Fairfax County's Municipal Separate Storm Sewer System (MS4) permit requires the county to prevent the discharge of pollutants (often called "non-point source" pollutants) such as engine oil, fertilizer, pet waste and trash from the stormwater management system into waterways to the maximum extent practicable. The permit also prohibits non-stormwater discharges into the storm drainage system, such as from sanitary sewer connections or illegal dumping. It also requires storm event monitoring and assessment of the effectiveness of stormwater controls being used in the county. Annual reports submitted to the Virginia Department of Environmental Quality (DEQ) summarize the efforts of government agencies, non-profit agencies and private organizations in managing stormwater runoff and limiting non-point source pollution to the maximum extent practicable

Activities and collective efforts in support of the mission of effective stormwater control include:

• Defining a strategic plan for comprehensive stormwater management.
• Developing watershed management plans.
• Implementing water quality and quantity control practices.
• Conducting inspection and maintenance programs for stormwater control systems and structures to ensure their effectiveness.
• Conducting stream monitoring and evaluation programs.
• Providing technical support to residents and developers.
• Sharing resources and information for the purposes of educating residents and developing strategies to promote good water quality improvement practices.

Permit and TMDL Action Plans

Fairfax County's MS4 permit is mandated by the Clean Water Act and by Environmental Protection Agency stormwater regulations. The Virginia Department of Environmental Quality administers MS4 permits as part of the Virginia Stormwater Management Program permit program. The permit covers the jurisdictional land area of Fairfax County, excluding the Towns of Clifton, Vienna, and Herndon; the Cities of Fairfax and Falls Church; Fort Belvoir; Dulles International Airport; and the Virginia Department of Transportation's road system.

The maximum amount of a pollutant a waterbody can receive while still meeting water quality standards is referred to as the Total Maximum Daily Load (TMDL). The TMDL is a comprehensive pollution diet for an impaired waterway. While DEQ develops the TMDLs, the county’s MS4 permit requires the development of an action plan to describe the process that will be used to achieve specific pollutant reductions through a stormwater management program.

For more information about the county's MS4 permit, or to request archived documents, please contact the Stormwater Planning Division by email at swpdmail@fairfaxcounty.gov or call 703-324-5500, TTY 711.