What about that massive release of crap from the mine in Colorado or someplace out that way.
That water was mine runoff, a chemical leachate high in metals, but not raw human sewage. Nasty, but it would not cause infections, just don't drink it (and admittedly, not good for the fish)
You don't even want to fall overboard in this stuff. It's a bioweapon.
Every fish, oyster, clam, and crab downriver will be rendered inedible as not just fecal coliform, but virtually any pathogen found in DC goes into the sewers, and now, the tidewater there. This isn't the same as a flowing river, the portion of the Potomac affected is tidewater.
Because it is tidewater, it's a Two steps forward, one step back progress to the mouth of the Chesapeake, and eventually Cape Charles and the Atlantic. Southern Maryland and the Virginia shores will be particularly affected, including the Wicomico River (the large tributary between Charles and St. Mary's Counties (MD), which is a National Scenic River.
