Public hearings are underway on a controversial proposal to reverse the flow and increase the capacity of a 38-year-old oil pipeline running between Montreal and southern Ontario.

The Montreal leg of the hearings, which run through Friday, are being conducted by the National Energy Board.

Enbridge, the pipeline’s owner, reversed the flow of oil in Line 9 once already in 1998. The Calgary-based company wants to reverse the flow once again to carry an expanded supply of crude oil from Alberta to Quebec’s two refineries and its petrochemical industries.

The National Energy Board has already approved the company’s application to reverse the flow of oil through an Ontario section of the pipeline, known as Line 9A.

It could take up to three months to rule on Enbridge’s application to reverse the flow on the 639-kilometre stretch known as Line 9B, which runs between southern Ontario and Montreal.

Opponents of the proposal say Line 9 is too old to handle both the reversal and the increased flow of what they believe will be heavier, more corrosive crude oil.

Steven Guilbeault, director of the environmental group Équiterre, believes the aging line and the added stress of more corrosive oil passing through it heightens the chances of a rupture and a major spill.

“This is a very risky proposal, especially for the greater Montreal area,” he said. “This is an old pipeline that was never built to handle heavy crude like the tarsands.”

Guilbeault pointed to an incident in 2010 that saw a ruptured Enbridge pipeline spill thousands of gallons of crude oil into Michigan’s Kalamazoo River as evidence that the company’s operations are not failsafe.

Enbridge said it learned from the Kalamazoo spill and claims Line 9’s safety is its chief concern.

The company denies the claim that diluted bitumen from Alberta’s oilsands is more corrosive, and pointed to studies suggesting this by the National Academy of Sciences.

“For us it’s a chance to bring science and make sure the debate is based on fact and not impressions,” said Enbridge spokesman Eric Prud’Homme.

The company says Line 9 is monitored closely 24 hours a day and valves can be shut down in under 10 minutes in the event of a rupture.

Dimitri Tsingakis, General Manager of the East Montreal Industrial Association, said the reversal of Line 9 would benefit the city’s beleaguered petrochemical industry.

“Line 9 reversal is critical for the east-end of Montreal because it provides us with an alternative supply which is more economical,” he said. “Refineries that don’t have access to western oil are at a disadvantage. It’s a more competitive source of crude oil.”