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Howard County’s National Pollutant Discharge Elimination System (NPDES) Municipal Separate Storm Sewer System (MS4) permit, issued by the Maryland Department of the Environment (MDE), requires a number of activities for permit compliance. The sections below include descriptions of some of the activities required and managed by the Stormwater Management Division.
Under Howard County’s National Pollutant Discharge Elimination System (NPDES) municipal separate storm sewer system (MS4) permit, the Maryland Department of the Environment (MDE) requires the County to annually submit all private and public storm sewer system data and all stormwater best management practice (BMP) data, including delineated drainage areas, in geographic information system (GIS) format. To comply with this permit condition, the County has been requiring that digital design information related to all private and public BMPs and storm drain systems be submitted with development plans and capital projects as of July 1, 2017. These data will be incorporated into the County’s GIS inventory for asset management and for submittal to MDE.
Design information required to be submitted digitally for all new private and public infrastructure includes:
- a PDF final plan for the project
- locations of Best Management Practices (BMPs), outfalls, manholes, inlets, pipes, and easements
- delineations of drainage areas to outfalls and BMPs
- data on BMP, outfall, manhole, inlet, and pipe design information (types, dimensions, materials, plan approval date, etc.)
- lot numbers and parcel boundaries
Data must be submitted as a dxf file with an associated completed Excel file and a PDF final plan for the project. Submittals should be emailed to stormwater@howardcountymd.gov. A link to the Excel template can be found here:
When any new construction, substantial improvement, or repair for a substantially damaged building is conducted in or adjacent to the Special Flood Hazard Area (SFHA), the Department of Inspections, Licenses & Permits (DILP) requires the following floodplain-related certificates to be included with the construction permits, where applicable:
- Elevation Certificate
- Non-residential Floodproofing Certificate
- Engineered Flood Opening Certificate
- No-Rise Certificate
- Nonconversion Agreement
Requiring development adjacent to the SFHA to follow development restrictions for the SFHA and complete Elevation Certificates and other floodplain-related certificates are higher regulatory standards adopted by Howard County.
The Howard County Design Manual - Volume I has been revised and is available for viewing. Of particular note is the revision to the 24-hour rainfall rates for all design storms used in stormwater management computations and their effective date. Other minor revisions and clarifications have also been made.
On December 18, 2014, Howard County received a new National Pollutant Discharge Elimination System (NPDES) Municipal Separate Storm Sewer System (MS4) Discharge Permit from the Maryland Department of the Environment (MDE). The County's MS4 permit includes requirements for watershed restoration activities, specifically preparation of a restoration plan within the first year of the permit term. To address this requirement, Howard County developed a Countywide Implementation Strategy (CIS) in 2015. A revised CIS was developed in 2017.
NOTE: The costs shown to implement the Financial Assurance Plan to meet the stated goals of the plan have been estimated. The cost estimates provided in the CIS will likely adjust as the County progresses with implementation of its program.
Learn more about Watershed Protection and Restoration Fund.
MDE reissued the County's National Pollutant Discharge Elimination System (NPDES) Municipal Separate Storm Sewer System (MS4) Permit (Number 22-DP-3318 MD0068322) with an effective date of December 30, 2022, and an expiration date of December 29, 2027. In accordance with Howard County's NPDES MS4 Permit, the County must prepare Annual Updates to report on the progress made during the preceding permit year. Progress is reported on compliance with pollutant source identification; management programs including stormwater management, erosion and sediment control, illicit discharge detection and elimination, property management and maintenance, and public education; stormwater restoration; Countywide Total Maximum Daily Load (TMDL) Implementation Plan; assessment of controls; program funding; and special programmatic conditions. The County submitted the Annual Update for its 30th permit year to the Maryland Department of the Environment (MDE) on December 30, 2025.