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John Petro

Swimming With the Sewage

On Monday the New York Times brought us some nasty details about the city's sewer system. New York City has a combined sewer system, meaning that both storm water and the waste from our apartments and businesses flow through the city's sewers and into waste treatment plants. When the city experiences heavy rains, the sewer system reaches capacity and untreated sewage is dumped into the city's waterways. This happens "essentially every other time it rains."

Besides being unquestionably gross, this poses a serious health risk to city residents. Unfortunately, it would cost $58 billion to upgrade the sewer system to prevent all future overflows--on top of to the $35 billion that has already been spent over the past three decades on improving the city's sewer system.

But there are other ways a city can reduce its stormwater runoff besides large, expensive capital improvements. By promoting the construction of green roofs, a city can significantly reduce the amount of storm water that runs into the city's sewers during heavy rains. A green roof is basically a roof with a thin layer of soil and vegetation on it. A green roof can absorb up to 45 percent of rain water and delay runoff by two hours, a critical amount of time for waste treatment plants during heavy rains.

There is also something compelling about the idea of growing plants on the city's vast expanse of rooftop space, giving a new meaning to the term "urban jungle." Mayor Daley of Chicago, the nation's leader in the construction of green roofs, visited New York earlier this year and told us about his vision of his city covered with green, "One day I want to fly out over the city and look at the skyscrapers and see all green roofs, both on commercial and downtown buildings."

Chicago has been aggressive in its promotion of green roof construction. By using a combination of incentives and regulations, the city now has 600 green roofs covering seven million square feet.

There is no reason why New York City can't do the same. By encouraging private property owners to construct green roofs, Chicago is reducing the strain on its sewer system with very little cost to the city. Compared to a city filled with green, the alternatives--more sewer overflows or billions of dollars for sewer upgrades--stink.

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Posted at 11:00 AM, Nov 25, 2009 in Environmental Justice | Urban Affairs
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