Maryland Stormwater Management Program

Why Stormwater Matters: Impacts of Runoff on Maryland's Watersheds

Urban development has a profound influence on the quality of Maryland’s waters. To start, development dramatically alters the local hydrologic cycle (see below). The hydrology of a site changes during the initial clearing and grading that occur during construction. Trees, meadow grasses, and agricultural crops that intercept and absorb rainfall are removed and natural depressions that temporarily pond water are graded to a uniform slope. Cleared and graded sites erode, are often severely compacted, and can no longer prevent rainfall from being rapidly converted into stormwater runoff.

The situation worsens after construction. Roof tops, roads, parking lots, driveways and other impervious surfaces no longer allow rainfall to soak into the ground. Consequently, most rainfall is converted directly to runoff. The increase in stormwater can be too much for the existing natural drainage system to handle. As a result, the natural drainage system is often altered to rapidly collect runoff and quickly convey it away (using curb and gutter, enclosed storm sewers, and lined channels). The stormwater runoff is subsequently discharged to downstream waters such as streams, reservoirs, lakes or estuaries.

Water Quality is affected by the accumulation of trash, oil and rubber from cars, fertilizers and pesticides applied to lawns, sediment from bare or poorly vegetated ground and other pollutants entering streams, rivers and the Chesapeake Bay. Inflow of sediment can cloud water, blocking sunlight from submerged plants. Sediment also settles to the bottom of streams, clogging the gravel beds used by fish for laying their eggs. Nutrients, such as phosphorus and nitrogen, from fertilizers enter the water and promote unusually rapid algae growth. As this algae dies, its decomposition reduces or eliminates oxygen needed by fish, shellfish, and other aquatic life for survival.

These are all examples of nonpoint source pollution, one of the major contributors to the degradation of quality in Maryland's waterways. Stormwater management practices help control nonpoint source pollution through the use of nonstructural and/or structural techniques to intercept surface runoff from developed areas, filter and treat this runoff, and then discharge it at a controlled rate. The overriding condition that governs the quantity of stormwater runoff is the amount of impervious surfaces located on your property (driveways, roofs, carports, sidewalks, etc.) Stormwater quality, however, is governed by the accumulation of pollutants on the entire surface area, regardless of whether it is grassed or paved. As the use of chemicals around the home such as fertilizers, pesticides, engine oils, deicing materials, and similar products increases, the more degraded the stormwater runoff from your property will be. Although the effect of one property on the quality and quantity of stormwater runoff may seem insignificant, the cumulative impact from hundreds of thousands of yards across the State continues to be destructive to our water quality.

These Activities Will Minimize Stormwater Runoff from Your Property:

• Limit the amount of impervious surfaces in your landscape. Use permeable paving surfaces such as wood decks, bricks, and concrete lattice to allow water to soak into the ground. Where possible, direct runoff from impervious surfaces across
  vegetated areas.
  
• Allow "thick" vegetation or "buffer strips" to grow alongside waterways to filter and slow runoff and soak up pollutants.
  
• Plant trees, shrubs, and groundcover. They will absorb up to fourteen times more rainwater than a grass lawn and they don't require fertilizer. For more information on environmentally-friendly planting and "Bayscaping", contact the Maryland Department of Natural Resources or the Alliance for the Chesapeake Bay.
  

These Activities Will Reduce Fertilizer, Pesticide, and Sediment Runoff:

Use natural alternatives to chemical fertilizers and pesticides. If you must use fertilizers or pesticides, test your soil to determine the appropriate amount. For more information, contact the Maryland Cooperative Extension Service at 1-800-342-2507.
If a lawn care company services your lawn, make certain it is not applying "blanket" applications of fertilizer and pesticides. Ask if they have conducted soil tests and a pest analysis to determine appropriate applications.
Resod or reseed bare patches in your lawn as soon as possible to avoid erosion
Stormwater Management Regulations

The regulations governing Maryland's stormwater management program may be found in the Code of Maryland Regulations (COMAR) 26.17.02. The Maryland Department of the Environment, Water Management Administration is pleased to announce the adoption the 2000 Maryland Stormwater Design Manual, Volumes I & II (COMAR 26.17.02.01-1). The effective date of the new regulations and the manual is October 2, 2000. The revised COMAR is available from the Office of the Secretary of State, Division of State Documents (DSD) (www.dsd.state.md.us).

2000 Maryland Stormwater Design Manual

The 2000 Maryland Stormwater Design Manual, Volumes I & II is available in print for $25.00 per copy. This is the official version and includes changes made prior to adoption. The Design Manual is also available online and may be downloaded in "PDF" format using the Adobe® Acrobat® Reader (version 4.x or newer).

NOTE: Several changes were made to the 2000 Maryland Stormwater Design Manual, Volumes I & II prior to adoption. The changes are nonsubstantive and in many cases correct minor typographical or grammatical errors. If you are using a copy of the manual published in April 2000, the replacement pages are available in PDF format or by contacting the Nonpoint Source Program at 410-537-3000.

Guidance on Design Manual Implementation

MDE has conducted several meetings with local jurisdictions and the regulated community across the State concerning the implementation of the stormwater management program.   In response to questions raised during these meetings, MDE will begin offering supplemental guidance for the more common issues on this site.  The first subject is the implementation of the channel protection criterion (Cp_v) found in the Design Manual.   Click here for more information.

NEW! (09/14/2004) Tentative Determination to Issue General Permit for Discharges from State and Federal Small Municipal Separate Storm Sewer Systems

The Maryland Department of the Environment (MDE) has made a tentative determination to issue a National Pollutant Discharge Elimination System (NPDES) General Permit for Discharges from State and Federal Small Municipal Separate Storm Sewer Systems.

MDE has drafted a general permit (No. 05-SF-5501) designed to control stormwater pollutant discharges from State and federal small municipal storm drain systems. Under the conditions of the permit, agencies will be required to implement programs for: personnel education and outreach; public participation and involvement; illicit discharge detection and elimination; construction site runoff control; post-construction runoff control; and pollution prevention/good housekeeping. Implementation of these minimum control measures will help efforts toward improving the quality of the State’s streams, rivers, and Chesapeake Bay.

All information supporting this tentative determination, including the draft general permit, may be reviewed by contacting Mr. Brian Clevenger at MDE\WMA, Sediment, Stormwater & Dam Safety Program, FL4, STE 440, 1800 Washington Boulevard, Baltimore, MD 21230-1708 or by telephone at 410-537-3543 to make an appointment during the hours of 8:00 a.m. to 5:00 p.m., Monday through Friday. Copies of the document may be obtained at a cost of $0.34 per page. The draft permit can also be viewed on MDE’s website here General Permit (No. 05-SF-5501). MDE will hold a public hearing concerning this tentative determination if a written request is received by October 11, 2004. Written requests should be directed to Mr. Brian Clevenger. Written comments concerning this tentative determination will be accepted through October 22, 2004.

Guidance on Proprietary Practices for Stormwater Treatment

Stormwater management practices help control nonpoint source pollution through various techniques that intercept, filter, and treat runoff from developed areas.   MDE recognizes that new structural best management practices (BMPs) are being developed, including many proprietary designs.  In response to the growing number of proprietary practices, MDE has published additional guidance concerning the use of these practices within Maryland.  This guidance also outlines the basic information that should be submitted to MDE as part of a formal review of new proprietary practices.  Click here for more information.

Stormwater Management Guidelines for State & Federal Projects

MDE is pleased to announce the publication of the "Maryland Stormwater Management Guidelines for State & Federal Projects". These Guidelines supplement the Stormwater Management Regulations (COMAR 26.17.02) and the "2000 Maryland Stormwater Design Manual, Volumes I & II". The Guidelines, which become effective July 1, 2001, provide information necessary for submittal of stormwater management plans by State and federal agencies to MDE's Water Management Administration for review and approval.

Questions about the Guidelines should be directed to Mr. Jim Tracy at (410) 537-3000.

Erosion & Sediment Control Guidelines for State and Federal Projects

MDE is pleased to provide the “Maryland Erosion And Sediment Control Guidelines For State And Federal Projects” on the Department’s web site. Supplementing the Erosion And Sediment Control Regulations (COMAR 26.17.01) and the “1994 Maryland Standards And Specifications For Soil Erosion And Sediment Control”, the Guidelines provide information necessary for submittal of erosion and sediment control plans by State and federal agencies to MDE's Water Management Administration for approval.

These guidelines have been serving the community since 1990 and have recently undergone a revision prior to publication on the Department’s web site. Most of the revisions correct typographical errors and/or clarify issues in the guidance text. However, several changes shall be reflected on plans that are submitted to the Program for approval.

Significant changes to the Guidelines include:

• Providing the correct COMAR citation;
• Clarifying the definition of Variance - two tests have to be met in order to issue a variance;
• Providing the correct law and regulation citations relative to Wetlands;
• Making requirements as to who must sign the Design Certification consistent with regulation;
• Changing SCS reference to NRCS;
• Emphasizing that WMA file number must accompany all submittals;
• Providing a revised checklist in the appendix; and
• Revising The Standard Erosion And Sediment Control Notes – these revised notes must be placed in their entirety on all plans.

Questions about the Guidelines should be directed to the Sediment, Stormwater And Dam Safety Program at (410) 537-3563.

Standard Stormwater Management Plan for Single Lot Residential Construction - MODEL

MDE is pleased to announce the publication of a model standard stormwater plan that may be of use to localities implementing stormwater for small development projects.   Regulation changes made in 2000 eliminated the exemption for residential developments with average lot sizes of two or more acres.  The "Standard Stormwater Management Plan for Single Lot Residential Construction - MODEL" is based on those nonstructural practices found in Chapter 5 of the Design Manual and will help localities provide management to some of those projects exempt from runoff control in the past.  If the limitations and conditions of the plan are met and site planning characteristics implemented, this model will address stormwater management appropriately.

Each jurisdiction may use a standard plan.  However, all local standard plans must be reviewed and approved by MDE.  Localities choosing to use a standard plan should review the model, tailor a similar tool to fit specific permitting processes and submit it for approval.

Questions about the Model Standard Plan should be directed to Mr. Stewart Comstock at (410) 537-3543.

Other Publications

In addition to the 2000 Maryland Stormwater Design Manual, the Sediment, Stormwater & Dam Safety Program has several publications related to nonpoint source pollution, stormwater management, erosion and sediment control, and dam safety issues. The list of these publications is available here and may be downloaded in PDF format as well.