When D.C. built its sewer system in the 19th century, it was state of the art — but it turned out to be seriously flawed. As the population continued to grow, so did the amount of sewage produced. Now, after a rainfall of an inch or more, the system overflows, spewing millions of gallons of sewage directly into the Potomac and Anacostia rivers, and into Rock Creek. The city is finally addressing the problem.

The 1972 Clean Water Act called for D.C.’s rivers to be swimmable and fishable, but decades have gone by without achieving that goal. But twenty years ago the Anacostia Watershed Society sued DC Water over the sewage pollution, which resulted in a consent decree — a legally binding agreement with the Environmental Protection Agency. DC Water agreed to build massive sewer tunnels to fix the problem. The cost? $2.7 billion, with the majority being paid by D.C. residents via a Clean Rivers fee.