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.