As US cities build green infrastructure, here’s one way they’re paying for it

In 2015, rainstorms in Washington DC would cause parts of the city’s sewer system to overflow dumping millions of gallons of raw sewage into the Anacostia and Potomac rivers. Pipes buried in the 19th century combined stormwater and sewage, discharging a noxious brew of trash, bacteria, and heavy metals that polluted the rivers. By 2005, the pollution had gotten so bad it violated Environmental Protection Agency clean water standards, killed wildlife, and posed a threat to people living in the area. The federal government ordered DC Water, the region’s sewer and water management authority, to clean up the rivers.

At first, DC Water tried to tackle the problem with traditional “gray” infrastructure: big underground tunnels to store excess stormwater. But the agency’s leaders were in search of a cheaper, more sustainable solution. So in 2015, DC Water proposed using parks, plants, and permeable pavements strategically distributed to absorb some stormwater runoff and prevent overflow.

This “green infrastructure” was appealing for engineers: it had the potential to be less costly than gray infrastructure, and had knock-on benefits for neighborhoods, like providing natural cooling in summers, and improving property values. But it was uncharted territory; DC Water had never built green infrastructure before, and few other US cities had.

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