Yep, old infrastructure is a problem. The MS4 program (Municipal separate storm sewer system? That's 4 s's right?) has done a lot, but much more can be done. I got to help "daylight" one of the streams that runs into the Anacostia back in 2009. That's daylighting as in taking a stream which was previously routed underground, and reverting it to its more natural state (i.e., exposed to sunlight and all kinds of biological processes and stuff).
That's not to be confused with daylighting used as a torture/killing technique in the film Daybreakers, starring Ethan Hawke.
Since I cannot resist posting nonsense, ironies, and cynical comments regarding almost anything, I'd like to point out that combined sewer systems can arguably function better than separate systems during periods of low rain, since combined systems tend to route everything directly to treatment. The problem is when there is a hard rain that overwhelms the combined system........then everyone's poop sloughs off into the streams.
Separate systems simply "unburden" the system by routing stormwater directly to the streams, with the idea that raw sewage then has a better chance of getting treated instead of being pushed into the streams during....well, storms.
You can read more about this ^^ and other lies about science in my new book, "Science so Stupid: 1001 of Gene's Favorite Science Lies".
Gene