• Saturday, November 17, 2018

Twelve truths about tanker traffic...By Robert G. Allan

By BCShippingNews 05 July 2018
Twelve truths about tanker traffic...By Robert G. Allan
To oppose the Trans Mountain Pipeline Expansion project on the basis of concerns about tanker oil spills is certainly not valid...

Credential qualification: Robert G. Allan, P.Eng., FRINA, FSNAME is the Executive Chairman, Robert Allan Ltd. Allan has a B.Sc. (Honours) in Naval Architecture (1971) from the University of Glasgow; Glasgow, Scotland. Summary of Experience Forty-two years of direct experience in the design of commercial workboats of all types, but especially high-performance tugboats for tanker escort and offshore terminal operations. Significant experience in the design of major ice-breaking supply vessels and tugs for the Beaufort Sea and more recently for the Caspian Sea and Sakhalin. Since 1980, has led Robert Allan Ltd. to a position of international prominence in the field, including several major International design awards for projects such as the unique Z-Tech tug design for the Port of Singapore. Internationally recognized as a leading authority on the subject of tug and workboat design. Recognized by peers for this work with following major awards: 2005 Royal Institution of Naval Architects (UK), Small Craft Group Medal for significant lifetime achievements in Naval Architecture. 2005 Awarded SNAME David W. Taylor Medal for Notable Achievement in Naval Architecture. (The only Canadian ever to be so honoured).

The debate about the merits of the Trans-Mountain Pipeline Expansion Project (TMX) continues, fuelled by opinions and often unsubstantiated claims by vested interest groups. While there may be perfectly valid reasons to oppose the pipeline on the basis of concerns regarding global climate change or pipeline safety (although there is little doubt that pipelines are the safest mode of bulk oil transportation on land), to oppose the project on the basis of concerns about tanker oil spills is certainly not valid. The City of Vancouver and others have commissioned at least one study[1] that shows how a spill in Vancouver Harbour will migrate to pollute virtually the entire perimeter of the port. The study was commissioned to, in part, “model four oil spill scenarios in Burrard Inlet.” However it does not address how any of those spills occur in the first place. It simply assumes that it will, regardless of the many layers of safeguards which already are in place and which will be enhanced in the future should TMX proceed. The much-touted Oceans Protection Plan is unfortunately fixated on spill recovery and fails to address in any meaningful way the means of spill prevention which are the essential key to safer coastlines. The old adage, “an ounce of prevention is worth a pound of cure,” has been recently extrapolated to “an ounce of prevention is worth a ton of cure” in the context of offshore oil activities.

This article highlights critical facts about marine oil transportation both locally and globally with a focus on the preventative safeguards which result in tanker shipping being one of the safest transportation modes in the world.

Twelve truths


Every powered vessel operating in coastal B.C. carries fuel on board and thus represents some (albeit extremely small) degree of risk. That includes all cargo ships, ferries, fishing vessels, tugs, yachts and cruise ships. None of the aforementioned is required by international regulation to have double-hull construction as are tankers.


Oil shipments worldwide show a steadily improving trend in safe cargo movement against a consistent increase in volume of product moved.[2] Figure 1 illustrates recorded oil spills for the past 48 years (2017 data), which contrasts significantly with the global increase in oil movements by tanker over the same period as shown in Figure 2.


Crude oil has been shipped from Alaska to refineries in Puget Sound along the entire outer coast of B.C. and through Juan de Fuca Strait on two out of every three days for the past 40 years: Shipment statistics (to 2017) are:[3]

  • ~2.49 billion tonnes since 1977.
  • Current average 27.3 million tonnes/year
  • (~ 79,000 T/day).
  • Average 248 ship moves/year.
  • Since 1991, 13,182 tug escorts have been performed.
  • Accidents in B.C. or Puget Sound waters = Zero.


The major accident associated with Alaskan oil shipments is of course the Exxon Valdez grounding in Prince William Sound in 1989. The regulatory changes subsequent to that accident (OPA ’90) completely transformed the nature of bulk oil shipments worldwide (as witnessed by the data in (2) above). The major consequences of these regulatory and safety culture changes are:

  • Worldwide, oil (since 2010) only moves in tankers with double-hull construction. No single hull tankers, such as Exxon Valdez, are still trading. No oil or fuel of any kind is located adjacent to the outer shell of such tankers.
  • The majority of oil terminal operations worldwide utilize large and powerful escort tugs to ensure safe tanker operations in near-coastal areas. These tugs are specifically designed and configured to provide steering and braking power at least equivalent to that of the tanker itself, thus providing fully redundant ship control capability.


The Port of Vancouver handled 3,219 foreign ship arrivals (and associated departures) in 2017, of which 260 were tankers, including the present approximately 50 tankers per year departing Westridge Terminals.[4] The proposed additional ~350 tankers per year associated with the TMX project represent a 215 per cent increase in total tanker traffic, but only an 11 per cent increase in total ship traffic through that port. Total petroleum product shipments through the Port of Vancouver in 2017 were about 6.1 million tonnes (mT), of which 1.7 mT was crude petroleum. It must be noted that while Vancouver is Canada’s busiest port, in world terms it is 28th overall in total cargo tonnage and 42nd overall in container traffic. [5] Ship traffic levels in this port are modest at best.


For the entire Pacific coast of Canada and the U.S.:

  • There are about 25,000 ship movements per year (Canada and U.S. port destinations).[6] (A movement means either an entry or a departure from a port.)
  • There have been approximately 12 incidents in the past 40 years (prior to 2008) that were — or had the potential — for a serious grounding incident. (Note: Not actual groundings but incidents that might have become a grounding.)
  • The probability of a serious “potential” incident (requiring intervention by tug or similar support vessel) is thus about 1 in 100,000 (0.001 per cent). The probability of an actual grounding incident is far lower.


Tanker Movements within the Port of Vancouver are very strictly controlled. The restrictions are clearly defined in the Vancouver Fraser Port Authority document “Port Information Guide: Harbour Practices and Procedures (HPP),”[7] and in particular the controls on tanker movements through First Narrows and Second Narrows are rigorously defined. Restrictions include:

  • Various marine traffic controls giving tanker movements the highest priority.
  • Ship speed limited to six knots.
  • Ship movements only during daylight hours and with tide state limits.
  • The use, according to ship size, of tethered escort tugboats. Aframax tankers moving through the port would have at least two escort tugs tethered to the tanker.
  • The use of two certified Canadian pilots on duty aboard any tanker >40,000 tonnes Dwt.

Note that this regulated use of tugs plus pilots involves not less than five fully certified mariners on watch in every tanker operation in this port.


Presently, tanker movements require the use of approved escort tugs from Westridge Terminal right through to Race Rocks near Victoria. TMX have proposed that: “Tug escort of outbound laden tankers will be expanded to cover the entire tanker shipping route through the Strait of Georgia and between Race Rocks and the Juliet Buoy at the western entrance to Juan de Fuca Strait.[8] The tugs required to perform the latter duty in Juan de Fuca Strait will be larger, more powerful, and certainly more capable in every respect than any tugs currently on the West Coast of Canada or the U.S.[9] A significant majority of such escort tugs worldwide are in fact designed here in B.C., as per the Australian and Norwegian escort tugs illustrated in Figure 3 above. These tugs, in the range of 8,000-10,000 HP, would dwarf the typical barge-towing tug commonly seen along the B.C. coast today.


One question which has not been addressed in any commentary heard on this topic is “what degree of protection from a spill does a double-hulled tanker actually represent?” In collaboration with Dr. Iain Braidwood, a colleague in the tanker industry and an acknowledged expert in tanker construction, this writer has recently completed a review of this very subject, which was presented at an International Conference in London in May, 2018.[10] The short answer is that double-hull tanker structures will resist penetration of the inner (cargo-carrying) tank structure in right angle collisions between ships of equal mass at speeds of up to five to six knots. Obviously, in collisions at less than 90 degrees the speed must increase to result in the same depth of penetration (e.g., ~8-8.5 knots for a 45-degree collision). Given the limits on other ship traffic within the Port of Vancouver during tanker movements, the fact that there are no right angle large ship movements possible within the confines of this port, and the restriction to six knots speed, a spill-causing collision is effectively impossible in Vancouver. A minor incident, such as say an allision with a bridge abutment, would not have sufficient energy to breach the cargo tanks. Impacts from small vessels (such as a Seabus) also lack sufficient energy to breach a cargo tank.


Tanker movements along the B.C. coast are already limited to designated traffic corridors in a “Tanker Exclusion Zone” defined by Transport Canada.[11] The zone boundary follows the Canada/Alaska border to a point approximately 115 miles west of Langara Island, (Haida Gwaii) thence southward to approximately 73 miles southwest of Cape St. James, thence to 40 miles southwest of Amphitrite Point and thence due east to just off Cape Flattery. Similar restrictions could easily be applied to all other tanker movements.


Presently, non-tanker traffic only has to be 12 miles offshore to be considered in international waters. As witnessed by the Simushir incident, this is insufficient to prevent almost any incident offshore from becoming a grounding or near-grounding. For reasonable rescue towing response times, additional controls are required:

  • The further offshore, the greater (and more realistic) the response time and the lower the risk of a grounding. Disabled tankers drift at speeds of two to three knots in the most severe of local conditions.
  • For a 24-hour response window, ship traffic needs to be kept at least about 100 miles offshore.
  • This concept is not new, espoused by both Brander-Smith[12] and Anderson.[13]


The escort tug system proposed by TMX will create a system of powerful and capable escort and rescue tugboats which presently do not exist on the B.C. coast. These vessels, though dedicated to TMX tanker movements, could in many circumstances respond to other serious vessel incidents on the B.C. coast, helping to close the current significant void in suitable emergency towing capability. These assets would not appear however in the absence of the TMX project. Anticipating that any “tug of opportunity” will be able to render towing assistance in the more severe met-ocean conditions encountered off this coast is sheer folly; the size and capability of rescue towing tugs required simply do not exist in B.C. waters.


Tanker Safety can be virtually assured on the coast of B.C. by adopting the use of high-performance escort and rescue-capable tugboats, similar to those in use in every other major oil port worldwide today. The key to safe oil tanker shipments is in prevention and not simply having extensive oil spill response capacity, although the latter is also certainly a safeguard which must be present. The type of controls and restrictions on tanker movements as defined by the Vancouver Fraser Port Authority, in company with modern double-hull construction and the use of high-performance escort tugs in any critical or sensitive areas, will provide more than enough risk mitigation to ensure safe tanker navigation off the coast of B.C.


In the interval since this article was submitted for publication,  the Government of Canada has announced its intention to purchase the Trans-Mountain Pipeline. One must hope that whoever is ultimately responsible for the operation of the pipeline and the associated oil tanker movements will honour the TMX commitment to use the full scope of escort and support tugs envisioned under the TMX plan and follow that plan to the fullest extent possible. To do otherwise would be an irresponsible failure to follow best available technologies in this critical part of the operation.


Oil Spill Trajectory Modeling Report in Burrard Inlet for the Trans Mountain Expansion Project Genwest Systems Inc. Edmonds, Washington, USA http://vancouver.ca/images/web/pipeline/Genwest-oil-spill-model-report.pdf


Source: Prince William Sound Regional Citizens Advisory Committee (2017)


World Shipping Council, 2015 data

Major Marine Vessel Casualty Risk and Response Preparedness in British Columbia; Stafford Reid, EnviroEmerg Consulting for Living Oceans Society, 2008            



https://s3-us-west-2.amazonaws.com/transmountain-craftcms/documents/17-0... )

A Risk Profile for Escorted Tankers and their Resistance to Collision Damage
I Braidwood, C Eng, Ph D, MRINA, MSNAME, & R G Allan, P Eng, FEC, FRINA, FSNAME,
to be presented May16-18, 2018: Royal Institution of Naval Architects, Damaged Ship IV Conference, London UK.


Public Review Panel on Tanker Safety and Marine Spills Response Capability; David Brander-Smith QC et al, for Minister of Supply & Services Canada, 1990. Cat. No. EN21-91/1990E; ISBN 0-662-18089-5

Report to the Premier on Oil Transportation and Oil Spills, David Anderson, Nov. 1989