The New York Times last week revealed the frightening state of our nation's urban sewer systems and the real consequences to human health: over 20 million people each year get ill from drinking, fishing, and swimming in water contaminated with sewer overflow.
When most sewer systems process waste from humans and industry, they are treating it before it goes into our water bodies and drinking water. But most sewer systems are designed to take the untreated waste right to the treatment facilities via gravity. When it rains, the bad sewage (the Times article references a load of chicken heads as an example) is swept up with the storm water, bypasses the treatment plants and goes into the Hudson River, or the Puget Sound, or Santa Monica Bay or the Chesapeake. These are called "combined sewer systems" and when they fail it's called "combined sewer overflows," or CSO's.
CSO's are the single biggest source of pathogens for many urban bodies of water (including Santa Monica Bay on the west coast where I'm spending my Thanksgiving holiday weekend.) The warning bells about sewers and the insufficient infrastructure have been ringing for decades. Though not the best for holiday table talk, it is critical that there is more discussion about new solutions in order to avoid the continuing circular logic of our current ones. Only by seriously looking at new paradigms (or spending billions and billions more on construction than we need to) can this stinky problem be solved.
Too much weight is currently put on the need for more "infrastructure," meaning more pipes, more engineering, more disruption, more trying to control the flow, especially when it combines with rain. (It is as futile a solution as holding back the waters of Lake Ponchartrain during a major hurricane.) These "end of pipe solutions" represent the traditional approach to solving a problem caused by too many people paving over too many acres.
So what can better solve the problem with our sewers? The most obvious -- and most affordable--solution is bringing vegetation back into the cities that paved over green space to get there. Green roofs can dramatically reduce runoff and sewage overflows. Green roofs--roofs covered with living plants, which are, by the way, beautiful -- as opposed to ones made of tar or other impervious materials, absorb water and are a less expensive way to capture water than trying to control it through end-of-pipe ideas. Nature becomes a bigger player, acting as the engineer. Building owners benefit and so do municipalities who have to spend much less on controlling their storm water.
Green roofs also can indirectly effect the entry of heavy metals, nitrate, diesel soot, volatile organic compounds (VOCs), hydrocarbons and pesticides into local waters by decreasing CSOs.
Green roofs would keep at bay the 27 billion gallons of raw sewage and polluted storm water that stream into New York Harbor each year. More than 16,000 acres of rooftop -- 19 Central Parks -- could be covered in living plants, insulating the city and its residents from rising temperatures, energy costs and an overtaxed and outdated storm water management system. Green roofs last 20 to 75 years longer than conventional ones. And, for good measure, they improve air quality and provide habitat to endangered butterflies and bees, and arguably improve humans' experience of the world by providing more visually accessible green space.
New York City talked a good game about green roofs but decided to spend its millions of dollars of our federal storm water stimulus money on traditional structures -- building more man-made holding tanks -- instead of looking at what is really the cause: lack of vegetation. Isn't that what got New York, Miami, Los Angeles (and countless other major cities) into trouble in the first place?
Green roofs are not only the economically superior strategy but their additional benefits are huge: reducing Co2 and particulate matter, and flooding cities with beauty instead of contaminated storm water. Looking even further -- and more globally -- down the road, scientists at Columbia University (NASA's Goddard Institute) have concluded that the combination of planting more street trees along with Green roofs looks like the best single mitigation strategy for the effects of climate change in urban areas.