process.
Produced water means water ex-
tracted from the earth from an oil or
natural gas production well, or that is
separated from oil or natural gas after
extraction.
Public means any person except em-
ployees or contractors at the station-
ary source.
Public receptor means offsite resi-
dences, institutions (e.g., schools, hos-
pitals), industrial, commercial, and of-
fice buildings, parks, or recreational
areas inhabited or occupied by the pub-
lic at any time without restriction by
the stationary source where members
of the public could be exposed to toxic
concentrations, radiant heat, or over-
pressure, as a result of an accidental
release.
Regulated substance is any substance
listed pursuant to section 112(r)(3) of
the Clean Air Act as amended, in
§68.130.
Replacement in kind means a replace-
ment that satisfies the design speci-
fications.
RMP means the risk management
plan required under subpart G of this
part.
39
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§68.10
40 CFR Ch. I (7-1-98 Edition)
SIC means Standard Industrial Clas-
sification.
Stationary source means any build-
ings, structures, equipment, installa-
tions, or substance emitting stationary
activities which belong to the same in-
dustrial group, which are located on
one or more contiguous properties,
which are under the control of the
same person (or persons under common
control), and from which an accidental
release may occur. The term station-
ary source does not apply to transpor-
tation, including storage incident to
transportation, of any regulated sub-
stance or any other extremely hazard-
ous substance under the provisions of
this part. A stationary source includes
transportation containers used for
storage not incident to transportation
and transportation containers con-
nected to equipment at a stationary
source for loading or unloading. Trans-
portation includes, but is not limited
to, transportation subject to oversight
or regulation under 49 CFR parts 192,
193, or 195, or a state natural gas or
hazardous liquid program for which the
state has in effect a certification to
DOT under 49 U.S.C. section 60105. A
stationary source does not include nat-
urally occurring hydrocarbon res-
ervoirs. Properties shall not be consid-
ered contiguous solely because of a
railroad or pipeline right-of-way.
Threshold quantity means the quan-
tity specified for regulated substances
pursuant to section 112(r)(5) of the
Clean Air Act as amended, listed in
§68.130 and determined to be present at
a stationary source as specified in
§68.115 of this part.
Typical meteorological conditions
means the temperature, wind speed,
cloud cover, and atmospheric stability
class, prevailing at the site based on
data gathered at or near the site or
from a local meteorological station.
Vessel means any reactor, tank,
drum, barrel, cylinder, vat, kettle,
boiler, pipe, hose, or other container.
Worst-case release means the release
of the largest quantity of a regulated
substance from a vessel or process line
failure that results in the greatest dis-
tance to an endpoint defined in
§68.22(a).
[59 FR 4493, Jan. 31, 1994, as amended at 61
FR 31717, June 20, 1996; 63 FR 644, Jan. 6, 1998]
§68.10 Applicability.
(a) An owner or operator of a station-
ary source that has more than a
threshold quantity of a regulated sub-
stance in a process, as determined
under §68.115, shall comply with the re-
quirements of this part no later than
the latest of the following dates:
(1) June 21, 1999;
(2) Three years after the date on
which a regulated substance is first
listed under §68.130; or
(3) The date on which a regulated
substance is first present above a
threshold quantity in a process.
(b) Program 1 eligibility require-
ments. A covered process is eligible for
Program 1 requirements as provided in
§68.12(b) if it meets all of the following
requirements:
(1) For the five years prior to the
submission of an RMP, the process has
not had an accidental release of a regu-
lated substance where exposure to the
substance, its reaction products, over-
pressure generated by an explosion in-
volving the substance, or radiant heat
generated by a fire involving the sub-
stance led to any of the following off-
site:
(i) Death;
(ii) Injury; or
(iii) Response or restoration activi-
ties for an exposure of an environ-
mental receptor;
(2) The distance to a toxic or flam-
mable endpoint for a worst-case release
assessment conducted under Subpart B
and §68.25 is less than the distance to
any public receptor, as defined in
§68.30; and
(3) Emergency response procedures
have been coordinated between the sta-
tionary source and local emergency
planning and response organizations.
(c) Program 2 eligibility require-
ments. A covered process is subject to
Program 2 requirements if it does not
meet the eligibility requirements of ei-
ther paragraph (b) or paragraph (d) of
this section.
(d) Program 3 eligibility require-
ments. A covered process is subject to
Program 3 if the process does not meet
the requirements of paragraph (b) of
this section, and if either of the follow-
ing conditions is met:
40
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Environmental Protection Agency
§68.12
(1) The process is in SIC code 2611,
2812, 2819, 2821, 2865, 2869, 2873, 2879, or
2911; or
(2) The process is subject to the
OSHA process safety management
standard, 29 CFR 1910.119.
(e) If at any time a covered process
no longer meets the eligibility criteria
of its Program level, the owner or oper-
ator shall comply with the require-
ments of the new Program level that
applies to the process and update the
RMP as provided in §68.190.
(f) The provisions of this part shall
not apply to an Outer Continental
Shelf ("OCS") source, as defined in 40
CFR 55.2.
[61 FR 31717, June 20, 1996, as amended at 63
FR 645, Jan. 6, 1998]
§68.12 General requirements.
(a) General requirements. The owner
or operator of a stationary source sub-
ject to this part shall submit a single
RMP, as provided in §§68.150 to 68.185.
The RMP shall include a registration
that reflects all covered processes.
(b) Program 1 requirements. In addi-
tion to meeting the requirements of
paragraph (a) of this section, the owner
or operator of a stationary source with
a process eligible for Program 1, as pro-
vided in§68.10(b), shall:
(1) Analyze the worst-case release
scenario for the process (es), as provided
in §68.25; document that the nearest
public receptor is beyond the distance
to a toxic or flammable endpoint de-
fined in §68.22(a); and submit in the
RMP the worst-case release scenario as
provided in §68.165;
(2) Complete the five-year accident
history for the process as provided in
§68.42 of this part and submit it in the
RMP as provided in §68.168;
(3) Ensure that response actions have
been coordinated with local emergency
planning and response agencies; and
(4) Certify in the RMP the following:
"Based on the criteria in 40 CFR 68.10,
the distance to the specified endpoint
for the worst-case accidental release
scenario for the following process(es) is
less than the distance to the nearest
public receptor: [list process(es)]. With-
in the past five years, the process(es)
has (have) had no accidental release
that caused offsite impacts provided in
the risk management program rule (40
CFR 68.10(b)(l)). No additional meas-
ures are necessary to prevent offsite
impacts from accidental releases. In
the event of fire, explosion, or a release
of a regulated substance from the proc-
ess(es), entry within the distance to
the specified endpoints may pose a dan-
ger to public emergency responders.
Therefore, public emergency respond-
ers should not enter this area except as
arranged with the emergency contact
indicated in the RMP. The undersigned
certifies that, to the best of my knowl-
edge, information, and belief, formed
after reasonable inquiry, the informa-
tion submitted is true, accurate, and
complete. [Signature, title, date
signed]."
(c) Program 2 requirements. In addi-
tion to meeting the requirements of
paragraph (a) of this section, the owner
or operator of a stationary source with
a process subject to Program 2, as pro-
vided in§68.10(c), shall:
(1) Develop and implement a manage-
ment system as provided in §68.15;
(2) Conduct a hazard assessment as
provided in §§68.20 through 68.42;
(3) Implement the Program 2 preven-
tion steps provided in §§68.48 through
68.60 or implement the Program 3 pre-
vention steps provided in §§68.65
through 68.87;
(4) Develop and implement an emer-
gency response program as provided in
§§68.90 to 68.95; and
(5) Submit as part of the RMP the
data on prevention program elements
for Program 2 processes as provided in
§68.170.
(d) Program 3 requirements. In addi-
tion to meeting the requirements of
paragraph (a) of this section, the owner
or operator of a stationary source with
a process subject to Program 3, as pro-
vided in§68.10(d) shall:
(1) Develop and implement a manage-
ment system as provided in §68.15;
(2) Conduct a hazard assessment as
provided in §§68.20 through 68.42;
(3) Implement the prevention re-
quirements of §§68.65 through 68.87;
(4) Develop and implement an emer-
gency response program as provided in
§§68.90 to 68.95 of this part; and
(5) Submit as part of the RMP the
data on prevention program elements
41
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§68.15
40 CFR Ch. I (7-1-98 Edition)
for Program 3 processes as provided in
§68.175.
[61 FR 31718, June 20, 1996]
§ 68.15 Management.
(a) The owner or operator of a sta-
tionary source with processes subject
to Program 2 or Program 3 shall de-
velop a management system to oversee
the implementation of the risk man-
agement program elements.
(b) The owner or operator shall as-
sign a qualified person or position that
has the overall responsibility for the
development, implementation, and in-
tegration of the risk management pro-
gram elements.
(c) When responsibility for imple-
menting individual requirements of
this part is assigned to persons other
than the person identified under para-
graph (b) of this section, the names or
positions of these people shall be docu-
mented and the lines of authority de-
fined through an organization chart or
similar document.
[61 FR 31718, June 20, 1996]
Subpart B—Hazard Assessment
SOURCE: 61 FR 31718, June 20, 1996, unless
otherwise noted.
§68.20 Applicability.
The owner or operator of a station-
ary source subject to this part shall
prepare a worst-case release scenario
analysis as provided in §68.25 of this
part and complete the five-year acci-
dent history as provided in §68.42. The
owner or operator of a Program 2 and 3
process must comply with all sections
in this subpart for these processes.
§68.22 Offsite consequence analysis
parameters.
(a) Endpoints. For analyses of offsite
consequences, the following endpoints
shall be used:
(1) Toxics. The toxic endpoints pro-
vided in appendix A of this part.
(2) Flammables. The endpoints for
flammables vary according to the sce-
narios studied:
(i) Explosion. An overpressure of 1
psi.
(ii) Radiant heat/exposure time. A ra-
diant heat of 5 kw/m2 for 40 seconds.
(iii) Lower flammability limit. A
lower flammability limit as provided in
NFPA documents or other generally
recognized sources.
(b) Wind speed/atmospheric stability
class. For the worst-case release analy-
sis, the owner or operator shall use a
wind speed of 1.5 meters per second and
F atmospheric stability class. If the
owner or operator can demonstrate
that local meteorological data applica-
ble to the stationary source show a
higher minimum wind speed or less sta-
ble atmosphere at all times during the
previous three years, these minimums
may be used. For analysis of alter-
native scenarios, the owner or operator
may use the typical meteorological
conditions for the stationary source.
(c) Ambient temperature/humidity.
For worst-case release analysis of a
regulated toxic substance, the owner or
operator shall use the highest daily
maximum temperature in the previous
three years and average humidity for
the site, based on temperature/humid-
ity data gathered at the stationary
source or at a local meteorological sta-
tion; an owner or operator using the
RMP Offsite Consequence Analysis
Guidance may use 25°C and 50 percent
humidity as values for these variables.
For analysis of alternative scenarios,
the owner or operator may use typical
temperature/humidity data gathered at
the stationary source or at a local me-
teorological station.
(d) Height of release. The worst-case
release of a regulated toxic substance
shall be analyzed assuming a ground
level (0 feet) release. For an alternative
scenario analysis of a regulated toxic
substance, release height may be deter-
mined by the release scenario.
(e) Surface roughness. The owner or
operator shall use either urban or rural
topography, as appropriate. Urban
means that there are many obstacles in
the immediate area; obstacles include
buildings or trees. Rural means there
are no buildings in the immediate area
and the terrain is generally flat and
unobstructed.
(f) Dense or neutrally buoyant gases.
The owner or operator shall ensure
that tables or models used for disper-
sion analysis of regulated toxic sub-
stances appropriately account for gas
density.
42
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Environmental Protection Agency
§68.25
(g) Temperature of released sub-
stance. For worst case, liquids other
than gases liquified by refrigeration
only shall be considered to be released
at the highest daily maximum tem-
perature, based on data for the pre-
vious three years appropriate for the
stationary source, or at process tem-
perature, whichever is higher. For al-
ternative scenarios, substances may be
considered to be released at a process
or ambient temperature that is appro-
priate for the scenario.
§68.25 Worst-case release scenario
analysis.
(a) The owner or operator shall ana-
lyze and report in the RMP:
(1) For Program 1 processes, one
worst-case release scenario for each
Program 1 process;
(2) For Program 2 and 3 processes:
(i) One worst-case release scenario
that is estimated to create the greatest
distance in any direction to an end-
point provided in appendix A of this
part resulting from an accidental re-
lease of regulated toxic substances
from covered processes under worst-
case conditions defined in §68.22;
(ii) One worst-case release scenario
that is estimated to create the greatest
distance in any direction to an end-
point defined in §68.22(a) resulting from
an accidental release of regulated flam-
mable substances from covered proc-
esses under worst-case conditions de-
fined in §68.22; and
(iii) Additional worst-case release
scenarios for a hazard class if a worst-
case release from another covered proc-
ess at the stationary source potentially
affects public receptors different from
those potentially affected by the worst-
case release scenario developed under
paragraphs (a) (2) (i) or (a) (2) (ii) of this
section.
(b) Determination of worst-case release
quantity. The worst-case release quan-
tity shall be the greater of the follow-
ing:
(1) For substances in a vessel, the
greatest amount held in a single vessel,
taking into account administrative
controls that limit the maximum quan-
tity; or
(2) For substances in pipes, the great-
est amount in a pipe, taking into ac-
count administrative controls that
limit the maximum quantity.
(c) Worst-case release scenario—toxic
gases. (1) For regulated toxic sub-
stances that are normally gases at am-
bient temperature and handled as a gas
or as a liquid under pressure, the owner
or operator shall assume that the
quantity in the vessel or pipe, as deter-
mined under paragraph (b) of this sec-
tion, is released as a gas over 10 min-
utes. The release rate shall be assumed
to be the total quantity divided by 10
unless passive mitigation systems are
in place.
(2) For gases handled as refrigerated
liquids at ambient pressure:
(i) If the released substance is not
contained by passive mitigation sys-
tems or if the contained pool would
have a depth of 1 cm or less, the owner
or operator shall assume that the sub-
stance is released as a gas in 10 min-
utes;
(ii) If the released substance is con-
tained by passive mitigation systems
in a pool with a depth greater than 1
cm, the owner or operator may assume
that the quantity in the vessel or pipe,
as determined under paragraph (b) of
this section, is spilled instantaneously
to form a liquid pool. The volatiliza-
tion rate (release rate) shall be cal-
culated at the boiling point of the sub-
stance and at the conditions specified
in paragraph (d) of this section.
(d) Worst-case release scenario—toxic
liquids. (1) For regulated toxic sub-
stances that are normally liquids at
ambient temperature, the owner or op-
erator shall assume that the quantity
in the vessel or pipe, as determined
under paragraph (b) of this section, is
spilled instantaneously to form a liquid
pool.
(i) The surface area of the pool shall
be determined by assuming that the
liquid spreads to 1 centimeter deep un-
less passive mitigation systems are in
place that serve to contain the spill
and limit the surface area. Where pas-
sive mitigation is in place, the surface
area of the contained liquid shall be
used to calculate the volatilization
rate.
(ii) If the release would occur onto a
surface that is not paved or smooth,
the owner or operator may take into
43
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§68.28
40 CFR Ch. I (7-1-98 Edition)
account the actual surface characteris-
tics.
(2) The volatilization rate shall ac-
count for the highest daily maximum
temperature occurring in the past
three years, the temperature of the
substance in the vessel, and the con-
centration of the substance if the liq-
uid spilled is a mixture or solution.
(3) The rate of release to air shall be
determined from the volatilization rate
of the liquid pool. The owner or opera-
tor may use the methodology in the
RMP Offsite Consequence Analysis
Guidance or any other publicly avail-
able techniques that account for the
modeling conditions and are recognized
by industry as applicable as part of
current practices. Proprietary models
that account for the modeling condi-
tions may be used provided the owner
or operator allows the implementing
agency access to the model and de-
scribes model features and differences
from publicly available models to local
emergency planners upon request.
(e) Worst-case release scenario—
flammables. The owner or operator shall
assume that the quantity of the sub-
stance, as determined under paragraph
(b) of this section, vaporizes resulting
in a vapor cloud explosion. A yield fac-
tor of 10 percent of the available en-
ergy released in the explosion shall be
used to determine the distance to the
explosion endpoint if the model used is
based on TNT-equivalent methods.
(f) Parameters to be applied. The owner
or operator shall use the parameters
defined in §68.22 to determine distance
to the endpoints. The owner or opera-
tor may use the methodology provided
in the RMP Offsite Consequence Analy-
sis Guidance or any commercially or
publicly available air dispersion model-
ing techniques, provided the techniques
account for the modeling conditions
and are recognized by industry as ap-
plicable as part of current practices.
Proprietary models that account for
the modeling conditions may be used
provided the owner or operator allows
the implementing agency access to the
model and describes model features and
differences from publicly available
models to local emergency planners
upon request.
(g) Consideration of passive mitigation.
Passive mitigation systems may be
considered for the analysis of worst
case provided that the mitigation sys-
tem is capable of withstanding the re-
lease event triggering the scenario and
would still function as intended.
(h) Factors in selecting a worst-case sce-
nario. Notwithstanding the provisions
of paragraph (b) of this section, the
owner or operator shall select as the
worst case for flammable regulated
substances or the worst case for regu-
lated toxic substances, a scenario based
on the following factors if such a sce-
nario would result in a greater distance
to an endpoint defined in §68.22(a) be-
yond the stationary source boundary
than the scenario provided under para-
graph (b) of this section:
(1) Smaller quantities handled at
higher process temperature or pres-
sure; and
(2) Proximity to the boundary of the
stationary source.
§68.28 Alternative release scenario
analysis.
(a) The number of scenarios. The
owner or operator shall identify and
analyze at least one alternative release
scenario for each regulated toxic sub-
stance held in a covered process(es) and
at least one alternative release sce-
nario to represent all flammable sub-
stances held in covered processes.
(b) Scenarios to consider. (1) For each
scenario required under paragraph (a)
of this section, the owner or operator
shall select a scenario:
(i) That is more likely to occur than
the worst-case release scenario under
§68.25; and
(ii) That will reach an endpoint off-
site, unless no such scenario exists.
(2) Release scenarios considered
should include, but are not limited to,
the following, where applicable:
(i) Transfer hose releases due to
splits or sudden hose uncoupling;
(ii) Process piping releases from fail-
ures at flanges, joints, welds, valves
and valve seals, and drains or bleeds;
(iii) Process vessel or pump releases
due to cracks, seal failure, or drain,
bleed, or plug failure;
(iv) Vessel overfilling and spill, or
overpressurization and venting through
relief valves or rupture disks; and
44
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Environmental Protection Agency
§68.39
(v) Shipping container mishandling
and breakage or puncturing leading to
a spill.
(c) Parameters to be applied. The
owner or operator shall use the appro-
priate parameters defined in §68.22 to
determine distance to the endpoints.
The owner or operator may use either
the methodology provided in the RMP
Offsite Consequence Analysis Guidance
or any commercially or publicly avail-
able air dispersion modeling tech-
niques, provided the techniques ac-
count for the specified modeling condi-
tions and are recognized by industry as
applicable as part of current practices.
Proprietary models that account for
the modeling conditions may be used
provided the owner or operator allows
the implementing agency access to the
model and describes model features and
differences from publicly available
models to local emergency planners
upon request.
(d) Consideration of mitigation. Ac-
tive and passive mitigation systems
may be considered provided they are
capable of withstanding the event that
triggered the release and would still be
functional.
(e) Factors in selecting scenarios.
The owner or operator shall consider
the following in selecting alternative
release scenarios:
(1) The five-year accident history
provided in §68.42; and
(2) Failure scenarios identified under
§68.50 or §68.67.
§ 68.30 Defining offsite impacts—popu-
lation.
(a) The owner or operator shall esti-
mate in the RMP the population within
a circle with its center at the point of
the release and a radius determined by
the distance to the endpoint defined in
§68.22(a).
(b) Population to be defined. Popu-
lation shall include residential popu-
lation. The presence of institutions
(schools, hospitals, prisons), parks and
recreational areas, and major commer-
cial, office, and industrial buildings
shall be noted in the RMP.
(c) Data sources acceptable. The owner
or operator may use the most recent
Census data, or other updated informa-
tion, to estimate the population poten-
tially affected.
(d) Level of accuracy. Population shall
be estimated to two significant digits.
§ 68.33 Defining offsite impacts—envi-
ronment.
(a) The owner or operator shall list in
the RMP environmental receptors
within a circle with its center at the
point of the release and a radius deter-
mined by the distance to the endpoint
defined in §68.22(a) of this part.
(b) Data sources acceptable. The
owner or operator may rely on infor-
mation provided on local U.S. Geologi-
cal Survey maps or on any data source
containing U.S.G.S. data to identify
environmental receptors.
68.36 Review and update.
(a) The owner or operator shall re-
view and update the offsite con-
sequence analyses at least once every
five years.
(b) If changes in processes, quantities
stored or handled, or any other aspect
of the stationary source might reason-
ably be expected to increase or de-
crease the distance to the endpoint by
a factor of two or more, the owner or
operator shall complete a revised anal-
ysis within six months of the change
and submit a revised risk management
plan as provided in §68.190.
§ 68.39 Documentation.
The owner or operator shall maintain
the following records on the offsite
consequence analyses:
(a) For worst-case scenarios, a de-
scription of the vessel or pipeline and
substance selected as worst case, as-
sumptions and parameters used, and
the rationale for selection; assump-
tions shall include use of any adminis-
trative controls and any passive miti-
gation that were assumed to limit the
quantity that could be released. Docu-
mentation shall include the antici-
pated effect of the controls and mitiga-
tion on the release quantity and rate.
(b) For alternative release scenarios,
a description of the scenarios identi-
fied, assumptions and parameters used,
and the rationale for the selection of
specific scenarios; assumptions shall
include use of any administrative con-
trols and any mitigation that were as-
sumed to limit the quantity that could
45
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§68.42
40 CFR Ch. I (7-1-98 Edition)
be released. Documentation shall in-
clude the effect of the controls and
mitigation on the release quantity and
rate.
(c) Documentation of estimated
quantity released, release rate, and du-
ration of release.
(d) Methodology used to determine
distance to endpoints.
(e) Data used to estimate population
and environmental receptors poten-
tially affected.
§68.42 Five-year accident history.
(a) The owner or operator shall in-
clude in the five-year accident history
all accidental releases from covered
processes that resulted in deaths, inju-
ries, or significant property damage on
site, or known offsite deaths, injuries,
evacuations, sheltering in place, prop-
erty damage, or environmental dam-
age.
(b) Data required. For each accidental
release included, the owner or operator
shall report the following information:
(1) Date, time, and approximate dura-
tion of the release;
(2) Chemical(s) released;
(3) Estimated quantity released in
pounds;
(4) The type of release event and its
source;
(5) Weather conditions, if known;
(6) On-site impacts;
(7) Known offsite impacts;
(8) Initiating event and contributing
factors if known;
(9) Whether offsite responders were
notified if known; and
(10) Operational or process changes
that resulted from investigation of the
release.
(c) Level of accuracy. Numerical esti-
mates may be provided to two signifi-
cant digits.
Sub pa it C—Program 2 Prevention
Program
SOURCE: 61 FR 31721, June 20, 1996, unless
otherwise noted.
§68.48 Safety information.
(a) The owner or operator shall com-
pile and maintain the following up-to-
date safety information related to the
regulated substances, processes, and
equipment:
(1) Material Safety Data Sheets that
meet the requirements of 29 CFR
1910.1200(g);
(2) Maximum intended inventory of
equipment in which the regulated sub-
stances are stored or processed;
(3) Safe upper and lower tempera-
tures, pressures, flows, and composi-
tions;
(4) Equipment specifications; and
(5) Codes and standards used to de-
sign, build, and operate the process.
(b) The owner or operator shall en-
sure that the process is designed in
compliance with recognized and gen-
erally accepted good engineering prac-
tices. Compliance with Federal or state
regulations that address industry-spe-
cific safe design or with industry-spe-
cific design codes and standards may be
used to demonstrate compliance with
this paragraph.
(c) The owner or operator shall up-
date the safety information if a major
change occurs that makes the informa-
tion inaccurate.
§68.50 Hazard review.
(a) The owner or operator shall con-
duct a review of the hazards associated
with the regulated substances, process,
and procedures. The review shall iden-
tify the following:
(1) The hazards associated with the
process and regulated substances;
(2) Opportunities for equipment mal-
functions or human errors that could
cause an accidental release;
(3) The safeguards used or needed to
control the hazards or prevent equip-
ment malfunction or human error; and
(4) Any steps used or needed to detect
or monitor releases.
(b) The owner or operator may use
checklists developed by persons or or-
ganizations knowledgeable about the
process and equipment as a guide to
conducting the review. For processes
designed to meet industry standards or
Federal or state design rules, the haz-
ard review shall, by inspecting all
equipment, determine whether the
process is designed, fabricated, and op-
erated in accordance with the applica-
ble standards or rules.
46
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Environmental Protection Agency
§68.56
(c) The owner or operator shall docu-
ment the results of the review and en-
sure that problems identified are re-
solved in a timely manner.
(d) The review shall be updated at
least once every five years. The owner
or operator shall also conduct reviews
whenever a major change in the proc-
ess occurs; all issues identified in the
review shall be resolved before startup
of the changed process.
§68.52 Operating procedures.
(a) The owner or operator shall pre-
pare written operating procedures that
provide clear instructions or steps for
safely conducting activities associated
with each covered process consistent
with the safety information for that
process. Operating procedures or in-
structions provided by equipment man-
ufacturers or developed by persons or
organizations knowledgeable about the
process and equipment may be used as
a basis for a stationary source's operat-
ing procedures.
(b) The procedures shall address the
following:
(1) Initial startup;
(2) Normal operations;
(3) Temporary operations;
(4) Emergency shutdown and oper-
ations;
(5) Normal shutdown;
(6) Startup following a normal or
emergency shutdown or a major change
that requires a hazard review;
(7) Consequences of deviations and
steps required to correct or avoid devi-
ations; and
(8) Equipment inspections.
(c) The owner or operator shall en-
sure that the operating procedures are
updated, if necessary, whenever a
major change occurs and prior to start-
up of the changed process.
§68.54 Training.
(a) The owner or operator shall en-
sure that each employee presently op-
erating a process, and each employee
newly assigned to a covered process
have been trained or tested competent
in the operating procedures provided in
§68.52 that pertain to their duties. For
those employees already operating a
process on June 21, 1999, the owner or
operator may certify in writing that
the employee has the required knowl-
edge, skills, and abilities to safely
carry out the duties and responsibil-
ities as provided in the operating pro-
cedures.
(b) Refresher training. Refresher
training shall be provided at least
every three years, and more often if
necessary, to each employee operating
a process to ensure that the employee
understands and adheres to the current
operating procedures of the process.
The owner or operator, in consultation
with the employees operating the proc-
ess, shall determine the appropriate
frequency of refresher training.
(c) The owner or operator may use
training conducted under Federal or
state regulations or under industry-
specific standards or codes or training
conducted by covered process equip-
ment vendors to demonstrate compli-
ance with this section to the extent
that the training meets the require-
ments of this section.
(d) The owner or operator shall en-
sure that operators are trained in any
updated or new procedures prior to
startup of a process after a major
change.
§68.56 Maintenance.
(a) The owner or operator shall pre-
pare and implement procedures to
maintain the on-going mechanical in-
tegrity of the process equipment. The
owner or operator may use procedures
or instructions provided by covered
process equipment vendors or proce-
dures in Federal or state regulations or
industry codes as the basis for station-
ary source maintenance procedures.
(b) The owner or operator shall train
or cause to be trained each employee
involved in maintaining the on-going
mechanical integrity of the process. To
ensure that the employee can perform
the job tasks in a safe manner, each
such employee shall be trained in the
hazards of the process, in how to avoid
or correct unsafe conditions, and in the
procedures applicable to the employ-
ee's job tasks.
(c) Any maintenance contractor shall
ensure that each contract maintenance
employee is trained to perform the
maintenance procedures developed
under paragraph (a) of this section.
47
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§68.58
40 CFR Ch. I (7-1-98 Edition)
(d) The owner or operator shall per-
form or cause to be performed inspec-
tions and tests on process equipment.
Inspection and testing procedures shall
follow recognized and generally accept-
ed good engineering practices. The fre-
quency of inspections and tests of proc-
ess equipment shall be consistent with
applicable manufacturers' rec-
ommendations, industry standards or
codes, good engineering practices, and
prior operating experience.
§68.58 Compliance audits.
(a) The owner or operator shall cer-
tify that they have evaluated compli-
ance with the provisions of this sub-
part at least every three years to ver-
ify that the procedures and practices
developed under the rule are adequate
and are being followed.
(b) The compliance audit shall be
conducted by at least one person
knowledgeable in the process.
(c) The owner or operator shall de-
velop a report of the audit findings.
(d) The owner or operator shall
promptly determine and document an
appropriate response to each of the
findings of the compliance audit and
document that deficiencies have been
corrected.
(e) The owner or operator shall retain
the two (2) most recent compliance
audit reports. This requirement does
not apply to any compliance audit re-
port that is more than five years old.
§68.60 Incident investigation.
(a) The owner or operator shall inves-
tigate each incident which resulted in,
or could reasonably have resulted in a
catastrophic release.
(b) An incident investigation shall be
initiated as promptly as possible, but
not later than 48 hours following the
incident.
(c) A summary shall be prepared at
the conclusion of the investigation
which includes at a minimum:
(1) Date of incident;
(2) Date investigation began;
(3) A description of the incident;
(4) The factors that contributed to
the incident; and,
(5) Any recommendations resulting
from the investigation.
(d) The owner or operator shall
promptly address and resolve the inves-
tigation findings and recommenda-
tions. Resolutions and corrective ac-
tions shall be documented.
(e) The findings shall be reviewed
with all affected personnel whose job
tasks are affected by the findings.
(f) Investigation summaries shall be
retained for five years.
Subpart D—Program 3 Prevention
Program
SOURCE: 61 FR 31722, June 20, 1996, unless
otherwise noted.
§68.65 Process safety information.
(a) In accordance with the schedule
set forth in §68.67, the owner or opera-
tor shall complete a compilation of
written process safety information be-
fore conducting any process hazard
analysis required by the rule. The com-
pilation of written process safety infor-
mation is to enable the owner or opera-
tor and the employees involved in oper-
ating the process to identify and under-
stand the hazards posed by those proc-
esses involving regulated substances.
This process safety information shall
include information pertaining to the
hazards of the regulated substances
used or produced by the process, infor-
mation pertaining to the technology of
the process, and information pertain-
ing to the equipment in the process.
(b) Information pertaining to the
hazards of the regulated substances in
the process. This information shall
consist of at least the following:
(1) Toxicity information;
(2) Permissible exposure limits;
(3) Physical data;
(4) Reactivity data:
(5) Corrosivity data;
(6) Thermal and chemical stability
data; and
(7) Hazardous effects of inadvertent
mixing of different materials that
could foreseeably occur.
NOTE TO PARAGRAPH (b): Material Safety
Data Sheets meeting the requirements of 29
CFR 1910.1200(g) may be used to comply with
this requirement to the extent they contain
the information required by this subpara-
graph.
(c) Information pertaining to the
technology of the process.
48
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Environmental Protection Agency
§68.67
(1) Information concerning the tech-
nology of the process shall include at
least the following:
(i) A block flow diagram or simplified
process flow diagram;
(ii) Process chemistry;
(iii) Maximum intended inventory;
(iv) Safe upper and lower limits for
such items as temperatures, pressures,
flows or compositions; and,
(v) An evaluation of the consequences
of deviations.
(2) Where the original technical in-
formation no longer exists, such infor-
mation may be developed in conjunc-
tion with the process hazard analysis
in sufficient detail to support the anal-
ysis.
(d) Information pertaining to the
equipment in the process.
(1) Information pertaining to the
equipment in the process shall include:
(i) Materials of construction;
(ii) Piping and instrument diagrams
(P&ID's);
(iii) Electrical classification;
(iv) Relief system design and design
basis;
(v) Ventilation system design;
(vi) Design codes and standards em-
ployed;
(vii) Material and energy balances for
processes built after June 21, 1999; and
(viii) Safety systems (e.g. interlocks,
detection or suppression systems).
(2) The owner or operator shall docu-
ment that equipment complies with
recognized and generally accepted good
engineering practices.
(3) For existing equipment designed
and constructed in accordance with
codes, standards, or practices that are
no longer in general use, the owner or
operator shall determine and document
that the equipment is designed, main-
tained, inspected, tested, and operating
in a safe manner.
§68.67 Process hazard analysis.
(a) The owner or operator shall per-
form an initial process hazard analysis
(hazard evaluation) on processes cov-
ered by this part. The process hazard
analysis shall be appropriate to the
complexity of the process and shall
identify, evaluate, and control the haz-
ards involved in the process. The owner
or operator shall determine and docu-
ment the priority order for conducting
process hazard analyses based on a ra-
tionale which includes such consider-
ations as extent of the process hazards,
number of potentially affected employ-
ees, age of the process, and operating
history of the process. The process haz-
ard analysis shall be conducted as soon
as possible, but not later than June 21,
1999. Process hazards analyses com-
pleted to comply with 29 CFR
1910.119(e) are acceptable as initial
process hazards analyses. These process
hazard analyses shall be updated and
revalidated, based on their completion
date.
(b) The owner or operator shall use
one or more of the following meth-
odologies that are appropriate to deter-
mine and evaluate the hazards of the
process being analyzed.
(1) What-If;
(2) Checklist;
(3) What-If/Checklist;
(4) Hazard and Operability Study
(HAZOP);
(5) Failure Mode and Effects Analysis
(FMEA);
(6) Fault Tree Analysis; or
(7) An appropriate equivalent meth-
odology.
(c) The process hazard analysis shall
address:
(1) The hazards of the process;
(2) The identification of any previous
incident which had a likely potential
for catastrophic consequences.
(3) Engineering and administrative
controls applicable to the hazards and
their interrelationships such as appro-
priate application of detection meth-
odologies to provide early warning of
releases. (Acceptable detection meth-
ods might include process monitoring
and control instrumentation with
alarms, and detection hardware such as
hydrocarbon sensors.);
(4) Consequences of failure of engi-
neering and administrative controls;
(5) Stationary source siting;
(6) Human factors; and
(7) A qualitative evaluation of a
range of the possible safety and health
effects of failure of controls.
(d) The process hazard analysis shall
be performed by a team with expertise
in engineering and process operations,
and the team shall include at least one
employee who has experience and
knowledge specific to the process being
49
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§68.69
40 CFR Ch. I (7-1-98 Edition)
evaluated. Also, one member of the
team must be knowledgeable in the
specific process hazard analysis meth-
odology being used.
(e) The owner or operator shall estab-
lish a system to promptly address the
team's findings and recommendations;
assure that the recommendations are
resolved in a timely manner and that
the resolution is documented; docu-
ment what actions are to be taken;
complete actions as soon as possible;
develop a written schedule of when
these actions are to be completed; com-
municate the actions to operating,
maintenance and other employees
whose work assignments are in the
process and who may be affected by the
recommendations or actions.
(f) At least every five (5) years after
the completion of the initial process
hazard analysis, the process hazard
analysis shall be updated and revali-
dated by a team meeting the require-
ments in paragraph (d) of this section,
to assure that the process hazard anal-
ysis is consistent with the current
process. Updated and revalidated proc-
ess hazard analyses completed to com-
ply with 29 CFR 1910.119(e) are accept-
able to meet the requirements of this
paragraph.
(g) The owner or operator shall re-
tain process hazards analyses and up-
dates or revalidations for each process
covered by this section, as well as the
documented resolution of recommenda-
tions described in paragraph (e) of this
section for the life of the process.
§68.69 Operating procedures.
(a) The owner or operator shall de-
velop and implement written operating
procedures that provide clear instruc-
tions for safely conducting activities
involved in each covered process con-
sistent with the process safety infor-
mation and shall address at least the
following elements.
(1) Steps for each operating phase:
(i) Initial startup;
(ii) Normal operations;
(iii) Temporary operations;
(iv) Emergency shutdown including
the conditions under which emergency
shutdown is required, and the assign-
ment of shutdown responsibility to
qualified operators to ensure that
emergency shutdown is executed in a
safe and timely manner.
(v) Emergency operations;
(vi) Normal shutdown; and,
(vii) Startup following a turnaround,
or after an emergency shutdown.
(2) Operating limits:
(i) Consequences of deviation; and
(ii) Steps required to correct or avoid
deviation.
(3) Safety and health considerations:
(i) Properties of, and hazards pre-
sented by, the chemicals used in the
process;
(ii) Precautions necessary to prevent
exposure, including engineering con-
trols, administrative controls, and per-
sonal protective equipment;
(iii) Control measures to be taken if
physical contact or airborne exposure
occurs;
(iv) Quality control for raw materials
and control of hazardous chemical in-
ventory levels; and,
(v) Any special or unique hazards.
(4) Safety systems and their func-
tions.
(b) Operating procedures shall be
readily accessible to employees who
work in or maintain a process.
(c) The operating procedures shall be
reviewed as often as necessary to as-
sure that they reflect current operat-
ing practice, including changes that re-
sult from changes in process chemicals,
technology, and equipment, and
changes to stationary sources. The
owner or operator shall certify annu-
ally that these operating procedures
are current and accurate.
(d) The owner or operator shall de-
velop and implement safe work prac-
tices to provide for the control of haz-
ards during operations such as lockout/
tagout; confined space entry; opening
process equipment or piping; and con-
trol over entrance into a stationary
source by maintenance, contractor,
laboratory, or other support personnel.
These safe work practices shall apply
to employees and contractor employ-
ees.
§68.71 Training.
(a) Initial training. (1) Each employee
presently involved in operating a proc-
ess, and each employee before being in-
volved in operating a newly assigned
process, shall be trained in an overview
50
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Environmental Protection Agency
§68.73
of the process and in the operating pro-
cedures as specified in §68.69. The
training shall include emphasis on the
specific safety and health hazards,
emergency operations including shut-
down, and safe work practices applica-
ble to the employee's job tasks.
(2) In lieu of initial training for those
employees already involved in operat-
ing a process on June 21, 1999 an owner
or operator may certify in writing that
the employee has the required knowl-
edge, skills, and abilities to safely
carry out the duties and responsibil-
ities as specified in the operating pro-
cedures.
(b) Refresher training. Refresher train-
ing shall be provided at least every
three years, and more often if nec-
essary, to each employee involved in
operating a process to assure that the
employee understands and adheres to
the current operating procedures of the
process. The owner or operator, in con-
sultation with the employees involved
in operating the process, shall deter-
mine the appropriate frequency of re-
fresher training.
(c) Training documentation. The owner
or operator shall ascertain that each
employee involved in operating a proc-
ess has received and understood the
training required by this paragraph.
The owner or operator shall prepare a
record which contains the identity of
the employee, the date of training, and
the means used to verify that the em-
ployee understood the training.
§68.73 Mechanical integrity.
(a) Application. Paragraphs (b)
through (f) of this section apply to the
following process equipment:
(1) Pressure vessels and storage
tanks;
(2) Piping systems (including piping
components such as valves);
(3) Relief and vent systems and de-
vices;
(4) Emergency shutdown systems;
(5) Controls (including monitoring
devices and sensors, alarms, and inter-
locks) and,
(6) Pumps.
(b) Written procedures. The owner or
operator shall establish and implement
written procedures to maintain the on-
going integrity of process equipment.
(c) Training for process maintenance
activities. The owner or operator shall
train each employee involved in main-
taining the on-going integrity of proc-
ess equipment in an overview of that
process and its hazards and in the pro-
cedures applicable to the employee's
job tasks to assure that the employee
can perform the job tasks in a safe
manner.
(d) Inspection and testing. (1) Inspec-
tions and tests shall be performed on
process equipment.
(2) Inspection and testing procedures
shall follow recognized and generally
accepted good engineering practices.
(3) The frequency of inspections and
tests of process equipment shall be con-
sistent with applicable manufacturers'
recommendations and good engineering
practices, and more frequently if deter-
mined to be necessary by prior operat-
ing experience.
(4) The owner or operator shall docu-
ment each inspection and test that has
been performed on process equipment.
The documentation shall identify the
date of the inspection or test, the name
of the person who performed the in-
spection or test, the serial number or
other identifier of the equipment on
which the inspection or test was per-
formed, a description of the inspection
or test performed, and the results of
the inspection or test.
(e) Equipment deficiencies. The owner
or operator shall correct deficiencies in
equipment that are outside acceptable
limits (defined by the process safety in-
formation in §68.65) before further use
or in a safe and timely manner when
necessary means are taken to assure
safe operation.
(f) Quality assurance. (1) In the con-
struction of new plants and equipment,
the owner or operator shall assure that
equipment as it is fabricated is suit-
able for the process application for
which they will be used.
(2) Appropriate checks and inspec-
tions shall be performed to assure that
equipment is installed properly and
consistent with design specifications
and the manufacturer's instructions.
(3) The owner or operator shall as-
sure that maintenance materials, spare
parts and equipment are suitable for
the process application for which they
will be used.
51
-------
§68.75
40 CFR Ch. I (7-1-98 Edition)
§ 68.75 Management of change.
(a) The owner or operator shall estab-
lish and implement written procedures
to manage changes (except for "re-
placements in kind") to process chemi-
cals, technology, equipment, and proce-
dures; and, changes to stationary
sources that affect a covered process.
(b) The procedures shall assure that
the following considerations are ad-
dressed prior to any change:
(1) The technical basis for the pro-
posed change;
(2) Impact of change on safety and
health;
(3) Modifications to operating proce-
dures;
(4) Necessary time period for the
change; and,
(5) Authorization requirements for
the proposed change.
(c) Employees involved in operating a
process and maintenance and contract
employees whose job tasks will be af-
fected by a change in the process shall
be informed of, and trained in, the
change prior to start-up of the process
or affected part of the process.
(d) If a change covered by this para-
graph results in a change in the process
safety information required by §68.65 of
this part, such information shall be up-
dated accordingly.
(e) If a change covered by this para-
graph results in a change in the operat-
ing procedures or practices required by
§68.69, such procedures or practices
shall be updated accordingly.
§68.77 Pre-startup review.
(a) The owner or operator shall per-
form a pre-startup safety review for
new stationary sources and for modi-
fied stationary sources when the modi-
fication is significant enough to re-
quire a change in the process safety in-
formation.
(b) The pre-startup safety review
shall confirm that prior to the intro-
duction of regulated substances to a
process:
(1) Construction and equipment is in
accordance with design specifications;
(2) Safety, operating, maintenance,
and emergency procedures are in place
and are adequate;
(3) For new stationary sources, a
process hazard analysis has been per-
formed and recommendations have
been resolved or implemented before
startup; and modified stationary
sources meet the requirements con-
tained in management of change,
§68.75.
(4) Training of each employee in-
volved in operating a process has been
completed.
§68.79 Compliance audits.
(a) The owner or operator shall cer-
tify that they have evaluated compli-
ance with the provisions of this section
at least every three years to verify
that the procedures and practices de-
veloped under the standard are ade-
quate and are being followed.
(b) The compliance audit shall be
conducted by at least one person
knowledgeable in the process.
(c) A report of the findings of the
audit shall be developed.
(d) The owner or operator shall
promptly determine and document an
appropriate response to each of the
findings of the compliance audit, and
document that deficiencies have been
corrected.
(e) The owner or operator shall retain
the two (2) most recent compliance
audit reports.
§68.81 Incident investigation.
(a) The owner or operator shall inves-
tigate each incident which resulted in,
or could reasonably have resulted in a
catastrophic release of a regulated sub-
stance.
(b) An incident investigation shall be
initiated as promptly as possible, but
not later than 48 hours following the
incident.
(c) An incident investigation team
shall be established and consist of at
least one person knowledgeable in the
process involved, including a contract
employee if the incident involved work
of the contractor, and other persons
with appropriate knowledge and experi-
ence to thoroughly investigate and
analyze the incident.
(d) A report shall be prepared at the
conclusion of the investigation which
includes at a minimum:
(1) Date of incident;
(2) Date investigation began;
(3) A description of the incident;
(4) The factors that contributed to
the incident; and,
52
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Environmental Protection Agency
§68.87
(5) Any recommendations resulting
from the investigation.
(e) The owner or operator shall estab-
lish a system to promptly address and
resolve the incident report findings and
recommendations. Resolutions and cor-
rective actions shall be documented.
(f) The report shall be reviewed with
all affected personnel whose job tasks
are relevant to the incident findings in-
cluding contract employees where ap-
plicable.
(g) Incident investigation reports
shall be retained for five years.
§ 68.83 Employee participation.
(a) The owner or operator shall de-
velop a written plan of action regard-
ing the implementation of the em-
ployee participation required by this
section.
(b) The owner or operator shall con-
sult with employees and their rep-
resentatives on the conduct and devel-
opment of process hazards analyses and
on the development of the other ele-
ments of process safety management in
this rule.
(c) The owner or operator shall pro-
vide to employees and their representa-
tives access to process hazard analyses
and to all other information required
to be developed under this rule.
§ 68.85 Hot work permit.
(a) The owner or operator shall issue
a hot work permit for hot work oper-
ations conducted on or near a covered
process.
(b) The permit shall document that
the fire prevention and protection re-
quirements in 29 CFR 1910.252(a) have
been implemented prior to beginning
the hot work operations; it shall indi-
cate the date(s) authorized for hot
work; and identify the object on which
hot work is to be performed. The per-
mit shall be kept on file until comple-
tion of the hot work operations.
§ 68.87 Contractors.
(a) Application. This section applies
to contractors performing maintenance
or repair, turnaround, major renova-
tion, or specialty work on or adjacent
to a covered process. It does not apply
to contractors providing incidental
services which do not influence process
safety, such as janitorial work, food
and drink services, laundry, delivery or
other supply services.
(b) Owner or operator responsibilities.
(1) The owner or operator, when select-
ing a contractor, shall obtain and
evaluate information regarding the
contract owner or operator's safety
performance and programs.
(2) The owner or operator shall in-
form contract owner or operator of the
known potential fire, explosion, or
toxic release hazards related to the
contractor's work and the process.
(3) The owner or operator shall ex-
plain to the contract owner or operator
the applicable provisions of subpart E
of this part.
(4) The owner or operator shall de-
velop and implement safe work prac-
tices consistent with §68.69(d), to con-
trol the entrance, presence, and exit of
the contract owner or operator and
contract employees in covered process
areas.
(5) The owner or operator shall peri-
odically evaluate the performance of
the contract owner or operator in ful-
filling their obligations as specified in
paragraph (c) of this section.
(c) Contract owner or operator respon-
sibilities. (1) The contract owner or op-
erator shall assure that each contract
employee is trained in the work prac-
tices necessary to safely perform his/
her job.
(2) The contract owner or operator
shall assure that each contract em-
ployee is instructed in the known po-
tential fire, explosion, or toxic release
hazards related to his/her job and the
process, and the applicable provisions
of the emergency action plan.
(3) The contract owner or operator
shall document that each contract em-
ployee has received and understood the
training required by this section. The
contract owner or operator shall pre-
pare a record which contains the iden-
tity of the contract employee, the date
of training, and the means used to ver-
ify that the employee understood the
training.
(4) The contract owner or operator
shall assure that each contract em-
ployee follows the safety rules of the
stationary source including the safe
work practices required by §68.69(d).
(5) The contract owner or operator
shall advise the owner or operator of
53
-------
§68.90
40 CFR Ch. I (7-1-98 Edition)
any unique hazards presented by the
contract owner or operator's work, or
of any hazards found by the contract
owner or operator's work.
Subpart E—Emergency Response
SOURCE: 61 FR 31725, June 20, 1996, unless
otherwise noted.
§ 68.90 Applicability.
(a) Except as provided in paragraph
(b) of this section, the owner or opera-
tor of a stationary source with Pro-
gram 2 and Program 3 processes shall
comply with the requirements of §68.95.
(b) The owner or operator of station-
ary source whose employees will not
respond to accidental releases of regu-
lated substances need not comply with
§68.95 of this part provided that they
meet the following:
(1) For stationary sources with any
regulated toxic substance held in a
process above the threshold quantity,
the stationary source is included in the
community emergency response plan
developed under 42 U.S.C. 11003;
(2) For stationary sources with only
regulated flammable substances held in
a process above the threshold quantity,
the owner or operator has coordinated
response actions with the local fire de-
partment; and
(3) Appropriate mechanisms are in
place to notify emergency responders
when there is a need for a response.
§ 68.95 Emergency response program.
(a) The owner or operator shall de-
velop and implement an emergency re-
sponse program for the purpose of pro-
tecting public health and the environ-
ment. Such program shall include the
following elements:
(1) An emergency response plan,
which shall be maintained at the sta-
tionary source and contain at least the
following elements:
(i) Procedures for informing the pub-
lic and local emergency response agen-
cies about accidental releases;
(ii) Documentation of proper first-aid
and emergency medical treatment nec-
essary to treat accidental human expo-
sures; and
(iii) Procedures and measures for
emergency response after an accidental
release of a regulated substance;
(2) Procedures for the use of emer-
gency response equipment and for its
inspection, testing, and maintenance;
(3) Training for all employees in rel-
evant procedures; and
(4) Procedures to review and update,
as appropriate, the emergency response
plan to reflect changes at the station-
ary source and ensure that employees
are informed of changes.
(b) A written plan that complies with
other Federal contingency plan regula-
tions or is consistent with the ap-
proach in the National Response
Team's Integrated Contingency Plan
Guidance ("One Plan") and that,
among other matters, includes the ele-
ments provided in paragraph (a) of this
section, shall satisfy the requirements
of this section if the owner or operator
also complies with paragraph (c) of this
section.
(c) The emergency response plan de-
veloped under paragraph (a)(l) of this
section shall be coordinated with the
community emergency response plan
developed under 42 U.S.C. 11003. Upon
request of the local emergency plan-
ning committee or emergency response
officials, the owner or operator shall
promptly provide to the local emer-
gency response officials information
necessary for developing and imple-
menting the community emergency re-
sponse plan.
Subpart F—Regulated Substances
for Accidental Release Prevention
SOURCE: 59 FR 4493, Jan. 31, 1994, unless
otherwise noted. Redesignated at 61 FR 31717,
June 20, 1996.
§68.100 Purpose.
This subpart designates substances
to be listed under section 112(r)(3), (4),
and (5) of the Clean Air Act, as amend-
ed, identifies their threshold quan-
tities, and establishes the requirements
for petitioning to add or delete sub-
stances from the list.
§68.115 Threshold determination.
(a) A threshold quantity of a regu-
lated substance listed in §68.130 is
54
-------
Environmental Protection Agency
§68.115
present at a stationary source if the
total quantity of the regulated sub-
stance contained in a process exceeds
the threshold.
(b) For the purposes of determining
whether more than a threshold quan-
tity of a regulated substance is present
at the stationary source, the following
exemptions apply:
(1) Concentrations of a regulated toxic
substance in a mixture. If a regulated
substance is present in a mixture and
the concentration of the substance is
below one percent by weight of the
mixture, the amount of the substance
in the mixture need not be considered
when determining whether more than a
threshold quantity is present at the
stationary source. Except for oleum,
toluene 2,4-diisocyanate, toluene 2,6-
diisocyanate, and toluene diisocyanate
(unspecified isomer), if the concentra-
tion of the regulated substance in the
mixture is one percent or greater by
weight, but the owner or operator can
demonstrate that the partial pressure
of the regulated substance in the mix-
ture (solution) under handling or stor-
age conditions in any portion of the
process is less than lO millimeters of
mercury (mm Hg), the amount of the
substance in the mixture in that por-
tion of the process need not be consid-
ered when determining whether more
than a threshold quantity is present at
the stationary source. The owner or op-
erator shall document this partial pres-
sure measurement or estimate.
(2) Concentrations of a regulated flam-
mable substance in a mixture, (i) General
provision. If a regulated substance is
present in a mixture and the con-
centration of the substance is below
one percent by weight of the mixture,
the mixture need not be considered
when determining whether more than a
threshold quantity of the regulated
substance is present at the stationary
source. Except as provided in para-
graph (b)(2) (ii) and (iii) of this section,
if the concentration of the substance is
one percent or greater by weight of the
mixture, then, for purposes of deter-
mining whether a threshold quantity is
present at the stationary source, the
entire weight of the mixture shall be
treated as the regulated substance un-
less the owner or operator can dem-
onstrate that the mixture itself does
not have a National Fire Protection
Association flammability hazard rat-
ing of 4. The demonstration shall be in
accordance with the definition of flam-
mability hazard rating 4 in the NFPA
704, Standard System for the Identi-
fication of the Hazards of Materials for
Emergency Response, National Fire
Protection Association, Quincy, MA,
1996. Available from the National Fire
Protection Association, 1
Batterymarch Park, Quincy, MA 02269-
9101. This incorporation by reference
was approved by the Director of the
Federal Register in accordance with 5
U.S.C. 552(a) and 1 CFR part 51. Copies
may be inspected at the Environmental
Protection Agency Air Docket (6102),
Attn: Docket No. A-96-O8, Waterside
Mall, 401 M. St. SW., Washington DC;
or at the Office of Federal Register at
800 North Capitol St., NW, Suite 700,
Washington, DC. Boiling point and
flash point shall be defined and deter-
mined in accordance with NFPA 30,
Flammable and Combustible Liquids
Code, National Fire Protection Asso-
ciation, Quincy, MA, 1996. Available
from the National Fire Protection As-
sociation, 1 Batterymarch Park, Quin-
cy, MA 02269-9101. This incorporation
by reference was approved by the Di-
rector of the Federal Register in ac-
cordance with 5 U.S.C. 552(a) and 1 CFR
part 51. Copies may be inspected at the
Environmental Protection Agency Air
Docket (6102), Attn: Docket No. A-96-
08, Waterside Mall, 401 M. St. SW.,
Washington DC; or at the Office of Fed-
eral Register at 800 North Capitol St.,
NW., Suite 700, Washington, DC. The
owner or operator shall document the
National Fire Protection Association
flammability hazard rating.
(ii) Gasoline. Regulated substances in
gasoline, when in distribution or relat-
ed storage for use as fuel for internal
combustion engines, need not be con-
sidered when determining whether
more than a threshold quantity is
present at a stationary source.
(iii) Naturally occurring hydrocarbon
mixtures. Prior to entry into a natural
gas processing plant or a petroleum re-
fining process unit, regulated sub-
stances in naturally occurring hydro-
carbon mixtures need not be considered
when determining whether more than a
55
-------
§68.120
40 CFR Ch. I (7-1-98 Edition)
threshold quantity is present at a sta-
tionary source. Naturally occurring
hydrocarbon mixtures include any
combination of the following: conden-
sate, crude oil, field gas, and produced
water, each as defined in §68.3 of this
part.
(3) Articles. Regulated substances con-
tained in articles need not be consid-
ered when determining whether more
than a threshold quantity is present at
the stationary source.
(4) Uses. Regulated substances, when
in use for the following purposes, need
not be included in determining whether
more than a threshold quantity is
present at the stationary source:
(i) Use as a structural component of
the stationary source;
(ii) Use of products for routine jani-
torial maintenance;
(iii) Use by employees of foods, drugs,
cosmetics, or other personal items con-
taining the regulated substance; and
(iv) Use of regulated substances
present in process water or non-contact
cooling water as drawn from the envi-
ronment or municipal sources, or use
of regulated substances present in air
used either as compressed air or as part
of combustion.
(5) Activities in laboratories. If a regu-
lated substance is manufactured, proc-
essed, or used in a laboratory at a sta-
tionary source under the supervision of
a technically qualified individual as de-
fined in §720.3(ee) of this chapter, the
quantity of the substance need not be
considered in determining whether a
threshold quantity is present. This ex-
emption does not apply to:
(i) Specialty chemical production;
(ii) Manufacture, processing, or use
of substances in pilot plant scale oper-
ations; and
(iii) Activities conducted outside the
laboratory.
[59 FR 4493, Jan. 31, 1994. Redesignated at 61
FR 31717, June 20, 1996, as amended at 63 FR
645, Jan. 6, 1998]
§ 68.120 Petition process.
(a) Any person may petition the Ad-
ministrator to modify, by addition or
deletion, the list of regulated sub-
stances identified in §68.130. Based on
the information presented by the peti-
tioner, the Administrator may grant or
deny a petition.
(b) A substance may be added to the
list if, in the case of an accidental re-
lease, it is known to cause or may be
reasonably anticipated to cause death,
injury, or serious adverse effects to
human health or the environment.
(c) A substance may be deleted from
the list if adequate data on the health
and environmental effects of the sub-
stance are available to determine that
the substance, in the case of an acci-
dental release, is not known to cause
and may not be reasonably anticipated
to cause death, injury, or serious ad-
verse effects to human health or the
environment.
(d) No substance for which a national
primary ambient air quality standard
has been established shall be added to
the list. No substance regulated under
title VI of the Clean Air Act, as amend-
ed, shall be added to the list.
(e) The burden of proof is on the peti-
tioner to demonstrate that the criteria
for addition and deletion are met. A pe-
tition will be denied if this demonstra-
tion is not made.
(f) The Administrator will not accept
additional petitions on the same sub-
stance following publication of a final
notice of the decision to grant or deny
a petition, unless new data becomes
available that could significantly af-
fect the basis for the decision.
(g) Petitions to modify the list of
regulated substances must contain the
following:
(1) Name and address of the peti-
tioner and a brief description of the or-
ganization^) that the petitioner rep-
resents, if applicable;
(2) Name, address, and telephone
number of a contact person for the pe-
tition;
(3) Common chemical name(s), com-
mon synonym(s), Chemical Abstracts
Service number, and chemical formula
and structure;
(4) Action requested (add or delete a
substance);
(5) Rationale supporting the petition-
er's position; that is, how the sub-
stance meets the criteria for addition
and deletion. A short summary of the
rationale must be submitted along
with a more detailed narrative; and
56
-------
Environmental Protection Agency
§68.130
(6) Supporting data; that is, the peti-
tion must include sufficient informa-
tion to scientifically support the re-
quest to modify the list. Such informa-
tion shall include:
(i) A list of all support documents;
(ii) Documentation of literature
searches conducted, including, but not
limited to, identification of the data-
base^) searched, the search strategy,
dates covered, and printed results;
(iii) Effects data (animal, human, and
environmental test data) indicating
the potential for death, injury, or seri-
ous adverse human and environmental
impacts from acute exposure following
an accidental release; printed copies of
the data sources, in English, should be
provided; and
(iv) Exposure data or previous acci-
dent history data, indicating the po-
tential for serious adverse human
health or environmental effects from
an accidental release. These data may
include, but are not limited to, phys-
ical and chemical properties of the sub-
stance, such as vapor pressure; model-
ing results, including data and assump-
tions used and model documentation;
and historical accident data, citing
data sources.
(h) Within 18 months of receipt of a
petition, the Administrator shall pub-
lish in the FEDERAL REGISTER a notice
either denying the petition or granting
the petition and proposing a listing.
§ 68.125 Exemptions.
Agricultural nutrients. Ammonia used
as an agricultural nutrient, when held
by farmers, is exempt from all provi-
sions of this part.
§68.130 List of substances.
(a) Regulated toxic and flammable
substances under section 112(r) of the
Clean Air Act are the substances listed
in Tables 1, 2, 3, and 4. Threshold quan-
tities for listed toxic and flammable
substances are specified in the tables.
(b) The basis for placing toxic and
flammable substances on the list of
regulated substances are explained in
the notes to the list.
TABLE 1 TO §68.130.—LIST OF REGULATED
Toxic SUBSTANCES AND THRESHOLD QUAN-
TITIES FOR ACCIDENTAL RELEASE PREVENTION
[Alphabetical Order—77 Substances]
Chemical name
Acrolein [2-
Propenal].
Acrylonitrile [2-
Propenenitrile].
Acrylyl chloride [2-
Propenoyl chlo-
ride].
Allyl alcohol [2-
Propen-l-ol].
Allylamine [2-
Propen-l-amine].
Ammonia (anhy-
drous).
Ammonia (cone
20% or greater).
Arsenous tri-
chloride.
Arsine
Boron trichloride
[Borane,
trichloro-].
Boron trifluoride
[Borane,
trifluoro-].
Boron trifluoride
compound with
methyl ether
(1:1) [Boron,
trifluoro [oxybis
[metane]]-, T-4-.
Bromine
Carbon disulfide ..
Chlorine
Chlorine dioxide
[Chlorine oxide
(CI02)].
Chloroform [Meth-
ane, trichloro-].
Chloromethyl
ether [Methane,
oxybis[chloro-].
Chloromethyl
methyl ether
[Methane,
chloromethoxy-].
Crotonaldehyde
[2-Butenal].
Crotonaldehyde,
(E)- [2-Butenal,
(E)-].
Cyanogen chlo-
ride.
Cyclohexylamine
[Cyclohexanam-
ine].
Diborane
Dimethyldichloros-
ilane [Silane,
dichlorodimeth-
yl-].
1,1-
Dimethylhydraz-
ine [Hydrazine,
1,1-dimethyl-].
CAS No.
1 07-02-8
107-13-1
814-68-6
107-18-61
107-11-9
7664-41-7
7664-41-7
7784-34-1
7784-42-1
10294-34-5
7637-07-2
353-42-4
7726-95-6
75-15-0
7782-50-5
1 0049-04-4
67-66-3
542-88-1
1 07-30-2
41 70-30-3
1 23-73-9
506-77-4
108-91-8
1 9287-45-7
75-78-5
57-14-7
Threshold
quantity
(Ibs)
5,000
20,000
5,000
15,000
10,000
10,000
20,000
15,000
1,000
5,000
5,000
15,000
10,000
20,000
2,500
1,000
20,000
1,000
5,000
20,000
20,000
10,000
15,000
2,500
5,000
15,000
Basis for
listing
b
b
b
b
b
a, b
a, b
b
b
b
b
b
a, b
b
a, b
c
b
b
b
b
b
c
b
b
b
b
57
-------
§68.130
40 CFR Ch. I (7-1-98 Edition)
TABLE 1 TO §68.130.—LIST OF REGULATED
Toxic SUBSTANCES AND THRESHOLD QUAN-
TITIES FOR ACCIDENTAL RELEASE PREVEN-
TION—Continued
[Alphabetical Order—77 Substances]
TABLE 1 TO §68.130.—LIST OF REGULATED
Toxic SUBSTANCES AND THRESHOLD QUAN-
TITIES FOR ACCIDENTAL RELEASE PREVEN-
TION—Continued
[Alphabetical Order—77 Substances]
Chemical name
Epichlorohydrin
[Oxirane,
(chloromethyl)-].
Ethylenediamine
[1,2-
Ethanediamine].
Ethyleneimine
[Aziridine].
Ethylene oxide
[Oxirane].
Fluorine
Formaldehyde
(solution).
Furan
Hydrazine
Hydrochloric acid
(cone 37% or
greater).
Hydrocyanic acid
Hydrogen chloride
(anhydrous)
[Hydrochloric
acid].
Hydrogen fluoride/
Hydrofluoric
acid (cone 50%
or greater)
[Hydrofluoric
acid].
Hydrogen sele-
nide.
Hydrogen sulfide
Iron,
pentacarbonyl-
[Iron carbonyl
(Fe(CO)S), (TB-
5-11)-].
Isobutyronitrile
[Propanenitrile,
2-methyl-].
Isopropyl
chloroformate
[Carbonochlori-
dic acid, 1-
methylethyl
ester].
Methacrylonitrile
[2-
Propenenitrile,
2-methyl-].
Methyl chloride
[Methane,
chloro-].
Methyl
chloroformate
[Carbonochlori-
dic acid,
methylester].
Methyl hydrazine
[Hydrazine,
methyl-].
Methyl isocyanate
[Methane,
isocyanato-].
CAS No.
106-89-8
107-15-3
151-56-4
75-21-8
7782-41-4
50-00-0
1 1 0-00-9
302-01-2
7647-01-0
74-90-8
7647-01-0
7664-39-3
7783-07-5
7783-06-4
13463-40-6
78-82-0
108-23-6
126-98-7
74-87-3
79-22-1
60-34-4
624-83-9
Threshold
quantity
(Ibs)
20,000
20,000
10,000
10,000
1,000
15,000
5,000
15,000
15,000
2,500
5,000
1,000
500
10,000
2,500
20,000
15,000
10,000
10,000
5,000
15,000
10,000
Basis for
listing
b
b
b
a, b
b
b
b
b
d
a, b
a
a, b
b
a, b
b
b
b
b
a
b
b
a, b
Chemical name
Methyl mercaptan
[Methanethiol].
Methyl
thiocyanate
[Thiocyanic
acid, methyl
ester].
Methyltrichlorosil-
ane [Silane,
trichloromethyl-].
Nickel carbonyl ....
Nitric acid (cone
80% or greater).
Nitric oxide [Nitro-
gen oxide (NO)].
Oleum (Fuming
Sulfuric acid)
[Sulfuric acid,
mixture with
sulfur trioxide] 1.
Peracetic acid
[Ethaneperoxoic
acid].
Perchloromethyl-
mercaptan
[Methanesulfen-
yl chloride,
trichloro-].
Phosgene [Car-
bonic dichloride].
Phosphine
Phosphorus
oxychloride
[Phosphoryl
chloride].
Phosphorus tri-
chloride [Phos-
phorous tri-
chloride].
Piperidine
Propionitrile
[Propanenitrile].
Propyl
chloroformate
[Carbonochlori-
dic acid,
propylester].
Propyleneimine
[Aziridine, 2-
methyl-].
Propylene oxide
[Oxirane, meth-
yl-].
Sulfur dioxide (an-
hydrous).
Sulfur tetrafluoride
[Sulfur fluoride
(SF4), (T-4)-].
Sulfur trioxide
Tetramethyllead
[Plumbane,
tetramethyl-].
Tetranitromethane
[Methane,
tetranitro-].
CAS No.
74-93-1
556-64-9
75-79-6
13463-39-3
7697-37-2
10102-43-9
8014-95-7
79-21-0
594-42-3
75-44-5
7803-51-2
10025-87-3
7719-12-2
1 1 0-89-4
107-12-0
109-61-5
75-55-8
75-56-9
7446-09-5
7783-60-0
7446-11-9
75-74-1
509-14-8
Threshold
quantity
(Ibs)
10,000
20,000
5,000
1,000
15,000
10,000
10,000
10,000
10,000
500
5,000
5,000
15,000
15,000
10,000
15,000
10,000
10,000
5,000
2,500
10,000
10,000
10,000
Basis for
listing
b
b
b
b
b
b
e
b
b
a, b
b
b
b
b
b
b
b
b
a, b
b
a, b
b
b
58
-------
Environmental Protection Agency
§68.130
TABLE 1 TO §68.130.—LIST OF REGULATED
Toxic SUBSTANCES AND THRESHOLD QUAN-
TITIES FOR ACCIDENTAL RELEASE PREVEN-
TION—Continued
[Alphabetical Order—77 Substances]
TABLE 1 TO §68.130.—LIST OF REGULATED
Toxic SUBSTANCES AND THRESHOLD QUAN-
TITIES FOR ACCIDENTAL RELEASE PREVEN-
TION—Continued
[Alphabetical Order—77 Substances]
Chemical name
Titanium tetra-
chloride [Tita-
nium chloride
(TiCI4) (T-4)-].
Toluene 2,4-
diisocyanate
[Benzene, 2,4-
diisocyanato-1-
methyl-] 1 .
Toluene 2,6-
diisocyanate
[Benzene, 1,3-
diisocyanato-2-
methyl-] 1 .
Toluene
diisocyanate
(unspecified
isomer) [Ben-
zene, 1,3-
diisocyanatome-
thyl-]1.
CAS No.
7550-45-0
584-84-9
91-08-7
26471-62-5
Threshold
quantity
(Ibs)
2,500
10,000
10,000
10,000
Basis for
listing
b
a
a
a
Chemical name
Trimethylchlorosil-
ane [Silane,
chlorotrimethyl-].
Vinyl acetate
monomer [Ace-
tic acid ethenyl
ester].
CAS No.
75-77-4
108-05-4
Threshold
quantity
(Ibs)
10,000
15,000
Basis for
listing
b
b
1 The mixture exemption in §68.115(b)(1) does not apply to
the substance.
NOTE: Basis for Listing:
a Mandated for listing by Congress.
b On EHS list, vapor pressure 10 mmHg or greater.
c Toxic gas.
d Toxicity of hydrogen chloride, potential to release hydro-
gen chloride, and history of accidents.
e Toxicity of sulfur trioxide and sulfuric acid, potential to
release sulfur trioxide, and history of accidents.
TABLE 2 TO §68.130.—LIST OF REGULATED Toxic SUBSTANCES AND THRESHOLD QUANTITIES FOR
ACCIDENTAL RELEASE PREVENTION
[CAS Number Order—77 Substances]
CAS No.
50-00-0
57-14-7
60-34-4
67-66-3
74-87-3
74-90-8
74-93-1
75-15-0
75-21-8
75-44-5
75-55-8
75-56-9
75-74-1
75-77-4
75-78-5
75-79-6
78-82-0
79-21-0
79-22-1
91-08-7
106-89-8
1 07-02-8
107-11-9
107-12-0
1 07-1 3-1
107-15-3
107-18-6
1 07-30-2
108-05-4
108-23-6
108-91-8
109-61-5
1 1 0-00-9
110-89-4
123-73-9
Chemical name
1,1-Dimethylhydrazine [Hydrazine, 1,1-dimethyl-]
Methyl hydrazine [Hydrazine, methyl-]
Methyl chloride [Methane, chloro-]
Carbon disulfide
Phosgene [Carbonic dichloride]
Propyleneimine [Aziridine, 2-methyl-]
Propylene oxide [Oxirane, methyl-]
Tetramethyllead [Plumbane, tetramethyl-]
Trimethylchlorosilane [Silane, chlorotrimethyl-]
Methyltrichlorosilane [Silane, trichloromethyl-]
Peracetic acid [Ethaneperoxoic acid]
Methyl chloroformate [Carbonochloridic acid, methylester]
Epichlorohydrin [Oxirane, (chloromethyl)-]
Propionitrile [Propanenitrile]
Ethylenediamine [1,2-Ethanediamine]
Allyl alcohol [2-Propen-1-ol]
Vinyl acetate monomer [Acetic acid ethenyl ester]
Isopropyl chloroformate [Carbonochloridic acid, 1-methylethyl ester]
Propyl chloroformate [Carbonochloridic acid, propylester]
Piperidine
Crotonaldehvde. fD- F2-Butenal. fD-1
Threshold
quantity
(Ibs)
15000
15,000
15,000
20000
10,000
2500
10000
20,000
10000
500
10,000
10,000
10,000
10,000
5000
5,000
20000
10,000
5,000
10000
20,000
5000
10000
10,000
20000
20,000
15,000
5000
15,000
15,000
15000
15,000
5000
15,000
20.000
Basis for
listing
b
b
b
b
a
a b
b
b
a b
a, b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
59
-------
§68.130
40 CFR Ch. I (7-1-98 Edition)
TABLE 2 TO §68.130.—LIST OF REGULATED Toxic SUBSTANCES AND THRESHOLD QUANTITIES FOR
ACCIDENTAL RELEASE PREVENTION—Continued
[CAS Number Order—77 Substances]
CAS No.
126-98-7
151-56-4
302-01-2
353-42-4
506-77-4
509-1 4-8
542-88-1
556-64-9
584-84-9
594-42-3
624-83-9
81 4-68-6
4170-30-3
7446-09-5
7446-11-9
7550-45-0
7637-07-2
7647-01-0
7647-01-0
7664-39-3
7664-41-7
7664-41-7
7697-37-2
7719-12-2
7726-95-6
7782-41^1
7782-50-5
7783-06^1
7783-07-5
7783-60-0
7784-34-1
7784-42-1
7803-51-2
8014-95-7
1 0025-87-3
10049-04-4
10102-43-9
1 0294-34-5
13463-39-3
13463-40-6
1 9287-45-7
26471-62-5
Chemical name
Methacrylonitrile [2-Propenenitrile, 2-methyl-]
Ethyleneimine [Aziridine]
trifluoro[oxybis[methane]]-, T-4-.
Cyanogen chloride
Chloromethyl ether [Methane, oxybis[chloro-]
Methyl thiocyanate [Thiocyanic acid, methyl ester]
Perchloromethylmercaptan [Methanesulfenyl chloride, trichloro-]
Crotonaldehyde [2-Butenal]
Sulfur trioxide
Titanium tetrachloride [Titanium chloride (TICI4) (T-4)-]
Hydrochloric acid (cone 37% or greater)
Ammonia (anhydrous)
Nitric acid (cone 80% or greater)
Phosphorus trichloride [Phosphorous trichloride]
Fluorine
Hydrogen selenide
Sulfur tetrafluoride [Sulfur fluoride (SF4) (T-4)-]
Arsenous trichloride
Arsine
Oleum (Fuming Sulfuric acid) [Sulfuric acid, mixture with sulfur trioxide]1
Chlorine dioxide [Chlorine oxide (CIO2)]
Nitric oxide [Nitrogen oxide (NO)]
Nickel carbonyl
Iron, pentacarbonyl- [Iron carbonyl (Fe(CO)5), (TB-5-11)-]
Toluene diisocyanate (unspecified isomer) [Benzene, 1,3-diisocyanatomethyl-
1]1.
Threshold
quantity
(Ibs)
10,000
10,000
15000
15000
10,000
10000
1,000
20,000
10000
10,000
10000
5000
20,000
5000
10,000
2,500
5000
15,000
5000
1 000
10,000
20000
15,000
15,000
10000
1,000
2500
10000
500
2500
15,000
1,000
5000
10,000
5000
1,000
10,000
5000
1,000
2,500
2500
10,000
Basis for
listing
b
b
b
b
c
b
b
b
b
a b
b
b
a b
a, b
b
b
d
a b
a, b
a b
b
b
a b
b
a b
a b
b
b
b
b
b
e
b
c
b
b
b
b
b
a
1 The mixture exemption in §68.115(b)(1) does not apply to the substance.
NOTE: Basis for Listing:
a Mandated for listing by Congress.
b On EHS list, vapor pressure 10 mmHg or greater.
c Toxic gas.
d Toxicity of hydrogen chloride, potential to release hydrogen chloride, and history of accidents.
e Toxicity of sulfur trioxide and sulfuric acid, potential to release sulfur trioxide, and history of accidents.
TABLE 3 TO §68.130.—LIST OF REGULATED FLAMMABLE SUBSTANCES AND THRESHOLD QUANTITIES
FOR ACCIDENTAL RELEASE PREVENTION
[Alphabetical Order—63 Substances]
Chemical name
Acetylene [Ethyne]
Bromotrif luorethylene [Ethene, bromotrif luoro-]
Butane
2-Butene
Butene
CAS No.
75_07-0
74-86-2
598-73-2
1 06-99-0
106-97-8
1 06-98-9
107-01-7
25167-67-3
Threshold
quantity
(Ibs)
10000
10,000
10,000
10000
10,000
10000
10000
10,000
Basis for
listing
f
f
f
f
f
f
f
60
-------
Environmental Protection Agency
§68.130
TABLE 3 TO §68.130.—LIST OF REGULATED FLAMMABLE SUBSTANCES AND THRESHOLD QUANTITIES
FOR ACCIDENTAL RELEASE PREVENTION—Continued
[Alphabetical Order—63 Substances]
Chemical name
2-Butene-cis
2-Butene-trans [2-Butene (E)]
Chlorine monoxide [Chlorine oxide]
2-Chloropropylene [1-Propene, 2-chloro-]
Cyclopropane
Dichlorosilane [Silane, dichloro-]
2,2-Dimethylpropane [Propane, 2,2-dimethyl-]
Ethane
Ethyl chloride [Ethane, chloro-]
Ethylene [Ethene]
Ethyl nitrite [Nitrous acid, ethyl ester]
Hydrogen
Isoprene [1,3-Butadinene, 2-methyl-]
Isopropylamine [2-Propanamine]
Methylamine [Methanamine]
3-Methyl-1-butene
2-Methyl-1-butene
Methyl formate [Formic acid, methyl ester]
2-Methylpropene [1-Propene, 2-methyl-]
1-Pentene
2-Pentene, (E)-
2-Pentene (Z)-
Propane
Propylene [1-Propene]
Tetrafluoroethylene [Ethene, tetrafluoro-]
Tetramethylsilane [Silane, tetramethyl-]
Trimethylamine [Methanamine, N,N-dimethyl-]
Vinyl acetylene [1-Buten-3-yne]
Vinyl fluoride [Ethene, fluoro-]
Vinylidene chloride [Ethene, 1,1-dichloro-]
Vinvl methvl ether FEthene. methoxv-1
CAS No.
590-18-1
624-64-6
463-58-1
7791-21-1
557-98-2
590-21-6
460-19-5
75-19-4
4109-96-0
75-37-6
1 24^10-3
463-82-1
74-84-0
1 07-00-6
75-04-7
75-00-3
74-85-1
60-29-7
75-08-1
109-95-5
1333-74-0
75-28-5
78-78-4
78-79-5
75-31-0
75-29-6
74-82-8
74-89-5
563-45-1
563-46-2
115-10-6
107-31-3
115-11-7
504-60-9
1 09-66-0
109-67-1
646-04-8
627-20-3
463-49-0
74-98-6
115-07-1
74_gg_7
7803-62-5
116-14-3
75-76-3
1 0025-78-2
79-38-9
75-50-3
689-97-4
75-01-4
1 09-92-2
75-02-5
75-35-4
75-38-7
107-25-5
Threshold
quantity
(Ibs)
10,000
10000
10000
10,000
10,000
10000
10000
10,000
10,000
10000
10000
10,000
10,000
10000
10000
10,000
10,000
10000
10000
10,000
10,000
10000
10000
10,000
10,000
10000
10000
10,000
10,000
10000
10000
10,000
10,000
10000
10000
10,000
10,000
10000
10000
10,000
10,000
10000
10000
10,000
10,000
10000
10000
10,000
10,000
10000
10000
10,000
10,000
10000
10.000
Basis for
listing
f
f
f
f
g
f
f
f
f
f
f
f
f
f
f
f
f
f
f
g
g
f
f
f
f
g
f
f
g
g
f
f
f
f
f
f
g
f
f
f
a f
f
g
f
f
NOTE: Basis for Listing:
a Mandated for listing by Congress.
f Flammable gas.
g Volatile flammable liquid.
61
-------
§68.130
40 CFR Ch. I (7-1-98 Edition)
TABLE 4 TO §68.130.—LIST OF REGULATED FLAMMABLE SUBSTANCES AND THRESHOLD QUANTITIES
FOR ACCIDENTAL RELEASE PREVENTION
[CAS Number Order—63 Substances]
Chemical name
CAS No.
Threshold
quantity
(Ibs)
Basis for
listing
60-29-7 Ethyl ether [Ethane, 1,1'-oxybis-] 60-29-7
74-82-8 Methane 74-82-8
74-84-0 Ethane 74-84-0
74-85-1 Ethylene [Ethene] 74-85-1
74-86-2 Acetylene [Ethyne] 74-86-2
74-89-5 Methylamine [Methanamine] 74-89-5
74-98-6 Propane 74-98-6
74-99-7 Propyne [1-Propyne] 74-99-7
75-00-3 Ethyl chloride [Ethane, chloro-] 75-00-3
75-01-4 Vinyl chloride [Ethene, chloro-j 75-01-4
75-02-5 Vinyl fluoride [Ethene, fluoro-] 75-02-5
75-04-7 Ethylamine [Ethanamine] 75-04-7
75-07-0 Acetaldehyde 75-07-0
75-08-1 Ethyl mercaptan [Ethanethiol] 75-08-1
75-19-4 Cyclopropane 75-19-4
75-28-5 Isobutane [Propane, 2-methyl] 75-28-5
75-29-6 Isopropyl chloride [Propane, 2-chloro-] 75-29-6
75-31-0 Isopropylamine [2-Propanamine] 75-31-0
75-35-4 Vinylidene chloride [Ethene, 1,1-dichloro-] 75-35-4
75-37-6 Difluoroethane [Ethane, 1,1-difluoro-] 75-37-6
75-38-7 Vinylidene fluoride [Ethene, 1,1-difluoro-] 75-38-7
75-50-3 Trimethylamine [Methanamine, N, N-dimethyl-] 75-50-3
75-76-3 Tetramethylsilane [Silane, tetramethyl-] 75-76-3
78-78-4 Isopentane [Butane, 2-methyl-] 78-78-4
78-79-5 Isoprene [1,3,-Butadiene, 2-methyl-] 78-79-5
79-38-9 Trifluorochloroethylene [Ethene, chlorotrifluoro-] 79-38-9
106-97-8 Butane 106-97-8
106-98-9 1-Butene 106-98-9
196-99-0 1,3-Butadiene 106-99-0
107-00-6 Ethyl acetylene [1-Butyne] 107-00-6
107-01-7 2-Butene 107-01-7
107-25-5 Vinyl methyl ether [Ethene, methoxy-] 107-25-5
107-31-3 Methyl formate [Formic acid, methyl ester] 107-31-3
109-66-0 Pentane 109-66-0
109-67-1 1-Pentene 109-67-1
109-92-2 Vinyl ethyl ether [Ethene, ethoxy-] 109-92-2
109-95-5 Ethyl nitrite [Nitrous acid, ethyl ester] 109-95-5
115-07-1 Propylene [1-Propene] 115-07-1
115-10-6 Methyl ether [Methane, oxybis-] 115-10-6
115-11-7 2-Methylpropene [1-Propene, 2-methyl-] 115-11-7
116-14-3 Tetrafluoroethylene [Ethene, tetrafluoro-] 116-14-3
124-40-3 Dimethylamine [Methanamine, N-methyl-] 124-40-3
460-19-5 Cyanogen [Ethanedinitrile] 460-19-5
463-49-0 Propadiene [1,2-Propadiene] 463-49-0
463-58-1 Carbon oxysulfide [Carbon oxide sulfide (COS)] 463-58-1
463-82-1 2,2-Dimethylpropane [Propane, 2,2-dimethyl-] 463-82-1
504-60-9 1,3-Pentadiene 504-60-9
557-98-2 2-Chloropropylene [1-Propene, 2-chloro-] 557-98-2
563-45-1 3-Methyl-1-butene 563-45-1
563-46-2 2-Methyl-1-butene 563-46-2
590-18-1 2-Butene-cis 590-18-1
590-21-6 1-Chloropropylene [1-Propene, 1-chloro-] 590-21-6
598-73-2 Bromotrifluorethylene [Ethene, bromotrifluoro-] 598-73-2
624-64-6 2-Butene-trans [2-Butene, (E)] 624-64-6
627-20-3 2-Pentene, (Z)- 627-20-3
646-04-8 2-Pentene, (E)- 646-04-8
689-97-4 Vinyl acetylene [1-Buten-3-yne] 689-97-4
1333-74-0 Hydrogen 1333-74-0
4109-96-0 Dichlorosilane [Silane, dichloro-] 4109-96-0
7791-21-1 Chlorine monoxide [Chlorine oxide] 7791-21-1
7803-62-5 Silane 7803-62-5
10025-78-2 Trichlorosilane[Silane,trichloro-] 10025-78-2
25167-67-3 Butene 25167-67-3
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
10,000
g
f
f
f
f
f
f
f
f
a, f
f
f
g
g
f
f
g
Note: Basis for Listing: a Mandated for listing by Congress. f Flammable gas. g Volatile flammable liquid.
[59 FR 4493, Jan. 31, 1994. Redeslgnated at 61 FR 31717, June 20, 1996, as amended at 62 FR 45132,
Aug. 25, 1997; 63 FR 645, Jan. 6, 1998]
62
-------
Environmental Protection Agency
§68.165
Sub pa it G—Risk Management
Plan
SOURCE: 61 FR 31726, June 20, 1996, unless
otherwise noted.
§ 68.150 Submission.
(a) The owner or operator shall sub-
mit a single RMP that includes the in-
formation required by §§68.155 through
68.185 for all covered processes. The
RMP shall be submitted in a method
and format to a central point as speci-
fied by EPA prior to June 21, 1999.
(b) The owner or operator shall sub-
mit the first RMP no later than the
latest of the following dates:
(1) June 21, 1999;
(2) Three years after the date on
which a regulated substance is first
listed under §68.130; or
(3) The date on which a regulated
substance is first present above a
threshold quantity in a process.
(c) Subsequent submissions of RMPs
shall be in accordance with §68.190.
(d) Notwithstanding the provisions of
§§68.155 to 68.190, the RMP shall ex-
clude classified information. Subject to
appropriate procedures to protect such
information from public disclosure,
classified data or information excluded
from the RMP may be made available
in a classified annex to the RMP for re-
view by Federal and state representa-
tives who have received the appro-
priate security clearances.
§68.155 Executive summary.
The owner or operator shall provide
in the RMP an executive summary that
includes a brief description of the fol-
lowing elements:
(a) The accidental release prevention
and emergency response policies at the
stationary source;
(b) The stationary source and regu-
lated substances handled;
(c) The worst-case release scenario(s)
and the alternative release scenario(s),
including administrative controls and
mitigation measures to limit the dis-
tances for each reported scenario;
(d) The general accidental release
prevention program and chemical-spe-
cific prevention steps;
(e) The five-year accident history;
(f) The emergency response program;
and
(g) Planned changes to improve safe-
ty.
§ 68.160 Registration.
(a) The owner or operator shall com-
plete a single registration form and in-
clude it in the RMP. The form shall
cover all regulated substances handled
in covered processes.
(b) The registration shall include the
following data:
(1) Stationary source name, street,
city, county, state, zip code, latitude,
and longitude;
(2) The stationary source Dun and
Bradstreet number;
(3) Name and Dun and Bradstreet
number of the corporate parent com-
pany;
(4) The name, telephone number, and
mailing address of the owner or opera-
tor;
(5) The name and title of the person
or position with overall responsibility
for RMP elements and implementation;
(6) The name, title, telephone num-
ber, and 24-hour telephone number of
the emergency contact;
(7) For each covered process, the
name and CAS number of each regu-
lated substance held above the thresh-
old quantity in the process, the maxi-
mum quantity of each regulated sub-
stance or mixture in the process (in
pounds) to two significant digits, the
SIC code, and the Program level of the
process;
(8) The stationary source EPA identi-
fier;
(9) The number of full-time employ-
ees at the stationary source;
(10) Whether the stationary source is
subject to 29 CFR 1910.119;
(11) Whether the stationary source is
subject to 40 CFR part 355;
(12) Whether the stationary source
has a CAA Title V operating permit;
and
(13) The date of the last safety in-
spection of the stationary source by a
Federal, state, or local government
agency and the identity of the inspect-
ing entity.
§68.165 Offsite consequence analysis.
(a) The owner or operator shall sub-
mit in the RMP information:
63
-------
§68.168
40 CFR Ch. I (7-1-98 Edition)
(1) One worst-case release scenario
for each Program 1 process; and
(2) For Program 2 and 3 processes,
one worst-case release scenario to rep-
resent all regulated toxic substances
held above the threshold quantity and
one worst-case release scenario to rep-
resent all regulated flammable sub-
stances held above the threshold quan-
tity. If additional worst-case scenarios
for toxics or flammables are required
by §68.25(a)(2)(iii), the owner or opera-
tor shall submit the same information
on the additional scenario(s). The
owner or operator of Program 2 and 3
processes shall also submit information
on one alternative release scenario for
each regulated toxic substance held
above the threshold quantity and one
alternative release scenario to rep-
resent all regulated flammable sub-
stances held above the threshold quan-
tity.
(b) The owner or operator shall sub-
mit the following data:
(1) Chemical name;
(2) Physical state (toxics only);
(3) Basis of results (give model name
if used);
(4) Scenario (explosion, fire, toxic gas
release, or liquid spill and vaporiza-
tion);
(5) Quantity released in pounds;
(6) Release rate;
(7) Release duration;
(8) Wind speed and atmospheric sta-
bility class (toxics only);
(9) Topography (toxics only);
(10) Distance to endpoint;
(11) Public and environmental recep-
tors within the distance;
(12) Passive mitigation considered;
and
(13) Active mitigation considered (al-
ternative releases only);
§68.168 Five-year accident history.
The owner or operator shall submit
in the RMP the information provided
in §68.42(b) on each accident covered by
§68.42(a).
§68.170 Prevention program/Program
2.
(a) For each Program 2 process, the
owner or operator shall provide in the
RMP the information indicated in
paragraphs (b) through (k) of this sec-
tion. If the same information applies to
more than one covered process, the
owner or operator may provide the in-
formation only once, but shall indicate
to which processes the information ap-
plies.
(b) The SIC code for the process.
(c) The name(s) of the chemical(s)
covered.
(d) The date of the most recent re-
view or revision of the safety informa-
tion and a list of Federal or state regu-
lations or industry-specific design
codes and standards used to dem-
onstrate compliance with the safety in-
formation requirement.
(e) The date of completion of the
most recent hazard review or update.
(1) The expected date of completion
of any changes resulting from the haz-
ard review;
(2) Major hazards identified;
(3) Process controls in use;
(4) Mitigation systems in use;
(5) Monitoring and detection systems
in use; and
(6) Changes since the last hazard re-
view.
(f) The date of the most recent review
or revision of operating procedures.
(g) The date of the most recent re-
view or revision of training programs;
(1) The type of training provided—
classroom, classroom plus on the job,
on the job; and
(2) The type of competency testing
used.
(h) The date of the most recent re-
view or revision of maintenance proce-
dures and the date of the most recent
equipment inspection or test and the
equipment inspected or tested.
(i) The date of the most recent com-
pliance audit and the expected date of
completion of any changes resulting
from the compliance audit.
(j) The date of the most recent inci-
dent investigation and the expected
date of completion of any changes re-
sulting from the investigation.
(k) The date of the most recent
change that triggered a review or revi-
sion of safety information, the hazard
review, operating or maintenance pro-
cedures, or training.
64
-------
Environmental Protection Agency
§68.190
§68.175 Prevention program/Program
3.
(a) For each Program 3 process, the
owner or operator shall provide the in-
formation indicated in paragraphs (b)
through (p) of this section. If the same
information applies to more than one
covered process, the owner or operator
may provide the information only
once, but shall indicate to which proc-
esses the information applies.
(b) The SIC code for the process.
(c) The name(s) of the substance (s)
covered.
(d) The date on which the safety in-
formation was last reviewed or revised.
(e) The date of completion of the
most recent PHA or update and the
technique used.
(1) The expected date of completion
of any changes resulting from the PHA;
(2) Major hazards identified;
(3) Process controls in use;
(4) Mitigation systems in use;
(5) Monitoring and detection systems
in use; and
(6) Changes since the last PHA.
(f) The date of the most recent review
or revision of operating procedures.
(g) The date of the most recent re-
view or revision of training programs;
(1) The type of training provided—
classroom, classroom plus on the job,
on the job; and
(2) The type of competency testing
used.
(h) The date of the most recent re-
view or revision of maintenance proce-
dures and the date of the most recent
equipment inspection or test and the
equipment inspected or tested.
(i) The date of the most recent
change that triggered management of
change procedures and the date of the
most recent review or revision of man-
agement of change procedures.
(j) The date of the most recent pre-
startup review.
(k) The date of the most recent com-
pliance audit and the expected date of
completion of any changes resulting
from the compliance audit;
(1) The date of the most recent inci-
dent investigation and the expected
date of completion of any changes re-
sulting from the investigation;
(m) The date of the most recent re-
view or revision of employee participa-
tion plans;
(n) The date of the most recent re-
view or revision of hot work permit
procedures;
(o) The date of the most recent re-
view or revision of contractor safety
procedures; and
(p) The date of the most recent eval-
uation of contractor safety perform-
ance.
§68.180 Emergency response program.
(a) The owner or operator shall pro-
vide in the RMP the following informa-
tion:
(1) Do you have a written emergency
response plan?
(2) Does the plan include specific ac-
tions to be taken in response to an ac-
cidental releases of a regulated sub-
stance?
(3) Does the plan include procedures
for informing the public and local
agencies responsible for responding to
accidental releases?
(4) Does the plan include information
on emergency health care?
(5) The date of the most recent re-
view or update of the emergency re-
sponse plan;
(6) The date of the most recent emer-
gency response training for employees.
(b) The owner or operator shall pro-
vide the name and telephone number of
the local agency with which the plan is
coordinated.
(c) The owner or operator shall list
other Federal or state emergency plan
requirements to which the stationary
source is subject.
§68.185 Certification.
(a) For Program 1 processes, the
owner or operator shall submit in the
RMP the certification statement pro-
vided in§68.12(b)(4).
(b) For all other covered processes,
the owner or operator shall submit in
the RMP a single certification that, to
the best of the signer's knowledge, in-
formation, and belief formed after rea-
sonable inquiry, the information sub-
mitted is true, accurate, and complete.
§68.190 Updates.
(a) The owner or operator shall re-
view and update the RMP as specified
in paragraph (b) of this section and
submit it in a method and format to a
65
-------
§68.200
40 CFR Ch. I (7-1-98 Edition)
central point specified by EPA prior to
June 21, 1999.
(b) The owner or operator of a sta-
tionary source shall revise and update
the RMP submitted under §68.150 as
follows:
(1) Within five years of its initial sub-
mission or most recent update required
by paragraphs (b)(2) through (b)(7) of
this section, whichever is later.
(2) No later than three years after a
newly regulated substance is first list-
ed by EPA;
(3) No later than the date on which a
new regulated substance is first
present in an already covered process
above a threshold quantity;
(4) No later than the date on which a
regulated substance is first present
above a threshold quantity in a new
process;
(5) Within six months of a change
that requires a revised PHA or hazard
review;
(6) Within six months of a change
that requires a revised offsite con-
sequence analysis as provided in §68.36;
and
(7) Within six months of a change
that alters the Program level that ap-
plied to any covered process.
(c) If a stationary source is no longer
subject to this part, the owner or oper-
ator shall submit a revised registration
to EPA within six months indicating
that the stationary source is no longer
covered.
Subpart H—Other Requirements
SOURCE: 61 FR 31728, June 20, 1996, unless
otherwise noted.
§68.200 Recordkeeping.
The owner or operator shall maintain
records supporting the implementation
of this part for five years unless other-
wise provided in subpart D of this part.
§68.210 Availability of information to
the public.
(a) The RMP required under subpart
G of this part shall be available to the
public under 42 U.S.C. 7414(c).
(b) The disclosure of classified infor-
mation by the Department of Defense
or other Federal agencies or contrac-
tors of such agencies shall be con-
trolled by applicable laws, regulations,
or executive orders concerning the re-
lease of classified information.
§68.215 Permit content and air per-
mitting authority or designated
agency requirements.
(a) These requirements apply to any
stationary source subject to this part
68 and parts 70 or 71 of this chapter.
The 40 CFR part 70 or part 71 permit for
the stationary source shall contain:
(1) A statement listing this part as
an applicable requirement;
(2) Conditions that require the source
owner or operator to submit:
(i) A compliance schedule for meet-
ing the requirements of this part by
the date provided in §68.10(a) or;
(ii) As part of the compliance certifi-
cation submitted under 40 CFR
70.6(c)(5), a certification statement
that the source is in compliance with
all requirements of this part, including
the registration and submission of the
RMP.
(b) The owner or operator shall sub-
mit any additional relevant informa-
tion requested by the air permitting
authority or designated agency.
(c) For 40 CFR part 70 or part 71 per-
mits issued prior to the deadline for
registering and submitting the RMP
and which do not contain permit condi-
tions described in paragraph (a) of this
section, the owner or operator or air
permitting authority shall initiate per-
mit revision or reopening according to
the procedures of 40 CFR 70.7 or 71.7 to
incorporate the terms and conditions
consistent with paragraph (a) of this
section.
(d) The state may delegate the au-
thority to implement and enforce the
requirements of paragraph (e) of this
section to a state or local agency or
agencies other than the air permitting
authority. An up-to-date copy of any
delegation instrument shall be main-
tained by the air permitting authority.
The state may enter a written agree-
ment with the Administrator under
which EPA will implement and enforce
the requirements of paragraph (e) of
this section.
(e) The air permitting authority or
the agency designated by delegation or
agreement under paragraph (d) of this
section shall, at a minimum:
66
-------
Environmental Protection Agency
§68.220
(1) Verify that the source owner or
operator has registered and submitted
an RMP or a revised plan when re-
quired by this part;
(2) Verify that the source owner or
operator has submitted a source cer-
tification or in its absence has submit-
ted a compliance schedule consistent
with paragraph (a) (2) of this section;
(3) For some or all of the sources sub-
ject to this section, use one or more
mechanisms such as, but not limited
to, a completeness check, source au-
dits, record reviews, or facility inspec-
tions to ensure that permitted sources
are in compliance with the require-
ments of this part; and
(4) Initiate enforcement action based
on paragraphs (e)(l) and (e)(2) of this
section as appropriate.
§68.220 Audits.
(a) In addition to inspections for the
purpose of regulatory development and
enforcement of the Act, the imple-
menting agency shall periodically
audit RMPs submitted under subpart G
of this part to review the adequacy of
such RMPs and require revisions of
RMPs when necessary to ensure com-
pliance with subpart G of this part.
(b) The implementing agency shall
select stationary sources for audits
based on any of the following criteria:
(1) Accident history of the stationary
source;
(2) Accident history of other station-
ary sources in the same industry;
(3) Quantity of regulated substances
present at the stationary source;
(4) Location of the stationary source
and its proximity to the public and en-
vironmental receptors;
(5) The presence of specific regulated
substances;
(6) The hazards identified in the
RMP; and
(7) A plan providing for neutral, ran-
dom oversight.
(c) Exemption from audits. A station-
ary source with a Star or Merit rank-
ing under OSHA's voluntary protection
program shall be exempt from audits
under paragraph (b) (2) and (b) (7) of this
section.
(d) The implementing agency shall
have access to the stationary source,
supporting documentation, and any
area where an accidental release could
occur.
(e) Based on the audit, the imple-
menting agency may issue the owner
or operator of a stationary source a
written preliminary determination of
necessary revisions to the stationary
source's RMP to ensure that the RMP
meets the criteria of subpart G of this
part. The preliminary determination
shall include an explanation for the
basis for the revisions, reflecting indus-
try standards and guidelines (such as
AIChE/CCPS guidelines and ASME and
API standards) to the extent that such
standards and guidelines are applica-
ble, and shall include a timetable for
their implementation.
(f) Written response to a preliminary de-
termination. (1) The owner or operator
shall respond in writing to a prelimi-
nary determination made in accord-
ance with paragraph (e) of this section.
The response shall state the owner or
operator will implement the revisions
contained in the preliminary deter-
mination in accordance with the time-
table included in the preliminary de-
termination or shall state that the
owner or operator rejects the revisions
in whole or in part. For each rejected
revision, the owner or operator shall
explain the basis for rejecting such re-
vision. Such explanation may include
substitute revisions.
(2) The written response under para-
graph (f)(l) of this section shall be re-
ceived by the implementing agency
within 90 days of the issue of the pre-
liminary determination or a shorter
period of time as the implementing
agency specifies in the preliminary de-
termination as necessary to protect
public health and the environment.
Prior to the written response being due
and upon written request from the
owner or operator, the implementing
agency may provide in writing addi-
tional time for the response to be re-
ceived.
(g) After providing the owner or oper-
ator an opportunity to respond under
paragraph (f) of this section, the imple-
menting agency may issue the owner
or operator a written final determina-
tion of necessary revisions to the sta-
tionary source's RMP. The final deter-
mination may adopt or modify the re-
visions contained in the preliminary
67
-------
§68.220
determination under paragraph (e) of
this section or may adopt or modify
the substitute revisions provided in the
response under paragraph (f) of this
section. A final determination that
adopts a revision rejected by the owner
or operator shall include an expla-
nation of the basis for the revision. A
final determination that fails to adopt
a substitute revision provided under
paragraph (f) of this section shall in-
clude an explanation of the basis for
finding such substitute revision unrea-
sonable.
(h) Thirty days after completion of
the actions detailed in the implemen-
tation schedule set in the final deter-
mination under paragraph (g) of this
section, the owner or operator shall be
40 CFR Ch. I (7-1-98 Edition)
in violation of subpart G of this part
and this section unless the owner or
operator revises the RMP prepared
under subpart G of this part as required
by the final determination, and sub-
mits the revised RMP as required
under §68.150.
(i) The public shall have access to the
preliminary determinations, responses,
and final determinations under this
section in a manner consistent with
§68.210.
(j) Nothing in this section shall pre-
clude, limit, or interfere in any way
with the authority of EPA or the state
to exercise its enforcement, investiga-
tory, and information gathering au-
thorities concerning this part under
the Act.
68
-------
Environmental Protection Agency
Pt. 68, App. A
Toxic end-
point (mg/L)
Chemical name
0
1
0
T— CDCN CD LOr^COCNCO T— CD CN COTr^
oooooooooooooooooooooooooooo
Acrolein [2-Propenal]
Acrylyl chloride [2-Propenoyl chloride]
Allyl alcohol [2-Propen-1-ol]
Ammonia (anhydrous)
Ammonia (cone 20% or greater)
: E
: =3
: ^~
; i 0
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: | 0 0
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8 :
Chlorine dioxide [Chlorine oxide (CIO2)]
Chloroform [Methane, trichloro-]
Chloromethyl ether [Methane, oxybis[chloro-]
Chloromethyl methyl ether [Methane, chlorom
Crotonaldehyde [2-Butenal]
Crotonaldehyde, (E)-, [2-Butenal, (E)-]
Cyanogen chloride
Cyclohexylamine [Cyclohexanamine]
0 "0 : :
O ' ">, •
i-lf
_ro -c u, c
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r^ r^ T- T- 1 CM CO : LO 1 : CO |: : T
CQT-COCOCDIIIITITI IT T- CM 1 CD T CO LO CO CO T 1
1 1 1 1 iT-T-TCMCOr^lLOOOOCOl IOI 1 1 T LO r^ 1 1 1 CO T- C
CMCOCQCQT-TTCOT IOCMCD |LO 1 1 CO O CO CO r^ T- | | ICDLOCD IT 1
r^r^Tr^r^cocococorMCOCorMTcoo 1 CM r^ r^ CO co co CM 1 Tcor^T- 1 co 1
; ; ; 'a1 ;
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Hydrochloric acid (cone 37% or greater)
Hydrocyanic acid
Hydrogen chloride (anhydrous) [Hydrochloric
Hydrogen fluoride/Hydrofluoric acid (cone 50°;
Hydrogen selenide
Iron, pentacarbonyl- [Iron carbonyl (Fe(CO)5), (TB-5-11)-]
O : O CO LO -s
CD CM 1 Illl
1 1 T- CO T- CD r^ CC
O T- O 1 O CO O C
0 0 1 0 1 1 1 1
1 1 S- CD S- T CO <^~
O CM T 1 T CO CO CC
CO
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Methacrylonitrile [2-Propenenitrile, 2-methyl-]
CO
CD
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CM
O Ł
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X
a
69
-------
Pt. 68, App. A
40 CFR Ch. I (7-1-98 Edition)
o
1
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o
LLJ
CL
o
X
a
Toxic end-
point (mg/L)
Chemical name
0
z
0
h- T-
ooooooooooooooooooooooooooooooooo
c
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1
Methyl chloroformate [Carbonochloridic acid, methylester]
Methyl isocyanate [Methane, isocyanato-]
Methyl thiocyanate [Thiocyanic acid, methyl ester]
Methyltrichlorosilane [Silane, trichloromethyl-]
Nitric acid (cone 80% or greater)
Nitric nxidp FNitrnnpn nxidp nMOYI
Oleum (Fuming Sulfuric acid) [Sulfuric acid, mixture with s
Peracetic acid [Ethaneperoxoic acid]
Perchloromethylmercaptan [Methanesulfenyl chloride, trich
Phosgene [Carbonic dichloride]
Phosphorus oxychloride [Phosphoryl chloride]
Phosphorus trichloride [Phosphorous trichloride]
Propionitrile [Propanenitrile]
Propyl chloroformate [Carbonochloridic acid, propylester] .
Propyleneimine [Aziridine, 2-methyl-]
|
-C
J C
1
'-c
(f
Sulfur tetrafluoride [Sulfur fluoride (SF4), (T-4)-]
Tetramethyllead [Plumbane, tetramethyl-]
; ^r1^
Titanium tetrachloride [Titanium chloride (TiCI4) (T-4)-] ....
Toluene 2,4-diisocyanate [Benzene, 2,4-diisocyanato-1-me
Toluene diisocyanate (unspecified isomer) [Benzene, 1,3-diisocyanatomethyl-] .
Vinyl acetate monomer [Acetic acid ethenyl ester]
: : ico'CD'i i'co' : : ' ' ' : ' : IT) :
: : 1 CM 1 1^ : :CMICM : IT) O CD : O 1
CD CD CDICOI CO 1 1^ 1 T O IT) III ODICD CM T
co T- T IT- I co co r^ T to o i to T- CQ CM I I I CD CD CD o T- T- I m I r^ co T I
r^CMTODCOCOCDCO ICM 1 T- T T 1 IT) T CO T- CO IT) CO 1 1 T ^t ^- |CQCQ-<-r^O
COCNCO ICD II^COI^O^JCN I^TCOCNCD 1 1 ILOLOCOCOCOI^ ICD lOI^I^ 1
1 1 l^i |co I ^r CD T— T— l^i IOOT— CDi^cD I I^TCQ^T icDLO^i l^r |co
70
T3
C
OJ
C
-------
Wednesday
January 6, 1999
Part IV
Environmental
Protection Agency
40 CFR Part 68
Accidental Release Prevention
Requirements; Risk Management
Programs Under Clean Air Act Section
112(r)(7), Amendments; Final Rule
-------
964
Federal Register/Vol. 64, No. 3/Wednesday, January 6, 1999/Rules and Regulations
ENVIRONMENTAL PROTECTION
AGENCY
40 CFR Part 68
[FRL-6214-9]
RIN 2050-AE46
Accidental Release Prevention
Requirements; Risk Management
Programs Under Clean Air Act Section
112(r)(7); Amendments
AGENCY: Environmental Protection
Agency (EPA).
ACTION: Final rule.
SUMMARY: This action modifies the
chemical accident prevention rule
codified in 40 CFR Part 68. The
chemical accident prevention rule
requires owners and operators of
stationary sources subject to the rule to
submit a risk management plan (RMP)
by June 21, 1999, to a central location
specified by EPA. In this action, EPA is
amending the rule to: add four
mandatory and five optional RMP data
elements, establish specific procedures
for protecting confidential business
information when submitting RMPs,
adopt the government's use of a new
industry classification system, and make
technical corrections and clarifications
to Part 68. However, as stated in the
proposed rule for these amendments,
this action does not address issues
concerning public access to offsite
consequence analysis data in the RMP.
DATES: The rule is effective February 5,
1999.
ADDRESSES: Supporting material used in
developing the proposed rule and final
rule is contained in Docket A-98-08.
The docket is available for public
inspection and copying between 8:00
a.m. and 5:30 p.m., Monday through
Friday (except government holidays) at
Room 1500, 401 M Street SW,
Washington, DC 20460. A reasonable fee
may be charged for copying.
FOR FURTHER INFORMATION CONTACT: Sicy
Jacob or John Ferris, Chemical
Emergency Preparedness and
Prevention Office, Environmental
Protection Agency (5104), 401 M Street
SW, Washington, DC 20460, (202) 260-
7249 or (202) 260-4043, respectively; or
the Emergency Planning and
Community Right-to-Know Hotline at
800-424-9346 (in the Washington, DC
metropolitan area, (703) 412-9810). You
may wish to visit the Chemical
Emergency Preparedness and
Prevention Office (CEPPO) Internet site,
at www.epa.gov/ceppo.
SUPPLEMENTARY INFORMATION:
Regulated Entities
Entities potentially regulated by this
action are those stationary sources that
have more than a threshold quantity of
a regulated substance in a process.
Regulated categories and entities
include:
Category
Examples of regulated entities
Chemical Manufacturers
Petroleum
Other Manufacturing
Agriculture
Public Sources
Utilities
Other
Federal Sources
Basic chemical manufacturing, petrochemicals, resins, agricultural chemicals, Pharmaceuticals,
paints, cleaning compounds.
Refineries.
Paper, electronics, semiconductors, fabricated metals, industrial machinery, food processors.
Agricultural retailers.
Drinking water and waste water treatment systems.
Electric utilities.
Propane retailers and users, cold storage, warehousing, and wholesalers.
Military and energy installations.
This table is not meant to be
exhaustive, but rather provides a guide
for readers to indicate those entities
likely to be regulated by this action. The
table lists entities EPA is aware of that
could potentially be regulated by this
action. Other entities not listed in the
table could also be regulated. To
determine whether a stationary source is
regulated by this action, carefully
examine the provisions associated with
the list of substances and thresholds
under §68.130 and the applicability
criteria under §68.10. If you have
questions regarding applicability of this
action to a particular entity, consult the
hotline or persons listed in the
preceding FOR FURTHER INFORMATION
CONTACT section.
Table of Contents
I. Introduction and Background
A. Statutory Authority
B. Background
II. Summary of the Final Rule
III. Discussion of Issues
A. NAICS Codes
B. RMP Data Elements
C. Prevention Program Reporting
D. Confidential Business Information
E. Other Issues
F. Technical Corrections
IV. Section-by-Section Discussion of the
Final Rule
V. Judicial Review
VI. Administrative Requirements
A. Docket
B. Executive Order 12866
C. Executive Order 12875
D. Executive Order 13045
E. Executive Order 13084
F. Regulatory Flexibility
G. Paperwork Reduction
H. Unfunded Mandates Reform Act
I. National Technology Transfer and
Advancement Act
J. Congressional Review Act
I. Introduction and Background
A. Statutory Authority
These amendments are being
promulgated under sections 112(r) and
301(a)(l) of the Clean Air Act (CAA) as
amended (42 U.S.C. 7412(r), 7601 (a)(l)).
B. Background
The 1990 CAA Amendments added
section 112(r) to provide for the
prevention and mitigation of accidental
chemical releases. Section 112(r)
mandates that EPA promulgate a list of
"regulated substances," with threshold
quantities. Processes at stationary
sources that contain a threshold
quantity of a regulated substance are
subject to accidental release prevention
regulations promulgated under CAA
section 112(r)(7). EPA promulgated the
list of regulated substances on January
31, 1994 (59 FR 4478) (the "List Rule")
and the accidental release prevention
regulations creating the risk
management program requirements on
June 20, 1996 (61 FR 31668) (the "RMP
Rule"). Together, these two rules are
codified as 40 CFR Part 68. EPA
amended the List Rule on August 25,
1997 (62 FR 45132), to change the listed
concentration of hydrochloric acid. On
January 6, 1998 ( 63 FR 640), EPA
amended the List Rule to delist Division
1.1 explosives (classified by DOT), to
clarify certain provisions related to
regulated flammable substances and to
clarify the transportation exemption.
Part 68 requires that sources with
more than a threshold quantity of a
regulated substance in a process
develop and implement a risk
management program that includes a
five-year accident history, offsite
consequence analyses, a prevention
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965
program, and an emergency response
program. In Part 68, processes are
divided into three categories (Programs
1 through 3). Processes that have no
potential impact on the public in the
case of accidental releases have minimal
requirements (Program 1). Processes in
Programs 2 and 3 have additional
requirements based on the potential for
offsite consequences associated with the
worst-case accidental release and their
accident history. Program 3 is also
triggered if the processes are subject to
OSHA's Process Safety Management
(PSM) Standard. By June 21, 1999,
sources must submit to a location
designated by EPA, a risk management
plan (RMP) that summarizes their
implementation of the risk management
program.
When EPA promulgated the risk
management program regulations, it
stated that it intended to work toward
electronic submission of RMPs. The
Accident Prevention Subcommittee of
the CAA Advisory Committee convened
an Electronic Submission Workgroup to
examine technical and practical issues
associated with creating a national
electronic repository for RMPs. Based
on workgroup recommendations, EPA is
in the process of developing two
systems, a user-friendly PC-based
submission system (RMP*Submit) and a
database of RMPs (RMP*Info).
The Electronic Submission
Workgroup also recommended that EPA
add some mandatory and optional data
elements to the RMP and asked EPA to
clarify how confidential business
information (CBI) submitted in the RMP
would be handled. Based on these
recommendations and requests for
clarifications, EPA proposed
amendments to Part 68 on April 17,
1998 (63 FR 19216). These amendments
proposed to replace the use of Standard
Industrial Classification (SIC) codes
with the North American Industry
Classification System (NAICS) codes,
add four mandatory data elements to the
RMP, add five optional data elements to
the RMP, establish specific
requirements for submission of
information claimed CBI, and make
technical corrections and clarifications
to the rule. EPA received 47 written
comments on the proposed rule.
Today's rule reflects EPA's
consideration of all comments; major
issues raised by commenters and EPA's
responses are discussed in Section III of
this preamble. A summary of all
comments submitted and EPA's
responses can be found in a document
entitled, Accidental Release Prevention
Requirements; Risk Management
Programs Under Clean Air Act Section
112(r)(7); Amendments: Summary and
Response to Comments, in the Docket
(see ADDRESSES).
II. Summary of the Final Rule
NAICS Codes
On January 1, 1997, the U.S.
Government, in cooperation with the
governments of Canada and Mexico,
adopted a new industry classification
system, the North American Industry
Classification System (NAICS), to
replace the Standard Industrial
Classification (SIC) codes (April 9, 1997,
62 FR 17288). The applicability of some
Part 68 requirements (i.e., Program 3
prevention requirements) is determined,
in part, by SIC codes, and Part 68 also
requires the reporting of SIC codes in
the RMP. Therefore, EPA is revising Part
68 to replace all references to "SIC
code" with "NAICS code." In addition,
EPA is replacing, as proposed, the nine
SIC codes subject to Program 3
prevention program requirements with
ten NAICS codes, as follows:
NAICS Sector
32211 Pulp mills
32411 Petroleum refineries
32511 Petrochemical manufacturing
325181 Alkalies and chlorine
325188 All other inorganic chemical
manufacturing
325192 Other cyclic crude and intermediate
manufacturing
325199 All other basic organic chemical
manufacturing
325211 Plastics and resins
325311 Nitrogen fertilizer
32532 Pesticide and other agricultural
chemicals
NAICS codes are either five or six digits,
depending on the degree to which the
sector is subdivided.
RMP Data Elements
As proposed, EPA is adding four new
data elements to the RMP: latitude/
longitude method and description, CAA
Title V permit number, percentage
weight of a toxic substance in a liquid
mixture, and NAICS code for each
process that had an accidental release
reported in the five-year accident
history. EPA is also adding five optional
data elements: local emergency
planning committee (LEPC) name,
source or parent company e-mail
address, source homepage address,
phone number at the source for public
inquiries, and status under OSHA's
Voluntary Protection Program (VPP).
Prevention Program Reporting
EPA is not revising Sections 68.170
and 68.175 as proposed. Prevention
program reporting, therefore, will not be
changed to require a prevention
program for each portion of a process for
which a Process Hazard Analysis (PHA)
or hazard review was conducted.
Instead, EPA plans to create functions
within RMP*Submit to provide
stationary sources with a flexible way of
explaining the scope and content of
each prevention program they
implement at their facility.
Confidential Business Information
EPA is clarifying how confidential
business information (CBI) submitted in
the RMP will be handled. EPA has
determined that the information
required by certain RMP data elements
does not meet the criteria for CBI and
therefore may not be claimed as such.
The Agency is also requiring submission
of substantiation at the time a CBI claim
is filed.
Finally, EPA is promulgating several
of the technical corrections and
clarifications, as proposed in the
Federal Register, April 17, 1998 (63 FR
19216).
III. Discussion of Issues
EPA received 47 comments on the
proposed rule. The commenters
included chemical manufacturers,
petroleum refineries, environmental
groups, trade associations, a state
agency, and members of the public. The
major issues raised by commenters are
addressed briefly below. The Agency's
complete response to comments
received on this rulemaking is available
in the docket (see ADDRESSES). The
document is titled Accidental Release
Prevention Requirements; Risk
Management Programs Under Clean Air
Act Section 112(r)(7); Amendments:
Summary and Response to Comments.
A. NAICS Codes
Two commenters asked that sources
be given the option to use either SIC
codes or NAICS codes, or both, in their
initial RMP because the NAICS system
is new and may not be familiar to
sources. EPA disagrees with this
suggestion. EPA intends to provide
several outreach mechanisms to assist
sources in identifying their new NAICS
code. RMP*Submit will provide a "pick
list" that will make it easier for sources
to find the appropriate code. Also,
selected NAICS codes are included in
the General Guidance for Risk
Management Programs (July 1998) and
in the industry-specific guidance
documents that EPA is developing. EPA
will also utilize the Emergency Planning
and Community Right-to-Know Hotline
at 800-424-9346 (or 703-412-9810) and
its web site at www.epa.gov/ceppo/, to
assist sources in determining the
source's NAICS codes. EPA also notes
that the Internal Revenue Service is
planning to require businesses to
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provide NAICS-based activity codes on
their 1998 tax returns, so many sources
will have become familiar with their
NAICS codes by the June 1999 RMP
deadline.
EPA believes it is necessary and
appropriate to change from SIC codes to
NAICS codes at this time. EPA
recognizes that NAICS codes were
developed for statistical purposes by the
Office of Management and Budget
(OMB). In the notice of April 9, 1997 (62
FR 17288) OMB stated that the "[u]se of
NAICS for nonstatistical purposes (e.g.,
administrative, regulatory, or taxation)
will be determined by the agency or
agencies that have chosen to use the SIC
for nonstatistical purposes." EPA has
determined that NAICS is appropriate in
this rule for several reasons. First, the
reason the SIC codes were replaced by
NAICS codes is because the SIC codes
no longer accurately represent today's
industries. The SIC codes will become
more obsolete over time because OMB
will no longer be supporting the SIC
codes; therefore, no new or modified
SIC codes will be developed to reflect
future changes in industries. Second, as
the SIC codes become obsolete, most
users of SIC codes will likely change to
NAICS codes over time, so future data
sharing and consistency will be
enhanced by use of NAICS codes in the
RMP program. Third, through this
rulemaking process, EPA has analyzed
specific conversions of SIC codes to
NAICS codes for the RMP program and
was able to identify NAICS codes that
were applicable to fulfilling the
purposes of this rule. Finally, because
the RMP reporting requirement is new,
it is reasonable to begin the program
with NAICS codes now rather than
converting to them later.
Three commenters expressed support
for the ten NAICS codes that EPA
proposed to use in place of the nine SIC
codes referenced in section 68.10(d)(l)
of Part 68 and one commenter partially
objected. Section 68.10(d)(l) provides
that processes in the referenced codes
are subject to Program 3 requirements (if
not eligible for Program 1). One
commenter objected to EPA's proposal
to replace the SIC code for pulp and
paper mills with only the NAICS code
for pulp mills that do not also produce
paper or paperboard. The commenter
asked EPA to reexamine the accident
history of paper and paperboard mills.
As discussed in the preamble of the
proposed rule, EPA reviewed the
accident history data prior to proposing
the new NAICS codes. Neither facilities
that classify themselves as paper mills
(NAICS Code 322121) nor paperboard
mills (NAICS code 32213) met the
accident history criteria that EPA used
to select industrial sectors for Program
3.
EPA notes that a pulp process at a
paper or a paperboard mill may still be
subject to Program 3 as long as the
process contains more than a threshold
quantity of a regulated substance and is
not eligible for Program 1. Section
68.10(d)(l) uses industrial codes to
classify processes, not facilities as a
whole. Since section 68.10(d)(l) will
continue to list the code for pulp mills,
pulpmaking processes will continue to
be subject to Program 3. In addition,
under section 68.10(d)(2), paper
processes will be in Program 3 (unless
eligible for Program 1) if they are subject
to OSHA's Process Safety Management
(PSM) standard. Most pulp and paper
processes are, in fact, subject to this
standard.
One commenter objected to assigning
NAICS codes to a process rather than
the source as a whole. EPA first notes
that the requirement to assign a SIC
code to a process was adopted in the
original RMP rulemaking two years ago.
Today's rule does not change that
requirement except to substitute NAICS
for SIC codes. In any event, EPA is
today modifying Part 68 to clarify that
sources provide the NAICS code that
"most closely corresponds to the
process." EPA believes that assigning an
industry code to a process will help
implementing agencies and the public
understand what the covered process
does; using the code makes it possible
to provide this information without
requiring a detailed explanation from
the source. In addition, the primary
NAICS code for a source as a whole may
not reflect the activity of the covered
process.
B. RMP Data Elements
EPA proposed to add, as optional
RMP data elements: local emergency
planning committee (LEPC), source (or
parent company) E-mail address, source
homepage address, phone number at the
source for public inquiries, and OSHA
Voluntary Protection Program (VPP)
status. EPA also proposed to add, as
mandatory data elements: method and
description of latitude/longitude, Title
V permit number, percent weight of a
toxic substance in a liquid mixture, and
NAICS code (only in the five-year
accident history section).
Commenters generally supported the
new optional data elements. One
commenter requested that the optional
elements be made mandatory. EPA
disagrees with this comment. While the
elements are useful, many sources
covered by this rule will not have e-mail
addresses or home pages. The RMP will
provide both addresses and phone
numbers so that the public will have
methods to reach the source. EPA has
learned that in some areas there are no
functioning LEPCs, therefore, at this
time, EPA will not add this as a
mandatory data element. However, in
most cases, the LEPC for an area can be
determined by contacting the local
government or the State Emergency
Response Commission (SERC) for which
the area is located. Therefore, reporting
these data elements will remain
optional at this time.
One commenter supported adding the
listing of local emergency planning
committee in the RMP data elements as
an optional data element. The
commenter stated that, although it is an
optional data element, this listing will
enhance the ability of local responders
and emergency planners to adequately
prepare and train for emergency events.
Of the data elements that were
proposed to be mandatory, one
commenter objected to the addition of
latitude/longitude method and
description. The commenter stated that
it was not clear in the proposal why the
method and description information is
needed. EPA is seeking latitude/
longitude method and description in
accordance with its Locational Data
Policy. Several EPA regulations require
sources to provide their latitude and
longitude, so that EPA can more readily
locate facilities and communicate data
between Agency offices. Sharing of data
between EPA offices reduces
duplication of information. Latitude/
longitude method and description
provides information needed by EPA
offices, and other users of the data, to
rectify discrepancies that may appear in
the latitude and longitude information
provided by the source under various
EPA requirements. Documentation of
the method by which the latitude and
longitude are determined and a
description of the location point
referenced by the latitude and longitude
(e.g., administration building) will
permit data users to evaluate the
accuracy of those coordinates, thus
addressing EPA data sharing and
integration objectives.
EPA believes this information will
also facilitate EPA-State coordination of
environmental programs, including the
chemical accident prevention rule. The
State/EPA Data Management Program is
a successful multi-year initiative linking
State environmental regulatory agencies
and EPA in cooperative action. The
Program's goals include improvements
in data quality and data integration
based on location identification.
Therefore, as proposed, the latitude/
longitude method and description will
be added to the existing RMP data
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967
elements. RMP*Submit will provide a
list of methods and descriptions from
which sources may choose.
EPA also proposed to require that
sources report the percentage weight
(weight percent) of a toxic substance in
a mixture in the offsite consequence
analysis (OCA) and the accident history
sections of the RMP. This information is
necessary for users of RMP data to
understand how worst case and
alternative release scenarios have been
modeled. EPA has decided to require
reporting of the weight percent of toxic
substance in a liquid mixture because
this information is necessary to
understand the volatilization rate,
which determines the downwind
dispersion distance of the substance.
The volatilization rate is affected by the
vapor pressure of the substance in the
mixture. For example, a spill of 70
percent hydrofluoric acid (HE) will
volatilize more quickly than a spill of
the same quantity of HE in a 50 percent
solution; consequently, over a 10-
minute period, the 70 percent solution
will travel further. Reviewers of the
RMP data, including local emergency
planning committees, need to know the
weight percent to be able to evaluate the
results reported in the offsite
consequence analysis and the impacts
reported in the accident history.
Without knowing the weight percent of
the substance in the mixture, users of
the data may compare scenarios or
incidents that appear to involve the
same chemical in the same physical
state, but in fact involve the same
chemical held in a different physical
state.
One commenter stated that for gas
mixtures, percentage by volume (or
volume percent) should be required to
be reported rather than weight percent.
In this final rule, EPA does not require
reporting of the weight percent (or
volume percent) of a regulated
substance in a gas mixture. If a source
handles regulated substances in a
gaseous mixture (e.g., chlorine with
hydrogen chloride), the quantity of a
particular regulated substance in the
mixture is what is reported in the RMP,
since that is what would be released
into the air. Its percentage weight in the
mixture is irrelevant.
Another commenter objected to this
data element, claiming that it could
result in reverse engineering and create
a competitive disadvantage. EPA does
not believe that this requirement would
create a competitive disadvantage, since
similar information is available to the
public under Emergency Planning and
Community Right-to-Know Act (EPCRA)
of 1986. Even so, if it were to have such
an effect, sources can claim this element
as CBI if it can meet the criteria for CBI
claims in 40 CFR Part 2. Another
commenter stated that the public would
be concerned if the percentages did not
add to 100, in the event that the source
handles both regulated and non-
regulated substances. EPA believes that
because a source must model only one
substance in a release scenario, the
source need not report the percentages
of the other substances in the mixture.
Therefore, it is expected that the weight
percent for mixtures would not always
add up to 100, because the mixture
could contain non-regulated substances.
A third commenter suggested that
requiring sources to report percentage
weight of a toxic substance in a liquid
mixture would create confusion with
the reporting of mixtures containing
flammable regulated substances.
In the January 6, 1998 rule (63 FR
640), EPA clarified that flammable
regulated substances in mixtures are
only covered by the RMP rule if the
entire mixture meets the National Fire
Protection Association (NFPA) criteria
of 4, thus the entire mixture becomes
the regulated substance. As a result, the
percentage of flammables in a mixture is
not relevant under the rule and the
requirement to report the percentage
weight will only apply to toxic
substances in a liquid mixture.
Finally, in the Federal Register notice
of June 20, 1996 (61 FR 31688), EPA
clarified the relationship between the
risk management program and the air
permit program under Title V of the
CAA for sources subject to both
requirements. Under section
502(b)(5)(A), permitting authorities
must have the authority to assure
compliance by all covered sources with
each applicable CAA standard,
regulation or requirement, including the
regulations implementing section
112(r)(7). Requiring sources covered by
Title V and section 112(r) to provide
their Title V permit number will help
Title V permitting authorities assure
that each source is complying with the
RMP rule.
In summary, with the exception of
adding the phrase "that most closely
corresponds to the process" in sections
68.42(b)(4), 68.160(b)(7), 68.170(b), and
68.175(b), EPA has decided to finalize
the optional and mandatory data
elements as they were proposed.
C. Prevention Program Reporting
The final RMP rule, issued June 20,
1996 (61 FR 31668), requires sources to
report their prevention program for each
"process." Because the applicable
definition of "process" is broad,
multiple production and storage units
might be a single, complex "process."
However, the Agency realizes that some
elements of a source's prevention
program for a process may not be
applicable to every portion of the
process. In such a situation, reporting
prevention program information for the
process as a whole could be misleading
without an explanation of which
prevention program element applies to
which part of the process. In order to get
more specific information on which
prevention program practices apply to
different production and storage units
within a process, EPA proposed to
revise the rule to require prevention
program reporting for each part of the
process for which a separate process
hazard analysis (PHA) or hazard review
was conducted. EPA further proposed
deleting the second sentence from both
sections 68.170(a) and 68.175(a), which
presently states that, "[i]f the same
information applies to more than one
covered process, the owner or operator
may provide the information only once,
but shall indicate to which process the
information applies."
A number of industry commenters
objected to the proposed revisions as
wrongly assuming that a one-to-one
relationship exists between a prevention
program and a PHA. The commenters
asserted that EPA's proposed revision
did not reflect how facilities conduct
PHAs or implement prevention
measures and would cause significant
duplicate reporting, creating
unnecessary extra work for facility
personnel. One commenter explained
that depending on a source's
circumstances, it might conduct a PHA
for each production line, including all
of its different units, or it might conduct
a PHA for each common element of its
different production lines. Accordingly,
the commenters claimed that EPA's
proposal to require the owner/operator
to submit separate prevention program
information for every portion of a
process covered by a PHA would result
in multiple submissions of much of the
same material, and would add no value
to process safety or accidental release
prevention. Commenters also opposed
the deletion of the second sentence in
sections 68.170(a) and 68.175(a). One
commenter noted that many of the
elements of the prevention program will
not only be common to a process, but
will be common to an entire stationary
source. Thus commenters argued that
EPA's proposals would result in
redundant submittals and place an
unjustified burden on the regulated
community.
EPA acknowledges that PHAs do not
necessarily determine the scope of
prevention program measures.
Moreover, EPA agrees that duplicative
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reporting should be reduced as much as
possible. At the same time, EPA,
implementing agencies, and other users
of RMP data need to have information
that is detailed enough to understand
the hazards posed by, and the safety
practices used for, particular parts of
processes and equipment. EPA
recognizes that some aspects of
prevention programs are likely to be
implemented facility-wide, rather than
on a process or unit basis, whereas other
aspects may apply to a particular
process or only to particular units
within a process. For example, most
sources are likely to develop an
employee participation plan and a
system for hot work permits facility-
wide, rather than on a process or unit
basis. For sources having processes that
include several units (e.g., multiple
reactors or purification systems), the
hazards, process controls, and
mitigation systems may vary among the
individual units. For example, one may
have a deluge fire control system while
another may have a runaway reaction
quench system.
EPA has concluded that its proposed
changes to prevention program
reporting would not lead sources to
prepare RMPs that accurately and
efficiently communicate the hazards
posed by different aspects of covered
processes and the safety practices used
to address those hazards. The Agency
now believes that no rule changes are
necessary to ensure that RMPs convey
that information. The current rule
already requires prevention program
reporting, and the issue has been how
to efficiently convey that information in
sufficient detail. EPA believes that its
electronic program for submitting RMPs
can be designed to provide for sufficient
specificity in prevention program
reporting without requiring duplicative
reporting. In particular, the Agency
plans to create a comment/text field in
RMP*Submit for specifying which parts
of a prevention program apply to which
portions of a particular process. For
example, if a deluge system only applies
to a certain part of the overall process,
the source would indicate in the
comment/text screen the portions of the
process to which the deluge system
applies.
To reduce the burden of reporting,
EPA also plans to create a function in
RMP*Submit which will allow a source
to automatically copy prevention
program data previously entered for one
process to fill blank fields in another
process's prevention program. The
source could then edit any of the data
elements that are different. For example,
where the prevention programs for two
processes are identical (e.g., two
identical storage tanks that are
considered separate processes), the
source could copy the data entered for
one to fill in the blank field for the
other. If some of the data elements vary
between the prevention programs, the
source will be able to autofill and
change only those items that vary
among processes or units.
Although the autofill option will
minimize the burden of reporting
common data elements for those sources
filing electronically, EPA has decided
not to delete the sentence, in both
sections 68.170(a) and 68.175(a), which
states, "[i]f the same information applies
to more than one covered process, the
owner or operator may provide the
information only once, but shall
indicate to which processes the
information applies ", as proposed.
D. Confidential Business Information
(CBI)
1. Background
A central element of the chemical
accident prevention program as
established by the Clean Air Act and
implemented by Part 68 is providing
state and local governments and the
public with information about the risk
of chemical accidents in their
communities and what stationary
sources are doing to prevent such
accidents. As explained in the preamble
to the final RMP rule (61 FR 31668, June
20, 1996), every covered stationary
source is required to develop and
implement a risk management program
and provide information about that
program in its RMP. Under CAA section
112(r)(7)(B)(iii), a source's RMP must be
registered with EPA and also submitted
to the Federal Chemical Safety and
Hazard Investigation Board ("the
Board"), the state in which the source
is located, and any local entity
responsible for emergency response or
planning. That section also provides
that RMPs "shall be available to the
public under section 114(c)" of the
CAA. Section 114(c) gives the public
access to information obtained under
the Clean Air Act except for information
(other than emission data) that would
divulge trade secrets.
As noted previously, in the final RMP
rule EPA announced its plan to develop
a centralized system for submitting
electronic versions of RMPs that would
reduce the paperwork burden on both
industry and receiving agencies and
provide ready public access to RMP
data. Under the system, a covered
source would submit its RMP on
computer diskette, which would be
entered into a central database that all
interested parties could access
electronically. The system would thus
make it possible for a single RMP
submission to reach all interested
parties, including those identified in
section 112(r)(7)(B)(iii).1
An important assumption underlying
the Agency's central submission plan
was that RMPs would rarely, if ever,
contain confidential business
information (CBI). Following
publication of the final rule, concerns
were raised that at least some of the
information required to be reported in
RMPs could be CBI in the case of
particular sources. While the June 20,
1996 rule provided for protection of CBI
under section 114(c) (see section
68.210(a)), EPA was asked to address
how CBI would be protected in the
context of the electronic programs being
developed for RMP submission and
public access.
In the April 17, 1998 proposal to
revise the RMP rule, EPA made several
proposals concerning protection of CBI.
It first reviewed the information
requirements for RMPs (sections
68.155-185) and proposed to find that
certain required data elements would
not entail divulging information that
could meet the test for CBI set forth in
the Agency's comprehensive CBI
regulations at 40 CFR Part 2.2
Information provided in response to
those requirements could not be
claimed CBI. EPA also requested
comment on whether some information
that might be claimed as CBI (e.g.,
worst-case release rate or duration)
would be "emission data" and thus
publicly available under section 114(c)
even if CBI.
EPA administers a variety of statutes
pertaining to the protection of the
environment, each with its own data
collection requirements and
requirements for disclosure of
information to the public. In the
implementation of these statutes, the
Agency collects emission, chemical,
process, waste stream, financial, and
other data from facilities in many, if not
most, sectors of American business.
Companies may consider some of this
information vital to their competitive
1 It is important to note that, as discussed in
Section III. E of this preamble, this rule does not
address issues concerning public access to offsite
consequence analysis data in the RMP.
Information is CBI if (1) the business has
asserted a claim which has not expired, been
waived, or been withdrawn; (2) the business has
shown that it has taken and will continue to take
reasonable steps to protect the information from
disclosure; (3) the information is not and has not
been reasonably obtainable by the public (other
than governmental bodies) by use of legitimate
means; (4) no statute requires disclosure of the
information; and (5) disclosure of the information
is likely to cause substantial harm to the business'
competitive position. 40 CFR section 2.208.
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position, and claim it as confidential
business information (CBI).
In the course of implementing
statutes, the Agency may have a need to
communicate some or all of the
information it collects to the public as
the basis for a rulemaking, to its
contractors, or in response to requests
pursuant to the Freedom of Information
Act (FOIA). Information found to be CBI
is exempt from disclosure under FOIA.
To manage both CBI claims and FOIA
requests, EPA has promulgated in 40
CFR Part 2, Subpart B a set of
procedures for reviewing CBI claims,
releasing information found not to be
CBI, and where authorized, disclosing
CBI. Subpart B lists the criteria that
information must meet in order to be
considered CBI, as well as the special
handling requirements the Agency must
follow when disclosing CBI to
authorized representatives.
For RMP requirements that might
entail divulging CBI, EPA proposed that
a source be required to substantiate a
CBI claim to EPA at the time that it
makes the claim. Under EPA's Part 2
regulations, a source claiming CBI
generally is required to substantiate the
claim only when EPA needs to make the
information public as part of some
proceeding (e.g., a rulemaking) or EPA
receives a request from the public (e.g.,
under the Freedom of Information Act
(FOIA)) for the information. In view of
the public information function of RMPs
and the interest already expressed by
members of the public in them, EPA
proposed "up-front substantiation" of
CBI claims to ensure that information
not meeting CBI criteria would be made
available to the public as soon as
possible. This approach of requiring up-
front substantiation is the same as that
used for trade secret claims filed under
the Emergency Planning and
Community Right-to-Know Act (EPCRA)
of 1986.3
3 Section 302 of EPCRA (codified in 40 CFR Part
355) requires any facility having more than a
threshold planning quantity of an extremely
hazardous substance (EHS) to notify its state
emergency response commission (SERC) and local
emergency planning committee (LEPC) that the
facility is subject to emergency planning. The vast
majority of toxic substances listed in 40 CFR
Section 68.130 were taken from the EHS list.
Section 303 of EPCRA requires LEPCs to prepare an
emergency response plan for the community that is
under their jurisdiction. Section 303 of EPCRA also
requires that facilities subject to section 302 shall
provide any information required by their LEPC
necessary for developing and implementing the
emergency plan. Section 304 of EPCRA requires an
immediate notification of a release of an EHS or
Hazardous Substances listed in 40 CFR Section
302.4 above a reportable quantity to state and local
entities. Section 304 also requires a written follow-
up which includes among other things, the
chemical name, quantity released and any known
or anticipated health risks associated with the
In addition, EPA proposed that any
source claiming CBI submit two
versions of its RMP: (1) a redacted
("sanitized"), electronic version, which
would become part of RMP*Info, and (2)
an unsanitized (unredacted) paper copy
of the RMP (see proposed section
68.151 (c)). The electronic database of
RMPs would contain only the redacted
version unless and until EPA ruled
against all or part of the source's CBI
claim, in keeping with the Part 2
procedures. In this way, the public
would have access only to the non-CBI
elements of sources' RMPs. EPA further
stated that state and local agencies
could receive the unredacted RMPs by
requesting them from EPA under the
Part 2 regulations. Those regulations
authorize EPA to provide CBI to an
agency having implementation
responsibilities under the CAA if the
agency either demonstrates that it has
the authority under state or local law to
compel such information directly from
the source or that it will "provide
adequate protection to the interests of
affected businesses" (40 CFR
2.301 (h) (3)).
The following sections of this
preamble summarize and respond to the
comments EPA received on the CBI-
related aspects of its proposal. At the
outset, however, EPA wants to
emphasize that it does not anticipate
many CBI claims being made in
connection with RMPs. The Agency
developed the RMP data elements with
the issue of CBI in mind. It sought to
define data elements that would provide
basic information about a source's risk
management program without requiring
it to reveal CBI. To have done otherwise
would have risked creating RMPs that
were largely unavailable to the public.
EPA continues to believe that the
required RMP data elements will rarely
require that a business divulge CBI. The
Agency will carefully monitor the CBI
claims made. If it appears that the
number of claims being made is
jeopardizing the public information
release. Sections 311 and 312 of EPCRA (codified
in 40 CFR Part 370) require facilities that are subject
to OSHA Hazard Communication Standard (HCS),
to provide information to its SERC, LEPC and local
fire department. This information includes the
hazards posed by its chemicals, and inventory
information, including average daily amount,
maximum quantity and general location. Section
313 of EPCRA (codified in 40 CFR Part 372)
requires certain facilities that are in specific
industries (including chemical manufacturers) and
that manufacture, process, or otherwise use a toxic
chemical above specified threshold amounts to
report, among other things, the annual quantity of
the toxic chemical entering each environmental
medium. Most facilities covered by CAA 112(r) are
covered by one or more of these sections of EPCRA.
Section 322 of EPCRA (codified in Part 350) allows
facilities to claim only the chemical identity as
trade secret.
objective of the chemical accident
prevention program, EPA will consider
ways of revising RMPs, including
further rulemakings or revising the
underlying program, to ensure that
important health and safety information
is available to the public.
2. RMP Data Elements Found Not CBI
Fifteen commenters representing
environmental groups and members of
the public opposed allowing some or all
RMP data to be claimed as CBI in light
of the public's interest in the
information RMPs will provide. A
number of commenters urged EPA not
to allow the following RMP data
elements (and supporting documents) to
be claimed as CBI:
• Mitigation measures considered by
the firm in its offsite consequence
analysis,
• Major process hazards identified by
the firm,
• Process controls in use,
• Mitigation systems in use,
• Monitoring and detection systems
in use, and
• Changes since the last hazard
review.
In addition, one commenter
contended that even chemical identity
and quantity should be ineligible for
CBI protection, since the requirement to
submit an RMP only applies to facilities
using a few well-known, extremely
hazardous chemicals, and the public's
right to know should always outweigh
a company's claim to CBI.
Along the same lines, a number of
commenters urged EPA to develop a
"corporate sunshine rule" that would
allow confidentiality concerns to be
overridden if the protected information
is needed by the public and experts to
understand and assess safety issues.
Another commenter recommended that
a business claiming a chemical's
identity as CBI should be required to
provide the generic name of the
chemical and information about its
adverse health effects so the public can
determine the potential risks.
One commenter argued that some of
the RMP data that EPA suggested could
reveal CBI, (e.g., release rate), were not
"emission data," because the worst case
scenario data are theoretical estimates,
and do not represent any real emissions,
past or present.
Representatives of the chemical and
petroleum industries disagreed with
EPA's proposal to list the data elements
that EPA believed could not reveal CBI
in any case. These commenters asserted
that EPA could not anticipate all the
ways in which information required by
a data element might reveal CBI, and
accordingly urged the Agency to make
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case-by-case determinations on CBI
claims. They also contended that
"emission data" under section 114(c)
does not extend to data on possible, as
opposed to actual, emissions, and thus
that RMP information concerning
potential accidental releases would not
qualify as "emission data," which must
be made available to the public.
As pointed out above, an important
purpose of the chemical accident
prevention program required by section
112(r) is to inform the public of the risk
of accidents in their communities and
the methods sources are employing to
reduce such risks. EPA therefore
believes that as much RMP data as
possible should be available to the
public as soon as possible. However,
section 112(r)(7)(B)(iii) requires that
RMPs be made "available to the public
under section 114(c)," which provides
for protection of trade secret
information (other than emission data).
Given the statute's direction to protect
whatever trade secret information is
contained in an RMP, EPA is not
authorized to release such information
even when the public's need for such
information arguably outweighs a
business' interest in its confidentiality.
The Agency also cannot issue a
"corporate sunshine rule" that conflicts
with existing law requiring EPA (and
other agencies) to protect trade secret
information.
As explained above (and in more
detail in the proposed rule), EPA
examined each RMP data element to
determine which would require
information that might, depending on a
business' circumstances, meet the CBI
criteria set forth in EPA's regulations
implementing section 114(c) and other
information-related legal requirements.
The point of this exercise was to both
protect potential trade secret
information and promote the public
information purpose of RMPs by
identifying which RMP information
might reveal CBI in a particular case and
by precluding CBI claims for
information that could not reveal CBI in
any case. EPA presented the results of
its analysis and an explanation of why
certain data elements could entail the
reporting of CBI depending on a
business' circumstances and why others
could not. No commenter provided any
specific examples or explanations that
contradicted the Agency's rationale for
its determinations of which data
elements could or could not result in
reporting of CBI.
However, EPA is deleting from the list
of40CFRPart68.151(b)(l) the reference
to 40 CFR Part 68.160(b)(9), to allow for
the possibility of the number of full-
time employees at the stationary source
to be claimed as CBI. Upon further
review, EPA was unable to determine
that providing the number of employees
at the stationary source could never
entail divulging information that could
meet the test for CBI set forth in the
Agency's comprehensive CBI
regulations at 40 CFR Part 2. Therefore,
EPA has removed this element from the
list of data elements that can not be
claimed CBI in Part 68. With this
exception, EPA is promulgating the list
of RMP data elements for which CBI
claims are precluded, as proposed
(Section 68.151 (b)).
EPA's justifications for its specific CBI
findings appear in an appendix to this
preamble. A more detailed analysis of
all RMP data elements and CBI
determinations is available in the docket
(see ADDRESSES). The Agency continues
to find no reasonable basis for
anticipating that the listed elements will
in any case require a business to reveal
CBI that is not "emission data." The
information required by each of the
listed data elements either fails to meet
the criteria for CBI set forth in EPA's
CBI regulations at Part 2 or meets the
Part 2 definition of "emission data." In
many cases, the information is available
to the public through other reports filed
with EPA, states, or local agencies (e.g.,
reports required by Emergency Planning
and Community Right-to-Know Act
(EPCRA) sections 312 and 313 provide
general facility identification
information and reports of most
accidental releases are available through
several Federal databases including
EPA's Emergency Release Notification
System and Accidental Release
Information Program databases).
In order to preclude CBI claims for
other data elements, the Agency would
have to show that the information
required by a data element either was
"emission data" under section 114(c) or
could not, under any circumstances,
reveal CBI. As explained below, EPA
does not believe such a showing can be
made for any of the data elements not
on the list. Therefore, CBI claims made
for information required by data
elements not on the list will be
evaluated on a case-by-case basis
according to the procedures contained
in 40 CFR Part 2 (except that
substantiation will have to accompany
the claims, as discussed below).
The Agency agrees with the
commenters who argued that
information about potential accidental
releases is not "emission data" under
section 114(c). EPA's existing policy
statement (see 56 FR 7042, Feb. 21,
1991) on what information may be
considered "emission data" was
developed to implement sections 110
and 114 (a) of the CAA, which the
Agency generally invokes when it seeks
to gather technical data from a source
about its actual emissions to the air.
While the policy is not explicitly
limited in its scope, EPA believes it
would be inappropriate to apply it to
RMP data elements concerning
hypothetical, as opposed to actual,
releases to the air. Under the definition
of "emission data" contained in Part 2,
information is "emission data" if it is (1)
"necessary to determine the identity,
amount, frequency, concentration, or
other characteristics * * * of any
emission which has been emitted by the
source," (2) "necessary to determine the
identity, amount, frequency,
concentration, or other characteristics
* * * of the emissions which, under an
applicable standard or limitation, the
source was authorized to emit," or (3)
general facility identification
information regarding the source which
distinguishes it from other sources (40
CFR section 2.301 (a)(2)(i) (emphasis
added)). Under these criteria, EPA has
concluded that only the RMP data
elements relating to source-level
registration information (sections
68.160(b)(l)-(6), (8)-(13)) and the five-
year accident history (section 68.168)
are "emission data." Of the RMP data
elements, only the five-year accident
history involves actual, past emissions
to the environment; the other data
elements would not, therefore, qualify
as "emission data" under the first prong
of the Part 2 definition. Moreover, the
data elements relating to a source's
offsite consequence analysis, prevention
program and emergency response
program do not attempt to identify or
otherwise reflect "authorized"
emissions; the data elements instead
reflect the source's potential for
accidental releases. Accordingly, these
data elements would not be "emission
data" under the second prong of the
definition. As for the third prong, some
of the source-level data are "emission
data" because they help identify a
source. Most other RMP data elements
are reported on a process level and are
not generally used to distinguish one
source from another.
The Agency believes it is unable to
show that the remaining data elements
could not, under any circumstances,
reveal CBI. EPA continues to believe
that it is theoretically possible for the
remaining data elements (the elements
not listed in section 68.151 (b)) to reveal
CBI either directly or through reverse
engineering, depending on the
circumstances of a particular case. At
the same time, EPA believes that, in
practice, the remaining data elements
will rarely reveal CBI. The purpose of
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the data in the RMP is for a source to
articulate its hazards, and the steps it
takes to prevent accidental releases. In
general, the kinds of information
specifying the source's hazards and risk
management program are not likely to
be competitively sensitive.
In particular, covered processes at the
vast majority of stationary sources
subject to the RMP rule are too common
and well-known to support a CBI claim
for information related to such
processes. For example, covered public
drinking water and wastewater
treatment plants generally use common
regulated substances in standard
processes (i.e., chlorine used for
disinfection). Also, covered processes at
many sources involve the storage of
regulated substances that the sources
sell (e.g., propane, ammonia), so the
processes are already public knowledge.
Other covered processes involve the use
of well-known combinations of
regulated substances such as
refrigerants. RMP information regarding
these types of processes should not
include CBI.
Even in the case of unusual or unique
processes, it is generally unlikely that
RMP information could be used to
reveal CBI through reverse engineering.
To begin with, required RMP
information is general enough that it is
unlikely to provide a basis for reverse
engineering a process. For example, a
source must report in its RMP whether
overpressurization is a hazard and
whether relief valves are used to control
pressure, but it is not required to report
information on actual pressures used,
flow rates, chemical composition, or the
configuration of equipment. Moreover,
while RMP information may provide
some data that could be used in an
attempt to discover CBI information
through reverse engineering, it typically
will not provide enough data for such
an attempt to succeed, because the
source is not required to provide a
detailed description of the chemistry or
production volume of the process.
Businesses claiming CBI based on the
threat of reverse engineering will be
required to show how reverse
engineering could in fact succeed with
the information that the RMP would
otherwise make public, together with
other publicly available information. A
business unable to do so will have its
claim denied.
While EPA is requiring that a source
claiming a chemical's identity as CBI
provide the generic category or class
name of the chemical, the RMP does not
require sources to provide information
about the adverse health effects of the
chemical. Chemicals were included in
the section 112(r) program because they
are acutely toxic or flammable; health
effects related to chronic exposure were
not considered because they are
addressed by other rules (see List Rule
at 59 FR 4481). EPA believes that
generic names are sufficient to indicate
the general health concerns from short-
term exposures. Should a member of the
public desire more information, EPA
encourages the use of EPCRA section
322(h), which provides a means for the
public to obtain information about the
adverse health effects of a chemical
covered by that statute, where the
chemical's identity has been claimed a
trade secret. The public will find this
provision of EPCRA useful because most
sources subject to the RMP rule are also
subject to EPCRA.
3. Up-front Substantiation of CBI Claims
One commenter supported the
proposal to require CBI claims to be
substantiated at the time they are made.
Another commenter stated that there is
no compelling need to require up-front
substantiation. The commenter stated
that up-front substantiation would place
a sizable burden on both industry and
EPA and would be in direct conflict
with the Paperwork Reduction Act. The
commenter claimed that, with the
exception of EPCRA, where a submitter
is allowed to claim only one data
element—chemical identity—as CBI, it
is EPA's standard procedure not to
require submitters to provide written
substantiation unless a record has been
requested. Further, the commenter
stated that the Agency has not shown
any reason for departing from that
procedure in this rule.
EPA believes that requiring up-front
substantiation of CBI claims made for
RMP data has ample precedent, is fully
consistent with the Agency's CBI
regulations and the Paperwork
Reduction Act, and is critical to
achieving the public information
purposes of the accident prevention
program. EPCRA is not the only
example of an up-front substantiation
requirement. The Agency has also
required up-front substantiation in
several other regulatory contexts,
including those where, like here,
providing the public with health and
safety information is an important
objective [see e.g., 40 CFR section
725.94, 40 CFR section 710.38, and 40
CFR section 720.85 (regulations
promulgated under Toxic Substances
Control Act)].
Even under its general CBI
regulations, the Agency need not wait
for a request to release data to require
businesses to substantiate their CBI
claims. When EPA expects to get a
request to release data claimed
confidential, the Agency is to initiate
"at the earliest practicable time" the
regulations" procedures for making CBI
determinations (40 CFR section
2.204(a)(3)). Those procedures include
calling on affected businesses to
substantiate their claims (see 40 CFR
section 2.204(e)). Since state and local
agencies, environmental groups,
academics and others have already
indicated their interest in obtaining
complete RMP data (see comments
received on this rulemaking, available
in the DOCKET), EPA fully expects to
get requests for RMP data claimed CBI.
Consequently, even if EPA did not
establish an up-front substantiation
requirement in this rule, under the
Agency's general CBI regulations it
could require businesses claiming CBI
for RMP data to substantiate their claims
without first receiving a request to
release the data. Establishing an up-
front requirement in this rule will
simply allow EPA to obtain
substantiation of CBI claims without
having to request it in every instance.
Requiring up-front substantiation for
RMP CBI claims is consistent with the
Paperwork Reduction Act. Any burden
posed by this requirement has already
been evaluated as part of the
Information Collection Request (ICR)
associated with this rulemaking. EPA
disagrees that up-front substantiation
will impose a substantial or undue
burden. As noted above, under EPA's
current CBI regulations, a source
claiming CBI could and probably would
be required to provide substantiation for
its claim, in view of the public interest
in RMP information. A requirement to
submit substantiation with the claim
should thus make little difference to the
source. Moreover, a source presumably
does not make any claim of CBI lightly.
Before filing a CBI claim, the source
must first determine whether the claim
meets the criteria specified in 40 CFR
section 2.208. Up-front substantiation
only requires that the source document
that determination at the time it files its
claim. Since it would be sensible for a
source to document the basis of its CBI
claim for its own purposes (e.g., in the
case of a request for substantiation),
EPA expects that many sources already
prepare documentation for their CBI
claims by the time they file them. Also,
submitting substantiation at the time of
claim reduces any additional burden
later, such as reviewing the Agency's
request, retrieving the relevant
information, etc. Therefore, providing
documentation at the time of filing
should impose no additional burden.
In view of the public information
function of RMPs, EPA believes that up-
front substantiation is clearly warranted
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for CBI claims made for RMP data. Up-
front substantiation will ensure that
sources filing claims have carefully
considered whether the data they seek
to protect in fact meets the criteria for
protection. Given the public interest
already expressed in RMP data, EPA
expects that CBI claims for RMP data
will have to be substantiated at some
point. Up-front substantiation will save
EPA and the public time and resources
that would otherwise be required to
respond to each CBI claim with a
request for substantiation. EPA is
therefore promulgating the up-front
substantiation requirement as proposed.
4. State and Local Agency Access to
Unredacted RMPs
One commenter objected to EPA's
statement in the proposal that it would
provide unredacted (unsanitized)
versions of the RMPs to a state and local
agency only upon meeting the criteria
required by the EPA's CBI rules at 40
CFR Part 2.4 The commenter, an
association of fire fighters, argued that
the Agency's position was inconsistent
with CAA section 112 (r) (7) (B) (iii),
which provides that RMPs "shall ... be
submitted to the Chemical Safety and
Hazard Investigation Board [a federal
agency], to the State in which the
stationary source is located, and to any
local agency or entity having
responsibility for planning for or
responding to accidental releases which
may occur at such source . . . ." The
commenter claimed that this provision
entitles the specified entities, including
local fire departments, to receive
unredacted RMPs without having to
make the showings required by EPA's
CBI regulations.
EPA is not resolving this issue today.
The Agency has reviewed the relevant
statutory text and legislative history, as
well as analogous provisions of EPCRA,
and believes that arguments can be
made on both sides of this issue. While
section 112(r)(7)(B)(iii) calls for RMPs to
be submitted to states, local entities and
the Board, it is not clear that Congress
intended CBI contained in RMPs to be
provided to those entities without
ensuring appropriate protection of CBI.
4 Section 2.301(h)(3) provides that a State or local
government may obtain CBI from EPA under two
circumstances: (1) it provides EPA a written
opinion from its chief legal officer or counsel
stating that the State or local agency has the
authority under applicable State or local law to
compel the business to disclose the information
directly; or (2) the businesses whose information is
disclosed are informed and the State or local
government has shown to a EPA legal office's
satisfaction that its disclosure of the information
will be governed by State or local law and by
"procedures which will provide adequate
protection to the interests of affected businesses."
At stake in resolving this issue are two
important interests—local responders'
interest in unrestricted access to
information that may be critical to their
safety and effectiveness in responding to
emergencies and businesses' interest in
protecting sensitive information from
their competitors. Before making a final
decision on this issue, EPA believes it
would benefit from further public input.
Because EPA stated that it would not
provide unredacted RMPs to states and
local agencies, those interested in
protecting CBI may not have considered
it necessary to lay out the legal and
policy arguments supporting their
views. State and local agencies, many of
which in the past have expressed
concern about the potential
administrative burden of receiving
RMPs directly from sources, also did not
comment on the issue. EPA has
therefore decided to accept additional
comments on this issue alone.
(Additional comments on any other
issues addressed in this rulemaking will
not be considered or addressed, since
the Agency is taking final action on
them here.) Comments should be mailed
to the persons listed in the preceding
FOR FURTHER INFORMATION CONTACT
section. In the meantime, unredacted
RMPs will be available to states, local
agencies and the Board under the terms
of the Agency's existing CBI regulations
at 40 CFR section 2.301 (h) (3) (for state
and local agencies) and 40 CFR section
2.209(c) (for the Board).
Section 112(r)(7)(B)(iii) states in
relevant part:
[RMPs] shall also be submitted to the
Chemical Safety and Hazard Investigation
Board, to the State in which the stationary
source is located, and to any local agency or
entity having responsibility for planning for
or responding to accidental releases which
may occur at such source, and shall be
available to the public under section 114(c)
of [the Act].
Section 114(c) provides for the public
availability of any information obtained
by EPA under the Clean Air Act, except
for information (other than emissions
data) that would divulge trade secrets.
From a public policy perspective,
there are some obvious advantages to
reading section 112(r)(7)(B)(iii) in the
way the commenter suggests. Local fire
departments and other local responders
are typically the first to arrive at the
scene of chemical accidents in their
jurisdictions. RMP information that first
responders could find helpful include
chemical identity, chemical quantity,
and potential source of an accident.
Under EPA's regulations, however, any
or all of this information could be
claimed CBI. In addition, state and local
authorities are often in the best position
to assess the adequacy of a source's risk
management program and to initiate a
dialogue with the facility should its
RMP indicate a need for improvement.
However, state and local authorities'
ability to provide this contribution to
community safety would be impeded to
the extent a source claimed key
information as CBI. While states and
local agencies may obtain information
claimed CBI under EPA's CBI
regulations (assuming they can make the
requisite showing), the time required to
obtain the necessary authority or
findings from state or local and EPA
officials could be substantial.
At the same time, there are also public
policy reasons for ensuring protection of
CBI contained in RMPs. Congress has in
many statutes, including the CAA and
EPCRA, provided for the protection of
trade secrets to safeguard the
competitive position of private
businesses. Businesses' ability to
maintain the confidentiality of trade
secrets helps ensure competition in the
U.S. economy and U.S. businesses'
competitive position in the world
economy. Protection of trade secrets
also encourages innovation, which is an
important contributor to economic
growth.
A reading of section 112 (r) (7) (B) (iii)
that demands submission of unredacted
RMPs to states, local entities, and the
Board may lead to widespread public
access to information claimed CBI. For
purposes of section 112(r)(7)(B)(iii),
"any local agency or entity having
responsibility for planning for or
responding to accidental releases"
includes local emergency planning
committees (LEPCs) established under
EPCRA. Section 301 (c) of EPCRA
provides that LEPCs must include
representatives from both the public and
private sectors, including the media and
facilities subject to EPCRA
requirements. Submission of an
unredacted RMP to an LEPC would thus
entail release of CBI to some members
of the public and potentially even
competitors.5 More generally, local
agencies may not be subject to any legal
requirement to protect CBI and may lack
the knowledge and resources to address
CBI claims. Arguably, it would be
5 EPA does not believe that submission of an RMP
containing CBI to the statutorily specified entities
would defeat a source's ability to claim information
as CBI for purposes of section 114(c) and EPA's CBI
regulations. Under those regulations, information
that has been released to the public cannot be
claimed CBI. Release of a RMP containing CBI to
the entities specified by section 112 (r) (7) (B) (iii),
including LEPCs, would not constitute such a
release. EPCRA similarly provides that disclosure of
trade secret information to an LEPC does not
prevent a facility from claiming the information
confidential (see EPCRA section 322(b)(l)).
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anomalous for Congress to require EPA
to protect trade secrets contained in
RMPs against release to the public only
to risk divulging the same information
by requiring submission of unredacted
RMPs to a broad range of entities that
may not have the need or capacity to
protect CBI themselves. It would also
appear inconsistent with the approach
Congress took to protecting trade secrets
in EPCRA, where Congress did not
provide for release of trade secret
chemical identity information to local
agencies.
Relatedly, many state and local
agencies objected to EPA's original
proposal in the RMP proposed
rulemaking (58 FR 54190, October 20,
1993) that sources submit RMPs directly
to States, local agencies, and the Board,
as well as EPA. They noted that
managing the information contained in
RMPs would be difficult without a
significant expenditure of typically
scarce resources. Many states and local
agencies thus supported EPA's final
decision to develop an electronic
submission and distribution system that
would allow covered sources to submit
their RMPs to EPA, which would make
them available to states, local agencies,
and the Board, as well as the general
public. If the statute is read to require
submission of RMP information to state
and local agencies, and the Board, to the
extent it is claimed as CBI, the resource
concerns raised by State and local
agencies commenters likely would be
raised to that extent again.
EPA also questions the extent to
which states, local entities and the
Board would be disadvantaged if they
did not receive unredacted RMPs
without making the showings required
by EPA's CBI regulations. As noted
earlier, EPA expects that relatively little
RMP information will be CBI. RMP data
will only rarely contain CBI, and the up-
front substantiation will minimize the
number of CBI claims it receives by
ensuring that sources carefully examine
the basis for any claims before
submitting them. Consequently, the
Agency believes that a state or local
agency will rarely confront a redacted
RMP.
Moreover, EPCRA provides state and
local entities, including fire
departments, with access to much of the
pertinent data already. EPA's
regulations under EPCRA cover a
universe of sources and chemicals that
includes most, if not all, the sources and
substances covered by the RMP rule.
The EPCRA regulations require
reporting of some of the same
information required by the RMP rule,
including chemical identity. EPCRA
withholds from public release only
chemical identities that are trade secrets
and the location of specific chemicals
where a facility so requests. In practice,
relatively few facilities have requested
trade secret protection for a chemical's
identity.
Additionally, EPCRA section 312(f)
empowers local fire departments to
conduct on-site inspections at facilities
subject to EPCRA section 312(a) and
obtain information on chemical
location. Most facilities subject to
EPCRA section 312(a) are also subject to
the RMP rule. On-site inspections could
also provide information on hazards and
mitigation measures. In addition,
EPCRA section 303(d)(3) authorizes
LEPCs, which include representatives of
fire departments, to request from
facilities covered by EPCRA section
302 (b) such information as may be
necessary to prepare an emergency
response plan and to include such
information in the plan as appropriate.
Some sources subject to the RMP rule
are also covered by EPCRA section
302 (b).
In light of the points made above, EPA
questions whether section
112(r)(7)(B)(iii) should be interpreted to
require submission of unredacted RMPs
containing CBI to the statutorily
specified entities without provision
being made for protecting CBI. EPA
invites the public to provide any
additional comment or information
relevant to interpreting the submission
requirement of section 112 (r) (7) (B) (iii).
5. Other CBI Issues
Two commenters disagreed with
EPA's statement that a source cannot
make a CBI claim for information
available to the public under EPCRA or
another statute. They claimed that a
request for information under EPCRA
cannot supersede the CBI provisions
applicable to data collected under the
authorities of the CAA or Toxic
Substances Control Act or any other
regulatory program.
EPA does not agree with this
comment. Claims of CBI may not be
upheld if the information is properly
obtainable or made public under other
statutes or authorities. For example,
chemical quantity on site is available to
the public under EPCRA Tier II
reporting. In addition, under EPCRA
section 303(d)(3), LEPCs have the
authority to request any information
they need to develop and implement
community emergency response plans.
If information obtained through such a
request is included in the community
plan, it will become available to the
public under EPCRA section 324.
Information obtainable or made public
under EPCRA would not be eligible for
CBI protection under 40 CFR section
2.208, which specifically excludes from
CBI protection information already
available to the public. Filing a CBI
claim under the CAA or another statute
does not protect information if it is
legitimately requested and made public
under other federal, state, or local law.
Information obtainable or made public
(through proper means) under existing
statutes cannot be CBI under EPA's CBI
regulations.
6. Actions Taken
In summary, the Agency is adding
two sections (68.151 and 68.152) to Part
68. Section 68.151 sets forth the
procedures for a source to follow when
asserting a CBI claim and lists data
elements that can not be claimed as CBI.
This section also requires sources filing
CBI claims to provide the information
claimed confidential, in a format to be
specified by EPA, instead of the
unsanitized paper copy of the RMP as
discussed in the proposal. Section
68.152 sets forth the procedures for
substantiating CBI claims. Sources
claiming CBI are required to submit
their substantiation of their claims at the
same time they submit their RMPs.
E. Other Issues
Two commenters asked why EPA had
proposed to drop the phrase "if used"
in section 68.165(b)(3) where the rule
asks for the basis of the offsite
consequence analysis results. EPA has
decided to retain the language, since
sources will have a choice of using
either EPA's RMP guidance documents
or a model. Where a model is used, the
source will have to provide the name of
the model. These commenters also
asked why EPA proposed to drop
(alternative releases only) from section
68.165(b) (13). EPA has also decided to
retain the parenthetical language.
One commenter stated that EPA
should allow sources to submit RMPs
either electronically or in hard copy.
The commenter stated that not allowing
hard copy submissions will be
burdensome on many sources who have
never filed an electronic report to the
government before. As stated in the
April proposal, EPA is allowing sources
to submit RMPs on paper. Paper
submitters are asked to fill out a simple
paper form to tell EPA why they are
unable to file electronically.
Two commenters objected to placing
offsite consequence analysis (OCA) data,
particularly worst-case release
scenarios, on the Internet, for security
reasons. Issues related to public access
to OCA data are beyond the scope of
this rulemaking, as this action is limited
to the issues discussed above. It does
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not include decisions regarding how the
public will access the OCA data
elements of the RMPs. Statements in the
preamble about EPA providing public
access to RMP data are not intended to
address which portions of the RMP data
will be electronically available.
A number of commenters were
concerned about a statement EPA made
in the preamble to the proposed rule
regarding the definition of "process",
and stated that EPA's interpretation of
"process" is not consistent with the
interpretation the Occupational Safety
and Health Administration (OSHA) uses
in its process safety management (PSM)
standard (29 CFR 1910.119). In this
rulemaking, EPA did not propose any
changes to the definition of process nor
is it adopting any changes to the
definition. As EPA stated in the
preamble to the final RMP rule, it will
interpret "process" consistently with
OSHA's interpretation of that term (29
CFR 1910.119). Therefore, if a source is
subject to the PSM rule, the limits of its
process (es) for purposes of OSHA PSM
will be the limits of its process (es) for
purposes of RMP (except in cases
involving atmospheric storage tanks
containing flammable regulated
substances, which are exempt from PSM
but not RMP). If a source is not covered
by OSHA PSM and is complicated from
an engineering perspective, it should
consider contacting its implementing
agency for advice on determining
process boundaries. EPA and OSHA are
coordinating the agencies' approach to
common issues, such as the
interpretation of "process".
F. Technical Corrections
When Part 68 was promulgated, the
text of section 68.79(a), was drawn from
the OSHA PSM standard, but it was not
revised to reflect the different structure
of EPA's rule. The OSHA PSM standard
is contained in a single section; EPA's
Program 3 prevention program is
contained in a subpart. Rather than
referencing "this section," the
paragraph should have referenced the
"subpart." Therefore, as proposed, EPA
is changing "section" to "subpart" in
section 68.79(a).
Under section 68.180(b), EPA
intended that all covered sources report
the name and telephone number of the
agency with which they coordinate
emergency response activities, even if
the source is not required to have an
emergency response plan. However, the
rule refers only to coordinating the
emergency plan. In this action, EPA is
revising this section to refer to the local
agency with which emergency response
activities and the emergency response
plan is coordinated.
IV. Section-by-Section Discussion of the
Final Rule
In Section 68.3, Definitions, the
definition of SIC is removed and
replaced by the definition of NAICS.
Section 68.10, Applicability, is
revised to replace the SIC codes with
NAICS codes, as discussed above.
Section 68.42, Five-Year Accident
History, is revised to require the
percentage concentration by weight of
regulated toxic substances released in a
liquid mixture and the five- or six-digit
NAICS code that most closely
corresponds to the process that had the
release. The phrase "five- or six-digit"
has been added before the NAICS code
to clarify the level of detail required for
NAICS code reporting.
Section 68.79, Compliance Audits, the
word "section" in paragraph (a) is
replaced by "subpart."
Section 68.150, Submission, is revised
by adding a paragraph to state that
procedures for asserting CBI claims and
determining the sufficiency of such
claims are provided in new Sections
68.151 and 68.152.
Section 68.151 is added to set forth
the procedures to assert a CBI claim and
list data elements that may not be
claimed as CBI, as discussed above.
Section 68.152 is added to set forth
procedures for substantiating CBI
claims, as proposed.
Section 68.160, Registration, is
revised by adding the requirements to
report the method and description of
latitude and longitude, replacing SIC
codes with five- or six-digit NAICS
codes, and adding the requirement to
report Title V permit number, when
applicable. This section is also revised
to include optional data elements. The
phrase "five- or six-digit" has been
added before NAICS code to clarify the
level of detail required for NAICS code
reporting.
Section 68.165, Offsite Consequence
Analysis, is revised by adding the
requirement that the percentage weight
of a regulated toxic substance in a liquid
mixture be reported.
Section 68.170, Prevention Program/
Program 2, is revised to replace SIC
codes with five- or six-digit NAICS
codes, as is Section 68.175.
Section 68.180, Emergency Response
Program, is revised to clarify that
paragraph (b) covers both the
coordination of response activities and
plans, as proposed.
V. Judicial Review
The proposed rule amending the
accidental release prevention
requirements; under section 112(r)(7)
was proposed in the Federal Register on
April 17, 1998. This Federal Register
action announces EPA's final decision
on the amendments. Under section
307(b)(l) of the CAA, judicial review of
this action is available only by filing a
petition for review in the U.S. Court of
Appeals for the District of Columbia
Circuit on or before March 8, 1999.
Under section 307(b)(2) of the CAA, the
requirements that are the subject of
today's action may not be challenged
later in civil or criminal proceedings
brought by EPA to enforce these
requirements.
VI. Administrative Requirements
A. Docket
The docket is an organized and
complete file of all the information
considered by the EPA in the
development of this rulemaking. The
docket is a dynamic file, because it
allows members of the public and
industries involved to readily identify
and locate documents so that they can
effectively participate in the rulemaking
process. Along with the proposed and
promulgated rules and their preambles,
the contents of the docket serve as the
record in the case of judicial review.
(See section 307(d)(7)(A) of the CAA.)
The official record for this
rulemaking, as well as the public
version, has been established for this
rulemaking under Docket No. A-98-08
(including comments and data
submitted electronically). A public
version of this record, including
printed, paper versions of electronic
comments, which does not include any
information claimed as CBI, is available
for inspection from 8:00 a.m. to 5:30
p.m., Monday through Friday, excluding
legal holidays. The official rulemaking
record is located at the address in
ADDRESSES at the beginning of this
document.
B. Executive Order 12866
Under Executive Order (E.O.) 12866,
[58 FR 51,735 (October 4, 1993)], the
Agency must determine whether the
regulatory action is "significant", and
therefore subject to OMB review and the
requirements of the E.O. The Order
defines "significant regulatory action"
as one that is likely to result in a rule
that may:
(1) Have an annual effect on the
economy of $100 million or more or
adversely affect in a material way the
economy, a sector of the economy,
productivity, competition, jobs, the
environment, public health or safety, or
state, local or tribal government or
communities;
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(2) Create a serious inconsistency or
otherwise interfere with an action taken
or planned by another agency;
(3) Materially alter the budgetary
impact of entitlements, grants, user fees,
or loan programs or the rights and
obligations of recipients thereof; or
(4) Raise novel legal or policy issues
arising out of legal mandates, the
President's priorities, or the principles
set forth in the E.O.
Pursuant to the terms of Executive
Order 12866, OMB has notified EPA
that it considers this a "significant
regulatory action" within the meaning
of the Executive Order. EPA has
submitted this action to OMB for
review. Changes made in response to
OMB suggestions or recommendations
will be documented in the public
record.
C. Executive Order 12875
Under Executive Order 12875, EPA
may not issue a regulation that is not
required by statute and that creates a
mandate upon a State, local or tribal
government, unless the Federal
government provides the funds
necessary to pay the direct compliance
costs incurred by those governments, or
EPA consults with those governments. If
EPA complies by consulting, Executive
Order 12875 requires EPA to provide to
the Office of Management and Budget a
description of the extent of EPA's prior
consultation with representatives of
affected State, local and tribal
governments, the nature of their
concerns, copies of any written
communications from the governments,
and a statement supporting the need to
issue the regulation. In addition,
Executive Order 12875 requires EPA to
develop an effective process permitting
elected officials and other
representatives of State, local and tribal
governments "to provide meaningful
and timely input to the development of
regulatory proposals containing
significant unfunded mandates."
EPA has concluded that this rule may
create a nominal mandate on State, local
or tribal governments and that the
Federal government will not provide the
funds necessary to pay the direct costs
incurred by these governments in
complying with the mandate.
Specifically, some public entities may
be covered sources and will have to add
the new data elements to their RMP. In
developing this rule, EPA consulted
with state, local and tribal governments
to enable them to provide meaningful
and timely input in the development of
this rule. Even though this rule revises
Part 68 in a way that does not
significantly change the burden
imposed by the underlying rule, EPA
has taken efforts to involve state and
local entities in this regulatory effort.
Specifically, much of the rule responds
to issues raised by the Electronic
Submission Workgroup discussed
above, which includes State and local
government stakeholders. In addition,
EPA has recently conducted seminars
with tribal governments; however, there
were no concerns raised on any issues
that are covered in this rule. EPA
discussed the need for issuing this
regulation in sections II and III in this
preamble. Also, EPA provided OMB
with copies of the comments to the
proposed rule.
D. Executive Order 13045
Executive Order 13045: "Protection of
Children from Environmental Health
Risks and Safety Risks" (62 FR 19885,
April 23, 1997) applies to any rule that:
(1) is determined to be "economically
significant" as defined under E.O.
12866, and (2) concerns an
environmental health or safety risk that
EPA has reason to believe may have a
disproportionate effect on children. If
the regulatory action meets both criteria,
the Agency must evaluate the
environmental health or safety effects of
the planned rule on children, and
explain why the planned regulation is
preferable to other potentially effective
and reasonably feasible alternatives
considered by the Agency.
This final rule is not subject to the
E.O. 13045 because it is not
"economically significant" as defined in
E.O. 12866, and because it does not
involve decisions based on
environmental health or safety risks.
E. Executive Order 13084
Under Executive Order 13084, EPA
may not issue a regulation that is not
required by statute, that significantly or
uniquely affects the communities of
Indian tribal governments, and that
imposes substantial direct compliance
costs on those communities, unless the
Federal government provides the funds
necessary to pay the direct compliance
costs incurred by the tribal
governments, or EPA consults with
those governments. If EPA complies by
consulting, Executive Order 13084
requires EPA to provide to the Office of
Management and Budget, in a separately
identified section of the preamble to the
rule, a description of the extent of EPA's
prior consultation with representatives
of affected tribal governments, a
summary of the nature of their concerns,
and a statement supporting the need to
issue the regulation. In addition,
Executive Order 13084 requires EPA to
develop an effective process permitting
elected and other representatives of
Indian tribal governments "to provide
meaningful and timely input in the
development of regulatory policies on
matters that significantly or uniquely
affect their communities."
Today's rule does not significantly or
uniquely affect the communities of
Indian tribal governments. Two of the
amendments made by this rule, the
addition of RMP data elements and the
conversion of SIC codes to NAICS
codes, impose only minimal burden on
any sources that may be owned or
operated by tribal governments, such as
drinking water and waste water
treatment systems. The third
amendment made by this rule addresses
the procedures for submission of
confidential business information in the
RMP. The sources that are mentioned
above handle chemicals that are known
to public (e.g., chlorine for use of
disinfection, propane used for fuel, etc.).
EPA does not, therefore, expect RMP
information on these types of processes
to include CBI, so any costs related to
CBI will not fall on Indian tribal
governments. Accordingly, the
requirements of section 3(b) of
Executive Order 13084 do not apply to
this rule.
Notwithstanding the non-applicability
of E. O. 13084, EPA has recently
conducted seminars with the tribal
governments. However, there were no
concerns raised on any issues that are
covered in this rule.
F. Regulatory Flexibility
EPA has determined that it is not
necessary to prepare a regulatory
flexibility analysis in connection with
this final rule. EPA has also determined
that this action will not have a
significant economic impact on a
substantial number of small entities.
Two of the amendments made by this
rule, the addition of RMP data elements
and the conversion of SIC codes to
NAICS codes, impose only minimal
burden on small entities. Moreover,
those small businesses that claim CBI
when submitting the RMP will not face
any costs beyond those imposed by the
existing CBI regulations. Even
considering the costs of CBI
substantiation, however, there is no
significant economic impact on a
substantial number of small entities.
EPA estimates that very few small
entities (approximately 500) will claim
CBI and that these few entities represent
a small fraction of the small entities
(less than 5 percent) affected by the
RMP rule. Finally, EPA estimates that
those small businesses filing CBI will
experience a cost which is significantly
less than one percent of their annual
sales. For a more detailed analysis of the
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small entity impacts of CBI submission,
see Document Number, IV-B-02,
available in the docket for this
rulemaking (see ADDRESSES section).
G. Paperwork Reduction
1. General
The information collection
requirements in this rule have been
submitted for approval to the Office of
Management and Budget (OMB) under
the Paperwork Reduction Act, 44 U.S.C.
3501 etseq. An Information Collection
Request (ICR) document has been
prepared by EPA (ICR No. 1656.05) and
a copy may be obtained from Sandy
Farmer, by mail at Office of Policy,
Regulatory Information Division, U.S.
Environmental Protection Agency
(2137), 401 M St, SW, Washington, DC
20460, by e-mail at
farmer.sandy@epamail.epa.gov or by
calling (202) 260-2740. A copy may also
be downloaded off the Internet at http:/
/www.epa.gov/icr. The information
requirements are not effective until
OMB approves them.
The submission of the RMP is
mandated by section 112(r)(7) of the
CAA and demonstrates compliance with
Part 68 consistent with section 114(c) of
the CAA. The information collected also
will be made available to state and local
governments and the public to enhance
their preparedness, response, and
prevention activities. Certain
information in the RMP may be claimed
as confidential business information
under 40 CFR Part 2 and Part 68.
This rule will impose very little
burden on affected sources. First, EPA
estimates that the new data elements
will require only a nominal burden, .25
hours for a typical source, because
latitude and longitude method and
description will be selected from a list
of options, the Title V permit number is
available to any source to which Title V
applies, and the percentage weight of a
toxic substance in a liquid mixture is
usually provided by the supplier of the
mixture. Second, the NAICS code
provision is simply a change from one
code to another.6 Third, as discussed
above in the preamble, EPA believes
that the CBI provisions of this rule will
add no additional burden beyond what
sources otherwise would face in
6 EPA intends to provide several outreach
mechanisms to assist sources in identifying their
new NAICS code. RMP*Submit will provide a
"pick list" that will make it easier for sources to
find the appropriate code. Also, selected NAICS
codes are included in the General Guidance for Risk
Management Programs (July 1998) and in the
industry-specific guidance documents that EPA is
developing. EPA will also utilize the Emergency
Planning and Community Right-to-Know Hotline at
800-424-9346 (or 703-412-9810) to assist sources
in determining the source's NAICS codes.
complying with the CBI rules in 40 CFR
Part 2. The Agency has calculated the
burden of substantiations made for
purposes of this rule below.
Burden means the total time, effort, or
financial resources expended by persons
to generate, maintain, retain, or disclose
or provide information to or for a
Federal agency. This includes the time
needed to review instructions; develop,
acquire, install, and utilize technology
and system for the purposes of
collecting, validating, and verifying
information, processing and
maintaining information, and disclosing
and providing information; adjust the
existing ways to comply with any
previously applicable instructions and
requirements; train personnel to be able
to respond to a collection of
information; search data sources;
complete and review the collection of
information; and transmit or otherwise
disclose the information.
An agency may not conduct or
sponsor, and a person is not required to
respond to a collection of information
unless it displays a currently valid OMB
control number. The OMB control
numbers for EPA's regulations are listed
in 40 CFR Part 9 and 48 CFR Chapter
15.
2. CBI Burden
In the Notice of Proposed Rulemaking
for these amendments, EPA proposed to
amend existing 40 CFR Part 68 to add
two sections which would clarify the
procedures for submitting RMPs that
contain confidential business
information (CBI). As proposed, CBI
would be handled in much the same
way as it presently is under other EPA
programs, except that EPA would
require sources claiming CBI to submit
documentation substantiating their CBI
claims at the time such claims were
made and EPA also would not permit
CBI claims for certain data elements
which clearly are not CBI. Aside from
these procedural changes, however, the
proposed rule was substantively
identical to the existing rules governing
the substantiation of CBI claims,
presently codified in 40 CFR Part 2.
At the time it proposed these
amendments, EPA estimated the public
reporting burden for CBI claims to be 15
hours for chemical manufacturers with
Program 3 processes, the only kinds of
facilities that EPA expects to be able to
claim CBI for any RMP data elements.
This estimate was premised upon EPA's
assessment that it would require 8.5
hours per claim to develop and submit
the CBI substantiation and 6.5 hours to
complete an unsanitized version of the
RMP, for a total of 15 hours. EPA also
estimated that approximately 20 percent
of the 4000 chemical manufacturers (out
of 64,200 stationary sources estimated to
be covered by the RMP rule) may file
CBI claims (800 sources). The 800
sources represent a conservative
projection based on the Agency's
experience under EPCRA program.
Consequently, the total annual public
reporting burden for filing CBI claims
was estimated to be approximately
12,000 hours over three years (800
facilities multiplied by an average
burden of 15 hours), or an annual
burden of 4,000 hours (Information
Collection Request No. 1656.04).
a. Comment received. EPA received
one comment on the ICR developed for
the proposed rule, opposing up-front
substantiation of any CBI claims. The
commenter stated that "[t]his is a major
departure from standard EPA procedure,
and would impose a substantial and
unjustified burden for several years."
The commenter further added that up-
front substantiation would significantly
increase the burden of this rule, and that
up-front substantiation unnecessarily
increases the volume and potential loss
of CBI documents. The commenter also
stated that the estimate of 15 hours for
chemical manufacturers "seems
unreasonably low," and cited the EPA
burden estimate of 27.7 to 33.2 hours
per claim (with an average of 28.8)
under the trade secret provisions of
EPCRA.
In the preamble to the proposed rule,
EPA estimated that 20 percent of the
4,000 chemical manufacturers will file a
CBI claim. The commenter contends
that "[t]he EPA analysis * * * excludes
facilities in other industries that will
need to file CBI claims."
Finally, the commenter stated that
claiming multiple data elements as CBI
will increase reporting burden.
b. EPA response. Burden Estimates:
EPA disagrees with these comments. As
pointed out above, the requirement to
submit up-front substantiation of CBI
claims imposes no additional burden. In
addition, the total burden of the CBI
provisions of this rule are not
understated. EPA has re-examined its
analysis in light of the commenter's
concerns and has determined—contrary
to the commenter's claim—that its
initial estimate of the total burden
associated with preparing and claiming
CBI was likely too conservative. As
explained below, the Agency's best
available information indicates that the
process of documenting and submitting
a claim of CBI should impose a burden
of approximately 9.5 hours per CBI
claimant.
First, EPA believes that the
requirement to submit, at the time a
source claims information as CBI,
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977
substantiation demonstrating that the
material truly is CBI imposes no burden
on sources beyond that which presently
exists under EPA's CBI regulations in
Part 2. In order to decide whether they
might properly claim CBI for a given
piece of information, a source must
determine if the criteria stated in section
2.208 of 40 CFR Part 2 are satisfied.
Naturally, a source goes through this
process before a CBI claim is made. EPA
agrees that most programs do not
require the information that forms the
basis for the substantiation to be
submitted at the time of the claim;
however, a facility must still determine
whether or not a claim can be
substantiated. Because existing rules
require sources to formulate a legitimate
basis for claiming CBI, even if those
rules do not require immediate
documentation, and because the Agency
fully expects requests for RMP
information which will necessitate
sources' submitting such
documentation, EPA believes that up-
front submission will not increase the
burden of the regulation.
Second, in response to the
commenter's claim that the Agency had
underestimated the total burden
associated with CBI claims, EPA
undertook a review of recent
information collection requests (ICRs)
covering data similar to that required to
be submitted in an RMP. Initially, EPA
examined the ICR prepared for Part 2
itself (ICR No. 1665.02, OMB Control
No. 2020-0003). Under an analysis
contained in the Statement of Support
for the ICR, the Agency estimated that
it takes approximately 9.4 hours to
substantiate claims of CBI, prepare
documentation, and submit such
documentation to EPA. Next, the
Agency reviewed a survey conducted by
the Agency (under Office of
Management and Budget clearance
#2070-0034), to present the average
burden associated with indicating
confidential business information
claims for certain data elements under
the proposed inventory update rule
(IUR) amendment under TSCA section
8. This survey specifically asked
affected industry how long it would take
to prepare CBI claims for two data
elements—chemical identity and
production volume range information.
Part 68 also requires similar information
(e.g., chemical identity and maximum
quantity in a process) to be included in
a source's RMP and, indeed, EPA
anticipates that they will be the data
elements most likely to be claimed CBI.
The average burden estimates for
chemical identity were between 1.82
and 3.13 hours, and the average burden
estimates for production volume in
ranges were between 0.87 and 2.08
hours. Thus, assuming that the average
source claims both chemical identity
and the maximum quantity in a process
as CBI, a conservative estimate for the
reporting burden would be 5.21 hours.
Finally, EPA examined the burden
estimate upon which it relied at
proposal. That estimate predicted that
the average CBI claim would take 15
hours, of which 8.5 would be
developing and submitting the CBI
claim, and 6.5 would be completing an
unsanitized version of the RMP. In view
of EPA's current plan not to require a
source claiming CBI to submit a full,
unsanitized RMP, but instead to submit
only the particular elements claimed as
CBI, the Agency expects the latter
burden to decrease to 1 hour, for a total
burden of 9.5 hours.
In light of its extensive research of the
burden hours involved in preparing and
submitting CBI claims, EPA believes
that the total burden estimate was not
understated in the April proposal.
Rather, other ICRs and the ICR proposal,
combined with the changes to the
method of documenting CBI claims,
indicate that a burden estimate between
5.21 and 9.5 hours is appropriate for
this final rule. EPA has selected the
most conservative of these, 9.5 hours, in
its ICR for this final rule.
EPA rejected one ICR's burden
estimate as being inapplicable to the
present rulemaking. Although the
commenter urged the Agency to adopt
the estimate associated with trade secret
claims under EPCRA (28 hours), EPA
believes that the estimates discussed
above are more accurate for several
reasons. First, the EPCRA figures are
based upon a survey with a very small
sample size, as compared to the TSCA
survey cited previously. Second, most
(if not all) of the facilities submitting
RMPs are likely to already be reporting
under sections 311 and 312 or section
313 of EPCRA, and many of the
manufacturers submitting an RMP are
subject to TSCA reporting requirements;
thus, most sources likely to claim CBI
for an RMP data element will have
already done some analysis of whether
or not such information would reveal
legitimately confidential matter.
Other Facilities Can Claim CBI: The
Agency does not agree with the
commenter's claim that facilities other
than chemical manufacturers might be
expected to claim CBI for information
contained in their RMPs. The other
industries affected by the RMP rule (e.g.,
propane retailers, publicly owned
treatment works) will not be disclosing
in the RMP information that is likely to
cause substantial harm to the business's
competitive position. For example,
covered public drinking water and
wastewater treatment plants generally
use common regulated substances in
standard processes (i.e., chlorine used
for disinfection). Also, covered
processes at many sources involve the
storage of regulated substances that the
sources sell (e.g., propane, ammonia), so
the processes are already public
knowledge. Other covered processes
involve the use of well-known
combinations of regulated substances
such as refrigerants. Therefore, it is not
likely that these businesses would claim
information as CBI.
As a point of comparison, EPA notes
that of the 869,000 facilities that are
estimated to be required to report under
sections 311 and 312 of EPCRA,
approximately 58 facilities have
submitted trade secret claims for under
those sections. For this reason, EPA
believes the estimate of 800 sources
may, in fact, be an overestimate of the
number of sources claiming CBI.
Reporting Multiple Data Elements:
The Agency disagrees with the
commenters assertion that it has
underestimated the reporting burden on
sources' claiming multiple data
elements as CBI. The burden figures
stated above are based on the Agency's
estimates of the average number of data
elements that a typical source will likely
claim CBI.
Public reporting of the new RMP data
elements is estimated to require an
average of .25 hours for all sources
(64,200 sources) and substantiating CBI
claims is estimated to take
approximately 9.5 hours for certain
chemical manufacturing sources (800
sources). The aggregate increase in
burden over that estimated in the
previous Information Collection Request
(ICR) for part 68 is estimated to be about
23,650 hours over three years, or an
annual burden of 7,883 hours for the
three years covered by the ICR.
H. Unfunded Mandates Reform Act
Title II of the Unfunded Mandates
Reform Act of 1995 (UMRA), P.L. 104-
4, establishes requirements for Federal
agencies to assess the effects of their
regulatory actions on State, local, and
tribal governments and the private
sector. Under section 202 of the UMRA,
EPA generally must prepare a written
statement, including a cost-benefit
analysis, for proposed and final rules
with "Federal mandates" that may
result in expenditures to State, local,
and tribal governments, in the aggregate,
or to the private sector, of $100 million
or more in any one year. Before
promulgating an EPA rule for which a
written statement is needed, section 205
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of the UMRA generally requires EPA to
identify and consider a reasonable
number of regulatory alternatives and
adopt the least costly, most cost-
effective or least burdensome alternative
that achieves the objectives of the rule.
The provisions of section 205 do not
apply when they are inconsistent with
applicable law. Moreover, section 205
allows EPA to adopt an alternative other
than the least costly, most cost-effective
or least burdensome alternative if the
Administrator publishes with the final
rule an explanation why that alternative
was not adopted. Before EPA establishes
any regulatory requirements that may
significantly or uniquely affect small
governments, including tribal
governments, it must have developed
under section 203 of the UMRA a small
government agency plan. The plan must
provide for notifying potentially
affected small governments, enabling
officials of affected small governments
to have meaningful and timely input in
the development of EPA regulatory
proposals with significant Federal
intergovernmental mandates, and
informing, educating, and advising
small governments on compliance with
the regulatory requirements.
EPA has determined that this rule
does not contain a Federal mandate that
may result in expenditures of $100
million or more for state, local, and
tribal governments, in the aggregate, or
the private sector in any one year. The
EPA has determined that the total
nationwide capital cost for these rule
amendments is zero and the annual
nationwide cost for these amendments
is less than $1 million. Thus, today's
rule is not subject to the requirements
of sections 202 and 205 of the Unfunded
Mandates Act.
EPA has determined that this rule
contains no regulatory requirements that
might significantly or uniquely affect
small governments. Small governments
are unlikely to claim information
confidential, because sources owned or
operated by these entities (e.g., drinking
water and waste water treatment
systems), handle chemicals that are
known to public. The new data
elements and the conversion of SIC
codes to NAICS codes impose only
minimal burden on these entities.
I. National Technology Transfer and
Advancement Act
Section 12(d) of the National
Technology Transfer and Advancement
Act of 1995 ("NTTAA"), Pub L. 104-
113, section 12(d)(15 U.S.C. 272 note),
directs EPA to use voluntary consensus
standards in its regulatory activities
unless to do so would be inconsistent
with applicable law or otherwise
impractical. Voluntary consensus
standards are technical standards (e.g.,
materials specifications, test methods,
sampling procedures, business
practices) that are developed or adopted
by voluntary consensus standards
bodies. The NTTAA requires EPA to
provide Congress, through OMB,
explanations when the Agency decides
not to use available and applicable
voluntary consensus standards.
This action does not involve technical
standards. Therefore, EPA did not
consider the use of any voluntary
consensus standards.
/. Congressional Review Act
The Congressional Review Act, 5
U.S.C. section 801 et seq., as added by
the Small Business Regulatory
Enforcement Fairness Act of 1996,
generally provides that before a rule
may take effect, the agency
promulgating the rule must submit a
rule report, which includes a copy of
the rule, to each House of the Congress
and to the Comptroller General of the
United States. EPA will submit a report
containing this rule and other required
information to the U.S. Senate, the U.S.
House of Representatives, and the
Comptroller General of the United
States prior to publication of the rule in
the Federal Register. This action is not
a "major rule" as defined by 5 U.S.C.
section 804(2). This rule will be
effective February 5, 1999.
APPENDIX TO PREAMBLE—DATA ELEMENTS THAT MAY NOT BE CLAIMED AS CBI
Rule element
Comment
68.160(b)(1) Stationary source name, street,
city, county, state, zip code, latitude, and lon-
gitude, method for obtaining latitude and lon-
gitude, and description of location that lati-
tude and longitude represent.
68.160(b)(2) Stationary source Dun and Brad-
street number.
68.160(b)(3) Name and Dun and Bradstreet
number of the corporate parent company.
68.160(b)(4) The name, telephone number, and
mailing address of the owner/operator.
68.160(b)(5) The name and title of the person
or position with overall responsibility for RMP
elements and implementation.
68.160(b)(6) The name, title, telephone number,
and 24-hour telephone number of the emer-
gency contact.
68.160(b)(7) Program level and NAICS code of
the process.
68.160(b)(8) The stationary source EPA identi-
fier.
68.160(b)(10) Whether the stationary source is
subject to 29 CFR 1910.119.
68.160(b)(11) Whether the stationary source is
subject to 40 CFR Part 355.
68.160(b)(12) If the stationary source has a
CAA Title V operating permit, the permit num-
ber.
This information is filed with EPA and other agencies under other regulations and is made
available to the public and, therefore, does not meet the criteria for CBI claims. It is also
available in business and other directories.
This information provides no information that would affect a source's competitive position.
This information is filed with state and local agencies under EPCRA and is made available to
the public and, therefore, does not meet the criteria for CBI claims.
This information provides no information that would affect a source's competitive position.
This information provides no information that would affect a source's competitive position.
This information provides no information that would affect a source's competitive position.
Sources are required to notify the state and local agencies if they are subject to this rule; this
information is available to the public and, therefore, does not meet the criteria for CBI
claims.
This information will be known to state and federal air agencies and is available to the public
and, therefore, does not meet the criteria for CBI claims.
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APPENDIX TO PREAMBLE—DATA ELEMENTS THAT MAY NOT BE CLAIMED AS CBI—Continued
Rule element
Comment
68.160(b)(13) The date of the last safety in-
spection and the identity of the inspecting en-
tity.
68.165(b)(4) Basis of the results (give model
name if used).
68.165(b)(9) Wind speed and atmospheric sta-
bility class (toxics only).
68.165(b)(10) Topography (toxics only)
68.165(b)(11) Distance to an endpoint
68.165(b)(12) Public and environmental recep-
tors within the distance.
68.168 Five-year accident history
68.170(b), (d), (e)(1), and (f)-(k)
68.175(b), (d), (e)(1), and (f)-(p)
NAICS code, prevention program compli-
ance dates and information.
68.180 Emergency response program
This information provides no information that would affect a source's competitive position.
Without the chemical name and quantity, this reveals no business information.
This information provides no information that would affect a source's competitive position.
Without the chemical name and quantity, this reveals no business information.
By itself, this information provides no confidential information. Other elements that would re-
veal chemical identity or quantity may be claimed as CBI.
By itself, this information provides no confidential information. Other elements that would re-
veal chemical identity or quantity may be claimed as CBI.
Sources are required to report most of these releases and information (chemical released,
quantity, impacts) to the federal, state, and local agencies under CERCLA and EPCRA;
these data are available to the public and, therefore, do not meet the criteria for CBI claims.
Much of this information is also available from the public media.
NAICS codes and the prevention program compliance dates and information provide no infor-
mation that would affect a source's competitive position.
This information provides no information that would affect a source's competitive position.
List of Subjects in 40 CFR Part 68
Environmental protection,
Administrative practice and procedure,
Air pollution control, Chemicals,
Hazardous substances,
Intergovernmental relations, Reporting
and recordkeeping requirements.
Dated: December 29, 1998.
Carol M. Browner,
Administrator.
For the reasons set out in the
preamble, title 40, chapter I, subchapter
C, part 68 of the Code of Federal
Regulations is amended to read as
follows:
PART 68—CHEMICAL ACCIDENT
PREVENTION PROVISIONS
1. The authority citation for Part 68
continues to read as follows:
Authority: 42 U.S.C. 7412(r), 7601 (a)(1),
7661-7661f.
2. Section 68.3 is amended by
removing the definition of SIC and by
adding in alphabetical order the
definition for NAICS to read as follows:
§68.3 Definitions.
* * * * *
NAICS means North American
Industry Classification System.
* * * * *
3. Section 68.10 is amended by
revising paragraph (d)(l) to read as
follows:
§68.10 Applicability.
* * * * *
(d) * * *
(1) The process is in NAICS code
32211, 32411, 32511, 325181, 325188,
325192, 325199, 325211, 325311, or
32532; or
* * * * *
4. Section 68.42 is amended by
revising paragraph (b) (3), redesignating
paragraphs (b)(4) through (b)(10) as
paragraphs (b)(5) through (b)(ll) and by
adding a new paragraph (b) (4) to read as
follows:
§68.42 Five-year accident history.
* * * * *
(b) * * *
(3) Estimated quantity released in
pounds and, for mixtures containing
regulated toxic substances, percentage
concentration by weight of the released
regulated toxic substance in the liquid
mixture;
(4) Five- or six-digit NAICS code that
most closely corresponds to the process;
* * * * *
5. Section 68.79 is amended by
revising paragraph (a) to read as follows:
§. 68.79 Compliance audits.
(a) The owner or operator shall certify
that they have evaluated compliance
with the provisions of this subpart at
least every three years to verify that
procedures and practices developed
under this subpart are adequate and are
being followed.
* * * * *
6. Section 68.150 is amended by
adding paragraph (e) to read as follows:
§68.150 Submission.
* * * * *
(e) Procedures for asserting that
information submitted in the RMP is
entitled to protection as confidential
business information are set forth in
§§68.151 and 68.152.
7. Section 68.151 is added to read as
follows:
§68.151 Assertion of claims of
confidential business information.
(a) Except as provided in paragraph
(b) of this section, an owner or operator
of a stationary source required to report
or otherwise provide information under
this part may make a claim of
confidential business information for
any such information that meets the
criteria set forth in 40 CFR 2.301.
(b) Notwithstanding the provisions of
40 CFR part 2, an owner or operator of
a stationary source subject to this part
may not claim as confidential business
information the following information:
(1) Registration data required by
§68.160(b)(l) through (b)(6) and (b)(8),
(b)(10) through (b)(13) and NAICS code
and Program level of the process set
forth in §68.160(b)(7);
(2) Offsite consequence analysis data
required by §68.1 65 (b) (4), (b)(9), (b)(10),
(3) Accident history data required by
§68.168;
(4) Prevention program data required
by §68. 170 (b), (d), (e)(l), (f) through (k);
(5) Prevention program data required
by §68.175(b), (d), (e)(l), (f) through (p);
and
(6) Emergency response program data
required by §68.180.
(c) Notwithstanding the procedures
specified in 40 CFR part 2, an owner or
operator asserting a claim of CBI with
respect to information contained in its
RMP, shall submit to EPA at the time it
submits the RMP the following:
(1) The information claimed
confidential, provided in a format to be
specified by EPA;
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Federal Register/Vol. 64, No. 3/Wednesday, January 6, 1999/Rules and Regulations
(2) A sanitized (redacted) copy of the
RMP, with the notation "CBI"
substituted for the information claimed
confidential, except that a generic
category or class name shall be
substituted for any chemical name or
identity claimed confidential; and
(3) The document or documents
substantiating each claim of confidential
business information, as described in
§68.152.
8. Section 68.152 is added to read as
follows:
§68.152 Substantiating claims of
confidential business information.
(a) An owner or operator claiming that
information is confidential business
information must substantiate that claim
by providing documentation that
demonstrates that the claim meets the
substantive criteria set forth in 40 CFR
2.301.
(b) Information that is submitted as
part of the substantiation may be
claimed confidential by marking it as
confidential business information.
Information not so marked will be
treated as public and may be disclosed
without notice to the submitter. If
information that is submitted as part of
the substantiation is claimed
confidential, the owner or operator must
provide a sanitized and unsanitized
version of the substantiation.
(c) The owner, operator, or senior
official with management responsibility
of the stationary source shall sign a
certification that the signer has
personally examined the information
submitted and that based on inquiry of
the persons who compiled the
information, the information is true,
accurate, and complete, and that those
portions of the substantiation claimed as
confidential business information
would, if disclosed, reveal trade secrets
or other confidential business
information.
9. Section 68.160 is amended by
revising paragraphs (b)(l), (b)(7), and
(b)(12) and adding paragraphs (b)(14)
through (b)(18) to read as follows:
§68.160 Registration.
* * * * *
(b) * * *
(1) Stationary source name, street,
city, county, state, zip code, latitude and
longitude, method for obtaining latitude
and longitude, and description of
location that latitude and longitude
represent;
* * * * *
(7) For each covered process, the
name and CAS number of each
regulated substance held above the
threshold quantity in the process, the
maximum quantity of each regulated
substance or mixture in the process (in
pounds) to two significant digits, the
five- or six-digit NAICS code that most
closely corresponds to the process, and
the Program level of the process;
* * * * *
(12) If the stationary source has a CAA
Title V operating permit, the permit
number; and
* * * * *
(14) Source or Parent Company E-Mail
Address (Optional);
(15) Source Homepage address
(Optional)
(16) Phone number at the source for
public inquiries (Optional);
(17) Local Emergency Planning
Committee (Optional);
(18) OSHA Voluntary Protection
Program status (Optional);
10. Section 68.165 is amended by
revising paragraph (b) to read as follows:
§68.165 Offsite consequence analysis.
* * * * *
(b) The owner or operator shall
submit the following data:
(1) Chemical name;
(2) Percentage weight of the chemical
in a liquid mixture (toxics only);
(3) Physical state (toxics only);
(4) Basis of results (give model name
if used);
(5) Scenario (explosion, fire, toxic gas
release, or liquid spill and evaporation);
(6) Quantity released in pounds;
(7) Release rate;
(8) Release duration;
(9) Wind speed and atmospheric
stability class (toxics only);
(10) Topography (toxics only);
(11) Distance to endpoint;
(12) Public and environmental
receptors within the distance;
(13) Passive mitigation considered;
and
(14) Active mitigation considered
(alternative releases only);
11. Section 68.170 is amended by
revising paragraph (b) to read as follows:
§68.170 Prevention program/Program 2.
* * * * *
(b) The five- or six-digit NAICS code
that most closely corresponds to the
process.
* * * * *
12. Section 68.175 is amended by
revising paragraph (b) to read as follows:
§68.175 Prevention program/Program 3.
* * * * *
(b) The five- or six-digit NAICS code
that most closely corresponds to the
process.
* * * * *
13. Section 68.180 is amended by
revising paragraph (b) to read as follows:
§68.180 Emergency response program.
* * * * *
(b) The owner or operator shall
provide the name and telephone
number of the local agency with which
emergency response activities and the
emergency response plan is
coordinated.
* * * * *
[FRDoc. 99-231 Filed 1-5-99; 8:45 am]
BILLING CODE 6560-50-P
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