Maryland Reported Sewer Overflow Database

New Overflow or Bypasses Regulation - Regulations that address reporting and public notification regarding sewage overflows and wastewater treatment plant bypasses became effective on March 28, 2005.

The Maryland Reported Sewer Overflow Database contains bypasses, combined sewer overflows (CSOs) and sanitary sewer overflows (SSOs) reported to the Maryland Department of the Environment (MDE) from January 2005 through the most recent update. MDE updates this database regularly. Although MDE requires that all public sewer system owners or operators report overflows to us, there may be incidents that were not reported. Note that overflow amounts provided by the person reporting the overflow may be estimated using best professional judgment or they may be actual readings from flow measurement devices when available.

The most up to date information is available through Maryland’s Open Data Portal

at  The search form below does not have data after January 2022. We are working to provide search functionality using the Open Data Portal.

If you have any questions about this database, please contact Andrew Gosden, Program Manager at 410-537-3510.


Database records will be searched using valid criteria entered. Text searches are done by keywords only. The date format is mm/dd/yyyy with no leading zeros. For example, 8/21/2001 and 11/1/2001 are valid entries; 08/21/2001 and 11/01/2001 are not. The zip has five digits only. You may leave any of the input boxes blank.

Please use the IE browser when generating an Excel spreadsheet.

Type of Overflow
Type of Overflow by Weather
Municipality / Facility
Zip Code
Receiving Water Body
Date Discovered (mm/dd/yyyy) From: To:
Collection System
Watershed data available since 2015 only. Type of Overflow by Weather data available since 2017 only.

Maryland Reported Sewer Overflow Search Results

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