Centre and Herron Green Stormwater project located in the Upper Hill District

We are building new stormwater solutions to reduce flooding, decrease water pollution, and change Pittsburgh's infrastructure for the better.



Pittsburgh’s first sewer lines were constructed in the 1840s in what is now present-day Shadyside and Oakland. These lines sent water directly to the Monongahela River. By 1908, nearly 400 miles of underground sewer lines were in place, establishing the start of our 1,200-mile combined sewer system.

Historic Photo, PGH2O

Today, Pittsburgh looks a lot different.

There are more buildings, more roads, less green space, and greater demand placed on our infrastructure. While many things have changed, the way we treat wastewater and stormwater largely remains the same.

What does all this mean?

Rendering of a completed stream restoration near Nobles Lane and Ansonia Place

Our combined sewer system sends wastewater and stormwater through one pipe to ALCOSAN, the regional wastewater treatment plant located along the Ohio River. Once water is treated, it is released into the river for downstream communities to use as drinking water.


Our sewer system is overwhelmed by the increasing intensity and frequency of rain. And with so much pavement and hard surfaces throughout the city, all this rain has nowhere to go.


Sewage frequently overflows into rivers, floods our streets, and overflows into basements throughout Pittsburgh. This method of sending wastewater and stormwater through one pipe is no longer acceptable.

How are we addressing this problem?

A bioretention area at the Hillcrest Stormwater Project in Pittsburgh's Garfield neighborhood.

We are building a new wave of stormwater infrastructure that captures the rain where it falls, soaks into the ground, and is slowly released back into the sewer system.


They use a combination of green and gray infrastructure that on the surface mimic nature using vegetation, engineered soils, and open channels that retain water. Underneath are storage systems that hold water back before slowly releasing it through our network of sewer pipes.


The new projects are cost-effective and help to reduce basement backups, sewer overflows, and improve water quality. As we build up our network of stormwater infrastructure throughout Pittsburgh, they will become more effective at addressing some of our most crucial stormwater challenges. 

See green stormwater infrastructure in action.



Man riding bike during rainstorm in Pittsburgh

As heavier and more intense rains overwhelm our sewer system, stormwater management is a growing concern throughout Pittsburgh. Heavy rains cause sewage to overflow into rivers and streams, flood our streets, and backup into basements. To solve the problem of too much stormwater, we are managing it more deliberately across Pittsburgh.

Read more about the stormwater program and the plans we are implementing.



New stormwater infrastructure in the Hill District

A stormwater fee, approved by the Pennsylvania Public Utility Commission, became effective on January 12, 2022. From this date forward, Pittsburgh Water and Sewer Authority customers who own property in Pittsburgh began seeing the new charge on their bill.


A stormwater fee for Pittsburgh is a notable change. Historically, we have funded our stormwater services from wastewater rates based on water usage.

Example of impervious surface on a property

The stormwater fee is based on a property's hard or impervious surfaces. All property owners in Pittsburgh contribute a share proportional to the amount of runoff generated by their property. Establishing a fee based on hard surfaces such as roofs, pavement, and asphalt is a more equitable way to charge for stormwater and fund the stormwater projects and initiatives needed to improve stormwater management in Pittsburgh.  


As part of implementing the stormwater fee, wastewater conveyance rates will decrease since the stormwater fee will begin to recover the previously included stormwater costs. 


Learn more about the stormwater fee by visiting

Impacts to Sewer System

Impacts to Sewer System

Close-up photo of a storm drain with rain entering and a curb marker next to it that says "drains to drinking water, please don't dump"

Approximately 75% of Pittsburgh sewer system is a Combined Sewer System meaning that wastewater (sewage) and stormwater (rainfall) flow through the same pipe. The remaining 25% is a Municipal Separate Storm Sewer System (MS4) where wastewater flows through one pipe and stormwater flows through the other. Both systems have one job to do - move water away from homes, buildings, parks, and roads so it is safely conveyed to either ALCOSAN, the reginal wastewater treatment plant or in the case of the MS4 system - sending stormwater to an outfall located along a river or stream. 


But there are instances when the sewer system doesn't operate as it should. Rain, age of the pipes, and human activity can impact the performance of Pittsburgh's sewer system, lead to basement backups and illicit discharges or cause pollution to enter our waterways and harm wildlife. There are things we all can do to protect our sewer system. Start by learning how these systems operate and explore the Resources tab below to understand what you can do to help! 

  • Visit the Combined Sewer System page to learn about the history of our sewer system, how it functions, and the challenges it experiences when it rains too hard.
  • Visit the Municipal Separate Storm Sewer System (MS4) page to learn about this portion of the sewer system, learn what PWSA is doing to reduce stormwater pollution, and the simple actions you can take every day to help.



A rain barrel collecting water from a house gutter by a garden

Everyone in Pittsburgh needs to become part of the stormwater solution. You can make a difference by taking small actions every day to manage stormwater on your property, improve the quality of our rivers and streams, and protect those you care about during the large storms that frequently occur in Pittsburgh. Explore our stormwater pages for helpful resources and tips.


  • Help Manage Stormwater: Learn how you can become part of the stormwater solutions that are needed in Pittsburgh.
  • Find Your Sewershed: Use this searchable map to find which sewershed you live in and its contribution to combined sewer overflows (CSOs) to our rivers. 
  • Flood Preparedness: Learn how to protect your family, property, and belongings from flooding. 

Building Stormwater Solutions Together