Stormwater Management Practices
Stormwater is rainfall or melting snow that flows over any impervious surface (paved surfaces, rooftops) that is not allowed to soak into the ground. Stream impairment in urban areas is partially caused by stormwater runoff.
Stormwater management includes controlling flooding, reducing erosion and improving water quality. This can be accomplished by implementing stormwater management practices, also called best management practices (BMPs). Stormwater management practices are structural, vegetative or managerial practices used to treat, prevent or reduce water pollution. See the Practices page for information on different type of stormwater management practices.
Building and Grading Permits
A building and grading permits with ground disturbance are reviewed for stormwater management. Please review the SWM Checklist. Stormwater Management Water Quality Volume (WQv) and Recharge Volume (Rev) must be treated for:
- Any new single family home
- Any non-waterfront lot disturbing 5000+ square feet
- Any waterfront lot disturbing 2000+ square feet
The goal of the City of Annapolis is to reduce impervious surfaces (asphalt, concrete, home footprints, etc) by 50%. If this cannot be done, WQv must be treated at a rate of 50% of the total WQv calculated (per MDE design manual and City Code).
Design Manual Methods
WQv and Rev may be treated per the design manual methods. All treatment must be quantified. Treatment examples include:
- Green roofs
- Infiltration trenches
- Rain gardens
- Rooftop and non-rooftop disconnect credits
See the MDE design manual for many further options. Please note tree plantings do not count for WQv treatment per the design manual.
Any Stormwater Management (SWM) facility must have a signed SWM maintenance agreement, ensuring it is properly inspected and maintained on a regular basis. Maintenance logs should be kept for each separate facility and shall be made available upon the City's request. If you need help setting up a maintenance log, please contact Public Works at 410-263-7949.
If your project has a SWM facility, you will be required to sign the SWM maintenance agreement before the grading permit will be issued. Information on obtaining the SWM maintenance agreement will be given upon initial review of the grading permit application.
CPV, Qp and Qf are required on a case-by-case basis. Please have your engineer verify if the site conditions require these additional controls.