AFFF is the stream the rules are still moving under
Aqueous film-forming foam containing per- and polyfluoroalkyl substances sits at installations in concentrate drums, in vehicle tanks, in fixed hangar systems and in the ground beneath the places it was tested. It is unusual among the streams on this site in that the regulatory position is actively developing rather than settled: federal and state requirements around PFAS have been changing, disposal and destruction routes are under scrutiny, and what is acceptable practice is not guaranteed to stay still. The operational consequence is that a PFAS decision should be documented with its reasoning and its date, because "this is how it was done" is a weaker position than "this is what applied when we did it, and here is the record". Rinsate from flushing a system counts as much as the concentrate, and frequently in far greater volume.