Boot road pump station annotatedv2 8-6-19
View looking south, showing the pumping station and other structures along Boot Road. (Google image.)

On Monday night (August 5, 2019), there was an explosion at Sunoco’s Mariner East pumping station at Route 202 and Boot Road in Chester County. It was felt from over half a mile away (some reports indicate it was over a mile). As it turns out, it had something to do with material that escaped from the Dragonpipe (the Mariner East pipeline system).  Sunoco is not willing to reveal much about the cause. Fortunately, as far as we know, no one was hurt.

Although details are scarce, the explosion did provide a good opportunity to test Sunoco’s alerting process and our local emergency response capabilities, which ranged from very poor to non-existent.

What was the nature of the explosion? It’s hard to say exactly what happened to cause the explosion. Sunoco has not been forthcoming with an explanation. They put out a message saying:

“During routine maintenance this evening at our Boot Station in West Goshen Township, there was a backfire on a flare at approximately 8:00 p.m. as the station was brought back online. This resulted in a loud noise, similar to a car backfiring. We apologize for any inconvenience this may have caused to our neighbors.”

Just what is meant by a “backfire on a flare”? An explosion in a flare stack could never be “routine”. Routine operation of a flare stack involves a constant pilot and a constant, small flow of air or natural gas for continuous ignition, 24 hours a day. To me, an explosion means one of two things: either there was a problem with the flare stack (pilot went out or normal flow was interrupted) or there was a sudden, unplanned release of explosive gas. Sunoco has mentioned “relighting the pilot” as a cause of the explosion.

A Sunoco spokesperson told StateImpact that “ME2” was affected and was shut down for maintenance at the time. There was no risk to the public, she said. (What Sunoco calls “ME2” is actually a string of old and new pipelines that were patched together at the end of 2018. In the area of the pumping station, the pipeline involved is a 12-inch pipeline from the 1930s.)

At the East Goshen Township supervisors’ meeting on Tuesday night, it was stated that failure of a safety valve was a factor in the explosion. There has been no public statement from Sunoco confirming this.

The explosion was quite powerful, shaking the houses in the area. There were reports of windows rattling and paintings falling off of walls. It was far more than “a loud noise, similar to a car backfiring.”

How serious could it have been? While the specifics are murky, this much seems to be clear: there was a large, unintentional release of explosive gas. My understanding of Sunoco’s use of “ME2” is that it currently transports butane and propane, so the gas involved was probably one of those, or a mixture. The gas ignited inside the flare stack.

If the pilot flame in the flare stack went out and had not been re-lit in time to burn the released gas, that would have been a very serious issue. Consider what would have happened in that case. The gas would have been carried out the top of the flare stack by the moving air, and then would have cascaded down the outside. These gases are heavier than air, so they would have spread along the ground into the surrounding area, accumulating in low-lying areas and forming a flammable cloud. Depending on the volume of gas and the elapsed time before an ignition source was encountered, a large area surrounding the pumping station could have been set on fire.

If there really was a failure of a safety valve, as reported at the supervisors’ meeting, that could have caused a pressure build-up, causing an equipment or pipeline failure and a release of gases in a location not connected to the flare stack. That sounds like the beginning of a worst-case nightmare.

The fact that there was “only” an explosion within the flare stack must be considered a blessing—and a warning about what might have happened.

What was the nature of the emergency response? In the wake of the explosion, there was confusion. Many people called 911 or the Sunoco emergency number, but they were not told what action to take. Sunoco has been telling us for years that, in case of a release, the best plan is for people to self-evacuate and walk upwind. They say that local emergency responders have received training in how to respond to an accident.

As far as I have been able to learn, Sunoco did not notify anyone (not even emergency teams and first responders) of the release that led to the explosion or of the explosion itself. And no one was notified to self-evacuate. The local police were the first to arrive on the scene, and I am told they did not know what to tell people to do. They did not cordon off the area. No one sent out any kind of notification to the general public.

What should have been done? Until we know the details of the event, we won’t really know what actions should have been taken by Sunoco and by the local authorities. There are many unanswered questions at this point. Here are some I’d like answers to:

  • Did Sunoco contact local emergency personnel the minute they knew there had been a release?
  • How long did the release go on before the explosion, and what was the volume of gas released?
  • Was Sunoco as surprised by the explosion as local residents were? If so, how did the release go undetected?
  • Was the explosion a result of operator error? Of equipment failure?
  • Did local authorities know what action to take in a case like this? Were those plans ever activated during this incident?
  • Did Sunoco know in advance that this kind of explosion was likely? Did they notify anyone?

What needs to happen now. We desperately need to learn the lessons of this event. We dodged a bullet this time. The next time, we may not be so lucky. If this explosion had not happened within the confines of a pumping station equipped with a flare stack, there is a good chance that people would have been killed.

The PUC needs to shut down the pipeline and review the details of this accident. We need to know why the appropriate emergency response measures were never activated. We need to know what caused the explosion and what failures (of people, procedures, or equipment) led up to it. We need clarity about exactly what Sunoco and first responders will do the next time—for there surely will be a next time, and its consequences could be far worse.

Let your elected representatives (and Governor Wolf in particular) know that this pipeline must be shut down until Sunoco can prove that it can be operated safely. There are many questions surrounding this explosion, but there is one thing we now know for sure: Sunoco is not ready to deal with a potential pipeline catastrophe, and neither are our local emergency systems. This situation must be remedied: people’s lives hang in the balance.

This post has been updated to reflect that Sunoco’s “Boot Station” is not just a valve station, it is a pumping station.