"Each year, Philadelphia's waterways are forced to swallow a dirty mix containing 15 billion gallons of untreated sewage and rainwater during storms because of an antiquated city system, according to a report released Thursday by PennEnvironment.
The waterways include the Delaware and Schuylkill Rivers, as well as Cobbs, Frankford, Tacony, and Pennypack Creeks.
The outflow is no threat to drinking water because river water gets treated before residents drink it, but it does create health threats for aquatic life and recreational users, said the study by the nonprofit advocacy group. Last year, for example, Philadelphia residents lost at least 162 days of water recreation on the Schuylkill because overflows created too much pollution to make the river safe to use—and that was before the recent torrent of downpours.
At issue is Philadelphia's combined sewer system where storm water and sewage flow through the same pipes during a storm. The volume overwhelms the city's three treatment plants and allows untreated water to flow directly into combined sewer overflows (CSOs) that empty into the waterways. The combined system serves roughly 60% of the city."