Frequently Asked Questions

Because Upper Uwchlan Township did not have any regulatory authority over the repurposing of Mariner East 1 and has not had any regulatory authority over Sunoco’s proposed construction of Mariner East 2. Upper Uwchlan Township does not have enforcement or regulatory authority over the location of underground transmission pipelines, or whether a pipeline is constructed by horizontal directional drilling or open trench construction, or the type of product that will flow through the new pipelines or any of the existing pipelines.  To the extent there are regulations for underground transmission pipeline siting, methods of construction or use, they are enforced by federal and state agencies.  

It depends on the incident.  There is no one size fits all response to a pipeline accident, or any other kind of accident or emergency. In some cases, emergency responders will want people to stay in place because they already are safe. In others, they will want people within a certain vicinity of the incident to evacuate. The extent and direction of an evacuation would depend on the nature of the accident, weather conditions at that time and any other factors affecting conditions on the ground.

If there were a major pipeline emergency, many fire, ambulance and police departments would respond. There would be numerous first responders on the scene working to get people to safety. As a result, people near the emergency would find out quickly what they should do.

They already have.  Every year, first responders from our local fire companies and Chester County’s Hazardous Materials Response Team receive hazmat training to respond to incidents involving natural gas, natural gas liquids and many other types of hazards.  They are trained and prepared to respond to a pipeline emergency and will direct people where to go (or stay) to be safe.

This scenario is not impossible, but it is very unlikely.  You would have to be close enough to the leak in an environment that has the exact mixture of flammable vapors and air required for ignition, and even then, the chance of the phone as an ignition source is small. The many benefits from calling in an emergency or receiving emergency notifications far outweigh the small risk of a spark.

As a reminder, if you smell or hear gas outside that you think may come from a leak, please walk away before calling 911.

The Mariner East 2 pipeline will be at least 4 feet underground.  The portions of the pipeline installed by horizontal directional drilling will be anywhere from 20 to 220 feet underground.  If there is a leak deep underground, you will not see it.  The first likely sign will be a decrease in pressure detected by the pipeline system, which would trigger shut off.  Required inspections also can detect issues that may arise inside the pipe or with the protective coating.

For leaks closer to the surface, here is guidance:    

• Because pipelines transporting NGLs are pressurized to keep the product in a liquid form, you would hear a hissing sound from a leak, like air coming out of a balloon.
• Similarly, if the leak occurred in water or even a puddle, the pressure would cause bubbling.
• NGLs that leak into the atmosphere typically would form a visible vapor cloud, like white mist or smoke, as water molecules in the air condense when mixing with the cold gas.  Because the vapors from the NGLs are heavier than air, they would tend to hang low to the ground.
• If the leak is underground but close enough to the surface to impact vegetation, you may see dead grass or a brown spot in otherwise healthy vegetation, or an isolated area of frost on the ground.

Companies transporting natural gas to end users, such as PECO, often add odorant to add in detection.  Sunoco cannot add odorant to the NGLs in the Mariner East system because of the potential end uses of the products, such as textiles and plastics.