Some of the largest issues I found in North Carolina (Raleigh area) were violations from waste water treatment plants (WWTP) used in mobile home parks. They're community based systems that are maintained by the park, but need a permit from the county to operate. One park has been in violation of the Clean Water Act, on and off, for years. They violated the CWA with continuous effluent exceedances, based on their permitted limit.

In summary, their pollutant is excessive effluent (if the system isn't running correctly this can push harmful bacteria and solids in and around the soil). This can also harm surrounding property owners and Poplar Creek-Neuse River that is near by. The park management is at fault, since this is a community WWTP. To my surprise the park has only paid $2,830 dollars in penalties in the past 5 years of violations. I was looking at CWA violations regarding WWTP in other counties, which were ranging upwards of $20,000 + in penalties paid for more significant violations of the same issue.