(Adds stress factor, interview with investigator)
By Rod Nickel
WINNIPEG, Manitoba, March 4 (Reuters) - An explosion and
fire in 2018 along an Enbridge Inc natural gas pipeline
in northern British Columbia was caused by normal stress that,
coupled with corrosion, created cracks, Canada's Transportation
Safety Board (TSB) said on Wednesday.
The pipeline operated by Enbridge subsidiary Westcoast
Energy Inc ruptured on Oct. 9, 2018, in a forested area near
Prince George. No one was injured, but the blast led to the
evacuation of 125 people, including from the Lheidli T'enneh
First Nation.
Police photos from a helicopter showed a nine-meter-deep
crater and dozens of scorched evergreen trees at the site.
The temporary shutdown of the line, which carries gas
destined for the Pacific Northwest, led to disruptions for
refineries owned by Royal Dutch Shell and Phillips 66
in the U.S. state of Washington.
The TSB said in a report that polyethylene tape used to
protect the pipeline's surface had deteriorated, allowing
moisture underneath and corrosion to develop. Stress on the
pipeline that was caused by normal operations, combined with the
corrosion, created the cracks, in a phenomenon known as "stress
corrosion cracking," said TSB senior investigator Jennifer
Philopoulos.
The board, an independent agency that reports to Parliament,
said it had investigated three other ruptures since 2002 with a
similar cause, all on TC Energy lines.
That section of line was last inspected 10 years before the
blast, and was scheduled for inspection the week the incident
occurred, said Michele Harradence, Enbridge's senior
vice-president of gas transmission and midstream.
"These are very stressful things to occur in your community
and we apologize for that," Harradence said in an interview from
Houston, Texas.
Enbridge has since begun integrity assessments of all its
gas pipelines in North America, adopted newer tools to detect
problems, expanded inspection criteria and increased scheduled
excavations to examine pipelines, she said.
The Canada Energy Regulator did not lay charges against
Enbridge.
(Reporting by Rod Nickel in Winnipeg, Manitoba; Editing by
Matthew Lewis and Grant McCool)
