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A federal investigation has found the puncture of a natural gas pipeline in northeastern B.C. last November was caused by an inaccurate identification of the pipeline’s location.
The Transportation Safety Board says in its investigation report that the accident happened along a stretch of pipeline operated by Westcoast Energy Ltd. about 150 kilometres northwest of Fort St. John.
The report says crews were installing a new pipe that was to cross underneath two existing pipelines, and the puncture happened as they created an observation hole to track the path of the boring operation.
The investigation shows that a pipe was inserted vertically into the hole to shore up unstable soil conditions and push through an obstruction, then the crew noticed a smell of gas and workers were evacuated from the area.
The safety board says about 47,000 cubic metres, or almost 20 Olympic-size swimming pools, of natural gas was released but it didn’t ignite and there was no explosion.
Investigators say a previous aboveground locator stake showing where the pipeline was had been removed during cleanup, and a new stake was placed without verification. Then, when the crew dug the hole, they hit the pipeline, cracking it by six centimetres.
“When changing site conditions resulted in the removal of the 2-inch-by-4-inch wooden post, the location of the pipeline was no longer positively identified,” the report says.
“The construction crew began [drilling] the observation hole, [and] they relied on the incorrectly positioned stake,” it concludes.
The federal agency says it is reminding construction crews to positively identify buried facilities before digging nearby.
No one was injured in the event.