What are CSOs? A combined sewer system collects stormwater runoff, domestic sewage, and industrial wastewater into one pipe. Normally, the system can transport all of these flows to a sewage treatment plant, but during heavy rains the volume of flows exceeds the capacity of the system of pipes. When that happens, stormwater runoff and untreated wastewater overflow into nearby waterbodies, causing what is known as a Combined Sewer Overflow, or a CSO. Nearly every creek, stream, and river in the Philadelphia and Camden region, including those flowing through our parks, are impacted by a combined sewer system. Why are we collecting this information? Annually, billions of gallons of raw sewage and polluted stormwater flow through Philadelphia’s creeks, neighborhoods, parks and playgrounds, and into the Schuylkill and Delaware rivers. Many neighborhoods that experience higher magnitudes of sewage flows are also some of the most economically challenged in the city. The Delaware Riverkeeper Network believes the pace and magnitude of CSO eliminations in Philadelphia must increase. Clean water is a basic right; but it has been taken from our communities that bear the burden of CSOs. Working with Riverways and other local organizations and individuals, our approach will center on community scientists engaging in the CSO landscape to advocate and demand near term improvements through CSO reductions. We will use our team of volunteers to document and monitor the effects of raw sewage overflows in Philadelphia’s waterways. These effects will be brought to the Philadelphia City Council, Pennsylvania Department of Environmental Protection, and US Environmental Protection Agency to demand CSO implementation that corrects persistent problems, prioritizes reductions in smaller streams with no dilution or assimilative capacity, and maximizes opportunities for capture and treatment of all sewage flows.