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Sewer Overflow Advisories

A combined sewer overflow (CSO) occurs when storm water and sewage, carried in a single pipe, overload the sewer system and flow untreated into rivers and streams. CSOs can carry a variety of pollutants, including raw sewage, debris, chemicals and bacteria.

ALCOSAN's Sewer Overflow Advisory Key (SOAK) and CSO Flag Alert Program are complimentary advisory programs to warn the general public of possible river contamination from CSOs.  While these programs do not prohibit or discourage river recreational activities, they do caution recreational users to limit contact with river water when boating, fishing, water skiing or engaging in other river recreational activities.

Advisory Programs operate annually from May 1 until October 31 to coincide with ALCOSAN’s NPDES permit summer reporting period.  The program will operate between the hours of 8:00 am and 7:00 pm, 7 days a week.  If overflows occur during this timeframe, ALCOSAN will raise orange CSO flags at designated points along the waterways and will notify the public accordingly via the ALCOSAN Sewer Overflow Advisory line (412-734-6249), the ALCOSAN website-based SOAK program, and our subscriber-based text/email notification program.  Users will also be notified when overflows have ceased, as well as when the system returns to dry weather operation, 48 hours later.  At this point, CSO flags are also lowered to indicate dry weather operation.

For current status and additional information regarding Sewer Overflow Advisories, please click on any one of the following links:

Sewer Overflow Advisory Key (SOAK)
          Current Season SOAK Status History

CSO Flag Alerts

          CSO Alert Data 2018
          CSO Alert Data 2017
          CSO Alert Data 2016
          CSO Alert Data 2015
          CSO Alert Data 2014
          CSO Alert Data 1995-2013

ALCOSAN posts informational signage at each of the Authority's 259 combined sewer overflow structures and 51 sanitary sewer overflow structures.  Each sign identifies a corresponding structure with the potential for sewer overflow discharge and are visible from both waterways and publicly accessible land sites. 
          CSO / SSO Outfall Signage
          CSO/SSO Outfall Signage Locations (Updated 9/1/19)

NOTE: If a sewer overflow discharge is observed during dry weather, please contact our 24-hour public hotline at 1-888-936-9363.

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

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