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National Pollution Discharge Elimination System

Runoff from rain is regulated under the NPDES permit program.

Runoff from rain storms
carries pollution to local

The National Pollution Discharge Elimination System (NPDES) program requires urban jurisdictions, such as 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. View and download either the entire document or chapters of the 2016 NPDES Annual Report on the links below. Past reports are also available in the archive.

2016 NPDES Annual Report

View and download individual sections of the 2016 NPDES Annual Report.

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.


  • Biological Data—Tidal benthic data with Benthic Index of Biological Integrity (BIBI) scores
  • 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 Datalayers

  • Grading Permits—Locations of approved grading permits in Baltimore County in Fiscal Year 2015
  • Impervious Surfaces—Locations of impervious surfaces using baseline data from 2002
  • 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
  • Storm Drain Layer—Locations of stormwater pipes, ponds, inflows, 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—Locations of Best Management Practices in Baltimore County
  • Water Quality Improvement Projects—Locations of water quality improvement projects such as stream restoration projects in Baltimore County.
  • Attachment A Data—Data tables as required by and described in NPDES MS4 Permit Attachment A.

Contact Information

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

Revised January 13, 2017         


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