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

​Department of the Environment Issues Stormwater Permits for Large Maryland Jurisdictions, Advances Climate Resiliency and Equity​

​The Maryland Department of the Environment (MDE) has issued a series of municipal stormwater permits to advance Chesapeake Bay restoration while reducing flooding and making communities more resilient to the effects of climate change.​


Maryland’s Municipal Stormwater Permits

When it rains, stormwater washes excess nutrients, chemicals, and dirt from impervious surfaces, such as buildings, roads, and parking lots into local waters and the Chesapeake Bay. Excess stormwater runoff can also flood local communities, scour sediment from waterways, and degrade the health of stream systems.
 
MDE’s MS4 permits continue the state’s robust work to reduce nutrient and sediment pollution from stormwater as part of a larger effort that requires all sectors, such as sewage treatment plants and septic systems, in Maryland and the surrounding region to protect and restore the Chesapeake Bay.
 
The MS4 permits are a result of extensive stakeholder engagement. Maintenance of existing infrastructure is essential and the new permits require local jurisdictions to maintain the previous stormwater pollution reduction efforts while also requiring additional  stormwater pollution reduction to restore waterways.  The additional restoration requirements are to reduce the impacts of  impervious surface areas that have little through stormwater treatment with green infrastructure and other techniques. These new permits meet Maryland’sChesapeake Bay commitments and also increase accountability, enhance public education and include innovative and cost-effective monitoring options.
   
In the next five years the new permits add another 19,000 acres to the 35,000 impervious acres restored under prior permits. This restoration encourages climate resiliency and green infrastructure and at the same time continues to advance innovations such as pay-for-performance contracting, public-private partnerships, and new technologies. The permits also include new incentives for climate resiliency and green and blue infrastructure projects.

Maryland’s 11 phase I urban jurisdictions have established themselves as national leaders in reducing stormwater pollution by collectively investing over $1 billion in clean water infrastructure. Since July 2019, MDE’s Water Quality Finance Administration has guaranteed $117.8 million in low interest loans to counties and local governments for stormwater restoration projects, and another $257 million in low interest loans are pending for planned projects. During the prior MS4 permit term, which started in 2014, the Chesapeake Bay Trust awarded an additional $36.5 million in grants to stormwater programs for restoration projects, which leveraged another $27.7 million in matching funds. Maryland continues to push for additional federal funding for local stormwater projects – especially for those that increase climate resiliency in underserved communities and for those that help sustain our Chesapeake Bay restoration efforts for decades to come.

Advancing Stormwater Resiliency in Maryland

Urban flooding is a growing issue in Maryland. The increasing number of extreme rainfall events that produce intense precipitation will continue to lead to more urban flooding events unless steps are taken to mitigate their impacts. The Maryland General Assembly recognized the need to address urban flooding with the passing of Senate Bill 227. The Bill tasks the Maryland Department of the Environment (Department) with developing plans to evaluate current flooding risks and update regulations to improve urban stormwater flood management. The "Advancing Stormwater Resiliency in Maryland" report provides a roadmap towards modernizing stormwater management in Maryland.​

Where Do We Start?

The Department is taking action through collection of data sets, development of tools and web applications, targeting funding opportunities, developing outreach and education and updating stormwater regulations. Step one is performing a statewide comprehensive urban flood management assessment. With the help of local floodplain and stormwater managers, the Department will identify and characterize Maryland’s urban flooding events and report the current state of local stormwater and flood management programs.​ For more information on this effort, please visit the Advancing Stormwater Resiliency in Maryland ​page here​.




Notice of Final Determination to Issue Stormwater Permit to Carroll County (December 30, 2022)

 

The Maryland Department of the Environment (Department) has reached a final determination to issue a National Pollutant Discharge Elimination System permit to Carroll County (Discharge Permit No. 22-DP-3319, NPDES No. MD0068331) for Discharges from Medium Municipal Separate Storm Sewer Systems (MS4) on December 30, 2022.  This permit covers stormwater discharges into, through, or from the storm drain system owned or operated jurisdiction-wide by Carroll County and the following incorporated municipalities: The Towns of Hampstead, Manchester, Mt. Airy, New Windsor, Sykesville, Union Bridge and the Cities of Taneytown and Westminster (co-permittees).  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 wasteload allocations for local water resources and the 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.

The Department has met with various stakeholders over the past several years regarding this permit, held a public hearing on April 12, 2022 to accept testimony, and accepted public comments through June 9, 2022.  It is the Department’s final determination that this permit complies with the United States Environmental Protection Agency’s NPDES regulations to control stormwater pollutant discharges from the County’s storm drain system to the maximum extent practicable.

The final permit and fact sheet can be viewed here:

MS4 Guidance Includes:

The Department used the following documents to help assess the physical and financial capacity of Carroll County to meet restoration goals proposed in the permit.

These analyses were based on instructions and spreadsheets sent to the County.  These instructions may be found here: 

Hard copies of the documents listed above may also be obtained from the Department at a cost of 36¢ per page.

The Department’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. Requests for judicial review in accordance with §1-601 and §1-605 of the Environment Article need to be made on or before January 29, 2023.​


Notice of Final Determination to Issue Stormwater Permit to Charles County (December 30, 2022)

 

The Maryland Department of the Environment (Department) reached a final determination to issue a National Pollutant Discharge Elimination System (NPDES) permit to Charles County (Discharge Permit No. 22-DP-3322, NPDES No. MD0068365) for Discharges from Medium Municipal Separate Storm Sewer Systems (MS4) on December 30, 2022.  This permit covers stormwater discharges into, through, or from the storm drain system owned or operated jurisdiction-wide 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 wasteload allocations for local water resources and the 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.  

The Department has met with various stakeholders over the past several years regarding this permit, held a public hearing on April 27, 2022 to accept testimony, and accepted public comments through June 9, 2022.  It is the Department’s final determination that this permit complies with the United States Environmental Protection Agency’s NPDES regulations to control stormwater pollutant discharges from the County’s storm drain system to the maximum extent practicable.

The final permit and fact sheet can be viewed here:

MS4 Guidance Includes:

The Department used the following documents to help assess the physical and financial capacity of Charles County to meet restoration goals proposed in the permit.

These analyses were based on instructions and spreadsheets sent to the County.  These instructions may be found here: 

Hard copies of the documents listed above may also be obtained from the Department at a cost of 36¢ per page.

The Department’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. Requests for judicial review in accordance with §1-601 and §1-605 of the Environment Article need to be made on or before January 29, 2023.


Notice of Final Determination to Issue Stormwater Permit to Frederick County (December 30, 2022)

 

The Maryland Department of the Environment (Department) reached a final determination to issue a National Pollutant  Discharge Elimination System (NPDES) permit to Frederick County (Discharge Permit No. 22-DP-3321, NPDES No. MD0068357) for Discharges from Medium Municipal Separate Storm Sewer Systems (MS4) on December 30, 2022.  This permit covers stormwater discharges into, through, or from the storm drain system owned or operated jurisdiction-wide 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 wasteload allocations for local water resources and the 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.  

The Department has met with various stakeholders over the past several years regarding this permit, held a public hearing on April 21, 2022 to accept testimony, and accepted public comments through June 9, 2022.  It is the Department’s final determination that this permit complies with the United States Environmental Protection Agency’s NPDES regulations to control stormwater pollutant discharges from the County’s storm drain system to the maximum extent practicable.

The final permit and fact sheet can be viewed here:

MS4 Guidance Includes:

The Department used the following documents to help assess the physical and financial capacity of Frederick County to meet restoration goals proposed in the permit.

These analyses were based on instructions and spreadsheets sent to the County.  These instructions may be found here: 

Hard copies of the documents listed above may also be obtained from the Department at a cost of 36¢ per page.

The Department'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. Requests for judicial review in accordance with §1-601 and §1-605 of the Environment Article need to be made on or before January 29, 2023.​

Notice of Final Determination to Issue Stormwater Permit to Harford County (December 30, 2022)

 

The Maryland Department of the Environment (Department) reached a final determination to issue a National Pollutant Discharge Elimination System (NPDES) permit to Harford County (Discharge Permit No. 22-DP-3310, NPDES No. MD0068268) for Discharges from Medium Municipal Separate Storm Sewer Systems (MS4) on December 30, 2022.  This permit covers stormwater discharges into, through, or from the storm drain system owned or operated jurisdiction-wide 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 wasteload allocations for local water resources and the 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.

The Department has met with various stakeholders over the past several years regarding this permit, held a public hearing on April 27, 2022 to accept testimony, and accepted public comments through June 9, 2022.  It is the Department’s final determination that this permit complies with the United States Environmental Protection Agency’s NPDES regulations to control stormwater pollutant discharges from the County’s storm drain system to the maximum extent practicable.

The final permit and fact sheet can be viewed here:

MS4 Guidance Includes:

The Department used the following documents to help assess the physical and financial capacity of Harford County to meet restoration goals proposed in the permit.

These analyses were based on instructions and spreadsheets sent to the County.  These instructions may be found here: 

Hard copies of the documents listed above may also be obtained from the Department at a cost of 36¢ per page.

The Department’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. Requests for judicial review in accordance with §1-601 and §1-605 of the Environment Article need to be made on or before January 29, 2023.



Notice of Final Determination to Issue Stormwater Permit to Howard County (December 30, 2022)

 

The Maryland Department of the Environment (Department) reached a final determination to issue a National Pollutant Discharge Elimination System (NPDES) permit to Howard County (Discharge Permit No. 22-DP-3318, NPDES No. MD0068322) for Discharges from Medium Municipal Separate Storm Sewer Systems (MS4) on December 30, 2022.  This permit covers stormwater discharges into, through, or from the storm drain system owned or operated jurisdiction-wide 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 wasteload allocations for local water resources and the 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.

The Department has met with various stakeholders over the past several years regarding this permit, held a public hearing on April 26, 2022 to accept testimony, and accepted public comments through June 9, 2022.  It is the Department’s final determination that this permit complies with the United States Environmental Protection Agency’s NPDES regulations to control stormwater pollutant discharges from the County’s storm drain system to the maximum extent practicable. 

The final permit and fact sheet can be viewed here:

MS4 Guidance Includes:

The Department used the following documents to help assess the physical and financial capacity of Howard County to meet restoration goals proposed in the permit.

These analyses were based on instructions and spreadsheets sent to the County.  These instructions may be found here: 

Hard copies of the documents listed above may also be obtained from the Department at a cost of 36¢ per page.

The Department’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. Requests for judicial review in accordance with §1-601 and §1-605 of the Environment Article need to be made on or before January 29, 2023.


Notice of Final Determination to Issue Stormwater Permit to Prince George's County (December 2, 2022)

 

​The Maryland Department of the Environment (Department) reached a final determination to issue a National Pollutant Discharge Elimination System (NPDES) permit to Prince George’s County (Discharge Permit No. 20-DP-3314, NPDES No. MD0068284) for Discharges from Large Municipal Separate Storm Sewer Systems (MS4) on December 2, 2022.  This permit covers stormwater discharges into, through, or from the storm drain system owned or operated by Prince George’s County and all incorporated municipalities within the County except for the City of Bowie.  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 wasteload allocations for local water resources and the 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.  The Department has met with various stakeholders over the past several years regarding this permit, held a public hearing on December 15, 2021 to accept testimony, and accepted public comments through February 4, 2022.  It is the Department’s final determination that this permit complies with the United States Environmental Protection Agency’s NPDES regulations to control stormwater pollutant discharges from the County’s storm drain system to the maximum extent practicable. 

The final permit and fact sheet can be viewed here:

MS4 Guidance Includes:

​The Department used the following documents to help assess the physical and financial capacity of Prince George's County to meet restoration goals proposed in the permit. These documents were submitted in July 2019 and April 2020 and some of the information contained within do not incorporate continued program activity and updates. 

These analyses were based on instructions and spreadsheets sent to the County.  These instructions may be found here: 

Hard copies of the documents may also be obtained directly from the Department at a cost of 36¢ per page. ​


​​

Notice of Final Determination to Issue Stormwater Permits to Anne Arundel County, Baltimore City, Baltimore County, and Montgomery County (November 5, 2021)

 

The Maryland Department of the Environment (Department) reached a final determination to issue a National Pollutant Discharge Elimination System (NPDES) permit to Anne Arundel County (Discharge Permit No. 20-DP-3316, NPDES Permit No. MD0068306), Baltimore City (Discharge Permit No. 20-DP-3315, NPDES Permit No. MD0068292), Baltimore County (Discharge Permit No. 20-DP-3317, NPDES Permit No. MD0068314), and Montgomery County (Discharge Permit No. 20-DP-3320, NPDES Permit No. MD0068349) for Discharges from Large Municipal Separate Storm Sewer Systems (MS4) on November 5, 2021. These permits cover stormwater discharges into, through, or from the storm drain system owned or operated by these Counties.  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 wasteload allocations for local water resources and Chesapeake Bay.  Also included in the permits 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.  The Department has met with various stakeholders over the past several years regarding these permits, held public hearings to accept testimony and accepted public comments.  It is the Department's final determination that these permits comply with the United States Environmental Protection Agency's NPDES regulations to control stormwater pollutant discharges from Counties' storm drain systems to the maximum extent practicable.  

The final permits, fact sheets, and Response to Comments can be viewed here:

MS4 Guidance Includes:

MEP Submissions:

Notice of Settlement - Prince George's County (December 1, 2021)

 

​​The Maryland Department of the Environment and the Prince George’s County Department of Environmental Protection entered into a court-sanctioned consent decree on December 1, 2021 resolving issues with the county’s performance pursuant to the National Pollutant Discharge Elimination System (NPDES) Municipal Separate Storm Sewer System (MS4) permit issued January 2, 2014.  The five-year permit expired on January 1, 2019.  

The settlement can be viewed here:

The consent decree imposes a $475,000 penalty for failure to complete all of the restoration work required by the 2014 permit.  The penalty can be satisfied through the construction of one or more Department-approved Supplemental Environmental Projects by December 31, 2024.  In addition, the decree requires that the restoration work remaining under the terms of the 2014 MS4 permit be completed in the same timeframe.  The settlement calls for additional penalties for failure to meet interim goals.  

Prince George’s County initiated efforts to address urban stormwater runoff well before the Chesapeake Bay Total Maximum Daily Load (TMDL) was established in 2010 and has been diligent in its efforts.  This consent decree requires the county to complete the impervious surface restoration work that remains to be performed notwithstanding the expiration of the 2014 permit.

"We appreciate Prince George’s County's commitment to improved environmental performance under its state permit and collaboration on the consent decree, including provisions on penalties, schedules, and supplemental environmental projects”, said Secretary Ben Grumbles.  “Preventing stormwater pollution can be challenging but it's important for local water quality and the Chesapeake Bay and the state will continue to enforce its laws and provide assistance to counties and communities."


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 can be found below.

The Department has revised Appendix B of the Accounting for Stormwater Wasteload Allocations and Impervious Acres Treated (MDE, November 2021). The revision corrects a technical error and provides additional clarification related to the calculation of total nitrogen load reductions for measuring progress toward meeting total maximum daily load (TMDL) goals. The revision ensures consistency with the guidance and the reporting criteria found in the Department’s Urban Stormwater Management Credit Calculator for TN, TP, TSS (MDE, April 28, 2022) and the TMDL Implementation Progress and Planning (TIPP) Tool (MDE, April 6, 2022).

The following documents were developed to help the Department assess the physical and financial capacity of Phase I Large permittees to meet proposed restoration goals. The first documents are the instructions and spreadsheets sent to each Phase I large permittee:
Other Guidance Documents:

Since 2014, MDE has distributed several memoranda that provide additional guidance concerning BMPs and impervious area crediting.  Please note that these memoranda are intended to clarify, supplement, or replace the information found in the Accounting for Stormwater Wasteload Allocations and Impervious Acres Treated (MDE, 2014).  When there are conflicts between these memoranda and the original 2014 guidance, the newest shall supersede. These documents may be found here:
Additionally, in March 2018, MDE sent a letter to OptiRTC, Incorporated that established requirements and interim credits for the use of continuous monitoring and adaptive control (CMAC) systems for restoration.  While this letter is addressed to OptiRTC, the conditions and restrictions apply to CMAC systems in general, includiong those marketed by others.  A copy of this letter is available here:
Phase I Large MS4 Permit Tentative Determination Comments

The Maryland Department of the Environment, Water and Science Administration (the Department) reached a final determination to issue a National Pollutant Discharge Elimination System (NPDES) permit to Anne Arundel County (Discharge Permit No. 20-DP-3316, NPDES Permit No. MD0068306), Baltimore City (Discharge Permit No. 20-DP-3315, NPDES Permit No. MD0068292), Baltimore County (Discharge Permit No. 20-DP-3317, NPDES Permit No. MD0068314), and Montgomery County (Discharge Permit No. 20-DP-3320, NPDES Permit No. MD0068349) for Discharges from Large Municipal Separate Storm Sewer Systems (MS4) on November 5, 2021. The Department met with various stakeholders over the past several years regarding these permits, held public hearings to accept testimony on each permit through online webinars in November 2020, and accepted public comments through January 21, 2021. The written comments recieved by the Department and the transcripts of the public hearings are posted below. 
​​

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

11/05/2021

Dept. of Public Works / Watershed Protection and Restoration

Baltimore County

11/17/1994

11/05/2021

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

Baltimore City

11/17/1993

11/05/2021

Dept. of Public Works

Montgomery County

03/15/1996

11/05/2021

Dept. of Environmental Protection

Prince George’s County

11/17/1993

​12/02/2022

Dept. of Environment​

Medium Jurisdictions

Carroll County

05/30/1995

12/30/2022

Land Use, Planning & Development

Charles County

05 /01/1997

12/30/2022

Planning & Growth Management

Frederick County

11/15/1994

12/30/2022

Sustainable Development - Watershed Management

Harford County

05/17/1994

12/30/2022

Dept. of Public Works - Water Resources

Howard County

04/17/1995

12/30/2022

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
 

 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. ​​​

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