Enbridge estimates about 31-thousand barrels of propane and butane vaporized because of a leak in the Line 5 pipeline near Saxon in Iron County.
Another 2,000 barrels of liquid product were believed to be in the excavation site as of Saturday evening.
The leak occurred when a parked, unoccupied semi rolled into an open excavation at a Line 5 valve project.
The truck struck the pipe and released natural gas liquids.
Natural gas liquids (NGLs), which are mainly propane and butane, are transported by pipeline as liquids.
When exposed to normal outdoor conditions, they rapidly vaporize into gases.
Enbridge says it will use trailer-mounted flare stacks to burn away hydrocarbon vapors in a controlled way.
Enbridge started using those flare stacks on Sunday.
A half mile evacuation zone around the site remains in place.
The Iron County Sheriff’s Office has instituted a “no fly” zone over the site.
Line 5 remains shut down, with the damaged section isolated.
Enbridge hopes to get the pipeline back into service by September 5th.
The company says air monitoring shows safe air quality where crews are working and in the surrounding area.
