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National Pollution Discharge Elimination System

The National Pollution Discharge Elimination System (NPDES) program requires urban jurisdictions like Baltimore County to have a discharge permit for their storm drain pipes. This is similar to the end-of-pipe restrictions with which industries or wastewater treatment plants must comply. These permit requirements are coordinated by the NPDES Management Committee. Related State and Federal resources are regularly referred to for program updates and meeting presentations are additional resources.

Storm drain systems are designed primarily to move stormwater away from developed areas as quickly as possible to prevent flooding. These developed areas are also referred to as impervious surfaces and are places that prevent rain from soaking back into the ground, roads, rooftops and parking lots. The result is an increase in stormwater runoff.

Stormwater runoff is now recognized as a major transporter of excess nitrogen, phosphorous and sediment generated within our urban communities. These pollutants come from a multitude of sources such as livestock and pet waste, chemicals leaked from cars and fertilizers on our lawns.

Baltimore County prepares an annual report of stormwater-related programs and projects targeted to reduce water quality pollution. This report has valuable data and information related to the monitoring and management of our watersheds. Past reports are also available.

2021 NPDES Annual Report

View and download individual sections of the 2021 NPDES Annual Report (PDF) below.

NPDES Permit Data

You will be directed to an FTP—GIS Download to display the data below. Please follow the Instructions on the site. This data includes excel spreadsheets and GIS information and is required for the NPDES permit and used in preparing the NPDES report.


  • Bacteria Data—Bacteriological data from County wide monthly bacteria trend program.
  • Chemical Data—Water chemistry data from Scotts Level Branch and County wide monthly trend data.
  • Geomorphic Data—Geomorphic data including cross sections of sites in Powder Mill, Scotts Level and Windlass Run in Baltimore County.

GIS Data Layers

  • Industrial Commercial Sources—Locations of businesses in Baltimore County.
  • Monitoring Locations—Locations of biological, chemical, bacteria, trash, random, trend, tidal and geomorphic monitoring stations in Baltimore County.

GIS data layers are now required by Maryland Department of the Environment (MDE) to be reported in a streamlined geodatabase (PDF). The following GIS data is provided:

  • Grading Permits—Locations of approved grading permits in Baltimore County in Fiscal Year 2017 and 2018.
  • Storm Drain System Layer—Locations of outfalls and drainage areas inside and outside of the URDL in Baltimore County. Locations of major and minor outfalls with drainage areas used in Illicit Connection monitoring.
  • Urban Best Management Practices (BMPs)—Locations of Best Management Practices in Baltimore County.
  • Water Quality Improvement Projects—Locations of water quality improvement projects such as stream restoration projects, septic projects, street sweeping, and inlet cleaning in Baltimore County.
  • Illicit Discharge Detection and Elimination (IDDE) Activities—shows screening results for both major and minor outfalls and investigations of complaints.
  • Pollutant Load Reductions—Pollutant load reductions from actions, projects and BMPs are tallied per eight-digit watershed.
  • Municipal Facilities Subject to NPDES Industrial Permits—shows locations of public facilities subject to NPDES industrial permits.

Past Annual Reports 

Below is a list of past annual reports in PDF format. Previous reports are available from the EPS office. 

Contact Information

Watershed Management and Monitoring
Phone: 410-887-5683
Fax: 410-887-4804

Revised January 18, 2022         


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