Different Types of Pipelines
There is quite a bit of misinformation that gets thrown around regarding the Mariner East pipeline and the Natural Gas Liquids it will carry. It is prudent to clarify exactly what is planned and what it means for public safety.
The proposed 20 inch diameter Mariner East 2 pipeline would move as many as 450,000 barrels or 18.9 million gallons of liquefied ethane, propane, and butane per day. These gas products, artificially liquefied within the pipeline under high pressure, are commonly referred to as Natural Gas Liquids (NGLs).
There is some confusion about NGLs and how they compare to naturally liquid petroleum or the natural gas with which we are more familiar. Let's address each type of product from a public safety perspective (ignoring environmental concerns):
Naturally Liquid Petroleum Products (NOT Carried by Mariner East): These products include unrefined crude oil, gasoline, and diesel fuels. These products are liquid inside the pipe and remain liquid if leaked. Leaked liquid product can catch fire but is not as easy to ignite as a gas. When gasoline is used in your car, it is sprayed into the combustion chamber in a way that ensures it has a fuel-to- air ratio that is ideal, typically 2-7%. When the gasoline leaks from a pipeline, it flows along the ground as a bulk liquid that is well above gasoline’s 8% maximum flammable range. The leaked liquid product certainly poses environmental impacts and requires Hazmat protocol. However, from a public safety perspective, it is less likely to explode, more likely to be contained, and far easier to stop active leaks than gaseous products.
Typical Natural Gas (NOT Carried by Mariner East): This Natural Gas refers to Methane, a gaseous fuel that is odorless, colorless, and poses high risk of asphyxiation when in atmosphere. Methane is always a gas inside a typical ground- based pipeline, even at the highest operating pressures. If it leaks, it remains a gas that is highly combustible and easily ignites. Methane is lighter than air and therefore rises and dissipates. As a result, the worst case emergency is relatively predictable. It occurs when leaked methane gas ignites at the pipeline or when the gas is unable to escape into the atmosphere. Both cases result in high risk of asphyxiation and a huge explosion if ignited. The size of the explosion has everything to do with how much fuel is present. Larger pipelines contain more product per linear foot. Higher pressure pipelines contain denser gas. Both pipe size and pressure have a direct effect on a pipeline’s explosive power. However, since Methane is always a gas, the threat can be significantly reduced by closing valves and isolating the leak. The gas pressure inside the pipe is relatively low in comparison to NGLs. Small leaks may even be approachable by emergency personnel once valves are closed and conditions are stable.
The United States has recognized the dangers associated with Methane Natural Gas. As a result, methane Natural Gas pipelines are regulated by the Natural Gas Act that gives the Federal Energy Regulatory Commission the authority to control, to some extent, where these methane pipelines are allowed to be run.
Natural Gas Liquids (NGLs) (Carried by Mariner East): NGLs are gaseous fuel products that are artificially liquefied under high pressure within pipeline. Ethane and Propane are examples of NGLs that are transferred via the Mariner East pipeline. These chemicals are colorless, odorless, and pose a high risk of asphyxiation when in atmosphere. If leaked, the gas is highly combustible and easily ignites, similar to Methane Natural Gas. This is where the similarities between Methane and NGLs end.
The fact that these products are only artificially liquids inside the pipe creates several potential hazards. These products do not want to be liquid in nature and if there is a leak, they behave very badly in their attempt to find equilibrium as a gas. NGLs will aerosol out of a leak at high speed and rapidly expand into a cryogenic gas. The same effect is experienced when you spray keyboard cleaner and the can gets cold as high speed gas removes dust from your keyboard. In the case of Mariner East, the product is a highly combustible fuel and the release temperatures are cryogenic. Due to the high speed and cryogenic properties of the leaked gas, virtually no leak is safe to approach and all leaks must fully purge before patching the hole.
Leaks cannot and will not be stopped before virtually all material is released. Even when valves are closed, the artificially liquefied fuel will continue to leak out as it seeks equilibrium as a gas until the segment between valves is virtually empty.
Due to NGLs highly condensed, liquefied condition, explosive energy is about 5 times greater than an equivalently sized and pressurized methane pipeline. As a result, the 8 mile segment between Thornbury and Middletown valve stations contains about 10,000 to 15,000 tons TNT combustion energy (depending on the NGL product), equivalent to the nuclear bomb dropped over Hiroshima.
It gets worse. The released ethane and propane gases are heavier than air. If ignition is delayed, these products will settle along the ground and can migrate as a vapor cloud for miles while remaining combustible. The gas is nearly impossible to contain and can spread out randomly according to the wind conditions. This means that delayed ignition, while possibly providing more time for evacuation, can result in a significantly larger impacted area. An area that is highly unpredictable. When the gas does find an ignition source, the entire blanketed area will ignite, with the fire tracing its way all the way back to the leak source.
Despite NGL products being referred to as natural gases and being substantially more dangerous than Methane, the Mariner East NGL pipelines are not regulated by the Natural Gas Act, nor are they considered Natural Gas in the regulatory code. Instead they are regulated as Liquids pipelines with code designed with naturally liquid petroleum products in mind. Since naturally liquid petroleum products pose a considerably lower risk of large-scale explosion, the regulatory code is much more relaxed for liquids pipelines compared to Methane Natural Gas pipelines. Although liquids regulatory code mentions Highly Volatile Liquids such as NGLs, it contains no significant requirements that protect the public from the risks associated with a volatile gas release. In fact, NGL and naturally liquid petroleum pipelines are seen as interchangeable within the regulatory framework, a loophole that is the very reason why Mariner East 1 was allowed, without fanfare, to be converted from an old 1930s era petroleum pipeline. It is also why Mariner East 2 is able to utilize many of those same existing rights of way.
The difference between Liquids and Natural Gas pipeline code is substantial. Natural Gas pipelines are regulated at the federal level where the Federal Energy Regulatory Commision (FERC) has siting authority. Liquids pipelines are the responsibility of the state. FERC does not have siting authority on Liquids pipelines, including NGL. PA’s Department of Environmental Protection (DEP) only oversees pipeline routing as it affects the environment. PA’s Public Utility Commission (PUC) has no siting authority at all. This means that no one has actually assessed the Mariner East pipeline route for public safety.
Let's stick to the facts and right now, we need more hard data. Middletown Township will soon have a Quantitative Risk Assessment (QRA) performed by an industry-accepted, independent company that will finally establish what emergencies the community must prepare for and how likely they are to occur. This type of unbiased emergency analysis should be required not only for the pipeline itself, but for every aspect of the project. The fact that Middletown’s QRA will be only the first location-specific QRA for Mariner East is extremely disturbing given the potential energy that will be flowing through the pipeline in densely populated suburban Philadelphia. If Sunoco has a problem with the township identifying risk and planning accordingly to protect its people, then there is something fundamentally wrong here. The science speaks for itself. Let's listen.
