Green First Update: Reducing Overflows at the Source

ALCOSAN has been working with our municipal partners to create an affordable and adaptive Clean Water Plan to meet the requirements of the regulators, improve water quality in our rivers and streams, spur continued economic development, and advance the quality of life and our environment in the region. 


Wet weather overflows are caused by excess stormwater and groundwater entering the region’s sewer and stormwater system during and following rain and snow events. As we pursue solutions to the overflow problem, it’s useful to remember a simple model that illustrates the options for handling storm water and sewage flows:

  1. First, you can stop flows from entering the system in the first place; 
  2. Second, you can move it through the network of pipes;
  3. Third, you can hold it; or
  4. Four, you can treat it.

Taking advantage of the right combination of these sewer and stormwater management methods to design an efficient and sustainable solution that’s right for our region is the goal.

Our first step is to stop flows at the source, which is why we are using green infrastructure (and we will continue to expand upon those efforts), as well as inflow and infiltration control projects that sustainably restore natural watershed features and our existing wastewater collection system.

ALCOSAN’s partnerships with our customers, the municipalities, have been a crucial part of our work. Together, we helped develop the original plan, and we continue working together to develop new strategies and procedures to reduce overflows.  One major key is:  how much stormwater can be diverted via green infrastructure, which will help us determine what other measures may be necessary.

Project Status and Path Forward

ALCOSAN and its 83 customers – the municipalities we serve – have already implemented numerous flow reduction projects and are identifying many more. In addition, ALCOSAN recently announced the first round of awards to totaling $9M for its Green Revitalization of our Waterways (GROW) program to support municipal partners’ efforts.

To advance our understanding and assist our partners, ALCOSAN has estimated flows from our municipal customers. This will assist our coordination of responsibilities, as well as comply with a June 2015 regulatory agency information requirement.

Regional System Management

One step in the Clean Water Plan has been to develop a regional approach by having ALCOSAN assume responsibility for the multi-municipal trunk sewers and wet weather facilities. We have met with all of the impacted municipalities to begin discussions of the transfers, and are proceeding with video inspection televising of the pipes. This project, once completed, will significantly reduce maintenance and operations costs for the municipalities, while allowing rehabilitation and other decisions to be made in the interest of the best overall system performance for the entire region.

To advance our understanding and assist our partners, ALCOSAN has proposed an approach to develop flow targets that would encourage our municipal customers to stop flows from entering the system in the first place. This will assist our coordination of responsibilities, as well as comply with a June 2015 regulatory agency information requirement.

On January 31, 2017, ALCOSAN provided the agencies with a recommended flow target approach that was developed with input from municipal representatives. While the proposed approach is preliminary, the regulatory agencies ultimately expect ALCOSAN to enter into legally-binding flow reduction agreements with its municipal customers as part of implementing the wet weather program. ALCOSAN will continue to partner with its customers on this topic.

For more information, contact ALCOSAN’s Public Information Officer Jeanne Clark at

Sewer Overflow Advisory key: Wet Weather overflows have ceased. Rivers, streams and creeks may still be impaired. For more information:

Customer Care at ALCOSAN, we believe it's our duty and privilege to protect, recover and reuse our most valuable resources for the benefit of our customers.

Consent Decree: To comply with provisions set forth in the Clean Water Act, ALCOSAN must meet a series of requirements for planning, design and construction, operation and permitting. For more information

Watershed Education: Leave small leftovers of paint and solvents to dry rather than pouring them down the drain. Learn more

Contact   |   News   |   Events   |   Consent Decree   |   Careers   |   Sitemap

All content © Copyright Allegheny County Sanitation Authority

3300 Preble Avenue
Pittsburgh, PA 15233
(412) 766-4810