The thousands who drive daily along Highway 403 in Mississauga probably don’t know it, but where the highway curves sharply northward at Cawthra Rd., they are passing the highest-risk portion of an aging 833-kilometre pipeline.

The section of Enbridge’s Line 9 at the highway’s bend at Cawthra Rd. ranks highest for risk of any section between Sarnia and Montreal.

The Calgary-based pipeline company assigns risk scores to each 305-metre section of the pipeline based on its condition and known flaws such as cracks or corrosion, combined with the potential impact of a spill. Densely populated areas, river crossings or environmentally sensitive zones, for example, would have higher potential impact.

More than a third of the top 100 riskiest sections are within the GTA, either in Peel Region or Toronto.

The news came as a surprise to Mississauga Mayor Hazel McCallion.

“We’re not aware of the statement that it’s (Cawthra Rd. and Highway 403) the highest risk rank of any section of the pipeline between Sarnia and Montreal,” she said.

“We’re following it (the pipeline’s risk) very closely. We’re waiting for a report from Enbridge.”

Enbridge has applied to increase permitted flow along the 38-year-old pipeline by 25 per cent, from 240,000 to 300,000 barrels of crude oil a day, though in recent years the pipeline has only transported about 64,000 barrels a day.

Enbridge also wants to reverse the flow from westbound to eastward and get permission to transport unconventional crude oil, including diluted bitumen from Alberta’s oilsands and light crude from the Bakken formation in North Dakota and south Saskatchewan.

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According to documents Enbridge submitted to the National Energy Board in its application, the No. 1 spot is “viewed as being at highest risk due to an assessment of external corrosion likelihood and the presence of high populated and environmentally sensitive areas.” It notes the defect that had been causing the external corrosion has been repaired.

Nearby sections, where Line 9 crosses Hurontario St., Etobicoke Creek and Tomken Rd., are also listed among the 30 highest-risk locations.

In Toronto, the section that passes along the Finch hydro corridor just north of Fountainhead Dr., where a cluster of four 23-storey apartment buildings stands, is ranked 15th. The section where it passes under G. Ross Lord Reservoir on Dufferin St. near Finch Ave. W. is 24th.

Meanwhile, other locations that Line 9 rubs up against, such as the Finch subway station and the Rouge River, which have generated considerable public attention, rank relatively low on the risk scale.

At the Finch subway station, the pipeline runs less than two metres below the sidewalk and 60 centimetres above the subway structure, cinched between the stairwell of the Bishop Ave. entrance and escalators leading to the Metrolinx terminal.

Toronto officials earlier warned that neither the transit commission, municipal emergency services nor Enbridge had any contingency plan for a leak near the Finch subway entrances.

“If any petroleum product was discharged either down the stairs or the escalators, or by other routes into the TTC concourse, platform or track level, there would be an enormous risk to thousands of daily passengers and TTC workers,” the city cautioned in written submissions to the energy board.

But the Finch subway area is ranked at 196th. The pipe is encased in concrete and steel where it passes the subway, which would direct oil flow away from the interior of the station, and Enbridge has since agreed to devise emergency plans with city officials.

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“If a location like the Finch subway station, for example, is not identified as a top risk location it would be because there are no known features or conditions on the pipeline at that location, making the likelihood of a release at that location very low,” said Enbridge spokesperson Graham White. “All locations that reach the threshold for inspection are investigated and repaired.”

The National Energy Board is considering Enbridge’s application. A decision, which would require the federal government’s approval, is expected soon.

With files from San Grewal

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