Risk Assessment for Marine Spills in Canadian Waters (Phase 1: Oil spills South of the 60th Parallel) 2014

Posted July 4, 2014 | Categories : Marine Reserves,Oil Spill Threat,Reports |

Risk Assessment for Marine Spills in Canadian Waters Phase 1, Oil Spills South of the 60th Parallel Final Version Presented to Transport Canada Approved by :Jérôme Marty, Ph.D.

from-WSP Canada Inc. JANUARY 2014 131-17593-00

Reference to be cited:

WSP. 2014. Risk Assessment for Marine Spills in Canadian Water: Phase 1, Oil Spills South of the 60th Parallel. Report from WSP Canada Inc. to Transport Canada. 172 p. and appendices.



Selected portions of this report referring to the Pacific Coast Sector are included here.

For the complete report see

( for some strange reason it is not accessible through Transport Canada’s website)



his study estimates the risk of pollution from marine oil spills in Canadian waters south of the 60th parallel. The need to conduct this risk assessment was identified by Transport Canada, following the 2010 recommendations of the Commissioner of the Environment and Sustainable Development (CESD). The Minister of Transport, in naming the Tanker Safety Expert Panel, also requested that the risk assessment be used to inform its review of Canada’s preparedness and response arrangements for ship-source spills. The objective of this pan-Canadian study is to provide an overall risk estimate, using a formal process that could be applied and further refined in future assessments. The approach developed in the study involved the following key elements:

  • ·  The Canadian coast was divided into four sectors (Pacific, Atlantic, Estuary/Gulf of St. Lawrence, and the Great Lakes/St. Lawrence Seaway System). Each sector was further divided into sub-sectors that were further divided into three zones representative of nearshore, intermediate and deep-sea environments. A total of 77 zones were allocated a frequency of spill and an environmental sensitivity, which were then applied to generate a risk estimate.
  • ·  Mean annual Canadian traffic data from vessels larger than 150 t was estimated using Lloyd’s worldwide 2011 to 2012 traffic data.
  • ·  Mean annual Canadian oil volumes were estimated using Lloyd’s APEX data (2002 to 2012) as well as Transport Canada’s commodity movement data, considering two classifications of oil: crude oil and refined products.
  • ·  Oil spill frequencies were described for crude, refined cargo, and fuel according to four spill volume categories ranging from 10 m3 to ≥ 10,000 m3. Spill frequencies were calculated using Lloyd’s worldwide casualty data (2003 to 2012) for large size spills and from actual oil spills in Canadian waters using the Canadian Coast Guard(CCG) incident database (MPIRS). The incident records were validated with data from the International Tanker Owners Pollution Federation (ITOPF) and other sources.
  • ·  The probability of an oil spill at sea impacting the shoreline were estimated by transport models that include variables of oil type, spill size and weather conditions.
  • ·  The Environmental Sensitivity Index (ESI) was based on environmental geographic layers describing the physical, biological and human environments in each of the 77 zones. Metrics entered in ESI calculations were derived from Geographic Information System (GIS) procedures.
    •   Shoreline types, wetlands and ice data were used to calculate the Physical Sensitivity Indicator (PSI). Several datasets (coastal zone delineation, ecologically and biologically significant areas (EBSAs); bird distribution) were combined to produce the Biological Resource Indicator(BRI). Similarly, social and economical data (commercial fisheries, tourism employment, freight tonnage and intensity of freshwater use) were compiled to calculate the Human-Use Resource Index(HRI). All data collected to produce the Environmental Risk Index (ERI) were retrieved from various federal departments of the Government of Canada.
    • ·  The spill frequencies, the ESI and the risk estimates were determined using spreadsheet calculations and displayed in a GIS layout.The chosen methodology is appropriate for a large scale risk assessment and provides a Canadian-wide estimate of risk. This method limits the level of details for which oil spill risks can be described.This report presents current oil spill risk results based on the most recent 10 years of vessel traffic and oil volumes combined with current environmental information. Appendix 4 describes the potential effects of future projects in terms of traffic, oil volumes and associated risks. This report describes the data that have been collected and explains the methodology that has been applied to calculate risk estimates. This report also identifies the data limitations and the assumptions made in the calculations. These elements are incorporated into recommendations on how to use the risk results to develop oil spill response and on how to improve the method and refine risk estimates in the future. The following key findings summarize the results of this analysis:
    • ·  The probability of spills varies greatly across the country. The largest marine traffic volumes are observed in the Pacific sector where the probability of small size fuel spills is the highest. The zones with the highest probability of a large spill occurring were thewaters around the southern tip of Vancouver Island, the Cabot Strait including southern Newfoundland, the eastern coast of Cape Breton Island and the Gulf of St. Lawrence and the St. Lawrence River.
    • ·  These spills have the potential to cause significant damage should they occur in a sensitive area. Environmental Sensitivity Index (ESI) results indicate that the zones of highest potential impact were located in the Estuary and the Gulf of St. Lawrence as well as in the southern coast of British Columbia, including Vancouver Island. Overall, a higher ESI score was observed in nearshore zones compared with intermediate and deep-sea zones.



    • ·  The combination of the probability and environmental sensitivity calculations produced the Environmental Risk Index (ERI). Risk values vary greatly across the country. Overall the highest values were observed for small spills, due to their relatively higher frequency of occurrence. The risk of large spills is generally low in Canada. The risk generally increases in nearshore zones compared with deep-sea zones with the exception of the Pacific sector where US traffic may increase deep-sea probabilities. This increase in risk in nearshore zones is related to an increase in environmental sensitivity.
    • ·  The results indicated that the Estuary and Gulf of St. Lawrence, the St. Lawrence River, the southern coast of British Columbia as well as sub-sectors 4, 5 and 6 in the Atlantic sector are the areas at the greatest risk from large oil spills (Maps 1 to 3). For the rest of the country, the risk posed by spills over 10,000 m3 was much lower. The study also identified that there is a higher risk of small and medium spills in every sector of the country, especially those in the 100 to 999 m3 range. These smaller spills can also cause significant damage and are likely to happen much more frequently than the larger spills.These results demonstrate the need for Canada to tailor its preparedness efforts for each sector of the country, as the risks across the country are demonstrably different.
    • Transport Canada 131-17593-00

WSP January 2014