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Finding cause of blast will take time

Clues sought in pipeline remains and soil

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It only took days to get the gas flowing again. It'll take a lot longer to find out why it stopped flowing in the first place.

With the restoration of natural gas service underway southeast of Winnipeg, TransCanada PipeLines must now figure out what caused an explosion along one of the lines it first strung through the Red River Valley more than 50 years ago.

At about 1 a.m. Saturday, a fireball erupted near the village of Otterburne at a valve station on TransCanada's Emerson Lateral line, a series of three parallel lines that carry gas from the Calgary-based energy company's east-west main line down to the Canada-U.S. border.

The explosion and resulting fire left behind a crater that appears to be about 10 metres wide, based on aerial photographs taken Monday.

It also created more unease about oil-and-gas transportation in a country already sensitized to petro-disaster by oil-train accidents in Quebec and New Brunswick.

The cause of the Otterburne blast won't be known for weeks at the very earliest. Investigators from the Transportation Safety Board, along with National Energy Board staffers and TransCanada officials, first must examine the remains of the pipeline as well as the soil around it for physical and chemical clues as to what transpired.

"We simply do not know at this time," said Karl Johansson, TransCanada's executive vice-president and the head of its natural-gas division, speaking to reporters in Ile-des-Chênes on Monday.

"It's going to take time before we can figure out the cause of this fire and it's going to take some evaluation and analysis before we can give you an answer on what exactly has occurred."

The last time a TransCanada line exploded in this province -- in 2002, near the western Manitoba village of Brookdale -- the cause was determined to be stress corrosion cracking, or the chemical weakening of the pipe.

The explosion prior to that, near St. Norbert in 1996, was caused by the interaction of a slumping riverbank and a pre-existing defect in the pipe.

This weekend's incident is unusual because it took place at a valve station, where the flow of gas can be controlled. "We haven't seen an instance like this at a valve site for a very, very long time," Johansson said.

All that is known right now is one of three pipes in the Emerson Lateral line caught fire and exploded, damaging a second line and leading to a temporary reduction in flow to a third.

The first line to explode, a 76-centimetre-wide pipe, was built in 1960. Johansson said the pipe gets inspected from the outside every year, both visually, through aerial images, and chemically, with methane-sniffing equipment.

The line was last inspected from the inside in 2009 and no problems were found. Internal inspections are conducted by deploying devices known as "smart pigs" into the lines. These machines use electrical sensors and sound waves to discover defects ranging from disbonded outer coating -- a layer of tar or asphalt that protects the pipe from corrosion -- to cracks in the pipe.

Mark Yeomans, TransCanada's vice-president of pipeline integrity, said the pipe that blew up was also outfitted with cathodic protection, which is a sacrificial metal wire that helps prevent the pipe from corroding.

"TransCanada is considered one of the experts in stress corrosion cracking and natural gas pipelines," said Johansson, opining a rigorous inspection and maintenance regime can extend the life of a pipe to many decades. "Properly maintained, we don't have a period of time when we would pull those lines out."

Corrosion may not be to blame, however. The TransCanada officials said it's too soon to even speculate about the cause of the explosion. They said their staff are directed every step of the way in their investigation by the Transportation Safety Board and National Energy Board, which have at least five people on the ground right now.

"TransCanada takes this very, very seriously," Johansson said.

bartley.kives@freepress.mb.ca

Republished from the Winnipeg Free Press print edition January 28, 2014 A4

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