A better plan was needed for Philadelphia's old combined sewer system. in combined systems, stormwater and sewage flow together in a single pipe; during heavy rains or snowmelts, the system can be overwhelmed, resulting in flooding and waterway pollution.
The Philadelphia Water Department went with a new "Go Green" approach. The new 25 year–$2 billion plan announced in 2007 and officially approved by the state this summer pledges to install as many green features as possible. Over the next 25 years, tools like porous pavement, rain gardens, rain barrels, sidewalk planters and stormwater tree trenches will help capture and manage Philadelphia stormwater.
Updated wastewater treatment facilities and pipe renewal are also part of the plan, but the hope is that the green features will keep water out of the sewer system altogether. In this new Green City, Clean Waters plan, waterways will be more quickly restored, and residents will more readily see and enjoy the improvements.