A Spill Risk Assessment of the Enbridge Northern Gateway Project

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Appendix A -‐ Detailed Summary of ENGP Spill Risk Analysis This appendix provides a detailed summary of the methodologies used by Enbridge and its consultants to estimate spill likelihood for ENGP tanker, terminal, and pipeline spills. This summary relies on the same regulatory documents referenced in section 3 in the main body of the report. 1. Spills from Tanker Traffic Accessing Kitimat Terminal DNV determines spill return periods for tanker traffic accessing Kitimat Terminal in the Marine Shipping Quantitative Risk Analysis prepared for the Northern Gateway Project on behalf of Enbridge. DNV uses a per-‐voyage methodology to forecast spills in the marine shipping QRA based on nautical miles (nm) travelled by tankers within the study area. The methodology consists of the following steps: • Determine base incident frequencies per nm • Apply scaling factors to base incident frequencies to adjust for local conditions • Determine conditional spill probabilities from an assessment of incident consequences • Calculate unmitigated spill return periods based on scaled incident frequencies and conditional probabilities • Conduct sensitivity analysis • Identify mitigation measures and recalculate spill return periods based on mitigation Base Incident Frequencies As part of the per-‐voyage methodology, DNV determines base incident frequencies from historical tanker incident data and uses various assumptions to estimate incident frequencies per nm. DNV determines frequencies for international tanker incidents based on data from Lloyds Register Fairplay (LRFP) for the period 1990-‐2006 (Brandsæter and Hoffman 2010 p. 5-‐49). DNV examines four types of potential incidents associated with tanker traffic: 1. Powered and drift grounding, whereby a tanker runs aground either with functional mechanical and navigation equipment (powered) or as a result of failed propulsion equipment (drift) 2. Collisions, whereby the navigational failure of one or both vessels results in a collision 3. Foundering, whereby a tanker sinks due to structural failure of the hull from weather or structural defects 4. Fire and/or explosion. As shown in Table A-‐1, DNV calculates LRFP incident frequencies per nm based on the following assumptions of the average distance travelled by a tanker per year for each tanker incident type: 84
• Tankers sail in coastal areas where a powered grounding may occur 10% of the time at sea (Rabaska 2004 as cited in Brandsæter and Hoffman 2010) • Tankers sail in areas with heavy traffic where collisions may occur 20% of the time at sea (Rabaska 2004 as cited in Brandsæter and Hoffman 2010) • Tankers sail in areas where land is within drifting distance and drift grounding may occur if the ship loses power 15% of the time at sea • Tankers sail in open water where foundering may occur 90% of the time at sea. DNV supports the first two assumptions with reference to a TERMPOL Study completed for Rabaska (2004), while the assumptions for drift grounding and foundering are not supported with evidence. Table A-‐1: Base Incident Frequencies for Tanker Incidents based on Per-‐Voyage Methodology Powered Grounding Drift Grounding Base LRFP incident frequency (per ship year*) Average distance sailed by 74,022 tanker (nm) Portion of total distance sailed by where incident may occur Distance sailed by tanker where incident may occur Base LRFP incident frequency (per nm) Source: Brandsæter and Hoffman (2010 p. 5-‐51). * One ship year represents a total sailing distance of 74,022 nm per year per tanker in operation. Collision Foundering Fire/ Explosion 4.42E-‐03 1.11E-‐03 6.72E-‐03 3.36E-‐05 2.41E-‐03 10% 15% 20% 90% 100% 7,402 11,103 14,804 66,620 74,022 5.98E-‐07 9.96E-‐08 4.54E-‐07 5.04E-‐10 3.26E-‐08 Local Scaling Factors DNV then calculates incident data for the BC study area by multiplying the international frequency data from LRFP by scaling factors that compare risks in the study area to the international areas on which the incident data are based. DNV identified scaling factors from a qualitative assessment of the international data and the scaling factors underwent a review by experts familiar with marine risk assessment, tanker operations, and global navigation (Brandsæter and Hoffman 2010 p. 5-‐52). DNV uses the following formula to calculate incident frequencies for the BC study area where FrequencyBC-‐Coast is the scaled incident frequency per nm, Fbase is the base incident frequency per nm from LRFP in Table A-‐1, and Klocal-‐scaling-‐factor is the total of local scaling factors identified in Table A-‐2: Frequency BC−Coast = F base * K local−scaling− factor DNV divides the BC study area into nine segments and assesses scaling factors for each incident type. The comparison uses 1.0 as a baseline and thus a scaling factor equal to 1.0 suggests that the local conditions affecting risk are equal to the world average (Brandsæter and Hoffman 2010 p. 5-‐52). Risk factors assessed by DNV depend on the type of incident and include the following categories: 85
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A Spill Risk Assessment of the Enbr
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Table ES-‐1: Results for the Qu
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These findings show that the defici
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Table ES-‐4: Probabilities for
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increases to 99.9% if the volume of
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List of Equations, Figures and Tabl
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1. Introduction This report provide
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Enbridge expects that tankers calli
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Major facilities at Kitimat Termina
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affecting risk are equal to the wor
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Table 5: Estimated Reduction in the
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medium size oil/condensate spills f
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Table 12: Return Periods for Spills
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adjustments ranging from 60 to 90%.
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Table 17: Evaluative Criteria for A
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Pollution from Ships (MARPOL) and N
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of escort and tethered tugs will re
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ENGP regulatory application. Furthe
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We acknowledge the difficulty in re
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Table 19: Spill Probabilities Over
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• Mortality of a small number of
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In its regulatory application for t
Page 45 and 46: accidents in Canada, the LRFP datab
Page 47 and 48: Evidence suggests that sulphur conc
Page 49 and 50: anging between 16 and 20 years 22 a
Page 51 and 52: The absence of expert review for th
Page 53 and 54: Risk Acceptability Risk Acceptabili
Page 55 and 56: the likelihood that environmental a
Page 57 and 58: 5. Extended Sensitivity Analysis fo
Page 59 and 60: Table 25: Five-‐Percentage Poin
Page 61 and 62: Sensitivity 6: Aggregating Paramete
Page 63 and 64: effects of different assumptions on
Page 65 and 66: combined, the NEB data suggests tha
Page 67 and 68: United States of America with the O
Page 69 and 70: 2. Estimate the volume of oil and c
Page 71 and 72: 1994 to 2008 international data and
Page 73 and 74: 6.3. Spill Probability Estimates fo
Page 75 and 76: 6.4. Summary of ENGP Spill Probabil
Page 77 and 78: The OSRA method clearly estimates s
Page 79 and 80: Evaluation: There is one major defi
Page 81 and 82: 7. Comparison of Spill Estimates fo
Page 83 and 84: operation. Our application of the O
Page 85 and 86: 8. Conclusion This report evaluates
Page 87 and 88: Figure 5: Number of ENGP Terminal S
Page 89 and 90: References Alberta Energy and Utili
Page 91 and 92: Enbridge. (2004). 2004 Corporate So
Page 93 and 94: MacDonald, K. (2012). Northern Gate
Page 95: United States Department of Transpo
Page 99 and 100: • Major Damage: Damage to the tan
Page 101 and 102: 25% for a collision (Brandsæter an
Page 103 and 104: the overall tanker spill return per
Page 105 and 106: Table A-‐11: Sensitivity Analys
Page 107 and 108: Group estimates risks from spills t
Page 109 and 110: In the event a tanker is struck by
Page 111 and 112: a spill. Expressed as a return peri
Page 113 and 114: 2012 as a response to an informatio
Page 115 and 116: Table A-‐23: Return Periods for
Page 117 and 118: The first Bercha Group (2012c) stud
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A Spill Risk Assessment of the Enbridge Northern Gateway Project

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