On any given day, a dozen deep-sea freighters rest at anchor in English Bay, waiting to dock in Vancouver's busy harbour.
For most people, those ships and the others in transit are a beautiful sight and part of the city's scenic backdrop. So you might think a proposal to add one more ship a day to that mix wouldn't raise any concerns.
But in nature-loving Vancouver, where about 8,000 people walk or bike the Seawall on a typical summer day, with 14,000 more using the beaches, that proposed increase in tanker traffic has raised real fears because the additional ships will be filled with oil.
If the Trans Mountain Pipeline proposal, now under review by a parliamentary panel, is approved, oil tanker traffic through the harbour will increase from about one a week, to one a day. (The exact figures are from five a month to 34 a month.)
To many, the increased risk of an oil spill from the growing traffic is just too great.
But just how big a risk is there?
Proponents of the project say there is almost no chance there will ever be a spill, while critics contend it's not a matter of if, but when a spill will occur.
Last week's column examined the safety record of tugs and Trans Mountain's claim that tugboat escorts will ensure tanker safety. In response to that column, experts have weighed in with strongly opposing views.
Robert Allan, executive chairman of the board for Robert Allan Ltd., a Vancouver-based naval architectural firm that designs high-performance tugboats for tanker escort, said the standards met by modern vessels are so high, the safety precautions so refined, that a significant accident of any kind involving an oil tanker in Vancouver harbour is almost zero.
"Of course any vessel can have an accident, but when a full-fledged tanker safety plan is in place with pilots, properly equipped double-hulled ships, multiple properly designed escort tugs, fully trained tug crews and a well-developed and practised operational plan, then the risks are as low as they can possibly be," he wrote in an e-mail.
Mr. Allan said no system is absolutely foolproof, but there are so many layers to the oil tanker safety plan that tankers transiting Vancouver harbour with proper escort tugs "will be as close to 100 per cent safe as any form of transportation [can be].
"Those who paint different pictures for whatever political purpose are simply displaying an unwillingness to recognize that the risk of an oil-spilling incident in local waters can be reduced to as close to nil as humanly possible through advanced engineering and the application of well-considered, safety-conscious operational plans," he states.
But Ricardo Foschi, a retired emeritus professor of civil engineering at the University of British Columbia, has a very different view of the risk factor.
Dr. Foschi examined the risk analysis Trans Mountain submitted to the National Energy Board and concluded it "has suffered from both flawed predictions (intentionally or not) and a lack of completeness in assessing risks and consequences."
In particular, he took issue with Trans Mountain's submission that the "return period" for a spill of any size from project-related tankers would be one in 237 years.
Dr. Foschi said most people would interpret that to mean that there likely won't be a spill for 237 years.
"This interpretation is wrong and misleading! In fact, the definition of a return period is the average of the time intervals elapsed between spills. Being an average, it means that, roughly, half of the spills would occur before 237 years and the other half after 237 years," he wrote. "The real question should be (which is not answered by the proponents) 'what is the chance that a spill of any volume may occur at any time within the operational life of the project?' Mathematically, if the return period is 237 years, then the chance (or probability) of a spill of any size occurring in 50 years (the life of the project) is 19 per cent. Is this safe? Certainly not."
Dr. Foschi is also worried that oil tankers, even with tug escorts, might collide with the Second Narrows highway and railway bridges.
What are the odds of that? We don't know, he said, because the NEB didn't ask that question.
Dr. Foschi says government approval of the pipeline project should be delayed "until a more thorough study is presented."
It is hard to see how the government can make a final decision on the project until they have a clear answer on fundamental questions, such as: What are the chances of an accident? Is it nil? Or is there a 19-per-cent likelihood of one in 50 years?
The federal government's decision is expected in December.