Wet Weather Issues

At Issue
When it rains or when snow melts, excess water can overload the sewer system resulting in sewage overflows into area creeks, streams and rivers. This flow also carries pollutants from untreated sewage as well as grit and debris found littered along roadways.

Correcting the sewage overflow problem is a priority for ALCOSAN and the 83 municipalities it serves. Under the United States Environmental Protection Agency’s Combined Sewer Overflow (CSO) Policy, combined sewer overflows as well as the pollutants discharged, must be controlled. On January 23, 2008, a binding Consent Decree was approved in federal court in which ALCOSAN, under the mandate of the EPA, the Pennsylvania Department of Environmental Protection and the Allegheny County Health Department, agreed to a comprehensive plan to greatly reduce the annual discharge of untreated sewage into area waterways by 2026.

Combined Sewer Overflow (CSO)
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. CSO’s usually carry a variety of pollutants, including debris, chemicals, bacteria, and animal waste. If you are a customer of ALCOSAN, there are a number of steps you can take to help minimize this problem. For more information about what you can do to help, please refer to the Eco-Responsibility page on this site.

Sewer Overflow Advisories
For current status and additional information regarding Sewer Overflow Advisories, please click on any one of the following links:
Sewer Overflow Advisory Key (SOAK)
ACHD CSO Flag Alerts
CSO Flag Locations
CSO Alert Data 2009
CSO Alert Data 1995-2009
River Water Advisory
CSO / SSO Outfall Signage
CSO/SSO Outfall Signage Locations (Updated 12/31/09)

ALCOSAN’s Demonstration Project
ALCOSAN is considering constructing overflow control facilities, which would be used to provide treatment to the combined sewage overflow. Left unaddressed, this CSO would otherwise flow into the receiving stream untreated during wet weather. The goals of the Demonstration Project are to:

Design facilities for intermittent operation that will require low maintenance, control solid and floatable materials, and demonstrate effective disinfection;
Improve water quality; and
Comply with the Federal Combined Sewer Overflow Policy.

To meet these goals, ALCOSAN is considering constructing two overflow control demonstration facilities in the Pittsburgh region. The proposed locations will be spread out along the north shore of the Allegheny River and at the mouth of Homestead Run, which drains into the Monongahela River.

EPA Nine Minimum Controls
In the future, Combined Sewer Overflow (CSO) communities will be required to apply for and maintain NPDES permits. As a result, communities will also be required to implement what the EPA has identified as the nine minimum controls under a long term CSO control plan.

Proper operation and regular maintenance programs for the sewer system and CSO outfalls
Maximum use of the collection system for storage
Review and modification of pretreatment requirements to ensure that CSO impacts are minimized
Maximization of flow to the POTW (ALCOSAN plant) for treatment
Elimination of CSOs during dry weather
Control of solid and floatable materials in CSOs
Pollution prevention programs to reduce contaminants in CSOs
Adequate public notification of CSO occurrences and CSO impacts
Monitoring to effectively characterize CSO impacts and the efficacy of CSO controls

Rainfall Data
Quality-assured data is gathered from 33 rain gauges throughout Allegheny County and is combined with NEXRAD Radar data to create this comprehensive, realtime map located on the 3 Rivers Wet Weather Program site.
View Rainfall Data

Click on the above link to view rainfall data. Creating a "New User" account will allow you to download rainfall data and save searches for future use. (Please complete all fields. Individuals may use "home" in place of an organization.) If you wish to view data without the ability to save or download, please select "Guest Login" and follow the instructions on the screen.

Collection System Map (Updated 12/31/09)
This map identifies each location and related feature of ALCOSAN's sanitary and combined sewer outfalls, as well as identifying area sewersheds, including continuous flowing waterways within each sewershed.

Sanitary Sewer & Combined Sewer Outfalls (Updated 12/31/09)
This map identifies sanitary sewer and combined sewer outfalls in ALCOSAN's conveyance and treatment system as well as outfalls in the regional collection system as reported by customer municipalities. (Updated on a quarterly basis as data becomes available.)

Water Recreation Areas (Updated 12/31/09)
This map identifies major water recreation areas in Allegheny County (including boat launches, marinas, approved trout fisheries, etc.) provided online by the Pennsylvania Fish & Boat Commission.

Impaired Waterways (Updated 12/31/09)
These maps identify continuous flowing streams and rivers listed as impaired by the Pennsylvania Department of Environmental Protection pursuant to Section 303 of the Clean Water Act:
Aquatic Life Designated Waterways
Fish Consumption Designated Waterways
Potable Water Supply Designated Waterways
Recreational Designated Waterways