We’re all happy that Hurricane Irene passed with minimal damage to New York City. But I’m here to be the bearer of bad news—the pessimist, if you will—and remind you that the waters surrounding New York were likely not quite so lucky.
With the Lab’s current focus on wastewater management, this weekend’s storm is a perfect opportunity to examine the alarming and downright disgusting impact that heavy rains have on the bodies of water surrounding New York.
As we’ve mentioned briefly before, one of New York’s greatest problems when it comes to wastewater management is the fact that it runs mostly on a combined sewer system.
While most modern American cities have separate systems for collecting wastewater from buildings and storm water from the streets, about 70 percent of New York’s outdated sewers still collect those two types of water together.
On normal dry days, this works fine. The water is collected together and whisked to one of New York’s 14 waste treatment facilities before being released as effluent into the ocean.
When the city experiences heavy rainfall, however, the system easily becomes overloaded. When the system overloads, it allows waste to bypass the treatment facilities and be released directly into the surrounding bodies of water. Raw.
This is called a Combined Sewer Overflow (see a great simple diagram explaining how this happens here) and in New York it happens more often than anyone would care to imagine.
According to the New York City Department of Environmental Protection, CSOs can occur during rainfall events as small as 0.05 to 0.1 inches per hour. This weekend we had an estimated seven inches of rain. I’ll let you do the math.
With even such small amounts of rain causing overflows, New York City’s wastewater system releases an average of 27 billion gallons of raw sewage into the surrounding waters every year from its nearly 500 CSO outfall points all around the city (see a map of them on page 6 of this U.S. Environmental Protection Agency report).
This is a massive problem and should not be underestimated. Basically, anything that residents or businesses or factories put down a drain or toilet or on the street might go straight into the water unchecked. This includes pollutants such as untreated human and industrial waste, toxic materials, and debris, as well as any oil, grease, garbage, or chemicals that get picked up as rain washes across roads or fields, as reported by the EPA. If you don’t believe me just how nasty this is, watch a real CSO in action in the video above.
The situation is slowly improving. This year, projects like the Paerdegat Basin and Alley Creek CSO Facilities have increased the city’s wastewater storage capacity during heavy rains by over one billion gallons. Plans to use green streets and roofs to help manage storm water runoff are also slowly being implemented.
But this is just a small dent.
Yes, many New Yorkers dodged a bullet as this weekend’s storm passed with minimal damage. But let’s not forget that beyond the shorelines of New York, the story is likely a little different. And with heavier storms only expected to increase with time, the city—and its water—are far from in the clear.