The District of Columbia, like many US cities, has a combined stormwater and sanitary sewage system, which often experiences frequent sewage overflows. Washington’s combined sewer overflows were dumping an average of 2.5 billion gallons of combined sewer water annually into three rivers, including the Rock Creek tributary that ultimately flows into the Chesapeake Bay. These polluted water overflows brought bacteria, trash and heavy metals along with them, negatively impacting DC’s water quality, air quality and natural habitats. The combined overflows reached volumes and frequency that violated the US Clean Water Act.