Regulations & Permits

Howard County Design Manual - Volume I Storm Drainage (2017 Revision)

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.


Submission of Digital Storm Drain System and Stormwater Management Data


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 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 BMPs and storm sewer systems be submitted with development plans as of July 1, 2017. These data will be incorporated into the County’s inventory for submittal to MDE.

Design information required to be submitted digitally includes:

  • locations of Best Management Practices (BMPs), outfalls, manholes, inlets and pipes and easements
  • delineations of drainage area to outfalls and BMPs
  • data on BMP, outfall, manhole, inlet and pipe design information (types, dimensions, materials, plan approval date, etc.)


Data can be submitted in a GIS geodatabase, as GIS shapefiles, or as AutoCAD dxf files with an associated completed Excel file. GIS format is preferred. Links to the GIS and Excel templates can be found here:

Excel Template
GIS Geodatabase
GIS Shapefiles


Countywide Implementation Strategy (CIS)


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 CIS.


Watershed Protection and Restoration Fund


Learn more here


NPDES MS4 Permit Annual Update Number 24


In accordance with Howard County's National Pollutant Discharge Elimination System (NPDES) Municipal Separate Storm Sewer System (MS4) Permit (Number MD0068322, 11-DP-3318), 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 and illicit discharge detection and elimination; restoration plans, watershed assessments, and Total Maximum Daily Loads (TMDLs); assessment of controls and monitoring; program funding; and special programmatic conditions. The County submitted the Annual Update for its 24th permit year to the Maryland Department of the Environment (MDE) on November 27, 2019. To view the County’s Annual Update Number 24, click here.


Howard County Code