When land is developed, the hydrology, or the natural cycle of water is altered. Dependent on the magnitude of changes to the land surface, the total stormwater runoff volume can increase dramatically. Development and impervious surfaces can also reduce the amount of water that infiltrates into the soil and groundwater, thereby reducing the amount of water that can recharge aquifers and feed steams during periods of low flow.
Stormwater & Water Quality
Not only does development increase the quantity of stormwater runoff, but it impacts water quality by increasing both the concentration and types of pollutants in the water. As runoff moves over lawns and rooftops, parking lots and roadways, it picks up and conveys a variety of contaminants to downstream water courses.
The Loudoun County Stormwater Management Program is modeled after the State of Virginia's program, with the addition of specific requirements and guidance found in the Loudoun County Stormwater Management Ordinance, the county’s Facilities Standards Manual, and in several other technical manuals. The goal of the county program is to prevent and mitigate the stormwater quantity and quality impacts discussed above. This is accomplished by achieving the following:
Best Management Practices
- Developing land in a way that minimizes its impact on the watershed
- Controlling stormwater runoff peaks, volumes and velocities to prevent downstream flooding and streambank channel erosion
- Treating post-construction stormwater runoff before it is discharged to a receiving channel or waterway
- Maintenance of the vegetative and structural best management practices (BMPs) that provide the necessary quantity and/or quality control for construction sites
These program objectives are primarily achieved through the evaluation of development applications for consistency with applicable local, state, and federal standards for stormwater management and implementing those plans with the appropriate BMPs. Development plans are reviewed to ensure the proper implementation of structural and vegetative BMPs to prevent non-point source pollution from exceeding pre-development levels as well as inhibit channel erosion and flooding.
These BMPs, which include rain gardens, wet ponds, constructed wetlands, water quality inlets, and stormwater conveyance channels, are designed and constructed to control erosion, prevent drainage problems and property damage, and minimize negative impacts to streams.
The review of development applications for adequate control and management of stormwater is the responsibility of the Engineering Division in the Department of Building & Development. Following the construction of stormwater management systems, the Department of General Services is responsible for the inspection and maintenance of most systems. Staff from the two departments work together closely to make sure that design and maintenance efforts result in effective BMPs and overall site design.
Read more about Stormwater Management Facility Maintenance & Reporting