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Stormwater is regulated in two ways in Annapolis. The City is subject to a Municipal Separate Storm Sewer (MS4) permit and the City regulates stormwater requirements for development.

Municipal Stormwater Permit

The City's MS4 permit is administered by the Maryland Department of the Environment (MDE) by purview of the Clean Water Act. Under the Clean Water Act, the Environmental Protection Agency (EPA) issues permits for point discharges of pollutants. Urban runoff is considered a point source of pollution and is regulated by the the National Pollutant Discharge Elimination System (NPDES) MS4 permits. The City of Annapolis was reissued a Phase II MS4 general permit in 2018 based on population and impervious coverage. Under its Phase II MS4 designation, the City is responsible for the implementation of six (6) Minimum Control Measures (MCM’s) prescribed by the General Permit to prevent the conveyance of harmful pollutants to the Chesapeake Bay and its tributaries:

  • Public Education and Outreach
  • Public Involvement/Participation
  • Illicit Discharge Detection and Elimination (IDDE)
  • Construction Site Runoff Control (also known as Erosion and Sediment Control)
  • Post-Construction Runoff Control
  • Pollution Prevention for municipal operations

The permit also establishes an untreated impervious area baseline.  Under the current permit, the City is responsible to mitigate 20% of its untreated impervious area with new Best Management Practices (BMPs) by the year 2025.

City of Annapolis National Pollutant Discharge Elimination System General Permit.

NPDES General Permit

For Additional Information


Stormwater Development Review

Development that triggers a grading permit application is reviewed for management of stormwater runoff during construction and post-construction. Chapter 17.10 of the City code establishes the City’s requirements and oversight of development as related to stormwater management. Planning and Zoning is the central point for all building and grading permit applications. The Stormwater Management team within the Department of Public Works (DPW) reviews permits for stormwater requirements. Disturbances of 5,000 square feet or 2,000 square feet of waterfront land require a grading permit and stormwater management. Any new single-family home also must have stormwater management. This means development plans must show stormwater management practices with accompanying calculations to show that the practices treat the required amount of runoff. The runoff volume to be treated from the Maryland Stormwater Design Manual is based on the one-year rain event or a design storm of 2.7 inches of rain over 24 hours and is adjusted based on infiltration testing at the location of the proposed stormwater practices. The practices are meant to treat the first flush of pollutants from larger rain events and then bypass or overflow additional runoff in a non-erosive manner. DPW policy also requires an additional 25% volume requirement above the State requirement. The City Code section 21.64.010 also requires stormwater management for Accessory Dwelling Units.

Any Stormwater Management (SWM) facility must have a signed SWM maintenance agreement, ensuring it is properly inspected and maintained on a regular basis.A maintenance agreement is recorded with the development approval that conveys to all future property owners. The maintenance agreement allows the City to inspect the stormwater management facilities. Maintenance is the responsibility of the property owner. The City is required to inspect stormwater facilities every three years for compliance with its MS4 permit.A template of the agreement as well as other public work stormwater review-related forms found in a typical application are listed on the Guidance and Forms page.

Development activities that trigger a grading permit also require management of stormwater runoff during construction. Planning and Zoning is the main point of contact for building and grading permit applications via the online application Citizen Self Service portal. DPW coordinates the review of Erosion and Sediment Control Plans with the Anne Arundel Soil Conservation District (AASCD). Here is an Erosion and Sediment Control Checklist to help you. City environmental compliance inspectors regularly visit construction sites to enforce AASCD-approved sediment and erosion control measures.

As-Built and Bond Process

During construction of SWM facilities, it is important to take pictures during critical steps of construction to include all underground installation of pipes and structures and installation of media. It is also important to avoid compaction of areas where SWM facilities will be placed. Usually SWM facilities are the last to be installed on a site. Once the facilities are finished, they must be surveyed by the design engineer and as-builts need to be submitted to Planning and Zoning for approval. As-builts are required before bond reduction and inspections can be scheduled. More information on adequate as-built plans can be found in the As-Built Supplemental Guidelines

Bonds are a way to guarantee that stormwater and other facilities are installed correctly by the developer before they become the responsibility of the property owner to maintain. Bond requirements are administered by the Planning and Zoning.  After completion of a project, the City inspects facilities to ensure they are installed correctly prior to reduction of a bond. One year later the facilities are inspected again before release of the bond. 


As part of the MS4 permit , the City of Annapolis completes Annual Progress Reports. The reports document compliance and progress towards the requirements of the NPDES General Permit and outlines the Impervious Surface Area Restoration Program.

BMP Fact Sheets


The City has a database of all BMPs in the City to include both privately maintained BMPs and publicly maintained BMPs. Click link to find out if you have a BMP in your neighborhood.

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