Some other things -- certain types of industries can ask for an exemption from this permit if they claim they have zero stormwater pollution exposure. See https://www3.epa.gov/npdes/pubs/noxguide.pdf
Wondered about that. The main plant Had a storm sewer. One of the small satellite plants had something labelled a storm sewer. But, when the sample was pulled, nasty things like toilet paper had to be pulled off the probe. The environmental engineer always said it was legit when asked.