Corrosion, construction defects and cracking are the main causes of pipeline incidents in Canada, according to a new report on the industry's performance.
Other causes of leaks include flooding, land movement and damage caused by digging often not related to pipeline activity.
The Canadian Energy Pipeline Association (CEPA), which represents the vast majority of all pipelines in the country, released the report.
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In 2015, about 16 barrels of crude oil spilled from pipelines, the equivalent of just over nine average-sized bathtubs filled to the brim, according to the report.
Meanwhile, 121.3 million cubic feet of natural gas leaked, which is the equivalent of 859,000 propane barbecue tanks, according to CEPA.
"It's not something to be concerned or alarmed about," said Chris Bloomer, CEPA's chief executive. "When you look at the natural gas pipelines moving over five trillion cubic feet a year, that's a very insignificant amount."
The report provided information about the various sources of pipeline leaks, of which metal loss (or corrosion) was the lead cause. Regardless of the type of metal and coatings used, pipeline walls can corrode. Inspectors use several tools to judge the severity of the metal loss.
"That is something you track and manage and it just comes with the turf," said Bloomer.
The other main cause was manufacturing and construction defects. Bloomer suggests it is hard to avoid since "even with the best construction practices, things happen."
There are two sources largely not at fault of industry. Some leaks occur when pipelines are accidently hit, such as by a construction or excavation crew.
"They do create issues where there is damage. Generally they aren't very severe, but they can be," he said.
In addition, heavy rainfall, flooding and land movement (known as geotechnical) have also created spills.
CEPA released its report to increase the industry's transparency. The full report is available here.