CITYLAB
By Jessica Leigh Hester
In Brooklyn, a developer plans to back dirt-filled dumpsters into parking spaces this summer, the Brooklyn Paper reported, in the hope that the soil and plants will soak up storm water before it breaches the nearby Gowanus canal—a Superfund site with a famous and fetid tendency to flood. In a borough that’s increasingly squeezed for space, these small-scale interventions make sense: real estate is at a premium, and green interventions can be wedged into any available sliver.
Detroit, on the other hand, has considerably more space to work with. “What comes to the rescue here is having plenty of land,” says Joan Nassauer, a professor of landscape architecture at the University of Michigan. It’s a sprawling city, with vacant or buckling properties scattered across its 139 square miles. As of April 2016, 66,125 vacant parcels were held by the Detroit Land Bank Authority, which has received more than $100 million in federal funds to demolish blighted structures. Already, 2,112 such buildings have been razed this year. “This is really good news in a way you wouldn’t necessarily expect for opportunities to be creative,” Nassauer says.
Like Detroit, Philadelphia and New Orleans are doubling down on green stormwater infrastructure. But in Detroit, where the available space exceeds the current market demand, environmental interventions are playing out on particularly large scales. There’s room to turn entire lots into proving grounds.
This spring and summer, researchers across the city are investigating the immediate and long-term ecological and sociological benefits of turning vacant land into stormwater basins topped with colorful plants. Can these parcels improve the health of the bodies of water around them—while also beautifying long-struggling properties?
Across the country, cities must manage the water that falls on impervious surfaces and align themselves with the mandates set forth in the Clean Water Act. The challenge is to keep runoff as clean as possible and slow its path to receiving waters.
Detroit feels that problem acutely. More than 3,000 miles of gravity-fed pipes wind beneath Detroit’s streets. Detroit, like many other older cities, has aging water infrastructure that uses combined sewer systems: Rainwater rushes to the same drains that ferry wastewater to treatment plants. Strong, unyielding storms, which have increased in the region over the last half-century, can overwhelm the pipes, causing a mix of runoff and untreated wastewater to back up into local rivers. This phenomenon contributes to algae blooms fueled by phosphorous and nitrogen. Last summer, a record-breaking toxic cluster in Lake Erie threatened drinking water for 400,000 Toledo residents. “The Rouge River and the Detroit River [were] a part of the cause of that problem,” Nassauer told the Detroit News last November.
Decades ago, the city offloaded tens of billions of gallons of untreated water into the local rivers annually. The volume continues to spike following storms. In August 2014, a storm battered the region with 5.5 inches of rainfall; the sewers then discharged 10 billion gallons of overflows into local waters, according to a Detroit Free Press analysis of data from the Michigan Department of Environmental Quality. Over the last two decades, the city has poured $1 billion into upgrading the system; now, its nine facilities and six treatment basins can accommodate approximately 95 percent of the untreated overflow—an improvement, but an imperfect solution. “How do you get to the last 5 percent of the problem?” asks Palencia Mobley, the deputy director of Detroit Water and Sewerage. “Spending another $1 billion or $2 billion doesn’t make a lot of economical sense.”
To bridge the gap, the city has pivoted to focus on green infrastructure, which, Mobley says, can be strategically placed to mitigate localized flooding. By 2029, her department will have spent $50 million on green infrastructure in the Upper Rouge area.