Blowdown Notification – SE 7-25-17 W4M

Date: May 6, 2025
Time: Daily between 8 a.m. to 12 p.m.

A blowdown is the act of releasing natural gas from the pipeline system so work can be done safely on the depressurized facilities. TC Energy employees will close the required valves to isolate the facilities and then open a blowdown valve to safely depressurize in a controlled manner. A loud roaring sound may occur when the natural gas is released, although TC Energy may employ tools to minimize this noise whenever possible.

The sound during a blowdown can be as loud as an airplane engine and may last anywhere from a few minutes to multiple hours, depending on the amount of pipe being depressurized. As the flow of gas gradually slows down, the noise also lessens.

After the natural gas is released, a funnel-shaped air expeller is placed on top of the blowdown valve opening, which draws any remaining gas out and makes it safe for activities such as welding.

Once maintenance is complete, work begins to safely bring the line back into service. Natural gas is sent back into the pipeline and, once it reaches pressure, the blowdown valve is opened once again to vent the atmospheric air. Once all the air is removed, the blowdown valve is closed. The line is then pressurized to its normal operating pressure.