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The report says crews were installing a new pipe that was to cross underneath two existing pipelines, and the puncture happened as the crew created an observation hole needed 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 crew dug the hole, they created a six-centimetre crack in the pipeline. 

"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. "Construction crews no longer knew the exact location of the pipeline and therefore requested re-staking." 

The federal agency says it is reminding construction crews to positively identify buried facilities before digging nearby.

No one was injured in the event.

This report by ¹ú²úÓÕ»ó¸£Àû was first published June 29, 2026.