TERMPOL. Vapour Cloud Modelling and Conditional Quantitative Risk Analysis

Transcription

1 BERCHA ENGINEERING LIMITED Vapour Cloud Modelling and Conditional Quantitative Risk Analysis ENBRIDGE NORTHERN GATEWAY PROJECT Bercha Engineering Limited Calgary, Alberta, Canada Frank Bercha 21

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3 Executive Summary Executive Summary Northern Gateway Pipelines Limited Partnership (Northern Gateway) contracted Bercha Engineering Limited (Bercha) to conduct condensate vapour cloud modeling and a conditional quantitative risk analysis (QRA) to help fulfill the requirements for marine traffic associated with the Enbridge Northern Gateway Project (the Project). Of the hydrocarbons that will be transported as part of the project, only condensate is expected to evaporate at a rate sufficient to potentially form a vapour cloud if a spill event occurred. To help meet Transport Canada 3.15 requirements associated with marine shipping of liquid hydrocarbons in Canadian waters Northern Gateway has requested Bercha conduct an accidental spill vapour cloud analysis and a conditional general risk assessment, on projectspecified spill occurrence scenarios. The present report describes in detail the vapour cloud dispersion, consequence, and conditional risk analysis carried out to assist in compliance with the stated requirements. The scope of work addresses the requirements specified by Northern Gateway and is summarized below: Phase 1: Consequence Analysis Task 1.1: Data Assimilation and Preliminary Analysis Task 1.2: Scenario Development Task 1.3: Consequence Analysis Phase 2: Risk Analysis Task 2.1: Data Assimilation from Northern Gateway Task 2.2: Risk Assessment Task 2.3: Reporting Spill scenarios locations were selected based on there being a receptor (individual, community or concentration of humans). Spill scenarios and their general locations are outlined below and in Table ES1: Scenario 1 Wright Sound Twoship collision (for potential effect to Hartley Bay) 7245 m 3 initial release, 1811 m 3 /hr for 12 hr. Scenario 2 Wright Sound Ground (for potential effect to Hartley Bay) 1896 m 3 initial release, 632 m 3 /hr for 12 hr. Scenario 3 Kitimat Terminal (for potential effect to Kitamaat Village, Kitimat Terminal and any populated areas between the site and Kitimat township) 25 m 3 instantaneous The estimated release volumes for both the hypothetical grounding and collision scenario are based on outputs from the marine transportation QRA [12]. The selected volumes represent the extreme oil outflow (9%) estimated by MonteCarlo Simulations. 21 Page i

4 Executive Summary Table ES1 Hazard Scenario Summary Scenario Description CRW Density (kg/m 3 ) Release based on MonteCarlo Simulations for SUEZMAX vessels or Terminal Offloading (DNV 21) Initial (m 3 ) Continuous (m 3 /hr) Duration (hr) Scenario 1 Wright Sound collision (WSC) 8 7,245 1, Scenario 2 Douglas Channel grounding 8 1, (WSG) on northwest side Scenario 3 Kitimat Terminal (KTW) unloading spill 8 25 n/a n/a In a sensitivity analysis carried out to identify worst case conditions, it was found that the maximum extent of the lower flammability limit (LFL) isopleths is associated with the low wind speeds and high ambient and water temperatures, with a maximum extent of ½ LFL occurring for the stable atmosphere, low wind speed, high temperature out to a distance of 1.53 km. Scenario 1 represents the largest release, resulting from a hypothetical midchannel collision of the CRW tanker with a sufficiently large vessel to cause the specified spill. Dispersion analysis carried out for worst case conditions indicates the dispersion time plans and profiles. For the given conditions, the maximum extent of the flammable zone occurs at approximately 8 minutes out to 1.7 km, and thereafter, due to dispersion, the flammable zone decreases from to LFL at approximately 1. km after 6 minutes. Scenario 2 involves the hypothetical grounding and resulting spill of a CRW tanker in the vicinity of Hartley Bay. Based on the sequential dispersion isopleths, the maximum extent of the flammable and potentially flammable (½ LFL) zone occurs at 6 minutes out to 1.1 km and at 1 minutes out to 1.7 km, respectively. Scenario 3 is characterized by a 25 m 3 instantaneous spill occurring at the CRW unloading arm at one of the terminal berths. Based on the time dispersion snapshots for the critical concentration levels associated with this scenario, the maximum flammable zone occurs after one minute out to a distance of approximately 2 m. A vapour cloud associated with a 25 m 3 hypothetical spill would be limited to the terminal area and would not reach any offsite residential communities. The fire and explosion modeling was carried out for the worst case vapour cloud flammability conditions for each of the scenarios, together with a subsequent pool fire. Table ES2 summarizes the results of the fire and explosion analysis for each of the scenarios, giving the maximum distances to critical isopleths associated with significant damage criteria. Page ii 21

5 Executive Summary Table ES2 Scenario 1. Wright Sound collision 2. Douglas Channel grounding 3. Kitimat Terminal unloading Fire and explosion analysis results summary Pool Fire Thermal Radiation (kw/m 2 ) FF LEL (ppm) Max Isopleth Distance (m) Flash Fire Thermal Radiation (kw/m 2 ) Explosion (2 min) Overpressure (kpa) Explosion Overpressure (LEL 1 m) Center (kpa) , , ,735 1,862 1, , ,17 1,24 1, Individual specific risks (ISR), the risks to a specific individual considering the time spent at the designated location indoors and outdoors, have been quantified in the form of risk transects for each of the three scenarios. Table ES3 summarizes the results from these individual risk transects. The maximum ISR for Scenarios 1 and 2 is less than 1 in 1 million, while the maximum ISR for the receptors nearest to the source effectively ranges between zero for Scenario 1 and 1 in 1 million per year for Scenario 2. Given a threshold of significance of 1 in 1 million per year, risk for both scenarios 1 and 2 is insignificant. Table ES3 Summary of individual specific risk (ISR) assessment results ISR for Nearest Receptor Acceptability Scenario Maximum ISR Public 1. Wright Sound collision 4 x 1 7 Insignificant Insignificant 2. Douglas Channel grounding 3 x x 1 7 Insignificant Insignificant 3. Kitimat Terminal unloading 8 x x 1 5 Grey Grey Northern Gateway Workers Scenario 3 ISR are higher, showing a level of 8 in 1 thousand per year as a maximum and the same for the nearest receptors, since receptors could be located anywhere up to the location of the spill. In terms of public ISR acceptability, levels below 1 in 1 thousand are considered tolerable but require mitigation. The acceptability of these risk levels for Northern Gateway personnel depends on the interpretation of worker individual risk thresholds. In general, risk thresholds for operator or project owner employees are relaxed to be somewhat higher than those for third parties or members of the public. Regardless of where these thresholds are set, the risks to personnel at the terminal require mitigation to ensure risk is as low as reasonably practicable. Such mitigation can include management of ignition sources, personnel movements, automatic shutdown and isolation of equipment, and other measures. Insignificant risks are posed to people 3 m from the loading operation; hence, no risks from unloading operations at the terminal to adjacent communities exist. 21 Page iii

6 Executive Summary Collective risk (the overall risk to the workers) was evaluated for the terminal. Collective risks are best depicted on a risk spectrum or frequency number (FN) curve such as that shown in Figure ES1. The risk spectrum solid line is above the lower and below the upper risk threshold shown on this spectrum, indicating that risks are in the acceptable region, but requiring risk mitigation. In the unlikely event of a large condensate spill resulting from grounding or collision, during the worst case environmental conditions, casualty risks are limited to within 2 km (approximately 1 nautical mile). In conclusion, it was shown that risks from the collision Scenario 1 and the grounding Scenario 2 are in the insignificant region for any receptors, while those associated with the terminal spill fall into the grey region requiring mitigation. Risks are highest at the terminal within 2 m but these can be mitigated by operational procedures such as ones which limit personnel access to the critical areas. Thus, terminal spill risks require mitigation to a lower level in accordance with riskcost benefits, while the other two scenarios do not require mitigation. Page iv 21

7 Executive Summary Terminal Collective Risk Spectrum 1.E3 Annual Chance of N or More Casualties 1.E4 1.E5 1.E6 1.E Number of People (N) Figure ES1 Terminal Collective Risk Spectrum 21 Page v

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9 Table of Contents Table of Contents 1 Introduction Overview Objectives Scope of Work Outline and Organization of Report Methodology Description of Approaches Overview of the Risk Analysis Process Hazard Scenario Definition Frequency Analysis Consequence Analysis General Description of Consequence Analysis Consequence Evolution Vapour Cloud Dispersion Vapour Cloud Fire and Explosion Modelling Risk Assessment Approaches to Public Risk Assessment Individual Risk Calculation Collective Risk Calculation Risk Acceptability Guidelines Individual Specific Risk Thresholds Risk Matrix Criteria Collective Risk Spectrum Thresholds Input Information and Hazard Scenario Definition Input Information Requirements Hazard Scenarios and Locations Spill Material Properties Environmental Information Meteorological Data Hydrography Ocean Currents Human Population Exposure Distributions Spill Occurrence Frequencies Spill Consequence Analysis General Description Vapour Cloud Dispersion Modeling Sensitivity Analysis Scenario 1 Dispersion Scenario 2 Dispersion Scenario 3 Dispersion Summary of Dispersion Analysis Results Page vii

10 Table of Contents 4.3 Fire and Explosion Modeling Conditional Risk Assessment Approaches to Conditional Risk Assessment Spill Occurrence Frequency Ignition Analysis Human Exposure Damage Criteria Scenario 1 Ship Collision Risk Assessment Scenario 2 Ship Grounding Risk Assessment Scenario 3 Terminal Risk Assessment Individual Risk at the Terminal Collective Risk at the Terminal Summary of Risk Results and Conclusions Risk Mitigation Measures References...61 Appendix A Meteorology... A1 Appendix B Vapour Cloud Modelling and QRA Memorandum #1 to Stantec and Enbridge, by Bercha Engineering Limited, 26 November B1 Appendix C Human Exposure Inputs... C1 Page viii 21

11 Table of Contents List of Tables Table 31 Hazard Scenario Summary Table 32 Spillrelated Properties of CRW Condensate Table 33 Constituent Properties of CRW Table 34 Scenarios 1 and 2 Wind Direction Summary Table 36 Summary of Individual Exposures for Risk Recipients Table 37 Summary of Preliminary Terminal Personnel Exposures Table 38 Probabilities of the Occurrence of a CRW Spill [12] Table 41 Scenario Summary Table 42 Summary of Sensitivity Analysis Results Table 43 Dispersion Analysis Results Summary Table 44 Fire and Explosion Analysis Results Summary Table 51 Probabilities of the Occurrence of a CRW Spill Table 52 Summary of Individual Risk Assessment Results List of Figures Figure 21 The Risk Analysis Process Figure 22 Comparative Individual Risks of Fatality Figure 23 MIACC IRI Acceptability Criteria Figure 24 Risk Matrix Figure 25 Typical Collective Risk Thresholds [5] Figure 31 Satellite Image of Wright Sound in the Vicinity of Hartley Bay Figure 32 Bathymetry in Area of Wright Sound and Hartley Bay Figure 33 Satellite Image in the Vicinity of the Kitimat Terminal Figure 34 Kitimat Terminal Plan Figure 41 Scenario 1 Horizontal and Vertical Dispersion Time Profile Figure 42 Scenario 2 Horizontal and Vertical Dispersion Time Profile Figure 43 Scenario 3 Horizontal and Vertical Dispersion Time Profile Figure 44 Scenario 3 Pool Fire Thermal Isopleths Figure 45 Scenario 3 Vapour Cloud Explosion Overpressure Isopleths Figure 51 Event Tree Figure 52 Thermal Casualty Criteria [28] Figure 53 Explosion Consequence Casualty Criteria [15] Figure 54 Scenario 1 (Ship Collision) Individual Risk Transects Figure 55 Scenario 2 (Ship Grounding) Individual Risk Transects Page ix

12 Table of Contents Figure 56 Scenario 3 (Terminal) Individual Risk Transects Figure 57 Terminal Collective Risk Spectrum Page x 21

13 Glossary of Terms and Acronyms Glossary of Terms and Acronyms AIR ALARP IRPA BC CRW CSRF DNV ECDIS FL FMEA Harm Hazard HAZID IR IRI ISR Average Individual Risk As Low As Reasonably Practicable Individual Risk per Annum British Columbia Condensate Blend CRW824 Collective Specific Risk Factors Det Norske Veritas Electronic Chart Display and Information System Flammability Limit Failure Modes and Effects Analysis Human injury, fatality or health damage; environmental damage; property damage; loss of value; or some combination of all of these. A condition with a potential to cause harm, such as accidental leakage of natural gas from a pressurized vessel. Hazard Identification Individual Risk Individual Risk Intensity. Annual risk to an individual located outdoors at a specific location continuously for one year (24 hrs/day, 365 days/yr) as a result of a nearby project or facility. Individual Specific Risk. The actual risk per year to an individual resulting from a specific facility or project considering the actual time and exposure by the individual in the zone of influence of the project. Isopleth A line of constant value of a variable such as a thermal isopleth of 12.5 kw/m 2. LFL NGPP nm QRA RFP Risk ROO Lower Flammability Limit Northern Gateway Pipeline Project Nautical mile Quantitative Risk Analysis Request for Proposal A compound measure of the probability and magnitude of adverse effect. Ratio of Occurrence 21 Page xi

14 Glossary of Terms and Acronyms TRACE UFL Transport Canada technical review process for marine terminal systems and transshipment sites A multipurpose consequence analysis software model developed by DuPont and sold by Safer Systems. Upper Flammability Limit Page xii 21

15 Section 1: Introduction 1 Introduction 1.1 Overview Northern Gateway Pipelines Limited Partnership (Northern Gateway) contracted Bercha Engineering Limited (Bercha) to conduct vapour cloud simulations and a conditional quantitative risk analysis (QRA) to help fulfill the requirements for marine traffic associated with the Enbridge Northern Gateway Project (the Project). To help meet Transport Canada requirements associated with marine shipping of liquid hydrocarbons in Canadian waters, a conditional risk assessment is required states: There is a need to model gas plumes in certain circumstances. The technological basis for modelling large liquefied gas vapour clouds is constantly evolving. The selection of a particular gas cloud model should be made in consultation with the TRC. Any risk or dispersion model should include an analysis of the sensitivity of varying the assumptions or values input into the model. Appendix 6, Representative Gas Cloud Models, lists a number of models currently used in predicting exercises. Predictions of specified gas cloud dimensions must be based on defined, worstcase, credible incidents involving the instantaneous release of one cargo tank at selected locations along the route and at the terminal or transshipment site. Northern Gateway has requested Bercha to carry out this requirement as well as a conditional risk assessment for scenario locations, in partial fulfillment of The present report describes in detail the vapour cloud dispersion, consequence, and conditional risk analysis carried out to assist in compliance with requirements, and to provide support for the environmental effects assessment for the Project. 1.2 Objectives The objectives of this study are: To predict the vapour cloud characteristics resulting from a worst case credible spill incident including the instantaneous release of cargo at Northern Gateway selected locations along the route and at the terminal site. To evaluate acute risks of casualties to exposed populations from effects of the vapour cloud associated with the selected spill scenarios. 21 Page 11

16 Glossary of Terms and Acronyms 1.3 Scope of Work The scope of work is as follows: Phase 1: Consequence Analysis Task 1.1: Data Assimilation and Preliminary Analysis a) Collection of background data for three spill scenarios (Wright Sound collision, Douglas Channel grounding, and terminal unloading) from Northern Gateway, including: Topographic or satellite maps in Autocad format for each location, including an approximate 3 km radius surrounding it Currents, air and water temperatures, meteorological data including Pasquil stability and wind direction and speed distributions for each location Population distributions and locations relative to spill location Release characteristics including spill volume, rate, fluid composition and characteristics. Note that spill occurrence probabilities are also required for Phase 2. b) Model documentation and preliminary sensitivity results, including: Model outputs illustrated with isopleths superimposed on maps for hypothetical spills Sensitivity of the dispersion results to key variables, showing the distances from spill site to lower flammability limit (LFL) locations for variables including stable, neutral, and unstable Pasquil stability classes three wind conditions two air and water temperatures two other variables to be determined. The model proposed is the multiconsequence model initially developed by Dupont chemicals for chemical release consequence quantification, called TRACE, and supported by Safer Systems. Task 1.2: Scenario Development a) Assimilate and review detailed data for each of the three spill scenarios covered b) Identify main hazard types to workers and public c) Conduct preliminary sensitivity analysis to identify candidate worst cases, considering: largest likely thermal and overpressure isopleths (i.e., hot, very stable, low wind) spill, stability class, and wind direction LFL isopleth. Page 12 21

17 Section 1: Introduction Task 1.3: Consequence Analysis a) Selection of hazard criteria (i.e., dosagefatality probits) for public, worker exposure for thermal and overpressure effects. Other hazards such as asphyxiation which applies in confined space locations will be reviewed however unlikely to be a factor in the open air scenarios considered. b) Flash, jetfire, and explosion for each scenario to produce thermal and overpressure isopleths. Phase 2: Risk Analysis Task 2.1: Data Assimilation from Northern Gateway a) Spill probabilistic characteristics, including spill probability (for each spill type) and associated environmental operational, and accident condition probabilities from QRA by others b) Human exposure probability spatial and temporal distribution c) Ignition (hard and soft) source probability distribution for all potential worst case scenarios. Task 2.2: Risk Assessment a) Ignition and consequence evolution (i.e., pool, flash fire, explosion) probability assessment for all worst case potential scenarios using event trees b) Combination of spill probability, ignition probability, exposure probability with spatial and temporal distribution of consequence isopleths to generate individual risk (IR) isopleths and transects for each worst case candidate c) Selection of worst case scenario for each spill location d) Individual specific risk (ISR) combining IR with population (worker and public) spatial temporal distributions to generate ISR (for each recipient group) and their superposition as isopleth plans on spill location and surroundings maps e) Collective risk spectra (fn curves) for terminal workers. Task 2.3: Reporting a) Memorandum #1 A discussion on sensitivity analysis b) Final Report. 1.4 Outline and Organization of Report Following the executive summary and this brief introduction as Section 1, sequential sections provide a summary of the methods, input information, consequence analysis, risk assessment, and conclusions based on the work carried out. Section 7 provides references. Appendices provide environmental information, the report on the vapour cloud sensitivity analysis, frequency inputs, and the human exposure inputs. 21 Page 13

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19 Section 2: Methodology 2 Methodology 2.1 Description of Approaches The analytical work was based on accepted and stateofart methods of consequence evolution, consequence analysis, and risk analysis in the following principal areas: Hazard scenario definition Ignition frequency evaluation Dispersion and fire and explosion consequence analysis Risk analysis Overview of the Risk Analysis Process What is risk? Risk is a compound measure of the probability and magnitude of an adverse effect [18]. That is, risk is a description of the chances of something undesirable happening and how undesirable it would be. It is important to keep in mind that there are always these two elements of risk; namely, the probability or likelihood and the size or magnitude of the associated damage or loss. A typical risk is the probability of 1 in 1 million per year of a specific individual casualty. Risk Analysis is an orderly process through which one can assess risk as well as methods of reducing the risk [1, 19]. When the risk analysis quantifies risks it is called Quantitative Risk Analysis (QRA). The five principal steps and various substeps of the Risk Analysis process are illustrated in Figure 21 for a pipeline natural gas release incident. The five principal steps are Hazard Definition, Frequency Analysis, Consequence Analysis, Risk Assessment, and Risk Mitigation. In Hazard Definition, essentially one determines the characteristics of the situation (System Data) which can pose a danger, and how the danger is likely to come about. The latter is called Hazard Scenario Development. For example, in Scenario Development, for the case of a natural gas pipeline, the ways in which the pipeline can fail, and how much hazardous material could be released would be assessed. In Frequency Analysis one determines how often it can happen. Thus, we assess how often the accident is likely to happen, in terms of number of accidents per year or per million years [4, 18]. In Consequence Analysis, one models the consequences. First one finds the relative likelihood of different outcomes of the release, using event trees. This is called Consequence Evolution. That is, for the natural gas release what is the relative likelihood of ignition and nonignition? And if ignition occurs, what are the Damage Criteria, or levels of thermal effect which can cause harm. Next, by quantifying hazard distances, one maps the zones or Effect Footprints in which damage to people or facilities could occur if they were present. 21 Page 21

20 Section 2: Methodology Figure 21 The Risk Analysis Process Page 22 21

21 Section 2: Methodology In the Risk Assessment, the results of the hazard analysis and the consequence analysis are melded with the presence of people or Receptors, in areas where they could be hurt and at the times when such damaging events could occur. The results are then integrated into Risk Evaluation to provide measures of risk. Measures of risk to people are primarily Individual Risk and Collective Risk. The Risk Acceptability is then investigated by comparison to regulatory or communityused risk thresholds and discussion with stakeholders. Finally, if the risks are of concern, the proactive portion of the risk analysis is performed through the definition of ways of reducing the risks and assessing just how much risk reduction can be achieved if these different Risk Mitigation measures are applied. Following the definition of risk mitigation measures, and their effect on the unmitigated risk, the residual or mitigated risk results for both individual and collective risk can be assessed. 2.2 Hazard Scenario Definition The initial hazard and its general location, a marine tanker condensate spill, was simply defined as input to the work by Northern Gateway. Following this initial definition, it was necessary to estimate the worst case location of spill occurrences for each of the three specified scenarios. This was carried out by an inspection of satellite, bathymetric, and route data made available through Bercha searches and Northern Gateway. Essentially, the hazard scenario definition consists of the identification of the initiating accident and its spatial and temporal characteristics. In the case of condensate blend CRW824 (CRW) tanker spills, this includes the spill location and release rate of the spill. For marine liquid hydrocarbon spills initiated by accidents such as groundings or collisions, there is generally an initial, nearly instantaneous release of volume, followed by a continuous decaying discharge for a period of time following the initial release. The behaviour of the spill is dependent on the material properties of the spill substance, including both hydrodynamic and evaporation characteristics, as well as the likely ambient conditions in this case, associated with the credible worst case for liquid and evaporate transport. 2.3 Frequency Analysis The frequency analysis entailed the identification of the associated credible worst case environmental condition probabilities, conditional consequence occurrence including ignition probabilities, and, finally, probabilities of recipient exposure to damaging effects resulting from the spill occurrence. The initial spill occurrence probabilities were interpreted from the DNV report [12], which deals primarily with the evaluation of spill probabilities for various aspects of the marine and terminal component of the Project. The probability of the worst credible case environmental conditions was assessed from environmental inputs provided by Northern Gateway [25], while ignition probability and consequence evolution was developed from an analysis of the available information on accident and ambient conditions, including ignition sources. Finally, probable exposure of public and worker recipients of the damaging effects of the evolved consequences, including explosion, fire, thermal radiation, and explosion overpressures, were developed through an interpretation of preliminary information on worker and shift distributions provided by Northern Gateway [21] and reproduced in Appendix C. Approaches to terminal transfer accident frequency estimates are given in [1, 11, 12, 29]. 21 Page 23

22 Section 2: Methodology 2.4 Consequence Analysis General Description of Consequence Analysis Consequence analysis includes the development of consequence evolution scenarios, generally utilizing event trees, and the evaluation of discrete consequences, including dispersion, pool fires, flash fires, and explosions. Such consequences are applicable to nontoxic flammable fluids including liquids and vapours, such as condensate Consequence Evolution Consequence evolution is generally evaluated utilizing event trees, which take into consideration, conditional probabilities of ignition, ignition timing, and the likely consequences of early ignition, delayed ignition, and nonignition. For the case of flammable evaporative liquid spills, possible consequences include pool fires, flash fires, explosions, and dispersion without ignition Vapour Cloud Dispersion A spill of flammable fluids on the ocean surface results in the creation of an expanding liquid pool together with evaporation of flammable vapours. These flammable vapours are released at rates dependent on the spill properties, together with ambient conditions including temperature and wind. Modelling for consequence analysis purposes of such flammable fluid spills on the ocean surface can be adequately accomplished utilizing a multipurpose consequence model, which is capable of predicting pool characteristics, evaporation, flammability properties, and dispersion characteristics for fluids of specified compositions. The model chosen is a multipurpose consequence model called TRACE. This proprietary multipurpose model meets or exceeds the capabilities of all models listed in Appendix 6 of and includes a capability to generate the following information: The discharge rate and duration of a gas and/or liquid release from a vessel or pipeline The size of any liquid pools that may form on the ground or sea surface The rate at which a liquid pool will evaporate or boil and the duration of these phenomena until the point in time that the pool is depleted The size of the downwind hazard zone within the facility topology, on terrain, or sea surface for given wind and atmospheric parameters The thermal radiation hazards resulting from an ignition of a flammable cloud or combustible pool of liquid The size and geometry of the downwind area that may be subjected to flammable, explosive, or toxic concentrations of gases or vapours in air due to the release of a gas or vapour. The maximum weight of potentially explosive gas or vapour in air that occurs during a release incident Page 24 21

23 Section 2: Methodology The consequences of an explosion arising from the internal overpressurization of a sealed or inadequately vented tank due to external heating or internal reaction The consequences of an explosion arising from ignition of a true explosive material in the solid or liquid state Full dispersion description including inertia, buoyancy, and multicomponent gas or multiphase fluid mixtures including light, neutral, and heavy vapours Graphics of isopleths for selected damage criteria for thermal, toxic, or overpressure effects Vapour Cloud Fire and Explosion Modelling Vapour cloud fire and explosion modelling is generally carried out utilizing an analytical technique or multipurpose consequence model such as TRACE (described in the above subsection). Pool fires, flash fires, or explosions, which can result from ignition of the flammable liquid pool or evaporating vapour cloud, resulting from the condensate CRW spill occurrence, were modelled utilizing TRACE. Specific damage criteria, discussed in the risk analysis section (Section 3.5) were first designated, and models were used to generate the spatial and temporal distribution of critical damage levels, thermal dosages from fires and overpressure levels from explosions, utilizing the multipurpose consequence model. 2.5 Risk Assessment Approaches to Public Risk Assessment In the previous four chapters, the assessments of hazard characteristics, frequencies, and consequences were described. This preceding work was done without regard to specific population distributions and the likelihood that they would be indoors or outdoors. In risk assessment, the results of the frequency and consequence analyses are integrated with an estimate of the likely population distribution to provide measures of public risk. Both individual and collective risk can be assessed Individual Risk Calculation Individual Risk Intensity (IRI) for a given location is defined as the probability that a specific adult individual will become a casualty if that individual remains outdoors continuously (24 hours a day, 365 days per year) at that location for one year. IRI, sometimes also called the Individual Risk Field, thus defined forms an upper bound to other measures of individual risk such as Individual Specific Risk (ISR), Average Individual Risk (AIR), or Individual Risk Per Annum (IRPA). Any other measure of individual risk for similar individuals is likely to be lower due to the introduction of mitigating factors such as reduction in time spent at the location, sheltering through indoor residence, use of protective gear, or evasive action. The upper bound Individual Risk Intensity quantified herein has the advantage that it is a clearly defined quantity which can be used as a basis for computation of any other measure of individual risk without major factoring or manipulation. Individual Specific Risk (ISR) for a given location is defined as the probability that a specific adult individual will become a casualty considering the actual proportion of time spent outdoors and indoors at that location. 21 Page 25

24 Section 2: Methodology Computation of individual risk can be conducted for two different types of sources; namely, point sources and linear sources. For point sources, such as marine tanker spills, the Individual Risk Intensity (IRI) is computed as follows: where IRI p = P R P S P F P D (2.1) IRI p = IRI for point source P R = probability of release per year P S = conditional probability of scenario occurrence (ROO from event trees) P F = probability of fatality = probability of hazard occurring in receptor direction P D Individual Specific Risk, ISR, the actual risk to which a specific individual is subjected, is computed as follows: ISR = IRI P L (P O + R I P I ) (2.2a) = IRI ISRF (2.2b) where, P L P O P I R I ISRF = Probability of being at location = Probability of being outdoors (exposed) = Probability of being indoors = Shelter factor = Individual Specific Risk Factor The above formulas are embedded in spreadsheets to generate base data for plotting individual risk transects or contours. The spreadsheet approach, embedding the applicable equations, is used for the computation of individual risk. This facilitates calculation of individual risk at various distances for each of the consequence scenarios. A common representation of individual risk (IRI and ISR) for a linear or point source is a risk transect, showing the variation in IRI and ISR with the distance from the source Collective Risk Calculation Collective or group risk results are usually represented as risk spectra. A risk spectrum is a graph of the frequency of occurrence and the number of individuals involved in the occurrence, with the frequency given on the vertical axis and the number of individuals on the horizontal axis. Specifically, the graph represents the probability that N or more (or at least N) individuals will become casualties in any given situation [1]. The data for the construction of the risk spectrum is obtained by combining the IRI distribution with actual population locations together with their appropriate dwell time and outdoor exposure factors combined with the Collective Specific Risk Factors (CSRF). This applies to either linear or point sources. Page 26 21

25 Section 2: Methodology To construct a risk spectrum, each of the hazard footprints is analyzed to assess the number of individuals exposed within each successive contour, commencing with the outermost or lowest probability contour. These data are then sorted according to groups associated with the same number of individuals, their frequencies are added to give a summary frequency for each group of equal number, and the probabilities are cumulated beginning with the lowest probability usually associated with the greatest number of people. 2.6 Risk Acceptability Guidelines Risk is a combined measure of the probability and magnitude of effect. Risk thresholds are a term generally used to designate the levels of risk, which are acceptable in certain situations. Possible measures of risk include individual risk, risk expectations, and risk spectra. Individual risk is simply the probability that a given individual will become a casualty as a result of the project over a period of exposure of 1 year. Collective Risk expectation can be described by the use of a risk matrix which relates various discrete levels of likelihood of occurrence and severity of consequences. A more rigorous assessment of collective risk, a risk spectrum, gives a continuous relationship between the probability of occurrence and a quantitative measure of the severity of consequences, such as the number of people affected. Although it cannot be claimed that any specific risk thresholds have gained universal acceptability, a sufficient number of individual risk, risk matrix, and risk spectrum thresholds have been adopted by various jurisdictions [5, 16] to make it worthwhile to use some of these, at least as indicators of risk acceptability for the present project Individual Specific Risk Thresholds Risk acceptability criteria are often based on the premise that the risk being evaluated should not make a substantial addition to the existing risk of everyday life. An increase of 1% or less in the individual risk of death, due to a specific hazardous activity, is the basis of some [19] criteria of unacceptable or intolerable risk. Acceptable or tolerable risk criteria are a factor of 1 to 1 lower than those for unacceptable risks. In a grey area where risk lies between unacceptable and acceptable levels, risk reduction must be carried out on a costbenefit basis. The judgment of risks in this grey area has shown that tolerable or acceptable risk levels will vary with the benefits and costs. Thus, in between the unacceptable risk level and the acceptable risk level is the grey area where risks may or may not be tolerable depending on the situation. Risk in this inbetween area is generally acceptable if all reasonably practical measures have already been taken to reduce it. Individual risk is often expressed in terms of an annual probability of death for the exposed person or Individual Specific Risk (ISR). An annual probability (or chance) of death of 1 in 1,, is often taken as a tolerable level [16]. Figure 22 summarizes ISR for a typical Canadian resident from common everyday sources and activities. Note that the values given are per million per year for one individual. 21 Page 27

26 Section 2: Methodology Comparative Individual Risk of Fatality Bites and Stings by Venomous Animals and Insects.2 Hurricanes.3 Lightning Floods Tornadoes Electrocution Accidental Poisoning: Solids and Liquids Accidental Poisoning: Gases and Vapours Firearms Inhalation and Ingestion of Objects 15 Fires Drowning Motor Vehicle Pedestrian Collisions Falls 62 Home Accidents 11 Motor Vehicle Accidents Individual Risk per Million per Year Figure 22 Comparative Individual Risks of Fatality The now defunct Major Industrial Accident Council of Canada (MIACC) [19] has proposed the risk acceptability criteria presented in Figure 23. These criteria are reflected in terms of allowable landuses for specified levels of Individual Risk Intensity (the upper bound IR). 1 in a million 1 in a million 1 in a million (1 4 ) (1 5 ) (1 6 ) Risk Source No other land use Manufacturing, warehouses, open spaces (parkland, golf courses, etc.) Available Land Uses Commercial, offices, lowdensity residential All other uses, including institutions, highdensity residential, etc. Figure 23 MIACC IRI Acceptability Criteria Page 28 21

27 Section 2: Methodology A more workable set of guidelines for individual risk thresholds are based on Individual Specific Risks (ISR) the actual risks to which specific individuals are subjected [5, 16]. Major oil and gas projects such as the Sable Offshore Energy Project (SOEP) under the jurisdiction of the Nova Scotia Offshore Petroleum Board or the Brunswick Pipeline under the jurisdiction of the National Energy Board, have adopted both ISR and CR thresholds. In both cases, there are three principal regions within which project risks are designated, depending on their level or intensity. The highest region is the intolerable region at which operations simply cannot proceed. The next region is the grey region, in the offshore industry termed the as low as reasonably practicable (ALARP) region, in which risks should be reduced in accordance with optimal cost beneficial activities. And finally, there exists the negligible risk region, in which risks are considered acceptable. The following hierarchy of Individual Specific Risk (ISR) levels is representative of that adopted by numerous Canadian oil and gas projects for third party or public risks: Intolerable: ISR > 1 4 Grey: 1 4 > ISR > 1 6 Insignificant: ISR < 1 6 ISR levels of acceptability for project employees are often up to one order of magnitude higher; that is, the intolerable level could be ISR > 1 3. Another simpler but more stringent ISR criterion used by various communities is the 1 in 1 million per year (1 6 /yr) threshold. Above this value of ISR, risk is unacceptable; at or below, it is acceptable Risk Matrix Criteria A relatively simple four rows by four columns risk matrix is often utilized in semiquantitative risk analysis. A more complex matrix with five or six rows and columns would require a level of parameter resolution unlikely to be justified for preliminary analysis. Figure 24 shows the geometry of the risk matrix and the simple multiplicative algorithm results in each of the squares used Collective Risk Spectrum Thresholds A risk spectrum, relating the probability to the associated expected number of casualties, is often used as a measure of group risk. The risk spectrum is a convenient graphical display of the variation in probability with the magnitude of consequences for a given risk scenario. It is plotted on loglog paper with the vertical axis giving the probability and the horizontal axis, the associated minimum number of people affected; that is, the risk spectrum is a probability of exceedance graph giving the probability that at least n people are at risk. Figure 25 shows the public risk of fatality thresholds on an FN curve or risk spectrum as adopted in the County of Santa Barbara [5], and developed in the UK [16]. The registration of the risk spectrum assessed for the present project with respect to the above set of collective risk thresholds is another indication of the level of acceptability of project risks. A somewhat higher set of thresholds (up to one order of magnitude) is often used for project personnel. 21 Page 29

28 Section 2: Methodology FREQUENCY Severity 1 Remote 1 Negligible 2 Unlikely 2 Minor 3 Likely 3 Major 4 Expected 4 Severe RISK RANKING Intolerable Severity 8 9 Grey or ALARP 1 6 Insignificant Figure 24 Risk Matrix Page 21 21

29 Section 2: Methodology Figure 25 Typical Collective Risk Thresholds [5] 21 Page 211

30

31 Section 3: Input Information and Hazard Scenario Definition 3 Input Information and Hazard Scenario Definition 3.1 Input Information Requirements The following general areas of input information need to be fulfilled for the conduct of the scope of work: Spill scenarios and their locations. Spill material properties Environmental information Human population distributions Spill scenario initial occurrence frequencies. 3.2 Hazard Scenarios and Locations Hazard scenarios were selected based on events with the highest probability determined through the QRA [12] and the locations were selected based on proximity to receptors. Spill scenarios are summarized as follows and in Table 41: Scenario 1 Wright Sound Twoship collision (for potential effect to Hartley Bay) 7245 m 3 initial release, 1811 m 3 /hr for 12 hr Scenario 2 Douglas Channel Grounding (for potential effect to Hartley Bay) 1896 m 3 initial release, 632 m 3 /hr for 12 hr Scenario 3 Kitimat Terminal (for potential effect to Kitamaat Village, Kitimat Terminal and any populated areas between the site and Kitimat township) 25 m 3 instantaneous. Table 31summarizes these scenarios in tabular form. The estimated release volumes for both the hypothetical grounding and collision scenario are based on outputs from the marine transportation QRA [12]. The selected volumes represent the extreme oil outflow (9%) estimated by MonteCarlo Simulations. Table 31 Hazard Scenario Summary Scenario Description CRW Density (kg/m 3 ) Release based on MonteCarlo Simulations for SUEZMAX vessels or Terminal Offloading (DNV 21) Initial (m 3 ) Continuous (m 3 /hr) Duration (hr) Scenario 1 Wright Sound collision 8 7,245 1, Scenario 2 Scenario 3 Douglas Channel grounding on northwest side Kitimat Terminal unloading spill 8 1, n/a n/a 21 Page 31

32 Section 3: Input Information and Hazard Scenario Definition Figure 31 shows a satellite image of the vicinity of Hartley Bay just north of Wright Sound, while Figure 32 shows the detailed bathymetry in the vicinity of Hartley Bay and Wright Sound. Scenario 1 is based on a potential Wright Sound midchannel high impact collision. One can see from Figures 31 and 32 that a midchannel collision would occur for this scenario spill location approximately 6 km from Hartley Bay, the nearest population concentration. Figure 32, the bathymetry in the vicinity of the possible Scenario 2 location, shows that water depth drops rapidly with distance from shore, dropping to 13 fathoms (8 feet) within roughly 5 m of the shoreline. Thus, a grounding of the CRW tanker traveling northward, if it were to veer off course, would occur very close to shore. The location of such a grounding would be somewhat at or somewhat west of Halsey Point, a distance of 8 to 1 m from the Hartley Bay village. It is therefore assumed that the credible worst case of a CRW tanker grounding is considered to occur 8 m east of Hartley Bay village. A tethered escort tug and an additional escort tug will accompany all loaded condensate tankers in the CCAA. Given this mitigation it is unlikely that a grounding would occur. If a grounding did occur, it is estimated that there is a 77 percent chance no spill would not occur and a 33 percent chance a spill might occur. If a spill did occur it is estimated that a spills volume similar to what has been considered a credible worst case (1, m 3 ), would occur less than four percent of the time [12]. Figure 33 shows a satellite image in the vicinity of the Kitimat Terminal, while Figure 34 shows a detailed plan of the terminal. The following characteristics of the terminal are assumed as a basis for the analysis. The two main berths will each be capable of loading oil and unloading condensate. Each berth will have similar features: A loading and unloading platform that supports the cargo transfer arms to transfer product from ship to shore Berthing Structures, which are mooring structures used to absorb the impact of the berthing vessel and help support the vessel s mooring lines Mooring structures to which the ship s mooring ropes are secured A gangway tower for crew to access the dock Walkway bridges between the platforms and breasting dolphins Cathodic protection to prevent corrosion of the steel structures First response equipment. Page 32 21

33 Section 3: Input Information and Hazard Scenario Definition Figure 31 Insert 8.5 x 11 Figure Satellite Image of Wright Sound in the Vicinity of Hartley Bay 21 Page 33

34 Section 3: Input Information and Hazard Scenario Definition Figure 32 Insert 8.5 x 11 Figure Bathymetry in Area of Wright Sound and Hartley Bay Page 34 21

35 Section 3: Input Information and Hazard Scenario Definition Figure 33 Insert 8.5 x 11 Figure Satellite Image in the Vicinity of the Kitimat Terminal 21 Page 35

36 Section 3: Input Information and Hazard Scenario Definition Figure 34 Insert 8.5 x 11 Figure Kitimat Terminal Plan Page 36 21

37 Section 3: Input Information and Hazard Scenario Definition During the loading and unloading of cargo, the terminal will operate according to industry best practices and will employ internationally recognized safety measures. Once vessels are moored securely and all loading or unloading preparations have been completed between terminal staff and the vessel s cargo officer, the cargo transfer arms will be manoeuvred into position and connected to the vessel Cargo operations will typically take 2 hours, depending on the vessel s size and flow rate. In the risk analysis, it has been assumed that CRW tanker unloading at the northernmost berth, will take in the worst case, an entire 24 hours, resulting in collective exposure of workers for a period of 24 hours, and individual exposure of external workers for one full 12 hour shift per unloading. 3.3 Spill Material Properties The RFP [17] provides a summary of CRW condensate blend 834 (CRW) including the spill related properties shown in Table 32. A chemical composition of CRW is provided by Crude Quality Inc. [17], May 29 report, with the results of the principal constituents as used in the subsequent modeling summarized in Table 33, and described in detail in Appendix B. 3.4 Environmental Information Meteorological Data Meteorological data used for inputs for dispersion modeling include annual distributions of Pasquil stability classes and wind speeds and directions. The worst case (see Section 4.2.1) stability class of stable (Class E) was assumed to occur 1% of the time. Wind speed and direction information that were provided for the two locations (Wright Sound and the terminal) were used, and are reproduced in Appendix A [25]. Wind speeds at both locations are dominated by relatively low speeds, with those in Wright Sound found to be 77% of the time less than 3 m/s, and those at the terminal 73% of the time less than 6 m/s. Since the worst case conditions for dispersion are associated with low wind speeds of 3 to 6 m/s, such low wind speeds were assumed to occur 1% of the time. 21 Page 37

38 Section 3: Input Information and Hazard Scenario Definition Table 32 Spillrelated Properties of CRW Condensate Spillrelated Properties CRW Condensate Evaporation (Volume %) Adhesion (g/m 2 ) Density (g/cm 3 ) 1 C C Dynamic Viscosity (mpa.s) 1 C C Kinematic Viscosity (mm 2 /s) 1 C C Interfacial Tension (dyne/cm) Oil/Air Oil/Seawater Pour Point ( C) <25 <22 <23 Flash Point ( C) Below 5 C Emulsion Formation Tendency and 1 C Emulsion Formation Tendency and 15 C ASTM Modified Distillation SOURCE: SL Ross 21 Tendency Unlikely Unlikely Unlikely Stability Unstable Unstable Unstable Water Content % % 5% Tendency Unlikely Unlikely Unlikely Stability Unstable Unstable Unstable Water Content % % % Evaporation (% volume) Liquid Temperature ( C) Vapour Temperature ( C) IBP Page 38 21

39 Section 3: Input Information and Hazard Scenario Definition Table 33 Constituent Properties of CRW Substance Formula Composition (%) Propane (C 3H 8).3 nbutane (C 4H 1) 4.3 npentane (C 5H 1) 31.3 nhexane (C 6H 14) 28.9 nheptane (C 7H 16) 2.8 Octanes (C 8H 18) 14.4 Total 1. Wind direction, however, is important for the flammable threats to Hartley Bay associated with both the Wright Sound and the Douglas Channel scenarios. For the midchannel collision case, critical wind directions can range from east to south (or a 9 quadrant). For the grounding case, critical wind directions range from NE to SE. Table 34 summarizes the prevalence by season and annual averages for the quadrant for the two scenarios. The terminal spill is assumed to be localized, generally on the water between the CRW tanker and the berths, so that generic wind directions are unlikely to prevail due to local turbulence and microclimactic effects of various obstacles, heat sources, and other diffusion effects. Therefore, it was conservatively assumed that winds from all directions can equally affect dispersion of the vapour cloud. Wind and ambient temperatures also significantly impact vapour cloud evaporation and dispersion characteristics. The worst case of 2 C water and ambient temperature was assumed to prevail 1% of the time. Table 34 Scenarios 1 and 2 Wind Direction Summary Wind (from) Season Wind (from) Quadrant Average Direction Spring Summer Fall Winter NW SW SE NE N NNW NW WNW W WSW SW SSW S SSE SE ESE Wind Existence 21 Page 39

40 Section 3: Input Information and Hazard Scenario Definition Table 35 Scenarios 1 and 2 Wind Direction Summary (cont d) Wind (from) Season Wind (from) Quadrant Average Direction Spring Summer Fall Winter NW SW SE NE E ENE NE NNE Calm Total % Relative % to Wind Existence Wind (to) Quadrant SE NE NW SW SOURCE: HAYCO 21. Wright Sound Meteorological Station Wind Existence Hydrography Bathymetric information is included in Figures 32 and 34 for Scenarios 1 and 2, and for Scenario 3, respectively Ocean Currents Maximum and mean ocean current speeds and directions were provided [25]. However, as the magnitude of the mean current speeds was in the order of.2 m/s, while wind speeds which dominate vapour cloud transport were generally 1 to 6 m/s, the effect of ocean or tidal currents was assumed to be insignificant in comparison to that from wind effects, and hence, was not explicitly included. 3.5 Human Population Exposure Distributions For the calculation of individual specific risk (ISR), the amount of time spent at the risk reception location and the proportion of that time spent indoors and outdoors for a specific individual is required. A specific individual, as it implies, means a particular worker, John Smith, and his indoor and outdoor average annual residence time at the location. The risk computations subsequently utilize these data to calculate the individual specific risk factor, which represents the proportion of renewal time (365 days per year, 24 hours per day) that the individual is exposed to the hazard at the location. Table 35 summarizes the exposure times assumed for the computation of the individual specific risk or exposure factors for the risk recipients in Hartley Bay. Page 31 21

41 Section 3: Input Information and Hazard Scenario Definition Table 36 Summary of Individual Exposures for Risk Recipients Hartley Bay Category Exposure Hours/Week Indoor Outdoor Shelter Factor Exposure Reduction (%) Hartley Resident For Hartley Bay, residents only are considered as they constitute the dominant population at that location. Accordingly, it is assumed that the Hartley Bay village is inhabited yearround by people who are onsite most of the time. It was assumed that residents spend 156 hours per week onsite, and 6% of their onsite time is spent indoors. As they are not expected to be housed in fire proof or fire retardant dwellings, a relatively low reduction in exposure has been assigned to them, with a 4% reduction over direct outdoor exposure. Terminal worker distributions are preliminary, and summarized in Table 36 based on personnel data given in Appendix C [21]. It has been assumed that there are two 12hour shifts per tanker visit, based on the loading and unloading scenario routine which indicates that unloading of condensate can take up to 2 hours. Further, the following assumptions have been made: 1. All terminal shifts are 12 hours, and each worker only works one shift per tanker visit. 2. The scenario probability is distributed over entire year on basis of 71 visits. 3. Shelter factor is the factor giving equivalent outdoor exposure time considering shelter effect. Factor of 1. means no reduction; factor of. means no exposure. Personnel indoors were assumed to have no exposure, either because they leave the hazard footprint entirely, or are in fire and explosion proof buildings. 4. The above are ISRF meaning individual specific risk factors hence only exposure during the shifts a specific individual would attend. 5. For collective risks we consider exposure for all shifts all days worked and locations. ISRF Table 37 Summary of Preliminary Terminal Personnel Exposures Category (Group of workers) Unloading (hour) Shift (hour) Outdoor Exposure (hour) ISRF Zone (m) a. Hookup, Unhook workers < 1 b. Line Tending Workers c. Dockside workers and monitors < 1 d. Admin., Vessel, Upland Personnel > 2 e. Other vessel Personnel > 2 f. Admin Personnel g. Upland Personnel > 4 21 Page 311

42 Section 3: Input Information and Hazard Scenario Definition 3.6 Spill Occurrence Frequencies The spill occurrence frequencies used in the present work are based on the spill occurrence frequencies developed for the quantitative risk assessment [12]. Table 37 summarizes these frequencies. Table 38 Probabilities of the Occurrence of a CRW Spill [12] Scenario Probability per Event Remarks Number of event per Year 1. Wright Sound collision 4.45E8 Per event nm 71 laden transits 2. Douglas Channel grounding 5.78E8 Per eventnm 71 laden transits Frequency (per year) 3.16E6/nm 4.1E6/nm 3. Kitimat Terminal unloading 1.54E5 Per unloading. 71 unloading 1.9E3 Page

43 Section 4: Spill Consequence Analysis 4 Spill Consequence Analysis 4.1 General Description The consequence modeling process results in the quantitative description of spatial and temporal distribution of the hazard footprint. The hazard footprint is the geometric mapping of zones in the vicinity of the incident associated with different levels of damage. For example, in the case of explosion effects on people, the limit of 35 kpa (5 psi) overpressure zone can be depicted as a circle of a given radius (determined by the consequence model) within which a specific fatality level may be expected for individuals that are outside and unprotected. In the present study, the consequences of three different spill scenarios under worst case conditions were evaluated. These consequences included, first, the generation through evaporation of a vapour cloud and its vertical and sea level concentration characteristic distribution. Of particular interest in this concentration or dispersion analysis were the expected locations of the boundaries of the flammable zone. Once the dispersion assessment was carried out, the thermal effects of an ignited flammable liquid pool and the associated flammable vapour cloud were considered. These thermal effects were associated with pool fires, flash fires, and possible explosions. Other potential consequences considered included asphyxiation and toxic effects. Asphyxiation would require sufficient concentrations in the vicinity of receptors to reduce oxygen levels by displacement to roughly 1% (from the normal 2%) atmospheric volume. As this would not occur due to the lack of confined spaces, where receptors could be located, asphyxiation was not considered as an acute potential hazard. Acute toxic effects, similarly, were not considered because the levels of potential airborne toxins generated were below acute damage levels; prevalence of these toxins in the vapour cloud was not of sufficient durations (hours or days) to cause chronic effects. A summary of the three scenarios and their associated consequence input properties are given in Table 41. The table also gives the mass density of the release, the initial release volume, subsequent continuous volume, and associated time. Tankerbased spill release rates were determined as part of the QRA. For these scenarios the extreme oil outflow (9%) estimated by MonteCarlo Simulations for a Suezmax condensate tanker for a grounding and collision even were used. The terminal release volume was calculated as part of QRA based on the offloading rate, the time to detect a spill and the shut down time. 21 Page 41

44 Section 4: Spill Consequence Analysis Table 41 Scenario Summary Scenario 1. Wright Sound collision (a) (5) (b) 2 m/s (c) 5 m (d) 2 C (e) 2 C 2. Douglas Channel grounding 3. Kitimat Terminal unloading Meteorology (a) Stability (b) Wind speed (c) Wind height (d) Ambient temperature (e) Water temperature (a) (5) (b) 2 m/s (c) 5 m (d) 2 C (e) 2 C (a) (5) (b) 2 m/s (c) 5 m (d) 2 C (e) 2 C CRW Density (kg/m 3 ) Initial (m 3 ) Release Continuous (m 3 /h) Time (h) 8 7,245 1, , n/a n/a 4.2 Vapour Cloud Dispersion Modeling Sensitivity Analysis For a given release, the pool and consequent vapour cloud dispersion properties are assumed to be a function of the following: Atmospheric stability class Wind speed and direction Water and ambient temperatures Current speed and direction. A sensitivity analysis for the above inputs for the Wright Sound spill dispersion characteristics was conducted. The CRW condensate characteristics are summarized in Appendix B in Tables B.1, B.2, and B.3, respectively. Scenario 1 (ship collision) results in an initial volume of 7,245 m 3, followed by release of 1,811 m 3 per hour for 12 hours. The following flammability limits were derived for the evaporating cloud: UFL 24, ppm Highest concentration at which condensate vapour might be expected to burn given an ignition source Page 42 21

45 Section 4: Spill Consequence Analysis LFL 12, ppm Lowest concentration at which a vapour might be expected to burn given an ignition source. ½ LFL 6, ppm half of the LFL and is included as a contingency factor Table 42 summarizes the results of the dispersion studies for the range of sensitivity parameters. Surface currents, found to be significantly lower than wind speeds (currents of.2 m/s, and wind speeds of 3 to 9 m/s), were excluded from the sensitivity studies after initial runs as their effect is negligible compared with the other inputs. The maximum extent of the LFL isopleths is associated with the low wind speeds and high temperatures, with a maximum extent of the ½ LFL isopleth occurring for the stable atmosphere, low wind speed, high temperature out to a distance of 1.5 km. All sensitivity results are summarized in the Table 42. Appendix B gives detailed outputs of the sensitivity analysis Scenario 1 Dispersion Scenario 1 is the scenario associated with the largest release, resulting from a midchannel collision of the CRW tanker with a sufficiently large vessel to cause the specified spill. This spill consists of an initial release of 7,245 m 3, followed by 12 hours of a 1,811 m 3 /hr release. Spill release rates were determined as part of the QRA and equal the as the 9 percent extreme oil outflow (9%) estimated by MonteCarlo Simulations for a Suezmax condensate tanker. Dispersion analysis carried out for worst case conditions gave the dispersion time plans and profiles shown in Figure 41. As can be seen, for the given conditions, the maximum extent of the LFL zone occurs at approximately 8 minutes out to 1.7 km, and thereafter, due to dispersion, the flammable zone decreases to a maximum extent of LFL of roughly 1. km after 6 minutes. 21 Page 43

46 Section 4: Spill Consequence Analysis Table 42 Summary of Sensitivity Analysis Results No. Pasquil, wind speed S= Stable N= Neutral U= Unstable (m/s) Study CRWTP1 Water Temperature ( C) Pool Area (m 2 ) Average Evaporation Rate (kg/min) Evaporation Time (min) Isopleth Limit (6 ppm ½ LFL) Maximum Distance (m) Maximum Half Width (m) Isopleth Limit (12 ppm LFL) Maximum Distance (m) Maximum Half Width (m) Isopleth Limit (24 ppm UFL) Maximum Distance (m) ,389 1,765 1, S, ,999 1,72 1, , ,398 1,653 1, S, ,96 1,468 1, ,377 1, S, ,87 1,214 1, ,389 1,765 1, N, ,999 1,72 1, , ,398 1, N, 6 5, ,96 1,468 1, ,377 1, N, ,87 1, ,389 1,765 1, U, ,999 1,72 1, ,398 1, U, ,96 1,468 1, ,377 1, U, ,87 1, Maximum Half Width (m) Page 44 21

47 Section 4: Spill Consequence Analysis Table 42 Summary of Sensitivity Analysis Results (cont d) T 1 Scenario 7245 m 3 initial release followed by 1811 m 3 /h for 12 hours. Stable Stability 5 Neutral Stability 4 Unstable Stability 2 Meteorology assumptions: Ambient temperature is 2 C, Humidity is 5%, Surface Roughness is.1 m, Solar Radiation is 3 W/m 2, Wind Reference Height is 1 m 21 Page 45

48 Section 4: Spill Consequence Analysis a C R WWS C S 2 min Dis pers ion b C R WWS C S 2 min Dis pers ion 6 (ppm) 12 (ppm) 24 (ppm) 6 (ppm) 12 (ppm) 24 (ppm) 2 12 Width [m Dis tance [m] Height [m Dis tance [m] c C R WWS C S 5 min Dis pers ion d C R WWS C S 5 min Dis pers ion 6 (ppm) 12 (ppm) 24 (ppm) 6 (ppm) 12 (ppm) 24 (ppm) Width [m Dis tance [m] Height [m Dis tance [m] Figure 41 Scenario 1 Horizontal and Vertical Dispersion Time Profile Page 46 21

49 Section 4: Spill Consequence Analysis e C R WWS C S 8 min Dis pers ion f C R WWS C S 8 min Dis pers ion 6 (ppm) 12 (ppm) 24 (ppm) 6 (ppm) 12 (ppm) 24 (ppm) Width [m Dis tance [m] Height [m Dis tance [m] g C R WWS C S 1 min Dis pers ion h C R WWS C S 1 min Dis pers ion 6 (ppm) 12 (ppm) 24 (ppm) 6 (ppm) 12 (ppm) 24 (ppm) Width [m Dis tance [m] Heig ht [m Dis tance [m] Figure 41 Scenario 1 Dispersion TIME Profile (cont d) 21 Page 47

50 Section 4: Spill Consequence Analysis i C R WWS C S 14 min Dis pers ion j C R WWS C S 14 min Dis pers ion 6 (ppm) 12 (ppm) 24 (ppm) 6 (ppm) 12 (ppm) 24 (ppm) Width [m Dis tance [m] Heig ht [m Dis tance [m] k C R WWS C S 2 min Dis pers ion l C R WWS C S 2 min Dis pers ion 6 (ppm) 12 (ppm) 24 (ppm) 6 (ppm) 12 (ppm) 24 (ppm) Width [m Dis tance [m] Heig ht [m Dis tance [m] Figure 41 Scenario 1 Dispersion Time Profile (cont d) Page 48 21

51 Section 4: Spill Consequence Analysis m C R WWS C S 6 min Dis pers ion n C R WWS C S 6 min Dis pers ion 6 (ppm) 12 (ppm) 24 (ppm) 6 (ppm) 12 (ppm) 24 (ppm) Width [m Dis tance [m] Heig ht [m Dis tance [m] Figure 41 Scenario 1 Dispersion Time Profile (cont d) 21 Page 49

52 Section 4: Spill Consequence Analysis Scenario 2 Dispersion Scenario 2 consisted of the grounding and consequence spill described in Table 41 of a CRW tanker in the vicinity of Hartley Bay. Figure 42 gives the Scenario 2 sequential dispersion isopleths. As can be seen, the maximum extent of the flammable and potentially flammable (½ LFL) zone occurs at 6 minutes out to 1.1 km and at 1 minutes out to 1.7 km, respectively, for this scenario Scenario 3 Dispersion Scenario 3 is characterized by a 25 m 3 instantaneous spill occurring at the CRW unloading arm at one of the terminal locations. Figure 43 shows the time dispersion snapshots for the critical concentration levels associated with this scenario. As can be seen, the maximum LFL occurs after 1. minute out to a distance of approximately 2 m. Page 41 21

53 Section 4: Spill Consequence Analysis a C R WWS G S 2 min Dis pers ion b C R WWS G S 2 min Dis pers ion 6 (ppm) 12 (ppm) 24 (ppm) 6 (ppm) 12 (ppm) 24 (ppm) Width [m Heig ht [m Dis tance [m] Dis tance [m] c C R WWS G S 6 min Dis pers ion d C R WWS G S 6 min Dis pers ion 6 (ppm) 12 (ppm) 24 (ppm) 6 (ppm) 12 (ppm) 24 (ppm) Width [m Heig ht [m Dis tance [m] Dis tance [m] Figure 42 Scenario 2 Horizontal and Vertical Dispersion Time Profile 21 Page 411

54 Section 4: Spill Consequence Analysis e C R WWS G S 8 min Dis pers ion f C R WWS G S 8 min Dis pers ion 6 (ppm) 12 (ppm) 24 (ppm) 6 (ppm) 12 (ppm) 24 (ppm) Width [m Dis tance [m] Heig ht [m Dis tance [m] g C R WWS G S 1 min Dis pers ion h C R WWS G S 1 min Dis pers ion 6 (ppm) 12 (ppm) 24 (ppm) 6 (ppm) 12 (ppm) 24 (ppm) Width [m Dis tance [m] Heig ht [m Dis tance [m] Figure 42 Scenario 2 Dispersion Time Profile (cont d) Page

55 Section 4: Spill Consequence Analysis i C R WWS G S 14 min Dis pers ion j C R WWS G S 14 min Dis pers ion 6 (ppm) 12 (ppm) 24 (ppm) 6 (ppm) 12 (ppm) 24 (ppm) Width [m Dis tance [m] Heig ht [m Dis tance [m] k C R WWS G S 2 min Dis pers ion l C R WWS G S 2 min Dis pers ion 6 (ppm) 12 (ppm) 24 (ppm) 6 (ppm) 12 (ppm) 24 (ppm) Width [m Dis tance [m] Heig ht [m Dis tance [m] Figure 42 Scenario 2 Dispersion Time Profile (cont d) 21 Page 413

56 Section 4: Spill Consequence Analysis m C R WWS G S 6 min Dis pers ion n C R WWS G S 6 min Dis pers ion 6 (ppm) 12 (ppm) 24 (ppm) 6 (ppm) 12 (ppm) 24 (ppm) Width [m Dis tance [m] Heig ht [m Dis tance [m] Figure 42 Scenario 2 Dispersion Time Profile (cont d) Page

57 Section 4: Spill Consequence Analysis a C R WK TWS 1 min Dis pers ion b C R WK TWS 1 min Dis pers ion 6 (ppm) 12 (ppm) 24 (ppm) 6 (ppm) 12 (ppm) 24 (ppm) 2 2 Width [m 1 Heig ht [m Dis tance [m] Dis tance [m] c C R WK TWS 2 min Dis pers ion d C R WK TWS 2 min Dis pers ion 6 (ppm) 12 (ppm) 24 (ppm) 6 (ppm) 12 (ppm) 24 (ppm) 2 2 Width [m 1 Heig ht [m Dis tance [m] Dis tance [m] Figure 43 Scenario 3 Horizontal and Vertical Dispersion Time Profile 21 Page 415

58 Section 4: Spill Consequence Analysis e C R WK TWS 4 min Dis pers ion f C R WK TWS 4 min Dis pers ion 6 (ppm) 12 (ppm) 24 (ppm) 6 (ppm) 12 (ppm) 24 (ppm) 2 2 Width [m 1 Heig ht [m Dis tance [m] Dis tance [m] g C R WK TWS 1 min Dis pers ion h C R WK TWS 1 min Dis pers ion 6 (ppm) 12 (ppm) 24 (ppm) 6 (ppm) 12 (ppm) 24 (ppm) 2 2 Width [m 1 Heig ht [m Dis tance [m] Dis tance [m] Figure 43 Scenario 3 Dispersion Time Profile (cont d) Page

59 Section 4: Spill Consequence Analysis i C R WK TWS 2 min Dis pers ion j C R WK TWS 2 min Dis pers ion 6 (ppm) 12 (ppm) 24 (ppm) 6 (ppm) 12 (ppm) 24 (ppm) 2 2 Width [m 1 Heig ht [m Dis tance [m] Dis tance [m] Figure 43 Scenario 3 Dispersion Time Profile (cont d) 21 Page 417

60 Section 4: Spill Consequence Analysis Summary of Dispersion Analysis Results Table 43 provides a summary of the dispersion analysis results described above. Table 43 Scenario 1. Wright Sound collision 2. Douglas Channel grounding 3. Kitimat Terminal unloading Dispersion Analysis Results Summary 6 ppm (½ LFL) 12 ppm (LFL) 24 ppm (UFL) Maximum Distance (m) Maximum Half Width (m) Time (min) Maximum Distance (m) Maximum Half Width (m) Maximum Distance (m) Maximum Half Width (m) 2,863 1, ,653 1, ,816 1,17 6 1, The vertical variations in atmospheric vapour concentrations can be seen Figures 41, 42, and Fire and Explosion Modeling The flammable vapour cloud is intrinsically capable of being ignited. The immediate results of ignition, as described in more detail in Chapter 5, include the following: Pool fires Flash fires Explosions. Pool fires are likely to result from all vapour cloud ignitions. Vapour cloud ignitions can result in flash fires or explosions, ultimately also resulting in a pool fire. Flash fires are the more likely result of vapour cloud ignition, as they occur at any point within the zone of flammability when an ignition source is introduced. Explosions are relatively unlikely because they require a very high concentration (unlikely to occur in the open area vapour cloud) and a hard or very strong ignition source. Explosions, although less likely, have been considered in consequence modelling. The fire and explosion modeling was carried out at the maximum vapour cloud flammability locations for each of the scenarios, together with a subsequent pool fire. Table 44 summarizes the results of the fire and explosion analysis for each of the scenarios, giving the maximum distances to critical isopleths associated with damage criteria introduced in Section 5.2 of the next chapter. Page

61 Section 4: Spill Consequence Analysis Table 44 Fire and Explosion Analysis Results Summary Maximum Isopleth Distance (m) Scenario 1. Wright Sound collision 2. Wright Sound grounding 3. Kitimat Terminal unloading Pool Fire Thermal Radiation (kw/m 2 ) FF LEL (ppm) Flash Fire Thermal Radiation (kw/m 2 ) Explosion (2 min) Overpressure (kpa) Explosion Overpressure (kpa) , ,735 1,862 1, , ,17 1,24 1, Figures 44 and 45 show, respectively, the thermal radiation and explosion overpressure isopleths associated with Scenario 3, the terminal release. The significance of the values of the isopleths will be discussed in the risk assessment section of subsection In the case of a flash fire, it was assumed that the flame front will sweep through the entire flammable zone (shown earlier in Figure 43), with high but transient thermal radiation levels. 2 C R WK TWS P ool F ire Thermal R adiation 5 (W/m^2) 1 (W/m^2) 2 (W/m^2) 1 Width [m Distance [m] Figure 44 Scenario 3 Pool Fire Thermal Isopleths 21 Page 419

62 Section 4: Spill Consequence Analysis 2 C RWKTWS Explosion Overpressure 25. (K P a) 35. (K P a) 7. (K P a) 1 Width [m Distance [m] Figure 45 Scenario 3 Vapour Cloud Explosion Overpressure Isopleths Page 42 21

63 Section 5: Conditional Risk Assessment 5 Conditional Risk Assessment 5.1 Approaches to Conditional Risk Assessment The assessment in this document is termed conditional, because it addresses specific hazard scenarios under worst case conditions. The risks generated are those conditional on the occurrence of the three specified scenarios. Given the spill volumes (9% worst case), environmental parameters (selected for worst case condition), and the proximity of the hypothetical spill locations to receptors (Hartley Bay and the Terminal) this is considered a conservative approach. In risk assessment, for each scenario, the results of the spill occurrence frequency, ignition analysis, human exposure, consequence analysis, and casualty probabilities are combined to provide measures of human risk. Casualty, here, is meant to be a fatality or a severe incapacitating injury Spill Occurrence Frequency Spill occurrence frequencies were prescribed by Northern Gateway based on the marine transportation QRA (DNV 21) and are reproduced in Table 51. Table 51 Probabilities of the Occurrence of a CRW Spill Scenario Probability per Event Remarks Number of event per Year 1. Wright Sound collision 4.45E8 Per eventnm 71 laden transits 2. Douglas Channel grounding 5.78E8 Per eventnm 71 laden transits Frequency (per year) 3.16E6 / nm 4.1E6 / nm 3. Kitimat Terminal unloading 1.54E5 Per unloading. 71 unloading 1.9E3 In Scenario 1 and 2, it was estimated that the incident needs to occur within 1 nm to have any impact on Hartley Bay. This would be an extremely unlikely event considering that all laden tankers will be tethered to an escort tug and an additional close escort tug will be present in this area Ignition Analysis In the ignition analysis, the evolution of consequences following the occurrence of the spill, and its probable exposure to ignition sources is evaluated. The results of the evaluation give the relative likelihood of different damaging consequences, including pool fires, flash fires, and explosions. Unignited vapour cloud concentrations are not of sufficient magnitude outdoors to cause casualties from asphyxiation. The probability of different outcomes from the spill is evaluated using an event tree, shown in Figure 51. As can be seen, starting at the left side, for each of the scenarios, the likelihood of ignition, given the occurrence of the spill, is estimated. The highest likelihood of ignition, of.6 or 6%, has been assigned to the collision scenario because of the likely high impact energies that could generate autoignition in the collision event, followed by escalating failures, including electrical equipment that is relatively likely to 21 Page 51

64 Section 5: Conditional Risk Assessment produce sparks. Scenario 1 addresses the possibility of both immediate and delayed ignition. As can be expected, immediate ignition is more likely than delayed ignition. The collision itself and its immediate aftermath are likely to cause sufficient sparking or fires to ignite the evaporating vapour cloud. Next, in the instance of immediate ignition, a fire would occur in the early stages of the collision aftermath. In the case of delayed ignition, with a 2% likelihood given that ignition does occur, the most likely outcome is a flash fire, which occurs when an ignition source is introduced into the vapour cloud, resulting in a wave front radiating from the ignition source in all directions throughout the flammable zone. Explosion, in the instance of sufficiently high concentration could occur, but has been deemed to occur at the very low probability of 1%. Scenario Ignition Timing Consequence Ratio of Occurrence (ROO) Immediate WSC.8 Early PoolFire.48 Pool Fire.6 WSC Ignition WSG WSG 1 WSC.6 KTW KTW 2 WSG.3 Flash Fire 3 KTW.2 inert expl proof WSC.99 Flash Fire.119 WSG CRWWSC KTW CRWWSG Delayed 3 CRWKTW WSC.2 Explosion WSG.8 WSC.1 Explosion.1 KTW.5 WSG.5.12 KTW.1.1 Non Ignition 1 WSC.4 Spill / Dispersion.4 WSC 2 WSG.7.7 WSG 3 KTW.8.8 KTW Figure 51 Event Tree For the case of the second scenario, the grounding, ignition is much less likely as there is unlikely to be significant abovewater impact to cause autoignition. Accordingly, a 3% probability has been assigned to Scenario 2, the grounding. Autoignition, therefore, is also unlikely with ignition if it does occur likely to be a delayed one, when the vapour cloud could reach an adjacent ignition source such as a fishing vessel or fire on the beach. Scenario 3, the terminal spill, has the lowest probability of ignition primarily because it is anticipated that, like most modern terminals, the proposed Kitimat Terminal will have explosion proof electrical fittings, forbid open fires (such as welding) during loading and unloading, and exercise other precautions that would significantly reduce the likelihood of ignition of any vapours of flammable concentrations at the terminal. In the event that ignition does occur, at the relatively low likelihood of 2%, it is estimated that it is equally likely that it is immediate or delayed. In the case of explosion, however, it is significantly more probable due to the potential of semiconfining spaces (such as the space between the hull and the Page 52 21

65 Section 5: Conditional Risk Assessment dock) that could result in vapour pockets of high concentration. Accordingly, an explosion, given delayed ignition, has been assigned a probability of.1 or 1%. The resultant probabilities are relative probabilities of occurrence or ratios of occurrence (ROO) and are given in the final column of each of the consequence streams Human Exposure The probability of exposure of individuals as well as collective exposure of any individuals can be calculated from the indoor, outdoor, shift times and exposures described earlier in Tables 35 and Damage Criteria Damage criteria are dosage criteria in terms of time and exposure likely to cause fatalities or casualties with different levels of probability. Two types of damage criteria are those associated with thermal dosage and those associated with explosion overpressures for the hazards considered in this work. Thermal dosage criteria based on the work by Opschoor et al. [28] are generated utilizing a probit equation 1 giving casualty probability results as graphically depicted in Figure 52. As can be seen, probabilities of fatality (including serious injury) are shown on the vertical axis, together with different exposure times for the thermal radiation levels shown along the horizontal axis. In the present study, the following dosage criteria were utilized for thermal effects of pool fires: 3 kw/m 2 2 seconds 61% mortality 1 kw/m 2 3 seconds 2% mortality 5 kw/m 2 3 seconds % mortality. Flash fire mortality of 5% within the flammable zone was used. In the case of explosion overpressures, the Health and Safety Commission [15] overpressure probit equation has been used, generating a single overpressure fatality rate graph, as shown in Figure 53. As overpressure varies with distance from the explosion epicenter, the following three levels of explosion overpressure with different associated fatality rates were used: 7 kpa 35% mortality 35 kpa 1% mortality 25 kpa 4% mortality. 1 Probit Equations are used to calculate the percentage of an exposed population that will suffer a certain type of consequence from a given magnitude of an adverse effect. 21 Page 53

66 Section 5: Conditional Risk Assessment Fatalities sec 6 sec 3 sec 2 sec 7 Exposure 1 sec Fatality Rate [%] Exposure 5 sec Thermal Radiation [kw/m 2 ] Figure 52 Thermal Casualty Criteria [28] Page 54 21

67 Section 5: Conditional Risk Assessment 1 Fatalities Fatality Rate [%] Overpressure [kpa] Figure 53 Explosion Consequence Casualty Criteria [15] 21 Page 55

68 Section 5: Conditional Risk Assessment 5.2 Scenario 1 Ship Collision Risk Assessment The integration of the above mentioned constituents to evaluate risk is achieved through a spreadsheet approach utilizing the formulas described in Section 2.5. Specifically, the software utilized is the Bercha Risk Integration Software Capability (BRISC), which generates risk profiles associated with point or linear sources [8]. In this case, point sources are utilized. For Scenario 1, the midchannel ship collision in Wright Sound, the risk transects are shown in Figure 5 4. As mentioned earlier, IRI, the individual risk intensity, is the risk to hypothetical individuals that could be exposed outdoors 24 hours per day, 365 days per year, while the resident (in this case Hartley Bay resident) risk transect is that which considers the likely indooroutdoor exposure and presence at the recipient location. As was pointed out earlier, a ship collision (if it were to occur) would necessarily be at least 5 km from Hartley Bay; accordingly, the risk transect of a maximum of 1.8 km would not reach Hartley Bay. Therefore, we can conclude that the ship collision poses zero risk to Hartley Bay residents. RISK TRANSECTS Wright Sound Collision 1.E5 IRI Hartley Resident 1.E6 Individual Risk per Annum 1.E7 1.E8 1.E Distance from source [m] Figure 54 Scenario 1 (Ship Collision) Individual Risk Transects Page 56 21

69 Section 5: Conditional Risk Assessment 5.3 Scenario 2 Ship Grounding Risk Assessment Risk transects for Scenario 2 (the ship grounding) in the vicinity of Halsey Point, at locations roughly as close as 8 m from Hartley Bay could generate a very low level risk to Hartley Bay residents. As can be seen in Figure 55, for the nearest grounding scenario, and therefore worst possible case, at 8 m from Hartley Bay, risks would be approximately 1 x 1 7 per year. As these risks are by all known standards considered to be insignificant, one can conclude that the Scenario 2, ship grounding near Halsey Point, only poses insignificant risk to Hartley Bay residents. 1.E5 RISK TRANSECTS Douglas Channel Grounding IRI Hartley Resident 1.E6 Individual Risk per Annum 1.E7 1.E8 1.E Distance from source [m] Figure 55 Scenario 2 (Ship Grounding) Individual Risk Transects 21 Page 57

70 Section 5: Conditional Risk Assessment 5.4 Scenario 3 Terminal Risk Assessment Individual Risk at the Terminal Computation of the individual risks for each of the four indooroutdoor exposure groups was calculated and is depicted in the risk transects in Figure 56. Generally accepted risk criteria, as discussed in Section 2.6, consider risks to third parties above 1 4 to be unacceptable. Certain worker populations, such as the military and dangerous occupations such as mining do consider risks tolerable up to a value of 1 3. For the more common risk criterion of 1 4, all personnel risks at the terminal are in the acceptable region; however, risks above 1 6 generally require mitigation to the lowest practical level. Personnel risks in locations within approximately 2 m from the spill location should be mitigated. RISK TRANSECTS Terminal Unloading Individual Risk per Annum 1.E2 1.E3 1.E4 1.E5 1.E6 1.E7 IRI a. Hookup, Unhook workers b. Line Tending Workers c. Assisting workers d. Outdoor workers outside of 2 m zone 1.E8 1.E Distance from source [m] Figure 56 Scenario 3 (Terminal) Individual Risk Transects Page 58 21

71 Section 5: Conditional Risk Assessment Collective Risk at the Terminal The collective risks, risks to groups of one or more individuals, are generally represented as a risk spectrum or frequencynumber (FN) curve. For collective risk, various thresholds and regions of acceptability have been identified by jurisdictions, as described earlier in Section These risk regions are as follows: Insignificant A region in which risks are considered negligible and no need for risk mitigation is required. Grey or As Low as Reasonably Practicable (ALARP) A region in which risks are tolerable but every effort should be made to reduce them as low as possible and preferably to the insignificant region. Intolerable A region in which risks are simply not acceptable, and if they cannot be mitigated at least to the grey region, the project is not considered viable. Different risk thresholds can be used for application to employees of the project proponent or operator (Northern Gateway), and third party workers or members of the public. The personnel information described in Table 36 has been applied to develop a risk spectrum for all terminal personnel. This risk spectrum is shown in Figure 57. As can be seen, the collective risk spectrum falls into the Grey or ALARP region, so mitigation to ensure risk is ALARP is recommended. 21 Page 59

72 Section 5: Conditional Risk Assessment Terminal Collective Risk Spectrum 1.E3 Annual Chance of N or More Casualties 1.E4 1.E5 1.E6 1.E Number of People (N) Figure 57 Terminal Collective Risk Spectrum Page 51 21

73 Section 5: Conditional Risk Assessment 5.5 Summary of Risk Results and Conclusions Individual specific risks, the risks to a specific individual considering the time spent at the designated location indoors and outdoors, have been quantified in the form of risk transects for each of the three scenarios. Table 52 summarizes the most significant results from these individual risk transects. The maximum ISR for Scenarios 1 and 2 is less than 1 in 1 million, while the maximum ISR for the receptors nearest to the source effectively ranges between zero for Scenario 1 and 1 in 1 million per year for Scenario 2. Utilizing the individual specific risk criterion, that risks of 1 in 1 million per year are insignificant, both Scenarios 1 and 2 individual risks fall into the insignificant region. Table 52 Summary of Individual Risk Assessment Results ISR for Acceptability Scenario Maximum ISR Nearest Receptor Public NGPP Workers 1. Wright Sound collision 4 x 1 7 Insignificant Insignificant 2. Wright Sound grounding 3 x x 1 7 Insignificant Insignificant 3. Kitimat Terminal unloading 8 x x 1 5 Grey, Mitigable Grey, Mitigable Scenario 3 individual risks are higher, showing a level of 8 in 1, per year as a maximum and the same for the nearest receptors, since receptors could be located anywhere up to the location of the spill. In terms of public ISR acceptability, levels below 1 in 1 thousand are considered tolerable but requiring mitigation. In general, risk thresholds for operator or project owner employees are relaxed to be somewhat higher than those for third parties or members of the public. Collective risks for the terminal are depicted in the risk spectrum shown in Figure 57 on page 511. The solid curved line, depicting terminal unloading risks, clearly falls between the two straight diagonal lines depicting upper and lower bounds for the grey or ALARP region described in Section and Figure 25. Therefore, the collective risks evaluated for terminal unloading operations are in a grey region of acceptable risk, but requiring mitigation. In conclusion, it was shown that risks from the collision Scenario 1 and the grounding Scenario 2 are in the insignificant region for any receptors, while those associated with the terminal spill specified by Northern Gateway Project fall into the grey or mitigation region. Thus, terminal spill risks should be mitigated to a lower level, while the other two scenarios do not require specific mitigation. The risk analysis was based on worst case scenarios. It is unlikely that consideration of the full spectrum of representative scenarios would significantly reduce risk levels, but it would reduce the spatial extent of the risks. Therefore the current risk analysis is considered conservative as actual spill scenarios would likely have smaller hazard zones that would not reach receptors. 5.6 Risk Mitigation Measures General spill risk mitigation measures are presented below. Because risk is a compound measure of frequency and consequence, risk mitigation addresses both of these risk components. Frequency reducing mitigation is discussed in detail in the QRA [12]. The frequencies used in the vapour cloud analysis included the risk reducing effect that the extensive use of escort tugs will have on incident frequency. 21 Page 511

74 Section 5: Conditional Risk Assessment Only the terminal risks require additional mitigation; the grounding and ship collision risks are considered to be in the insignificant region. Risk mitigation for the terminal can be summarized as follows: Provide stateofart ignition source prevention and suppression facilities and procedures, including explosion proof electrical facilities, and full range of work place ignition protection practices and provisions as is common in most offshore production facilities, to reduce ignition probability in the instance of a spill and ensuing vapour cloud. Provide accredited third party safety training for all personnel involved in cargo transfer procedures Limiting personnel access to the berth area during cargo transfer operations. On the consequence side, the following is proposed: Development of measures to reduce the spread of flammable liquids and vapours in the terminal area, particularly where ignition sources or personnel may be present. Page

75 Section 6: References 6 References 1 American Institute of Chemical Engineers (AIChE), Centre for Chemical Process Safety (CCPS). "Guidelines for Chemical Process Quantitative Risk Analysis". Second Edition. CCPS, AIChE Bea, Robert, Karlene Roberts, Tom Mannarelli, and Paul Jacobson. High Reliability Tanker Loading and Discharge Operations: Chevron Long Wharf, Richmond, California. Paper presented at the Society of Naval Architects and Marine Engineers (SNAME) Ship and Structure Symposium 96. Arlington, Virginia, USA. 182 November Bercha Engineering Limited. Vapour cloud Modelling and QRA, Memorandum #1 to Stantec and Enbridge. 26 November Bercha, FG. Fault Trees for Everyday Risk Analysis, Proceedings Canadian Society for Chemical Engineering, Risk Analysis Seminar, Edmonton, Bercha, FG. and Anthony, D. "Implementation of Risk Based Land Use Guidelines," MIACC PPR '97, October Bercha Engineering Limited. NGP Vapour Cloud Dispersion, Consequence, and Conditional Risk Modeling. Proposal to Stantec. 3 October Bercha Engineering Limited. Concept Safety Evaluation for the Alma Development Project. Final Report (Draft for Certifying Authority Review). Bercha Report No. P213. For Sable Offshore Energy Inc., Halifax, NS, Canada. 26 July Bercha International Inc. Hermosa Beach Integrated Risk Analysis. Final Report (P984) to City of Hermosa Beach, California, USA. December Bercha International Inc. Alternative Oil Spill Occurrence Estimators for the Beaufort and Chukchi Seas Fault Tree Method. Final Report (P21) to US Department of the Interior (DOI), Minerals Management Service (MMS), Alaska Outer Continental Shelf Region (OCS). OCS Study MMS August BTC. BTC Project EIA, Turkey, Final EIA. Section 14: Marine Terminal Accidental Events and Incidents. October ConocoPhillips. Britannia Project, Risk Screening Pipeline and Terminal Operations Det Norske Veritas (DNV). General Risk Analysis and Intended Methods of Reducing Risks. Draft Prepared for Northern Gateway Pipelines Limited Partnership E&P Forum (The Oil Industry International Exploration and Production Forum) Page 61

76 Section 6: References 14 Enbridge Northern Gateway Pipelines website. URL: Accessed: 18 December Health and Safety Commission (HSC). Major Aspects of the Transport of Dangerous Substances. HSC, London, UK Health and Safety Executive (HSE). Risk Criteria for Land Use Planning in the Vicinity of Major Industrial Hazards. HSE. London, UK Jacques Whitford Stantec AXYS Limited. Re: Scope of Work Vapour Cloud Simulations and Quantitative Risk Assessment (File:145654). 19 October Lowrance, WW. "Of Acceptable Risk". Kaufmann Inc, New York, NY Major Industrial Accident Council of Canada (MIACC). Hazardous Substances Risk Assessment A Mini Guide for Municipalities and Industry Muhlbauer, WK. Pipeline Risk Management Manual, Second Edition. Gulf Publishing Co NGPP. Terminal Worker Distribution ( ). 11 March NGPP. Berth Procedures and Provisions June NGPP. Cargo Transfer and Transhipment Systems May NGPP. Site Plans and Technical Data May NGPP. Technical Data Report: Marine Physical Environment. Appendix B: Ocean Currents. (Draft) May NGPP. Origin, Destination & Marine Traffic Volume Survey March NGPP. Ship Particulars and Characteristics February Opshoor, G, ROM van Loo, and HJ Pasman. Methods for calculation of damage Resulting from Physical Effects of the Accidental Release of Dangerous Materials. In International Conference on Hazard Identification and Risk Analysis, Human Factors and Human Reliability in Process Safety. Pages Center for Chemical Process Safety, AIChE Pacific LA Marine Terminal LLC Crude Oil Terminal Final SEIS/SEIR. 3. Modifications to the Draft SEIC/SEIR 3.12 Risk of Upset/Hazardous Materials. November 28. Page 62 21

77 Appendix A: Meteorology Appendix A Meteorology 21 Page A1

78

79 Appendix A: Meteorology A.1 Wright Sound Wind Data 21 Page A3

80 A.11

81 WIND VECTORS [m/s] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec WIND VECTORS [m/s] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec WIND VECTORS [m/s] Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec A.12

82 N NW NE W E 1% 2% SW SE 3% S m/s Station Name: Wright Sound NAD 27 Location: N53 o " W129 o " Elev. above SL: 5 m Tower height: 1 m March to May Wind Speed & Direction Frequency Distribution Table Percent Occurrence (%) Total Direction m/s m/s m/s m/s m/s m/s m/s m/s (%) ENE NE NNE N NNW NW WNW W WSW SW SSW S SSE SE ESE E Calm Total (%) A.13

83 N NW NE W E 1% 2% SW SE 3% S m/s Station Name: Wright Sound NAD 27 Location: N53 o " W129 o " Elev. above SL: 5 m Tower height: 1 m June to August Wind Speed & Direction Frequency Distribution Table Percent Occurrence (%) Total Direction m/s m/s m/s m/s m/s m/s m/s m/s (%) ENE NE NNE N NNW NW WNW W WSW SW SSW S SSE SE ESE E Calm Total (%) A.14

84 N NW NE W E 1% 2% SW SE 3% S m/s Station Name: Wright Sound NAD 27 Location: N53 o " W129 o " Elev. above SL: 5 m Tower height: 1 m September to November Wind Speed & Direction Frequency Distribution Table Percent Occurrence (%) Total Direction m/s m/s m/s m/s m/s m/s m/s m/s (%) ENE NE NNE N NNW NW WNW W WSW SW SSW S SSE SE ESE E Calm Total (%) A.15

85 N NW NE W E 1% 2% SW SE 3% S m/s Station Name: Wright Sound NAD 27 Location: N53 o " W129 o " Elev. above SL: 5 m Tower height: 1 m December to February Wind Speed & Direction Frequency Distribution Table Percent Occurrence (%) Total Direction m/s m/s m/s m/s m/s m/s m/s m/s (%) ENE NE NNE N NNW NW WNW W WSW SW SSW S SSE SE ESE E Calm Total (%) A.16

86 Sep 1/5 Nov 1/5 Jan 1/6 Mar 3/6 May 3/6 Jul 3/6 Sep 2/6 Nov 2/6 Jan 2/7 Mar 4/7 May 4/7 Jul 4/7 Sep 3/7 Nov 3/7 Jan 3/8 Mar 4/8 May 4/8 A.17 Wind Speed (m/s)

87 Appendix A: Meteorology A.2 Terminal Wind Data 21 Page A13

88 N NW NE W E 1% 2% SW SE 3% S Station Name: Kitimat Eurocan Dock NAD 27 Location: N54 o." W128 o 41." Elev. above SL: Unknown Tower Height: Unknown March to May Direction ENE NE NNE N NNW NW WNW W WSW SW SSW S SSE SE ESE E Calm Total (%) m/s Wind Speed & Direction Frequency Distribution Table Percent Occurrence (%) Total m/s m/s m/s m/s m/s m/s m/s m/s (%) A.21

89 N NW NE W E 1% 2% SW SE 3% S Station Name: Kitimat Eurocan Dock NAD 27 Location: N54 o." W128 o 41." Elev. above SL: Unknown Tower Height: Unknown June to August Direction ENE NE NNE N NNW NW WNW W WSW SW SSW S SSE SE ESE E Calm Total (%) m/s Wind Speed & Direction Frequency Distribution Table Percent Occurrence (%) Total m/s m/s m/s m/s m/s m/s m/s m/s (%) A.22

90 N NW NE W E 1% 2% SW SE 3% S Station Name: Kitimat Eurocan Dock NAD 27 Location: N54 o." W128 o 41." Elev. above SL: Unknown Tower Height: Unknown September to November Direction ENE NE NNE N NNW NW WNW W WSW SW SSW S SSE SE ESE E Calm Total (%) m/s Wind Speed & Direction Frequency Distribution Table Percent Occurrence (%) Total m/s m/s m/s m/s m/s m/s m/s m/s (%) A.23

91 N NW NE W E 1% 2% SW SE 3% S Station Name: Kitimat Eurocan Dock NAD 27 Location: N54 o." W128 o 41." Elev. above SL: Unknown Tower Height: Unknown December to February Direction ENE NE NNE N NNW NW WNW W WSW SW SSW S SSE SE ESE E Calm Total (%) m/s Wind Speed & Direction Frequency Distribution Table Percent Occurrence (%) Total m/s m/s m/s m/s m/s m/s m/s m/s (%) A.24

92 Appendix B: Vapour Cloud Modelling and QRA Memorandum #1 to Stantec and Enbridge, by Bercha Engineering Limited, 26 November 29 Appendix B Vapour Cloud Modelling and QRA Memorandum #1 to Stantec and Enbridge, by Bercha Engineering Limited, 26 November Page B1

93

94 1 P298 MEMORANDUM #1 MEMORANDUM #1 on Vapour Cloud Modelling and QRA TO: STANTEC AND ENBRIDGE BY: BERCHA ENGINEERING LIMITED November 26, Introduction Stantec has contracted Bercha Engineering Limited (Bercha) to conduct vapour cloud simulations and a conditional quantitative risk analysis (QRA) to fulfill requirements for marine traffic associated with the Enbridge Northern Gateway Project. The first deliverable is this memo providing the following: The proposed dispersion and fire and explosion model description Modelling assumptions Sensitivity results Example of dispersion map output 2. Model Description In this study, modeling of source, dispersion, and thermal and overpressure characteristics of the release scenarios will be conducted using TRACE. This proprietary multipurpose model meets or exceeds the capabilities of all models listed in Appendix 6 of and includes the following capabilities: Estimating the discharge rate and duration of a gas and/or liquid release from a vessel or pipeline. Estimating the size of any liquid pools that may form on the ground or sea surface. Estimating the rate at which a liquid pool will evaporate or boil and the duration of these phenomena until the point in time that the pool is depleted. Estimating the size of the downwind hazard zone within the facility topology, on terrain, or sea surface for given wind and atmospheric parameters. STANTEC AND ENBRIDGE 11/25/29

95 2 P298 MEMORANDUM #1 The thermal radiation hazards resulting from an ignition of a flammable cloud or combustible pool of liquid. The size and geometry of the downwind area that may be subjected to flammable, explosive, or toxic concentrations of gases or vapours in air due to the release of a gas or vapour. The maximum weight of potentially explosive gas or vapour in air that occurs during a release incident. The consequences of an explosion arising from the internal overpressurization of a sealed or inadequately vented tank due to external heating or internal reaction. The consequences of an explosion arising from ignition of a true explosive material in the solid or liquid state. Full dispersion modeling capability including inertia, buoyancy, and multicomponent gas or multiphase fluid mixtures including light, neutral, and heavy vapours. Graphic generation of isopleths for selected damage criteria for thermal, toxic, or overpressure effects, such as those shown in Figure A.1 of Appendix A, which can be georeferenced and superimposed on Autocad maps or images in plan view. A detailed description of TRACE is given in Appendix A. 3. Modelling Assumptions The principal modelling assumption used is that the input data provided by the client are sufficiently accurate to satisfy requirements. The Trace model has the capability to model the specified releases material properties under the gamut of environmental conditions considered. Specifically, for a given release, the pool and consequent vapour cloud dispersion properties are assumed to be a function of the following: Water and ambient temperatures Wind speed and direction Current speed and direction Atmospheric stability class 4. Sensitivity Analysis Results A sensitivity analysis for the above inputs for the Wright Sound spill dispersion characteristics was conducted. Specifically, the spill considered was one of the specified CRW condensate material with the derived gas, liquid, and flammability properties summarized in Appendix B in Tables B.1, B.2, and B.3, respectively. The spill considered was one of initial volume of 7245 m3, followed by 1811 m3 per hour for 12 hours. The following flammability limits were derived for the evaporating cloud: STANTEC AND ENBRIDGE 11/25/29

96 3 P298 MEMORANDUM #1 UFL 74ppm LFL 12 ppm.5lfl 6 ppm Table 1 summarizes the results of the dispersion studies for the range of sensitivity parameters. Surface currents, found to be significantly lower than wind speeds (currents of.2m/sec and wind speeds of 3 to 9 m/sec), were excluded from the sensitivity studies after initial runs as their effect is negligible compared with the other inputs. As can be seen the maximum extent of the LFL isopleths is associated with the low wind speeds and high temperatures, with a maximum extent of.5lfl occurring for the stable atmosphere, low wind speed, high temperature out to a distance of 1.53km. All sensitivity results are summarized in the table. Appendix C gives graphical summaries of the sensitivity results. 5. Example of Dispersion Map Output Figure 1 gives sequential isopleth plans and sections for a selected sequence of time intervals at 1, 15, and 6 minutes following the spill occurrence. The full sequence from 1 minute to 4 hours is shown in Appendix D. The maximum extent of the LFL (12 ppm) isopleths can be seen to occur at 6 minutes, with recedence thereafter. Once digital maps of the spill location are provided by the client, the maximum (6 minute) isopleth plans will be superimposed on these, in a manner similar to the examples shown in Figures 2 and 3. STANTEC AND ENBRIDGE 11/25/29

97 4 P298 MEMORANDUM #1 Table 1 Summary of Sensitivity Analysis Results N Pasquil, wind speed Study CRWTP1 Water Temp. Pool Area [m 2 ] Average Evaporation Rate [kg/min] Evaporation Time [min] Isopleth Limit [6 ppm 1/2 LFL] Maximum Distance [m] Maximum Half Width [m] Isopleth Limit [12 ppm LFL] Maximum Distance [m] Maximum Half Width [m] Isopleth Limit [74 ppm UFL] Maximum Distance [m] 1 T5 35,389 1,765 1, S, 3mps 2 T2 52,999 1,72 1, , T5 54,398 1,653 1, S, 6mps 4 T2 82,96 1,468 1, T5 63,377 1, S, 9mps 6 T2 14,87 1,214 1, T5 35,389 1,765 1, N, 3mps 8 T2 52,999 1,72 1, , T5 54,398 1, N, 6mps 5, 1 T2 82,96 1,468 1, T5 63,377 1, N, 6mps 12 T2 14,87 1, T5 35,389 1,765 1, U, 3mps 14 T2 52,999 1,72 1, T5 54,398 1, U, 6mps 16 T2 82,96 1,468 1, T5 63,377 1, U, 9mps 18 T2 14,87 1, Maximum Half Width [m] TP1 Scenario TP m 3 initial release followed by 1811 m 3 /h for 12 hours. S, 3mps Meteorology Stability 5(E) Stable, Wind Speed 3 m/s S, 6mps Meteorology Stability 5(E) Stable, Wind Speed 6 m/s S, 9mps Meteorology Stability 5(E) Stable, Wind Speed 9 m/s N, 3mps Meteorology Stability 4(D) Neutral, Wind Speed 3 m/s N, 6mps Meteorology Stability 4(D) Neutral, Wind Speed 6 m/s N, 9mps Meteorology Stability 4(D) Neutral, Wind Speed 9 m/s U, 3mps Meteorology Stability 2(B) Unstable, Wind Speed 3 m/s U, 6mps Meteorology Stability 2(B) Unstable, Wind Speed 6 m/s U, 9mps Meteorology Stability 2(B) Unstable, Wind Speed 9 m/s All Meteorologies: Ambient temperature 1 C, Humidity 5%, Surface Roughness.1 m, Solar Radiation 3 W/m 2, Wind Reference Height 1 m T5 Water temperature 5 C T2 Water temperature 2 C STANTEC AND ENBRIDGE 11/25/29

98 5 P298 MEMORANDUM # (ppm) 12. (ppm) 74. (ppm) (ppm) 12. (ppm) 74. (ppm) Width (m) 4 4 Height (m) Distance (m) 1 min Distance (m) 8 6. (ppm) 12. (ppm) 74. (ppm) (ppm) 12. (ppm) 74. (ppm) Width (m) 4 4 Height (m) Distance (m) Distance (m) 15 min 8 6. (ppm) 12. (ppm) 74. (ppm) (ppm) 12. (ppm) 74. (ppm) Width (m) 4 4 Height (m) Distance (m) Distance (m) 6 min Figure 1 Sequential Isopleth Plans and Sections at 1, 15, and 6 minutes Following the Spill Occurrence STANTEC AND ENBRIDGE 11/25/29

99 6 P298 MEMORANDUM #1 Figure 2 Example Dispersion Isopleths on Map NE Wind Figure 3 Example Dispersion Isopleths on Map SW Wind Zoomed STANTEC AND ENBRIDGE 11/25/29

100 A.1 P298 MEMORANDUM #1 APPENDIX A: DETAILED MODEL DESCRIPTION TRACE PROGRAM DESCRIPTION (Source: A.1 General Description of Trace Program In 1986, TRACE (Toxic Release Analysis of Chemical Emissions) was introduced. Since then it has become a stateoftheart engineering tool for evaluating the dispersion, explosive, or flammable properties of a chemical. TRACE incorporates an intelligent wizard feature that allows the user to easily and rapidly describe a scenario. Once processed, results are easily viewed in tabular or graphical formats. Output information can be exported to other applications like word processors, spreadsheets and presentation managers TRACE is used for facility siting studies, emergency preparedness planning, meeting regulatory requirements, and quantitative risk analysis studies. TRACE scenarios can be exported to other digital products, allowing an engineer to evaluate the impact and then decide if it should be part of the emergency response system. TRACE is a multipurpose tool for chemical risk management. It is comprehensive hazard assessment software for analyzing the impact of toxic, flammable, and explosive chemical releases into the atmosphere, on the ground, or water surface. Key Benefits Stateoftheart program for analyzing the details of a release of hazardous material into the atmosphere. User friendly graphical interface makes it easy to simulate toxic chemical releases to do complex modeling for planning purposes. TRACE can be used to provide realistic representations of potential hazards to use in meeting regulatory requirement and industry initiatives such as OSHA PSM, SARA Title III, EPA RMP Rule and more. Tool for quantitative risk assessment Used in emergency response planning and training of response personnel Includes more than 7 chemicals from the DIPPR database STANTEC AND ENBRIDGE 11/25/29

101 A.2 P298 MEMORANDUM #1 A.2 Modelling Algorithms Algorithms in TRACE are based on accepted scientific methods and have been validated with fieldtest data. Release Rates: Source calculations are available for timevarying releases from tank/pipe systems or steady releases from pipes. Release rate, temperature and composition are determined by algorithms with multiple configuration options. Source Dynamics: TRACE models phenomena such as flashing, aerosol dynamics, air entrainment and pool evaporation. TRACE can handle multicomponent pool evaporation for aqueous solutions and fuming acids. There is also the capability for modeling gas mixtures. Vapor Cloud Dispersion: TRACE has the ability to model groundlevel or elevated releases in the form of high momentum jets, dense gas clouds or neutral and buoyant plumes. Special models are also included for hydrogen fluoride and titanium tetrachloride dispersion. Infiltration calculations are available for determining indoor and outdoor concentration profiles. Fires: TRACE evaluates thermal radiation variables from several firerelated scenarios. These include fireballs (Bleves), liquid pool fires, jet fires, flash fires and generic sources (userspecified shapes). The fire models account for the geometry of the source, the source strength, view factor and atmospheric transmissivity. Explosions: BakerStehlow or MultiEnergy methodologies can be used for modeling explosions. The algorithms account for type of ignition source, degree of confinement, congestion level, chemical reactivity and initial blast strength. Separate algorithms are also available for simulating pressurized vessel bursts. Population Impact: Within the Consequence Analysis enhancement to TRACE, separate algorithms are available to evaluate the number of people impacted by a release. Various criteria like Concentration, Thermal Radiation, Overpressure Levels, Dose, Load and Probit effects can be used as the impact criteria A.3 Consequence Analysis The Consequence Analysis module evaluates the consequences of an accidental release on the surrounding community. The module comprises of three different groups of algorithms: Accidental Release Modeling, Human Response Modeling and Population Impact Modeling. Accidental release modeling algorithms are used to model the release rates, evaporation and subsequent atmospheric dispersion. These algorithms are similar to those used in other modules of SAFER (e.g. Hazard Assessment, TRACE, Fire and Explosion, etc.). Human response modeling algorithms predict the toxic response of an individual within an average population by taking into account the chemical specific toxicity.results of the accidental release algorithms are imputted into the human response model. STANTEC AND ENBRIDGE 11/25/29

102 A.3 P298 MEMORANDUM #1 A.4 TRACE Descriptive Brochure (from website cited) STANTEC AND ENBRIDGE 11/25/29

103 A.4 P298 MEMORANDUM #1 STANTEC AND ENBRIDGE 11/25/29

104 A.5 P298 MEMORANDUM #1 STANTEC AND ENBRIDGE 11/25/29

105 A.6 P298 MEMORANDUM #1 STANTEC AND ENBRIDGE 11/25/29