The Maryland Department of Environment (MDE) has circulated its first public draft of revised stormwater regulations that incorporate updated rainfall data and require significant expansion of management practices to address runoff from higher-intensity, short-duration storms.

The changes were initiated by legislation passed by the General Assembly in 2021 which required MDE to report on the most recent precipitation data and update Maryland’s stormwater management standards for flood control.

An initial review by industry stormwater practitioners indicates the proposed rules would significantly increase the cost of compliance and reduce buildable area. Among the proposed changes are:

  • Increased volume of water quality treatment and flood control using Environmental Site Design techniques.
  • Reclassifying open space to assume less infiltration and higher peak runoff rates.
  • Applying new development standards to redevelopment in selected environmental justice locations.
  • A transition period that applies current regulations to projects that reach concept plan approval by June 30, 2028, and complete construction by June 30, 2035.

MDE will accept public comments on the preliminary draft until August 29, 2023.  The draft regulations can be viewed and downloaded here. MDE has requested that comments and questions be submitted to Raymond Bahr at 410-537-3545 or

NAIOP will submit a unified set of industry comments, but members are urged to review the draft regulations and either submit comments directly to MDE or forward comments to to be incorporated into the NAIOP letter.