Philadelphia Water Department and the city's combined sewer system

The Philadelphia Water Department (PWD) manages the city's combined sewer and stormwater system, reporting roughly 3,200 miles of combined and storm sewers and 164 combined sewer overflow (CSO) outfalls that discharge to the Schuylkill and Delaware Rivers. PWD operates the Green City, Clean Waters program, which installs green infrastructure-rain gardens, bioswales, green roofs, and permeable pavement-to reduce and treat stormwater before it reaches the sewer system. The program is a central municipal effort to decrease storm drain pollution and lessen CSO events in Philadelphia.