When it rains heavily in D.C., the surrounding ecosystem takes a beating.
A full 43 percent of land in the city is impervious to rainwater. As it flows down the streets, it picks up motor oil, pet waste, fertilizers, garbage, and whatever else is lying there, flushing it into the sewer. For two-thirds of the city, that all empties into the nearest river or stream, with enough force to gauge the banks of the smaller tributaries.
For the rest of the city, the runoff flows into a combined sewer, which overloads and projects a sludgy mess of feces into the river system. Before the city took action in 2005, those overflows added up to 3.2 billion gallons per year. In either situation, the rivers then carry the junk into the Chesapeake Bay, where runoff is the fastest-growing source of pollution.
Read the whole article on citylab here.