Yeah I'm curious where they're charging $2000/yr for a homeowner. I'm a stormwater engineer and just had a client contact me that his company was being charged $5000/yr for a commercial property with almost 5 acres of impervious area. These fees are usually based on the impervious area on the property, not property size. And most of what I've seen residential owners are looking at between $50-$200/yr.
The fees are not federally mandated, but municipalities are required to participate in the MS4 program which is federally mandated in a roundabout way. They basically must map all of their stormwater outfalls and BMPs (like detention basins) and then prove that they are meeting water quality goals. The Chesapeake Bay issues have exacerbated the requirements and stormwater is under more scrutiny. Therefore, municipalities are starting to have to undergo stormwater projects (lots of riparian/stream corridor projects) to improve water quality and are also being held accountable for maintenance of stormwater BMPs and conveyance systems. Street sweeping is a very common BMP for municipalties. All of these things cost money, lots of it.