Stormwater does Affect Water Quality.

PWSA draws water from the Allegheny river. Anything that enters the storm sewer is ultimately released, untreated, into the rivers and streams. 

The PWSA system is made up of sanitary, dedicated stormwater and combined sewers. All new development is required to have separate storm sewers into Municipal Separate Storm Sewer Systems, known as MS4's.

Clean Water is Everybody's Business


 What is Stormwater?

Stormwater is water from precipitation, like rain, snow melt, and ice melt.


Why does Stormwater Matter?

Stormwater matters because the water that does not soak into the soil can run off into the river system, carrying pollutants on lawns, roads, sidewalks, roofs, and parking lots. If not properly managed, stormwater can flood roadways and basements. Excess stormwater leads to combined sewer overflow (CSO), which contaminates the waterways.


Combined Sewer Overflow

In most Pittsburgh streets, the same sewer pipes carry both stormwater and sanitary wastewater from residential properties and businesses to the ALCOSAN wastewater treatment facility. During rainstorms, the combined sewage and stormwater often exceeds the capacity of the sewer system and overflows directly into Pittsburgh’s rivers and streams.


What is PWSA doing to combat Combined Sewer Overflow?

The PWSA is committed to improving water quality affected by stormwater runoff. In addition to upgrades to our existing infrastructure, the Authority is making green stormwater infrastructure part of our solution to these wet weather issues. Green infrastructure can be a cost-effective, sustainable and environmentally friendly way to manage stormwater runoff while providing many additional benefits to communities. PWSA is conducted a City-wide assessment to determine where green infrastructure will be most effective.


What is Green Infrastructure and why is it beneficial?

Green infrastructure uses soil, plants, and trees to manage and filter stormwater where it falls, before it enters the sewer. Systems like rain gardens and permeable pavement provide a place for stormwater to slow down and soak into the ground.  Planted green roofs absorb stormwater and help insulate the building below. In addition to stormwater management benefits, green infrastructure can beautify neighborhoods, stimulate economic development, raise property values, improve air quality, and create jobs. 


What can you do to help?

  • Dispose of trash properly. Don’t Litter.
    • You can help reduce costs and keep our rivers clean by properly disposing of waste.
  • Consider the location where you wash your car
    • If you’re washing your car in the driveway, all the soap is going into the street, entering the storm sewer and eventually ending up in the river.
  • Properly dispose of Pet Waste
    • If pet waste is not properly disposed of, during rain events, the bacteria will enter storm sewers and eventually end up in the river.
  • Use fertilizer sparingly
    • During rain events, fertilizer runs down the street, enters the storm sewers and eventually ends up in the river. Don’t fertilize before a rain storm.
  • Stop oil leaks immediately
    • Leaking oil runs down the street, enters the storm sewers and eventually ends up in the river. Check for oil leaks regularly and dispose of oil properly.

Related Links


  • Three Rivers Wet Weather
    • Three Rivers Wet Weather was created in 1998 to help Allegheny County municipalities address the region's aging and deteriorating sewer infrastructure and to meet the requirements of the federal Clean Water Act.
  • Nine Mile Run Watershed Association
    • The mission of this group is to ensure the restoration and protection of the Nine Mile Run Watershed, located in Pittsburgh's East End.