Maryland’s NPDES Municipal Separate Storm Sewer System (MS4) Permits

​The Environmental Protection Agency’s (EPA) National Pollutant Discharge Elimination System (NPDES) stormwater regulations were published in 1990. Phase I of these regulations require large urban jurisdictions to control pollution in stormwater to the maximum extent practicable (MEP). For permitting purposes,municipalities with populations of greater than 250,000 are considered “large” and those with populations of between 100,000 and 250,000 as “medium.” Municipalities with less than 100,000 are handled separately under Phase II NPDES stormwater rules discussed here ( click here to learn more about Phase II ). After receiving applications from Phase I municipalities in 1991 and 1992, MDE began issuing NPDES municipal stormwater permits in 1993. These permits are updated every five years. The following provides information on the most current activities on the Phase I permits. ​

Notice of Final Determination to Modify a Stormwater Permit to Baltimore County (December 7, 2018)

 

​The Maryland Department of the Environment (MDE) has reached a final determination to modify the National Pollutant Discharge Elimination System (NPDES) Municipal Separate Storm Sewer (MS4) permit issued to Baltimore County to control storm drain system pollutant discharges. MDE has drafted permit modifications designed to comply with the United States Environmental Protection Agency’s (EPA) regulations, control stormwater pollutant discharges from the County’s storm drain system, and allow Baltimore County to use Maryland’s newly authorized nutrient trading program as an option to meet its 20 percent impervious surface restoration requirement.

 
The EPA regulations (40 CFR Part122.62) and current permit conditions (see PartVII.E.1, Permit Revocation and Modification) allow for NPDES permits to be modified for an appropriate cause. Baltimore County officially requested a modification of its current permit (Discharge Permit Number 11-DP-3317 MD0068314) on July 18, 2018 to allow the use of nutrient trading to meet the 20 percent impervious surface restoration requirement by the end of the current permit term (i.e., December 23, 2018). MDE has determined the use of nutrient credits by the County for meeting the 20 percent impervious surface restoration requirement is acceptable. Therefore, MDE hereby proposes to add a new paragraph that allows for nutrient trading to meet this requirement in PART IV.E.3; and to rename the original permit’s PART IV.E.3 and PART IV.E.4 as PART IV.E.4 and PART IV.E.5, respectively.
 
MDE’s final determination is subject to judicial review at the request of any person that meets the threshold standing requirements under federal law and participated in the public participation process through the submission of written or oral comments. The modified permit and the Basis for Final Determination may be viewed here:
 
The modified permit is also available by contacting Mr. Raymond Bahr at 410-537-3545 or 1-800-633-6101. Requests for judicial review in accordance with §1-601 and §1-605 of the Environment Article need to be made on or before January 6, 2019.


Notice of Final Determination to Modify a Stormwater Permit to Anne Arundel County (December 7, 2018)

 

The Maryland Department of the Environment (MDE) has reached a final determination to modify the National Pollutant Discharge Elimination System (NPDES) Municipal Separate Storm Sewer (MS4) permit issued to Anne Arundel County to control storm drain system pollutant discharges. MDE has drafted permit modifications designed to comply with the United States Environmental Protection Agency’s (EPA) regulations, control stormwater pollutant discharges from the County’s storm drain system, and allow Anne Arundel County to use Maryland’s newly authorized nutrient trading program as an option to meet its 20 percent impervious surface restoration requirement.
 
The EPA regulations (40 CFR Part122.62) and current permit conditions (see PartVII.E.1, Permit Revocation and Modification) allow for NPDES permits to be modified for an appropriate cause. Anne Arundel County officially requested a modification of its current permit (Discharge Permit Number 11-DP-3316 MD0068306) on August 10, 2018 to allow the use of nutrient trading to meet the 20 percent impervious surface restoration requirement by the end of the current permit term (i.e., February 11, 2019). MDE has determined the use of nutrient credits by the County for meeting the 20 percent impervious surface restoration requirement is acceptable. Therefore, MDE hereby adds a new paragraph that allows for nutrient trading to meet this requirement in PART IV.E.3; and to rename the original permit’s PART IV.E.3 and PART IV.E.4 as PART IV.E.4 and PART IV.E.5, respectively.
 
MDE’s final determination is subject to judicial review at the request of any person that meets the threshold standing requirements under federal law and participated in the public participation process through the submission of written or oral comments. The final determination may be found on MDE’s website at:  
The modified permit is also available by contacting Mr. Raymond Bahr at 410-537-3545 or 1-800-633-6101. Requests for judicial review in accordance with §1-601 and §1-605 of the Environment Article need to be made on or before January 6, 2019.

Notice of Tentative Determination to Modify a Stormwater Permit to Baltimore County (August 31, 2018)

 

​The Maryland Department of the Environment (MDE) has reached a tentative determination to modify the National Pollutant Discharge Elimination System (NPDES) Municipal Separate Storm Sewer (MS4) permit issued to Baltimore County to control storm drain system pollutant discharges. MDE has drafted permit modifications designed to comply with the United States Environmental Protection Agency’s (EPA) regulations, control stormwater pollutant discharges from the County’s storm drain system, and allow Baltimore County to use Maryland’s newly authorized nutrient trading program as an option to meet its 20 percent impervious surface restoration requirement.

The EPA regulations (40 CFR Part122.62) and current permit conditions (see PartVII.E.1, Permit Revocation and Modification) allow for NPDES permits to be modified for an appropriate cause. Baltimore County officially requested a modification of its current permit (Discharge Permit Number 11-DP-3317 MD0068314) on July 18, 2018 to allow the use of nutrient trading to meet the 20 percent impervious surface restoration requirement by the end of the current permit term (i.e., December 23, 2018). MDE has determined the use of nutrient credits by the County for meeting the 20 percent impervious surface restoration requirement is acceptable. Therefore, MDE hereby proposes to add a new paragraph that allows for nutrient trading to meet this requirement in PART IV.E.3; and to rename the original permit’s PART IV.E.3 and PART IV.E.4 as PART IV.E.4 and PART IV.E.5, respectively. The proposed permit modifications and fact sheet are located here:
Copies of these documents may be procured at a cost of $0.36 per page. MDE will hold a public hearing concerning the tentative determination to modify Baltimore County’s MS4 permit on Thursday, October 11, 2018 at 5 PM, MDE first floor, 1800 Washington Boulevard, Baltimore, Maryland, 21230. Comments on this tentative determination to modify Baltimore County’s MS4 permit will be accepted by Raymond Bahr, Maryland Department of the Environment, Water and Science Administration, 1800 Washington Boulevard, Baltimore, Maryland, 21230, or raymond.bahr@maryland.gov, if received within 90 days of publication of this notice. The 60-day extension of the comment period allowed for by section 1-606 (d) (1) (ii) of the Maryland Environmental Article is being invoked to extend the usual 30-day comment period to 90 days.

Notice of Tentative Determination to Modify a Stormwater Permit to Anne Arundel County (August 31, 2018)

 

​The Maryland Department of the Environment (MDE) has reached a tentative determination to modify the National Pollutant Discharge Elimination System (NPDES) Municipal Separate Storm Sewer (MS4) permit issued to Anne Arundel County to control storm drain system pollutant discharges.  MDE has drafted permit modifications designed to comply with the United States Environmental Protection Agency’s (EPA) regulations, control stormwater pollutant discharges from the County’s storm drain system, and allow Anne Arundel County to use Maryland’s newly authorized nutrient trading program as an option to meet its 20 percent impervious surface restoration requirement.
The EPA regulations (40 CFR Part122.62) and current permit conditions (see PartVII.E.1, Permit Revocation and Modification) allow for NPDES permits to be modified for an appropriate cause.  Anne Arundel County officially requested a modification of its current permit (Discharge Permit Number 11-DP-3316 MD0068306) on August 10, 2018 to allow the use of nutrient trading to meet the 20 percent impervious surface restoration requirement by the end of the current permit term (i.e., February 11, 2019).  MDE has determined the use of nutrient credits by the County for meeting the 20 percent impervious surface restoration requirement is acceptable.  Therefore, MDE hereby proposes to add a new paragraph that allows for nutrient trading to meet this requirement in PART IV.E.3; and to rename the original permit’s PART IV.E.3 and PART IV.E.4 as PART IV.E.4 and PART IV.E.5, respectively.  The proposed permit modifications and fact sheet are located here:

Copies of these documents may be procured at a cost of $0.36 per page.  MDE will hold a public hearing concerning the tentative determination to modify Anne Arundel County’s MS4 permit on Thursday, October 18, 2018 at 5 PM, MDE first floor, 1800 Washington Boulevard, Baltimore, Maryland, 21230. Comments on this tentative determination to modify Anne Arundel County’s MS4 permit will be accepted by Raymond Bahr, Maryland Department of the Environment, Water and Science Administration, 1800 Washington Boulevard, Baltimore, Maryland, 21230, or raymond.bahr@maryland.gov, if received within 90 days of publication of this notice. The 60-day extension of the comment period allowed for by section 1-606 (d) (1) (ii) of the Maryland Environmental Article is being invoked to extend the usual 30-day comment period to 90 days.

Notice of Tentative Determination to Modify a Stormwater Permit to Prince George's County (September 14, 2018)

 

​The Maryland Department of the Environment (MDE) has reached a tentative determination to modify the National Pollutant Discharge Elimination System (NPDES) Municipal Separate Storm Sewer (MS4) permit issued to Prince George's County to control storm drain system pollutant discharges.  MDE has drafted permit modifications designed to comply with the United States Environmental Protection Agency’s (EPA) regulations, control stormwater pollutant discharges from the County’s storm drain system, and allow Prince George's County to use Maryland’s newly authorized nutrient trading program as an option to meet its 20 percent impervious surface restoration requirement.
The EPA regulations (40 CFR Part122.62) and current permit conditions (see PartVII.E.1, Permit Revocation and Modification) allow for NPDES permits to be modified for an appropriate cause.  Prince George's County officially requested a modification of its current permit (Discharge Permit Number 11-DP-3314 MD0068284) on August 31, 2018 to allow the use of nutrient trading to meet the 20 percent impervious surface restoration requirement by the end of the current permit term (i.e., January 1, 2019).  MDE has determined the use of nutrient credits by the County for meeting the 20 percent impervious surface restoration requirement is acceptable.  Therefore, MDE hereby proposes to add a new paragraph that allows for nutrient trading to meet this requirement in PART IV.E.3; and to rename the original permit’s PART IV.E.3 and PART IV.E.4 as PART IV.E.4 and PART IV.E.5, respectively.  The proposed permit modifications and fact sheet are located here:

Copies of these documents may be procured at a cost of $0.36 per page.  MDE will hold a public hearing concerning the tentative determination to modify Prince George's County’s MS4 permit on Thursday, October 25, 2018 at 5 PM, MDE first floor, 1800 Washington Boulevard, Baltimore, Maryland, 21230. Comments on this tentative determination to modify Prince George's MS4 permit will be accepted by Raymond Bahr, Maryland Department of the Environment, Water and Science Administration, 1800 Washington Boulevard, Baltimore, Maryland, 21230, or raymond.bahr@maryland.gov, if received within 90 days of publication of this notice. The 60-day extension of the comment period allowed for by section 1-606 (d) (1) (ii) of the Maryland Environmental Article is being invoked to extend the usual 30-day comment period to 90 days.

Consent Decree w/Montgomery County (April 13, 2018)

 

​The Maryland Department of the Environment and the Montgomery County Department of Environmental Protection have reached tentative agreement on a consent decree to be filed in Montgomery County Circuit Court resolving issues with the county’s performance pursuant to the National Pollutant Discharge Elimination System (NPDES) Municipal Separate Storm Sewer System (MS4) permit issued February 15, 2010. The five-year permit expired in 2015.

Final Determination to Issue Stormwater Permit to Anne Arundel County (February 12, 2014)

 

​The Maryland Department of the Environment (MDE) has reissued a National Pollutant Discharge Elimination System (NPDES) stormwater permit to Anne Arundel County, Maryland. This permit covers stormwater discharges from the storm drain system owned or operated by Anne Arundel County. Permit requirements include implementing comprehensive stormwater management programs for addressing runoff from new and redevelopment projects, restoring urban areas where there is currently little or no stormwater management, and working toward meeting stormwater waste load allocations for local water resources and Chesapeake Bay. Also included in the permit are conditions that require the County to possess the necessary legal authority to control stormwater discharges, map its storm drain system, monitor urban runoff, and eliminate illicit discharges to the storm drain system. It is MDE's final determination that this permit complies with the United States Environmental Protection Agency’s NPDES regulations to control stormwater pollutant discharges from Anne Arundel County’s storm drain system to the maximum extent practicable.

This permit and the Basis for Final Determination may be viewed here:

Final Determination to Issue Stormwater Permit to Baltimore City (December 27, 2013)

 

​The Maryland Department of the Environment (MDE) has reissued a National Pollutant Discharge Elimination System (NPDES) stormwater permit to Baltimore City, Maryland. This permit covers stormwater discharges from the storm drain system owned or operated by Baltimore City. Permit requirements include implementing comprehensive stormwater management programs for addressing runoff from new and redevelopment projects, restoring urban areas where there is currently little or no stormwater management, and working toward meeting stormwater waste load allocations for local water resources and Chesapeake Bay. Also included in the permit are conditions that require the City to possess the necessary legal authority to control stormwater discharges, map its storm drain system, monitor urban runoff, and eliminate illicit discharges to the storm drain system. It is MDE's final determination that this permit complies with the United States Environmental Protection Agency’s NPDES regulations to control stormwater pollutant discharges from Baltimore City’s storm drain system to the maximum extent practicable.

This permit and the Basis for Final Determination may be viewed here:

Final Determination to Issue Stormwater Permit to Baltimore County (December 23, 2013)

 

​The Maryland Department of the Environment (MDE) has reissued a National Pollutant Discharge Elimination System (NPDES) stormwater permit to Baltimore County, Maryland. This permit covers stormwater discharges from the storm drain system owned or operated by Baltimore County. Permit requirements include implementing comprehensive stormwater management programs for addressing runoff from new and redevelopment projects, restoring urban areas where there is currently little or no stormwater management, and working toward meeting stormwater waste load allocations for local water resources and Chesapeake Bay. Also included in the permit are conditions that require the County to possess the necessary legal authority to control stormwater discharges, map its storm drain system, monitor urban runoff, and eliminate illicit discharges to the storm drain system. It is MDE's final determination that this permit complies with the United States Environmental Protection Agency’s NPDES regulations to control stormwater pollutant discharges from Baltimore County’s storm drain system to the maximum extent practicable.

This permit and the Basis for Final Determination may be viewed here:

Final Determination to Issue Stormwater Permit for Carroll County (December 29, 2014)

 

​The Maryland Department of the Environment (MDE) has reissued a National Pollutant Discharge Elimination System (NPDES) stormwater permit to Carroll County, Maryland. This permit covers stormwater discharges from the storm drain system owned or operated by Carroll County. Permit requirements include implementing comprehensive stormwater management programs for addressing runoff from new and redevelopment projects, restoring urban areas where there is currently little or no stormwater management, and working toward meeting stormwater waste load allocations for local water resources and Chesapeake Bay. Also included in the permit are conditions that require the County to possess the necessary legal authority to control stormwater discharges, map its storm drain system, monitor urban runoff, and eliminate illicit discharges to the storm drain system. It is MDE's final determination that this permit complies with the United States Environmental Protection Agency’s NPDES regulations to control stormwater pollutant discharges from Carroll County’s storm drain system to the maximum extent practicable.

This permit and the Basis for Final Determination may be viewed here:

Final Determination to Issue Stormwater Permit for Charles County (December 26, 2014)

 

​The Maryland Department of the Environment (MDE) has reissued a National Pollutant Discharge Elimination System (NPDES) stormwater permit to Charles County, Maryland. This permit covers stormwater discharges from the storm drain system owned or operated by Charles County. Permit requirements include implementing comprehensive stormwater management programs for addressing runoff from new and redevelopment projects, restoring urban areas where there is currently little or no stormwater management, and working toward meeting stormwater waste load allocations for local water resources and Chesapeake Bay. Also included in the permit are conditions that require the County to possess the necessary legal authority to control stormwater discharges, map its storm drain system, monitor urban runoff, and eliminate illicit discharges to the storm drain system. It is MDE's final determination that this permit complies with the United States Environmental Protection Agency’s NPDES regulations to control stormwater pollutant discharges from Charles County’s storm drain system to the maximum extent practicable.

This permit and the Basis for Final Determination may be viewed here:

Final Determination to Issue Stormwater Permit for Frederick County (December 30, 2014)

 

​The Maryland Department of the Environment (MDE) has reissued a National Pollutant Discharge Elimination System (NPDES) stormwater permit to Frederick County, Maryland. This permit covers stormwater discharges from the storm drain system owned or operated by Frederick County. Permit requirements include implementing comprehensive stormwater management programs for addressing runoff from new and redevelopment projects, restoring urban areas where there is currently little or no stormwater management, and working toward meeting stormwater waste load allocations for local water resources and Chesapeake Bay. Also included in the permit are conditions that require the County to possess the necessary legal authority to control stormwater discharges, map its storm drain system, monitor urban runoff, and eliminate illicit discharges to the storm drain system. It is MDE's final determination that this permit complies with the United States Environmental Protection Agency’s NPDES regulations to control stormwater pollutant discharges from Frederick County’s storm drain system to the maximum extent practicable.

This permit and the Basis for Final Determination may be viewed here:

Final Determination to Issue Stormwater Permit for Harford County (December 30, 2014)

 

​The Maryland Department of the Environment (MDE) has reissued a National Pollutant Discharge Elimination System (NPDES) stormwater permit to Harford County, Maryland. This permit covers stormwater discharges from the storm drain system owned or operated by Harford County. Permit requirements include implementing comprehensive stormwater management programs for addressing runoff from new and redevelopment projects, restoring urban areas where there is currently little or no stormwater management, and working toward meeting stormwater waste load allocations for local water resources and Chesapeake Bay. Also included in the permit are conditions that require the County to possess the necessary legal authority to control stormwater discharges, map its storm drain system, monitor urban runoff, and eliminate illicit discharges to the storm drain system. It is MDE's final determination that this permit complies with the United States Environmental Protection Agency’s NPDES regulations to control stormwater pollutant discharges from Harford County’s storm drain system to the maximum extent practicable.

This permit and the Basis for Final Determination may be viewed here:

Final Determination to Issue Stormwater Permit for Howard County (December 18, 2014)

 

​The Maryland Department of the Environment (MDE) has reissued a National Pollutant Discharge Elimination System (NPDES) stormwater permit to Howard County, Maryland. This permit covers stormwater discharges from the storm drain system owned or operated by Howard County. Permit requirements include implementing comprehensive stormwater management programs for addressing runoff from new and redevelopment projects, restoring urban areas where there is currently little or no stormwater management, and working toward meeting stormwater waste load allocations for local water resources and Chesapeake Bay. Also included in the permit are conditions that require the County to possess the necessary legal authority to control stormwater discharges, map its storm drain system, monitor urban runoff, and eliminate illicit discharges to the storm drain system. It is MDE's final determination that this permit complies with the United States Environmental Protection Agency’s NPDES regulations to control stormwater pollutant discharges from Howard County’s storm drain system to the maximum extent practicable.

This permit and the Basis for Final Determination may be viewed here:

Final Determination to Issue Stormwater Permit to Prince George's County (January 2, 2014)

 

​The Maryland Department of the Environment (MDE) has reissued a National Pollutant Discharge Elimination System (NPDES) stormwater permit to Prince George's County, Maryland. This permit covers stormwater discharges from the storm drain system owned or operated by Prince George's County. Permit requirements include implementing comprehensive stormwater management programs for addressing runoff from new and redevelopment projects, restoring urban areas where there is currently little or no stormwater management, and working toward meeting stormwater waste load allocations for local water resources and Chesapeake Bay. Also included in the permit are conditions that require the County to possess the necessary legal authority to control stormwater discharges, map its storm drain system, monitor urban runoff, and eliminate illicit discharges to the storm drain system. It is MDE's final determination that this permit complies with the United States Environmental Protection Agency’s NPDES regulations to control stormwater pollutant discharges from Prince George's County’s storm drain system to the maximum extent practicable.

This permit and the Basis for Final Determination may be viewed here:

Final Determination to Issue Stormwater Permit for the Maryland State Highway Administration (October 9, 2015)

 

​The Maryland Department of the Environment (MDE) has reissued a National Pollutant Discharge Elimination System (NPDES) stormwater permit to the Maryland State Highway Administration (SHA). This permit covers stormwater discharges from the storm drain system owned or operated by SHA. Permit requirements include implementing comprehensive stormwater management programs for addressing runoff from new and redevelopment projects, restoring urban areas where there is currently little or no stormwater management, and working toward meeting stormwater waste load allocations for local water resources and Chesapeake Bay. Also included in the permit are conditions that require SHA to possess the necessary legal authority to control stormwater discharges, map its storm drain system, monitor urban runoff, and eliminate illicit discharges to the storm drain system. It is MDE's final determination that this permit complies with the United States Environmental Protection Agency’s NPDES regulations to control stormwater pollutant discharges from SHA's storm drain system to the maximum extent practicable.

This permit and the Basis for Final Determination may be viewed here:

NPDES Phase I Permits

 

​You can view background information on each jurisdiction by clicking on the municipality's name in the chart below. Initial permits, current permits, and links to the agency responsible for administering each local permit are also accessible by clicking on the respective links below.

 

Initial Permit Issued Current Permit Issued Local Agency Responsible for Annual Reporting

Large Jurisdictions

Anne Arundel County

12/02/1993

02/12/2014

Dept. of Public Works / Watershed Protection and Restoration

Baltimore County

11/17/1994

12/23/2013

Dept. of Environmental Protection & Sustainability (EPS) / NPDES

Baltimore City

11/17/1993

12/27/2013

Dept. of Public Works

Montgomery County

03/15/1996

02/16/2010

Dept. of Environmental Protection

Prince George’s County

11/17/1993

01/02/2014

Dept. of Environment

Medium Jurisdictions

Carroll County

05/30/1995

12/30/2014

Land Use, Planning & Development

Charles County

05 /01/1997

12/26/2014

Planning & Growth Management

Frederick County

11/15/1994

12/30/2014

Sustainable Development - Watershed Management

Harford County

05/17/1994

12/30/2014

Dept. of Public Works - Water Resources

Howard County

04/17/1995

12/18/2014

Dept. of Public Works / Stormwater Management Division

State Storm Drain Systems

State Highway Administration

01/08/1999

10/09/2015

Office of Environmental Design

Summary of Local Requirements
 
NPDES municipal stormwater permits require the jurisdictions to develop comprehensive programs to reduce storm drain system pollution to the MEP. Typical NPDES stormwater permit conditions require jurisdictions to: 
  • Legal Authority: provide certification from appropriate legal counsel that adequate authority exists to control discharges from the municipal storm drain system
  • Source Identification: map storm drain pipes and best management practices (BMPs), land use, impervious cover, and watershed restoration projects in geographical information system (GIS) format
  • Management Programs: implement erosion and sediment control, stormwater management, illicit connection detection and elimination, and public education and outreach programs
  • Watershed Assessment: evaluate all urban watersheds thoroughly regarding water quality and develop goals and action plans for restoration,
  • Restoration Projects: restore 20% of uncontrolled impervious surfaces based on watershed assessments during each five-year permit cycle
  • Assessment of Control: document work toward meeting watershed restoration goals, including total maximum daily loads (TMDLs)*, using chemical, biological, and physical monitoring
  • Program Funding: provide an annual fiscal analysis of the capital, operation, and maintenance expenditures necessary to comply with permit conditions
More information on TMDLs may be found on MDE's webpage here: Introduction to TMDLs
 

Additional Resources

 

Guidance for Maryland's NPDES Stormwater Permits

NPDES municipal separate storm sewer system permits in Maryland require the restoration of a certain percent of a jurisdiction's impervious surface area (e.g., 20%) that has little or no stormwater management. How to calculate impervious surface requirements and treatment credits has generated numerous questions. This document standardizes procedures for reporting of traditional, new, and alternative best management practices (BMPs) and the impervious area each controls. The guidance may be found here:
 

 

Contact Info

Questions about NPDES municipal permits may be directed to the Sediment, Stormwater, and Dam Safety Program at 410-537-3543 or emailed to Mr. Raymond Bahr at Raymond.Bahr@maryland.gov. ​​​