After a 13-month investigation into a rupture and fire in northern British Columbia (BC), Enbridge Inc. has received permission to refill Canada’s oldest natural gas export pipeline, Westcoast Transmission.

The approval by the Canada Energy Regulator (CER) ends a safety restriction that cut the Enbridge subsidiary’s operating pressure, disrupting supplies and prices along the Pacific coast of the United States and BC since the accident Oct. 9, 2018.

Westcoast deliveries to the U.S. Pacific Northwest shrank by an estimated 200 MMcf/d. BC consumers in the thickly populated Vancouver region adopted gas conservation measures.

The lingering BC supply loss fueled the tallest American spot price spike recorded in five years by NGI -- $161.330/MMBtu on March 1 at the Sumas border crossing into Washington.

The CER described the long investigation and flow cut on the 62-year-old Westcoast system as an example of thorough safety control enforced on all Canadian pipelines under federal jurisdiction.

“We expect our regulated companies to have zero spills or incidents,” CER said in a statement that disclosed Westcoast’s clearance to restore shipping service to full capacity as of Nov. 28.

“What many people may not realize is that our work continues long after the immediate threat of an incident has passed,” said CER chief engineer Iain Colquhoun.

“Figuring out precisely why it happened, and what improvements need to be made to minimize the likelihood of it happening again is what matters as we continue to ensure companies prevent harm to people and protect our environment.”

In the Westcoast accident investigation Colquhoun led a team of six pipeline integrity specialists and engineers who performed detailed safety inspections on all 1,040 kilometers (650 miles) of the BC pipeline.

While CER and Enbridge have not yet disclosed precise causes of the October 2018 accident, a parallel facilities improvement case indicated that increased traffic strained the Westcoast system.

Enbridge received approval in September for a C$740 million ($555 million) upgrade of Westcoast. CER authorized compressor upgrades and a 15% capacity increase to 1.5 Bcf/d to improve reliability.

Westcoast gas traffic grew at a brisk pace for six years before the 2018 accident. The number of days when deliveries topped 1.6 Bcf jumped from zero in 2012 to 30 in 2013, then quadrupled to 130 last year.

The BC gas pipeline subsidiary of Enbridge also disclosed worsening wear and tear. The annual number of unplanned repairs on the pipeline rose by 60% to 2,400 during 2017 from 1,500 in 2012.

“Beginning in 2013/2014, there was a fundamental shift in demand [for deliveries],” according to the BC pipeline disclosures. “Winter season demand is now consistently at levels formerly only seen during weather-related peaks.”