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How is Stormwater Regulated?

In urban areas, like Montgomery County, rainwater in the form of stormwater is carried through the storm drain system before being released in local streams and waterbodies. The stormwater runoff can carry trash or pollutants, such as fertilizers and oils, as well as cause erosion and physical damage to streams. The negative impact of stormwater runoff to watersheds is a concern nationwide and is regulated by the federal government as well as state agencies. 

Graphic of a family watching stormwater flow down a storm drain.

The Environmental Protection Agency (EPA) regulates everything that goes through storm drains under the National Pollutant Discharge Elimination System (NPDES) Municipal Separate Storm Sewer System Permit Program (MS4). The MS4 program was established to reduce and eliminate stormwater pollution throughout the United States. The primary goal of the program is to restore and maintain the chemical, physical, and biological integrity of the nation's waters.


What is the MS4 Permit?

In Maryland, the Maryland Department of the Environment is responsible for issuing all NPDES permits in the state, including the MS4 Permits. Read more about the Maryland MS4 Permitting program. (The state of Maryland has the authority to issue permits on behalf of EPA.)

The MS4 Permit Program is intended to reduce and eliminate pollution from rainfall runoff.  The County's Permit requires the County to restore poor quality streams and meet water quality protection goals. To protect our local streams and meet regulatory requirements, runoff must be intercepted, slowed and treated by stormwater best management practices.

The Department of Environmental Protection is the lead department coordinating a multi-department/agency response to meet the requirements of the MS4 Permit. The permit is a key driver of the County's strategic watershed management program. 

View the County's MS4 Permit. (PDF, 1.3MB)


MS4 Permit Requirements

The MS4 Permits are issued for a five year cycle.  The County’s current MS4 Permit was issued on February 16, 2010 and expires February 15, 2015.  If the County does not comply with the MS4 Permit requirements, it may be subject to civil or criminal fines.

Image of a restored section of Booze Creek
The restoration of Booze Creek was one of many projects completed to meet the MS4 Permit requirements.

During this five-year cycle, the County is required to: 


Current Permit: Annual Report


Annual Reports


How Much Progress Has the County Made

In the most recent Annual Report to the Maryland Department of the Environment, the County noted the following progress towards meeting its MS4 Permit requirements. 


Image of a stormwater management pond
The new pond installed at the National Institutes of Health captures and slows stormwater and removes pollutants.

Watershed Restoration

DEP is the lead agency for projects to reduce stormwater runoff impacts. During Fiscal Year 2012, DEP:

  • Had stormwater restoration projects in design or construction that will treat the runoff from over 2,000 acres of impervious areas. 

  • Continued the Great Seneca and Muddy Branch studies that identify stormwater management and restoration opportunities in those watersheds.

  • Provided stormwater management to over 12 acres of impervious area through the RainScapes Program, which supports and constructs small scale residential stormwater management practices for both single lots and neighborhoods.


Reducing Pollution

DEP is the lead agency for enforcement of water quality laws that reduce pollution to our waterways. During Fiscal Year 2012, DEP:

  • Discovered 21 illegal discharges through the storm drain system, identified 8 of the sources, and is continuing to conduct further investigations to identify the remaining sources.

  • Responded to 208 water quality issue complaints, and 20 hazardous materials incidents, resulting in 31 enforcement actions.

DEP partnered with other County agencies to reduce pollution.

  • DEP, the Department of General Services (DGS) and the Department of Transportation (DOT) work together to reduce pollution from County Highway Depots.  During FY12, the  DGS built more effective materials (salt and sand) storage structures at 4 Depots to prevent accidental contamination to stormwater runoff.

  • The DEP and the DOT jointly funded street sweeping that covered  4,046 curb miles, removing 916 tons of street pollutants

  • The DOT removed 367 tons of roadway pollutants from storm drain inlets and pipes through its infrastructure maintenance program.

Image of a street sweeper
County contractors removed 916 tons of roadway
pollutants from County Streets.


Meeting County Total Maximum Daily Loads (TMDLs)

DEP began developing a watershed assessment and implementation plan to meet the sediment TMDL in the Seneca Watershed.  The County must reduce the sediment from urban sources by 44.6 percent.  The TMDL implementation plan will combine the preliminary work done for the Countywide Implementation Strategy for the Great Seneca,  Dry Seneca, and Little Seneca watersheds.

DEP made progress towards meeting the Chesapeake Bay TMDL by reducing nitrogen and phosphorous through watershed restoration and other stormwater best management practices.  In FY 12, County pollutant reductions achieved .84% of the nitrogen pollution reduction goal required to meet County’s share of Chesapeake Bay TMDL, and 2.26% of the phosphorous pollution goal.

Learn more about Total Maximum Daily Loads


Improving Stormwater Management Laws and Regulations

The Department of Permitting Services (DPS) modified the County's Stormwater Management ordinance to comply with all current State standards, including requiring Environmental Site Design (ESD) non-structural stormwater BMPs to the maximum extent possible for new development and redevelopment. 

The DPS conducted 11,191 erosion and sediment control inspections, resulting in 248 Notices of Violation and 105 civil citations during construction of development projects.

Image of the Geneva Day School conservation landscaping
Volunteers at the Geneva Day School 
Train the Trainer Workshop


Environmental Site Design Strategy

The Planning Department continued to make progress on the comprehensive update of its zoning code, which was transmitted to Countil for review during 2013.  This zoning code update included recommendations from the DEP's Code Review on incorporating ESD to the MEP, completed in 2012.


Maintaining Existing Stormwater Management (Facilities)

The DEP oversaw inspection and maintenance of 1,667 stormwater management facilities as part of its three-year cycle to complete inspections throughout the County.


Educating and Engaging

The DEP 's Watershed Management Division (WMD) is the lead for implementing the Public Outreach and Education Workplan.  During FY12, the WMD :
  • Continued to expand outreach and education to increase stormwater awareness by reaching out to 6,400 residents at 71 events.

  • Launched the Stream Stewards program to train County volunteers to further watershed outreach in communities.

  • Supported local watershed groups through capacity building and training workshops.


Montgomery County Public Schools

Montgomery County Public Schools (MCPS) is an MS4 Co-Permittee and thus required to implement and report on programs to address runoff pollution.  The MCPS is responsible for maintaining many of the Stormwater Best Management Practices on their sites and for implementing stormwater pollution prevention programs at the MCPS Bus Depots.   The MCPS participates with DEP to identify and implement stormwater retrofit opportunities, including Environmental Site Design practices on school property. The MCPS is aggressively incorporating ESD practices into school building renovations, like the Green Roof shown here at Weller Road Elementary School.


Image of a Stream Steward educating a Montgomery County resident
The Stream Steward program trains volunteers to serve as ambassadors for the DEP. 

Reducing Litter

In May 2011, the County adopted a carry-out bag fee  to increase awareness about the problem of litter in our local streams and to offset costs of clean up for those who chose to use disposable bags.  The law went into effect in January 2012.

DEP is the lead agency for regional efforts to reduce trash and litter to the Potomac River and its tributaries through the Regional Anti-Litter Campaign with the Alice Ferguson Foundation.  During FY12, DEP
  • Used the regional anti-litter campaign materials in mass media outreach, including on metro buses and at bus stops.

  • Worked with volunteers for litter clean ups in streams and at stormwater management ponds.

  • Participated in the annual Potomac Trash Summit sponsored by the Alice Ferguson Foundation.



DEP is the lead agency for the monitoring required in the MS4 Permit.

The MS4 permit requires the County to conduct monitoring to determine how well stomwater management practices reduce stormwater quantity and pollution.  DEP will be constructing several small scale stormwater management practices in the Breewood tributary, a small subwatershed of the Anacostia. The County currently monitors biological, water chemistry, and physical conditions in the Breewood tributary in the Anacostia watershed to document pre-restoration conditions. Project construction is scheduled to begin during FY14.  

DEP also monitors the physical condition of streams in the Clarksburg Special protection Area (SPA) to determine the effectiveness of stormwater management meeting the criteria of the Maryland Stormwater Design Manual.



The County reported that $30,302,000 was budgeted to meet the MS4 Permit required programs. The majority of these funds are provided through the Montgomery County Water Quality Protection Charge.  In FY12, the WQPC provided $18, 274,245.



Interjurisdictional Agreements

Montgomery County is situated in the central corridor of Maryland between Baltimore and Washington, D.C. The County, given its drainage area size and population density, has a considerable impact on both regional and local environmental resources. It is a signatory to regional watershed protection agreements and coordinates watershed management with neighboring jurisdictions to protect and improve shared resources.



Anacostia Watershed Restoration Agreement

The Anacostia River flows through Montgomery and Prince George's counties into Washington, D.C., and then to the Potomac River. It has been identified as one of the three most polluted rivers in the entire Chesapeake Bay watershed. In 1987, the Anacostia Watershed Restoration Agreement was signed by the local, state, and federal agencies with land and management responsibilities in the Anacostia watershed. Since the agreement was signed, significant strides have been made to:

  • Develop a committee structure to determine how the goals of the agreement are to be reached

  • Establish a process for developing a work plan and milestones for the various restoration activities

  • Provide a framework for evaluating pollution control efforts with regard to observed water quality and aquatic life benefits

  • Institute mechanisms and measures for tracking progress and reporting on it as it occurs

The Metropolitan Washington Council of Governments supports the website on behalf of the members of the Anacostia Watershed Restoration Partnership. Visit for background on natural and cultural resources, along with news, meeting minutes, recent progress reports, and other watershed-based information.


Patuxent River Commission

Montgomery County is a member of the Patuxent River Commission, an interjurisdictional group that addresses environmental protection issues throughout the Patuxent River watershed. The 930-square-mile watershed is entirely within Maryland. It has been the focus of innovative policy, planning, and implementation efforts since 1980, beginning with a "charrette" that resulted in establishing the state's first nutrient reduction goals for wastewater treatment plants.

Commission members are committed to identifying relative roles and responsibilities to protect the watershed, tributaries, river, and reservoirs in the Upper Patuxent. They established six priority resources for protection:

  • Reservoirs

  • Tributary streams

  • Aquatic life

  • Terrestrial habitat

  • The watershed's rural character and landscape

  • People in the watershed

Every year the Commission reports on funding and policy commitments and progress in achieving long-term protection of these water resources.


Image of a litter bus ad produced by the Potomac Watershed Trash Initiative.

Potomac River Watershed Trash Treaty 

Since 1989, the Alice Ferguson Foundation has organized annual cleanups along the Potomac and its tributaries. In 2003, the Foundation began to galvanize federal, state, and local elected officials to participate in a strategy to prevent trash from entering local waterways. Montgomery County signed the Potomac River Watershed Trash Treaty and has committed, along with other local jurisdictions, to achieving a trash-free Potomac by 2013 by:

  • Supporting and implementing regional strategies aimed at reducing trash and increasing recycling

  • Increasing education and awareness of the trash issue throughout the Potomac River watershed

  • Reconvening annually to discuss and evaluate measures and actions addressing trash reduction


Maryland Local Government Agreement for Chesapeake Bay Restoration

In 1992, the Chesapeake Bay Program completed a reevaluation of the status and trends in water quality of the bay and its tidal tributaries. This led to both the allocation of nutrient reduction targets among the signatory states and the Maryland Local Government Agreement. Originally signed by the Governor, counties, and the City of Baltimore in 1993, the Agreement was updated in 2000 to outline commitments by the state and local governments to address the goals of the Chesapeake Bay Agreement at the local level.


Maryland Water Monitoring Council

The Maryland Water Monitoring Council was created in 1996 by the Maryland Department of Natural Resources. The Council serves as a statewide collaborative body to help achieve effective collection, interpretation, and dissemination of environmental data related to issues, policies, and resource management objectives involving water monitoring.

The Council addresses the full range of aquatic resources—groundwater and surface waters; freshwater, estuarine, and marine environments—and associated watershed resources in Maryland. Montgomery County has participated in all Council activities since 1996, which helps to protect and manage the County's aquatic resources with increased scrutiny from a broad scientific and water resource management network.