Underground horizontal directional drilling (HDD) for the Mariner East 2 pipelines (two of them, 2 and 2X) have a history of springing leaks. They’re called “inadvertent returns”–when you drill horizontally underground for a pipeline and the drilling mud you put down the hole pops up in a place it’s not supposed to. The good news is that the drilling mud is non-toxic, the same stuff used in toothpaste. The bad news is that it can overwhelm little fishies and other aquatic life and kill (suffocate) them. ME2X drilling had another such incident earlier this week–in Chester County, PA.