All over the country, cities with old, often crumbling, sewer systems are turning to “green infrastructure” to help manage stormwater, reduce flooding and sewage overflows, and handle the impacts of climate change. But how well these systems will work is still unknown.
In Philadelphia, they’re spending more than a billion dollars on green infrastructure, including planting more than 700 trees to soak up stormwater. In Cincinnati, they’re bio-engineering a stream to stop pollution from getting into the Ohio River. And in the next year, Pittsburgh is planning a dozen projects on the East End, including installing special pavement that soaks in water so it doesn’t rush into the sewer system. The cost? Ten million dollars.
That’s big bucks. But it’s still a lot less than laying new sewer pipes and building new water treatment systems. Still, one big question remains: Will green infrastructure actually work as well as traditional gray infrastructure?
Soil scientist John Buck, who works with Civil & Environmental Consultants, Inc., is among the researchers trying to figure this out. At Chatham University’s Eden Hall Campus north of Pittsburgh, Buck is digging holes with a giant fence post digger. He’s not actually building a fence. He’s putting metal sensors into the holes to measure how water moves through the layers of soil.
“The sensors are going to be laid in three inches, 12 inches and 20 inches below ground surface,” Buck says. “And from there, we can see how fast it’s moving through the soil.”
Buck and his students bury the sensors, leaving long wires sticking out of the ground. They plug the wires into a sensor hub, which kind of looks like a circuit breaker box zip-tied to a wooden pole. It also has a wireless transmitter, so Buck can check the soil readings from the box at any time, right from his phone.
And that will tell policymakers whether rain gardens, green roofs and porous pavement can help solve their cities’ water problems.
“At a bare minimum, you’re going to want to measure how much water is coming into your green infrastructure system and how much is going out of it,” Buck says. “And the difference between those two things is what your effectiveness is.”
Buck helps monitor several projects around the region. One rain garden in Pittsburgh’s East Liberty neighborhood captured almost all—99 percent—of stormwater runoff last year. This past August, it even handled what experts called a “once-in-167-year-storm,” when the garden soaked up nearly three inches of rain in just two hours.
That kind of effectiveness is important in regions like Pittsburgh, where untreated sewage regularly drains into the rivers after it rains. The Environmental Protection Agency is pushing sewer districts to reduce overflows into the waterways. And in Allegheny County and elsewhere, the agency is allowing the use of green infrastructure to help solve the problem.
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