Board of Supervisors Meeting Date:

William G. Downey, Scott District Supervisor


November 8, 2007

Staff Lead:


Kimberley Fogle, Assistant Director


Community Development




An Ordinance to Amend Subsection 3 of Section 204.2 of the Design Standards Manual to Clarify Its Application to Point Source Stormwater Runoff


Topic Description: 

Section 204.2 of the Design Standards Manual provides a general policy for water quality in stormwater management and BMP facilities.  Subsection 3 requires the adequate treatment of stormwater runoff generated from new development sites prior to discharge into a jurisdictional wetland or local water body.  This proposed amendment clarifies that the provision is intended to apply to point source discharges of stormwater and not from non-point source runoff, such as dispersed sheet flow from residential lawns.


Requested Action of the Board of Supervisors:

Conduct a public hearing and consider adoption of the attached Ordinance.


Financial Impact Analysis:

There is no financial impact.


Summary Staff Report:

Subsection 3 of Section 204.2 provides that all stormwater generated by new development shall not be discharged into a jurisdictional wetland or local water body without adequate treatment.  The standard for adequate treatment has been the use of a vegetative filter strip of about 25 feet in width to filter out pollutants and particulate matter prior to the water entering the wetland or water body.  A similar provision was part of the draft Virginia Stormwater Management Model Ordinance at the time the County adopted its Stormwater Management Ordinance (and this provision) in 2002.  The Stormwater Management Ordinance was subsequently incorporated into an overall Design Standards Manual.  The State eliminated this provision from their model ordinance, as the Corps of Engineers and the Department of Environmental Quality have oversight related to impacts to wetlands and water bodies.   The DEQ permits have a clause in them that requires pre-treatment of surface water runoff prior to entering into regulated wetland areas. 

Since adoption of this provision in 2002, it has been interpreted as including both point source and non-point source discharges into wetlands.  The non-point sources are primarily lawns and yards associated with residential development.  This has shown to be problematic for residential projects, such as Brookside, where there are a considerable amount of wetlands and they have already paid for or mitigated their impacts to the wetlands in accordance with a Memorandum of Understanding with the Corps of Engineers.

This proposed amendment clarifies the requirement for adequate treatment for point source discharges.  Having pre-treatment of stormwater runoff prior to being discharged into jurisdictional wetlands is a good practice because it helps to preserve the overall health of the ecosystem as well as the vibrancy of the wetlands.  To overload them with concentrated pollutants suspended in stormwater runoff that will primarily be collected from roadway areas and/or other impervious areas would contribute to the wetlands premature degradation and possible destruction.  In addition, pre-treatment will allow for screening out trash, debris, and other large material, as well as for initial filtering of other smaller suspended particulate matter in the runoff that over time will eventually choke the wetlands ability to thrive.

The addition of the point source language in our Design Standards Manual reinforces the importance of pre-treatment in the preservation and protection of these wetland areas.


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