Stormwater, and… Worse

Every time there is a snow melt or rainfall, the water that goes along the gutters of New York and then into the sewers has to go somewhere. Because we have a combined sewage system, during rainfall (depending on the load) what we flush down the toilet can be merged with sewer rainwater, and not cleaned by sewage treatment plants (shown in purple starts here):

but instead is directed to the red dots which indicates spots where rainwater and… worse, may be directly discharged into our surrounding bodies of water.

When you look a the map, note how many more red dots East Harlem has compared to West Harlem – the waterfront of East Harlem is thick with discharge outlets, whereas they are spread pretty thinly on the west side.

Note how in the view (above) that takes in all of Manhattan, the west side, from around 59th Street up to Inwood has the fewest discharge outlets (to the Hudson River), compared to midtown and below, and on the east side of the island all the way up to Inwood.

What’s going on here?

Well, actually topography and gravity are going on here. Sadly, Harlem’s east side sees far more pollution in the East and Harlem Rivers simply because the higher land (think Morningside Heights and Washington Heights) is to the west, and rainwater and… worse, flows downhill. Essentially, rainwater that falls over by Amsterdam or St. Nicholas Avenues, could go either way, but anything to the east, is certainly headed to the East River or the Harlem River, not west to the Hudson.

On days when it hasn’t recently rained, city waters are typically safe for kayaking and recreation. Really! But almost every time it rains, polluted stormwater runoff mixes with raw sewage in the combined sewer system and overflows into our waterways where people swim, fish, and boat. These are called “combined sewer overflows.” New York City discharges more than 20 billion gallons of sewage each year.

The problem is as gross — and as dangerous — as it sounds. People who come into contact with contaminated water are at risk of developing intestinal illnesses, rashes, and infections.

Sadly, New York City, is the worst polluting city in the US because of our combined sewer system and overflow discharges. Our waterways are undoubtedly better than they were a generation or two ago, but we have a long way to go.


  • Avoid doing water-intensive things during rainstorms
  • Never believe the marketing hype that something is “Flushable“. The only thing going down your toilet should be, well, you know, and toilet paper. Nothing else – use the trash.
  • Never dump oil down your sink. Use paper towels and sop it up (and put it in the trash) or collect it in a container in the freezer, then toss it in the trash when it’s full.
  • Ask your landlord for low flow faucets, showers, and toilets, and make sure your super keeps the gutters/sidewalks clean so trash doesn’t flow down into the sewer, clogging things up