In some parts of the country, sewers are single – home and business waste is piped to sewage treatment centers and storm water (from rain or snow) is separately sent to the nearest body of water (POTW stands for Publicly Owned Treatment Works, where waste water is treated):
As you can see, when it rains, the storm water overflows and the mixed storm water and sewage flow untreated into local rivers. EWWW!!!!!! This is called a Combined Sewage Outflow or CSO and it is major contributor to the pollution of local water.
Where does this happen in NYC? Red Tier 1 dots are where the worst CSOs happen.
And this is not confined to New York City. Large parts of the country have combined sewer systems, leading to the risk of CSOs:
Now that we see the problem – what is the solution? One answer is better infrastructure, including things like green roofs. The idea is that the right blend of soil and plants absorbs rainwater and then gradually releases it into the storm drains, preventing the overflow. Again, the EPA has lots of information on green infrastructure if you want to learn more.
Why are we talking about this now? Well, first of all it’s information that most New Yorkers (children and adults) do not know, and learning new things is cool. But also, we will be talking more on this blog about green infrastructure in the future and we wanted to explain the problem before considering possible solutions.
… and don’t forget to check out Icky Fest at Brooklyn Children’s Museum this Saturday for more icky information about NYC’s sewers.
(Thanks to the EPA for diagrams 1, 2, and 4. For more information about sewer problems across the United States, check out the EPA’s webpage on CSO’s.)