The Maryland Department of the Environment (“MDE”) has proposed long anticipated regulations that implement key provisions of Maryland’s Stormwater Management Act of 2007. The regulations represent the most significant change to the State’s Stormwater Management program since 2000. The proposed regulations advance the concept of “Environmental Site Design” (ESD”) by promoting its use “to the maximum extent practicable” in place of traditional structural best management practices.

ESD is defined under the proposed regulations as “using small scale stormwater management practices, nonstructural techniques and better site planning to mimic natural hydrologic runoff characteristics and minimize the impact of land development on water resources.” Methods for designing and implementing ESD are specified in the newly revised Chapter 5 of the Maryland Stormwater Design Manual (the “Design Manual”) which is likewise being amended and released for comment in conjunction with the proposed regulations.

The proposed regulations require that ESD be incorporated into stormwater management plans to the “maximum extent practicable”, which is defined under the regulations as “designing stormwater management systems so that all opportunities for using ESD planning techniques and treatment practices are exhausted”. More traditional structural stormwater management practices are allowed only after all potential ESD has been considered. The proposed regulations provide that the “maximum extent practicable” standard is met when channel stability is maintained, predevelopment groundwater recharges replicated, non-point source pollution is minimized and structural stormwater management practices are used only if determined to be absolutely necessary. According to the proposed Design Manual, ESD practices are to be sized so that the runoff leaving a site is reduced to a level equivalent to a wooded site in good condition.

ESD techniques and practices include, among other things:

  • Conserving natural drainage patterns
  • Minimizing impervious areas
  • Using green roofs, permeable pavements, reinforced turf and other alternative surfaces
  • Clustering development

In addition to encouraging the use of ESD practices, the proposed regulations make other significant changes to the State’s stormwater management practices. The critical features of the new regulations include:

  • Requiring local jurisdictions to submit amended stormwater management ordinances and programs incorporating the new ESD criteria to MDE by July 1, 2009 and ensuring that the new practices are implemented by December 31, 2009;
  • Providing that redevelopment projects with existing site impervious area of greater than 40% reduce existing impervious area by at least 50%, implement ESD to provide water quality treatment for at least 50% of the existing impervious area, use a combination of these two practices for at least 50% of the existing site and imperious area, or employ alternative measures on- or off-site to provide water quality treatment for an area equal to 50% of the existing impervious area;
  • Providing that, for redevelopment projects with less than or equal to 40% impervious area, the stormwater requirements for new development will apply;
  • Mandating that counties and municipalities modify planning and zoning ordinances to eliminate any impediments to implementing ESD to the maximum extent practicable;
  • Establishing a three-part stormwater management plan development process requiring preparation of a concept plan, development plan and final stormwater management plan;
  • Establishing an ESD inspection and maintenance process to ensure that owners properly install and maintain both structural and ESD stormwater features.

MDE published the proposed final regulations on the agency’s website on October 17. Notice of a public hearing to be held the week of December 8 at MDE headquarters will be published in the Maryland Register on November 7. The proposed regulations will be published in the Maryland Register on November 21. MDE hopes to issue the final regulations in the first week of January, 2009.

A copy of the proposed regulation and revised Design Mutual are available at the following link

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