I had begun hearing about the Mariner East 2 pipeline (the Dragonpipe) during the summer and fall of 2016. But it wasn’t until January of 2017 that the magnitude of the risk started to become clear to me. That was when I learned of the San Bruno pipeline explosion in California.

I will return shortly to the question of whether the San Bruno event is really comparable to a Dragonpipe explosion, if one occurred in our area. First, though, what happened in San Bruno?

The San Bruno explosion. On September 9, 2010, just after 6pm, a 30-inch natural gas pipeline serving San Francisco blew up in a huge fireball in the suburban neighborhood of San Bruno. Since the area is near the San Francisco airport, the explosion was initially thought to be due to a jetliner crash. But within an hour it became clear that a gas line was at fault.

San Bruno destruction

After the San Bruno explosion. Source of photos: Pipeline Accident Report Pacific Gas and Electric Company Natural Gas Transmission Pipeline Rupture and Fire San Bruno, California September 9, 2010.

Eight people were killed, dozens more were injured, and 38 homes were destroyed. The fire, which continued to be fed by gas remaining in the pipe, could not be extinguished and continued burning until noon the next day. Minor fires and hotspots continued to be a problem for many hours more. The power of the explosion was such that a 3,000-pound section of the steel pipe, which had been buried under a paved street, ended up 100 feet from its original location.

I’ve been to San Bruno, and it is relatively densely populated, similar to many of the suburban Philadelphia communities through which the Dragonpipe will pass. Could an explosion of the Dragonpipe in Aston, Goshen, or Exton create the kind of disaster that San Bruno experienced? Is our pipeline as dangerous as theirs was?

Unfortunately, the answer is a clear “yes”. In fact, it could be worse.

The San Bruno pipe was 30 inches in diameter, bigger than any of the three comprising the Dragonpipe (which is actually a trio of pipes with diameters of 8, 16, and 20 inches). But the San Bruno pipe carried only natural gas (mostly methane), and the products flowing through the Dragonpipe (ethane, butane, and propane) are several times more explosive than methane at the same pressure. And they will NOT be at the same pressure. The San Bruno pipeline’s pressure was less than 400 psi, compared with 1,500 psi in the Dragonpipe (the pressure needed to keep the gases condensed into a dense liquid). A back-of-the-envelope calculation shows that the explosive power that would be released in the event of an explosion of either the 16-inch or the 20-inch Dragonpipe would be far greater than that of the San Bruno event.

As you can see from the photo below, the destruction in San Bruno reached a maximum distance of about 700 feet from the site of the pipeline rupture. Damage from a rupture in the Dragonpipe could easily extend well beyond 1000 feet and encompass more than double the area.

San Bruno houses destroyedDamage to San Bruno neighborhood. (Photo source: Pipeline Accident Report, cited above)

San Bruno neighborhood now

San Bruno neighborhood now (Google Maps)

No one in San Bruno recognized, and prepared for, the dangers posed by their pipeline. Would our local preparedness and evacuation plans help minimize the destruction? Sadly, no. With a fireball like the one in San Bruno, there is no warning and no escape. Even if the pipeline operators were able to detect a drop in pipeline pressure and provide a timely warning before the gas ignited (unlikely), there is no safe procedure for evacuation in the presence of an invisible, odorless fog of highly-explosive gas.

The existence of evacuation plans may be reassuring to those in the area of the Dragonpipe, but they are a sham. If there is a significant leak, there will almost certainly be an explosion. And if the leak and explosion are in a populated area, people will die.

If you want more details about the San Bruno explosion, read the report of the panel that analyzed what led to it and what the emergency response was.  It is a sobering document. The resources available in San Bruno were far greater than those in most communities along the Dragonpipe, and still there was little they could do.