vapor cloud at refinery 10-17-19
A security camera captured this image of the vapor cloud starting to flow through the Philadelphia refinery, just before it exploded.

In case there’s a leak in the Dragonpipe (Mariner East pipeline system), Sunoco tells us to “walk uphill and upwind half a mile”. The newly-released security-camera video from the Philadelphia refinery explosion on June 21 shows exactly how futile that would be.

The video can be viewed here.

In the video, a vapor cloud (which we now know was primarily created by escaping propane, one of the highly-volatile liquids that is also carried by the Mariner East system) flows into the picture and then explodes.

Note that the visible vapor is probably water droplets, condensed from the air because the propane had become extremely cold as it escaped from its pressurized tank. The propane itself is invisible and presumably extends well beyond the visible vapor cloud.

Some preliminary details about the accident have been published by investigators from the Chemical Safety Board. Their report, called a “Factual Update”, is available here. They have determined that the flammable cloud was 95% propane. (The rest was mostly hydrofluoric acid, a really vicious chemical which we are fortunate that Mariner East does not carry.)

The probable rupture site was in the elbow joint of a pipe, installed in the 1970s, that had corroded to 0.012 inch (“about half the thickness of a credit card”, according to the report). The remaining metal was only 7% of the thickness that is supposed to be maintained prior to replacing the pipe. Pressure in the pipe was about 380 psi—a fraction of the Mariner East pressure. Chemical analysis suggests that sub-standard steel was used in the elbow.

What if this happened in a residential area? Now imagine a rupture like this in a residential area along the Mariner East system. Suppose you saw a rapidly-spreading cloud like the one in the video coming down your street, or coming toward you across a parking lot. Suppose you were driving and you saw it suddenly start flowing across the road in front of you.

At that point, it’s too late. A disaster is inevitable. People will be killed.

NBC 10 reports that “Federal investigators said that one of the most amazing things in their findings was that no one died.” But that’s because that leak was in a sparsely-staffed refinery in the middle of the night. If that had been a residential area instead of an industrial one, the result would have been far different.

The time to prevent a disaster is not when there is an actual rupture. Of course, the best time to stop the Mariner East project would have been years ago, when Sunoco was deciding whether to build this deadly pipeline. But the next-best time is now: we must shut this pipeline down, now.

Once there is a major leak, Sunoco’s emergency plan will not work. No emergency plan will work. It is too late.